ML20002E361

LER 80-016/03L-0:on 801217,during Testing,Emergency Diesel Generator 4D Failed to Close in on Bus.Caused by Slippage of Flexible Shaft Coupling on Speed Sensing Frequency Generator Drive Shaft.Coupling Secured

ML20002E361
Person / Time
Site:	Point Beach
Issue date:	01/15/1981
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20002E360	List: ML20002E359 ML20002E361
References
LER-80-016-03L, LER-80-16-3L, NUDOCS 8101270574
Download: ML20002E361 (2)

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7 8 68 68 69 EVENT DATE 80 EVENT DESCRIPTION ANO PROBABLE CONSEQUENCES h 1 o l a l l At 1210 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.60405e-4 months <br /> , 12-17-80, during testing the 4D emergency Diesel gener- I m l ator (common to Units 1 and 2) failed to close in on the bus. The 3D 1

[o ;4 i l emergency Diesel generator was tested to verify its operability. The I m l 4D emergency diesel generator was returned to service at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br />. I l O (6 l l Because the redundant emergency Diesel generator was operable, the t l 0 l 7 l l public health and safety was not af fected. This event led to a degradec) i O is i i mode of operation permitted by the Technical Specifications. l

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44 47 CAUSE DESCRIPTION ANO CORRECTIVd ACTIONS h li l 0 l l Adequate engine speed was not sensed by the bus breaker closina loaic I g l due to slippage of a General Motors Electromotive Division flexibla I g l shaft coupling (P.N. 8276102) on the speed sensing frequencv generator I i,i3l l drive shaft. The coupling was secured. I U_L4 j l I 7 8 9 80 STA  % POWER OTHER STATUS ISCO RY DISCOVERY DESCRIPTION

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ATTACHMENT TO LICENSEE EVENT ' REPORT NO. 80-016/03L Wisconsin Electric Power Company Point Beach Nuclear Plant, Unit 1 Docket No. 50-266 During an. Operations refueling test, Safety Injection with Loss of Engineered Safeguards AC - Unit 1, at 1210 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.60405e-4 months <br /> December-17, 1980, the 4D emergency diesel generator, common to Units 1 and 2, failed to close in on the Unit 1 bus automatically. The 3D emergency diesel generator was started and load tested at 1243 hours0.0144 days <br />0.345 hours <br />0.00206 weeks <br />4.729615e-4 months <br /> to verify its operability.

The 4D emcrgency diesel generator was returned-to-service at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> after completion of initial repairs and testing.

Unit I was in the refueling cond1 tion. Unit 2 was operating at full power.

4 The event led to a degraded mode of operation permitted by the Technical Specifications. The redundant emergency diesel generator was operable and the public health and safety was not affected. It should be noted that the 4D emergency diesel generator tested satisfactorily at 0536 hours0.0062 days <br />0.149 hours <br />8.862434e-4 weeks <br />2.03948e-4 months <br /> the same day, December 17, 1980, prior to performance of the Operations refueling test.

The event was due to a failure in the 4D emergency diesel generator speed sensing equipment. Initially it was thought that the high speed relay setpoints (in the General Motors, Electromotive Division, Model EMD 8409614, speed sensine panel' assembly) had drifted preventing an indication of adequate engine speed to the bus breaker closing logic.

The setpoints were reset and the 4D emergency diesel generator was tested and returned-to-service that same day. At 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br /> on December 30, 1980, the 4D emergency diesel generator was taken out-of-service for additional maintenance investigations regarding the' speed sensing panel relay setpoint drift. At this time it was discovered that the basic cause for the event was not relay setpoint drift. The event was caused by loosening of the setscrew that secures the flexible shaft coupling (General Motors, Electromotive Division, Part Number 8276102) to the frequency generator drive shaft. This resulted in inadequate signal generation from the speed sensing frequency generator due to insufficient rotational energy transmission from the camshaft adapter to the frequency generator drive shaft. The setscrew that locks the coupling to the shaft and the jam setscrew had both backed out of the coupling probably due to vibration.

As.a precautionary measure, both of the setscrews were replaced, lectighted, and staked. The shaft coupling was secured and the 4D emergency diesel generator was tested and returned-to-service at 1312 hours0.0152 days <br />0.364 hours <br />0.00217 weeks <br />4.99216e-4 months <br /> the same day. Based upon four satisfactorv tests (December-17, 25. and two tests on the 27th) , it was determined that the'4D emergency diesel cenerator would have nerformed its recuired safety function with the-initial setcoint adiustment.

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