ML20206S610
| ML20206S610 | |
| Person / Time | |
|---|---|
| Issue date: | 12/23/1998 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-3130, NUDOCS 9905210171 | |
| Download: ML20206S610 (7) | |
Text
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CERTIFIED BY:
Date issued: 12/23/98 George Apostolakis - 12/29/98 ADVISORY COMMITTEE ON REACTOR SAFEGUARDS MEETING OF THE SUBCOMMITTEES ON RELIABILITY AND PROBABILISTIC RISK ASSESSMENT AND ON REGULATORY POLICIES AND PRACTICES MEETING MINUTES - OCTOBER 29,1998 ROCKVILLE, MARYLAND INTRODUCTION The ACRS Subcommittees on Reliability and Probabilistic Risk Assessment (RPRA) and on Regulatory Policies and Practices met on October 29,1998, at 11545 Rockville Pike, Rockville, MD, in Room T-283. The purpose of this meeting was to continue the Subcommittee's discussion of proposed options to make 10 CFR part 50 risk-informed, Nuclear Energy Institute Whole Plant Study, and options for developing a risk-informed approach to revising 10 CFR 50.59 (Changes, Tests and Experiments). The Subcommittees also reviewed the staff's safety evaluation report (SER) for the Westinghouse Owners Group (WOG) topical report (WCAP-14572, Revision 1) on risk-informed inservice inspection (ISI) of piping and associated Structural Reliability and Risk Assessment (SRRA) model (Supplement 1).
The entire meeting was open to public attendance. Mr. Michael T. Markley was the cognizant ACRS staff engineer for this meeting. The meeting was convened at 8:30 a.m. and adjoumed at 4:30 p.m.
ATTENDEES ACRS Members G. Apostolakis, Chairman R. Seale, Member T. Kress, Co-chairman W. Shack, Member M. Fontana, Member G. Wallis, Member D. Miller, Member M. Markley, ACRS Staff D. Powers, Member Princioal NRC Speakers S. Ali, NRR*
S. Dinsmore, NRR G. Bagchi, NRR G. Holahan, NRR S S~ O h E
J. Strosnider, NRR 9905210171 981223
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t Joint RPRNReg. Pol. & Prac. Subete. 10/29/98 Minutes PrincipalIndustry Speakers K. Balkey, WOG*
B. Bishop, WOG B. Bradley, NEl*
N. Closky, WOG A. McNeill, WOGNa. Power Co.
D. Weakland, WOG/DuQuesne Light Co.
R. West, WOG/ Northeast Utilities NRR Office of Nuclear Reactor Regulation RES Office of Nuclear Regulatory Research WOG Westinghouse Owners Group NEl Nuclear Energy Institute l
l There were approximately 16 members of the public in attendance at this meeting. A l
complete list of attendees is in the ACRS Office File, and will be made available upon request. The presentation slides and handouts used during the meeting are attached to the office copy of these minutes.
OPENING REMARKS BY THE SUBCOMMITTEE CHAIRMAN l
l Dr. Apostolakis convened the meeting at 8:30 a.m. He introduced ACRS Members in attendance and stated that purpose of this meeting was to review the staff's safety evaluation report (SER) for the Westinghouse Owners Group (WOG) topical report (WCAP-14572, Revision 1) on risk-informed inservice inspection (ISI) of piping at nuclear power plants, as well as associated pilot applications. He also stated that the Subcommittee's would continue their discussion of proposed options to make 10 CFR part 50 risk-informed, Nuclear Energy Institute Whole Plant Study, and options for developing a risk-informed approach to revising 10 CFR 50.59 (Changes, Tests and Experiments).
Dr. Apostolakis stated that the Subcommiitee had received no written comments or requests for time to make oral statements from members of the public.
