ML20209F997
| ML20209F997 | |
| Person / Time | |
|---|---|
| Issue date: | 07/17/1985 |
| From: | Ward D Advisory Committee on Reactor Safeguards |
| To: | Palladino N NRC COMMISSION (OCM) |
| Shared Package | |
| ML20209G002 | List: |
| References | |
| REF-10CFR9.7 NUDOCS 8508050546 | |
| Download: ML20209F997 (8) | |
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- i 8 n NUCLEAR REGULATORY COMMISSION
{o, I ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, D. C. 20555 ,
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July 17,1985 Honorable Nunzio J. Palladino Chairman U. S. Nuclear Regulatory Comission Washington, D. C. 20555
Dear Dr. Palladino:
SUBJECT:
ACRS COMtENTS ON PROPOSED NRC SAFETY GOAL EVALUATION REPORT During its 303rd meeting, July 11-13, 1985 and its 302nd meeting, June 6-8, 1985, the Advisory Comittee on Reactor Safeguards met with repre-sentatives Steering of thereport Group NRC dated Staff and Aprilreviewed the NRC Safety 1985 (Reference 1. )During Goal Evaluation our review, we had the benefit of three meetings of the ACRS Subcomittee on Safety Philosophy, Technology, and Criteria held on December 12, 1984, May 8,1985, and July 10, 1985. We also had the benefit of the docu-ments referenced.
The Executive Director for Operations has not completed his formulation of recomendations to the Comission. However, recomendations have been provided by the Steering Group, by Mr. Harold Denton, Director, Office of Nuclear Reactor Regulation, by Mr. Robert Minogue, Director,-
Office of Nuclear Regulatory Research, and by other senior NRC Staff members. Some of these recomendations suggest significant changes in the proposed 1983 Safety Goal Policy Statement.
Our coments at this time are based primarily on our review of the Steering Group report. We expect to make further coments after the Executive Director for Operations has formulated his recomendations to the Comission.
We conclude that the NRC is not ready to reaffirm and implement the 1983 Safety Goal Policy Statement in its original or even some slightly modified form. Much progress has been made and the effort should continue. However, the fann of the design objectives and the plan for implementation are - not yet well enough developed. We believe that greater attention should be placed on working toward an objective of a mean-core-melt frequency of 10-4 per reactor year and use of a contain-ment performance objective. . We are concerned that the ~ Safety Goal Policy Statement may not give sufficient emphasis to defense-in-depth and may place too much emphasis on benefit-cost analyses.
Areas of Agreement
. We agree with many of the findings and conclusions of the NRC Staff 7 Safety Goal Steering Group, including the following, l
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5 Honorable Nunzio J. Palladino -2.. July 17, 1985 PRA methods and resulting insights have proven to be very valuable in establishing priorities for regulatory activities, the develop-ment of- regulatory positions on- generic safety issues, and the assessment'of plant-specific safety issues.
. PRA has limitations that must be understood when the results are t
used. The results of-a PRA should normally.be used in conjunction l l with traditional safety - review methods :in making regulatory de- :
cisions. l The statement of the Qualitative Safety Goals in the 1983. Safety Goal . Policy Statement is satisfactory.
For sites where no people reside within-a mile of the site bound-ary, for purposes of calculation of early fatalities, an individual 3
should : ordinarily be assumed to reside one mile from .the site boundary.
! . In applying the latent cancer fatality numerical guideline, we ;
agree with the Steering Group that it is better to consider the l 1 population within 10 miles of the site. rather than 50 miles as ;
i proposed in the 1983 Policy Statement. This goal is not a societal i risk goal but an individual risk goal because it is not related to the number of persons affected. Consideration should be given to
- the use of a one-mile. distance, as suggested by Mr. Denton.
s
- . We support the general principle that no more than about 10 percent i of any quantitative design objective should be accounted for by a
- single major issue or accident.
Implementation Procedures, Particularly Core Melt Objective-The Steering Group has proposed a . number of detailed implementation -
procedures. The: Committee has a range of questions on the proposed operating limits, and wishes to discuss these matters in detail with the NRC Staff. The implementation procedures should 'not be adopted in their current forw.
I - In : its letter : to -you ' dated September 15,1982 '(Reference 2), the ACRS stated that mean, not median vagues should be used and that an opera-
- tional level for core melt of 10- per reactor-year is'too large for all ,
i but a few,: small existing nuclear plants. Even a mean value of core-i melt of 10-3 per reactor-year. is .too ' large.. As part ofs defense-in-
- depth, action to reduce such a core-melt-frequency should be part of the
- Commission's policy, not subject to the current benefit-cost backfit
- requirements as specified in the proposed Backfit Rule and implementing l
Manual Chapter.
