ML20029B293
| ML20029B293 | |
| Person / Time | |
|---|---|
| Issue date: | 02/20/1991 |
| From: | Carr K NRC COMMISSION (OCM) |
| To: | Reilly W ENVIRONMENTAL PROTECTION AGENCY |
| References | |
| NACNUCLE, NUDOCS 9103070013 | |
| Download: ML20029B293 (1) | |
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february 20, 1991 CHAIRMAN The Honorable William K. Reilly Administrator U. S. Environmental Protection Agency Washington, D. C.
20460
Dear Mg,
I am providing the following two reports prepared by the Nuclear Regulatory Commission's Advisory Committee on Nuclear Waste (ACNW) in response to inquiries from Mr. Floyd L. Galpin, Office of Radiation Programs, OAR, regarding the basis for several ACNW recommendations in a number of previous reports:
o Guidance On Limits On Dosos and Risks lo Individual Members of the Population, and o
Stringency Of U.S Environmental Protection Agency High-Level Radioactive Waste Repository Standards Both of these reports address concerns regarding the methodology used and proposed limits in the draf t version of the Environmental Protection Agency's high-level radioactive waste repository standards, it should be noted that these reports represent the opinions of the ACNW and not necessarily those of the Commission or its staff.
It should also be noted that it is standard practice for ACNW reports and documents to oc made available to the public and placed in our Public Document Room (PDR).
In keeping with this practice, the enclosed reports have already been sent to the PDR.
Sincerely, u
Kenneth M. Ca -
Enclosures:
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% e..,+y January 29, 1991 The Honorable Kenneth M. Carr-Chairman U.S. Nuclear Regulatory Commission Washington, D.
C.
20555 Dear Chairman Carr
SUBJECT:
GUIDANCE ON LIMITS ON DOSES AND RISKS TO INDIVIDUAL MEMBERS OF THE POPULATION i
During the 25th meeting of the Advisory Committee on Nuclear Waste (ACNW), held on October 24 and 25, 1990, Mr. Floyd L.
- Galpin, Chief, Waste Management Standards Branch, Office of Radiation Programs,- U.S.
Environmental Protection Agency (EPA), requested that the ACNW provide the bases for the recommendation, made in several of our earlier reports to
- you, that EPA consider incorporating into its high-level radioactive vaste repository standards some guidance on limits for doses and risks to individual members of the general population.
The foundations-for our position are outlined in' the recommendations of the International Commission on Radiological Protection (ICRP), the International Atomic Energy Agent y (IAEA) and the so-called " NORDIC" report.
As will be noted, all three of these groups endorse the use of individual dose and risk limits in-the development of standards for a high-level radioactive vaste repository.
This approach has also been endorsed by the Board on Radioactive Waste Management, National Research Council.
The principal comments and/or recommendations of these organizations are summarized below.
1.
Recommendations of the ICRP The basic principles on this subject, as recommended by the ICRP, are presented in their report on " Radiation Protection Principlea for the Disposal of Solid Radioactive Waste,"
published in.1985.
In this report, the ICRP separates the releases from a repository into two categories:
(a) those that are gradual and lead to normal releases that are reasonably predictable in terms of estimates of their exposure pattern in space and time; and (b) those that are not gradual and have to be thought of as probabilistic.
Included in the latter category are releases that might occur as a result of seismic and tectonic phenomena.
(Paragraphs 28 and 29, Reference 1.)
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The Honorable }enneth M. Carr 2
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for releases in the first category (i.e.,
normal releases) the ICRP recorrends that its individual dose limits for members of the public should apply.
Expanding on this, the ICRP states that its recensendations with respect to the assessment and monitoring of radioactive materials in the environment would also apply, with the results being used in the optimization of protection and in judging compliance of a high-level radioactive vaste disposal facility with the applicable dose limits and source upper bounds.
(Paragraph 30, Eeference 1.)
The ICRP goes on to say that "The application of the individual dose limits to the dose distribution from normal releases frem a waste repository is the same as for releases from other types of facilities.
