Background Report
Considerations of
Environmental Protection Criteria
for
Radioactive Waste
February 1978
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Radiation Programs
Waste Environmental Standards Program
Washington, D.C. 20460
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FEDERAL REGISTER, VOL 43, NO. 10-MONDAY, JANUARY 16, 1978
[6560-01]
ENVIRONMENTAL PROTECTION
AGENCY
[FRL 843-1]
ENVIRONMENTAL PROTECTION CRITERIA FOR
RADIOACTIVE WASTES
Announcement of Public Forum
AGENCY: Environmental Protection
Agency.
ACTION: Announcement of Public
Forum.
SUMMARY: The Environmental Pro-
tection Agency (EPA) will hold a
Public Forum on Environmental Pro-
tection Criteria for Radioactive
Wastes at the Stouffer's Denver Inn,
Denver. Colo., March 30 to April 1.
1978. The purpose is to provide for ex-
tensive public review of a background
report, available February 1, which in-
cludes the Office of Radiation Pro-
grams' initial formulation of proposed
guidance for all types of radioactive
wastes.
FOR FURTHER INFORMATION
CONTACT:
Project Leader for Environmental
Criteria, Waste Environmental Stan-
dards Program (AW-460), Environ-
mental Protection Agency, 401 M
Street SW.. Washington, D.C. 20460,
telephone 703-557-8927.
SUPPLEMENTARY INFORMATION:
Notice has been given (41 FR 53363)
that EPA intends to develop environ-
mental radiation protection standards
for -high-level radioactive waste to
assure protection of the public health
and the general environment. This de-
velopment will focus initially on two
major outputs: General environmental
protection criteria for all radioactive
wastes, which are the subject of the
Forum announced here, and numerical
standards for high-level radioactive
waste. These criteria and standards
will be developed under the broad au-
thorities transferred to the Agency
from the former Atomic Energy Com-
mission and the former Federal Radi-
ation Council by Reorganization Plan
No. 3 of of 1970.
Prior to developing its initial formu-
lation of proposed guidance, the
Agency has sought broad public input
through two open workshops: at
Reston. Va., on February 3-5. 1977.
.and at Albuquerque. N. Mex.. on April
12-14, 1977. The purposes were to
define key terms related to the radio-
active waste problem, and to examine
basic concepts concerning both the
risks associated with wastes and the
long term implications of their man-
agement, including disposal. Partici-
pants were free to advise EPA on any
matter they consider appropriate.
EPA has now developed an initial
formulation of proposed guidance for
radioactive waste storage and disposal.
using the inputs received from these
workships to the extent feasible.
Before finalizing this formulation into
formal proposed guidance, the Agency
feels it is desirable to have further
public review and discussion, since
many of the concepts involve new pre-
cedents in radiation protection. The
initial formulation will be the basis for
discussion at the Forum, and will be
available as a source document by Feb-
ruary 1,1978.
The Forum will take place in
Denver, Colo., at the Stouffer's
Denver Inn on March 30 to April 1,
1978. Following brief presentations by
EPA staff on how and why its recom-
mendations were developed, working
groups will be set up according to the
topics the background report covers.
Participants will be expected to direct
their attention specifically to EPA's
initial formulation of proposed guid-
ance and to develop comments accord-
ingly, rather than to explore the
issues in general.
The Forum is free, but, to assist
EPA in planning sufficient meeting ar-
rangements, people who wish to par-
ticipate are asked to pre-register with
the Manager, EPA Workshop. Ecologi-
cal Analysts. 257 Broad Hollow Road,
Melville. N.Y. 11746. Anyone who at-
tended either of the two previous
workshops will automatically receive
an invitation and a copy of the back-
ground document containing the
Agency's initial formulation of pro-
posed guidance. Those who would like
to provide written comments instead
of attending the Forum may request
the same information from EPA at the
above address. All comments received
by either process will be considered in
preparing the criteria for formal pro-
posal in the FEDERAL REGISTER.
Dated: January 8,1978.
DAVID HAWKINS.
Assistant Administrator for Air
and Waste Management
IFR Doc. 78-1176 Hied 1-13-78; 8:45 am]
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BACKGROUND REPORT
CONSIDERATIONS OF ENVIRONMENTAL PROTECTION
CRITERIA FOR RADIOACTIVE WASTE
Waste Envirpnmental Standards Program
Office of Radiation Programs
U.S. Environmental Protection Agency
Washington, D.C. 20460
February 1978
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PREFACE
When EPA was formed in 1970, one of its charges was -to "advise the
President with respect to radiation matters, directly or indirectly
affecting health, including guidance for Federal agencies in the
formulation of radiation standards...1* This responsibility includes
protection of the public health from potential hazards associated with
the various forms of radioactive waste.
This Background Report develops considerations for and initial
formulations of environmental protection criteria for radioactive
wastes, and as such, will provide the basis for additional public
participation in developing the criteria. In this regard, public input
was received from two public workshops held by EPA in February and April
1977 to address relevant policy and technical issues. A third public
forum of similar format is planned in the spring of 1978 to discuss this
Background Report and its initial formulations. The public is invited
to further assist the Agency by attending this forum or by providing
written comments, which will be considered and responded to before
formally proposing the criteria. Both the scope and details of the
initial forumulations are subject to change to accommodate these
comments.
The Agency has also begun the technical environmental impact
assessments needed to develop a standard specifically directed at high-
level, long-lived radioactive wastes. The standard will be in
accordance with the criteria, and it will be the first of a series of
environmental standards for major classes of radioactive wastes.
E. Martin,/Ph. D.
Manager, Wastte Environmental Standards Program
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CONTENTS
Introduction 1
Radioactive Wastes and Hazards 3
Risk Considerations for Radioactive Wastes 14
Control of Radioactive Waste 22
Risk Perspectives 30
Other.Considerations for Radioactive Waste 43
Summary and Recommendations 47
Glossary 54
Appendix A 56
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INTRODUCTION
The responsibility of present generations to maintain environmental
quality for future generations is well recognized. As enunciated in the
National Environmental Policy Act of 1969, it is an important national
goal to "fulfill the responsibilities of each generation as trustee of
the environment for succeeding generations." Many radioactive waste
materials are both long-lived and highly radioactive, and therefore
could represent substantial risk that could be transferred from present
generations to future ones. Because of this potential risk not only to
present generations but to future ones as well, it is important that
such materials be properly controlled.
It is generally conceded that risk estimates for many of the long-
lived radionuclides would depend on numerous imprecise variables which
would be little more than speculation after certain time periods. For
example, C-14, Pu-239 and 1-129 could present potential dose commitments
for hundreds of thousands to millions of years. Such uncertainty could
result in intense controversy over any calculations or judgments upon
which environmental protection criteria or standards would be based.
This circumstance places a considerable burden on government decisions
regarding radioactive wastes. These decisions should recognize the
public's perception of the problem; however, to date there seems to be
little public concensus concerning appropriate management of radioactive
wastes.
Development of environmental protection requirements for
radioactive wastes basically involves: 1) features of radioactive
materials that require them to be designated as radioactive wastes and
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their hazard potential over time and at various levels of controls, 2)
the importance of risk estimates in arriving at levels of control and
the factors that should be reflected in such determinations, 3) the
goals of control and the types of institutional, engineered, and
natural-barrier controls for meeting such goals, U) the approaches for
determining the allowable levels of short- and long-term risks
associated with various means of disposal for types of waste materials,
and 5) other considerations for environmental protection such as
retrievability, monitoring, and transfer of information to succeeding
generations. This Background Report addresses these five areas in
sequence in order to make recommendations for environmental protection
criteria which are to be used in the development of environmental
standards for major classes of radioactive waste.
The Agency held two workshops in 1977 to gather a variety of views
on major issues, and has given careful consideration to the views
expressed there in drafting this document and the initial formulations
of environmental criteria. The major findings of the workshops are
summarized in Appendix A and referred to in this document where they
apply.
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RADIOACTIVE WASTES AND HAZARDS
Radioactive Wastes
Radioactive wastes are a consequence of the use of either human-
produced or naturally-occurring radioactive materials. These wastes are
produced in a broad range of forms, concentrations, and quantities.
They may be gaseous, liquid, or solid in form, may be soluble or
insoluble in water, and may emit several types of radiation over a wide
range, of energy and rate. The concentration of wastes varies from
highly radioactive spent reactor fuel wastes and disused radium sources
to very low natural radioactivity in residues from certain mineral
processing activities. Between these extremes is a broad range of
wastes of varying radioactivity resulting from medical, industrial, and
scientific radioisotope applications. The two extremes generally
encompass the range of sources, potential hazards, and inventories of
radionuclides that need to be considered in establishing environmental
protection criteria for the disposal of materials containing them.
In order to designate a material as radioactive waste, it should be
first declared a waste, that is, it has no anticipated use or value.
