05000346/LER-1977-078-03, /03L-0:on 771011,during Functional Test,Reactor Protection Sys Channel 1 Accidentally de-energized.Caused by Error in Maint Work Order.Personnel Instructed

/03L-0:on 771011,during Functional Test,Reactor Protection Sys Channel 1 Accidentally de-energized.Caused by Error in Maint Work Order.Personnel Instructed

ML19329A830
Person / Time
Site:	Davis Besse
Issue date:	11/03/1977
From:	Hitchens D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19329A823	List: 05000346/LER-1977-078, Forwards LER 77-078/03L-0 05000346/LER-1977-078-03, /03L-0:on 771011,during Functional Test,Reactor Protection Sys Channel 1 Accidentally de-energized.Caused by Error in Maint Work Order.Personnel Instructed
References
LER-77-078-03L, LER-77-78-3L, NUDOCS 8001150723
Download: ML19329A830 (3)

LER-1977-078, /03L-0:on 771011,during Functional Test,Reactor Protection Sys Channel 1 Accidentally de-energized.Caused by Error in Maint Work Order.Personnel Instructed

Event date:
Report date:
3461977078R03 - NRC Website

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U.S. NUCLEAR REGULATORY COMMlWON m

NRC FORM 364 p.nl LICENSEE EVENT REPORT

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60 61 COCK ET NUMSER 6a 69 EVENT DATE 74 75 REPORT DATE 60 EVENT DESCRIPTION AND PRCSABLE CONSEQUENCES h I o 121 l At 1450 hours0.0168 days <br />0.403 hours <br />0.0024 weeks <br />5.51725e-4 months <br /> on October 11, 1977 while performina ST 5C30.12, " Channel Functional I

l Test of the Reactor Trip Module Logic and Control Rod Drive Trip Breakers", Reactor i

g o l3; ITTT1 1 Protection System (RPS) Channel 1 was accidentally de-energized. This de-energized i

I the power supply for Source Range Detector NI-2 placing the station in the Action I

Ioisl l o is 1 I Statement of Technical Soecification 3.3.'..l.

The redundant Source Ranga Detector.

1 [ot'n l NI-l was operable and in service.

(NP-33-77-78)

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DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION

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TOLEDO EDIS0rt COMPANY SUPPLEF"'NTAL INFORMATION FOR LER NP-33-77-78 i

DATE OF EVENT: October 11, 1977 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of Source Range Neutron Flux Detector NI-2 indication.

Conditions Prior to Occurrence: The plant was in !! ode 3, with Power (MWT) = 0, and Load (MWE) = 0.

Technical Specification 3.3.1.1 was applicable as the Cnntrol Rod Drive Trip Breakers were closed and the Control Rod Drive System was capable of rod withdrawal.

Decription of Occurrence: At 145C hours on October 11, 1977, while performing Surveillance Test, ST 3030.12, " Channel Functional Test of the Reactor Trip Module Logic and Control Rod DriveTrip Breakers", Reactor Protection System (RPS)

Channel 1 was accidentally de-energized. This de-energi=ed the po'sar supply for

/~rce Range Detector NI-2 placing the station in the Action Statement of Techni-l' Specific.ation 3.3.1.1.

The redundant Source Range Detector, NI-1, was opera-( ))and in service.

D:signation of Anoarent Cause of Occurrence: The cause of this occurrence was an Error in the Maintenance Work order (MWO) which provided the instructions for the Surveillance Test.

The linear bridge for RPS Channel 1, Reactor Coolant System (RCS) Temperature String had been returned to the vendor for rework. The RPS is such that whenever a module is missing the char tel trips.

With the linear bridge missing, the resistance input to the temperature signal converter is infinite causing the high temperature trip bistable to trip. The MWO instructed the Instrument and Control (ISC) Mechanic to jumper the pins which correaponded to the missing =odule interlock and the high temperature trip bistablas trip contacts. When the jumpers were placed, the power supply was thtrted to ground. This caused the system power supplies to trip on overcurrent, de-energizing the channel.

ThIse instructions on the MWO were in error.

It should have instructed the I&C M chanic to place the channel in Channel Bypass. This would have allowed the ptrformance of the Surveillance Test wf thout the installation of jumpers.

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

This thermal power level was maintained at less than 0-10 amps on the Intermediate Range Flux Instrumentation.

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4 TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLLMENTAL INFORMAIION FOR LER NP-33-77-78 PAGE 2

Corrective Action

The I&C Mechanic was instructed to remove the jumpers and Operations personad then re-energized the channel, in accordance with SP 1105.02, " Reactor Protection System and Nuclear Instrumentation Operating Procedure". At approximately 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on October 11, 1977, Source Range Detector NI-2 was re-energized which removed the station from the Action State-ment of Technical Specification 3.3.1.1.

Failure Data: No previous losses of Source Range Nuclear Instrumentat. ion were caused by maintenance instruction errors.

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