Two basic requirements are it.velved.
First, the critical group, i.e.
those who are expected to receive the greatest exposure, must be identified.
Second, the design and operation of the repccitory must provide assurance that the average dose in the critical group will not exceed the dose limits.
(paragraph 45, Reference 1.)
b.
Evaluation and_ Control Qf ProbahillfLtig_,RgD.gagg The ICRP recommends that risks from probabilistic events should be limited on a similar basis.
In this regard, the ICRP states that "Since significant doses might result from events that disrupt the normal behavior of a disposal f acility and which have an assumed probability of occurrence, in a given time, less than one, the objective of protecting individuals from all of the exposure events associated with radioactive vaste disposal is best achieved by reverting to an individual rinh limitation recuirement.
By dealing consistently in terms of risk, both the probability of an exposure and the magnitude of the exposure can be included.
To take account of this, the coraission recommends that a risk limit and risk upper bound be established in direct analogy to the doso limits and upper bounds for normal releases."
(Emphasis Added. ) (Paragraph 47, Reference 1.)
Allowances for_Juture Activities and Indiyldanin c.
"To allow for dose contributions from present practices and to provide a margin for unforeseen future activities, the Commission recorrends that national authorities select a fraction of the dose limits as a source upper bound for each source of exposure, to ensure that the l
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The honorable 1:enneth M. Carr 3
exposure of individuals will remain below the relevant dose limit."
(Paragraph 54, Reference 1.)
"In a manner similar to the establishment of the source upper bound, the Couission recouends that national 1
authorities select some fraction of the risk limit as a ris);
upper bound for the source being evaluated."
(Paragraph 57, Reference 1.)
Expanding on this theme, the ICRP recommends "... that risks to future individuals should be limited on the sa.
i basis as are those to individuals living nm (Paragraph 50, Reference 1.)
2.
Recommendations of thtJALL Recomendations of the IAEA on this subject are presenteG 4..
their preliminary draft report, " safety Princip1cs and Technical Crit. aria f or the Underground Disposal of High-Level Radioactive Wastes." In this document, the IAEA separates th+
releases from a re into those that result fr
" gradual processes" pository and those tant result from "dicruptive events."
Since the annual doso limit for prolonged exposure to individuals within the critical group due to releases arising through
" gradual processes" is 1 nSv, the.AEA reco= ends that the dose rate due to " gradual processe.s" occurring within a single repository be limited to some fraction of this value, for " disruptive events," the annual dose limit for individuals within the critical group is that which has an associated ".
. risk of health effects of one in a hundred thousand per year."
On the basis of estimates made at the time, this vould correspond to a dose rate limit of 1 mSV per year.
(Sections 3.2.1 and 3.2.2, Reference 2.)
In essence, the IAEA report endorses the recommendations of the ICRP.
3.
Recorsendations of the Nordic Countries The recommendations of the Nordic countries pertaining to the disposal of high-level radioactive wastes are presented in a-
- report,
" Disposal of High Level Radioactive Waste Consideration of Some Basic criteria A
Consultative Document,"
issued in 1989.
Recommendations of this group on standards for a high-level radioactive waste repository are specified in terms of four general objectives and principles.
Statenents of significance are as follows:
l The Nordic group endorses the ICRP recommendation by stating that "The predicted risks to human health and the l
l effects on the environment from waste disposal, at any
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4 The Honorable Kenneth M. Carr 4
e time in the futare, shall be low and not greater than would be currently acceptabin.
The judgement of the acceptability of a disposal option shall be based on radiological impacts to individuals irrespective of any national boundaries."
(Enphasis added.)
(Paragraph 66, Ref wence 3.)
In terms of radiation protection et 4teria, the Nordic countries recommend that "The predicted radiation dose to any individual, excluding doses from unlikely disruptive events, shall be less than 0.1 mSv per year.
