ML19257D471

LER 80-002/03L-0:on 800103,during Surveillance Testing of HPCI Sys,Turbine Tripped & HPCI Steam Valves Were Isolated. Latter Caused by Spurious High Steam Flow.Cause of Turbine Trip Not Determined.Sys Tested Monthly

ML19257D471
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	02/01/1980
From:	Conway W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19257D467	List: ML19257D466 ML19257D471
References
LER-80-002-03L, LER-80-2-3L, NUDOCS 8002040449
Download: ML19257D471 (2)

Text

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LICENSEE EVENT REPORT LER 80-02/3L

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. . VTVYS1 05000271 LER 80-2/3L EVENT DESCRIPTION AND PROBABLE CONSE0UENCES During monthly operability surveillance testing of the HPCI System, the turbine tripped when initially started. Coincident with the turbine trip, the HPCI steam valves isolated and the high turbine exhaust pres-sure annunciator was observed. The HPCI isolation valves were reopened and the turbine started successfully. This immediate demonstration of HPCI operability precluded taking the action specified in Tech. Spec.

Section 3.5.E.2. Based on the above, the potential consequences to the health and safety of the public were minimal. There have been no pre-vious similar occurrences reported to the Commission.

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS The cause of the HPCI steam valve isolation was diagnosed as a spur-ious high steam flow, although the high steam line D/P annunciator was not observed to operate. The isolation signal is provided with a seal-in circuit so that a signal of very short duration can cause isolation with-out activating the annunciator. It is not known whether the turbine trip was caused by high exhaust pressure or the automatic isolation signal.

The high exhaust pressure switches, steam line D/P switches and turbine controller were checked and all components were found to be operable. In addition, surveillance testing of the annunciator for high steam line D/P was performed on January 14, 1980, which showed this annunciator to be operational. Although the root cause of this event could not be deter-mined, it is concluded that the trip was the result of a spurious signal of unknown origin. This system is tested monthly and all parameters will be carefully monitored during the next surveillance test.

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