Since virtually everything in use contains some measure of
radioactivity, a drastic narrowing is obviously required to decide which
materials should be designated as radioactive wastes. Almost any waste
would be included if the only required characteristics were that a
material be radioactive and have no future use. As a starting point, it
seems clear that radioactive wastes should include materials restricted
by regulatory controls from discharge to the general environment.
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Recognizing that most substances contain some natural
radioactivity, it is necessary to differentiate when they should be
considered radioactive wastes rather than assuming they are just wastes
with no need to consider their radioactivity content in disposing of
them. Such waste materials could be reasonably classified as being non-
radioactive wastes if nothing is done to make the radioactivity content
more accessible for exposure of humans than would normally exist due to
natural conditions. Using the same consideration, if disposal of these
i
materials in the environment would not increase the pre-existing
exposure level to humans via any pathway at the site, they should hot
require special care due to their radioactivity. It also seems
reasonable that the location of a disposal site should not be chosen
just to be able to dispose of material with high natural radioactivity
concentration without consideration of the fact that the radioactivity
has been made more available for human exposure. For example, shipping
Florida phosphate tailings to a high background area for disposal would
not be .justified even if it were feasible.
Many artifically-produced radioactive materials, such as those
produced by nuclear fission or activation, are subject to regulatory
controls to avoid unjustified exposure of the public by discharge to
environmental pathways or other means. Such materials are by mode of
production under human control and thus the perspective for their
designation as radioactive wastes and. required care is somewhat
different from naturally-occurring diffuse radioactive materials. Any
waste material that is restricted from discharge to the general
environment should be considered radioactive waste and subjected to
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environmental protection requirements when being managed or disposed of;
this condition is especially applicable to retained human-produced
materials such as fission products from fuel reprocessing, or liquid or
gaseous wastes removed from effluent streams to meet environmental
requirements. It is also reasonable to apply the same condition to
naturally radioactive materials removed from effluents because of
discharge restrictions.
The designation of radioactive wastes and the controls they receive
is influenced by the potential for individuals and populations to be
exposed to them and the timeframe over which they persist as
radiological hazards. If any waste material containing human-produced
radionuclides were reasonably controllable to reduce potential human
exposure, then this would also be a justifiable basis for designating it
as a radioactive waste.
Types and Hazards of Radioactive Wastes
The sources, potential hazards, and inventories of radioactive
wastes are represented by: 1) radioactive materials either artificially
produced or fabricated from natural materials such as radium into
discrete sources, and 2) diffuse naturally-occurring radionuclides such
as the by-products of mining and milling operations. Radioactive wastes
in the first group are deliberately produced or assembled. They vary
greatly in activity, form, volume, and radiological hazard implications,
and consist primarily of high-level, low-level, and transuranic
contaminated wastes. Other sources of this nature are naturally-
occurring nuclides concentrated in discrete sources such as Ra-226
needles used in medical therapy.
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Materials in the second group are not institutionally produced, but
are rearranged as a result of human activities such as the
redistribution of naturally-occurring radioactive materials due to
mining and milling of ore bodies. The majority of these wastes are
associated with mining and milling operations; uranium tailings and
residues of phosphate mining are prime examples of these wastes.
"High-Level Waste" traditionally refers only to the liquid stream
resulting from reprocessing of spent reactor fuel, and to any solidified
derivatives of that liquid. Because other materials present hazardous
levels of risk, "high-level wastes" as used here will also include all
forms of radioactive wastes which have the capability to produce
radiation exposures with acute effects. The major source of such wastes
is currently nuclear fission reactors resulting in either spent fuel, or
the products of reprocessing the fuel.
High-level wastes containing fission products emit penetrating
gamma radiation, which means that mere proximity to the material may be
hazardous. Also, most quantities of such wastes produce sufficient heat
from radioactive decay to increase the potential for uncontrolled
release to the environment. Following such a release, dilution would
reduce the direct radiation hazard so that inhalation and ingestion
hazards would then, predominate. These pathways to people arise from
volatilization, particulate dispersion, and dissolution of the waste.
The actual hazard would vary with the isotopic composition of the
material. In the case of the waste from reprocessed nuclear fuels, for
example, Sr-90 and Cs-137 would be the controlling inhalation hazard.
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and Sr-90 would be the controlling ingestion hazard for the first few
hundred years after the material is produced.
The total inventory of high-level fission product waste at Federal
sites is about 76 million gallons with an activity of about 400 million
curies (JCAE, 1975). It has been estimated that these wastes will
continue to accumulate at a rate of about 300 thousand gallons per year.
Since most of the spent fuel from commercially operated reactors has not
been reprocessed, the resulting high-level liquid waste is currently
only 0.6 million gallons, which contains approximately 310 million
curies (NRC, 1976; EPRI, 1976). The remaining unprocessed spent fuel
elements from commercial nuclear power plants are in temporary storage,
pending a decision on future disposition. It has been estimated that
spent fuel elements in storage as of 1975 corresponded to 1365 metric
tons of uranium (ERDA, 1976). If reprocessing becomes an element of the
commercial nuclear fuel cycle, it is estimated that each metric ton of
fuel processed would result in 400 gallons of high-level liquid wastes
(Cohen, 1972). It should be noted, however, that the expected total
amount of liquid may not exist at any one time if the current
regulations requiring solidification after five years remain in effect.
Other high-level wastes include certain discarded sources used in
medicine and industry such as Co-60, Cs-137, Sr-90, etc. High-level
sources such as Ir-192 are also used for industrial applications such as
nondestructive testing. The current inventories and annual production
rates of high-level wastes from medical and industrial applications are
difficult to estimate, but it is expected that the amounts of wastes
containing such sources would increase.
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"Low-Level Waste" has generally been used to include substances not
readily classified otherwise; therefore, the term has covered material
with a very broad range of origins, physical and chemical forms,
radioactive lifetimes, and radiological hazards. For present purposes,
low-level wastes include materials which would not present an acute
hazard (induction of radiation sickness over a relatively short period
of time) to maximally exposed individuals. In applying this principle,
certain wastes usually designated as low-level, such as some reactor
wastes and discrete medical and industrial sources, may no longer fit
this classification. A potential hazard to the public from low-level
wastes is radiation exposure via water that may come into contact with
the waste material and leach various radionuclides into solution. These
may eventually be ingested by humans through their food, milk, and
drinking water. The resulting exposure depends upon the rate of
transfer of the radionuclides through the surrounding soil and
groundwater, the amount of dilution or concentration that occurs, and
other factors. Radioactive dust may result from poor handling of
materials during disposal operations, and subsequent inhalation of the
dust could pose a serious health hazard.
Through 1976, the commercial sector generated 15 million cubic feet
of waste packages containing 3.8 million curies of low-level waste
(Holcomb, 1977). It has been estimated that in 1974 Government sites
contained 17 million curies in 42 million cubic feet of packaged waste
(GAO, 1976; NAS, 1976). Wastes from the commercial sector are being
generated at a rate of approximately 2 million cubic feet per year, and
are increasing each year (O'Connell, 1974). Production of low-level
8
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wastes from Government programs is stable at approximately 1.3 million
cubic feet per year (AEC, 1975; Wong, 1973).
Long-Lived Wastes are especially significant because their
persistence represents continued risk to humans far into the future even
in small amounts. Transuranic (TRTJ) contaminated wastes (isotopes with
atomic number greater than 92, e.g. Np, Pu, Am) are especially
significant because they have long half-lives and some are highly
radiotoxic. TRU's are primarily produced by single or multiple neutron
capture by O-238 in fuel elements during the operation of a nuclear
reactor. Reprocessing of spent fuel elements removes plutonium, but
since the separation is not complete, the resulting high-level liquids
still contain some plutonium (less than about 0.5 percent) as well as
other transuranic material. Likewise, transuranic contamination of low-
level wastes also occurs when the transuranic materials are handled or
processed, which is primarily at Government facilities involved in
nuclear weapons production.
Transuranic wastes are persistent in the environment, but as a
general rule, are strongly retained by soils. They are not easily
transported through most food chains, although some concentration does
take place in the aquatic food chain. They pose only a slight
biological hazard to humans upon ingestion because absorption through
the gastrointestinal tract is slight. A greater potential hazard
results from inhalation of dust particles containing TRO materials
because a significant fraction would be retained in the lung or be
absorbed into other tissue. The potential to produce adverse health
effects depends upon the particle size and solubility of the inhaled
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material. Upon entry into the bloodstream (either by ingestion or
inhalation), TRD wastes readily accumulate in bone and liver tissues and
can significantly increase the risk of cancer.
Prior to 1970, TRU-contaminated wastes were not segregated from
other low-level wastes. At sites used by the Federal Government for its
own wastes, materials are not placed in the site if they contain greater
than 10 nanocuries of alpha-emitting radionuclides per gram. About one
million cubic feet containing some 215 thousand grams of TRD wastes are
currently in storage at Federal sites. Such wastes are accumulating at
a rate of about UQQ thousand cubic feet per year (NAS, 1976). Five of
the six operating commercial burial grounds currently exclude wastes
containing greater than 10 nanocuries of transuranic radionuclides per
gram.
