ML19326A181

LER 78-005/03L-0:on 780106,auxiliary Feed Pump Turbine 1-1 Speed Control Lost & Declared Inoperable.Caused by Short Circuits & Blown Fuses Due to Design Deficiency.Higher Current Rated Relays Installed & Circuit Modified

ML19326A181
Person / Time
Site:	Davis Besse
Issue date:	02/01/1978
From:	Beeler T TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19326A179	List: ML19326A178 ML19326A181
References
LER-78-005-03L, LER-78-5-3L, NUDOCS 8002030045
Download: ML19326A181 (3)

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Q ~ 6/NIS-GCSSE UUIT 0::E ::tCLFAR PC*.?E'1 STATION SUPPLE:!E.':TAL INFOPdMTIO:: FOR LER NP-33-78-06 DATE OF EVE::T: _ January 6, 1978

~ FACILITY: Davis-3 sse Unit 1 IDENTIFICATI0M OF OCC"nRE :CE: Auxiliary Feed Pump Turbine 1-1 was declared in-opersole on January 6, 1973.

Conditions Prior ta Occurrence: The unit was in Mode 1, with Power (MWT) = 100 and Load (M.'E) = 0, 1

Descrintien of Occurrence: The unit experienced a Steam and Feedwater Rupture Control System (SFRCS) efip at 0430 hours0.00498 days <br />0.119 hours <br />7.109788e-4 weeks <br />1.63615e-4 months <br /> on January 6, 1973. This trip automa-tically started both Auxiliary Feed Pumps. Auxiliary Feed Pump (AFP) 1-2 operated properly but on Auxiliary feed Pump Curbine (AFFT) 1-1, speed control was lost, and the pump was declared incuerable. This placed the unit in the Action State-ment of Technical Specification 3.7.1.2, which requires two independent AFPs in Modes 1, 2 and 3.

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j -s ~ ,) A t 1230 hours0.0142 days <br />0.342 hours <br />0.00203 weeks <br />4.68015e-4 months <br /> on January 6,1978 during the performance of ST 5071.01, Auxiliary Feed Pump Monthly Survaillance Test". it was discovered that the high speed stop on AFPT l-1 was not set at the proper speed. AFPT l-1 had been previously de-

_clared inoperable at 0430 hours0.00498 days <br />0.119 hours <br />7.109788e-4 weeks <br />1.63615e-4 months <br />.

After reviewing the events, the Station Review Board convened and recommended to the Station Superintendent that the plant be shut down until such time that the AFP speed control prcblems are resolved. The unit entered Mode 4 at approximately 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> on January-7, 1978, removing the unit from the Action Statement of Technical. Specification 3.7.1.2, uell within the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />' time requirement.

Desienation of Apparent Cause of Occurrence: The cause of this occurrence is a design deficiency. The "Ceuch" relays used in the AFPT speed control circuit were subiect to excessive failure for the following reasons:

1. The DC interrupting rating of the contacts was not adequate to break

- the governor drive motor locked rotor current. The contacts arced en opening, causine e::cessive wear.

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2. The contact opening is very small and the opening time is very short.

The nature of the circuit was such that if the "N.O." centact uns arcing while the "U.C." contact closed, a short was created across 4

the 125 VDC supply. This caused-the control ocwer fuses to blow.

. f "ss resulting in_a less of speed control to the AFPT.

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LER #78-003

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i ic te unit. ;-a.re tnncl. The r2cetor cas previously tripped and the unit

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n to lict Shutdeun. Auxiliary Feed Pu=o 1-2 cas operable if cunilicry feeductar was rcquired.

Correctice J.tticn: A =cdification was made (Facilit~J Chan:;e Request 77-221) 4 unnr ;cintant.nce Ucrh Crder 73-0094 on both Auxiliary Feed Pump Speed Control Circuits installing nau A;astat r21cys. The codification left the " Couch" relays in the centrol circuit, but the motor centact is new the functicn of the Agastat relays.

The A3astat rel:7 is a heavy duty relay with larger contacts and a DC inter-rupting rating censisten ulch the circuit requirc ents. Tne circuit has dean endified such that there are no ":!.C." contacts used in the Bodina motor .

raversing circuit. I* crc is conseq:cnti/ no ptssibility of simultanccus closin;;s of :he ":!.0. and " :.C." contacts . a. = edification (T-2521) was made tc ST 5071.21, "Au::iliar'. Feeducter Syste= Monthly Test" to check the relichility of the speed control c:.rcuits after the =cdificatien was cc=pleted par Facility Ch:nge Request 77-221. Under Maintenance 1.*ork Order 76-0091, s the Auniliary Fe d Pump Turbine 1-1 high spaed stop was adjusted.

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VSurveillance Test ST 5071.01, " Auxiliary Feeduater System Monthly Test", was ptricrned at 0':35 heurs, and the Auxiliary Feed Pumps were declared operable at 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> on January 16, 1978, re=cving the unit frc= the Action Statement of Technical Specificaticn 3.7.1.2.

Failure Data _: Bicun fuses have occurred in the AF"T speed control units before because or relay failurcs (see I.icensee Event Raports NP-32-77-51, 52, 110 and 115). Iharc have been no high spend stop problens previousif reported.

LER #73-005

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