ML20150C615
| ML20150C615 | |
| Person / Time | |
|---|---|
| Issue date: | 05/04/1988 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-2571, NUDOCS 8807120559 | |
| Download: ML20150C615 (35) | |
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'TBI?UR9 L n=~ ri=3 Fr* 2W Ji l 3 !'] t i; DATE ISSVED: 5/4/88 i k k) b i sMu ACRS Subcommittee Meeting Sumary/ Minutes For the Severe Accidents April 26, 1988 Washington, D.C.
Purpose The ACRS Subcomittee on Severe Accidents met on April 26, 1988. The purpose of this meeting was to discuss the Staff's proposed generic
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letter (latest and intended final) for Individual Plant Examinations (IPEs) which is part of the implementation plan for the Severe Accident Policy Statement. Copies of the agenda and selected slides from the presentation are attached. The meeting began at 8:30 a.m. and adjourned at 4:00 p.m., and was held entirely in open sessien. The principal attendees were as follows:
Attendees ACRS NRC/RES W. Kerr, Chaiman B. Sheron C. Michelson, Member F. Eltawila l P. Shewmon, Member J. Chen l C. Siess, Member B. Beckner D. Ward, Member C. Wylie, Member NRC/NRR l I. Catton, Consultant T. Cox M. Corradini, Consultant P. Davis, Consultant J. Lee, Consultant D. Houston, Staff
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Discussion As background, the Subcomittee and the Full Comittee had discussed an earlier draft of the proposed generic letter for IPEs in the May-June EDIGNATED ORIGINAL 8807120559 880504 PDR 2571 ACRS PDR Co.4;c ca By M N
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Severe Accidents Mtg Minutes April 26, 1988 l
. I 1987 time period and a 'Comittee report on that draft was issued on June 9, 1987. Since than, the Staff revised the proposed generic letter to l respend to ACRS comnents and to reflect the latest Staff position on l varicus issues. The latest draft of the letter as issued on April 1, l 1988 was the basic document for discussion at this meeting.
B. Sheron (RES) was the principal speaker for the Staff and in his presentation, he discussed the details of the proposed generic letter for IPEs and an overview of the Staff's integrated plan to resolve l severe accident issues. In regard to the proposed generic letter, his ;
presentation dealt mostly with the following topics: (1)Issuanceof the Generic Letter and Schedule for Utility Response, (2) Methods for Examination, (3) Deferral of External Events, (4) Relationship to USI A-45 (Decay Heat Removal Systems), (5) Severe Accident Sequence Se-lection(ScreeningCriteria),(6)GuidanceonBack-EndAnalysis,and(7)
, Future Workshop and Development of a Staff Review Document. In regard to the severe accident integration plan, B. Sheron discussed the purpose and objectives of the plan, a listing of the various severe accident activities and a flow chart showing the interrelationship of these activities.
Briefly, the proposed generic letter would request all operating nuclear power plants to perform an IPE to identify severe accident vulnerabi)- l ities. The proposed letter offered guidance on the method of examina- .!
tion (essentially a Level 11 PRA or enhanced IDCOR-IPEM) and on the 'l examination of containment system perfomance. In addition, the pro- l posed letter defined nutterically the screening criteria to be used to determine potentially important functional sequences and functional !
failures that tu ght lead to core damage or unusually poor containment f perfomance. On the basis of the CRGR review, the Staff would intend to issue the generic letter for immediate implementation. However, in the i process,theStaffwoulddevelopareviewdocument(somethinglikea l
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/ Severe Accidents Mtg Minutes April 26, 1988 Standard Review Plant (SRP) for the Staff to use in the review of IPEs) and discuss a draft of this document with all interested parties at a workshop. This document is intended to provide well developed guidance to the utilities on how to do the analysis. The schedule for plant IPEs would start after the review document is issued in final form. The Staff would expect the ACRS Subcomittee to review this final document.
During the presentation, Subcomittee members and consultants extensive-ly discussed the Staff's proposed generic letter and the guidanca for analysis to be performed at each plant. The following topics were pursued during the discussion:
(1) Methodology - the Staff was asked to identify acceptable PRA's and provide exartples of state-of-the-art PRAs. It appeared that the PRAs for Indian Point, Limerick and Zion were acceptable. The Staff indicated that NUREG-1150 may not be acceptable, accept-ability would depend upon a review of the input assumptions. The Subcomittee recomended that a pilot plant program be undertaken to better develop the Staff's position. It was also recomended j that the Staff perform an evaluation review of the NUREG-1150 plant analyses as a training program.
(2) Back-End Analysis - It was stated that the back-end analysis l (Appendix 1) does not provide a clear description of what is needed. It was suggested that performance of the back-end analysis should be deferred until u better definition is provided. The Staff was asked why they did not consider catastrophic vessel failure since its probability was about the same as direct contain-mentheating(DCH). They were also asked to provide the technical data base for the selection of 25 cm as a maximum depth for a coolable debris bed. .