Other long-lived radionuclides which may be of special concern are
1-129 and c-14. iodine-129 is a volatile nuclide with a half-life of
seventeen million years; thus, its isolation from the biosphere over the
long term will be difficult to assure. Carbon-14 has a half-life of
5600 years andr if released to the biosphere, would represent exposure
of the entire world's population due to rapid movement into the carbon
cycle.
Fabricated Naturally Radioactive Wastes are discrete sources such
as radium needles and radon seed implants commonly used for therapeutic
medical purposes. Other such sources are neutron sources fabricated
from beryllium and polonium or radium which are used in industrial
drilling applications. Wastes resulting from these uses range from
high-level to low-level and the radiological hazards vary accordingly.
10
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The radiological hazard from a Ra-226 source, for instance, is largely
due to external gamma irradiation or, when inhaled or ingested, to
internal alpha emission. Because the hazards from discrete sources of
naturally-occurring nuclides vary so greatly, they need to be determined
on a case-by-case basis. Inventories of these sources are estimated to
be small.
Diffuse Wastes of Naturallv-Occurring Radionuclides exist, which,
by virtue of their natural origin and the methods of production, are
dispersed through a bulky nonradioactive matrix. Common examples are
uranium mill tailings and phosphate mining and processing wastes.
Similar wastes, though of much lower radioactivity concentration, result
from activities such as copper mining and coal combustion. These wastes
contain the naturally-occurring radioisotopes of uranium, thorium,
radium and other uranium daughter products.
Diffuse wastes represent chronic rather than acute exposure. The
primary pathway to humans for such exposure is the inhalation of radon
and its daughters. This results in radionuclide deposition in the lung,
skeleton, and liver. Past experience indicates that radon gas produced
by radium decay migrates into residential structures built on or near
uncontrolled waste and tailings piles. In -a number of instances, as
observed with uranium mill tailings in Grand Junction, Colorado, and
reclaimed phosphate mining land in Florida, elevated levels of radon
daughters were measurable in structures, although in numerous cases the
total radium source term was relatively low (EPA, 1976a). This
indicates that radium levels in diffuse waste could present a potential
hazard and still not greatly exceed background levels.
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Compounding this waste management problem is the longevity of the
radionuclides involved. Thorium-230, the parent nuclide of radium-226,
has a physical half-life of about 80 thousand years, which can be
considered the effective half-life of the radon exposure hazard. The
persistence of this waste makes it impossible to control public access
to it by any institutional means. The current practice of stabilizing
the tailings by cover has been only a temporary solution of limited
value due to the ability of radon to diffuse through most natural media.
The very large quantities of waste involved, the variability of natural
background radium concentrations, and the cost and availability of
control technologies are important considerations in determining
management of these materials.
By far the largest quantities of naturally-occurring, diffuse
radioactive wastes are the solid residues from mining and milling of
uranium and phosphates. These include the overburden and excavated
materials from open pit and underground mining, and the tailings from
milling operations. Tailings contain about 99 percent of the original
ore mass, and more than 97 percent of the uranium series radioactive
decay products. The accumulated volume of uranium tailings through 1976
is assumed to be equal to the total volume of mined ore, which is
thought to be near 138 million tons. Approximately 23 million tons of
tailings are located at inactive mill sites and the remaining 115
million tons are at operating sites (Hendricks, 1977). The total
radioactivity of the mill tailings is estimated at 140 thousand curies
(EPA, 1977a). There are some 300 million tons of phosphate mill
tailings containing approximately 10,000 curies of Ra-226 (EPA, 1977b).
12
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Radioactive Waste Materials
Application of the factors and considerations above leads to a
conclusion that radioactive material which has no foreseen value would
be radioactive waste if it contains artificially produced radionuclides,
contains naturally-occurring radionuclides in such concentrations that
release to the general environment would increase exposure to humans
above that normally occurring in pathways due to the natural state of
the area, or contains either type of material which is restricted by
regulations from routine release to the general environment. Examples
of such materials that would be radioactive wastes subject to
environmental protection criteria in determining their storage and
disposal are:
All radioactive materials associated with the operation of
nuclear reactors for either military or other purposes and the
supporting fuel cycles including spent fuel, fuel reprocessing
wastes, and radionuclides removed from effluents.
Artificially produced radioisotopes for medical, industrial, and
research use, including discrete radium sources, and waste
materials contaminated with them.
The naturally radioactive residues of uranium and phosphate ore
recovery and associated milling and conversion operations.
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RISK CONSIDERATIONS FOR RADIOACTIVE WASTES
Radioactive wastes represent a risk of potential exposure to people
which varies considerably with time. The risks are dependent to a large
extent on whether the wastes are controlled, the type of controls that
could be adopted, and how long the controls would last. In a practical
sense, risk considerations and control considerations are necessarily
interrelated because each influences the other. Therefore the risks due
to the presence of radioactive wastes in the human environment need to
be assessed without controls and at different levels of control. The
risk assessed at a particular level of control is especially important
to the consideration of whether a risk is acceptable, which is discussed
further in a later section.
Technical, Economic, and Social Considerations
It should be noted in this regard that there is no way to guarantee
absolute protection from pollutants such as radioactive materials, which
are assumed to have no threshold for effects, other than by prohibiting
their production. In order to receive the benefits of an activity in
which radioactive wastes are produced, regulatory and advisory bodies
have considered the costs of achieving a given level of health and
environmental protection. Provided that basic health and social
objectives are being satisfied, it has long been the practice in
radiation protection to apply additional controls until further
expenditures are no longer justified because of the minimal improvements
in health protection.
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A significant: issue is whether the possibility of exposure to
radiation from waste can be justified at all, in view of the universal
understanding that waste itself is a material which is not being used
for any beneficial purpose. This issue is somewhat different, however,
if one is trying to reach conclusions about existing wastes as opposed
to wastes which have not yet been produced. For existing waste, the
only possible justification for accepting any risk other than zero is
that the expenditure and commitment of resources required to eliminate
all chance of exposure to humans, if that should be possible, may not be
warranted by the increase in safety that would thereby be achieved. The
only policy issue for existing waste, therefore, is whether at any given
level of control the expenditures or other costs to gain additional
control are justified by the degree of risk reduction that would result.
For wastes which have not yet been produced, it is logical to view
the requirements for safe management of any radioactive wastes as part
of the economic, social, and health and environmental costs of achieving
the desired product. Justification for any risks permitted due to the
wastes must be found in the beneficial aspects of the enterprise, which
should exceed the costs. Analyzing and comparing these total costs and
benefits for a complex enterprise is well known to be profoundly
difficult (see for example, BEIR II, 1977). However, in cases where any
risks associated with radioactive wastes could be avoided by not
producing the waste, justification for assuming the risk would be
related to the net value of the productive enterprise.
A wide range of viewpoints exists over the nature of the
responsibility of the waste producers to provide protection for future
15
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populations, such a range was observed at the EPA workshops. It is
argued by some that because only the waste producers receive the
benefits associated with the production activities, future people should
not be subjected to any burden at all because they had no role in the
decision-making process. A divergent view is that future societies are
indeed beneficiaries of the technological activities which produce the
waste, and therefore it is not unfair for them to share some portion of
any potential risks. Moreover, if future poeple were more
technologically advanced, they would be more able to provide for their
own protection than are the waste producers. On the other hand, if less
technologically advanced, the potential consequences to any amount of
exposure may well be less than already assumed. A caution is necessary,
however, in that a decision not to take action to mitigate a problem may
place economic burdens on future generations. An example of this
circumstance is evidenced by existing uranium tailings piles which were
originally placed in their current location at a fraction of today's
costs, but would be quite expensive to relocate.
Many variations and elaborations of these views have been
expressed. However, one of the clearest conclusions to emerge from the
discussions at the EPA workshops was that limitation of the long-term
risk should be an important element of environmental protection criteria
for radioactive wastes. Similarly, a study of public attitudes, and
values associated with radioactive waste disposal based on polling
techniques showed that long-term safety is widely held to be at least as
important as safety over the short term (Maynard, 1976) . Protection of
future populations from the potential hazards of radioactive waste
16
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indeed should be a primary objective of waste storage and disposal
programs. Any potential risks should also be no greater than those
acceptable to the producers, and preferably should be less in view of
the unavoidably greater uncertainties in risk estimation for the long-
term.
Risk Determination
The potential to produce adverse health effects is directly related
to the total amount of a given radioactive material in a location, the
relative concentration of radionuclides in the waste, their availability
for exposure, and their respective radiotoxicities. Also, the timeframe
i
for concern with radioactive wastes is determined by the half-lives of
the various radionuclides; thus their availability is dependent upon the
time they are contained. These exposure-temporal relationships and the
mode of control establish whether potential effects are acute (promptly
observable physical changes) or chronic (potential increase in cancer
rate, genetic disorders, etc.) and whether they occur over short or long
periods or both. Each of these is important to decisions on the degree
of control imposed for any radioactive waste; thus, an estimate of the
type and amount of exposure over time is basic to risk determination for
radioactive wastes.
