05000366/LER-1981-038-03, /03L-0:on 810421,LPCI Inverter a Tripped Resulting in Limited Conditions for Operation Per Tech Spec 3.8.2.1.e. Caused by Logic Failure.Inverter Reset

/03L-0:on 810421,LPCI Inverter a Tripped Resulting in Limited Conditions for Operation Per Tech Spec 3.8.2.1.e. Caused by Logic Failure.Inverter Reset

ML19347E710
Person / Time
Site:	Hatch
Issue date:	05/07/1981
From:	Coggin C GEORGIA POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19347E709	List: 05000366/LER-1981-038, Forwards LER 81-038/03L-0 05000366/LER-1981-038-03, /03L-0:on 810421,LPCI Inverter a Tripped Resulting in Limited Conditions for Operation Per Tech Spec 3.8.2.1.e. Caused by Logic Failure.Inverter Reset
References
LER-81-038-03L, LER-81-38-3L, NUDOCS 8105130261
Download: ML19347E710 (2)

LER-1981-038, /03L-0:on 810421,LPCI Inverter a Tripped Resulting in Limited Conditions for Operation Per Tech Spec 3.8.2.1.e. Caused by Logic Failure.Inverter Reset

Event date:
Report date:
3661981038R03 - NRC Website

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EVENT DESCRIPTION AND PROBABLE CoNSEoOENCES h 0121 l Whil e reducina nower for condenser tube repair the

'A' LPCI inverter

_l 0131 1 ( 2 R4 4-S002 ) tripped resulting in an LC0 per Tech Specs 3.8.2.1.e.

Pow-1 IO'l41ler to essential notor control center (2R24-S018A) which feeds the_LPCI I

for

'A' recirc was lostl 101s1linjection valve and suction and. discharge valves 10161 I nomen t a ril y as a result of this event.

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33 34 35 3o 31 40 41 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h 111011 Investication revealed that logic failure caused the inverter to trin.

I 11111IThe cause for the inverter tripping in this manner is unknown.

Conduit I iil2llbracing was drooped on the floor eleven feet from the inverter immedi-l lilal l ately prior to the trip, but did not contribute to the trip.

The in-l 111411 verter was reset and put back into service, thereby clearir.g the LCO.

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Narrative

Repod for LER 50-366/1981-038

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While reducing power for condenser tube rc.uir, the

'A' LPCI inverter (2R44-S002) tripped resulting

!a an LCO per Tech Specs 3.8.2.1.c.

Power to essential motor control center (MCC) 2R24-S018A which feeds the LPCI injection valve (2E11-F015A) and the suction and discharge valves for

'A'. loop of recirc was lost momentarily.

The cause of the inverter trip was initially assumed to result from the dropping of conduit bracing onto the inverter room floor approximately cleven (11) feet from the inverter.

Further investigation revealed that i

the inverter tripped as a result of the logic failure trip on the inverter.

The logic failure trip alarm and trip light i

were also illuminated on the front panel of the inver-ter.

This type trip results from improper timing of the gate pulses on the silicon control rectifiers (SCRs) in any of the twelve inverter legs.

The cause for the inverter tripping in this manner is. unknown, and the vibration that resulted from the dropping of the conduit brace was ruled out since the logic trip occurs as a

change of state of digital logic which t

vibration does not affect.

This is a nonrepetitive occurrence and did not affect the remaining inverter on Unit 2 or either of the two units on Unit'1.

The alternate source for the essential MCC 2R24-5013A was availabic for immediate use, but was not necessary since the inverter was reset and returned to service.

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