ML20085G058

Final Deficiency Rept Re Derating of 250-volt Fuses in 4-kV & 480-volt Switchgear.Initially Reported on 750129.Fuses Scheduled for Replacement

ML20085G058
Person / Time
Site:	Browns Ferry
Issue date:	04/30/1975
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Knuth D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
Shared Package
ML20085G057	List: ML20085G058 ML20085G061 ML20085G076
References
NUDOCS 8308240222
Download: ML20085G058 (2)

Text

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,j0 ' o, 831PowerBuffdng 9 8

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%r,.1916 April 30, 1975 Mr. Donald F. Knuth, Director

Office of Inspection and Enforcemer i

U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear ifr. Knuth:

I BROWNS FERRY NUCLEAR PLANT UNIT 3 - REPORTABLE DEFICIENCY -

DERATING OF 250-VOLT FUSES IN 4-kV AND 480-VOLT SWITCHGEAR -

IE CONTROL NO. H00583F2 Initial Report of the subject deficiency was made on January 29, 1975, and followed by our February 28 and March 31, 1975, letters, J. E. Cilleland to Donald F. Knuth. In compliance with paragraph 50.55(e) of 10 CFR Part 50, we submit the enclosed final report

, of the deficiency.

Very truly yoyrs, U J. E. Uilieland i

Assistant Manager of Power 1

i j Enclosure CC (Enclosure):

4 1

Mr. Norman C. Moseley, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission

, Region II - Suite 818 j

230 Peachtree Street, NW.

] Atlanta, Georgia 30303 i

i l- o 8308240222 750515 PDR ADOCK 05000296 G PDR i

3 An Equal Opportunity Employer

( )

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EUCLO3U12 BROWNS FERRY NUCLEAR PLANT UNIT 3 DERATING OF 250 VOLT FUSES IN THE 4 kV AND 480 VOLT SWITCHGEAR 1

FINAL REPORT Description of Occurrence on January 27, 1975, it was discovered that most of the installed fuses in the 250 volt de control circuits of the 4 kV and 480 volt switchgear are one-time class H 250 volt fuses of Bussmann or Economy manufacture.

This class of fuse has been derated to 250 volt ac only. As a result, the subject fuses are no longer appropriate for this type of service.

1 Safety Implications The subject fuses would not have caused a failure in the 4 kV and 480 volt switchgear that had not been considered in the initial design. Assuming j the subject fuses to fail, other protective devices in the circuits would

protect the switchgear.

The derated fuses may have been sufficient for the circuits in which they

were contained. However, since it was more expedient to replace them once a suitable substitute was found than it was to test the circuits and fuses, we elected to replace the fuses.

Corrective Action The subject fuses are scheduled to be replaced in the near future. The replacement fuses, Chase-Shawnut A2Y35, have been purchased.

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