DISCUSSION OF AGENDA ITEMS Safety Evaluation Report on WCAP-14572 f
i' e
Joint RPRNReg. Pol. & Prac. Subete. 10/29/98 Minute. s NRC Presentation l
Mr. Jack Strosnider, NRR, provided introductory remarks for the staff presentation of the staffs safety evaluation report for the WOG topical report (WCAP-14572, Revision
- 1) on risk-informed ISI of piping and associated Structural Reliability and Risk Assessment (SRRA) model (Supplement 1). Mr. Goutam Bagchi, NRR, led the discussion for the NRC staff. Messrs. Richard Barrett, Syed Ali, and Steven Dinsmore, NRR, provided supporting discussion. Significant points made during the presentation include:
The staff concluded that ISI of piping is a very good application for risk-informed decisionmaking.
1 e
The staff plans to issue an Information Notice allowing a 2-year extension on the 10-year ISI interval for plants desiring to use a risk ' informed approach.
e The WOG application meets the criteria in Regulatory Guide 1.174 (General Guidance) and Regulatory Guide 1.178 (ISI) for risk-informed decisionmaking.
e The staff agrees with the WOG commitments in response to NRC requests for additional information are acceptable and will be incorporated as part of the i
l sk#s SER.
Although the codes used to derive pipe segment failure probabilities are valuable tools, the results are highly reliant on the judgement of the analyst.
Augmented programs for known failure mechanisms such as erosion / corrosion e
I remain unchanged. Also, all systems will continue to get pressure tests.
i industry Presentation Mr. Biff Bradley, NEl, introduced the industry participants and made introductory remarks regarding the importance of risk-informed ISI application. Messrs. Ken Balkey, WOG, and Dennis Weakland, WOG/DuQuesne Light Co., led the discussions for WOG.
Ms. Nancy Closky, WOG, and Messrs. Bruce Bishop, WOG, Alex McNeill, WOGNirginia Power Co., and Ray West, WOG/ Northeast Utilities provided supporting discussion. Significant points made during the presentation include:
e The WOG approach makes use of plant-specific PRA models to evaluate interactions and' responses among multiple systems from direct and indirect effects of potential piping integrity failure modes: small leak, large leak, and rupture.
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Joint RPRA/ Reg. Pol. & Prac. Sutete.
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The WOG approach uses the SRRA model to estimate the likelihood of various piping mode failure modes, accounting for generic industry and plant-specific operating experience.
Risk-importance measures are applied to define high-and low-safety-significant I
e piping segment categories.
e The plant will utilize an expert panel to systematically review PRA models, failure mode / probability information and risk importance measures along with deterministic and operational insights to make categorization determinations for P ping segments.
i e
A 2x2 structural element selection matrix is used to guide the location and method of examination and a statistical model is used to define the minimum number of locations for examination of HSS segments.
e inspection program requirements are defined using the latest ASME Code Cases and industry guidance.
e This methodology meets the criteria in Regulatory Guides 1.174 (General Guidance) and 1.178 (ISI) for risk-informed decisionmaking.
e Risk-jnformed ISI will enhance safety, reduce occupational radiation exposure to workers, and reduce operations and maintenance costs (O&M).
Risk-Informed 10 CFR Part 50 NRC Staff Presentation Messrs. Mark Cunningham, RES, and Richard Barrett, NRR, led the discussions for the NRC staff regarding options to make 10 CFR Part 50 risk-informed. Mr. Gary Holahan, NRR, provided supporting discussion. Significant points made during the presentation include:
e A major problem with making Part 50 risk-informed is the definition and requirements associated with the term " safety-related." Many components classifiexf as safety-related are not risk significant and some risk-significant items are not safety-related.
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e Joint RPRNReg. Pol. & Prac. Subete. 10/29/98 Minutes Potential areas for revising Part 50 include: the definition of safety-related, the e
maintenance rule, quality assurance requirements in Appendix B of 10 CFR 50, and 10 CFR 50.5g. Additional changes should be considered in license amendments, enforcement, and performance assessment.
-e Potential options to make Part 50 risk-informed include:
Make selected specific changes (e.g.,10 CFR 50.5g,50.72 and 50.73, Maintenance Rule, and revised source term).
Redefine scope of requirements including the definitions of" safety-related,""important to safety," and conforming changes.
Modify Part 50 to allow for risk-informed alternatives to current rules (i.e.,
process changes only).
