ML20210H243
| ML20210H243 | |
| Person / Time | |
|---|---|
| Issue date: | 05/28/1997 |
| From: | Apostolakis G Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-3022, NUDOCS 9708130319 | |
| Download: ML20210H243 (12) | |
Text
G orgo Aposto3ckie - 5/28/97 gg,g ADVISORY COMMITTEE ON REACTOR SAFEGUARDS PPG JOINT MEETING OF THE SUBCOMMITTEES ON PROBABILISTIC RISK ASSESSMENT AND PIANT OPERATIONS MEETING MINUTES - JULY 17-18, 1996 ROCKVILLE, MARYLAND INTRODUCTION l
The ACRS Subcommittees on Probabilistic Risk Assessment (PRA) and on Plant Operations met on July 17-18, 1996, at 11545 Rockville Pike, Rockville, MD, in Room T-2B3.
The purpose of this meeting was to discuss the NRC programs for risk-based analysis of reactor operating experience (July 17) and to discuss issues identified in the Staff Requirements Memoranda (SRMs) dated May 15 and June 11, 1996, including the role of the performance-based regulation ir. the PRA Implementation Plan, plant-specific application of safety goals, risk neutral versus the allowance for acceptable increases in risk, risk-informed inservice testing (IST) and inservice inspection (ISI) requirements, and the pilot applications for risk-informed, performance-based regulation (July 18).
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. each day, recessed at 5:09 p.m. on July 17, and adjourned at 6:31 p.m. on July 18.
ATTENDEES ACRS G. Apostolakis, co-Chairman D. Miller, Member C. Wylie, co-Chairman R. Seale, Member I. Catton, Member W. Shack, Member M. Fontana, Member S. Kaplan, Invited Expert T. Kress, Member M. Markley, ACRS Staff W. Lindblad, Member R. Sherry, ACRS Fellow Princioal NRC Sceakers I
P. BaranowMty, AEOD*
J. Murphy, RES M. Cheok, NRR*
S. Mays, AEOD l
M. Cunningham, RES*
D. Rasmuson, AEOD M. Drouin, RES A. Ramey-Smith, RES G. Holahan,_NRR M. Rubin, NRR T. Hsia, NRR A. Thadani, NRR T. King, RES d ( /"' 9
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9708130319 970811 PDR ACRS 3022 PDR
Joint PRA/P1 nt Ops. Subete.
3 2-Minutes ***#
7/17-10/96 Industrv/Public Presenters D. Brewer, WOG*
A. Hackenrott, CEOG*
G.
Kreuger, BWROG*
B.
Parkinson, SAIC*
T. Pietrangelo, NEI*
D. True, ERIN Engineering i
AEOD - Office for Analysis and Evaluation of Operational Data RES - Office of Nuclear Regulatory Research NRR - Office of Nuclear Reactor Regulation WOG - Westinghouse Owners Group CEOG - Combustion Engineering Owners Group DWROG - Boiling Water Reactor Owners Group SAIC - Science Applications International Corporation NEI - Nuclear Energy Institute A complete list of meeting attendees is in the ACRS Office File, and will be made available upon request.
The presentation slides I
and handouts used during the meeting are attached to the office copy of these minutes.
JULY 17. 1996 Openino Remarks Dr. George Apostolakis, Chairman of the joint Subcommittees, convened the meeting and stated that the purpose of the meeting was to discuss the NRC programs for risk-based analysis of reactor operating experience (July 17) and to discuss the issues identified in the SRMs dated May 15 and June 11, 1996, including the role of the performance-based regulation in the PRA Implementation Plan, plant-specific application of safety goals, risk neutral versus the allowance for acceptable increases in risk, risk-informed IST and ISI requirements, and the pilot spplications for risk-informed, performance-based regulation (July 18).
He also stated that he had a conflict with portions of the meeting and indicated that Mr. Hv11e, Chairman of the Plant operations Subcommittee, would serve as Chairman for those portions of the meeting.
Dr. Apostolakis noted that no written comments or requests for time to make oral statements were received from members of the public for this portion of the meeting.
Joint PRA/Plcnt Opo. Subeto. 7/17-18/96 Minutes NRC Staff Presentation Mr. Patrick Baranowsky, Chief, Reliability and Risk Assessment Branch (RRAD), Safety Programs Division (SPD), AEOD, led the I
discussion for the NRC staff.
Messrs. Steven Mays, Chief, Reactor Risk Assessment Section, RRAB, and Dale Rasmuson, RRAB, made presentations and provided supporting discussion.
