Wednesday,
June 13, 2001
Part IV
Environmental
Protection Agency
40 CFR Part 197
Public Health and Environmental
Radiation Protection Standards for Yucca
Mountain, NV; Final Rule
-------
-------
600R03050ES
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
OFFICE OF
RESEARCH ANDDEVELOPMENT
Thank you for your interest in the U.S. Environmental Protection Agency's Draft Report
on the Environment 2003, Technical Document (EPA/600/R-03/050). Unfortunately, we are
able to provide only one printed copy per customer at this time. We are sending you extra copies
of the CD-ROM and hope that this will meet your needs. The document is also available on the
Internet at http://epa.gov/indicators/roe/html/tsd/index.htm.
If you need more copies of the CD-ROM, please contact the
National Service Center for Environmental Publications
U.S. Environmental Protection Agency
P.O. Box 42419
Cincinnati, OH 45242
telephone: 1-800-490-9198 or 513-489-8190
facsimile: 513-489-8695
email: ncepiwo@one.net
Internet: www.epa.gov/ncepihom/ordering.htm.
Printed on Recycled Paper
-------
-------
Errata Sheet
Onsite Wastewater Treatment
Systems Manual
EPA/625/R-00/008^
June 2003
Page
Number
xi
3-29
4-33
TFS-8
TFS-23
TFS-57
TFS-65
Errata
The following names were omitted from the list of contributors:
William C. Boyle, Ph.D.,PE, and Damann L. Anderson, Ayres
Associates.
In Table 3-19, in the row entitled "Phosphorus," and the columns
entitled "Sand Filter Effluent" and "Foam or textile filter effluent" both
superscripts "4" should be "3" to correspond with footnote #3 below
the table. These numbers are not exponents.
The last paragraph on this page should be removed from the box and
moved to page 4-32, as the last paragraph of section 4.4.7. The
following should be added after the first sentence of that paragraph:
"However, siphons distribute wastewater to treatment media on
demand rather than via timed dosing approach, resulting in more
frequent dosing cycles during heavy use periods and fewer cycles
during off-peak times."
Figure 2 should be disregarded. Peat is more generally used as
media in a filter and is discussed in Section 4.7.
Arrows above and below Figure 1 should be disregarded.
The headings for Table 2 should be:
BOD (mg/L) TSS (mg/L)
TKN (mg/L) TN (mg/L) Fecal Conform
(CFU7100ml)
The second formula under Step 6 of Recirculating tank sizing should
be: Freeboard volume = (CL + Q^ - Qeff) x T
Under conditions of peak flows (Qln»>QdoJ there is no recycle flow so
QMFQM-. Therefore the freeboard volume necessary is (Qrt-QdoJx
-------
-------
32074 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
ENVIRONMENTAL PROTECTION
AGENCY
40 CFR Part 197
[FRL-6995-7]
RIN 2060-AG14
Public Health and Environmental
Radiation Protection Standards for
Yucca Mountain, NV
AGENCY: Environmental Protection
Agency (EPA).
ACTION: Final rule.
SUMMARY: We, the Environmental
Protection Agency (EPA), are
promulgating public health and safety
standards for radioactive material stored
or disposed of in the potential
repository at Yucca Mountain, Nevada.
Section 801 of the Energy Policy Act of
1992 (EnPA, Pub. L. 102-486) directs us
to develop these standards.- Section 801
of the EnPA also requires us to contract
with the National Academy of Sciences
(NAS) to conduct a study to provide
findings and recommendations on
reasonable standards for protection of
the public health and safety. The health
and safety standards promulgated by
EPA are to be "based upon and
consistent with" the findings and
recommendations of NAS. On August 1,
1995, NAS released its report (the NAS
Report), titled "Technical Bases for
Yucca Mountain Standards." We have
taken the NAS Report into consideration
as the EnPA directs.
The Nuclear Regulatory Commission
(NRC) will incorporate these final
standards into its licensing regulations.
The Department of Energy (DOE) must
demonstrate compliance with these
standards. The NRC will use its
licensing regulations to determine
whether DOE has demonstrated
compliance with our standards prior to
receiving the necessary licenses to store
01 dispose of radioactive material in
Yucca Mountain.
DATES: Effective Date: This rule becomes
effective July 13, 2001.
ADDRESSES: Documents relevant to the
Tulemaking: You can find and access
materials relevant to this rulemaking in:
(1) Docket No. A-95-12, located in
Waterside Mall Room M-1500 (first
floor, near the Washington Information
Center), 401 M Street, SW., Washington,
DC 20460; (2) an information file in the
Government Publications Section, Lied
Library, University of Nevada-Las
Vegas, 4505 Maryland Parkway, Las
Vegas, Nevada 89154; and (3) an
information file in the Public Library in
Amargosa Valley, Nevada 89020.
Background documents for this
action. We have prepared additional
documents that provide more detailed
technical background in support of
these standards. You may obtain copies
of the Background Information
Document (BED), the Economic Impact
Analysis (EIA), the Response to
Comments document, and the Executive
Summary of the NAS Report, by writing
to the Office of Radiation and Indoor Air
(6608J), U.S. Environmental Protection
Agency, Washington, DC 20460-0001.
We placed these documents into the
docket and information files. You also
may find them on our Internet site for
Yucca Mountain (see the Additional
Docket and Electronic Information
section later in this document).
FOR FURTHER INFORMATION CONTACT: Ray
Clark, Office of Radiation and Indoor
Air, U.S. Environmental Protection
Agency, Washington, DC. 20460-0001;
telephone 202-564-9310.
SUPPLEMENTARY INFORMATION:
Whom Will These Standards Regulate?
The DOE is the only entity direcdy
regulated by these standards. Before it
may accept waste at the Yucca
Mountain site, DOE must obtain a
license from NRC. Thus, DOE will be
subject to our standards, which NRC
will implement through its licensing
proceedings. Our standards affect NRC
only because, under the Energy Policy
Act of 1992 (EnPA, Pub. L. 102-486, 42
U.S.C. 10141 n. (1994)), NRC must
modify its licensing requirements, as
necessary, to make them consistent with
our final standards.
Additional Docket and Electronic
Information
When may I examine information in
the docket? You may inspect the
Washington, DC, docket (phone 202-
260-7548) on weekdays (8 a.m.-5:30
p.m.). The docket personnel may charge
you a reasonable fee for photocopying
docket materials (40 CFR part 2).
You may inspect the information file
located in the Lied Library at the
University of Nevada-Las Vegas,
Research and Information Desk,
Government Publications Section (702-
895-2200) when classes are in session.
Hours vary based upon the academic
calendar, so we suggest that you call
ahead to be certain that the library will
be open at the time you wish to visit (for
a recorded message, call 702-895-2255).
You may inspect the information file
in the Public Library in Amargosa
Valley, Nevada (phone 775-372-5340).
As of this date, the hours are Tuesday
through Thursday (10 a.m.-7 p.m.);
Friday (10a.m.-5 p.m.); and Saturday
(10 a.m.-2 p.m.). The library is closed
daily from 12:30 p.m.-l p.m. It also is
closed Sundays and Mondays.
Can I access information by telephone
or via the Internet? Yes. You may call
our toll-free information line^f^^^^l
^^H 24 hours per day. By calling this
number, you may listen to a brief update
describing our rulemaking activities for
Yucca Mountain, leave a message
requesting that we add your name and
address to the Yucca Mountain mailing
list, or request that an EPA staff person
return your call. You also can find
information and documents relevant to
this rulemaking on the World Wide Web
at http://wwnr.epa.gov/radiation/yucca.
We also recommend that you examine
the preamble and regulatory language
for the proposed rule, which appeared
in the Federal Register on August 27,
1999 (64 FR 46976).
What documents are referenced in
today's action? We refer to a number of
documents that provide supporting
information for our Yucca Mountain
standards. All documents relied upon
by EPA in regulatory decisionmaking
may be found in our docket (Docket No.
A-95-12). Other documents, e.g.,
statutes, regulations, proposed rules, are
readily available from other public
sources. The documents below are
referenced most frequently in today's
action.
Item No.
II-A-1 Technical Bases for Yucca
Mountain Standards (The NAS
Report), National Research Council,
National Academy Press, 1995
V-A-4 Draft Environmental Impact
Statement for Yucca Mountain, DOE/
EIS-0250D, July 1999
V-A-5 Viability Assessment for Yucca
Mountain, DOE/RW-0508, December
1998
V-B-1 Final Background Information
Document (BID) for 40 CFR 197, EPA-
402-R-01-004
V-C-1 Final Response to Comments
Document for 40 CFR 197, EPA-402-
R-01-009
V-A-17 Nevada Risk Assessment/
Management Program (NRAMP)
Acronyms and Abbreviations
We use many acronyms and
abbreviations in this document. These
include:
ALARA-as low as reasonably achievable
APA-Administrative Procedure Act
B ID-background information document
CAA-Clean Air Act
CEDE-committed effective dose
equivalent
CG-critical group
DEIS-Draft Environmental Impact
Statement
DOE-U.S. Department of Energy
DOE/VA-DOE's Viability Assessment
EIS-Environmental Impact Statement
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001 /Rules and Regulations 32075
EnPA-Energy Policy Act of 1992
EPA-U.S. Environmental Protection
Agency
GCD-greater confinement disposal
HLW-high-level radioactive waste
IAEA-International Atomic Energy
Agency
ICRP-lnternational Commission on
Radiological Protection
LLW-low-level radioactive waste
MCL-maximum contaminant level
MCLG-maximum contaminant level goal
MTHM-metric tons of heavy metal
NAS-National Academy of Sciences
NCRP-National Council on Radiation
Protection and Measurements
NEPA-National Environmental Policy
Act
NESHAPs-National Emission Standards
for Hazardous Air Pollutants
NID-negligible incremental dose
NIR-negligible incremental risk
NRC-U.S. Nuclear Regulatory
Commission
NRDC-Natural Resources Defense
Council
NTS-Nevada Test Site
NTTAA-National Technology Transfer
and Advancement Act
NWPA-Nuclear Waste Policy Act of
1982
NWPAA-Nu clear Waste Policy
Amendments Act of 1987
OMB-Office of Management and Budget
RCRA-Resource Conservation and
Recovery Act
RME-reasonahle maximum exposure
RMEI-reasonably maximally exposed
individual
SAB-Science Advisory Board
SDWA-Safe Drinking Water Act
SNF-spent nuclear fuel
TDS-total dissolved solids
TRU-transuranic
UlC-underground injection control
UMRA-Unfiinded Mandates Reform Act
of 1995
UNSCEAR-United Nations Scientific
Committee on the Effects of Atomic
Radiation
USDW-underground source of drinking
water
WIPP LWA-Waste Isolation Pilot Plant
Land Withdrawal Act of 1992
Outline of Today's Action
I. What is the History of Today's Action?
A. What is the Relationship of 40 CFR part
191 to the Yucca Mountain Standards?
1. Evolution of 40 CFR part 191
2. The Role of 40 CFR part a 91 in the
Devel opment of 40 CFR part 197
H, Background Information
A. In Making Our Final Decisions. How
Did We Incorporate Public Comments on
the Proposed Rule?
1. Introduction and the Role of Comments
in the Rulemaking Process
2. How Did We Respond to General
Comments on Our Proposed Rule?
B. What Are the Sources of Radioactive
Waste?
C. What Types of Health Effects Can
Radiation Cause?
D. What Are the Major Features of the
Geology of Yucca Mountain and the
Disposal System?
E. Background on and Summary of the
NAS Report
1. What Were NAS's Findings
("Conclusions") and Recommendations?
HI. What Does Our Final Rule Do?
A. What Is the Standard for Storage of the
Waste? (Subpart A, §§ 197.1 through
197.5)
B. What Are the Standards for Disposal?
C§§197.11 through 197.36)
1. What Is the Standard for Protection of
Individuals? (§§ 197.20 and 197.25)
a. Is the Limit on Dose or Risk?
b. What Factors Can Lead to Radiation
Exposure?
c. What Is the Level of Protection for
Individuals?
d. Who Represents the Exposed
Population?
e. How Do Our Standards Protect the
General Population?
f. What Do Our Standards Assume About
the Future Biosphere?
g. How Far Into the Future [s K Reasonable
To Project Disposal System Performance?
2. What Are the Requirements for
Performance Assessments and
Determinations of Compliance?
(§§ 197.20. 197.25. and 197.30)
a. What Limits Are There on Factors
Included in the Performance
Assessments?
b. What Limits Are There on DOE's
Elicitation of Expert Opinion?
c. What Level of Expectation Will Meet
Our Standards?
d. Are There Qualitative Requirements to
Help Assure Protection?
3. What Is the Standard for Human
Intrusion? (§ 197.25)
4. How Does Our Rule Protect Ground
Water? (§197.30)
a. Is the Storage or Disposal of Radioactive
Material in the Yucca Mountain
Repository Underground Injection?
b. Does the Class-IV Well Ban Apply?
c. What Ground Water Does Our Rule
Protect?
d. How Far Into the Future Must DOE
Project Compliance With the Ground
Water Standards?
e. How Will DOE Identify Where to Assess
Compliance With the Ground Water
Standards?
f. Where Will Compliance With the Ground
Water Standards be Assessed?
TV. Responses to Specific Questions for
Public Comment
V. Severability
VI. Regulatory Analyses
A- Executive Order 12866
B. Executive Order 12898
C. Executive Order 13045
D. Executive Order 13084
E. Executive Order 13132
F. National Technology Transfer and
Advancement Act
G. Paperwork Reduction Act
H. Regulatory Flexibility Act as amended
by the Small Business Regulatory
Enforcement Fairness Act of 1996
(SEREFAJ 5 U.S.C. 601 et seq.
I. Unfunded Mandates Reform Act
). Executive Order 13211
I. What Is the History of Today's
Action?
Spent nuclear fuel (SNF) and high-
level radioactive waste (HLW) have
been produced since the 1940s, mainly
as a result of commercial power
production and defense activities. Since
then, the proper disposal of these wastes
has been the responsibility of the
Federal government. The Nuclear Waste
Policy Act of 1982 (NWPA, Pub. L. 97-
425) formalizes the current Federal
program for the disposal of SNF and
HLW by:
(l) Making DOE responsible for siting,
building, and operating an underground
geologic repository for the disposal of
SNF and HLW;
(2) Directing us to set generally
applicable environmental radiation
protection standards based on authority
established under other laws;: and
(3) Requiring NRC to implement our
standards by incorporating them into its
licensing requirements for SNF and
HLW repositories.
This general division of
responsibilities continues for the Yucca
Mountain disposal system. Thus, today
we are establishing public health
protection standards (specific to the
Yucca Mountain site, rather than
generally applicable). The NRC will
issue implementing regulations for this
rule. The DOE will submit a license
application to NRC. The NRC then will
determine whether DOE has met the
standards and whether to issue a license
for Yucca Mountain, The NRC will
require DOE to comply with all of the
applicable provisions of 40 CFR part
197 before authorizing DOE to receive
radioactive material at the Yucca
Mountain site.
In 1985, we established generic
standards for the management, storage,
and disposal of SNF, HLW, and
transuranic fTRU] radioactive waste (see
40 CFR part 191, SO FR 38066,
September 19, 1985), which apply to
any facilities for the storage or disposal
of these wastes, including Yucca
Mountain. In 1987, the U.S. Court of
Appeals for the First Circuit remanded
the disposal standards in 40 CFR part
191 (NRDCv. EPA, 824 F.2d 1258 (1st
Cir. 1987)). As discussed below, we later
amended and reissued these standards
to address issues that the court raised.
1 These laws include the Atomic Energy Act of
1954, as amended (42 U.S.C. 2011-2296);
Reorganization Plan No. 3 of t970 [5 U.S.C.
Appendix 1).
-------
32076 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
Also in 1987, the Nuclear Waste
Policy Amendments Act (NWPAA, Pub.
L. 100-203) amended the NWPA by,
among other actions, selecting Yucca
Mountain, Nevada, as the only potential
site that DOE should characterize for a
long-term geologic repository.
In October 1992, the Waste Isolation
Pilot Plant Land Withdrawal Act (WIPP
LWA, Pub. L. 102-579) and the EnPA
became law. These statutes changed our
obligations concerning radiation
standards for the Yucca Mountain
candidate repository. The WIPP LWA:
(1) Reinstated the 40 CFR part 191
disposal standards, except those
portions that were the specific subject of
the remand by the First Circuit;
(2) required us to issue standards to
replace the portion of the challenged
standards remanded by the court; and
(3) exempted the Yucca Mountain site
from the 40 CFR part 191 disposal
standards.
We issued the amended 40 CFR part
191 disposal standards, which
addressed the judicial remand, on
December 20, 1993 (58 FR 66398).
The EnPA, enacted in 1992, set forth
our responsibilities as they relate to the
Yucca Mountain repository. In the
EnPA, Congress directed us to set public
health and safety radiation standards for
Yucca Mountain. Specifically, section
801 (a) (1) of the EnPA directs us to
"promulgate, by rule, public health and
safety standards for the protection of the
public from releases from radioactive
materials stored or disposed of in the
repository at the Yucca Mountain site."
The EnPA also directed.us to contract
with NAS to conduct a study to provide
us with its findings and
recommendations on reasonable
standards for protection of public health
and safety. Moreover, it provided that
our standards shall be the only such
standards applicable to the Yucca
Mountain site and are to be based upon
and consistent with NAS's findings and
recommendations. On August 1, 1995,
NAS released its report, "Technical
Bases for Yucca Mountain Standards"
(the NAS Report) (Docket No. A-95-12,
Item II-A-1).
A. What Is the Relationship of 40 CFR
Part 191 to the Yucca Mountain
Standards?
Throughout today's action, we refer to
the provisions of 40 CFR part 191 to
support the decisions we made
regarding the components of the final
Yucca Mountain rule. Pursuant to
section 8(b)(2) of the WIPP LWA, 40
CFR part 191 is not applicable to the
characterization, licensing,
construction, operation, or closure of
the Yucca Mountain repository. We
believe, however, that while 40 CFR
part 191 is not directly applicable to
Yucca Mountain, because it contains the
fundamental components for the
protection of public health and the
environment that apply to any SNF,
HLW, or TRU radioactive waste
repository, certain of its basic concepts
must be applied to Yucca Mountain as
appropriate. Further, because 40 CFR
part 191 provides fundamental support
for today's rule, we believe it is useful
to explain here the process by which 40
CFR part 191 evolved.
1. Evolution of 40 CFR Part 191
We used the rulemaking for 40 CFR
part 191 to define the fundamental
components of any environmental
standard applicable to the disposal of
SNF, HLW, and TRU radioactive waste.
In our proposal (47 FR 58196, December
29, 1982), we recognized two basic
considerations regarding the disposal of
SNF, HLW, and TRU radioactive waste:
• The intent of disposal is to isolate
the wastes from the environment for a
very long time, longer than any time
over which active institutional controls
might be effective; and
• The disposal systems will be
designed to allow only very small
releases to the environment, if not
disturbed. A principal concern is the
possibility of accidental releases due to
unintended events or failure of
engineered barriers.
These considerations mean that any
standard that we establish and that NRG
and DOE implement: (1) Can only be
implemented during development and
operation of the repository, (2) must
address unintentional releases, and (3)
must accommodate significant
uncertainties. (See 47 FR 58198,
December 29, 1982)
From these considerations, we
proposed standards consisting of
Containment Requirements, which limit
the total amount of radionuclides that
may enter the environment over 10,000
years; Assurance Requirements, which
provide several principles enhancing
confidence that the containment
requirements will be met; and
Procedural Requirements, which assure
the proper application of the
containment requirements. We also
invited public comment on alternative
approaches for the standards,
specifically on the alternative of
establishing exposure limits for
individuals. Although the containment
requirements, as proposed, were
designed to protect people and the
environment for a long time, we did not
propose an individual exposure limit.
We believed the compliance point for
such a limit would have to be some
distance from the repository. Otherwise,
it would have to ignore the risks from
unplanned events such as human
intrusion. It seemed likely that
individuals located extremely near the
repository or who intrude into the
repository would receive doses far
exceeding any existing or reasonably
acceptable radiation limits.
EPA received substantial public
comment on the 40 CFR part 191
proposal. As a direct result of
information provided in many of the
comments, we issued a final rule (50 FR
38066, September 19,1985) that differed
in many respects from the proposal. In
addition to containment and assurance
requirements, the final rule included
two new components:
• Individual Protection
Requirements, which protect members
of the public for 1,000 years of
undisturbed performance; and
• Ground Water Protection
Requirements, which protect "special
sources of ground water" for 1,000 years
of undisturbed performance.
The risk objectives for the
containment requirements in the final
rule maintained the same limiting level
of health impacts as the proposal (1000
fatal cancers over 10,000 years for a
repository containing 100,000 metric
tons of heavy metal (MTHM)); however,
we did modify the radionuclide-specific
release limits to reflect updated
performance analyses and undated
information on the health effects of
ionizing radiation. However, members
of the public and our Science Advisory
Board (SAB) expressed some concerns
regarding residual risks and the ability
of the licensee of any repository to
demonstrate compliance with the
standards given the uncertainties about
these facilities that arise over the long
time periods at issue (see the "Report on
the Review of Proposed Environmental
Standards for the Management and
Disposal of Spent Nuclear Fuel, High-
Level and Transuranic Radioactive
Wastes," January 1984, Docket No. A-
95-12, Item V-A-21). To address these
concerns, we incorporated the concept
that the standards be met with
"reasonable expectation" (§ 191.13(b)).
Improved performance assessments
indicated that the containment
requirements could, in fact, be achieved
by a variety of repository site/design
combinations without significant effects
on disposal costs. The final rule also
defined for the first time a "controlled
area," or tract of land inside of which
compliance is not evaluated. The
concept of a controlled area was carried
from the proposal, where it was
included in the definition of "accessible
environment". In addition, we added
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32077
"Guidance for Implementation," which
replaced the previous procedural
requirements section. It addresses some
of the uncertainties with demonstrating
compliance, such as the limitations of
passive and active institutional controls
and the degree of certainty required to
demonstrate compliance with the
individual and ground water protection
requirements.
On the basis of public comments and
our analyses of disposal systems, we
incorporated individual protection
requirements, applicable to all pathways
of exposure effective for 1,000 years
after disposal. In addition, our analyses
of disposal systems supported setting
ground water protection requirements to
protect "special sources of ground
water" to limits very similar to the
Maximum Contaminant Levels [MCLs)
at 40 CFR part 141. Public comment was
very influential towards our
incorporation of individual-protection
requirements and ground-water
protection requirements. To address the
concerns expressed in the proposed rule
related to protection of individuals who
are extremely near the repository or who
may intrude into the repository, the
individual-protection requirements
apply to any member of the public in
the accessible environment for the case
of undisturbed performance.
Legal challenges required us to
reconsider the individual and ground
water protection requirements in a
subsequent rulemaking to amend 40
CFR part 191 (see 58 FR 66398,
December 20,1993). In 1987, the U.S.
Court of Appeals for the First Circuit
remanded subpart B of the 1985
standards to EPA for further
consideration (Natural Resources
Defense Council, Inc. v. United States
Environmental Protection Agency, 824
F.2d 1258 (1st Cir. 1987)). The court
questioned the appropriateness of the
1,000 year time frame for the individual
protection requirement, the inter-
relationship of the individual-protection
requirement with the Safe Drinking
Water Act (SDWA), and whether the
Agency provided proper notice for the
ground water protection requirements.
For a more detailed discussion of the
court's decision, see the preamble to the
final amendments to 40 CFR part 191
(58 FR 66399-66411, December 20,
1993). The Waste Isolation Pilot Plant
Land Withdrawal Act of 1992 reinstated
the 1985 version of 40 CFR part 191
except for those portions of the rule that
were the subject of the remand. In the
final amendments to 40 CFR part 191,
which replaced the remanded portions
of 40 CFR part 191, we set the
individual-protection requirement at IS
mrem/yr, calculated as an annual
committed effective dose, for all
pathways of exposure of any member of
the public in the accessible
environment, effective for 10,000 years
after disposal. The ground water
protection provisions limit the
concentrations of radioactivity in any
underground source of drinking water
(USDW) in the accessible environment
to the MCLs of the SDWA (40 CFR part
141).
2. The Role of 40 CFR Part 191 in the
Development of 40 CFR Part 197
The EnPA directs us to develop site-
specific public health protection
standards for the Yucca Mountain site.
To perform this task properly, WE must
answer two fundamental questions
relative to the content of the standards.
These two questions are:
(I) What are the relevant components
of such standards?
(2) How can they be applied in more
detail in a reasonable but conservative
manner to the Yucca Mountain site?
There are two primary sources of
information, insight, and guidance on
repository performance standards in
general and the standards applicable to
the Yucca Mountain site in particular.
These sources are the generic standards
for land disposal of SNF, HLW, and
TRU radioactive waste (40 CFR part
191) and the NAS report mentioned
above. We relied heavily on these
sources in developing the Yucca
Mountain standards.
As described in the previous section,
we developed 40 CFR part 191 as
generic standards that apply to the land
disposal of SNF, HLW, and"TRU
radioactive wastes. The components of
generic standards like 40 CFR part 191,
such as the individual-protection
requirement, would all apply to some
degree to any candidate site, but may
not be equally important at any
particular site. The WIPP LWA exempts
the Yucca Mountain site from being
licensed under the generic standards;
however, the basic components of the
generic standards clearly are valid
components for consideration in
developing standards that apply to a
specific site. For example, in the EnPA,
Congress specifically instructs us to
"prescribe the maximum annual
effective dose equivalent to individual
members of the public" (EnPA section
801(a)(l)); such an individual dose
standard is an integral part of 40 CFR
part 191.
We believe that 40 CFR part 191 is a
logical starting point for developing the
site-specific Yucca Mountain standards
because it contains the fundamental
components necessary to evaluate
whether a potential geologic repository
site will perform satisfactorily relative
to the protection of public health and
the environment. Where appropriate in
the site-specific context of the Yucca
Mountain standards, we rely on the
precedent of, and the reasoning in, 40
CFR part 191 throughout this preamble
as support for including specific
components in the Yucca Mountain
standards. This statement does not
mean that we have applied the 40 CFR
part 191 standards to Yucca Mountain.
Rather, we evaluated the 40 CFR part
191 standards de novo to determine
whether it may he appropriate for us to
apply any of them in the Yucca
Mountain context. The NAS Report is
relevant because it contains
recommendations on scientific issues
involved with geologic disposal in
general, as well as specific
recommendations based upon
examination of the Yucca Mountain site.
We refer to these two sources in the
discussions that follow to explain why
we structured the standards in a
particular way and how we considered
the public comments we received in
response to the proposed standards.
We evaluated each generic component
of 40 CFR part 191 on an individual
basis to determine whether it is
appropriate to apply it to the Yucca
Mountain site as a component of a
standard protective of public health. If
we found it was appropriate to apply
one of 40 CFR part 191's generic
components to Yucca Mountain, we
included that component in the Yucca
Mountain standards. Next, we
considered how to incorporate each
appropriate component in a reasonable,
but conservative, manner to the site-
specific conditions at the Yucca
Mountain site. The NAS Report was a
primary source of guidance and insight
in answering that question,
supplemented by the available data on
the characteristics of the site including
information on the distribution,
lifestyles, and other demographic
characteristics of the population in the
vicinity of the site. The BID
accompanying the 40 CFR part 197
standards contains much of this
information. Other sources of
information, such as DOE's Yucca
Mountain DEIS, are noted in the
following discussions as appropriate.
Before selecting and formulating
specific elements of the standards, we
must consider that radiological hazards
to public health from a deep geologic
repository come from the release of
radionuchdes and the subsequent
exposure of the population to these
radionuclides. This exposure occurs as
a result of two different processes: the
expected degradation over time (caused
-------
32078 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
by natural processes and events) of the
natural and engineered barriers in the
repository; and the breaching of these
barriers by human activities. It is
necessary to include both of these
release modes in a health-based
standard if it is to be protective. It also
is necessary to develop standards
against which it is possible, using
reasonable means, to judge repository
performance to determine compliance.
Based upon basic principles of health
physics, we believe that, any releases
and consequent exposures to the public
from the radionuclides emplaced into
the repository could affect public
health. Therefore, it is appropriate for us
to evaluate the effects of these releases
to determine whether we should
address them in our standards. The NAS
Report (Chapters 2 & 3) describes the
potential pathways through which
exposures to the public can occur from
geologic disposal. Part 191 contains
three provisions related to these
potential release pathways that we
believe are appropriate for application
at Yucca Mountain. More specifically,
40 CFR part 191 contains an individual-
protection standard (which limits
exposure from all pathways by which an
individual can be exposed), ground-
water protection standards (aimed at the
protection of ground water resources for
use by individuals who may be exposed
from using those resources), and a
human-intrusion component of the
containment requirements (aimed at
protection from the inadvertent
breaching of the repository containment
barriers and subsequent exposures to
the population). We believe these three
basic components of the generic 40 CFR
part 191 standards apply to the Yucca
Mountain site because they represent
avenues of exposure and mechanisms of
release that are reasonably foreseeable
given the conditions at Yucca Mountain.
We did not see the need to include in
40 CFR part 197 the containment
requirements in 40 CFR part 191 for
several reasons. First, we decided that,
unlike the generic analyses supporting
the development of release limits in 40
CFR part 191, the potential for large-
scale dilution of radionuclides (and
consequent wider exposure to large
populations), through ground water and
into surface water, as modeled in the
supporting analyses for 40 CFR part 191,
does not exist at Yucca Mountain. As
discussed in Chapters 7 and 8 and
Appendix IV of the BID and the
preamble to proposed 40 CFR part 197
(64 FR 46991, August 27,1999), the
Yucca Mountain repository will be
located in an unsaturated rock
formation with limited amounts of
infiltrating water passing through it and
into the underlying tuff aquifer. Any
releases into the ground water will be
heavily constrained by the geologic
features of the surrounding rocks to
move in relatively confined pathways,
rather than widely dispersed into the
surrounding area around the repository.
The aquifer is within a ground water
system that discharges into arid areas
having high evaporation rates and very
little surface water, further limiting the
potential for widespread population
exposures.
As discussed in the preamble to the
proposed 40 CFR part 191 (58 FR
46991), we developed the containment
requirements in 40 CFR part 191 during
the siting process mandated by the
NWPA in the 1980s. In that context,
population doses are an important
consideration. The release limits in 40
CFR part 191 were found to be
reasonably achievable for several types
of geologic settings (including tuff) and
would keep the risks to future
populations acceptably small. Because
the potential for significant exposures
from the Yucca Mountain repository is
primarily through a strongly directional
ground water pathway (BID, Chapters 7
and 8), a "cautious, but reasonable"
individual-protection standard will offer
the same protection as the containment
requirement included in 40 CFR part
191.
Although we included important
components of 40 CFR part 191 in our
Yucca Mountain standards, we did not
simply replicate the provisions of 40
CFR part 191. For example, as discussed
above, we do not include containment
requirements because we believe that
the individual-protection requirements
adequately will protect the general
population given the specific conditions
at Yucca Mountain. Similarly, we do not
include assurance requirements because
we expect NRC to incorporate
equivalent requirements into its
implementing regulations. Because the
assurance requirements in 40 CFR part
191 do not apply to NRC-licensed
facilities2, NRC will need to include
assurance requirements in its
implementing regulations for the Yucca
Mountain repository. Measures that are
effectively equivalent to the 40 CFR part
191 assurance requirements have been
included in NRC's proposed 10 CFR
part 63. The site-specific nature of the
Yucca Mountain standards requires us
to evaluate the unique characteristics of
the Yucca Mountain site to develop the
2 NRC agreed to include assurance requirements
in its regulations for geologic repositories (10 CFR
part 60. "Disposal of High-Level Radioactive Wastes
in Geologic Repositories", 46 FR 13980, February
25, 1981).
more detailed aspects of our standards,
such as appropriate compliance points.
The relative importance of the three
regulatory components of 40 CFR part
191 in determining compliance in the
regulatory review process is a direct
reflection of site-specific conditions. For
example, for WIPP, evaluating releases
from human intrusion (by drilling to
explore for or exploit the oil, gas and
mineral resources present at the site)
was the primary test for compliance
against the standards because under
expected undisturbed conditions no
releases from the repository are
anticipated. Compliance with the
individual-protection standard was
consequently based upon a scenario
related to the migration of radionuclides
from the repository to a near surface
aquifer via an abandoned deep borehole.
Consequently, we defined details for
assessing an intrusion scenario at the
WIPP site on the basis of current and
historical practices regarding exploring
for and recovering natural resources in
the area. In contrast, the Yucca
Mountain site is relatively poor in
known attractive natural resources,
other than ground water (see Chapter 8
of the BID). Therefore, consistent with
NAS's recommendations, we adopted-a
stylized human-intrusion scenario for
analysis. The NAS's recommendations
and the data base of information
available about the site allowed us to
develop the specific details of the
human-intrusion scenario, which we
proposed in the draft rule. Comments
we received during the public comment
process also played an important role in
framing the contents of the scenario. See
the Response to Comments document
for a more detailed discussion of these
issues.
II. Background Information
A. In Making Our Final Decision, How
Did We Incorporate Public Comments
on the Proposed Rule?
1. Introduction and the Role of
Comments in the Rulemaking Process
Section 801(a)(l) of the EnPA requires
us to set public health and safety
radiation protection standards for Yucca
Mountain by mlemaking.3 Pursuant to
Section 4 of the Administrative
Procedure Act (APA), regulatory
agencies engaging in informal
rulemaking must provide notice of a
proposed rulemaking, an opportunity
for the public to comment on the
proposed rule, and a general statement
of the basis and purpose of the final
:'EnPA. Public Law No. 102-486, 106 Stat. 2776,
42 U.S.C. 10141 n. (1994).
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32079
rule.4 The notice of proposed
rulemaking required by the APA must
"disclose in detail the thinking that has
animated the form of the proposed rule
and the data upon which the rule is
based." (Portland Cement Association v.
Ruckelshaus, 486 F. 2d 375, 392-94
(D.C. Cir. 1973)) The public thus is
enabled to participate in the process by
making informed comments on the
proposal. This provides us with the
benefit of "an exchange of views,
information, and criticism between
interested persons and the agency." (Id.)
There are two primary mechanisms by
which we explain the issues raised in
public comments and our reactions to
them. First, we discuss broad or major
comments in the succeeding sections of
this preamble. Second, we are
publishing a document, accompanying
today's action, entitled "Response to
Comments" (Docket No. A-95-12, Item
V—C-l). The Response to Comments
document provides more detailed
responses to issues addressed in the
preamble. It also addresses all other
significant comments on the proposal.
We gave all the comments we received,
whether written or oral, consideration
in developing the final rule.
2. How Did We Respond to General
Comments on Our Proposed Rule?
We received many comments that
addressed broad issues related to the
proposed standards. Several
commenters simply expressed their
support for, or opposition to, the Yucca
Mountain repository. The purpose of
our standards is to ensure that any
potential releases from the repository do
not result in unacceptably high
radiation exposures. Our standards
make no judgment regarding the
suitability of the Yucca Mountain site or
whether NRG should issue a licBnse for
the site. Such a decision is beyond the
scope of our statutory authority.
Some comments suggested our
standards should consider radiation
exposures from all sources because of
the site's proximity to the Nevada Test
Site (NTS) and other sources of
potential contamination. We are aware
of the other such sources of
radionuclide contamination in the area.
However, our mandate under the EnPA
is to set standards that apply only to the
storage or disposal of radioactive
materials in the Yucca Mountain
repository, not to these other sources.
Our standards do follow the widely
accepted principle that, to allow for the
consideration of other exposures in
developing a total acceptable dose, any
"5 U.S.C. 553.
specific source accounts for only a
fraction of one's total exposure.
Several comments supported our role
in setting standards for Yucca
Mountain. Other comments thought that
aspects of our standards duplicate
NRC's implementation role. We believe
the provisions of this rule clearly are
within our authority and they are
central to the concept of an public
health protection standard. We also
believe our standards leave NRC the
necessary flexibility to adapt to
changing conditions at Yucca Mountain
or to impose additional requirements in
its implementation efforts, if NRC
deems them to be necessary.
We received some comments that
suggested we should have provided
more or better opportunities for public
participation in our decision making
process. For example, that we should
have rescheduled public hearings,
extended the public comment period,
and provided alternatives to the public
hearing process. We provided numerous
opportunities and avenues for public
participation in the development of
these standards. For example, we held
public hearings in four locations:
Washington, DC; Las Vegas, NV;
Amargosa Valley, NV; and Kansas City,
MO. We also opened a 90-day public
comment period and met with key
stakeholders during that time, including
Native American tribal groups. We fully
considered all comments that we
received through May 1, 2000. We have,
in effect, provided more than 240 days
of public comment on the proposal.
These measures greatly exceed the basic
requirements for notice-and-comment
rulemaking, and they are in full
compliance with the public
participation requirements of the APA.
Some comments argued that our
standards for Yucca Mountain do not
protect Nevadans to the same level as
New Mexicans around WIPP. In fact, the
individual-protection standards for
Yucca Mountain and WIPP are the
same: 15 mrem annual committed
effective dose equivalent. The
differences between the standards for
Yucca Mountain and those for WIPP
begin with the various statutes and the
subsequent regulations promulgated
under those authorities. The WIPP LWA
required us to apply our generic
radioactive waste standards (40 CFR
part 191) to WIPP. The standards for
Yucca Mountain, which we promulgate
under authority granted in the EnPA,
are site-specific, and therefore there are
some differences compared with the
standards applicable to WIPP; however,
we are confident that the standards
provide essentially the same level of
protection from radiation exposure at
both sites, as the exposure limits are the
same for both.
Many comments requested
consideration of issues outside the
scope of our authority for this
rulemaking. For example, a number of
commenters suggested that we should
explore alternative methods of waste
disposal, such as neutralizing
radionuciides. Comments also
expressed concern regarding risks of
transporting radioactive materials to
Yucca Mountain. Considerations like
these all are outside the scope of this
rulemaking. Congress delegated to us
neither the authority to postpone the
promulgation of these standards in favor
of the development of other disposal
methods nor the regulation of
transportation of waste to Yucca
Mountain.
B. What Are the Sources of Radioactive
Waste?
Radioactive wastes result from the use
of nuclear fuel and other radioactive
materials. Today, we are issuing
standards pertaining to SNF, HLW, and
other radioactive waste (we refer to
these items collectively as "radioactive
materials" or "waste") that may be
stored or disposed of in the Yucca
Mountain repository. (When we discuss
storage or disposal in this document in
reference to Yucca Mountain, please
understand that no decision has been
made regarding the acceptability of
Yucca Mountain for storage or disposal.
To save space and to avoid excessive
repetition, we will not describe Yucca
Mountain as a "potential" repository;
however, we intend this meaning to
apply.) These standards apply only to
facilities on the Yucca Mountain site.
Once nuclear reactions have
consumed a certain percentage of the
uranium or other fissionable material in
nuclear reactor fuel, the fuel no longer
is useful for its intended purpose. It
then is known as "spent" nuclear fuel
(SNF). Sources of SNF include:
(1) Commercial nuclear power plants;
(2) Government-sponsored research
and development programs in
universities and industry;
(3) Experimental reactors, such as
liquid metal fast breeder reactors and
high-temperature gas-cooled reactors;
(4) Federal government-controlled,
nuclear-materials production reactors;
(5) Naval and other Department of
Defense reactors; and
(6) U.S.-owned, foreign SNF.
It is possible to recover specific
radionuciides from SNF through
"reprocessing," which is a process that
dissolves the SNF, thus separating the
radionuciides from one another.
Radionuciides not recovered through
-------
32080 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
reprocessing become part of the acidic
liquid wastes that DOE plans to convert
into various types of solid materials.
High-level wastes (HLW) are the highly
radioactive liquid or solid wastes that
result from reprocessing SNF. The only
commercial reprocessing facility to
operate in the United States, the Nuclear
Fuel Services Plant in West Valley, New
York, closed in 1972. Since then, there
has been no reprocessing of commercial
SNF in the United States. In 1992, DOE
decided to phase out reprocessing of its
SNF, which supported the defense
nuclear weapons and propulsion
programs. The SNF that does not
undergo reprocessing prior to disposal
becomes the waste form.
Where is the waste stored now?
Today, storage of most SNF occurs in
water pools or in above-ground dry
concrete or steel canisters at more than
70 commercial nuclear-power reactor
sites across the nation. Approximately
three percent of SNF is produced by
DOE, and is in storage at several DOE
sites (see Appendix A, Figure A-2, of
DOE's Draft Environmental Impact
Statement (DEIS) for Yucca Mountain
(DOE/EIS-0250D, Docket No. A-95-12,
Item V-A-4)). The storage of HLW
occurs at Federal facilities in Idaho,
Washington, South Carolina, and New
York.
What types of waste will be placed
into Yucca Mountain? We anticipate
that most of the waste emplaced in
Yucca Mountain will be SNF and
solidified HLW (in the rest of this
document, HLW will refer to solidified
HLW, unless otherwise noted). Under
current NRG regulations (10 CFR
60.135), liquid HLW must be solidified,
through processes such as vitrification
(mixing the waste into glass), because
non-solid waste forms are not to be
stored or disposed of in Yucca
Mountain. The DOE estimates that, by
the year 2010, about 66,000 metric tons
of SNF and 284,000 cubic meters
(containing 450 million curies of
radioactivity) of HLW in predisposal
form and 2,900 cubic meters (containing
235 million curies) of the disposable
form of HLW will be in storage at
various locations around the country
(DOE/RW-0006, Rev. 13, December
1997). For more information, see the
waste descriptions in Appendix A of
DOE's DEIS for Yucca Mountain (DOE/
EIS-0250D, Docket No. A-95-12, Item
V-A-4).
In the future, other types of
radioactive materials could be identified
for storage or disposal in the Yucca
Mountain repository. These materials
include highly radioactive low-level
waste (LLW), known as "greater-than-
Class-C waste," and excess plutonium
or other fissile materials resulting from
the dismantlement of nuclear weapons.
Because the plans for the disposal of
these materials have not been finalized,
neither NRC nor DOE has analyzed their
impact upon the design and
performance of the disposal system.
However, regardless of the types of
radioactive materials that finally are
disposed of in Yucca Mountain, the
disposal system must comply with 40
CFR part 197.
C. What Types of Health Effects Can
Radiation Cause?
Ionizing radiation can cause a variety
of health effects, which can be either
"non-stochastic" or "stochastic." Non-
stochastic effects are those for which the
damage increases with increasing
exposure, such as destruction of cells or
reddening of the skin. These effects
appear in cases of exposure to large
amounts of radiation. Stochastic effects
are associated with long-term exposure
to low levels of radiation. The types or
severity of stochastic effects does not
depend on the amount of exposure.
Instead, the chance that a stochastic
effect, such as cancer, will occur is
assumed to increase with increasing
exposure. For a detailed discussion of
potential health effects related to
exposure to radiation, see the preamble
to the proposed rule (64 FR 46978-
46979) and Chapter 6 of the BID.
Teratogenic effects can occur
following fetal exposure. We believe
that fetuses are more sensitive than are
adults to the induction of cancer by
radiation (see Chapter 6.5 of the BID).
The fetus also is subject to radiation-
induced physical malformations, such
as small brain size (micro encephaly),
small head size (microcephaly), eye
malformations, and slow growth prior to
birth. Recent studies have focused on
the apparently increased risk of severe
mental retardation (as measured by the
intelligence quotient). These studies
indicate that the sensitivity of the fetus
is greatest during 8 to 15 weeks
following conception and continues, at
a lower level, between 16 and 25
weeks.5 We.do not know exactly the
relationship between mental retardation
and dose; however, we believe it
prudent to assume that there is a linear,
non-threshold, dose-response
relationship between these effects and
the dose delivered to the fetus during
the 8-to 15-week period (see Chapter 6.5
of the BID).
The NAS published its reviews of
human health risks from exposure to
low levels of ionizing radiation in a
series of reports issued between 1972
and 1990. However, scientists still do
not agree on how best to estimate the
probability of cancer occurring as a
result of the doses encountered by
members of the public 6 because it is
necessary to base estimates of these
effects on the effects observed at higher
doses (such as effects seen in the
survivors of the Hiroshima and Nagasaki
atomic bombs). Many organizations,
including the National Council on
Radiation Protection and Measurements
(NCRP), the International Commission
on Radiological Protection (ICRP), the
United Nations Scientific Committee on
the Effects of Atomic Radiation
(UNSCEAR), and the National
Radiological Protection Board of the
United Kingdom, have recommended
the use of the linear non-threshold
model for estimating cancer risks.
Over the last decade, the scientific
community has performed an extensive
reevaluation of the doses and effects in
the Hiroshima and Nagasaki survivors
(see Chapter 6.3 of the BID). These
studies have resulted in increased
estimates (roughly threefold between
1972 and 1990) of the extrapolated risk
of cancer occurring because of exposure
to environmental (background) levels of
radiation. Nonetheless, the estimated
number of health effects induced by
small incremental doses of radiation
above natural background levels
remains small compared with the total
number of fatal cancers that occur from
other causes. In addition, because
cancers that result from exposure to
radiation are the same as those that
result from other causes, it may never be
possible to identify them in human
epidemiological studies (see Chapter 6
of the BID and the example discussed
later in this section). This difficulty in
identifying stochastic radiation effects
does not mean that such effects do not
occur. It also is possible, however, that
effects do not occur as a result of these
small doses. That is, there might be an
exposure level below which there is no
additional risk above the risk posed by
natural background radiation. Sufficient
data to prove either possibility
scientifically is lacking. Thus, we
believe that the best approach is to
assume that the risk of cancer increases
linearly starting at zero dose. In other
s Health Effects of Exposure to Low Levels of
Ionizing Radiation. National Academy Press.
Washington, DC, 1990.
"The risk of interest is not at or near zero dose,
but that due to small increments of dose above the
pre-existing background level. Background in the
U.S. is typically about 3 millisieverts (mSv), that is,
300 millirem (mrem), effective dose equivalent per
yearr or 0.2 Sv (20 rem) in a lifetime. Approximately
two-thirds of this dose is due to radon, and the
balance comes from cosmic, terrestrial, and internal
sources of exposure.
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
32081
words, any increase in exposure to
ionizing radiation results in a constant
and proportionate increase in the
potential for developing cancer.
The NAS Report stated that radiation
causes about five cancers for every
severe hereditary disorder caused by
radiation exposure. Also, NAS
concluded that nonfatal cancers are
more common than fatal cancers.