(3) External Events - The Staff was asked to define what they con-sidered as external events, especially in regard to internal fires
e i 6 Severe Accidents Mtg Minutes April 26, 1988 and internal flooding by pipe breaks. The Staff indicated that NUMARC would provide guidance on how to handle external events. An external events steering group (L. Shao, Chairman) has also been established by the Staff for this purpose. B. Sheron suggested that the steering group brief the ACRS on their activities at some futu m meeting. It was suggested that any plant modifications proposed to resolve vulnerabilities from the internal event anaiy-sis be carefully reviewed to determine if they might contribute to risk from external events.
(4) Definitions - The Staff was asked to provide better definition and to provide additional guidance in many areas. Specifically, definitions were asked for terms such as: Core Melt, Outliers, Vulnerabilities and Large Radioactive Release.
, (5) Severe Accident Management - The Staff was asked to delete the appendix on severe accident management since it is incomplete and the issue is not required as part of the IPE. They were also asked how they intend to perform reviews of plant Emergency Operating Procedures.
(6) Utility participation - It was noted that staff of the utilities will be encouraged to participate in the performance of the IPE.
The Staff was asked how utilities were to be encouraged in regard !
to this activity. The Subcomittee agreed that direct utility participation would be very valuable if not essential.
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NOTE: Additional meeting details can be obtained from a transcript i of this meeting available in the NRC Public Document Room, l 1717 H Street, N.W., Washington, D.C., or can be purchased j from Heritage Reporting Corporation, 1220 L Street, N.W., i Washington, D.C. 20555, (202) 628-4888. l l
4 ACRS Severe Accidents Subcommittee Meeting '
April 26, 1988 Washington, D.C.
- Tentative Presentation Schedule -
Proposed Generic Letter for Individual Plant Examinations (IPEs)
W. Kerr, ACRS 8:30 a.m.
A. Subcomittee Chairman Remarks 4.54ewh
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,, RES 8:40 a.m.
B. Severe Accident Issues B. She on, RES 9:30 a.m.
C. Content of IPE Generic letter
- Examination Process NMMM
' External Events (Deferred Item)
- Pethods of Examination
- Relationship to USI A-45
- PRA Benefits
- Severe Accident Sequence Section f
- BREAK *** 10:15 - 10:30 a.m.
- Staff Use of IPE Results *
- Accident Management
- Severe Accident Prevention and l Mitigation Features Report -
- Documentation of Examination Results
' Licensee Response
- Regulatory Basis
i ACRS Severe Accidents April 26, 1988 4
Subcommittee Meeting
- Tentative Presentation Schedule -
- LUNCH ***
12:00 - 1:00 p.m.
4.S4he T. 0;;i:,RES 1:00 p.m.
D. Guidance on Containment Performance (Appendix 1) 1:20 p.m.
E. C:-t:i n: t ":-f m:r:: !-i t h t h: J. " M :n, "E!
'": ' ?:) o ': tit :'i; t: I'E n____._
- BREAK *** 2:30 - 2:45 p.m.
All 2:45 p.m.
F. General Discussion Adjourn 3:45 p.m. j G.
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AC3S Y3ETING ON THE IMPLEMENTATION PIAN FOR THE SEVERE ACCIDENT POLICY STATEMENT INDIVIDUAL PLANT EXAMINATION (IPE)
GENERIC LETI'ER THEMIS P. SPEIS DEPUTY DIRECTOR FOR GENERIC ISSUES OFFICE OF NUCLEAR REGULATORY RESEARCH BRIAN W. SHERON, DIRECTOR DIVISION OF REACTOR AND PLANT SYSTEMS OFFICE OF NUCLEAR REGULATORY RESEARCH APRIL 26,1988
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..T GENERIC Irnu CONCERNING INDIVIDUAL PIANT EXAMINATION FOR SEVERE ACCIDENT VULNERABIllTIES