Messrs. Baranowsky and Mays provided an overview of the AEOD programs for risk-based analysis of reactor operating experience.
They discussed the mission of AEOD, the use of plant operating experience for assessing and trending risk indicators, comparing actual plant experience with probabilities assumed in the licensee Individual Plant Examinations and Probabilistic Risk Assessments (IPEs/PRAs), and the use of insights to enhance the effectiveness of the regulatory process.
They also discussed AEOD programs as part of the PRA Implementation Plan.
Significant points made during the discussion includes AEOD is requesting feedback from the ACRS with regard to the e
overall direction and technical approach of its programs.
The overall approach is based on the systematic decomposition of industry risk.
Overall plant risk is decomposed into measures of core damage frequency (CDF),
containment failure probability, and health effects, etc.
Each of these areas is decomposed further to consider subsidiary aspects of each element.
AEOD has the following programs for risk-based analysis of reactor operating experience:
Accident sequence precursor (ASP) analysis Event frequency evaluations based on initiator groupings System reliability studies Common-cause failures Component studies Initiating events Performance indicators (PIs)
Operational databases - data systems for search and sequence coding analysis of reliability and availability Special studies - as needed Mr. Rasmuson presented the Accident Sequence Precursor Program.
He discussed the overall objectives of the program, the process for screening operational events, the results of ASP evaluations, and trends realized from the results of these evaluations.
Significant points made during the discussion include
Joint PRA/ Plant Ops. Subete.
-4 7/17-18/96 "inutes The objectives are to identify and rank risk-significant e
events, to determine generic implications, to evaluate licensee PRAs to assess the validity of assumptions, and to develop useful insights and trends from actual operating experience.
The program uses licensee event reports as the primary source of information for screening the large volume of industry operating experience.
This program has highlighted individual plant events which were not fully reald2ed by other NRC programs in terms of risk.
The overall frequency of risk-significant events decreased e
over the ten-year period examined from 1984-1994, The staff plans to continue its development of ASP models e
and methods,. including those that can be used on a plant-specific basis and for simplified Level 2 and Level 3 PRAs.
Mr. Rasmuson also presented the Common-Cause Failure (CCF)
Program.
He provided an overview of the CCF Program, discussed the CCF failure analysis methodology, described development of the CCF database, and summarized the results from that database.
Significant points made during the discussion includes e
A common-cause failure is a dependent failure in which one or more component fault states exist simultaneously, or within a short time interval, and are a direct result of a shared cause, o
In system modeling, the basic event which represents the unavailability of a specific set of shared components because of shared causes are not explicitly represented in the system logic model.
e Attributes of a CCF event include a failure of two or more components; failures exist simultaneously, or within a short time interval; and failures are a direct result of shared Causes.
e Elements of CCF analysis include:
Data collection
- common-cause failure event assessment of the degradation of components, etc.
o I
Joint PRA/ Plant Ops. Subete. 7/17-18/96 i_
Minutes V
i j
system modeling i
- common-cause basic event
- common-cause component group (CCCG)
- estimation of CCF probabilities o
CCF quantification methodh includes Binomial failure rate Basic parameter method
}
- basic parameter method - quantification 3
i
- Alpha factor - estimation of parameters i
- Multiple. Greek Letter Method (MGL) - conditional 3
j probability formulation Attributes of a CCF model includes assumptions, component i
failure model, probability model, data collection, i
estimation of parameters, and quantification.
Bube- -4ttee Questions and Comments
- Drs. Apostolakis and Powers asked about the applicability of l
analyses to all modes of operation (i.e., shutdown and low power-operations, etc.).
The staff stated that most of the analyses j
were for operating events.
The staff added, however, that some shutdown events had revealed the potential for significant risk during other modes of operation, but acknowledged that models had a
not been developed to adequately address these other modes of operation.
Drs. Kress, Kaplan, Powers, and Apostolakis questioned the use of models (Fussel-Vesely, Risk Achievement Worth, etc.) in analyzing i
events.
The staff stated each model has its supporters and critics.
The staff emphasized that the models can be used appropriately or inappropriately but acknowledged that more work was needed in this area..
Mr. Lindblad asked how the staff considered information and trending required by the Maintenance Rule.
The staff stated-that it does not have direct access to information licensees are using pursuant to the Maintenance Rule.
However, the-staff noted the efforts being pursued with Institute _of Nuclear Power Operations (INPO) regarding information that might be subject to the proposed Reliability Data Rule, i
Dr. Apostolakis questioned how the results of the ASP studies
)
were provided to inspectors and licensees.
