ML20198M099
| ML20198M099 | |
| Person / Time | |
|---|---|
| Issue date: | 09/12/1997 |
| From: | Callan L NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| References | |
| FACA, SECY-97-208, SECY-97-208-01, SECY-97-208-1, SECY-97-208-R, NUDOCS 9710280041 | |
| Download: ML20198M099 (17) | |
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POLICY ISSUE (Notation Vote)
Seotember 12.1997 SECY-97-208 EQB: The Commissioners EHQM: L. Joseph Callan Executive Director for Operations
SUBJECT:
ELEVATION OF THE CORE DAMAGE FREQUENCY OBJECTIVE TO A FUNDAMENTAL COMMISSION SAFETY GOAL PURPOSE:
To respond to Chairman Jackson's July 2,1997, memorandum, providing the staff's vlews and recommendations on elevating the subsidiary objective of core damage frequency to a fundamental safety goal.
BACKGROUND:
The Commission's Safety Goal Policy Statement, issued in 1986, expressed "the Commission's views on the level of risks to public health and safety that the industry should strive for in its nuclear power plants." Two qualitative goals were established:
Individual members of the public should be provided a level of protection from the consequences of nuclear power plant operation such that individuals bear no significant additional risk to life and health.
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. Societal risks to life and health from nuclear power plant operation should be comparable to or less than the risks of generating electricity by viable competing technologies and should not be a significant addition to other societal risks.
To quantify these goals, two quantitative health objectives (OHOs) were also established:
. The risk to an average individualin the vicinity of a nuclear power plant of prompt fatalities that might result from reactor accidents should not exceed one-tenth of one percent (0.1 percent) of the sum of prompt fatality risks resulting from other accidents to which members of the U.S. population are generally exposed.
- The risk to the population in the area nett a nuclear power plant of cancer fatalities that might result from nuclear power plant operation should not exceed one-tenth of one percent (0:1 percent) of the sum of cancer fatality risks resulting from all other causes.
Several other key points regarding the policy statement include:
. The policy statement noted that "the Commission intends to continue to pursue a regulatory program that has as its objective providing reasonable assurance...that a severe core damage accident will not occur at a U.S. nuclear power plant." This intention was not, however, explicitly defined in the policy statement as a qualitative goal, nor was a corresponding quantitative goal for core damage frequency (CDF) defined. Commissioner Bernthal, in his separate views attached to the Safety Goal Policy Statement, suggested such a CDF goal be included in the policy statement and implied 10d/RY as the goal for the current population of plants. Subsequent to publication of the policy str. w, a subsidiary CDF objective of 1 x 104 per reactor year for accident prevention wa ,sroposed by the ACRS in a May 13,1987, letter to Chairman Zech as one element in a hierarchical structure for safety goal implementation. The Commission, in a November 6,1987, SRM requested the staff to develop a safety goal implementation plan that included the elements in the May 13, 1987 ACRS letter. The staff proposed such a plan in SECY 89102 and the Commission approved the use of a 10d/RY CDF as a subsidiary benchmark for accident prevention m their June 15,1990, SRM.
- The orig;nalintendea use of the safety goals, as indicated in the policy statement and the Commission's June 15,1990, SRM, was for examination of regulations and other generic matters, and not for making plant specific decisions. In this context, the staff developed and the Commission endorsed criteria based on the Safety Goal subsidiary objectives (including the 1 x 104 per reactor year CDF objective) to screen potential backfits for their risk significance. This process and the criteria are described in the Regulatory Analysis Guidelines (NUREG/BR-0058, Rev 2).
The safety goals are not substitutes for the NRC's regulations or the defense-in-dspth concept, nor are they a atatement of adequate protectiori As stated in the June 15,
The Commissioners 3 1990, SRM, the safety goals are intended to define "how safe is safe enough."
