_ ___^_ United States Science Advisory EPA-SAB-RAC-94-013
£B L.P/V Environmental Board (1400F) May 1994
Protection Agency
AN SAB REPORT:
REVIEW OF DIFFUSE
NORM DRAFT SCOPING
DOCUMENT
REVIEW OF THE OFFICE OF RADIATION
AND INDOOR AIR DRAFT DOCUMENT
ON DIFFUSE NATURALLY-OCCURRING
RADIOACTIVE MATERIAL (NORM):
WASTE CHARACTERIZATION AND
PRELIMINARY RISK ASSESSMENT
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^tO STj,.
* 4^\ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
\ WASHINGTON, D.C. 20460
May 16, 1994
EPA-SAB-RAC-94-013 OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460
Re: Naturally Occurring Radioactive Materials (NORM)
Dear Ms. Browner:
At the request of the Office of Radiation and Indoor Air (ORIA), the Science
Advisory Board (through its Radiation Advisory Committee) has reviewed the Agency's draft
document titled "Diffuse NORM - Waste Characterization and Preliminary Risk Assessment,"
dated May 1993 (hereinafter called the "NORM document"). This Committee has responded
to the six specific questions asked by ORIA and has also provided more general comments
and suggestions.
The NORM document is the latest draft in a series that spans several years and
reflects the responsiveness of ORIA to comments by EPA internal reviewers, by the public,
and by the Radiation Advisory Committee (RAC). It appears to have accessed and summa-
rized most of the information about diffuse NORM that was generally available at the time
the document was prepared. However, the NORM document does not meet its stated goal
of providing a scoping analysis of the NORM problem sufficient to determine the need for
additional investigations or for regulatory initiatives.
With regard to the six specific questions asked in the charge, the RAC finds the
following:
1. The NORM document does not adequately convey the deficiencies and
uncertainties in the information available to characterize the sources of
NORM. The choices of nominal values for volume and concentration used
in the risk assessment are not sufficiently justified. Some values appear to
be overestimates (especially for concentrations), while others appear to be
underestimates.
Recycled/Recyclable
Printed on paper that contains
at least 75% recycled liber
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2. The justification provided for parameter values used in the risk assessment
is not sufficient. In addition, the NORM document uses aggregate factors
for food uptake and dose conversion that incorporate many other assump-
tions and parameter choices, making evaluation difficult. The RAC sus-
pects that the food uptake factors may tend to underestimate exposures.
3. With few exceptions as noted in the RAC report, the NORM document has
selected reasonable scenarios and pathways of exposure for analysis.
4. The NORM document has used appropriate models for the most part. The
RAC notes, however, that advective flow was not considered in the model
for radon exposures, and suspects that this omission may have led to
underestimates of exposures for radium in the waste.
,5«Jl ' --.»
5. While the greatest uncertainties are in the estimates of risks from pathways
that probably do not contribute much to total risk, the risks from specific
sources are probably not known within a factor of three, despite what might
be inferred from the language in the NORM document.
6. The NORM document does not meet its stated goal of providing a scoping
analysis of the NORM problem sufficient to determine the need for addi-
tional investigations or for regulatory initiatives. The RAC believes that, if
the EPA addressed the deficiencies identified in this review, then the
revised NORM document could serve as a useful compilation of informa-
tion for the public on NORM source terms and potential exposure scenari-
os. Any language suggesting that the NORM document could be used to
justify regulatory decisions should be removed from the document. To go
beyond this limited use and to meet the goal of serving as a screening tool
for identifying those categories that ma)t require regulatory attention, it
would be necessary for the Agency to conduct its risk assessment analysis
using a consistent approach in addressing uncertainties, such as the method-
ology suggested by the RAC in its report.
The RAC believes that, despite its shortcomings, the NORM document nonetheless
provides indications that some categories of NORM may produce risks that exceed those of
concern from other sources of radiation. Consequently, the RAC is of the opinion that the
issue of NORM deserves substantial attention within EPA, and is concerned that timely
resolution of this issue will require an increased commitment of resources.
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The Radiation Advisory Committee appreciates the opportunity to comment on the
NORM assessment. We look forward to receiving the EPA's plans for further work on the
NORM issue, particularly as it relates to our explicit recommendations.
Sincerely,
Dr. Genevieve M. Matanoski Dr.James E. Watson, Jr.
Chair, Executive Committee Chair, Radiation Advisory Committee
Science Advisory Board Science Advisory Board
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NOTICE
This report has been written as a part of the activities of the Science Advisory
Board, a public advisory group providing extramural scientific information and
advice to the Administrator and other officials of the Environmental Protection
Agency. The Board is structured to provide a balanced, expert assessment of
scientific matters related to problems facing the Agency. This report has not been
reviewed for approval by the Agency; hence, the comments of this report do not
necessarily represent the views and policies of the Environmental Protection
Agency or of other Federal agencies. Any mention of trade names or commercial
products does not constitute endorsement or recommendation for use.
The bulk of this report was prepared while Dr. Genevieve M. Matanoski was
Chair of the SAB's Radiation Advisory Committee (RAG), and Dr. Raymond C.
Loehr was Chair of the SAB's Executive Committee. Subsequently, Ms. Carol M.
Browner, Administrator of the EPA, selected Dr. Matanoski as Chair of the SAB's
Executive Committee and Dr. James E. Watson, Jr., as Chair of the SAB's RAG.
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ABSTRACT
The Radiation Advisory Committee (RAC) of the Science Advisory Board (SAB)
has reviewed the Agency's Office of Radiation and Indoor Air (ORIA) study
entitled "Diffuse NORM - Waste Characterization and Preliminary Risk
Assessment," dated May, 1993. The RAC responded to the six specific questions
asked by ORIA and also provided more general comments and suggestions.
The RAC believes that, despite its shortcomings, the NORM document
nonetheless provides indications that some categories of NORM may produce risks
that exceed those of concern from other sources of radiation. Consequently, the
RAC is of the opinion that the issue of NORM deserves substantial attention
within EPA, and is concerned that resolution of this issue will require an
increased commitment of resources. If the EPA addressed the deficiencies
identified by the RAC in its response to the charge, then the revised NORM
scoping document could serve as a useful aM much-needed compilation of
information for the public on NORM source terms and potential exposure
pathways.
However, to go beyond this limited use and to meet the goal of serving as a
screening tool for identifying those categories that may require possible regulatory
attention, it would be necessary for the Agency to conduct its risk assessment
analysis using a consistent approach for addressing uncertainties, such as the
methodology suggested by the RAC in its report. Care should be taken to
recognize the differences between those categories of NORM that may be rated
high with respect to individual risk and those that may be rated high with respect
to population risk.
Key Words: Diffuse Naturally Occurring Radioactive Material (NORM), NORM,
NORM Sources, NORM Exposures, NORM Risks
n
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SCIENCE ADVISORY BOARD
RADIATION ADVISORY COMMITTEE
Chair
Dr. James E. Watson, Jr., Professor, Department of Environmental Sciences and
Engineering, University of North Carolina at Chapel Hill, NC
Members and Consultants
Dr. Stephen L. Brown, Director, R2C2 (Risks of Radiation and Chemical
Compounds), Oakland, CA
Dr. June Fabryka-Martin, Staff Scientist, Chemical Science and Technology
Division, Los Alamos National Laboratory, Los Alamos, NM
if, m^,
Dr. Ricardo Gonzalez, Associate Professor, Department of Radiological Sciences,
University of Puerto Rico School of Medicine, San Juan, PR
Dr. F. Owen Hoffman, President, SENES Oak Ridge, Inc., Center for Risk
Analysis, Oak Ridge, TN
Dr. Arjun Makhijani, President, Institute for Energy and Environmental Research,
Takoma Park, MD
Dr. James E. Martin, Associate Professor of Radiological Health (and Certified
Health Physicist), University of Michigan, School of Public Health, Ann Arbor, MI
Dr. Genevieve M. Matanoski, M.D., Professor of Epidemiology, The Johns Hopkins
University, School of Hygiene and Public Health, Department of Epidemiology,
Baltimore, MD
Dr. Oddvar F. Nygaard, Professor Emeritus, Division of Radiation Biology,
Department of Radiology, School ^f Medicine, Case Western Reserve ^University,
Cleveland, OH
Dr. Richard G. Sextro, Staff Scientist, Indoor Environment Program, Lawrence
Berkeley Laboratory, Berkeley, CA
Science Advisory Board Staff
Dr. K. Jack Kooyoomjian, Designated Federal Official, U.S. EPA, Science Advisory
Board (1400F), 401 M Street, S.W., Washington, D.C. 20460
Mrs. Diana L. Pozun, Secretary
Dr. Donald G. Barnes, Staff Director
iii
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TABLE OF CONTENTS
1. EXECUTIVE SUMMARY 1
2. INTRODUCTION AND MAJOR CONCLUSIONS 7
3. NORM SOURCES 9
3.1 Uranium Mine Overburden 9
3.2 Phosphate/Fertilizer Materials 10
3.2.1 Phosphate Industry Wastes 10
3.2.2 Radionuclide Concentrations 12
3.3 Phosphate Fertilizers and Potash 13
3.4 Fossil Fuels - Coal Ash 14
3.4.1 Coal Ash Generation 14
3.4.2 Radionuclide Concentrations <,*>v. .» 15
3.5 Oil and Gas Production 17
3.5.1 Summary 17
3.5.2 Waste Volume Characterization 17
3.5.3 Radionuclide Concentrations 19
3.5.4 Other Issues 20
3.6 Water Treatment Sludges 20
3.6.1 Waste Volume Characterization 20
3.6.2 Radionuclide Concentrations 21
3.6.3 Other Issues 21
3.7 Metal Mining and Processing Wastes 22
3.7.1 Rare Earths 22
3.7.2 Zirconium, Hafnium, Titanium, and Tin 23
3.7.3 Large Waste Volume Processes 23
3.8 Geothermal Energy Waste 24
4. MODEL PARAMETERS 25
4.1 Documentation of Parameter Selection Process 25
4.2 Parameter Selection for Specific Pathways 26
4.3 Dose Conversion Factors 26
4.4 Substantial Bias in Risk Estimates 27
5. SCENARIOS 28
5.1 Identification of Pathways 28
5.2 Identification of Receptors 28
5.3 Matrix of Pathways vs. Receptors 29
5.4 Source Term vs. Scenario 29
6. MODEL FORMULATION 31
6.1 General Overview 31
6.2 Radon Transport Model 31
IV
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7. UNCERTAINTY ANALYSIS 34
8. PRIORITIES FOR ADDITIONAL WORK 37
9. ADDITIONAL COMMENTS 39
APPENDIX A - REFERENCES CITED A-l
APPENDIX B - WRITTEN PUBLIC COMMENTS RECEIVED BY THE
SAB/RAG B-l
APPENDIX C - EVALUATION OF FOOD UPTAKE FACTORS, AND DOSE
AND RISK CONVERSION FACTORS USED IN THE NORM RISK
ASSESSMENT C-l
Table C-l Comparison of food uptake factors (kg/yr) from various sources C-l
Table C-2 Ratios (unitless) of food uptake factors (calculated from values in
Table C-l) C-2
Table C-3 Comparison of dose and risk conversion factors for ingestion
from various sources C-3
Table C-4 Comparison of dose and risk conversion factors for inhalation
from various sources C-4
Table C-5 Comparison of ingestion dose and risk conversion factors (using
revised ICRP report) C-5
APPENDIX D - VALUATION OF SPECIFIC PATHWAYS, MODEL
FORMULATIONS, AND PARAMETERS USED IN THE NORM RISK
ASSESSMENT D-l
APPENDIX E - GLOSSARY OF TERMS AND ACRONYMS E-l
LIST OF TEXT TABLES
Table 7-1 Direction of Conservatism in NORM Assessment Parameters .... 35
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1. EXECUTIVE SUMMARY
At the request of the Office of Radiation and Indoor Air (ORIA), the Science
Advisory Board (through its Radiation Advisory Committee) has reviewed the
Agency's May 1993 draft report titled "Diffuse NORM - Waste Characterization
and Preliminary Risk Assessment," prepared by SC&A, Inc., and Rogers &
Associates Engineering Corporation (See Appendix A - Dehmel & Rogers, May
1993, hereinafter called the "NORM document"). The Committee has responded to
six specific questions asked by ORIA and also has provided more general
comments and suggestions.
The NORM document is the latest draft in a series that spans several years
and reflects the responsiveness of ORIA staff to comments by EPA internal
reviewers, by the public, and by the Radiation Advisory Committee (RAC, or "the
Committee"). The Agency appears to"H^vle accessed and Summarized most of the
information about diffuse NORM that was generally available at the time the
document was prepared. However, the RAC does not believe that the NORM
document meets its goal of providing a scoping analysis of the NORM problem
sufficient to determine the need for additional investigations or for regulatory
initiatives. The following discussion summarizes the Committee's responses to the
six specific issues raised by ORIA in its charge to the RAC.
Issue 1. NORM sources. Does the information in the document present an
adequate characterization of processes and sources of NORM,
including the adequacy of the data?
Findings
The information in the document does not present an adequate characterization
of sources of NORM to the extent required to conduct a useful screening analysis
of the risks associated with these sources. In some cases, the presentation of
available data is inadequate while in ather cases the basic data that are needed
are lacking.
The volume of the source of NORM and the radionuclide concentrations in the
source are key parameters for a risk assessment. The adequacy of this
information varies for the different sources of NORM considered in the document.
In general, the volumes of the sources are better characterized than are the
radionuclide concentrations. For most sources, a wide range of radionuclide
concentrations is noted, and a single value is selected for the assessment. In some
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cases the selected value appears to be conservative , i.e., it is more likely to be
biased high than low; but in other cases it is not known whether the selected
value is likely to be biased high or low. Furthermore, for cases in which the
radionuclide concentration in a given source of NORM spans more than an order
of magnitude, it may be inappropriate to adopt a single value to characterize the
radioactivity of wastes from that sector in risk assessment calculations.
Recommendations
la. Information in the NORM document does not provide an adequate basis
for omitting particular sources because of negligible risk, nor for
identifying particular sources for regulatory initiatives. The RAC
recommends that EPA re-evaluate the literature on volumes and
radionuclides concentrations in sources of NORM, with attention given to
comments in the RAC report as well as to comments received from the
public, and make needed (•affections to the NORM document. Publications
since the last literature search should also be considered in the re-
evaluation.
Issue 2. Model parameters. Are parameters used in the risk assessment
reasonable? Are the references and justifications adequate? Does the
presentation properly reflect the best available scientific information?
Findings
In most cases, the references and justifications for the parameters used in the
risk assessment have not been provided in the reviewed NORM document, making
it difficult to determine whether or not the adopted values are reasonable. In fact,
the procedure used to select parameter values is not clearly articulated. Moreover,
some of the parameters represent highly aggregated constructs, requiring
substantial effort to trace them back to their experimental or theoretical basis.
To a limited extent, the RAC was able to compare the adopted values to the range
aof values published in the literatusp in order to judge the degree to which the
adopted values are reasonable or conservative estimates. Some of the adopted
parameter values (e.g., food uptake factors) appear to fall outside the range of
measured values, in the direction of non-conservatism. While many of the
choices are consistent with standard risk assessment practices, the parameter
A "conservative" risk analysis is one in which the parameter values used in
the risk models are biased so as not to underestimate the true risk, and to
provide an upper bound estimate of the risk. In an "anti-conservative"
analysis, parameter values are biased so as to intentionally underestimate the
true risk, and to provide a lower bound estimate of the risk. A "non-
conservative" analysis is designed so as not to over-estimate the true risk, but
may not necessarily underestimate it.
