ML20084U115

Ro:On 720707,during Turbine Control Valve Exercise Test, Reactor Protection Sys Limit Switch on Turbine Control Valve 2 Found Inoperable.Caused by Missing Bolt in Switch.Mounting Bolts Reversed to Insure Nut Remains Tight

ML20084U115
Person / Time
Site:	Dresden
Issue date:	07/17/1972
From:	Worden W COMMONWEALTH EDISON CO.
To:	Bloch E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U117	List: ML20084U115 ML20084U127
References
NUDOCS 8306270055
Download: ML20084U115 (2)

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Mr. Edward J. Bloch, Acting Director Directorate of Licensing U. S. Atomic Energy Commission Washington, D. C. 20545

SUBJECT:

LICENSE DPR-25. DRESDEN NUCLEAR PO'/IER STATION, UNH E-3, SECTION o.b.D.2 OF THE TECHNIC!.L SIICIFICA-TIONS

Dear Mr. Bloch:

This is to report a condition relating to the operation of the staticn in which a reactor protection system (RPS) limit switch on the #2 turbine ccntrol valve was found to be inoperable, contrary to the requirements of Section 3.1 of the Technical Specifications.

PROBLEM AND I!NESTIGATION The reactor was in the "run" mode and oneratine at 480 IGle on July 7,1972. At 2320, during the turbine control valve exercise test, it was noticed that the turbine generator load mismatch scram on channel B did not activate when the #2 control valve was closed. When the control valve fast closure solenoid' operates, a switch opens contacts de-energizing its RPS relay; this causes a channel "B" trip when above 40s power.

Load was reduced to less than 407o of rated to satisfy the requirements of Section 3.1 of the Technical Specifications.

Investigation of the switch showed that one of the

/twomountingboltshadcomeout. The switch was mounted with

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the bolts going upward through the top of the switch, and then through a bracket, so that the nut was on the top. With one bolt gone, the plunger that activates the switch rotated it around on the remaining bolt, instead of activating the switch.

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Mr.EdwardJ.(,ch July 17, 1972 CORRECTIVE ACTION The mounting bolts were reversed so that the bolt goes through the bracket and then through the top of the switch so that the nut goes on from the bottom. This was to insure that if the nut worked loose again, the bolt would remain in place preventing the switch from rotating. The switch was then tested and worked satisfactorily. These switches will all be checked at the next opportune time and corrective measures applied if required.

Sincerely, Y>tsc 1 . 8, li i e N W. P. Worden Superintendent WPW:rr A

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