The staff stated that an annual ASP report is published.
More urgent safety issues arc 4
A s
1 b
Joint PRA/ Plant ops. Subete. 7/17-18/96 Minutes
+
addressed via generic communications such as Information Notices, Generic Letters, NRC Bulletins, etc.
The Subcommittee and staff extensively discussed the CCF Program.
Dr. Apostolakis asked about the technical bases for the CCF models.
In particular, he questioned the use of judgment for evaluating data where the actual numbers are very low.
The staff stated that there is a problem with the fact that not many events fall into this category.
There is some need for expert judgment.
Mr. Parkinson of SAIC stated that it is an improvement to break the event down into a series of disciplined judgments rather than making global judgements.
Dr. Apostolakis questioned the use of uncertainty analysis for impact vectors.
The staff stated that it was a difficult issue to resolve for small measures.
At the conclusion of the July 17 session, Dr. Seale expressed the view that there is a need for more sharing of these important databases between the NRC and the industry.
Mr. Lindblad-stated that a lot of work could be done to improve the risk analysis _of the models and that process and conclusions should be subjected to peer review.
Dr. Apostolakis noted that there were some significant achievements in the staff's work in this area but questioned what research was being done and where it would go next.
JULY 18_ 1996 Onanina R-- rks Dr. George Apostolakis, Chairman of the joint Subcommittees, convened the meeting and stated that this was the second day of a two-day meeting of the joint-Subcommittees and the purpose of the meeting was to discuss the issues identified in the SRMs dated
- May 15 and June 11,-1996, including-the role of performance-based regulation in the PRA Implementation Plan, plant-specific
-application of safety goals, risk neutral versus the allowance for acceptable increases in risk, risk-informed IST and ISI requirements, and the pilot, applications for risk-informed, performance-based regulation.
Dr. Apostolakis stated that the Subcommittees had received a request from Mr. Bill Parkinson of SAIC to make a presentation on risk. ranking.- He also noted that Mr. Tony Pietrangelo of NEI'had requested-to discuss industry initiatives related to risk-informed. regulation.
4
Joint PRA/ Plant Ops. Subete. 7/17-18/96 Minutes NRC Staff Presentation Mr. Ashok Thadani provided an overview of the NRC effort to develop Standard Review Plan (SRP) Sections and associated Regulatory Guides for risk-informed, performance-based regulation.
Messrs. Gary Holahan, Director, Division of Systems safety and Analysis, NRR, and Mark Cunningham, Chief, Probabilistic Risk Analysis Branch, PRAB/RES, led the discussions for the NRC staff.
Messrs. Mark Rubin and Michael Cheok, NRR, o
and Ms. Ann Ramey-Smith provided supporting discussion.
Mr.-Thadani requested ACRS feedback on the policy and technical issues identified in the Staff Requirements Memorandum dated May 15, 1996.
He stated that the Commission had established a challenging schedule.for completion of the SRP sections and Regulatory Guides.
He added that the Commission was concerned about consistency of the regulatory process and the adequacy of the NRC infrastructure for such changes.
Mr. Thadani requested ACRS involvement in the early stages of development of the SRP sections and associated Regulatory Guides.
Messrs. Cunningham and Ms. Ramey-Smith discussed issues associated with the integration of deterministic and probabilistic evaluations, plant-specific application of safety goals, risk neutral versus increases in risk.
They reviewed the traditional or deterministic approach to evaluating submittals for changes to the current licensing basis (CLB) and the key issues requiring resolution for use of the risk-informed approach.
Significant points made during the discussion include:
e Plant-specific application of safety goals e
Consideration of total plant risk o-Risk neutral versus allowance for increases in risk e
Accounting for uncertainty e
Use of partial PRAs PRA issues include e
Quality of PRA e
Standard treatment of issues e
-Peer-review The overall staff approach would entails i
e Implementation and use of safety goals and subsidiary objectives to derive plant-specific objectives, o
Use of risk-informed initiatives would involve total plant risk or some subset.
Joint PRA/ Plant Ops. Subete. 7/17-18/96 Minutes Small increases in risk would be acceptable except for e
plants that already exceed the safety goals.
Neutral changes and those that reduce risk would be acceptable.
Other factors such as presence on the NRC "watchlist" of problem plants would be considered.
Packaging or grouping of risk submittals would be considered e
with some limitations, Further clarification is needed on how to use uncertainty o
analysis in evaluating against submittals (e.g., use mean values).
Plants with partial PRAs may be considered with margins to
'e account for unanalyzed modes of operation.
i The staff had not resolved options for minimum acceptable e
standards for PRA quality nor how to reconcile differences L
between PRAs.
