ML20045D081
| ML20045D081 | |
| Person / Time | |
|---|---|
| Issue date: | 12/29/1992 |
| From: | Wylie C Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-2845, NUDOCS 9306250309 | |
| Download: ML20045D081 (11) | |
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DATE ISSUED:
12/4/92 CERTIFIED BY:
Charles Wylie - 12/29/92 l ::: -
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SUMMARY
HIGHLIGHTS / MINUTES OF THE ACRS SUBCOMMITTEE ON IMPROVED LIGHT WATER REACTORS MEETING SEPTEMBER 9, 1992 BETHESDA, MARYLAND INTRODUCTION The ACRS Subcommittee on Improved Light Water Reactors held a meeting on September 9, 1992, in Room P-110, 7920 Norfolk Avenue, Bethesda, Maryland, to discuss additional policy issues identified in the draft Commission Paper, " Design Certification and Licensing Policy Issues Pertaining to Passive and Evolutionary Advanced Light Water Reactor Design," dated June 25, 1992.
The entire meeting was open to public attendance.
Mr. Elpidio Igne was the cognizant ACRS staff engineer for this meeting. The presentation schedule for the meeting in included in the Attachment. The meeting was convened at 3:00 p.m. and adjourned at 6:20 p.m.
ATTENDEES ACRS C.
Wylie, Chairman C. Michelson, Member T. Kress, Member J.
Carroll, Member P.
Davis, Member W.
Lindblad, Member NRC Staff R.
Borchardt T.
Foley M.
Case C. Chiramal T.
Hiltz G.
Bagchi D. Terao M. Rubin J. Wermiel A.
Levin l
J.
Sharkey W.
Beckner DEFIC?iATD ORIGINAL s
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62 9 921229 0
Certified 37 _
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32845 PDR
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- s ILWR Subcommittee Meeting September 9,.1992 i
Others J. Trotter, EPRI J.
Chambers, GE T. Mersenheimer, Bechtel SUBCOMMITTEE CHAIRMAN'S OPENING REMARKS Mr. Wylie, the Subcommittee Chairman, convened the meeting at 3:00 p.m.
and stated that the staff on June 25, 1992, issued the draft commission paper to identify additional policy issues for design certification and licensing of evolutionary and passive advanced light water reactor designs, and requested that the ACRS comment on these additional policy issues. Assignments for review.of these issues were made to various Subcommittee Chairmen and they would develop comments and recommendations for use by the ACRS in preparing a report to the NRC.
Regarding Policy Issue A, Defense Against Common Mode Failures in Digital Instrumentation and Control (I&C) systems, Mr. Wylie, stated that the EDO, in a separate memorandum, has requested ACRS comments during the-September 1992 Committee meeting. Dr. Lewis has the responsibility for developing a position on this issue during the September 1992 ACRS meeting.
This issue will not be discussed at today's meeting.
Mr. Wylie said that the following ACRS members are responsible to review the additional policy issues:
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i ILWR Subcommittee Meeting September 9, 1992 A.
Defense against Common Mode Failures in Digital Instrumenta-tion and Control Systems, H. Lewis B.
Analysis of external events beyond the design
- basis, C. Michelson C.
Elimination of the operating basis earthquake from= seismic design, T. Kress D.
Multiple steam generator tube ruptures, I. Catton E.
Probabilistic risk assessment (PRA) beyond design certifica-tion, T. Kress F.
Role of a passive plant control room operator, J. Carroll G.
Control room annunciator reliability, J.
Carroll H.
Regulatory treatment of nonsafety system in passive plant designs, T. Kress j
l Mr. Wylie stated that issues A, B, C, D, E, and G are applicable to 1
evolutionary and passive plant designs, while issues F and H apply i
i only to passive plant' designs.
y ILWR Subcommittee Meeting
-4 September 9, 1992 In response to a question by Mr. Michelson, Mr. Wylie stated that this matter may be recommended for Committee consideration during the September 1992 meeting, subject to completion of the review of these issues by cognizant Subcommittee Chairmen.
