ML13317B201
| ML13317B201 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/02/1990 |
| From: | Ray H SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9010120183 | |
| Download: ML13317B201 (4) | |
Text
Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 HAROLD B. RAY TELEPHONE SENIOR VICE PRESIDENT October 2, 1990 714-458-4400 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Small Break LOCA Analysis San Onofre Nuclear Generating Station, Unit 1 The purpose of this letter is to inform you that Southern California Edison Company (Edison) will request plant-specific NRC approval on an expedited basis for use of the Westinghouse NOTRUMP computer code to perform Small-Break Loss of Coolant Accident (SBLOCA) analyses for San Onofre Nuclear Generating Station, Unit 1 (SONGS 1).
Expedited approval will be required because we have determined, as discussed below, that restart from the current Cycle 11 refueling and modification outage should be based on use of NOTRUMP, and we are proceeding accordingly.
The time required for the development and validation of the NOTRUMP code for use on SONGS 1, and its submittal for NRC approval, will require that return to service from the current outage be delayed. We will provide the necessary information for your review by November 15, 1990, and we plan to have preliminary SBLOCA analysis results available by December 15, 1990.
Since the NRC has previously directed that NOTRUMP be used for any SONGS 1 SBLOCA reanalysis (see below), we trust that its approval for use in this instance can be expedited. We regret that the necessity for use of NOTRUMP was not identified by Edison sooner as a restart restraint. Several considerations led to the decision, primarily the further evaluation of our response to NRC Bulletin 88-04 in the wake of your letter dated July 17, 1990.
Existing SONGS 1 SBLOCA The existing SBLOCA for SONGS 1 was performed in 1980 to
...verify that the generic small break loss of coolant accident analyses presented in WCAP-9600 and WCAP-9584 apply to San Onofre 9010120163 901002 PDR ADOCK 05000206 P
PNU-
Document Control Desk
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October 2, 1990 Unit 1."
(Ref. Small Break Loss of Coolant Accident Study, SONGS 1, Edison letter dated July 28, 1981.)
This analysis used the WFLASH and LOCTA computer codes. These codes were an enhancement over the SLAP computer code which had previously been used to evaluate SONGS 1 under the Interim Acceptance Criteria.
In a letter dated May 30, 1985, the NRC clarified that resolution of TMI Action Plan Item II.K.3.30, Small Break LOCA Methods, could be accomplished for SONGS 1 using WFLASH. Use of that code was based on generic analysis which had shown that WFLASH yielded results that were conservative when compared to evaluations performed using NOTRUMP.
The NRC letter also directed that, future plant specific analysis performed for your plant by Westinghouse for reloads or Technical Specification amendments (those beyond 90 days of the date of this letter) should be calculated with the new code, NOTRUMP."
Edison has determined that return to service from the current Cycle 11 refueling and modification outage must be based on such a Westinghouse SBLOCA analysis. Also, in addition to the use of NOTRUMP being required by the NRC letter, the use of WFLASH for SBLOCA reanalysis is no longer supported by Westinghouse.
NRC Bulletin 88-04 Requirements In a letter dated July 17, 1990, the NRC provided comments on Edison's initial response to Bulletin 88-04. We have determined that resolution of these comments requires modification of the safety injection mode recirculation system for the main feedwater pumps. This modification will increase the recirculation flowrate in accordance with pump vendor recommendations for sustained operation at minimum delivery.
Edison has decided that our revised response to Bulletin 88-04 requires a SBLOCA reanalysis by Westinghouse for the following two reasons:
o Modifications to increase the recirculation flowrate must be analyzed based on test data to be obtained prior to restart.
o The potential duration of sustained operation at minimum delivery cannot be determined from the current SBLOCA analysis. This analysis does not include consideration of Reactor Coolant System cooldown due to operation of the Auxiliary Feedwater System or containment heat removal, and it therefore projects an unrealistically long duration.
Document Control Desk October 2, 1990 Cycle 11 Reload Safety Analysis Having decided that the safety injection mode recirculation system for the main feedwater pumps must be modified prior to restart, and that the SBLOCA must be reanalyzed using NOTRUMP in order to satisfy NRC Bulletin 88-04, Edison will also use NOTRUMP as part of the Cycle 11 reload safety analysis. This will ensure that the bases for restart are uniformly consistent with current SBLOCA methodology.
Conduct of NOTRUMP Analysis The NOTRUMP analysis will also play an important role in the subsequent development and approval of the Cycle 12 modifications. Therefore, the analysis will be performed so that SONGS 1 is conservatively modeled and its operating space is as large as is compatible with clearly acceptable results. The analysis will assume reduced safety injection flowrates, conservative delays in the initiation of safety injection flow and other conservative assumptions which will allow Edison to more easily evaluate actual plant conditions in the future.
As indicated above, Edison will provide to the NRC by November 15, 1990 the information necessary to review and approve NOTRUMP for plant-specific use on SONGS 1. We plan to have preliminary SBLOCA analysis results available by December 15, 1990 for your information prior to restart. We expect to restart the unit following verification and validation of these results, based on NRC approval of the plant-specific NOTRUMP application, shortly thereafter.
SUMMARY
Edison has concluded that the Westinghouse NOTRUMP code should be used to complete a SBLOCA reanalysis prior to restart of SONGS 1 from the current outage. Unit return to service is being delayed accordingly. We believe this decision will provide the best assurance that all existing requirements, including those in NRC Generic Letter 88-04, will be satisfied during Cycle 11 operation.
The NRC has previously directed that NOTRUMP be used for SONGS 1, and expedited approval of the plant-specific application will be requested in a submittal by November 15, 1990. We expect to complete the reanalysis and to be prepared for unit restart in the latter half of December 1990.
Document Control Desk 4
October 2, 1990 Edison will make every effort to assist the NRC in the requested expedited approval. Your response to our request in this regard will be greatly appreciated.
Sincerely, cc:
John B. Martin, (Regional Administrator, NRC Region V)
J. E. Tatum, (NRR, SONGS Project Manager)
C. Caldwell, (NRC Senior Resident Inspector, SONGS)