05000271/LER-1981-001-03, /03L-0:on 810101,MSIV 80B & 86A Closing Times Exceeded Tech Spec.Caused by Improper Adjustment of Hydraulic Dash Pot Closure Time Adjustment Mechanism in B & Broken Spring in Mechanism A.Pot Adjusted & Spring Replaced

/03L-0:on 810101,MSIV 80B & 86A Closing Times Exceeded Tech Spec.Caused by Improper Adjustment of Hydraulic Dash Pot Closure Time Adjustment Mechanism in B & Broken Spring in Mechanism A.Pot Adjusted & Spring Replaced

ML19345E696
Person / Time
Site:	Vermont Yankee File:NorthStar Vermont Yankee icon.png
Issue date:	01/30/1981
From:	Murphy W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19345E695	List: 05000271/LER-1981-001, Forwards LER 81-001/03L-0 05000271/LER-1981-001-03, /03L-0:on 810101,MSIV 80B & 86A Closing Times Exceeded Tech Spec.Caused by Improper Adjustment of Hydraulic Dash Pot Closure Time Adjustment Mechanism in B & Broken Spring in Mechanism A.Pot Adjusted & Spring Replaced
References
LER-81-001-03L, LER-81-1-3L, NUDOCS 8102050564
Download: ML19345E696 (2)

LER-1981-001, /03L-0:on 810101,MSIV 80B & 86A Closing Times Exceeded Tech Spec.Caused by Improper Adjustment of Hydraulic Dash Pot Closure Time Adjustment Mechanism in B & Broken Spring in Mechanism A.Pot Adjusted & Spring Replaced

Event date:
Report date:
2711981001R03 - NRC Website

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EVENT DESCRIPTION AND PLOBABLE CONSEQUENCES

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During routine surveillance testing at 38% reactor power, MSIV 80 B and MSIV 86 A were found to close in 5.5 and 5.3 seconds respectively, which exceeds the Tech. Spec. limit of 5 seconds. As required by Tech.

Spec. Section 3.7.D.2, MSIV 80 A and MSIV 86 B were closed.

Additionally, while testing MSIV 80 C, relay SA-K 3F failed to de-energize-due to a failed limit switch in the closed position on >$IV 80 C.

i Vermont Yankee incorrectly reported this occurrence a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> reportable occurrence (LER 81/01/IP).

Further investigation has determined that 4 instrument channels per trip system were operable as required by Tech.

i Spec. Table 3.1.1 since closure of MSIV 86 C did cause relay 5A-K3F to operate. RPS Limit swite'es on MSIV 80 C and MSIV 86 C'are redundant and it was determined that this instrument channel was operable bue degraded. If a Group 1 isolation signal had occurred, a reactor scram would have resulted as required.

Since the second isolation valve in main steam lines A, B and C was operable as required by Tech. Spec., there were no potential consequences

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to the health and safety of the general public.. Similar slow MSIV closure times were reported in LER 79-29 and LER 78-32.-

CAUSE DESCRIPTION AND CORRECTIVE ACTION The cause of MSIV 80 B slow closure time was due to improper adjustment j

of the hydraulic dash pot closure time adjustment mechanism.. The valve actuator had been rebuilt and preventative maintenance had been performed during the annual refueling outage. The hydraulic dash. pot had been adjusted with the valve in the cold condition. Valve closure time was within Tech.

Spec. req ~direments in the cold condition but changed slightly in the hot condition. Readjustment of the hydraulic dash pot returned MSIV 80.B to the' required-Tech. Spec. closing. time.

The cauce of MSIV 86 A slow closure time was determined to be due to a i

broken spring in the hydraulic dash pot closure time adjustment mechanism (a Colorflow Control, 3/8 Range, manufactured by Manatol of Elyria, Ohio).

i The broken spring was replaced,l the hydraulic dash pot was reassembled and -

adjusted and MSIV 86 A was subsequently retim'ed and determined to close s

4 within the required Tech. Spec. closure time.

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