Despite this conclusion, NAS cited an
ICRP study that judged that non-fatal
cancers contribute less to overall health
impact than fatal cancers "because of
their lesser severity in the affected
individuals." (NAS Report pp. 37-39).
We based our risk estimates for
exposure of the population to low-dose-
rate radiation on fatal cancers rather
than on all cancers for the same reasons
enumerated by NAS.
For radiation-protection purposes, we
estimate (using a linear, non-threshold,
dose-response model) an average risk for
a member of the U.S. population of 5.75
in 100 (5.75 x 10-2) fatal cancers per
sievert (Sv) 7 (5.75 x 10~4 fatal cancers
per rem] delivered at low dose rates.8
For this calculation, as long as the
exposure rate is low, the number of
incremental cancers depends on the
amount of radiation received, not the
time period over which the dose is
delivered, because the linear non-
threshold model assumes that any
incremental dose carries a risk (see
Chapter 6.3 of the BID). For example, if
100,000 people randomly chosen from
the U.S. population each received a
uniform dose of 1 millisievert (mSv) (0.1
rem) to the entire body at a rate
equivalent to that observed from natural
background sources, the assumption is
that approximately five to six people
will die of cancer during their
remaining lifetimes because of that
exposure. These five to six deaths are in
addition to the roughly 20,000 fatal
cancers that would occur in the same
population from other causes. The risk
of fatal childhood cancer that results
from exposure while in the fetal stage is
about 3 in 100 (3 x 10~2) per Sv (that
is, 3 x 10—* effects per rem). The risk
of severe hereditary effects in offspring
is estimated to be about 1 x io~2 per Sv
7 The traditional unit for dose equivalent has been
the rem. The unit "sievert" (Sv}, a unit in the
International System of Units that was adopted in
1979 by the General Conference on Weights and
Measures, is now in general use throughout the
world. One sievert equals 100 rem. The prefix
"milli" (m) means one-thousandth. The individual-
protection limit being finalized today may be
expressed equivalently in either unit.
* "Low dose rates" here refers to dose rates on the
order of or less than those from background
radiation.
(1 x 10-4 effects per rem). 9 The risk of
severe mental retardation from doses to
a fetus is estimated to be greater per unit
dose than the risk of cancer in the
general population.10 However, the
period of increased sensitivity is much
shorter. Hence, at a constant exposure
rate, fatal cancer risk in the general
population remains the dominant factor.
Please see the BID for more details on
this subject.
Of course, our risk estimates do
contain some uncertainty. A recent
uncertainty analysis published by NCRP
(NCRP Report 126, Docket A-95-12,
Item II-A-13) estimated that the actual
risk of cancer from whole-body
exposure to low doses of radiation could
be between 1.5 times higher and 4.8
times lower (at the 90-percent
confidence level) than our basic
estimate of 5.75 x 10~2 per Sv (5.75 x
lO"4 per rem). The risks of genetic
abnormalities and mental retardation
are less well known than those for
cancer. Thus, they may include a greater
degree of uncertainty. Further, existing
epidemiological data does not rule out
the existence of a threshold. If there is
a threshold, exposures below that level
would pose no additional risk above the
risk posed by natural background
radiation. However, in spite of
uncertainties in the data and its
analysis, estimates of the risks from
exposure to low levels of ionizing
radiation are known more clearly than
are those for virtually any other
environmental carcinogen. See Chapter
6 of the BID.
D. What Are the Major Features of the
Geology of Yucca Mountain and the
Disposal System?
The geology. Yucca Mountain is in
southwestern Nevada approximately
100 miles northwest of Las Vegas. The
eastern part of the site is on NTS. The
northwestern part of the site is on the
Nellis Air Force Range. The
southwestern part of the site is on
Bureau of Land Management land- The
area has a desert climate with
topography typical of the Basin and
Range province. For more detailed
yThe risk of seveie hereditary effects in the fiist
two generations, for exposure of the reproductive
part of the population (with both parents exposed),
is estimated to be 5 x 10~-' per Sv (5 x I0-!i per
rem). For all generations, the risk is estimated to be
1.2 xlO~2 perSv (1.2 X10~4 per rem). For
exposure of the entire population, which includes
individuals past the age of normal child-bearing,
each estimate is reduced to 40% of the cited value.
10 Assuming a linear, non-threshold dose
response, estimated risk for mental retardation due
to exposure during the 8th through 15th week of
gestation is 4 x 10"a per Sv (4 x 10~:I per rem);
under the same assumption, Lbe estimated risk from
the 16th to 25th week is 1 x 10~' per Sv (1 x 10~:l
per rem).
descriptions of Yucca Mountain's
geologic and hydrologic characteristics,
and the disposal system, please see
chapter 7 of the BID and the preamble
to the proposed rule (64 FR 46979-
46980). These documents are in the
docket for this rulemaking (Docket No.
A-95-12, Items HI-B-2, V-B-1).
Yucca Mountain is made of layers of
ashfalls from volcanic eruptions that
happened more than 10 million years
ago. The ash consolidated into a rock
type called "tuff," which has varying
degrees of compaction and fracturing
depending upon the degree of
"welding" caused by temperature and
pressure when the ash was deposited.
Regional geologic forces have tilted the
tuff layers and formed Yucca
Mountain's crest (Yucca Mountain's
shape is a ridge rather than a peak).
Below the tuff is carbonate rock formed
from sediments laid down at the bottom
of ancient seas that existed in the area.
There are two general hydrologic
zones within and below Yucca
Mountain. The upper zone is called the
"unsaturated zone" because the pore
spaces and fractures within the rock are
not filled entirely with water. Below the
unsaturated zone, beginning at the water
table, is the "saturated zone," in which
water completely fills the pores and
fractures. Fractures in both zones could
act as pathways that allow for faster
contaminant transport than would the
pores. The DOE plans to build the
repository in the unsaturated zone about
300 meters below the surface and about
300 to 500 meters above the water table
(DOE Viability Assessment (DOE/VA),
Docket No. A-95-12, Item V-A-5).
There are two major aquifers in the
saturated zone under Yucca Mountain.
The upper one is in tuff. The lower one
is in carbonate rock. Regional ground
water in the vicinity of Yucca Mountain
is believed to flow generally in a south-
southeasterly direction. See Chapters 7
and 8 of the BID for a fuller discussion
of the aquifers and the other geologic
attributes of the Yucca Mountain region.
The disposal system. The NAS Report
described the current concept of the
potential disposal system as a system of
engineered barriers for the disposal of
radioactive waste located in the geologic
setting of Yucca Mountain (NAS Report
pp. 23-27). Based on DOE's current
design, entry into the repository for
waste emplacement would be on
gradually downward sloping ramps that
enter the side of Yucca Mountain.
Section 114(d) of the NWPAA limits the
capacity of the repository to 70,000
metric tons of SNF and HLW. Current
DOE plans project that about 90 percent
(by mass) would be commercial SNF;
and 10 percent would be defense HLW
-------
32082 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
(NAS Report p. 23). The NAS further
stated that within 100 years after initial
emplacement of waste, the repository
would be sealed by closing the opening
to each of the tunnels and sealing the
entrance ramps and shafts (NAS Report
pp. 23, 26).
We expect the engineered barrier
system to consist of at least the waste
form (SNF assemblies orborosilicate
glass containing the HLW), internal
stabilizers for the SNF assemblies, and
the waste packages holding the waste.
Spent nuclear fuel assemblies consist of
uranium oxide, fission products, fuel
cladding, and support hardware, all of
which will be radioactive (see the What
are the Sources of Radioactive Waste?
section above).
E. Background on and Summary of the
NAS Report
Section 801(a)(2) of the EnPA directs
us to contract with NAS to conduct a
study to provide findings and
recommendations on reasonable
standards for protection of public health
and safety^ Section 801(a)(2) specifically
calls for NAS to address the following
three issues:
(A) Whether a health-based standard
based upon doses to individual
members of the public from releases to
the accessible environment (as that term
is defined in the regulations contained
insubpart B of part 191 of title 40, Code
of Federal Regulations, as in effect on
November 18,1985) will provide a
reasonable standard for protection of the
health and safety of the general public;
(B) Whether it is reasonable to assume
that a system for post-closure oversight
of the repository can be developed,
based upon active institutional controls,
that will prevent an unreasonable risk of
breaching the repository's engineered or
geologic barriers or increasing the
exposure of individual members of the
public to radiation beyond allowable
limits; and
(C) Whether it is possible to make
scientifically supportable predictions of
the probability that the repository's
engineered or geologic barriers will be
breached as a result of human intrusion
over a period of 10,000 years.
On August 1,1995, NAS submitted to
us its report, entitled "Technical Bases
for Yucca Mountain Standards." The
NAS Report is available for review in
the docket (Docket No. A-95-12, Item
II-A-1) and the information files
described earlier. You can order the
report from the National Academy Press
by calling 800-624-6242 or on the
World Wide Web at http://
www.nap.edu/catalog/4943.html.
I. What Were NAS's Findings
("Conclusions") and Recommendations?
The NAS Report contained a number
of conclusions and recommendations.
(The EnPA used the term "findings;"
however, the NAS Report used the term
"conclusions"). A summary of NAS's
conclusions appears below. See pages
1-14 of the NAS Report, or the preamble
to our proposed rule (64 FR 46980), for
a list of NAS's conclusions and
recommendations. For details on public
participation in our review of the NAS
Report, please see the preamble to the
proposed rule (64 FR 46980-46981).
Conclusions. The conclusions in the
Executive Summary of the NAS Report
(pp. 1-14) were:
(a) "That an individual-risk standard
would protect public health, given the
particular characteristics of the site,
provided that policy makers and the
public are prepared to accept that very
low radiation doses pose a negligibly
small risk" (later termed "negligible
incremental risk"). (This conclusion is
the response to the issue Congress
identified in EnPA Section
801(a)(2)(A));
(b) That the Yucca Mountain-related
"physical and geologic processes are
sufficiently quantifiable and the related
uncertainties sufficiently boundable that
the performance can be assessed over
time frames during which the geologic
system is relatively stable or varies in a
boundable manner;"
(c) "That it is not possible to predict
on the basis of scientific analyses the
societal factors required for an exposure
scenario. Specifying exposure scenarios
therefore requires a policy decision that
is appropriately made in a rulemaking
process conducted by EPA;"
(d) "That it is not reasonable to
assume that a system for post-closure
oversight of the repository can be
developed, based on active institutional
controls, that will prevent an
unreasonable risk of breaching the
repository's engineered barriers or
increasing the exposure of individual
members of the public to radiation
beyond allowable limits." (This
conclusion is the response to the issue
Congress identified in EnPA section
801(a)(2)(B));
(e) "That it is not possible to make
scientifically supportable predictions of
the probability that a repository's
engineered or geologic barriers will be
breached as a result of human intrusion
over a period of 10,000 years." (This
conclusion is the response to the issue
Congress identified in EnPA Section
801(a)(2)(C));and
(f) "That there is no scientific basis for
incorporating the ALARA (as low as
reasonably achievable) principle into
the EPA standard or USNRC (U.S.
Nuclear Regulatory Commission)
regulations for the repository."
Recommendations. The
recommendations in the Executive
Summary of the NAS Report were:
(a) "The use of a standard that sets a
limit on the risk to individuals of
adverse health effects from releases from
the repository;"
(b) "That the critical-group approach
be used";
(c) "That compliance assessment be
conducted for the time when the
greatest risk occurs, within the limits
imposed by long-term stability of the
geologic environment;" and
(d) "That the estimated risk calculated
from the assumed intrusion scenario be
no greater than the risk limit adopted for
the undisturbed-repository case because
a repository that is suitable for safe long-
term disposal should be able to continue
to provide acceptable waste isolation
after some type of intrusion."
Other Conclusions and
Recommendations. The NAS made
other conclusions and recommendations
in addition to those listed above. Most
of them were related to or supported
those presented in the Executive
Summary.
III. What Does Our Final Rule Do?
Our rule establishes public health and
safety standards governing the storage
and disposal of SNF, HLW, and other
radioactive material in the repository at
Yucca Mountain, Nevada.
As noted earlier, section 801(a)(l) of
the EnPA gives us rulemaking authority
to set "public health and safety
standards for the protection of the
public from releases from radioactive
materials stored or disposed of in the
repository at the Yucca Mountain site."
The statute also directs us to develop
standards "based upon and consistent
with the findings and recommendations
of the National Academy of Sciences."
Section 801(a)(2) of the EnPA directs us
to contract with NAS to conduct a study
to provide findings and
recommendations on reasonable
standards for protection of the public
health and safety. Because the EnPA
directs us to act "based upon and
consistent with" NAS's findings, a
major issue in this rulemaking is
whether we must follow NAS's findings
and recommendations without
exception or whether we have
discretionary decision-making
authority.
As we discussed in the preamble to
the proposed rule, we believe we have
discretionary decision-making authority
and, therefore, are not required to adopt,
-------
Federal Register/Vol. 66, No. 114 / Wednesday, June 13, 2001/Rules and Regulations
32083
without exception, NAS's findings and
recommendations. See 64 FR 46981-
46983 for this discussion. As a practical
matter, the difficulty of resolving this
issue is reduced because NAS expressed
some of the findings and
recommendations in a non-binding
manner. In other words, in many
instances NAS either stated its findings
and recommendations as starting points
for the rulemaking process or
recognized those recommendations that
involve public policy issues that are
addressed more properly in this public
rulemaking proceeding. However, the
report also contains some findings and
recommendations stated in relatively
definite terms. These issues present
most squarely the question of whether
we are to treat all of NAS's findings and
recommendations as binding.
Whether the EnPA binds us to
following exactly NAS's findings and
recommendations is a question that
warrants close attention because it
affects the scope of our rulemaking. If
we must follow every view expressed in
the NAS Report, we would have to treat
any such issue as having been addressed
conclusively by NAS. We would not
need to entertain public comment upon
the affected issues because the outcome
would be predetermined by NAS.
We believe the EnPA does not bind us
absolutely to follow the NAS Report.
Instead, we used it as the starting point
for this rulemaking. As Congress
directed, today's rule is based upon and
consistent with the NAS findings and
recommendations. We were guided by
the panel's findings and
recommendations because of the special
role Congress gave it and because of
NAS's scientific expertise. However, the
entirety of our standards is the subject
of this rulemaking. Therefore, we have
not treated the views expressed by NAS
as necessarily dictating the outcome of
this rulemaking, thereby foreclosing
public scrutiny of important issues. For
the reasons described below, we believe
this interpretation of the EnPA is both
consistent with the statute and prudent.
because it avoids potential
constitutional issues. Further, this
interpretation supports an important
EPA policy objective and legal
obligation: Ensuring an opportunity for
public input regarding all aspects of the
issues presented in this rulemaking.
Section 801{a)(2) of the EnPA requires
NAS to provide "findings and
recommendations on reasonable
standards for protection of the public
health and safety." This section of the
EnPA calls for NAS to address three
specific issues; however. Congress did
not place any restrictions on other
issues NAS could address. The report of
the Congressional conferees
underscored that "the (NAS) would not
be precluded from addressing additional
questions or issues related to the
appropriate standards for radiation
protection at Yucca Mountain beyond
those that are specified." (H.R. Rep. No.
102-1018, 102nd Cong., 2d Sess. 391
(1992)). Thus, given the potentially
unlimited scope of NAS's inquiry under
the statute, it could have provided
findings and recommendations that
would dictate literally all aspects of the
public health and safety standards for
Yucca Mountain, rendering our function
a merely ministerial one.
Section 801(a)(l) of the EnPA plainly
gives us the authority to issue, by
rulemaking, public health and safety
standards for Yucca Mountain. If at the
same time that Congress gave NAS the
authority to provide findings and
recommendations on any issues related
to the Yucca Mountain public health
and safety standards, Congress also
intended that NAS's findings and
recommendations would bind us, then
Congress effectively would have
delegated to NAS a standard-setting
authority that overrides our rulemafcing
authority. Carried to its logical
conclusion, under this view of the
statute, NAS would have authority to
establish the public health and safety
standards without a public rulemaking
process. Congress' direction to EPA to
set standards "by rule" would be
unnecessary or relatively meaningless. It
is both reasonable and appropriate to
resolve this tension in the statute by
interpreting NAS's findings and
recommendations as non-binding, but
highly influential, expert guidance to
inform our rulemaking.
Thus, we do not believe the statute
forces our rulemafcing to adopt
mechanically NAS's recommendations
as standards. If it did. the statutory
provisions would allow us to consider
only those issues that NAS did not
add'ress. Further, the provisions calling
for us to use standard rulemaking
procedures in issuing the standards
would be unnecessary to reach results
that NAS already established. We
consider the NAS Report's explicit
references to decisions that should be
made during the rulemaking process to
be support for our position.
The EnPA conference report also
reveals that Congress did not intend to
limit our rulemaking discretion. The
conference report clarifies that Congress
intended NAS to provide "expert
scientific guidance" on the issues
involved in our rulemaking and that
Congress did not intend for NAS to
establish the specific standards:
The Conferees do not intend for the
National Academy of Sciences, in making its
recommendations, to establish specific
standards for protection of the public but
rather to provide expert scientific guidance
on the issues involved in establishing those
standards. Under the provisions of section
801, the authority and responsibility to
establish the standards, pursuant to
rulemaking, would remain with the
Administrator, as is the case under existing
law. The provisions of section 801 are not
intended to limit the Administrator's
discretion in ihe exercise of his authority
related to public health and safety issues.
(H.R. Rep. No. 102-1018. p. 391)
Our interpretation of the EnPA as not
limiting the issues for consideration in
this rulemaking is consistent with the
views we expressed to Congress during
deliberations over the legislation. The
Chair of the Senate Subcommittee on
Nuclear Regulation requested our views
regarding the bill reported by the
conference committee. The Deputy
Administrator of EPA indicated the
NAS Report would provide helpful
input. Moreover, the Deputy
Administrator pointed to the language,
cited above, stating the intent of the
conferees not to limit our rulemaking
discretion and assured Congress that
any standards for radioactive materials
that we ultimately issue would be the
subject of public comment and
involvement and would fully protect
human health and the environment (138
Cong. Rec. 33,955 (1992))-
Our interpretation also is consistent
with the role that both NAS and
Congress understood NAS would fulfill.
During the Congressional deliberations
over the legislation, NAS informed
Congress that while it would conduct
the study, it would not assume a
standard-setting role because such a role
is properly the responsibility of
government officials. (138 Cong. Rsc.
33,953 (1992)] Our interpretation of the
NAS Report also avoids implicating
potentially significant constitutional
issues. Construing the EnPA as
delegating to NAS the responsibility to
determine the health and safety
standards at Yucca Mountain may
violate the Appointments Clause of the
Constitution (Art. II, sec. 2, cl. 2), which
imposes restrictions against giving
Federal governmental authority to
persons not appointed in compliance
with that Clause. In addition, the
Constitution places restrictions arising
under the separation of powers doctrine
upon the delegation of governmental
authority to persons not part of the
Federal government. We are not
concluding, at this time, that an
alternative interpretation necessarily
would run afoul of constitutional limits.
We believe, however, that it is
-------
32084 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
reasonable both to assume that Congress
intended to avoid these issues when it
adopted section 801 of the EnPA and to
interpret the EnPA accordingly.
In summary, we do not believe we
must, in this rulemaking, adopt all of
NAS's findings and recommendations.
The statute does, however, give NAS a
special role. As noted previously, NAS's
findings and recommendations were
instrumental in this rulemaking. Our
proposal is consistent with those
findings and recommendations. We
included many of the findings and
recommendations in this rule. We
tended to .give greatest weight to NAS's
judgments about issues having a strong
scientific component, the area in which
NAS has its greatest expertise. In
addition, we reached final
determinations that are congruent with
NAS's analysis whenever we could do
so without departing from the
Congressional delegation of authority to
us to promulgate, by rule, public health
and safety standards for protection of
the public. We believe our mandate
from Congress required the
consideration of public comments and
the exercise of our own expertise and
discretion.
We requested public comments
concerning: how we should view and
weigh NAS's findings and
recommendations in the context of the
specific issues presented in this
rulemaking; whether we have given
proper consideration to NAS's findings
and recommendations; and whether we
should give them more or less weight,
and what the resulting outcome should
be.
We received many comments
regarding our EnPA authority and our
interpretation of the NAS Report.
Several comments took issue with our
reasons for not simply adopting each of
the NAS recommendations verbatim
and stated that we are bound to do so.
One comment asserted that our
reasoning "exaggerates the impact of the
NAS Report" on our rulemaking
authority. However, these comments
generally recognized that we can depart
from the NAS panel's recommendations
if it specifically stated that policy
considerations could play a role in the
decision, or if the recommendation at
issue otherwise was not definitive (e.g.,
there was disagreement among the panel
members). In particular, some
comments suggested that we cannot
include any provision if NAS did not
recommend it. We disagree with this
position. In the preamble to the
proposed rule, we clearly stated our
intentions regarding our use of the NAS
Report (see 64 FR 46980-46983). We
gave the NAS Report special
consideration as "expert scientific
guidance." However, as discussed
above, we do not believe that Congress
intended the NAS Report to bind us
absolutely. We note that NAS, in its
comments on our proposed rule, did not
offer an opinion on this point. Also,
NAS acknowledges in several places in
its report that, for policy or other
reasons, we may elect to take
approaches that differ from its
recommendations. These statements
show NAS did not consider its
recommendations to be binding
directions to EPA. The NAS did,
however, identify aspects of the
proposal it believes are inconsistent
with its recommendations. A copy of
NAS's comments on the proposal is in
the docket (Docket No. A-95-12, Item
IV-D-31). See the Response to
Comments document for additional
discussion of comments regarding our
incorporation of the NAS
recommendations (Docket No. A-95-12,
Item V-C-1).
The following sections describe our
public health and safety standards for
Yucca Mountain and the considerations
that underlie these standards. The next
section addresses the storage portion of
the standards. All of the other sections
pertain to the disposal portion of the
standards.
A. What Is the Standard far Storage of
the Waste? (Subpart A, §§197.1
Through 197.5)
Section 801(a)(l) of the EnPA calls for
EPA's public health and safety
standards to apply to radioactive
materials "stored or disposed of in the
repository at the Yucca Mountain site."
The repository is the excavated portion
of the facility constructed underground
within the Yucca Mountain site (to be
differentiated from the disposal system,
which is made up of the repository, the
engineered barriers, and the natural
barriers). The EnPA differentiates
between "stored" and "disposed"
waste, although it indicates that we
must issue standards that apply to both
storage and disposal. Congress was not
clear regarding its intended use of the
word "stored" in this context. Also,
NAS did not address the issue of storage
versus disposal (see § 197.2 for our
definition of "storage" and §197.12 for
our definition of "disposal"). The DOE
currently conceives of the Yucca
Mountain repository as a disposal
facility, not a storage facility; however,
this situation could change, Therefore,
we decided to interpret the statutory
language as directing us to develop
standards that apply to waste that DOE
either stores or disposes of in the Yucca
Mountain repository. The storage
standard, therefore, applies to waste
inside the repository, prior to disposal.
We received several comments
regarding our proposed definition of
"disposal" in § 197.12, arguing that the
potential benefits of backfilling are
unknown at present. In response to
these comments, we changed the
definition in the final rule to exclude
the requirement that DOE use
backfilling in the Yucca Mountain
repository. We believe that DOE should
have the flexibility to design the
repository so that it is as protective of
public health and the environment as
possible. Therefore, in order not to
constrain DOE unnecessarily in its
choice of repository designs, we
changed the definition of "disposal" as
the comments suggested. Thus, under
the revised definition in our final rule,
it is no longer necessary for DOE to use
backfilling for waste disposal to occur.
Several comments also suggested that
our proposed definitions of "disposal"
and "barrier" run counter to established
notions of deep geologic repositories
because they allow DOE to rely upon
both engineered and natural barriers,
instead of natural bameis alone, to
contain the radioactive material to be
stored in Yucca Mountain. These
comments suggested we amend these
definitions, as appropriate, to delete
references to engineered barriers.
According to the comments, the Yucca
Mountain repository must meet public
health and safety standards with no
assistance from manmade structures or
barriers. The EnPA mandates that we
establish site-specific standards for
Yucca Mountain. Under this mandate,
we believe it is appropriate, based on
the conditions present at Yucca
Mountain, to allow DOE the flexibility
to develop a combined system, using
engineered barriers and natural barriers,
to contain radioactive material to be
disposed of in Yucca Mountain. For
additional discussion of this topic,
please see Chapter 7 of the BID.
The DOE also will handle, and might
store, radioactive material aboveground
(that is, outside the repository). Our
existing standards for management and
storage, codified at subpart A of 40 CFR
part 191, apply to such storage
activities. Subpart A of 40 CFR part 191
requires that DOE manage and store
SNF, HLW, and transuranic radioactive
wastes at a site, such as Yucca
Mountain, in a manner that provides a
reasonable assurance that the annual
dose equivalent to any member of the
public in the general environment will
not exceed 25 millirem (mrem) to the
whole body. (Note that a demonstration
of "reasonable assurance" is necessary
to comply with the standard for storage,
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32085
while subpart B of both 40 CFR part 191
and today's 40 CFR part 197 specify a
demonstration of "reasonable
expectation" to comply with the
disposal standards. "Reasonable
assurance" is an appropriate measure to
apply to storage, as the facility will be
in operation, with active monitoring and
personnel present, during this time. The
level of certainty connected with this
period of active operation is
significantly higher than can be attached
to the much longer regulatory time
period applicable to disposal standards.
See our discussion of "reasonable
expectation" in section IH.B.2.C., What
Level of Expectation Will Meet Our
Standards?} This standard is the one
that DOE must meet for WIPP and the
greater confinement disposal (GCD)
facility. (The GCD facility is a group of
120-feet deep boreholes, located within
NTS, which contain disposed
transuranic wastes.)
We take this position regarding the
applicability of subpart A of 40 CFR part
191 because section 801 of the EnPA
specifically provides that the standards
we issue shall be the only "such
standards" that apply at Yucca
Mountain. Thus, the EnPA is the
exclusive authority for today's action
regarding storage inside the repository.
The WIPP LWA does not exclude Yucca
Mountain from the management and
storage provisions in subpart A of 40
CFR part 191. The 40 CFR part 197
standards supercede our generally
applicable standards (40 CFR part 191)
only to the extent that the EnPA
requires site-specific standards for
storage inside the repository at Yucca
Mountain. Otherwise, the 40 CFR part
197 standards have no effect on our
generic standards. As noted, we
interpret the scope of section 801 to
include both storage and disposal of
waste in the repository. Thus, waste
inside the repository is subject to the
standards in today's action. Our generic
standards (subpart A of 40 CFR part
191) will apply to waste stored at the
Yucca Mountain site, but outside of the
repository.
The storage standards in 40 CFR
191.03(a) are stated in terms of an older
dose-calculation method and are set at
an annual whole-body-dose limit of 25
mrem/yr. The storage standard for
Yucca Mountain uses a modern dose-
calculation method known as
"committed effective dose equivalent"
(CEDE). Even though today's final rule
uses the modern method of dose
calculation, we believe that the dose
level maintains a similar risk level as in
40 CFR 191.03(a) at the time of its
promulgation [see the discussion of the
different dose-calculation methods in
the What Is the Level of Protection Far
Individuals? section later in this
document). The difference between
these dose calculation procedures
presents a problem in combining the
doses for regulatory purposes. However,
we have begun to develop a rulemaking
to amend both 40 CFR parts 190 and
191. That rulemaking would update
these limits to the CEDE methodology.
However, because we have not yet
finalized that change, we need to
address the calculation of doses under
the two methods in another fashion (see
the last paragraph in this section for
more detail).
As discussed in the preamble to the
proposed rule (64 FR 46983), we
considered the differences among the
conditions covered by the storage
standards in 40 CFR 191.03(a) and the
conditions that could affect storage in
the Yucca Mountain repository. The
most significant difference is that the
storage in Yucca Mountain would be
underground, whereas most storage
covered under 40 CFR part 191 is
aboveground. Otherwise, the technical
situations we anticipate under both the
existing generic standards and the
Yucca Mountain standards are
essentially the same. Also, our final rule
extends a similar level of protection as
in the 1985 version of subpart A of 40
CFR part 191. In other words, under the
40 CFR part 197 storage standard,
exposures "of members of the public
from waste storage inside the repository
would be combined with exposures
occurring as a result of storage outside
the repository but within the Yucca
Mountain site (as defined in 40 CFR
197.2). The total dose could be no
greater than 150 microsieverts (p.Sv) (15
mrem) CEDE per year (CEDE/yr).
We requested comments regarding our
interpretation of section 801 and our
approach to coordinating the doses
originating from inside and outside the
Yucca Mountain repository. We
received two comments regarding this
issue. One comment urged us to
establish a single, new, and separate
standard for the Yucca Mountain site
that would encompass the pre-closure
operations both aboveground and in the
repository. The comment further stated
that the suggested approach would
avoid using two different rules for the
same site. This suggested approach also
would avoid the need to use the older
dose methodology currently in 40 CFR
part 191. Another comment stated that
the application of subpart A of 40 CFR
part 191 would not be inappropriate,
We considered establishing a new
standard to cover the entirety of the
management and storage operations at
Yucca Mountain, as was suggested by
one comment. This had the attractive
feature of applying one standard,
instead of two, to the management and
storage activities in and around Yucca
Mountain.
However, after considering the
comments, the wording in section
801(a)(l) of the EnPA, and the
impending rulemaking to amend
subpart A of 40 CFR part 191, we have
decided to cover the surface
management and storage activities
within the Yucca Mountain site under
40 CFR part 191 and management and
storage activities in the Yucca Mountain
repository under 40 CFR part 197.
However, the combined doses incurred
by any individual in the general
environment from these activities must
not exceed 150 uSv (15 mrem) CEDE/yr.
This will require the conversion of
doses from the surface activities from
the older dose system (under which the
40 CFR part 191 standards were
developed) into the newer system to be
able to combine the doses from the two
areas of operation. There are established
methods to do this, e.g., in the appendix
to 40 CFR part 191, but we are leaving
the methodology in this case to NRC's
implementation process. We are
continuing to develop a rulemaking to
update the dose system used in subpart
A of 40 CFR part 191. When that
amendment is finished, the conversion
for the activities subject to subpart A of
40 CFR part 191 will be unnecessary.
B. What Are the Standards for Disposal?
(§§197.11 through 197.36)
Subpart B of this final rule consists of
three separate standards (or sets of
standards) that apply after final
disposal, which are discussed in more
detail in the appropriate sections of this
document. The disposal standards are:
• An individual-protection standard;
• Ground-water protection standards;
and
• A human-intrusion standard.
1. What Is the Standard for Protection of
Individuals? (§§197.20 and 197.25)
The first standard is an individual-
protection standard. It specifies the
maximum dose that a reasonably
maximally exposed individual (RMEI)
may receive from releases from the
Yucca Mountain disposal system.
a. Is the Limit on Dose or Risk?
Section 801(a)(l) of the EnPA directed
that our standards for Yucca Mountain
"shall prescribe the maximum annual
effective dose equivalent to individual
members of the public from releases to
the accessible environment from
radioactive materials stored or disposed
of in the repository * * *." The EnPA
also requires us to issue our standards
-------
32086 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
"based upon and consistent with"
NAS's findings and recommendations.
The NAS recommended that we adopt
a risk-based standard to protect
individuals, rather than a dose-based
standard as Congress prescribed. The
NAS offered two reasons for its
recommendation. First, a risk-based
standard is advantageous relative to a
dose-based standard because it "would
not have to be revised in subsequent
rulemakings if advances in scientific
knowledge reveal that the dose-response
relationship is different from that
envisaged today" (NAS Report p. 64).
Second, NAS believes a risk-based
standard more readily enables the
public to comprehend and compare the
standard with human-health risks from
other sources.
We reviewed and evaluated the merits
of a risk-based standard as
recommended by NAS (NAS Report, pp.
41-ff.). However, we chose to adopt a
dose-based standard for the following
reasons. First, EnPA section 801(a)(l)
specifically directs us to promulgate a
standard prescribing the "maximum
annual dose equivalent to individual
members of the public from releases to
the accessible environment from
radioactive materials stored or disposed
of in the repository." Also, the
Conference Committee specifically
stated that EPA's standards "shall
prescribe the maximum annual dose
equivalent to individual members of the
public from releases to the accessible
environment from radioactive materials
stored or disposed of in the repository.
(H. R. Rep. 102-1018, 102nd Cong., 2d
Sess. 390 (1992)). In a situation such as
this, where both the statutory language
and the legislative history are clear, we
are obliged to implement the clearly
stated plain language of the statute and
to carry out the unambiguous intent of
the Congress.
Second, both national and
international radiation protection
guidelines developed by bodies of non-
governmental radiation experts, such as
ICRP and NCRP, generally have
recommended that radiation standards
be established in terms of dose. Also,
national and international radiation
standards, including the individual-
protection requirements in 40 CFR part
191, are established almost solely in
terms of dose or concentration, not risk.
Therefore, a risk standard will not allow
a convenient comparison with the
numerous existing dose guidelines and
standards.
However, we did establish the dose
limit using the risk of developing a fatal
cancer. The level of risk, about 8.5 fatal
cancers per million members of the
population per year (see the preamble to
the proposed rule at 64 FR 46984), is a
level the Agency has judged to be
acceptable taking into account many
factors, including existing radiation
standards (such as subpart B of 40 CFR
part 191), Congressional action (the
WIPP LWA), and the comments
received on the proposed standards. On
page 46985 of the preamble to the
proposed rule, we cited a risk of
approximately seven in a million per
year. This value was based upon the
NAS risk value of 5 x 10~2 per Sv (5
x ID"4 per rem, NAS Report p. 47).
However, for consistency, we should
have used the value which was first
discussed on page 46979 of the
preamble to the proposed rule, 5.75 x
10~2 per Sv (5.75 x 10~2 per rem), and
which is from Federal Guidance Report
13 (Docket A-95-12, Item V-A-20).
This higher value associates an annual
risk of about 8.5 in a million with 150
|iSv (15 mrem). Because this underlying
risk level is a matter of public policy, it
is possible that the level could change
if future decisionmakers make a
different judgment as to the level of risk
acceptable to the general public.
Likewise, as NAS noted, it could
become necessary to change the dose
limit as a result of future scientific
findings about the cancer-inducing
aspects of radiation (i.e., in correlating
dose with risk). Therefore, no matter
which form of standard is used, it is
subject to change in the future, though
the reasons for change may not be
identical. However, either way, risk is
the underlying basis of the standards. It
is for the other reasons cited in this
section that we chose to use dose. In
addition, dose and risk are closely
related. It is possible to convert one to
the other by using the appropriate
conversion factor. We have discussed
the correlations that we used in
converting risk to dose, both in this
preamble and in Chapter 6 of the BID.
Finally, we did not receive any
comments in favor of a risk standard
that provided either a compelling
technical or policy rationale for
promulgating such a standard (see the
Response to Comments document).
Therefore, we establish a standard
stated as a dose rather than a risk.
We requested comments as to whether
the standard should be expressed as risk
or dose. Not unexpectedly, the
comments were divided between the
alternatives. Most of the comments
supported the use of dose.
One comment stated that the
calculation of a dose limit through a
probabilistic performance assessment is
a reasonable way to assure that the
repository will meet the overall health
risk objective. It is NRC's responsibility
to determine how DOE must
demonstrate compliance with our
standards; however, we envision the use
of a probabilistic assessment for the
compliance demonstration. Another
comment stated that a dose limit is a
reasonable way for us to incorporate
cancer risk into the regulation.. As
discussed to some extent in section
III.B.l.b (WhatFactors Can Lead to
Radiation Exposure?), and in more
detail in the preamble to the proposed
standards [beginning on 64 FR 46984),
the risk of fatal cancer, an annual risk
of about 8.5 in a million for an exposure
of 150 (iSv, is the basis of the level of
protection that we have established.
A few comments supported stating
the standard in terms of risk rather than
dose. For example, NAS was concerned
that a dose standard would preclude the
public from being able to compare risks
with other hazardous materials.
According to NAS, the use of a dose
standard also makes it difficult for the
public to compare the risks inherent in
the ground-water protection standards
with the risks inherent iu the
individual-protection standard. The
NAS also stated that its
recommendation to use a risk standard
did not preclude us from using a dose
standard, as long as the underlying risk
basis was clearly understood. We
believe that we have been sufficiently
clear in describing the risk basis of the
standards within this preamble and the
Response to Comments document.
b. What Factors Can Lead to
Radiation Exposure? Protection of the
public from exposure tu radioactive
pollutants requires knowledge and
understanding of three factors: the
sources of the radiation, the pathways
leading to exposure, and the recipients
of the radiation dose. The standards
must consider all three factors. This
section discusses the sources of
radiation and the pathways of exposure.
The following two sections discuss the
recipients of the dose. Dose assessments
are conducted through a type of
calculational analysis called
"performance assessment". The
performance assessment is the
quantitative analysis of the projected
behavior of the disposal system, which
considers release scenarios for the
repository and carries the analysis
through various pathways in the
environment that culminate in
exposures to members of the public.
Sources. The waste disposed of in
Yucca Mountain will contain many
radionuclides, including unconsumed
uranium, fission products (such as
cesium-137 and strontium-90), and
transuranic elements (such as
plutonium and americium).
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32087
The inventory of radionuclides over
time will depend upon the type and
amount of radionuclides originally
disposed of in the repository, the half-
lives of the radionuclides, and the
amount of any radionuclides formed
from the decay of parent radionuclides
(see Chapter 5 of the BID). In the time
frame of tens to hundreds of thousands
of years, the short-lived radionuclides
initially present in SNF and HLW will
decay. Therefore, the waste eventually
will have radiologic hazards similar to
a large uranium ore body; such ore
bodies naturally occur in a variety of
settings throughout the country. A
typical uranium ore body contains
relatively low concentrations of very
long-lived radionuclides similar to those
present in the radioactive wastes to be
disposed of in Yucca Mountain (see the
preamble to the final rule establishing
40 CFR part 191 (50 FR 38083,
September 19, 1985)).
Barriers to Radionuclide Movement.
To delay and limit the movement of
radionuclides into the biosphere, DOE
plans to use multiple barriers. These
barriers will be both engineered
(human-made) and natural based on the
design of, and conditions in and around,
the disposal system.
Both the natural and engineered
barriers must delay and limit releases of
radionuclides from the repository. For
example, an engineered barrier could be
the waste form. The DOE plans to
convert liquid HLW, derived from
reprocessing SNF, into a solid by
entraining the radionuclides into a
matrix of borosilicate glass. The molten
glass then would be poured into and
solidified in a second engineered
barrier, a metal container (see Chapter 7
of the BID). In addition, it is possible to
have other engineered barriers in the
repository to serve as part of the
disposal system (see Chapter 7 of the
BID).
Natural barriers at Yucca Mountain
also could slow the movement of
radionuclides into the accessible
environment. For instance, DOE plans
to construct the repository in a layer of
tuff located above the water table. The
relative dryness of the turnaround the
repository would limit the amount of
water coming into contact with the
waste, and would retard the future
movement of radionuclides from the
waste into the underlying aquifer. Any
radioactive material that dissolved in
infiltrating water, originating as surface
precipitation, still would have to move
to the saturated zone. In the saturated
zone, which lies below the unsaturated
zone, water completely fills the pores
and fractures in the rock. Minerals, such
as zeolites, in the tuff beneath the
repository could act as molecular filters
and ion-exchange agents for some of the
released radionuclides, thereby slowing
their movement. These minerals also
could limit the amount of water that
contacts the waste and could help retard
the movement of radionuclides from the
waste to the water table. This
mechanism would be most effective if
flow was predominantly through the
matrix (the pores in the rock) (see
Chapter 7 of the BID).
Pathways. Once radionuclides have
left the waste packages, water or air
could carry them to the accessible
environment. Ground water will carry
most of the radionuclides released from
the waste packages away from the
repository. However, air moving
through the mountain will carry away
those radionuclides, such as carbon-14
(1<1C) in the form of carbon dioxide, that
escape from the waste packages in a
gaseous form. For more detailed
discussions of the ground water and air
pathways, see the preamble to the
proposed rule {64 FR 46986) and
Chapters 8 and 9 of the BID.
Movement via water. Radionuclides
will not move instantaneously into the
water table. The length of time it will
take for radionuclides to reach the water
table depends partly on how much the
water moves via fractures or through the
matrix of the rock. Once radionuclides
reach the saturated zone, they would
move away from the disposal system in
the direction of ground water flow.
There are currently no perennial
rivers or lakes adjacent to Yucca
Mountain that could transport
contaminants. Therefore, based on
current knowledge and conditions,
ground water and its usage will be the
main pathways leading to exposure of
humans. Current knowledge suggests
that the two major ways that people
would use the contaminated ground
water are: (1) Drinking and domestic
uses; and (2) agricultural uses (see
Chapters 8 and 9 of the BID). In other
words, radionuclides that reach the
public could deliver a dose if an
individual: (I) Drinks contaminated
ground water or uses it directly for other
household uses; (2) drinks other liquids
containing contaminated water; (3) eats
food products processed using
contaminated water; (4) eats vegetables
or meat raised using contaminated
water; or (5) otherwise is exposed as a
result of immersion in contaminated
water or air.or inhalation of wind-driven
parliculates left following the
evaporation of the water.
Movement via air. Releases of gaseous
14C from the wastes can move through
the tuff overlying the repository and exit
into the atmosphere following release
from the waste package. Once the
radioactive gas enters the atmosphere, it
would disperse across the globe. This
global dispersion would result in
significant dilution of the 14C. The
major pathway for human exposure to
14C is the uptake of radioactive carbon
dioxide by plants that humans
subsequently eat (see Chapter 9 of the
BID).
c. What Is the Level of Protection for
Individuals? Our individual-protection
standard sets a limit of 150 u,Sv (15
mrem) CEDE/yr. This limit corresponds
approximately to an annual risk of fatal
cancer of about 8.5 chances in 1,000,000
(8.5 x 10~6). It is within NAS's
recommended starting range of 1 in
100,000 to 1 in 1,000,000 annual risk of
fatal cancer (see the NAS Report p. 5,
Docket No. A-95-12, Item H-A-l). The
NAS's recommended risk range
corresponds to approximately 20 to 200
jiSv (2 to 20 mrem) CEDE/yr.
We considered NAS's findings and
recommendations in our determination
of the CEDE level that would be
adequately protective of human health.
We also reviewed established EPA
standards and guidance, other Federal
agencies' standards for both radiation
and non-radiation-related actions, and
other countries' regulations. In addition,
we evaluated guidance on dose limits
provided by national and international
non-governmental advisory groups of
radiation experts.
Section 801(a)(l) of the EnPA calls for
our Yucca Mountain standards to
"prescribe the maximum annual
effective dose equivalent to individual
members of the public from releases of
radioactive materials." Development of
the individual-protection standard
required us to evaluate and specify
several factors, which include the level
of protection, whom the standards
should protect, and how long the
standards should provide protection.
Determining the appropriate dose level
is ultimately a question of both science
and public policy. As NAS stated: "The
level of protection established by a
standard is a statement of the level of
the risk that is acceptable to society.
Whether posed as 'How safe is safe
enough?' or as 'What is an acceptable
level?', the question is not solvable by
science" (NAS Report p. 49).
We requested comment regarding the
reasonableness of our proposed 15
mrem CEDE/yr individual-protection
standard. We received many comments,
some of which supported the proposal,
while others stated that we should make
the level higher or lower. This final rule
establishes a limit of 15 mrem CEDE/yr
for the reasons discussed in the
preamble to the proposed rule (see 64
-------
32088 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
FR 46984 and following). Principally,
the reasons were: This level is within
the NAS-recommended range (which
NAS based upon its review of other
Federal actions, guidelines developed
by national and international advisory
bodies, and the regulations in other
countries); the fact that many existing
standards are at this level, particularly
the EPA standards (40 CFR part 191) "
applicable to WEPP (in the case of some
older standards, the equivalence is
based upon more recent understanding
of the damage that radiation can cause);
and, after consideration of the
comments and the site-specific
conditions, we believe that this level is
a sufficiently stringent level of
protection for this situation.
Many comments argued that the
proposed level was too low. For
example, a few comments preferred a
dose level of 25 mrem/yr to maintain
consistency with current NRC
regulations. Another comment
advocated a dose level of 70 mrem/yr,
given the long time frames, the national
importance of the repository, and other
factors. Other comments thought that
the standard should be lower. Several of
these comments supported a limit of 5
mrem/yr. Other comments supported a
zero dose limit.
Some comments stated that, though
they preferred a zero-release standard,
they realized that our level was
implementable. We agree that the
disposal program should ideally have a
goal of no releases. However, we believe
it is incumbent upon us to set a
stringent, yet reasonable, standard. We
are establishing a standard that provides
comparable protections to those of other
activities related to radioactive and non-
radioactive wastes. Given the current
state of technology, it may not be
possible to provide absolute certainty
that there will be no releases over a
10,000 year or longer time frame.
Therefore, we have attempted to
establish a standard that is protective
that can be implemented to show
compliance.
Our finai consideration in selecting a
level of protection was guidance from
national and international non-
governmental bodies, such as ICRP and
NCRP, which have recommended a total
annual dose limit for an individual of 1
mSv (100 mrem) effective dose from
exposure to all radiation sources except
background and medical procedures.
The dose level of 1 mSv (100 mrem)
corresponds to an annual risk of fatal
cancer of about 6 in 100,000 (6 x 10~s).
In its Publication No. 46, "Radiation
Protection Principles for the Disposal of
Solid Radioactive Waste," the ICRP
recommends apportionment of the total
allowable radiation dose among specific
practices. (Docket No. A-95-12, Item V-
A-12). The apportionment of the total
dose limit among different sources of
radiation is used to ensure that the total
of all included exposures is less than 1
mSv (100 mrem) CED/yr. Thus, ICRP
recommends that national authorities
apportion or allocate a fraction of the 1
mSv (100 mrem)-CED/yr limit to
establish an exposure limit for SNF and
HLW disposal facilities. Most other
countries have endorsed the
apportionment principle.