In
- addition, the probabilities and consequences of unlikely disruptive events shall be studied, discussed and presented in qualitative terms and whenever practtcable, assessed in quantitative terms in relation to tha risk corresponding to a dose of 0.1 mSv per year."
(Paragraph 85, Reference 3.)
As in the case of the IAEA, the Nordic group endorses the recommendations of the ICRP.
4.
Comments-of 3he Board _on Radioactive Waste Manaaement, liational-Research Council The most recent recommendations of the Board on this subject are presented in their
- report,
" Rethinking High-Level i
Radioactive Waste Disposal," published in 1990.
In the recommendations included at the end of this report, the Board makes the following statements:
"The Environmental protection Agency, during its revision of the remanded 40 CFR Part 191, should reconsider the detailed performance standards to be. net by the repository, to determine how they affect the level of health risks that will be considered acceptable.
In addition, EPA should reexamine the use of quantitative probabilistic release criteria in the standard and examine what will constitute a reasonable level of assurance. (i.e.,
by what combination of methods and strategies can DOE demonstrate that those standards will be met?).
"All other countries use oniv a dose recuirement.
In-
_settina reculatory standards and licensina recuirements, the EPA should consider usina only dose recuirements."
(Emphasis added.)
(Page 35, Reference 4.)
As may be seen, all four of the organizations and/or groups cited endorse standards for a high-level radioactive waste repository that have an associated limit on dose for normal or gradual releases and an-associated limit on risk for
4 The Honorable Kenneth M. Carr 5
disruptive or probabilistic releases.
In all cases, the limits apply to individuals within a critical population group.
The reasons that the ACIN endorses this approach, and is critical of the EPA approach, may be sursarized as f ollows:
a.
The high-level radioactive waste repository standards, currently proposed by epa, are based on limiting the
" global" collective dese, and estimates of the associated health effects, to a certain value (i.e.,
1,000 health effects in 10,000 years).
In taking this approach, neither the population to be protected nor the associated dose or risk limits are specified.
Any advantage to using collective done as a r.ethod for avoiding the dilution and dispersion of radioactive wasten in the environment will be offset by the difficulties in determining compliance with standards based on this approach. There are other regulatory approaches that can be applied to prohibit unacceptable disposal practices such as these.
b.
The projection of collectivo dose estimates far into the future (as is necessary to comply with the high-level radioactive vaste repositcry standards as proposed by EPA) is extrer.oly dif ficult, ractors that complicato such estimates include errors in predictions of regional and global population demographics (size and location) and of potential radionuclido pathways (groundwater flow and agricultural practices).
In contrast, long-range projections of the locations and living habits of individuals who may reside near a
repository are relatively straightforward, and estimates of their potential doses can be made with greater certainty.
It appears that the epa is alone in the approach that it c.
reconzends.
No other country or agency endorses this approach.
Sincerely, Dade W. Moeller Chairman 1
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International Commission on Radiological Protection,
" Radiation Protection Principles for the Disposal of Solid Radioactive Wasto," Publication 46, Annals of the ICRP, Vol.
15, No. 4 (1985).
2.
International Atomic Energy Agency, " Safety Principles and Technical criteria for the Underground Disposal of High-Level Radioactive Wastes" (Preliminary Draft, 1989).
3.
" Disposal of High Level Radioactive Waste - Consideration of Some Basic Criteria - A Consultative Document," Report of The Radiation Protecticn and Nuclear Safety Authorities in Denmark, Finland, Iceland, Norway and Sweden (1989).
4.
Board on Radioactive Maste Management, National Research Council, "Rothinking High-Level Radioactive Waste Disposal,"
National Academy Press, Weshington, DC (1990).
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....+s January J9, 1991 The Honorable }lenneth M. Carr Chairman U.S. Nuclear Regulatory Commission Washington, D.
C.
20555 Dear Chairman Carrt
SUBJECT:
STRINGENCY OF U.S.
