ML19324B652

Responds to Generic Ltr 88-20 Re Individual Plant Exam for Accident Vulnerabilities.Util Proposes to Perform Level 1 PRA Plus Containment Performance Analysis Following PRA Procedures in NUREG/CR-2300

ML19324B652
Person / Time
Site:	Davis Besse
Issue date:	10/27/1989
From:	Shelton D TOLEDO EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-NUREG-CR-2300 1723, GL-88-20, TAC-74402, NUDOCS 8911070258
Download: ML19324B652 (3)

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TOLEDO l L EDISON

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i DONALD C. SHELTON I vre Pree.orit Amr J Docket Number 50-346 M'8M'" " l License Number NPF-3 Serial Number 1723 I October 27, 1989 I

United States Nuclear Regulatory Commission Document Control Desk i Vashington, D. C. 20555 i Subjec t : Response to NRC Generic Letter 88-20 Individual Plant )

Examination for Severe Accident Vulnerabilities (TAC Number 74402)

Gentlemen:

The Nuclear Regulatory Commission issued Generic Letter 88-20 on November 23, 1988 requesting that each licensee perform an Individual Plant Examination (IPE) to identify severe accident vulnerabilities and submit the results to the NRC. Generic Letter 88-20 requested that a proposed program for completing the IPE be submitted to the NRC within 60 days of receiving final guidance for the conduct of the IPE. Final guidance, in the form of NUREG 1335, " Individual Plant Examination: Submittal Guidance", became available on September 1, 1989. The purpose of this letter is to provide Toledo Edison's proposed program to accomplish the IPE objectives for the Davis-Besse Nuclear Pover Station (DBNPS).

Toledo Edison proposes performing a Level 1 Probabilistic Risk Assessment (PRA) plus a containment performance analysis that follows the PRA procedures described in NUREG/CR-2300, "PRA Procedures Guide." The assessment vill consider current severe accident phenomenological issues and vill be based on current plant design. The plant configuration utilized for this assessement vill include modifications made to the plant through the sixth refueling outage which is scheduled to end in June, 1990. The IPE will also include evaluation of the decay heat removal function to identify severe accident vulnerabilities.

Toledo Edison proposes performing a Level 1 PRA for the front end analysis to determine the core-damage frequencies based on system and human-factor evaluations. This systems analysis portion of the IPE vill identify accident sequences that occur as a result of internal initiating events, including internal flooding, followed by failure of systems or plant personnel to respond correctly to the event. This vill be used to identify any plant-specific vulnerabilities to severe accidents. For the systems analysis, the small event tree and large fault tree linking method vill be employed, hCOI THE TOLEDO EDISON COMPANY EDISON PLAZA 300 MADISON AVENUE TOLEDO. OHIO 43652 ,

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License Number NPF-3 Serial Number 1723 l Page 2 CAFTA (Computer Aided Fault Tree Analysis Code) vill be utilized for such

, analysis. Toledo Edison proposes performing a containment performance analysis that follows the general guidance provided in Appendix 1 to Generic Letter 88-20 for the back-end analysis. This portion of the IPE vill identify any unusually poor containment performance given a core melt accident. The results of previous assessments vill be used to the extent possible ( a template approach as described in NUREG-1335). For areas where previous analyses are judged to be insufficient or do not exist, limited supplemental ,

calculations vill be performed using the NAAP 3.08 Code. ,

Performance of the IPE vill include examination and understanding of the plant '

emergency procedures, design, operations, maintenance, and surveillance from ,

the standpoint of identifying potential severe accident sequences. The leading contributors to core damage and unusually poor containment performance as well se the underlying causes vill be determined.

It is intended that DBNPS engineers vill be involved in the performance of the i IPE and independent internal technical reviews. Toledo Edison also plans to develop a plant specific data base to be used in conjunction with generic data, and to address common cause failures.

The DBNPS IPE results vill be submitted to the NRC by September 1, 1992.

Performance of the Level 1 PRA has commenced and is expected to continue through March 1991. Vork on the containment performance analysis is anticipated to begin by September 1990 and continue through March 1992. Final integration of the results is expected by May 1992, leading to the IPE being submitted by September 1, 1992.

Toledo Edison believes that the process for conduct of the DBNPS IPE as outlined above vill achieve the overall IPE objectives. If you have any questions regarding the DBNFS IPE please contact Mr. R. V. Schrauder, Nuclear Licensing Manager at (419) 249-2366.

Very trul yours, hsJf~I ~

j h PVS/ssg Enclosure cci P. H. Bryon, DB-1 NRC Senior Resident Inspector A. B. Davis, Regional Administrator, NRC Region III T. V. Vambach, NRC/NRR DB-1 Senior Project Manager

i ,o Docket Number 50-346

Licens] Number NPF-3

, , ." ' Serial Number 1723 Enclosure Page 1 RESPONSE TO GENERIC LETTER NUMBER 88-20 INDIVIDUAL PLANT EXAMINATION FOR SEVERE ACCIDENT VULNERABILITIES PROPOSED PROGRAM POR DAVIS-BESSE NUCLEAR POWER STATION UNIT NUMBER 1 Toledo Edison's proposed program for the conduct of an Individual Plant Examination for the Davis-Besse Nuclear Power Station as outlined in Generic Letter Number 88-20, Individual Plant Examination for Severe Accident Vulnerabilities, is hereby submitted under letter Serial Number 1723. This letter is submitted pursuant to 10CFR50.54(f).

By: J IA/b D. C. Shelton, Vice President Nuclear Sworn and subscribed before me this 27th day of October.1989.

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Notary Public, State of Ohio EVELYN L DRESS NOTARY PUGUC, STATE OF OfiK)

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