ML19350D003
| ML19350D003 | |
| Person / Time | |
|---|---|
| Site: | Indian Point, Diablo Canyon, Zion  |
| Issue date: | 10/24/1980 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-1784, NUDOCS 8104130054 | |
| Download: ML19350D003 (8) | |
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COPY ISSUED:
10/24/80
- 4 to MINb7ES OF THE ACRS SUBCOMMITTEE MEETING ON SAFETY PHILOSOPHY, TECHNOLOGY, AND CRITERIA OCTOBER 8,1980 WASHINGTON, D.C.
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On October 8,1980, the ACRS Safety Philosophy, Technology, and Criteria Subcommittee held a meeting in Washington, D.C.
The purpose of the meeting was for the Subcommittee to discuss the Diablo Canyon systems interaction study, receive an overview on the Zion / Indian Point studies, and discuss the design philosophy for the decay heat removal system.
The principle, attendees of the meeting are noted below:
ACRS NRC STAFF D. Okrent, Chairman B. Buckley J. Ebersole J. Stolz W. Kerr C. Thomas W. Mathis T. Speis J. Ray J. Meyer C. Siess F. Orr J. C. Mark (part-time)
H. Etherington*
PACIFIC GAS &
R. Burns, Consultant ELECTRIC (PG&E)
P. Davis, Consultant T. Hickman, Consultant J. Hoch W. Lipinski, Consultant V. Killpack tember Emeritus A complete list of attendees is attached to the office copy of these minutes.
INTRODUCTORY REMARKS - D. OKRENT, SUBC fiMITTEE CHAIRMAN Dr. Okrent called the meeting to order at 9:02 am. The Chairman explained the purpose of the meeting and the procedures for conducting the meeting, and noted.that Dr. Richard Savio was the Designated Federal Employee.
DIABLO CANYON SYSTEMS INTERACTION REVIEW - B. BUCKLEY, C. THOMAS, NRC -
J. H0CH, V. KILLPACK, PG&E Messrs. B. Buckley and C. Thomas (NRC Staff) introduced discussion of the Diablo Canyon systeas interaciton Proaram for seismically-induced events.
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4 Safety Phil., Tech. & Criteria Mtg October 8, 1980 e
This Program was developed as a result of discussions begun at the November 5, 1979 ACRS THI-2 Accident Implications Subcommittee meeting, and was subsequently-documented in Task II.C.3 of the NRC Action Plan. NRC mandated completion of this Program prior to full-power operation.
The Program objectives are to assure that plant non-safety grade equipment will not compromise safety equipment functions during physical interactions caused by seismic events up to and including the postulated 7.5 Magnitude Hosgri event. Another Program objective is that the single failure criterion be assured for safety-related equipment as a result of these physical interactions. The approach used for the Program is as follows:
(1) all safety-related structures, systems, and components are defined as
" targets"; (2) non-safety-related structures, systems, and components are defined as " sources"; and (3) interactions between sources and targets were postulated by an interdiciplinary team of engineers during in-plant walkdowns of target equipment.
Messrs. J. Hoch and V. Killpack of Pacific Gas and Electric (PG&E) discussed the details of the systems interaction Program. Mr. Hoch noted that a Systems Interaction Review Board consisting of outside consultants hired by PG&E has notified PG&E via letter that the Program is acceptable. Mr. Hoch also noted that at the Review Board's suggestion, all documents associated with the study are in a retrievable form (computerized and microfiched) and can be audited.
Mr. Killpack discussed the various interactions studied and showed examples for each interaction category. The interaction study categories included: (i) laterial movement and clearances 'which was founded to be the most prevelant problem (pipes supports swinging into other pipes, instruments, etc.); (2) swingins cranes and hoists; (3) falling objects; (4) seismically unqualified substructures; (5) exposed tubing (air systems for critical valves, etc.);
and (6) overturning of items (antennas, etc.).
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Safety Phil., Tech. & Criteria Mtg October 8, 1980
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In reponse to a question from Dr. Okrent, PG&E stated that they did not examine possible interactive effects between control and safety systems; only physical effects on a given system were studied (electrical cabinets vibrating,'etc.).