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SUMMARY
- 2. EXAMINATION PROCESS
- 3. EXTERNAL EVENTS (DEFERRED ITEM)
- 4. MET]IODS OF EXAMINATION
- 5. RELATIONSIIIP TO USl A-45
- 6. BENEFITS OF PRA
- 7. SEVERE ACCIDENT SEQUENCE SELECTION
- 8. SEVERE ACCIDENT MANAGEMENT
- 0. SEVERE ACCIDENT PREVENTION AND MITIGATION FEATURES REPORTS
- 10. DOCUMEhTATION OF EXAMINATION RESULTS
- 11. UCENSEE RESPONSE 1
- 12. REGULATORY BASIS I l
l APPENDIX 1, GUIDANCE ON THE EXAMINATION OF CONTAINMENT SYSTEMS PERFORMANCE (BACK-END ANALYSIS)
APPENDIX 2, CRITERIA FOR SELECTING IMPORTANT SEVERE ACCIDEhT SEQUENCE APPENDIX 3, ACCIDENT MANAGEMENT '
APPENDIX 4, DOCUMEhTATION APPENDIX 5. DECAY IIEAT REMOYAL VULNEPABluTY INSIGBTS ATTACITMEhT 1, UST OF REFERENCES 2
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SUMMARY
o A 10 CFR 50.54(f) LETTER REQUESTING THE INDIVIDUAL PLANT EXAMINATIONS FROM ALL LICENSEES HOLDING OPERATING LICENSES AND CONSTRUCTION PERMITS FOR NUCLEAR POWER PLANTS o BASIS FOR REQUESTING INDIVIDUAL PLANT EXAMINATIONS IS TIIE COMMISSION SEVERE ACCIDENT POLICY ISSUED ON AUGUST 8,1985 (50 FR 32138)
- PLANT SPECIFIC PRAs EXPOSED RELATIVELY UNIQUE VULNERABILITIES TO SEVERE ACCIDENTS
- THE UNDESIRABLE RISK FROM THESE UNIQUE FEATURES liAS BEEN REDUCED BY LOW-COST CHANGES VIA PROCEDURES OR MINOR DESIGN MODlFICATION
- ANALYSIS WILL BE MADE OF ANY PLANT THAT HAS NOT YET
,. UNDERGONE AN APPROPRIATE EXAMINATION WHEN NRC AND INDUSTRY SUFFICENTLY PROGRESSED TO DEFINE TllE METHODS OF ANALYSIS o SINCE ISSUANCE OF THE POLICY STATEMENT TILE STAFF INTERACTED EXTENSIVELY WITH INDUSTRY AND DEVELOPED APPROPRIATE DOCUMENTATION FOR TIIE IPEs o PURPOSE OF IPE IS FOR THE UTILITIES TO:
IDENTIFY / UNDERSTAND TlE MOST LIKELY SDTRE ACCIDENT SEQUENCES THAT C0ULD OCCUR AT THEIR PLETS; EVALUATE /lMPLDENT MEANS FOR IMPROVEMENTS DDTLOP AN AWARENESS FOR SEVERE ACCIDENT BEIIAVIOR 3
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- 2. EXAMINATION PROCESS o LICENSEE'S STAFF SHOULD PARTICIPATE IN AIL ASPECTS OF THE IPE S0 THAT KNOWLEDGE GAINED BECOMES AN INTEGRAL PART OF OPEPATING, TRAINING AND PROCEDURE PROGRAM.
o LICENSEES SHOULD CONDUCT SYSTEMATIC EXAMINATION OF PIAh7 DESIGN, OPERATION, MAINTENANCE AND EMERGENCY OPERATION T0:
- IDENTIFY PLINT SPECIFIC VULNERABILITIES (DESIGN AND PROCEDURAL) TO SEVERE ACCIDENTS (FOR BOTH CORE DAMAGE AND CONTAINMENT PERFORMANCE): BOTH INTERNAL AND EXTERNAL INITIATORS ARE TO BE CONSIDERED (EXTERNAL INITIATORS ARE DEFERRED)
- QUANTIFY RESULTS OF EXAMINATION FOR THE SEQUENCES THAT CONTRIBUTE TIIE MOST TO THE TOTAL CORE DAMAGE OR LARGE RELEASE FREQUENCY
- UNDERSTAND WHAT COULD POSSIBLY G0 WRONG IN A PLANT.
- IDENTIFY AND EVALUATE MEANS FOR IMPROVING PLANT /
CONTAINMENT PERFORMANCE (VIA HARDWARE ADDITIONS /
MODIFICATIONS, ADDITIONS TO PROCEDURES, TRAINING);
- DECIDE WHICH IMPROVEMENTS WILL BE IMPLEMENTED AND SCHEDULE FOR IMPLEMENTATION 4
IPE BENEFITS l
l 0 PLANT-SPECIFIC PRA's YIEIEED INSIGHTS TO UNIQUE SEVERE ACCIDENT VULNERABILITIES LEADING TO IAW-COST MODIFICATIONS o UTILITY INVOLVEMENT IN UNDERSI'ANDING POSSIBLE RANGE l OF SEVERE ACCIDENT BEHAVIOR IN ITS PIANT(s) AND THUS IS BrlTER PREPARED TO PREVENT, AND/0R MITIGATE ACCIDENT PROGRESSION AND CONSEQUENCES 1
o INCORPORATE THE PIANT SPECIFIC INSIGHTS (e.g., RECOGNITION OF ROLE OF PREVENTION AND MITIGATION SYSTEMS AND OPERATOR ACTIONS) AND IMPROVEMENTS (e.g., HARDWARE, PROCEDURES)
RESULTING FROM THE IPE INTO A stytKE ACCIDENT MANAGEMENT PROGRAM l 5
- 3. EXTERNAL EVENTS o COMMISSION SEVERE ACCIDENT POUCY DOES NOT EXCLUDE EXTERNAL EVENTS.