We believe that the - Comnission . should L state that a mean-core-melt i L frequency of not more than 10 L per-reactor year is an NRC objective for all but a few, small, existing' nuclear plants, and that, keeping;in~ mind i 4
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' Honorable Nunzio J. Palladino July 17,1985
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the considerable uncertainties, prudence and judgment will tend to take 4
priority over benefit-cost analysis in working toward this goal.
Containment Performance Objective The NRC Staff has not developed a containment perfor1 nance guideline, nor l has any serious NRC Staff effort to do so been apparent to the Connit- l tee.- The ACRS continues to believe, as it did in its report of June 9, 1982 (Reference 3) that the development of a containment perforinance guideline warrants high priority, and recommends that the Connission require early NRC Staff attention to this matter as part of maintaining
- its defense-in-depth principle. Approximate compliance to ' an appro-priate criterion should be an NRC objective.
- Use of Median Values 4
I The Steering Group proposes to use median values for assessing compli-1 ance with the quantitative guidelines "so as to . provide stability to
~
! estimates even if the uncertainties are 'much larger in one case than ,
- l. another." We disagree with the use of median values for purposes of ;
input into decision making. If it is available, we believe that knowl--
edge of the uncertainty range and the frequency distribution of conse-quencas (whether they be core melt or individual risk) is important to have for decision making. However, we believe that when a single value
- is used for comparison against a numerical guideline, it should be the
! mean, not the median .value of the parameter involved. The mean should be evaluated in as appropriate a manner as .the available information permits.
While addition of the mean values for each of a set of sequences does i provide the mean value of the combined sequences the addition of the medians does not provide the median value for the combined set nor, for I that matter, does it provide any clearly defined property of the com-bination.
l If the pattern and extent of uncertainties are so ill-defined as to make
~
any assignment of mean-core-melt frequency-or risk not meaningful, the median likewise will lack sufficient meaning to have an important input
! into decision making.
I Additional consents by ACRS Members -Harold W. Lewis, Forrest J. Remick, ,
l Max W. Carbon, and Glenn A. Reed are presented below, i Sincerely,
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. :o Honorable Nunzio J. Palladino - 4- July 17, 1985 Additional Conments by ACRS Member Harold W. Lewis I disagree very strongly with the overall thrust of the Connittee's letter on the Safety Goal Policy Statement, even though I agree com-pletely with the recommendation that the Commission not affinn the 1983 Statement. My reasons are so different from those of the Consnittee that they point toward different directions for future development, and therefore warrant separate expression. Some reasons have been expressed before [see additional comments to ACRS letter dated June 9, 1982 incorporated herein by reference (Reference 3)].
- To avoid wallowing in the details and 'thereby losing the point, it may I' be useful to first say what I think the Connission should do. The rest i will fall into context.
I believe the Commission should issue a declarative and arbitrary quantitative safety goal statement at this time, stating it as an objective, acknowledging its arbitrariness, inviting discussion of the exact numbers, and acknowledging that tradeoffs between containment and prevention will sometimes be necessary to meet the objectives. It should nonetheless -- this is not contradictory -- connit itself to
, maintaining the principle of. defense-in-depth. The risk used should be
, societal -- that is NRC's responsibility. It should recognize uncer-i tainty, and accept the responsibility for decision making in the face of uncertainty -- there are no pat formulas.
i -
l The Connission should further connit itself to cost-benefit analysis --
l not to assure an adequate level of safety, but to assess the value of
, improvements to safety. Cost-benefit analysis is not now done very well i by the NRC Staff, but the proper response to that is to improve crafts-manship, not reject the tool. (This is also important for the back-
! fitting issue.) There will indeed be great uncertainties in both cost-benefit analyses and in the assessment of where a particular reactor stands with respect to the quantitative goals. These uncer-tainties are not created by the analysis -- they are revealed by it.
The Connission should acknowledge this. ;
i With that preamble, detailed coseents on the Connittee letter follow:
- The Committee is, concerned that "too much emphasis [may be placed] on benefit-cost analyses." That will surely be read by some to mean that '
- the Committee rejects cost-benefit analysis as a tool in the management
- of nuclear safety. If it does mean that, it is a grievous error. If it i does not, it is inappropriate wording. It is particularly disturbing in view of the Connission's efforts to rationalize the regulatory process.
