ML19256F274

Responds to NRC 791023 Ltr.Discusses Analysis Performed by Henry Pratt Co,Demonstrating That Bettis Valve Operators Are Capable of Closure Under LOCA Conditions.Purging During Operation w/18-inch Valves Safe Under Accident Conditions

ML19256F274
Person / Time
Site:	Farley
Issue date:	12/10/1979
From:	Clayton F ALABAMA POWER CO.
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 7912180405
Download: ML19256F274 (3)

Text

,o k Alabama Power Company

. 600 North 18th Street Post Office Box 2641 Birmingham. Alabama 35291 Telephono 205 323-5341 F. L CLAYTON, JR.

u Senior Wce President Alabama Power tN southern cla:rc s,1:em December 10, 1979 Docket No. 50-348 Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn: Mr. A. Schwencer

Dear Mr. Schwencer:

J. M. FARLEY NUCLEAR PLANT CONTAINMENT PURCE This is in response to your letter dated October 23, 1979 concerning operability of containment purge valves.

Alabama Power Company is conducting a qualification program on the main (48-inch) containment purge valves used at Farley Nuclear Plant.

Alabama Power Company committed, by letter to you dated August 7,1979, to maintain these valves closed in modes 1, 2, 3, and 4 until their operability can be demonstrated. The qualification program for the 48-inch valve is currently in progress.

Alabama Power Company's operability verification program has been com-pleted on the Farley 18-inch mini-purge valves.

A detailed analytical analysis was performed by the valve manufacturer (Henry Pratt Co.) which demonstrated that the 18-inch Henry Pratt Company valves with the Bettis valve operators are capable of closure without loss of structural integrity during LOCA conditions in conjunction with seismic and other loads. The following guidelines were incorporated into the analysis.

1. Valve closure time during a LOCA will be less than or equal to the no flow time demonstrated during shop tests, since fluid dynamic ef fects tend to close a butterfly valve. Tests showed that the 18-inch valves close within 2.5 to 4 seconds.

2. The analysis considered the direction of flow which is the direc-tion resulting in the greatest torque.

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,b Director of Nuclear Reactor Regulation Page 2 December 10, 1979

3. The worst case was determined to be a single valve closure with pressure on one side and atmospheric pressure on the other.

4. Containment back pressure will have no effect on closing since the same back pressure will be present at the inlet side of the cylinder and the differential pressure will be the same during normal operation.

5. Farley purge valves do not have accumulators.

6. Torque limiting devices only apply to electric motor operators which were not furnished on purge valves for Farley Nuclear Plant.

7. The effect of upstream and downstream piping was ignored as a conservative approach.

8. For compressible fluid flow, the effects of valve orientation relative to the pipe line are considered to be insignificant.

The analysis consisted of a static analysis of the valve components demonstrating that the stress levels under combined seismic and LOCA con-ditions are less than 90 percent of yield strength of the materials used.

The valve operator structural evaluation was based on the operators ability to resist the reaction of LOCA induced fluid dynamic torques.

Sealing materials include EPT material on a 304 stainless steel surface. Molded EPT seats have a maximum cumulative radiation resistance of LX103 rad at a maximum temperature of 3500F.

Valves at outside ambient temperatures below 0 F could be affected due to thermal contraction, however, during a LOCA the valve temperature would be high which tends to increase scaling. Also, temperatures below OoF in the geographical area where Farley Nuclear Plant is located are rare.

Concerning debris, the purge supply and exhaust lines are protected by registers.

Based on the results of the analysis as outlined above, Alabama Power Company's position remains that continuous purging during plant operation with the 18-inch (mini-purge) valves is safe under all accident conditions.

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Director of Nuclear Reactor Regulation Page 3 December 10, 1979 Further information on the 48-inch main purge valve analysis will be supplied when available.

Yours very truly, m0-cs) V@ cW-F. L. Clayton,(Jr.

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cc: Mr. R. A. Thomas Mr. G. F. Trowbridge 1608 205