ML20236B094

Special Rept:On 890206,emergency Diesel Generator Secured Due to Failure of Speed Control Circuit While Generator in Manual Operation.Caused by Oxidation of Relay Contacts in Governor Control Circuitry.Contacts Replaced

ML20236B094
Person / Time
Site:	Waterford
Issue date:	03/08/1989
From:	Carns N LOUISIANA POWER & LIGHT CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
W3A89-0116, W3A89-116, NUDOCS 8903200337
Download: ML20236B094 (4)

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Ref:

10CFR50.36(c)(2) p I 0UISIANA P O W E R & L I G H T! WATERFORD 3 SES

• RO. BOX B + KILLONA, LA 70066-0751 1

tassawa j

March 8, 1989 s

f W3A89-0116 A4.05-QA i

U.S. Nuclear Regulatory Commission ATTENTIOils Document Control Desk l

Washington, D.C.

20555

SUBJECT:

Waterford 3 S:ES Docket No. 50-3832 I

License No. NPF-38 Reporting of Special Report Attached is Special Report Number SR-89-001-00 fc-h terford Steam

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Electric Station Unit 3.

This Special Report is submitted per 10CFR50.36(c)(2) and Technical Specifications 4.8.1.1.3 end 6.9.2.

Very truly yours,

,/

f68 c-N.S. Carns i

Plant Manager - Nuclear NSC/WMCirk Attachment l

cc:

R.D. Martin, NRC Resident Inspectors Office, INPO Records Center (J.T. Wheelock), E.L. Blake,'W.M. Stevenson, D.L. Wigginton l

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*37 890309

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1 SPECIAL REPORT SR-89-001-00 Emergency Diesel Generator Secured Due to Failure Of Speed Control Circuitry

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.1 INTRODUCTION i

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At 2218 hours0.0257 days <br />0.616 hours <br />0.00367 weeks <br />8.43949e-4 months <br /> on February 6, 1989, Waterford Steam Electric Station Unit 3 was i

operating at 100% power when Emergency Diesel Generator (EDG) A was declared

~ inoperable due to a failure of the electronic speed control while the EDG was in manual operation.

EDGAwassifttedforanEngineeredSafeguardFeatures test trip of the EDG output breaker.

After a successful manual start without

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Icading, the EDG would not respond to electronic speed control and was secured and declared inoperable. Troubleshooting could not find any speed control 4

problems. This event has been classified as a non-valid failure.

t The root cause of the event is attributed to oxidation of relay contacts in

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the governor control circuitry. This has been an intermittent problem requiring the contacts r.o be cleaned in the past.

Oxidation of the contacts' changes the.fr resistance and affects frequency control..The contacts were cleaned 4

after a high resistance was measured. A Condition Identification has been issued to clean the contacts again before the refueling outage.

A Station l

Modification Request has been approved to replace the contacts with more reliable mercury wetted contacts. The speed control circuit is bypassed in the emergency mode and would not have affected the EDG's ability to perform its designed safety function. Therefore, there was no hazard to plant equipment or public safety.

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o' NARRATIVE k

I At 2218 hcv's on February 6, 1985, Waterford' Steam Electric Station l' nit 3 wac j

d operating at 100% power when Emergency Diesel Generator A was declared inoperable due to failure of the electronic spe64 cont.rol while the EDG was in manual operation. Operating Procedure OP-903-094, ' Engineered Safeguard Features Actuation System Subgroup Relay Test - Cperating", was being performed j

to meet requirements of Technical Specifications (TSs) 4.3.2.1 and 4 1.12 1.

As part of OP-903-094, EDG A was operated in the isochronous mode from 2113 to 2129 hours0.0246 days <br />0.591 hours <br />0.00352 weeks <br />8.100845e-4 months <br />. Operations personnel noted that EDG speed was within operational limits but lower than usual and slightly erratic during this part of the test.

Continuing with OP-903-094, EDG A was secured and cooled down.

At 2204 hours0.0255 days <br />0.612 hours <br />0.00364 weeks <br />8.38622e-4 months <br />, EDG A was restarted minually to perform a test trip of the EDG output breaker.

After a successful start without loading, Operations personnel discovered that j

EDG speed was controlling at 60 Hz but could not be adjusted by the electronic local or remote control station.

The EDG was secured and declared inoperable.

1 The event has been classified as a non-valid diesel generator failure by the criteria of Regulatory Guide 1.108 C.2.e. (2) due to malfunction of equipment that is not operative in the emergenef operating mode.

Therefore, this report le submitted pursuant to TSs 4.8.1.1.3 and 6.9.2.

Troubleshooting of the EDG vas performed.

The only problem that could be found was a blown fuse which did not affect the governor speed control circuitry.

The EDG was started and the speed control problems did not recur.

Operating Procedure OP-903-068, "EDG Operability Verification", was successfully completed

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and EDG A was declared operable at 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br /> on February 7, 1989.

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The root lcause of.this event is. attributed to oxidation'of' relay contacts in

.the governor control' circuitry. This'has been an intermittent problem rea.uiring these contacts to be cleaned in the past.. Oxidation _of the contacts changes-

~their resistance and effects-frequency control. On March 6,-1989,-EDG A speed >

ccontrol contacts.were inspected and after a high resistance was measured, the contacts were cleaned. The Maintenance-Departnent has-initiated Condition.

. Identification 261885' to clean'the'EDG A governor speed control contacts in' June.1989 and the EDG B governor. speed control. contacts in May'1989. A Station

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' Modification Request-(SMR) has been approved to replace the contacts with'more reliable mercury wetted contacts. 'This SMR will.be. implemented in refueling'

!. 1 outage 3 which is scheduled fer Novembbr 1989. The dulay is due to the long-(40 week) procurement time' required for the new contacts.

i There has only been~one failure during a valid test of EDG A since the operating,

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' license was' issued. The surveillance test interval required by TS Table 4.841' J

has always been."at least once.per 31 days" since issuance of the operating license. Thel speed control circuit is bypassed in the emergency mode end.vould not : affect the EDG's ability.to perform its safety function. The blown' fuse discovered during troubleshooting would-also have been bypassed in the EDG emergency mode of operation.. Therefore, this event did not present a hazard to plant' equipment or public safety.

i PLANT CONTACT j

~l T.H. Smith, Plant Engineering Superintendent,'504/464-3127.

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