ML19256B677

LER 79-016/03L-0 on 790717:redundant Containment Isolation Capability Not Available.Caused by Requirement to Disassemble Valve for Maint.Valve Cleaned,Reassembled,Tested & Returned to Svc

ML19256B677
Person / Time
Site:	Vermont Yankee
Issue date:	08/16/1979
From:	Conway W VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19256B676	List: ML19256B675 ML19256B677
References
LER-79-016-03L, LER-79-16-3L, NUDOCS 7908210417
Download: ML19256B677 (2)

Text

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VTVYS1 05000271 LER 79-16/3L EVENT DESCRIPTION AND PROBABLE CONSEQUENCES The movement of radioactive equipment near the spent fuel pool radia-tion monitors by Maintenance personnel caused a Group 3 containment isola-tion during normal power operations. This condition was corrected and the Group 3 isolation valves reset. Valve V-16-20-22B located in the dry-well to torus pressurization system would not reopen. SEGT was started in accordance with plant procedures to maintain drywell to torus AP as required by Tech. Spec. 3.7.A.9. The valve was later disassembled for maintenance leaving only one closed isolation valve availabic between drywell and V-16-20-22B. As a consequence, redundant contait. ment isola-tion cannbility as required by Tech. Spec. 3.7.D.1 was not available. The valve was repaired cnd returned to service within three hours. In accord-ance with Tech. Spec. Section 3.7.D.2, there was at least one valve oper-able and ir. the CLOSLD position as req < ired to isolate this line from the containment; therefore, there were no consequences to the health and safety of the public. There have been no similar occurrences reported to the Commission.

CAUSE DESCRIPTION AND CORRECTIVE ACTIONS The cause of this occurrence was the requirement to disassemble V-16-20-223 for maintenance leaving only one operable valve available for containment isolation. Valve 16-20-22B is an Atkomatic, Catalog No.

31840VPlMOD, solenoid operated, one inch, globe isolation valve. This valve has a magnetic type indicator in a well below the valve body which is actuated by a valve stem extension. The well had accumulated suffi-cient dirt to prevent the stem extension from traveling its full range.

The valve was cleaned, reassembled, tested and returned to service.

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