ML20133J601

Proposed Summary of ACRS Class 9 Accidents Subcommittee 850802 Meeting in Washington,Dc Re Implementation Plan for Severe Accident Program & Idcor Plant Analysis Program.List of Attendees Provided

ML20133J601
Person / Time
Issue date:	08/17/1985
From:	Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-2343, NUDOCS 8510180538
Download: ML20133J601 (6)

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ACRS-Ah45 Q Y

/W! /H1/E 4,bs B DATE ISSUED: 8/17/85 PROPOSED MEETING

SUMMARY

/ MINUTES FOR THE ACRS CLASS 9 ACCIDENTS SUBCOMMITTEE AUGUST 2, 1985 - WASHINGTON, DC Purpose The ACRS Subcommittee on Class 9 Accidents met on August 2, 1985 at Washington, DC. The purpose of this meeting was to continue the dis-cussion of the implementation plan for the Severe Accident Program with NRR Staff and the IDCOR Plant Analysis Program with representatives of Industry. The meeting was to inform the Subcommittee of the above stated programs and to solicit their viewpoints. The meeting began at 8:30 a.m. and adjourned at 4:01 p.m., and was held entirely in open session. The principal attendees were as follows:

Attendees:

ACRS NRR W. Kerr, Chairman T. Speis R. Axtmann, Member G. Hulman D. Moeller, Member Z. Rosztoczy C. Siess, Member R. Barrett P. Shewmon, Member D. Ward, Member RES M. Bender, Consultant M. Silberberg I. Catton, Consultant J. Mitchell M. Corradini, Consultant P. Davis, Consultant IDCOR J. Lee, Consultant J. Howard R. Savio, Staff T. Buhl D. Houston, Staff E. Burns -

M. Hitchler M. Kenton J. Garbor i

IEc.IGNATED GRIGINAL Certified By B510180538 850817 3 PDR

Class 9 Meeting Minutes August 2, 1985 NRR The NRR presentation began with a status report on the Commission's Severe Accident Policy Statement. The policy statement with the Commis-sioner's comments and the Staff's evaluation were scheduled to be issued as NUREG-1070 on August 7, 1985. The implementation program addressed three major areas:

1. Systematic Examination of Existing Plants.

2. Issuance of Guidance ~on the Role of PRAs.

3. Amendment of NRC Regulations as Appropriate.

The interrelationship between the studies at RES, NRR and IDCOR was discussed. NDR intends to interface with IDCOR on the development of methodology for existing plant analysis and to adopt the method for this phase of the program. NRR acknowledged the usefulness of ACRS comments received to date, and recommended a series of future meetings with the Subcommittee.

As the basis for the systematic evaluation of existing plants, NRR discussed their plans and schedule to perform an analysis of four reference plants (Peach Bottom, Sequoyah, Grand Gulf and Zion). The analyses should be completed by April 1986. The results will be used to evaluate the IDCOR methodology applied to the same plants. The remaining tasks for this program are concerned with: (1) development of generic guidelines and procedural criteria for the prevention and mitigation of severe accidents, and (2) basis for recommendations for Commission consideration on the resolution of the severe accident issue.

The NRR plans for evaluating Peach Bottom and for reviewing the IDCOR methodology were discussed. Subcommittee concerns were expressed about the lack of treatment of external initators. NRR indicated that future discussions with RES will focus on this issue. They will also consider

, ways to analyze operator performance. In the ongoing review of IDCOR l

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t Class 9 Meeting Minutes August 2, 1985 methodology, a list of 19 items has been identified by NRR that require resolution. This list is included as Attachment A. Another part of the review will evaluate the uncertainties in the calculations.

NRR next addressed the regulatory areas that were targeted for source term related changes. The changes were based on studies other than NUREG-0956, specifically TMI Action Items, AIF-Industry comments and NUREG-0771. Ten areas of regulatory change were discussed. These are given in Attachment B. Numerous questions related to containment performance were raised by the Committee and consultants and responded to by NRR.

IDCOR The scope of the IDCOR program was presented by various representatives from Industry. The program addresses three major areas:

1. BWR and PWR Source Term Assessment.

2.

BWR and PWR Plant Methodology.

3. In-Depth Analysis of Seven Plants.

..The seven plants selected for the study include 4 PWRs and 3 BWRs and will represent all domestic reactor vendors and general containment types. The study will not address external initiators and will not be a full blown PRA, although it could be expanded to one. Input will be provided by plant operating staff. The study is tentatively scheduled for completion at the end of 1985.

