ML19329B900

RO NP-33-74-14:on 770622,safety Features Actuation Sys Channel 1 & Reactor Protection Sys Channel 1 Tripped Due to Shorting to Ground Slide Link,Supplying Ac Voltage to Decay Heat Essential Flow Instrumentation Cabinet

ML19329B900
Person / Time
Site:	Davis Besse
Issue date:	07/19/1977
From:	Batch S, Lingenfelter J TOLEDO EDISON CO.
To:
Shared Package
ML19329B835	List: ML19329B834 ML19329B900
References
NUDOCS 8002060894
Download: ML19329B900 (3)

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@l 7 eo Essential Inverter YV1 was accidentally tripped causing losis of j so gl Essential Bus Y1. This resulted in a loss of SFAS Channel k and RPS l 7 o sa EEli Channel 1. (NP-33-77-14)  !

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Personnel error _ caused a short to ground while closing a slide link. l

@a,l The subsequent loss of Y1 has been deter::ined to be a design proble=

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TOLEDO EDISCN COMPAUY DAVIS-BESSE UNIT ONE HUCLEAR PCiiER STATION p) SUPPLEMEIITAL ILFORMATION FOR LER NP-33-77-14

'NJ DATE OF EVENT: June 22, 1977 -

FACILITY: Davis-Besse Unit 1 -3 IDEhTIFICATION OF OCCURRENCE: .

Ioss of Safety Features Actuation System Channel 1 due to loss of Y1 Conditions Drior to Occurrence:

The plant was in Mode 5, with power ET = 0, MWE = 0.

Description of Occurrence:

On June 22, 1977 at 06 W , an Instrument and Control Technician shorted to ground a slide link which supplied AC voltage to the Decay Heat Essential Flow Instru=entation Cabinet. This caused a loss of Essential Instru=en-tation Distribution Panel Y1, resulting in the tripping of Safety Features Actuation System (SFAS) Channel 1 and Reactor Protection System (RPS)

Channel 1. The Essential Instrumentation Distribution Panel Y1 was

(' supplied by its alternate source YAR, and RPS Channel 1 and SFAS Channel.1 were re-energized at 0720 hours0.00833 days <br />0.2 hours <br />0.00119 weeks <br />2.7396e-4 months <br />.

Designation of Aprarent Cause of Occurrence:

The shorting of the slide link supplying the Decay Heat Essential Flow l Instrumentation Cabinet was due to a personnel error on the part of the Instrument and Control Technician. The loss of Essential Instrumentation l Panel Y1, and subsequent trip of SFAS Cha e l 1 and RPS Channel 1, however,  !

can be attributed to a desi6 n problem in the Inverter YV1.

Analysis of Occurrence:

Since three of four SFAS channels were still operable, and SFAS Channel 1 was tripped, the SFAS would operate if required. The health and safety of the public and station personnel were not endangered. -

Corrective Action:

Panel Y1 was supplied by its alternate source, YAR, and SFAS and RFS Channels 1 were re-energized within an hour after tripping occurred. This re=oved the station from the Action Statement' of Technical Specification N 3 3 2.1. The manufacturer has been previously notified as to the defective g ) inverter desi6n, and is working to modify it.

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. - .. , . ,a i TOLEDO EDISON COMPA!Tf l DAVIS-EESSE tETIT ONE frJCLEAR POWER STATIC!!

. SUPPLEME:frAL INFCRMATION FOR LER NP-33-77-14 - Page 2 l

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. Failure Data: ,

Shorting of slide link has not previously occur;ed, but defective inverter design was partial cause in another event: NP-33-77-6 i

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