ML20084S806

AO 50-254/75-9:on 750503,failure of Diode Transient Voltage Suppressors Was Experienced.Caused by Shorting of Field Diode Selenium Surge Suppressors.Selenium Surge Suppressors Replaced

ML20084S806
Person / Time
Site:	Quad Cities
Issue date:	05/13/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
Shared Package
ML20084S808	List: ML20084S806 ML20084S809
References
AO-254-75-9, AO-50-254-75-09, AO-50-254-75-9, NJK-75-273, NUDOCS 8306170434
Download: ML20084S806 (3)

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< A". C:mmrvealth Edison h)

Guad CI JJuclear Power Stat:on

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• 3d Post OthdtBox 216 v MJ3 : Cordova,1:hnois 61242 i.

~ Telephone 309/654-2241 .

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NJK-75-273 / g May 13. 1975 .

Director of Office of Nuclear Reactor Regulation "

U. S. Nucitaar Regulatory Commission i.

Washington,-D.-C. 20555

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Reference:

Quad-Ci ties Nuclear' Power Station Docket No. 50-254, DPR-29 h Appendix A, Sections 1.0.A.2, 3.9.A.1, 6.6.B.1.a i

. Enclosed please find Abnormal Occurrence Report No. A0-50-254/75-9 for j Quad-Cities Nuclear Power Station. This occurrence was previously reported t to ' Region lil, Directorate of Regulatory Operatfor.3 by_ telephone on May 4, 1975 and to you and Pcgion 111, Directorate of Regulatory Operations by telecopy on May 5,1975

.Thi s report is submitted to you in accordance with the requirements of Technical Speci fication 6.6.B.1' a. .

t Very truly yours,  !

COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION l i

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N. J. Kalivianakis Station Superintendent

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~cc: Region li t , Directorate of Regulatory-Operations J. S. Abel l

f 8306170434 750513 PDR ADOCK 05000254 PDR e

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" -6 ' A A V V REPORT i1UltBER: A0 50-254/75-9 REPORT DATE : May 13, 1975 OCCURRENCE DATE: May 3, 1975 e 4

FACI LITY: Quad-Citics Nuclear Power Station Cordova, Illinois 61242 g

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IDENTI FICATl0ll 0F OCCURRENCE:

k Failure of the Unit One diode transient voltage suppressors e, 4

i CONDITIONS PRIOR TO OCCURRENCE:

• t Unit One was in cold shutdown condition for rod pattern change and minor ka plant maintenance. f f

DESCRIPTION OF OCCURRENCE:

At 10:18 c.m. cr. "cy 3, 1573 v.hlle peiTun..ing tiie Unit One Core 5 pray iogic test, a diesel generator troubic alarm was received in the control room.

The #1 diesel generator control swi tch was put in the STOP position and an y equipment operator was dispatched to investigate the alarm. E lect rica l i arcing, caused by shorting of the field diode selenium surge suppressors, I was discovered above the excitation cabinet. .

Y DESIGNATION OF APPARENT CAUSE OF OCCURREi4CE:

4 Equipment Failure N The apparent cause of this occurrence is equipment failure. The six selenium surge suppressors had shorted out. The electrical circuitry is such that if one scienium surge suppressor fails, tne remain:ng selenium surge suppressors  !

will likely also fall. Work request #1607-75 was initiated to replace the failed suppressors.

ANALYSIS OF OCCURRENCE:

h The safety implications of this occurrence are minimized by the fact that W Unit One was in the cold shutdown condition and the Unit 1/2 diesel gence- l ator and of f-site power were available, i f necessary, the diesel generator y could have been started and loaded in tha event of an accident condition 4 in spite of the failed surge suppressors. )

There were no personnel injuries and the incident had no effect on the health and safety of the public. d i

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. s_, 1 A0-50-254/75-9 May 13, 1975 CORRECTIVE ACTION:

The immediate corrective action was to shutdown the Unit One diesel gener-ator and replace the failed selenium surge suppressors. On May 3,1975 at 10:10 p.m., the Unit One diesel generator was placed back in service and successfully operated.

FAILURE DATA:

There were failures of the selenium surge suppressors on the Unit Two diesel generator on April 26, 1972 and on April 8, 1975 Modifications have been initiated to provide for the replacement of the existing selenium surge suppressors with a more reliable type. The modifications that have been initiated plus the testing of the existing selenium surge suppressors should preclude any similar failures in the future, v

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