ML19324B641

Responds to Generic Ltr 88-20,Suppl 1, Individual Plant Exam (Ipe). IPE Will Be Submitted for TMI-1 by 890901

ML19324B641
Person / Time
Site:	Three Mile Island
Issue date:	10/31/1989
From:	Hukill H GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
C311-89-2121, NUDOCS 8911070243
Download: ML19324B641 (2)

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. 717 944 7621 l TELEX 84 2386 Writer's Direct Dial Number

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October 31, 1989 ,

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L U. S. Nuclear Regulatory Commission Attn: Document Control Desk h Washington, D.C. 20555

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L' Gentlemen:

Three Mile Island Nuclear Generating Station, Unit 1 (TMI-1)

Operating License No. DPR-50 Docket No. 50-289 -

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Response to Generic Letter 88-20, Supplement 1 .

Individual Plant Examination (IPE)

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In response to NRC Generic Letter 88-20, Supplement 1, this letter outlines L GPUN's plan for completing the IPE for TMI-1. GPUN letter 5211-87-2157, dated December 7,1987 transmitted a Level 1 Probabilistic Risk Assessment (PRA) for

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TMI-1,'which includes treatment of internal floods and a spectrum of external initiators. This study, which took four years to complete, used the large event tree-small fault tree PRA approach and resulted in a number of

}. recommendations for improving safety at TMI-1. A status sumary of our consideration of the recomendations'was submitted in GPUN letter C311-89-2020, '

dated March 17, 1989. NRC staff review of the Level 1 PRA'is continuing; we -

i expect a report on that review by the end of 1989.

4, For the front-end portion of the TMI-1 IPE, the existing Level 1 PRA analyses will be used as a foundation. The existing data base will be updated to .

reflect operating experience through 1989, and to incorporate needed changes to the event sequence and fault tree models to reflect current plant design, procedures, and practices. This will be dore using the same PRA methodology r employed in the previous study. Submittal guidance for the PRA method for

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performing the IPE, contained in NUREG-1335, will be utilized and any issues raised by the staff in their forthcoming review report will be addressed.

Since the format of the TMI-1 PRA report is different from that specified in NUREG-1335 a " road map" will be provided to aid the NRC staff's review. We also plan to convert the PRA models from their current form on an IBM mainframe computer to a state-of-the-art, more user friendly, format on personal computers. These changes are expected to make the TMI-1 PRA more useful as a risk management tool once the IPE is completed. l 31015789 8911070243 891031 gok l

PDR ADOCK 05000289 P PDC l

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GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation

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( , .' C31.1-89-2121 October 31, 1989

< The back-end (containment response) portion of the TMI-1 IPE will be performed

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utilizing the guidance in NUREG-1335. We are developing the capability to use

, the MAAP computer code as needed. We will also take advantage of other '

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analyses that may be performed by owner's groups, EPRI, consultants, etc.

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As required by Generic' Letter 88-20, appropriate parts of the crganization will be involved in the conduct and review of the IPE. Our experience indicates

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that heavy involvement of the operations staff as well as technical support groups.is necessary to develop useful results. This involvement necessarily '

l requires significant manpower expenditure across several organizations to reach ,

and properly document consensus conclusions. These factors, in conjunction p

with the need for an independent review as specified in Generic Letter 88-20, and the need to coordinate a number of activities with owners' groups, indicate to us that the three year schedule for submittel of the IPE has little or nc

margin for delays. We will make every effort to submit the IPE for TMI-1 by September 1,1992, consistent with our Long Range Plan Implementation Schedule.

Sincerely, Ltd H. D. Hu dll Vice President and Director, TMI-1 HDH/DJD/ag 31015789

.cc: J. Stolz, USNRC W. Russell, USNRC Region I R. Hernan, USNRC F. Young, USNRC, TMI-1 Site 31015789

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