ML20064H174

/03L-0 on 780626:during Reactor Pwr Increase Noted That Local Critical Pwr Ratio in 4 Symmetrically Located Fuel Bundles Was Lower than Tech Spec Levels.Caused by Pwr Increasing Xenon Transient

ML20064H174
Person / Time
Site:	Vermont Yankee
Issue date:	07/24/1978
From:	Conway W VERMONT YANKEE NUCLEAR POWER CORP.
To:
Shared Package
ML20064H166	List: ML20064H164 ML20064H174
References
LER-78-017-03L, LER-78-17-3L, NUDOCS 7812180199
Download: ML20064H174 (2)

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VT"Y S1 05000271 LER 78-17/3L EVENT DESCRI? TION AND PR03A3LE CONSEOUINCES Reactor power was being increased within FCICMR :enstraints following a scheduled power reduction. Nuclear calculations at 1100 revealed that the local critical power ratio in four sysneerically located fuel bundles was lower than that required by Techni. cal Specification Section 3.11.C.

Updated calculations performed at 1614 indicated that the critical power ratio (CPE) was 0.022 below the Technical Specification value of 1.31.

Reactor power was then reduced by insarring control rods and calculations demonstrated that the actual CPR was restored to within the Technical Specification limit as a result of that action. There were no previously reported sM1ar occurrences.

CAUSE DESCRIPTION AND CORRECTIVE ACTION The cause of the occurrence is attributed to a power increasing

(- xenon transient. There were no control rods withdrawn or recirculation flow increases during the interval of the two critical power ratio cal-culations.

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