. The policy statement proposed for further study a ' general performance guideline
- In terms of a large release of radioactive material with an associated frequency of 1 x 104 per reactor year. As discussed in SECY 93138, the staff attempted to define a guideline using this frequency, but was unable to do this without making the guideline significantly more restrictiva than the OHOs. Work on defining a large release of radioactive material with this associated frequency was terminaied in 1993.
. The policy statement Indicated that mean values should be used for comparison with the OHOs, and that " quantitative techniques usert for regulatory decision making take into account the potential uncertainties that exist so that an estimate can be made on the confidence level to be ascribed to the quantitative results." In practice, staff uses of the safety goals have not included quantitative statements on associated confidence levels.
Recent activities in developing guidance for use of probabilistic risk analysis (PRA)in the regulatory process have raised several issues related to the Commission's safety goal policy:
- The staff recommended draft guidelines for plant specific decision making that are derived from the Commission's current Safety Goals and the subsidiary objectives. The Commission approved publication of the draft guidelines (draft Regulatory Guides and Standard Review Plans) for public comment.
. in DG 1061, the staff proposes to use two subsidiary objectives to the OHOs core damage frequency (with a value of 1x104 per reactor year) and large early release frequency (LERF) (with a value of 1x104 per reactor year) for purposes of examining proposed changes to the current licensing bases (CLB) of individual plants.
. The Commission has instructed the staff to " develop a methodology for assessing changes in risk that uses statistical concepts and gives considerations to uncertainties."
In an August 15,1996, letter (Attachment 1), the ACRS recommended that the 1x104 CDF subsidiary objective be raised to a fundamental safety goal. Further, in a June 17,1997, letter (Attachment 2), the ACRS discussed the concept of defense-in-depth, as it relates to PRA and the safety goals, and recommended that a new policy statement be developed which *would provide more guidance on the extent and nature of defense-in depth expected by the Commission.'
Chairman Jackson's July 2,1997, memorandum requested that the staff provide its views on the ACRS recommendation (in their August 15,1996, letter) on elevating the CDF to a fundamental safety goal, including pros and cons and a proposed mechanism for stating CDF as a fundamental goal. The staff's views are provided below, along with discussion of other issues related to the safety goals.
In a July 23,1997, letter (Attachment 3), NEl noted Chairman Jackson's July 2,1997, rnemorandum, indicated that they believed 'the safety goals should retain their current, direct focus on public health and safety,' and provided several reasons for this belief.
The Commissioners 4 DISCMSS103 Chairman Jackson's July 2,1997, tremorandum, defines u number of pros and cons, with which the staff is in general agreement. In the staff's view, the key benefits of modifying the Safety Goal Policy Statement to include CDF as a fundamental goolinclude:
It clearly states the Commission's philosophical expectation regarding the prevention of core damage accidents, whether or not such accidents have serious public health consequences. Such a goal may be more clearly understood by the public than health goals, and is not as uncertain (e g., it is not affected by the highly variable post-core-melt physical processes).
. The CDF, in conjunction with the OHOs, would provide the Commission'r. views on the relative importance of accident prevention versus mitigation. Such a statement could help to relate better the traditional defense in-depth concept with PRA and the safety goals, thereby addressing the ACRS concern in this area.
The key detriments include:
. A CDF goal of 1 x 10dper reactor year would be more restrictive than the QHOs. Some plants, which are considered " safe enougn" from a QHO perspective, would not be " safe enough" frorn a CDF perspective.
. Statement of a CDF goal without a corresponding containment performance goal (e g., the DG 1001 LERF goal) willlead to placing a higher importance on preventive features than on mitigative features, and thus fore 0oing the Commission's traditional defense in-depth policy. For example, a CDF goal set at 1 x 104 per reactor year, without a containment performance (LERF) goal, could be taken to imply little need for accident mitigative capabilities in plants if the QHOs are the only expressions of mitigation. That is, plants meeting the CDF goal could have poor containment capability and still meet the OHOs.