The Connittee agrees with the statement of the Qualitative Goala in the
- 1983 Cosmission Statement. For my disagreement, see the reference cited
, above.
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Honorable Nunzio J. Palladino July 17,1985 :
The Comittee has a series of detailed comments about averaging radii, which serve to further obfuscate the societal / individual risk issue. It further states, incorrectly in my view, that the latent cancer fatality goal is an individual goal. It is, in fact, an obscure mixture of the two -- neither fish nor fowl. I support societal goals, and would rather deal with individuals as individuals. I even believe that is NRC's charter.
4 The Comittee takes no position on the ' on-site /off-site question. I believe that on-site costs of an accident are not the responsibility of NRC, which is charged with the protection of the health and safety of the public. The exception is that of on-site radiation exposure of 3
people, which is its responsibility.
The Committee coments about median versus mean are, if anything, understated. It is a disgrace that NRC Staff should continue to recom-mend criteria based on medians of core-melt probabilities. This is not a matter of taste -- it is simply wrong to add median probabilities. I find it extremely disturbing that, despite the number of times this has been brought up, your Staff continues to fall short of even ilementary textbook-level awareness of this. If this is harsh, so be it.
The Committee states that a core-melt probability of 10-3 per reactor- ,
! year is too large, independent of containment considerations. I do not believe the core-melt probability should t,e so arbitrarily separated from the other issues. It may be convenient for regulatory purposes, '
- but it is not appropriate public policy.
I would also have made some coments about the importance of pressing
- the Staff to make realistic calculations for safety goal compliance.
The regulatory habit of erring' on the conservative side is inappropriate here, and people seem to have trouble shedding their regulatory customs.
In sumary, I recomend that the Comission continue the tedious process of learning how to deal with quantitative risk analysis, and with
- decision making in the face of uncertainty. The time is not yet ripe for the promulgation of quantitative safety goals other than on an arbitrary basis, as recommended above. Progress A being made on the "how safe is safe enough" question. Let it continue.
Additional Coments by ACRS Member Forrest J. Remick I disagree very strongly with much of the Committee's letter on the i Safety Goal Policy Statement. I'see a number of the Comittee's com-ments as restatements of prior views which indirectly attack the Com-mission's promulgation of a safety goal policy statement, in contrast to a thorough evaluation of the Safety Goal Evaluation Report prepared by the Safety Goal Evaluation Steering Group at the- end of -a two-year evaluation period.
Honorable Nunzio J. Palladino 6- July 17,1985 I think that, based on the two year evaluation and the generally excel-lent Steering Group report, tne : Commission is ready to utilize its Safety Goal Policy Statement to augment its - traditional safety review -
methods in making. regulatory decisions. Like the Steering Group, I think -such use will help . add -objectivity and predictability to the regulatory process and can be used as a ' regulatory yardstick against I which a wide range of regulatory issues can be measured.
. I do1 take exception' to the Steering Group's proposed change to the benefit-cost guideline from that defined in NUREG-0880, Revision 1. The basis for my exception is as follows:
! .The Commission's responsibility under the Atomic Energy Act' is to !
l- promote common defense and security and to protect the health and safety i
! of the public. The extent to which the health and safety of the public !
is . to be protected is neither specified in the Act nor in the Com -
r
- mission's regulations.
- The Comission's Policy Statement on Safety Goals for-the Operation of Nuclear Power Plants expresses the Comission's view on the acceptable .
level of risk to public health and safety and on the afety-cost trade- !
offs in regulatory decision making. Therefore, the Commission has defined for the first time how safe is safe enough with respect to protecting the health and' safety of the public - from the risks of the
- operation of nuclear power plants.
- i. The Atomic Energy Act does not indicate that the Commission has the - .
responsibility to protect licensees from the risk of potential economic
. loss of investment resulting from the operation of their nuclear power plants. Therefore, the Comission's Policy Statement on Safety Goals '
1- does not define acceptable levels of risk of such losses.
!. The Commission adopted a benefit-cost guideline in its Policy Statement 4
.to encourage the efficient , allocation of resources in safety-cost ;
tradeoff decisions related to Comission-imposed plant modifications.
~
. Consistent with the Atomic Energy Act. - the benefit in the benefit-cost guideline is defined as a reduction in public risk (in terms of a
- reduction in the collective -population exposure measured in person-rems). Averted economic risks to the licensee which hypothetically 3 might result from a Commission-imposed modification, rightfully 'are .not defined .as a benefit in the benefit-cost guideline. Therefore, a Commission-imposed modification could not be justified on-the basis that it might reduce economic risk to the licensee.
