ML20071Q200

Informs of Decision to Change Scope of Review for Seismic Events Portion of IPEEE Re GL 88-20,suppl 4

ML20071Q200
Person / Time
Site:	Peach Bottom, Limerick
Issue date:	07/28/1994
From:	Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-88-20, NUDOCS 9408110121
Download: ML20071Q200 (2)

Text

Stztion Support Dzpartment L y i.. .

fy PECO ENERGY ft2J=3 Ls 965 CheMerbrook Doulevard Wayne, PA 19087-5691 July 28,1994 Docket Nos. 50-277 50-278 50-352 50-353 License Nos. DPR-44 DPR-56 NPF-39 NPF-85 U. S. Nuclear Regulatory Commission Attn: Document Control Desk l Washington, DC 20555 1 l

Subject:

Peach Bottom Atomic Power Station, Units 2 and 3 Limerick Generating Station, Units 1 and 2 Response to NRC Generic Letter 88-20, Supplement 4,

" Individual Plant Examination of External Events for )

Severe Accident Vulnerabilities" l l

Reference:

1) Letter from D. R. liclwig. (PECO Energy) to NRC dated j December 26,1991 i

2) Letter from G. J. Beck (PECO Energy) to NRC dated September 18,1992

Dear Sir:

1 Our reference letter 1 provided PECO Energy Company's (PECO Energy) respons: to Generic Letter 88 20, Supplement 4, wherein we identified the methods and approach for performing the Indhidual Plant Examination of External Events (IPEEE) at Peach Bottom Atomic Power Station (PBAPS) and Limerick Generating Station (LGS). The selected method for the scismic events portion was the Electric Power Research Institute (EPRI) seismic margin assessment (SMA) as described in NUREG-1407," Procedural and Submittal Guidance for the Indhidual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities.*

The purpose of this letter is to inform you of our decision to change the scope of review for the scismic ewnts portion of the IPEEE. PECO Energy remains committed to the EPRI SMA, but believes that the binning as described in NUREG-1407 is no longer appropriate. Based on new seismic hazard estimates developed by Lawrence Livermore National Laboratory (LLNL) and published in NUREG-1488," Revised Livermore Scismic Ilazard Estimates for 69 Nuclear Power Plant Sites East of the Rocky Mountains," PECO Energy has decided that for both PBAPS and LGS a focused-scope SMA is no longer warranted, and a reduced-scope SMA is 4e appropriate. The reasons are as follows:

9408110121 940728 PDR ADOCK 05000277 P PDR

July 23,1994 Page 2

. The 1993 LLNL results demonstrate that the seismic ha7ard is much less than what the NRC

- staff originally believed.

. The probability of exceeding the safe shutdown earthquake (SSE) using the revised 1993 LLNL mean hazard results is less than the mean probability of exceeding the SSE at the reduced scope plants identified in NUREG-1407.

• The probability of exceeding the SSE based upon 1993 LLNL mean hazard results is less than the probability of exceeding the 03g NUREG/CR-0098," Development of Criteria for Scismic Review of Selected Nuclear Power Plants," review level spectrum based on the 1989 LLNL mean harard results.

In light of the conclusions drawn from NUREG-1488, the reduced-scope SMA provides the most cost effective method for satisfying the goals of the scismic IPEEE. The detailed walkdowns which are the key element of this approach are the most beneficial aspect of the SMA and,in various studies conducted by the industry, have effectively found seismic vulnerabilities. PECO Energy is committed to performing the detailed plant walkdowns; therefore, the change in scope of review will have no impact on plant safety.

The change in the scope of review for the seismic events portion of the IPEEE does not affect the scheduled completion of the LGS and PBAPS IPEEEs, which was provided in our reference letter 2.

The PBAPS IPEEE is being coordinated with the resolution of Unresolved Safety Issue A-46, "Scismic Qualification of Equipment in Operating Plants." A signiGcant portion of the scismic walkdown effort is dictated by LGS and PBAPS refueling outage schedules. The non-scismic portions of the IPEEE are not impacted by the change in scope of review for the seismic events portion of the IPEEE. For these reasons, the LGS and PBAPS IPEEEs remain scheduled for completion by June 30,1995, and November 20,1995, respectively.

In conclusion, PECO Energy has determined that a reduced-scope SMA is appropriate for the scismic events portion of the IPEEE for both PBAPS and LGS, and therefore will complete the scismic events portion of the IPEEEs consistent with reduced-scope binning. PECO Energy will maintain the other commitments regarding scismic activitics.

If you have any questions or require additionalinformation, please contact us.

Very truly yours, G. A. Ilunger, Jr. ,/ ,

Director Licensing JLP/eas cc: T. T. Martin, Administrator, Region I, USNRC W. L Schmidt, USNRC Senior Resident inspector, PBAPS N. S. Perry, USNRC Senior Resident inspecter, LGS R. R. Janati, Commonwealth of Pennsylvania 4

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