ELV-00336, Requests NRC Comments Re Reactor Trip Breaker Maint Frequency by 890421.Based on Westinghouse Recommendations, Maint Interval of 500 Operations,Or 18 Months,Whichever Comes First,More Appropriate for Group a Maint

Requests NRC Comments Re Reactor Trip Breaker Maint Frequency by 890421.Based on Westinghouse Recommendations, Maint Interval of 500 Operations,Or 18 Months,Whichever Comes First,More Appropriate for Group a Maint

ML20247J307
Person / Time
Site:	Vogtle
Issue date:	03/28/1989
From:	Hairston W GEORGIA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ELV-00336, ELV-336, NUDOCS 8904050068
Download: ML20247J307 (3)

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ELV-00336 l

0198e March 28, 1989 U. S. Nuclear Regulatory Commission l ATTN: Document Control Desk l

Washington, D. C. 20555 PLANT V0GTLE - UNITS 1, 2 NRC DOCKETS 50-424, 50-425 OPERATING LICENSES NPF-68, NPF-79 REACTOR TRIP BREAXER MAINTENANCE FREQUENCY Gentlemen:

By letter GN-671 dated August 1, 1985, Georgia Power Company (GPC) indicated that certain reactor trip breaker (RTB) maintenance items would be performed every 500 breaker operations or six months, whichever occurs first. This was consistent with Westinghouse recommendations for the initial performance of Group A maintenance items as discussed in the " Westinghouse Maintenance Manual for the DS-416 Reactor Trip Circuit Breaker", Revision 0, dated October 1984.

Based on more recent Westinghouse recommendations and the operating and maintenance history of the Vogtle reactor trip breakers, GPC now believes that a maintenance interval of 500 operations or 18 months, whichever occurs first, is more appropriate for Group A maintenance. Our reasons are as follows:

1. Westinghouse has issued a revised RTB maintenance manual, " Maintenance Program Manual MPM-WOGRTSDS416-01 for Westinghouse Type DS-416 Reactor Trip Circuit Breakers and Associated Switchgear", Revision 0, dated November 30, 1986. This revised manual recommends performing Group A l maintenance every 500 breaker operations or 18 months, whichever occurs i first. This recommendation was based 'on a reliability analysis which l indicated that the minimum RTB unavailability occurred when preventive maintenance was limited to refueling outages.

2. The operating and maintenance history of the Vogtle RTBs does not reveal any failures, unusual wear, or degradation which would indicate a need to continue semi-annual maintenance. As stated in letter GN-671, GPC records and trends (a) undervoltage trip attachment dropout voltage, (b) trip force, (c) breaker response time for undervoltage trip, and (d) breaker insulation resistance. No adverse trends in these parameters have been observed. The trending of these parameters will continue.

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U. S. Nuclear Regulatory Commission ELV-00336 Page Two ,

3. Each of the elements of the Westinghouse recommended maintenance program will continue to be performed; only the frequency of the Group A l 1

maintenance will change.

4. The semi-annual RTB maintenance may need to be performed during full-power operation, which increases the probability of a reactor trip and the l probability of challenges to safety systems. Increasing the maintenance )

interval to 500 operations or 18 months, whichever occurs first, allows j performance of maintenance during refueling outages and precludes such  !

events. l

5. Handling of the RTBs is excessive. Every six months, the RTBs must be racked out and removed from their cubicles to perform maintenance and testing. The likelihood of electrical or mechanical damage to the breaker increases with the frequency of handling. Similarly, the chance for human 1 error increases when the equipment maintenance and testing increase. The i risk of human error will thus be reduced by reducing the frequency of l maintenance. l i

6. Periodic surveillance testing of the RTBs will continue on a bi-monthly basis as required by Technical Specifications. This testing cycles each breaker and independently verifies operability of the undervoltage trip attachment and the shunt trip attachment. The breaker response time is measured during refueling outages.

For these reasons, GPC believes that RTB reliability and the safety of plant operations will increase as a result of extending the Group A maintenance interval to 500 operations or 18 months, whichever occurs first. GPC plans to implement this change prior to the expiration of the current semi-annual maintenance period for Unit 1, which occurs on or about April 21, 1989. We request that any NRC comments be provided to us before that date.

Sincerely, a).4.Id O ' s W. G. Hairston, III JH/gm

i 1 .m. 1 Georgiaibkver d U. S. Nuclear Regulatory Commission ELV-00336 Page Three xc: Georgia Power Company Mr. P. D. Rice Mr. C. K. McCoy Mr. J. P. Kane Mr. G. Bockhold, Jr.

NORMS U. S. Nuclear Regulatory Commission Mr. S. Ebneter, Regional Administrator Mr. J. B. Hopkins, Licensing Project Manager, NRR (2 copies)

Mr. J. F. Rogge, Senior Resident Inspector, Vogtle l

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