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values for food uptake factors may be anticonservative in the sense of potentially
underestimating risk.
Recommendations
2a. The RAG recommends that the original data sources and justifications for
the selection of representative values for all parameters be incorporated
into the NORM document (or in an appendix thereto).
2b. The RAG recommends that a complete list of terms be added to the
appendix to the NORM document, that would clearly define each
parameter used and that would cite the mathematical expression used to
derive any lumped parameters.
2c. The RAG recommends that EPA document the reasons for the
discrepancies between the dose and risk conTSfslon factors used Iff the
NORM document and those recommended by the ICRP.
Issue 3. Scenarios. Does the preliminary risk assessment adequately identify
and characterize the key scenarios needed for evaluating individual
and population risks from the sources characterized?
Findings
In general, the list of pathways is reasonably comprehensive and may even
include some pathways that are very unlikely to contribute substantially to total
risk. However, it does not include at least one pathway that is commonly assessed
in EPA programs covering hazardous wastes (Superfund and RCRA): soil ingestion
by humans and by grazing animals. The NORM document also does not appear to
have considered leaching of potassium-40 from waste piles; the consequences for
risk of this omission are not clear. The list of receptors is reasonable, and the
matrix of pathways vs. receptors is reasonably complete.
^»-
Recommendations
3a. The RAG recommends that the list of pathways to be considered include,
to the extent appropriate, those pathways used in other programs of the
EPA (e.g., Superfund). In particular, the soil ingestion pathway seems
relevant.
Issue 4. Model formulations. Does the PATHRAE methodology presented in
this document adequately quantify risks from the sources and
scenarios characterized?
Findings
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With the exception of the radon transport model, the models and their
submodels appear to be reasonably complete formulations for developing
preliminary scoping estimates of doses and risks, with inclusion of an appropriate
choice of generic site parameters (although not necessarily of parameter values; see
issue 2 above). Underlying assumptions for the models are for the most part
clearly stated. Detailed documentation for the models is apparently to be found in
other EPA documents which presumably describe the mathematical basis of the
models; in some cases, as discussed in the main text of the Committee's review,
this basis is not sufficiently clear.
Recommendations
4a. The RAG recommends that advective flow be incorporated into the
scenarios having to do with exposures to radon; its omission from these
scenarios probably leads to underestimates of exposure for radium in the
waste. 4 - »
4b. The choice of computer models for assessing NORM risks may have been
driven by existing software, rather than by the needs of the document.
The Agency should consider using more flexible and transparent modern
programming tools in future work.
Issue 5. Uncertainty analysis of risk estimates. Risk estimates calculated
using the PATHRAE methodology are estimated to be within a factor
of three of calculations made with more detailed codes. Given this
error band, the methodology employed, and the lack of knowledge
associated with the waste streams; is the Agency's characterization of
uncertainty and sensitivity adequate for the purposes of this scoping
study?
Findings
The NORM document claims that risk estimates using the PATHRAE
methodology are estimated to be within a factor of three of those obtained using
more sophisticated codes, but does not support that assertion with calculations. In
fact, in the single very limited comparison between the simplified methodology and
the results from PRESTO-CPG-PC, the dose estimates were significantly different,
by as much as a factor of 50 in one case.
However, the magnitude of the uncertainties introduced by model formulations
for many scenarios and pathways may be exceeded by uncertainties that are
inherent in the parameter estimates themselves. Uncertainties in source volumes,
average radionuclide concentrations, transport parameters and dose-to-risk
conversions may each be on the order of a factor of ten or more. As a result, for
some pathways, the RAG would estimate that dose and risk estimates may be
uncertain by several orders of magnitude. Some of these pathways (e.g.,
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consumption of vegetables grown in soil upon which contaminated dust has
settled) are often relatively minor contributors to overall risk, such that
uncertainties associated with these doses are somewhat less important than those
for major pathways (e.g., direct gamma radiation and radon) where uncertainties
should generally be less.
Because the NORM document is neither consistently conservative nor
consistently nonconservative, the Agency's characterization of uncertainty and
sensitivity is not adequate, even for the purposes of this scoping study.
Concentrations of radionuclides in NORM materials are typically estimated with
conservative assumptions, but the same may not be true for the source volumes,
and many of the pathway and risk assumptions are probably nonconservative.
The document's qualitative uncertainty analysis, while informative about the
professional judgments made by the authors, does not permit the reader to
conclude that one source is definitely of more concern than another, that some
«diirces can be dismissed as posing negligible risks, or that some sources clearly
need further attention.
Recommendations
5a. The RAG recommends that the EPA better document its assertion that
risk estimates calculated using the PATHRAE methodology are within a
factor of three of calculations made with more detailed codes.
5b. The RAG recommends that the EPA revise its screening risk analysis for
NORM sources by consistently using either conservative or
nonconservative assumptions about exposure and risk coefficients. These
revisions should be included in any risk estimates appearing in the final
version of the NORM.
Issue 6. Priorities for additional work. In what areas does the SAB's RAC
recommend the greatest priority be given for developing additional
information?
The RAC believes that the issue of NORM deserves substantial attention
within EPA, and is concerned that timely resolution of this issue will require an
increased commitment of resources. Despite its shortcomings, the NORM
document nonetheless provides indications that some categories of NORM may
produce risks that exceed those of concern from other sources of radiation. The
RAC recommends that greatest priority be given to two aspects:
6a. First priority should be given to revising the NORM document to address
the more demanding of the RAC's comments: the inclusion of more recent
information on source volumes and concentrations, disaggregation and
updating of food uptake factors and dose/risk conversion factors,
documentation and justification of parameter selection, and consideration
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of advective flow as a means for radon transport. The revised NORM
document could then serve as a useful and much-needed compilation of
information for the public on NORM source terms and potential exposure
pathways. However, any language suggesting that the present NORM
document could be used to justify regulatory decisions should be removed
from that document.
6b. To go beyond this limited use and to meet the goal of serving as a
screening tool for identifying those categories that may or may not require
further attention and possible regulatory action, it would be necessary for
the Agency to conduct its risk assessment analysis using a consistent
approach in addressing uncertainties, such as the methodology suggested
by the RAG in this review report.
6
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2. INTRODUCTION AND MAJOR CONCLUSIONS
The Radiation Advisory Committee (RAC, or "the Committee") has had a keen
interest in the scientific issues surrounding the assessment of NORM materials
and welcomes this opportunity to review ORIA's draft document on diffuse NORM
(Dehmel and Rogers, May 1993, see Appendix A for full citation). The RAC is
mindful that NORM is a "federal orphan," falling outside the Nuclear Regulatory
Commission's (NRC's) mandate to regulate Atomic Energy Act materials and not
having attracted significant levels of staff attention or research funding within
EPA. Therefore, the intent of the NORM document, to serve as a scoping
document that could support the EPA's need to make informed decisions about
further research or regulation, is laudable.
The RAC believes that the issue of NORM as a potential environmental
problem deserves substantial attention within EPA, land is concerned that the
issue may not be resolved in a timely manner without increased resources being
devoted to it. Despite the shortcomings that are described in this RAC report,
the NORM document nonetheless provides indications that some categories of
NORM may produce risks that exceed those of concern from other sources of
radiation. It is therefore advisable that EPA move forward toward a decision on
the necessity to regulate NORM.
The RAC is of the opinion that the NORM document in its current form is
insufficient to provide a basis for such a decision. If the EPA addresses the
deficiencies identified in the RAC responses to the charge, then the revised NORM
document could serve as a useful and much-needed compilation of information for
the public on NORM source terms and potential exposure pathways. However, to
go beyond this limited use and to meet the stated goal of serving as a screening
tool for identifying those categories that may or may not require further attention
and possible regulatory action, it would be necessary for the Agency to conduct its
risk assessment analysis using a consistent approach in addressing uncertainties,
such as the methodology suggested by the RAC in this review report. Any
Unfortunately, the actual uses that EPA envisioned for the NORM document
are not as clear as they might be, and the RAC's review is influenced by the
Committee's notion of what the intent should be. On page ES-1 of the
NORM document, it is stated that the document "was prepared as an initial
step to help determine if standards governing the disposal and reuse of
NORM waste and material are warranted" and that "(i)f EPA decides
regulation is warranted, a much more detailed and complete risk analyses
(sic) and waste characterization will be developed and presented in a
Background Information Document that will accompany proposed regulations.
This preliminary risk assessment will not be used as the primary source of
information for developing such regulations."
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language suggesting that the present NORM document could be used to justify
regulatory decisions should be removed from that document.
A risk analysis appropriate for screening the NORM categories so as to
determine those that definitely should (or definitely should not) be candidates for
regulatory attention would need to take an approach that was either consistently
conservative (which would serve to identify categories of NORM that definitely
would not require regulatory attention) and/or consistently nonconservative (which
would serve to identify categories that might require regulatory attention).
In its documentation of the results of its risk analysis, EPA should also be
careful to draw the reader's attention to the differences between those categories
of NORM that may be rated high with respect to individual risk (where a few
people may be exposed to estimated risks ordinarily thought to deserve EPA
attention) and those that may be rated high with respect to population risk (where
estimated risks to even the maximally exposed person^ar'e relatively low btrt many
people are exposed). A discussion of the policy implications of these two
categories of risks, particularly with respect to the issues involved in imposing
regulatory controls on the latter, would be useful.
The remainder of this report is organized to follow the six specific questions
that the RAG was asked by ORIA to address in its review of the NORM
document, followed by a section containing additional comments.
The term "conservative" is used in the same sense as is commonly employed
in risk assessment, i.e., implying the use of assumptions and procedures
designed with a bias to ensure that the true risk will not be underestimated
(instead of toward overestimating risk) so that health-protective decisions can
be made. Compound conservative assumptions are therefore very likely to
overstate risk, and a NORM category that ranks low in risk even with
conservative methods is not a candidate for regulation. Categories that rank
high in risk after conservative screening are not necessarily worthy of
regulation, however, and more realistic evaluation is required to make the
ultimate regulatory decisions.
8
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3. NORM SOURCES
Issue 1: NORM sources
Does the information in the document present an adequate characterization of
processes and sources of NORM, including the adequacy of the data?
The information in the document does not present an adequate characterization
of sources of NORM to the extent required to conduct a useful screening analysis
of the risks associated with these sources. In some cases, the presentation of
available data is inadequate while in other cases the basic data that are needed
are lacking.
The volume of the source of NORM and the radionuclide concentrations in the
source are key parameters for a risk assessment. Individual and population risks
are related to the radionuclide concentration, but only the population risk is
affected by the volume or distribution of the source. The adequacy of this
information varies for the different sources of NORM considered in the NORM
document. In general, the volumes of the sources are better characterized than
are the radionuclide concentrations. For most sources, a wide range of
radionuclide concentrations is noted, and a single value is selected for the
assessment. In some cases the selected value appears to be conservative, that is, it
is more likely to be high than low, but in other cases it is not known whether the
selected value is likely to be biased high or low. Furthermore, for cases in which
the radionuclide concentration in a given source of NORM spans more than an
order of magnitude, it may be inappropriate to adopt a single value to characterize
the radioactivity of wastes from that sector in risk assessment calculations.
The RAG recommends that EPA re-evaluate the literature on volumes and
radionuclides concentrations in sources of NORM, with attention given to
comments in the RAG report as well as to comments received from the public (e.g.,
See Appendix B), and make needed corrections to the NORM document.
Publications since the last literature search should also be considered in the re-
evaluation.
3.1 Uranium Mine Overburden
This section of the NORM document provides a good overview of the subject.
However, the adoption of one set of risk assessment parameters "for representative
disposal of uranium mining overburden" (p. B-l-23) is too sweeping and will
result in misleading and not very useful risk assessments.
Page numbers throughout this report refer to those in the NORM document
(Dehmel and Rogers, May 1993).
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The range of radioactivity levels in uranium mining overburden is very large --
for instance, the NORM document cites a range of Ra-226 concentrations from
three to several hundred picocuries per gram. The range of uranium values is not
cited. The NORM document should cite the full range of values for both the
uranium and thorium decay chains. At secular equilibrium, uranium activity levels
would be double those of Ra-226, with half coming from U-238 and half from
U-234, and this is presumably the case for uranium overburden, according to the
average values shown in Table B.l-5 (p. B-l-23). It would be useful to cite
available data on U-238/Ra-226 and U-238/Th-230 ratios in overburden to
determine the extent to which differential solubility may have affected the
equilibrium ratios and how these ratios might be expected to evolve with time in
an unremediated pile.
The use of a 5% figure for the U-235 decay chain in the absence of data is
reasonable (p. B-l-17), and can be applied to all uranium calculations in this
NORM document. It is not clear whether all decay products of U-235 have been
included; they should be. The coefficients for radon and radon daughters
discussed in the top half of page B-l-17 appear reasonable. However, these ratios
would appear to depend on the physical configuration of the tailings and the
NORM document should discuss the range of values to be expected.
On p. B-l-10, the RAG notes that, although it is true that surface mining
dominates the overburden, the problem of overburden from underground mines
could be very important locally, depending on radionuclide concentrations and the
likelihood that the area may be used for residential, commercial, or agricultural
purposes in the future.
3.2 Phosphate/Fertilizer Materials
3.2.1 Phosphate Industry Wastes
Although the mining and processing of phosphate rock is a large industry (the
fifth largest mining industry in the U.S.), the activities that surround it are
concentrated in the southeast U.S., mostly Florida and Tennessee, and in the west,
primarily in southeast Idaho, Utah, Wyoming, and Montana. This focused
industry is well understood and represented by organizations familiar with process
rates and production rates of products containing phosphate. The NORM
document mirrors the data from these organizations and major studies of the
industry, and thus presents a responsible compilation of the amount of product
and waste produced over the past few decades for elemental phosphorous and
phosphoric acid, the two principal products.
Mining, beneficiation, and processing of the ore to produce phosphoric acid (the
wet process) and elemental phosphorous (the thermal process) are adequately
described in terms of how radioactive material distributes in the products and
wastes. These estimated distributions are based on fairly extensive measurements
made by EPA and others. In particular, a series of studies by EPA's Office of
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Radiation Programs in the 1970's and 80's provided much of the data for these
estimates. Thus, the NORM document presents estimates based on good
measurements, which is very desirable. Nonetheless, consideration of the huge
volumes of materials requires extrapolation from this data set, and the inevitable
uncertainties that accompany such extrapolation are not adequately presented.
For example, one extrapolated statistic for phosphoric acid production that
perpetuates throughout the analysis is that about 80% of the Ra-226 in the
original phosphate rock goes into the phosphogypsum wastes while about 86% of
the uranium and 70% of the thorium remain in the phosphoric acid (and
presumably about 20% of the Ra-226). This statistic is based on measurements for
the wet process only; no such statistic is presented for the thermal process. Since
70-80% of the elemental phosphorous produced is used in fertilizers, which become
widely distributed sources of NORM, data for both the wet and thermal processes
are needed. The mix of thermal phosphorus production versus the wet process is
already changing due to increasing energy costs for thermal process plants.
