ML20213A613

Summary of ACRS Safety Philosphy,Technology & Criteria Subcommittee 861105 Meeting in Washington,Dc

ML20213A613
Person / Time
Issue date:	11/25/1986
From:	Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-2470, NUDOCS 8702030392
Download: ML20213A613 (10)

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November 5,1986 Safety Philosophy, Technology and Criteria Subcomittee Meeting Washington, DC The ACRS Subcomittee on Safety Philosophy, Technology and Criteria met on November 5,1986 at 1717 H Street, N.W., Washington, DC. The purpose of this meeting was to discuss the implications of the Chernobyl acci-dent for U.S. nuclear power plants. A NRC Staff draft report was avail-able prior to the Subcomittee meeting for the Subcomittee's review.

ACRS action on this matter is planned for the December 11-13, 1986 meeting with a second Subcomittee meeting scheduled for December 10, 1986. The Subcommittee meeting began at 9:00 a.m. and adjourned at 5:30 p.m. All discussions were held in open session. The principle attend-ees were as follows:

ACRS NRC D. Okrent, Subcomittee Chairman T. Spets D. Ward, Member B. Sheron M. Carbon, Member B. Boger H. Lewis, Member H. Richings C. Michelson, Member J. Stang J. C. Mark, Member S. Schwartz -

C. Wylie, Member L. Soffer R. Savio, Staff 0. Lynch S. Acharya FEMA B. Morris M. Sanders F. Congel G. Sege W. Russell Highlights

1. The NRC Staff has produced a preliminary draft of a Chernobyl implications report. The report was transmitted to the Subcomit-tee under an October 30, 1986 and October 31, 1986 cover letters 8702030392 86112S r--- y y g PDR AhS- Cecung y p [ g

SPT&C Meeting Minutes November 5, 1986 for the Subcommittee's review. (See Meeting Briefing Book for the November 6-8, 1986 ACRS Meeting.) This draft of the report is currently also being reviewed and comented on by NRC management.

A revised report will be transmitted to ACRS in the later part of November. The hRC Staff has requested ACRS comment at the December 11-13, 1986 ACRS meeting and will present their recommendations to the Commission later in December. The NRC Staff's fact-finding report (reporting of the sequence of events) is expected to be completed by the end of November 1986. The information provided by the Soviets at the Vienna meeting will provide the primary basis for this report. The contents of the fact-finding and implications reports are summarized on Figures 1 and 2.

2. The NRC Staff's objective in the implications report is to identify the candidate issues and assess the importance of these issues.

Judgements are to be then made as to: (1) whether the issue can be resolved on the basis of what is currently known, (2) whether it is likely to be resolved by ongoing work, or (3) whether new programs are needed. The NRC Staff intent is to focus this evaluation on the direct implications of the Chernobyl accident. The NRC Staff has concluded that no immediate regulatory action is needed for U.S. reactors and that existing U.S. practices and regulations

, protect against Chernobyl-like events. The NRC Staff believes that j the lessons learned from Chernobyl can be used to reinforce and

! improve requirements which already exist or are being developed.

Studies will also be conducted to further evaluate the need for additional action. The NRC Staff's implications report discusses their recommendations in some det til. The major conclusions drawn are as follows:

(1) Reactor Operations - The emphasis given to human factors needs to be reinforced. Particular attention needs to be given to the adequacy of administrative controls, control of safety l

.SPT&C Meeting Minutes November 5, 1986 system status, and engineered safety features availability.

The NRC will be evaluating the mechanisms by which reactor modifications, tests, and experiments are controlled and the joint NSAC/AIF effort to develop criteria in this area, operator attitudes toward safety and night shift operation were issues in the Chernobyl accident. The NRC Staff feels that the U.S. practices provide adequate safeguards against unacceptable operator attitudes and the problems associated with night shift operation. An assessment of the NRC require-ments on manaaement systems will be conducted with emphasis on making determinations of the particular skills required for the various tasks. The NRC's current approach is to monitor licensee performance and to deal with problems on a case-by-case basis rather than to issue additional regulatory require-ments.

