ML20044B834
| ML20044B834 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 03/05/1993 |
| From: | Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 88-564C, NUDOCS 9303100106 | |
| Download: ML20044B834 (2) | |
Text
i R VIRGINIA ELECTHIC AND POWER COMPANY Ricituoxn, VIRGINIA 23001 March 5, 1993 U.S. Nuclear Regulatory Commission Serial No.
88-564C Attention: Document Control Desk NAPS /JHUMAE R5 Washington, D.C. 20555 Docket Nos. 50-338 50-339 License Nos. NPF-4 NPF-7 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 REVISED RESPONSE TO NOTICE OF VIOLATION FROM NRC INSPECTION REPORT 50-338/88-16 AND 50-339/88-16 NRC Inspection Report 50-338/88-16 and 50-339/88-16 identified a violation for having two inoperable North Anna Unit 2 emergency diesel generators (EDG).
Specifically, one EDG was inoperable for preventative maintenance and the other EDG was inoperable because the charging spring motor on its 4160 volt output breaker was disengaged from the breaker housing due to missing bolts. At the time of the event, the breaker preventative maintenance procedure did not require the bolts on the charging spring motor to be checked for tightness.
In a July 6,1988 meeting on the issue and in our September 16,1988 response to the August 17,1988 Notice of Violation, we identified that 137 safety and non-safety related 4160 volt breakers (except tho emergency bus feeder breakers) had been included in a breaker inspection program. This inspection checks for loose charging i
spring motor bolts. The initial inspection of 60 breakers that could be inspected at power identified 9 breakers that had loose charging spring motor bolts. We also indicated that the breaker maintenance procedure had been revised to specifically check that the charging spring motor was secure.
The breaker preventative j
maintenance procedure's acceptance criteria now requires that the charging spring motor bolt lockwashers be fully compressed, as required by the manufacturer. In cddition, we indicated that the preventative maintenance frequency had been increased. We elected to increase the preventative maintenance frequency to every refueling outage (i.e., every 18 months).
Since our 1988 response, two breakers have been identified that had the charging i
spring motor bolt lockwashers compressed in accordance with the maintenance procedure's acceptance criteria, although the charging spring motor bolts could still be tightened. One breaker on the non safety related "G" bus (breaker 01-EP-BKR-15G03) had two charging spring motor bolts that were tightened 1/2 turn. The other breaker was on the safety related "J" bus (breaker 01-EP-BKR-15J11) and had a charging spring motor bolt that was tightened 1/4 turn. In each event, the breakers were 9303100106 930305 PDR ADOCK 0500 8
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N d6termined to be fully operable. However, to provide more definitive acceptance criteria, we are developing a torque value to ensure consistency in future tightness checks.
There are currently 138 breakers in our preventative maintenance program that have charging spring motors. Each charging spring motor has three bolts that hold it in place. Proventative maintenance has been performed on each breaker at least twice.
All of the breakers that have been inspected have met the preventative maintenance procedure's acceptance criteria. This is indicative of the enhanced preventative maintenance that is being performed. As a result, it is our intention to revise the breaker preventative maintenance frequency from every refueling outage (i.e., overy 18 months) to overy 54 months. This revised frequency will coincide with other breaker maintenance that is performed.
Should you have any questions or require additional information, please contact us.
Very truly yours, (Ln.,bw
[ee W. L Stewart Senior Vice President - Nuclear cc:
U.S. Nuclear Regulatory Commission Region 11 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. S. Lesser NRC Senior Resident inspector North Anna Power Station