ML19269C595

RO NP-09-79-02:on 790104,svc Water Sys Header Outflow Radiation Monitor Re 8432 Found Inoperable.Caused by Design Error Resulting in Component Deficiency.Flow Switch on Re 8432 Replaced & Facility Change Request Prepared

ML19269C595
Person / Time
Site:	Davis Besse
Issue date:	02/01/1979
From:	TOLEDO EDISON CO.
To:
Shared Package
ML19269C592	List: ML19269C591 ML19269C595
References
NUDOCS 7902060193
Download: ML19269C595 (1)

Text

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TOLEDO ED150N COMPANY .

hlf ~ ~ DAVIS-3 ESSE NUCLEAR POWER STATION UNIT ONE REPORTA3LE OCCURRENCE NP-09-79-02 ,

DATE OF EVE';T: January 4, 1979 FACILITY: Davis-Besse Unit 1 l t

i IDENTIFICATION OF OCCURRENCE: RE 8432, Service Water System Header Outflow Radia- l tion Monitor, was inoperable i 6

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i Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MNT) = 2734, and Load (Gross MW'E) = 912.

i Description of Occurrence: /.t 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on January 4, 1979 during performance of  !

ST 5032.01, " Monthly functional Test of the Radiation Monitoring System", it was ,

discovered that RE S432 had a low flow light. The monitor was thus inoperable. The unit was not in ccepliance with Environmental Technical Specification (ETS) Table '

2.4-3, uhich requires the operability of one continuous Service Water System monitor.

No Action Statement was applicable.

Designation of Accarent Cause of Occurrence: The apparent cause of the occurrence is component deficiency due to design error. There is not enough pressure differential to maintain correct sarple flow in all modes of operation of the Service Water System.

The flow switch tends to stick, and will not operate when there is insufficient flow to keep it flushed cut.

Analysis of occurrence: There was no danger to the health and safety of the public or to unit personnel. RE 1412 and RE 1413 in Component Cooling Lines 1 and 2, res-I pectively, are upstream frca RE 5432 and would indicate activity if any were present.

RE 1412 and RE 1413, as well as weekly grab samples, have never indicated any leaks.

Corrective Action: On January 4, 1979, the flow switch on RE 8432 was replaced and ST 5032.02, " Radiation Mcnitoring System Channel Calibration" was completed.

ST 5032.01 was then resc:ed, but the RE was again found to be inoperable due to low flow conditions. The RE remains inoperable as of January 29, 1979. Implementation of Facility Change Request 78-503 is expected to resolve this problem. Facility Change Request 78-503 requests either the addition of a sample pump to attain correct flow through the RE, er reroute the sample outflew to a floor drain with a regulating valve.

Failure Data: This is a repetitive occurrence. There has been one previous report on the inoperability of RE 8432, Licensee Event Report NP-09-78-01.

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