05000271/LER-1979-029-03, /03L-0:on 791104,during Surveillance Testing, MSIV-80 B & 86 C Closed in 2.5-s.Min Closure Time Is 3-s. Caused by Operator Failure to Recognize Potentially Degraded Condition of Msivs.Retimed within 3- to 5-s

/03L-0:on 791104,during Surveillance Testing, MSIV-80 B & 86 C Closed in 2.5-s.Min Closure Time Is 3-s. Caused by Operator Failure to Recognize Potentially Degraded Condition of Msivs.Retimed within 3- to 5-s

ML19262A999
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	12/04/1979
From:	Conway W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19262A984	List: 05000271/LER-1979-029, Forwards LER 79-029/03L-0 05000271/LER-1979-029-03, /03L-0:on 791104,during Surveillance Testing, MSIV-80 B & 86 C Closed in 2.5-s.Min Closure Time Is 3-s. Caused by Operator Failure to Recognize Potentially Degraded Condition of Msivs.Retimed within 3- to 5-s
References
LER-79-029-03L, LER-79-29-3L, NUDOCS 7912110402
Download: ML19262A999 (2)

LER-1979-029, /03L-0:on 791104,during Surveillance Testing, MSIV-80 B & 86 C Closed in 2.5-s.Min Closure Time Is 3-s. Caused by Operator Failure to Recognize Potentially Degraded Condition of Msivs.Retimed within 3- to 5-s

Event date:
Report date:
2711979029R03 - NRC Website

text

LICENSEE EVENT REPORT LER 79-29/3L CONTROL BLOCK:

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VTVYS1 05000271 LER 79-29/3L EVENT DESCRIPTION AND PROBABLE CONSEQUENCES During routine surveillance testing of the Main Steam Isolation Valves, MSIV-80 B and MSIV-86 C were recorded to close in 2.5 seconds.

Approximately two days later, during the Department Head review of the data, it was noted that the minimum required closure time is 3 seconds in accordance with Tech. Spec. Section 4.7.D.l.a.l.

The sacond isola-tion valve was operable in each of the potentially degraded lines. The three second minimum closure time is significant only if all four main steam lines were simultaneously isolated.

Based on the above, there were no potential consequences to the health and safety of the public.

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS The cause of the occurrence was the operators failure to immediately recognize the potentially degraded condition of the two Main Steam Isolation Valves. In accordance with Tech. Spec. Section 3.7.D.l.,

the seccnd valve in each of the degraded lines chould have been isolated until corrective action was taken or the valves were confirmed to be operable. Upon review of the surveillance data, a power reduction was commenced for a controlled isolation of the affected lines. At the same t ime, the MSIV's were retimed.

This retest proved that all the Main Steam Isolation Valve closure times were within the three to five second tand as required by the Tech. Specs. and therefore no adjustments were necessary.

Operators were reinstructed to more carefully review the appropriate acceptance criteria when evaluating the surveillance test results.

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