ML19354E685

Special Rept 89-009-00:on 891218,diesel Generator 11 Failed. Potential Transformer Fuse Holders Found Loose.No Obvious Cause of Event Identified.Diesel Retested Satisfactorily W/O Recurrence of Original Incident

ML19354E685
Person / Time
Site:	Grand Gulf
Issue date:	01/17/1990
From:	Cottle W SYSTEM ENERGY RESOURCES, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-009-00, 89-9, AECM-90-0020, AECM-90-20, NUDOCS 9002010119
Download: ML19354E685 (2)

Text

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NEene- mr, n u ns~m wa.sem e, vce Resdent January 17, 1990 Ntclear Opedons U.S. Nuclear Regulatory Commission Mail Station P1-13*/

Washington, D.C. 20555 Attention: Document Control Desk Gentlemen:

SUBJECT:

Grand Gulf Nuclear Station Unit 1 Docket-No. 50-416 License No. NPF-29 Special Report. 89-009-00 Emergency Diesel Generator 11 Failure AECM-90/0020 On December 18, 1989 at 2016,-Operators started Diesel Generator 11 for performance of the monthly functional test-in accordance with Technical Specification 4.8.1.1.2. The test was intended to verify system operability following planned maintenance.

The diesel was successfully started and loaded for approximatell' 56 minutes. At this time, the Potential Transformer Fuse Failure annunciator alarmed at the local operator's panel. Following the alarm, it was noticed that the Voltage Balance Relay right flag had dropped.

The annunciator alarmed again and the local operator noticed that the left flag on the Voltage Balance Relay dropped. Shortly after the I

Potential Transformer Fuse Failure alarm cleared,-several other alarms came in on the local panel, including Generator / Ground Overcurrent.

1 When the Generator / Ground Overcurrent-annunciator alarmed, the Diesel Generator output breaker. tripped. The diesel continued to run in a ~

l 4 stable condition; then field voltage and amps began to oscillate.

] Generator voltage was stable, pegged.high, and then was stable again.

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,-i o n., The oscillations occurred again and.the diesel was manually tripped from

$8 the Control Room. The diesel generator.was then secured for a y maintenance investigation.

1 Q No obvious problems were found during the maintenance investigation.

gg The diesel was retested in an attempt to reproduce the original mq incident. During the test tha output voltaw and megawetts were

@ increased and decreased'to exercise their control circuits. The test

.gg was completed satisfactorily without recurrence of the original o.n.v; incident.

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,. After the surveillance run, another independent troubleshooting.

investigation was performed. No obvious problems which-could have caused the event were found. However, some Potential Transformer fuse holders were found loose. There was no evidence of arcing on the holders.- The fuses were' removed and the holders were tightened.

SERI considered the test to be a valid failure pursuant'to Position C.2.e(5) of the Regulatory Guide 1.108 since the ability of the diesel generator in this condition to power ESF loads in response to_a bonafide signal.is indeterminate. This was the second valid failure in the last 20 tests and the fifth in the last 100 valid tests.. Therefore, the testing frequency was increased to once per 7 days in accordance with the test schedule of Technical Specification Table'4.8.1.1.2-1.

This Special Report is submitted pursuant to Technical Specification 4.8.1.1.3.

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.Yours truly, l

wY r- - , l i

WTC:cwg -l Attachment cc: Mr. D. C. Hintz (w/a) .l Mr. T. H. Cloninger (w/a)

Mr. R. B. McGehee (w/a) '

Mr. N. S. Reynolds (w/a)

Mr. H. L. Thomas (w/o) l Mr. H. O. Christensen (w/a)

Mr. Stewart D. Ebneter (w/a)

Regional Administrator U.S. Nuclear Regulatory Commission Region II

}

l 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30323 {

Mr. L. L. Kintner, Project Manager (w/a) office of Nuclear Reactor Regulation  !

U.S. Nuclear Regulatory Commission Mail Stop 14B20 ,

Washington, D.C. 20555 i

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