The NORM document is deficient in its description of the distribution of
beneficiation wastes, primarily the slimes and tailings. Beneficiation waste control
practices have changed over the years, and the risk assessment needs to recognize
current trends and their implications for ways in which diffuse NORM from this
sector could affect the general public. For example, the slimes produced during
ore beneficiation contain appreciable amounts of Ra-226 and, when used as shallow
fill, they can produce elevated radon levels in structures built on filled areas.
Recent practices of restricting slime use have reduced these circumstances.
Waste production rates are reasonably described for the phosphogypsum;
however, the phosphate slag inventory is estimated to range between 224 and 424
million metric tons (MT) (three significant figures appear out of place for such a
wide-ranging estimate). More recent data on slag production should be obtained,
if available (the NORM document references 1975 production data).
The NORM document describes the production of concentrated radioactivity in
scale deposits (primarily Ra-226) and then dismisses it because the volume is low.
EPA should assure that these NORM wastes are properly managed - perhaps the
practice of emplacing scale in phosphogypsum piles is appropriate if it occurs;
perhaps not. Ferrophosphorus is reported (page B-2-9) to be a product of the
thermal process. The radioactivity content appears to be low as shown in Table
B.2-4 of the document.
Phosphate Slag is described as a fused matrix that minimizes radon emanation,
an assumption which appears to be reasonable considering the experience with
basement fills in Soda Springs and Pocatello, Idaho. The assumption of an
emanation fraction of 0.01 for radon is noted as arbitrary; however, data are
presented from Montana slag that suggest it was calculated from these
measurements. Measurement of a few samples would confirm this estimate and/or
support the use of the Montana data. It is further reported that radionuclides can
be leached from slag, but no more is said of it. It should be stated whether or
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not, and why, this may be a significant pathway of exposure. Furthermore, the
document neglects another potential pathway, that of suspension of slag dust in
precipitation.
3.2.2 Radionuclide Concentrations
In the NORM document, most of the radionuclide concentration data for the
phosphate industry are based on measured data or extrapolations of these data to
other matrices and forms using assumed fractions. The original measurements
were done primarily by EPA using state-of-the-art laboratories and reported in
well documented studies. A few inconsistencies can be noted.
An informative statistic is that about 80% of the Ra-226 in phosphate ore goes
to phosphogypsum waste while 86% of the uranium goes into the phosphoric acid.
These data are based on Florida phosphate ore deposits and are useful for
establishing potential exposure pathways for NORM in phosphate ore. Yet, Table
B.2-4, which is based on measured data, shows that the Ra-226 in the ore is
somewhat less than 80% of the Ra-226 concentration in the phosphogypsum.
Perhaps this apparent discrepancy is due to density changes in the processing, but
it should be reconciled.
Extrapolations for phosphogypsum are generally based on concentrations in
Florida phosphate ore which is generally higher than other ores; thus, these
estimated values are probably conservative for phosphogypsum wastes overall.
Decay products of uranium and Ra-226 are calculated based on radiological
equilibrium conditions for a selected source term which is usually chosen near the
high end of measured values. Assumed ingrowth periods appear reasonable, and
the calculated values are correct for these periods. Decay products of U-235 are
reasonably calculated to be 5% of the U-238 activity (the actual value is 4.6%).
These ingrowth radionuclides are adjusted for radon emanation fractions which are
assumed to be 0.2 for phosphogypsum and 0.3 for fertilizer applications,
respectively. The difference is presumably to account for differences in soil
conditions, but it is not explained. Average concentrations of U-238, Ra-226,
U-235, and Th-232 in phosphogypsum are estimated to be 6.0, 33, 0.30, and 0.27
pCi/g, respectively.
Phosphogypsum Concentrations are based on measured data and appear to
have been extrapolated correctly both for direct disposal in stacks and reuse in
fertilizers and soil conditioners. The reuse scenarios also appear reasonable.
The largest deficiencies in the radionuclide concentration data are the absence
of concentrations of key radionuclides in elemental phosphorus, phosphoric acid
manufactured from it that may be used in fertilizers, and phosphoric acid from the
wet process. These data would be useful for assessing the risks associated with
the widespread application of these materials as products.
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Phosphate Slag Concentrations (Table B.2-6) appear to be conservative because
a value near the upper end of measured concentrations for Ra-226 was used for
the exposure estimates. Average concentrations of U-238, Ra-226, U-235, and
Th-232 in phosphate slag are estimated to be 25, 35, 1.3, and 0.77 pCi/g,
respectively. The radon emanation from slag is expected to be very low because of
its vitrified matrix. Decay products of the above nuclides are also present in the
phosphogypsum and phosphate slag.
3.3 Phosphate Fertilizers and Potash
Processes for production of fertilizers that contain phosphoric acid and potash
are described in section B.3 of the NORM document. These processes and
consumption rates are reasonable descriptions -- there is obviously widespread
application of radioactive substances in these materials in U.S. agriculture. The
two major issues to be resolved are: 1) whether the distribution of uranium and
.g.^jp, *--•>>
ra*fflum in fertilizers leads to exposurtTpathways that represent significant
population impacts, and 2) whether current understanding of the sources of
fertilizer components is sufficient to determine the cost-effectiveness of procedures
that might reduce the potential radiological consequences to the population.
Radionuclide Concentration data in section B-3.4.1 of the NORM document are
not consistent with the data in Table B.2-4 for Florida phosphate rock, which is
the major source of fertilizer components and hence entrained radioactivity. It is
interesting that the process of making phosphoric acid eliminates 80% of the
Ra-226 and its decay products, only to have some of it reintroduced by mixing the
phosphoric acid with crushed phosphate rock to produce a bag of marketable
product. Nonetheless, the data in Table B.3-3 are based on measured values and
appear to be the most appropriate for use in exposure scenarios. The NORM
document emphasizes that most of the uranium goes with the product and most of
the Ra-226 goes to the waste, yet the concentration of Ra-226 is about equal to
that of U-238 in normal and triple superphosphate. (The concentrations of
uranium and radium in other forms of phosphate are closer to what would be
forecast from this statistic). Because normal and triple superphosphate are
pceduced in quantities that are smaller than that for phosphoric acid, the average
fertilizer (Table B.3-4) contains considerably more radioactivity from uranium than
from radium.
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3.4 Fossil Fuels - Coal Ash
3.4.1 Coal Ash Generation
The NORM document, on page B-4-1, states that there are over 1,300 coal-fired
boilers operated by electric utilities and nearly 60,000 industrial boilers in the
U.S., and that about 889 million MT of coal were consumed in 1989. Table B.4-1,
on page B-4-2, indicates that 889 million MT of coal were produced in 1989 and
that 800 million MT were consumed. The difference in the data presented on
pages B-4-1 and B-4-2 is only about 10%, but this difference in production vs.
consumption raises concern about the attention to details in the preparation of the
NORM document.
The NORM document states that coal production has increased by about 60%
from 1970 to 1989. The NORM document also states that the coal production
rate has been assumed to rise at 1.3% per year during the 1990s and at 2.8% per
year into the next century.
It is reported that in 1985 the representative ash content of coals used by
utilities ranged from 5.9% to 29.4%, with a national average of 10.5%. The
average ash content of coal burned has decreased from about 14% in 1975 to the
1985 value of about 10%. The NORM document quotes an EPA prediction that
the ash content will remain at about 10% until the end of the century.
The NORM document notes that the ash content of coal can be reduced by as
much as 50% to 70% by washing the coal. Washing the coal could also remove
some of the radioactive material, but the NORM document indicates that no data
could be located to support this contention.
An estimate presented of the relative fractions of the different types of ash
produced in modern furnaces that burn pulverized coal is: fly ash: 74%, bottom
ash: 20%, boiler slag: 6%. These values are based on 1984 data and it is stated
that the data are believed to be typical of the ash distribution for currently
operating furnaces and those that will operate for the next decade (EPA, 1988a;
EPA, 1988b). The NORM document did not provide an estimate of the percentage
of furnaces that use pulverized coal.
Citing data from the American Coal Ash Association , Inc. (ACAA), the NORM
document states that in 1990 the combustion of coal in utility and industrial
boilers generated 61.6 million MT of coal ash and slags and 17.2 million MT of
sludges. These were broken down into 45.6 million MT of fly ash, 12.3 million
MT of bottom ash, 3.7 million MT of boiler slag, and 17.2 million MT of sludges
(flue gas desulfurization sludges). The ACAA data show that the yearly ash
production rate almost tripled between 1966 and 1990.
The NORM document notes that, although the demand for electricity has
increased an overall average of 2.7% per year, over the "past 10 years" the annual
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production rate of ash has remained relatively stable, ranging from 57.9 to 65.2
million MT. The NORM document does not explain why the yearly ash
production rate has remained relatively stable.
The NORM document states that the yearly ash generation rate (including
bottom ash and boiler slags) is predicted to be 109 to 136 million MT by the turn
of the century (EPA, 1988b; EEI, 1988). The bases for this prediction are not
presented and, because the ash generation rate did not increase much during the
period 1980-1990, it is not clear why the rate would be expected to increase this
much by the turn of the century.
The production and utilization of ash varies by region throughout the United
States and Table B.4-4 presents data on the production and utilization by region.
Table B.4-5 presents a breakdown of ash and sludge utilization by type of
utilization. The table indicates that the utilization is a percentage of production,
but the data appear more likely to be a percentage of utilization rather than of
production.
In summary, data are presented for yearly ash production rates from 1966 to
1990 based on ACAA yearly data sheets. These data sheets have not been
reviewed by the RAG, but are assumed to be reliable. It appears that the annual
production rates from these data were used with the estimates of the relative
fractions of the different types of ash produced to estimate the annual quantities
of fly ash, bottom ash, and boiler slag. As previously stated, these estimates of
the relative fractions are based on 1984 data for "modern furnaces that burn
pulverized coal," and it is assumed in the NORM document that these data are
typical of the ash distribution for currently operating furnaces and those that will
operate for the next decade. The EPA report referenced for this assumption has
not been reviewed by the RAG. The NORM document quotes EPA and EEI
projections that the yearly ash generation rate will vary from 109 to 136 million
MT by the turn of the century (compared to 61.6 million MT in 1990). The bases
for these projections are not presented and it is not clear why the ash generation
rate would increase this much by the turn of the century when there was so little
increase between 1980 and 1990.
3.4.2 Radionuclide Concentrations
The NORM document notes that coal contains naturally occurring uranium and
thorium, as well as their radioactive decay products. It is also noted that the
radioactivity of coal varies over two orders of magnitude depending on the type of
coal and the region from which it is mined. On page B-4-20, it is stated that the
concentrations of U-238 and Th-232 in coal range from 0.08 to 14 pCi/g and 0.08
to 9 pCi/g, respectively (UNSCEAR, 1982). U-238 and Th-232 concentrations are
0.6 and 0.5 pCi/g, respectively, calculated as arithmetic means, and 0.34 and 0.26
pCi/g, respectively, calculated as geometric means (Beck et al., 1980; Beck and
Miller, 1989).
15
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On page B-4-21, the U-238 and Th-232 concentrations in coal ash are stated to
range from 1.5 to 8.6 pCi/g and 0.4 to 7.5 pCi/g, respectively (Beck et al., 1980;
Beck and Miller, 1989). The NORM document references a 1982 UNSCEAR
report for U-238 and Th-232 average concentrations in fly ash of 5.4 and 1.9
pCi/g, respectively (UNSCEAR, 1982). Thus, it is noted that the radioactivity of
fly ash is typically higher than that of coal and that the enrichment is dependent
upon the type of coal used, the ash content, and the type of boiler in which the
coal is used. It is also noted that the enrichment ratio is dependent upon the
radionuclide and that higher enrichment ratios have been observed for Ra-226,
Po-210, and Pb-210 than for U-238 and Th-232.
Page B-4-21 contains a statement that a limited review of the published
literature was conducted to identify commonly reported radionuclides and their
respective concentrations. It is not clear whether the radionuclide concentrations
used in this NORM document were based on the literature review or on
UNSCEAR (1982) alone. If the concentrations are based on data other than those
from UNSCEAR, the data are not presented and discussed.
On page B-4-21, it is stated that radionuclide distributions and concentrations
were grouped in two categories, fly ash and bottom ash, and it was assumed that
ash materials were comprised of 80% fly ash and 20% bottom ash, which includes
boiler slags. Then weighted average radionuclide concentrations in coal ash were
estimated (page B-4-22). The values given for U-238 and Th-232 are 3.3 pCi/g and
2.1 pCi/g, respectively. (This weighted concentration would not necessarily be
applicable to reuse scenarios since the use of coal ash is not necessarily in an
80:20 mix.) Values of the concentrations of the various radionuclides in fly ash
and in bottom ash that were used to compute the weighted concentrations are not
presented, and it is not clear how the values used were determined. Thus the
adequacy of the concentrations of radionuclides in coal ash used in this NORM
document cannot be evaluated.
William Russo of ORIA determined, for the RAC, that the values used for the
radionuclide concentrations were "engineering judgments," by the contractor,
based on the review of the literature noted. The values were not taken from
the UNSCEAR report cited, nor from any other single reference.
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3.5 Oil and Gas Production
3.5.1 Summary
A fundamental flaw of the source term analysis for this sector is that none of
the risks from NORM containing more than 2,000 pCi/g have been included
because they have been assigned to the "discrete" NARM (Naturally-Occurring and
Accelerator-Produced Material) category. This action has eliminated from
consideration in the source-term analysis a portion of NORM waste that may
represent the largest risks to exposed individuals. As a result of imposing this
arbitrary threshold of 2,000 pCi/g, which is based on a transportation standard (49
CFR 173.403) and not on risk assessment considerations, the risks from NORM
for this sector are not adequately characterized. The RAG recommends that either
these wastes be included in the risk analysis or else that the rationale for and
consequences of their omission from the analysis be explicitly stated.
«fesK«J * :
3.5.2 Waste Volume Characterization
From the data presented in the NORM document one can obtain the following:
Oil production dropped in the USA from 9.6 million barrels per day (mbd) to
8.2 mbd in the period from 1970-1977. It then increased up to 9.0 mbd by 1985,
and dropped again to 7.6 mbd by 1989. This was due to worldwide economic
fluctuations.
o o
Gas production declined steadily from 22 trillion ft to 17 trillion ft between
1970 and 1983. It was steady from 1983 to 1989 at 17-18 trillion ft3.
Oil and gas production are a regional activity in the USA. Eight states
(Alaska, California, Kansas, Louisiana, New Mexico, Oklahoma, Texas, and
Wyoming) accounted for 92% of all oil production and 70% of all producing wells
in 1989. The same eight states accounted for 92% of all natural gas production
and 48% of the wells in 1989.
*
Calculations of scale and sludge NORM volumes are based on a 'generic' oil
production facility incorporated into the NORM document from the 'Louisiana
Report' (Rogers & Associates, 1993). A full evaluation of the adequacy of the
calculations and underlying assumptions would require a thorough review of the
Louisiana Report. As a minimum, however, the RAG recommends that the Agency
revise the NORM document so as to emphasize that NORM source-term data in
the Louisiana Report may not be representative of oil and gas producing facilities
elsewhere in the U.S., and that the Agency evaluate the possible consequences for
the risk assessment.
An important assumption is that only 30% of all wells generate elevated NORM
levels. Although a reasonable assumption at face value, it should be noted that
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various references quoted have this value ranging from 0 to 90%, depending on
the region or age of the wells.