The degree of risk that the producing generation passes on to the
future represents an important legacy of radioactive wastes. This
transference involves a moral judgment of responsibility, including the
length of time for which responsibility extends into the future. An
ethical basis for decisions regarding risk transference is needed not
only for philosophical reasons, but also for the practical purpose of
17
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implementing evaluation techniques such as cost-effectiveness and risk-
cost analyses. Unfortunately, society has not established clear
approaches for dealing with the imposition of such risks far into the
future.
Once it is accepted that the waste producing society is responsible
to provide environmental protection and limitation of risk for future
populations, it still remains to be decided how far into the future
responsibility should extend. The implications of such a decision are
not purely philosophical, however. One of the bases upon which
alternate waste storage and disposal systems would be compared, and with
respect to which judgments of acceptability of technology will be made,
is their associated risks. The farther into the future the
responsibility extends the greater will be the number of people to be
protected, and, it may be supposed, the greater the justification for
additional measures of control.
For long-lived radioactive materials such as 1-129, environmental
impact calculations may be estimated over indeterminately long times.
Although there is certainly a need to evaluate the long-term impacts of
waste storage and disposal decisions, there are serious and intrinsic
practical limitations to the performance of such evaluations.
Assumptions regarding population sizes, future food and water supplies,
and the effectiveness of medical interventions become purely speculative
when performed for periods of thousands to-millions of years, and
therefore provide little, if any, basis for waste disposal evaluations.
These circumstances argue for some practical time interval upon
which to base health effect estimates to future people during which some
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meaningful representation of the potential health risk may be achieved.
Selection of this time interval is, of course, arbitrary, but two
authors (Schiager, 1977 and Rochlin, 1977a) who have examined the
question have suggested that future social conditions beyond a few
hundred years were not sufficiently predictable to be relied upon.
However, because of the long term duration of the potential risk
involved, it appears reasonable to use a conservative approach and
stretch to its outer limits the period of time during which
extrapolation of current trends and expectations may make some sense.
Population trend estimates break down after a few hundred years, but the
physical parameters of source terms, environmental transport models, and
geological parameters may be reasonably predictable for a few thousand
years. A good balance between these would suggest that about 1,000
years is a reasonable time for such estimates.
Risk estimates performed for more than 1,000 years would probably
not influence the degree to which available waste management systems
would be required, even if improvements in basic scientific knowledge
were to reduce the inherent uncertainties after a thousand years or so.
Some general cases may be exceptional such as transport of some
transuranics, 1-129, or C-14, and general estimates of long-term effects
on the environment and public health beyond 1,000 years may be
reasonable for an assumed population and release time. In such
circumstances it would be useful for risk estimates to be extended
beyond 1,000 years to gain general understanding of the potential risk,
especially if these determinations could influence the type of control
chosen. Also, long-term estimates may be reasonably important in
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justifying the production of new wastes containing long-lived nuclides
such as 1-129.
Consideration of controls, how they are used, and how they perform
with time is also essential to risk estimations. It is especially
important that the timeframe over which particular radioactive waste
materials remain hazardous be considered from two basic standpoints, the
performance of the control alternatives in reducing the risks over time
and the probability of any containment being breached. A range of
controls exists that are either institutionally based, technologically
imposed, or dependent on natural barriers such as geological media to
provide public health protection. These can also be used in combination
depending on the circumstances and whether imposing multiple barriers
would reduce the probability of potential impacts. The performance
level of such controls and the probability of their failure should also
be included in risk determinations. Even if wastes are of such
persistence that they can be assumed to eventually get back to the
environment, the reduction of collective dose over the period of
successful containment is very desirable.
Role of Risk Determination in Criteria
The factors discussed above make risk determination a pivotal part
of any environmental and public health protection policy for radioactive
wastes. This leads to the general conclusion that the key consideration
in deciding whether and how to store or dispose of radioactive wastes
should be based primarily on an assessment of the risk for a wide range
of relevant factors, especially the level of potential exposure, the
time involved, and levels of control. Because of the long term
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implications of many of the waste materials and the ethical
responsibility to minimize intergenerational risk transference, it is
concluded that as a limiting case the risks imposed on future
generations be no greater than those the producing generation is willing
to accept, as expressed in the public health protection standards and
policies it adopts.
Risk determinations rest on a number of key factors, especially the
total amount of waste material in a location, its persistence due to
form and concentration, the potential to enter the biosphere and produce
adverse health effects on individuals and populations, the effectiveness
of various controls imposed, and the inherent uncertainty of many of the
parameters. Risk determinations which address these factors should be
performed for at least 1000 years. General estimations for longer
periods are also appropriate for very long-lived materials where this
consideration would be an important aspect in determining the proper
disposal option for existing wastes or justifying the production of new
wastes.
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CONTROL OF RADIOACTIVE WASTE
Avoidance of potential exposure of individuals or populations due
to radioactive waste depends on the control methodology used to isolate
the material and whether the period over which control is assured is
long enough for the radiological hazards to decrease to an acceptable
level. In this respect, the ultimate goal of radioactive waste
management is total isolation of wastes from the biosphere to the degree
that this is achievable considering technical, economic, and social
factors. Control of the potential impact on humans is essential;
however, it is not in itself a totally sufficient condition because of
the trustee responsibility each generation has to succeeding ones. For
this reason, it is also necessary to prevent any unnecessary
contamination of the environment which is reasonably achievable even
though human interactions with the wastes could not be presently
- i
predicted. From these considerations, the goal for control of
radioactive wastes should be to prevent its introduction into the
biosphere over its hazardous lifetime.
Control of radioactive wastes can be provided by institutional
forms of management or by disposal. Institutional management is used
primarily to control exposure to present populations and includes the
acquisition, treatment, preparation, and storage of radioactive wastes.
The disposal of radioactive wastes, on the, other hand, presumes no such
dependence on formal institutional mechanisms to maintain isolation of
the wastes from the biosphere. Rather, disposal is achieved by placing
tne wastes in an acceptable location with no intent of recovery. In
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general, institutional management of radioactive wastes is a short term
process; disposal is a long term action.
With respect to ultimate disposal, which generally would depend on
environmental barriers, proper site selection is important to
maintaining protection of. the materials over the period of time a
radiological hazard exists. In this respect, it is desirable for sites
to provide stable isolation over time; thus, the action over time of
natural forces, such as erosion, sedimentation, and crystallization
ideally should be projected to improve environmental isolation rather
than reduce it. For example, wind may be expected to erode the covering
of an elevated shallow land burial site, but if the location of such a
site were carefully chosen, the action of wind might be expected to
»
increase earth cover with time. All other things being about the same,
this latter situation would be more desirable.
Isolation of waste materials is an important consideration for
reducing their risk-producing potential. For waste materials of low or
short term risk potential, temporary isolation may be satisfactory. For
materials which represent long term risk, the ideal goal would be
permanent isolation over the hazardous lifetime of the radionuclides
with the probability of breaching the containment or intrusion being
very low. In general, permanent isolation cannot be expected;
therefore, isolation by some form of optimized containment is usually
selected based on a balance between uncertain future risks and more
certain near-term risks. An example of optimized containment would be
the disposal of uranium mill tailings where, even though the half-life
of the material would make permanent isolation desirable, it is not
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practicable because of the large volumes of the materials involved.
Optimal containment for such wastes may require a compromise between
practically providing earth cover to reduce radon emissions and
recognition that a finite probability of intentional or accidental
intrusion could still exist.
Institutional Controls
It is reasonable to rely on institutional mechanisms to provide
control of radioactive waste for the immediate future. However, some of
the materials will remain potentially hazardous for time periods well in
excess of the several years to decades for which societies routinely lay
and execute plans. The question arises: for how long into the future
should decision-makers plan to rely on institutional controls as a
substantial means of protecting the environment and public health from
today*s radioactive waste?
As an initial step in examining this issue it is illuminating to
compare the longevities of radioactive waste and institutional
structures. Three general time scales for such comparisons have been
suggested (Schiager, 1977):
1. Human lifespans - the industrial-technological experience of
human society, as well as human life itself, occurs on a time
scale on the order of a few decades, within this period there
may be some validity to technological, economic, or
sociological projections, projections for the more distant
future, however, become increasingly uncertain and dependent
upon broader assumptions of socio-economic conditions.
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2. Political lifespans - time scale based on the recorded
history of civilizations and political entities would be on
the order of centuries to millenia. From such a perspective,
though, it is clear that the preservation of materials or
structures from past civilizations has been in spite of, not
because of, political activities. Dependence on political
stability with regard to institutional longevity would
therefore be questionable.
3. Geologic time - on the order of millions of years, the basis
for this scale is natural forces, and not social or
technological assumptions. Although the time scale is great,
extrapolations to the future on this basis may be valid
because of the relative predictability of such forces.
