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iCarohna Power & Light Company '.

-Brunswick Nuclear Project'

P. O. Box 10429Southport,,N.C. 20461-0429

October 16, 1992

FILE: B09-13510C IV.FR50.73SERIAL: BSEP-92-0034

U.S. Nuclear Regulatory Ctm issionATTN Document Control veskWashington, D. C. 205ES

BRUNSWICK STEAM ELECTRIC PLANT UNIT 1DOCKET NO. 50-325

LICENSE NO. DRP-71LICENSEE EVENT REPORT 1-92-Q14

Gentlemen

In accordance with Title 10 of tha code of Federal' Regulations,. the enclosed.Licensee Event Report is submitted. This report fulfills the requirement.for awritten report within thirty (30) days of a reportable occurrence and fis ,

submitted in accordance with the ft.cmat set forth in NUREG-1022, September 1983.

j_ Very truly yours,"

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R. E.. Morgan, Plant Manager - Unit 1

|;- Brunswick' Nuclear Project'

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-Enclosure~

cc t ' Mr. S. D. EbneterMr. R. H. LoBSEP NRC Resident Office

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05000325Unit 1 2

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Tr m e RELAY FAILURE RESULTING IN RPS BUS *B" POWER LOSS CAUSING EST ACTUATION SIGNALS

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The "B" bus of the neactor Protection System (nPS) was being powered from thealternate source. At 1515, RPS bus B was transferred back to normal power. Thetransfer momentarily de-energizes the bus resulting in equipment actuations.Approximately two to three seconds after transfer completion, a second de-energization occurred (indicated by the lose of the " normal" power light).Additional actuations did not occur because the original signals-had not beenreset; however,. identical actuation signals were generated, The cause of thisevent was a broken contactor arm (T-Bar) in the normally energized RPS motorgenerator set B feeder circuit relay (GE model # CR105P002). The broken T-Barallowed the relay armature to fall resulting in excessive relay coil current.The excessive current blew the corresponding actuation circuit fuse and resultedin the observed de-energization of RPS bus B. The relay was repaired, the fusewas replaced, and RPS bus B was restored to its normal power source. Actionitems to determine the cause of the broken T-Bar and to identify and inspect

| other similar relays have been initiated. This event was of no safety

j significance; equipment performed as designed. Events involviTig unexpected

(_ equipment actuations caused by relay failures have been reported in LER3 1-92-011, 1-91-028, 1-90-029, 1-90-023, and 2-89-020

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FMl!JTY NAME 0) IKXYET NUMBI'R Cl IJA NUMB 13 41 - } . 3)'_*

Brunswick Steam Electric Plant 05000325 YF.AR IN ' "U 2"' "'

Unit 1

92 024 00

tnt al . bw4 .Ma a Nnc t ui ),6A's) U F)

TITLE

RELAY FAILURE RESULTING IN RPS BUS "B" POWER LOSS CAUSING ESF ACTUATION SIGNALS

INITIAL CONDI710NS

The Unit I reactor was in COLD SHUTDOWN, on September 19, 1992, in day 151 of amaintenance outage. The "B" train of the Standby Cas Treatment (SBGT) system was

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removed from service. The "B" bus of the Reactor Frotection System (RPS) wasbeing powered from the alternate source during replacement of the "B" RPS motor-generator set (.uc set) motor (i.e. , the normal power source) . The work had beencompleted on the motor and, at 1515, RPS bus B was transferred back to the normalpower supply, in accordance with plant procedures.

-EVENT NARRATIVE

At 1515 on September 19, 1992, a reactor operator (RO) returned the RPS bus B tothe normal power supply in accordance with Operating Procedure (CP) 03 section8.2, Transfer from RPS Alternate Power to Normal Power Source. The transfer isa dead bus transfer. Actuation of the "A" SBGT train, Secondary ContainmentIsolation system and Primary containment Isolation System (PCIS) groups 1, '2, 3,6 and 8 valves occurred as expected. Approximately two to three seconde afterthe power transfer, the normal power indicating light extinguished (i.e. , the RPSbus B de-energized). Additional actuatione did not occar during the second de-energization because the original signals had not been reset. However, identicalactuation signals were generated.

The RO locally verified that the RPS Ed set was operating and the associatedelectrical protection assembly (EPA) circuit breakers were closed.

At 1545, RPS bus B was transferred back to the alternate power supply, The actuationand isolation signals were reset and affected equipment.was subsequently restored toits normal configuration.

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At 1605, Operations personnel determined that RPS MG set B feed actuation circuit fuse

(1-C71B-F1B) had blown. Work request / job order (WR/JO) 92-AZSAl was initiated toinvestigate the reason for the blown fuse.

The cause of the blown fuse was determined to be the failure of RPS MG set Bfeeder circuit relay (1-C71B-K18) contactor arm (i.e. , the "T-Bar" had broken atthe end) . 1-C71B-K18 is a normally energized, General Electric model # CR105P002relay.

The T-Bar and fuse were replaced and, at 0840 on September 20, 1992, the "B" RPS

Bus was successfully transferred to its normal power supply.

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5'4 kW 3Brunswick Stease Electric Plant 05000325 vuaexi. No.

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92 024 00

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p3USE OF EVENl

The cause of this event was the broken T-Bar in relay 1-C71B-K1B. The broken T-Bar allowed the relay armature to f all resulting in excassive relay coil curront.

CORRECTIVE ACTIONS

The roley was repaired, the fuse was replaced, and RPS bus B was restored to itsnorms.1 power source. Engineering Tvaluation Report (EER) 92-0355 was written andapproved September 20, 1992, concerning the repair of the 1-C71B-K1B relay. TheEER has initiated action items to determine the root cause of the broken T-Barand to identify and inspect other relays for a similar condition.

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SAFETY ASSESSMEUI

This event was of no safety significance. The failure of the relay resultod inactuation of the RPS bus B, according to design.

PREVIOUS SIMILAR EVENTS

Relay failures resulting in unexpocted equipment actuations have been reported~

in LERs 1-92-011, 1-91-028, 1-90-029, 1-90-023, and 2-89-020. The referencedevents were caused by coil failures and excessive heat at contacts but did notinvolve a failed T-Bar.

EIIS COMPONENT IDENTIFICA'QOJ

S.ystem/Cgsponent EIIS Code

RPS MG set JC/MG1-C71B-FIB (fuse) JC/FU1-C71B-K1B (relay; JC/RLYRPS/ EPA circuit breaker JC/BKRSBGT VA/BHSecondary Containment HG/VAPCIS BD

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ATTAcitMENT 1- -|NRC REPORT REVIEW SilEET :i

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(X) LER: 1-92-024[ ] Special Report:

Event Date: 09/19/92 NRC Due Dates. 10/19/92 '||

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Event description:

RELAY FAILURE RESULTING IN RPS BUS "b" POWER LOSS CAUSING ESFACTUATION SIGNALS

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Prepared trf: ~jIt t/ 4wc.). Date /C, /S, 7d/ I /Lea $ Investigator

EIfrMgr - Rog Programa _ Nf Dato: 3 c.0W7 yI 'Approvals '/

PNSC Approval: hhkfod- Datos /C-/4 'i 3

Chairmafi - PNSC

0 RCI-06.1 Rev. 9 Page.10 of~13

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