A further consideration to note in deciding whether to proceed to establish an additional safety goal is that, in practice, the staff is already using a 1 x 104 per reactor year CDF as a benchmcrk for accident prevention in both generic and plant specific activities. As noted above, the CDF objective was used in the Regulatory Analysis Guidelines to develop criteria to screen potentia! backfits and is used in draft DG-1061 in the CLB-change review process.
Elevation of this benchmark to a fundamental safety goal will have little practicalimpact on these activities.
Furthermore,lnitiation of staff work to make changes to the policy statement at this time would divert resources away from ongoing, high prionty activities associated with risk informed regulatory approaches.
As discussed above, the staff's recent risk informed guidance development activities have identified three issues related to the policy statement - use of the goals in plant specific regulatory activities, an appropriate definition for LERF as a subsidiary objective to the safety goals, and the development of a methodology which gives consideration of l uncertainties in risk informed decision making Regarding the first issue, the Commissicn l tentatively approved, in a January 22,1997, SRM, use of the Safety Goals in a plant specific I
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The Commissioners 5 manner, but requested that the legal ramifications be explored prior to finalizing the draft risk-informed guidance documents. The staff believes that the impact of this decision,11 final approvalis obtained, is sufficiently large as to justify a modification of the policy statement. The second issue, relating to the definition of LERF, is an integral part of the decisio,1 making process described in DG 1061, and thus is being assessed as part of the public comment and guide finakation process. If the current LERF definition remains, or a similar definition is developed, it would likely require a modification to the policy statement to replace tne general performance guideline proposed in the poliev statement. The resolution of the third issue will be addressed as part of the finalization of the risk informed regulatory guides, associated policy issues on this will be raised to the Commission and decisions reflected in the final version of DG 1061. The results of Commission decisions on this issue could also necessitate a change in the policy statement.
Should the staff undertake a modification of the policy statement to address these issues,it may be appropriate to address other issues. Concerns which have been noted since publication of the policy statement include:
. The second qualitative goal and its co. responding QHO address societal risk; however, the supplemental discussion in the Rafety Goal Policy associated with this goal le:d to a practice of calculating risk to an individual for comparison to the QHO, in lieu of risk to society. Concem with this approach was discussea in the separate views of Commissioner Bemthal, attached to the Safety Goal Policy Statement.
. The goals and QHOs are described in terms of health risks; no goal has been established with respect to potentialland contamination and interdiction. As ovidenced by the Chemobg accident, this can be a major societal impact of accidents involving core damage and containment failure.
. The QHOs are expressed in terms of annual average frequencies. It may be appropriate to also provide a quantitative goal on risks during temporary pitnt configurations such as during PWR mid-loop operations, where risk can be substantially higher for a short period of time.
. The rehtionship between the safety goals sind " adequate protection,' as raised in the ACRS's April 11,1997, letter, may merit further discussion in the policy s,atement.
. Further discussion of the rel tionship among the defense-in-depth concept, PRA, and the safety goals, as raised in the ACRS's June 17,1997, letter, should be considered in the policy statement.
COORDINATION; This paper has been coordinated with OGC, which has no legal objection.
The Office of the Chief Financial Officer has reviewed this Commission Paper for resource l
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The Commissioners o implications and has no objections.
RECOMMENDATIONS:
The present Safety Goal Policy Statement could benefit from revision to reflect Commission policies and decisions of the past several years, including recent decisions made in the context of developing risk-informed regulatory guidance. One potential change is the elevation of coie damage frequency to a fundamental safety goal. The principal benefit to be achieved from this change would be to state more clearly that, as a matter of public policy, the Commission is acting to prevent core damage accidents. The change may be achievable whether the proposed new goalis qualitative or both qualitative and quantitative (as are the present goals) in nature, and should be considered in the context of a possible associated defense in-depth goal such as LERF.
