ML20094F445

RO MM-3-01:on 840622 & 25,moisture Sensors in Recirculation Sys Moisture Monitoring Sys Functioned Improperly.Cause Unknown.Drywell Sump Collection Sys Monitored Hourly Until Next Outage

ML20094F445
Person / Time
Site:	Peach Bottom
Issue date:	07/23/1984
From:	PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Murley T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
MM-3-01, MM-3-1, NUDOCS 8408100048
Download: ML20094F445 (3)

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PHILADELPHIA ELECTRIC COMPANY 23o1 MARKET STREET P.O. BOX 8699 PHILADELPHIA, PA.19101 1215)841 4000 July 23, 1984 Docket No. 50-278 Dr. Thomas E. Murley, Administrator Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406

SUBJECT:

Peach Bottom Atomic Power Station - Unit 3 Moisture Monitoring System

Dear Dr. Murley:

This letter is a report of moisture monitoring system inoperability in accordance with Philadelphia Electric Company's commitment to report moisture monitoring system problems and alarms unrelated to actual system leakage as stated in letter, J. S.

Kemper, PECo, to Dr. T. E. Murley, USNRC, dated September 15, 1983.

Reference:

Docket No. 50-278 Report Number: MM-3-01 Revision No.: 00 Event Date: June 22, 1984 Report Date: July 23, 1984 Facility: Peach Bottom Atomic Power Station RD #1, Box 208, Delta, PA 17314 ABSTRACT On June 22, 1984, with Unit 3 operating at 42% power, routine

- surveillance testing indicated a moisture sensor in the recirculation system moisture monitoring system was functioning improperly. On June 25, 1984, an additional sensor was found to be functioning improperly. Hourly monitoring of the drywell samp pump out rates is being performed until the sensors can be replaced or repaired during the next outage of sufficient duration to carry out the work.

8408100048 840723 PDR ADOCK 05000278PDR sl0 S pE 2a

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Dr. Thomas E. Murley July 23, 1984 Page 2 DESCRIPTION OF,THE EVENT On June 22, 1984, with Unit 3 operating at 42% power, routine sucveillance testing (ST 13.40, " Checkout of Moisture Monitoring System") to verify the operability of the recirculation system moisture monitoring system indicated that Point 23 had failed. Point 23 is installed on weld 2-AD-12 in the 28-inch recirculation pump discharge piping.

On June 25, 1984, with Unit 3 operating at 85% power, the moisture monitoring system display in the control room indicated a moisture alarm and a trouble alarm. Investigation determined that the alarms originated from Point 7. Point 7 is installed on weld 10-0-5 in the 20-inch residual' heat removal system suction pining. Remote testing of the sensor at Point 7 indicated that the moisture alarm and trouble alarm was triggered by the failure of the sensor.

Following the identification of the sensor failure of Point 7, the moisture monitoring system was removed from service.

CONSEQUENCEg,OF,THg_gVgNT After the system was removed from service, enhanced surveillance requirements (ST 13.41, " Hourly Drywell Leak Detection") were initiated and will be continued until an outage of sufficient duration to make the system operable. The purpose of ST 13.41 is to provide early warning of reactor coolant leakage via the drywell sump collection system when the moisture monitoring system is inoperable and reactor temperature is aoove 212 degre2s. These surveillance requirements ensure that drywell leakage rates do not exceed the' limits of Technical Specification 3.6.C.l. Therefore, the safety consequences of this event are considered minimal.

gAugg_gg_ Igg _gvgNI The cause of the event will be determined during the next unit outage of sufficient duration with the drywell deinerted.

CORRECTIVE ACTIONS Hourly monitoring of the drywell sump collection system in being performed until the next unit outage of sufficient duration with the drywell deinerted so that these sensors can be made operable. Additionally, the system is restored to operable status once per day to perform ST 13.40, " Checkout of u >

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Dr. Thomas E. Murley July 23, 1984 l Page 3 Moisture Monitoring System", as an additional surveillance i requirement on all but the two inoperable sensors.

f PREVIOUS SIMILAR OCCURRENCES i LER 2-83-26/3L, 3-83-16/3L, 3-81-21/3L, 3-83-24/3L letter: W. l T. Ullrich, PECo, to Dr. T. E. Murley, USNRC, dated March 5, "

1984, and letter: W. T. Ullrich, PECo, to Dr. T. E. Murley, ,

USNRC, dated March 23, 1984. '

i Very ly you a,

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endent Nuclear Services cc A. R. Blough, Site Inspector _

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