In response to Committee concerns about the non-consideration of ex-

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ternal events, IDCOR stated that they took the historic approach to this concern which was not to consider them, and that they chose a

methodology that was manageable and could be applied without further

development. They indicated that appropriate treatment of the seismic

. issue required some advance in technology.

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Class 9 Meeting Minutes August 2, 1985 IDCOR members described the analytical methods and the source term assessment for BWR and for PWR plants. The method uses event trees, fault trees, support system matrices, plant data and engineering in-sights. A different approach is used for those plants that have a PRA and those that don't. Analyses will be performed for various initiating events and accident sequences. The source term assessment is based on early or late core melt and early or late containment failure.

d Committee members and consultants expressed concerns about the IDCOR method similar to those expressed about the Nh2 studies, e.g., plant operator performance, external events, sensitivity arialysis and maintenance control.

Concluding Remarks The Chairmen stated at the close of the meeting that the NRC Staff should tentatively plan to make a presentation to the ACRS at the September full Committee meeting on the subject of source term assessment and associated regulatory changes.

NOTE: Additional meeting details can be obtained from a transcript of this meeting available in the NRC Public Document Room, 1717 H Street, N.W., Washington, D.C., or can be purchased from Ann Riley & Associates, Ltd., 1625 I Street, NW, Suite 921, Washington, DC 20006,(202)293-3950.

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TECRNICAL ISSUES EVOLVED FROM IDCOR/NRC MEETINGS

1. FISSION PRODUCT RELEASE PRIOR TO VESSEL FAILURE.

2. RECIRCULATION OF COOLANT IN THE REACTOR VESSEL.

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3. RELEASE MODELS FOR CONTROL R0D MATERIALS.

4. FISSION PRODUCT AND AEROS0L DEPOSITION IN A PRIMARY SYSTEM.

5. MODELING OF IN-VESSEL HYDROGEN GENERATION.

6. CORE SLUMP, CORE COLLAPSE, AND REACTOR VESSEL FAILURE MODELS.

7. CONTAINMENT FAILURE BY IN-VESSEL STEAM EXPLOSIONS.

8. DIRECT HEATING OF THE CONTAINMENT ATMOSPHERE BY EJECTED CORE MATERIAL.

9. EX-VESSEL FISSION PRODUCT RELEASE MODELING.

10. EX-VESSELHEATTRANSFERBETWEENMOLTENCOREbEBRIS, CONCRETE AND AIR.

11. REVAPORIZATION OF FISSION PRODUCTS IN THE UPPER PLENUM'0F A REACTOR VESSEL.

12. DEPOSITION MODEL FOR FISSION PRODUCTS IN A CONTAINMENT.

13. (A) AMOUNT AND TIMING OF SUPPRESSION POOL BYPASS.

(s) RETENTION OF FISSION PRODUCTS IN ICE BEDS.

14. MODELING OF EMERGENCY RESPONSE.

15. CONTAINMENT PERFORMANCE. -

16. SECONDARY CONTAINMENT PERFORMANCE.

17. CRITERIA FOR IGNITING AND BURNING HYDROGEN.

l , 18. PERFORMANCE OF ESSENTIAL EQUIPMENT.

ATTACHMENT A

i PRELIMINARY BENEFIT-COST SU W RY OF AREAS TARGETED FOR SOURCE TERM RELATED CHANGES CHANGE IN REGULATORY REGULATORY IMPLEMENTATION AREA COSTS BENEFITS REQUIREMENTS

• TARGET i .

1 IDCOR-NRC Staff Search TO BE DETERMINED For Risk Outliers 2 Containment Performance Near Term Low High D/I 1-2 years Future Unknown Unknown D/I U 3 Equipment Moderate Moderate

-Qualification to High to High D/I 2-3 years 4 Emergency Planning Moderate High D 1-2 years 5 Accident Consequences Unknown ** Unknown ** U 1-2 years

& Indemnification 6 Air Filtration Low High U 1-2 years

, & Other Fission Product Attenu-ation Methods 7 Accident High High U 1-2 years Monitoring &

Management Onsite

& Offsite Instru-mentation 8 Offsite Con-tamination & Low. High D 1-3 years Recovery 9 Safety Issue Moderate High U 1-2 years Evaluations 10 Siting Moderate High D 2-3 years ,

o Increase (I), Decrease (D), Unknown (U)

• • Depends on Congress '

_ATTACMENT B

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