ML19242B457
| ML19242B457 | |
| Person / Time | |
|---|---|
| Site: | Point Beach  |
| Issue date: | 06/29/1979 |
| From: | Fay C WISCONSIN ELECTRIC POWER CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 7908080553 | |
| Download: ML19242B457 (2) | |
Text
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Wisconsin Electnc mia coup >~r 231 W. MICHIGAN, P O. BOX 2046 MlLWAUKEL WI 53201 June 29, 1979 Mr. J. G. Keppler, Director Office of Inspection and Enforcement U. S. NUCLEAR REGULATORY COMMISSION 799 Roosevelt Road Glen Ellyn, Illinois 60137
Dear Mr. Keppler:
DOCKET NOS. 50-266 AND 50-301 RESPONSE TO IE BULLETIN NO. 79-11 FAULTY OVERCURRENT TRIP DEVICES POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 Westinghouse type DB-50 and DB-75 breakers are used in safety-related service at the Point Beach Nuclear Plant. As you know, the recent experience at Point Beach prompted the issuance of IE Bulletin 79-11 and our review and evaluation of this issue has been previously documented in our LER 79-004/0lT-0 and letters of April 12, April 26 and May 10, 1979.
As we have reported previously, a review of the overcurrent trip device test and calibration records for the safety-related DB breakers shows that except for the bus 2B03 supply breaker, there have been no failures of the breakers to operate properly either in service or during periodic maintenance testing.
Since replacement end caps were installed on the 108 overcurrent trip devices used on safety-related DB-50 or DB-75 breakers at Point Eeach in response to IE Bulletin No. 73-01, there have been 27 instances of individual overcurrent trip devices requiring recalibration because periodic testing indicated that the delay tim:ts were either outside of the acceptable band or marginally low.
In all cases except the previously mentioned 2B03 supply breaker which was the subject of LER 79-004/0lT-0, the overcurrent trip devices passed the subsequent tests.
As reported in LER 79-004/0lT-0, the overcurrent trip device on the bus 2B03 supply breaker which exhibited the erratic behavior had a cracked end cap. Subsequent investigation revealed that several of the spare end caps also had cracks.
The cracked end caps have been discarded and will not be used.
The current Point Beach maintenance procedures call for annual Multi-Amp testing of the safety-related circuit breakers for each unit dur'ng that jul 6 137B \\\\0 SM 03 h
7908080
Mr. J. G. Keppler, Director June 29, 1979 l
unit's refueling outage to confirm that the overcurrent protection devices are nrerable and are properly calibrated. We trust that this response adequately addre:ses the concerns expressed in IE Bulletin 79-11.
Very truly yours, k[
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