ML20043E887

Proposed Tech Specs to Support Replacement of Uninterruptible Power Supply at Plant

ML20043E887
Person / Time
Site:	Vermont Yankee
Issue date:	06/07/1990
From:	VERMONT YANKEE NUCLEAR POWER CORP.
To:
Shared Package
ML20043E879	List: ML20043E878 ML20043E887
References
NUDOCS 9006130492
Download: ML20043E887 (1)

Text

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4 VYNPS -\

AUXILIARY ELECTRIC POWER SYSTEMS A. The objective of this Specification is to assure that adequate power will be available to operate the emergency safeguards equipment. Adequate power can be provided by any one of the following sources:

yy, either of the startup transformers, backfeed through the main transformer, the 4160 volt line from the gg Vecnon Hydroelectric Station or either of the two diesel generators. The backfeed through the main o- transformer and 4160 volt Vernon line are both delayed access off-site power sources. Backfeeding through-3G the main transformer can be accomplished by disconnecting the main generator from the main transformer and energizing the auxiliary transformer from the 345 kV switchyard through the main transformer. The time QO04 required to perform this disconnection is approximately six hours. The 4160 volt line from the Vernon 7"* Hydroelectric Station can be connected tc either of the two emergency buses within seconds by simple manual switching operation in the Main Control Room.

oo m8o Two 480 V Uninterruptible Power Systems supply power to the LPCIS valves via designated Motor Control gt[4 Centers. The 480 V Uninterruptible Power Systems are redundant and independent of any on-site power

- sources.

This Specification assures that at least two off-site and two on-site power sources, and both 480 V Uninterruptible Power Systems will be available before the reactor is taken beyond "just critical" testing. In addition to assuring power source availability, all of the associated switchgear must be operable as specified to assure that the emergency cooling equipment can be operated, if required, f rom the power sources.

Station service power is supplied to the station through either the unit auxiliary transformer or the startup transformers. In order to start up the station, at least one startup transformer is required to supply the station auxiliary load. After the unit is synchronized to the system, the unit auxiliary transformer carries the station auxiliary load, except for the station cooling tower loads which are always supplied by one of the startup transformers. The station cooling tower loads are not required to perform an engineered safety feature function in the event of an accident; therefore, an alternate source of power is not essential. Normally one startup transformer supplies 4160 volt Buses 1 and 3, and the other supplies Buses 2 and 4; however, the two startup transformers are designed with adequate capacity such that, should one become or be made inoperable, temporary connections can be made to supply the total station load (less the cooling towers) from the other startup transformer.

Amendment No. 58, Ill 178

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