ML20084U166

AO 50-265/75-11:on 750408,during Surveillance Test,Field Diode Transient Voltage Suppressors Failed.Caused by Short Out of Selenium Surge Suppressors.Suppressors Replaced

ML20084U166
Person / Time
Site:	Quad Cities
Issue date:	04/18/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J Office of Nuclear Reactor Regulation
Shared Package
ML20084U167	List: ML20084U166 ML20084U171
References
AO-50-265-75-11, NJK-75-207, NUDOCS 8306270082
Download: ML20084U166 (3)

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l ilJ K-75-207 April 18, 1975 .

Mr. John F. O' Leary, Director Directorate of Licensing Regulation U. S. fluclear Regulatory Commission Washington, D. C. 20545

REFERENCE:

Quad-Citics Nuclear Power Station Docket ?!o. 50-265, DRP-30 Appendix A, Secticas 1.0.A.2, 3 9.A.1 Daar Mr. O' Leary:

Enclosed please find Abnorrnal Occurrence Report No. 50-265/75-11 for quad-Citics Nuclear Power Station. This occurrence was previously reported to Region Ill, Directorate of Regulatory Operations on April 9, 1975 and to you and Region IiI, Directorate of Regulatory Operations by telecopy on April 9, 1975 This report is submitted to you in accordance with the requirements of Technical Specification 6.6.B.I .a.

Very truly yours, COMMONWEALTH EDI50!1 COMPANY QUAD-CITIES llUCLEAR POWER STATION

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N. J. Kalivianakis l~

Station Superintendent flJ K/SRH/vnn cc: Region 111, Directorate of Regulatory Operations J. S. Abel N d b $*

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4 REPORT NUMBER: A0-50-265/75-il REPORT DATE: April 15, 1975 OCCURRENCE DATE: April 8, 1975 FACILITY: Quad-Cities. Nuclear Power Station Cordova, Ill. 61242

_ IDENTIFICATION OF OCCURRENCE:

While performing the monthly Unit 2 Diesel Generator surveillance test, the field _

diode transient vol.tage_suppresson_f_a l l edy CONDITIONS PRICR TO OCCURRENCE:

Unit 2 was in the cold shutdown condition for tha current refueling outage.

DESCRIPTION OF OCCURRENCE:

At 3:25 PM on April 8. 1975, during Unit 2 Diesel Generator monthly operability surveillance testing, electrical arcing above the excitation cabinet was dis-covered by the operational enalysis department. The arcing was caused by the shorting of the field diode selenium surge suppressors. The diesel generator output breaker was immediately tripped and the diesel generator was shut down.

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:

E0UIPMENT FAILURE - The apparent cause of this occurrence is equipment fa i l u re.

All six selenium surge suppressors had shorted out. The electrical circuitry is such that if one selenium surge suppressor fails, the remaining selenium surge suppressors will likely also fail. tbrk request #1259-75 was initiated to replace the failed suppressors.

ANALYSIS OF OCCURRENCE:

The safety implications of this occurrence are minimized by the fact that Unit 2 was in the cold shutdown condition for refueling and both the Unit 1/2 Diesel Generator and off-site power were availabic. Moreover, in spite of the failed surge suppressors, the Diesel Generator could have been started and loaded in the event of an accident condition.

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

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i CORRECTIVE ACTION _:

l The inmediate corrective action was to shutdown the Unit 2 Olesel Generator and replace the failed selenium surge suppressors. On April 10, 1975 at 1:44 PM, the i Unit 2 Diesel Generator was placed back in service, and was successfully operated.

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- Work request #1334-75 was initiated to check the scienium surge suppressors on

- the other two diesel generator field' diodes. Additional corrective action taken to prevent repetition was to initiate modification M-4-1-75-25, M-4-2-75-25, and H-4-1/2-75-4. These modifications provide for the replacement of the existing scienium surge suppressors with a more reliable type.

FAILURE DATA:

There was a failure of the scieniu:a sur ge sw cressors on the Unit 2 Diesel Gen-erator April 26, 1972. The modifications,the.t have been initiated plus the testing of the existing selenium surge seppressors should preclude any similar failures in the future.

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