ML13330B537
| ML13330B537 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 07/29/1991 |
| From: | Rosenblum R SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9107300198 | |
| Download: ML13330B537 (2) | |
Text
Southern Caifornia Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 R. M. ROSENBLUM TELEPHONE MANAGER OF (714) 454-4505 NUCLEAR REGULATORY AFFAIRS July 29, 1991 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D. C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Schedule for Re-Performing Large Break Loss of Coolant Accident Analysis San Onofre Nuclear Generating Station, Unit 1
References:
- 1. Letter, R. M. Rosenblum (SCE) to NRC Document Control Desk "Underestimation of Refill Volume Assumed in Large Break LOCA Analysis," March 29, 1991.
- 2. Letter, R. M. Rosenblum (SCE) to NRC Document Control Desk "Volume Differences Identified in Accident Analyses,"
May 10, 1991.
- 3. Letter, R. M. Rosenblum (SCE) to NRC Document Control Desk, "Evaluation of Volume Differences in Accident Analysis,"
May 17, 1991.
This letter identifies the schedule for re-performing the large break loss of coolant accident (LBLOCA) analysis using modern methods and practices and revised reactor coolant system (RCS) volumetric information. The LBLOCA re-analysis is necessary to reflect revised RCS volumetric information that was described in References 1, 2, and 3. In the interim, we are operating SONGS 1 within restricted limits on incore axial offset and average RCS coolant temperature, Tavg, to ensure the plant continues to be operated within its design basis.
BACKGROUND Reference 1 informed the NRC on March 29, 1991, that the refill volume used in the LBLOCA analysis was underestimated by approximately 182 ft3. We have established administrative controls on incore axial offset to compensate for the refill volume discrepancy. Subsequent to March 29, 1991, we extended our confirmation efforts to ensure the accuracy of volumetric information in other accident analyses. Reference 2 documents additional RCS volume differences that were identified by our expanded investigation. Reference 3 described our conservative evaluation of the identified volume differences and established that existing administrative controls on incore axial offset and Tavg provided sufficient margin to assure the plant is operated within its design basis.
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-2 SCHEDULE FOR RE-PERFORMING LBLOCA ANALYSIS A teleconference with the NRC was held on July 17, 1991, to discuss the three SCE submittals on this subject. During the discussion, we agreed to document the schedule for re-performing the LBLOCA analysis using revised RCS volumetric information. That re-analysis will be completed, using modern methods and practices, prior to restart from the Cycle 12 refueling outage.
Please contact me if you have any questions concerning our schedule for the LBLOCA re-analysis.
Very truly yours, cc:
George Kalman, NRC Senior Project Manager, San Onofre Unit 1 J. 0. Bradfute, 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