This benefit notwithstanding, the staff recommends that the decision to proceed with modifying the policy statement, including elevating CDF to a fundamental goal be deferred, for the following reasons:
. The staff's risk-informed ngulatory guides are being circulated for public comment, with comment explicitly sought on issues such as the appropriateness of 1 x 10d per reactor year as a CDF acceptance guideline, use of safety goals in plant-specific decision making, an appropriate LERF definition, and treatment of uncertainties. Consideration of public comments on these issues will help shape their use in the final versions of the regulatory guides, and could also help better define the need for changes to the policy statement.
As noted above, the Regulatory Analysis Guidelines and draft DG 1001 already make use of the CDF subsidiary objective. Therefore, the elevation of the CDF subsidiary objective alone to a fundamental goal will have, in practice, little effect on ongoing staff activities.
However, if the policy statement is to be revised, the additional issues noted above (e.g.,
the development of a goal on land contamination ) should be considered. These other
.ssues have the potential to impact regulatory activities and, sinco they have not been the subject of extensive Intemal staff discussion, nor have they been discussed with the ACRS, time for these discussions is needed.
The Safety Goal Policy Statemerit is closely related to the PRA Policy Statement, to fundamental staff concepts such as defense in depth, adequate protection, and the need for compliance with existing regulations, as well as to the backfit process. Possible revisions to the policy statement will require detailed review by the staff and OGC to assure that a CDF goalis property defined and characterized with respect to these issues.
As such, the staff recommends that a decision on modifying the policy statement be made after finalization of DG 1061 and related documents, acheduled for December 31,1997, and after staff discussions with the ACRS. The staff recommends that a Commission paper providing staff recommendations be prepared after these activities are completed, with a proposed completion date of March 31,1998. The staff notes that, pending a Commission decision, no l
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staff or continctor resources have been allocated in planning documents to modify the policy statement, A decision to proceed will require reprogramming available resources from other, l
lower priority, work. The staff octimates that the effort would require approximately 2 FTE per ;
- year for si twogear period. This estimate assumes the normal process for policy statonient :
revisions wouid be followed (i.e., initial ACRS, CRGR and Commission interaction, public ;
comment and final ACRS, CRGR and Commission interactions) as well as at least one public i workshop to discuss the issues.
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L Jopph Callan Executive Director i for Operations ;
, A*tachments:
-As stated Commissioners' comments or consent should be provided directly to the Office
- of the Secretary by COB Tuesday, September 30, 1997.
Commissi.n Staff Office comments, if any, should be submitted to the Commissioners NLT Septe mber 23, 1997, with an information copy to the Office of the Secretary.
If the p4per is of such a nature that it requires additional review and comment, the Commissioners and the Secretariat shoudl be apprised of when conurents may be expected.
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y" N NUCLEAR REGULATORY COMMISSION c;
ADVISORY COMMITTEE ON REACTOR 8AFEGUARDS WASHINGTON,0, C. 20684 o
...<* l August 15, 1996 i
The Honorable Shirley Ann Jackson ,
Chairman U.S. Nuclear Regulatory Commission ,
Washington, D.C. 20555-0001
Dear Chairman Jackson:
SUBJECT:
RISK-INFORMED, PERFORMANCE-BASED REGULATION AND RELATED MATTERS During the 4.33rd meeting of the Advisory Committee on Reactor ,
Safeguards, August 8-10, 1996, we discussed the issues identified in the Staff Requirements Memorandum dated May 15, 1996. We also discussed the pilot applications for risk-informed, performance-based regulation. Our Subcommittee on Probabilistic Risk Assessment (PRA) met with representatives of the NRC staff and the nuclear industry on July 18 and August 7, 1996. We also had the benefit of the documents referenced.
The staff presentations dealt only with the development of guidelines from the Commission's safety goals to be used as an element of the evaluation of licensee-initiated changes to licensing commitments. All of our comments address the application of risk-informed regulation in that context. At a later time, we will discuss the larger question of the application of the safety goals on a plant-specific basis.
CONCLU85 IONS Issue 1t Should the Commission's safety goals and subsidiary objectivas be referenced or used to derive guidelines for plant-specific applications and, it so, how?