In another analysis of the temporal question, however, it has been
suggested that a distinction between phases of institutional control can
be made solely on the basis of predictive reliability. Three time
periods have been proposed within this framework (Rochlin, 1977b):
1. Short term - less than 50 years. It is postulated that over
this period of time, reasonably sure predictions can be made
about the stability, goals, and operation of human
institutions, as well as the degree of uncertainty in making
these projections.
2. Intermediate term - one to two hundred years. Predictions for
such time periods, based largely on extrapolation or
projection of present trends, can be made with some limited
degree of confidence. It is recognized, however, that the
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cumulative error resulting from new circumstances and
unforeseen developments over such periods can result in
radical structural and policy changes. The degree of
uncertainty in projection, therefore, increases sharply during
this period.
3. Long term - greater than one to two hundred years.
Uncertainties dominate predictive ability. For more than a
few thousand years, there is only uncertainty.
Deciding on a reasonable time for dependency on institutional
controls is essentially equivalent to estimating the shortest likely
period of institutional continuity. .It is clear that there is no
definitive scientific method for such a determination, but it is
difficult to predict the course of events from current trends for more
than several hundred years. The cumulative effect of future events and
developments may result in unforeseen radical changes in social
structures and policies. For example, the depletion of certain
resources (petroleum, for example) may adversly impact society and the
stability of its institutions in just a few decades. Although it may be
argued that there are numerous examples of public and private
institutions which have functioned for periods of much more than several
hundreds of years, there is little basis for presuming that a given
current social organization will survive for a like period of time or
that it will be aware of or have concern for radioactive wastes. The
distinction is one of perspective; historical citations are certain,
while predictions are not. The wastes in question are not only useless
but will often be in remote locations and some may be hazardous only in
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the sense of chronic exposure. Therefore, some radioactive wastes may
be easily forgotten following social discontinuities.
Clearly, institutional means of controlling radioactive wastes
should be used as supplements to other methods for as long as they are
effective and efficient. In view of the matters discussed above,
however, it does not appear to be prudent to plan waste storage and
disposal systems in which basic elements of safety rely on the
performance of human functions for more than about 100 years. This is
not to suggest that society or its institutions would not be expected to
exist beyond 100 years, only that those institutional activities such as
maintaining a controlled site boundary could not be relied upon to
protect wastes which have no artistic or other value that would make
future people want to continue to give them special care. A better
approach is warranted. The planned institutional phase could be still
shorter, of course, to allow a greater margin for error, but 100 years
of institutional continuity appears from a historical perspective to be
reasonabe. Alternate time periods could also be chosen depending on the
degree of reliance one is willing to place on technical, economic, and
social considerations.
Environmental Controls
Environmental controls are mainly represented by geological media
with physical properties that inhibit the movement of radioactive waste.
In general, they are used in conjunction with engineered barriers such
as containers or solidification in matrices to contain the materials.
Despite the fact that some engineered structures have survived intact
through the ages, others, even if comparably designed, have not. The
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key consideration for radioactive wastes is to assure environmental and
public health protection. In this lightr engineered barriers generally
can be considered only as interim measures for containment. The
physical, radiological, and chemical characteristics of the waste
largely determine the balance between the degree to which engineered or
natural barriers are used. For example, where natural barriers with
superior containment characteristics are available, the requirements for
engineered barriers may be reduced.
The type of containment utilized for storage or disposal should
provide isolation consistent with the characteristics and hazard
potential of the waste. With the basic safety requirements met, other
factors, including cost and engineering convenience, become important.
In general, however, disposal methodologies for radioactive wastes
»
should rely primarily on containment by environmental barriers,
especially if long term isolation needs to be provided. In choosing
such environmental media it is important to select those that will
reduce to the greatest extent possible the effect of potential
interaction of the wastes with water, since water transport is probably
the major pathway for long term exposure of humans.
Control Requirements
The use of controls is basic to reducing potential risk of acute
and chronic exposures from radioactive wastes to a degree that they
would be acceptable to society for both short and long time periods. A
range of institutional, engineered, and natural barrier controls can be
used to isolate radioactive waste materials from humans, depending on
their nature and form. Such controls should be applied either singly or
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in combination with a goal of obtaining total isolation of the wastes
from the biosphere over their hazardous lifetime. When institutional
control is the method chosen to provide environmental protection, no
restrictions should be required on customary uses of associated land
areas and surface and ground waters after 100 years; for radioactive
wastes that would require protection beyond 100 years, as many physical
and natural barriers as is practicable should be used to minimize
environmental impact if one or more fails or is accidentally or
intentionally breached. Also, environmental isolation media should be
selected that reduce the effect of potential interaction with water to
the greatest extent possible and for which natural forces such as
erosion, sedimentation, and crystallization will enhance, rather than
reduce, environmental isolation.
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RISK PERSPECTIVES
The term risk expresses a general concept encompassing both the
probability of occurrence of adverse effects and their severity (ICRP,
1977; Otway 8 Pahner, 1976) The concept may be used (Lowrance, 1976) as
a measure of the degree of safety, since it is often not possible to
eliminate all risk associated with an otherwise beneficial activity, a
judgment of "how safe is safe enough", under the circumstances, must be
made. This is equivalent to deciding on a level above which the risk is
unacceptable.
A society that is dependent on high technology necessarily abandons
the concept of zero risk (Lapp, 1973). Individuals, consciously or
unconsciously, make daily choices on a voluntary (or at least perceived
to be voluntary) basis which lead to the acceptance of risks: how fast
to drive, how much to smoke, whether or not to remain overweight, and so
on. Governments have been delegated authority to allow levels of
involuntary risks in the form of standards and regulations. Allowance
of involuntary risks by government decisions requires that the
considerations and assumptions upon which they are based be part of the
public record. This section discusses factors basic to such
determinations for radioactive wastes.
Radiation effects on health at low doses and dose rates are
presumed to have a linear dose-response relationship for public health
protection purposes. This implies that any radiation dose, however
small, conveys a proportionate chance of producing a genetic alteration
or a somatic health effect such as cancer. Neither of these effects is
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certain to occur in an individual exposed below acute levels, and
genetic effects in .any case can materialize only in progeny. Within
this context, therefore, the appropriate goal is to avoid any increment
of radiation in the general environment due to radioactive waste.
Because total avoidance of exposure may be very costly or difficult to
guarantee, people might choose to forego the benefits of the waste-
producing activities. Therefore, it is desirable to establish some
guidelines to determine, when and if it appears to be necessary, levels
of risk other than zero that may be permitted.
Methods for Examining Risks
There is no established rigorous procedure to determine levels of
risk that society would accept for a given activity or enterprise
(Otway, 1977). Several approaches have been proposed, however, as
either complete or partial bases for regulatory actions. Although none
of these methods provides all the elements that should be present in
such a basis, the following discussion shows that a framework for
decision-making can be established to which elements of each method may
contribute some insight.
It has been suggested (Starr, 1969, 1972), for example, that
analysis of risk acceptance experiences could lead to the establishment
of relationships between risk and associated benefits for broad
categories of societal activities. A regulatory body could then
classify the nature of a particular hazard, and use the relations to
guide a determination of the corresponding acceptable level of risk.
The method has a technical weakness, in that the postulated
relationships appear to be very difficult to develop from the available
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data (Otway, Cohen, 1975). Perhaps of greater significance is the
inherent deficiency that, even if these relations were quantitatively
well determined, they would not describe optimal decisions, but only
circumstantial ones. A further problem arises in applying the method to
radioactive wastes because of the long-term persistence of the potential
hazards they present, which implies that most of the people potentially
at risk are not yet born. Current and future attitudes towards risks
may differ significantly from those of even the recent past, especially
for a technologic situation such as that of radioactive waste, whose
impact on public consciousness has been growing. It is clear, then,
that considerable caution is warranted when attempting to apply past
experiences with other hazards to the determination of current and
future levels of risks associated with radioactive wastes.
Another potential guide to the determination of levels of risks to
be restricted is comparison with the involuntary risks due to exposure
to the natural radiation background. It has been concluded that
"...exposure to manmade radiation below the level of background
radiation will produce additional effects that are less in quantity and
no different in kind from those which man has experienced and has been
able to tolerate throughout his history" (BEIR, 1972). This finding
refers explicitly to genetic risks to a population and may be less
applicable to somatic injuries to individuals. Acceptance of the linear
nonthreshold hypothesis means that there can be no logical permissible
lower limit based on dose alone.
Alsor comparisons of risks associated with radioactive waste to
more commonly understood societal risks can have considerable
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communication value, but are of very limited usefulness as a determinant
of permissible risk levels. For the reasons discussed above, and
others, it is not clear that risk-benefit relations for past experience
with other activities are necessarily pertinent to radioactive wastes.
Therefore, even if such relations were quantitatively well determined,
the logical basis for their applicability to this specific purpose would
remain to be established.
An alternate approach which could guide the determination of
acceptable levels of risk involves a variety of methods of assessing the
attitudes and opinions of the general public. The participants at the
EPA workshop defined "general public" to mean all members of society
except those government officials with responsibilities regarding
radioactive waste. Methods of assessment are the formal sampling and
analysis procedures of sociology and psychology, which are designed to
elucidate the opinions or the attitudes of representative population
samples, or the less formal ones of opinion gathering in public forum,
and by examination of available literature.