PG&E also noted that some of the interactive effects I
were the result of backfits mandated by safety regulations.
In response to a que'stion from Dr. Kerr, Mr. Hoch noted that PG&E intends to study the backfits they make'as a result of this Program to assure that no additional potential interactions have been created. Messrs. Ebersole and Kerr asked if PG&E would recommend all plants understake a similar type Program.
PG&E said that they would do so for any other nuclear plant they build, but feel it would be better to incorporate such a Program into the CP stage of review.
Mr. C. Thomas (NRC) stated that NRC has reviewed the above Program and has found it acceptable. The Staff review of the Program is documented in Supplement 11 to the Diablo Canyon SER.
Implementation of the Program will be followed by I&E during the c,o'urse of their inspection activities.
Dr. Okrent asked if NRC is convinced that seismically induced failure of non-safety control systems won't impare decay heat removal capability.
Mr. Stolz said that based on the subject Program, the Staff is reasonably assured that no seismic event will adversely affect a control system such that the plant cannot be shutdown. Dr. Okrent suggested the NRC was not responding to the question. Dr. Okrent also suggested that PG&E examine the situation of what would be the effect of failure of non-seismically qualified systems on control room displays, and what actions the operators would have to take, given a severe earthquake.
NRC refuested ACRS comment on the adequacy of the systems interaction Program irr the near future.
Full Comittee consideration of this matter is presently scheduled for the November 1980 ACRS meeting.
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Safety Phil., Tech. & Critsrf a Mtg October 8,1980 t
ZION / INDIAN POINT (Z/IP) SEVERE ACCIDENT MITIGATION FEATURES STUDY UPDATE J. MEYER - NRC Dr. Jim Meyer (NRC) gave a brief presentation on the status of the portion of the Zion / Indian Point (Z/IP) Task Action Plan addressing the severc accident mitigation features study. Dr. Meyer referred to his September 29, 1980 memo to T. Speis that discusses action on the severe accident mitigation features.
Referring to a flow chart contained in the above memo (Figure 1), Dr. Meyer said the plan contains two activities in parallel:
(1) a mitigation features study (composed of a utility and NRC study) designed to answer the question: '"Will mitigation features for Z/IP substantially reduce risk?"
and (2) a Z/IP Risk Analysis study that is designed to answer the questions:
(a) "Is the Utility Risk Analysis study (Offshore Power Systems " Mini-WASH-1400 Study") adequate"? and (b) "Do the 2/IP plants represent undue risk to the public"?
Drs. Okrent and Kerr asked Dr. Meyer what was the definition of " undue risk" and what yardstick would be used to make a decision whether Z/IP constituted undue risk. After considerable discussion, Dr. Meyer indicated ~that these items are still under discussion within NRC. Dr. Kerr also asked if NRC has considered whether or not the results of the industry risk study will be
" believable"; i.e., how will NRC make use of risk estimates that cannot be demonstrate {with reasonable certainty ? NRC stated that they are committted to understaking a serious consideration of the study's results. Mr. P. Davis (ACRS Consultant) asked how one can adequately design mitigating equipment if you do not know what the major accident risks are. Dr. Meyer said that NRC believes it has a understanding of'the major accident risks and iooks to ilha Pickard. Lowe, and Garrick risk assessment report to fine-tune their understandings.
Dr. Meyer ddressed a concern raised in an ACRS letter written in September 1980,. questioning why the NRC Iterim Rule on degraded core cooling did not require all licensees to study mitigation features. Dr. Meyer referred to a September 25, 1980 memo fr6m H. Denton to Chainnan A'iearne that addresses l
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Safety Phil., Tech. & Criteria Mtg October 8, 1980 this concern. Drs. Okrent and Kerr however felt the letter was not responsive to the ACRS concern.