There are multiple sources of
potential radionuclide contamination on
and near NTS, one of which is the
Yucca Mountain site. Portions of NTS
have been subjected to both
underground and aboveground nuclear
weapon detonations. A substantial
, quantity of radionuclides was created by
these tests. An estimated inventory of
300 million curies remains underground
(see Appendix II of the BID; Chapter 8
of DOE's Draft Environmental Impact
Statement for Yucca Mountain (DOE/
EIS/0250D), Docket No. A-95-12, Item
V-A-4; and Nevada Risk Assessment/
Management Program (NRAMP), Docket
No. A-95-12, Item V-A-17). Elsewhere
on the NTS, DOE is burying LLW in
near-surface trenches and TRU
radioactive waste has been disposed of
in the Greater'Confinement Disposal
facility. Finally, there is a commercial
LLW disposal system located west of
Yucca Mountain near Beatty, Nevada.
Each of these facilities could have
releases of radioactivity into the ground
water (see Chapter 8 of DOE's Draft
Environmental Impact Statement for
Yucca Mountain (DOE/EIS/0250D),
Docket No. A-95-12, Item V-A-4; and
Nevada Risk Assessment/Management
Program (NRAMP), Docket No. A-95-
12, Item V-A-17). The regional flow of
ground water is believed to be generally
from the locations where some of these
practices have occurred toward the area
where radionuclides released from the
Yucca Mountain disposal system are
presumed to go (see Nevada Risk
Assessment/Management Program
(NRAMP), Docket No. A-95-12, Item V-
A-17). The total of the releases from
these sources should be constrained to
the total dose limit of 1 mSv (100 mrem)
CED/yr, as recommended by ICRP,
because the releases from these sources
could affect the same group of people.
The potential doses from these other
sources might contribute to individual
doses for the reasonably maximally
exposed individual (RMEI) over
different time frames. According to
Chapter 8 of the DEIS for Yucca
Mountain (DOE/EIS/0250D, Docket No.
A-95-12, Item V-A-4), potential
releases from LLW management and
disposal operations may contribute very
small individual doses. A quantitative
attempt to allocate potential dose from
these other sources would be highly
speculative; however, it would be
reasonable to maintain the allocation
approach reflected in the established
dose limits in both the United States
and internationally.
In summary, based on our review of
the guidance, regulations, and standards
cited above, and the NAS Report, we are
establishing a standard of 150 pSv (15
mrem) CEDE/yr for the Yucca Mountain
disposal system (40 CFR 197.13). This
level is 15% of the ICRP-recommended
total dose limit. It falls within the range
of standards used in other countries and
the range recommended by NAS, and is
also consistent with the individual-
protection requirement in 40 CFR part
191. This level will be the CEDE level
with which the dose over the
compliance period must be compared.
The compliance period is the time
interval over which projections of the
performance of the disposal system
must be made for the purpose of
assessing the future performance of the
disposal system (see the How Far Into
the Future is it Reasonable to Project
Disposal System Performance? section
later in this document for more detail).
d. Who Represents the Exposed
Population1? To determine whether the
Yucca Mountain disposal system
complies with our standard, DOE must
calculate the dose received by some
individual or group of individuals
exposed to releases from the repository
and compare the calculated dose with
the limit established in the standard.
The standard specifies, therefore, the
representative individual for whom
DOE must make the dose calculation.
We expect that NRC will define the
details, beyond those which we have
specified, necessary for the dose
calculation.
Our approach for the protection of
individuals. We examined two possible
approaches: the critical group (CG)
approach recommended by NAS (NAS
Report, pp. 49-54, Appendix C, and
Appendix D) and the reasonably
maximally exposed individual (RMEI)
approach. The goal in representing the
exposed population is to estimate the
level of exposure that is protective of
the vast majority of individuals in that
population, but still within a reasonable
range of potential exposures. We chose
the RMEI approach because we believe
it more appropriately protects
individuals and is less speculative to
implement than the CG approach given
the unique conditions present at Yucca
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32089
Mountain. Also, it remains a
conservative but reasonable approach
that accomplishes the same goal as the
CG approach.
The NAS definition of critical group.
The NAS Report recommended that we
use the risk to a CG as the basis for the
individual-protection standard. The CG
would be the group of people that,
based upon cautious, but reasonable,
assumptions, has the highest risk of
incurring health effects due to releases
from the disposal system. In its report,
NAS discussed two specific examples of
critical groups. The NAS considered the
probabilistic critical group based upon a
present-day fanning community to be
more appropriate and less reliant on
speculative assumptions than the other
critical group it discussed, which was
based upon subsistence fanning.
However, following due consideration,
we decided that the subsistence^farmer
approach discussed by NAS would be
inappropriate, since we could not find
nor did any other party demonstrate that
there is the subsistence-former lifestyle
at, or downgradient from, Yucca
Mountain. For detailed discussions of
NAS's CG approaches, please see the
preamble to the proposed rule, 64 FR
46986-46988, and the NAS Report at
pp. 49-34 and 145-159.
The Reasonably Maximally Exposed
Individual (RMEI). As just mentioned,
NAS recommended that the standard
incorporate a CG approach for
estimating individual exposures from
repository release projections (NAS
Report p. 52). As NAS pointed out, the
CG approach has been examined
internationally and recommendations
for its application have been proposed
(NAS Report, Chapter 2). In addition to
recommending the use of the CG
approach, NAS posited the use of a
"probabilistic" CG, which is a CG
evaluated using probabilistic techniques
for assessing exposures, not only for the
parameters that affect repository
releases but also for the probability that
an individual will use contaminated
ground water away from the site. As
NAS points out, "the components of a
probabilistic computational approach
have considerable precedent in
repository performance, we are not
aware that they have previously been
combined to analyze risks to critical
groups" (NAS Report, Appendix C). In
that sense, NAS "probabilistic" CG is a
departure from the more widely
understood application of the CG
concept. The approach we have chosen
embodies the intent of the
internationally accepted concept to
protect those individuals most at risk
from the proposed repository but
specifies one or a few site-specific
parameters at their maximum values.
We chose to use an approach involving
limiting exposure to a defined
"reasonably maximally exposed
individual", the RMEI. There are
similarities between the probabilistic
CG and RMEI approaches, and also
some significant differences arising from
the Yucca Mountain site, that caused us
to select the RMEI alternative (see also
"Characterization and Comparison of
Alternative Dose Receptors for
Individual Radiation Protection for a
Repository at Yucca Mountain", Docket
No. A-95-12, Item V-B-3).
In both approaches, the attempt is
made to consider a range of conditions
for the exposed individuals that affect
exposures, including geographic
population distributions, lifestyles, and
food .consumption patterns for
populations at risk. The characteristics
of the RMEI are defined from
consideration of current population
distribution and ground water usage,
and average food consumption patterns
for the population in question. Such
characterizations typically are done by
surveying existing populations, and a
"composite" RMEI is defined with one
or more parameters that significantly
affect exposure estimates set at high
values so that the individual is
"reasonably maximally exposed." The
CG approach typically is used under the
assumption of a larger population
within which a smaller group (the
critical group) incurs a more
homogeneous risk from exposures, in
contrast to the larger population group
where exposures will vary widely.
Characteristics of the CG also are
derived from information or
assumptions about the potentially
exposed population; however, a small
group within the larger population,
rather than a composite individual, is
defined. Both the CG and the RMEI are
then located above the path of the
contamination plume and the exposure
variations are calculated as a function of
the parameters that control radionuclide
transport from the contamination source
(here, the repository). The
"probabilistic" CG defined in the NAS
Report (Appendix C) adds an additional
layer of analytical detail by introducing
the idea that the path of the
radionuclide contamination is subject to
considerable uncertainty and the
exposure of the CG is further qualified
by the probability that the
contamination plume is tapped by the
CG at any point in time. This approach
assumes the location of the probabilistic
CG is fixed independently of the
projected path(s) for radionuclide
migration from the repository, and the
potential exposures then are a direct
function of the probability that the
contamination plume reaches the
location of the group. The more
common approach to locating the CG,
for the purpose of estimating exposures,
is to determine where the group can
receive exposures from the
contamination plume and then locating
the CG at that place, regardless of
whether a population is currently at that
location or not. Both of these
approaches appear to give essentially
the same maximum dose levels to at
least some individuals, because at some
point in time the CG would tap into the
contamination plume and receive the
exposures. However, if assumed to be
widely distributed geographically, many
members of the CG could receive
considerably smaller doses, or no dose,
resulting in an average dose which does
hot reflect the intent of the CG concept.
Overall, as explained further, below, the
difference in the distribution of doses
using the CG approach depends upon
the implementation details describing
how the total spectrum of dose
assessments would be calculated.
We relied upon many factors in
making the decision to use the RMEI
concept. First, this approach is
consistent with widespread practice,
current and historical, of estimating
dose and risk incurred by individuals
even when it is impossible to specify or
calculate accurately the exposure habits
of future members of the population, as
in this case where it is necessary to
project doses for very long periods.
Second, we believe that the RMEI
approach is sufficiently conservative
and that it is fully protective of the
general population [including women
and children, the very young, the
elderly, and the infirm). The risk factor
upon which the dose level was
established is very small, 5.75 chances
in 10,000,000 per mrem for fatal cancer.
The lifetime risk then is this factor
multiplied by the total dose received in
each year of the individual's lifetime.
We believe that the risk prior to birth is
very similar to this risk level; however,
relative to the rest of that individual's
lifetime, the difference is small. Third,
we believe that it provides protection
similar to the CG recommended by
NAS. The RMEI model uses a series of
assumptions about the lifestyle of a
hypothetical individual. This belief was
supported by NAS in its comments on
the proposed 40 CFR part 197. The NAS
agreed that EPA's RMEI approach is
"broadly consistent with the TYMS
report's recommendation" (Docket No.
A-95-12, IV-D-31). Fourth, it is
possible to build the desired degree of
-------
32090 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
conservatism into the model through
choices of assumed values of RME
parameters. However, these values
would be within certain limits because
we require the use of Yucca Mountain-
specific characteristics in choosing
those parameters and their values. In
subpart B of 40 CFR part 197, we
establish a framework of assumptions
for NRC to-incorporate into its
implementing regulations. Fifth, we
believe that the RMEI approach is more
straightforward in its application than
the CG approach (particularly the
probabilistic CG approach). The RMEI
can reasonably be assumed to incur
doses from the plume of contamination.
By locating the RMEI for dose
assessment purposes above the plume's
direct path, high-end dose estimates
will result A probabilistic CG implies
some, or even many, locations of the
members across a broader geographic
area than the plume covers. This
dispersal inescapably involves
additional decisions for the method to
be used for combining dose estimates
for the group members and comparison
against regulatory limits and could
average some, or many, doses with a
zero magnitude. In addition, specifying
certain assumptions regarding
consumption habits, e.g., requiring the
assumption that the RMEI drinks a high-
end estimate of 2 liters/day of ground
water and that dietary intake is
determined using surveys of today's
population in the Town of Amargosa
Valley, assure that the RMEI is
"reasonably maximally" exposed
(§ 197.21). We believe this approach is
consistent with the NAS
recommendation of "cautious, but
reasonable" assumptions for repository
dose assessments (NAS Report p. 6).
With these assumptions about the
location to be used for dose assessments
and food and water consumption, we
believe that the RMEI approach would
result in dose estimates comparable to a
small CG. For a CG, food and water
consumption patterns would also be
determined from surveys of the local
population and, possibly, by some
assumptions to push the dose
assessments toward higher-end dose
estimates. The important difference
between the composite RMEI and
probabilistic CG approaches is in the
assumed distribution of the group
members relative to the projected path
of xadionuclide contamination from the
repository. And, finally, sixth, we
previously have used the RMEI
approach in our regulations (see FR
22888, 22922, May 29, 1992). We have
not used the CG approach. For example,
the WIPP certification criteria (40 CFR
part 194) use an approach involving
estimating doses to individuals rather
than to a defined CG.
We believe the RMEI approach is
more direct and easily understood than
the probabilistic CG approach because
the uncertainties of estimating doses for
a randomly located population is
avoided, but the approach is still
"cautious, but reasonable." We believe
that the "probabilistic" CG described by
NAS would give essentially the same
high-end dose results for situations
where the group is small, located in a
relatively small area, and is above the
path of the contamination plume.
However, this was not the concept
recommended by NAS. Therefore, we
believe our RMEI approach captures the
essential "cautious, but reasonable"
approach recommended by NAS while
minimizing speculative aspects of the
probabilistic CG approach. We do not
mean to imply that a CG approach
would never be appropriate, or that we
would never use a CG approach in a
regulatory action or other decision.
However, in this particular site-specific
situation, had we used a CG, we would
have considered it necessary to define it
in detail (in terms of size and location)
using cautious, but reasonable,
assumptions, but as discussed
elsewhere in this document, we believe
that the RMEI approach is preferable for
Yucca Mountain.
Our RMEI is a theoretical individual
representative of a future population
group or community termed "rural-
residential" (see Chapter 8 of the BID for
a description of this concept). The DOE
will calculate the CEDE the RMEI
receives using cautious, but reasonable,
exposure parameters and parameter-
value ranges as described below. The
NRC would use the projected CEDE in
determining whether DOE complies
with the standard. The DOE will
perform the dose calculation to estimate
exposure resulting from releases from
the waste into the accessible
environment based upon the
assumption of present-day conditions in
the vicinity of Yucca Mountain. Under
our standard, the RMEI will have food
and water intake rates, diet, and
physiology similar to those of
individuals in communities currently
living in the downgradient direction of
flow of the ground water passing under
Yucca Mountain.
We did, however, receive comments
from tribal representatives expressing
concern regarding an alternative
approach. The Paiute and Shoshone
Tribes stated that they use the Yucca
Mountain area for traditional and
customary purposes, including
traditional gathering, and it is their
belief that these uses should be
incorporated into the formula upon
which the final standards are based. We
considered the Tribes' comments, but,
for several reasons explained below, we
conclude, after considering their
description of tribal uses of the area,
that the rural-residential RMEI is fully
protective of tribal resources.
First, the tribal use of natural springs
is apparently occurring in the vicinity of
Ash Meadows, since we are not aware
of another area downgradient from
Yucca Mountain where water discharges
in natural springs, with the possible
exception of springs in the more distant
Death Valley. These natural springs are
likely fed by the "carbonate" aquifer,
which is beneath the "alluvial" aquifer
being used Town of Amargosa Valley
(including at Lathrop Wells) now, and
which we assume will be used in the
future. The available data indicate that
although it is likely that the alluvial
aquifer would be contaminated by
releases from the potential Yucca
Mountain repository, flow is generally
upward from the carbonate aquifer into
the overlying aquifers, suggesting that
there is no potential for radionuclides to
move downward into the carbonate
system. If downward movement were to
occur, however, radionuclide
concentrations would be significantly
diluted in the larger carbonate flow
system. As a result, springs fed from the
carbonate aquifer would have lower
contamination levels than would wells
at the Lathrop Wells location, which tap
aquifers closer to, and more directly
affected by, the source of potential
contamination. A more extensive
discussion of the aquifer systems and
geology in the Yucca Mountain area
may be found in sections II.D and
III.B.4.e of this preamble, and Chapters
7 and 8 of the BID.
Second, the tribal use of wildlife and
non-irrigated vegetation should not
contribute significantly to total
individual dose estimates. Gaseous
releases from the repository are not a
significant contributor to individual
doses (NAS report, pg. 59) through
inhalation or rainfall, and should
contribute less to contamination of
wildlife and non-irrigated vegetation
than the use of contaminated well water
for raising crops and animals for food
consumption. We believe our
requirement that DOE and NRC base
food ingestion patterns on current
patterns for the agricultural area directly
down gradient from the repository is a
more conservative requirement.
Third, the dose incurred by the RMEI
is calculated at a location closer to the
disposal system than, the Ash Meadows
area (approximately 18 km versus 30
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001 /Rules and Regulations 32091
km). The RMEI would receive a higher
dose from ground water consumption
than would an individual at Ash
Meadows, even if the carbonate aquifer
could be contaminated by repository
releases, for the reasons mentioned
above.
Fourth, the RMEI is assumed to be a
full-time resident continually exposed
to radiation coming from the disposal
system. It appears that the tribal uses are
intermittent and involve resources
which are Jess likely to be
contaminated, resulting in lower doses
than those to the RMEI.
Presently, we expect the ground water
pathway to be the most significant
pathway for exposure from
radionuclides transported from the
repository (NAS Report p. 48; Chapter 8
of the BID). Our initial evaluation of
potential exposure pathways from the
disposal system to the RMEI suggests
that the dominant fraction of the dose
incurred by the RMEI likely will be from
ingestion of food irrigated with
contaminated water (see Chapter 8 of
the BID). It is possible, however, that
DOE and NRC will determine that
another exposure pathway is more
significant. Consequently, DOE and
NRC must consider and evaluate all
potentially significant exposure
pathways in the dose assessments. As a
result of the dose assessments using
different combinations of parameter
values, there will be a distribution of
potential doses incurred by the RMEI.
The NRC will use the mean value of that
distribution of KMEI doses to determine
DOE's compliance with the individual-
protection standard. We requested
comments regarding both the use of the
RMEI approach and the use of the
higher of the mean or median value to
determine compliance with the
individual-protection standard. We also
requested comments regarding the
desirability of adopting the CG approach
rather than the RMEI approach. We
further requested that comments
supporting the CG approach address the
level of detail our rule should include
for the parameters used to describe the
CG. Comments on various aspects of the
RMEI approach appear later in this
section. Comments on the mean/median
compliance level are in the answer to
Question #13 in section IV.
We received comments supporting
both the RMEI and the CG approaches.
For example, one commenter felt that
NRC's proposed licensing regulation for
Yucca Mountain (64 FR 8640, February
22,1999) was more consistent with the
NAS recommendation because it
included a farming community CG (see
NRC's proposed 10 CFR 63.115). This
commenter also stated that the proposed
10 CFR part 63 contains the appropriate
level of detail to define the CG. Other
commenters recommended the use of a
subsistence farmer CG approach on the
grounds that such an approach is more
protective than the rural-residential
RMEI. These groups staled that the
RMEI is "purely speculative."
As noted earlier, NAS recommended
using the CG concept. This approach
can account for differences in age, size,
metabolism, habits, and environment to
avoid heavily skewing the results based
upon personal traits that make certain
people more or less vulnerable to
radiation releases than the average
within the group. In comparison, under
the RMEI approach, the dose that the
RMEI incurs is calculated using some
maximum values and some average
values for the factors that are important
to estimating dose. Physical differences
such as age, size, and metabolism are
also incorporated into the risk value for
development of cancer, in effect making
the RMEI a "composite" individual.
This procedure also projects doses that
are within a reasonably expected range
rather than projecting the most extreme
cases. «
Regarding the comments stating that
the RMEI is "purely speculative," we
agree that the RMEI approach is
speculative; however, it is less
speculative than the scenario suggested
in the comments supporting the use of
a subsistence farmer. We are not aware
of any subsistence farmers (as defined
by the comments) in Amargosa Valley.
If we used the comments' approach we
would, therefore, be engaging in even
more speculation than we are by using
a current lifestyle. Any future projection
involves speculation. Our basis for
using the RMEI is that we are following
NAS's recommendation to use current
technology and living patterns because
speculation upon future society and
lifestyle variations can be endless and
not scientifically supportable (NAS
Report p. 122). As stated earlier, the
danger in defining a probabilistic CG is
that it may be skewed by including
randomly located people who will have
minimal exposures, resulting in less
conservative estimates for the group.
Given the conditions at Yucca
Mountain, we considered this to be a
very real possibility. We consider using
a composite individual to be a much
simpler means of accomplishing the
same purpose while maintaining more
control over who is represented in the
exposure assessments. Had ws opted to
use a probabilistic CG, we would have
identified certain characteristics of the
group in order for it to meet our intent,
as we have done with the RMEI.
Overall, we believe that the RMEI
approach both meets the intent of NAS
and the EnPA and continues a
regulatory methodology that we
previously have used successfully.
Further, though it recommended that we
use aCG approach, NAS seemed to
recognize that a non-CG approach could
accomplish the same purpose. In its
report, NAS stated "fijt is essential that
the scenario that is ultimately selected
be consistent with the critical-group
concept that we have advanced" (NAS
Report p. 10, emphasis added). In its
comments on the proposed 40 CFR part
197, NAS stated that our RMEI approach
is "broadly consistent with the TYMS
report's recommendations" (Docket No.
A-95-12, Item IV-D-31). Given this
acknowledgment by NAS, and that our
evaluation of public comments
identified no significant deficiencies in
our proposed approach, we see no
compelling reason to change our
position that the RMEI is the
appropriate method to use at Yucca
Mountain.
Exposure scenario for the RMEI. A
major part of the exposure scenario is
the RMEI's location. To make this
decision, we collected and evaluated
information about the Yucca Mountain
area's natural geologic and hydrologic
features that may preclude drilling for
water at a specific location, such as
topography, geologic structure, aquifer
depth and quality, and water
accessibility. Based upon this
information and the current
understanding of ground water flow in
the Yucca Mountain area, it appears that
individuals theoretically could reside
anywhere along the projected ground
water flow path extending from Forty-
Mile Wash, starting approximately five
kilometers (km) from the repository
location, to the southwestern part of the
Town of Amargosa Valley, Nevada,
where the ground water is close to the
land surface and where most of the
farming in the area occurs. However, in
practice an individual's ability to reside
at any particular point depends upon
the available resources. To explore these
variations, we developed four scenarios
(described in the preamble to the
proposed rule). See Chapter 8 of the BID
for a fuller version of our evaluation of
the factors associated with these
scenarios. In developing scenarios, we
assumed that the level of technology
and economic considerations affecting
population distributions and life styles
in the future are the same as today (for
more detail on this assumption, see the
What Do Our Standards Assume About
the Future Biosphere? section below).
See below for a fuller discussion of our
-------
32092 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
choice for the RMEI's location. We
requested comments regarding the
appropriateness of these scenarios and
our preferred choice.
We selected a rural-residential RMEI
as the basis of our individual exposure
scenario. We assume that the rural-
residential RMEI, is exposed through
the same general pathways as a
subsistence farmer. However, this RMEI
would not be a full-time farmer. Rather,
this RMEI, as part of a community
typical of Amargosa Valley, might do
personal gardening and earn income
from other sources of work in the area.
We assume further that the RMEI drinks
two liters per day of water contaminated
with radionuclides, and some of the
food (based upon surveys) consumed by
the RMEI is from the Town of Amargosa
Valley. We consider the consumption of
two liters per day of drinking water to
be a high-exposure value because
people consume water and other liquids
from outside sources, such as
commercial products. We intended that
it would push the dose estimates
towards a "reasonably maximal
exposure." Similarly, we assume that
local food production will use water
contaminated with radionuclides
released from the disposal system. We
believe this lifestyle is similar to that of
most people living in Amargosa Valley
today.
We received comments stating that:
we should be more specific in defining
characteristics of the RMEI; we should
take future changes in population, land
use, climate, and biota into
consideration; and that something other
than a rural-residential lifestyle would
be a more appropriate choice.
One comment suggested that we
should be more specific in setting the
location, behavior, and lifestyle, or
allow NRC to make that choice. There
were also a few comments stating that
NRC should specify the parameter
values. We believe that we have
specified the characteristics of the rural-
residential RMEI in the detail necessary,
given our current understanding, for the
concept to be implemented as we
intend. We also believe that our
specification of the parameter values
such as location for the RMEI and
drinking water intake rate is appropriate
and necessary for our standard to be
implemented in the context in which
we developed it. We further believe we
have the authority to specify other
parameter values; however, we believe
that NRC, in its role as the licensing
authority, can and should set most of
the details for implementing the
standard, such as water usage in the
community where the RMEI resides.
Also, under our standard, NRC has the
flexibility to make any assumptions,
other than those we specified
(assumptions we specified include
location, water intake rate, and diet
reflective of current residents of the
Town of Amargosa Valley), if alternative
selections prove to be more appropriate
for implementing the standard as we
intend. The location we specified is not
a fixed point but rather it must be in the
accessible environment above the
highest concentration of radionuclides
in the plume of contamination. To
assess water usage in the hypothetical
community, DOE and NRC could use an
approach similar to the representative
volume approach described later in this
document (How Does Our Rule Protect
Ground Water?}, In doing so, the NRC
may wish to consider the volume we
specified as the representative volume
for ground water protection (i.e., 3,000
acre-feet). Given the extreme technical
difficulty in modeling the small
volumes of water used by an individual,
it would be reasonable for DOE and
NRC to assume that the RMEI is one of
a number of people (in the hypothetical
"community" of which the RMEI is a
member) withdrawing water from the
plume of contamination. Such an
approach would involve assumptions
about the number of people
withdrawing water and the various uses
for which the water is withdrawn,
which would define the overall volume
of water. The RMEI would then be a
representative person using water with
"average" concentrations of
radionuclides. These assumptions
should be reflective of current water
uses in the projected path of the plume
of contamination.
Among the comments regarding our
assumptions about future populations,
land use, climate, and biota, one stated
that it is arrogant, as well as insensitive,
to assume that all future people will be
like us today, and that it is unrealistic
to assume that future population
distribution, patterned as it is today,
will be static. The comment is correct in
that there are many possible futures.
However, it is necessary to limit
speculation about possible futures so
that the performance assessments can
provide meaningful input into the
decision process and the decision
process itself is not confounded with
speculative alternatives. Therefore, we
agreed with and followed NAS when it
recommended, "[i]n view of the almost
unlimited possible future states of
society * * * we have recommended
that a particular set of assumptions be
used about the biosphere * * * we
recommend the use of assumptions that
reflect current technologies and living
patterns" (NAS Report p. 122).
A similar question arose when we
developed the implementing regulations
for WIPP. We resolved the question by
developing the "future states"
assumption (see 40 CFR 194.25). The
position we have taken for the Yucca
Mountain standards is consistent with
our previous approach to this question.
There was a spectrum of suggestions
recommending alternative RMEls (from
a fetus to the elderly and infirm). For
example, one comment suggested
pregnant women and the unborn within
their wombs, children, the infirm, and
the elderly as appropriate RMEIs. Other
commenters urged using a subsistence
farmer. Regarding the various ages and
stages of human development, the risk
value used for the development of
cancer is an overall average risk value
(see Chapter 6 of the BID for more
details) that includes all exposure
pathways, both genders, all ages, and
most radionuclides. However, it does
not cover the "unborn within the
womb." It is thought that the risk to the
unborn is similar to that for those who
have been born; however, the exposure
period for the unborn is very short
compared to the rest of the individual's
average lifetime (see Chapter 6 of the
BID for a discussion of cancer risk from
in utero exposure). Therefore, the risk is
proportionately lower and thus would
not have a significant impact upon the
overall risk incurred by an individual
over a lifetime. On the other end of the
spectrum, radiation exposure of the
elderly at the levels of the individual-
protection standard would be less than
the overall risk value because they have
fewer years to live and, therefore, fewer
years for a fatal cancer to develop.
Some comments on our RMEI
characteristics stated that they need to
be more site-specific and should
consider the alternative lifestyles of
Native Americans. Other comments
stated that the characteristics and
location of the RMEI are
implementation issues that should be
left for determination.by NRC. We
believe that the final rule achieves the
proper balance of site-specific
characteristics that is fully protective of
the public health and safety, and that
the attributes of the RMEI specified in
this rule are necessary to ensure that the
Yucca Mountain disposal system
achieves the level of protection that we
intend.
Location of the EMBL The location of
the RMEI is a basic part of the exposure
scenario. We considered locations
within a region occupying an area
bordering Forty-Mile Wash, within a
few kilometers of the repository site, to
-------
Federal Register /Vol. 66, No. 114 / Wednesday, June 13, 2001/Rules and Regulations 32093
the southwestern border of the Town of
Amargosa Valley. This region, which we
believe is hydrologically downgradient
from Yucca Mountain, can be
considered as three general subareas.
See the preamble to the proposed rule,
64 FR 46989-46990, for a fuller
discussion of these subareas.
Based upon these considerations of
the subareas, we proposed the
intersection of U.S. Route 95 and
Nevada State Route 373, known as
Lathrop Wells, as the point where the
RMEI would reside. We consider it
improbable that the rural-residential
RMEI would occupy locations
significantly north of U.S. Route 95,
because the rough terrain and increasing
depth to ground water nearer Yucca
Mountain would likely discourage
settlement by individuals because
access to water is more difficult than it
would be a few kilometers farther south.
Also, there are currently several
residents and businesses near this
location whose source of water is the
underlying aquifer (which we
understand flows beneath Yucca
Mountain). Therefore, we believe it is
reasonable to assume that a rural
community could be located near this
intersection in the future, and that
population increases in the short term
would cluster preferentially around the
main roads through the area.
We are requiring that the RMEI be
located in the accessible environment
[i.e., outside the controlled area) above
the highest concentration of
radionuclides in the plume of
contamination. Based upon a review of
available site-specific information (see
Chapter 8 of the BID), we have chosen
the latitude of the southern edge of the
Nevada Test Site (corresponding to the
line of latitude 36° 40' 13.6661" North
(described in Docket A-95-12, Item V-
A-29)), as the southernmost extent of
the controlled area, i.e., DOE and NRC
could establish the southern boundary
of the controlled area farther north (and
presumably the location of the RMEI),
but no farther south (see Where Will
Compliance With the Ground Water
Standards be Assessed?). (Even if the
RMEI were to be located north of this
line of latitude, the RMEI must stHl have
the characteristics described in
§ 197.21.). As noted above, we proposed
the intersection of U.S. Route 95 and
Nevada State Route 373 [i.e., Lathrop
Wells) as the location of the RMEI. After
further review, we determined that the
southern edge of NTS would be a more
appropriate maximum distance from the
repository footprint than the location we
proposed because of Nye County's plans
to develop the area between the
intersection at Lathrop Wells and NTS
and the potential for members of the
public to reside in that same area
(Docket No. A-95-12, Items V-14, 15,
16). This location is also slightly more
protective than the Lathrop Wells
location since it is approximately 2 km
closer to the repository footprint, but
still falls within the conditions which
led us to propose the Lathrop Wells
intersection, e.g., the ground water is
not significantly deeper than at the
intersection and the soil conditions are
the same.
Commercial farming occurs today
farther south, in the southwestern
portion of the Town of Amargosa Valley
in an area near the California border and
west of Nevada State Route 373.
However, soil conditions in the vicinity
of Lathrop Wells are similar to those in
southwestern Amargosa Valley.
Therefore, it should be feasible for the
RMEI to grow some food, using
contaminated water tapped by a well.
We believe that it is reasonable to
assume that other gardening, farming,
and raising of domestic animals could
occur using contaminated water (see
Appendix IV of the BID). We have
specified that selected parameters, such
as the percentage of food grown by the
RMEI, should reflect the lifestyles of
current residents of the Town of
Amargosa Valley.
Finally, we believe a rural-residential
RMEI slightly north of Lathrop Wells
would be among the most highly
exposed individuals downgradient from
Yucca Mountain, even though the
ground water nearer the repository
could contain higher concentrations of
radionuclides. If individuals lived
nearer the repository, they would be
unlikely to withdraw water from the
significantly greater depth for other than
domestic use, and in the much larger
quantities needed for gardening or
farming activities because of the
significant cost of finding and
withdrawing the ground water. It is
possible, therefore, for an individual
located closer to the repository to incur
exposures from contaminated drinking
water, but not from ingestion of
contaminated food. Based upon our
analyses of potential pathways of
exposure, discussed above, we believe
that use of contaminated ground water
(e.g., drinking water and irrigation of
crops) would be the most likely
pathway for most of the dose from the
most soluble, more mobile
radionuclides (such as technetium-99
and iodine-129). The percentage of the
dose that results from irrigation would
depend upon assumptions about the
fraction of all food consumed by the
RMEI from gardening or other crops
grown using contaminated water, which
should reflect the lifestyle of current
residents of the Town of Amargosa
Valley. Therefore, the exposure for an
RMEI located approximately 18 km
south of the repository (where ingestion
of locally grown contaminated food is a
reasonable assumption) actually would
be more conservative than an RMEI
located much closer to the repository
who is exposed primarily through
drinking water. We also are establishing
that protection of a rural-residential
RMEI would be protective of the general
population downgradient from Yucca
Mountain (see the How Do OUT
Standards Protect the General
Population? section below).
As stated above, the method of
calculating the RMEI dose is to select
average values for most parameters
except one or a few of the most
sensitive, which are set at their
maximum. We believe that an RMEI
location above the highest concentration
in the plume of contamination in the
accessible environment and a
consumption rate of two liters per day
of drinking water from the plume of
contamination represent high-end
values for two of these factors. The NRC
may identify additional parameters to
assign high-end values in projecting the
dose to the RMEI. To the extent
possible, NRC should use site-specific
information for any remaining factors.
For example, NRC should use site-
specific projections of the amount of
contaminated food that would be
ingested in the future. The NRC might
base projections upon surveys that
indicate the percentage of the total diet
of Amargosa Valley residents from food
grown in the Amargosa Valley area.
We requested comment regarding the
potential approaches and assumptions
for the exposure scenario to be used for
calculating the dose incurred by the
RMEI, particularly whether:
(1) Based upon the above criteria,
there is now sufficient information for
us to adequately support a choice for the
RMEI location in the final rule or should
we leave that determination to NRC in
its licensing process based upon our
criteria;
(2) Another location in one of the
three subareas identified previously
should be the location of the RMEI; and
(3) Lathrop Wells and an ingestion
rate of two liters per day of drinking
water are appropriate high-end values
for parameters to be used to project
doses to the RMEI.
Of the three subjects listed above, the
only comments we received suggested
different locations for the RMEI. A few
commenters thought that the Lathrop
Wells location is appropriate. However,
a number of others stated that the
-------
32094 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
RMEI's location should be at the edge of
the footprint of the repository. Finally,
one commenter suggested that 30
kilometers away from the repository (in
the current farming area in southern
Amargosa Valley) would be reasonable;
however, this commenter also stated
that Lathrop Wells would be acceptable
using the rural-residential scenario to
provide conservatism to protect public
health and safety.
As stated earlier, we are designating
the location above the point of highest
concentration in the plume of
contamination in the accessible
environment (no farther south than 36°
40' 13.6661" North) as the location of
the RMEI. This point would be
approximately 18 kilometers south of
the repository footprint. We do not
believe that an RMEI likely would live
much farther north of the compliance
point (toward Yucca Mountain) because
of the increasing depth to ground water
and the increasing roughness of the
terrain. In addition, we believe that, at
approximately 18 km, a rural-resident
RMEI will likely have the highest
potentiai doses in the region because of
both drinking contaminated water and
eating food grown using contaminated
water. That is, the rural resident at 18
km will receive a higher dose than
would an individual living much closer
to Yucca Mountain because the cost of
extracting the water likely will allow
only drinking the water and not having
a garden capable of supplying a portion
of an individual's annual food
consumption (see Chapters 7 and 8 of
the BID). Likewise, we do not believe
that hypothesizing that the RMEI lives
30 km away is a cautious, but
reasonable, assumption because: (1) At
30 km, the RMEI likely would use water
that contains much lower
concentrations of (i.e., more diluted)
radionuclides; (2) the downgradient
residents closest to Yucca Mountain are
currently near Lathrop Wells; and (3)
Nye County's short-term projections (20
years) show population growth at and
near that location (see Docket No. A-
95-12, Items V-A-14, V-A-15, and V-
A-16). Therefore, a distance of 18 km
adds to the conservatism and provides
more protection of public health,
relative to one commenter's suggested
distance of 30 km.
There were a few other comments
related to the location of the RMEI. For
example, one comment stated that the
location should take into account the
geology and hydrology of the site rather
than be chosen in advance. Another
comment believes that we should base
the location upon the ability of the
RMEI to sustain itself consistent with
topography and soil conditions. Further,
this commenter believes that depth to
ground water should not be a factor
because it is impossible to predict either
human activities or economic
imperatives.
We determined the point of
compliance for the individual -
protection standard using site-specific
factors and NAS's recommendation to
use current conditions (NAS Report p.
54). In preparing to propose a
compliance point for the RMEI, we
collected and evaluated information on
the natural geologic and hydrologic
features, such as topography, geologic
structure, aquifer depth, aquifer quality,
and the quantity of ground water, that
may preclude drilling for water at a
specific location (see Chapter 7 of the
BID). For example, as stated above, we
do not believe that a rural-residential
individual would occupy areas much
closer to Yucca Mountain because of the
increasingly rough terrain and the
increasing depth to ground water. With
increasing depth to ground water come
higher costs: (1) To drill for water; (2)
to explore for water; and (3) to pump the
water to the surface. We agree that it is
impossible to predict either human
activities or economic imperatives.
Therefore, we followed NAS's
recommendation to use current
conditions to avoid highly speculative
scenarios. This approach leads us to
considering the depth to ground water
as a key factor in determining the
location and activities of the RMEI. The
current location of people living in the
vicinity of the repository is a reflection
of this key factor.
And, finally, one commenter stated
that the proposed RMEI concept forces
DOE to assume the RMEI will withdraw
water from the highest concentration
within the plume without consideration
of its likelihood. Forcing such an
assumption neglects the low probability
that a well will intersect the highest
concentration within the plume.
This commenter's approach, which
would use a probabilistic method to
determine the radionuclide
concentration withdrawn by the RMEI,
is similar to one of the example CG
approaches that NAS provided in its
report (NAS Report Appendix C). The
NAS approach would use statistical
sampling of various parameters, i.e.,
considering the likelihood (probability)
of various conditions existing to arrive
at a dose for comparison to the standard.
However, we did not use the
probabilistic CG approach for the
following reasons: (1) There is no
relevant experience in applying the
probabilistic CG approach, (2) the CG
approach is very complex relative to the
RMEI approach and is difficult to
implement in a manner that assures it
would meet the requirements of
defining a CG, and (3) we are concerned
that this approach does not appear to
identify clearly which individual
characteristics describe who is being
protected. Finally, a significant majority
of the public comments we received on
the NAS Report opposed the
probabilistic CG approach. We further
believe that prudent public health
policy requires that our approach be
followed to provide reasonable
conservatism. In this case, this is not a
prediction of exactly whom will be
exposed as much as it is a reasonable
test of the performance of the repository.
To allow the probability of any
particular location being contaminated
is not a prudent approach to the
ultimate goal of testing acceptable
performance.
e. How Do OUT Standards Protect the
General Population? Pursuant to section
801(a)(2)(A) of the EnPA, one of the
issues to be addressed by NAS in its
study is whether an individual-
protection standard will provide a
reasonable standard for protection of the
health and safety of the general public.
NAS concluded that an individual-
protection standard could provide such
protection in the case of the Yucca
Mountain disposal system. The NAS
premised this conclusion on the
condition that the public and
policymakers would accept the idea that
extremely small individual radiation
doses spread out over large populations
pose a negligible risk (NAS Report p.
57). The NAS refers to this concept as
"negligible incremental risk" (NIR)
(NAS Report p. 59). See the preamble to
the proposed rule for a detailed
discussion of NAS's concept of NIR (64
FR 46990-46991).
We agree with NAS that an
individual-protection standard can
adequately protect the general
population near Yucca Mountain
because of the particular characteristics
of the Yucca Mountain site. However,
we chose not to adopt either a negligible
incremental dose (NID) or NIR level
because we are concerned that such an
approach is not appropriate in all
circumstances, and because of
reservations regarding NAS's reasoning
and analysis. We based our
determination that an individual-risk
standard is adequate to protect both the
local and general population on
considerations unique to the Yucca
Mountain site. This is not, however, a
general policy judgment by us regarding
other uses of the NID or NIR concepts.
As noted in the preamble to the
proposal (64 FR 46990), NAS referred to
the NID level of 10 uSv (1 mrem)/yr per
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
32095
source or practice recommended by the
NCRP, The International Atomic Energy
Agency (IAEA) has made similar
recommendations regarding exemptions
in its Safety Series No. 89, "Principles
for the Exemption of Radiation Sources
and Practices from Regulatory Control"
(1998) (Docket No. A-95-12,"ltem Il-A-
6). The IAEA has recommended that
individual doses not exceed 10 uSv (1
mrem)/yr from each exempt practice
(IAEA Safety Series No. 89, p. 10). The
IAEA's recommendations relate to
criteria for exempting whole sources or
practices, such as waste disposal or
recycling generally, not whether
radiation doses from a portion of a given
practice, such as the release of gases
from a specific geologic repository, may
be considered negligible. Finally, the
IAEA's recommendations intend the
exemption to be for sources and
practices "which are inherentiy safe"
(IAEA Safety Series No. 89, p. 11). It is
not clear that the low individual doses
or risks projected from gaseous releases
from the Yucca Mountain repository
should be considered on their own as a
"source" or "practice," given the
definitions of these terms in IAEA's
Safety Series No. 89. Further, given the
extraordinarily large inventory of long-
lived radionuclides to be disposed of in
the Yucca Mountain repository, it is not
clear that such a source or practice
should be considered inherently safe.
Also, we believe it is inappropriate to
not calculate a radiation dose merely
because the dose rate from a particular
source is small.
Further, we do not believe it is
appropriate to apply the NIR concept to
consideration of population dose. A
recent NCRP report questions the
application of the NID concept to
population doses. According to NCRP
Report No. 121: "(a) Concept such as the
NID (Negligible Incremental Dose)
provides a legitimate lower limit below
which action to further reduce
individual dose is unwarranted, but it is
not necessarily a legitimate cut-off dose
level for the calculation of collective
dose. Collective dose addresses societal
risk while the NID and related concepts
address individual risk." (Principles
and Application of Collective Dose in
Radiation Protection, NCRP Report No.
121, Docket No. A-95-12, Item II-A-8).
Based upon this principle, we think it
inappropriate to use the NID or NIR
concept to evaluate whether an
individual-protection standard
adequately protects the general
population.
In summary, we are establishing an
individual-protection standard for
Yucca Mountain that will limit the
annual radiation dose incurred by the
RMEI to 150 uSv (15 mrem) CEDE. At
the same time, we chose not to adopt a
separate limit on radiation releases for
the purpose of protecting the general
population. Instead, we recommended
in our proposal that DOE estimate and
consider collective dose in its analyses.
We based this recommendation upon
several factors. The first factor is NAS's
projection of extremely small doses to
individuals resulting from air releases
from Yucca Mountain. That dose level
is well below the risk corresponding to
our individual-protection standard for
Yucca Mountain. It is also well below
the level that we have regulated in the
past through other regulations. Further,
while we decline to establish a general
Negligible Incremental Risk (NIR) level,
we do agree with NAS that estimating
the number of health effects resulting
from a 0.0003 mrem/yr dose equivalent
rate (NAS Report p. 59), in addition to
the dose rate from background radiation,
in the general population is uncertain
and controversial. The second major
factor is that, based upon current and
site-specific conditions near Yucca
Mountain, there is not likely to be great
dilution resulting in exposure of a large
population. In addition, we are
establishing additional ground water
protection standards that would set
specific limits to protect users of ground
water and that protect ground water as
a resource. Finally, we require that all
of the pathways, including air and
ground water, be analyzed by DOE and
considered by NRC under the
individual-protection standard. We
requested comment on this approach.
We requested that commenters who
disagree with this approach specifically
address why it is inappropriate for the
Yucca Mountain disposal system and
make suggestions about how we might
reasonably address this issue.
Most comments supported not
establishing a collective-dose limit for
Yucca Mountain. Two comments
supported our decision not to establish
an NIR or NID level. The NAS went
further by also opposing our suggestion
that DOE estimate collective dose for
use in examining design alternatives
because it is inconsistent with the NAS
Report and with our conclusion that a
collective-dose limit is unnecessary for
the purpose of protecting the general
public. On page 57 of its report, NAS
stated:
"Earlier in this chapter, we recommend the
form for a Yucca Mountain standard based nn
individual risk. Congress has asked whether
standards intended to protect individuals
would also protect the general public in the
case of Yucca Mountain. We conclude that
the form of the standards we have
recommended would do so. provided that
policy makers and the public are prepared to
accept that very low radiation doses pose a
negligibly small risk. This latter requirement
exists for all forms of the standards,
including that in 40 CFR (part) 191. We
recommend addressing this problem by
adopting the principle of negligible
incremental risk to individuals.
"The question posed by Congress is
important because limiting individual dose
or risk does not automatically guarantee that
adequate protection is provided to the
general public for all possible repository sites
or for the Yucca Mountain site in particular.
As described in the previous section, the
individual-risk standard should be
constructed explicitly to protect a critical
group that is composed of a few persons most
at risk from releases from the repository. The
standards are then set to limit the risk to the
average member of that group. Larger
populations outside the critical group might
also be exposed to a lower, but still
significant, risk. It is possible that a higher
level of protection for this population
represented by a lower level of risk than the
one established by the standards might be
considered."
The NAS also states: "(O)n a
collective basis, the risks to future local
populations are unknowable. We
conclude that there is no technical basis
for establishing a collective population-
risk standard that would limit risk to the
nearby population of the proposed
Yucca Mountain repository" (NAS
Report p. 120)
After consideration of comments
received on this question, we have
determined that it is not necessary for
us to recommend that DOE calculate
collective dose, primarily because we
believe the individual-protection
standard will adequately protect the
general population.
f. What Do OUT Standards Assume
About the Future Biosphere? For
assessments of potential exposures,
there are two important aspects of
defining the future biosphere
characteristics: the selection of
parameter values to define the natural
characteristics of the site, and the
assumptions necessary to define the
characteristics of the potentially
exposed population. Examples of the
site's natural characteristics include
rainfall projections and the hydrologic
characteristics of the rocks through
which radionuclides may migrate.
Examples of the assumptions necessary
to define the potentially exposed
population's characteristics include
assumptions regarding population
distributions, lifestyles, and eating
habits.
In conducting required analyses of
repository performance, including the
performance assessment for determining
compliance with the standards, the
assessment for determining compliance
-------
32096 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
with the ground water standards, and
the human-intrusion analysis, DOE and
NRC may not assume that future
geologic, hydrologic, and climatic
conditions will be the same as they are
at present. We require that these
conditions be varied within reasonably
ascertainable bounds over the required
compliance period. We are imposing
this requirement, which is consistent
with the recommendation of the NAS
Report, because we believe it is possible
to reasonably bound the parameter
values in the performance assessment
that relate to these conditions.
