ML19345D330

LER 80-064/03L-1:on 800822,station Experienced Loss of Essential Instrument Ac Panel Y2.Caused by Failure of YV-2 Inverter Input Fuse & Other Undetermined Causes.Failed Fuse Replaced

ML19345D330
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
ML19345D332	List: ML19345D330 ML19354C395
References
LER-80-064-03L, LER-80-64-3L, NUDOCS 8012120512
Download: ML19345D330 (3)

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6d EV ENT D ATE 74 7'J REPORT D ATE I d 6d 61 OOCAETNyYdER EVENT DESCRIP'. TON AND PROB A6LE CCNSECUENCES h IO f 2l I(SP-33-SO-70 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 The result was the de-energiza-l 93,3, lperienced s. loss of Essential Instrument AC 'anel Y2.

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, o ,,,, l tion of Safety Features Actuation System (SFAS) Channel 2, Reactor Protection l'

,g,3, g(RPS) Channel 2 and Steam and Feedwater Rupture Control System (SFRCS) Channel 2 wh This placed the  ;

,3,e,, caused the containment radiation string for SFAS Channel 2 to fail.

There was no danger to the public or station j

l i o I 7 I I station in violation of T.S. 3.3.2.1.

t radiation monitoring were operable.l

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33 CAUSE DESCRIPTION AND CORRECTIVE ACflONS q

1 101 IThe cause was the f ailure of the YV-2 inverter input fus5. however. the exact caitse of!

k Ii li l Ithe ftise failure has not been determined. The first ew.it was corrected under Ma in teT4-SFAS Channel 2 was re-energized I g

Iii?Ii ace Work Order 80-3049 by replacing the failed fuse.

t I1 13 I lat 1645 heurs on 8/22/80. The second event was corrected similarily under MUO 80-3051 l l

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! m land at 1346 hours0.0156 days <br />0.374 hours <br />0.00223 weeks <br />5.12153e-4 months <br /> on 8/23/80 SFAS Channel 2 was again re-energized. 80

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TOLEDO EDISON COMPAhT DAV' -BEGSE NUCLEAR POWER STATION UNIT ONE sui r cAESTAL INFORMATION FOR LER NP-33-80-74 .

0 ATE OF EVENT: . ,st 22, 1980 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of Essential Instrument AC Panel Y2.

Conditions Pric r to Occurrence: The unit was in Mode 5 with Power (WT) = 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 This resulted in the de-energization of a loss of Essential Instrument AC Panel Y2.

Safety Features Actuation System (SFAS) Channel 2, Reactor Protection System (RPS) This Channel 2, and Steam and Feedwater Rupture Control System (SFRCS) Channel 2.

caused the containment radiation string for SFAS Channel 2 to fail. ais also failed the Channel 2 Borated Water Storage Tank (BWST) low level bistable. Since BWST Chan-nel 4 vas already in the tripped condition for maintenance, the station expe rienced an Incident Level 5 actuation on actuation ChannelNI-2 The loss of RPS Channel 2 also

2. was caused the loss of Source. Range Indication NI-1. operable at the time.

The loss of the containment radiatior string for SFAS Ch'annel 2 is reportable per Technical Specific _ ton 3.3.2.1 which _ -m: ires all four channels of containment radf a-tion to be operable in all modes. The action statement, which requires the failed

= channel to be placed in the tripped condition, was met.

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

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- Being in Mode 5, it is not reportable.

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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 CManel 2, RPS Chan-l nel 2, and SFRCS Channel 2. This caused the loss of the SFAS Channel 2 centainment b ,

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 1 a failed YV-2 inverter input fuse. The exact cause of the. fuse failure has not been And

[ pinpointed. There was facility change request work ongoing in the cabinet room.

a failure in the SFAS Channel 2, RFS Channel 2, or SFRCS Channel 2 cabinet would have g This U fed back to the YV-2 fuse before the fuse in the individual cabinetItcould appearsfail.that

! is because YV-2 is designed to fast fail to protect the inverter.

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

g LER #80-064 L

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l TOLEDO EDISON COMPANY I

DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE

' PAGE 2 SUPPLEMENTAL INFORM TION FOR LER NP-33-80-74 Analysis of Occurrence: There was no danger to the health and safety of the public 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.

t 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 hours0.019 days <br />0.457 hours <br />0.00272 weeks <br />6.259225e-4 months <br /> on August 22, 1980. The second event was corrected under Nbintenance Work Order 80-3051 by again replacing the failed fuse. At 1346 hours0.0156 days <br />0.374 hours <br />0.00223 weeks <br />5.12153e-4 months <br /> on August 23, 1980,-SFAS 7 Channel 2 again was re-energized, which removed the station from the action' statement of Technical Specification 3.3.2.1.

Failure Data:

Previous similar events were reported in NP-33-79-13 (79-009) and NP-33-80-70 (80-056) .

LER #80-064 l

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