ML19210E368

Updated LER 79-013/03X-1:on 790525,periodic Check of Control Room Chlorine Detection Sys Revealed Inoperable Detectors. Caused by Low Drip Rates of Detector Solution Onto Sensor Assembly.Clogged Dispeners Cleaned

ML19210E368
Person / Time
Site:	Millstone
Issue date:	11/29/1979
From:	Bates R NORTHEAST UTILITIES
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19210E366	List: ML19210E365 ML19210E368
References
LER-79-013-03X, LER-79-13-3X, NUDOCS 7912040413
Download: ML19210E368 (2)

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EVENT DESCRIPTION AND PROBAfiLE CONSEGUENCES h Io l2l l Following a periodic check of the control room chlorine detection system: both I I

lO13l l detectors were declared inoperable due to having low drip rates in the sensor o 4 l assembly. The control room emergency ventilation system was immediately placed 'l

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[o lT] l in the recirculation mode in accordance with technical specification Section 3.3.3.6, I o o l Action Statement b. Following sensor cleaning, the detectors were returned to service f

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CAUSE DESCnlPTioN AND COnRECTIVE ACT!oNS h i Oj lThe chlorine detectors were declared inoperable due to low drip rates of detector l li li I solution onto the sensor assembly. Clogoed dispensers were cleaned restoring I

[, i 2 l l proper drip rate. Following a second occurrence on 11/1/79, clogged dispensers l 1,l3j lwere cleaned and adjusted. The frequency of drip rate checks has been increased l

[i14i l from dails to once per shift with specified criteria for correction. l 80 7 8 9 ST S  % POWER OTHER STATUS blSCOV RY DISCOVERY DESCRIPTION

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Attachment liillstone Unit 2 LER 79-13/3X-1 Docket tio. 50-336 Event Dc:,cription On 5/25/79, following a periodic check of the control room chlorine detection system, both detectors were declared inoperable due to having low drip rates in the sensor assembly. The control room emergency ventilation system was immediately placed in the recirculation mode in accordance with Technical Specifications Section 3.3.3.6, Action State-ment b. Following sensor cleaning, the detectors were returned tc service with daily drip rate checks made.

On 11/1/79, the control room chlorine detectors experienced a similar decrease in sensor drip rate. The detectors were declared inoperable and the sensors were cleaned and adjusted to prevent further clogging.

The detectors were then returned to service and the control room ventila-tion restored to normal.

_Cause Description The initial cause of the low drip rate was a clogged dispenser in the sensor assembly which was cleaned restoring proper drip rate. Following the second occurrence on 11/1/79, the dispenser was cleaned and adjusted to prevent further clogging. In addition, the frequency of sensor drip rate checks has been increased to once per shift, and specified limits added for investigation and corrective action.

1473 355

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