To avoid unsupportable speculation
regarding human activities and
conditions, we believe it is appropriate
to assume that other parameters
describing human activities and
interactions with the repository (such as
the level of human knowledge and
technical capability, human physiology
and nutritional needs, general lifestyles
and food consumption patterns of the
population, and potential pathways
through the biosphere leading to
radiation exposure of humans) will
remain as they are today. Consistent
with the NAS Report, we believe there
may be an essentially unlimited number
of predictions that could be made about
future human societies, with an
unlimited number of potential impacts
on the significance of future risk and
dose effects. Regulatory decision making
involving many speculative scenarios
for future societies and impacts would
become extraordinarily difficult without
any demonstrable improvement in
public health and safety and should be
avoided as much as possible. Therefore,
DOE and NRC must assume that future
states applicable to the repository,
except for geologic, hydrologic, and
climatic conditions, will remain
unchanged from the time of licensing.
Comments we received on this subject
strongly favored our approach,
particularly with respect to changes in
natural conditions. The comments noted
that climatic variations should be
expected to occur over the time frames
for which performance projections are
made because the climate has changed
in the past. Another reason to consider
climatic changes is that these changes
could have a significant effect on
repository performance in comparison
to performance projections made using
current day conditions. Comments also
pointed out the seismically active
nature of the area and implied that DOE
should examine the effects of seismic
activity on the disposal system's
performance. Here again, we require
DOE to consider variations in geologic
conditions. The approach we proposed
on this subject is consistent with the
approach we used for the WIPP
certification (40 CFR 194.25) and NAS's
recommendations. We received no
comments opposing this approach.
g. How Far Into the Future Is It
Reasonable To Project Disposal System
Performance? The NAS recommended
that the time over which compliance
should be assessed (the compliance
period) should be "the time when the
greatest risk occurs, within the Limits
imposed by long-term stability of the
geologic environment" (NAS Report p.
7). The NAS stated that the bases for its
recommendation were technical, not
policy, considerations (NAS Report pp.
54-56). The NAS acknowledged,
however, that this is not solely a
technical decision, and that policy
considerations could be important to the
decision (NAS Report p. 56). We agree
that the selection of the compliance
period necessarily involves both
technical and policy considerations. For
example, as NAS pointed out, we could
decide that it is appropriate to establish
similar policies for managing risks
"from disposal of both long-lived
hazardous nonradioactive materials and
radioactive materials" (NAS Report p.
56). Such a decision necessarily would
result in a compliance period that is less
than the period of geologic stability. As
NAS recognized, we had to consider, in
this rulemaking, both the technical and
policy issues associated with
establishing the appropriate compliance
period for the performance assessment
of the Yucca Mountain disposal system.
We offered for comment two
alternatives for the compliance period
for the individual-protection standard.
One alternative was to adopt a
compliance period as the time to peak
dose within the period of geologic
stability. The second alternative was to
adopt a fixed time period during which
the repository must meet the disposal
standards.
For the reasons discussed below, we
selected the second alternative, which
establishes a regulatory time period of
10,000 years. Therefore, the peak dose
within 10,000 years after disposal must
comply with the individual-protection
standard. In addition, we require
calculation of the peak dose within the
period of geologic stability. The intent
of examining the disposal system's
performance after 10,000 years is to
project its longer-term performance. We
require DOE to include the results and
bases of the additional analyses in the
EIS for Yucca Mountain as an indicator
of the future performance of the
disposal system. The rule does not,
however, require that DOE meet a
specific dose limit after 10,000 years.
We have concerns regarding the
uncertainties associated with such
projections, and whether very long-term
projections can be considered
meaningful; however, existing
performance assessment results indicate
that the peak dose may occur beyond
10,000 years (see Chapter 7, Section 7.3,
of the BID). Such results may, therefore,
give a more complete description of
repository behavior. We acknowledge,
however, that these results, because of
the inherent uncertainties associated
with such long-term projections, are not
likely to be of the quality necessary to
support regulatory decisions based upon
a quantitative analysis and thus need to
be considered cautiously. In any case,
these very long-term projections will
provide more complete information on
disposal system performance.
As discussed below in section III.B.2.a
(What Limits Are There on Factors
Included in the Performance
Assessment?}, the principal tool used to
assess compliance with the individual-
protection standard is a quantitative
performance assessment. This method
relies upon sophisticated computer
modeling of the potential processes and
events leading to releases of
radionuclides from the disposal system,
subsequent radionuclide transport, and
consequent health impacts. To consider
compliance for any length of time,
several facets of knowledge and
technical capability are necessary. First,
the scientific understanding of the
relevant potential processes and events
leading to releases must be sufficient to
allow quantitative estimates of projected
repository performance. Second,
adequate analytical methods and
numerical tools must exist to
incorporate this understanding into
quantitative assessments of compliance.
Third, scientific understanding, data,
and analytical methods must be
adequately developed to allow
evaluation of performance with
sufficient robustness to judge
compliance with reasonable expectation
over the regulatory period. Finally, the
analyses must be able to produce
estimated results in a form capable of
comparison with the standards.
The NAS evaluated these
requirements for Yucca Mountain. First,
it concluded that those aspects of
disposal system and waste behavior that
depend upon physical and geologic
properties can be estimated within
reasonable limits of uncertainty. Also,
NAS believed that these properties and
processes are sufficiently understood
and boundable al over the long periods
11 We define "boundable" to mean that these
properties and processes fall within certain limits.
We are defining probabilities of occurrence below
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32097
at issue to make such calculations
possible and meaningful. The NAS
acknowledged that these factors cannot
be calculated precisely, but concluded
that there is a substantial scientific basis
for making such calculations. The NAS
concluded that by considering
uncertainties and natural variations, it
would be possible to estimate, for
example, the concentration of
radionuclides in ground water at
different locations and the times of
gaseous releases. Second, NAS
concluded that the mathematical and
numerical tools necessary to evaluate
repository performance are available or
could be developed as part of the
standard-setting or compliance-
determination processes. Third, NAS
concluded that: "[s]o long as the
geologic regime remains relatively
stable, it should be possible to assess the
maximum risks with reasonable
assurance" (NAS Report p. 69), The
NAS used the term "geologic stability"
to describe the situation where geologic
processes, such as earthquakes and
erosion, that could affect the
performance assessment of the Yucca
Mountain disposal system are active or
are expected to occur (NAS Report pp.
91-95). Based upon the use of the terms
"stable" and "boundable" throughout
the NAS Report, one can infer that NAS
applied the term "geologic stability" or
"stable" to the situation where the rate
of processes and numeric range of
individual physical properties could be
bounded with reasonable certainty. The
subsequent use of the term "stable" will
not imply static conditions or processes.
Rather, it will describe the properties
and processes that can be bounded.
Finally, NAS found that the established
procedures of risk analysis should
enable the results of each performance
simulation of the disposal system to be
combined into a single estimate for
comparison with the standard.
We previously considered the
question of the appropriate compliance
period for land disposal of SNF, HLW,
and TRU radioactive waste in the 40
CFR part 191 standards, where we
promulgated a generic compliance
period of 10,000 years. We set the 40
CFR part 191 compliance period at
10,000 years for three reasons:
(!) After that time, there is concern
that the uncertainties in compliance
assessment become unacceptably large
(50 FR 38066, 38076, September 19,
1985);
which events are considered very unlikely and need
not be considered in performance assessments. We
are not otherwise constraining DOE or NRC in
identifying bounding limits.
(2) There are likely to be no
exceptionally large geologic changes
during that time (47 FR 58196, 58199,
December 29, 1982); and
(3) Using time frames of less
thanlO,000 years does not allow for
valid comparisons among potential
sites. For example, for 1,000 years, all of
the generic sites analyzed appeared to
contain the waste approximately equally
both because of long ground water travel
times at well-selected sites {47 FR
58196, 58199, December 29,1982) and
because of the containment capabilities
of the engineered barrier systems (58 FR
66401, December 20, 1993).
The purpose of geologic disposal is to
provide long-term barriers to the
movement of radionuclides into the
biosphere (NAS Report p. 19). As
described earlier, DOE plans to locate
the Yucca Mountain repository in tuff
about 300 meters above the local water
table. When the waste packages release
nongaseous radionuclides, the released
radionuclides most likely will be
transported by water that moves through
Yucca Mountain from the surface
toward the underlying aquifer both
horizontally between individual tuff
layers and vertically downward,
through fractures in the tuff layers. Once
the radionuclides reach the aquifer, the
ground water will carry them away from
the repository in the direction of ground
water flow in the aquifer. The most
probable route for exposing humans to
radiation resulting from releases from
the Yucca Mountain disposal system is
via withdrawal of contaminated water
for local use- In the case of Yucca
Mountain, DOE estimates that most
radionuclides would not reach currently
populated areas within!0,000 years,
because of the expected performance of
the engineered barrier system (see
Chapter 7 of the BID).
This finding alone seems to indicate
that the compliance period for Yucca
Mountain should be longer than 10,000
years to be protective; however, NAS
concluded that the need to consider the
exposures when they are calculated to
occur must be weighed against the
uncertainty associated with such
calculations (NAS Report p. 72). As
discussed below, exposures could occur
over tens-of thousands to hundreds-of-
thousands of years. As the compliance
period is extended to such lengths,
however, uncertainty generally
increases and the resulting projected
doses are increasingly meaningless from
a policy perspective. The NAS stated
that there are significant uncertainties in
a performance assessment and that the
overall uncertainty increases with time.
Even so, NAS found that, "* * * there
is no scientific basis for limiting the
time period of the individual-risk
standard to 10,000 years or any other
value" (NAS Report p. 55). The NAS
also stated that data and analyses of
some of the factors that are uncertain
early in the assessment might become
more certain as the assessment
progresses(NAS Report p. 72), though
this would tend to apply more to
assessments covering very long periods
(i.e., longer than 10,000 years). Also,
NAS stated that many of the
uncertainties in parameter values
describing the geologic system are not
due to the length of time but rather to
the difficulty in estimating values of site
characteristics that vary across the site.
Thus, NAS concluded that the
probabilities and consequences of the
relevant features, events, and processes
that could modify the way in which
radionuclides are transported in the
vicinity of Yucca Mountain, including
climate change, seismic activity, and
volcanic eruptions, "are sufficiently
boundable so that these factors can be
included in performance assessments
that extend over periods on the order of
about one million years" (NAS Report p.
91). As discussed below, we believe that
such an approach is not practical for
regulatory deeisionmaking, which
involves more than scientific
performance projections using computer
models.
Today's rule requires that DOE
demonstrate compliance for a period of
10,000 years after disposal. As
discussed above, NAS concluded "there
is no scientific basis for limiting the
time period of the individual-risk
standard to 10,000 years or any other
value" (NAS Report p. 55). Despite
NAS's recommendation, we conclude
that there is still considerable
uncertainty as to whether current
modeling capability allows
development of computer models that
will provide sufficiently meaningful and
reliable projections over a time frame up
to tens-of-thousands to hundreds-of-
thousands of years. Simply because
such models can provide projections for
those time periods does not mean those
projections are meaningful and reliable
enough to establish a rational basis for
regulatory decisionmaking.
Furthermore, we are unaware of a policy
basis that we could use to determine the
"level of proof' or confidence necessary
to determine compliance based upon
projections of hundreds-of-thousands of
years into the future. The NAS indicated
that analyses of the performance of the
Yucca Mountain disposal system
dealing with the far future can be
bounded; however, a large and
cumulative amount of uncertainty is
-------
32098 Federal Register/Vol, 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
associated with those numerical
projections. Setting a strict numerical
standard at a level of risk acceptable
today for the period of geologic stability
would ignore this cumulative
uncertainty and the extreme difficulty of
using highly uncertain assessment
results to determine compliance with
that standard. We requested comments
regarding the reasonableness of
adopting the N AS-recommended
compliance period or some other
approach in lieu of the 10,000-year
compliance period, which we favor and
describe below. We also sought
comment regarding whether it is
possible to implement the NAS-
recommended compliance period in a
reasonable manner and how that could
be done.
The selection of the compliance
period for the individual-protection
standard involves both technical and
policy considerations. It was our
responsibility to weigh both during this
rulemaking. In addition to the technical
guidance provided in the NAS Report,
we considered several policy and
technical factors that NAS did not fully
address, as well as the experience of
other EPA and international programs.
As a result of these considerations, we
aie establishing a 10,000-year
compliance period with a quantitative
limit and a requirement to calculate the
peak dose, using performance
assessments, if the peak dose occurs
after 10,000 years. Under this approach,
DOE must make the performance
assessment results for the post-10,000-
year period part of the public record by
including them in the EIS for Yucca
Mountain.
In its discussion of the policy issues
associated with the selection of the time
period for compliance, NAS suggested
that we might choose to establish
consistent risk-management policies for
long-lived, hazardous, nonradioactive
materials and radioactive materials
(NAS Report p. 56). We previously
addressed the 10,000-year compliance
period in the regulation, of hazardous
waste subject to land-disposal
restrictions. Although they are subject to
treatment standards to reduce their
toxicity, some of these wastes, such as
heavy metals, can essentially remain
hazardous forever. Land disposal, as
defined in 40 CFR 268.2(c), includes,
but is not limited to, any placement of
hazardous waste in land-based units
such as landfills, surface
impoundments, and injection wells.
Facilities may seek an exemption from
land disposal restrictions by
demonstrating that there will be no
migration of hazardous constituents
from the disposal unit for as long as the
waste remains hazardous (40 CFR
268.6), This period may include not
only the operating phase of the facility,
but also what may be an extensive
period after facility closure. With
respect to injection wells, we
specifically required a demonstration
that the injected fluid will not migrate
from the injection well within 10,000
years (40 CFR I48.20(a)). We chose the
10,000-year performance period
referenced in our guidance regarding
no-migration petitions, in part, to be
equal to time periods cited in draft or
final DOE, NRC, and EPA regulations
(10 CFR part 960, 10 CFR part 60, or 40
CFR part 191, respectively) governing
siting, licensing, and releases from HLW
disposal systems. With respect to other
land-based units regulated under the
Resource Conservation and Recovery
Act (RCRA) hazardous-waste
regulations, we concluded that the
compliance period for a no-migration
demonstration is specific to the waste
and site under consideration. For
example, for the WIPP no-migration
petition, we found that "it is not
particularly useful to extend this model
beyond 10,000 years into the future
* * * (However, t)he agency does
believe * * * that modeling over a
10,000-year period provides a useful
tool in assessing the long-term stability
of the repository and the potential for
migration of hazardous constituents"
(55 FR 13068, 13073, April 6, 1990).
Thus, establishing a 10,000 year
compliance period for Yucca Mountain
is consistent with risk-management
policies that we have established for
other long-lived, hazardous materials.
Second, the individual-protection
requirements in 40 CFR part 191 (58 FR
66398, 66414, December 20, 1993) have
a compliance period of 10,000 years.
The 40 CFR part 191 standards apply to
the same types of waste and type of
disposal system as will be present at
Yucca Mountain. Therefore, the use of
a 10,000 year time period in this
regulation is consistent with 40 CFR
part 191. However, as we explained in
the What is the History of Today's
Action? section earlier in this document,
by statute the 40 CFR part 191
requirements do not apply to Yucca
Mountain (WIPP LWA, section 8(b)).
Nevertheless, we deem this consistency
appropriate'because both sets of
standards apply to the same types of
waste. Moreover, though the WIPP LWA
exempts Yucca Mountain from the 40
CFR part 191 standards, it does not
prohibit us from imposing standards on
Yucca Mountain that are similar to the
40 CFR part 191 standards, if, as
discussed previously, we determine in
this rulemaking that the imposition of
such standards is appropriate. The
question of uncertainties over long time
frames and the use of performance
projections over those time frames for
regulatory decisiomnaking has been
examined a number of times in our
rulemaking (40 CFR parts 191 and 194)
with a consistent conclusion that 10,000
years is the appropriate choice for a
compliance period.
Although 40 CFR part 191 itself does
not directly apply to Yucca Mountain,
the necessity to identify a generic
compliance period is an important
component of the development of
radioactive waste standards, including
the Yucca Mountain standards. In a
regulatory approval process, a judgment
is necessary about the technical
reliability of repository performance
projections. This consensus would
involve the applicant, the regulatory
authority, and the technical community
in general. In the face of increasing
uncertainties in projecting repository
performance over hundreds-of-
thousands of years, the potential for
technical consensus on the reliability of
these projections would decrease
sharply. This decrease would lead to a
dramatic increase in the difficulty of
making a compliance decision related to
such an extended time period. In setting
the compliance period in 40 CFR part
191 at 10,000 years, we addressed the
issue of increasing uncertainty by
having a fixed time period rather than
requiring that the time period be
determined individually for any
repository undergoing evaluation.
Third, we are concerned that there
might be large uncertainty in projecting
human exposure due to releases from
the repository over extremely long
periods. We agree with NAS's
conclusion that it is possible to evaluate
the performance of the Yucca Mountain
disposal system and the surrounding
lithosphere within certain bounds for
relatively long periods. However, we
believe that NAS might not have fully
addressed two aspects of uncertainty.
One of the aspects of uncertainty
relates to the impact of long-term
natural changes in climate and its effect
upon choosing an appropriate RMEI.
For extremely long periods, major
changes in the global climate, for
example, a transition to a glacial
climate, could occur (see Chapter 7 of
the BID). We believe, however, that over
the next 10,000 years, the biosphere in
the Yucca Mountain area probably will
remain, in general, similar to present-
day conditions due to the rain-shadow
effect of the Sierra Nevada Mountains,
which lie to the west of Yucca Mountain
(see Chapter 7 of the BID). As discussed
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32099
by NAS, however, for the longer periods
contemplated for the alternative of time
to peak dose, the global climate regime
is virtually certain to pass through
several glacial-interglacial cycles, with
the majority of time spent in the glacial
state [NAS Report p. 91). These longer
periods would require the specification
of exposure scenarios that would not be
based upon current knowledge or
cautious, but reasonable, assumptions,
but rather upon potentially arbitrary
assumptions. The NAS indicated that it
knew of no scientific basis for
identifying such scenarios (NAS Report
p. 96). It is for these reasons that such
extremely long-term calculations are
useful only as indicators, rather than
accurate predictors, of the long-term
performance of the Yucca Mountain
disposal system (IAEA TECDOC-767, p.
19, 1994, Docket No. A-95-12, Item II-
A-5).
The other aspect of uncertainty
concerns the range of possible biosphere
conditions and human behavior. As
IAEA noted, beyond 10,000 years it may
be possible to make general predictions
about geological conditions; however,
the range of possible biospheric
conditions and human behavior is too
wide to allow "reliable modeling"
(IAEA-TECDOC-767, p. 19, Docket No.
A-95-12, Item H-A-5). It is necessary to
make certain assumptions regarding the
biosphere, even for the 10,000-year
alternative, because 10,000 years
represents a very long compliance
period for current-day assessments to
project performance. For example, it is
twice as long as recorded human history
(see What Do Our Standards Assume
About the Future Biosphere?, section
III.B.l.f, earlier in this document). For
periods approaching the 1,000,000 years
that NAS contemplated under the peak-
dose alternative, even human
evolutionary changes become possible.
Thus, reliable modeling of human
exposure may be untenable and
regulation to the time of peak dose
within the period of geologic stability
could become arbitrary. Again, the
rational basis necessary for regulatory
decisionmaking would be difficult or
impossible to achieve because of the
speculative assumptions that would be
involved.
Fourth, many international geologic
disposal programs use a 10,000-year
period for assessing repository
performance (see, e.g., Chapter 3 of the
BID, Docket No. A-9S-12, Item IE-B-2
orGAO/RCED-94-172, 1994, Docket
No. A-95-12, Item V-A-7). These
disposal programs also have examined
this question and have opted to use a
fixed time rather than one based only on
a site-specific compliance period.
Finally, an additional complication
associated with the time to peak dose
within the period of geologic stability is
that it could lead to a period of
regulation that has never been
implemented in a national or
international radiation regulatory
program. Focusing upon a 10,000-year
compliance period forces more
emphasis upon those features over
which humans can exert some control,
such as repository design and
engineered barriers. Those features, the
geologic barriers, and their interactions
define the waste isolation capability of
the disposal system. By focusing upon
an analysis of the features that humans
can influence or dictate at the site, it
may be possible to influence the timing
and magnitude of the peak dose, even
over times longer than 10..000 years.
Based on the extensive public
comment, consistency with other EPA
radioactive and non-radioactive waste
disposal programs, and a consideration
of the numerous uncertainties
associated with projecting repository
performance over extended time
periods, our final rule establishes the
following requirements for the
individual-protection standard and the
human-intrusion analysis. For the
individual-protection standard, a
10,000-year performance assessment is
required for comparison against the 15
mrem standard. In addition, a post-
10,000-year analysis of peak dose
incurred by the RMEI is to be included
in the EIS for Yucca Mountain, but js
not to be held to a particular dose limit.
We view the post-10,000-year analysis
as an indicator of long-term
performance that provides more
complete information. For the human-
intrusion analysis, DOE must determine
the earliest time at which the human
intrusion specified in the standard will
occur. Should the intrusion occur at or
before 10,000 years after disposal, DOE
must demonstrate that the RMEI
receives no more than 15 mrem/yr as a
result of the intrusion (again, analytical
results beyond 10,000 years are not
judged against a dose limit, but must be
included in the EIS). Should the
intrusion occur after 10,000 years, DOE
must include the analysis in the EIS for
Yucca Mountain as an indicator of long-
term disposal system performance.
Public comment supported a
compliance period that ranged from
10,000 years to a million years and
beyond (i.e.; no time limitation).
Comments supporting the ID,000-year
time period expressed concern that such
a time period was the longest time over
which it is possible to obtain
meaningful modeling results. Some
comments agreed with our position on
the reliability of dose calculations well
in excess of 10,000 years. Other
comments noted that, aside from the
unprecedented nature of compliance
periods exceeding 10,000 years, the
greater uncertainties present at such
times only serve to complicate the
licensing process with no clear cut
greater public health benefit. A few
comments agreed that, because there
likely will be radiation doses to
individuals beyond 10,000 years, DOE
should calculate peak dose, within the
time period of geologic stability, and
include these doses in the Yucca
Mountain EIS.
Numerous comments suggested that
the compliance period should extend to
times beyond 10,000 years. Foremost
among these comments, NAS suggested
a compliance period that would extend
to the time of peak dose or risk, within
the period of geologic stability for Yucca
Mountain (as long as one million years),
based on scientific considerations.
Though NAS based its recommendation
on scientific considerations, it
recognized that such a decision also has
policy aspects (NAS Report, p. 56), and
that we might select an alternative more
consistent with previous Agency policy.
We believe the unprecedented nature of
a compliance period beyond 10,000
years was very persuasive and related
strongly to developing a meaningful
standard that is reasonable to
implement. We also harbored strong
concerns related to uncertainty in
projecting human radiation exposures
over extremely long time periods, for
the reasons mentioned earlier.
Some comments suggested that the
compliance period of the standard
should be comparable to the amount of
time that the materials to be emplaced
in the Yucca Mountain repository will
remain hazardous. While the hazardous
lifetime of radioactive waste is
important, it is but one of a variety of
factors that must be considered in
projecting the potential risks from
disposal. The ability of the disposal
system to isolate such long-lived
materials relates to the retardation
characteristics of the whole
hydrogeological system within and
outside the repository, the effectiveness
of engineered barriers, the
characteristics and lifestyles associated
with the potentially affected population,
and numerous other factors in addition
to the hazardous lifetime of the
materials to be disposed.
Thus, for a variety of technical and
policy reasons, we believe that a 10,000-
year compliance period is meaningful,
protective, and practical to implement.
We also believe that its use will result
in a robust disposal system that will
-------
32100 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
protect public health and the
environment for time periods exceeding
10,000 years. We have included a
10,000-year compliance period in
regulations for non-radioactive
hazardous waste. A 10,000-year
compliance period for Yucca Mountain,
in conjunction with the requirements of
our existing generally applicable
standard at 40 CFR part 191, ensures
that SNF, HLW, and TRU radioactive
wastes disposed anywhere in the United
States have the same compliance period.
Imposing a compliance period beyond
10,000 years would be unprecedented
both nationally and internationally.
Further, such an action would carry
significant and unmanageable
uncertainties. Moreover, provisions to
consider radiation dose impacts beyond
10,000 years as a part of the
environmental impact review process
provide more complete information on
long-term disposal system performance.
We believe this approach provides the
appropriate balance that allows for
meaningful consideration of the issues
related to 10,000-year and post-10,000-
year aspects of disposal system
performance.
2. What Are the Requirements for
Performance Assessments and
Determinations of Compliance?
(§§ 197.20, 197.25, and 197.303
The NRC must decide whether to
license the Yucca Mountain disposal
system. It must make that decision
based upon whether DOE has
demonstrated compliance with our 40
CFR part 197 standards. We proposed
the quantitative analysis underlying that
decision will be a performance
assessment (as defined in § 197.12). The
DOE and NRC must also make some
decisions about what factors to include
in the performance assessments, and
how extensive those assessments must
be to satisfactorily demonstrate
compliance. We have addressed some of
these performance assessment aspects in
our proposal and final rule.
a. What Limits Are There on Factors
Included in the Performance
Assessments? We proposed that the
performance assessment exclude natural
features, events, and processes based on
the probability of occurrence. We based
our proposed requirements for
performance assessment on a review of
NAS's recommendations, our
knowledge regarding the extensive
performance assessment work that DOE
and NRC have undertaken regarding the
Yucca Mountain site, and consistency
with 40 CFR part 191 and its application
in the WIPP certification. We also
require NRC to determine, taking into
consideration that performance
assessment, whether the disposal
system's projected performance
complies with § 197.20. Projecting
repository performance is the major tool
to be used to develop information that
will be used to make compliance
decisions relative to our standards. To
provide the necessary context for these
assessments to generate results for
regulatory decisionmaking, we must
specify sufficient details to assure the
standards are implemented as we intend
through the use of performance
assessments. We have specified only
what we believe to be the minimum
detail necessary. The remainder we
believe should be left to NRC to
determine, consistent with its
implementing responsibilities and
decisionmaking authority.
For repository performance
assessments, our standards also require:
(1) That DOE exclude from
performance assessments those natural
features, events, and processes whose
likelihood of occurrence is so small that
they are very unlikely, which are those
that DOE and NRC estimate to have less
than a 1 in 10,000 (1 x 10~4) chance of
occurring during the 10,000 years after
disposal. Probabilities below this level
are associated with events such as the
appearance of new volcanoes outside of
known areas of volcanic activity or a
cataclysmic meteor impact in the area of
the repository. We believe there is little
or no benefit to public health or the
environment from trying to regulate the
effects of such very unlikely events;
(2) Unlikely events with probabilities
higher than stated in (1) above may be
excluded from analyses for the human
intrusion and ground water protection
standards. We leave it to NRC to set the
probability limit for these unlikely
events in its implementing regulations;
and
(3) That the performance assessment
need not evaluate the releases from
features, events, processes, and
sequences of events and processes
estimated to have a likelihood of
occurrence greater than 1 x 1Q~* of
occurring during the 10,000 years
following disposal, if there is a
reasonable expectation that the results
of the performance assessment would
not be changed significantly by such
omissions. As necessary, NRC may
provide DOE with specific guidance
regarding scenario selection and
characterization to assure that DOE does
not exclude features, events, or
processes inappropriately.
We received only a few comments on
the question of including low
probability events; however, the
comments we Tecewed supported OUT
proposal. The comments also pointed
out some potential contusion in the
terms we used in describing unlikely
versus very unlikely features, events,
and processes. Our intent is to establish
that there is no need to include, in the
performance assessments used to
demonstrate compliance with the
individual-protection standard, features,
events, and processes, and sequences of
events and processes, with probabilities
of less than 1 x 10~4 chance of
occurring ia the next 10,000 years. We
consider it unlikely that features,
events, and processes with such low
probabilities of occurrence will occur.
We intended to establish another
demarcation for excluding unlikely
features, events, and processes with a
higher probability than stated above but
that still have a low probability of
occurrence. The DOE must include
processes and events in this second
category in the assessments for the
individual-protection standard, unless
NRC determines that excluding them
would not affect the results of the
assessments. The DOE may, however,
exclude them from consideration in
demonstrating compliance with the
human-intrusion and ground water
protection standards. We did not
establish a particular probability level
for these unlikely features, events, and
processes. Instead, we deferred this
decision to the implementing authority
in § 197.36 of our final rule.
The comments we received on this
question supported our contention that
the geologic record is the best source of
evidence for the frequency and
magnitude of natural features, events,
and processes that could affect
repository performance, and that the
geologic record is best preserved in the
relatively recent past. More specifically,
some comments suggested that the
Quaternary Period shcruld be the time
frame over which DOE should examine
evidence for rates and magnitudes of
natural features, events, and processes.
Because the Quaternary Period includes
episodes of glaciation, it provides a
means to estimate the potential effects
of future climate variations. Further, we
believe that the Period's duration
(approximately two million years)
provides an adequate time frame for
estimating the frequency and severity of
past seismic activity in the repository
area. The NAS in its recommendations
indicated that the repository area could
be assumed to be "geologically stable"
over a period of one million years for
the purpose of bounding natural
features, events, and processes. We
believe that the Quaternary Period is a
sufficiently long period of the geologic
record to allow DOE to make reasonable
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32101
estimates of natural features, events, and
processes. We chose not to identify a
specific time frame in the regulatory
language. We leave this choice to the
implementing authority.
We allow the exclusion of unlikely
natural features, events, and processes
from both the ground water and human-
intrusion assessments. The approach for
the ground water protection
requirements is consistent with subpart
C of 40 CFR part 191, "Environmental
Standards for Ground-Water
Protection." The approach for the
human-intrusion analysis is consistent
with NAS's recommendation (see the
What Is the Standard far Human
Intrusion? section later in this
document). We requested public
comment regarding whether this
approach is appropriate for Yucca
Mountain. See the response to Question
#10 in section IV later in this document
and the Response to Comments
document for more information.
b. What Limits Are There on DOE's
Elicitation of Expert Opinion? We
requested public comment on whether
we should include requirements on the
use of expert opinion and, if so, what
those requirements should be. We
consider it likely, given the long time
frames involved and the significant
uncertainties in the likelihood of
features, events, processes, and
sequences of events and processes
affecting the Yucca Mountain disposal
system, that DOE will find it useful to
obtain expert opinion to help it arrive at
cautious but reasonable estimates of the
probability of future occurrence of these
features, events, processes, and
sequences of events and processes. We
also expect DOE to find expert opinion
useful in assessing available
performance assessment models, or in
evaluating the uncertainties associated
with the variation of parameter values.
In requesting public comment on this
issue, we distinguished between expert
judgment, which often is obtained
informally, and expert elicitation, in
which a more formal process is used.
We focused on expert elicitation, and
considered including one or all of the
following requirements: (1) NRC must
consider the source and use of the
information so gathered; (2) we would
have expected NRC to assure that, to the
extent possible, experts with both
expertise appropriate for the subject
matter and independence from DOE will
be on the expert elicitation panel
consulted to judge the validity and
adequacy of the model[s) or value(s) for
use in a compliance assessment; and [3)
we would have expected that, when
DOE presents information to the expert
elicitation panel, it should do so in a
public meeting, and qualified experts,
such as representatives of the States of
Nevada and California, should be given
an opportunity to present information.
The comments we received were
uniformly opposed to our setting
requirements to address expert opinion.
There was general agreement among
commenters that it would be more
appropriate for NRC to use the licensing
process to address any requirements
relating to expert elicitation. Some
commenters referred to NRC's NUREG—
1563 ("Branch Technical Position on
the Use of Expert Elicitation in the
High-Level Radioactive Waste
Program"), and to the fact that DOE has
used it on several occasions. These
comments reinforced our opinion that
issuing requirements would be an
implementation function better left to
NRC. We do not expect to issue
guidance on this topic, although we
reserve the right to do so. We also
recognize that such guidance would not
be binding, unless it is promulgated by
notice and comment rulemaking.
One comment suggested that we
restrict the form the expert elicitation
could take. The comment stated that it
is inappropriate to estimate parameter
values using Delphi surveys or other
similar techniques that tend to "exclude
the public from vital areas of debate."
Given that we leave the expert
elicitation process to NRC and DOE, we
choose not to address only this one
particular aspect of that process because
we believe that it would be inconsistent
to impose any specific requirements on
how DOE and NRC should use expert
opinion. We believe that NRC and DOE
are sufficiently sensitive to public
opinion regarding the licensing of Yucca
Mountain to avoid the appearance of
secrecy or targeted polling of experts to
obtain a specific outcome. Therefore,
our rule does not address any aspects of
DOE's ability to use expert elicitation.
c. What Level of Expectation Will
Meet OUT Standards? We use the
concept of "reasonable expectation" in
these standards to reflect our intent
regarding the level of "proof' necessary
for NRC to determine whether the
projected performance of the Yucca
Mountain disposal system complies
with the standards (see §§197.20,
197.25, and 197.30). We intend for this
term to convey our position that
unequivocal numerical proof of
compliance is neither necessary nor
likely to be obtained for geologic
disposal systems. We believe
unequivocal proof is not possible
because of the extremely long time
periods involved and because disposal
system performance assessments require
extrapolations of conditions and the
actions of processes that govern disposal
system performance over those long
time periods. The NRC has used a
similar qualitative test, "reasonable
assurance," for many years in its
regulations, and has proposed applying
this concept in its Yucca Mountain
regulations [proposed 10 CFR part 63).
However, the NRC approach was taken
from reactor licensing, which focuses on
engineered systems with relatively short
lifetimes, where performance
projections can be verified and if
necessary corrective actions are
possible. We believe that for very long-
term projections where confirmation is
not possible, involving the interaction of
natural systems with engineered
systems complicated by the
uncertainties associated with the long
time periods involved, an approach that
recognizes these difficulties is
appropriate. Although NRC has adapted
the reasonable assurance approach from
the reactor framework and has applied
it successfully in regulatory situations
related to facility decommissioning and
shallow-land waste burial, it has not
been applied in a situation as complex
as the Yucca Mountain disposal system.
We believe that reasonable expectation
provides an appropriate approach to
compliance decisions; however, with
respect to the level of expectation
applicable in the licensing process, NRC
may adopt its proposed alternative
approach. We expect that any
implementation approach NRC adopts
will incorporate the elements of
reasonable expectation listed in
§197.14. A more thorough discussion of
our intent concerning the application of
reasonable expectation is given below
and a more exhaustive discussion of the
subject is presented in the Response to
Comments document for this regulation.
We intend that the information in
§197.14 of the rule and discussions of
reasonable expectation presented below
and in the Response to Comments
document will provide the necessary
context for implementation of this
concept.
The primary means for demonstrating
compliance with the standards is the
use of computer modeling to project the
performance of the disposal system
under the range of expected conditions.
These modeling calculations involve the
extrapolation of site conditions and the
interactions of important processes over
long time periods, extrapolations that
involve inherent uncertainties in the
necessarily limited amount of
information that can be collected
through field and laboratory studies and
the unavoidable uncertainties involved
in simulating the complex and time-
-------
32102 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
variable processes and events involved
in long-term disposal system
performance. Simplifications and
assumptions are involved in these
modeling efforts out of necessity
because of the complexity and time
frames involved, and the choices made
will determine the extent to which the
modeling simulations realistically
simulate the disposal system's
performance. If choices are made that
make the simulations very unrealistic,
the confidence that can be placed on
modeling results is very limited.
Inappropriate simplifications can mask
the effects of processes that will in
reality determine disposal system
performance, if the uncertainties
involved with these simplifications are
not recognized. Overly conservative
assumptions made in developing
performance scenarios can bias the
analyses in the direction of
unrealistically extreme situations,
which in reality may he highly
improbable, and can deflect attention
from questions critical to developing an
adequate understanding of the expected
features, events, and processes. For
example, a typical approach to
addressing areas of uncertainty is to
perform "bounding analyses" of
disposal system performance. If the
uncertainties in site characterization
information and the modeling of
relevant features, events, and processes
are not fully understood, results of
bounding analyses may not be bounding
at all. The reasonable expectation
approach is aimed simply at focusing
attention on understanding the
uncertainties in projecting disposal
system performance so that regulatory
decision making will be done with a full
understanding of the uncertainties
involved.
We received comments both
supporting and opposing the concept of
"reasonable expectation" and its
application to the Yucca Mountain
standards. Comments in favor of the
approach agreed that the consideration
of uncertainty is extremely important to
a proper perspective on the degree of
confidence possible for projections of
disposal system performance over the
long time frames involved in assessing
repository performance. Comments
against the concept voiced variations on
three basic concerns: (1) That the
concept is "new," "untested," and of
"dubious legal authority" in the
regulatory framework; (2) that it implies
that less rigorous, and therefore
unacceptable, science and analysis
would result from the use of reasonable
expectation; and (3) that the choice of
approach to compliance decision
making is solely an implementation
concern that we should leave to NRC.
With respect to the legal authority and
use of the reasonable expectation
concept in the regulatory process, we
believe that the reasonable expectation
concept is well established in both the
regulatory language in standards, as
well as in actual application to deep
geologic disposal of radioactive wastes,
and has been judicially tested. We
developed the "reasonable expectation"
approach in the context of developing
40 CFR part 191, the generic standards
for land disposal of SNF, HLW, and
TRU radioactive waste, and more
importantly the concept has been
applied successfully in the EPA
certification of the Waste Isolation Pilot
Plant (WIPP), a deep geologic repository
for TRU radioactive wastes. The WIPP
repository is to date the only deep
geologic repository for radioactive
wastes in the United States that has
been carried through a regulatory
approval process. Therefore, we believe
that the reasonable expectation concept
is neither "new" nor "untried", nor of
"dubious legal authority" in the
geologic repository regulatory
experience. In fact, the use of reasonable
expectation for the application to
geologic disposal has been upheld in
court (Natural Resources Defense
Council, Inc. versus U.S. E.P.A. (824
F.2d 1258, 1293 (IstCir. 1987))).
In contrast, the reasonable assurance
concept was developed and applied
many times in the context of reactor
licensing—not in the context of deep
geologic disposal efforts—and has not
been used in a regulatory review and
approval process for a deep geologic
disposal system. The judicial decision
cited in one comment refers to the use
of reasonable assurance in the context of
reactor licensing, not in the context of
deep geologic disposal. While the
reasonable assurance concept has an
established record of successful
application and judicial approval in
reactor licensing, it is in fact largely
untried in the arena of geologic
disposal.
Some comments suggested our
approach would allow the use of less
rigorous science to the assessment of
disposal system performance in
licensing. This perception may have
arisen from our choice of wording in the
proposal, where we stated that NRC may
elect to use a more "stringent"
approach. Such an interpretation was
not our intent: the full text of our
statement is that NRC may impose
requirements that are "more stringent"
than the "minimum requirements for
implementation" that our rule
establishes; in addition, we clearly
stated that reasonable expectation "is
less stringent than the reasonable
assurance concept that NRC uses to
license nuclear power plants" {proposed
§ 197.i4(b), emphasis added). However,
we will clarify our meaning here.
Performance projections for deep
geologic disposal require the
extrapolation of parameter values (site
characteristics related to performance)
and performance calculations
(projections of radionuclide releases and
transport from the repository) over very
long time frames that make these
projections fundamentally not
conformable, in contrast to the situation
of reactor licensing where projections of
performance are only made for a period
of decades and confirmation of these
projections is possible through
continuing observation. In this sense, a
reasonable expectation approach to
repository licensing would be
necessarily "less stringent" than an
approach to reactor licensing. We
therefore must disagree with these
comments that reasonable expectation
requires less rigorous proof than NRC's
reasonable assurance approach.
We do not believe that the reasonable
expectation approach either encourages
or permits the use of less than rigorous
science in developing assessments of
repository performance for use in
regulatory decision making. On the
contrary, the reasonable expectation
approach takes into account the
inherent uncertainties involved in
projecting disposal system performance,
rather than making assumptions which
reflect extreme values instead of the full
range of possible parameter values. It
requires that the uncertainties in site
characteristics over long time frames
and the long-term projections of
expected performance for the repository
are fully understood before regulatory
decisions are made. This approach has
a number of implications relative to the
data and analyses that would be used in
making regulatory decisions. Cautious
use of bounding assessments is implied
since sufficient understanding of
uncertainties must be developed to be
sure such analyses are truly bounding.
Performance scenarios should be
developed realistically without omitting
important components simply because
they may be difficult to quantify with
high accuracy, or always assuming
worst case values in the absence of
information. Elicited values for relevant
data should not be substituted for actual
field and laboratory studies when they
can be reasonably performed, simply to
conserve resources or satisfy scheduling
demands. The gathering of credible
information that would allow a better
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32103
understanding of the uncertainties in
site characterization data and
engineered barrier performance that
would bear on the long-term
performance of the repository should
not be subjugated simply for
convenience. We do not believe that
reasonable expectation in any way
encourages less than rigorous science
and analysis. In contrast, adequately
understanding the inherent
uncertainties in projecting repository
performance over the time frames
required must involve a rigorous
scientific program of site
characterization studies and laboratory
testing.
Some comments expressed the
opinion that our use of the reasonable
expectation approach intrudes
inappropriately into the area of
implementation, which is the province
of NRC. We do not believe that is the
case. We have included the concept of
reasonable expectation in the Yucca
Mountain standards to provide a
necessary context for understanding the
standards and as context for the
implementation of the licensing process
NRC will perform. Projecting disposal
system performance involves the
extrapolation of physical conditions and
the interaction of natural processes with
the wastes for unprecedented time
frames in human experience, i.e., many
thousands of years. In this sense, the
projections of the disposal system's
long-term performance cannot be
confirmed. Not only is the projected
performance of the disposal system not
subject to confirmation, the natural
conditions in and around the repository
site will vary over time and these
changes are also not subject to
confirmation, making their use in
performance assessments equally
problematical over the long-term (see
Chapter 7 of the BID). In light of these
fundamental limitations on assessing
the disposal system's long-term
performance, we believe that the
approach used to evaluate disposal
system performance must take into
account the fundamental limitations
involved (including the basic guidance
given in § 197.14), and not hold out the
prospect of a greater degree of "proof
than in reality can be obtained.
Relative to implementation, the
primary task for the regulatory authority
is to examine the performance case put
forward by DOE to determine "how
much is enough" in terms of the
information and analyses presented, i.e.,
implementation involves how
regulatory authority determines when
the performance case has been
demonstrated with an acceptable level
of confidence. We have proposed no
specific measures in our standards for
that judgment. We have not specified
any confidence measures for such
judgments or numerical analyses, nor
prescribed analytical methods that must
be used for performance assessments,
quality assurance measures that must be
applied, statistical measures that define
the number or complexity of analyses
that should be performed, nor have we
proposed any assurance measures in
addition to the numerical limits in the
standards. We have specified only that
the mean of the dose assessments must
meet the exposure limit, without
specifying any statistical measures for
the level of confidence necessary for
compliance. We believe that measure is
a minimal level for compliance
determination, and we selected it to be
consistent with the individual
protection requirement we applied for
the WIPP certification (40 CFR
194.55(f)). For the WIPP certification,
EPA was also the implementing agency,
and in 40 CFR part 194 we also
included implementation requirements,
including statistical confidence
measures for the assessments and
analytical approaches (§§ 194.55(b), (d],
(f)) along with quality assurance
requirements (§ 194.22), other assurance
requirements (§ 194.41), requirements
for modeling techniques and
assumptions (§§ 194.23 and 25), use of
peer review and expert judgment
(§§ 194.26 and 194.27). We have not
incorporated a similar level of detail in
the Yucca Mountain standards because
we believe we must specify only what
is necessary to provide the context for
implementation. We believe that our
reasonable expectation approach
provides a necessary context for
understanding the intent of the
standards and for its implemsntation.
We have provided guidance statements
in the standards (§197.14) relative to
the approach that we believe
appropriately address the inherent
uncertainties in projecting the
performance of the Yucca Mountain
disposal system. The implementing
agency is responsible for developing
and executing the implementation
process and, with respect to the level of
expectation applicable in the licensing
process, is free to adopt an approach it
believes is appropriate, but we believe
whatever approach is implemented
must incorporate the aspects of
reasonable expectation we have
described in the standards and
amplified upon in the Response to
Comments document.
d. Are There Qualitative
Requirements To Help Assure
Protection? In the preamble to our
proposed standards (64 FR 46998), we
requested comment upon whether it is
appropriate for us to establish assurance
requirements in this final rule and if so,
what those requirements should be. The
majority of public comments on the
issue stated that it was unnecessary for
us to include assurance requirements in
this rule. The commenters also generally
stated that the inclusion of such
requirements is an implementation
matter that is properly within NRC's
jurisdiction. No comments suggested
what, if any, assurance requirements we
should include in this final rule.
Therefore, based upon the public
comments we received regarding this
rule, the provisions in 40 CFR part 191,
and the provisions of NRC's proposed
10 CFR part 63, we did not include
assurance requirements in this rule,
though we believe we have the authority
to do so pursuant to the AEA and the
EnP A. For example, our generally
applicable standards for the disposal of
SNF, HLW, and TRU radioactive wastes
(40 CFR part 191, 58 FR 66402,
December 20, 1993; 50 FR 38073 and
38078, September 19,1985) require the
consideration of assurance
requirements. The assurance
requirements in 40 CFR part 191,
however, do not apply to facilities that
NRC regulates, based upon the
understanding between EPA and NRC
that NRC would include them in its
licensing regulations in 10 CFR part 60,
The NRC is the licensing agency for
Yucca Mountain; therefore, at first
glance it appears that requiring
assurance requirements at Yucca
Mountain would be inconsistent with
our approach in 40 CFR part 191. The
EnP A, however, mandates that we set
site-specific standards for Yucca
Mountain. We believe, therefore, that
we could include assurance
requirements in this rule. Because
NRC's proposed licensing criteria (see
10 CFR 63.102, 63.111, and 63.113; 64
FR 8640, 8674-8677, February 22,1999)
contain requirements similar to the
assurance requirements in 40 CFR part
191 for multiple barriers, institutional
controls, monitoring, and the
retrievability of waste from Yucca
Mountain, we believe that it is
unnecessary for us to include similar
requirements in this rule. We encourage
NRC to include the assurance
requirements in the proposed 10 CFR
part 63 (64 FR 8640), or requirements
similar to those in 40 CFR part 191, in
its final licensing regulations for Yucca
Mountain.
-------
32104 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
3. What Is the Standard for Human
Intrusion? (§197.25)
We adopted NAS's suggested starting
point for a human-intrusion scenario.
