ML20073G402

Advises NRC of Changes to Previous Commitment to Have Internal Stop Installed on Containment Purge Isolation Valves

ML20073G402
Person / Time
Site:	Davis Besse
Issue date:	09/25/1994
From:	Stetz J CENTERIOR ENERGY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
2235, NUDOCS 9410040155
Download: ML20073G402 (2)

Text

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%W GNTERf0R ENERGY 300 Madison Avenue m p, se loledo, OH 43652 0001 V ce President - Nuclear 419 249-2300 Ms-Besse Docket Number 50-346 License Number NPF-3 Serial Number 2235 September 25, 1994 United States Nuclear Regulatory Commission Document Control Desk Vashington, D. C. 20555 Subj ec t : Containment Purge Isolation Valve Internal Stops Gentlemen:

The purpose of this letter is to advise the NRC of a change to a previous commitment to have internal stops installed on the Davis-Besse Nuclear Power Station (DBNPS) containment purge isolation valves. The subject valves, valve numbers CV5005, CV5006, CV5007, and CV5008, are 48-inch butterfly valves with air-operated actuators. As described below, a later commitment to maintain these valves closed in Modes 1 through 4 obviates the commitment regarding the internal stops.

An NRC letter dated November 29, 1978 (Toledo Edison Log No. 363) noted generic concerns regarding the ability of containment purge isolation valves to close against the dynamic forces of a design basis loss-of-coolant accident (LOCA). A later NRC letter dated October 23, 1979 (Toledo Edison Log No. 453) further noted concerns with containment purging during normal plant operation. Toledo Edison (TE) responded to these concerns by letter dated December 13, 1979 (TE Serial No. 564), stating that the valve position of the containment purge valves vould be restricted to 65 degrees open (90 degrees being full open) in Mode 1 (power operation) through Mode 4 (hot shutdown),

based on preliminary vendor calculations. This commitment was re-affirmed by TE letter dated January 18, 1980 (TE Serial No. 577).

On March 25, 1982 (TE Serial No. 801), TE submitted to the NRC a vendor analysis that concluded that certain valve components are over-stressed during a LOCA with the valve disc opened beyond 55 degrees. On December 3, 1982 (TE Log No. 1143), the NRC requested confirmation that TE vould restrict valve position to 55 degrees during Modes 1 though 4.

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' O coveland Electnc muminating Toledo Edison 9410040155 940925 PDR ADOCK 05000346 P PDR

Docket Numbar 50-346

,; ,e s License Number NPF-3 Serial Number 2235 Page 2

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By letter dated December 30, 1982 (TE Serial No. 890), TE committed to l maintaining the valves closed in Modes 1 through 4 pending further l h evaluation. An NRC letter dated February 16, 1983 (TE Log No. 1217) )

reiterated concerns regarding valve operability. On March 16, 1983 (TE l Serial No. 920), TE stated that mechanical restrictions had been installed to limit valve opening to 55 degrees (valves CV5006 and CV5007) or 65 degrees (valves CV5005 and CV5003). TE further stated that in light of the uncertainty that exists in the ability of the valves to close under certain conditions, the valves would be maintained closed pending resolution. By letter dated June 24, 1988  ;

(TE Serial No. 1504), TE summarized various concerns regarding the i containment purge isolation valves and stated that the valves are being maintained closed with control power off in Modes 1 through 4, and that there were no plans to revise this practice.

In light of the commitment to maintain the containment purge isolation valves closed in Modes 1 through 4, the internal stops which vere installed to limit valve opening during containment purging during Modes 1 through 4, are no longer necessary. Toledo Edison intends to remove the stops so as to increase airflow and provide more effective cooling during system operation in Mode 5 (cold shutdovn) and Mode 6 (refueling).

As stated earlier, the purpose of this letter is to advise the NRC of a change to a previous commitment. No NRC action is required with regards to this letter.

Should you have any questions or require additional information, please contact Mr. Villiam T. O'Connor, Manager - Regulatory Affairs, at (419) 249-2366.

Very truly yours, i

HKL/laj cc: L. L. Gundrum, DB-1 NRC/NRR Project Manager J. B. Martin, Regional Administrator, NRC Region III S. Stasek, DB-1 NRC Senior Resident Inspector Utility Radiological Safety Board

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