05000346/LER-1978-023-03, /03L-0:on 780224,temp Indication for Reactor Protection Sys Channel 2 Spiked Tripping Channel & Shut Down Reactor.Caused by Faulty Connector Due to Dirt on Contacts. Channel 2 Temp String Modules Removed & Connectors Cleaned

/03L-0:on 780224,temp Indication for Reactor Protection Sys Channel 2 Spiked Tripping Channel & Shut Down Reactor.Caused by Faulty Connector Due to Dirt on Contacts. Channel 2 Temp String Modules Removed & Connectors Cleaned

ML19329B866
Person / Time
Site:	Davis Besse
Issue date:	03/21/1978
From:	Kovach S TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19329B803	List: 05000346/LER-1978-023, Forwards LER 78-023/03L-0 05000346/LER-1978-023-03, /03L-0:on 780224,temp Indication for Reactor Protection Sys Channel 2 Spiked Tripping Channel & Shut Down Reactor.Caused by Faulty Connector Due to Dirt on Contacts. Channel 2 Temp String Modules Removed & Connectors Cleaned
References
LER-78-023-03L, LER-78-23-3L, NUDOCS 8002060873
Download: ML19329B866 (3)

LER-1978-023, /03L-0:on 780224,temp Indication for Reactor Protection Sys Channel 2 Spiked Tripping Channel & Shut Down Reactor.Caused by Faulty Connector Due to Dirt on Contacts. Channel 2 Temp String Modules Removed & Connectors Cleaned

Event date:
Report date:
3461978023R03 - NRC Website

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I O I 2 I l On 2/24/78 at 0554 hours0.00641 days <br />0.154 hours <br />9.160053e-4 weeks <br />2.10797e-4 months <br />, Reactor Protection System (RPS) Channel 2 high tennerature Io ial I indication " spiked", 4-ediately tripping the channel. The channel was declared in-l J

l operable placing the unit in Action Statement 3 of Tech Spec 3.3.1.1, which recuires [O ;4 l l o q s ; l reactor coolant hig'a te=perature indication in Modes 1 and 2.

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IO t6 l l Reactor Co61 ant Sys tem high tecoerature. Te=cerature indication for RPS Channel 2 l

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i O I e l I channel and shutdown the reactor.

(NF-33-78-28).

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/ 33 34 35 36 37 40 41 42 43 44 47 CAUSE OESCRIPTION ANO CORRECTIVE ACTIONS i,;o;lThe reactor trip resulting from the trip of RPS Channel 2 re=oved the unit from l

,,,,,l Action 3 of Technical Specification 3.3.1.1.

The apparent cause is believed to have

been a faulty connector at the linear bridge module due to dirt on its contacts. All l

RPS Channel 2 te=perature string modules were recoved and the connectors cleaned.

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TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION g

SUPPLEMENTAL INFORMATION FOR LER NP-33-78-28 tG DATE OF EVENT:

February 24, 1978 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Reactor Protection System (RPS) Channel 2 high temperature trip and resultant reactor trip.

The unit was in Mode 1, with Power (MWT) = 2058 Conditions Prior to Occurrence:

and Load (MWE) = 720.

Description of Occurrence: On February 24,1978 at 0554 hours0.00641 days <br />0.154 hours <br />9.160053e-4 weeks <br />2.10797e-4 months <br />, RPS Channel 2 high temperature indication " spiked" immediately tripping the channel and the reactor.

RPS Channel 3 had tripped on February 23,1978 (Licensee Event Report NP-33-78-24).

Since the Technical Specification requires the channel to be in the " tripped" mode rather than the " bypass" mode, when Channel 2 tripped, the "tvo out of four" logic was satisfied and the reactor was trippe.d by the RPS.

The inoperable channel placed the unit in Action Statement 3 of Technical Specification 3.3.1.1, which requires reactor coolant high temperature instrumentation to be operable in Modes h1 and 2.

This Action Statement requires that the ' inoperable channel be placed in

/ the " tripped" condition within one hour. RPS Channel 2 was tripped immediately by the spike.

Designation of Anparent Cause of Occurrence:

The cause of. this occurrence is believed to have originated at a connector at the linear bridge =odule.

Instru-ment and Control personnel found dirt on a connec1!or at this module.

Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. There was no actual Reactor Coolant Syste= high temperature.

Temperature indication for RPS Channel 2 rose above the high limit for only a few moments (" spiked"), which tr1pped the channel and shut down the reactor.

l

Corrective Action

All RPS Channel 2 te=perature string modules were removed, and all connectors cleaned under Maintenance Work Order I&C 218-78. After the appli-cable sections of Survel.' lance Test ST 5030.02, "EPS Monthly Check" were perfor=ed, Channel 2 was returned to operable status on February 25, 1978.

Channel 3 was restored to operable statu: on February 26, 1978.

The unit was re=oved from Action State =ent 3 of Technical Specification 3.3.1.1 i==ediately after the RFS Chtnnel 2 trip and resultant reactor trip. The trip placed the unit in Mode 3.

• 'he Technical Specification applies only while in Modes 1 or 2.

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LER B78-023 e

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TOLEDO EDISON COMPMW DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NP-33-78-28

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Failure Data: There have been no previously reporcable RPS Channel 2 high tempera-ture trips.

LER #78-023 O

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