ML20049A861

LER 81-051/03L-0:on 810820 & 29,borated Water Storage Tank Channel 3 Failed High.Caused by Faulty Amplifier Board. Board Replaced

ML20049A861
Person / Time
Site:	Davis Besse
Issue date:	09/18/1981
From:	Isley T TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20049A854	List: ML20049A851 ML20049A861
References
LER-81-051-03L, LER-81-51-3L, NUDOCS 8110020348
Download: ML20049A861 (3)

Text

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55"* LICENSEE EVENT REPORT t

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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EVENT OESCRIPTION AND PROB ABLE CONSEQUENCES h '

Q l(NP-33-81-62) Borated Water Storage Tank (BWST) Channel 3 level failed high on 8/20/811 i o 3 land again on 8/29/81. The unit entered the action statement of Technical Specificatiori l l

I t ITTTlI 3.3.2.1 on 8/20/81 and on 8/29/81. Power operation may proceed when the channel is

.I ITTTl Iplaced in a tripped condition, and the other three charnels are operable. There was l loisl lno danger to the health and safety of the public or station personnel. There were no l i I

l j g l unit power reductions. _

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42 lAl@ l F l 1 l 8 l 047 l@ i 43 44 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h i O lThe cause of the occurrence was a component failure. A faulty amplifier board war l I

3 i ldetermined to have caused the indication to fail high. The board was replaced under I

, 7 l Maintenance Work Order IC-517-81, and the transmitter was declared onerable on I

i 3 l September 12, 1981 at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />.

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NAME OF PREPARER i

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-81-62 DATE OF EVENTS: August 20, 1981 and August 29, 1981 EACILITY: Davis-Besse Unit 1.

IDENTIFICATION OF OCCURRENCE:

Failure of Borsted Water Storage Tank (EWST) Level Indication, Channel 3 fonditions Prior to Occurrence: The unit was in Mode 1 with Power (MRT) = 2759 ctd Load (Gross MWE) = 907. .

Description of Occurrence: On August 20, 1981 at 1215 hours0.0141 days <br />0.338 hours <br />0.00201 weeks <br />4.623075e-4 months <br /> and again on August 29, 1981 at 0129 hours0.00149 days <br />0.0358 hours <br />2.132936e-4 weeks <br />4.90845e-5 months <br />, Channet 3 BWST level failed high. In both cases, indicat ion re-turned to normal beforu .ny troubleshooting could be done. After the first failure, BWST Channel 3 level ~~ .eclared inoperable placing the unit in the action statement of Technical Specifica clon 3.3.2.1, and the BWST level low-low bistable was tripped.

A string check was thet. oerformed per Surveillance Test ST 5031.05 proving the level atring was operating cor;ectly. During a walkdown of the signal cable on August 21, 1981, an area of welding was found near the signal cable. Since no problem was found by the string check, BWST level to Channel 3 was declared operable on August 21, 1981, removing the unit from the action statement.

When the second failure cecurred on August 29, 1981, no evidence of welding could be found, and the BWST Channel 3 level was again declared inoperable, placing the unit in the action statement of Technical Specification 3.3.2.1. There were no unit power reductions.

Designation of Apparent Cause of Occurrence: The cause of the occurrence was a com-ponent failure. Initially, the cause of the spike was believed to be due'to an in-l duced current from the welding cables. However, the second occurrence of the spike

on August 19, 1981 occurred on the absence of any welding. Maintenance Work Order l IC-570-81 was issued to tr.ubleshoot BWST Channel 3 level. The results of the test-l ing indicated an intermittent failure in the amplifier board.

Analysis of Occurrence: There was no danger to the health and safety of the public cr to station personnel. The three remaining BWST levels were operable during the

[ BWST Channel 3 level failures.

Corrective Action: The amplifier card was replaced in the level transmitter under laintenance Work Order IC-570-81, and a string check perforned per Surveillance Test ST 5031.05. The transmitter was declared operable on September 12, 1981 at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, removing the station from the action statement of Technical Specification

! 3.3.2.1.

LER #81-051 l

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)i IOLEDO EDISON COMPANY f

DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE -- {

SUPPLEMENTAL INFORMATION FOR LER NP-33-81-62 PAGE 2 ,

Failure Data: There have been no previous occurrences of BWST level failure due to 4, a bad amplifier board.

I LER #81-051 ,

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