05000346/LER-1980-064-03, /03L-0:on 800822,station Experienced Loss of Essential Instrument Ac Panel Y2.Caused by Failure of YV-2 Inverter Output Fuse.No Cause Determined for Fuse Failure. Failed Fuse Replaced

/03L-0:on 800822,station Experienced Loss of Essential Instrument Ac Panel Y2.Caused by Failure of YV-2 Inverter Output Fuse.No Cause Determined for Fuse Failure. Failed Fuse Replaced

ML19338D709
Person / Time
Site:	Davis Besse
Issue date:	09/18/1980
From:	Isley T TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19338D703	List: 05000346/LER-1980-064, Forwards LER 80-064/03L-0 05000346/LER-1980-064-03, /03L-0:on 800822,station Experienced Loss of Essential Instrument Ac Panel Y2.Caused by Failure of YV-2 Inverter Output Fuse.No Cause Determined for Fuse Failure. Failed Fuse Replaced
References
LER-80-064-03L, LER-80-64-3L, NUDOCS 8009230680
Download: ML19338D709 (3)

LER-1980-064, /03L-0:on 800822,station Experienced Loss of Essential Instrument Ac Panel Y2.Caused by Failure of YV-2 Inverter Output Fuse.No Cause Determined for Fuse Failure. Failed Fuse Replaced

Event date:
Report date:
3461980064R03 - NRC Website

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8 60 61 DOCKET NUVBER 68 69 EVENT DATE 74 75 REPORT DATE 80 3o EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h lo 121 l(NP-33-80-74) On 8/22/80 at 1446 hours0.0167 days <br />0.402 hours <br />0.00239 weeks <br />5.50203e-4 months <br /> and on 8/23/80 at 0922 hours0.0107 days <br />0.256 hours <br />0.00152 weeks <br />3.50821e-4 months <br />, the station ex-l g erienced a loss of Essential Instrument AC Panel Y2.

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lolijlstation in violation of T.S. 3.3.2.1.

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS l i l o l lThe cause was the f ailure of the YV-2 invert er output fuse, however, the exact cause ofl l1 11l lthe fuse failure has not been determined.

The first event was corrected under Ma in teni-ITITl lance Work Order 80-3049 by replacing the failed fuse.

SFAS Channel 2 was re-energized l [i 13 l lat 1645 hours0.019 days <br />0.457 hours <br />0.00272 weeks <br />6.259225e-4 months <br /> on 8/22/80. The second event was corrected similarily under MWO 80-3051 l l1Id.Iland at 1346 hours0.0156 days <br />0.374 hours <br />0.00223 weeks <br />5.12153e-4 months <br /> on 8/23/80 SFA'S Channel 2 was again re-energized.

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t TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE

,SLOPLEMENTAL INFORMATION FOR LER NP-33-80-74 DATE OF Tiv.NT: August 22, 1980 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss 'of Essential Instrument AC Panel Y2.

Conditions Prior to Occurrence: The unit was in Mode 5 with Power (MRT) = 0 and Load (Gross MWE) = 0.

Description of Occurrence: On August 22, 1980 at 1446 hours0.0167 days <br />0.402 hours <br />0.00239 weeks <br />5.50203e-4 months <br />, the station experienced

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a loss of Essential Instrument AC Panci Y2.

This resulted in *:he de-energization of Safety Features Actuation System (SFAS) Channel 2, Reactor Protection System (RPS)

Channel 2, and Steaa and Feedwater Rupture Control System (SFRCS) Channel 2.

This caused the containment radiation string for SFAS Channel 2 to fail.

This also failed the Channel 2 Borated Water Storage Tank (BWST) low level bistable.

Since BWST Chan-nel 4 was already in the tripped condition for maintenance, the station experienced an Incident Level 5 actuation on actuation Channel 2.'

The loss of RPS Channel 2 also caused the loss of Source Range Indication NI-1.

NI-2 was operable at the time.

The loss of the containment radiation string for SFAS Ch'annel 2 is reportable per Technical Specifica~ tion 3.3.2.1 which requires all four channels of containment radia-tion to be operabic in all modes.

The action statement, which requires the failed channel to be'placed in the tripped condition, was met.

The Incident Level 5 actuation is only required to be operabic in Modes 1, 2, 3, and 4.

Being in Mode 5, it is not reportable.

Again at 0922 hours0.0107 days <br />0.256 hours <br />0.00152 weeks <br />3.50821e-4 months <br /> on August 23, 1980, the station repeated its loss of Essential Instrument AC Panel Y2.

The result was a de-energization of SFAS Channel 2, RPS Chan-nel 2, and SFRCS Channel 2.

This caused the loss of the SFAS Channel 2 containment radiation string, the failure of the BWST low level bistable for Channel 2 and with the BWST Channel 4 already tripped, the, station experienced an Incident Level 5 actua-tion'on actuation Channel 2.

The same action statement was entered as with the first occurrence.

Designation of Apparent Cause of Occurrence: The loss of Y2 in each event was due to a failed YV-2 inverter output fuse. The exact cause of the fuse failure has not been pinpointed. There was facility change request work ongoing in the cabinet room.

And a failure in the SFAS Channel 2, RPS Channel 2, or SFRCS Channel 2 cabinet would have fed back to the YV-2 fuse before the fuse in the individual cabinet could fail. This is because YV-2 is designed to fast f ail to protect the inverter.

It appears that the failure occurred when wires were being connected in these cabinets. Apparently, Icads touched some wrong terminals and caused a short that caused the YV-2 failure.

LER #80-064

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TOLEDO EDISON COMPANY:

DAVIS-BESSE NUCLEAR ' POWER' STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-80-74

.' PACE 2 Analysis ~of Occurrence:.There was no danger to theLhealth and safety of the public'

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or to station; personnel. -The other three channels of. containment radiation monitor-

' ing.were' operable. The.SFAS Incident Level 5~ actuation did not cause any water to

- reach the emergency sump as-the'. Emergency Sump, Isolation Valves DH9A and.DH9B were closed, and power.: removed..

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Corrective Action

The first event was' corrected under: Maintenance Work Order ~

80-3049 by replacing the failed fuse..SFAS: Channel 2 was re-energized at.1645 hour0.019 days <br />0.457 hours <br />0.00272 weeks <br />6.259225e-4 months <br />s-on August 22, 1980.~ The second event was corrected under Maintenance Work Order.

80-3051 by again replacing the failed fuse.. fat 1346 hours0.0156 days <br />0.374 hours <br />0.00223 weeks <br />5.12153e-4 months <br /> on August 23, 1980, SEAS Channel 2 again was re-energized, which removed the station from the action statement of Technical Specification 3.3.2.1.

Previous similar' events were reported in NP-33-79-13 (79-009) and

lailure Data:

~ NP-33-80-70 (80-056).

LER #80-064 1

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