o LICENSEES ARE ONLY REQUESTED TO PROCEED TITH THE EXAMINATIONS FOR INTERNAL EVENTS o STAFF IS WORKING WITH NUMARC FOR DEVELOPMENT OF ACCEPTABLE MET 110D0 LOGY o QUESTION IS Il0W TO DEST HANDLE EXTERNAL EVENTS IN SEVERE ACCIDENT POUCY IMPLEMENTATION STAFF CURRENTLY EXAMINING EXTENT TO WHICII EXTERNAL EVENTS MUST BE TREATED WORK TO DATE INDICATES:
o SOME EXTERNAL EVENTS SHOULD DE LOOKED AT BY ALL PLANTS o SOME EXTERNAL EVENTS ARE UNIQUE ONLY TO A FEW PLANTS o SOME EXTERNAL EVENTS MAY BE ACCEPTABLY TREATED BY
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EXISTING DESIGN BASIS.
o THE STAFF INTENDS TO EFFECTIVELY INTEGRATE ALL ONG0ING PROGR.OfS DEAUNG WITil EXTERNAL EVENTS (e.g., A-46 SDMP)
SO NO DUPUCATION OF EFFORT BY INDUSTRY WILL OCCUR 6
l EXTERNAL 3VEXTS 'C0XT.)
STEERING GROUP MISSION o RECOMMEND HOW BEST TO TREAT EXTERNAL EVENTS IN CONTEXT OF THE SEVERE ACCIDENT POLICY o ENSURE THAT RECOMMENDED TREATMENT IS COORDINATED WITH OTHER AGENCY PROGRAMS RELATED TO EXTERNAL EVENTS AND NC DUPLICATION OF EFFORTS RESULTS o COMPLETE TASK IN APPROXIMATELY 18 MONTHS I
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- 4. METHODS OF ANLYSIS o THE GENERIC IrnEx SPECIFIES SEVERAL OPTIONS THAT COULD BE USED TO SATISFY THE EXAMINATION REQUIREMENTS IDCOR IPEMs FRONT END WITH STAFF ENHANCEMENTS +
CONTAINMENT PERFORMANCE ANALYSIS CONSISTENT WITH APPENDIX 1 LEVEL-I PRA + CONTAIh"4ENT PERFORMANCE. ANALYSIS-CONSISTENT WITH APPENDIX I ( OR LEVEL-II OR -III PRA WITH "BACK-END" CONSISTENT WITH APPENDIX 1)
OTHER SYSTEMATIC EVAL"ATION METHODS (STAFF PREVIEW MIGHT BE NECESSARY) 9
IDCOR METHOD FROXT EXD 0 IDCOR IPEMs COVER SEQUENCES INITIATED BY INTERNAL EVENTS, IASS OF 0FFSITE POWER AND INTERNAL FLOODS.
O IDCOR IPEMs INVOLVE THE FOILOWING BASIC ETEMENTS OF IEVEL-I PRA:
- PIANT FAMIIJARIZATION AND SYSTEMS NOTEBOOKS .
INCLUDES SUBSTANTIAL AMOUNT OF DESIGN, OPERATIONAL, AND PRA INFORMATION (SCIIEMAlCS, INTERFACES, DATA, CUT-SLTS (PWR [PEM ONLY))
- ACCIDENT SEQUENCE DEFINITION AND QUANTIFICATION RECOGNIZES THE IMPORTANT ROLE PLiYED BY SUPPORT SYSTEMS. INTERDEPENDENCE AMONG SUPPORT SYb7 EMS IS ANALYZED TO IDENTIFY A SET Or SUPPORT STATE.
DATA ASSESSMENT AND PARAMETER ESTIMATION INYOLVES [NVESTICATION OF DATA APPLICABillTY, AND ANALYSIS OP PLtNT SPECIFIC EXPERIENCE (FAILURE RATES AND [NITIATOR FREQUENCIES)
INTERPRETATION OF TIIE RESULTS 10
IDCOR IPEMs EVALUATION o THE IDCOR IPEMs TAKE ADVANTAGE OF AVAILABLE IDCOR REFERENCE PLANT ANALYSES, SIMILARITIES AMONG PLANTS AND UP-TO-DATE
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KNOWLEDGE OF SEVERE ACCIDENT PHENOMENA. THE IPEMs SYSTEM ANALYSIS IS LESS RIG 0ROUS TBAN A FULL SCOPE PRA.
o THE IDCOR IPEMs WERE SUBMITTED TO THE NRC MAY 1986 o INITIALLY MODIFED BY IDCOR IN DECEMBER 1986 TO ACCOMODATE NRC COMMENTS. FURTHEP. MODIFICATIONS WERE RECEIVED IN APRIL 1987 o NRC EVALUATION OF THE IDCOR IPEMs IS COMPLETE ,
o IT IS EXPECTED THAT THE LEVEL 0F EFFORT REQUIRED IF A UTILITY USES THE IDCOR IPEM IS EQUIVALENT TO LEVEL-I PRA BUT IS LESS THAN IF A FULL-SCOPE LEVEL-III PRA WERE USED i
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IDCOR IPEMs EVALUATION { CONT.)
