ML19289C421

LER 78-035/03L-0 on 781210:indicated Torus Water Level Rose Too Fast.Indication Was False Due to Loss of Water in the Reference Leg of the Torus Level Transmitters, LT-16-19-38A/B

ML19289C421
Person / Time
Site:	Vermont Yankee
Issue date:	01/08/1979
From:	Conway W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19289C419	List: ML19289C418 ML19289C421
References
LER-78-035-03L, LER-78-35-3L, NUDOCS 7901120159
Download: ML19289C421 (2)

Text

NRC FOR,M 366 U. S. NUCLE AR REGULATORY COMMISSION

• VI ' LICENSEE EVENT REPORT LER 78-35/3L -

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• 05000271 LER78-35/3L EVENT DESCRIPrION AND PROBABLE CONSEQUENCES During normt1 plant operations, it was observed that the indicated torus water level was increasing at a f aster than normal rate. While in-vestigations into'.the abnormal level increase were in progress, approxi-mately 3,000 cubic feet of water was transferred to Radwaste. This was s

done to prevent exiteeding the Order for Modification specified maximum torus volume of 70,000 cubic feet. The investigation subsequently re-vealed that the corison reference leg to the torus level transmitters, LT-16-19-38A/B was n'at full. This canned the level indicators to show a higher than actual 1evel. Upon refilling the reference leg, the actual 1

level indicated a vol4.ine of only 65,200 cubic feet. Technical Specifi-cation Section 3.7.A.1,.e requires a minimum volume of 68,000 cubic feet.

Preparations for an orlierly reactor shutdown were initiated as well as efforts to refill the torus to the required volume. The torus was re-stored to its required irolume approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> af ter the discovery.

Since the volume was requced to within a few percentage points of the required volume and for gnly a short time period, the potential conse-quences to the health and, safety of the pttblic were minimal. There were no previously reported sitsilar occurrences.

CAUSE DESCRIPTION AND CORRE'CTIVE ACTION The cause of this occurkence is attributed to loss of water in the reference leg of the torus level transmitters. This caused an apparent level that was higher than the actual level. The reason the reference leg decreased has not been deiermined. The reference leg,has been moni-tored for the last few weeks to verify that there is no significant change in icvel during normal station operation. This event is consid-ered an isolated incident and no further corrective action is planned.

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