ML19208A778

LER 79-020/03L-0:on 790815,during Surveillance Testing of Msiv,Inboard Valve V2-80A in Main Steam Line Closed Properly But Did Not Fully Reopen.Caused by Spring Plate Binding on Guide Shaft

ML19208A778
Person / Time
Site:	Vermont Yankee
Issue date:	09/13/1979
From:	Conway W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19208A765	List: ML19208A764 ML19208A778
References
LER-79-020-03L, LER-79-20-3L, NUDOCS 7909170455
Download: ML19208A778 (2)

Text

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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o 2 l o 3 l See attached sheet I 10 4 I o s 1 I O 6 l l o 7 I I O 8 l 80 7 8 9 SYSTEY CAUSE CAUSE C OY P. VALVE CUCE CODE SUBCODE COMPONENT CODE SUBCODE SUBCODE o 9 l C l D lh [E_jh l B lh 9 10 11 12 13 V A lL V l0 lP lh l D l@ l Z l h 18 19 20 7 8 SEQUENT; AL OCCUR RE NCE REPORT REVISION LE R RO EVENT YE AR REPOR T NO. CODE TYPE NO Ogg _ 21 7 l9 l 22 l-l 23 l0 l2 l0 l 24 26 l/l 27 l 0l 3[

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I VTVYS1 05000271 LER 79-20/3L EVENT DESCRIPTION AND PROBABLE CONSEQUENCES During routine surveillance testing of the MSIVs, inboard valve V2-80A in the "A" main steam line was successfully closed but when posi-tioned to open was found to be only partially open. This was verified by both the valves' position lights and main steam flow indication. The valve was then positioned to closed and was verified to have closed pro-perly by observing main steam flow indication. The valve position lights, however, indicated that the valve was still partially open. Maintenance personnel investigated the occurrence and observed that the actuator spring plate was binding on its guide rods.

The actuator is designed such that either air or spring force is capable of closing the valve. Tech. Spec. Section 3.7.D.1 requires that these valves be operable during reactor power operation. Although V2-80A was capable of closure pneumatically, the design bases of MSIVs requires that they be capable of operating on both air and spring force during re-actor operation. The plant was maintained as allowed by Tech. Spec. Sec-tion 3.7.D.2 when V2-86A the outboard MSIV in main steam line "A" was closed. This valve was maintained closed during the time V2-80A was de-clared inoperable. Based on the above, there were no adverse consequences to the health and safety of the public. A similar occurrence was reported to the Commission in R0 79-11/3L.

CAUSE DESCRIPTION AND PRORABLE CONSEOUENCES The cause of this occurrence is attributed to the spring plate binding on the guide shaf t(s). The surface of the guide shafts was smoothed. The valve was successfully stroked several times, verified op-erable and returned to service.

During the upcoming refueling outage, V2-80A's actuator will be dis-mantled and examined for wear. Guide rods and spring plate bushings will be inspected and repaireo as required. The guide rods and spring plates of all other MSIVs will be examined for wear and disassembled and repaired as necessary.

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