ML19347C808

Ao:On 731227,during Quarterly Calibr Test of Main Steam Line High Radiation monitors,RN05A Log Count Rate Monitor Failed to Trip at Normal Setpoint of 1,000 Cps.Caused by Cold Soldered Connection in High Alarm Trip Section of Assembly

ML19347C808
Person / Time
Site:	Oyster Creek
Issue date:	01/09/1974
From:	Ross D JERSEY CENTRAL POWER & LIGHT CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8103040741
Download: ML19347C808 (2)

Text

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hersey Central Power & Light Company 4% 9 MADISON AVENUE AT PUNCH BOWL ROAD

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Mr. A. Giambusso

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Directorate of Licensing United States Atomic Energy Commission D,  %.g ,

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Dear Mr. Giambusso:

Subj ect: Oyster Creek Station -

Docket No. 50-219 Main Steam Line liigh Radiation :ionitor Failure ..

This letter serves to report the failure of main steam line high radiation monitor RN05A to trip at a level of 10 times backgrotmd during the quarterly calibration test. This event is considered to be an abnormal occurrence as defined in the Technical Specifications, para-graph 1.15A. Notification of this event, as required by the Technical Specifications, paragraph 6.6.2.a, was made to AEC Region 1, Directorate of Regulatory Operations, by telephone on Thursday, December 27, 1973, and by telecopier on Friday, December 28, 1973.

While conducting the quarterly calibration test of the main steam line high radiation monitors, it was observed that the RN05A log count rate monitor failed to trip at its normal set point of 1000 cgs.source, An attempt was made to determine the actual trip point by moving the Co s used to introduce the test signal, closer to the detector. The monitor would not trip regardless of the signal applied.

A half scram was introduced into the reactor protection system and the monitor was removed from service so that it could be bench-checked.

It was observed that the trip would actuate at a 1cvel of approximately 40,000 cps. It was further observed that subsequent trips occurred intermittently at 1000 cps and 40,000 cps levels on a random basis.

The faulty RN05A log count rate monitor assembly was replaced with a spare unit which, when tested, was also found to be defective. A half scram was introduced into the reactor protection system until the original monitor assembly could be repaired. Once the repaired unit was reinstalled, a successful surveillance test was performed. The other three in-service monitors were also satisfactorily tested.

7/0309'0 7 l w

e 0 a Mr. Giambusso January 9,1974 The cause of the intermittent failure was traced to a cold sold-ered connection in the high alarm / trip section of the monitor assembly.

The exact location of the failure was not determined but the portion of the circuit involved was narrowed down and after all soldered connections in this section were reworked, the problem disappeared.

Pertinent information concerning the monitor assembly is given below:

Equipment: RN05A Manufacturer: General Electric Company Drawing No.: 194X62961 Serial No.: S,478,616 The purpose of the main steam line high radiation monitoring system is to isolate and scram the reactor should gross fuel failures occur causing a sudden release of fission products. Since the other three monitors were proven operable, they would have performed the scram and isolation functions associated with a main steam line high radiation condition. Therefore, the' safety significance of this event was a loss of system redundancy.

Since the problem with the monitor trip circuit was found and satisfactorily repaired, corrective action other than continued surveillance is not planned. A review will be made of all of the surveillance procedures for the main steam line high radiation monitors to ensure that they are sufficient for detec+ing malfunctions in these units.

Enclosed are forty copies of this report.

Very truly yours, W8 VP W Donald A. Ress Manager, Nuclear Generating Stations es Enclosures cc: Mr. J. P. O'Reilly, Director Directorate of Regulatory Operations

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