(BACK-END) o THE IDCOR BACK-END IPEMs ARE T00 NARROWLY FOCUSED AND WILL NOT PROVIDE UTILITIES WITIl INFORMAT10N NEEDED TO EXAMINE CONTAINMENT PERFORMANCE FOR THE FULL RANGE OF SEVERE ACCIDENTS o RELY VERY HEAVILY ON IDCOR VIEWS OF SEVERE ACCIDENT PIIENOMEN0 LOGY AND THE IDCOR MAAP CODE o SOME OF IDCOR VIEWS AND MET 110D0 LOGY ARE IN DISAGREEMENT WITH CURRENT RANGE OF ASSUMPTIONS o NO RECOGNITION OF UNCERTAINITIES IN TllE PHENOMENOLOGY o OPTIMISTIC ASSESSMENT OF CORRECT OPERATOR ACTIONS TO MAINTAIN CONTAINMENT INTEGRITY DURING SEVERE ACCIDENTS o LOOSE INTERPRETAT[0N OF T11E IPEM QUESTIONS PY TIIE UTILITIES COULD RESULT IN A IACK OF SUFFICIENT ATTENTION TO MEASURES TO MITIGATE THE CONSEQUENCES OF AN ACCIDENT o APPENDIX 1 TO THE GENERIC LETI'ER PROVIDES ADDITIONAL GUIDANCE ON HOW TO ASSESS THE CONTAINMENT PERFORMANCE 13
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SCOPE /0BJECTIVES-STAFF GUIDANCE
'BACK-END) o THE IPE SHOULD PROVIDE BASIS FOR UTILITY'S
- APPRECIATION OF SEVERE ACCIDENT BEHAVIOR
- RECOGNITION OF ROLE OF MITIGATION SYSTEMS
- DEVELOPMENT OF ACCIDENT MANAGEMENT PROCEDURES o THE IPE SHOULD PROVIDE A REALISTIC EVALUATION OF CONTAINMENT PERFORMANCE o HENCE STAFF GUIDANCE FOCUSES ON HAVING UTILITIES:
- EVALUATE CONTAINMENT FAILURE MECHANISMS AND TIMING
- SIMPLY LOOK UP RELEASES FROM TABLES PREPARED ON THE BASIS OF REFERENCE PLANT EVALUATIONS INTEGRATE SYSTEMS RESPONSE (PROBABILlSTICALLY) INTO ;
SIMPLIFIE1,BUT REALISTIC, CONTAINMENT EVENT TREES (ALLOW FOR RECOVERY OR OTHER ACCIDENT MANAGEMENT PROCEDURES) 1
- EXAMINE ALL CLASSES OF SEQUENCES WITH SIGNIFICANT PROBABILITY
- RECOGNIZE AND AS APPROPRIATE, ACCOUNT FOR UNCERTAINITIES 14 l
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- 5. RELATIONSHIP TO USI A-45 l
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- o A-45 ANALYSES IIAVE SHOWN THAT DECAY HEAT REMOVAL FUNCTION f FAILURE ARE SUFFICIENTLY PLANT SPECIFIC AND NOULD REQUIRE SYSTEMATIC EXAMINATION o PROPOSED STAFF RESOLUTION OF A-45 IS TO SUBSUME ISSUE INTO IPEs o
TIIE PROPOSED GENERIC LETTER STATES TEAT THE IPE SHOULD
/. IDENTIFY THE VULNERABLE ASPECTS OF DHR FUNCTION 1
o TIIE PROPOSED GENERIC LETTER PROVIDES INSIGIITS GAINED FROM SIX LIMITED SCOPE PRA PERFORMED BY NRC UNDER THE A-45 PROGRAM
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- 7. SEVERE ACCIDENT SEQUENCE SELECTION (SCREENING CRITERIA) o USED TO DETERMINE THE POTENTIALLY IMPORTANT FUNCTIONAL SEQUENCES WIUCH REQUIRE CONTAINMENT EVENT TREE ANALYSIS. NOT TO DE7 ERMINE IT PLANT IMPROVEMENTS ARE REQUIRED o INCLUDE SEQUENCES WHICH CONTRIBUTE MORE THAN 5% TO THE PREDICTED CORE DAMAGE FREQUENCY o INCLUDE SEQUENCES FOR WHICE THE CORE DAMACE FREQUENCY IS GREATER THAN LE-6/PIACTOR YEAR o INCLUDE SEQUENCES USEFUL FOR IDENTIFYING SYSTEMS YEAKNESS OR OPERATOR ACTIONS BASED ON DETEP3DNISTIC EVALUATIONS, u
ENG'YEERING JUDGEMENT AND CONSIDERATION OF UNCERTAINITIES IN THE PROBABILISTIC ANALYSIS o INCLUDE SEQUENCES FOR THICE THE CDF IS GREATER TBAN 1E-6/