Analysis of Externhl Events Beyond the Desian Basis - Mr.
W.
Beckner, NRR Mr. Beckner stated that for future plants, the staff will require that PRAs or margin analysis be performed for both external and
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internal events.
This position is consistent with the staff's
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1 requirement that PRAs or margin analysis be performed for existing plants as part of the Individual Plant Examination (IPE) program.
'j Mr. Michelson questioned the meaning of term "beyond the design l
basis."
Mr. Beckner explained that analysis of external' events "beyond the design basis" is another term for the performance of a probabilistic risk analysis.
Further, beyond the design basis includes both the design basis events and beyond the design-basis events with its corresponding frequency of occurrence. Mr. Beckner admitted that the term beyond the design basis as used in the title is a misnomer and may be confusing.
Mr.
Beckner described the comparison of the Individual Plant Examination of External Event (IPEEb) program that evaluated the risk from different types of external hazards, e.g., fire, internal i
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ILWR Subcommittee Meeting September 9, 1992 flood, high winds and others.
For seismic, fire and internal flood hazards, PRAs and walkdowns of plants by the Combined Operating License (COL) applicant are required.
Further, PRA-like margin analysis for seismic and fire hazards are also allowed.
For high winds and other hazards, the current Standard Review Plan (SRP) applied to site-specific characteristics by COL applicants provide t
adequate margins.
Mr. Beckner stated that he answered or clarified all of Dr. Siess' written comments during his presentation -- Mr.
Michelson and Mr. Kress agreed.
Mr. Michelson said that the staff's position on this matter seems appropriate.
Elimination of 3he Operatino Basis Earthauake (OBE) from Seismig Desion - Mr. R. Terao, NRR Mr. Terao discussed briefly the elimination of the OBE for the ABWR design.
The OBE level being proposed by the staff in the revised Appendix A to 10 CFR Part 100 is one-third of the Safe Shutdown Earthquake (SSE). The OBE is then eliminated from design consider-ations.
The elimination of the OBE directly impacts the design of piping
- systems, concrete and steel structures and equipment qualification.
In these areas, the staff is replacing the SSE with
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fractional SSE loadings such that the margins will remain similar to current practice.
It was noted that the staff is not requesting
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ILWR Subcommittee Meeting September 9, 1992 the Commission to approve the interim positions noted above.
Mr.
Kress noted that Dr. Siess, in his writ"en comment, endorsed the staff's interim position.
Multiple Steam Generator Tube Ruotures - Mr. A.
Levin, NRR Mr. Levin, presented a brief discussion on the history of multiple steam generator tube ruptures (SGTRs).
Based on operating experience data, Westinghouse plants have accumulated about 535 reactor years of operation, resulting in a frequency of a single tube rupture of about 1.1E-2 per reactor year.
Using binomial-statistics, the staff has estimated the frequency of multiple steam generator tube rupture events as 8.4E-4 per reactor year at the 50 percent confidence level.
Mr.
Levin stated that single SGTR i
frequency based on operating experience is about two orders of magnitude above that of other design-basis events.
He said that conventional PWRs would respond to multiple SGTRs in a manner similar to that for a single SGTR, but emphasized that a major concern.for the Westinghouse AP600 passive plant design is that response to multiple SGTRs may not be.similar to that for single SGTR.
Multiple SGTRs may accelerate inventory loss resulting in automatic depressurization system actuation, which could lead to inhibiting passive emergency core coolant injection, reactivity increase, and provide a substantial path for containment bypass.
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ILWR Subcommittee Meeting September 9, 1992 The staff is recommending that the applicant for design certifica-tion perform additional analyses to determine the AP600 response to multiple breaks of up to five steam generator tubes.
The staff will evaluate these analyses during the final design approval and determine the number of SGTRs that will be incorporated into the design basis for the passive plants.
The Subcommittee requested that it would like to review these analyses when they are completed and documented.
P_BA Beyond Desicm certification - Mr. Beckner, NRR Mr. Beckner did not have a formal presentation for this matter, but entertained questions from the Subcommittee.
