ML20135E193

Forwards Status of Regulatory Treatment of Nonsafety Sys (Rtnss) Subissues.Rtnss Program Should Be Revitalized & Given Required attention.WCAP-13856 Submitted in Sept 1993 Providing Results of Application of Criteria to SP600

ML20135E193
Person / Time
Site:	05200003
Issue date:	12/02/1996
From:	Mcintyre B WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:	Quay T NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
DCP-NRC0644, DCP-NRC644, NUDOCS 9612110066
Download: ML20135E193 (4)

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Westinghouse Energy Systems gg,ggn Pennsyivania 15230 0355 Electric Corporation NSD-NRC-96-4867 DCP/NRC0644 Docket No.: SlN-52-003 December 2,1996 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555 ATIlNflON: T. R. QUAY

SUBJECT:

REGULATORY TREAlMFNF OF NONSAFETY SYSTEMS (RTNSS) stall]S References 1: NRC letter to Westinghouse, Crutchfield to Liparulo, " List of Key Licensinr, Issues on the AP600 Design," dated 3/21/95.

2: Westinghouse letter to NRC, McIntyre to Quay, "AP600 Passive Systtm Reliability Roadmap," dated 8/9/96.

Dear Mr. Quay-The simplified nature of the AP600 design results in a number of systems that are classified as safety-related in current plants being classified as nonsafety-related. While the licensing basis for the AP600 relies solely on these safety-related systems, the NRC has raised the issue of what, if any, additional regulatory oversight should be applied to these systems. The initial discussions on the regulatory treatment of nonsafety systems (RTNSS) wem held between the NRC staff and the ALWR Utility Steering Committee in January,1993. In May,1993, agreement was reached between the NRC staff and the industry on the RlNSS resolution process, which included both probabilistic and deterministic evaluation criteria. In September,1993, Westinghouse submitted a report, "AP600 Implementation of the Regulatory treatment of Nonsafety-Related Systems",WCAP-13856, that provided the results of the application of these criteria to the AP600. This submittal included proposed additional regulatory oversight to provide the staff with the high level of confidence that active systems would be available when challenged. As described in the agreed to approach, this prop %cd regulatory oversight was I

consistent with the identified systems reliability / availability mission.

lhe agreed to RTNSS resolution process was reviewed by the Commission in SECY-94-084, " Policy \

and Technical Issues Associated with the Regulatory Treatment of Nonsafety Systems in Passive Plant Designs", March 28,1994. The SRM on SECY-94-084 was issued on June 30,1994.

During a March 29,1995 RTNSS meeting, the application of the RTNSS process to the nonnai IU1R system was reviewed with the staff as a specific example of the implementation process.

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• NSD-NRC-96-4867 December 2,1996 DCP/NRC0644 -

t During the February 9,1995 Westinghouse /NRC AP600 Senior Management Meeting (SMM). several ,

key subissues were identified and discussed which constitute the elements that requim closure to complete implementation of the RBSS process.

The attachment to this letter documents the status for each of the identified R1NSS subissues.

Implementation of the R1NSS msolution process is a key item with respect to completion of the

AP600 FSER. It is therefom essential that this program be mvitalized and given the attention it i j requires.

I will contact you prior to the Westinghouse /NRC senior management meeting on December 9 to discuss how to go forth on this issue so as to reach msolution in a time frame tlut supports our schedule.

ll Brian A. McIntyre, Manager Advanced Plant Safety and Licensing

/nja Attachment cc: T. Martin, NRC/NRR W.11uffman, NRC/NRR N. Liparulo, Westinghouse (w/o attachment)

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• l l ATTACHMENT TO DCP/NRC0644 i l

STATUS OF RTNSS KEY SUBISSUES  :

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1. . Thermal-hydraulic Uncertainty l l I We believe consensus was n: ached on a resolution path for acceptability of the baseline PRA, including passive system reliability and T&H uncertainty issues and that there is enough conservatism in the baseline PRA to offset the T&H uncertainty issues. Westinghouse submitted a passive system reliability madrnap by Reference 2 in response to an NRC request.

Westinghouse has the action to benchmark MAAP4 against NO1 RUMP and to complete the T&H Uncertainty Evaluation. There activities are included on the AP600 Design Certification Activity Schedule provided to the NRC.

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2. .NRC acceptance of the AP600 PRA l i

The final Focused PRA was submitted on September 30,1996. The initiating event frequency j evaluation was submitted on October 14,1996 and the focused PRA RTNSS evaluation is j scheduled for transmittal on November 1,1996. No additional RTNSS-important systems l have been identified. It is an NRC action to document acceptability of the Focused PRA. l

3. Adverse Systems Interactions ,

- On October 3,1996, the NRC provided review comments on WCAP 14477 the Adverse ,

Systems Interactions, submitted in Mamh of 1996. Westinghouse is addmssing those i comments in prepamtion for a resolution meeting with the NRC, tentatively scheduled for the l week of December 12,1996.  !

4. Post-72 hour Actions i

Post-72 hour actions is one of the policy issues before the Commission in SECY-96-128 and l requires Commission action to go fonh. This action is anticipated in the very near future. ,

I Westinghouse has reviewed the proposed policy statement before the Commission and is prepared to rapidly move forth with whatever actions are necessary to address this issue once I the Commission makes a decision on the SECY paper. I l

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Attachment to DCP/NRC0644

5. Safe shutdown The safe stable condition for the AP600 is dermed as hot standby since the passive RIIR system is highly reliable and no single active failure can prevent its termination. Ilowever, the staff was concemed that a small earthquake can make le standby ac power supply unavailable and has not determined acceptability of this design.

l As discussed during the January 1995 RINSS meeting, the Westinghouse position is that seismic design and qualineation is beyond the criteria agreed to in development of the R1NSS l

process. Thermal cysling issues resulting from passive system actuation during small seismic i events (less than SSE) were also addressed. This issue is closed, with NRC agreement that no l seismic criteria will be applied uniformly to RINSS-imponant equipment but can be applied if that equipnent performs a mission with seismic implications. l

6. Additional oversight once RINSS functions are identified beyond what is already prosided, (SSAR review, D-RAP, ITAAC, maintenance rule, etc.).

WCAP-13856, provided proposed additional regulatory oversight for the systems identified as RINSS inportant to provide the staff with the high level of confidence that active systems would be available when challenged. As described in the agreed on approach, this proposed regulatory oversight was consistent with the identified systems reliability / availability mission.

To assist the NRC with completion of their RINSS-related activities for the AP600 FSER, Westinghouse has created the attached AP600 Regulatory Oversight table which shows what additional regulatory oversight is appropriate for RTNSS-important systems identified. Also included in this table to provide a proper perspective on regulatory oversight are the regulatory oversights applied to safety related, as well as RINSS, DID, and other non-safety related systems and filnctions. If new RTNSS important systems are identified, the appropriate regulatory oversight will be established.

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