ML19274D124

LER 78-121/03L-0 on 781210:borated Water Storage Tank Level in Safety Features Actuation Sys Channel 3 Failed.Caused by Open Circuit in the Thermocouple for a Heat Trace Controller

ML19274D124
Person / Time
Site:	Davis Besse
Issue date:	01/05/1979
From:	Naylor R TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19274D121	List: ML19274D120 ML19274D124
References
LER-78-121-03L, LER-78-121-3L, NUDOCS 7901120178
Download: ML19274D124 (2)

Text

U. S. NUCLEAR REGULATORY COMMISSloN NRC FORM 36G (7 77)

LICENSEE EVENT REPORT l l l l l l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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f. VENT DFSCRIPT!ON AND PROBABLE CONSEQUENCES h __j o 2 l On 12/10/78, Borated Water Storage Tank level in Saf ety Features Actuation System

, j Channel 3 failed. The unit was placed in Action Statement 9 of Technical Specifica j g

, l tion 3.3.2.1, requiring the inoperable channel to be tripped within one hour with thel o

remaining units operable except as noted. The inoperable channel was tripped within 22 0 s I Repnirs were conducted. The channel was satisfactorily tested and placed j inutes.

(O [6 l g 7 in operation, and the unit was removed from the Action Statement. There was no l danger ta the health and safety of the pubJic or to unit personnel. (NP-33-78-142) l g g 60 C OY P. VALVE SYSTE M CAUSE CAUSE SUSC0DE COYPONENT CODE SUSCODE CODE COLE SUBCOCE O 9 8 9 lI!Bl@ 10 11 h l Alh lI lN l S lT l R lU lh lE lh M h 12 13 18 39 23 REVISION 7

SEQUENTI A L OCCURRENCE REPORT CODE TYPE No.

REPORT NO.

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lJ3A lgl34Z g l35Zl@ lZl@ 36 31 41 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l The apparent cause of this occurrence was an open circuit in the ther- ocouni a for

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[i_jzj l heat trace controller. The heai trace provides freeze protection for the level indi- !

A freezing condition subsequently occurred rendering the unit inoDern-1

,,;,y { cation system.

g,y3j l ble. The thermocouple was replaced and the circuit operationally tested and found J

to be satisfactory.

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TOLEDO EDISON CO:IPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-78-142 DATE OF EVENT: December 10, 1978 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Safety Features Actuation System (SFAS) Channel 3 Borated Water Storage Tank (BWST) Level Transmitter Inoperable Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MWT) = 1330, and Load (Gross MWE) = 412.

Description of Occurrence: On December 10, 1978, at 0547 hours0.00633 days <br />0.152 hours <br />9.044312e-4 weeks <br />2.081335e-4 months <br />, a high level fail alarm was received for the BWST level on SFAS Channel 3. This placed the unit in the Action Statement (9) of Technical Specification 3.3.2.1.b which requires the inope.rable functional unit be placed in the tripped condition within one hour.

BWST Channel 3 level transmitter was placed in the tripped condition at 0609 hours0.00705 days <br />0.169 hours <br />0.00101 weeks <br />2.317245e-4 months <br /> on December 10, 1978.

Designation of Apparent Cause of Occurrence: The apparent cause of this occurrence was an open circuit in the thermocouple for the local controller of the heat trace.

The heat trace provides freeze protection for the level indication system. The freezing condition which r.bsequently occurred resulted in the inoperability of SFAS Channel 3 BUST levex indication and the high level fail alarm.

Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. The remaining three SFAS BUST level channels were operating properly and would 1. ave transferred the decay heat and containment spray suction to the emergency sump if a loss of coolant accident had occurred.

Corrective Action: The thermocouple for the local controller was replaced under Maintenance Work Order (MWO) 78-2871 and circuit operation was checked and found to be satisfactory.

The transmitter sas returned to operability at 1455 hours0.0168 days <br />0.404 hours <br />0.00241 weeks <br />5.536275e-4 months <br /> on December 10, 1978.

Failure Data: There have been previously reported occurrences of freezing of the BWST level transmitters sensing lines but none due to temperature controller difficulties.

LER #78-121