ML13322B134
| ML13322B134 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/20/1990 |
| From: | Nandy F Southern California Edison Co |
| To: | NRC/IRM |
| References | |
| NUDOCS 9004260344 | |
| Download: ML13322B134 (3) | |
Text
Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 F. R. NANDY April 20, 1990 TELEPHONE MANAGER OF NUCLEAR LICENSING (714) 587-5400 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Docket Nos. 50-206 Overpressure Mitigation System San Onofre Nuclear Generating Station Unit 1 OMS Amendment Schedule The purpose of this letter is to provide you with the schedule for submittal of the Overpressure Mitigation System (OMS) amendment application and to explain the basis for delay of the submittal. The amendment application which will revise the OMS and other related technical specifications will be submitted by June 30, 1990.
Previous Schedule As you know, we committed to perform a detailed and comprehensive review of the OMS design basis. The amendment application revising the OMS technical specification was originally scheduled to be submitted by January 31, 1990.
The review began in November 1989. A significant engineering effort has been required to reconstruct the design basis and the analyses necessary to support the technical specifications which would be submitted with the amendment application. This was pointed out in our letter of January 30, 1990.
The January 30, 1990 letter briefly explained that NRC Standard Review Plan guidance would be used to develop the OMS setpoint, heatup and cooldown curves would be revised, PORV flow capacity would be revised, overpressure protection of the RHR system would be incorporated into the OMS design basis, and the OMS design was being evaluated for single failure. As a result, six new calculations were being developed and an existing calculation was being revised. We anticipated this effort to be completed and the amendment application submitted by March 30, 1990.
On March 30, 1990, we informed you that a further schedule delay was necessary. This was due to the errors identified in the calculation for the reactor vessel material adjusted reference temperature which could affect the heatup and cooldown curves and information from Westinghouse which identified inconsistencies in the RHR system relief valve flow capacities. We were unable to assess the impact of the additional issues and could not determine a PDR DCC K 050o0206 P
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Document Control Desk April20, 1990 new submittal date at that time. We committed to provide you with a schedule by April 20, 1990.
Basis for Current Schedule Delay The June 30, 1990 submittal date, identified above, is based on a review of all the ongoing efforts which need to be completed to support the amendment application. These are:
o Relief Valve Flow Capacity Westinghouse informed us (and others) that the RHR system relief valve flow capacity may be less than previously analyzed. The impact of this potentially reduced flow on the RHR and OMS design basis is being evaluated. In addition, this issue has resulted in the need to validate our existing PORV flow assumptions.
o Instrumentation Instrumentation associated with the OMS design is being reevaluated for response times and uncertainties.
o Single Failure Evaluation Review of event specific single failure analyses associated with the OMS is still ongoing.
o Energy Addition Following review of the Westinghouse letter on RHR relief valve flows, the thermal energy addition analysis may have to be reexamined.
o RCS and Steam Generator Delta T The method for calculating the delta T between the RCS and steam generators for determining compliance with the administrative limits on RCP operation has been reexamined. The method has been determined to be acceptable and instrumentation uncertainties are being documented and incorporated.
As indicated, the above efforts need to be completed prior to submittal of an OMS amendment application. Based on our review of the status of these efforts, a submittal date of June 30, has been scheduled. In addition, as soon as we complete the activity identified above, we will confirm the adequacy of adminsistrative controls for interim operation of the OMS. We expect to provide this confirmation by May 31, 1990.
Document Control Desk April 20, 1990 Summary The effort required to review the OMS design basis and update the associated analyses has been significantly greater than originally anticipated. However, all problem areas identified during the process are being addressed, and complete documentation is being developed.
If you have any questions regarding this matter or would like to discuss it further, please give me a call.
Sincerely, cc: J. B. Martin, Regional Administrator, NRC Region V C. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3