Utilizing psychometric techniques based on responses to
questionnaires has only recently been applied to the problem of
determining acceptable levels of risk, and is not yet available as an
established procedure. Clearly, to be most useful to the determination
of policy, such studies of attitude and opinion should satisfy high
standards of fairness of execution and be representative of the entire
society. Even if a definitive study of people's expressed preferences
were done, it could serve as an adequate guide to regulatory action only
if present opinions were accepted as a basis for decision. However,
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people do not consistently act in accordance with their expressed
preferences. Another problem is that planning guidelines logically
would have to change with changes in public opinion, possibly resulting
in social chaos (Slovic, 1976). Deciding relatively narrow issues, such
as the acceptability of levels of risk for waste management systems, by
public referendum as has been suggested (EPA, 1977b) suffers from the
same serious deficiency and has severe problems of implementation.
If polling and psychometric techniques are incapable of providing
the basis for environmental protection standards, they nevertheless
offer helpful insight into the elements of risk that most significantly
affect public acceptability. Attitude measurements are also capable of
revealing differences in perception among groups of respondents. For
example, commenting on a study of attitudes and values with regard to
nuclear waste (Maynard, et al», 1976), one analyst found "...fairly
consistent evidence that respondents who are representative of planners
and decision makers differ considerably on many key issues from
respondents who were more representative of the general public" (Slovic,
1976).
It could of course be argued that planners and decision makers are
better informed than the general public, on the average, and could thus
be expected to have differing views. However, when the differences
concern basic attitudes and values, the decision makers should be
especially careful and deliberate to assure that they receive and give
full consideration to all points of view. Although no simple
prescription for achieving this can be specified, open and timely
opportunities for public participation in the decision-making process
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would play a beneficial role, particularly at early stages (Campbell,
1976, Kuhlman, 1976).
The above discussion indicates that determining levels of risk that
may be acceptable to society due to radioactive waste could not be
accomplished with current methodologies solely by:
1. reference to past risk and benefit relations for activities
and situations not related to radioactive wastes;
2. comparisons with risk due to the natural radiation background
or commonly understood risks not related to radiation; or
3. assessment of public attitudes and opinions.
The absence of any single completely satisfactory procedure has not
and should not prevent effective regulation of radiation exposure. Thus
a framework for decision-making has evolved, in which the circumstances
corresponding to each source of exposure are examined, and guidelines
and regulations then developed which are intended to assure that any
allowed exposures are reasonable, under the circumstances. The guiding
principles of this approach to radiation protection are: a) that any
allowed exposures or releases of radioactive material be associated with
some justifying benefit, b) that exposures be kept as low as is
reasonable in view of technical, economic, and social considerations, c)
the inequitable distribution of risks among individuals in a given
population should be minimized, and d) that certain stated levels of
exposures of the general population are not to be exceeded, virtually
without regard to circumstances. These general principles are
subscribed to by Federal entities with responsibility in this area (EPA
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1976b) as well as by the major quasi-official advisory bodies on
radiation protection.
Attitudes Toward Assumption of Risks
Humans, by their nature, are risk-aversive, i.e. they normally seek
to minimize risks unless the assumption of increased risk is compensated
for by apparent benefits, or it is so low they do not particularly care
about it. It is clear as well that the bearer's evaluation of risk, and
hence its acceptability, varies according to factors other than the
quantitatively expressed consequences and their probability of
occurrence. These factors and their evaluation may also be significant
elements of regulatory decisions for radioactive wastes, and may provide
a social or psychological basis for accepting different levels of risk
for wastes having different risk characteristics, even apart from
technical or economic considerations.
Many authors have discussed these risk evaluation factors
(Lowrance; Rowe; Otway) , but only very preliminary attempts to associate
numerical weights to them have been undertaken, and these efforts are
yet controversial. Broadly speaking, however, risks appear to be more
acceptable if: they are assumed voluntarily; the effects are delayed
rather than prompt; they are not easily avoidable; the consequences are
common ones and not highly dreaded, or are reversible; they are
equitably distributed; and if the risk-taker is confident that the
situation is well understood. Risks of comparable magnitude may be far
less willingly assumed if they are associated with other
characteristics. Therefore, when the adequacy of a given level of
control of a particular form of radioactive waste is being evaluated, it
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is appropriate to consider both quantitative and qualitative
characteristics pf the risk. As with other aspects of the regulatory
process, however, the scope of the considerations and the bases for
decisions should be fully documented.
Risks for Naturally Radioactive Wastes
Radioactive wastes containing naturally occurring radioactivity are
materials which all people encounter in nature to varying degrees, and
for which average doses as components of natural background radiation
are known. The excavation and processing of the materials makes them
more accessible to humans, but even in the undisturbed state they
contribute some level of radioactivity to the general environment.
Since the parent isotopes of much of this natural radioactivity have
half-lives of billions of years, natural processes such as erosion,
leaching, glaciation, and tectonism might ultimately release into the
biosphere most of those naturally occurring radionuclides currently
trapped in the earth's crust. It is therefore not clear whether mining
them has any effect other than releasing them to the biosphere sooner
and more surely. Whatever the natural state may be, it is reasonable to
suppose it to be stable enough to assure against substantial increases
in the level of background radiation due to naturally occurring
radionuclides for some thousands of years. A condition for
acceptability of the control of such materials as wastes would be to
prevent individual or population exposures in excess of background
levels which already exist at the undisturbed site.
For time periods considerably longer than thousands of years,
requirements for these naturally occurring materials are less obvious,
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since natural processes would be expected to release the radioactivity
eventually. Therefore, while considerable efforts are justified in
attempting to provide protection for much longer than thousands of
years, a disposal method for naturally-radioactive wastes which does not
appear capable of achieving this will not necessarily be unacceptable.
Naturally-radioactive wastes which are substantially modified from
their natural state, such as discarded radium sources, are essentially
human-produced materials. The considerations discussed above are
clearly not applicable to these materials.
Risks for Human-Produced Radioactive Waste
Setting long-term disposal objectives for human-produced wastes is
especially problematic in view of the difficulty in accurately
forecasting conditions and events far into the future. For virtually
any means of disposal on earth, even though designed not to release the
waste, there always will be a chance of failure over a very long time.
It is therefore necessary to decide upon an allowable probability that a
given set of consequences may occur as a result of radioactive waste
disposal, even though these consequences may be unintended. Some useful
perspectives on these long-term risks of chronic exposure may be gained
through certain comparisons.
The first observation, in this regard, is that quantities of many
of the same radionuclides present in such radioactive wastes have
already been dispersed in the biosphere by explosions of nuclear
weapons. Additional inventories of the same or comparable radionuclides
are contributed by natural processes, i.e. those which occur without
human intervention. Some appreciation of the long-term significance of
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the potential effects of human-produced radioactive wastes may be gained
by comparison of the concentrations of long-term radionuclides in air,
soil, and water with concentrations due to other sources. In order to
assure limitation of the consequences due to the waste, and to allow for
continued use of radioactivity in the future, it is clearly desirable
that these waste concentrations be small compared to those of the same
or similarly hazardous nuclides which already exist. Furthermore, any
eventual chronic radiation exposures to any organ of the body due to
waste should be small compared to exposure due to natural background
radiation.
These conclusions are proposed as necessary conditions to be
satisfied even if attempts to isolate long-lived waste should fail over
a very long period of time. Within these conditions, the levels of risk
which are sufficiently low to be acceptable must be determined by
examination of all the technical, economic, and social factors
pertaining to a specific form and quantity of material.
Low Probability-High Consequence Events
A few kinds of radioactive wastes are capable of producing severe
environmental and public health impacts on at least a regional scale if
they were dispersed, such as large quantities of nuclear reactor fuel
reprocessing wastes or the spent fuel itself. This potential hazard is
intrinsic to the material although it generally declines with time in
accordance with the laws of radioactive decay. So long as the
radioactivity exists, however, the control system will be required to
reduce to very low levels the probability of occurrence of high
consequence events. For these potentially high consequence events, as
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for others, the level of protection that should be considered adequate
is still a controversial matter.
It has already been noted that there is no definitive basis for
deciding acceptable levels of risk. For events with high consequences,
however, it is possible to achieve useful perspectives on the waste
management requirements by means of certain comparisons. The first
observation is that, since the waste itself serves no useful purpose,
its management system should provide greater security against a major
disaster than is acceptable for dams, dikes, large stores of toxic or
explosive chemicals, and other beneficial situations having high
potential hazards. This provides reasonable guidance for a necessary
constraint on radioactive waste, but it certainly does not define
conditions which are sufficient.