Based on the above, an annual production rate of NORM/scale waste of 25,000
MT/yr is calculated (p. B-5-16; also note that 17,900 MT would be located in the
aforementioned eight states). However, using a production rate of 6 x 10" MT of
scale per barrel produced, based on a survey of U.K. facilities (SC&A, Inc. 1988), a
NORM/scale annual production rate of 1,500 MT/yr is calculated. It is stated in
the NORM document that this lower value is more reasonable and expected. The
NORM document justifies the lower number for present-day scale production rates
because "newer facilities produce less entrained water in the crude oil," citing a
1992 report by Rogers & Associates (p. B-5-16) (Rogers & Associates, 1992).
Finally, the NORM document estimates total production of about 1,000,000 MT
of NORM/scale over the 40-yr period 1949-89. This calculation was based on the
2^00 MT/yr production rate, despifcr'tfhe statement that the lower value is
expected. For this calculation, the RAG assumed that the Agency considered the
lower value to be appropriate for estimating present-day and future rates of
NORM production, and not for historic rates. No uncertainty range is given. It is
difficult to evaluate the validity of that estimate, but the reader can calculate
reasonable upper and lower bounds of 20,700,000 MT to 60,000 MT of stockpiled
NORM/scale in the USA between 1949-89.
The same 'generic' facility and assumptions were used to model NORM/sludge
volumes. An annual rate of production of 225,000 MT/yr of NORM/sludge was
calculated (=160,000 MT/yr in the eight states mentioned).
/?
For calculation of a reasonable upper bound for NORM scale waste (refer to
Appendix A - Diffuse NORM Wastes: Waste Characterization and Preliminary Risk
Assessment by Dehmel, J-C, and V. Rogers, May 1993, pg. B-5-16). Assume 115 billion
barrels produced in the USA from 1949-1989; 6xlO"4 MT scale/barrel produced; 30%
of scale contains NORM. •»
The Reasonable Upper Bound (UB) is then the product of the above numbers as
follows:
UB = (l.lSxlO11 barrels produced) x (6xlO'4 MT scale/barrel produced) x (0.30% of
scale containing NORM)
= 20.7 million MT NORM containing scale produced in the USA between 1949 and
1989
The reasonable Lower Bound (LB) is calculated as follows:
LB = (40 years) x (1,500 MT NORM scale/year)
= 60,000 MT NORM containing scale produced in the USA between 1949 and 1989
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The NORM document estimates that =10,000,000 MT of NORM/sludge have
accumulated in the USA in the 1949-89 period. No uncertainty data were shown
for this calculation.
In summary, a total annual production of =250,000 MT/yr of NORM in the
form of sludge and scale in oil production is calculated in the NORM document,
with a total stockpile of =11,000,000 MT of NORM for the period of 1949-89. No
data were presented that addressed uncertainty issues.
3.5.3 Radionuclide Concentrations
According to the NORM document, radium is the main concern in NORM
wastes from this sector, and Ra-226 and Ra-228 and their progenies are the main
sources of risk. A 3:1 ratio of Ra-226:Ra-228 is assumed (p. B-5-9, citing Rogers &
Associates, 1988) without further justification. The assumption of secular
equilibrium with respect to Ra-226 and its decay prodiaefcs* seems reasonable*1^
radon does not diffuse quickly out of the scale or sludge. However, the RAG was
confused by the discussion in the NORM document about the 3:1 ratio because Ra-
226 is a daughter product of U-238 decay, while Ra-228 is a daughter product of
Th-232 decay. One would not expect these two nuclides to vary systematically;
the discussion of this issue on p. B-6-3 is much more reasonable.
An average concentration of 480 pCi/g for radium in scale is quoted from the
Louisiana Report (Rogers & Associates, 1993); and, using the 3:1 ratio, 360 pCi/g
and 120 pCi/g concentrations are assigned to Ra-226 and Ra-228 (and their
progenies), respectively. The validity of these concentrations cannot be fully
evaluated without a thorough review of the Louisiana Report. It is important to
note that these concentrations were not measured. Rather, the exposure rate was
measured and was then transformed to pCi of radium using a 'standard formula'.
The data were then log-transformed, and the distribution of values was 'censored'
for those below the detection limit. Finally, applying linear least squares line
fitting procedures to the various censored data sets (which in some cases only
included two points), a log-normal distribution was constructed. The
concentrations used in the NORM document being re\aewed are the medians of
that distribution. A range of uncertainty of 10 pCi/g to 100,000 pCi/g can be
gleaned from the NORM document based on various references quoted.
For sludge the same assumptions and arguments apply, except that the average
concentration for radium in sludge is given as 75 pCi/g, and for Ra-226 and
Ra-228 (and their progenies) values of 56 pCi/g and 19 pCi/g are derived as
described in the previous paragraph. A range of uncertainty of 1 pCi/g to 1,000
pCi/g can also be obtained as a reasonable approximation based on references
quoted.
Radon emanation coefficients of 0.05 for scale and 0.22 for sludge are assumed
due to lack of knowledge regarding the true but unknown value.
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External exposure rates of 30-70 nR/hr are assumed, but can range from
background to several mR/hr (API, 1989).
3.5.4 Other Issues
Although the RAG agrees with some of the conclusions drawn in the NORM
document (E-2-1 through E-2-4), it finds that the one-page qualitative uncertainty
analysis shown (E-2-7 to E-2-8) is inadequate, and disagrees with the description
of this source term as well-characterized (a ranking of '2')-
3.6 Water Treatment Sludges
3.6.1 Waste Volume Characterization
The NORM document does not address any of the risks associated with
selective-sorbent technologies, such as ion exchange resins, or with spent Granular
Activated Carbon (GAC). These omissions result in an incomplete and inaccurate
source term characterization.
The NORM document states throughout this section that only 700 facilities are
expected to have significant problems with NORM/sludge production (out of 60,000
utilities in the USA). These data are relatively old and should be updated with
more recent EPA reports. The numbers presented deal only with radium, because
no projections exist for the impact of the proposed radon and uranium standards.
Furthermore, waste generation and disposal practices related to the use of
selective sorbent technologies such as radium-selective complexers are not
addressed in the NORM document, because it is assumed that their radioactivity
will be sufficiently high as to require disposal as low-level radioactive waste (p. B-
6-10). Consequently, a major portion of NORM risks (i.e., NORM waste that may
represent higher risks to exposed individuals) from water treatment is absent from
the exposure estimates. In addition, no attempt has been made to characterize the
historical production of NORM by water treatment facilities, which would have
been a daunting endeavor given the lack of reliable information.
Based on two surveys by the American Water Works Association (AWWA, 1986,
1987), and the assumption that only 700 systems have waters with high NORM
levels, an annual production rate of 260,000 MT/yr is calculated. Underlying
assumptions for this value are that the annual generation of sludge per water
utility is 2,140 MT, that only 28% of water treatment processes have the capability
to remove radionuclides (and hence have the potential to create NORM-
contaminated sludge), that 700 water utilities in the U.S. process water with
elevated radionuclide concentrations, and that only 60% of these 700 utilities
actually produce sludge (p. B-6-17 to -18). No discussion of uncertainties or
variabilities is presented. No attempt is made to tie this analysis to the
Radionuclides in Drinking Water Criteria Documents (See Appendix A - EPA/SAB
Letter Report EPA-SAB-RAC-LTR-92-018, September 30, 1992 and references cited
therein, including the 1991 Proposed Rules for Drinking Water).
20
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The best evaluation of the validity of this analysis comes from the NORM
document itself (p. B-6-18):
"It is also not clear from past survey data what number of utilities have
passed the EPA Drinking Water Standards for finished water, but may still
generate water treatment sludges at concentrations that are of concern in
the context of this assessment. Although in those cases the radionuclide
concentrations may be relatively low, the wastes may be generated in much
larger quantities."
It is the opinion of the RAG that the analysis underestimates present and
future volumes of NORM/sludge wastes from this sector.
3.6.2 Radionuclide Concentrations
* Radionuclides of concern are radium, uranium, radon, and their progeny.
Almost all calculations are for radium. Ra-226 concentrations are said to vary
from 0.5 pCi/L to 25 pCi/L. The NORM document estimates that for every pCi/L
in water, 2 pCi/g would be found in sludge. The critical assumptions are a 90%
removal efficiency (which is reasonable based on the available technologies), and a
sludge generation rate of 3.1 m per million gallons (or 0.82 cm /L) of treated
water (Hahn, 1988).
Table B.6-7 of the NORM document presents a set of concentrations that are
to be used for the risk assessment model waste pile. These are based on the
upper value of the radium concentration range. Pb-210 and Po-210 are calculated
assuming a radon emanation coefficient of 0.30. Uranium and thorium
concentrations are assumed without further justification. Because no justification
is provided for most of the parameter values, the RAG cannot evaluate the validity
of the concentrations chosen except for radium. The radium concentrations are
high, but may be representative of utilities treating waters with elevated NORM
levels. No analysis is given of the uncertainty inherent in the calculated values.
Such an analysis should address the likelihood that these values vary from
location to location.
Radon fluxes were assumed to be similar to those of typical soils due to lack of
information.
External exposure rates of 86 ^R/hr were calculated based on the
concentrations from Table B.6-7. Given that no data were presented, the validity
of this value is questionable.
3.6.3 Other Issues
The RAG finds that the one-page qualitative uncertainty analysis shown (E-2-7
to E-2-8) is inadequate, and disagrees with the description of this source term as
well-characterized (a ranking of '2')-
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3.7 Metal Mining and Processing Wastes
3.7.1 Rare Earths
The NORM document states (p. B-7-24) that in 1985 the U.S. produced about
20,800 MT of crude rare-earth concentrates and that these crude concentrates
typically consist of titanium and zirconium minerals and 1 to 20% monazite. It is
further stated that the rare-earth oxide content is about 55% in monazite, which
also contains about 6% ThOo and 0.4% U3Og (Hedrick and Templeton, 1985). The
NORM document contains the assumption that the rare-earth waste production
rate is about equal to the annual crude concentrate consumption rate of 20,800
MT and that this waste contains 20% monazite. No reference or basis is given for
this assumption. The activities in the waste are given as 3,900 pCi/g for thorium
and 18,000 pCi/g for uranium.
On page B- 7-38, it is stated that rare*earth elements are recovered primarily
from mineral types such as bastnasite, monazite, and xenotime. Monazite ores are
stated to contain the highest concentrations of thorium and uranium, which range
from 3-10% ThO2 and 0.1-0.5% UoOo equivalent. It is stated that, assuming
monazite ores average about 4% ThO2, the activity from ThO2 in U.S. rare earths
is about 3,900 pCi/g. The activity from natural uranium in the same ore type at
0.3% U3Og is given as about 1,800 pCi/g. Pages B-7-24 and B-7-25 present
relative activities of 3,900 pCi/g for thorium and 18,000 pCi/g for uranium,
apparently corresponding to 6% ThO2 and 0.4% UgOo. Thus the same activity is
given for two somewhat different percentages of thorium, and the difference in the
activity stated for uranium is an order of magnitude, which may be a
typographical error.
On page B-7-53, for the generic rare earth site, the assumption is stated that
the ores are "composed of 50% monazite sands". No reference or basis for this
assumption is presented. For this generic site, the source term is based on a
Th-232 activity of 2,000 pCi/g and a U-238 activity of 900 pCi/g.
In summary, the NORM document, o» page B-7-24, refers to a 1-20% range of
monazite in rare-earth concentrates and states an assumption of 20% monazite in
rare-earth waste. On page B-7-52, there is a statement that the ores are assumed
to be composed of 50% monazite sands for the generic site. A single reference is
presented for the 1-20% range and no basis is presented for the 20% and 50%
assumptions. Thus, it is not clear what the appropriate fraction of monazite
should be. In addition, there are inconsistencies in the activities of the U-238 and
Th-232 reported.7
William Russo of ORIA determined, for the RAG, that the compositions of
ThO2 and U3Og used in the analyses were 4% and 0.3%, respectively. He
also determined that the concentration of 18,000 pCi/g stated for uranium
was a typographical error and that the value of 1,800 pCi/g is high by a
22
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3.7.2 Zirconium, Hafnium, Titanium, and Tin
Zirconium, hafnium, titanium, and tin are grouped together for consideration in
the NORM document. The estimated annual waste generated from production of
these metals is given as 50,000 MT for zirconium and hafnium, 4,000 MT for tin,
and 414,000 MT for titanium (p. B-7-26; Hedrick and Templeton, 1989; EPA,
1990).
The source term used to assess risk from a generic zirconium, hafnium,
titanium, and tin waste site is given in Tables B.7-21 and B.7-22 of the NORM
document. (Table B.7-21 is mislabeled; the term "rare earth" in the table title
should be replaced by "Zr, Hf, Ti and Sn.") It is stated that the generic source
term is representative of radionuclide concentrations for titanium and tin waste.
The NORM document states that the source term is based on a conservative
Ra-226 activity of 43 pCi/g, based on tin slag (Conference of Radiation Control
Program Directors, 1981) and also typical of measurements in chloride process
waste, solids, and leachate for titanium tetrachloride production (EPA, 1990).
Pb-210 and Po-210 concentrations were estimated by assuming a radon emanation
coefficient of 0.3.
The reports by the Conference of Radiation Control Program Directors (1981)
and by the EPA (1990) have not been reviewed by the RAC, making it difficult to
comment on the adequacy of the radionuclide source terms used to assess risk
from these wastes. Data presented on pages B-7-40 through B-7-42 show that
elevated NORM concentrations are associated with zirconium, titanium, and tin
mining and processing and that, in some cases, the concentrations exceed 1,000
pCi/g.
3.7.3 Large Waste Volume Processes
For the risk assessment, a generic site is assumed for aluminum, copper, iron,
zinc, lead, and precious metal mining and processing waste. Table B.7-10 presents
estimated amounts of waste generated by the extraction and beneficiation of these
metal ores in 1980. The amounts vary from 280 million MT for copper and 200
million MT for iron to 1 million MT for lead and zinc.
The NORM document presents limited data on radionuclide concentrations in
waste from aluminum mining and processing that show these wastes can contain
elevated levels of U-238 and Th-232. The NORM document also notes that several
studies have reported uranium and thorium concentrations in various copper
mining and processing materials. The NORM document notes (page B-7-50) that
factor of 2. The statement on page B-7-52 that the ores are assumed to be
composed of 50% monazite sands for the generic site was determined to mean
that it was assumed that there was a 50% dilution of the ore with sand and
other materials.
23
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"it is difficult to characterize the radiological properties of overburden and tailings
associated with the mining and processing of copper ores" and recommends "a
more detailed survey of wastes and tailings, especially from the copper mines and
mills of Arizona and New Mexico". The NORM document states that it is
conservatively assumed that the large waste volume metal mining and processing
waste industry exhibit waste sites with radionuclide concentrations equal to the
screening criteria values used in the EPA Report to Congress on Special Wastes
from Mineral Processing (EPA, 1990) of 10 pCi/g for U-238 and Th-232 and 5
pCi/g for Ra-226 (p. B-7-62). The use of source terms corresponding to screening
levels appears indicative of the uncertainty in the characterization of the
radionuclide concentrations.
3.8 Geothennal Energy Waste
The NORM document notes that there is a lack of data on which to base
estimates of overall waste generation from geotherm^iehergy sources. The 50%
escalation factor for going from an estimate of 20,000 m for liquid dominated
wastes to 30,000 m for the whole sector is rather arbitrary (p. B-8-15). The
Sonoma vapor generation stations are the largest in this NORM sector and thus a
better attempt should be made to characterize its waste generation. The station
operators are likely to have some record of solid waste generation that would
enable a more justifiable estimate to be made.