As NAS recommends, our standard
requires a single-borehole intrusion
scenario based upon Yucca Mountain-
specific conditions. The intended
purpose of analyzing this scenario
"* * * is to examine the site-and
design-related aspects of repository
performance under an assumed
intrusion scenario to inform a
qualitative judgment" (NAS Report p.
111). The assessment would result in a
calculated RMEI dose arriving through
the pathway created by the assumed
borehole (with no other releases
included). Consistent with the NAS
Report, we also require "that the
conditional risk as a result of the
assumed intrusion scenario should be
no greater than the risk levels that
would be acceptable for the
undisturbed-repository case" (NAS
Report p. 113). We interpreted NAS's
term "undisturbed" to mean that the
Yucca Mountain disposal system is not
disturbed by human intrusion but that
other processes or events that are likely
to occur could disturb the system.
We require that the human-intrusion
analysis of disposal system performance
use the same methods and RMEI
characteristics for the performance
assessment as those required for the
individual-protection standard, with
two exceptions. The first exception is
that the human-intrusion analysis
would exclude unlikely natural features,
events, and processes. The second
exception is that the analysis only
would address the releases occurring
through the borehole {see the What Are
the Requirements for Performance
Assessments and Determinations of
Compliance? section earlier in this
document).
As noted earlier, our rule uses the
same RMEI description for this analysis
and scenario as in the assessment for
compliance with the individual-
protection standard. It is possible that
one could postulate that an individual
occupies a location above the repository
footprint in the future and is impacted
by radioactive material brought to the
surface during an intrusion event;
however, the level of exposure of such
an individual would be independent of
whether the repository performs
acceptably when breached by human
intrusion in the manner prescribed in
the scenario. Movement of waste to the
surface as a result of human intrusion is
an acute action. The resulting exposure
is a direct consequence of that action.
Thus, we interpret the NAS-
recommended test of "resilience" to be
a longer-term test as measured by
exposures caused by releases that occur
gradually through the borehole, not
suddenly as with direct removal. In
addition, the effects of direct removal
depend on the specific parameters
involved with the drilling, not on the
disposal system's containment
characteristics. We also require that the
test of the disposal system's resilience
be the dose incurred by the same RMEI
used for the individual-protection
standard. This approach is consistent
with NAS's recommendation.
The DOE must determine when the
intrusion would occur based upon the
earliest time that current technology and
practices could lead to waste package
penetration without the drillers noticing
the canister penetration. In general, we
believe that the time frame for the
drilling intrusion should be within the
period that a small percentage of the
waste packages have foiled but before
significant migration of radionuclides
from the engineered barrier system has
occurred because, based upon our
understanding of drilling practices, this
period would be about the earliest time
that a driller would not recognize an
impact with a waste package. Our
review of information about drilling and
experiences of drillers indicates that
special efforts, such as changing to a
specialized drill bit, would likely be
necessary to penetrate intact, non-
degraded waste packages of the type
DOE plans to use. As stated earlier, DOE
would determine the timing as part of
the licensing process. The DOE's waste-
package performance estimates indicate
that a waste package would be
recognizable to a driller for at least
thousands of years (see Chapter 8 of the
BID).
We requested comment regarding how
much the human-intrusion analysis.will
add to protection of public health. Also,
given current drilling practice in the
vicinity of Yucca Mountain, we sought
comment regarding whether our
stylized, human-intrusion scenario is
reasonable.
Comments on our intrusion scenario
focused on a number of concerns. Some
comment expressed opinions that the
intrusion scenario was unrealistic since
actual drilling to tap ground water
would more probably be done not from
the crest of Yucca Mountain but rather
from the adjacent valley floors. Other
comments stated that multiple drilling
intrusions should be assumed rather
than only one, and offered alternative
scenarios for intrusion frequency and
purposes other than tapping ground
water. Some comments acknowledged
that the scenario was an adequate test of
repository resiliency independent of the
question of attempting to predict future
activities, and that the difficulty of
reliably predicting future activities and
human intention were unavoidable, as
NAS concluded. Some comment stated
that the probability of such an intrusion
was so remote as to make the scenario
useless for any type of repository
analysis, while some comment
expressed opinions that the entire
question of human intrusion was an
implementation issue that should be left
to the discretion of NRC. Detailed
responses to comments we received on
the human intrusion question is found
in the Response to Comments document
accompanying this rule. Our response to
some of the most common issues raised
in the comments is given below.
A number of comments criticized the
stylized definition of the scenario on the
grounds it did not address the reality of
the site location and resource potential.
A convincing case can be made that
intrusion is unlikely because of the low
resource potential of the immediate
Yucca Mountain area (see BID, Chapter
8), and that actual drilling to tap the
underlying ground water would most
probably be done in the valleys adjacent
to Yucca Mountain, as some comments
pointed out. We recognize these
conditions and the relatively low
resource potential; however, as NAS
pointed out, there is no scientifically
defensible basis to preclude intrusion
(NAS Report p. 111). For this reason, the
panel recommended that an intrusion
scenario should be assessed separately
from the expected repository
performance case (NAS Report p. 109),
and that a stylized intrusion scenario
consisting of one borehole penetration
should be considered (NAS Report p.
112) as a test of repository resilience to
modest intrusion (p. 113). We agree
with the NAS conclusions in this
regard. As we have pointed out early in
the preamble, releases and consequent
exposures can come from either the
gradual degradation of the disposal
system under expected conditions or
through disruption, most notably by
human activities. Since intrusion cannot
unequivocally be ruled out, and
exposures can result from intrusions
that release radionuclides, we believe it
is necessary to consider human
intrusion in the context of a repository
standard focused on public health
protection, even though the resource
potential at the site is low. The nature
of the intrusion, how it is analyzed and
how it should be evaluated in the
regulatory context, are the next issues to
consider after the basic need to assess a
human intrusion scenario is recognized.
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32105
The NAS was very specific in its
recommendations about assessing
human intrusion. The panel
recommended that the intrusion
scenarios be considered in the EPA's
rulemaking process (NAS Report p. 109)
and that "EPA should specify in its
standard a typical intrusion scenario to
be analyzed" [p. 108). The panel
recommended that a drill hole
penetration through a waste package be
assumed, which would mate a
connection from the repository to the
underlying saturated zone [pp. 12 and
111). The panel recommended that a
"consequences-only analysis" be
performed (p. Ill) and that the standard
"should require such an analysis" (p.
Ill), i.e., the analysis should only deal
with the fate of releases through the
borehole and the potential doses
resulting. The NAS recommended that
"the conditional risk as a result of the
assumed intrusion scenario should be
no greater than the risk levels * * *
acceptable for the undisturbed
repository case" (NAS Report p. 113).
We agree with these NAS
recommendations and therefore we have
constructed the stylized intrusion
scenario as described as separate from
the individual-protection standard, and
imposed a dose limit no greater than the
dose limit imposed for the individual-
protection standard. We have also
followed the NAS recommendation for
the time frame for the intrusion (NAS
Report p. 112) by linking it to the
expected time when the containers first
reach a state when a drilling penetration
can occur unnoticed by the drillers.
This time frame serves as a means of
establishing the radionuclide inventory
available for release and the transport
and dose analysis required by the
standard. Comments we received
proposing alternative drilling
frequencies and intentions, such as
deliberately drilling into the repository,
did not provide a sufficient rationale to
abandon the NAS recommendations and
we therefore retained our original
framing for the scenario. Additional
discussion of the intrusion scenario is to
be found in the discussion of comments
we received on Question 10 from the
proposed rule preamble (see section IV
below).
Another line of comment we received
stated that framing the intrusion
scenario in part, or in any way
whatever, should be considered an
implementation detail that should be
left to NRC. As stated earlier in this
document (see section I.A.2, The Role of
40 CFR part 191 in the Development of
40 CFR part 297), human intrusion is a
process that can contribute to exposures
of the public, and it is therefore
appropriate to address it in a public
health protection standard. In addition,
we believe the NAS recommendations
as mentioned above were very explicit
in stating that human intrusion should
be included in the EPA standard and
that framing the intrusion scenario
should be part of the EPA rulemaking,
rather than in implementing regulations.
We have followed the NAS
recommendations closely, as noted in
its comments on our proposed rule. We
are also concerned that the
implementing authority have some
flexibility in implementing the rule and
we have framed the standard to allow
that flexibility. We have specified in the
rule only enough of the details of the
scenario to assure it is implemented as
we intend. We have in fact not specified
enough of the detail to allow an analysis
to actually be performed from our
description alone. For example, we have
not specified the mechanisms by which
radionuclides are released from the
breached container and make their way
down the borehole to the ground water
table. Without specifying release and
transport mechanisms the analysis
cannot be performed. We have left this
essential detail for the implementation
process. We believe this flexibility is
necessary so that the intrusion analyses
can consider a range of conditions for
the stylized intrusion so it can be an
actual test of the repository "resilience"
for a limited by-passing of the
engineered barrier system. Although we
have defined the stylized drilling
intrusion scenario to closely follow the
NAS recommendations, if NRC
determines during its implementation
efforts that additional intrusion
scenarios are necessary to make a
licensing decision, NRC can require
additional analyses as part of its
implementing authority.
We offered for comment two
alternatives for the human intrusion
standard. The first alternative simply
stated that DOE must demonstrate a
reasonable expectation that the annual
dose incurred by the RMEI would not
exceed 15 mrem CEDE as a result of an
intrusion event, for 10,000 years after
disposal. This parallels the basic
individual-protection standard.
The second alternative incorporated
our concern that assessments of longer-
term performance be made available, if
not explicitly used for compliance
purposes. Under this alternative, we
made a distinction based on how long
after disposal the intrusion could occur.
If the intrusion were to occur at or
earlier than 10,000 years after disposal,
DOE must demonstrate a reasonable
expectation that annual exposures to the
RMEI as a result of the intrusion event
would not exceed 15 mrem CEDE. There
would be no time limit for this analysis;
as our proposal stated, "[i]f that
intrusion can happen within 10,000
years, then DOE must do an analysis
which projects the peak dose that would
occur as a result of the intrusion within
10,000 years." (64 FR 46999, August 27,
1999) However, if the intrusion
occurred after 10,000 years, DOE would
not have to compare its results against
a numerical standard, but would have to
include those results in its EIS.
We have selected the second
alternative for our final human intrusion
standard (§ 197.25). However, we are
not requiring that DOE calculate a peak
dose beyond 10,000 years for
comparison against a numerical
standard. If the intrusion event occurs
earlier than 10,000 years after disposal,
DOE need only compare the dose within
10,000 years to the numerical standard.
DOE must include post-10,000-year
results in its EIS, no matter when the
intrusion occurs. We believe this
alternative provides assurance that the
full effects of an intrusion event will be
assessed, regardless of when it occurs.
We also believe that the selected
alternative is more consistent with the
NAS recommendations that a
"consequence-based" analysis be
performed (NAS Report p. 111).
The time frame for the intrusion has
implications on how the projected doses
are handled and evaluated. We are
distinguishing between intrusion events
that occur within 10,000 years and those
that occur later than 10,000 years after
disposal. En assessing events that occur
within 10,000 years, we further
distinguish the results based on whether
exposures are incurred by the RMEI
within the 10,000-year period. We have
established the 10,000-year compliance
period to reflect past precedents and a
realization of the inherent uncertainties
in long-term performance projections
(see section m.(B)(l)(g)). For intrusion
events that occur within 10,000 years
and exposures are incurred by the RMEI
within 10,000 years, doses are compared
against the 15 mrem/yr limit given in
the standard as part of the compliance
case for licensing. For consistency in the
treatment of post-10,000-year dose
assessments, we are specifying that,
when the dose to the RMEI from human
intrusion events occurs after the 10,000
year period, the dose assessments are to
be included in the EIS, along with the
post-10,000 year performance
assessments for the individual
protection standard. Regardless of when
the intrusion occurs, if exposures are
incurred later than 10,000 years, they
-------
32106 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
are to be included in the EIS up to the
time of peak dose.
We formulated the selected
alternative to be responsive to the NAS
recommendations, in addition to
addressing our concern regarding the
availability of post-10,0DO year analyses.
A key factor in evaluating an intrusion
scenario is predicting when such an
event might take place. However, as
NAS concluded, "there is no scientific
basis for estimating the probability of
intrusion at far-future times' but that
"we believe it is useful to assume that
the intrusion occurs during a period
when some of the canisters will have
failed * * *" NAS Report p. 107, 112.
Therefore, we specify that DOE must
assume the intrusion occurs at "the
earliest time after disposal that the
waste package would degrade
sufficiently that a human intrusion
could occur without recognition by the
drillers' (proposed §197.25). This time
would be determined through the
licensing process, presumably by
assessing the expected performance of
the engineered barrier system. This
provides DOE the flexibility to
demonstrate that its engineered barrier
system is sufficiently robust to
withstand intrusion for a predictable
time period, which then determines the
nature of the waste inventory used in
the analysis, i.e., the relative
proportions of long-and short-lived
radionuclides.
4. How Does Our Rule Protect Ground
Water? (§197.30)
The inclusion of separate ground
water protection standards in today's
rule continues a longstanding Agency
policy of protecting ground water
resources and the populations who may
use such resources. This policy is
articulated in our primary ground water
protection strategy document titled
"Protecting the Nation's Ground Water:
EPA's Strategy for the 1990's" {Docket
No. A-95-12, Item V-A-13). We
designed today's standards to protect
the ground water in the vicinity of
Yucca Mountain to benefit the current
and future residents of the area who
could use this ground water as a
resource for drinking water and other
domestic, agricultural, and commercial
purposes. The following sections
discuss the Agency's general approach
to ground water protection, the NAS
comments regarding ground water
protection at Yucca Mountain, and some
of the legal and regulatory issues
associated with our final ground water
protection standards.
Policy and Technical Rationales for
Separate Ground Water Protection
Standards
Our General Approach to Ground Water
Protection
Ground water is one of our nation's
most precious resources because of its
many potential uses. A significant
portion (over 50 percent in the early
1990s) of the U.S. population draws on
ground water for its potable water
supply ("Protecting the Nation's Ground
Water: EPA's Strategy for the 1990's,"
Docket No. A-95-12, Item II-A-3). In
addition to serving as a source of
drinking water, people use ground water
for irrigation, stock watering, food
preparation, showering, and various
industrial processes. When that water is
radioactively contaminated, each of
these uses completes a radiation
exposure pathway for people. Ground
water contamination is also of concern
to us because of potential adverse
impacts upon ecosystems, particularly
sensitive or-end angered ecosystems
("Protecting the Nation's Ground Water:
EPA's Strategy for the 1990's," Docket
No. A-95-12, Item II-A-3). For these
reasons, we believe it is a resource that
needs protection. Therefore, we require
protection of ground water that is a
current or potential source of drinking
water to the same level as the maximum
contaminant levels (MCLs) for
radionuclides that we established
previously under the authority of the
Safe Drinking Water Act (SDWA).
In January 1990, the Agency
completed a strategy to guide future
EPA and state activities in ground water
protection and cleanup. The Agency-
wide Ground Water Task Force
developed two papers, which it issued
for public review: an EPA Statement of
Ground Water Principles and an options
paper covering the issues involved in
defining the Federal/State relationship
in ground water protection. We
combined these papers and other Task
Force documents into an EPA Ground
Water Task Force Report: "Protecting
The Nation's Ground Water: EPA's
Strategy for the 1990's" ("the Strategy,"
EPA 21Z-1020, July 1991 (Docket No.
A-95-12, Item II-A-3)). Our approach
in this rule is consistent with this
strategy.
Key elements of our ground water
protection and cleanup strategy are the
strategy's overall goals of preventing
adverse effects on human health and the
environment and protecting the
environmental integrity of the nation's
ground water resources. Our strategy
also recognizes, however, that our
efforts to protect ground water must
consider the use, value, and
vulnerability of the resource, as well as
social and economic values. We believe
it is important to protect ground water
to ensure the preservation of the
nation's currently used and potential
underground sources of drinking water
(USDWs) for present and future
generations. Also, we believe it is
important to protect ground water to
ensure that where it interacts with
surface water it does not interfere with
the attainment of surface-water-quality
standards; these standards are also
necessary to protect human health and
the integrity of ecosystems. We employ
MCLs to protect ground water in
numerous regulatory programs. OUT
regulations pertaining to hazardous-
waste disposal (40 CFR part 264);
municipal-waste disposal (40 CFR parts
257 and 258); underground injection
control (UIC) (40 CFR parts 144, 146,
and 148); generic SNF, HLW, and TRU
radioactive waste disposal (40 CFR part
191); and uranium mill tailings disposal
(40 CFR part 192) reflect this approach.
These programs have demonstrated that
such protection is scientifically and
technically achievable, within the
constraints that each program applies
("Progress In Ground Water Protection
and Restoration," EPA 440/6-90-001,
Docket No. A-95-12, Item V-A-6).
Another critical issue in ground water
protection is that ground water
generally is not directly accessible.
Thus, it is much more difficult to
monitor and/or decontaminate ground
water than is the case with other
environmental media ("Ground-Water
Protection Strategy" p. 11, August 1984,
Docket No. A-95-12, Item V-A-13).
Because of the expenses and difficulties
associated with remediation of
contaminated ground water, it is
prudent and cost-effective to prevent the
occurrence of such contamination (Id.).
It is possible for large amounts of
contaminants to enter a body of ground
water and remain undetected until the
contaminated water reaches a water
well or surface-water body. Moreover,
ground water contaminants, unlike
contaminants in other environmental
media such as air or surface water,
generally move in plumes with limited
mixing or dispersion into
uncontaminated water surrounding the
plume. These plumes of relatively
concentrated contaminants can move
slowly through aquifers. They may
persist, and thus may make the
contaminated resource unusable, for
extended periods of time (Id.}. Because
an individual plume may underlie only
a very small part of the land surface, it
can be difficult to detect by aquifer-wide
or regional monitoring. Also, monitoring
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32107
is unlikely to occur over greatly
extended time periods, during which
time an aquifer may become
dangerously contaminated [Id.]. Further,
the affected area may become quite large
over long time periods. Thus, we believe
that it is prudent and responsible to
protect ground water resources from
contamination through pollution
prevention rather than to rely on clean-
up of preventable pollution. The
pollution prevention approach to
protecting ground water resources we
are adopting for Yucca Mountain avoids
requiring present or future communities
to implement expensive clean-up or
treatment procedures. This approach
also protects individual ground water
users. Moreover, absent the protection
we have built into the rule, the ground
water in aquifers around the repository
itself could be subject to expensive
clean-up by future generations if
releases from the repository contaminate
the surrounding ground water to levels
that exceed legal limits. A guiding
philosophy in radioactive waste
management, as well as waste disposal
in general, has been to avoid imposing
burdens on future generations for clean-
up efforts as a result of disposal
approaches that would knowingly result
in pollution in the future (see, for
example, IAEA Safety Series No. lll-F,
"The Principles of Radioactive Waste
Management," Docket No. A-95-12,
Item V-A-10). With respect to
radioactive waste disposal, we believe
the fundamental principle of inter-
generational equity is important. We
should not knowingly impose burdens
on future generations that we ourselves
are not willing to assume. Disposal
technologies and regulatory
requirements are developed with the
aim of preventing pollution from
disposal operations, rather than
assuming that clean-up in the future is
an unavoidable cost of disposal
operations today. Designing a disposal
system, and imposing performance
requirements that avoid polluting
resources that reasonably could be used
in the future, therefore, is a more
appropriate choice than imposing clean-
up burdens on future generations. The
approach to ground water protection in
today's standards is consistent with our
overall approach to ground water
protection: it prevents the
contamination of current and potential
sources of drinking water downgradient
from Yucca Mountain,
NAS Comments on Ground Water
Protection
In its report, NAS clearly identified
the ground water pathway as the
significant pathways of to the biosphere
in the vicinity of Yucca Mountain(NAS
Report pp. 52 and 81). The NAS also
recognized that ground water modeling
for the Yucca Mountain site is complex.
Because the modeling for Yucca
Mountain involves water movement
through pore spaces (the matrix) and
fractures in the rocks, as well as the
degree of interconnectedness between
the water moving in the two pathways,
there is uncertainty regarding which
model or models to use in the analysis:
Because of the fractured nature of the tuff
aquifer below Yucca Mountain, some
uncertainty exists regarding the appropriate
mathematical and numerical models required
to simulate advective transport * * * (EJven
with residual uncertainties, it should be
possible to generate quantitative (possibly
bounding) estimates of radionuclide travel
times and spatial distributions and
concentrations of plumes accessible to a
potential critical group. (NAS Report p. 90)
In its report, NAS did not recommend
specifically that we include a separate
ground water protection provision in
our environmental protection standards
for Yucca Mountain. Neither, however,
did NAS state that we should not
include such a provision.
However, in its comments on the
proposed rule, NAS specifically
addressed our decision to include
separate ground water protection
standards for the Yucca Mountain site:
"(i)n the preamble (to the proposed rule),
EPA implies that there is a scientific basis for
inclusion of separate ground-water limits in
the standards " for example, EPA provides a
detailed analysis of approaches to calculating
such limits * * * The (MAS) respectfully
disagrees and does not believe that there is
a basis in science for establishing such limits
for the reasons described above. The (NAS}
recognizes EPA has the authority under the
Energy Policy Act to establish separate
ground-water limits as a matter of policy, but
if it does so it should explicitly state the
policy decisions embedded in the proposed
standard and ask the public to comment on
those decisions.
"If EPA wishes to establish such standards
on the basis of science, it must make more
cogent scientific arguments to justify the
need for this standard"
(NAS Comments, p. 11. Docket No. A-95-
12. Item IV-D-31).
EPA's Review of the Ground Water
Standards
For the reasons discussed above (see
Our Genera! Approach to Ground Water
Protection), we believe that separate
ground water protection standards
designed to protect the ground water
resource are necessary elements of our
Yucca Mountain standards. Our
decision to include separate ground
water standards is a policy decision that
we make pursuant to our statutory
authority under the Energy Policy Act.
Regarding the protectiveness of the
standards, 40 CFR part 197 incorporates
the current MCLs. We believe that this
approach is necessary to provide
stability for NRC and DOE in the
licensing process. We based these MCLs
on the best scientific knowledge
regarding the relationship between
radiation exposure and risk that existed
in 1975 when they were developed.
Scientific understanding has evolved
since 1975. We recently concluded a
review of the existing MCLs based on a
number of factors, including the current
understanding of the risk of developing
a fatal cancer from exposure to
radiation; pertinent risk management
factors (such as information about
treatment technologies and analytical
methods); and applicable statutory
requirements. See 65 FR 76708-76753,
December 7, 2000. Our analyses indicate
that, when the risks associated with the
individual radionuclide concentrations
derived from the MCLs are calculated in
accordance with the latest dosimetry
models described in Federal Guidance
Report 13, they still generally fall within
the Agency's current risk target range for
drinking water contaminants of 1 D~4 to
10~6 lifetime risk for fatal cancer.
Therefore, the MCLs for the
radionuclides of concern at Yucca
Mountain have not changed.
Our analyses, and those of NAS,
indicate that, of all the potential
environmental pathways for
radionuclides, travel through ground
water is the most likely pathway to lead
to human exposure to radiation from the
Yucca Mountain disposal system (see
Chapters 7 and 8 of the BID). The
ground water protection standards in
this rule protect ground water that is
being used or that might be used as
drinking water by restricting potential
future contamination. Water from the
aquifer beneath Yucca Mountain
currently serves as a source of drinking
water 20 to 30 km south of Yucca
Mountain in the communities direcdy
protected by the individual-protection
standard. It is also a potential source of
drinking water for more distant
communities. As noted by NAS, the
available ground water supply in the
vicinity of Yucca Mountain could
sustain a substantially larger population
than that presently in the area (NAS
Report p. 92).
Technical Approach for Protecting
Ground Water at Yucca Mountain
As noted above, NAS asserted in its
comments regarding the proposed rule,
that we implied that there was a
scientific basis for including separate
ground water limits in the regulations.
The NAS urged us to clearly state the
-------
32108 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
policy reasons for including such limits.
We believe that we clearly articulated in
the preamble to the proposed rule that
we included a ground water protection
provision in the proposal based upon
our long-standing policy.
In keeping with the site-specific
nature of these standards, we believe
that it is appropriate to outline an
approach to determining compliance
with the ground water standards
consistent with the geologic conditions
along the anticipated ground water flow
path for.releases from the repository.
The approach that we have devised
consists of several components. The first
component is to define a ground water
resource use common for the current
population making use of the ground
water along the potential path of
releases. The population living
downgradient from the repository
typically uses the ground water for
domestic consumption and for
agricultural activities. The dominant
agricultural activity is alfalfa cultivation
(see Chapter 8 of the BID). The next
component of the approach is to define
a method for assessing the extent of
potential contamination in the aquifer
that can be used for comparison against
established limits. To address the
unique setting of the repository, we are
defining a "representative volume" of
ground water consistent with the uses of
the resource (see § 197.31(b)). The third
component is to propose alternatives to
defining how DOE could use the
representative volume in making
assessments of potential ground water
contamination (see § 197.31). See the
Representative Volume of Ground Water
discussion later in this section for our
responses to comments on the
representative volume approach.
We proposed to use the MCLs as
appropriate standards against which to
measure compliance. Comment upon
our proposal was mixed. Some
comments claimed that we misapplied
the MCL concept in the Yucca Mountain
standards compared with how we apply
MCLs in other situations, such as the
use of MCLs to define when drinking
water from public water supplies is
acceptable. Some comments supported
the use of MCLs. Other comments
pointed out that the dosimetry system
used for the current MCLs has been
superceded by newer approaches to
assessing dose and risk from ground
water use and that we should, therefore,
not use the MCLs. A number of
comments claimed that the use of
separate ground water standards is
completely unnecessary because the
individual-protection standard includes
the drinking water exposure pathway
and, therefore, the ground water
standards are unnecessary as a health
protection measure.
Retaining separate ground water
protection standards is consistent with
both our national policy to protect
ground water resources and with
previous Agency regulations for
geologic disposal facilities. Our generic
standards in 40 CFR part 191, which
apply to the same kinds of wastes
contemplated for disposal at Yucca
Mountain, contain separate ground
water protection provisions. We believe
that there is no question that separate
ground water protection standards are
appropriate for deep geologic disposal
facilities. We believe that the use of
contaminated ground water for purposes
that could result in exposures to
individuals should be of concern, and
that avoiding contaminating useable
ground water resources is in the general
interest of the public at large. More
specifically, contamination of water
resources could result in the exposure of
individuals well removed from the
repository location. Also, if ground
water were withdrawn from the
repository sub-basin, and transported to
other locations to supply water needs, a
larger population would be exposed
than if the water were used only locally.
We commonly apply MCLs to water
treatment facilities to assure that
exposures to the subsequent users of the
water are acceptable and the users are
protected. The intent of using the MCLs
as a compliance measure for the Yucca
Mountain disposal system is to
encourage a robust containment and
isolation design that will not result in
unacceptable contamination during the
regulatory time frame, which would
require future generations to shoulder
the burden of water treatment due to
contamination from the wastes. We also
included ground water protection
requirements in our certification process
for WIPP, which is the only deep
geologic disposal facility in the country
that has actually gone through a
regulatory review and approval process.
We see no reason why we should not
apply the same approach to protection
for the Yucca Mountain disposal facility
as we afforded to the population around
WIPP. In fact, the Yucca Mountain
disposal system will he located above
aquifers that are the ground water
supply for the residents living
downgradient from the repository,
whereas the aquifers potentially subject
to contamination at the WIPP facility are
highly saline, non-potable water
sources. We recognize that the
individual-protection standard includes
a drinking water exposure pathway;
however, from a policy perspective it is
appropriate and consistent for us to
provide separate protection for ground
water resources in the Yucca Mountain
area. As illustrated by the examples
above, the protection of ground water
resources is in the general interest of the
public at large, because it is easily
conceivable that uses of the resource
could result in exposures well beyond
the immediate vicinity of the repository.
From a more practical perspective, it
would be extremely difficult to predict
with any reliability what the total range
of potential exposures (and consequent
health effects} would be for all possible
uses of the resource, because such
predictions would involve considerable
speculation. It makes more sense to
assure the resource is not contaminated
in the first place. We are taking the more
prudent course of attempting to prevent
ground water contamination above the
MCLs by imposing separate ground
water protection requirements.
The NRC's determination of
compliance with the ground-water
protection standards will be based
largely upon DOE's projections of
potential future contaminant
concentrations. The DOE will include
these projections in the license
application it submits to NRC. These
projections, by their very nature,
inevitably will contain uncertainty. An
important cause of uncertainty, as NAS
recognized, is the choice of conceptual
site models (NAS Report p. 75). The
conceptual models used for Yucca
Mountain can differ fundamentally. For
example, water can be presumed to flow
through either pores in the rock or
conduits through the rock (such as
discrete fractures or a network of
fractures that can act as preferential
pathways for faster ground water flow),
or a combination of the two. To further
complicate the situation, any of these
flow scenarios, with the possible
exception of flow through conduits, can
occur at Yucca Mountain whether or not
the rock is saturated completely with
water.
We believe that adequate data and the
choice of models will be critical to any
compliance calculation or
determination because such data and
models are the backbone of the
performance assessment used to show
compliance. The NAS examined the use
of ground-water flow and contaminant-
transport models in regulatory
applications ("Ground Water Models:
Scientific and Regulatory Applications,"
1990, Docket No. A-95-12, Item V-A-
26). In that report, NAS concluded that
data inadequacy is an impediment to
the use of unsaturated fracture flow
models for Yucca Mountain. However,
NAS noted that data inadequacy also
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32109
was an impediment to using models that
assume the pores in the rock are either
saturated or unsaturated or that assume
flow through fractures that are filled
completely with water. However,
despite the recognition of the
importance of the choice of the site
conceptual model, we believe that the
need for sufficient quantity, types, and
quality of data to adequately analyze the
site, because of its hydrogeologic
complexity, is even more important. In
other words, the complexity of the
ground water flow system requires
adequate site characterization to justify
the choice of the conceptual flow
model.
The choice of modeling approaches to
address the ground water system in the
area of Yucca Mountain, based upon the
conceptual model of the site developed
from site characterization activities, is
important to characterize contaminant
migration, particularly the mixing of
uncontaminated water with water that
has been contaminated with
radionuclides released from breached
waste packages. The extent of the
dilution afforded by mixing
contaminated water with other ground
water moving through the rocks below
the repository but above the water table
and the dispersion of the plume of
contamination within the saturated zone
as the ground water system carries
radionuclides downgradient are critical
elements of the dose assessments.
At one end of the spectrum of
approaches to modeling the Yucca
Mountain area's ground water system is
the assumption that it is possible to
model the system based upon flow
through pores over a large area (tens of
square kilometers). At the other extreme
is the assumption that radionuclides are
carried through fast-flow fractures in the
unsaturated zone separately from
uncontaminated ground water also
passing through the repository footprint.
Those radionuclides then are assumed
to be carried through the saturated zone
in fractures that allow little or no
dispersion within, or mixing with,
uncontaminated water in the saturated
zone. This scenario is essentially "pipe
flow" from the repository to the
receptor. Although the flow of ground
water at the site is influenced strongly
by fractures, which the models should
reflect, we believe that it is
unreasonable to assume that no mixing
with uncontaminated ground water
would occur along the radionuclide
travel paths because such mixing is a
natural process, and would be governed
by the degree of interconnection
between individual fractures in the
rocks. We requested comment upon this
approach, including consideration of
the practical limitations on
characterizing the flow system over
several or tens of square kilometers.
Comments varied from statements
that we should not allow DOE to
consider mixing of contaminated water
from the repository with
uncontaminated water along potential
flow paths, that such dilution is an
expected process in the natural system,
and that these decisions about the flow
system modeling are implementation
details which we should defer to NRC.
We agree that some degree of mixing
along the ground water flow paths is to
be expected and, if supported by the
hydrogeologic characterization, should
be considered in modeling approaches
used to make projections of
radionuclide migration from repository
releases. We also agree that detailed
decisions about the approach to
modeling the ground water flow system
at the site are an implementation
concern for NRC. We therefore make no
specific requirements in this regard. We
do believe that whatever specific
modeling approach and attendant
assumptions that DOE or NRC make
should attempt to model realistically the
expected behavior of the actual flow
regime downgradient from the
repository. Recalling the "pipe-flow"
scenario described above, we believe it
would be highly unrealistic to assume
that no mixing of the contaminated
water with ground water along the flow
path occurs along the distance from the
repository to the furthest allowable
boundary of the controlled area.
Although the actual dispersion effects
for the fractured rock geohydrologic
setting are anticipated to be small (see
Chapter 7 of the BED), ignoring such
processes is still inappropriately over-
conservative because it would neglect a
natural process that is expected to
occur. Consistent with this perspective,
we specify two alternative methods that
DOE could use for determining
radionuclide concentrations in the
representative volume of ground water.
We believe these two alternatives
provide appropriate direction for
making the compliance determination
while allowing ample flexibility for the
implementation decisions concerning
the details of characterizing the ground
water flow and modeling approaches
that DOE ultimately must select and
defend in the licensing process.
Our intent was to develop ground
water protection standards that NRC can
reasonably implement. In this regard,
NAS indicated that quantitative
estimates of ground water
contamination should be possible (NAS
Report p. 90). We thus require DOE to
project the level of radioactive
contamination it expects to be in the
representative volume of ground water.
The representative volume could be
calculated to be in a contaminated
aquifer that contains less than 10,000
mg/L of TDS and that is downgradient
from Yucca Mountain. Through the use
of this method, we intend to avoid
requiring DOE and NRC to project the
contamination in every smalj, possibly
unrepresentative amount of water
because we believe that this approach is
not scientifically defensible considering
the inherent uncertainties in hydro! ogic
data and the limitations of modeling
calculations. For example, we do not
intend that NRC must consider whether
a few gallons of water in a single
fracture would exceed the standards.
Thus, we allow use of a larger volume
of water that must, on average, meet the
standards. See below for a discussion of
this larger volume, the "representative
volume."
Because the purpose of the engineered
and natural barriers of the geologic
repository at Yucca Mountain is to
contain radionudides and minimize
their movement into the general
environment, we anticipate that
radionuclide releases from the
repository will not occur for a long
period of time. With this assumption in
mind, we believe that ground water
protection for the Yucca Mountain site
should focus upon the protection of the
ground water as a resource for future
human use. It is the general premise of
this rule that the individual-protection
standard will adequately protect those
few current residents closest to the
repository. The intent of the ground
water standards is protecting the aquifer
as both a resource for current users, and
a potential resource for larger numbers
of future users either near the repository
or farther away in communities
comprised of a substantially larger
number of people than presently exist in
the vicinity of Yucca Mountain. To
implement this conceptual approach
and develop an approach for
compliance determinations, we believe
that the ground water standards
currently used, the MCLs, should apply
to public water supplies downgradient
from the repository in aquifers at risk of
contamination from repository releases.
There is presently no public water
supply providing treatment to meet
MCLs before the water reaches
consumers downgradient of Yucca
Mountain, and there is no guarantee that
such a system will be in place to protect
future users from contamination caused
by releases from the disposal system.
Applying the MCLs in the ground water
assures that the level of protection
-------
32110 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
currently required for public water
supplies elsewhere in the nation also is
maintained for future communities
using the water supply downgradient
from the Yucca Mountain disposal
system.
Representative Volume of Ground Water
To implement the standards in
§ 197.30, we require that DOE use the
concept of a "representative volume" of
ground water. Under this approach,
DOE and NRC will project the
concentration of radionuclides released
from the Yucca Mountain disposal
system, for comparison against the
MCLs, that would be present in the
representative volume in the accessible
environment over the 10,000-year
period of the standards. The
representative volume will be a volume
of water projected to supply the annual
water demands for defined resource
uses. We believe that water demand
estimates for calculation of the
representative volume should reflect the
current resource demands for the
general lifestyles and demographics of
the area, but not be rigidly constrained
by current activities, because potential
contamination would occur far into the
future. In the area south of Yucca
Mountain, people currently use ground
water for domestic purposes,
commercial agriculture (for example,
dairy cattle, feed crops, other crops, and
fish farming), residential gardening,
commercial, and municipal uses (see
Chapter 8 of the BID). The ground water
resources, as reflected by estimates of
current usage and aquifer yields,
indicate that there is theoretically
enough water to support a substantially
larger population than presently exists
at each of the four alternative locations
we proposed for the point of compliance
[Id.]. The representative volume
approach sets an upper bound on the
size of the hypothetical community and
its water demand. On the other hand,
the SDWA defines the minimum size for
a public water system as a system with
15 service connections or that regularly
supplies at least 25 people. The SDWA
was designed to address, and typically
is applied to, situations where
contamination can be monitored in the
present and where monitoring is done
close to the disposal facility rather than
many kilometers away. If necessary,
corrective actions can be taken if
contamination limits are exceeded. In
contrast, the geologic disposal
application involves potential
contamination releases that are expected
to occur no sooner than far into the
future. It simply is not reasonable to
assume that monitoring for the purpose
of detecting radionuclide contamination
around the repository will be performed
continually far into the future.
Consequently, it is not prudent to
assume that corrective actions would be
taken to reduce contamination levels.
As noted by NAS, active institutional
controls (including active monitoring
and maintenance) can play an important
role in assuring acceptable repository
performance for some initial period, not
exceeding a time scale of centuries
(NAS Report p. 106). Another approach
to protecting the ground water resource
into the future is necessary. Projecting
repository performance, and
consequently assessing potential
repository releases to the surrounding
ground waters, can only be based upon
mathematical modeling of the
repository's engineered and natural
barrier performance. A method of
assessing potential contamination must
be developed that involves ground
water modeling capabilities. The
approach we have developed to assess
ground water contamination (described
previously) is the use of a representative
volume of ground water in modeling
calculations.
We believe that, ideally, the
representative volume should be fully
consistent with the protection objectives
of the ground water protection strategy;
however, we also recognize the unusual
features of these standards. That is, the
10,000-year compliance period
introduces unresolvable uncertainties
that make this situation fundamentally
different from the situations of clean-up
or foreseeable, near-term potential
contamination to which the SDWA
ground water protection strategy
ordinarily applies. The size of the area
that must be modeled (tens of km2)
around the site and the complexity of
the site characteristics introduce
fundamental limitations on the size of
the water volume that it is possible to
model with reasonable confidence. It is
Agency policy to protect ground water
as a resource and we intend our ground
water protection standards to
accomplish that policy goal. We intend
the representative volume concept we
have incorporated into the standards to
serve as context for the application of
our ground water protection policy to
the Yucca Mountain site, which differs
from the more common application of
the SDWA as described above. The
representative volume concept
addresses two needs in this respect.
First, the size of the representative
volume (measured as an annual volume
in acre-feet) must be sufficiently large
that the uncertainties in projecting site
characteristics (such as the hydrologic
properties along the flow paths) that
control ground water flow are not so
great that performing calculations to
determine radionuclide concentrations
in that volume becomes meaningless
from an analytical perspective. That is,
we should not expect a higher level of
confidence and exactness than the
scientific tools and available data are
capable of providing. Second, the
representative volume should be an
appropriate measure of the resource to
be protected. From both perspectives,
analytical limitations and resource
characterization, the representative
volume of 1,285 acre-feet that we
proposed is the potential choice that
could satisfy those needs. As described
in the preamble to the proposed rule, we
preferred the 1,285 acre-feet alternative
because we believed it reflected both
perspectives. The major resource use for
ground water in the area downgradient
from the repository is agriculture, and
the most water intensive agricultural
activity in the area is alfalfa farming.
The 1,285 acre-feet representative
volume (including 10 acre-feet for
domestic use for the farm community) is
the water demand for an average alfalfa
farm in the Amargosa Valley area (see
Chapter 8 of the BID). From
consideration of the inherent limitations
of modeling the geohydrologic setting at
the site, we believe that approximately
a 100 acre-feet representative volume is
the smallest volume for which it is
possible to perform reasonably reliable
calculations (Memo to Docket from
Frank Marcinowski, EPA, Docket No.
A-95-12, Item II-E-10). The 1,285 acie-
feet volume is sufficiently above this
limit; therefore, questions about the
scientific capabilities of performance
modeling to assess radionuclide
concentrations in the 1,285 acre-feet
volume should not be a concern. While
still feasible to model, 120 acre-feet is
much closer to the lower limit of
defensible modeling, and uncertainties
at this volume are potentially unwieldy
and overwhelming. We requested
comment regarding both our use of a
representative volume of ground water
and possible alternatives for the size of
the representative volume. We based
these alternative volumes upon
variations in possible lifestyles for
residents downgradient from the
repository and upon current and near-
term projections of population growth
and land use in the area.
We specifically requested comment
upon whether 1,285 acre-feet is the most
appropriate representative volume of
ground water, or whether other values
within the ranges discussed below are
more appropriate. We believe that there
may be significant technical, policy, or
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001 /Rules and Regulations 32111
practical obstacles with the use of either
very small or very large water volumes.
Modeling capabilities limit the volumes
of ground water for which it is possible
to make meaningful and scientifically
defensible calculations. At the other
extreme, excessively large volumes of
water allow artificially high dilution of
radionuclide releases, and do not
actually simulate the natural process
that would occur along the radionuclide
ground water travel path from the
repository to the compliance point. The
selection of the representative volume
must consider both modeling
limitations and realistic approaches to
modeling, and must be both a
reasonable representation of the
resource to be protected and be possible
to implement from a modeling
perspective.
Comments on our alternatives for the
representative volume size varied from
agreement with our preferred volume of
1,285 acre-ft to favoring larger and
smaller volumes. We believe that the
larger volume mentioned in the
proposed rule, 4,000 acre-ft, is not a
suitable choice for a number of reasons.
This number is an estimate of the
perennial yield in the sub-basin
containing Yucca Mountain. It is an
estimate of the amount of ground water
that can be removed annually without
seriously depleting the aquifer. Because
there are relatively few wells in this
sub-basin, the 4,000 acre-ft estimate is
not highly reliable and is difficult to
justify. This is one reason why we did
not select this number. Perhaps more
importantly, the perennial yield is not a
physical location in the aquifer and the
challenge of projecting repository
performance is to project the path of
potential contamination from the
repository. The perennial yield concept
is not consistent with the idea that the
modeling of potential contamination
from the repository should use an actual
volume of water, the representative
volume, to determine compliance with
the standards. Small volumes of ground
water would be difficult to model with
confidence over the long time frames
and distances appropriate for the Yucca
Mountain repository. More specifically,
we believe it is not possible to model ibr
the 10 acre-ft representative volume [see
the Response to Comments document
for more detail). Comment on the 120
acre-ft volume was generally that this
volume was too small for defensible
modeling, which agrees with our
assessment. As stated above, we
consider 120 acre-ft to be within the
range of feasible modeling, but very
close to the lower limit of scientifically
defensible modeling capabilities. It also
does not reflect the typical use of the
ground water resource, which is better
represented by the agricultural scenario
we have selected.
There are a number of fundamental
limitations involved in modeling the
flow of ground water over long
distances that are direct functions of the
variability of the hydrologic properties
in the aquifers along its dimensions.
Averaging assumptions are used in
modeling to greater and lesser extents to
address these limitations, as a function
of the information available regarding
the natural variability of hydrologic
properties along the flow paths. Our
approach to calculating ground water
contaminant concentrations (the well
capture zone or slice-of-the-plume
methods described in §197.31(b))
centers the representative volume to
include the highest concentration
portion of the projected plume. If the
representative volume is too small, it
does not capture a volume large enough
to reflect the natural processes that will
occur along the flow path. Therefore,
the concentrations will be
unrealistically high and will not be a
reasonable representation of the
variations that should be expected in
the actual situation. The exact limit on
the lowest size of the representative
volume adequately reflecting modeling
limitations and the data base of
hydrologic information about the site is
a difficult expert judgment. An exact
lower limit is not possible to identify
because of the inherent limitations in
gathering site data and performing
modeling. Our opinion after extensive
discussions with qualified experts is
that a representative volume on the
order of 100 acre-ft or below is the lower
limit of modeling capability for the
Yucca Mountain ground water flow
regime (Yucca Mountain Docket, A-95-
12, ItemII-E-10).
We based the 1,285 acre-ft
representative volume on a hypothetical
small farming community of 25 people
and an alfalfa farm with 255 acres under
cultivation. This approach assumes a
small community whose water needs
include domestic consumption and an
agricultural component comparable to
present water usage in the vicinity of
the repository. We based the size of the
average area of alfalfa cultivation, 255
acres, on site-specific information for
the nine existing alfalfa-growing
operations in Amargosa Valley in 1998,
which ranged in size from about 65
acres to about HOD acres (see Chapter 8
of the BID). Using a water demand for
alfalfa farming in Amargosa Valley of 5
acre-feet per acre per year, we estimate
that the annual water demand for the
average operation is 1,275 acre-ft
(Chapter 8 of the BID). An average value
of 0.4 acre-ft per person for domestic
water use is typical of the area (Chapter
8 of the BID), which for the small
community of 25 people would add 10
acre-ft for domestic uses, resulting in a
total representative volume of 1,285
acre-ft. Comments on the derivation of
the 1,285 acre-ft representative volume
supported this size as being technically
feasible for modeling and consistent
with water resource demands in the area
downgradient from the repository.
To implement the standards in
§ 197.30, we require that DOE use the
concept of a "representative volume" of
ground water. Under this approach,
DOE will project the concentration of
radionuclides or the resultant doses
within a "representative volume" of
ground water for comparison against the
standards. We have selected a value of
3,000 acre-ftVyr as the representative
volume. This value is a "cautious, but
reasonable" figure for protecting users
of the ground water downgradient of the
repository, as described below. Our
approach focuses on the anticipated
water use immediately downgradient of
the repository, and is closely aligned
with the alternatives offered for public
comment hi our proposed rule.
The preamble to the proposed rule
noted that the representative volume
should reflect the water usage of a
hypothetical community that may exist
in the future. The preamble also noted
that the water usage should reflect the
current general lifestyles and
demographics of the area, but not be
rigidly constrained by current activities.
Using current activities and near-term
projections of planned activities in the
downgradient area leads us to three
types of water demands that can be
identified for the downgradient area:
Water demand for individual domestic
and municipal uses, water demand for
commercial/industrial uses, and water
demand for agricultural uses.
