ML13317B152

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Discusses Background & Schedule for Providing New Info Re Adequacy of Station Electric Distribution Sys Voltages (Multiplant Action Item B-48).List of Documents to Be Reviewed Encl
ML13317B152
Person / Time
Site: San Onofre Southern California Edison icon.png
Issue date: 08/03/1990
From: Nandy F
Southern California Edison Co
To:
NRC/IRM
References
NUDOCS 9008070015
Download: ML13317B152 (3)


Text

Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 F. R. NANDY August 3, 1990 TELEPHONE MANAGER, NUCLEAR LICENSING (714) 587-5400 U. S. Nuclear Regulatory Commission Attention:

Document Control Desk Washington, D.C. 20555 Gentlemen:

Subject:

Docket No. 50-206 Adequacy of Station Voltages San Onofre Nuclear Generating Station Unit 1 This letter deals with the adequacy of the station electric distribution system voltages (Multi-Plant Action Item No B-48), as it applies to San Onofre Unit 1. This letter formally notifies you that we will be submitting new information to facilitate the NRC's review and closure of this issue. The background and schedule for providing the new information are discussed below.

Background

On August 8, 1979, the NRC requested all power licensees to:

(1) Determine the capability of the offsite power system to start and operate all required loads within their required voltage ratings in the event of a transient or accident without manual load shedding, and (2) Determine if there are any events or conditions which could result in violating the requirements of General design Criterion 17, with respect to the offsite to onsite power circuits.

SCE responded to this request with several submittals during the 1980-1982 time frame. On February 24, 1982, the NRC issued a safety evaluation and on July 29, 1983, issued an updated safety evaluation. The NRC's conclusion was that the power system is adequately designed, but SCE must optimize the tap settings on the auxiliary transformer which feeds the auxiliary electric loads. As a result, SCE performed new calculations to optimize the tap settings. In addition, as the result of a voltage monitoring program, SCE implemented administrative controls to maintain the desired 480V bus voltage.

This information was provided to the NRC by references numbered 2 through 5 in to this letter.

9008070015 900803 PDR ADOCK 05000206, P

_PDC

//

00 Document Control Desk August 3, 1990 Since these events, significant modifications have taken place in the SONGS electrical distribution system. During the present outage, additional major improvements will be made to the 480V system. In view of these modifications and the amount of time that has passed since our last submittal, the system voltage analysis and other previously submitted information need to be updated. This is necessary in order that the NRC may finish its review.

Schedule We currently anticipate that the new information will be submitted by March 31, 1991.

This will give us sufficient time to evaluate the impact of the Cycle 11 modifications on the voltages and the transformer tap settings. lists the documents that contain the information which will be reviewed and updated as necessary.

If you have any questions, please call me.

Very truly your Enclosures cc: J. B. Martin, Regional Administrator, NRC Region V C. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3

ENCLOSURE 1 LIST OF DOCUMENTS THAT WILL BE REVIEWED

1.

Letter dated July 29, 1983, from Dennis M. Crutchfield (NRC) to R. Dietch (SCE) 1983, Adequacy of Station Electric Distribution System Voltages.

(Also References 2, 3, and 4 listed at the end of this reference.)

2. Letter dated December 20, 1984, from M. 0. Medford (SCE) to the NRC, Auxiliary Transformer Tap Settings Optimization.
3.

Letter dated March 6, 1985, from M. 0. Medford (SCE) to the NRC, Auxiliary Transformer Tap Settings Optimization.

4.

Letter dated December 4, 1985, from M. 0. Medford (SCE) to the NRC, Auxiliary Transformer Tap Settings Optimization.

5.

Letter dated June 19, 1986, from M. 0. Medford (SCE) to the NRC, Auxiliary Transformer Tap Settings Optimization.