We believe the safety - goals and subsidiary objectivac can and '
should be used to derive guidelines for plant-specific applications. It is,=however, impractical to rely exclusively on the Quantitative Health Objectives (QHos) for routine use on an individual plant. basis. Criteria based on core damage frequency (CDF) and large, early release frequency (LERF) focus more sharply on safety issues and can provide assurance that the QHos are met.
{ They should be used in developing detailed guidelines.
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Issue 28 Row are uncertainties to be accounted for? l This is a difficult issue. There are models and formal methods to account explicitly for a large number of uncertainties. However, other uncertainties, are unquantifiable. The staff proposes to explore a number of options, such as estsb11shing margins in the acceptance guidelines, placing more in portance on defense-in-depth,.
and others, to deal with such uncerta;.nties. Such approaches seen ,
appropriate, although much work remains to be done. i 1ssue 3t should requested changes to the current licensing basis
. be risk-neatral or should-increases be permitted?
We agree with the staff and industry that increases in risk should be. permitted in some situations. Acceptanca guidelines expressed
- in terms of. the proposed change in risk and the current risk -
estimates should have three regions: a region in which some -i increase in risk is acceptable, one in which it is unacceptable,
- and one in which further analysis and evaluation would be required.
i Issue 4 s How should performance-based regulation be implemented in the context of risk-informed regulation?
- We agree with the staff that, where practical, performance-based strategies should be included in the implementation and monitoring step of ' the risk-informed decision-making process. The pilot '
programs may provide an opportunity for a more concrete definition and development of performance-based strategies.
DISCUSSION Issue 1 Even though a CDF could be derived from the QHos that could be greater than 10*8 per reactor-year, the current subsidiary gop1 of ,
' 10 per reactor-year should be maintained and should be stated as
- a. fundamental safety goal, along with the QHO. Accident sequences that have a high probability of leading to severe consequences could be controlled by the QHos,-but a more workable measure would be a subsidiary goal. on the LERF. The definition of the latter reeds'to be-improved. Whether the LERF should be a fixed value or
- derived'from the QHos,1which would allow-the LERF-goal to include
- site-specific characteristics, needs to be investigated.
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We recummend that- the staff develop guidance' for handling situations in which high values of.the CDF occur for short periods of time (for example,-10~8 per reactor-year for a day). ;
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i Issue 2 l
In accounting for uncertainties, it is. important to distinguish between those plant characteristics or phenomena that are modeled in the FRA and those that are not modeled (e.g., the actual layout i of components and organisational factors). For those -that are i modeled, parameter and model uncertainties should be explicitly l quantified and propagated through the PRA. The resulting i distributi~ons should be an input to tne decision-making process !
along with other' qualitative input. !
'Mean values of distributions should, in general, be used for !
comparison with goals-or criteria, although the sensitivity of the ,
mean value to the high. tail of a distribution should not be :
-overlooked.' For very broad distributions, such as those _ that ;
Ltypically result when significant model uncertainty is present, i reliance on the mean values may not be appropriate and a more :
detailed investigation of_the reasons for this large uncertainty should be undertaken. This could possibly lead to decisions to <
conduct additional research or to take other maastres. (
Accounting for uncertainty in the case of plant characteristics or ,
phenomena that are not currently modeled at all is > much more difficult. The staff proposes to explore a number of options, such as establishing margins in the acceptance guidelines, placing more importance on defense-in-depth, and others. We agree and encourage the staff to actively pursue the resolution of this issue.
Issue 3 The concept of a "three-region" approach is consistent- with the :
Electric Power Research Institute's PSA Applications Guide (PSAAG),
although the boundaries of the regions used in the PSAAG are not necessarily the ones-that the staff will adopt.
