ML13326A766
| ML13326A766 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/11/1991 |
| From: | Nandy F SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9104170088 | |
| Download: ML13326A766 (2) | |
Text
Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 F. R. NANDY April 11, 1991 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 Submittal Schedule for Technical Specification Revision to Incorporate Restrictions on Core Axial Offset San Onofre Nuclear Generating Station, Unit 1
Reference:
Letter, R. M. Rosenblum, SCE to NRC, "Underestimation of Refill Volume Assumed in Large Break LOCA Analysis," March 29, 1991 SCE recently discovered that the value for the reactor vessel refill volume used by Westinghouse in the SONGS 1 large break Loss of Coolant Accident (LBLOCA) analysis was underestimated. Therefore, the reactor vessel volume below the core will take longer to refill after a LBLOCA than presently calculated by our accident analysis. The purpose of this letter is to fulfill the requirements of 10 CFR 50.46(a)(3)(ii) by providing a schedule for submittal of a proposed Technical Specification change needed to compensate for the underestimated volume.
Administrative controls are in place to restrict reactor operation in the interim so that adequate safety margins are maintained.
ADMINISTRATIVE CONTROLS Administrative controls, as described in the above reference, were implemented to compensate for the underestimated refill volume (i.e., the sum of the reactor vessel lower plenum and downcomer volumes). The controls entailed
- 1) immediately limiting plant power level to less than 75% to ensure that adequate margin would be maintained while the effect of the volume underestimation was evaluated and 2) subsequently allowing full power operation with more restrictive requirements on core axial offset than those specified in Technical Specification 3.11, "Continuous Power Distribution Monitoring."
NRC concurrence on these administrative controls was obtained prior to plant operation above the 75% power level.
TECHNICAL SPECIFICATION CHANGE SUBMITTAL SCHEDULE The nature of the underestimated refill volume and its effect on the LBLOCA analysis was reported in the above referenced letter as required by 10 CFR 50.46(a)(3)(ii). The letter demonstrated that sufficient margin on peak clad temperature existed to allow full power operation with additional restrictions on core axial offset. We also committed to incorporate 910 417008E i 91041 1 PDR ADOCK 05000206 ROO P
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Document Control Desk April 111, 1991 the provisions of the above administrative controls in Technical Specification 3.11. The corresponding amendment application will be submitted by June 15, 1991, for NRC review and approval.
If you have any questions on this matter, please let me know.
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