It is understandable that these radionuclide concentrations have been used to
make risk estimates in the absence of adequate data. However, a theoretical
analysis of the geological and solubility factors at the Sonoma sites relative to the
Imperial Valley sites might enable a more refined estimate to be made.
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4. MODEL PARAMETERS
Issue 2: Model parameters
Are parameters used in the risk assessment reasonable? Are the references and
justifications adequate? Does the presentation properly reflect the best available
scientific information?
In most cases, the references and justifications for the parameters used in the
risk assessment have not been provided in the reviewed NORM document, making
it difficult to determine whether or not the adopted values are reasonable. To a
limited extent, as discussed below and in Appendices B and C, the RAG was able
to compare the adopted values to the range of values published in the literature in
order to judge the extent to which the adopted values are reasonable or
conservative estimates. Some of the adopted parameter values appear to fall
outside the range of measured values, in the direction of non-conservatism (e.g.,
food uptake factors; see discussion in section 4.2 below). In addition, the dose and
risk conversion factors in the NORM document differ substantially from those
currently endorsed by ICRP and NCRP (section 4.3 below). The reasons for these
discrepancies should be discussed.
4.1 Documentation of Parameter Selection Process
Supporting rationale for the selection of "representative" parameter values is
often found only in other documents. For example, the selection process used to
adopt representative values for hydrologic parameters (Tables D.2-1 and -3 of the
NORM document) is not found elsewhere in the document, but rather in a series
of handwritten letter reports prepared by R.F. Weston, Inc., for Rogers &
Associates (Madonia, 1989a, 1989b, 1989c, 1989d). Some of these letter reports
were examined in a cursory manner by the RAG, which found the quality of data
to be quite variable and the explicit justification for representative values to be
generally inadequate. For example, no data source or discussion could be found
for any of the distribution coefficients (KA which govern the rate of leaching of
the radionuclides from the source material, and its subsequent transport through
the subsurface. The RAG recommends that the original data sources and
justifications for the selection of representative values for all parameters be
incorporated into the NORM document (or in an appendix thereto).
Documentation of the meaning of parameter values is sometimes mystifying.
For example, two terms that need explanation are the "humid impermeable default
values" and the "humid impermeable value" that serve as the basis for the water
uptake factors and the river flow rate qr> Similarly, the appendix containing the
spreadsheet calculations is welcomed, but the parameters in these tables often
differ from those defined in the main body of the NORM document. Presumably,
some values are lumped together to form new parameters. Consequently, one
cannot easily double check or reconstruct model results from these appendix
25
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tables. The RAC recommends that a complete list of terms be added to the
appendix that would clearly define each parameter used, and that would cite the
mathematical expression used to derive any lumped parameters.
4.2 Parameter Selection for Specific Pathways
Even with recourse to the original references (see above), it is difficult to
assess the underlying rationale and validity of many of the adopted parameter
values, although in some cases it is possible to compare the values to those in the
literature. A related problem is inadequate definition of what is included in a
particular parameter. For example, it is difficult to review the food chain pathway
calculations in the draft NORM document because the entire food chain is
subsumed into an aggregated parameter called the food uptake factor, U™, in units
of kg/yr. Comparison with values derived from other references (Appendix Table
C-J.) shows that the UF values used in the document are not necessarily
conservative (Appendix Table C-2), because they are exceeded substantially by
values derived from the other three references. The most glaring discrepancies are
observed for the ingestion of vegetables by humans for Pb, Po, and Ra.
The NORM document not only fails to justify the selection of default values for
most parameters, but also fails to provide any explanation when adopted
parameter values vary substantially from one type of NORM source to another.
For example, selected values for saturated hydraulic conductivity (K t) and for
distribution or sorption coefficients (Kd) range over several orders 01 magnitude
among the various NORM sources for the hydrologic pathways. This aspect of the
assessment is sufficiently critical that documentation within the text or an
appendix is warranted.
Additional questions and comments on some of the parameter values included
in other pathway scenarios are presented in Appendix D.
4.3 Dose Conversion Factors
Discrepancies appear in comparisons between the dose and risk conversion
factors used in the draft NORM document and those in ICRP Publication 60
(ICRP, 1991) and in revisions to ICRP Publication 56 (ICRP, 1989; ICRP, in
press). Appendix Tables C-3 and C-4 compare the risk conversion factors for
ingestion and inhalation between values listed in Table D.2-4 of the NORM
document and those obtained from ICRP 60 (Phipps et al., 1991). Appendix Table
C-5 shows the same comparison for a few selected radionuclides that are
considered in a recent revision to ICRP Publication 56 (ICRP, in press).
26
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The apparent reason for the above discrepancy is EPA's own analysis of the
risk of radiogenic bone cancer in which Puskin et al. (1992) have asserted that
ICRP 60 (ICRP, 1991) confused the average skeletal dose with that of the bone
surface. The result is a bias in ICRP 60 towards overestimation of the effective
dose by about a factor of 4 to 5 for radionuclides that deposit primarily on the
bone surface. This bias has been acknowledged by Bair and Sinclair (1992) to
have existed for at least 15 years. Appendix Tables C-3 through C-5, however,
show discrepancies for Th-230, Th-232, Th-228, Ra-228, and Po-210 that greatly
exceed a factor of 5, with the EPA's values being substantially lower than the
values derived using the ICRP revisions to its Publication No. 56 (ICRP, 1989;
ICRP, in press). The reasons for these large discrepancies should be investigated
and discussed by EPA. If EPA has risk coefficients that are more defensible than
those recommended by NCRP and ICRP, every effort should be made to ensure
wide dissemination of the rationale for EPA's estimates.
4.4 Substantial Bias in Risk Estimates
The combined effect of revisions to the dose factors in ICRP Publication 56
(ICRP, 1989; ICRP, in press) and the use of the "detriment" risk conversion factor
of 0.073 per Sv as recommended by ICRP 60 (ICRP, 1991) and NCRP Publication
116 (NCRP, 1993) results in substantial discrepancies with respect to the factors
listed in Table D.2-4 of the draft NORM document in the estimate of health risk
per unit intake of a radionuclide (Appendix Table C-5). The sources of the
discrepancy should be discussed in the NORM document, particularly because the
direction of bias is in many cases towards underestimation when the risk estimates
are combined with values assumed for Up. The RAC also notes that the EPA risk
values refer only to cancer fatality, while the ICRP values include weighted values
for morbidity and severe hereditary disorders.
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5. SCENARIOS
Issue 3: Scenarios
Does the preliminary risk assessment adequately identify and characterize the
key scenarios needed for evaluating individual and population risks from the
sources characterized?
5.1 Identification of Pathways
In general, the list of pathways is reasonably comprehensive and may even
include some pathways that are very unlikely to contribute substantially to total
risk. However, it does not include at least one pathway that is commonly assessed
in EPA programs covering hazardous wastes (Superfund and RCRA): soil ingestion
by humans and by grazing animals. EPA risk assessments commonly assume that
residentially exposed persons ingest 100 mg/aay soil as adults and 200 mg/day as
young children. Radionuclide concentrations in the ingested soil would probably
be the same as used for dust lofting or leaching by infiltration of rainfall. For
secondary deposition of wind-blown dust, the hazardous waste programs assume
mixing into the top 1 cm of soil for soil ingestion purposes, because not all soil is
tilled. The RAG recommends that the list of pathways to be considered include, to
the extent appropriate, those pathways used in other programs of the EPA (e.g.,
Superfund).
For radon and radon progeny, two pathways not assessed include dermal
absorption and volatilization of radon from potable water. However, exclusion of
these pathways from the risk assessment appears warranted. Dermal absorption
from soil or water is probably insignificant, because inorganic substances typically
are not easily absorbed through the skin. Radon doses associated with
volatilization are also likely to be negligible relative to those from all radionuclides
via ingestion.
5.2 Identification of Receptors
The list of receptors is reasonable. Many hazardous waste assessments would
not include an on-site worker scenario, arguing that such would be included under
OSHA provisions. In that case, the workers would be monitored for exposure (at
least for the gamma component), and exposures would be limited to 5 rem/yr.
Both the on-site resident and the nearest off-site resident downwind (which the
NORM document calls the Critical Population Group (CPG)) might easily be
included in a hazardous waste assessment, depending upon the plausibility of
releasing the waste site for unlimited use.
Scenarios for dose calculations always contain speculative elements. However,
the rationale for using a particular assumption or for selecting a particular
parameter value should be explicitly explained so far as possible. For instance, the
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assumption that a house will be 100 meters from the boundary of a disposal site
(p. B-l-20) appears to be quite arbitrary.
EPA hazardous waste assessments typically would not examine anything akin
to the general population scenario. However, this focus on a more widespread
population risk appears quite appropriate as a basis for establishing general
priorities and public policies, and is a consideration in the air programs of EPA
and the State of California.
5.3 Matrix of Pathways vs. Receptors
The matrix of pathways vs. receptors is reasonably complete. EPA hazardous
waste programs might well argue that the full list of pathways assessed for the
CPG should also be assessed for the on-site resident, but simply adding the risk
from these pathways for the CPG to the risks of direct exposure for the on-site
Tesidents is sufficient to indicate tHStthe indirect pathways are generally
negligible sources of risk for the on-site resident.
5.4 Source Term vs. Scenario
The RAC has identified some issues that overlap questions 1 (on sources) and 3
(on scenarios and pathways). While many of the pathways and scenarios are
common to most of the NORM waste source types, the application of a scenario or
its parameters to a specific source type is sometimes in question.
The assumptions for exposures of individuals and populations due to
phosphogypsum disposal are reasonable because the number, design, and location
of stacks are well known and they do not appear destined for relocation. The
reuse of phosphogypsum, especially in fertilizers, is more uncertain.
Most of the exposure scenario data for phosphate slag were taken from the
EPA studies of southeastern Idaho (EPA, 1990). The RAC believes that these
data do not provide an adequate basis for remedial action decisions where slag has
teen used, because of concerns raised by the RAC in its review of the Idaho
Radionuclide Study (EPA/SAB, 1992). This review identified concerns about the
method used to estimate doses to the average individual and to the maximally
exposed individual (reported in Table B.2-7 of the NORM document). However,
the approximate and average nature of these data may be adequate for providing a
broad overview of the NORM content of slag which could provide a basis for
considering whether or not future uses of slag should be controlled.
The reuse scenario for phosphate slag in highway and street paving appears
reasonable; however, an analysis is not given for its use in building materials and
as fill material in a way that would allow population impacts to be broadly
determined. The data provided are based on EPA's Idaho Radionuclide Study
report. Until the Agency addresses the RAC's concerns on calculated exposures
for average and maximally exposed individuals, the RAC would doubt the accuracy
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of projected impacts of slag uses in building and fill materials. Reuse of slag as a
fill material around buildings or in construction material for buildings is an
important potential exposure pathway because of long exposure times for
homemakers and children; the NORM document should analyze the risks
associated with such a reuse scenario.
In the fertilizer application scenario, concentrations of K-40 in soil would
increase due to applications of potash containing an average of 420 pCi per gram
of potash (which contains 696 pCi/g-KoO). Because K-40 is very soluble, it is
leached from the soil. From the data in the NORM document, about 2/3 of that
applied to soil is leached away. This pathway does not appear to be analyzed; it
should be addressed. The soil concentrations of K-40 are calculated on the basis
of a leach rate assuming 20 years of application to a typical Illinois field using
equation B-l (p. B-3-15). It would appear more realistic to base the calculations
on a saturation condition in which the K-40 application rate and the K-40 leach
rate are in equilibrium with one another, a condition that would be achieved
(99+%) in 30 years. The calculated soil buildup by equation B-l is highly
dependent on the leach rate fraction that is calculated from equation D-13. The
calculations of soil buildup by equation D-13 depend on an equilibrium distribution
coefficient. Values for these are listed in Table B.3-6 for the radionuclides
considered, and they appear reasonable, although they are all derived from the
same reference.
Table B.3-6 also contains risk assessment parameters reflective of the
discussions in Section B.3.2 of the NORM document and other assumptions for
radon emanation and respirable fraction of resuspended NORM. The latter
fraction appears high, but conservative.
The underlying basis for the radiation exposure rate determinations appears
weak. Whereas it is true that increases in the exposure rate would be
proportional to the added concentration of gamma emitters, the actual exposure
rate due to the application of fertilizer containing NORM is not really determined,
only asserted to be only about 0.25% of that from soil that has not received
fertilizer containing NORM (NORM document, p. E-3-12). The RAC recommends
that the Agency support this contention by referencing actual measurements
collected during aerial surveys of gamma radiation.
The exposure rate due to leached materials is not provided, as pointed out
earlier for K-40.
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6. MODEL FORMULATION
Issue 4: Model formulations
Does the PATHRAE methodology presented in this document adequately
quantify risks from the sources and scenarios characterized?
6.1 General Overview
Following a cursory overview, all of the models and their submodels appear to
be reasonable formulations for developing preliminary scoping estimates of doses
and risks, with inclusion of an appropriate choice of generic site parameters
(although not necessarily of parameter values; see discussion of issue 2 in Section
4 of this report). Underlying assumptions for the models are for the most part
clearly stated. Detailed documentation for the modefe'ls apparently to be found in
other EPA documents which presumably describe the mathematical basis of the
models.
6.2 Radon Transport Model
Five exposure pathways or scenarios for radon and radon progeny are analyzed
in the NORM document:
1. worker exposure to indoor radon, under the assumption that there is an office
on the NORM storage/disposal site. The exposure time is assumed to be 2,000
hours per year. A 75% "occupancy factor" is incorporated in the risk factor
used (p. D-l-10).
2. individual exposure to indoor radon in a house built on a NORM storage/
disposal site. The exposure time is assumed to be all year, with a 75%
occupancy factor.
3. member of the critical population group (CPG) (defined as living 100 m
downwind of the edge of the NORM storage/disposal site), exposed to indoor
radon, again with a 75% occupancy factor. In this case, the indoor radon
pathway is from the outdoor air.
4. same individual, but exposed to indoor radon produced by NORM in building
materials used in the house. This scenario is restricted to the use of coal ash
in making concrete blocks for basement walls or in the concrete used for the
floor slab.
5. general population (defined as living in the area within 50 miles of the NORM
storage/disposal site) exposed to radon in an unspecified location (presumably
the relevant exposure condition is to ambient air concentrations, although the
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risk factor used in the equation still contains the correction for a 75% indoor
occupancy factor).
A number of issues are raised by the analysis of these exposure pathways,
probably the most significant of which is the use of only diffusive transport of
radon in scenarios 1 and 2. The dominant transport process for houses with
elevated indoor radon concentrations is the advective flow of radon-bearing soil gas
into the house. Diffusion alone cannot account for elevated indoor levels, with the
possible exception of some of the extreme radium concentrations assumed in the
NORM source term scenarios (e.g., rare earth wastes with assumed radium
concentrations of 900 pCi/g). If advective flow were also incorporated in this
analysis, potential radon exposures would be significantly higher, or conversely,
the radium concentration in the waste materials needed to produce indoor radon
concentrations of concern would be substantially lower.