In deciding how to make this
projection, we have concluded in the
final rule that OUT focus in developing
an appropriate representative volume
should be to consider the spectrum of
likely downgradient uses of the ground
water resources, as well as the site-
specific hydrologic characteristics of the
disposal system itself. To avoid
speculation on all possible uses of
ground water, we have been guided by
the premise that current uses in the
immediate downgradient area, as well
as shorHerm projections for water uses
reflecting growth projections for the
area, should be considered in defining
an appropriate representative volume
for the ground water standard. We
believe that the most likely future uses
-------
32112 Federal Register/Vol. 66, No. 114 /Wednesday, June 13, 2001/Rules and Regulations
will in fact take place where they are
currently located, since there is no
reason to anticipate that they will cease
occurring.
Deriving a representative volume
involves identifying water demands for
the spectrum of likely uses, and
includes an examination of projected
plume characteristics. This leads us to
focus primarily on projected uses
occurring downgradient of the
repository. As noted above, the current
and anticipated water demands
downgradient of the repository consist
of residential/municipal uses,
commercial/industrial uses and
agricultural uses.
Currently, the population at the
Lathrop Wells is small, about ten people
(BID Chapter 8), however near-term
projections for the area between Lathrop
Wells and the NTS boundary indicate
that a science museum and industrial
park are under development (Docket No.
A-95-12, Items V-A-16, V-A-19).
There are also growth projections for the
Amargosa Valley area (Docket No. A—
95-12, Items V-A-14, 15), leading us to
believe that residential/municipal water
demands as well as commercial/
industrial water demands are likely in
the near-term for the area between
Lathrop Wells and the NTS boundary.
Projected water demand for the
science museum and industrial park are
on the order of 100 acre-ft/yr (Docket
No. A-95-12, Item V-A-19). Based
upon the growth projections, we believe
that some residential population growth
should be anticipated for the area in
addition. In the preamble for the
proposed rule, we included a
representative volume of 120 acre-ft/yr
for a small residential community of
approximately 150 persons, which
included water uses for individuals and
municipal uses. We believe that these
water demands should be incorporated
into the representative volume, so that
the representative volume addresses all
potential water users. Limiting the water
demand to only one of these uses, we
believe, would not be representative of
the spectrum of potential users that
might be exposed to contaminated water
from repository releases. For example,
the water demand for the small
population at Lathrop Wells would be
on the order of less than 10 acre-ft/yr.
Our evaluations of representative
volume options in the proposed rule
(Docket No. A-95-12, Item II-E-10),
and the responses we received
concerning these options, consistently
concluded that such small volumes
would not allow credible scientifically
defensible projections to be made.
The contribution of agricultural
activities to the representative volume
can be derived from a consideration of
current farming activities in Amargosa
Valley. In the Town of Amargosa Valley,
agricultural activities consume the
largest volumes of ground water, but are
largely confined to the location
approximately 25-30 km downgradient
from the repository location. However,
the ground water used for these
activities could be contaminated if
radionuclide releases from the disposal
system were sufficiently high to exceed
the limits given in § 197.30. To protect
the agricultural resource use, we have
used alfalfa farming as a measure of
water demand. Although there is no
alfalfa farming currently at the
compliance location, and no near-term
planning for it, our approach to
protecting the resource is to include the
appropriate water demand in the
representative volume at the compliance
location. By protecting this volume
upgradient of where the actual resource
is anticipated to be tapped, we will be
protecting the larger actual volume of
water that will be used for agricultural
purposes downgradient from the
compliance location.
As described previously, alfalfa
cultivation is the largest water consumer
in the agricultural sector, and this
activity is anticipated to continue (BID
Chapter 8). We have defined an average-
sized alfalfa form based upon current
information about acreage under
cultivation in Amargosa Valley (BID
Chapter 8). We have retained this value
to avoid speculation about the future of
this particular activity for the following
reasons. The demand for alfalfa
cultivation to support the local dairy
industry in Amargosa Valley is
anticipated to he strong for the near-
term. The hydrologic basin in which
this activity takes place is fully
allocated, suggesting that dramatic
increases in. alfalfa cultivation are
unlikely since the water allocations
necessary for dramatic increases are not
readily available (BID Chapter 8).
Therefore, we are using the value of
1,275 acre-feet/yr for an average-sized
farm for developing a representative
volume figure (this represents the
proposed value of 1,285 acre-feet, less
the 10 acre-feet assumed for purely
domestic use).
The anticipated behavior of the
ground-water flow system from Yucca
Mountain is important in determining
the total contribution of the agricultural
water demand to the representative
volume, since the width of potential
contamination plumes will determine
how large a volume of contaminated
ground water could be tapped for
agricultural purposes and consequently
should be protected from unacceptable
contamination. Projections of ground
water flow, from particle-tracking
analyses, have been performed by DOE
to determine the path of possible
contaminant flow from advective
transport (ground water movement)
alone (Docket No. A-95-12, Kerns V-A-
5, V-A-27). The particle tracks near the
compliance boundary, the
south westernmost corner of NTS (a
distance of approximately 18 km from
the southern end of the repository),
indicate that the width of a potential
contamination plume at the compliance
location is about 1.8-2.0 kilometers.
Farther downgradient, the width of the
particle-track ground water travel path
widens slightly to a width of between 2
and 3 km. This width does not consider
dispersive effects that will occur, which
contribute to uncertainty in projecting
the actual size of a potential
contamination plume. The actual width
will be a function of a number of other
factors, including the location of failed
waste packages over time within the
repository and the particular values of
dispersion parameters chosen for
analyses. Somewhat smaller or larger
contamination plume widths could
result, but the particle track approach
results offer a satisfactory
approximation.
The average alfalfa farm we have
defined (255 acres in a square shape) is
only approximately one kilometer on an
edge. Since the exact location of a
contamination plume and the variations
in radionuclide contaminant
concentrations within it are uncertain
and cannot be projected with high
confidence, we are using two average
sized alfalfa farms across the path of the
contamination plume to increase
confidence that the highest
concentration portions of a potential
contamination plume will be included
in the representative volume, giving a
total contribution of 2,550 acre-ft/yr for
the agricultural component of the
representative volume. Again, we are
not assuming the existence of actual
farms at the compliance location, but we
are assessing the effects of radionuclide
contamination on the water volume that
they could use at more distant locations.
In. total, the contributions to the
representative volume consist of the
agricultural use water demand for two
average size alfalfa farms (2,550 acre-ft/
yr), the commercial/industrial water
demand for the Lathrop Wells
development projections (100 acre-ft/
yr), and individual/municipal use water
demand for a small community
consistent with the near-term growth
projections for the area (120 acre-ft/yr).
These three components amount to
2,770 acre-ft/yr. As mentioned above,
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32113
there is significant uncertainty in the
exact location and radionuclide
concentrations in potential
contamination plumes from the
repository, and therefore we cannot be
absolutely certain that two average-sized
alfalfa farms will cover the total possible
width of a contamination plume, but we
believe including the water demand
from more than two farms would not be
entirely justified. Our intent in using the
two alfalfa farms (each 1 km in width)
is to assure that the highest
concentration portion of any
contamination plume is tapped by the
wells supplying this water demand. We
have also modified § 197.31 to allow the
use of multiple pumping wells (rather
than a single well as described in the
proposed rule) to tap the representative
volume so that technical limitations on
constructing a well withdrawal scenario
can be eliminated or minimized, should
DOE elect this alternative for calculating
radionuclide concentrations in the
representative volume.
There is, of course, uncertainty in
projecting the size and shape of
contamination plumes from the
repository as well as projecting human
activities into the future, and we have
limited this source of uncertainty by
considering only near-term projections
for growth and development in the area,
but some degree of inherent uncertainty
will always remain. To address these
residual uncertainties in this approach,
we increase the representative volume
by about 10%, to a total 3,000 acre-ft/
yr. We believe that this figure represents
a cautious, but reasonable, estimate of
the representative volume to protect the
ground water resource downgradient of
the repository.
We considered an alternative way of
evaluating the representative volume
concept for application to the ground
water protection standards. This
approach considers the larger scale
ground water flows and uses in the
larger basin (Basin 230) which receives
outflow from the basin where the
repository is located (Basin 227A). The
primary water use in this region is in
the Amargosa Desert hydrographic basin
(Basin 230, see BID Chapter 8), where
farming, mining, and other industrial
uses occur. This water comes from four
basins that have an estimated total water
budget of about 43,800 acre-feet, which
represents ground water that flows into
the Amargosa Desert basin.
The Jackass Flats basin (Basin 227A,
which includes Yucca Mountain and
the point of compliance location) is one
of four basins that flow from the north
into the Amargosa Desert basin and
provide the ground water that is used
for these activities. It is the only one of
these basins into which it is reasonable
to anticipate that water contaminated by
releases from the repository would flow.
The Jackass Flats basin contributes
about 8,100 acre-feet to the total
Amargosa Valley water budget (Table 8-
6, BID). Considering the approximate
nature of these values, it is reasonable
to approximate the contribution of the
Jackass Flats to flow into the Amargosa
Desert basin and to current water uses
at 20%.
Although the Amargosa Desert basin
has a water appropriation limit of about
41,093 acre-feet, in 1997, the reported
ground water use in the Amargosa
Desert basin was about 13,900 acre-feet
(BID Chapter 8). That is, the use was
less than appropriated. Moreover, actual
water use fluctuates significantly,
depending primarily on the level of
irrigation and mining activities in a
given year (BID Chapter 8). To estimate
the actual contribution of flow from
Jackass Flats, we again refer to the
largest water use in the area
downgradient from the repository,
which is for irrigation, particularly for
the cultivation of feed for livestock
(primarily alfalfa). There are nine alfalfa
farms in the affected area, ranging from
approximately 65 to 800 acres (BID
Chapter 8). Estimates of acreage under
cultivation for feedstock has shown a
steady increase from 1994 to 1999
(Table 8-6, BED), with an increase of
50% from 1997 to 1999. Assuming that
it also increased by 50%, the 1997
irrigation use of 9,379 acre-feet (Table
8-4, BED) could have increased by
approximately 4,700 acre-feet in 1999.
This assessment gives a range of water
use from approximately 13,900 acre-feet
in 1997 to an estimate of 18,600 acre-
feet in 1999, placing the corresponding
20% contribution from Jackass Flats in
a range of approximately 2,800 to 3,700
acre-feet. From this range of possible
values, we again selected 3,000 acre-feet
as a value that is conservative (toward
the low end of the range), but also
makes an allowance for the uncertainty
inherent in these estimates.
In summary, both approaches to
deriving a "cautious, but reasonable"
representative volume for the purpose of
ground water protection converge on a
value of 3,00Q acre-ft/yr. Our approach
to developing an appropriate
representative volume considered the
size of the ground water resource and its
current and projected uses. Accordingly,
we have selected a representative
volume of 3,000 acre-feet for this rule.
This volume is within the 10 to 4,000
acre-feet range described in the
proposed rule and addressed in the
public comments and represents a
reasonable and site-specific approach to
protecting groundwater resources in the
vicinity of Yucca Mountain.
Our standards require DOE to assume
that the entire representative volume is
drawn at the compliance point, that is,
18 km south of the repository,, rather
than in the Amargosa Valley itself, at 25
to 30 km south of the repository.
Therefore, it is adequate not only to
protect downgradient uses, but also to
protect all of these reasonably projected
uses, should the representative volume
be withdrawn at the compliance point.
As noted above, we believe that given
the uncertainties of projecting any
particular future and the difficulties of
modeling that using the small volumes
that would be required by relying only
on current projected uses, this is a
reasonable approach for determining
how ground water should be protected
at this particular site.
There are two basic approaches that
DOE must choose between for
calculating the concentrations of
radionuclides in the accessible
environment. The DOE may perform
this analysis by determining how much
contamination is in: (1) A "well-capture
zone;" or (2) a "slice of the plume" (see
immediately below for explanations of
these approaches). For either approach,
the volume of water used in the
calculations is equal to the
representative volume, i.e., the annual
water demand for the future group using
the ground water.
The "well-capture zone" is the
portion of the aquifer containing a
volume of water that one or more water
supply wells, pumping at a defined rate,
withdraw from an aquifer. The
dimensions of the well-capture zone are
determined by the pumping rate in
combination with aquifer characteristics
assumed for calculations, such as
hydraulic conductivity, gradient, and
the screened interval. If DOE uses this
approach, it must assume that the:
(1) Wells have characteristics
consistent with public water supply
wells in Amargosa Valley, for example,
well bore size and length of the
screened interval;
(2) Screened interval includes the
highest concentration in the plume of
contamination at the point of
compliance; and
(3j Pumping rate is set to produce an
annual withdrawal equal to the
representative volume.
To include an appropriate measure of
conservatism in the compliance
calculations for the well-withdrawal
approach, for the purpose of the
analysis, DOE should assume that
pumping wells that tap the highest
concentration within the projected
plume of contamination would supply
-------
32114 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
the community water demand. This
approach achieves conservatism by
requiring that the entire water demand
is withdrawn from wells intercepting
the center of the plume of
contamination so that the highest
radionuclide concentrations in the
plume are included in the volume used
for the compliance calculations. The
well-capture zone concept is described
in more detail in Bakker and Strack,
"Capture Zone Delineation in Two-
Dimensional Groundwater Flow
Models," [1996) (Docket No. A-95-12,
Item V-A-2S).
The "slice of the plume" is a cross-
section of the plume of contamination
centered at the point of compliance with
sufficient thickness parallel to the
prevalent flow of the plume such that it
contains the representative volume. If
DOE uses this approach, it must:
(1) Propose to NRC, for its approval,
where the edge of the plume of
contamination occurs, for example,
where the concentration of
radionuclides reaches 0.1% of the level
of the highest concentration at the point
of compliance;
(2) Assume that the slice of the plume
is perpendicular to the prevalent
direction of flow of the aquifer; and
(3) Set the volume of ground water
contained within the slice of the plume
equal to the representative volume.
Both alternatives require DOE to
determine the physical dimensions and
orientation of the representative volume
during the licensing process, subject to
approval by NRC. Factors that would go
into determining the orientation of the
representative volume would include
hydrologic characteristics of the aquifer
and the well.
The DOE must demonstrate
compliance with the ground water
protection standards (§197.30)
assuming undisturbed performance of
the disposal system. The term
"undisturbed performance" means that
human intrusion or the occurrence of
unlikely, disruptive, natural processes
and events do not disturb the disposal
system. The intent of the ground water
protection standards is to assess
whether the expected performance of
the repository system will lead to
contamination of the ground water
resource above the MCLs. The
assessment of resource pollution
potential is based upon the engineered
design of the repository being
sufficiently robust under expected
conditions to prevent unacceptable
degradation of the ground water
resource over time. Disruption of the
disposal system is inconsistent with that
intent. For this reason we have specified
that the ground water standards apply to
undisturbed performance. Our approach
also recognizes that human behavior is
difficult to predict and, if human
intrusion occurs, that individuals may
be exposed to radiation doses that
would be more attributable to human
actions than to the quality of repository
design (NAS Report p. 11). The
requirement that DOE project
performance for comparison with the
ground water protection standards
based on undisturbed-performance
scenarios is consistent with our
generally applicable standards for SNF,
HLW, and TRU radioactive waste in 40
CFR part 191 (58 FR 66402, December
20, 1993; 50 FR 38073 and 38078,
September 19, 1985).
We also require that DOE combine
certain estimated releases from the
Yucca Mountain disposal system with
the pre-existing natuially occurring or
man-made radionuclides to determine
the concentration in the representative
volume. This requirement means that
DOE must show a reasonable
expectation that the releases of
radionuclides from radioactive material
in the Yucca Mountain disposal system
will not cause the projected level of
radioactivity in the accessible
environment to exceed the limits in
§197.30.
We requested public comment
regarding these approaches to ground
water protection [i.e.. the use of the
MCLs, the concept of representative
volume and the alternatives for its size
and modeling approaches, and
calculational approaches for the
representative volume application). We
also requested comments regarding
whether it is desirable and appropriate
for us to provide additional detail for
the representative volume in the final
standards.
Comments generally approved of the
idea of providing alternate approaches
for determining the concentration of
contaminants in the representative
volume. Other comments requested
additional clarification of the
approaches. We developed these
approaches to measuring the
representative volume in the plume of
contamination to provide conservative
but reasonable methods of assessing
contaminant concentrations. We intend
both methods to avoid extreme
assumptions that would involve using
only the highest potential area of
contamination in a contamination
plume for comparison against the
standards and to allow reasonable
consideration of the expected behavior
of the flow regime downgradient of the
repository. For example, the well
capture-zone approach has conservative
aspects consistent with our general
approach to regulations (a "cautious,
but reasonable", approach). These
aspects include locating the well in the
path of the plume and requiring it to
have characteristics similar to water
supply wells in the area, while also
allowing DOE to consider well-bore
dilution effects for the water supply
wells that realistically would be
expected in actual practice. To keep the
modeling analyses from becoming too
complicated to perform and assess with
a reasonable degree of confidence, we
specify that DOE use average hydrologic
properties to avoid the problem of
summing up possibly thousands of
individual model runs. We attempt to
specify only the most important
specifics for the two methods to provide
a necessary context to assure the
standards are understood as we intend,
but still to provide flexibility for NRC in
• its implementation of the standards. For
example, we neither established
requirements nor made
recommendations regarding models to
be used for the plume modeling
methods. We left the applicant (DOE)
and the implementing authority (NRC)
the decision on defining the outer
boundary of the contamination plume
for this approach.
We received some comment asking for
additional clarification concerning the
two methods proposed for calculating
radionuclide concentrations in a
contamination plume, and in response
we have made some wording changes in
the final standards. We proposed that
the screened interval for the withdrawal
well be centered in the middle of the
contamination plume (proposed
§ 197.36 (b)(l)(ii)). The intent was to
take a conservative approach and
assume that the well taps the
contamination plume where the highest
contamination occurs, rather than being
positioned such that only a portion of
the lower concentration margin of the
plume is included in the representative
volume—such a situation would allow a
high dilution of the contamination from
pumping effects. For a physical
situation where the contamination
plume is very narrow and located at the
top of the aquifer, a physically
unrealistic situation could occur if the
well's screened interval must be
centered on the middle of the
contamination plume, i.e., the screened
interval could extend into the
unsaturated zone above the aquifer
making calculations of well capture
zones unrealistic since a water supply
well would not be deliberately screened
in that way. To remove this unrealistic
physical situation from consideration,
we have modified the language
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32115
describing the location of the screened
interval to state that it must include the
highest concentration portion of the
plume, with the intent being that the
screened interval should cross as much
of the plume diameter as possible so
that the conservative approach is taken
to calculating radionuclide
concentrations in the ground water
(finals 197.31 (b](l)(ii)).
Another clarifying change we have
made addresses the "averaging" of
hydrologjc properties (§ 197.31 (a)(2)) in
the downgradient portions of the ground
water flow system for the purpose of
making calculations for comparison
against the ground water protection
standards. In the proposed standards,
we used the phrase "average hydrologic
characteristics". We did not intend to
imply that a simple arithmetic averaging
process would adequately represent the
expected variation in hydrologic
properties that results from
heterogeneity of the flow system at the
site (Chapter 7 and Appendix VI of the
BID), or that simple arithmetic averaging
would be an allowable approach. We
believe that a simple arithmetic
averaging approach would mask the
expected heterogeneity of the flow
system. The values for hydrologic
properties of [he aquifers along the flow
path used in calculations should be
conservative but reasonable values,
which are representative of the expected
heterogeneity in the aquifers.
Heterogeneity can be accounted for by
using spatial statistical averaging
methods that can limit extrapolation of
data obtained from field measurements
in one locale and which are applied to
other locations represented by fewer or
poorer quality data. By using such
techniques, conservative but reasonable
data can be developed that adequately
represent the heterogeneity of the
aquifers for modeling purposes. We
have modified the proposed language to
reflect that the "averaged" values
should be conservative but reasonable
representations of the aquifer's
hydrologic properties.
o. Is the Storage or Disposal of
Radioactive Material in the Yucca
Mountain Repository Underground
Injection? As we discussed in detail in
the preamble to the proposed rule, we
do not believe that the disposal of
radioactive waste in geologic
repositories is underground injection for
purposes of the SDWA (42 U.S.C. 300f
to 300j—26). We received one comment
supporting our position and one
comment disagreeing with us. See 64 FR
47004-47007 (August 27, 1999) for our
comprehensive discussion of this issue.
b. Does the Class-lV Well Ban Apply?
We previously indicated that we would
review whether the Class-IV injection-
well ban would apply to Yucca
Mountain. See 64 FR 47006-47007 for
our previous discussion of this issue.
This rulemaking does not apply the
Class-IV injection-well ban to the Yucca
Mountain repository. We believe this
approach is appropriate in light of the
statutory and regulatory provisions,
discussed above and in the preamble to
the proposed rule, relating to
"underground injection," and the
differences in the purposes of the
Underground Injection Control (UIC)
program and the authority delegated to
us under the EnPA to establish public
health and safety standards for Yucca
Mountain.
It is important to emphasize that our
decision not to apply the Class-IV well
ban to Yucca Mountain does not affect
other disposal systems that dispose of
hazardous or radioactive waste into or
above a formation which, within one-
quarter (1/4) mile of the disposal
system, contains a USDW. We based
today's rule upon site and facility-
specific characteristics of the Yucca
Mountain disposal system. Today's rule
is limited to the Yucca Mountain
disposal system.
c. What Ground Water Does Our Rule
Protect? Although we find that the
Yucca Mountain disposal system is not
underground injection as contemplated
by the SDWA, we nevertheless consider
the ground water protection principles
embodied in the SDWA to be important.
Therefore, although we do not apply all
aspects of the SDWA, we are
establishing separate ground water
protection standards consistent with the
levels of the radionudide MCLs under
the SDWA.
We requested public comment upon
our approaches designed to protect
ground water resources in the vicinity of
the repository. We are concerned that
ground water resources in the vicinity of
Yucca Mountain receive adequate
protection from radioactive
contamination. The primary purpose of
our ground water standards is to prevent
contamination of drinking-water
resources. Because the compliance
period is 10,000 years after disposal,
references to levels of contamination
mean those levels projected to exist at
specific future times, unless otherwise
noted. However, these projections will
be made at the time of licensing. This
approach prevents placing the burden
upon future generations to
decontaminate that water by
implementing expensive clean-up or
treatment procedures. We believe it is
prudent to protect drinking water from
contamination through prevention
rather than to rely upon clean-up
afterwards. Absent the protection this
prevention provides, future generations
might find it necessary to intrude into
the sealed repository to remediate
radionuclides released from waste
packages inside the repository, in
addition to treating contaminated
ground water along the ground water
flow path. Thus, our ground water
protection standards stress pollution
prevention and provide protection from
contamination of sources of drinking
water containing up to 10,000 mg/L of
total dissolved solids (TDS). We
emphasize that the individual-
protection standard (§197.20) covers all
ground water pathways, including
drinking water.
The definition of USDW received
extensive discussion in the legislative
history of the SDWA as reflected in the
report of the House Committee on
Interstate and Foreign Commerce. To
guide the Agency, the Committee Report
suggested inclusion of aquifers with
fewer than 10,000 mg/L of TDS (H.R.
Rep. No. 1185, 93d Cong., 2d Sess. 32,
1974). We have reviewed the current
information regarding the use of
aquifers for drinking water which
contain high levels of TDS. This review
found that ground water containing up
to 3,000 mg/L of TDS that is treated is
in widespread use in the U.S. In the
Yucca Mountain vicinity, with few
exceptions (one being the Franklin
Playa area), ground water contains less
than 1,000 mg/L of TDS. Our review
also found that ground water elsewhere
in the nation, containing as much as
9,000 mg/L of TDS, currently supplies
public water systems. Based upon this
review and the legislative history of the
SDWA, we are proposing that it is
reasonable to protect the aquifers
potentially affected by releases from the
Yucca Mountain disposal system.
Therefore, the provisions in § 197.30
would apply to all aquifers, or their
portions, containing less than 10,000
mg/L of TDS. We took the definitions
associated with § 197.30 directly from
our UIC regulations [40 CFR parts 144
through 146).
One comment suggested that we
change the definition of "aquifer" in the
final rule to exclude perched water
bodies. A perched water body is a static
area of ground water, usually above the
water table, that is unconnected to an
aquifer but that may infiltrate into an
aquifer over time. Based upon our
review of this comment, typical
definitions of "aquifer" in the technical
literature, and the available site-specific
information regarding the existence of
perched water bodies in the vicinity of
Yucca Mountain, we decided to make
the suggested change. This comment
-------
32116 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
argued for this change based upon the
fact that perched water would be of
little value to future residents because
few such formations exist in the area
and because of abundant water in the
aquifer underlying Yucca Mountain.
The comment, also argued that it would
be difficult to make specific predictions
regarding the location and
characteristics of perched water bodies.
Finally, the comment stated it would
not be meaningful to attempt to model
perched water bodies in any
performance assessment. There are only
a few, small perched water bodies
known to be in the vicinity of Yucca
Mountain (see Chapter 7 of the BID).
Also, traditional definitions of "aquifer"
usually do not include perched water
bodies (see the Glossary in the BID). Our
intent also is to provide protection to
water resources of sufficient size to
supply water on a continuing basis to
targeted uses. Perched water bodies,
particularly as they have been observed
in the Yucca Mountain area, are
relatively small and would not provide
a continual source of water to wells
used for irrigation or for community
water demands. Based upon this
information, we believe that it is
unnecessary to include these bodies in
the definition of "aquifer" because it is
extremely unlikely that they could serve
as a consistent source of drinking water.
Therefore, we amended the definition of
"aquifer" to exclude perched water
bodies.
d. How Far Into the Future Must DOE
Project Compliance With the Ground
Water Standards? We are establishing a
10,000-year compliance period for
ground water protection. The primary
rationale for establishing a 10,QOO year
compliance period is that we are
significantly concerned about the
uncertainty associated with projecting
radiation doses over periods longer than
10,000 years. The NAS indicated that
beyond 10,000 years it is likely that
uncertainty will continue to increase
(NAS Report p. 72). As a result, it will
become increasingly difficult to discern
a difference between the radiation dose
from drinking water containing
radionuclides (limited by the MCLs) and
the total dose arriving through all
pathways (limited by the individual-
protection standard). Moreover, this
approach is consistent with the 10,000-
year compliance period we are
establishing for the individual-
protection standard. Therefore, it
provides internal consistency within the
standards. It is also consistent with
regulations covering long-lived
chemically hazardous wastes, which
present potential health risks similar to
those from radioactive waste, and with
the compliance period that we
established in our generally applicable
radioactive waste disposal standards at
40 CFR part 191.
We requested comment regarding our
proposal to impose the ground water
protection standards during the first
10,000 years following disposal.
Question 14 in the preamble to our
proposal specifically asked: "Is the
10,000-year compliance period for
protecting the RMEI and ground water
reasonable or should we extend the
period to the time of peak dose?" (64 FR
47010^7011} Comments related to the
compliance period applied to both the
RMEI and ground water. See the
discussion of issues pertaining to both
the RMEI and ground water protection
in section III.B.l.g (How Far Into the
Future Is It Reasonable to Project
Disposal System Performance?) along
with our rationale for adopting a 10,000-
year compliance period.
e. How Will DOE Iden tify Where to
Assess Compliance With the Ground
Water Standards? To provide a basis for
determining projected compliance with
the ground water protection standards
in § 197.30, it is necessary to establish
a geographic location where DOE must
project the concentrations of
radionuclides in the ground water over
the compliance period. This location is
the "point of compliance."
Our understanding, based upon
current knowledge, of the flow of
ground water passing under Yucca
Mountain is as follows (except where
noted otherwise, Chapter 7 and
Appendix VI of the BID are the sources
for the information in this paragraph).
The general direction of ground water
movement in the aquifers under Yucca
Mountain is south and southeast. The
major aquifers along the flow path are
in fractured tuff, alluvium, and,
underlying both of these, the deeper
carbonate rocks. At the edge of the
repository, the tuff aquifer is relatively
(several hundred meters) thick. The tuff
aquifer gets closer to the surface toward
its natural discharge points. Potential
releases of radionuclides from the
engineered barrier system into the
surrounding rocks would be highly
directional and would reflect the
orientation of fractures, rock unit
contacts, and ground water flow in the
area downgradient from Yucca
Mountain. Directly under the repository,
we anticipate that any waterborne
releases of radionuclides will move
through the unsaturated zone and
downward into the tuff aquifer, in an
easterly direction, between layers of
rocks that slant to the east, and
downward along generally vertical
fractures in the rock units until reaching
the saturated zone. The layer of tuff
gradually thins proceeding south
(downgradient) from Yucca Mountain.
As the tuff aquifer thins, the overlying
alluvium becomes thicker until the tuff
disappears and the water in the aquifer
moves into the alluvium to become the
"alluvial aquifer." Along the flow path,
there might be movement of water
between the carbonate aquifer and
either the tuff or alluvial aquifers. If
there is significant upward flow from
the carbonate aquifer, contamination in
overlying aquifers could be diluted. It is
generally believed, however, that any
such flow would not significantly affect
the concentration of radionuclides in
the overlying aquifers. Conversely,
downward movement of ground water
from the tuff aquifer could contaminate
the carbonate aquifer. Limited
information currently available
indicates that ground water from the
lower carbonate aquifer moves upward
into the overlying aquifer; however, this
interpretation may not be correct for the
entire flow path from beneath the
repository to the compliance points
southward from Yucca Mountain.
Today, most of the water for human use
is withdrawn between 20 and 30 km
away from the repository footprint (that
is, at Lathrop Wells and farther south
through the Town of Amargosa Valley)
where it is more easily and
economically accessed for agricultural
use and human consumption. It is likely
that the alluvial aquifer is the major
source of this water (see Chapter 8 and
Appendix V of the BID).
Another basis of our understanding is
the historical record of water use in the
region. The record indicates that
significant, long-term human habitation
has not occurred in the southwestern
area of NTS, or for that matter anywhere
in the vicinity of Yucca Mountain,
except where ground water is very
easily accessed (for example, in Ash
Meadows) (see Chapter 8 of the BID).
This observation coincides with current
practice whereby the number of wells
generally decreases with greater depth
to ground water (see Chapter 8 of the
BID). The difficulty in accessing ground
water in the tuff aquifer in the near
vicinity of Yucca Mountain increases
because of the rough terrain, the relative
degree of fracturing of the tuff
formations containing the aquifer, and
the great depth to ground water there.
As described earlier, the ground water
flow from under Yucca Mountain is
thought to be generally south and
southeast. In those directions, the
ground water gets progressively closer
to the Earth's surface the farther away it
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32117
gets from Yucca Mountain until it is
thought to discharge to surface areas 30-
40 km away (the southwestern boundary
of NTS is about 18 km from Yucca
Mountain). This means that access to
the upper aquifer is easier at increasing
distance from Yucca Mountain.
Because of DQE's ongoing site
characterization studies, it is possible
that, at the time of licensing, data not
now available will reveal important
inaccuracies in the preceding
conception of the ground water flow
under, and downgradient from, Yucca
Mountain. We intend compliance with
the ground water standards to be
assessed where DOE and NRC project
the highest concentrations of
radionuclides in the representative
volume of ground water in the
accessible environment. The DOE will
determine this location by modeling
releases into the saturated zone beneath
the repository and the subsequent
movement of radionuclides
downgradient from Yucca Mountain.
After selecting a location, however, DOE
must continue to evaluate new
information regarding ground water
flow. If this new information indicates
that the highest concentrations would
occur at a location in the accessible
environment different from the one
selected by DOE and NRC, DOE must
propose a new compliance location to
NRC. The new location is subject to
NRC's approval. The next section
discusses the concept of accessible
environment as it relates to the
controlled area,
/. Where Will Compliance With the
Ground Water Standards be Assessed?
We presented four alternatives for
comment prior to determining the
location of the point of compliance. See
the preamble to the proposed rule (64
FR 47000-47004) for a detailed
discussion of these four alternatives. We
asked commenters to address the
effectiveness of these or other
alternatives for protecting ground water,
including consideration of site-specific
characteristics and reasonable methods
of implementing the alternatives.
After reviewing and evaluating the
public comments, various precedents,
the EnPA, and NAS's recommendations,
we adopted the concept of a controlled
area as an essential precondition to
assessing compliance with the ground
water standards. The ground water
standards must be met in the accessible
environment where the highest
radionuclide concentrations in the
representative volume of ground water
are projected to occur during the
compliance period (10,000 years). The
highest projected concentrations will be
compared to the regulatory limits
established in today's rule. The
accessible environment includes any
location outside the controlled area. The
controlled area may extend no more
than 5 km in any direction from the
repository footprint, except in the
direction of ground water flow. In the
direction of ground water flow, the
controlled area may extend no farther
south than latitude 36°40'13.6661"
North, which corresponds to the
latitude of the southwest corner of the
Nevada Test Site, as it exists today
(Department of Energy submittal of
Public Land Order 2568, dated
December 19, 1961, Docket No. A-95-
12, Item V-A-29). The size of the
controlled area may not exceed 300 km2
(see below for further discussion). Such
a limitation is derived by combining the
concept of the controlled area as used in
40 CFR part 191 and the requirement for
a site-specific standard in the case of
Yucca Mountain. If fully employed by
DOE, and based on current repository
design, the controlled area could extend
approximately 18 km in the direction of
ground water flow (presently believed to
be in a southerly direction) and extend
no more than 5 km from the repository
footprint in any other direction.
Allowing for a nominal repository
footprint of a few square kilometers, this
results in a rectangle with approximate
dimensions of 12 km in an east-west
direction and 25 km in a north-south
direction, or approximately 300 km2.
The DOE may define the size and %hape
of the controlled area, but the
boundaries cannot extend farther south
than latitude 36°4Q'13.6661" North in
the direction of ground water flow and
5 km in any other direction.
The alternatives for the ground water
standards' compliance point presented
in the proposed rule correspond to
downgradient distances of
approximately 5, 18, 20, and 30 km from
the repository footprint. The first
alternative mirrored the approach used
in 40 CFR part 191. This approach
incorporates the concept of a controlled
area, not to exceed 100 km 2, and not to
extend more than 5 km in any direction
from the repository footprint. The
second alternative also incorporated the
concept of a controlled area, not to
extend more than 5 km in any direction
from the footprint, except that DOE
could include any contiguous area
within the boundary of NTS. The last
two alternatives described specific
points of compliance at distances of
about 20 and 30 km, respectively, from
the repository footprint. We also
intended these controlled areas and
points of compliance to be in the
predominant direction of ground water
movement from the repository.
Consequently, they would reflect the
transport path for radionuclides
released from the repository. We
intended the controlled area options to
describe that area of land dedicated to
the sole use of serving as the natural
barrier portion of the disposal system.
Compliance with the standards within
the controlled area is not an issue in
regulatory decision making because this
area is considered part of the overall
disposal system and is dedicated to
limiting radionuclide transport by
means of the natural processes operative
within it. Rather, compliance will be
judged at the location where projected
concentrations are highest and that is no
closer to the repository than the edge of
the controlled area. The controlled area
also serves as the basis for institutional
control measures intended to limit
access around the repository site. This
use of the controlled area, to limit
access to the site, is an assurance
measure we have left to the discretion
of NRC as the implementing authority.
Our rule does not require any specific
institutional controls to be applied to
the controlled area. As part of the
licensing process, DOE will propose the
specific shape and size of the controlled
area. The NRC's proposed rule
establishing licensing criteria for the
Yucca Mountain facility specifically
requires that DOE have permanent
control of the land. We anticipate that
Congress and the President will
authorize a legislative withdrawal of an
area within which the site is located.
The DOE will determine the extent of
land that will be requested of Congress
to legislatively withdraw from all other
public or private use. For its DEIS
(Docket No. A-95-12, Item V-A^l),
DOE analyzed a potential land
withdrawal area of 600 km2 in the
context of site characterization needs.
The legislative land withdrawal
represents the societal decision on the
area of land to be dedicated to the
characterization and operation of a
disposal system. Although the land
withdrawal may exceed 300 km2, we
limit the controlled area to 300 km2 for
the purpose of defining the maximum
geological volume which may be
included in the disposal system.
We adopted the concept of a
controlled area from the generic
standards in 40 CFR part 191. Those
standards state that the maximum size
of the controlled area is 100 km2 (40
CFR 191.12). After examining the
available information concerning the
characteristics of the Yucca Mountain
site, the current understanding of the
expected performance of the disposal
-------
32118 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
system and'the repository engineered
barrier system design, and comments
received on our proposed approach to
ground water protection, we believe that
a controlled area of up to 300 km2 will
adequately address the site-specific
conditions at Yucca Mountain.
It would be unreasonable for us to
limit DOE's flexibility while site
characterization and disposal system
design are continuing, or to issue
standards that do not account for the
uncertainties of ground water flow in
the region. Therefore, today's rule
provides that the size of the controlled
area may be up to 300 km2.
In reaching this decision regarding die
maximum size of the controlled area, we
must draw a contrast between the
approach used in 40 CFR part 191 and
today's rule. As mentioned earlier,
although the WIPP LWA exempted the
Yucca Mountain site from licensing
under the provisions of 40 CFR part 191,
the radiation protection principles in 40
CFR part 191 are still applicable, and we
examined them while developing site-
specific standards for Yucca Mountain.
Throughout this preamble, we note
where and why we have carried some of
the concepts forward from 40 CFR part
191 if we believe they are necessary for
protective standards at Yucca Mountain,
and how we have applied them in ways
consistent with the site-specific
information and understanding of the
Yucca Mountain site. Part 191
established a controlled area with a.
maximum distance in any direction of 5
km from the repository footprint to
provide a location for judging
compliance with the individual-
protection (§ 191.15), ground water
protection (§ 191.24), and containment
requirements (§ 191.13). Thus, the
controlled-area concept in 40 CFR part
191 links a 5 km maximum distance
from the repository footprint to a limit
on the size of the controlled area (100
km2 maximum). Within this area,
compliance with the standards is not
required because the geologic media
therein comprise an essential part of the
disposal system. This combination of
controlled area and protection of
individuals and ground water is
appropriate for generic standards
because generic standards' provisions
must account for the wide variety of
possible site conditions (e.g., releases
could move in many directions from the
repository toward the population),
engineered alternatives, and population
characteristics. Note that in the 1980s,
when 40 CFR part 191 was being
developed, DOE was considering nine
candidate HLW repository sites. It is
also important to recognize that 40 CFR
part 191 contained a mechanism for
substituting alternative provisions,
should they be deemed necessary.
By contrast, 40 CFR part 197 is site-
specific. The 1987 NWPA amendments
specified Yucca Mountain as the only
potential repository site where DOE may
conduct characterization activities.
Therefore, since passage of the 1987
amendments, the Yucca Mountain site
has been under an intense
characterization effort. Because of these
efforts, a significant amount of
information has been generated
regarding past, present, and planned
population patterns, land use,
engineered design, and the
hydrogeological characteristics of the
host rock and ground water systems at
the Yucca Mountain site. Based upon
information currently available, it
appears that contaminated ground water
will flow predominantly in a relatively
narrow path frojn the Yucca Mountain
repository. See the Yucca Mountain
DEIS, Chapter 3 (DOE/EIS-0250 D, July
1999, Docket No. A-95-12, Item V-A-
4, and the Viability Assessment, Docket
No. A-95-12, Item V-A-5). In addition
to the extensive data base compiled over
the years, we have the recommendations
of NAS. Significantly, NAS endorsed
the use of present knowledge using
"cautious, but reasonable" assumptions
in defining exposure scenarios (NAS
Report p. 100).
Concerning the size of the controlled
area, though we have a general
understanding of the primary direction
of ground water flow, our present
knowledge continues to evolve through
site characterization. As a result, we
believe the "cautious, but reasonable"
approach allows DOE the flexibility to
utilize a controlled area up to a
maximum of 300 km2. Given the
uncertainty in ground water flow paths,
and the fact that releases could occur
anywhere within the repository, we
believe it is prudent to ensure that any
potential contamination plumes from
repository releases are contained within
the controlled area, and to ensure that
access to and human activity within the
area of potential contamination is
limited, thereby minimizing the
potential for human exposure. We
recognize that 300 km2 represents an
increase in the maximum size of the
controlled area, and is larger than we
allow in 40 CFR part 191. However, for
site-specific reasons, we are increasing
the maximum extent of the controlled
area only in the direction of ground
water flow to no farther south than
latitude 36" 40' 13.6661" North, while
simultaneously limiting the extent of
the controlled area in any other
direction, to no greater than. 5 km. from
the repository footprint.
The size and shape of the controlled
area proposed by DOE in the licensing
process will depend upon two
fundamental elements: (1) The
dimensions of the repository layout for
the waste inventory and thermal
loading, as defined in the final
repository design; and (2) uncertainty in
ground water flow directions. Both of
these aspects are evolving since studies
for both site characterization and
repository design are Still in progress.
However, DOE provides some
indication in its DEIS of the range of
repository-design layouts under various
assumed waste inventories and thermal
loading alternatives. Combining these
repository alternatives in the DEIS, with
projected ground water flow paths to the
southern most extension of the
controlled area at latitude 36° 40'
13.6661" North., gives potential
controlled area sizes from 100 km2 or
less to around 300 km2. These estimates
are based upon the uncertainties in
ground water flow directions and
repository designs that currently exist.
When characterization and design
studies are completed, a well-defined
controlled area size can be determined
during the licensing process, where the
uncertainties will be examined in closer
detail and a final controlled area size
can be determined. However,
uncertainties can only be reduced, not
eliminated completely, even when site
characterization is completed—some
residual uncertainty will remain. As
stated earlier, we believe it is important
to allow flexibility for DOE and NRC at
this time to continue the
characterization and design work, and
allow the licensing process to operate
within certain bounds while knowledge
of the site is evolving.
In addition to ground water flow path
uncertainties, the size and shape of the
controlled area also depend upon
understanding how and where (in
relation to the repository layout)
radionuclides could be introduced into
the ground water. Failed waste packages
during the regulatory time-frame supply
the releases carried into the ground
water system. While DOE has adopted a
new highly engineered waste package
anticipated to have containment
lifetimes into the tens of thousands of
years (TRW Environmental Safety
Systems Inc., "Repository Safety
Strategy: Plan to Prepare the Postclosare
Safety Case to Support Yucca Mountain
Site Recommendation and Licensing
Considerations'', TDR-WIS-RL-000001,
January 2000, Docket No. A-95-12, Item
V-A-24), some small number of waste
packages can be anticipated to fail
within the regulatory period due to
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32119
undetected manufacturing defects.
While these failures can be minimized
through rigorous quality control efforts
during manufacturing, the potential
cannot be totally eliminated. The
location of such "premature failures" in
the repository is, however,
unpredictable. Other unpredictable
disruptive events and processes, such as
roof falls that damage waste packages
and accelerate corrosion processes,
could also result in releases in advance
of the anticipated containment lifetime
of the containers under expected
conditions. The location of these types
of waste package failures is also not
amenable to reliable prediction.
Therefore, releases from such failures
could originate anywhere within the
repository footprint and would
consequently enter the ground water
flow envelope at any location.
Recognizing this, the process of defining
the controlled area would focus upon
the two factors discussed above, the
repository footprint, which will reflect
the waste inventory and the repository
design choices, and the envelope of
potential ground water flow paths
around that footprint. "Cautious, but
reasonable" assumptions regarding
these factors can then be applied to
define a controlled area that will
include potential releases from a small
number of premature waste package
failures. A more detailed discussion of
the influence of these factors on the
potential size of the controlled area may
be found in "Considerations for
Defining a Site-Specific Controlled Area
for the Yucca Mountain Proposed
Repository Location" (Docket No. A-
95-12, Item V-B-7).
Regarding the alternatives we
proposed for the ground water point of
compliance, none of the information we
have reviewed suggests that it is likely
or reasonable to assume that year-round
residents will live within 5 km of the
repository footprint. As discussed in
Chapter 8 and Appendix IV of the BID,
it would be extremely difficult to farm
that close to Yucca Mountain, partly
because extracting ground water at that
location would be both technically
challenging and very expensive for an
individual or small group. In addition,
much of this area has rough terrain and
soils not conducive to farming. Our
understanding of projections of future
land use does not indicate significant
population growth much farther north
of Lathrop Wells, i.e., closer than about
18 km from the repository footprint (see
Appendix I of the BID, Docket No. A-
95-12, Items V-A-14, 15,16). Given the
small likelihood of a year-round
resident at 5 km, we chose not to select
a distance of 5 km as the limiting
distance from the repository footprint to
the controlled area boundary.
As one goes farther away from Yucca
Mountain in the direction of ground
water flow, it is easier to drill for ground
water because the water table is closer
to the ground surface and the geologic
medium changes from tuff to alluvium.
In addition, the soil characteristics
improve such that agricultural pursuits
become more feasible, as evidenced by
the widespread agricultural activity in
Amargosa Valley some 30 km from
Yucca Mountain. There are
approximately 10 residents at about 20
km (Lathrop Wells) and hundreds of
residents at a distance of 30 km. Current
projections of population growth
indicate southern Nevada as one of the
fastest growing areas in the country (see
the Yucca Mountain DEIS, Chapter 3
(DOE/EIS-0250D, July 1999, Docket No.
A-95-12, Item V-A-4), and reports
prepared for Nye County and Amargosa
Valley (Docket'No. A-95-12, Items V--
A-14, V-A-15, and V-A-16)). We
selected latitude 36° 40' 13.6661" North,
which corresponds to the southwest
corner of NTS as it exists today (Docket
No. A-95-12, Item V-A-29), a's the
maximum distance that the controlled
area may extend in the direction of
ground water flow (south). Given the
expected population growth in southern
Nevada, it is reasonable to project that
some population growth may occur
slightly north of Lathrop Wei is,
although the boundaries of NTS are
likely to remain and restrict population
expansion in this direction, at least for
the near future. As indicated previously,
the representative volume of ground
water used to demonstrate compliance
would reflect a small community
including alfalfa cultivation and some
residential and light industrial
development. At distances progressively
closer than 18 km to the repository, it
becomes more difficult to drill for water,
soil conditions become less favorable for
agriculture, and more land is subject to
restricted access by the Federal
government. We believe, based upon the
site-specific information now available,
and using cautious, but reasonable
assumptions, the southwest corner of
NTS, or an equivalent distance in the
direction of ground water flow, would
be the closest location for a small group
to be accessing ground water.