ENVIRONMENTAL PROTECTION AGONCY 4
HIGil-LEVEL RADIOACTIVE WASTE REPOSITORY STANDARDS During our 25th meeting, October 24 and 25, 1990, Mr. Floyd L.
- Galpin, Chief, Waste Management Standards
- Branch, office of Radiation Programs, U.S.
Environmental Protection Agency (EPA),
requested that the Advisory Committee on Nuclear Waste (ACNW) provide EPA the bases for the statements, made in several of our reports to
- you, that the standards developed by EPA for a
high-level radioactive vaste repository were overly stringent.
There are, several f actors and considerations that served as a basis for our statements.
These are summarized below.
1.
Cpapar.igLon. of a Repository to a Natural Ore Body The introductory information provided in the EPA standards (Reference 1) implies that one of EPA's goals was to ensure that the health impacts of a repository were no greater than those that would have been associated with a comparable amount of unmined uranium ore.
Although conservative in its own right, this appeared to be a reasonable approach.
Later we learned that this approach did not, in the final version, serve as a basis for the EPA standards.
Rather, EPA based its standards for the repository on what was considered to be achievable using modern technology.
Nonetheless, the manner in which the existing standards are presented implies that they were based on releases from a comparable ore body.
As a result, most groups, including the ACNW, have evaluated the EPA standards with this consideration in mind.
If one assesses the EPA standards for a repository on the basis of a comparable ore body, there appear to be at least two steps taken by EPA that have led to undue stringency:
a.
Reports published by EPA (Reference 2) of analyses of actual uranium ore bodies (assuming 100,000 MTHM) indicate that annual releases of Ra-226 over a 10,000-year period would range from 300,000 to 3,000,000 curies.
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January 29, 1991 The limit on releases for Ra-226 in the EPA standards is 10,000 curios.
In a similar manner, estimates of the associatnd health effects (deaths) due to radionuclide releas ta from existing oro bodies over a 10,000-year period ranged from 1,000,000 to 10,000,000.
Tho limit in the EPA standards is 1,000, b.
An unmined uranium cre body represents a continuous source of release of radioactivo materials into the environment.
In other words, the chance or probability that the ore body would cause radiation exposures to neighboring populations is one.
In translating the estimated health etfects from unmined ore bodies irito a table of equivalent radionuclido releases froto a higha level radioactive waste repository, EPA stated that there must be no more than one chance in ten of exceedirig tho given radionuclide release limits (or more than one chance in one thousand of exceeding tan timos the release limits) over the initial 10,000-year period of operation of the repository.
In other words, EPA added a f actor of ten conservatism to releasen from a high-level vaste repository that are only slightly greator than releases from an unmined ore body.
Limits for_ Individual Radiongelide Rolemn 2.
In setting permissible limits for reloaaos of individual radionuc14. des from the repository EPA assumed that the releanos affected the population,of the entire world projected to number a constant level of 10 billion people over the 10,000-year assessment period.
In taking this approach, EPA did not specify a " critical" population group, nor did it specify a doso limit for the people who might be rixposed.
- Rather, it summed the resulting collectivo dosos over the population of the world and set the individual radionuclide release limits so as not to exceed a given collective dose limit (which, in turn, was used to predict the associated health impacts).
Data indicate that a major contribution to the coltective dose apparently consisted of dose rates to individual membars of the world's population of 0.01 mSv (1 mrem) por year or leau.
This calculational methodology is in sharp contrast to the procedures recommended by the National Council on Radiation Protection and Measurements (NCRP, Reference 3).
To be ripecific, the NCRP recommends that "
astsossments of increments of collectivo annual. effective dose equivalents from any particular i'idividual source or practice should exclude those indiviauals whose annual effective dose equivalents from such a source is 0.01 mSv (0.001 rem) or less."
(Section 20, Reference 3.)
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The Honorsble Kenneth H. Carr 3
January 29, 1991 The overall impact of the calculational approach used by EPA is to inflate," by a considerable margin, estimates of the health impacts of radionuclide releases from a repository.