The staff supports the use of third party for licensee peer l
e reviews (subject to NRC audit).
Mr. Holahan discussed performance-based regulation and its relationship to the-pilot applications. -He summarized the key elements of a performance-based regulatory approach.
Significant points made during the discussion include:
Key elements of a performance-based approach:
e Measurable parameters e
objective criteria Flexibility in how to meec performance criteria e
Failure to meet criteria must not result in unacceptable e
consequences Uses of performance-based approach:
e Validates assumptions (deterministic and probabilistic) of regulatory framework Places emphasis on " output" rather than " input" (i.e.,
results rather than efforts)
Helps define purpose or goal of regulatory approach in terms e
.of performance characteristics and safety significance Industry Presentations Mr. Tony Pietrangelo of NEI coordinated industry presentations.
Mr. Duncan Brewer, representing Duke Power Company and the-Westinghouse owners Group, discussed the PSA Model Methods and
4 Joint PRA/ Plant Ops. Subete. 7/17-18/96 Minutes Results Comparison Program.
Mr. Alan Hackenrott, representing the Combustion Engineering Owners Group, discussed the Owners Group's participation in the pilot applications, for Technical Specifications, IST and ISI.
Mr. Greg Kreuger, representing the Boiling Water Reactor Owners Group, dincussed the peer review certification process.
Mr. Pietrangelo discussed the HEI " white paper" detailing the proposed probabilistic safety assessment (PSA) certification process.
He also discussed the NEI PSA Action Plan.
Mr. Doug True of ERIN Engineering provided supporting discussion.
Significant points made during the discussion includes The suggestion that a Commission policy statement on e
performance-based regulation is a good idea, The NRC approach, as dencribed during these presentations, o
is an additional layer of regulatory burden.
The NRC should focus on the specifics of licensee requests and not the breadth and depth of what may be accomplished.
The industry proposes to use the PSA certification initiative to establish the requisite quality for PRAs.'
NEI proposes to use the three-region zone in the PSA Applications Guide as criteria for acceptance of proposed
- changes, i
Core damage is an unacceptable situation even if the plant l
e can fully maintain containtaent to preclude a large, early j
release.
Mr. Parkinson of Science Applications International Corporation I
discussed risk ranking.
Significant points made during the discussion includes Risk ranking validates Fussel-Vesely and Risk Achievement e
Worth for basic plant features, e
A net safety benefit can be derived from risk ranking.
Risk importance results depend on basic plant features.
l Redundancy within a safety function has the most effect on l
4 importance.
Benefits include:
extending importance measures to unmodeled components reduced truncation concerns links PSA to design basis
Joint PRA/ Plant Ops. Subete. 7/17-18/96 o
Minutes treats unmodeled issues (i.e., shutdown, etc.)
exposes critical model assumptions and data (ubcassaittee Questions and C=- -ats Dr. Apostolakis and Powers asked how the staff would handle proposed changes that involve short-term high peaks in risk.
The staff expressed agreement and cited "on-line maintenance" as an l
example where the risk might be higher than previously analyzed.
Drs. Apostolakis and Kress expressed the view that it was total risk that should be considered in reviewing licensee submittals.
Accordingly, they stated that this would allow for small, incremental increases in risk. - They added that this would require some definition of "small" and quantification of uncertainty where possible.
Dr. Kress expressed the view that licensees should have a Level 3 PRA with appropriate analysis of uncertainty.
He stated that these studies are needed to get to surrogate or subsidiary plant-specific safety goals.
Dr. Powers stated that some increase in risk could be justified with reduced uncertainty.
Dr. Apostolakis expressed the view that the staff's approach was too prescriptive for a voluntary program.
He stated that licensee modeling and assumptions should be considered in the context of the proposed-change.
Mr. Lindblad questioned the quality of PRA that will be expected.
The staff ~ stated that proposed program would require a peer review. The staff acknowledged that this may add another level of subjectivity but emphasized that this-discipline was intended to reduce the. subjectivity and add increased confidence.
Dr. catton asked whether licensee peer review panels would be composed of PRA practitioners of expert panels.
Industry representatives stated that it would most likely be a cross section of plant personnel including PRA practitioners.
Dr.
Apostolakis expressed the view that practitioners would be suitable for most changes.
Dr.-Powers questioned why_there was so much emphasis on containment integrity when containment bypass evente are dominant segaences for offsite exposure.
Industry representatives expressed the view that this was a good example where there was too much_ emphasis on numbers =in the-NRC approach.
