ML20081K610

RO 83-091:on 831028,during Routine Performance of Monthly Reactor Plant Protection Sys,Undervoltage Armatures for Reactor Trip Breakers 5 & 8 Observed in Midposition. Breakers Reset.Investigation Underway

ML20081K610
Person / Time
Site:	San Onofre
Issue date:	10/31/1983
From:	Haynes J SOUTHERN CALIFORNIA EDISON CO.
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
RO-83-091, RO-83-91, NUDOCS 8311100195
Download: ML20081K610 (2)

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Southern California Edison Company &'"T S AN ONOFRE NUCLE AR GENER ATING ST ATION P.O. Bo x 12 8 S AN C LEMENTE, C A LIFORNI A 92672 October 31, 1983 b

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'1A 59 ib U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region V 1450 Maria Lane, Suite 210 Walnut Creek, California 94596-5368

, Attention: Mr. J. B. Martin, Regional Administrator

Subject:

Docket No. 50-362 Prompt Report Licensee Event Report No.83-091 San Onofre Nuclear Generating Station, Unit 3 Pursuant to Section 6.9.1.12.i of Appendix A Technical Specifications to Facility Operating License NPF 'M for San Onofre Unit 3, this letter provides confirnation of prompt notification made to Messrs. D. F. Kirsch and A. E. Chaffee of your staff on October 31, 1983, of a reportable occurrence involving operation of reactor trip breakers (RTB's) on their undervoltage trip devices. (As in the past, tra breakers continue to function acceptably using the shunt trip device.) This matter was

• discussed in a special Onsite Safety Review Committee meeting on October 31, 1983, attended by Messrs. A. E. Chaffee and J. P. Stewart of your staff.

On October 28, 1983, with Unit 3 in Mode 3, during routine performance of the monthly Reactor Plant Protection System surveillance in accordance with Instrument and Test Procedure SO23-II-1.1, the undervoltage armatures for Unit 3 RTB's 5 and 8 were observed to be in a midposition (with the undervoltage coil ~

energized) rather than in contact with the air gap adjusting n screw. The RTB's were reset, observed to operate properly and the undervoltage armatures remained properly-positioned.

On October- 31, 1983, with both Units 2 and 3 in Mode 1, the possibility that such a midposition of the undervoltage armature could result in the RTB undervoltage trip device failing to trip within specified acceptance criteria was recognized. As a result, 8311100195-831031 PDR S

ADDCK 05000362 PDR I

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J. D. Martin October 31, 1983 4

all Unit 2 and Unit 3 RTB undervoltage armatures were verified to 1 be properly positioned with the exception of Unit 2 RTB 4 and Unit 3 RTB's 5 and 8. These RTB's were reset, observed to operate properly and the undervoltage armatures remained properly positioned.

Our preliminary conclusion is that the undervoltage armature can remain in a midposition as a result of interference betwaen the undervoltage armature and the copper shading ring around she core of the coil. Testing has demonstrated that visual confirmation that the undervoltage armature is properly positioned is sufficient to ensure no such interference exists. Administrative controls to provide such visual confirmation have been implemented.

Our investigation of this matter is continuing with the support and assistance of SCE and CE organizations and the vendor, as appropriate, and our conclusions will be included in our 14-day follow-up report and Licensee Event Report No.83-091 to be submitted prior to November 14, 1983.

If there are any questions regarding the above, please contact me.

J /r % m / W A %

J. G. HAYNES STATION MANAGER cc: A. E. Chaffee (USNRC Resident Inspector, Units 2 and 3)

J. P. Stewart (USNRC Resident Inspector, Units 2 and 3)

H. Rood (USNRC Office of Nuclear Reactor Regulations) i

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