ML19241A982

LER 78-042/03L-0 on 780819:inverter VBIT-1A Failed,Causing Isolation of Decay Heat Removal.Caused by Electronic Component Failure in Inverter VBIT-1A.Inverter Undergoing Rectifier Mods to Improve Reliability

ML19241A982
Person / Time
Site:	Crystal River
Issue date:	09/11/1978
From:	Cooper J FLORIDA POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
LER-78-042-03L, LER-78-42-3L, NUDOCS 7907110490
Download: ML19241A982 (2)

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g ; At 1740, inverter VBIT-1A failed causing the loss of power to the 120 volt

, A.C. vital bus 3-A. This caused DHV-3, decay heat removal outlet valve, te y

close, isolating decay heat removal. Redundancy was maintained with the

,, , auxiliary power supply to vital bus 3-A. This is the second occurrence t,m_ j W, , ; of inverter VBIT-1A failure. No effects upon public health and safety sinc i] g , decay heat . ras minimal and auxiliary power was available within five minutc _

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"IN CAL /St Ot5;*I87 ton ANo CC AmtCfl\ ! ACTIONS h

[iGy . c. l Cause of this event was due to electronic component failures within the CJ ,,  ; inverter VBIT-1A. The inverter is presently undergoing rectifier modific 5.i k W ,,, , tions to improve reliability.

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. a - ,e _--- , - ,__ ,,a SUPPLEMENTARY INFORMATION

1. Report No.: 50-302/78-042 /03L-0

2. Facility: Crystal River Unit #3

3. Report Date: 11 September 1978

4. Occurrence Date: 19 August 1978

5. Identification of Occurrence:

Less than one operable decay heat removal loop contrary to Technical Specificatior 3.9.8.

5. Conditions Prier to Occurrence:

Mode 6 refueling.

6. Description of Occurrence:

At 1740, the duel input inverter, VBIT-1A failed, causing the loss of power to the 120 volt A.C. Vital Bus 3-A. As a result of this power loss, a closing circuit to DHV-3, decay heat removal outlet valve, was energized, thus isolating the decay heat removal system. An auxiliary power source, utilizing the isolation power supply VBTR-3A, was placed into service to provide power to Vital Bus 3-A. The initial conditions for decay heat removal were re-established and the system was returned to full operability within fifteen minutes.

7. Dasignation of Apparent Cause:

The cause of this event was due to electronic _ component failures within inverter VBIT-1-A. -

3. Analysis of Occurrence:

There was no safety hazard to the plant or general public as decay heat was minit; due to the fact that the plant was shut down for an extended period and auxiliary power was available within five minutes. ,

9. Corrective Action:

Inverter VBIT-1A is presently unde rgoing rectifier modifications to improve reliability.

10. Failure Data:

This is the second occurrence of inverter VBIT-1A failure as reported by LER 77-1_

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Florida 15 Septe=ber 1978 3-o -1 c 3.o.o a a n 2 ~P wer CS-78-190 Mr. J. P. O'Reilly, Director Docket No. 50-302 U.S. Nuclear Regulatory Commission Licensee No. DPR-72 Office of Inspection & Enforcement LER No. 78-042/03L-0 101 Marietta St., Suite 3100 Crystal River Unit #3 Atlanta, CA 30303 Occurrence Date:

19 August 1978

Dear Mr. O'Reilly:

Enclosed please find Licensee Event Report 78-042/03L-0 and the attached supplementary sheet, which are submitted in accordance with Technical Specification 6.9.1.9.b.

Should there be any questions, please contact us.

Very truly yours, FLORIDA POWER CORPORATION

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,T otd W. P. Stewart Director, Power Production GMW/rc Nuclear Plant Manager Attach: (2) ..

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