Analysis of an advective transport pathway requires knowledge about the
characteristics of the soil or waste pile medium, particularly the air permeability
(or the parameters that affect it, such as soil moisture). The PATHRAE code is
not equipped to estimate advective transport, although there are several codes now
available to perform such analyses. One such code, RAETRAD (Nielsen et al.,
1992), is reasonably adaptable and is currently being used by the EPA to make
estimates of radon transport as part of the waste criteria effort also being
conducted by ORIA and is also being used by the State of Florida as part of a
radon "potential" mapping project. Because radon exposures are potentially among
the most important risks attributable to NORM wastes , a more realistic
assessment approach is needed than is provided by a simple diffusion model.
Although less important overall, the present NORM document does not assess
the exposures to outdoor radon for the individuals in scenarios 1 and 2.
Presumably the outdoor radon concentrations on-site are much higher than those
off-site, even though the latter concentrations are the basis for the assessment of
scenarios 3 and 5. For the sake of consistency and comparison, these exposure
pathways should also be analyzed as part of scenarios 1 and 2.
The release of radon into the outdoor air from a NORM waste pile is largely
based on diffusive transport through the soil cover, although the equations used
for scenarios 3 and 5 appear to be based on the assumption that the NORM waste
materials are exposed (uncovered). However, the reference disposal pile
parameters shown in Table D.2.1 (p. D-2-2) list a cover thickness assumed for
some of the NORM waste categories. The estimated radon release rates do not
appear to take these cover materials into account.
In a memo to Bill Russo, Vernon Rogers (one of the authors of the NORM
document) argued that the diffusive transport assumptions were sufficiently
conservative to cover the contribution of advective flow (Rogers, 1993), but
the RAC was unable to evaluate the validity of that assertion.
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6.3 Other Individual Models
Comments on individual models are provided in Appendix D to this review.
6.4 Choice of Software
The RAG notes that the PATHRAE spreadsheet method for estimating NORM
risks is derived from the PATHRAE code in the PRESTO family that was
originally developed to deal with risks from the disposal of low-level waste in
unregulated sanitary landfills . As a readily available tool, it has been attractive
to EPA contractors. Since that original development, the PRESTO code has been
modified in many ways to deal with a variety of issues not originally considered in
its design. As a readily available tool, it has been attractive to EPA contractors
because of precedent and economy. However, it does not contain some of the
more recently recognized pathways of exposure (e.g., advective flow of radon) and
it aggregates some parameters (e.g., fo
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7. UNCERTAINTY ANALYSIS
Issue 5: Uncertainty analysis
Risk estimates calculated using the PATHRAE methodology are estimated to be
within a factor of three of calculations made with more detailed codes. Given
this error band, the methodology employed, and the lack of knowledge
associated with the waste streams; is the Agency's characterization of
uncertainty and sensitivity adequate for the purposes of this scoping study?
The adequacy of an uncertainty analysis in a risk assessment and
characterization study depends on the use to which the results and conclusions of
the study will be put. In its description of the purposes of the NORM document,
EPA variously describes the study as for scoping or as a basis for deciding on the
need for regulation. The RAG views/'scoping" as essentially synonymous with
' ""Screening," in the sense of separaTu^g sources of NORM on the basis of their
priority for further study and possible regulation. The screen can be either
conservative (i.e., is intended not to underestimate risk), which screens out low-
priority areas from the need for further study, or nonconservative (i.e., is intended
not to overestimate risk), which allows the identification of areas definitely in need
of study and probably of regulatory attention. Unless uncertainties are relatively
small, a conservative screen cannot reliably identify high priority sources, and a
nonconservative screen cannot reliably identify low priority sources. Note that the
degree of conservatism should be kept as small as feasible to avoid a useless
screen; all that is required is to be able to assert with some confidence that the
results are, on balance, conservative or nonconservative.
Because the document is neither consistently conservative nor consistently
nonconservative, however, the Agency's characterization of uncertainty and
sensitivity may not be adequate, even for the purposes of this scoping study.
Concentrations of radionuclides in NORM materials are typically estimated with
conservative assumptions, but the same may not be true for the source volumes,
and many of the pathway and risk assumptions are probably nonconservative.
* The apparent degree of conservatism or non-conservatism in key parameters for
the NORM assessment are shown in Table 7-1 on the following page. Table 7-1
was developed by the RAC to illustrate the points raised in this text. The
document's qualitative uncertainty analysis, while informative about the
professional judgments made by the authors, does not permit the reader to
conclude that one source is definitely of greater concern than another, that some
sources can be dismissed as posing negligible risks, or that some sources clearly
need further attention.
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Table 7-1 Direction of Conservatism in NORM Assessment Parameters
Parameters
Source volume
Concentration
Transport and fate
Receptor definition
Food uptake factors
Other exposure factors
Dose/risk conversion
factors
Overall risk estimates
Conservative
Bias Likely
X
X
Direction of
Bias Uncertain
X
X
_~ ,n
X
X
X
Non-
Conservative
Bias Likely
X (radon)
••«3f
The NORM document claims overall accuracy to within a factor of three, but
does not demonstrate that claim with calculations. For the source volume and
concentration terms, the uncertainties are sometimes several orders of magnitude.
For some pathways, it is clear from the RAC's review that uncertainties in the
dose and risk estimates may be as much as one or two orders of magnitude, given
the uncertainties in the estimated average parameter values and the simplistic
models and assumptions. These pathways (e.g., consumption of vegetables grown
in soil upon which contaminated dust has settled) are often relatively minor
contributors to overall risk, such that uncertainties associated with these doses are
somewhat less important than those for major patKways (e.g., direct gamma
radiation and radon) where uncertainties should generally be less. Thus, the
Agency's claim may be valid, but the RAG recommends further documentation of
its assessment of uncertainty.
The Agency's characterization of uncertainty and sensitivity consisted of two
parts: benchmarking the risk estimates against PRESTO and providing a
qualitative ranking of uncertainties associated with parameter estimates for each
scenario (Table E.2-1). Benchmarking the risk estimates against PRESTO begs
the question of the validity of PRESTO and the parameters used for the NORM
assessment.
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Another concern is that estimates of risks averaged over all sites for a given
source type may not be useful; if conducted on a site by site basis, then it may
well be that a significant proportion of sites have risks that are well above the
threshold of acceptable risk. Similarly, the aggregate risk calculated if one were to
simulate the releases as time-dependent pulses (typical of arid regions) may not be
the same as when calculated with steady annual rates, as in the NORM document.
Consequently, the Agency might consider undertaking a preliminary uncertainty
analysis to estimate the expected distribution of risks for each source and pathway
for which the screening analysis suggests that the risks may possibly be
significant. If requested, the RAG would be willing to provide additional
suggestions to the Agency as to how such an analysis could be done.
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8. PRIORITIES FOR ADDITIONAL WORK
Issue 6: Priorities for additional work
In what areas does the SAB's RAC recommend the greatest priority be given for
developing additional information?
The RAC believes that the issue of NORM deserves substantial attention
within EPA, and is concerned that the issue may not be resolved in a timely
manner without increased resources being devoted to it. Despite its shortcomings,
the NORM document nonetheless provides clear indications that some categories
of NORM may produce risks that exceed those of concern from other sources of
radiation. The RAC recommends that greatest priority be given to two aspects:
(a) First priority should be given to revising the NORM document to address
the more demanding of the RAC's comments: the inclusion of more recent
information on source volumes and concentrations, disaggregation and
updating of food uptake factors and dose/risk conversion factors,
documentation and justification of parameter selection, and consideration
of advective flow as a means for radon transport. The revised NORM
document could then serve as a useful and much-needed compilation of
information for the public on NORM source terms and potential exposure
pathways. However, any language suggesting that the present NORM
document could be used to justify regulatory decisions should be removed
from that document.
(b) To go beyond this limited use and to meet the stated goal of serving as a
screening tool for identifying those categories that may or may not require
further attention and possible regulatory action, it would be necessary for
the Agency to conduct its risk assessment analysis using a consistent
approach in addressing uncertainties, such as the methodology suggested
by the RAC in this review report.
An ultimate goal of risk analysis appropriate for screening the NORM
categories so as to determine those that are most likely (or not) to be
candidates for regulatory attention would need to take an approach that
was either consistently conservative (which would serve to identify
categories of NORM that definitely would not require regulatory attention)
and/or consistently nonconservative (which would serve to identify
categories that might require regulatory attention).
(c) In its documentation of the results of its risk analysis, EPA should also be
careful to draw the reader's attention to the differences between those
categories of NORM that may be rated high with respect to individual risk
(where a few people may be exposed to estimated risks ordinarily thought
to deserve EPA attention) and those that may be rated high with respect
to population risk (where estimated risks to even the maximally exposed
37
-------
persons are relatively low but many people are exposed). A discussion of
the policy implications of these two categories of risks, particularly with
respect to the issues involved in imposing regulatory controls on the latter,
would be useful.
38
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9. ADDITIONAL COMMENTS
In this section, the RAG provides additional comments that it believes to be
relevant to the overall review of the NORM document, although outside the
purview of specific charge provided by ORIA.
One stated purpose of the NORM document is to develop information from
which EPA will make a determination of whether or not to control materials
and/or wastes that contain NORM under the Toxic Substance Control Act (TSCA),
the Resource Conservation and Recovery Act (RCRA), or other enabling legislation.
The data and assumptions in the NORM document for many of the materials and
wastes will, therefore, be of enormous importance in decisions affecting the general
public and the industries that serve them. To this end, it is very important that
the information on radionuclides and exposure/risk scenarios be as realistic as
possible and address attendant uncertainties. Presentation of a conservative
analysis to avoid missing potential exposure could be very costly to society in
terms of potential future actions, as could an analysis that fails to take all
potential impacts into account. The Introduction to the NORM document
downplays this by pointing out that any regulatory action will need to be based on
a much more extensive background document — this may not be so; the important
decision as to whether or not to control diffuse NORM might be based on this
preliminary assessment. Thus, the Committee needs to be assured that the
assessment is as rigorous as possible at this stage of the review of this important
topic.
Members of EPA's Radiation Programs have been concerned that full
consideration has not been given to the public implications (i.e., health effects) of
radionuclides in such materials as phosphate deposits. There is (and has been) too
much of a tendency to downplay its implications because it is diffuse, at low levels,
and huge amounts of materials would need to be dealt with; a tone that comes
through in the NORM document. On the other hand, the radionuclides in NORM
materials have the potential to come into contact with large numbers of people
and to expose some of them to significant levels of radiation due to usual
practices. These usual practices appear to be taken as givens and not examined
critically to determine if logical and justifiable procedures should be used that may
significantly decrease public exposures. Two important situations come to mind:
a) greater production of phosphoric acid from elemental phosphorous would
appear to reduce considerably the radioactivity applied to crops, yet the
thermal process is thought to be a declining industry because of increasing
energy costs; and
b) it is possible to remove uranium in the wet phosphoric acid process by
installation of a separation loop, but this has not been actively pursued
because the price of uranium would not make recovery of uranium by such
a process cost-effective. Such processes could reduce the amount of
NORM distributed in fertilizers, and even though it is dilute and
39
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individual exposures are low, the cumulative population effects due to
uranium in fertilizers could possibly be reasonably diminished by use of
technologies to remove uranium during the process of producing
phosphoric acid. The NORM document should address this potential, and
whether it could be justified in a broader context than just profitable
uranium production.
40
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APPENDIX A - REFERENCES CITED
API (American Petroleum Institute), 1989. "A National Survey on Naturally
Occurring Radioactive Materials (NORM) in Petroleum Producing and Gas
Processing Facilities," Dallas TX.
AWWA (American Water Works Association), 1986. "1984 Water Utility
Operating Data," Denver CO.
AWWA (American Water Works Association), 1987. "1985 Water Utility
Operating Data," Denver CO.
Bair, W.J., and W.K. Sinclair, 1992. Response to Drs. Puskin and Nelson
Note, Health Physics, 63(5):590.
Barnard R.W., M.L. Wilson, H.A. Dockery, J.H. Gauthier, P.G. Kaplan, R.R.
Eaton, F.W. Bingham, and T.H. Robey, 1992. TSPA 1991: An Initial Total-
System Performance Assessment for Yucca Mountain. Sandia Report
SAND91-2795.
Beck H.L., et al, 1980. "Perturbations on the Natural Radiation
Environment due to the Utilization of Coal as an Energy Source," Natural
Radiation Environment, CONF-780422, Vol. 2, pp. 1521-1558.
Beck H.L., and K.M. Miller, 1989. Letter transmittal, paper titled "Some
Radiological Aspects of Coal Combustion," January 13, 1989.
Conference on Radiation Control Program Directors, 1981. "Natural
Radioactivity Contamination Problems," Report No. 2, Frankfort KY.
Daniels W.R. and K. Wolfsberg (compilers), 1981. Laboratory Studies of
Radionuclide Distributions between Selected Groundwaters and Geologic
Media, April 1 - June 30, 1981; Los Alamos National Laboratory Progress
Report LA-8952-PR, 27 p.
Dehmel, J-C., and V. Rogers, 1993. Diffuse NORM Wastes: Waste
Characterization and Preliminary Risk Assessment. Report RAE-9232/1-2,
prepared by SC&A, Inc., and by Rogers & Associates Engineering
Corporation for U.S. Environmental Protection Agency, Office of Radiation
and Indoor Air, draft dated May 1993, 2 vols.
EEI (Edison Electric Institute), 1988. "Ashes and Scrubber Sludges-Fossil
Fuel Combustion By-Products: Origin, Properties, Use and Disposal,"
Publication No. 48-88-05.
A-l
-------
EPA (U.S. Environmental Protection Agency), 1988a. "Low-Level and
NARM Radioactive Wastes, Draft Environmental Impact Statement for
Proposed Rules, Volume 1, Background Information Document," EPA/520/1-
87-012-1, June 1988.
EPA (U.S. Environmental Protection Agency), 1988b. "Wastes from the
Combustion of Coal by Electric Utility Power Plants," Report to Congress,
EPA/530-SW-88-002.
EPA (U.S. Environmental Protection Agency), 1990. "Report to Congress on
Special Wastes from Mineral Processing," EPA/530-SW-90-070C, Office of
Solid Waste and Emergency Response, Washington D.C.
EPA (U.S. Environmental Protection Agency), 1991. National Primary and
Secondary Ambient Air Quality Standards, 40CFR Part 50.6, 1991.
EPA (U.S. Environmental Protection Agency), 1993. Health Effects
Assessment Summary Tables: FY-1993 Annual. March. EPA Office of
Research and Development and Office of Emergency and Remedial
Response, Washington, D.C.
EPA/SAB (U.S. Environmental Protection Agency, Science Advisory Board),
1992. "Review of the Idaho Radionuclide Study," EPA-SAB-RAC-LTR-92-
004, January 21, 1992.
EPA/SAB (U.S. Environmental Protection Agency, Science Advisory Board),
1992. "Review of Drinking Water Treatment Wastes Containing NORM,"
EPA-SAB-RAC-LTR-92-018, September 30, 1992
Erdal B.R., W.R. Daniels, and K. Wolfsberg (compilers), 1981. Research and
Development related to the Nevada Nuclear Waste Storage Investigations,
January 1 - March 31, 1981; Los Alamos National Laboratory Progress
Report LA-8847-PR, 66 p.
Gilbert T.L., Yu C., Yuan Y.C., Zielen A.J., Jusko M.J., and Wallo III A.,
1989. A Manual for Implementing Residual Radioactive Materials
Guidelines. RESRAD version 4.35. Argonne National Laboratory. U.S.