Several comments suggested that we
should locate !he point of compliance
for ground water protection purposes at
the boundary of the Yucca Mountain
repository footprint. As discussed
above, 40 CFR part 191 established the
concept that a certain amount of geology
surrounding a repository is part of the
overall disposal system. The controlled-
area concept limited considerations of
radiation dose to individuals or
contamination of ground water to areas
outside of this controlled area. The
controlled area in 40 CFR part 191
applies at a distance from the
repository, to be determined by the
implementing agency, but not to exceed
5 km from the footprint. We continue to
support the concept of a compliance
point at some distance beyond the
repository footprint. In the case of
Yucca Mountain, most of the land
within the repository footprint is rugged
terrain, with extreme depths to ground
water, and land unsuitable for
agricultural pursuits (see Chapter 8 of
the BID). Therefore, we did not choose
a compliance point at the edge of the
Yucca Mountain repository footprint.
A number of comments suggested we
locate the point of compliance, or limit
the distance to the boundary of the
controlled area, at distances ranging
from 5 km to 30 km from the repository
footprint. As we indicated previously,
we adopted NAS's recommendations to
use present knowledge and cautious,
but reasonable, assumptions in making
regulatory decisions. For the reasons
discussed earlier, we did not choose to
base compliance with the standards
upon a uniform 5 km distance from the
repository. Other comments supported
placing the compliance point at 30 km,
citing the volume of water currently
withdrawn at that distance. Indeed,
most of the agricultural activities in the
vicinity of Yucca Mountain currently
take place in this area, and it is home
to hundreds of residents. This situation
occurs because of the easy accessibility
of ground water and soil conditions
conducive to a variety of agricultural
activities. However, a distance of 30 km
would effectively ignore the existence of
populations who presently access
ground water closer to the repository.
Given the prospect of future population
growth as well, at distances of about 20
to 30 km from the repository footprint,
it would appear more reasonable to
protect ground water resources at
distances closer than 30 km. Therefore,
we did not choose the "30 km"
alternative as the compliance point.
Distances approximating 20 km
appear more reasonable to consider to
assess compliance with the ground
water standards. As described in
Chapter 8 of the BID, no fanning
currently occurs closer than about 23
km from the repository footprint. Also,
as one gets closer than about 18 km to
the repository footprint, the depth to
water begins to increase dramatically
from about 100 m at a distance of 20 km
to a few hundred meters at a distance of
-------
32120
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
5 km. Given the expectation of future
population growth and the precious
nature of ground water resources in the
area, it is reasonable to assume that a
small group may annually extract the
representative volume of ground water
at a distance slightly closer than 20 km,
namely, latitude 36° 40' 13.6661" North,
which corresponds to the southwest
corner of NTS as it exists today (Docket
No. A-95-12, Item V-A-29). This
approach is protective of the ground
water resources reasonably anticipated
to be accessed in the vicinity of Yucca
Mountain. To determine compliance
with the ground water standards, DOE
must define the controlled area and
calculate the concentrations of
radionuclides in the representative
volume of ground water at a location
outside the controlled area where the
concentrations are the highest. The
controlled area may encompass no more
than 300 km2 and may extend no farther
south, in the direction of ground water
flow, than latitude 36° 40' 13.6661"
North, which corresponds to the
southwest corner of NTS (Docket No. A-
95-12, Item V-A-29). In any other
direction, the controlled area may
extend no more than 5 km from the
repository footprint. We emphasize that
these dimensions describe the
maximum size of the controlled area. In
defining the actual dimensions of the
controlled area, DOE may extend the
southern boundary of the controlled
area as far as latitude 36° 40' 13.6661"
North, which corresponds to the
southwest corner of the NTS (Docket
No. A-95-12, Item V-A-29). The DOE
could place the boundary of the
controlled area anywhere along that
distance. Therefore, when we say we
did not base compliance with the
standard upon a distance of 5 km from
the repository footprint, we mean that
we neither selected the alternative that
would have set the maximum
dimension of the controlled area as 5
km in any direction, nor did we identify
a specific point of compliance at that
distance. The DOE is free to define the
controlled area such that it extends only
5 km, or less than 5 km, in any direction
(i.e., DOE is not required to extend the
controlled area as far as latitude 36° 40'
13.6661" North in the direction of
ground water flow, or as far as 5 km
from the repository footprint in any
other direction), and to assess
compliance at the location outside the
controlled area where concentrations
are highest. In the context of waste
disposal, the ground water protection
standards do not apply inside the
controlled area, consistent with the
approach in 40 CFR part 191.
IV. Responses to Specific Questions for
Public Comment
In addition to requesting comments
regarding all aspects of this rulemaking,
many of which we have highlighted in
the preceding sections of this document,
we also requested comment based upon
sixteen specific questions. These
specific questions appear below, along
with brief summaries of the comments
we received and our responses to those
comments. As with each of the
comments discussed elsewhere in this
document, we present detailed and
comprehensive responses in the
accompanying Response to Comments
document.
1. The NAS Recommended That We
Base The Individual-protection
Standard Upon Risk. Consistent With
This Recommendation and the
Statutory Language of the EnPA, We are
Proposing a Standard in Terms of
Annual CEDE Incurred by Individuals.
Is Our Rationale for This Aspect of OUT
Proposal Reasonable?
Comments/Our Responses. Many of
the comments we received on this issue
supported the promulgation of a
standard stated in terms of dose.
Moreover, section 801(a)(l) of the EnPA
specifically provides that EPA shall
"promulgate, by rule, public health and
safety standards for protection of the
public from releases from radioactive
materials stored or disposed of in the
repository at the Yucca Mountain site.
Such standards shall prescribe the
maximum annual effective dose
equivalent to individual members of the
public from releases from radioactive
materials stored or disposed of in the
repository." Consistent with the specific
statutory language of the EnPA, and the
numerous comments supporting the use
of a standard stated in terms of dose, we
choose to use dose as the form of the
individual-protection standard. See
section III.B.l.a above for a discussion
of our rationales for making this choice.
As discussed to some extent in section
III.B.l.c, and in more detail in the
preamble to the proposed standards
(beginning on 64 FR 46984), the primary
basis of the dose limit, 150
microsieverts (15 mrem), is the risk of
fatal cancer. This level equates to an
annual risk of about 8.5 in one million
of developing a fatal cancer. This level
is within the risk range recommended
by NAS. Thus, the 15 mrem CEDE
standard is consistent with NAS's
recommendation.
2. We Are Proposing an Annual Limit of
150 uSv (15 mrem) CEDE To Protect the
RMEI and the General Public From
Releases From Waste Disposed of in the
Yucca Mountain Disposal System. Is
Our Proposed Standard Reasonable To
Protect Both Individuals and the
General Public?
Comments/Our Responses. As noted
in section III.B.l.c above, we are
establishing an individual-protection
standard for Yucca Mountain that limits
the annual radiation dose incurred by
the RMEI to 150 uSv (15 mrem) CEDE.
See section IlI.B.l.c for a discussion of
the comments regarding the
appropriateness of the level of
protection. We chose not to adopt a
separate limit on radiation releases for
the purpose of protecting the general
population. There is a full description of
our reasoning in section IILB.l.e, above.
However, in summary, we based this
decision upon several factors. The first
factor is NAS's estimate of extremely
small doses to be received by
individuals resulting from air releases
from the Yucca Mountain disposal
system. The projected level of these
doses is well below the risk level
corresponding to our individual-
protection standard for Yucca
Mountain. It also is well below the level
that we have regulated in the past
through other regulations. We also
declined to establish a negligible
incremental dose (NID) level below
which doses would not have to be
calculated. The second factor is that,
based upon current, site-specific
conditions near Yucca Mountain, it is
unlikely that there will be great dilution
and wide dispersal of radionuclides
transported in ground water leading to
exposure of a large population. This
means that the individual-dose standard
will suffice to protect the general
population. There should be no
confusion between establishment of this
standard and our establishment of
ground water protection standards
intended to protect that water for future
use. The final factor is that we require
all of the pathways, including air and
ground water, to be analyzed by DOE
and considered by NRC under the
individual-protection standard.
Regarding the concepts of negligible
incremental dose or risk, though we
have recognized elsewhere in this
preamble that individual doses from
14 C are below the level at which the
Agency has historically regulated
individual doses, we have declined to
establish an NID or NIR level for the
reasons enumerated in section III.B.l.e
in this preamble. As described by NCRP,
the concepts of NID and NIR relate to
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32121
individual-dose assessments, not
collective dose assessments (Docket A-
95-12, Item II-A-8). Therefore, we are
not prepared to accept the NIR concept
as discussed by NAS.
We also disagree with NAS when it
states on page 120 of its report: "On a
collective basis, the risks to future local
populations are unknowable." There is
no question that there will be
uncertainty in the estimate; however,
even without our recommendation, DOE
has already published projected
collective doses for Yucca Mountain
(see Table 4—34 on p. 4-39 of the Yucca
Mountain DEIS, Docket No. A-95-12,
Item V-A-4), and is likely to refine
these estimates. These estimates could
fulfill the NCRP recommendation to use
collective dose in a non-regulatory
fashion to assess acceptability of a
facility (Docket No. A-95-12, Item II-
A-8)."
Most comments on this issue
supported not establishing a collective-
dose limit for Yucca Mountain. Two
other comments supported our decision
to not establish an NJR or NID level.
One comment went further by opposing
our suggestion that DOE use estimated
collective dose to examine design
alternatives on the grounds that such
action is unnecessary to protect the
general public. That comment also
stated that we have not provided
guidance on what to do with the
collective dose estimates and that we
are making policy judgments with
respect to collective dose estimation.
Upon consideration of those comments,
we are not recommending that DOE
estimate collective dose, primarily
because ive believe that the individual-
protection standard will adequately
protect the general population.
3. To Define Who Should Be Protected
by the Proposed Individual-protection
Standard, We Are Proposing To Use an
RMEI as the Representative of the Rural-
residential CG. Is Our Approach
Reasonable? Would it be More Useful to
Have DOE Calculate the Average Dose
Occurring Within the Rural-residential
CG Rather Than the RMEI Dose?
Comments/Our Responses. We
decided that the RMEI in the individual-
protection scenario will have a rural-
residential lifestyle. A number of
comments supported the use of the CG
approach. One commenter suggested
specifically that it preferred a rural-
residential CG to the rural-residential
RMEI because it is possible to estimate
exposures with much greater
confidence. However, in general, we
decided to use the rural-residential
RMEI rather than a rural-residential CG
for the same reasons that we selected
RMEI instead of the CG (see section
III.B.1 .d above, and Docket No. A-95-
12, Item V-B-3).
In summary, those reasons are that the
RMEI approach:
(1) Is consistent with widespread
practice, current and historical, of
estimating dose and risk incurred by
individuals even when it is impossible
to specify or calculate accurately the
exposure habits of future members of
the population (as in this case where it
is necessary to project doses for very
long periods);
(2) Is sufficiently conservative and
fully protective of the general
population;
(3) Provides protection similar to the
probabilistic CG approach
recommended by NAS for small
groups—it has the same goal and
purpose as does NAS's recommended
probabilistic CG approach, i.e., to
protect the vast majority of the public
while ensuring that the acceptability of
the repository is not driven by
unreasonable and extreme cases. It
accomplishes this by employing some
maximum parameter values and some
average parameter values (similar to the
NAS's concept of using "cautious, but
reasonable" assumptions) for the factors
most important to estimating the doss to
arrive at a conservative, but reasonable,
projection of future dose;
(4) Allows the desired degree of
conservatism to be built but within the
site-specific limits and the framework
which we have established.
(5) Is straightforward and relatively
simple to understand, and is more
appropriate than the probabilistic CG for
the situation at Yucca Mountain. It is
less speculative to implement than is
the probabilistic CG approach given the
unique conditions present at Yucca
Mountain (and is a cautious, but
reasonable, approach). For example,
given the known characteristics of
ground water flow at Yucca Mountain,
locating the receptor in the direct path
is more protective, and easier to
implement, than assessing an average
dose incurred by a randomly-located
group of receptors; and,
(6) Has been used by us in the past
(whereas we have not used the CG
concept).
A number of other comments.
suggested other groups or individuals
that would represent more appropriately
the individual to be protected by the
individual-protection standard. The
suggestions included a fetus, the elderly
and infirm, and subsistence farmers.
Regarding the various ages and stages of
development, the risk value used for the
development of cancer is an overall
average risk value (see Chapter 6 of the
BID for more details) that includes all
exposure pathways, both genders, all
ages, and most radionuclides. However,
it does not cover the "unborn within the
womb" (see Chapter 6 of the BID). It is
thought that the risk per unit dose for
prenatal exposures is similar to the
average risk per unit dose for postnatal
exposures; however, the exposure
period is very short compared to the rest
of the individual's average lifetime. (See
Chapter 6 of the BID for a discussion of
cancer risk from in utero exposure).
Therefore, the risk is proportionately
lower and would not have a significant
impact upon the overall risk incurred by
an individual over a lifetime (see
Chapter 6 of the BID). On the other end
of the age spectrum, radiation exposure
of the elderly at the levels of the
individual-protection standard would
be less than the overall risk value
because they have fewer years to live
and, therefore, fewer years for a fatal
cancer to develop (see Chapter 6 of the
BED). Finally, we did not use
subsistence farmers because we do not
believe that they are representative of
the current lifestyle in Amargosa Valley
and that, therefore, they would not
constitute a cautious, but reasonable,
assumption in relation to the guidance
from NAS to use current technology and
lifestyle.
4. Is it Reasonable To Use RMEI
Parameter Values Based Upon
Characteristics of the Population
Currently Located in Proximity to Yucca
Mountain? Should We Promulgate
Specific Parameter Values in Addition
To Specifying the Exposure Scenarios?
Comments/Our Responses. The basis
of the RMEI dose calculations will be
the current population downgradient
from Yucca Mountain. This approach is
consistent with NAS's recommendation
to use current lifestyles to avoid the
endless speculation that could result
from trying to project future human
activities. See section III.B.1.d above for
a discussion of this issue. Most
commenters supported this approach.
However, a number of commenters
preferred using a subsistence-farmer
lifestyle. We have been unable to
identify this lifestyle in the area around
the Yucca Mountain site. Also, a few
commenters stated that we should take
future changes in population, land use,
climate, and biota into consideration.
Again, with the exception of climate
and geologic processes, these factors are
subject to the potentially endless
speculation of which NAS spoke in its
report. We do require DOE and NRC to
take climate change and probable
variations in geologic conditions into
-------
32122 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
account because they are factors that
scientific study can reasonably bound.
5. Is it Reasonable To Consider, Select,
and Hold Constant Today's Known and
Assumed Attributes of the Biosphere for
Use In Projecting Radiation-related
Effects Upon the Public of Releases
From the Yucca Mountain Disposal
System?
Comments/Our Responses. The
comments we received on this question
generally favored our position of
holding present biosphere conditions
constant for the purpose of making
performance projections for the disposal
system. Some comments pointed to the
unexpected dynamic population growth
in the southern Nevada area, or stated
that current conditions were not a
reliable means to predict future
conditions. Some comments also
pointed out that the target receptor for
dose assessments could not be defined
independently of assumptions about the
biosphere. The tenor of these comments
is a general agreement that unreasonably
speculative assumptions about
biosphere conditions are inappropriate
and should be avoided. We agree with
this general theme of not making
unreasonably speculative assumptions
about the future. The NAS also made
this point in its recommendations for a
reference biosphere. We made some
fundamental assumptions in this rule
about biosphere conditions to assure
that dose assessments for the RMEI are
cautious, but reasonable. For example,
we require that DOE assume that the
RMEI consumes 2 liters/day of drinking
water and that DOE base food
consumption patterns on surveys of the
current residents in the area
downgradient from Yucca Mountain.
We have left it to NRC to establish other
details of the biosphere dose assessment
calculations for Yucca Mountain, such
as details of path way-specific dose
conversion factors and details necessary
for assessing all potential exposure
pathways. For additional discussion of
these issues, see section IILB.l.f above.
A related aspect of fixing biosphere
conditions for dose assessments is the
question of potential variations in
climate and geologic conditions because
these factors play an important part in
developing the ground water
contaminant concentrations that serve
as input for the biosphere dose
assessments. We specify that DOE
should vary climate and geologic
conditions over a reasonable range of
values based on an examination of
evidence in the geologic record for
conditions in the area. The evidence
preserved in the relatively recent
geologic record provides a means to
reasonably bound the range of possible
conditions.
6. In Determining the Location of the
RMEI, We Considered Three Geographic
Subareas and Their Associated
Characteristics. Are There Other
Reasonable Methods or Factors Which
We Could Use to Change the Conclusion
We Reached Regarding the Location of
the RMEI? For Example, Should We
Require an Assumption That for
Thousands of Years Into the Future
People Will Live Only in the Same
Locations That People do Today? Please
Include Your Rationale for Your
Suggestions
Comments/Our Responses. See
section HI.B.l.d above for a further
discussion of this subject. The many
comments we received on this topic
suggested a variety of locations, some
closer and some farther than Lathrop
Wells. A few commenters thought that
the Lathrop Wells location is
appropriate. However, a number of
others stated that the location should be
at the repository footprint. One
commenter stated that the current
farming area in southern Amargosa
Valley would be a reasonable location
for the RMEI.
Based on further review of site-
specific information, we decided to
locate the RMEI in the accessible
environment above the highest
concentration of radionuclides in the
plume of contamination. The accessible
environment begins at the edge of the
controlled area, which may extend no
farther south than the southern
boundary of NTS (latitude 36° 40'
13.6661" North), which is
approximately 18 km south of the
repository (roughly 2 km closer than the
Lathrop Wells location we proposed).
We do not believe that an RMEI likely
would live much closer to the Yucca
Mountain repository because of the
increasing depth to ground water and
the increasing roughness of the terrain
(see Chapter 8 of the BID), although the
RMEI would still have rural-residential
characteristics described in § 197.21 if
the controlled area does not extend as
far south as the NTS boundary. In
addition, we believe that, at 18 km, a
rural resident likely will receive the
highest potential doses in the region
because, as we have defined the RMEI,
the potential dose at this location will
be from drinking water, as well as
throngh jngestion of food grown with
contaminated ground water. With the
RMEI eating food grown using
contaminated water, the rural resident
at 18 km will have a higher dose than
an individual would have living much
closer than 18 km because the cost of
water likely would preclude a garden
and likely would allow only drinking
the water and domestic uses (see
Chapter 8 of the BID). Likewise, we do
not think that hypothesizing that the
RMEI lives 30 km away is a cautious or
reasonable assumption because: (1) At
30 km, the RMEI likely would use water
in which contaminants would be much
more diluted; (2) the downgradient
residents closest to Yucca Mountain are
currently near Lathrop Wells; and (3)
Nye County projects short-term (20
years) growth between U.S. Route 35
and the southern boundary of NTS;
therefore, population there is not an
ephemeral phenomenon. Therefore,
placing the RMEI at about 18 km from
the repository footprint reflects the
location of existing residents, is
reasonably conservative, and provides
more protection of public health,
relative to one commenter's suggested
location of 30 km.
There were a few other comments
related to the location of the RMEI. For
example, one comment suggested that,
in selecting the location, we should
consider the geology and hydrology of
the site rather than choosing the
location in advance. Another comment
stated that we should base the location
of the RMEI on the ability of the RMEI
to sustain itself consistent with
topography and soil conditions. This
comment also stated that depth to
ground water should not be a factor
because it is impossible to predict either
human activities or economic
imperatives.
We determined the point of
compliance for the individual-
protection standard using site-specific
factors and NAS's recommendation to
use current conditions (NAS Report p.
54). In preparing to propose a location
for the RMEI, we collected and
evaluated information on the natural
geologic and hydrologic features such as
topography, geologic structure, aquifer
depth, aquifer quality, and the quantity
of ground water, that may preclude
drilling for water at a specific location
(see Chapters 7 and 8, and Appendices
IV and VI, of the BID). We also
considered geologic conditions, for
example, we do not believe that a rural-
residential individual would occupy
areas much closer to Yucca Mountain
because of the increasing rough terrain
and the increasing depth to ground
water (see Chapter 8 of the BID). With
increasing depth to ground water come
higher costs: (1) To explore for water; (2)
to drill for water; and (3) to pump the
water to the surface (see Appendix IV of
the BID). Our final standard requires
DOE and NRC to consider other, more
appropriate locations based upon
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32123
potential, future site characterization
data. We agree that it is impossible to
predict either human activities or
economic imperatives. Therefore, we
followed NAS's recommendation to use
current conditions. This approach
allows us to avoid forcing the use of
potentially excessive speculative
assumptions as the bases of regulatory
decisionmaking. It also leads us to
consider the depth to ground water as
a key factor in determining the location
and activities of the RMEI and the
current location of people living
downgradient from the repository as a
reflection of this key factor. We note
that some wells providing drinking
water are located less than 18 km from
the repository footprint; however, those
wells have been installed by the Federal
government to serve the needs of NTS,
and we do not consider them typical of
wells that would serve, or be installed
by, a rural-residential RMEI. See
Chapter 8 (Table 8-5) of the BID.
Finally, one comment stated that the
proposed RMEI concept forces DOE to
assume the RMEI will withdraw water
from the highest concentration within
the plume without consideration of the
likelihood. According to this comment,
forcing such an assumption neglects the
low probability that a well will intersect
the highest concentration within the
plume.
This comment's approach, which
would utilize a probabilistic method to
determine the radionuclide
concentration withdrawn by the RMEI,
is similar to one of the example critical
group approaches thatNAS provided in
its report (NAS Report, Appendix C).
The NAS's approach would use
statistical sampling of various
parameters, i.e., considering the
likelihood (probability) of various
conditions existing, to arrive at a dose
for comparison to the standard.
However, we did not use this CG
approach for the following reasons: {1}
There is no relevant experience in
applying the probabilistic CG approach,
(2) the probabilistic CG approach is very
complex and is difficult to implement in
a manner that assures it would meet the
requirements of defining a CG (i.e., a
small group of people who are
homogeneous in regards to exposure
characteristics, including receiving the
highest doses among the genera}
population), and (3) we are concerned
that this approach does not appear to
identify clearly which individual
characteristics describe who is being
protected. A probabilistic approach for
CG dose assessment could include
members that would receive little or no
exposure and members that would
receive much higher exposures. An
RMEI is a more conservative approach,
based upon site-specific conditions,
because the RMEI serves to represent
those individuals in the community
who would receive the highest doses,
based on cautious, but reasonable,
assumptions. Finally, a significant
majority of the comments on the NAS
Report opposed the use of the
probabilistic CG approach. We further
believe that prudent public health
policy requires that our approach be
followed to provide reasonable
conservatism. To allow the probability
of any particular location being
contaminated is not a prudent approach
to the ultimate goal of testing acceptable
performance.
7. The NAS Suggested Using an NIR
Level to Dismiss From Consideration
Extremely Low, Incremental Levels of
Dose to Individuals When Considering
Protection of the General Public. For
Somewhat Different Reasons, We are
Proposing To Rely Upon the Individual-
Protection Standard To Address
Protection of the General Population. Is
This Approach Reasonable in the Case
of Yucca Mountain? If Not, What is an
Alternative. Implementable Method To
Address Collective Dose and the
Protection of the Genera) Population?
Comments/Our Responses. A number
of commenters agreed with us that the
general population is protected by the
individual-protection standard in the
site-specific case of Yucca Mountain.
Nearly all commenters agreed with our
position that a collective-dose limit is
unnecessary, again, in the site-specific
case of Yucca Mountain. Some
commenters stated that EPA should not
use an NIR level. One commenter stated
that we should not suggest that DOE use
a collective-dose estimate in the
consideration of design alternatives. We
decided not to include a collective-dose
limit (see section HLB.l.e), and are not
recommending that DOE estimate
collective doses.
Regarding the NIR, we decline to set
such a level. We agree with NAS's
conclusion that " * * * an individual
risk standard [will] protect the public
health, given the particular
characteristics of the site * * *" (NAS
Report p. 7). However, we do not accept
the remainder of that statement:''* * *
provided that policy makers and the
public are prepared to accept that very
low radiation doses pose a negligibly
small risk" (NAS Report p. 7). We do
not agree that collective doses made up
of very small individual doses are
necessarily negligible. We base our
decision on the site-specific
characteristics of Yucca Mountain and
the levels of individual risk that we
previously have used. See the preamble
to the proposed rule (64 FR 46991) for
the full discussion of our reasoning. We
summarize this discussion immediately
below.
The NAS based its recommendations
upon guidance from NCRP in which
NCRP proposed a "Negligible
Incremental Dose" level of 1 mrem/yr.
Dose levels below 1 mrem/yr would be
considered "negligible" for any source
or practice (see the NAS Report pp. 59-
61 and NCRP Report No. 116, p. 52,
Docket No. A-95-12, Item E-A-7). The
IAEA has made similar
recommendations to define an "exempt
practice" (see IAEA Safety Series No.
89, p. 10, Docket No. A-95-12, Item II-
A-6). However, it is not clear to us that
an exemption for whole sources or
practices, such as waste disposal in
general, should apply to such specific
situations such as gaseous releases from
a particular repository because gaseous
releases comprise only one category of
releases from a repository; other releases
are projected via the ground water
pathway. In addition, we believe that it
is inappropriate to avoid calculating a
radiation dose merely because it is small
on an individual basis (NCRP Report
No. 121, p. 62, Docket No. A-95-12,
Item II-A-8). Finally, we do not believe
that it is appropriate to apply the NIR
concept to population doses (NCRP
Report No. 121, p. 62, Docket A-95-12,
Item II-A-8). In its Report No. 121,
NCRP stated: "[a] concept such as the
NID (Negligible Incremental Dose)
* * * is not necessarily a legitimate cut-
off dose level for the calculation of
collective dose. Collective dose
addresses societal risk while the NID
and related concepts address individual
risk" (NCRP Report No. 121, p. 62,
Docket No. A-95-12, Item II-A-8).
Despite our belief that it is
inappropriate to set an NID level, we
acknowledge that the extremely low
levels of individual risk from the doses
that NAS cited (NAS Report p. 59) (i.e.,
0.0003 millirem/yr, for airborne
releases) are well below those levels that
we have used for other regulations.
In addition, the standards in 40 CFR
part 191 provide both release limits,
which act as a form of collective dose
protection, and individual-protection
limits. The release limits act to restrict
the potential of dilution being used by
disposal system designers to meet the
individual-protection limit. However,
the potential for large-scale dispersal of
radionuclides through ground water and
into surface water does not exist at
Yucca Mountain.
Therefore, for the reasons enumerated
above, we believe that we do not need
to include a general population-
-------
32124 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
protection provision in our Yucca
Mountain standards. See the Response
to Comments document for a fuller
discussion of our responses to
comments we received on these issues.
8. Is Our Rationale for the Period of
Compliance Reasonable in Light of the
NAS Recommendations?
Comments/Our Responses. Public
comments supported a compliance
period that ranged from 10,000 years to
a million years and beyond (i.e., no time
limitation). Most of the comments
supporting the 10,000-year period were
concerned that such a period was the
longest time over which it would be
possible to obtain meaningful modeling
results. Comments noted that just
because performance assessment modefs
may be set to run dose calculations to
times well in excess of 10,000 years
does not necessarily mean that at this
time the level of confidence in the
reliability of these calculations remains
the same. Other comments noted that
because of the unprecedented nature of
compliance periods exceeding 10,000
years, the greater uncertainties at such
times only serves to complicate the
licensing process without providing a
clearly identifiable increased benefit to
public health. A few commenters
suggested that because there will likely
be radiation doses incurred by
individuals beyond 10,000 years, DOE
should calculate peak dose, within the
time period of geologic stability, and
include these doses in the Yucca
Mountain Environmental Impact
Statement. These comments essentially
supported the rationale upon which we
based our final rule.
On the other hand, numerous
comments suggested that a compliance
period of 10,000 years is not reasonable.
They urged us to extend the compliance
period beyond 10,000 years for a variety
of reasons. Foremost among these
reasons is that NAS suggested a
compliance period that would extend to
the time of peak dose or risk, within the
period of geologic stability for Yucca
Mountain, which it estimated could be
as long as one million years. The NAS
based its recommendations on scientific
considerations. The NAS concluded that
it is possible to assess the performance
of the repository over times during
which the geologic system is "relatively
stable" or varies in a "boundahle
manner" (NAS Report p. 9). It also
noted that policy considerations could
act to shorten this period. Other
comments suggested that the
compliance period of the standard
should be comparable to the hazardous
lifetime of the materials to be emplaced
in the Yucca Mountain repository.
It is unclear whether an assessment of
the disposal system based on N AS's
recommendation for a standard that
would apply to time of peak dose within
the period of geologic stability (about
one million years) would be meaningful
given the expected rigor of a licensing
process. As discussed above in section
III.B.l.g, we believe that the substantial
uncertainty in projecting human
radiation exposures over extremely long
time periods, such as a million years, is
unacceptable. For example, analyzing
long-term natural changes would
require unprecedented performance
assessment modeling of numerous and
different climate regimes including
several glacial-interglacial cycles. This
situation could require the specification
of exposure scenarios based on arbitrary
assumptions rather than "cautious, but
reasonable" assumptions rooted in
present-day knowledge. In fact, NAS
indicated it knew of no scientific basis
for identifying such scenarios (NAS
Report p. 96). Another concern relates to
the possible biosphere conditions and
human behavior. Even for a period as
"short" as 10,000 years, it is necessary
to make certain assumptions. For
periods on the order of one million
years, even natural human evolutionary
changes become a consideration.
Regulating to such long time periods
could become arbitrary. Moreover, NAS
based its time-frame recommendation
on scientific considerations; however, it
recognized that such a decision also has
policy aspects (NAS Report p 56). The
NAS recognized that the existence of
these policy aspects might lead us to
select an alternative more consistent
with previous Agency policy. Indeed,
we considered the longest practical
regulatory periods associated with other
Agency programs, as well as 40 CFR
part 191. We believe the unprecedented
nature of a compliance period beyond
10,000 years argues against imposing
such a long regulatory period here. Also,
numerous international disposal
programs use a 10,000-year compliance
period. Many of these same programs
have committed to consider more
qualitative evaluations beyond 10,000
years. (See GAO/RCED-94-172, 1994,
Docket No. A-95-12, Item V-A-7.
Chapter 3 of the BID also contains
information on international programs.)
Of course, as knowledge and technical
capabilities grow, this situation could
change over time.
The hazardous lifetime of radioactive
waste is important; however, it is but
one of several factors that a regulator
must consider in projecting the
potential risks from disposal. Indeed,
some of the radionuclides expected to
be in the waste inventory at Yucca
Mountain have half-lives extending to
thousands or hundreds of thousands of
years (and even a million years or more
in a few cases). The ability of the
repository to isolate such long-lived
materials relates to the retardation
characteristics of the whole
hydrogeological system within and
outside the repository, the effectiveness
of engineered barriers, the
characteristics and lifestyles associated
with the potentially affected population,
and numerous other factors in addition
to the hazardous lifetime of the
materials to be disposed.
With respect to uncertainty in the
projected peak dose, one commenter
suggested that NRG should deny the
license application if modeling results
show an uncertainty range of five orders
of magnitude above the dose limit in our
individual-protection standard.
Modeling results, and their associated
uncertainties, are but a part of the
complete record on which NRC will
determine whether the disposal system
complies with 40 CFR part 197. For the
reasons cited above, we consider a
10,000-year compliance period, and the
additional requirement that DOE
calculate the peak dose beyond 10,000
years and include this assessment in the
Yucca Mountain Environmental Impact
Statement, to be the most appropriate
approach, given the state of technology •
and knowledge today. In addition, we
require DOE to provide a "reasonable
expectation" that disposal system
performance will meet the standard.
Calculation of doses to the RMEI
involves projecting doses that are within
a reasonably expected range rather than
projecting the most extreme case. This
approach is in concert with NAS's
recommendations to use "cautious, but
reasonable" assumptions to define who
is to be protected (NAS Report pp. 5-
6). The degree of uncertainty in the dose
assessments considered acceptable in
the licensing process is, in our opinion,
an implementation decision that should
be the responsibility of NRC. We believe
that we have provided sufficient detail
in the standard to provide the context
needed to assure the standard is applied
as we intend (see, e.g., our discussions
of "reasonable expectation" in section
III.B.2.C and in the Response to
Comments Document that accompanies
this rule); however, the final decision
regarding the acceptable degree of
uncertainty is NRC's responsibility.
For a variety of technical and policy
reasons, we believe that a 10,000-year
compliance period is meaningful,
protective, practical to implement, and
will result in a robust disposal system
protective for periods beyond 10,000
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32125
years. In other programs we have
regulated nan-radioactive hazardous
waste for as long as 10,000 years.
Having a 10,000-year compliance period
for Yucca Mountain, in conjunction
with 40 CFR part 191, ensures that SNF,
HLW, and TRU radioactive wastes
disposed anywhere in the United States
must be regulated for a 10,000-year
compliance period.
9. Does Our Requirement That DOE and
NRC Determine Compliance with
§ 197.20 Based Upon the Mean of the
Distribution of the Highest Doses
Resulting From the Performance
Assessment Adequately Address
Uncertainties Associated With
Performance Assessments?
Comments/Our Responses. Comments
on this question ranged from advocating
that we should use the maximally
exposed individual and "worst-case"
measures to expressing general
agreement with the proposed approach.
Some comments stated that any measure
applied to the performance assessments
should be considered an
implementation decision that we should
leave to NRC. See the Response to
Comments document for additional
discussion of comments we received
regarding performance assessments.
We specify a compliance measure we
believe is reasonable but still
conservative: the mean of the
distribution of projected doses from
DOE's performance assessments. The
primary reason we impose this
requirement is that it provides a
necessary context for implementation of
the standard. En addition, we note that
it is also consistent with the approach
we implemented in certifying WIPP.
We consider it necessary to supply
context for understanding the intent of
the standard to constrain and direct the
otherwise unbounded range of
approaches to demonstrating
compliance that could be justified in the
absence of such context. For example, it
would be possible to use only a small
number of assessments to demonstrate
compliance if the standard specified
only an exposure limit, hi such a case,
the full range of relevant site conditions
and processes might not he considered.
Further, the analyses and the regulatory
decision making might not capture the
uncertainties in projecting long-term
performance. At the other extreme,
without a defined performance measure,
endless and exhaustive site
characterization studies and analyses
could be required. The impetus for these
endless and exhaustive studies and
analyses would be a perceived need to
identify the most extreme "worst-case"
scenarios [regardless of their actual
likelihood of occurring). We believe that
a thorough assessment of repository
performance expectations should
examine the full range of reasonably
foreseeable site conditions and relevant
processes expected during the
regulatory time frame. In making
quantitative estimates of repository
performance, we believe that unrealistic
or extreme situations or assumptions
should not dominate estimates of
expected performance (see additional
discussions about "reasonable
expectation" in this preamble and the
Response to Comments Document).
With these considerations in mind, we
believe that specifying a performance
measure is necessary to supply the
proper context for implementing the
standard in the regulatory process, as
well as providing the applicant (DOE) a
focus for its efforts to build the
compliance arguments and supporting
calculations.
In line with our use of the term
"reasonable expectation," the
fundamental compliance measure
consistent with a literal mathematical
interpretation of this term would be the
mean value of the distribution of
calculated doses. However, as the only
alternative for a compliance measure,
the mean may in some cases be
interpreted too restrictively. In actuality,
some situations may result in very high
dose estimates for situations that have
low probabilities. Simply averaging
these "outliers" into the distribution of
calculated dose estimates can bias the
mean levels that may be unrealistically
high. Although this is certainly a
conservative (and therefore desirable)
approach, its effects can be
unrealistically conservative (not a
desirable situation). The result of overly
conservative effects is to drive
regulatory decision making on the basis
of very low probability and potentially
unrealistic situations.
Because of these potential situations,
we also proposed using the median of
the expected range of calculated values
as another interpretation of the
"expected" situation. The median
(reflecting a value exceeded half of the
time) may be more conservative if some
of the variables involved in the
performance calculations have skewed
distributions. However, we conclude
that, in the case of Yucca Mountain, the
mean is an appropriate measure.
By specifying the mean as the
performance measure and probability
limits for the processes and events to be
considered (§ 197.36), and in conceit
with the intent of our "reasonable
expectation" approach in general, we
have implied that probabilistic
approaches for the disposal system
performance assessments are expected.
The probabilistic approach is well
established in DOE's approach to
performance projections (see the DEIS
and Vol. 3 of the Viability Assessment,
Docket No. A-95-12, Items V-A-4 and
V-A-5). Based on DOE's past actions
and stated intent, we believe that DOE
will continue to follow this approach
and that, therefore, it is unnecessary for
us to specify additional requirements in
the standard to assure that DOE
continues to follow this approach. We
also believe that specifying such
requirements could be interpreted to
exclude the use of deterministic
analyses. These analyses can be useful
for carefully focused bounding analyses
and sensitivity studies. For these
reasons we have specified only the
fundamental performance measures to
provide the context for understanding,
without additional qualifications, the
intent of the standard for
implementation efforts.
A number of comments stated that,
though they agreed with our selection of
performance measures, the choice
should be left as an implementation
detail for NRC. Relative to the
implementation question, we believe
that specifying the fundamental
compliance measure is necessary as a
means to supply the proper context for
understanding the intent of the rule and
for implementation guidance as
explained above. We feel this is
distinctly different than the
implementation responsibility of NRC,
as explained below.
We do not believe that setting the
fundamental compliance measure
intrudes into NRC's implementation
authority because the primary task for
the regulatory authority is to examine
the performance case put forward by
DOE to determine "how much is
enough" in terms of the information and
analyses presented (i.e., how will the
regulatory authority determine when the
performance case has been
demonstrated with an acceptable level
of confidence). Our standard contains
no specific measures for that judgment.
We do not specify any confidence
measures for such judgments or
numerical analyses. Also, we do not
prescribe analytical methods that must
be used for performance assessments,
quality assurance measures that must be
applied, statistical measures that define
the number or complexity of analyses
that should be performed, or any
assurance measures in addition to the
numerical limits in the standard. We
specify only that the mean of the dose
assessments must meet the exposure
limit. There are many other
considerations and decisions that
-------
32126 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules .and Regulations
describe the extent of the assessments or
level of rigor necessary to ensure that
the mean is a meaningful measure upon
which a licensing decision can rest.
These considerations and decisions
properly belong to the implementing
authority. For example, we believe
setting a confidence level clearly is an
implementation function that should be
left to NRC; therefore, we make no
requirements in the standard to
foreclose NRC's flexibility in setting
appropriate confidence measures. In the
development of the WIPP certification
criteria, where we had both the
standard-setting and implementing
authority, we did establish a confidence
measure" (40 CFR 194.55 (d) and (f)) in
addition to the basic performance
measure. We also included
implementation requirements in the
WIPP certification criteria, including
analytical approaches (§ 194.55(b)),
quality assurance requirements
(§ 194.22), other assurance requirements
(§194.41), requirements for modeling
techniques and assumptions (§§ 194.23
and 194.25), and use of peer review and
expert judgment (§§ 194.26 and 194.27).
These requirements go well beyond the
simple statement of a compliance
measure. We did not incorporate a
similar level of detail in the Yucca
Mountain standards because we believe
we must specify only what is necessary
to provide the context for
implementation that NRC will execute.
We therefore agree with comments that
support our choice of the performance
measure, but disagree for the reasons
described above that this choice is an
intrusion into the implementation
responsibilities of NRC.
For the WIPP certification, the
compliance measure selected for the
individual-protection standard was the
higher of the mean or median of the
calculated distributions of doses from
releases (40 CFR 194.55(fJ). The mean or
median are reasonably conservative
measures because they are influenced
by high exposure estimates found when
analyzing the full range of site
conditions and relevant processes,
without being geared to exclusively
reflect high-end results, as would be the
case if we selected as the measure a
high-end percentile of the calculated
dose distribution (such as the 95th or
99th percentile). Our final rule for
Yucca Mountain specifies only that the
mean be used, as we believe that it is
appropriately conservative in this
situation.
10. Is the Single-borehole Scenario a
Reasonable Approach To Judge the
Resilience of the Yucca Mountain
Disposal System Following Human
Intrusion? Are There Other Reasonable
Scenarios Which We Should Consider,
for Example, Using the Probability of
Drilling Through a Waste Package Based
Upon the Area of the Package Versus
the Area of the Repository Footprint or
Drilling Through an Emplacement Drift
but not Through a Waste Package? Why
Would Your Suggested Scenario(s) be a
Better Measure of the Resilience of the
Yucca Mountain Disposal System than
the Proposed Scenario?
Comments/Our Responses. Comments
upon this question varied from
agreement that the proposed intrusion
scenario is an adequate test of repository
resiliency to opinions that the analysis
of any human-intrusion scenario would
be irrelevant to the Yucca Mountain
setting. Some comments proposed
alternative intrusion scenarios, most
commonly the use of multiple drilling
intrusions. Some comments also
proposed alternative ways of treating
the intrusion scenario relative to
repository requirements. We also
received comments concerning other
aspects of the intrusion scenario as well
as in response to the specific questions
asked above. Discussion on all the
issues raised in comments about the
human-intrusion scenario appears in the
Response to Comments document.
Comments in favor of the intrusion
scenario as we framed it in the proposed
rule focused upon the difficulties in
defending any predictions about the
probability of drilling intrusions
through the repository and in reliably
predicting a hypothetical drilling
intrusion in any detail. These comments
echoed NAS's conclusions about the
reliability of post-closure institutional
controls to prevent intrusion, and the
inability to make scientifically
supportable predictions of the
probability of human-intrusion events
over the regulatory period (NAS Report
pp. 104-109). The NAS reasoned that
because it is not possible to reliably
eliminate the potential for human
intrusion, the only reasonable approach
would be to assume an intrusion occurs
and assess the consequences on disposal
system performance. In this light, NAS
recommended that a simple stylized
drilling intrusion through the repository
to the underlying ground water table be
assessed as a test of the resiliency of the
disposal system (NAS Report Chap. 4).
Because it is impossible to scientifically
exclude the potential for an intrusion,
and because proposing the nature of an
intrusion is at best speculative, these
comments agreed that the stylized
approach that assumes an intrusion and
assesses the consequences is
appropriate. We have followed the
NAS's recommendations closely in
framing the human intrusion standard.
Some comments on the framing of the
intrusion scenario proposed that, for
various reasons, multiple intrusions
should be considered, rather than
simply assuming one borehole
penetration through the repository.
Because of certain site-specific
considerations with respect to Yucca
Mountain, and in light of the rationale
underlying the NAS recommendations,
it is not appropriate to modify the
scenario to include multiple
penetrations through the repository. It is
impossible to accurately predict the
potential for intrusion in the distant
future. Therefore, postulating multiple
intrusions is just as speculative as
postulating a single intrusion at any
given time or specific location over the
repository. For this reason, NAS
recommended that we develop a
stylized intrusion in our rulemaking
(NAS Report p. 111). We agree with this
recommendation because disruption of
the engineered and natural barriers is a
means through which radionuclides can
escape the repository and be transported
to the accessible environment where
exposures of individuals can result.
Therefore, an evaluation of human-
intrusion consequences is appropriate
for a repository standard. The NAS also
recommended that we define a typical
intrusion scenario for analysis (NAS
Report p. 108) and recommended a
stylized approach to framing the
scenario (NAS Report p. Ill) and a
consequence analysis of the scenario
(NAS Report p. 111). The intent of this
approach is that the disposal system
should be resilient "to at least moderate
inadvertent intrusions" (NAS Report p.
113). Scenarios ranging from single
penetrations to many penetrations
through the repository over the
regulatory time period would give a
very wide range of results—none more
or less defensible than any other,
making their use in regulatory decision
making ambiguous at best. To avoid the
speculative aspects of defining intrusion
scenarios, we believe the stylized single
intrusion recommended by NAS is
sufficient and would provide a suitable
test of the Yucca Mountain disposal
system's performance.
Related comments offered opinions
that the prospect of drilling for water
resources at the top of Yucca Mountain
is not a credible scenario because
drilling for water would be more
sensible in the adjacent valleys. These
comments, however, did not offer
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32127
alternatives for the drilling intrusion.
Rather, they staled or implied that the
intrusion scenario was unnecessary. We
agree that drilling for water, or any other
mineral resources at Yucca Mountain, is
unlikely because of the very limited
resource potential at the site (see
Chapter 8 of the BID). However, as NAS
concluded, it is impossible to totally
eliminate the possibility of intrusion
(see Chapter 4 of the NAS Report). This
question again goes back to the
difficulty in making defensible
predictions about the probability of
human activities over very long time
periods and the fact that intrusion is a
means through which releases, and
consequent exposures, can occur.
Therefore, it is necessary to consider the
consequences of inadvertent intrusions
in a health-based standard. Some
comments suggested that there is a
strong possibility for deliberate
intrusion into the repository to access
its contents as possible resources. We
believe that there is no useful purpose
to assessing the consequences of
deliberate intrusions because in that
case the intruders would be aware of the
risks and consequences and would have
decided to assume the risks. This is
consistent with NAS's conclusion
regarding intentional intrusion (NAS
Report p. 114).
Some comments stated that defining
the stylized scenario as we did
effectively makes the human-intrusion
dose assessment results into design
constraints for the repository. We do not
believe the stylized scenario imposes
any design constraints because the
waste package penetration is assumed to
occur regardless of the particular design
chosen for the waste package. Here
again, none of these comments proposed
alternative scenarios. Rather, they
simply questioned the basic relevance of
a human intrusion standard. For the
reasons mentioned previously, however,
we reiterate our belief that an analysis
of human-intrusion is necessary, and we
also note that NAS (NAS Report p. 108)
stated that "EPA should specify in its
standard a typical intrusion scenario...".
We do not believe it should be regarded
as a design constraint unless the results
of the consequence analyses indicate
that the limited breaching of the natural
and engineered barriers would result in
the standard being exceeded. Even
though the probability of drilling
intrusions may be low, it is impossible
to unequivocally eliminate them.
Therefore, we agree with NAS's
conclusion that the "repository should
be resilient to at least modest
inadvertent intrusions" (NAS Report p.
113).
11. Is it Reasonable To Expect That the
Risks to Future Generations Be No
Greater Than the Risks Judged
Acceptable Today?
Comments/Our Responses. Comments
we received upon this question strongly
favored the position that we should not
allow greater risks for future generations
than what is judged to be acceptable
today. Some comments speculated that
with advances in medical technology
and other areas, the risks assessed today
most likely would be less in the future
because society would be more effective
in mitigating the effects of radiation
exposures. Some comments advised that
risks from the disposal effort should be
reviewed periodically so that decisions
could be made about their acceptability
at a future date. We believe we have set
the standards conservatively, but
reasonably, and consistent with our
policies for radiation exposure from
radioactive waste disposal applications
and NAS's recommendations. In this
regard, our standards apply over the
entire regulatory period of 10,000 years.