This, in turn, results in the allowable quantities of specific radionuclide releases from a
repository to be overly conservativo) that is, too lov.
In making this consent it is important to acknowledge that i
the NCRP recorzendation was not published until June 1,1987.
Now that it has been issued, however, EPA should be encouraged to reassess its calculations.
3.
Enease Linit for qqrAgn-14 over the past year or two, an ircreasing number of comments and pspers in the literature indicaten t;.at gaseous emissions, specifically carbon-14 in the form of carbon-dioxide, may prohibit the proposed Yucca Mountain repository from complying with the EPA standards.
The permissible release limits for this radionuclide, as specified in the EPA standards, are one more example of its stringency.
This is illustrated by the following examples at The total inventory of carbon-14 in a
repository containing 100,000 MTHM is estimated to be about 100,000 curies.
This compares to a global production of carbon-14 by cosmic radiation of 28,000 curies per year, a global inventory of about 230 million curies, and an atmosphoric inventory of 4 million curies (Reference 4).
In fact, release of all of the carbon-14 inventory in a ropository would increase the atmospheric inventory by only about 2 percent; this compares to naturel variationo in the ati.ospheric inventory of 10 percent to 40 percent.
b.
Desed on an assured Anventory of 100,000 MT104, the permissible rate of release of carbon-14 from a
repository would 1.e about 1 curie pnr year.
Experience shows that any carbon-14 that is released would rapidly mix in the atmosphere, and estinates are that the accompanying dose rate to a person on top of Yucca Mountain would be far less than 0.01 mSv (1 mrem) per year.
It is also interesting to note that the limit on the release rate of 1 curie per year for a repository compares to an average release rate of 10 curies per year from a typical 1,000 MWs light water reactor (Reference 4).
i At the time the EPA standards were developed, considerations were limited to evaluations of a saturated site.
In such a caso, water transport and geochenichl barriers would have been strongly influential in retaining the carbon-14, Subsequent L,.-
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January 29, 1991 consideration of Yucca Mountt.n (an unsaturated site) makes the existing EPA standards inappopriate, overly stringent, and in need of revision.
4.
Intr 911.h69.D Tht Cf f.ce of Radiation Programs of the U.S.
Environmental procecuen Agency has the responsibill.ty for setting limits fcr li door radon as well as settang standards for the high-l vel wasts repository.
A comparisor, of the risks for indoce cidtn and those for the repository indicates that the health eJfoeta resulting from radon exposures at permissible levels is he vill h significantly greater than those from the repoettery.
i "u., mary,14 i statements by the ACNW that the EPA standards are string. tit are based on: (1) restrictit.M' that limit the p mility of exceeding the release limits by em a small amount to an order of magnitude less than that for a natuW5 cre bodf; (2) the application of inappropriate methodology ir calculating cc '.lective doses that, in turn, were used to ostablice; adionuclide release liMts from a repository; (3) the establishme.1 of release limits f m c4 nin radionuclides, most notably carbon-14 R amounts that are caly a mall fraction of the quantities naturaby present 1
witM n the vnvin ament; and (4) the inconsistencier-of 1he risk standbrds p2 epose for the repository and those for other rrd'ation sources, such as 1: door radon.
Sincerely,
/f Dade W. Moeller Chairman Etf.erences t 1.
U.S. Ccde af Federu' Regulations, " Environmental Radiation Protection 5'andarda for Management and Disposal of Spent Nuclear Fuel, #9h-LWel and Transuranic Radioactive Wastes,"
4 0 CFR Part 19b 2.
U.S.
Environmental Piotection
- Agency, epa 520/3-80-009,
" Population Risks trut Uranium Ore Bodies," Cotober 1980.
S.
National Council on,1idiation Protection and Measurements, Report No.
91, "Recortendations on Limits for Exposure to Ionizing Radiation," 15 0.
4.
14tional Council on Rt.diation Protect '. n and Measurements, Re port No. 81, "Curbon-14 in the Envirou ent," 1985.
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