Dept. of Energy, Office of Remedial Action and Waste Technology.
Hahn, N.A., Jr., 1988. Disposal of Radium removed from drinking water,
AWWA Journal, Denver CO.
Hedrick, J.B., and D.A. Templeton, 1985. "Rare-Earth Minerals and Metals,"
Rare-Earth Minerals and Metals Yearbook, U.S. Dept. of the Interior,
Washington D.C.
A-2
-------
Hedrick, J.B., and D.A. Templeton, 1989. "Zirconium and Hafnium,"
Zirconium and Hafnium Yearbook.
ICRP (International Commission on Radiological Protection), in press. Age-
Dependent Doses to Members of the Public from Intake of Radionuclides.
Report of Committee 2. (Revision of ICRP Publication No. 56).
ICRP (International Commission on Radiological Protection), 1989. Age-
Dependent Doses to Members of the Public from Intake of Radionuclides:
Part 1. ICRP Publication No. 56. Vol. 20, No. 2. Pergamon Press, Inc.
New York, NY.
ICRP (International Commission on Radiological Protection), 1991. 1990
Recommendations of the International Commission on Radiological
Protection. ICRP Publication No. 60. Vol. 21, No. 1-3. Pergamon Press,
Inc., New York.
Madonia, M., 1989a. "Input Parameters for Mineral Processing Wastes,"
R.F. Weston letter report to Rogers & Associates Engineering Corp., August
7, 1989.
Madonia, M., 1989b. "Input Parameters for Phosphate Wastes," R.F. Weston
letter report to Rogers & Associates Engineering Corp., August 2, 1989.
Madonia, M., 1989c. "Input Parameters for Risk Assessment," R.F. Weston
letter report to Rogers & Associates Engineering Corp., August 3, 1989.
Madonia, M., 1989d. "Input Parameters for Uranium Mining Wastes," R.F.
Weston letter report to Rogers & Associates Engineering Corp., August 2,
1989.
Meijer A., 1992. A strategy for the derivation and use of sorption coefficients
in performance assessment calculations for the Yucca Mountain site, pp 9-40
in: J.A. Canepa (compiler), Proceedings of the DOE/Yucca Mountain Site
Characterization Project Radionuclide Adsorption Workshop at Los Alamos
National Laboratory, September 11-12, 1990; Los Alamos National
Laboratory Conference Report LA-12325-C, 238 p.
Miller C.W., 1984. Models and Parameters for Environmental Radiological
Assessments. Technical Information Center, Office of Scientific and
Technical Information, U.S. Dept. of Energy, DOE/TIC-11468.
NCRP (National Council on Radiation Protection and Measurements), 1993.
Limitation of Exposure to Ionizing Radiation. NCRP Report No. 116.,
Bethesda MD.
A-3
-------
NCRP (National Council on Radiation Protection and Measurements), in
press. Screening Models for Releases of Radionuclides to Air, Surface
Water, and Ground Water. Scientific Committee 64, Bethesda MD.
Nielsen, K.K., V. Rogers, and V.C. Rogers, 1992. RAETRAD Version 3.1
User Manual, Rogers & Associates Engineering Corp., Report RAE-9127/10-
2, Salt Lake City UT.
Phipps A.W., Kendall G.M., Stather J.W., and Fell T.P., 1991. Committed
Equivalent Organ Doses and Committed Effective Doses from Intakes of
Radionuclides. National Radiological Protection Board. NRPB-R245.
Puskin, J.S., N.S. Nelson, and C.B. Nelson, 1992. Bone cancer risk
estimates, Health Physics, 63(5):579-580.
Rogers, V., 1993. "Model for Indoor Radon Gas Scenario in the Diffuse
NORM Report," memorandum to Bill Russo, dated June 20, 1993.
Rogers & Associates Engineering Corp., 1988. "Safety Analysis for the
Disposal of Naturally-Occurring Radioactive Materials in Texas," prepared
for the Texas Low-Level Radioactive Waste Disposal Authority, RAE-8818-1.
Rogers & Associates Engineering Corp., 1992. "A Risk Assessment of the
Use and Reuse of NORM-Contaminated Waste," REA-8964-13-3 (July 1992).
Rogers & Associates Engineering Corp., 1993. "A Preliminary Risk
Assessment of Management Options for Oil Field Wastes and Piping
Contaminated with NORM in the State of Louisiana," prepared for the U.S.
Environmental Protection Agency, under Contract 68-D20185, RAE-9232/1-1,
Rev. 1 (March 1993).
SC&A, Inc., 1988. "Technical Supplements for the Preliminary Risk
Assessment of Diffuse NORM Wastes - Phase I," prepared for the U.S.
Environmental Protection Agency, under Contract 68-02-4375.
Thomas K.W., 1987, Summary of Sorption Measurements Performed with
Yucca Mountain, Nevada, Tuff Samples and Water from Well J-13, Los
Alamos National Laboratory Manuscript Report LA-10960-MS, 99 p.
UNSCEAR (United Nations Scientific Committee on the Effects of Atomic
Radiation), 1982. 1982 Report to the General Assembly, United Nations,
New York.
A-4
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APPENDIX B
WRITTEN PUBLIC COMMENTS RECEIVED BY THE SAB/RAC
1) Alvarez, Joseph L., Ph.D., CHP , and John A. Auxier, Ph.D., CHP, Letter and
report on diffuse NORM waste, Submitted on behalf of the phosphate industry,
to Dr. Genevieve Matanoski, Chair of the SAB's Radiation Advisory Committee,
September 17, 1993
2) API Briefing entitled "NORM OCCURRENCE," A Presentation by Mr. Kevin
Grice of API (Texaco, Houston) to the SAB's Radiation Advisory Committee,
February 23, 1994
3) James E. Gilchrest, Vice President, American Mining Congress, A Transmittal
Letter to K. Jack Kooyoomjian, Ph.D., dated February 24, 1994 on Diffuse
NORM, with attachment entitled "Review of EPA's Final Version -Diffuse
NORM Wastes- Waste Characterization and Preliminary Risk Assessment, April
1993," Prepared for the American Mining Congress by SENES Consultants
Ltd., Richmond Hill, Ontario, February 1994
4) Don W. Hendricks, C.H.P., A Letter dated February 12, 1994 to Dr. K. Jack
Kooyoomjian, Designated Federal Official, Radiation Advisory Committee,
Science Advisory Board (1400F), U.S. Environmental Protection Agency, with
an enclosed executive summary from the final report documenting various
radiological and non-radiological environmental contaminants in the environs
of a uranium mill site. The report is entitled "Winter Baseline Investigation
of Surface Media in the Vicinity of the Uravan Uranium Mill, Uravan,
Colorado, Volume I, Results of January 1986 Field Investigation," Prepared for
The State of Colorado, Department of Law, Office of the Attorney General,
Prepared by ERI, Logan, Inc, Logan, UT, August 11, 1986
5) Jones, Ronald L., Vice President, American Petroleum Institute, Letter and
attached report submitted to Dr. James E. Watson, Jr., Chair of the SAB's
Radiation Advisory Commffctee, (five-page transmittal memo dated January 18,
1994, with a) Attachment A entitled "Critical Review of A Preliminary Risk
Assessment of Management and Disposal Options for Oil Field Wastes and
Piping Contaminated with NORM in the State of Louisiana"), Prepared for API
by SENES Consultants, Ltd., Richmond Hill, Ontario, November 1993; and b)
Attachment B from Morley Davis to Mike Loudermilk of API, entitled
"Cumulative Distribution of Estimated Ra-226 Concentrations in Combined
Sludges and Scales," a Memorandum from SENES Consultants Ltd., dated Jan
12 and 13, 1994)
B-l
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6) Roewer, James R., Utility Solid Waste Activities Group (USWAG) Program
Manager, a letter to Mr. William E. Russo, Jr. of the Office of Radiation and
Indoor Air (ORIA), U.S. Environmental Protection Agency, Washington, B.C.,
in which he attached the Radian Report and the Comments presented by Jim
Lingle of Wisconsin Electric Power Company on behalf of USWAG and the
American Coal Ash Association (ACAA), March 4, 1994
7) Utility Solid Waste Activities Group (USWAG) and the American Coal Ash
Association (ACAA), Comments on NORM Document by James W. Lingle,
Senior Project Chemist, Wisconsin Electric Power Company, on behalf of the
Utility Solid Waste Activities Group (USWAG) and the American Coal Ash
Association (ACAA) Before the Radiation Advisory Committee of the Science
Advisory Board, Washington, D.C., February 23, 1994
8) USWAG & ACAA, an additional submittal to the SAB/RAC by USWAG &
ACAA entitled "Radian Review of EPA Report on Coal Ash Diffuse NORM
Waste," dated February 21, 1994 (Originally presented by Richard G. Strickert
of Radian Corporation, Austin, TX to Central and Southwest Services, Inc.,
Dallas TX, February 21, 1994)
B-2
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APPENDIX C
EVALUATION OF FOOD UPTAKE FACTORS, AND DOSE AND RISK
CONVERSION FACTORS USED IN THE NORM RISK ASSESSMENT
NOTE: The following five tables provide a comparison of the parameter values
derived from other published references commonly used by the risk assessment
community. The purpose of the comparison is to assess whether the values
adopted in the NORM document are reasonable, or the extent to which they may
be either conservative or nonconservative for the purposes of risk assessment.
These tables are discussed in sections 4.2, 4.3 and 4.4 in the main body of this
review.
Table C-l Comparison of food uptake factors (kg/yr)
from various sources
Element
Ac
K
Pa
Pb
Po
Ra
Th
U
NORM
0.18
113
0.25
0.013
0.013
0.013
0.013
0.022
RESRAD*
0.61
—
0.61
11
1.5
0.27
0.92
0.65
NCRP
0.20
230
2.0
1.0
0.99
9.2
0.21
0.69
Miller*
0.49
—
0.49
0.80
0.059
2.7
0.068
0.064
Modified to include the effects of soil uptake from grazing cattle
Data sources:
NORM : Dehmel and Rogers, 1993 (NORM document)
RESRAD : Gilbert et al. (1989)
NCRP : NCRP (in press)
Miller : Miller (1984)
C-l
-------
Table C-2 Ratios (unitless) of food uptake factors
(calculated from values in Table C-l)
Element
Ac
Pa
Pb
Po
Ra
Th
U
Ratio
RESRAD/NORM
3
2
846
115
21
71
30
Ratio
NCRP/NORM
1
1 Q
J_O
8
77
76
708
16
31
Ratio
Miller/NORM
3
2
62
5
208
5
3
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APPENDIX D
VALUATION OF SPECIFIC PATHWAYS, MODEL FORMULATIONS, AND
PARAMETERS USED IN THE NORM RISK ASSESSMENT
NOTE: The NORM risk assessment considers the pathways of exposure marked
with alphanumeric codes in the table below. The codes refer to comments
provided in the text of this appendix. These detailed comments are intended to
augment discussions in Section 4 (Model Parameters), Section 5 (Scenarios), and
Section 6 (Model Formulation) of this review.
PATHWAY
A. Direct gamma
B. Dust inhalation
C. Indoor radon
D. Outdoor radon
E. NORM in
building
materials
F. Radon in
building
materials
G. Drinking
contaminated
well water
H. Food
contaminated by
dust deposition
I. Food
contaminated by
irrigation water
J. Food from
fertilized soil
K. Gamma from
road pavement
and aggregate
L. Dust from steel
mill stack
releases
M. Resuspended
dust
N. River water
contaminated by
ground water
O. River water
contaminated by
surface runoff
ON-SITE
WORKER
Al
Bl
Cl
ON-SITE
RESIDENT
A2
B2
C2
CRITICAL
POPULATION
GROUP (CPG)
A3
B3
C3
Dl
El
Fl
Gl
HI
11
Jl
Kl
LI
GENERAL
POPULATION
D2
L2
Ml
Nl
Ol
D-l
-------
A Direct Gamma Exposure
Al. On-site Worker
Model formulation appears reasonable. Parameter values appear reasonable,
with the possible exception of DFG and the shielding factor f ^. Does the
DFG include self-shielding? What is the basis for assuming 25% shielding for
a bulldozer?
A2. On-site Resident
Same comments as for on-site worker (comment Al). Additionally, gamma
exposure indoors is assumed to be only one-third of that for outdoors. What
is the basis for this assumption: does it, for example, assume that there is no
waste under the house itself or that there is a basement? In contrast, when
fallout radiation is involved, the assumed reduction is typically only about
25%.
Time spent outdoors is assumed to be 25% of the total, with 75% indoors.
The latter can be easily supported with survey data, but the other 25% is
more likely spent away from home than outdoors at home.
A3. CPG
What is the basis for the empirical attenuation with distance; what was the
size of the pile observed? The use of 100 m as the distance to the nearest
residence seems reasonable but is clearly arbitrary. How sensitive are results
to this value? The average value would probably vary by waste type; for
example, some people living in West Chicago are closer to the rare earths pile
than 100 m, but to live that close to a mining waste pile is probably rare.
B. Dust Inhalation
Bl. On-site Worker
o
The model uses 50 jig/m as the total dust level and assigns a fraction of that
load as respirable and formed of waste particles. The value of 50 jig/m is the
national ambient air quality standard for PM10 (Particulate Matter, 10
microns, most of which is respirable) (EPA, 1991), but the allowable dust
levels for workplace exposures are much higher (up to 10 mg/m , depending
upon silica content). Dust levels on construction sites probably exceed the
ambient standard frequently, even if they do not approach the workplace
standard.
The key parameter for this calculation is the fraction of the dust level that is
respirable and consists of waste particles (as opposed to "clean" particles
blowing across the waste area from upwind sources). Respirable fractions
D-2
-------
cited in the NORM document range from 0.05 to 0.7, with many of the values
falling in the 0.2-0.5 range. These fractions are probably biased high, but
perhaps not enough to offset the suspected low bias in the assumed total dust
loading. This pathway also is the first to use the DF. h that converts the
inhaled pCi to effective dose equivalent, based upon distribution in and
elimination from the body, target organ affinities, and other factors. These
dose conversion factors, which are intended for protection decisions, may be
inappropriate for risk assessments. They need to be updated to be consistent
with new ICRP lung model (see Appendix Table C-4).
B2. On-site Individual
o
A lower dust level (10 ng/m ) is used here than for the on-site worker. While
it is reasonable to assume that dust levels would be lower in the absence of
bulldozer activity, it may not h£Mp,asonable to assume that the levels would be
quite this low. What are typicaFdust concentrations where no human activity
is present? Would the respirable fraction be the same as in a construction
area, as seems to be implied, or might it be higher? See also the comment
about time spent outdoors at home (comment A2).
B3. CPG
Inadequate basis to comment on model formulation and adopted parameter
values.
C. Indoor radon and radon daughter inhalation
Cl. On-site Worker
C2. On-site Resident
C3. Critical Population Group
D. Outdoor radon **
Dl. CPG
How does the parameter Va (average wind speed) enter the dose equation? It
would appear that the dose would become infinite as V& goes to zero; is this
reasonable?
D2. General population
The general population living in the area within 50 miles of the NORM
storage/disposal site) is exposed to radon in an unspecified location
(presumably the relevant exposure condition is to ambient air concentrations,
D-3
-------
although the risk factor used in the equation still contains the correction for a
75% indoor occupancy factor).
