ML19259D203

LER 79-093/03L-0:on 790917,output Relay Driver Lamp for Relay K303A in Steam & Feedwater Rupture Control Sys Channel 3 Was Extinguished.Caused by Inoperable Optical Isolator on Relay Driver Board.Failed Board Was Replaced

ML19259D203
Person / Time
Site:	Davis Besse
Issue date:	10/12/1979
From:	Nelson J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19259D201	List: ML19259D200 ML19259D203
References
LER-79-093-03L, LER-79-93-3L, NUDOCS 7910170358
Download: ML19259D203 (2)

Text

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EVET.T CEOCRIPTIG"J AND PROBABLE CONSEQUENCES h'8 j o 2 [ On September 17, 1979 at 2330 hours0.027 days <br />0.647 hours <br />0.00385 weeks <br />8.86565e-4 months <br />, the output relay lamp for relay K303A in Stcan o 3; l and Feedwatcr Rupture Contro1 Systen (SFRCS) Channel 3 was extinguished which indicatcq

[Tg] [ that K303A uas in the tripped condition. This placed the unit in Action Statement 13 l o ., jof T.S. 3.3.2.2 which allows operation to continue provided the inoperabic section of l o n j the channel in piaced in the tripped conditica within one hour. There was no danger j _

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42 43 44 47 CAUSt DESCRIPTION %D CORRECTIVE ACTIONS i o [The cause was an inoperable optical isolator on the relay driver board of SFRCS Chan-l li li l lnel 3. Under Maintenance Work Order IC-428-79, the failed board was replaced . The l i 7 lnew board was functionally bench tested and declared operable at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> on Septen _J i

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POUER STATION LTNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-108 DATE OF EVENT: September 17, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Failure of output relay driver card 2-10 circuit 3 in the Steam and Feedwater Rupture Control System (SFRCS) Channel 3 Conditions Prior to Occurrence: The unit was in Mode 1, with Power (>nZE) = 2772, and Load (Cross SME) = 910.

Description of Occurrence: At 2330 hours0.027 days <br />0.647 hours <br />0.00385 weeks <br />8.86565e-4 months <br /> on September 17, 1979, during performance of Surveillance Test ST 5099.01, " Miscellaneous Instrument Shift Checks", it was found that the output relay lamp for relay K303A in SFRCS Channel 3 was extinguished showing that K303A was in the tripped condition. The K303A relay is one of the two out of two relay logic on the open circuit of AF608, auxiliary feedwater isolation valve to OTSG l-1.

This placed the unit in Action Statement 13 of Technical Specification 3.3.2.2 which allows operation to continue provided the inoperable section of the channel is placed in the tripped condition within one hour.

Designation of Apparent Cause of Occurrence: The cause of the occurrence was an in-operable optical isolator (Consolidated Controls Corporation part number FCD820) on their relay driver board part number 6N177.

Analvs;; of Occurrence: There was no danger to the health and safety of the public or to station personnel. The failure of the component automatically put the affected circuit in a tripped condition. AF608 would have performed as designed durind an actual SFRCS trip.

Corrective Action: On Septembcr 18, 1979, under Maintenance Work Order (MWO) IC-428-79, it was found that the relay driver board 2-10 circuit 3 in SFRCS Channel 3 was inopera-ble. A new board serial number 050 was taken from stock, functionally bench tested, and placed in service for the inoperable board serial number 012. The card was func-tionally tested per MWO IC-428-79 and returned to operability at 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on Septem-ber 18, 1979. The inoperabic board serial number 012 was repaired under MWO IC-112-79 in which an inoperable optical isolator part number FCD820 was found. The board was then tested and alaced back into stock.

Failure Data: There has been one previous f ilure of an optical isolator, see Licensee Event Report NP-33-79-106.

LER #79-093  ? n-

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