REACTOR YEAR AND CONTAINMENTS PAIIS IN LESS THAN 12 HOURS FROM TIME OF YESSEL PENETRATION o INCLUDE SEQUENCES THICH IIAD TO CONTAINMENT BYPASS AND HAVE A PROBABILITY OF OCCURRENCE GREATER THAN IE-7/RXY 17
l 8. ROI2 0F SEVERE ACCIDENT MANAGEMENT o
SEVERE ACCIDENT MANAGEMENT IS A PROCESS IN TIUCH ACTIONS THAT CAN PREVENT CORE DAMAGE OR MITIGATE THE CONSEQUENCES OF SEVERE ACCIDENT ARE [DENTIFIED, EVALUATED, INCORPORATED INTO A STRUCTURED PROGRAM, IMPLEMENTED AT A PIANT SITE AND ARE AVAlIABLE TO TIIE OPEPATOPS AND PIANT MANAGEMENT IN THE EVENT OF SEVERE ACCIDENT o SEVERE ACCIDENT MANAGEMENT ENCOMPASSES HARDWARE, HUMAN, AND ORGANIZAT]ONAL FACTOPS o
IT PROVIDES DECISION MAKERS AT TILE PLANT A STRUCTURED PROGRAM FOR MANAGING A SEVERE ACCIDENT o
PROPOSED GENERIC IITTER ADDRESSES SEVERE ACCIDEhT MANAGEMENT AS FOLLOWS
- UTIUTIES ARE EXPECTED TO DEVELOP AN ACCIDENT MANAGEMENT PROGRAM FOR PREVENTION OR MITlGATION OF RISK IMP 0f? RANT SEVERE ACCIDENTS
- IDENTIFY MEASURES THAT PIAhT PEPSONNEL CAN AND SHOUIl) TAKE IN CASE OF SEVERE ACCIDENT. ASSESS AGAINST TBE CRITERIA 0F 10 CFR 50.59 AND, IF APPROPRIATB, SUBMTI7 FOR NRC REVIEW IN ACCORDANCE YlTH 10 CFR 50.90 .
UTDlTIES SHOULD PREPARE TO SUCCESSFULLY EXCUTE MEASURES THAT YERE FOUND T0 (1) PREVENT CORE DAMAGE, (2) PREVENT CORE DEBRIS FROM PENETRATING THE VESSEL OR, (3) MANAGE THE C0 SEQUENCES o
STAFF AND NUMARC DISCUSSING TIIE NEED TO DEVEIAP AND IMPLEMENT ADDITIONAL SEVERE ACCIDENT MANAGEMENT PIAN g
- 10. DOCUMENTAION OF IPE RESULTS o PROVIDE THE BASES FOR THE FINDINGS IN A TRACABLE MANNER o TWO TIERS OF DOCUMENTATIONS o TIER-1 REPORTS THE RESULTS OF THE EXAMINATION TO NRC
- TILE LEADING SEQUENCES AND SCREENING CRITERIA
- Tile CORE DAMAGE FREQUENCY AND THE LIKEllH00D OF LARGE RELEASE
- Tile MAIN UUNTHilJUTORS FOR CDF AND CONTAINMENT FAILURE DISPOSTION OF CONTRIBUTORS
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o TIER-2 DOCUMENTS THE EXAMINATION THAT WOULD BE RETAINED BY LICENSEES o NRC YrlLL EVALUATE TIER-1 c.EPORTS AND MAY AUDIT TIER-2 20
IPE RESULTS REVIEY o PREPARE AN IPE REVIEW DOCUMENT FOR THE STAFF AND
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CONTRACTOR REVIEWERS TO INCLUDE:
AREAS OF REYmW I DLTERMINATION OF ADEQUACY OF IPE RESULTS
- ACI' ION LEVELS j
INTERPRE'I'ATION OF THE RESULTS l SAMPLE EVAIEATIONS l
, o IPE REYEW DOCUMENT WILL BE MADE AVAILABLE TO ALL UTILITIES SHORTLY AFTER THE ISSUANCE OF THE GENERIC IrrmR 21
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STAFF USE OF IPE RESULTS o REVIEW 0F IPE RESULTS FOR THE FOLLOWING:
- TO ENSURE ADEQUATE ANALYSIS OF PLANT DESIGN AND OPERATIONS TO DISCOVER PARTICULAR VULNERABILITY TO CORE DAMAGE AND UNUSUALLY POOR CONTAINMENT PERFORMANCE
- FOR CONSISTENCY IN TBB. IDENTIFICATION AND TREATMENT OF LEADING CORE DAMAGE SEQUENCES
- TO ENSURE SEQUENCES AND SEQUENCE FREQUENCES ARE APPROPFJATE
- TO INDEPENDENTLY CONCLUDB TIIAT DECISIONS ON WHETIIER TO MAXE IMPROVEMENTS ARE JUSTIFIED
- TO ALLOW COMMISSION TO CONCLUDE THAT THE SEVERE ACCIDENT POLICY HAS BEEN RESPONSIBLY IMPLEMENTED DY INDUSTRY o
