ML20028C181

LER 82-167/03L-0:on 821201,drywell Oxygen Monitoring Sys Failure Alarm Sounded in Control Room.Caused by Low Calibr Gas Bottle Pressure,Faulty Analyzing Cell & Defective Flow Regulator.Calibr Gas Bottle & Faulty Parts Replaced

ML20028C181
Person / Time
Site:	LaSalle
Issue date:	12/30/1982
From:	Dus R COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20028C169	List: ML20028C168 ML20028C181
References
LER-82-167-03L, LER-82-167-3L, NUDOCS 8301070164
Download: ML20028C181 (2)

Text

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h

,2i l Tech Spec 3.3.7.5. requires the drywell oxygen monitoring channels to be operable l g

during conditions 1&2. On 12/1/82 the system failure alarm came up in the control  ;

3,3, 7 ; ,, , l room which resulted from a local low cal gas pressure alarm. Also, the Div II post j 3; ;

LOCA cxygen channel began reading erratically. The Div II channel was subsequently l declared inoperable. At the time, LSCS was at 1474 MWT and 450 MWE. The drywell  ;

0 l6 ] I was not inerted. The Div I oxygen channel remained fully operable at all times. [

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43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h io j l System failure alarms came up as a result of low calibration cas bottle pressure. I l

j.jl Pres'ently these bottles are not monitored for level. The erratic readines resulted I

; from a faulty analyzing cell. It is also suspected that the flow remil arnr uns l l

,3 g l defective. The calibration gas bottle was replaced and tanks level will now be l g,,; monitored on a routine basis. Faulty parts were replaced and calibration was performes, 80 a 9

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• I. LER NUMBER: 82-167/03L-0 II. LASALLE COUNTY STATION: Unit 1 III. DOCKET NUMBER: 050-373 IV. EVENT DESCRIPTION:

Technks.al Specification 3.3.7.5 requires the drywell oxygen monitoring channels to be operable during conditions 1&2. On 12/1/82 the system failure alarm came up in the Control Room which resulted from a local low cal gas pressure alarm. Also, the Div II post LOCA oxygen channel began reading erratically in a manner similar to a previous occurrence described in LER #82-148/03L-0 and 82-139/03L-Q,The Div II channel was subsequently declared inoperable.

V. PROBABLE CONSEQUENCES:

At the time of the occurrence, LSCS was at 1474 MWT and 450 MWE. The drywell was not inerted with nitrogen since inerting is not required for the present phase of the startup test program (Re: special test l cxemption 10.3.5) the Div I oxygen channel remained fully operable 1 at all times. Safe operation of the plant was maintained.

VI. CAUSE:

The system failure alarms came up as a result of low calibration gas i bottle pressure. Presently these bottles are not routinely monitored for replacement on low level.

The erratic oxygen reading resulted from a faulty analyzing cell which failed to accurately measure the oxygen concentration in the sample gas. It is also suspected that the sample flow regulator was defective thereby disrupting the flow metering of the sample and reagent gas flows through the analyzing cell. The combined effects resulted in false indication in the control room.

VII. CORRECTIVE ACTION:

Work Request #L20834 was written to troubleshoot and repair the system.

Immediate action was taken to clear the alarms by replacing the cal-ibration gas bottle. The calibration gas and reagent gas tanks will now be monitored under a general surveillance on a monthly basis to j ensure that proper tank icvels are maintained.  ;

1 The faulty analyzing cell and flow regulator was replaced. The instru- l ment was recalibrated in accordance with LIS-PC-07. The Div II post LOCA oxygen channel was declared operable on 12/1/82. l l

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l Prepared by: R. S. Dus