ML19350B969

Ro:On 810223,isolation Valve V546B Failed to Move to Fully Opened Position Following Normal Shutdown.Caused by Difficulty in Movement of Valve Actuator.Valve Rebuilt, Lubricated & Reinstalled

ML19350B969
Person / Time
Site:	University of Missouri-Columbia
Issue date:	03/17/1981
From:	Mckibben J MISSOURI, UNIV. OF, COLUMBIA, MO
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8103240510
Download: ML19350B969 (2)

Text

Research Reactor Facility UNIVERSITY OF MISSOURI g,,,,,cn p,,,

columbia. M.ssoun 65211 March 17, 1981 Teleonone (314) 882-4211 y 19%..

/4x Director of Licensing S' U. S. Nuclear Regulatory Commission Washington, D.C. 20555 g

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Reference:

Docket 50-186 University of Missouri , ,1 g" r.

License R-103 J, s'

Subject:

Report as required by  % )'

Technical Specification 6.1.h(2).

Description On February 23, 1981, following a normal reactor shutdown when the isolation valves for the reactor convective cooling loop (V546 A/B) automatica.ly open, valve V546B failed to move to the fully opened position. This could be inter-preted as a violation of Technical Specification 3.9.a(3) which requires the reactor convective cooling loop to be operable. Valve V546A was operable and the reactor requires only one of the two valves to open to perform the system design function.

Analysis On February 23, 1981, when primary systems were secured, valve V5468 failed to move to the fu!1y open position. Valve V546A operated properly. Later test-ing of valve V546B showed that the valve actuator was no longer capable of moving the valve to either the full open or shut position without manual assistance.

After the valve was removed from the system, it was disassembled and the operating mechanism examined. The mechanism was found to require a great deal of force to operate properly. The valve was then rebuilt, lubricated and reinstalled in the system. ,

No unresolved safety question exists. Section 3.4 of Addendum 3 to the

' Hazards Summary Report describes the operation of the reactor convective cooling loop. The analysis has determined the reactor convective cooling loop is not re-quired for core protection, but that its operation will prevent the formation of steam in the loop and prevent thermal cycling of the fuel. The analysis is de-veloped assuming only one of the two parallel valves (V546 A/B) operate in the re-quired manner. Valve V546A. functioned properly during the period valve V546B failed to function.

kOSO s Wy c j p COLUMBIA KANSAS CITY ROLLA ST. LOUIS M an equal opportunity institution

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a Director of Licensing March 17, 1981 Page 2 Corrective Action Valve V546B was rebuilt and tested satisfactorily prior to returning the reactor to operation. Additionally, valves V546 A/B will be checked routinely to verify proper operation.

Sincerely, )

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J.C. McKibben Reactor Manager JCMK:vs cc: James Keppler, Director Regulatory Operatiors - Region III Document Management Branch, NRC Reactor Advisory Comittee Reactor Safety Subcomittee c