ML19331D960

Ro:On 800829,primary Inlet Isolation Valve 507B Failure to Shut When Securing Primary Sys Following Shutdown.Caused by Separation of Lower Seat from Metal Insert in Schrader Valve & Consequent Blockage of Exhaust Port

ML19331D960
Person / Time
Site:	University of Missouri-Columbia
Issue date:	08/29/1980
From:	Brugger R, Mckibben J MISSOURI, UNIV. OF, COLUMBIA, MO
To:
Shared Package
ML19331D961	List: ML19331D960 ML19331D962
References
NUDOCS 8009040418
Download: ML19331D960 (4)

Text

_ _ ______ _ _ _ _

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

Columbia, Missoun 65211 August 29, 1980 Teieonone (314) 8824211 Director of Licensing U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Reference:

Docket 50-186 University of Missouri License R-103 1

Subject:

Report as required by Technical Specification 6.1.h(2)

Enclosures:

(1) Letter to the Directorate of Licensing from MURR dated June 20, 1975.  ;

(2) Letter to Scovill Fluid Power Division from MURR dated lurch 13, 1975. l (3) Letter to MURR from Scovill Fluid power Division dated May 13, 1975.

(4) Letter to MURR from Scovill Schrader l Bellows Division dated August 21, 1980.

Description At 2230 on August 3,1980, the primary inlet isolation valve (valve 507B) failed to shut when securing the primary system following a reactor shutdown.

This was in violation of Technical Specification 3.9.a requiring the primary coolant isolation valves to be operable when operating the reactor in ftdes I or II. l Analysis l l

All primary remotely operated valves at the University of Missouri Research Reactor are operated valves controlled by Schrader Bellows Type 972S three-way solenoid valves. When the operator attempted to shut valve 507B while securing  ;

the primary system following a reactor shutdown, the valve failed in the open '

po si tion. The cause of the failure was the separation of the lower seal from the metal insert in valve 507B's Schrader valve and the consequent blockage of CN S

E E g \)j 4 COLUMBIA KANSAS CITY ROLLA ST. LOUIS an eausi coportunity insttution THIS DOCUMENT CONTAINS 8000040418 .5 POOR QUAUTY PAGES

Director of Licensing August 29, 1980 Page 2 the exhaust port. This failure has occurred in the past as described in 'a letter to the Directorate of Licensing dated June 20,1975 (Enclosure 1) and a letter from the University of Missouri to Scovill Fluid Power Division dated March 13,1975 (Enclosure 2). The valve was operated by manually venting off the Schrader valve.

When this type of failure was previously identified, a temporary corrective measure of gluing the seal to the brass insert as described in the letter from Scovill Fluid Power Division to the University of Missouri dated May 13, 1975 (Enclosure 3) was taken. The permanent corrective action was a new smaller bottom seal design by the manufacturer (See drawing on page 3.). However, they also continued to make valves of the previous design but MURR was not informed of this. -The Schrader type 9725 valve that operated valve 507B was a valve installed on December 18, 1979 which had been sent to us with the older large bottom type seal installed. The valve was last operated satisfactorily on the July 28,1980 shutdown.

While the failure of valve 507B to shut constitutes a violation of Techni-cal Specification 3.9.a requiring the primary isolation valves to be operable in Mode I or II, it does not constitute a failure of the safety system. The propei operation of the isolation valves is not required for the protection of f" a' element integrity as described in the bases to the Technical Specifications, section 3.9. The primary protection from the loss of core water lies with the check valve located on the reactor side of valve 507B, the invert loop, and the syphon break system.

Corrective Action An immediate inspection was conducted on all Schrader Type 9725 valves used in the system. Valves with the older type seal were found on the pressurizer isolation valve (valve 527C) and the nitrogen charging isolation valve to the pressurizer (valve 526). Both of these valves operated satisfactorily. An in-spection of the Schrader Type 972S valves held in the supply system was also compl eted. Scovill has since assigned new part numbers to the Type 972S used by us to prevent the reoccurrence of this incident. This change is described ir a letter from Scovill Schrader Bellows Division to the University of Missouri dated August 21,1980 (Enclosure 4) . The reactor supply system has been changed to reflect Scovill's action; additionally all new seal kits and valves will be inspected on receipt to verify they are the proper type.

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August 29, 1980 Page 4 Sincerely, . ,

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C. McKibben Reactor Manager Endorsement Reviewed and approved:

A Robert M. Brugger Director JCMK:vs

Enclosures:

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, cc: James Keppler, Director Regulatory Operations - Region III Reactor Advisory Committee Reactor Safety Subcommittee Document Managment Branch, NRC

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