- Earlier the Cosmission solicited _ and received public. comments- on this
- point. Most comenters were opposed to the proposed change in. the -
benefit-cost guideline. The following' partial quote from the comment by.
. Duke Power Company sumarizes the' views of, the twenty-four commenters l
opposed- "The benefit side of tha benefit-cost analysis should repre-i sent 3 ' measure of ' the potential reduction in risk only -in terms- of
! public health and safety. The NRC is not charged with. and should not w .
7 l
- Honorable Nunzio J. Palladino July 17, 1985 4
concern itself with, protecting the financial investment of a utility and its shareholders in a nuclear plant ...." (p. 74, NUREG-0880, Rev.
1).
Some proponents of including hypothetically averted economic costs to licensees as a benefit in the benefit-cost guideline are concerned that unless this, is permitted, certain proposed plant modifications or backfits might not prove cost beneficial. That is, the cost of the modification would preclude its imposition because the modification would not substantially reduce risk to the health and safety of the ;
public.
The continued efforts to impose modifications regardless of their cost
- compared to their public health and safety benefit have contributed 2
greatly to the loss of control of the regulatory process. Further, they have contributed to making' nuclear plants more complex and perhaps less safe than would be the case otherwise.
For these reasons I strongly disagree with the proposed ciw;nge in the
. benefit-cost guideline. Hypothetically averted economic risks to 4
licensees are not justifiable benefits from the standpoint of protecting
! public health and safety. Therefore, they should not be included as a benefit under the benefit-cost guideline of the Commission's Policy Statement on Safety Goals for the Operation of Nuclear Power Plants.
I j Additional Comments by ACRS Member Max W. Carbon l'
I share Forrest Remick's disagreement with the Steering Group's proposed change to the benefit-cost guideline from - that defined in NUREG-0880, Revision 1.
I Additional Coments by ACRS Member Glenn A. Reed I agree with most of the ACRS letter and particularly I agree with a safety goal for core-melt frequency of 10-4 Also, I agree with the additional coments of Forrest Remick. It is my considered opinion that the adoption of the core-melt frequency approach, rather than any use of >
L averted on-site benefit-cost analysis, is more likely to lead to safety
- improvements since averted costs will involve many more uncertainties,
- j. delay and confusion. .
References:
! 1. NRC safety Goal Evaluation Steering Group report dated April 1985,
- " Safety Goal Evaluation Report " transmitted by memorandum from Thomas E. Murley, Chairman, Safety Goal Steering Group, ~ to Raymond F. Fraley, Executive Director, ACRS, dated April 18, 1985
'2. Letter from P. Shewmon, ACRS Chairman, to Nunzio J. Palladino, NRC l Chairman,
Subject:
ACRS Report'on the Draft Action Plan for Imple-
' menting the Commission's Safety Goals for Nuclear Power Plants, dated September 15, 1982 u , .e - , . _ y w w # w9- -p%-..,-- .,w, -, w w w . - - , , .+,-_..r-.,,,,.rv, ,..,,.-.,,,,--...,m --,,,,.rws, -g+o+,-y-,-.-,ym
i Honorable Nunzio J. Palladino July 17, 1985
- 3. Letter from P. Shewmon, ACRS Chairman, to Nunzio J. Palladino, NRC ,
Chairman,
Subject:
Comments on proposed Policy Statement on Safety i Goals for Nuclear Power Plants (NUREG-0880, A Discussion Paper), I dated June 9, 1982
- 4. U. S. Nuclear Regulatory Commission " Safety Goals for Nuclear Power Plant Operation," USNRC Report NUREG-0880, Revision 1, dated May 1983
- 5. Memorandum from Malcom L. Ernst, Deputy Director, Office of Nuclear Regulatory Research, to Thomas E. Murley, Regional Administrator, Region I,
Subject:
Emphasis on Defense-in-Depth and Accident Pre-vention in Safety Goals, dated May 10, 1985
- 6. Memorandum from Robert B. Minogue, Director, Office of Nuclear Regulatory Research, to William J. Dircks, Executive Director for Operations,
Subject:
Safety Goal Evaluation Report, dated May 21, 1985
- 7. Memorandum from Harold Denton, Director, Office of Nuclear Reactor Regulation, to William J. Dircks Executive Director for Operations.
Subject:
Safety Goal Evaluation Report, dated June 12, 1985 4
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