ML19323H988

Informs NRC of Proposed Mod to Limit Containment Purge & Vent Valve Opening to 65 Degrees.Util Is Proceeding W/Mod W/Understanding That NRC Concurs Unless Informed to Contrary by 800612

ML19323H988
Person / Time
Site:	Kewaunee
Issue date:	06/11/1980
From:	Mathews E WISCONSIN PUBLIC SERVICE CORP.
To:	Schwencer A Office of Nuclear Reactor Regulation
References
NUDOCS 8006170426
Download: ML19323H988 (2)

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. l WISCONSIN P U B LI C S ERVICE CO RPORATION P.O. Box 1200, Green Bay, Wisconsin 5A305 June 11, 1980 Mr. A. Schwencer, Chief Operating Reactors Branch #1 Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:

Docket 50-305 Operating License DPR-43 Kewaunee Nuclear Power Plant Containment Purge and Vent Valve Modification In our letter of January 21, 1980, we stated that we would install a mechanism that would limit the opening angle of the subject valves after receipt of a favorable safety evaluation;, The preliminary results of that safety evalua-tion indicate that limiting the valves to a 500 opening angle would result in unsatisfactory o;,eration of the Reactor Building Vent (RBV) System due to system characteristics. Therefore, it is inappropriate to limit the valves to a 500 open position.

The NRC staff has repeatedly suggested that we install devices on these valves to limit their opening angle. We have evaluated the effects of limiting the valve opening to 65 . This preliminary evaluation indicates that limiting the valves to a 65 0open angle is marginal in terms of f an performance and may cause flow instabilities in the RBV system. In the event of instabilities in system performance with partially opened valves, modifications could be made to the fans to restore satisfactory system operation at significantly reduced flow. Therefore, we are proceeding with the modification to limit the valves to an opening angle of 650 To date we have not received verification from the RBV valve manufacturer which addresses safe operation of the valves in a partially blocked position.

We are aware, however, that similar devices have been employed at other ye l

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Mr. A. Schwencer  !

June 11, 1980 Page 2 licensed facilities. While the NRC staff has suggested partially blocking to improve margin by reducing potential impact load during valve closure, we have not been provided with the detailed basis of that position by the staff.

Although we have no reason to suspect that a hazard is presented by valve blocking, we are not in a position to completely justify the NRC suggested action. We are proceeding with the understanding that the NRC staff concurs with the above addressed resolution unless informed of the contrary by June 12,1980.

> Very truly yours, 4

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, . . - 0 A-5 , ,s E. R. Mathews, Vice President Power Supply & Engineering J

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