Our standards thus protect future
generations for a very significant time
period. In addition, we require DOE to
calculate the peak dose to the RMEI
beyond 10,000 years. Although our
standards do not apply to the results of
this calculation, this post-10,000-year
analysis will provide more complete
information regarding disposal system
performance beyond 10,000 years. This
approach to the post-10,000-year period
is consistent with our understanding of
the limits imposed by inherent
uncertainties in making such long-term
performance projections. The question
of periodic re-evaluation of repository
performance is an implementation
question that should be left to the
discretion of NRC.
12. What Approach Is Appropriate for
Modeling the Ground Water Flow
System Downgradient From Yucca
Mountain at the Scale (Many Kilometers
to Tens of Kilometers) Necessary for
Dose Assessments Given the Inherent
Limitations of Characterizing the Area?
Is it Reasonable To Assume That There
Will be Some Decree of Mixing With
Uncontaminated Ground Water Along
the Radiomiclide Travel Paths From the
Repository?
Comments/Our Responses. Comments
on this question shared a general theme
that we should not be prescriptive in
indicating a preference or requirement
for any specific modeling approach that
should be used. Rather, the bulk of the
comments suggested that DOE (the
organization responsible for developing
the license application) and NRC (the
authority responsible for the approval of
the disposal facility) should make these
decisions. We agree with this general
theme; therefore, our rule does not
specify that DOE must use a particular
modeling approach to demonstrate
compliance with the standards. We
believe that DOE and NRC should avoid
extreme assumptions and approaches
and should identify and consider the
inherent uncertainties in projecting
performance in the regulatory process.
More specifically for Yucca Mountain,
we believe that it is necessary to avoid
extreme modeling approaches. One
example of an extreme modeling
approach is assuming the transportation
of releases from the repository through
the natural barriers without mixing with
other ground waters. In this regard we
retained our recommendation that
"reasonable expectation" be the
standard used to assess repository
performance. We have provided detail
in the standards only to the extent
needed to provide the context necessary
to assure that the components of the
standards are implemented in the
manner we intended when we
developed the standards. Ultimately, it
is NRC's task to select and apply the
appropriate measure to determine
compliance with our standards.
13. Which Approach for Protecting
Ground Water in the Vicinity of Yucca
Mountain is the Most Reasonable? Is
There Another Approach Which Would
be Preferable and Reasonably
Implementable? If so, Please Explain the
Approach, Why It Is Preferable, and
How It Could Be Implemented
Comments/Our Responses. We
received public comments advising us
of a variety of approaches towards
protecting ground water in the vicinity
of Yucca Mountain. Two primary
approaches emerged. One group of
public comments suggested that an all-
pathways, individual-dose standard,
with no separate or specific ground
water protection provisions, would be
fully protective of the public health. On
the other hand, a second set of public
comments suggested that we should
promulgate separate ground-water
protection standards applicable to the
Yucca Mountain disposal system. The
final rule reflects the latter approach.
We believe as a matter of prudent
policy that ground water protection
standards are neither redundant nor
unnecessary because they address
specific aspects of natural resource
protection not covered by the
individual-protection standard. Rather,
such standards are complementary to
the public health and safety standards
applicable to the Yucca Mountain
-------
32128 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
disposal system. In particular, we
consider ground water that is, or that
could be, drinking water to be the most
valuable ground water resource. We
believe that it deserves the highest level
of protection. At Yucca Mountain, water
from the aquifer beneath the proposed
repository currently serves as a source
of drinking water in communities 20 to
30 km south of Yucca Mountain. This
aquifer has the potential to supply
drinking water to a substantially larger
population than that presently in the
area (NAS Report p. 92),
Over the years, many of our regulatory
programs have incorporated the MCLs
as an. important part of our regulations
related to both radioactive and non-
radioactive wastes. This approach grew
out of the development and
implementation of our ground water
protection strategy, "Protecting the
Nation's Ground-Water: EPA's Strategy
for the 1990s" ("the Strategy," Docket
No. A-95-12, Item II-A-3). The use of
ground water protection requirements,
including the use of MCLs, is reflected
in our regulations pertaining to
hazardous waste disposal (40 CFR part
264), municipal waste disposal (40 CFR
parts 257 and 258), underground
injection control (UIC) (40 CFR parts
144,146, and 148), and uranium mill
tailings disposal (40 CFR part 192). We
also have incorporated the MCLs into
our generally applicable standards for
the disposal of SNF, HLW, and TRU
radioactive waste (40 CFR part 191).
These generic regulations apply to the
land disposal of these materials
everywhere in the United States except
at Yucca Mountain. Extending
comparable ground-water protection
standards to the proposed Yucca
Mountain disposal system will assure
reasonable and similar protections
wherever the disposal of SNF, HLW, or
TRU radioactive waste occurs in this
country.
In our response to Question 15, we
note our concerns related to adopting
only an all-pathways individual-
protection standard with no specific
ground-water protection provisions. For
a more detailed discussion of the issues
associated with these two options (all-
pathways with and without separate
ground water protection), please see the
Response to Comments document.
14. Is the 10.000-year Compliance
Period for Protecting the RMEI and
Ground Water Reasonable or Should we
Extend the Period to the Time of Peak
Dose? If We Extend it. How Could NRC
Reasonably Implement the Standards
While Recognizing the Nature of the
Uncertainties Involved in Projecting the
Performance of the Disposal System
Over Potentially Extremely Long
Periods?
Comments/Our Responses. As
discussed in the response to Question 8
above, comments both supported and
questioned our compliance period for
the RMEI and ground water protection
standards. Commeriters who supported
the 10,000-year compliance period
thought that this time period was
"sufficient" and that it represented an
appropriate balance between long-term
coverage and implementability. These
commenters agreed with us that, though
it is possible to make longer-term
calculations, such calculations should
be used only for regulatory insight
because of the considerable uncertainty
involved in making the calculations.
These comments support our rationale
and choice of a 10,000-year compliance
period for protecting the RMEI and
ground water.
Numerous commenters suggested that
we should extend the compliance
period beyond 10,000 years for a variety
of reasons. Foremost is that NAS
suggested a compliance period
extending up to the time of peak dose
or risk, within the period of geologic
stability for Yucca Mountain (i.e., up to
one million years). Other commenters
suggested that the compliance period
should be comparable to the hazardous
lifetime of the materials to be emplaced
in the Yucca Mountain repository. As
indicated in our response to Question 8
above and in section III.B.l.g, we have
significant concerns relating to making
meaningful projections of repository
performance over the time periods
implied by NAS's recommendations.
These concerns extend to modeling the
time to peak concentration to judge
compliance with the ground water
standards, which NAS did not explicitly
consider. Modeling of exposure
scenarios and climatic conditions very
different from those experienced over
the last 10,000 years, coupled with the
potential for human evolutionary
changes over such extended time
frames, introduces tremendous
uncertainties. This situation may result
in making arbitrary assumptions in
performance assessment modeling,
rather than making informed choices
based upon cautious, but reasonable,
assumptions rooted in present-day
knowledge. Regarding the hazardous
lifetime of the materials to be emplaced
in the Yucca Mountain repository, it is
true that there will be radioactive
materials remaining after the end of the
10,000-year regulatory period.
Nevertheless, the ability of a repository
to isolate such long-lived radionuclides
depends upon a variety of other factors,
including the retardation characteristics
of the whole hydrogeological system
within and outside of the repository, the
effectiveness of the engineered barriers,
the characteristics and lifestyles
associated with the potentially affected
population, as well as the hazardous
lifetime of the materials to be emplaced
in the repository.
Although we received numerous
comments suggesting that 10,000 years
was insufficient as a compliance period,
we received little in the way of
suggestions regarding on how to
reasonably implement standards
covering these potentially very extended
time periods. For example, one
commenter suggested that we put the
burden on NRC and DOE to develop
methods to estimate, with some degree
of certainty, the effects after 10,000
years without explaining how the
agencies could achieve these results.
Please note that NAS specifically
addressed this matter (NAS Report, pp.
12-13):
"It might be possible that some of the
current gaps in scientific knowledge and
uncertain lies thai we have identified might
be reduced by future research * * *.
Conducting such an appraisal, however.
should not be seen as a reason to slow down
ongoing research and development programs,
including geologic site characterization, or
the process of establishing a standard to
protect public health."
We agree with NAS's conclusion. We
expect more information will be
developed in the time between the
promulgation of this rule and the NRC
licensing decision to address some of
the remaining uncertainties.
15. As Noted by NAS, Same Countries
Have Individual-Protection Limits
Higher Than We Have Proposed. In
Addition, Other Federal Authorities
Have suggested Higher Individual-dose
limits With No Separate Protection of
Ground Water. Therefore, We Request
Comment Upon the Use of an Annual
CEDE of 250 [iSv (25 mrem) With No
Separate Ground Water Protection,
Including the Consistency of Such a
Limit With Our Ground Water
Protection Policy
Comments/Our Responses. Our
promulgation of only an all-pathways,
individual-protection standard, such as
25 mrem/yr, with no ground-water
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32129
protection provisions, would provide no
assurance that ground water resources
will be protected adequately. The
separate ground water protection
standards in our rule will preserve the
integrity of the ground-water resources
in the vicinity of Yucca Mountain for
present and future generations.
The all-pathways, individual-
protection standard is the primary
mechanism to protect public health
from releases of radioactivity from the
Yucca Mountain repository. We believe
that an all-pathways limit,
supplemented with ground water
protection standards, provides complete
public health protection and assures
that ground water resources will be safe
for use by future generations. In
addition, the ground water resources in
the vicinity of Yucca Mountain support
a diverse agricultural community and
important ecological systems (e.g., the
endangered Devil's Hole pupfish).
We believe that separate ground water
protection standards designed to protect
the ground water resource in the
vicinity of Yucca Mountain is a
necessary element of our Yucca
Mountain standards. Our decision to
include separate ground water
protection standards is a policy
decision. As explained in section IH.B.4
[How Does Our Rule Protect Ground
Water?}, we developed a ground water
protection strategy to guide Agency
programs in their efforts to prevent
adverse effects on human health and the
environment and in protecting the
environmental integrity of the nation's
ground water resources (see "The
Strategy," Docket No. A-95-12, Item II-
A-3). We have employed ground water
protection programs and standards in a
variety of regulatory programs for
hazardous and non-hazardous waste.
We also have incorporated ground water
protection standards in our generally
applicable disposal regulations for SNF,
HLW, and TRU radioactive wastes (see
40 CFR part 191), and implemented
them at WIPP. Incorporation of ground
water standards in our overall Yucca
Mountain standards provides
consistency with other Agency
programs and assures consistent
protection wherever SNF, HLW, and
TRU radioactive waste may be disposed
of in this country.
We believe that both ground-water
protection standards, incorporating the
MCLs to protect ground-water resources,
and an individual-protection standard,
as embodied in an all-pathways
standard, are complementary and
necessary to provide adequate public
health protection and protection of an
invaluable national natural resource.
For a more detailed discussion of the
issues associated with the options for
the individual-protection standard and
the ground-water protection standards,
please see the Response to Comments
document.
16. We Are Proposing To Require, in the
Individual-Protection Standard, That
DOE Must Project the Disposal System's
Performance After 10,000 Years. Are the
Specified Uses of the Projections
Appropriate and Adequate?
Comments/Our Responses. Some
comments supporting our 10,000-year
compliance period also endorsed the
idea that projections of the disposal
system's performance beyond 10,000
years would, among other things, be
fraught with greater uncertainties and
would not necessarily provide greater
public health protection. A few
comments supported our requirement
that DOE project doses beyond 10,000
years and include the results of these
projections in the Yucca Mountain EIS.
In addition, a few comments suggested
that any post-10,000-yeaT projection
should serve only to provide "regulatory
insight."
Comments supporting the use of a
post-10,000-year projection for
regulatory purposes cited the long-term
hazard posed by the wastes planned for
Yucca Mountain, the need to protect
future generations, and the possibility
that the individual doses would exceed
our standard in the post-10,000-year
time frame. -As indicated in our
response to Question 8 above, we
considered these and other issues in
determining that a 10,000-year
compliance period is most appropriate.
This compliance period is protective,
meaningful, and practical to implement.
By also including a post-10,000-year
dose assessment in the EIS, which
provides more complete information on
long-term performance, we believe a
robust disposal system protective for
time periods beyond 10,000 years will
result.
In considering the appropriate use of
the post-10,000-year dose assessment,
we have had to balance these very
difficult issues. It is possible to set
computer models to run for time periods
beyond 10,000 years; however, this
approach does not necessarily result in
an equal or higher level of confidence
that the exposed individuals will be
protected. As numerous comments
pointed out, it is likely that such results
will contain greater uncertainties. We
agree with these comments. Yet, despite
these greater uncertainties, such
assessments can be somewhat
informative though not necessarily
reliable dose predictions. We note, for
example, the considerations that
supported Sweden's proposed
regulations for SNF and nuclear waste
("The Swedish Radiation Protection
Institute's Proposed Regulations
Concerning the Final Management of
Spent Nuclear Fuel or Nuclear Waste,"
SSI Report 97:07, May 1997, Docket No.
A-95-12, Item V-A-11). Regarding
long-term assessments (beyond 1,000
years), such studies "do not mean that
the full protective capacity of the
repository can be forecasted, e.g., on the
scale of a million years into the future.
However, studies of such (repository)
subsystems can provide valuable
information without actually being
considered as a prediction of doses to
living organisms' (Id. at 11). We believe
that requiring DOE to include a post-
10,000-year dose assessment in the EIS
is an appropriate means to address the
issues associated with such long-term
impacts. We note that in our proposal,
we stated that "NRC is not to use" post-
10,000-year results in assessing
compliance with the individual-
protection standard. However, in its
comments on our proposal, NRC stated
that, if DOE uses post-10,000-year
results to bolster its compliance case,
"the Commission should not be
constrained from considering such
information" (Docket No. A-95-12, Item
II-D-92). We agree. At the very least,
more complete information on long-
term disposal system performance will
be available. In addition, during this
time, the repository design will become
more clearly defined by new
information. For more extensive
discussions of this issue, please see our
response to Question 8 above and the
Response to Comments document.
VI. Severability
As discussed above at Section III.B.l,
the purpose of the Individual Protection
Standard is to protect public health and
safety. As discussed in Section IILB.4,
the Ground Water Protection Standard
serves two purposes. First, it protects
the ground water resource. Second, by
protecting that resource, the Ground
Water Protection Standard also furthers
the goal of public health and safety.
Consistent with the recommendations of
the National Academy of Sciences, the
Individual Protection Standard is
adequate in itself to protect public
health and safety. In addition, EPA is
adopting the Ground Water Protection
Standard in its discretion in order to
provide additional protection to the
vital ground water resource, and in so
doing, is also providing an extra
measure of public health and safety
protection. Thus, notwithstanding that
the Individual Protection and Ground
Water Standards have coincident
-------
32130 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
compliance points and, as implemented
by NRG, may have other similarities,
these two provisions are wholly
severable.
VI. Regulatory Analyses
A. Executive Order 12866
Under Executive Order 12866 [58
Federal Register 51735 (October 4,
1993J], the Agency must determine
whether the regulatory action is
"significant" and therefore subject to
review by the Office of Management and
Budget (OMB) and the requirements of
the Executive Order. Executive Order
12866 defines a "significant regulatory
action" as one that is likely to result in
a rule that may:
(l) Have an annual effect upon the
economy of $100 million or more or
adversely affect in a material way the
economy, a sector of the economy,
productivity, competition, jobs, the
environment, public health or safety, or state,
local, or tribal governments or communities;
(Z) Create a serious inconsisteacy or
otherwise interfere with an action taken or
planned by another agency;
(3) Materially alter the budgetary impact of
entitlements, grants, user fees, or loan
programs or the rights and obligations of
recipients thereof; or
(4) Raise novel legal or policy issues
arising out of legal mandates, the President's
priorities, or the principles set forth in the
Executive Order.
In accordance with the terms of
Executive Order 12866, EPA determined
that this rule is a "significant regulatory
action" because it raises novel legal or
policy issues arising out of the specific
legal mandate of Section 801 of the
Energy Policy Act of 1992. Thus, this
action was submitted to OMB for
review.
In accordance with the terms of
Executive Order 12866, EPA determined
that this rule is a "significant regulatory
action" because it raises novel legal or
policy issues arising out of the specific
legal mandate of Section 801 of the
Energy Policy Act of 1992. Thus, this
action was submitted to OMB for
review. Any changes to the rule that
were made in response to OMB
suggestions or recommendations have
been documented in the public record.
B. Executive Older 12898
Executive Order 12898, "Federal
Actions to Address Environmental
Justice in Minority Populations And
Low-income Populations
(Environmental Justice)," directs us to
incorporate environmental justice as
part of our overall mission by
identifying and addressing
disproportionately high and adverse
human health and environmental effects
of programs, policies, and activities
upon minority populations and low-
income populations.
We find no disproportionate impact
in the outcome of this rulemaking. No
plan has thus been devised to address
a disproportionate impact.
C. Executive Order 13045
Executive Order 13045, "Protection of
Children from Environmental Health
Risks and Safety Risks," (62 FR 19885,
April 23,1997) applies to any rule that
(1) is determined to be "economically
significant" as defined under Executive
Order 12866, and (2) concerns an
environmental health or safety risk that
we have reason to believe may have a
disproportionate effect upon children. If
the regulatory action meets both criteria,
we must evaluate the environmental
health or safety effects of the planned
rule upon children, and explain why the
planned regulation is preferable to other
potentially effective and reasonably
feasible alternatives that we considered.
As discussed in the preamble in
sections ILC and HI.B.l.a, the primary
risk factor considered in our risk
assessment is incidence of fatal cancer.
We have derived a risk value for the
onset of fatal cancer that considers
children, since it is an overall average
risk value (see Chapter 6 of the BID for
more details) that includes all ages from
birth onward, all exposure pathways,
both genders, and most radionuclides.
We do note that ths risk factor does not
include the fetus. However, we believe
that the risk of fatal cancer per unit dose
incurred by the unborn is similar to that
for those who have been horn, but the
exposure period is very short compared
to the rest of the individual's average
lifetime, so the risk of fatal cancer to the
unborn is proportionately lower and
does not have a significant impact upon
the overall risk of fatal cancer incurred
by an individual over a lifetime. (See
Chapter 6 of the BID for more discussion
of the risk of fatal cancer resulting from
in utero exposure.)
Therefore, this final rule is not subject
to Executive Order 13045 because we do
not have reason to believe the
environmental health risks or safety
risks addressed by this action present a
disproportionate risk to children.
D. Executive Order 13084
On January 1, 2001, Executive Order
13084 was superseded by Executive
Order 13175. However, this rule was
developed when Executive Order 13084
was still in force, and so tribal
considerations were addressed under
Executive Order 13084.
Under Executive Order 13084,
"Consultation and Coordination with
Indian Tribal Governments," we may
not issue a regulation that is not
required by statute, that significantly or
uniquely affects the commumtiss of
Indian tribal governments, and that
imposes substantial direct compliance
costs upon those communities, unless
the Federal government provides the
funds necessary to pay the direct
compliance costs incurred by the tribal
governments, or we consult with those
governments. If we comply by
consulting, Executive Order 13084
requires us to provide to OMB, in a
separately identified section of the
preamble to the rule, a description of
the extent of our prior consultation with
representatives of affected tribal
governments, a summary of the nature
of their concerns, and a statement
supporting the need to issue the
regulation. In addition, Executive Order
13084 requires us to develop an
effective process permitting elected
officials and other representatives of
Indian tribal governments "to provide
meaningful and timely input in the
development of regulatory policies on
matters that significantly or uniquely
affect their communities."
The radiological protection standards
promulgated by today's rule are
applicable solely and exclusively to the
Department of Energy's potential storage
and disposal facility at Yucca Mountain.
Therefore, this rule does not
significantly or uniquely affect the
communities of Indian tribal
governments, nor does it impose any
direct compliance costs on such
communities. Accordingly, the
requirements of section 3(b) of
Executive Order 13084 do not apply to
this rule.
B. Executive Order 13132
Executive Order 13132, entitled
"Federalism" (64 FR 43255, August 10,
1999), requires EPA to develop an
accountable process to ensure
"meaningful and timely input by State
and local officials in the development of
regulatory policies that have federalism
implications." "Policies that have
federalism implications" is defined in
the Executive Order to include
regulations that have "substantial direct
effects on the States, on the relationship
between the national government and
the States, or on the distribution of
power and.responsibilities among the
various levels of government."
This final rule does not have
federalism implications. It will not have
substantial direct effects on the States,
on the relationship between the national
government and the States, or on the
distribution of power and
responsibilities among the various
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32131
levels of government, as specified in
Executive Order 13132. Thus, Executive
Order 13132 does not apply to this rule.
Nonetheless, in developing its proposed
rule EPA held public meetings in
Nevada and Washington, D.C. during
"which comment was received from and
discussions were had with
representatives from the State of Nevada
and various county officials. EPA also
had informal meetings with State and
local officials to apprise them of the
status of the rulemaking.
F- National Technology Transfer and
Advancement Act
Section 12(d) of the National
Technology Transfer and Advancement
Act of 1995 (NTTAA), Public Law 104-
113, section 12(d) (15 U.S.C. 272 note)
directs us to use voluntary consensus
standards in our regulatory activities
unless to do so would be inconsistent
with applicable law or otherwise
impractical. Voluntary consensus
standards are technical Standards (e.g.,
materials specifications, test methods,
sampling procedures, and business
practices) that are developed or adopted
by voluntary consensus standards
bodies. The NTTAA directs us to
provide Congress, through OMB,
explanations when we decide not to use
available and applicable voluntary
consensus standards.
In our proposal, we requested public
comment on potentially applicable
voluntary consensus standards that
would be appropriate for inclusion in
the Yucca Mountain rule. We received
no comments on this aspect of the rule.
The closest analogy to consensus
standards for radioactive waste disposal
facilities are our regulations at 40 CFR
part 191. As discussed above in this
preamble, Congress expressly prohibited
the application of the 40 CFR part 191
standards to the Yucca Mountain
disposal facility, and, therefore, the
standards promulgated today are site-
specific standards developed solely for
application to the Yucca Mountain
disposal facility.
G. Paperwork Reduction Act
We have determined that this rule
contains no information collection
requirements within the scope of the
Paperwork Reduction Act, 42 U.S.C.
3501-30.
H. Regulatory Flexibility Act f.RFA), as
amended by the Small Business
Regulatory Enforcement Fairness Act of
1996 (SBREFA), 5 U.S.C. 601 et seq
The Congressional Review Act, 5
U.S.C. 801 et seq., as added by the Small
Business Regulatory Enforcement
Fairness Act of 1996, generally provides
that before a rule may take effect, the
agency promulgating the rule must
submit a rule report, which includes a
copy of the rule, to each House of the
Congress and to the Comptroller General
of the United States. Section 804,
however, exempts from section 801 the
following types of rules: rules of
particular applicability; rules relating to
agency management or personnel; and
rules of agency organization, procedure,
or practice that do not substantially
affect the right or obligations of non-
agency parties. (5 U.S.C. 804(3)) The
EPA is not required to submit a rule
report regarding today's action under
section 801 because this is a rule of
particular applicability.
/. Unfunded Mandates Reform Act
Title II of the Unfunded Mandates
Reform Act of 1995 (UMRA, Public Law
104~4) establishes requirements for
Federal agencies to assess the effects of
their regulatory actions upon state,
local, and tribal governments and the
private sector. Under section 202 of
UMRA, we generally must prepare a
written statement, including a cost-
benefit analysis, for proposed and final
rules with "Federal mandates" that may
result in expenditures by state, local,
and tribal governments, in the aggregate,
or to the private sector, of $100 million
or more in any one year. Before we
promulgate a rule for which a written
statement is needed, section 205 of
UMRA generally requires us to identify
and consider & reasonable number of
regulatory alternatives and adopt the
least costly, most cost-effective, or least
burdensome alternative that achieves
the objectives of the rule. The
provisions of section 205 do not apply
when they are inconsistent with
applicable law. Moreover, section 205
allows us to adopt an alternative other
than the least costly, most cost-effective,
or least burdensome if the
Administrator publishes with the final
rule an explanation as to why that
alternative was not adopted. Before we
establish any regulatory requirements
that significantly or uniquely affect
small governments, including tribal
governments, we must develop, under
section 203 of UMRA, a small-
govemment-agency plan. The plan must
provide for notifying potentially
affscted small governments, enabling
officials of affected small governments
to have meaningful and timely input
into the development of regulatory
proposals with significant Federal
intergovernmental mandates, and
informing, educating, and advising
small governments on compliance with
the regulatory requirements.
Today's rule contains no Federal
mandates [under the regulatory
provisions of Title H of UMRA) for
State, local, or tribal governments or the
private sector. The final rule
promulgates radiological protection
standards applicable solely and
exclusively to the Department of
Energy's potential storage and disposal
facility at Yucca Mountain. The rule
imposes no enforceable duty on any
State, local or tribal governments or the
private sector. Thus, today's rule is not
subject to the requirements of sections
202 and 205 of UMRA.
/. Executive Order 13211
Executive Order 13211, "Actions
Concerning Regulations That
Significantly Affect Energy Supply,
Distribution, or Use," (66 PR 28355
(May 22, 2001)), provides that agencies
shall prepare and submit to the
Administrator of the Office of
Information and Regulatory Affairs,
Office of Management and Budget, a
Statement of Energy Effects for certain
actions identified as "significant energy
actions." Section 4{b) of Executive
Order 13211 defines "significant energy
actions" as "any action by an agency
(normally published in the Federal
Register) that promulgates or is
expected to lead to the promulgation of
a final rule or regulation, including
notices of inquiry, advance notices of
proposed rulemaking, and notices of
proposed rulemaking: (l)(i) That is a
significant regulatory action under
Executive Order 12866 or any successor
order, and (ii) is likely to have a
significant adverse effect on the supply,
distribution, or use of energy; or (2) that
is designated by the Administrator of
the Office of Information and Regulatory
Affairs as a significant energy action."
We have not prepared a Statement of
Energy Effects because this rule is not a
significant energy action, as defined in
Executive Order 13211. While this rule
is a significant regulatory action under
Executive Order 12866, we have
determined that it is not likely to have
an adverse effect on the supply,
distribution, or use of energy-
List of Subjects in 40 CFR Part 197
Environmental protection, High-level
radioactive waste Nuclear energy,
Radiation protection, Radionuelides,
Spent nuclear fuel, Uranium, Waste
treatment and disposal.
Dated-. June 5,2001.
Christine Todd Whitman,
Administrator,
The Environmental Protection Agency-
is adding a new part 197 to Subchapter
-------
32132 Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations
F of Chapter I, title 40 of the Code of
Federal Regulations, as follows:
Subchapter F—Radiation Protection
Programs
PART 197—PUBLIC HEALTH AND
ENVIRONMENTAL RADIATION
PROTECTION STANDARDS FOR
YUCCA MOUNTAIN, NEVADA
Subpart A—Public Health and
Environmental Standards for Storage
Sec.
197.1 What does subpart A covet?
197.2 What definitions apply in subpart A?
197.3 How is subpart A implemented?
197.4 What standard must DOE meet?
197.5 When will this part take effect?
Subpart B—Public Health and
Environmental Standards tor Disposal
19 7,11 What does subpart B cover?
197.12 What definitions apply in subpart B?
197.13 How is subpart B implemented?
197.14 What is a reasonable expectation?
197.15 How must DOE take into account
the changes that will occur durjog the
10,000 years after disposal?
Individual-Protection Standard
197.20 What standard must DOE meet?
197.21 Who is the reasonably maximally
exposed individual?
Human-Intrusion Standard 197.25 What
standard must DOE meet?
197.26 What are the circumstances of the
human intrusion?
Ground Water Protection Standards
197.30 What standards must DOE meet?
197.31 What is a representative volume?
Additional Provisions
197,35 What other projections rnust DOE
make?
197.36 Are there limits on what DOE must
consider in the performance
assessments?
197.37 Can EPA amend this rule?
197.38 Are The Individual Protection and
Ground Water Protection Standards
Severable?
Authority: Sec. 801, Pub. L. 102-486, 106
Stat. 2921. 42 U.S.C. 10141 n.
Subpart A—Public Health and
Environmental Standards for Storage
§197.1 What does subpart A cover?
This subpart covers the storage of
radioactive materia! by DOE in the
Yucca Mountain repository and on the
Yucca Mountain site.
§ 197.2 What definitions apply in subpart
A?
Annual committed effective dose
equivalent means the effective dose
equivalent received by an individual in
one year from radiation sources external
to the individual plus the committed
effective dose equivalent.
Committed effective dose equivalent
means the effective dose equivalent
received over a period of time (e.g., 30
years,), as determined by NRC, by an
individual from radionuclides internal
to the individual following a one-year
intake of those radionuclides.
DOE means the Department of Energy,
Effective dose equivalent means the
sum of the products of the dose
equivalent received by specified tissues
following an exposure of, or an intake
of radionuclides into, specified tissues
of the body, multiplied by appropriate
weighting factors.
EPA means the Environmental
Protection Agency.
General environment means
exrerywhere outside the Yucca Mountain
site, the Nellis Air Force Range, and the
Nevada Test Site.
High-level radioactive waste means:
(1) The highly radioactive material
resulting from the reprocessing of spent
nuclear fuel, including liquid waste
produced directly in reprocessing and
any solid material derived from such
liquid waste that contains fission
products in sufficient concentrations;
and
(2) Other highly radioactive material
that the Commission, consistent with
existing law, determines by rule
requires permanent isolation.
Member of the public means anyone
who is not a radiation worker for
purposes of worker protection.
NKC means the Nuclear Regulatory
Commission.
Radioactive material means matter
composed of or containing
radionuclides subject to the Atomic
Energy Act of 1954, as amended (42
U.S.C 2014 etseq.j. Radioactive
material includes, but is not limited to,
high-level radioactive waste and spent
nuclear fuel.
Spent nuclear fuel means fuel that has
been, withdrawn from a nuclear reactor
following irradiation, the constituent
elements of which have not been
separated by reprocessing.
Storage means retention (and any
associated activity, operation, or process
necessary to carry out successful
retention) of radioactive materia! with
the intent or capability to readily access
or retrieve such material.
Yucca Mountain repository means the
excavated portion of the facility
constructed underground within the
Yucca Mountain site.
Yucca Mountain site means:
(1) The site recommended by the
Secretary of DOE to the President under
section 112(b)(l)(B) of the Nuclear
Waste Policy Act of 1982 (42 U.S.C.
10132(b)(l)(B)) on May 27, 1986; or
(2) The area under the control of DOE
for the use of Yucca Mountain activities
at the time of licensing, if the site
designated under the Nuclear Waste
Policy Act is amended by Congress prior
to the time of licensing.
§ 197.3 How is subpart A implemented?
The NRC implements this subpart A.
The DOE must demonstrate to NRC that
normal operations at the Yucca
Mountain site will and do occur in
compliance with this subpart before
NRC may grant or continue a license for
DOE to receive and possess radioactive
material within the Yucca Mountain-
site.
§ 197.4 Wh at standard must DOE meet?
The DOE must ensure that no member
of the public in the general environment
receives more than an annual
committed effective dose equivalent of
150 microsieverts (15 millirems) from
the combination of:
(a) Management and storage (as
defined in 40 CFR 191.2) of radioactive
material that:
(1) Is subject to 40 CFR 191.3 (a); and
(2) Occurs outside of the Yucca
Mountain repository but within the
Yucca Mountain site; and
(b) Storage (as defined in §197.2) of
radioactive material inside the Yucca
Mountain repository.
§ 197.5 When will this part take effect?
The standards in this part take effect
on July 13,2001.
Subpart B—Public Health and
Environmental Standards for Disposal
§ 197.11 What does subpart B cover?
This subpart covers the disposal of
radioactive material in the Yucca
Mountain repository by DOE.
§ 197.12 What definitions apply in subpart
B?
All definitions in subpart A of this
part and the following:
Accessible environment means any
point outside of the controlled area,
including-.
(1) The atmosphere (including the
atmosphere above the surface area of the
controlled area);
(2) Land surfaces;
(3) Surface waters;
(4) Oceans; and
(5) The lithosphere.
Aquifer means a water-bearing
underground geological formation,
group of formations, or part of a
formation (excluding perched water
bodies) that can yield a significant
amount of ground water to a well or
spring.
Barrier means any material, structure,
or feature that, for a period to be
determined by NRC, prevents or
substantially reduces the rate of
-------
Federal Register/Vol. 66, No. 114/Wednesday, June 13, 2001/Rules and Regulations 32133
movement of water or radionuclides
Scorn the Yucca Mountain repository to
the accessible environment, or prevents
the release OT substantially reduces the
release rate of radionuclides from the
waste. For example, a barrier may be a
geologic feature, an engineered
structure, a canister, a waste form with
physical and chemical characteristics
that significantly decrease the mobility
of radionuclides, or a material placed
over and around the waste, provided
that the material substantially delays
movement of water or radionuclides.
Controlled area means:
(1) The surface area, identified by
passive institutional controls, that
encompasses no more than 300 square
kilometers. It must not extend farther:
(a) South than 36° 40' 13.6661" north
Latitude, in the predominant direction of
ground water flow; and
(b) Than five kilometers from the
repository footprint in any other
direction; and
(2) The subsurface underlying the
surface area.
Disposal means the emplacement of
radioactive material into the Yucca
Mountain disposal system with the
intent of isolating it for as long as
reasonably possible and with no intent
of recovery, whether or not the design
of the disposal system pennits the ready
recovery of the material.
Disposal of radioactive material in the
Yucca Mountain disposal system begins
when all of the ramps and other
openings into the Yucca Mountain
repository are sealed.
Ground water means water that is
below the land surface and in a
saturated zone.
Human intrusion means breaching of
any portion of the Yucca Mountain
disposal system, within the repository
footprint, by any human activity.
Passive institutional controls means:
(1) Markers, as permanent as
practicable, placed on the Earth's
surface;
(2) Public records and archives;
(3) Government ownership and
regulations regarding land or resource
use; and
(4) Other reasonable methods of
preserving knowledge about the
location, design., and contents of the
Yucca Mountain disposal system.
Peak dose means the highest annual
committed effective dose equivalent
projected to be received by the
reasonably maximally exposed
individual.
Performance assessment means an
analysis that:
(l) Identifies the features, events,
processes, (except human intrusion),
and sequences of events and processes
(except human intrusion) that might
affect the Yucca Mountain disposal
system and their probabilities of
occurring during 10,000 years after
disposal;
(2) Examines the effects of those
features, events, processes, and
sequences of events and processes upon
the performance of the Yucca Mountain
disposal system; and
(3) Estimates the annual committed
effective dose equivalent incurred by
the reasonably maximally exposed
individual, including the associated
uncertainties, as a result of releases
caused by all significant features,
events, processes, and sequences of
events and processes, weighted by their
probability of occurrence.
Period of geologic stability means the
time during which the variability of
geologic characteristics and their future
behavior in and around the Yucca
Mountain site can be bounded, that is,
they can be projected within a
reasonable range of possibilities.
Plume of contamination means that
volume of ground water in the
predominant direction of ground water
flow that contains radioactive
contamination from releases from the
Yucca Mountain repository. It does not
include releases from any other
potential sources on or near the Nevada
Test Site.
Repository footprint means the
outline of the outermost locations of
where the waste is emplaced in the
Yucca Mountain repository.
Slice of the plume means a cross-
section of the plume of contamination
with sufficient thickness parallel to the
prevalent direction of flow of the plume
that it contains the representative
volume.
Total dissolved solids means the total
dissolved (filterable) solids in water as
determined by use of the method
specified in 40 CFR part 136.
Undisturbed performance means that
human intrusion or the occurrence of
unlikely natural features, events, and
processes do not disturb the disposal
system.
Undisturbed Yucca Mountain
disposal system means that the Yucca
Mountain disposal system is not
affected by human intrusion.
Waste means any radioactive material
emplaced for disposal into the Yucca
Mountain repository.
Well-capture zone means the volume
from which a well pumping at a defined
rate is withdrawing water from an
aquifer. The dimensions of the well-
capture zone are determined by the
pumping rate in combination with
aquifer characteristics assumed for
calculations, such as hydraulic
conductivity, gradient, and the screened
interval.
Yucca Mountain disposal system
means the combination of underground
engineered and natural barriers within
the controlled area that prevents or
substantially reduces releases from the
waste.
§ 197.13 Now is subpart 5 implemented?
The NRC implements this subpart B.
The DOE must demonstrate to NRC that
there is a reasonable expectation of
compliance with this subpait before
NRC may issue a license. In the case of
the specific numerical requirements in
§ 197.20 of this subpart, and if
performance assessment is used to
demonstrate compliance with the
specific numerical requirements in
§§ 197.25 and 197.30 of this subpart,
NRC will determine compliance based
upon the mean of the distribution of
projected doses of DOE's performance
assessments which project the
performance of the Yucca Mountain
disposal system for 10,000 years after
disposal.
§ 197.14 What is a reasonable
expectation?
Reasonable expectation means that
NRC is satisfied that compliance will be
achieved based upon the full record
before it. Characteristics of reasonable
expectation include that it:
(a) Requires less than absolute proof
because absolute proof is impossible to
attain for disposal due to the
uncertainty of projecting long-term
performance;
(b) Accounts for the inherently greater
uncertainties in making long-term
projections of the performance of the
Yucca Mountain disposal system;
(c) Does not exclude important
parameters from assessments and
analyses simply because they are
difficult to precisely quantify to a high
degree of confidence; and
(d} Focuses performance assessments
and analyses upon the full range of
defensible and reasonable parameter
distributions rather than only upon
extreme physical situations and
parameter values.
§197.15 How must DOE take into account
the changes that will occur during the next
10,000 years after disposal?
The DOE should not project changes
in society, the biosphere (other than
climate), human biology, or increases OT
decreases of human knowledge or
technology. In all analyses done to
demonstrate compliance with this part,
DOE must assume that all of those
factors remain constant as they are at
the time of license application
submission to NRC. However, DOE must
-------
32134 Federal Register/Vol. 66, No, 114/Wednesday, June 13, 2001/Rules and Regulations
vary factors related to the geology,
hydrology, and climate based upon
cautious, but reasonable assumptions of
the changes in these factors that could
affect the Yucca Mountain disposal
system over the next 10,000 yeais.
Individual-Protection Standard
§ 197.20 What standard must DOE meet?
The DOE must demonstrate, using
performance assessment, that there is a
reasonable expectation that, for 10,000
years following disposal, the reasonably
maximally exposed individual receives
no more than an annual committed
effective dose equivalent of 150
microsieverts (15 millirems) from
releases from the undisturbed Yucca
Mountain disposal system. The DOE's
analysis must include all potential
pathways of radionuclide transport and
exposure.
§ 197.21 Who is the reasonably maximally
exposed individual?
The reasonably maximally exposed
individual is a hypothetical person who
meets the following criteria:
(a) Lives in the accessible
environment above the highest
concentration of radionuclides in the
plume of contamination;
(b) Has a diet and living style
representative of the peopie who now
reside in the Town of Amargosa Valley,
Nevada. The DOE must use projections
based upon surveys of the people
residing in the Town of Amargosa
Valley, Nevada, to determine their
current diets and living styles and use
the mean values of these factors in the
assessments conducted for §§ 197.20
and 197.25; and
(c) Drinks 2 liters of water per day
from wells drilled into the ground water
at the location specified in paragraph (a)
of this section.
Human-Intrusion Standard
§ 13?.25 What standard must DOE meet?
The DOE must determine the earliest
time after disposal that the waste
package would degrade sufficiently that
a human intrusion (see § 197.26) could
occur without recognition by the
drillers. The DOE must:
(a) If complete waste package
penetration is projected to occur at or
before 10,000 years after disposal:
(Ij Demonstrate that there is a
reasonable expectation that the
reasonably maximally exposed
individual receives no more than an
annual committed effective dose
equivalent of 150 microsieverts (15
millirems) as a result of a human
intrusion, at or before 10,000 years after
disposal. The analysis must include all
potential environmental pathways of
radionuclide transport and exposure;
and
(2) If exposures to the reasonably
maximally exposed individual occur
more than 10,000 years after disposal,
include the results of the analysis and
its bases in the environmental impact
statement for Yucca Mountain as an
indicator of long-term disposal system
performance; and
(b) Include the results of the analysis
and its bases in the environmental
impact statement for Yucca Mountain as
an indicator of long-term disposal
system performance, if the intrusion is
not projected to occur hefore 10,000
years after disposal.
§ 197.26 What are the circumstances of
the human intrusion?
For the purposes of the analysis of
human intrusion, DOE must make the
following assumptions:
Ja) There is a single human intrusion
as a result of exploratory drilling for
ground water;
(b) The intruders drill a borehole
directly through a degraded waste
package into the uppermost aquifer
underlying the Yucca Mountain
repository;
(c) The drillers use the common
techniques and practices that are
currently employed in exploratory
drilling for ground water in the region
surrounding Yucca Mountain;
(d) Careful sealing of the borehole
does not occur, instead natural
degradation processes gradually modify
the borehole;
(e) Only releases of radionuclides that
occur as a result of the intrusion and
that are transported through the
resulting borehole to the saturated zone
are projected; and
(f) No releases are included which are
caused by unlikely natural processes
and events.
Ground Water Protection Standards
§ 137.30 What standards must DOE meet?
The DOE must demonstrate that there
is a reasonable expectation that, for
10,000 years of undisturbed
performance after disposal, releases of
radionuclides from waste in the Yucca
Mountain disposal system into the
accessible environment will not cause
the level of radioactivity in the
representative volume of ground water
to exceed the limits in the following
Table 1:
TABLE 1.—LIMITS ON RADIONUCLIDES IN THE REPRESENTATIVE VOLUME
Radionuclide or type of radiation emitted
Limit
Is natural back-
ground in-
cluded?
Combined radium-226 and radium-228
Gross alpha activity (including radium-226 but excluding radon
and uranium).
Combined beta and photon emitting radianuclides
5 picocuries per liter ...
15 picocuries per liter .
40 microsieverts {4 millirem) per year to the whole bady or
any organ, based on drinking 2 liters of water per day from
the representative volume.
Yes.
Yes.
No.
§ 197.31 What is a representative volume?
(a) It is the volume of ground water
that would be withdrawn annually from
an aquifer containing less than 10,000
milligrams of total dissolved solids per
liter of water to supply a given water
demand. The DOE must project the
concentration of radionuclides released
from the Yucca Mountain disposal
system that will be in the representative
volume. The DOE must then use the
projected concentrations to demonstrate
a reasonable expectation to NRC that the
Yucca Mountain disposal system
complies with § 197.30. The DOE must
make the following assumptions
concerning the representative volume;
(1) It includes the highest
concentration level in the plume of
contamination in the accessible
environment;
(2) Its position and dimensions in the
aquifer are determined using average
hydrologic characteristics which have
cautious, but reasonable, values
representative of the aquifers along the
radionuclide migration path from the
Yucca Mountain repository to the
-------
Federal Register/Vol. 66. No. 114/Wednesday, June 13, 2001 /Rules and Regulations 32135
accessible environment as determined
by site characterization; and
(3) It contains 3,000 acre-feet of water
(about 3,714,450,000 liters ox
977,486,000 gallons}.
(b) The DOE must use one of two
alternative methods for determining the
dimensions of the representative
volume. The DOE must propose its
chosen method, and any underlying
assumptions, to NRC for approval,
(1) The DOE may calculate the
dimensions as a well-capture zone. If
DOE uses this approach, it must assume
that the:
(i) Water supply wellfs) has (have)
characteristics consistent with public
water supply wells in the Town of
Amargosa Valley, Nevada, for example,
well-bore size and length of the
screened intervals;
(ii) Screened inteival(s) include(s) the
highest concentration in the plume of
contamination in the accessible
environment; and
fiii) Pumping rates and the placement
of the well(s) must be set to produce an
annual withdrawal equal to the
representative volume and to tap the
highest concentration within the plume
of contamination.
(2) The DOE may calculate the
dimensions as a slice of the plume. If
DOE uses this approach, it must;
(i) Propose to NRC, for its approval,
where the location of the edge of the
plume of contamination occurs. For
example, the place where the
concentration of radionuclides reaches
0.1% of the level of the highest
concentration in the accessible
environment;
(ii) Assume that the slice of the plume
is perpendicular to the prevalent
direction of flow of the aquifer; and
(iii) Assume that the volume of
ground water contained within the slice
of the plume equals the representative
volume.
Additional Provisions
§ 197.35 What other projections must DOE
make?
To complement the results of
§ 197.20, DOE must calculate the peak
dose of the reasonably maximally
exposed individual that would occur
after 10,000 years following disposal but
within the period of geologic stability.
No regulatory standard applies to the
results of this analysis; however, DOE
must include the results and their bases
in the environmental impact statement
for Yucca Mountain as an indicator of
long-term disposal system performance.
§ 197.36 Are there limits on what DOE
must consider in the performance
assessments?
Yes. The DOE's performance
assessments shall not include
consideration of very unlikely features,
events, 01 processes, i.e., those that are
estimated to have less than one chance
in 10,000 of occurring within 10,000
years of disposal. The NRC shall
exclude unlikely features, events, and
processes, or sequences of events and
processes ftom the assessments for the
human intrusion and ground water
protection standards. The specific
probability of the unlikely features,
events, and processes is to be specified
by NRC, In addition, unless otherwise
specified in NRC regulations, DOE's
performance assessments need not
evaluate, the impacts resulting from any
features, events, and processes or
sequences of events and processes with
a higher chance of occurrence if the
results of the performance assessments
would not be changed significantly.
§197.37 Can EPA amend this rule?
Yes. We can amend this rule by
conducting another notice-and-
comment rulemaking. Such a
rulemaking must include a public
comment period. Also, we may hold one
or more public hearings, if we receive a
written request to do so.
§197.38 Are The Individual Protection and
Ground Water Protection Standards
Severable?
Yes. The individual protection and
ground water protection standards are
severable.
[FRDoc. 01-14626 Filed 6-8-01; 2:05 pro]
BILLING CODE 65W-50-P
-------
-------
-------
-------
------- |