A second useful observation is that, as a general rule, it will not
be fruitful to attempt to reduce the probability of already highly
improbable modes of disrupting waste which, if they occurred, would
independently produce consequences hundreds of times greater than those
attributable to the waste. This implies that undue consideration need
not be devoted to designing against major disruptions of waste by
massive meteorite impacts, nuclear war, ice ages, or comparable
cataclysms. This condition provides guidance regarding a sufficient
degree of protection, but only for a certain category of disruptions.
In applying this condition, however, both the immediate and the long-
term consequences of the released radioactivity should be considered.
Since no mechanism can be prescribed for judging the adequate degree of
protection against a disaster associated with radioactive waste, public
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policy decisions should be guided by the perspectives and the necessary
and sufficient conditions described above.
Perspectives for Restricting Risks
No prescription can be stated for judging an adequate degree of
protection for radioactive wastes independent of circumstances. A
number of conditions are generally regarded as basic to sound public
health practice: a) any allowed exposures to or releases of radioactive
materials should be associated with some justifying benefit; b)
exposures should be kept as low as is reasonable to achieve in view of
technical, economic, and social considerations; and c) inequitable
distribution of risks among individuals in a given population should be
minimized, and d) certain stated levels of exposures of the general
population are not to be exceeded, virtually without regard to
circumstances.
Naturally-radioactive wastes should be disposed of in a manner that
will prevent for thousands of years individual or population radiation
exposures in excess of those that natural processes might produce if the
material had remained undisturbed by people. While considerable efforts
may be justified to provide protection for much longer than thousands of
years, a disposal method which appears incapable of achieving this will
not necessarily be unacceptable. Disposal systems for human-produced
radioactive wastes should isolate these materials from humans until
their radioactivity has essentially disappeared. This may not be
possible to achieve for very long-lived radionuclides.
Radioactive wastes should be provided greater security against
major adverse consequences of failure than is acceptable for dams,
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dikes, toxic chemicals, and other generally useful situations having
high potential hazards. Little useful purpose would be served by undue
consideration for protection of radioactive wastes against cataclysmic
disruptions which, if they should occur, would have consequences greatly
exceeding any that are attributable to the waste.
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OTHER CONSIDERATIONS FOR RADIOACTIVE WASTE
A number of other subjects pertinent to protection of the public
from radioactive wastes were discussed in the EPA workshops. Three
subjects that received a good deal of attention were considerations for
monitoring, retrievability, and passive communication of the nature of
the hazard to future generations that could be impacted, tn general, it
was determined that, while each is desirable in the conventional sense
for dealing with radiological hazards, their application might undermine
the goal of providing permanent isolation for wastes. It is difficult
to maintain retrievability or conduct a monitoring program without
compromising the ability to provide isolation; communication, even
though of value, cannot appropriately be depended on as a form of
control. Nonetheless, each may, in certain cases, enhance overall
protection from wastes, and in such cases it would be prudent to use
them.
Monitoring
During the operational phase of a waste facility, offsite
monitoring of environmental radiation may be required in order to:
a. extend knowledge of baselines of radiation in the general
environment near the facility
b. verify that any effects produced by releases from the site by
any pathways are and may be expected to remain within acceptable levels
c. provide information in the event of unanticipated releases
which will be useful in assessing the extent of environmental
contamination and will allow for timely consideration of remedies.
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The nature and extent of offsite environmental monitoring during
operation of a waste facility would depend on the form and potential
hazard of the waste material, the character of the operations performed
upon them, the types of containment barriers used, and the mechanisms by
which these barriers might be breached. However, all waste facilities -
should be designed in such a manner that monitoring for more than 100
years would not be required as a basic element of environmental
protection.
Retrievability
A waste management system provides for retrievability of the waste
if it incorporates a designed provision for recovery of the waste
materials. The necessity of such a feature is obvious for any phase of
the management system prior to disposal.
The principal reasons in favor of retrievable waste management
systems are:
a. They offer an opportunity for correction of unanticipated
failures of the isolation methodology.
b. They may allow future societies the prerogative of applying
advanced knowledge to improve upon earlier efforts in waste disposal.
c. They permit recovery of the waste as a resource, if uses for
it should develop in the future.
The disadvantage of retrievability is that it necessarily increases
the probability that the waste will not remain isolated from humans.
Systems with designed provisions for recovery of the radioactive
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materials in general cannot be as secure from intrusion as those *hich
lack such features.
It should be recognized that the incorporation of retrievability
itself injects a degree of uncertainty since it increases accessibility.
In justifying its application, a tradeoff of these uncertainties is
necessary, with the maintenance of an acceptable level of safety
remaining the major consideration. Although conclusions regarding the
desirability of a retrievable design may vary with the features of
individual disposal systems, certain general considerations apply to all
cases. The most important of these is the effect that provisions for
retrieval would have on the integrity, and thereby the safety, of an
otherwise adequate disposal technology. For example, access tunnels
(however sealed) and monitoring probes within an underground disposal
site would, to a certain extent, compromise the integrity of the natural
barriers. If retrievability is to be justified, this lessened degree of
safety should be compensated for by other advantages. One case where
retrievability may well be justified as enhancing protection is the
packaging of materials for near surface disposal so they may be exhumed
early if circumstances make such action desirable. In this case, the
packaging would not be expected to make the materials more available for
environmental release.
•
It would appear that, in general, retrievable disposal systems
should be avoided. However, the possibility remains that the
characteristics of some particular waste and its disposal technology may
be such that retrievability would be judged to offer a net advantage.
Future Identification
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A means of disposal may satisfy the environmental and public health
protection criteria, but the possibility may remain that, after the
period during which institutional controls can be relied on, an
accidental or intentional disturbance of the disposed materials could
present a hazardous situation to an individual or a population. Where
this possibility exists, it may be determined that such disturbances may
be prevented by the use of passive means of communicating the nature of
the hazard to future people. The efficacy of this approach should be
evaluated for each source and its corresponding disposal circumstances.
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SUMMARY AND RECOMMENDATIONS
Although most waste materials contain some radioactivity, their
designation as radioactive wastes is dependent on their having no
perceived value, their origin, and whether the materials pose
undesirable exposure circumstances. Radioactive wastes can for the most
part be grouped into two broad categories: discrete sources of human-
produced and naturally-occurring radioactive materials, and diffuse
naturally-occurring radioactive materials such as mining residues.
Included in this characterization are all radionuclides retained because
of regulatory restrictions on their release to the environment.
\ The overriding consideration for establishing a level of control
required for the storage and disposal of radioactive wastes involves
judgments on the amount and rate of exposure to humans and environmental
contamination that are to be accepted. An essential element of such
judgments is the estimation of health effects which would result from
acute and chronic exposure of individuals and populations at various
levels of possible control, recognizing the various types, forms, and
physical characteristics of wastes.\ Although controlling the potential
impact on humans is essential, it is in itself not a totally sufficient
condition because of the trustee responsibility each generation has to
succeeding ones. For this reason, it is also essential to prevent any
unnecessary contamination of the environment which is reasonably
achievable even though human interactions with the wastes in
concentrated form could not be presently predicted. From these
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considerations, the goal for control of radioactive wastes should be to
prevent its introduction into the biosphere over its hazardous lifetime.
Predictions of risks are uncertain due to a number of factors. For
practical purposes such determinations would not generally be
dependable, informative, and therefore not very useful for time periods
extending much beyond 1000 years, although certain general
considerations may be useful for certain radionuclides beyond this
period. Decisions on the levels of risk to be controlled are dependent,
however, on such determinations and on a range of technical, economic,
and social considerations. Radiation protection policies need to
reflect this framework of factors; the type and degree of controls will
be determined accordingly.
The long-term nature of some radioactive wastes requires decisions
on risk transference and the extent to which institutions may be
depended upon to provide public health and environmental protection.
Although it is a desirable goal to insure that risks to future
generations will be no more than those to present generations due to the
persistence of the waste, it is questionable whether current techniques
can provide this assurance. It is obvious, however, that unplanned
events resulting in population exposure are more probable subsequent to
lapse of institutional care by virtue of eventual degradation of the
barriers which provide isolation through natural and, possibly, human
activities. It would therefore be reasonable, in the face of these
uncertainties, to recommend equity of risk transference as a goal to be
achieved. There are practical limitations to relying on institutions
alone to provide the required control beyond about 100 years.
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Therefore, environmental and public health protection for the
storage and disposal of radioactive wastes involves a number of factors.
Among these are: (1) a clear distinction of which radioactive materials
are properly considered to be radioactive wastes, (2) assessment of the
potential health risk of the various wastes over appropriate time
periods representative of their possible impact and concern for future
generations, (3) the long-term implications and the persistence of risk
in determining the ability of institutions to maintain protection of
both humans and the general environment, (4) isolation of the waste by
the application of engineering controls and environmental barriers to
minimize probability of re-entry to the environment within time periods
of concern, (5) considerations of risks at a given level of control and
their acceptability, and (6) other considerations for operational
controls, retrievability, monitoring, and the transfer of information to
succeeding generations to aid in providing environmental protection.