Rewrite some or all of Part 50 (i.e., phased-in approach).
i Policy issues include: mandatory versus voluntary changes; possible exemptions e
for pilot plants, categorization of systems, structures, and components (SSCs);
and the scope of what is to be risk-informed, and the relationship to ongoing rulemakings (e.g., maintenance rule).
implementation issues include: selection of SSCs (e.g., risk-metrics, defense-in-i e
depth, and safety margin); PRA quality; inclusion of requirements for non-safety-related SSCs; documentation related to FSARs and PRAs; and the need for revised guidance in SRP/RGs, inspection, enforcement, and performance assessment.
Attributes of a risk-informed 10 CFR Part 50 include: providing clear, consistent, e
and coherent requirements; addressing design and operational characteristics commensurate with importance to safety; preserves defense-in-depth philosophy; accommodates plant-specific design and operational requirements; and it can be performance-based to the extent practicable, i
NEl Presentation Mr. Tony Pietrangelo of the Nuclear Energy Institute (NEI) provided a brief discussion of the NEl Whole Plant Study and options to make 10 CFR Part 50 risk-informed.
Significant points made during the discussion include:
l NEl has had a lot of input into the staffs deliberations regarding possible e
revisions to 10 CFR Part 50. However, many licensees are reluctant to consider broad changes to Part 50. NEl stated that this skepticism could be addressed through early success of pilot applications and suggested that the current
i Joint RPRA/ Reg. Pol. & Prac. Subete. 10/29/98 Minutes rulemaking proposal for the Maintenance Rule be modified for use as a pilot for L.
making Part 50 risk-informed.
SUBCOMMITTEE COMMENTS. CONCERNS. AND RECOMMENDATIONS Dr. Powers questioned the Justification for determining that PRAs are of sufficient quality for reasonable decisionmaking. The staff stated that PRAs are have been reviewed through the Individual Plant Examination process and Maintenance Rule inspections. The staff added that the licensee expert panels are expected to evaluate the quality of PRA appropriate to the proposed change. The staff noted that industry certification programs and ASME Standards development efforts are expected to improve the results as more progress is made.
Dr. Apostolakis questioned how risk is considered when PRA focuses on systems and not individual pipe segments. The staff stated that risk is based on the evaluation of systems affected by piping failures.
Dr. Apostolakis questioned how erosion / corrosion mechanisms were considered for the various geometries of pipe bonds. WOG representatives reiterated that augmented programs for known degradation mechanisms such as erosion / corrosion remain unchanged.-
Dr. Apostolakis questioned the guidance in both the SER and WCAP-14572 regarding consideration of uncertainties. Dr. Aposto!akis suggested that the guidance be modified to clarify consideration of uncertainties (parameter versus model uncertainty).
The staff and WOG representatives agreed to take the suggestion under consideration.
Dr. Shack questioned how to define " design limiting events." WOG representatives stated that it varies from system to system and noted that the decision relies heavily on the judgement of the analyst.
Drs. Apostolakis and Wallis questioned the objectives for 10 CFR Part 50 and what is to be accomplished in the proposed revisions. Dr. Wallis suggested that the staff clarify what it means by " safety" and "important to safety." The staff stated that adequate safety means meeting regulatory requirements but acknowledged that some improvement could be made in the definition of terms.
Dr. Apostolakis questioned the possible use of frequency-consequence (F-C) curves in risk-informed decisionmaking and noted that the use of F-C curves allows one to get away from core damage frequency (CDF) and large, early release frequency (LERF).
Dr. Kress stated that F-C curves can consider smaller radioactive releases for which CDF/LERF analysis are insensitive but are still of concern to the industry and the public.
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Joint RPRNReg. Pol. & Prac. Subete. 10/29/98
. Minutes The staff stated that it would be an enormous effort to generate F-C curves and noted that they may be difficult to use on a practical basis.