(2) Reactor Design - A wider range of reactivity insertion acci-dents than are currently considered under the SRP will be evaluated. The NRC Staff believes that these scenarios are less probable than those treated in the SRP. Accidents occurring when the reactor is shut down or at low power and the multiple unit aspects of reactor accidents will be reeval-uated. Current fire fighting procedures will be reviewed to determine if adequate consideration has been given to the problems associated with the presence of high levels of radiation.

(3) Containment Capabilities - The NRC Staff has concluded that the Chernobyl and Three Mile Island accidents graphically demonstrate the importance of containment performance in a severe accident. Containment performance in a severe accident and the use of containment venting or filtered venting as a

SPT&C Meeting Minutes November 5, 1986 mitigation strategy are being evaluated as part of ongoing NRC programs. The NRC Staff has concluded that no additional evaluations are necessary and that the containment performance issue can be resolved by the ongoing NRC and Industry work.

(4) Emergency Planning - The lessons learned of the Chernobyl accident will be evaluated. Emphasis will be given to issues of sheltering vs evacuation and the effectiveness of the various protective actions. The NRC Staff believes that issues associated with long-term relocation, decontamination and use of contamination foodstuffs, the use of potassium pills, medical treatment, and accident recovery need to be carefully examined.

(5) Severe Accident Phenomena - The NRC Staff believes that the current NRC treatment of steam explosions is adequate and will not initiate any new work in this area unless their examina-tion of reactivity insulation accidents indicates a risk-based need for examining energy depositions beyond 280 cal /gm-UO 2

. The NRC Staff has also concluded that the generation of combustible gases is adequately cddressed in the current programs. The current work on accident source tems will be

expanded to include more work on:

(a) mechanical fuel fragmentation and dispersal by high energy processes.

I (b) conv2rsion of U0 to 2 loose / porous foms which could enhance aerosolization or radionuclide stripping of the fuel.

t (c) effect of accident minagement on the release.

l

SPT&C Meeting Minutes Npvember 5, 1986 (d) revaporization/resuspension of radionuclides.

(e) mechanisms for release of single element hot particles.

(f) hydrogen generation by dispersed fuel fragments.

(6) Economics Effects - The NRC Staff will use what has been learned on the economic effects of the Chernobyl accident to reevaluate the NRC's cost benefit methodology.

3. The Subcommittee members commented extensively of the NRC Staff's proposal. The summary of the comments made are as follows:

(1) The Chernobyl accident demonstrated the importance of human performance in safe operation of U.S. reactors. In particu-lar:

(a) The operators should have a good understanding of the principles of reactor saf.ety, the technical basis for the operating procedures, and potential accident scenarios.

Their training should build on this basic understanding.

(b) The onsite plant personnel should include individuals with through understanding of the plant design and operational characteristics.

(c) A single competent individual whose primary concern is plant safety should exist and have the authority to order plant shutdown.

o SPT&C Meeting Minutes November 5, 1986 (2) The administrative controls which are intended to assure that procedures (in particular emergency procedures) are adequate and are followed should be very carefully evaluated.

(3) More attention needs to be paid to the fires which might be associated with a severe accident. Some issues to be con-sidered are overall fire fighting strategies (methods, fight-ing the fire vs letting it burn, providing better fire barri-ers, etc.) radiation protection, availability of equipment and personnel to fight multiple fires, and the impact of fires on the course of the accident, the accident release, and the safety of the potential for fires / explosions caused by leaks from process hydrogen stored in the plant should be considered adjacent units.

(4) Accidents which can cause reactivity insertion need to be examined. Multiple rod ejections, cold water insertions, void collapse, early-core-life positive temperature coefficients, and low power operation need to be examined.

