ML19259C138

LER 79-012/01T-0 on 790522:during Rise to 30% Power,Two of Four Linear Power Range Channels Found to Be Inoperable. Open Connections Found Between Detector Cables & Field Wiring.Caused by Connector Pins Pushed Into Connector

ML19259C138
Person / Time
Site:	Millstone
Issue date:	06/05/1979
From:	Stratman R NORTHEAST UTILITIES
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19259C132	List: ML19259C131 ML19259C138
References
LER-79-012-01T, LER-79-12-1T, NUDOCS 7906120401
Download: ML19259C138 (2)

Text

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ATTACHt1ENT LER 79-12/lT-0 MILLSTONE UNIT 2 DOCKET UO. 50336 EVENT DESCRIPTI0fl During power ascension to 30 percent following a shutdown for refueling, two of four linear power range channels were noted to be i noperable. The power ascension was halted and channel D was placed in the " bypass" condition and channel A was placed in the

' tripped" condition. The facility was operat2d in accordance with the Action Statement of Section 3.0.3 of the Technical Specifications and an investigation into the cause of the failures was conducted.

Open connections were found between the channel A and D detector cables and the field wiring. The connections were repaired and the channels were returned to service. The channels were inoperable for approximately 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

CAUSE DESCRIPTION The open connection in the connectors between the channel A and D linear power range detector cables and the field wiring was the resu't of the center pin on the high voltage connector being pushed into the connector body during reassenbly following detector replacement during the refuel outage.

Detector operability cannot be verified without neutron flux from power range operation.

The connectors were repaired and the channels were restored to service. The connectors are Amphenol Triaxial connectors, part number 53175.

The consequences of this occurrence were minimized by the placing of one channel in bypass and the other channel in trip, resulting in one out of two trip logic for variable high power, thermal margin / low pressure and local power density. It should also be noted that the protection system utilizes an auctioneered highest value of nuclear or thennal power. Hence, a trip signal from thennal power was available in the affected channels.

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' "E Z Ltj@l.n_I c in lo in iti ,I c l@l _o I s 12'l217 Io l@LO1_al 60 01 DOCKLT NUMDER C8 09 EVENT O ATE 74 75 ni nl 7J_9JG RE PORT DAT E EO EVENT DESCn!PTION AND PROBAULE CONSEOUCNCES O'o yl During power ascension to 30 percent following a shutdown for refueling two of four ,

3 g linear power range channels were noted to be inoperabic. The power ascension was ,

, , y halted and channel D was placed in bypass and Chtnnel A in the tripped condition. The; s  ; facility was operated in accordance with the Action Statement of Technical Specificatiop

, y  ; 3.0.3. Open connections were found in the connectors between the detector cables and ,

7 ; the field wiring. lThe connections were repaired and t'he channels returned to service;.

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3 o l The cause of the open in the connectors between the detector cables and the field ,

, 3 g wiring was the conductor center pins which were 'found to be pushed into the connector  ;

(Amphenol Triaxia'1 connector - P/ft 53175). The connectors were repaired and both ,

, 3  ; channels restored 'to service. i i 4 1 1 8 9 80 STA S  % POWER OTHERSTATUS IS Y DISCOVERY DESCRIPTION i 5

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NAME OF PREPAHEH R. A. Stratman ruoNE:

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