The staff has raised the issue of how " packaged" requests are to be -l handled. Packaging is the process by which risk trade-offs can be accomplished. It is - a significant benefit of risk-informed
, regulation.- We believe that it.is the overall impact on plant risk
. that is important, and related changes should be handled as a
- package. .-such changes should be consistent with the current philosophy-of risk management;:1.e. , that the " bottom-line" numbers
- should not.be'_theVonly input to the decision-making-process, and- :
other concepts such as' defense-in-depth must be maintained.
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Wo will continue to monitor the progress of the staff on these issues.
Sincerely, h.
T. S. Kress Chairman
References:
- 1. Staff Requirements Memorandum dated May 15, 1996, from John C.
Hoyle, Secretary, NRC, to James M. Taylor, Executive Director for Operations, NRC, regarding Briefing on PRA Implementation Plan on April 4, 1996
- 2. Memorandum dated June 20, 1996, from James M. Taylor, Executive Director for Operations, NRC, to the Commission,
Subject:
Status Update of the Agency-Wide Implementation Plan for Probabilistic Risk Assessment (PRA) (from March 1, 1996 to May 31, 1996)
- 3. Electric Power Research Institute, EPRI TR-105396, Final Report dated August 1995, "PSA Applications Guide" 1
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June 17, 1997 {
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The Honorable Shirley Ann Jackson l Cha h an" * ' !
U. S. Nuclear Regulatory Commission Washington,..D.C. 20555-0001 i
. Dear Chairahn Jacksont SUBJECT PROPOSED STAFF POSITION REGARDING INCLtisION OF A CONTAINNENT SPRAY SYSTEM IN THE APG00 DESIGN During the 442nd meeting of the Advisory Committee on Reactor i
Safeguards, June 11-14, 1997, we met with representatives of the NRC staff and the Westinghouse Electric Corporation to discuss the '
proposed staff position that the AP600 desig,. should include a !
containment - spray system or equivalent for accident management following -.a severe, accident. We also had the benefit of the documents referenced. !
j The staff position is that the . addition of a nonsafety-related containment spray system in the AP600 design =would achieve an appropriate balance between prevention and mitigation of severe accidents. The staff stated that.such a system would' compensate for the uncertainties associated with natural removal mechanisms ;
for aerosols during severe accidents and provide for accident
' mitigation and operator intervention capability as part of a long-
- tera accident management strategy. The staff bulieves that a
-containment spray system'or equivalent is consistent with the AP600
_ passive design philosophy and ' the commission's defense-in-depth philosophy.
The Westir; house position is that the AP600 desittn meets existing regulatory prevention and mitigation criteria, including the Safety Coals. This may well be the case; however, we has e not yet completed our review. Westinghouse also - contends that a '
requirassent'.for additional systems is neither justified nor warranted. The information presented to us by Westinahouse~ did not Lcddress -the relevant 1 uncertainties associated with the AP600
'probabilistic risk assessment.- ;
' cystem Ideally,,should. the -determination be based. on a of the - need for a containment spray -l l judgment as to the levele of
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uncertainties associated with aerosol depletion and overall risk, as well as on the value of additional accident management capability. The first question of interest is, what are the nature and extent of the uncertainties of concern. If all uncertainties were quantifiable, it would be fairly straightforward to determine whether sufficient defense-in-depth is built into the system by ass 9ssing the risk status with respect to the subcidiary Safety Goals (core damage frequency and large, early release f requency) .
At present, however, a large component of uncertainties remain unquantified. The identification of these uncertainties rand the qualitative judgments regarding their impact on regulatory decisions would make the debate more specif tc and would enhance .
communication among the stakeholders.
In judging the usefulness of a containment spray system in compensating for these uncertainties, roth positive and negative impacts of this system should be evalut.ced in a quantitative and qualitative way. A judgment based on such an evaluation would help make the decision more acceptable to stakeholders because the basis for the decision would be explicit and transparent. Furthermore, such an evaluation process would be a good first step to. cards the integration of risk and traditional concepts such as defense-in-depth.