(5) The effectiveness of U.S. reactor containments under severe accident condition should be carefully examined in view of the fact that such accidents were not part of the design basis.

It was noted that France, Germany and Sweden appear to be committed to the use of filter-vented containment designs.

Mechanisms for containment failure (in particular early failure) such as missiles, degraded penetration, etc., such be carefully and objectively reevaluated.

(5) There was some disagreement with the NRC Staff's expressed satisfaction with U.S. administrative controls, operator training and attitude, and operational procedures. It was noted that the reasons for the failure of the system used by

J SPT&C Meeting Minutes November 5, 1986 the Soviets is not well understood. The vulnerabilities in the Chernobyl infrastructure need to be understood before it can be concluded that similar problems do riot exist in the U.S.

(7) Technical Specifications are designed to control normal  ;

operations and may not adequately control tests, experiments, or other unusual reactor conditions.

(8) Methods for accident management need additional study and evaluation.

(9) Damage to large areas of land and other major societal re-sources need to be more carefully examined in NRC cost / benefit evaluations.

(10) The design process for advanced reactors should be directed as much as practicable to producing designs which will revert to a stable configuration when scrammed.

(11) It is essential that the important lessons learned from the Chernobyl accident be developed. A through and critical evaluation of the accident will be important.

(12) It is important that the significance of safety issues be i understood and remembered even after resolutions have been found and implemented. These issues may need to be reevalu-ated in the future in the light of new information or changes which have been made in reactor design or operation.

i SPT&C Meeting Minutes November 5, 1986 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, DC, or can be purchased from ACE-Federal Reporters, 444 North Capitol Street, Washington, DC 20001, (202) 347-3700.

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STATUS - FJb=* o Y CHAPTER TITLE LEAD AGENCY 1

SUMMARY

NRC 2 INTRODUCTION NRC 3 PLANT DESIGN DESCRIPTION DOE 4 SAFETY ANALYSIS EPRI 5 ACCIDENT SCENARIO NRC 6 ROLE OF OPERATING PERSONNEL INP0 7 SOURCE TERM NRC 8 EMERGENCY PREPAREDNESS FEMA 9 ENVIRONMENTAL CONSEQUENCES EPA SCHEDULE -

,- ALL DRAFT CHAPTERS PREPARED AND SENT TO NRC (EXCEPT EPA)

NRC WILL ISSUE COMPLETE DRAFT FACTUAL REPORT TO PARTICIPANTS BY 11/7 MEETING TO REVIEW AND FINALIZE REPORT SCHEDULED FOR 11/18 EXPECT TO ISSUE FACTUAL REPORT BY END OF NONTH D

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.CHERNOBYL ACCIDENT CANDIDATE ISSUES I. OPERATIONS (AdministrativeControls)

I.1 Approval of Tests and Other Unusual Operations I.2 Controls to Assure Administrative Procedures are Followed .

I.3 Bypassing Safety Systems ...  :. ,. . .

I.4 Availability of Engineered Safety Featutes .

I.5 Operator Attitude Toward Safety .

I.6 Night Shift Operations I.7 Management Systems -

II. DESIGN -

II.1 Reactivity Accidents *

• II.2 Accidents at Low Power and When Shut Down II.3 Multiple Unit Protection II.4 Fires III. CONTAINMENT III.1 Beyond DBA Capabilities III.2 Venting IV. EMERGENCY PLANNING IV.1 Adequacy of Zone Distances IV.2 Long-Term Relocation, Decontamination Issues IV.3 Use of KI Pills IV.4 Data Acquisition & Reporting IV.5 Ingestion Pathway Monitoring & Ingestion of Foodstuffs IV.6 Emergency Medical Services IV.7 Onsite Response V. SEVERE ACCIDENT PHENOMENA Y.1 Source Terms V.2 Steam Explosions V.3 Combustible Gas VI. ECONOMIC EFFECTS .

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