ML19319B788

RO NP-33-77-63:on 770812,absolute Position Indicator for Control Rod 4 Showed Fluctuation Reading.Caused by Defective Relay in Position Indicator Panel.Relay Replaced Returning Absolute Position Indicator to Svc

ML19319B788
Person / Time
Site:	Davis Besse
Issue date:	09/12/1977
From:	Lingerfelter J, Vallade S TOLEDO EDISON CO.
To:
Shared Package
ML19319B691	List: ML19319B690 ML19319B788
References
NUDOCS 8001270256
Download: ML19319B788 (2)

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[NJ 43 44 47 48 CAUST DESCRIPiioN l9 Instru:nent and_Cggt.r_o_1 Technicians found that a relay in the Position I e9 l Indicator Panel was defective. It was replaced by the vendor.

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( TOLEDO EDISON COMPANY

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/ DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-33-77-63

_DATE OF EVENT: August 12, 1977 F_ACILITY: Davis-Besse Unit 1

_IDE!TIIFICATION OF OCCURRENCE:

Rod 4 of Group 4 was inoperable.The Absolute Position Indicator (API) for Control Conditions Prior to Occurrence: The plant was in Mode 2, with Power (MWT) = 0 and Load (M Tr) = 0.

Description of Occurrence: At 1910 hours0.0221 days <br />0.531 hours <br />0.00316 weeks <br />7.26755e-4 months <br /> on August 12, 1977, the Absolute Position Indicator (API) for Control Rod 4 of Group 4 was inoperable. The Control Room operator could not determine Control Rod 4 position within + 6.5%

This placed the Station in Action State =ent (a) of Technical Specification , 3.1.3.3.

The 100%indicator withdrawn, light but (relative position indicator) for Rod 4 showed that it was the API reading fluctuated frem 70-100% withdrawn. Since the indicator lights and API readings for the other reds in Group 4 shewed 100%

thdrawal, it was suspected that the API for Rod 4 was defective .

Designation of Aeoarent Cause of Occurrence:

Upon investigation, Instrument and Control Technicians round that a relay in the Position Indicator Panel was defective.

Dianond Controls.The relay, along with connecting cable, was replaced by the vendor, Analysis of Occurrence:

public or Station personnel.There was no danger to the health and safety of the The cont nl red was m-+= Thy aligned with the group, and relative indication was still operable.

properly. The cvuisol rod was operating t

Corrective Action: On August 13, 1977  !

operability to the API for Control Rod 4the relay was replaced, returning .

Statenent (a) of Technical Specification 3.1.3.3.This removed the Station from Action  ;

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5 I ; I Failure Data: *i There have been no previous similar occurrences. .e l

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