Although we prefer to have the information from the evaluation outlined above, based on our current state of knowledge, we support the staff's contention that the addition of a severe accident mitigation system is appropriate. The addition of a spray system to the AP600 containment would significantly increase its effectiveness in fission product control and provide the ability to intervene and control the course of an accident. We believe, however, that the spray design concept suggested by the staff is marginally adequate.
The debate associated with this issue and the difficulty of making a decision highlight our belief that the NRC needs to develop a new I
policy statement that would provide more guidance on the extent and nature of defense-in-depth expected by the commission.
Dr. Dcna A. Powers did not participate in the committee's deliberations regarding this matter.
sincerely, R. L. Saale Chairman l
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References:
- 1. ACRS letter dated June 15, 1995, from T. 8. Kress, Chairman, ,
ACRS, to James M. Taylor, Executive Director for Operations, 5 NRC,
Subject:
Proposed Consiosion Paper on Staff Positions on
- Technical Issues Pertaining to the Westinghouse AP600 Standardized Passive Reactor Design. ;
- 2. ACRS report dated August 15,1996, from T. 8. Kress, Chairman, 6 ACR8, to Shirley Ann Jackson, Chairman, NRC, Subjects SECY-94-128, " Policy and Key Technical Issues Pertaining to the
- 3. Westinghouse Memorandum dated AP,600 Standardised November 12, 199hPasci",: Reactor t.on JamesDesign."
M. Taylor, Executive Director for operations, NRC, to the NRC Commissioners, Subjects Clarification of Staff Position in i SECY-96-128, " Policy and Key' Technical Issues. Pertaining to :
the Westinghouse A?600 Standard1997, Memorandum dated January 15, Pressurized from John C. Hoyle, Reacter Design.". ;
. 4.
Secretary, NRC, to Hugh L. Thompson, Jr., Acting Executive Director for operations, NRC, and Karen D. Cyr, General Counsel, NRC,
Subject:
Staff - Requirements - SECY-96-128 -
Policy and Key Technical Issues Pertaining to the Westinghouse AP600 Standardized Passive Reactor Design.
- 5. Memorandum dated February 19, 1997, for the Commissioners, I from Hugh L. Thompson, Jr., Acting Executive Director for operations, NRC,
Subject:
SECY-97-044, " Policy and Key
. Technical- Tssues . Pertaining to the Westinghouse AP500 Standardized Passive Reactor Design."
- 6. Memorandum dated March 18, 1997, from L. Joseph Callan, j Executive Director for Operations, NRC, to Chairman Jackson, '
Subjects Use of Non-Safety-Related Equipment to Address Safety Concerns on Nuclear Power Plants.
- 7. Letter dated March 13, 1997, from Brian A. -McIntyre, '
Westinghouse Electric Corporation, to John Hoyle, Secretary, NRC,
Subject:
Westinghouse Comments on SECY-97-044, " Policy ;
.and Key Technical _ Issues Pertaining to the Westinghorse AP600 Standard Pressurized Reactor Design."
- 8. Memorandum dated _ May _
10, 1997, from L. Joseph _ Callan, Executive Director for 0 perations, NRC, _to the_ NRC Commissioners,
Subject:
WestLnghouse Comments on SECY-97-044,
" Policy and Key Technical Issues Pertaining to the Westinghouse AP600 Standard Pressurised Reactor Design."
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, ' July 23,1997 : -
CHitt IseCLTTivt Of f 6 Cit 4= - The Honorable Shirley Ann Jackson c Chairman ,
. U.S. Nuclear Regulatory Commission ;
, ! Mail Stop O 16 015 -
zWashington, DC 20555 0001
Dear Chairman Jackson:
1 We read with interest your lets of July 2,1997, to Mr. Joseph Calla regarding
,clavation of the core damage frequency subsidiary objective to e fundamental safety '
goal,'as well as your letter of June 26,1997, that expressed support for a structured,
- broad based, risk informed, performance based pilot project. We look forward to ,
working with Mr. Ashok Thadani during the pilot project.
