05000346/LER-1980-036-03, /03L-1:on 800407,reactor Protection Sys Initiated High Flux Trip of Reactor.Channel 2 Trip Module Reflected Trip Signals from Only Three of Four Sys Channels.Caused by Failure of Trip Relay K1 in Channel 2 Trip Module

/03L-1:on 800407,reactor Protection Sys Initiated High Flux Trip of Reactor.Channel 2 Trip Module Reflected Trip Signals from Only Three of Four Sys Channels.Caused by Failure of Trip Relay K1 in Channel 2 Trip Module

ML19323H710
Person / Time
Site:	Davis Besse
Issue date:	05/06/1980
From:	Werner B TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19323H707	List: 05000346/LER-1980-036, Forwards LER 80-036/03L-1 05000346/LER-1980-036-03, /03L-1:on 800407,reactor Protection Sys Initiated High Flux Trip of Reactor.Channel 2 Trip Module Reflected Trip Signals from Only Three of Four Sys Channels.Caused by Failure of Trip Relay K1 in Channel 2 Trip Module
References
LER-80-036-03L, LER-80-36-3L, NUDOCS 8006160085
Download: ML19323H710 (2)

LER-1980-036, /03L-1:on 800407,reactor Protection Sys Initiated High Flux Trip of Reactor.Channel 2 Trip Module Reflected Trip Signals from Only Three of Four Sys Channels.Caused by Failure of Trip Relay K1 in Channel 2 Trip Module

Event date:
Report date:
3461980036R03 - NRC Website

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8 60 61 DOCKET NUMBER 68 b9 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h l(NP-33-80-41) On 4/7/80 at 1515 hours0.0175 days <br />0.421 hours <br />0.0025 weeks <br />5.764575e-4 months <br />, the Reactor Protection System (RPS) initiated a j o 2 All four channels tripped as designed. However, Chan-l lhigh flux trip of the reactor.

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It did l g o g,, lnel 2's trip module only reflected trip signals from 3 of the 4 RPS channels.

l o l s l lnot see a signal f rom RPS Channel 3.

Channel 2 was declared inoperable, and the statiqn l o is i lenteced the action statement of T.S. 3.3.1.1.

At 1640 hours0.019 days <br />0.456 hours <br />0.00271 weeks <br />6.2402e-4 months <br />, it was decided to remaing j o l 7 l l shutdown and begin the refueling outage. There was no danger to the public or station l

,o,g, l personnel. Only 2 of 4 channel trip signals are required to actuate a channel trip mo ule.

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43 44 47 33 36 31 40 CAUSE OESCRIPTION AND CORRECTIVE ACTIONS lThe cause of the malfunction of the one sympathy trip to Channel 2 was the component I

1 o l failure of trip relay K1 in the RPS Channel 2 trip module. Under MWO TC-321-80 the I

i i Contacts in the K1 relay did not I g l Channel 2 trip module was removed and bench tested.

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A new module was installed and successfully g l tested. The channel was returned to service at 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br /> on 4/8/80.

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A f a TOLEDO EDIS014 COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-80-41 DATE OF EVENT: April 7, 1980 FACILITY:

Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE:

Reactor Protection System (RPS) Channel 2 Trip Module Logic Malfunction Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MWT) = 2023, and Load (Gross MUE) = 672.

Description of Occurrence: On April 7, 1980 at about 1515 hours0.0175 days <br />0.421 hours <br />0.0025 weeks <br />5.764575e-4 months <br />, the RPS initiated a high flux trip of the reactor.

The trip was caused by work on a feedwater heater which affected condenser vacuum.

All four RPS trip modules tripped their respective control rod drive (CRD) trip breakers shutting down the reactor.

However, RPS Channel It 2's trip module only reflected trip signals from three of the four RPS channels.

did not reflect the trip signal from RPS Channel 3.

The station had entered the action statement of Technical Specification 3.3.1.1 which requires all four channels of RPS high flux trip to be operable in Modes 1 and 2.

Following the reactor trip the station was in Mode 3.

At 1640 hours0.019 days <br />0.456 hours <br />0.00271 weeks <br />6.2402e-4 months <br /> on April 7, it was decided to remain shutdown and begin the refueling outage, thus removing the station from the action statement requirements.

Designation of Apparent Cause of Occurrence: The apparent cause of this occurrence was component failure of trip relay K1 in the RPS Channel 2 trip module which I

de-energizes upon receipt of a trip signal from RPS Channel 3.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel.

RPS Channel 2 tripped its associated CRD trip breaker as designed since only two out of four RPS channel trip signals are requried to trip the channel.

Corrective Action

RPS Channel 2's trip module was removed under Maintenance Work Order IC-321-80 and bench tested.

Relay K1 was found'to be faulty in that its contacts J

1 did not always make when the relay de-energized. A new trip module was bench tested and installed in RPS Channel 2.

ST 5030.12, RPS Trip Module Logic Surveillance Test was performed on Channel 2 and the channel returned to service at 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br /> on April 8, 1980.

Failure Data: There have been no previous failures of RPS trip modules.

LER #80-036 L

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