STAFF AND INDUSTRY COMMITMENTS At the conclusion of the meeting, Dr. Apostolakis informed the staff and WOG that he believed that some of the methodology and equations related to uncertainty were incorrect. The staff and WOG representatives agreed to address these concems at the November 5-7,1998 ACRS Meeting.
j SUBCOMMITTEE DECISIONS At the conclusion of the meeting, Dr. Apostolakis informed the staff and industry representatives that the Committee plans to prepare a report regarding the staff's SER and WCAP-14572 at the November 5-7,1998 ACRS meeting. He informed attendees that 10 CFR Part 50 would be discussed at a future Subcommittee meeting and would not be discussed at the November ACRS meeting.
FOLLOW-UP ACTIONS None.
BACKGROUND MATERIALS PROVIDED TO THE SUBCOMMITTEE PRIOR TO THIS I
MEETING 1.
Subcommittee agenda.
2.
Subcommittee status report.
3.
Memorandum received October 19,1998, from Goutam Bagchi and Richard J.
J Barrett, NRR, to John T. Larkins, Executive Director, ACRS,
Subject:
Safety Evaluation Report Related to Westinghouse Owners Group Application of Risk-Informed Methods to Piping Topical Report (WCAP-14572, Revision 1).
4.
Handouts from Octotier 8,1998 meeting between the NRC staff, the Westinghouse Owners Group, and NEl regarding WCAP-14572.
5.
Letter dated September 30,1998, from Louis F. Liberatori, Jr., Chairman, i
Westinghouse Owners Group, to Peter C. Wen, NRC,
Subject:
Transmittal of Responses to NRC Open items on WOG RI-ISI Program and Reports.
6.
Letter dated August 10,1998, from Brian W. Sheron, NRR, to Anthony R.
Pietrangelo, NEl,
Subject:
Staff's Plans for Reviewing Risk-Informed Inservice Inspection Submittals.
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s, w
Joint RPRA/ Reg. Pol. & Prec. Subete. 10/29/98
, Minutes 7.
Report dated June 12,1998, from R.L. Seale, Chairman, ACRS, to Shirley Ann Jackson, Chairman, NRC,
Subject:
Proposed Final Standard Review Plan Section 3.9.8 and Regulatory Guide 1.178 for Risk-informed inservice inspection.
8.
Meeting summary dated September 17,1998, from Noel Dudley, ACRS Staff, to ACRS Members,
Subject:
Meeting with NEl regarding Whole Plant Study and proposed schedule for Part 50 Rulemaking.
l 9.
Memorandum dated October 15,1998, from Richard J. Barrett, NRR, to Gary M.
Holahan, NRR,
Subject:
Public Meeting on C_onsideration of Risk-informed 10 CFR Part 50 Regulations, including handouts.
10.
Draft report dated October 19,1998, from Drs. Apostolakis and Kress, ACRS, for consideration by the Committee in advising the Commission on the use of i
frequency-consequence curves in risk-informed decisionmaking.
11.
Staff Requirements Memorandum dated September 25,1998, from John C.
Hoyle, Secretary, NRC, to L. Joseph Callan, EDO,
Subject:
12.
Response dated July 29,1998, from Shirley Ann Jackson, Chairman, NRC, to John C. Hoyle. Secretary,
Subject:
SECY-98-171 (pre-decisional, for ACRS use only) 13.
. Response dated September 2,1998, from Commissioner Diaz, to John C.
Hoyle, Secretary,
Subject:
SECY-98-171 (pre-decisional, for internal ACRS use only).
14.
Response dated September 19,1998, from Commissioner McGaffigan, to John C. Hoyle, Secretary, NRC,
Subject:
SECY-98-171 (pre-decisional, for intamal ACRS use only).
15.
Report dated July 16,1998, from R. L. Seale, Chairman, ACRS, to Shirley Ann Jackson, Chairman, NRC,
Subject:
Proposed Revisions to 10 CFR 50.59 (Changes, Tests and Experiments).
Ngte: Additional details of this meeting can be obtained from a transcript of this meeting available in the NRC Public Document Room,2120 L Street, N.W.
Washington, D.C. 20006, (202) 634-3274, or can be purchased from Ann Riley &
Associates, Ltd., (Court Reporters and Transcribers) 1250 l Street, NW, Suite 300, Washington, D.C. Rhode Island Avenue, N.W. Washington, D.C. 20005 (202) 842-0034.
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