CONSIDERATION WILL INCLUDE BOTB QUANTITATIVE MEASURES AND NON QUANTITATIVE JUDGMENT TO DETERMINE [F A PLANT IS ACCEPTABLE OR NOT o
IP NRC COSIDERATION IDICATES THAT PIANT DESIGN OR OPERATION COULD BE ENilANCED BY ADDITIONAL PROTECTION BBYOND NRC REGULATION, IMPLEMENTATION WOULD BE IN ACCORDANCE WITB 10 CFR 50.109 o
IF CONSIDEPATION INDICATES PLANT DESlGN OR OPERATION SHOULD BE CHANGED TO MEET NRC REGUIATION, IMPLEMENTATION WOULD BE WITIIOUT REGARD TO COST EXECPT TO SELBCT AMONG ALTERNATIVES o
IPE RESULTS WILL BE USED TO IDENTIFY SEVERE ACCIDENT VULNERABIllTY j GENERIC TO CIASS OR SEVERAL CLASSES OF PIANTS
- TBIS INFORMATION ON GENERIC VULNERABILIT1BS WOULD BE USED l TO EXAMINE 1F DEFICIENCIES IN THE REGULATION EXIST IF GENERIC DEFICIENCIES TERE IDENTIFIED SAFETY GOAL WOULD BE USED TO DETERMINB IF REGUIATION MODIFICAT10NS WERE NEEDED 23
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CRGR RECOMMENDATIONS o ISSUE TBE IPE GENERIC LE' ITER WITH AIL ITS APPENDICES. BOTH FRONT-END AND BACE-END ANALYSES ARE TO BE INCLUDED.
o ISSUE NUREG/CR-4920 SEPERATELY S0 IT WILL NOT BE CONSIDERED AS REQUIREMENTS.
o STAFI"S REVIEW DOCUMENT WILL BE DISCUSSED IN DRAFT FORM VITII IlCENSEES AT NORKSBOP(S) o PURPOSE OF THE WORKSHOP (S):
- PRESENTS TO IlCENSEES ( NOT NEGOTIATE ) WELL DEVELOPED GUIDANCE ON HOW TO DO THE ANALYSIS, PARTICULARLY THE FACK-END
- I'lFORM THE UCENSEES HOW THE STAFF IS G0ING TO REVIEW THE IPE SUBMITIAIS SHARPEN THE NRC GUIDANCE. WHERE APPROPRIATE o ISSUE THE REVIEW DOCUMENT IN FINAL FORM, TO START THE CLOCK
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SEVERE ACCIDENT INTEGRATED PLAN 4
BY
. ,s THEMIS P. SPEIS, DEPUTY DIRECTOR OFFICE OF NUCLEAR REGULATORY-RESEARCH (PRESENTATIONBYBRIANSH2.RON,DIVISIONDIRECTOR,REh FOR ACRS SEVERE ACCIDENTS SUBCOMMITTEE MEETING APRIL 26, 1988
. n i BACKGROUND o AUGUST 8, 1985, "SEVERE ACCIDENT POLICY STATEMENT,"
50 FR 32138 o FEBRUARY 28, 1986, "IMPLEMENTATION PLAN FOR SEVERE ACCIDENT POLICY STATEMENT," SECY-86-76 o DECEMBER 1, 1986, STAFF REQUIREMENTS MEMO, CHAIRMAN REQUESTED PAPER ON INTEGRATION OF SEVERE ACCIDENT ISSUES o FEBRUARY 17, 1987, MEMO FROM EDO TO COMMISSIONERS ON PRELIMINARY PLAN FOR INTEGRATION OF SEVERE ACCIDENT ISSilES o JULY 15, 1987, STAFF BRIEFED COMMISSION ON A PLAN FOR CLOSURE OF SEVERE ACCIDENT ISSUES ,
o DECEMBER 8, 1987, "MARK I CONTAINMENT PERFORMANCE PROGRAM PLAN,"
SECY-87-297 o FEBRUARY 9-11, 1988, BALTIM0RE MANAGEMENT MEETING ON SEVERE ACCIDENT ISSUES l
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SEVERE ACCIDENT INTEGRATED PLAN o PURPOSE: TO PRESENT STAFF PLANS FOR INTEGRATION AND CLOSURE OF ALL SEVERE ACCIDENT ISSUES o 0BJECTIVES:
TO PROVIDE AN UNDERSTANDING 0F THE STAFF ACTIVITIES THAT ARE UNDER WAY TO IMPLEMENT THE COMMISSION'S SEVERE ACCIDENT POLICY TO ASSURE THAT THESE ACTIVITIES ARE CONSISTENT WITH THE COMMISSION'S POLICY AND STRATEGIC G0ALS TO ASSURE THAT THE STAFF ACTIVITIES ARE CONSISTENT AMONG THEMSELVES, HAVE A COMMON G0AL OF ULTIMATELY LEADING TO IMPROVED PLANT SAFETY, AND ARE PROPERLY COORDINATED AMONG THE RESPONSIBLE NRC ORGANIZATIONS TO ASSURE THAT THE COMMISSION IS AWARE OF THE KEY TECHNICAL AND POLICY ISSUES, SOME OF WHICH NEED COMMISSION GUIDANCE OR APPROVAL l