Initial Formulations of Criteria
The considerations presented above have been addressed by the EPA
in order to arrive at an initial formulation of criteria for public
review and discussion. These formulations, which are yet to be proposed
in formal language in the Federal Register, are believed to represent
the major areas for which criteria are indicated and the substance of
the criteria that will be issued. Following response to these initial
criteria by the public, they will be formally proposed as guides for
developing standards to protect the environment and the public due to
the storage and disposal of radioactive wastes.
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Initial formulations of criteria for waste materials, risks and
their acceptability, and controls are recommended as follows:
Radioactive Waste Materials
1. Radioactive material which has no designated resource or
product value should be considered radioactive waste requiring
environmental protection if it: a) is produced by nuclear fission or
activation, b) contains naturally-occurring radioactive material that if
disposed into the biosphere would increase exposure above that normally
occurring in pathways due to the natural state of the area, or c) is
restricted from routine release to the biosphere; examples* of such
radioactive waste materials that should be subject to environmental
protection requirements are:
- All radioactive materials associated with the operation and
decommissioning of nuclear reactors for either military or
other purposes and the supporting fuel cycles, including spent
fuel, fuel reprocessing wastes, and radionuclides removed from
effluents.
Artificially produced radioisotopes for medical, industrial,
and research use, including discrete radium sources, and waste
materials contaminated with them.
The naturally radioactive residues of uranium and phosphate
ore recovery and associated milling and conversion operations.
*The Agency has determined that the materials listed should be subject
to environmental protection criteria even though some such materials may
not upon examination require any control above that they would receive
as ordinary wastes; other radioactive materials may also be included if
they are found to satisfy similar considerations.
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Risk and Risk Acceptability
2. Environmental protection determinations for radioactive wastes
should be based primarily on an assessment of risk to individuals and
populations; such assessments should be based on examination of at least
the following factors:
a. The total amount of radioactive waste in a location and its
persistence due to its physical form and the lifetime and
concentration of the radionuclides contained in the wastes;
b. The potential adverse health effects on human individuals and
populations for a reasonable range of future population sizes
and distributions and uses of land, air, water, and mineral
resources for one thousand years, and general estimates of
adverse effects for longer periods for materials having
potential impact beyond one thousand years when such
estimations could determine the selection of a more effective
disposal option.
c. The projected effectiveness of alternative methods of
institutional, engineered, and natural barrier controls used
singly or in combination; and,
d. The probabilities of releases of radioactive materials to the
general environment due to disruption of the waste through
failures of natural or engineered barriers, loss of
institutional controls, or intrusion; and
e. The uncertainties in the risk assessments and the models used
for their determination.
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3. Risks due to radioactive waste should be deemed unacceptable
unless it is justified that more complete isolation of such wastes is
unreasonable in view of technical, economic, and social considerations;
any potential risks to a future generation should be no greater than
those accepted by the current generation. Any potential risk for
radioactive waste storage or disposal at a particular level of control
should be considered unacceptable if:
a. any exposure having a high probability of occurrence could
result in more than a chronic risk which could not be further
reduced by reasonable controls,
b. the levels of any chronic risks are not less than those for
comparable high probability circumstances acceptable to
society, or
c. high consequence events do not have a probability of
occurrence less than that for comparable high consequence
events accepted by society for similar productive
technologies.
Control of Radioactive Waste
4. Controls should be applied with a goal of isolating radioactive
wastes from the biosphere over their hazardous lifetime to protect
humans and minimize unnecessary contamination of the environment. When
institutional control is the.method chosen to provide environmental
protection of radioactive wastes, no restrictions on customary uses of
associated land areas and surface and ground waters due to any residual
risks should be required after 100 years; radioactive wastes that would
require protection beyond 100 years should not be isolated by
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institutional means, but rather by as many physical and natural barriers
as is practicable to minimize environmental impact if one or more fails
or is accidentally or intentionally breached.
5. Locations for radioactive waste disposal should be chosen
whenever practicable such that the action over time of natural forces
such as erosion, sedimentation, and crystallization could be projected
to improve, rather than reduce, environmental isolation; if used to
isolate wastes, geological media should reduce the effect of potential
*
interaction of the waste with water to the greatest extent possible.
6. Certain additional procedures and techniques should also be
applied to waste disposal systems which otherwise satisfy these criteria
if they provide a net improvement in environmental and public health
protection; among these are:
a. monitoring prior to completion of disposal to determine for
I
timely correction any unanticipated effects which could result
in releases of radioactivity to the general environment,
b. procedures or techniques designed to enhance the
retrievability of the waste, and
c. passive methods of communicating to future people the
potential hazards which could result from an accidental or
intentional disturbance of radioactive wastes.
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GLOSSARY
barrier - any medium which stops or significantly retards the movement
of emplaced radioactive materials
engineered barrier - a barrier of human manufacture, sucn as a
container or solidified waste matrix
natural barrier - a barrier consisting of a geological or other
natural medium
disposal of radioactive waste - the placement of radioactive waste with
no intent of recovery
facility, waste management - the structure and/or the location at which
some waste management activity is performed or occurs
general environment - the total terrestrial, atmospheric, and aquatic
environments outside sites upon which any radioactive waste management
activity is conducted (see also; site, waste management)
institutional controls - activities, devices, combinations of each which
involve the performance of functions by human beings to limit contact
between the waste and the human environment
isolation, radioactive waste - the placement of radioactive waste such
that contact between the waste and the human environment will be highly
unlikely for a chosen period of time
monitoring - a program to measure the quantity and type of discharges or
releases from a waste management facility or to measure changes in
physical, chemical, or biological characteristics of the site and its
surrounding region
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retrievability - a designed capability to recover waste from an emplaced
location, whether temporary or permanent
risk - a general concept encompassing the probability and the severity
of adverse effects
site, waste management - any location that is contained within a
boundary across which transit by the members of the general public is
controlled because of the operation or presence of a waste management
facility
storage, radioactive waste - retention of radioactive waste at
facilities with designed provisions for recovery
waste management - a generic term describing the range of activities for
dealing with radioactive waste, including preparation, storage, and
disposal
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APPENDIX A
Summary of Workshop Findings
Issues pertaining to the establishment of these criteria were
discussed in two informal workshops held by EPA in Reston, Virginia
(February 3-5, 1977) and Albuquerque, New Mexico (April 12-14, 1977).
While discussion of various problems inherent in radioactive waste
management elicited a diversity of responses from the workshop
participants, a general consensus was reached in many areas. In
formulating the initial criteria in this Background Report, EPA took
into account the major items recommended by the Workshops which can be
summarized as follows:
1. Radioactive waste criteria should not address disposal of
high-level wastes alone but should also address other types of
radioactive wastes and other methods of waste management such as storage
of wastes. In particular, clear definitions should exist for
radioactive wastes and waste management.
2. Participants in the Reston Workshop felt that criteria may
have to be categorized based on such factors as concentration, relative
hazard, and the waste form and/or disposal techniques; however,
discussion at the Albuquerque Workshop raised doubts concerning the
feasibility of this approach, due to-the disparate characteristics of
the various waste types. It was generally concluded by both Workshops
that it is desirable for the criteria to address radiation exposure.
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regardless of its source, which may preclude the necessity of
distinguishing between waste types.
3. It was generally agreed at the Albuquerque Workshop that both
maximum individual dose and population dose limitations should be
considered, and that natural background radiation levels are the
appropriate lower limit below which efforts to decontaminate an area
would not be justifiable.
4. Concerning risk acceptability, participants in both workshops
felt strongly that the criteria should be based on a consideration of
risk and its acceptability, and that, while calculated risk is
important, perceived risk must also be taken into account. Some
participants felt that risks associated with radioactive wastes should
be placed in the context of other risks from similar pollutants or
environmental hazards. The intention here would be not to relax
controls of radioactive waste but to improve the controls of other
environmental hazards.
5. Considerable discussion about the concept of "zero" release
and "zero" dose took place at Reston. Some participants felt these
goals to be very desirable. Others felt strongly that zero should not
appear in a criterion or standard since it is impossible to attain.
Most participants felt that criteria should specify levels of control
which isolate wastes from the biosphere for the period of concern.
6. Many participants in both workshops supported the premise that
wastes be managed such that risks to future generations be no greater
than the present generation is willing to accept for itself. The
majority of the Reston participants believed that cost is of secondary
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importance to safety although the economic aspect should not be ignored.
Many felt that, in considering long-term safety, an unending time period
should be employed. Some participants in Albuquerque emphasized that
since this generation has little control over the stability of future
societal institutions, the criteria should address a specified future
time.
7. A consensus was reached at Albuquerque that all unplanned
events and accidents should be considered by EPA in developing criteria
and setting standards. No consensus was reached, however, on how this
consideration should be addressed.
8. A clear consensus was voiced at Reston that isolation of high-
level radwastes in suitable geological formations is desirable.
Monitoring should be performed and assumptions on isolation and storage
techniques should be checked while the site receives waste. While the
Albuquerque participants felt that bases for retrievability existed,
this option should only be considered when safety will not be
compromised.
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