ML19262A226

Abnormal Occurrence 50-289/74-26:on 741129,current Trip Device on Feeder Breaker to 18 Engineered Safeguards Motor Control Ctr Malfunctioned During Testing.Caused by Component Failure.Overcurrent Device Replaced

ML19262A226
Person / Time
Site:	Three Mile Island
Issue date:	12/10/1974
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
GQL-0568, GQL-568, NUDOCS 7910260565
Download: ML19262A226 (4)

Text

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F ROM: Metroplitan Fdison Co. DATE OF DOC DATE REC'D LTR. TWX RPT OTHER Reading. Fa I 12410-74 12 12-74 xxyl R.C .A rn 7Id xxx:C<

TO: ORIG CC OTHER SENT AEC PDR Directorate of I.icensini 1-signed SENT LOCAL POR xxt CLASS UNCLASS PROPINFO INPUT NO CYS REC'O ' DOCKET NO:

xxxxxx 1 50-2S9 DESCRIPTION: ENCLOSURES:

I.tr reporting Abnormal Occurre..ce #74-2t; on 11-29-74 concerning defective overcurrent -

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trip device on the Feeder Breaker to the

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Dear Sir:

Dcchet No. 50-289 Operating License EPR-50

~~. [ 7 In accordance with the Technical Specifications fer our Three Mile Island Nuclear Station, Unit 1, we are reporting the following abnormal cccurrence:

1. Repcrt Number: A0 50-289/Th-26 2a. Repcrt Date:re s

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2b. Occurrence Date: Nove=ter 29, 197L 3 Facility: Three Mile Island Nuclear Statien, Unit 1 L. Identificatien of Occurrence

Title:

Eefective Cvercurrent Trip Device en the Feeder Breaker to the 13 Engineered Safeguards Motcr Centrol Center.

Type: An abncr:al occurrence as defined by the Technical Specifi-caticns, paragraph 1.8d, in that the defective overcurrent trip device en the feeder breaker to the 13 Engineered Safeguards Motor entrol Center threatened to cause an Engineered Safeguards feature or system to be incapable of performing its intended functicn.

5 Ccnditions Prior to Cccurrence: S.e reactor was in a Ocid shutdevn ecndition with major plant parameters as follevs:

Pcver: Cere: 05 Elec: 0W 1

a. ee.%v ^d '.,

1482 291

Dtrectcrate er Licensing . .

RC Flow: 8 x 10" lbs/hr EC Pressure: O psig C

RC Terp: 91 F PRZR Level: 272 in FRZR Te:p: 1LO F

6. tescriptica of Cccurrence:

The feeder breaker to the 13 Engineered Safeguards Motor Centrcl Center had been suspected to not be functiening prcperly and vas, therefcre, tested on August 18, 197h. The breaker appeared to be functioning prcperly during this test, and 4t was not until the performance of specially recc= rended vende; :ests en October 24, 197h, that a problem could be identified within the breaker. Upen discovery of the problem, the breaker was then repaired and returned to service.

The above-listed events were reviewed en November 29,197h, by the Station Staff, and it was at this time that the decisien was made to ecnrider this prcblem reportable as an abnormal occurrence.

7 Designatien of Apparent Cause of Cccurrence:

Cc=penent failure was the apparent cause of the occurrence in that the plunger en the evercurrent trip-delay device suffered frce mechanical binding and would net always return to its fully retractei positicn folleving a relatively large starting =ctor current surge; thus, it would nct have as far tc travel to trip the breaker.

8. Analysis of Cecurrence:

Fcr the fc11cving reascns it is believed that neither the health ncr safety cf the public was threatened by the defective overcurrent device:

a. The breaker to the 13 Engineered Safeguards Motor Centrcl Center probably would nct have tripped in the event of an ESAS actuatien in that current surzes of greater than 1000 a=ps vould have been required to cause premature tripping of the breaker; but because the largest lead is started at sicv speed during an ESAS actuaticn, the resulting current surge is significantly less than 10C0 amps ,

and

b. Even if the subject breaker had tripped prematurely, the "A" Engineered Safeguards Actuaticn System (ESAS) is ccepletely redundant to the "3" ESAS. -

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h' Direetcrate of Licensing s 9 Corrective Action:

As an 1.rediate corrective acticn the defective overcurrent device was replaced with a spare and the breaker tested. Having verified that the spare device vn.3 functiening properly, the breaker was then returned to service.

At a meeting held scen after this occurrence was reported, the Plant Operaticns Review Cc ittee and the Station Superintendent reviewed and approved these acticns.

10. Failure Data:

revicus Failures:

Ucne.

Equip .ent Identificaticn:

Westinghcuse #DB 50 Circuit Ereaker Rating: 1600 amps 600 volts AC Westinghouse Series Overcurrent Trip Device Rating: 1000 a=ps

- r Sincerely, t

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R. C. ' Arnold Vice President RCA:JFV:sh cc: Mr. J. P. O'Reilly (DORC-Regicn 1)

File 20.1.1 7 7 3 5.1 982 2N

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