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SEVERE ACCIDENT ACTIVITIES o INDIVIDUAL PLANT EXAMINATIONS (IPE) o CONTAINMENT PERFORMANCE IMPROVEMENTS (CPI) o IMPROVED PLANT OPERATIONS (IPO) o SEVERE ACCIDENT RESEARCH PROGRAM (SARP) o ACCIDENT MANAGEMENT (AM) PROGRAM o NUREG-1150, "REACTOR RISK REFERENCE DOCUMENT" o SAFETY G0ALS o GENERIC SAFETY ISSUES o EXTERNAL EVENTS o INTEGRATED SAFETY ASSESSMENT PROGRAM (ISAP) o SEVERE ACCIDENT POLICY FOR FUTURE P'. ANTS o SEVERE ACCIDENT CLOSURE l
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Role of NUREG-1150 Objective: -
) Provide up-to-date assessment of severe accident i frequencies and risks for five plants, refiecting data I obtained since Reactor Safety Study Roles in Regulatory Process:
Independent staff assessment of risks Technical data base as input to:
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IPE accident management containment performance initiatives l
safety goal implementation i
generic issue resolution i
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Prioritization/ focus of research l
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SEVERE ACCIDENT RESEARCH
- BEGINNING IN 1980, AFTER THE TMI-2 EVENT, RESEARCH HAS PROVIDED A DATA BASE AND MODELS FOR:
o FISSION PRODUCT RELEASE, TRANSPORT, DEPOSITION, 8 REVAPORIZATION o CONTAINMENT LOADING BY HIGH PRESSURE MELT EJECTION (HPE) o HYDROGEN DETONATION AND BURNING o CORE / CONCRETE INTERACTIONS (CCI) THERMAL 8 CHEMICAL o CONTAINMENT PERFORMANCE TESTING o EFFECTS OF NATURAL CIRCULATION ON THE PRIMARY SYSTEM o CORE MELT PROGRESSION (EARLY STAGES)
FUTURE RESEARCH EFFORTS WILL FOCUS ON SPECIFIC ISSUES SUCH AS:
o CONTAINMENT FAILURE PROBABILITY BY DIRECT CONTAINMENT HEATING (DCH) INCLUDING EFFECT OF NATURAL CIRCULATION o MELT SPREADING AND CONTAINMENT SHELL FAILURE IN MARK l'S o RESEARCH DATA AND MODELS TO ASSESS ACCIDENT MANAGEMENT STRATEGIES o LONGER TERM CONFIRMATORY RESEARCH ON:
DCH CONSEQUENCES l
REFINEMENT OF HYDROGEN BEHAVIOR MODELS CORE MELT PROGRESSION (LATE STAGES)
CORE / CONCRETE INTERACTIONS REFINED FISSION PRODUCT HIGH TEMPER.4T' IRE PROPERTIES FURTHER MODEL ASSESSMENT AND REFINEMENTS
AN EXAMPLE OF AN ISSUE AND ITS -
1 ASSOCIATED NEAR AND LONG-TERM RESEARCH ,
CONTAINMENT TYPE LARGE DRY PWR ASSOCIATED ISSUES o CONTAINMENT FAILURE MODES DIRECT CONTAINMENT HEATING (DCH)
IlYDROGEN BURN / DETONATIONS LATE FAILURE BY CCI LOADS (OVER T8P) o CONTAINMENT PERFORMANCE-o ACCIDENT MANAGEMENT STRATEGIES DEPRESSURIZATION OF PRIMARY SYSTEM RESEARCH TO ADDRESS ISSUE o DCH PROBABILITY OF HIGli PRESSURE MELT EJECTION 1
(NATURAL CIRCULATION)
CUT 0FF PRESSURE FOR HPE MANAGEMENT THROUGH DEPRESSURIZATION CONSEQUENCES ANALYSES OF PERFORMANCE TESTS ON CONCRETE CONTAINMENTS (1/6 SCALE)