E. External gamma radiation from NORM in building construction materials
El. CPG
Documentation of the assumptions and equations for this scenario is very
sketchy. It seems to assume residency in a room in which NORM is present
in floors, walls and ceiling, a possibly extreme case. See also comments for
pathway A.
F. Radon in building materials
Fl. CPG
This scenario is restricted to the use of coal ash in making concrete blocks for
basement walls or in the concrete used for the floor slab.
G. Drinking contaminated well water
Gl. CPG
The following assumptions are stated in the NORM document and are
reasonable for the stated purpose:
a) Constant release rate from the waste to the groundwater
b) Release rate is directly proportional to waste concentration. Question:
Would the assumed leaching rate significantly deplete the wastes over 20
years?
c) Infiltration rate is 50% of annual precipitation
d) KJ in waste is same as for aquifer
e) 1-dimensional, porous media flow
f) Instantaneous transport through unsaturated zone to groundwater without
decay or retardation. Question: Does this mean instantaneous depletion of
surface materials, with reduction in potential for direct gamma and radon
also? Given the amount of material moving to the groundwater, is there
any double-counting?
g) Time to peak concentration in well is a function of the retardation factor,
groundwater velocity, and distance to the well but is always <> 10,000 years
h) CPG obtains all water from well
i) Well is located 100 m from edge of waste pile
j) Short-lived radionuclides 227Ac, 210Po, and Pb are in secular equilibrium
with their parents at the point of water withdrawal for consumption
An additional assumption that is implied but not stated is that:
D-4
-------
k) All water withdrawn through the well is recharged through the waste pile;
no dilution of waste by water occurs other than that which has passed
through the waste. This latter assumption is quite conservative; one would
expect in most cases that the waste would be diluted to a large extent by
water which entered the aquifer upgradient of the waste pile.
The dilution volume is annual rainfall times pile area; is this consistent with
the assumption that half of the rainfall infiltrates?
Why is 481 L/yr used for drinking (730 at 2 L/day; 511 at 1.4 L/day)?
Comments on distribution coefficients, Kd:
Uranium - Adopted values in the NORM document range from 45 to 450 ml/g,
with no justification provided for the variation.. The lower value appears ^
reasonable, but justification for the highest value is needed. For comparison,
apparent distribution coefficients measured at Los Alamos National Laboratory
for the Yucca Mountain Project range from 0 to 30 ml/g for uranium in
contact with tuff under oxidizing conditions (Barnard et al., 1992; Meijer,
1992). For these conditions, Kd values for pure minerals phases usually
exceed 100 ml/g over a pH range of 6.5 to 8.0 (Meijer, 1992). U adsorption on
hematite, goethite and silica is very sensitive to pH, showing sharp decreases
for pH values outside of the range 6.5 to 8.0, and relatively insensitive to ionic
strength. At high pH (> 8.0), U adsorption decreases sharply due to
complexation of U by carbonate ions in solution.
Radium - Adopted values in the NORM document range from 45 to 2500
ml/g, with no justification provided for the variation. These values do not
appear to be unreasonable. The distribution coefficient for radium should be
similar to that for another divalent alkaline earth, barium (Thomas, 1987).
For comparison, values for this chemical analog were measured by Los Alamos
National Laboratory and found to range from 200 to 105 ml/g (Daniels and
Wolfsberg, 1981; Erdal et al., 1981). The value is highly dependent upon the
mineralogy of the media, with highest sorptton ratios observed for clay-rich
media.
Thorium - Adopted values in the NORM document are the highest among all
of the radionuclides included in the NORM assessment, ranging from 3000 to
150,000 ml/g. Again, no justification is provided for the variation. The low
end of this range is consistent with those measured at Los Alamos National
Laboratory for thorium in contact with tuff, which exceeded several hundred
ml/g (Thomas, 1987). Migration of this element is probably often controlled by
solubility limits; a check should be made for model validity by comparing the
peak Th concentrations in groundwater predicted by the model to the
solubility limits for this element.
D-5
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Protactinium - Adopted values in the NORM document range from 1500 to
15,000 ml/g. This element is known to be highly sorptive. For a first order
comparison, sorption parameters are expected to be roughly comparable to
those of Americium. Thomas (1987) reported that americium sorption showed
no correlation with mineralogy and that, with two exceptions involving
devitrified tuff, sorption coefficients exceeded 1000 ml/g in all samples.
The major problem in this pathway relates to inadequate justification provided
for those parameter values -- and their variations from one NORM source
term to another -- for which the range of observed values is several orders of
magnitude: particularly, K^ and sorption coefficients.
H. Ingestion of food contaminated by dust deposition
HI. CPG
This scenario includes plant uptake of radionuclides deposited on and tilled
into the soil, but not direct deposition on edible above-ground fruits and
vegetables, in contrast to the approach often taken for hazardous waste
assessments. It also seems to exclude consumption of meat and milk products
that might be affected by animals grazing on contaminated pasture and
ingesting contaminated soil. However, these considerations may all be buried
in the equivalent food uptake factor, a construct that seems designed to
obfuscate rather than to enlighten. The validity of the model formulation
cannot be evaluated until the meaning of the food uptake factor is clearly
defined.
It is very difficult to review the food chain pathway calculations in the draft
NORM document because the entire food chain is subsumed into an
aggregated parameter called the food uptake factor, UF, in units of kg/yr.
Comparison with values derived from other sources (Appendix Table C-l) show
that the UF values used in the NORM document are not necessarily
conservative (Appendix Table C-2) because they are exceeded substantially by
values derived from the other three sources. The main source of these
discrepancies are for the ingestion of vegetables by humans for Pb, Po, and
Ra.
The time of deposition is arbitrarily set at 20 years; justification is needed for
the assumption of cessation of deposition after this time. In some scenarios
for high-level waste, deposition is assumed to occur forever, producing ever
increasing risks for succeeding generations.
See also comment B2 about dust parameters. Also the comment about DFinh
factors applies to the DF- factors.
o
/. Ingestion of food contaminated by irrigation water
D-6
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II. CPG
The list of assumptions is identical to those stated for the groundwater
pathway (comment Gl), except h is replaced by the assumption that the CPG
obtains all of its annual equivalent foodstuff consumption uptake from the
contaminated well. A term that needs explanation is the "humid permeable
default values" that serve as the basis for the water uptake factors used in the
model.
J. Food from fertilized soil
Jl. CPG
See comment HI.
The estimate of exposure from ingesting vegetables from fertilized soil appears
at first to assume that concentrations in soil and vegetation are the same. Is
this a case of parameters hidden in the uptake factors?
K. Gamma from road pavement and aggregates
Kl. CPG
The CPG here is a police officer spending almost all his/her working hours on
the highway, and in fact in the middle of the road. Such a scenario seems
fairly extreme. Otherwise, the radiation transport formulations looks
reasonable. See also comments for pathway A.
L. Dust from steel mill stack releases
LI. CPG
The general idea is the same as for dust blowing off of a waste pile, except the
source term is different. The model formulation appears to include all the
important variables.
The parameter selection is for a stack only 30 feet high and 10 feet in
diameter. Is this typical for a steel mill using recycled feedstock?
L2. General population
The model integrates the CPG equations over distance. See comment LI
above.
M. Resuspended dust
Ml. General population
D-7
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This scenario averages the exposures as estimated for the CPG (comment B3)
over the range from 100 m to 50 miles and applies a state-specific population
density to obtain population dose. It includes direct inhalation of dust,
ingestion of dust on plants, and gamma from deposited dust. See comment B3
on CPG dust pathway. The equation does not clearly deplete the plume by
the amount of dust assumed to be deposited. How sensitive are the results to
the maximum distance, which is arbitrary? Is it reasonable to use state-wide
population density independent of the type of waste?
N. River water contaminated by ground water
Nl. General population
The pathway for ingestion of river water contaminated by groundwater
includes a parameter q , the river flow rate, which serves to dilute the
radionuclide concentration introduced via groundwater. The NORM document
states that the river flow rate q is assumed to be 1/3 of the "humid
impermeable value" in EPA (1988a); what is the meaning of a "humid
impermeable value"?
The population dose arises from consumption (as drinking water or from
agricultural use) of river water contaminated by NORM migration through
groundwater. Assumptions underlying the model are the same as assumptions
a-g for the groundwater model (see comment Gl). Additional assumptions are:
h) Rate of use of contaminated river water includes equivalent foodstuff
consumption uptake (as a consequence of food irrigation) as well as direct
water consumption
Additional assumptions that are implied but not stated:
i) Short-lived radionuclides Ac, Po, and Pb are in secular equilibrium
with their parents at the point of water use
j) The extent of dilution of waste is determined by the river volumetric flow
rate. Dilution by groundwater is negligible.
O. River water contaminated by surface runoff
Ol. General population
Assumptions are:
a) Constant release rate from the waste to surface runoff
b) Release rate is directly proportional to waste concentration
c) Infiltration rate is 50% of annual precipitation
d) Kd for soil is same as for aquifer
e) No time delay in runoff process
D-8
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Question. We don't understand what this assumption means. Does it mean
instantaneous transport from waste to river, with no radioactive delay or
retardation along the surface path? Can't be this because retardation factor is
included in model.
Additional assumptions that are implied but not stated include:
f) Exposed population obtains all drinking and irrigation water from the river
immediately downstream of the entry point for the contaminated
groundwater
g) Short-lived radionuclides 227Ac, 210Po, and 210Pb are in secular equilibrium
with their parents at the point of water withdrawal for use
h) Radionuclide concentration in runoff is same as in waste leachate in the
unsaturated zone.
The rationale behind the selection of 0.1 as the dilution factor fdt for surface
water transport of waste is not clearly stated.
D-9
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APPENDIX E - GLOSSARY OF TERMS AND ACRONYMS
Ac
ACAA
AWWA
API
Bq
CFR
Ci
cm
cm
CPG
DOE
E
EEI
EPA
ES
5*
fsh
ft3
g
GAG
HEAST
Hf
hr
ICRP
kg
K
Kd
{^at
L
LB
M
MT
V-
m
m
m3
mbd
mg
Actinium, as an element or as an isotope of thorium or uranium
alpha-decay chains (e.g., Ac-227)
American Coal Ash Association
American Water Works Association
American Petroleum Institute
Beccjuerel (1 disintegration per second)
Code of Federal Regulations
Curies (3.7xl010 disintegration per second)
Centimeter
Cubic centimeter
Critical Population Group
Dose Conversion Factor
Dose Factor for Ingestion
Dose Factor for Inhalation
Dose Factor for Gamma
U.S. Department of Energy
Exponent (106)
Edison Electric Institute
U.S. Environmental Protection Agency (U.S. EPA, or "The Agency")
Executive Summary
Dilution factor for surface water transport of waste
Shielding Factor
Cubic feet
Gram
Granular Activated Carbon
Health Effects Assessment Summary Table
Hafnium
Hour
International Commission on Radiological Protection
Kilogram *
Potassium
Distribution coefficient
Saturated hydraulic conductivity
Liter
Lower Bound
Mole
Metric Tons
Micro-, [10 ] in combination with specific units
Milli-, [10"3] in combination with specific units
Meter
Cubic meter
Million Barrels per Day
E-l
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APPENDIX E - GLOSSARY OF TERMS AND ACRONYMS: CONTINUED:
ml Milli-liter
mR Milli-Roentgens
mR/hr Milli-Roentgens per Hour
NARM Naturally-Occurring and Accelerator-Produced Radioactive Material
nat Natural
NCRP National Council on Radiation Protection and Measurements
NORM Naturally-Occurring Radioactive Material
NRC Nuclear Regulatory Commission
NRPB National Radiological Protection Board
O Oxygen
O2 Oxide (Also oxygen; Oxide of a specific ores, such as ThO2
or UgOg
ORIA Office of Radiation and Indoor Air (U.S. EPA)
OSHA Occupational Safety and Health Administration
PATHRAE Computer code used to assess the maximum annual dose to a critical
(EPA) population group resulting from waste disposal. It is a member of the
PRESTO-EPA family of codes and emphasizes two areas: (1) the
addition of exposure pathways pertaining to on-site workers during
disposal operations, off-site personnel after site closure, and
reclaimers and inadvertent intruders after site closure; and (2) the
simplification of the sophisticated dynamic submodels to quasi-steady
state submodels.
1 *?
p pico-, [10" ] in combination with specific units
Pb Lead, as an element or as an isotope of thorium or uranium alpha-
decay chains (e.g., Pb-210)
PC Personal Computer
pH Negative log of hydrogen ion concentration
PM 10 Particulate Matter, 10 microns
Po Polonium, as an element or as an isotope of thorium or uranium
alpha-decay chains (e.g., Po-210)
PRESTO-CPG-PC A PC version of PRESTO pertaining to the Critical
Population Group (CPG) (a variant of PRESTO-EPA-CPG; See also
EPA 1989 User Manual EPA 520/1-89-017, April 1989)
PRESTO A family of codes developed to evaluate doses resulting from the
(EMF) disposal of low-level radioactive waste. These codes include PRESTO-
EPA-CPG (assesses annual effective dose equivalents to a critical
population group), PRESTO-EPA-DEEP (assesses cumulative
population health effects resulting from the disposal of low-level waste
using deep geologic repositories), PRESTO-EPA-BRC (assesses
cumulative population health effects to the general population residing
in the downstream regional basin as a result of the disposal of low-
level waste in an unregulated sanitary landfill), PRESTO-EPA-POP
(assesses cumulative population health effects to the general
population residing in the downstream regional basin on a low-level
waste site), and PATHRAE (see above)
E-2
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APPENDDC E - GLOSSARY OF TERMS AND ACRONYMS: CONTINUED:
qr River flow rate
R Roentgen
Ra Radium, as an element or as an isotope of thorium or uranium alpha-
decay chains (e.g., Ra-223, Ra-224, Ra-226)
RAC Radiation Advisory Committee (U.S. EPA/SAB/RAC)
RAETRAD Radon Emanation and Transport into Dwellings, a computer code for
radon risk assessment which was developed to provide a means of
estimating the rates of radon gas entry into slab-on-grade dwellings
from underlying soils and concrete components (See Appendix A -
Nielsen et al., 1992)
RCF Risk Conversion Factor
RCRA Resource Conservation and Recovery^Act
rem roentgen equivalent man
RESRAD Residual Radioactive Materials Guidelines (The DOE Model). This is
a computer code developed by DOE to implement its guidelines for
deriving guidelines for allowable concentrations of residual radioactive
material in soil.
Rn Radon, as an element or as an isotope of thorium or uranium alpha-
decay chains (e.g., Rn-219, Rn-220, Rn-222)
SAB Science Advisory Board (U.S. EPA)
Sn Tin
Sv Sievert (equal to 100 rem)
Th Thorium, as an element or as an isotope (e.g., Th-228, Th-230, Th-
232, Th-234)
Ti Titanium
TSCA Toxic Substances Control Act
TSPA Total System Performance Assessment
U Uranium, as an element or as an isotope (e.g., U-234, U-235, U-238)
UF Uptake factor for food ingestion
UB Upper Bound
Hg/m micro-gram/cubic meter
U.K. United Kingdom
\iM micro moles
U.N. United Nations
UNSCEAR United Nations Scientific Committee on the Effects of Atomic
Radiation
tiR/hr micro-Roentgen per hour
U.S. United States
U.S.A. United States of America
USWAG Utilities Solid Waste Activities Group
Va Average wind speed (average Velocity)
yr Year
Zr Zirconium
E-3
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