ML20064E328

/03L-0 on 781014:during Surveillance Test of Main Steam Isolution Valves,V2-86C Closed in 2.6 Seconds Rather than 3-5 Seconds Req in Tech Spec 4.7.D.1.a.1.Caused by Closing Speed Control Valve Coming Loose from Actuator

ML20064E328
Person / Time
Site:	Vermont Yankee
Issue date:	11/13/1978
From:	Conway W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20064E326	List: ML20064E323 ML20064E328
References
LER-78-032-03L, LER-78-32-3L, NUDOCS 7811160130
Download: ML20064E328 (2)

Text

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. LICENSEE EVENT REPORT LER 78-32/3L r.

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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' VTVYS1 f 05000271 LER 78-32/3L EVENT DESCRIPTION AND PROBABLE CONSEOUENCES During routine surveillance testing of the Main Steam Isolation Valves, V2-86C closed in 2.6 seconds. Technical Specification 4.7.D.1.a.1

. requires _that_ the Main Steam Isolation Valves close fully in 3 to 5 seconds. V2-80C, the second isolation valve in the "C" Main Steam Line, was immediately closed and remained closed until V2-86C was repaired and made operable. V2-86C remained inoperable for approximately three days following the discovery. The three second minimum closure time is sig-nificant 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. There have been no previously reported occur-rences of this type.

! CAUSE DESCRIPTION AND CORRECTIVE ACTIONS The cause of this occurrence is attributed to the closing speed con-trol valve becoming loose from the actuator resulting in a slightly fast closure time. The failed speed control valve was replaced and all other valves were inspected and found to be satisfactory. V2-86C was manufac-tured by Rockwell, Model 1612 JMMY Flice Flow Stop Valve.

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