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10CFR50.73

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*Piignm Nuclear fiwer Stationn

Rock y Rll RoadPlymouth, MasMousetts 023r>0

November 14. 1990Ralph G. Bird{ 5'"''' V"' P'edider9 -- Nucleat BECo 9t1'3

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h U.S. Nurlear Regulatory Commissionr. Document Control Desk

Hashington, DC 20555j

License DPR-35Docket 50-293

NOTIFICATION OF VALVE DEFECTr

; On September 2, 1990, Pilgrim Station experienced a problem with the reactor.

water level. The events regarding this matter were reported via the LicenseeEvent Report.(LER) system on October 2, 1990 (BECo letter 2.90-118).

'During this a nt, the Reactor Core Isolation Cooling System (RCIC) injection'

c. heck valve #1301-50 did not close completely following a RCIC startup- attempt. A Substantial Safety Hazard Evaluation was performed which

d6termined that incomplete closure of the RCIC check valve did not pose asuostantial safety hazard.=

E While not a substantial problem for Pilgrim, the possibility exists thatshould a failure of this type occur at another plant, the consequences couldbe substantial. Therefore, we are taking this opportunity to inform you ofthe specific nature and resolution of the valve failure for your use.

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yblVE DESIGN_

Tht RCIC injection valve is an Anchor Darling Model E3112-3, four inchexercisable swing type check valve. The disc can be moved by manually turningthe actuator shaft which extends out of the valve. This valve also has a tab

;- on the shaft bushing which causes the bushing to turn with disc motion(originally intended to facilitate valve position indication - now obsolete).

ES.CRIPTION OF Fall 0RE

following a RCIC system trip, the injection check valve did not fully close.A field inspection of the as-found condition indicated that the check valvewas open approximately one and one-eighth inches. When moved by-hand, thecheck valve disc stayed in place and did not fall into its seat by gravity.The shaft key (located under the shaft), that allows exercising, was loose andtended to bind resulting in the disc and shaft moving together. This made thedisc rotate against the packing load rather than freely on the shaft. Theobushing was also forced to rotate because of the tab. This provided furtherresistance to disc closure.

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BOSTON 20! SON COMPANY,, ,

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U. S. Nuclear Regulatory Commission

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VALVE MODIFICATION

The key was modified to provide more clearance from the hinge arm and thedesign drawing has been revised to require staking of the key during valveassembly. Also, the tab on the shaft bushing was machined off. This willallow the hinge shaft to rotate against the bushing without engaging the disc.

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If you have any further questions regarding this valve design or our $modifications to it, please contact our Nuclear Engineering Department at(617) 849-8800.

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7/ 1R.G.Bi'rd

HTL/njm/4936

cc: Mr.R.Eaton,ProjectManagerDivision of Reactor Projects - I/IIOffice of Nuclear Reactor RegulationMail Stop: 14D1U. S. Nuclear Regulatory Commission1 White Flint North11555 Rockville Pike >

Rockville, MD 20852

U. S. Nuclear Regulatory CommissionRegion I475 Allendale Road

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King of Prussia, PA 19406

Senior FRC Resident InspectorPilgrim Nuclear Power Station

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