Dr. Kress stated that the staff's position is reasonable.
Role of the ODerator in a Passive Plant Control Room - J. Wermiel, NRR
,4 r. Wermiel stated that fer passive plant designs, the staff's position was that a fully functional prototype of the control room would be necessary to demonstrate satisfactory operator perfor-mance, but that the staff with proper justification would consider l
an alternative approach.
Based on its current study of passive j
i plant designs, the staff believes that, a fully functional prototype i
control room is needed to demonstrate satisfactory operator l
ILWR Subcommittee Meeting September 9, 1992 performance. Mr. Wermiel stated that the EPRI Utility Requirements Document is in agreement with the staff's position.
In response to a question by Mr. Carroll, Mr. Wermiel stated that he believes a fully functional prototype should be built in steps and in parallel with the design and development of the control room.
Mr. Trottier, EPRI, in response to Mr. Carroll's question, stated that he agrees with the staff's position.
Mr. Carroll stated that we have a non-technical issue in that the language is confusing; citing in one area the requirements for a fully functional control room and in another area a conditional requirement.
In reply to Mr. Carroll's concern, Mr. Wermiel stated that it was intentionally written, as such, to offer alternatives that may very well be justified by the vendor.
Control Room Annunciator (Alarm) Reliability - Mr. M. Chiramal, NRR Mr. Chiramal stated that the staff agrees with the requirements of the plant system defined in the EPRI Utility Requirements Document.
Reculatory Treatment of Nonsafety Systems in Passive Plant Desions
- Mr.
M. Rubin i
ILWR Subcommittee Meeting September 9, 1992 Mr. Rubin stated that the issues are as follows:
(1) the passive ALWR design philosophy depart in a very significant way from current licensing practice, in that all active systems are designated as nonsafety systems, (2) the licensing design basis analyses are based on passive safety systems only, and (3) EPRI claims that active systems are not subject to NRC oversight because they only provide defense-in-depth functions for investment protection.
Mr. Rubin stated that in the staff por' tion active systems are not required to meet strict safety-related require-ments, but must conform to graded requirements based on their importance to safety.
He then provided the technical rationale for the staff's position and stated that the following information is needed for staff evaluation:
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An evaluation of relative importance of both passive and active systems, An evaluation to determine the limiting single failures.
e Performance and reliability assurance requirements for important active systems to ensure operability when needed.
In reply to a question by Mr. Kress, Mr. Rubin stated that the staff did not propose active systems be subject to safety grade requirements.
Further, Mr. Rubin indicated that they are concerned
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ILWR Subcommittee Meeting September 9, 1992 about the additional requirements to ensure functional performance of the active systems.
Mr.
Borchardt,
- EPRI, stated that this matter is still being discussed with the staff and remains open.
It was suggested by the Subcommittee that since this matter is still open, it should not be presented at the full ACRS meeting, and that a Subcommittee meeting be held in the future to review this matter.
SUBCOMMITTEE ACTIONS The Subcommittee plans to refer this matter to the full Committee during the September 1992 meeting.
FOLLOW-UP ITEMS The Subcommittee plans to discuss the following at a future meeting:
i Results of the staff's evaluation of regulatory treatment of e
i nonsafety systems.
Results of multiple steam generator tube ruptures (up to 5 tube breaks) analyses.
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i ILWR Subcommittee Meeting September 9, 1992 APPENDIX 1.
Marked-up copy of agenda 2.
Document provided to the Subcommittee during the meeting:
Memorandum for Dennis M. Crutchfield, NRR from William T.
Russell, NRR,
Subject:
" Preliminary Evaluation on the Use of a Single-Earthquake Design - for Systems, Struc-tures, and Components in the ABWR," dated September 4, 1992 i
3.
Handouts I
NOTE:
Additional meeting details 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) 634-3273 or can be purchased from Ann Riley and Associates, LTD.,
1612 K Street, N.W.,
Suite 300, Washington D.C.
20006, (202) 292-3950.
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