ML20090D418

Responds to Re Control Circuit Design Deficiencies.Review Revealed Deficiencies Do Not Exist in safety-related Equipment.Procedures Reviewed & Updated as Necessary to Ensure Functional Testing of Components

ML20090D418
Person / Time
Site:	Nine Mile Point, 05000000
Issue date:	02/02/1973
From:	Brosnan T NIAGARA MOHAWK POWER CORP.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20090D412	List: ML20090D414 ML20090D418 ML20090D425 ML20090D429
References
899, NUDOCS 8302280134
Download: ML20090D418 (2)

Text

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.. . O -O NIAGARA MOHAWK POWER CORPORATION NIAGARA MOHAWK 300 ERIE SOULEVARD. WEST SYRACU$E.N.Y.13202 b 5* . :3 w  ;

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v. 5=1 Mr. Donald J. Skovholt r h3 os Assistant Director for Operating Reactors Division of Licensing

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United States Atomic Energy Commission Washington, D. C. 20545 Re: Nine Mile Point Nuclear Station - Unit 1 Provisional Operating License - DPR-17 Docket No. 50-220

Dear Mr. Skovholt:

In response to your letter dated December 22, 1972, a thorough review of the control circuit design of all safety related equipment was conducted .

I am pleased to inform you that control circuit deficiencies in safety related equipment do not exist at Nine Mile Point Nuclear Station Unit 1. '

Although auxiliary contacts are used on those breakers, the review showed that where these interlocking components do exist, the components are part of the circuit breaker stationary device and " racking" out of a breaker does not change the state of the remaining stationary contacts in a manner which would prevent operation of the corresponding redundant component. Also, a review was conducted on all safety related equipment concerning possible deficiencies in the breaker control switch design.

It was found that rendering of redundant components inoperative could occur in one of the safety systems but only if existing procedures were completely disregarded. Specifically, this could occur upon the removal of either R1012 or R1013 breakers from service resulting in de-energizing of an (one of two) emergency safeguard bus (102 or 103) followed by subsequent energizing of this

! bus by illegal means (an alternate feed set up through the station service system) without returning the 115 KV breaker control switch to the red flag position. This would render the diesel-generator sta' t signal inoperative even on loss of voltage to the emergency safeguard bus. Therefore, whenever breaker R1012 or R1013 is removed from service the associated diesel-generator will either be i operated and run until normal supply conditions are established on that .

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, Mr. Donald J. Skovholt February 2,1973 emergency bus or the diesel-generator will be established as inoperative in the automatic mode provided two 115 KV lines are available. In either case the diesel-generator could manually be operated and provide a manual back-up to the other diesel-generator, ,

The situation just described does not exist in any other safety system at liine Mile Point Unit 1.

In connection with this analysis, our procedures have been reviewed and updated as necessary to ensure that provision for functional testing of redundant components exists when a component of that system is removed from service. * -

Sincerely, M

Thomas Brosnan Vice President and Chief Engineer TJB:sn

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