ML20050B394

LER 82-005/03L-0:on 820223,uninterruptible Ac Electric Power Sys Tripped & Lost Power to Motor Control Ctr 89B, Rendering Sys Inoperable.Caused by Shorted Out Transient Suppression Capacitor Due to Aging.Capacitor Replaced

ML20050B394
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	03/25/1982
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20050B384	List: ML20050B383 ML20050B394
References
LER-82-005-03L, LER-82-5-3L, VTYS1, NUDOCS 8204050282
Download: ML20050B394 (2)

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- LICENSEE EVENT REPORT LER 82-5/3L CONTROL BLOCK; l l l l l l l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) t e i O l ai 9l l V lLICENSEE 1

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l L }@l 0 ] 5 l 0 l 0 l0 l 2 l 7 l1 @l 0 l 2 l 2 l 3 l 8 l 2 l@l750 l 3 l 2 l 5 l 8 l280l@ 74 I d 60 61 DOCK ET NUVBER 68 69 EVENT DATE REPORT DATE EVENT DESCRIPTION AND PROBA8LE CONSEQUENCES h l o ;;; l With the plant at normal full power operation, Control Room personnel reported UPS B l yg,3, ;

tripped and lost power to MCC 89B. The Maintenance Department was immediately informed l

g y , y , and testing of the alternate system was commenced in accordance with Tech. Spec. ,

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,g g ,3.5.A.4. UPS B was declared inoperable and alternate action taken in accordance with  ;

,g g ; Tech. Spec., Section 3.10.B.4. Maintenance tie breakers for MCC 89B were closed. Thereg g were no adverse consequences to public health and safety as a result of this event. l A similar event was reported as LER 82-2/3L.  ;

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CAUSE DESCRIPTION AND CORRECTIVE ACTIONS 4

A transcient suppression capacitor (GE 86F231L, 2900 MF) shorted out causing UPS B to trip. The capacitor malfunctioned due to aging. All 16 capacitors in the transcient suppression circuit were replaced. Also, all 16 capacitors in the UPS A transcient suppression circuit were replaced as preventive maintenance. The system was operationally tested and placed back in service. The current PM program will be reviewed and ' modified as appropriate in view of the recent UPS failures.

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