Dr. Meyer reviewed the options that he said were available to the NRC in order to initiate licensee study of mitigation features. The options noted are:
(1) to incorporate the design study in the Interim Rule now out for public comment, (2) issue a new Rule requiring mitigation concept designs, (3) issue Orders requiring mitigation concept designs, (4) make the Study a requirement in the long-term Rule (this is not favored by NRC because of the delay it would impose on implementation), (5) NRC could perform the studies independent of the utilities, and (6) vendor Owners Groups could, perform mitigation features studies similar to the Z/IP effort. Dr. Meyer solicited Subcommittee comment on these options.
Dr. Okrent felt that any comment to be made should be made by the full Comittee.
DESIGN PHILOSOPHY FOR DECAY HEAT REMOVAL SYSTEMS - COMMISSIONER GILINSKY'S QUESTIONS ON THE NORTii ANNA LPI AND RHR SYSTEM, F. ORR, NRC Mr. Orr (NRC) addressed comments made by Commissioner Gilinsky concerning the North Anna Unit 2 full power authorization of August 20, 1980.
In his comments, Dr. Gilinsky suggested that: (1) the residual heat removal system be environmentally qualified, and (2) the need for heat exchangers in the low pressure injection system be studied. Mr. Orr said that NRC believes the current system at North Anna meets NRC criteria and therefore is acceptable. NRC noted that the RHR system is not part of the ECCS and there are features available to assure the LPI water will be sufficiently cooled.
Dr. Okrent and Mr. Ebersole questioned whether the Staff was being responsive l
to Dr. Gilinsky's concerns.
Following extensive discussion of the particular LPI and RHR systems at North Anna, NRC said that they had requested a study by Brookhaven Laboratories that will examine from a probabilistic f
standpoint the desirability of adding heat exchangers to the LPI system.
The results of the study will be provided to the Subcommittee when completed. Both Messrs. Okrent and Hickman (ACRS Consultant) urged that
4 Safety Phil., Tech. & Criteria Mtg October 8,1980
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the study's scope be made broader to assure that no important failure modes are overlooked.
Mr. T. Speis (NRC) outlined the Staff's efforts on the study of decay heat removal systems. The study's focus is outlined in the Action Plan - Item II.E.3.
Mr. Speis said that a detailed outline of the NRC effort in this area should be available in a few months. Dr. Okrent urged that NRC report to the Subcommittee when the Program outline is complete.
g Dr. Kerr raised the question of what is an adequate reliability for the decay heat removal system. Mr. Novak (NRC) suggested a number in the neighborhood of 10-4 Dr. Okrent commented that he would like to see such reliability criteria in writing and also suggested that a confidence level be. appropriated to such numbers as the one noted above.
The meeting was adjourned at 3:02 p.m.
NOTE: Additional details of the meeting are available in a transcript located in the NRC Public Document Room, 1717 H Street, N.W.,
-Washington, D.C.
The transcript can also be obtained at cost from Alderson Reporting Company, Inc., 400 Virginia Avenue, S.W.,
Washington, D.C. 20024.
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LIST OF DOCUMENTS MADE AVAILABLE FOR OCTOBER 8,1980 SAFETY PHILOSOPHY, TECHNOLOGY AND CRITERIA SUBCOMMITTEE MEETING Vu-Graphs: NRC - 10 Letters and Reports 1.
"NRC Safety Evaluation Report Related to Operation of Diable Canyon Nuclear Power Station Units 1 & 2" - Supplement No.11 September 1980.
2.
" Description of the Systems Interaction Program for Seismically -
Induced Events - Diablo Canyon Units 1 and 2" - Pacific Gas and Electric Co., August 29, 1980.
3.
NRC Memo, J. Meyer, Reactor Systems Branch, DSI, to T. Speis Chief Reactor Systems Branch, DSI,
Subject:
Update of Zion / Indian Point Action: Task 3 " Severe Accident Mitigation Features" dated September 29, 1980.
4.
ACRS Letter " Additional ACRS Comments on Hydrogen Control and Improvement of Containment Capability" dated September 8, 1980.
S.
" Commissioner Gilinsky's Separate Statement on North Anna 2 Full Power Authorization," dated August 20, 1980.
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