Dr. Fontana expressed concern that this initiative might be viewed as another form of deregulation.
He expressed the view that there should be some safety benefit and that the regulations should not be relaxed based on cost savings alone.
.o Joint PRA/ Plant Ops. Subete.
11 7/17-18/96 Minutes Followuo Actions At the conclusion of the July 17 session, the Subcommittees decided not to refer the AEOD programs for risk-based analysis of
(
reactor operating experience to the full Committee for consideration at the August 8-10, 1996 meeting.
The Subcommittees decided to have another meeting at a future date and the Chairman agreed to provide the staff with c. list of issues to be discussed at that meeting.
At the conclusion of the July 18 session, the Subcommittee decided another subcommittee meeting was needed to review the policy and technical issues discussed by the staff.
The Subcommittees agreed to have another meeting on August 7, and refer this matter for full Committee review during the August 8-10, 1996 meeting.
Subcommittee Chairman Apostolakis requested copies of the CEOG risk-informed licensing submittals and the associated requests for additional information (RAIs),
i Backaround Material Provided to Subcommittee for this Meetina 1.
AEOD program guidance document dated December 15, 1995, from S. Mays, AEOD, through P. Baranowsky, AEOD, to C. Rossi, AEOD, Subj: " Risk-Based Analysis of Reactor Operating f
Experience" 2.
Memorandum dated March 22, 1996, from C. Rossi, AEOD, to NRR Directors and Regional Directors, Division of Reactor Safety, Subj: "Special Report - Emergency Diesel Generator Power System Reliability 1987-1993," INEL-95/0035 (1 volume) 3.
Memorandum dated December 22, 1995, from C. Rossi, AEOD, to G. Holahan, NRR, and W. Hodges and L. Shao, RES, Subj:
" Common-Cause Failure Parameter Estimates for Selected Components," INEL-94/0064 (6 volumes) 4.
Staff Requirements Memorandum dated June 11, 1996, from J.
Hoyle, SECY, to John T. Larkins, ACRS, Subj Requested ACRS actions regarding meeting with the Commission on May 24, 1996 5.
Staff Requirements Memorandum dated May 15, 1996, from J.
Hoyle, SECY, to J. Taylor, EDO, Subj Requested actions regarding Commission briefing on PRA Implementation Plan on April 4, 1996 6.
Memorandum dated March 26, 1996, from J. Taylor, EDO, to Chairman Jackson, NRC, Subj: " Status Update of the Agency-Wide Implementation Plan for Probabilistic Risk Assessment (PRA) (from March 30, 1995 to February 29, 1996)"
7.
Memorandum dated March 26, 1996, from A. Thadani, NRR, to G.
Apostolakis, ACRS, Subj: " Transmittal of OECD/CSNI Report
t Joint PRA/ Plant Ops. Subete. 7/17-18/96 e
Minutes Summarizing Workshops on Living PSA Development and Application ir Member Countries" 8.
Letter dated vune 12, 1996, from T. Pietrangelo, NEI, to M.
Markley, ACRS, Subj Industry White Paper, NEI 96-04,
" Enhancing Nuclear Plant Safety and Reliability Through Risk-Based and Performance-Based Regulation," dated May 1996 9.
Draft paper prepared for International Topical Meeting on Probabilistic Risk Assessment (PSA '96), Park City, Utah, September 29-October 3, 1996, Subj: " Standardizing PSA Methods Through Owners Group Comparisons," prepared by Westinghouse Owners Group 10.
Letter dated April 17, 1996, from W. Vesely, to M.
Cunningham, RES, Subj
" Objection to the Way Fessell-Vesely Importance is Being Used for Risk-Informed Applications" 11.
Letter dated April 23, 1996, from W. Vesely, to A. Thadani, NRR, Subj: " Copy of My Reservations to the Present Risk-Informed Approaches" 12.
Letter dated April 23, 1996, from W. Vesely, to V. Bier, University of Wisconsin-Madison, Subj: Response to Paper
- EA-003, "ASME Risk-Based Inservice Inspection and Testing -
An Outlook to the Future" 13.
Letter dated April 25, 1996, from K. Balkey, ASME Research Task Forces on Risk-Based Inservice Inspection and Testing, to W. Vesely, SAIC, Subj: Response to W. Vesely objections to risk-based ISI/IST methods NOTE:
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 Neal R. Gross & Co.,
Inc. Court Reporters and Transcribers, 1323 Rhode Island Avenue, N.W.
Washington, D.C. 20005, (202) 234-4433.
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