ML13317B336
| ML13317B336 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/02/1991 |
| From: | Nandy F Southern California Edison Co |
| To: | NRC/IRM |
| Shared Package | |
| ML13317B337 | List: |
| References | |
| NUDOCS 9105070171 | |
| Download: ML13317B336 (1) | |
Text
Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 May 2, 199.1 F. R. NANDY TELEPHONE MANAGER, NUCLEAR LICENSING (714) 454-4504 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Amendment Application 188, Supplement 1--Transmittal of PRA San Onofre Nuclear Generating Station, Unit 1 Enclosed is the Probabilistic Risk Assessment (PRA) study that provides a basis for increasing the allowed outage time (AOT) for a Component Cooling Water (CCW) heat exchanger from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to seven days. This PRA was referred to in Amendment Application 188, Supplement 1. We are transmitting this PRA at the request of the NRC staff.
The PRA has been revised since our submittal of Supplement 1 to Amendment Application 188, dated November 1, 1990.
The main reason for revising the PRA was to reflect improved event and fault tree models. These improved models were developed during recent analysis of the High Energy Line Break (HELB) issue. Additionally, plant design enhancements implemented during the Cycle 11 refueling outage have been incorporated into the enclosed PRA.
Accordingly, the enclosed PRA revision supersedes the PRA information previously submitted in Supplement 1. The new PRA results indicate that the contribution to overall core damage frequency due to the increased AOT is insignificant (2.9E-7 per year).
This value is lower (more conservative) than our previously submitted PRA results.
If you have any questions, or desire additional information, please contact me. We would be pleased to meet with you to further discuss this subject.
Very truly yours, cc:
George Kalman, NRC Project Manager, San Onofre Unit 1 J. B. Martin, Regional Administrator, NRC Region V C. W. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2.3 C. D. Townsend, NRC Resident Inspector, San Onofre Unit 1 9105070171 91050:2 PDR ADOCK 05000206.