t As you noted, the pilot project will explore possible ways to improve the efficiency and -
cffectiveness of the regulatory framework by considering the integrated effects of plant cctivities on overall plant safety. This integrated approach differs significantly from ,
the previous regulation. specific pilot projects that were used to develop Draft
- . ' Regulatory Guide (DG) 1061, "An Approach for Using Probabilistic Risk Assessment in J
- Risk Informed Decisions on Plant Specific Changes to the Current Licensing Basis." 4 Fcr this reason, we believe it is inappropriate to constrain the project with the I
' principles and expectations associated with the much narrower risk applications {
guidance in DG 1061. Since a regulatory guide represents but one way to meet
!- ' regulatory requirements, the pilot project will be the opportunity to develop alternative cpproaches.
p We wish to reaffirm that the piloi ptoject is not intended to diminish the defense in- i i dipth philosophy, h fact, the objective of the project is to identify ways to maintain or e improve safety margins by improving the effectiveness and efficiency of the regalatory.
. process. We fully intent ik pu it project to be consistent with the Commission's I
Probabilistic Risk Asses 6m RA) policy.
1 LYcur letter also iddicated the NRC staffs preference for using the subsidiary objectives on core damage frequency and large early release frequency for regulatory decisionmaking. We agree that the frequency of undesirable severe accident events should be 1 ept sufficiently low. The proposed project will trend core damage frequency to ensure that adverse'trendT are not developing.
- We? are concerned, however, that the guidance in DG 1061 could cause the NRC staff to treat core damage frequency and large early release frequency values as absolute p
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N Honorchis Shirley Ann Jcckton July 23,1997 Page 2 Emits. We believe such a move would be too restrictive and would preclude regulatory enhancements. Focus on these values would divert both NRC and indastry resources to matters that have insignificant core damage frequency impact for plants that were at or slightly above the subsidiary objective.
We also note in your memorandum to Mr. Joseph Callan dsted July 2,1997, that consideration is being givan H!v'rting the core damage fre mency subsidiary objective of 104 per reactor. year to a fundamental safety goal. We believe the cafety goals should retain their current, direct focus on public health and safety fo" the following reasons:
. ' While core damage frequency is a useful value in managing plant risk, a "one size Sta all" value does not relate directly to public health and safety effectively for all plant sites, e It is inappropriate to raise the 104 per reactor. year core damage frequency subsidiary objective to a fundamental safety goal for existing plants. The subsidiary objective has been historically characterized as being a mean industry value and not applied on a plant specific basis. It is unfair to backfit a specific core damage frequency criteria to a generation of plants that were designed without this criteria.
Given that the safety goals are widely viewed as the Commission's expression of
- how safe is safe enough," using core damage frequency as a fundamental safety goal now would send a message to the public that plants that exceed the core damage frequency objective are unsafe, even though they may be well below the safety goal quantitative health objectives.
4 e in addition, establishing a 104 per reactor year core damage frequency value as a funiamental goal could have a chilling effect on licensee willingness to develop more t.nplete core damage frequency risk analyses that could put their plants close to or chwe an established goal.
We believe a better course of action would be to assess a realistic range of core damage frequency values, based on complete core damage frequency risk analyses, performed by both the industry and the NRC. These more accurate, and more certain, values could then be used to determine the margins to the quantitative health objectives of the safety goal policy. Information being developed in conjunction with the proposed pilot project supports this approach.
Sincerely, I
k .)c.c oc fF. Colvin l- -
.. - . ..- .= . -- .- -. . - - . - - - -. --.
,. . i The H:norable Shirley Ann Jfckson July 23,1997 Page3
c: The Honorable Greta J. Dieus-The Honorgble Nils J. Diaz The Honorable Edward McGafBgan, Jr.
Mr. L. Joseph Callan .-
Mr. Ashok C. Thadani e
1 en a
9 y <.~m . 4