ML20137G353

RO 50-20/1985-1:on 850408,main Intake Valve Failed Light Test Maint Procedure.Caused by Excessive Wear of Valve Gasket.Gasket Replaced

ML20137G353
Person / Time
Site:	MIT Nuclear Research Reactor
Issue date:	04/18/1985
From:	Lisa Clark, Kwok K NUCLEAR REACTOR LABORATORY
To:	Robertson G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
RO-50-20-1985-1, NUDOCS 8508270274
Download: ML20137G353 (3)

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7 NUCLEAR REACTOR LABORATORY 3;' E AN INTERDEPARTMENTAL CENTER OF MASSACHUSETTS INSTITUTE OF TECHNOLOGY O K. HARLING 138 A!bany Street Cambridge, Mass. 02139 L CLARK, JR.

Dirsctor (617)253-4211/4202 Director of Reactor Operations April 18,1985 Director, Region I U.S. Nuclear Regulatory Commission Attn Mr. Geoffrey Robertson 631 Park Avenue King of Prussia, PA 19406  :

Subject:

Reportable Occurrence 50-20/1985-1, License R-37 Failure of Ventilation Valve Casket Centlement Massachusetts Institute of Technology hereby submits the 10-day report of an occurrence at the MIT Research Reactor, in accordance with paragraph 7.13.2(d) of the Technical Specifications. An initial report of this occurrence was made by telephone to Mr. Ebe McCabe of Region I on April 9, 1983.

The format of the following report is based on Regulatory Guide 1.16, Revision I.

1. Report No: 50-20/1985-1 2a. Report Date: 18 April 1985 2b. Occurrence Date: 8 April 1985

3. Facility: MIT Nuclear Reactor Laboratory 138 Albany Street Cambridge, MA 02139

4. Identification of Occurrence:

The penetrations for the ventilation system of the reactor containment building may be sealed by the closure of two 30-inch hydraulically-actuated butterfly valves which form gas-tight scals with rubber gaskets. A routine preventive maintenance pro-cedure for inspection of these valves was performed and the main intake valve was found to have failed the initial portion (a light test) of this maintenance procedure. Further investigation showed that the failure was due to excessive wear on the lower half of the valve's gaske t. Accordingly, the test was discon-tinued and the gasket replaced.

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j. 5. Condition Prior to Occurrence:

, . The reactor had been shutdown as usual for the weekend and

, was being prepared for startup in accordance with the standard

operating procedures. In addition to the full power startup

checklist, a semi-annual preventive maintenance procedure for inspection of the main ventilation valves was in progress, in accordance with MITR Technical Specification 4.2-la.

6. Description of the Occurrence :

l Inspections of the main ventilation valves are routinely

performed in accordance with the standard maintenance schedule.

4 One portion of the procedure stipulates that a beam of light be

shone on the valve seat 360' around the gasket while an observer

! is stationed on the other side of the valve to detect any light j leakage. Light leakage was found near the six o' clock position on the lower half of the gasket of the main ventilation valve.

j 7. Description of Apparent Cause of Occurrence The failure was attributed to excessive wear on the lower j half of the gasket (H. Pratt and Co. part #7-1846-1-AR). The gasket was last replaced in 1974. It had been adjusted in 1976,

! 1979, and 1983.

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8. Analysis of the Occurrence

! The main ventilation isolation valves are in series with

{ auxiliary valves which will close automatically within ten i seconds af ter a high radiation signal from any one of the facility's plenum effluent monitors if the corresponding main isolation valve has failed to close. The auxiliary valves can

, also be operated manually at the valve location and remotely in the control room. Operability of the auxiliary valves is tested

at least monthly and prior to reactor startup if the reactor has been shutdown for more than 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />. The automatic closing i function of ' the auxiliary intake valve was tested immediately

, after the identification of'the main valve's gasket failure, and

! the interlock was found to function satisfactorily. Also, a leak

test was performed on this auxiliary valve. It was found to pass j the test. Given the redundant protection provided by this

auxiliary isointion valve there was little or no possibility of a i

hazard to the general public from failure of the main valve's i gasket.

i 9. Corrective Actions l The ventilation valve was disassembled, the gaskets were l replaced with a new set, the throw of the valve's lever arm was

! readjusted, and both light and pressure tests were conducted.

i The new ventilaton valve gasket passed both tests. In addition, j the preventive maintenance procedure on the main ventilation

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valve inspection was updated to include explicit steps to inspect visually the gasket surfaces for major wear, cracks and defects.

10. Failure Da ta :

A similar failure occurred on 13 June 1983 and was documented as UOR #83-3. This valve failed the light test but passed the pressure test. This occurrence was reported to NRC Region I on 14 June 1983. It was determined by NRC at that time that the occurrence was not reportable.

Sincerely, Kwan S. Kwok Assistant Superintendent Linccin Clark, Jr.

Director of Reactor Operations KSK/gw cc MITRSC USNRC-0MIPC USNRC-DMB