ML20084M111

AO 4-73-4:on 730510,generic Back Leakage Through Primary Sys Check Valves 4-873 A,B & C Recognized.Caused by Failure of Soft Seats in Valves.Valves to Be Replaced

ML20084M111
Person / Time
Site:	Turkey Point
Issue date:	05/18/1973
From:	Schmidt A FLORIDA POWER & LIGHT CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
AO-4-73-4, NUDOCS 8306010284
Download: ML20084M111 (2)

Text

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Mr. John F. O' Leary, Director I -

Directorate of Reactor Licensing ,Q' {t ;.' T '

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U. S. Atomic Energy Commission Q , .w 3 Washington, D. C. 20545 ... ,

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TURKEY PolNT UNIT No. 4 6' u. ,. ' -

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C DOCKET UUMBER 50-251 -

R' ABNORMAL OCCURRENCE NO. 4-73-4 eN t . i :.a ,s - -

GENERIC FAILURE OF_ PRIMARY SYSTEM CHECK VALVES 'p

Dear Mr. O' Leary:

This report is submitted in accordance with Technical Specification 6.6.2 a and in amplification of Mr. J. K. Hays' telephone notification to Mr. R. C. Lewis, Region II, Directorate of Regulatory Operations, on May 10, 1973.

On May 10, 1973, it was first recognized that backleakage through check valves in Unit 4 constituted en Abnormal Occurrence because of the generic nature of the problem. These valves are check valves 4-873 A,~B, and C, the check valves in the high head ~safetylinjection lines to the Loop A, B, and C, RCS cold legs, respectively. The valves are two inch Rockwell soft seat check valves. In addition to the safety injection application, these valves are installed in the Reactor Coolant Pump seal water injection lines as valves 4-298 A, B, and C, for pumps A, B, and C, respectively.

The maximum leakage was 1/3 gallon per minute with 180 psi of water pressure applied on one of the safety injection valves. Only slight Icakage has been detected on the other two safety injection check valves. No leakage is apparent on the RCP seal water check valves, although, due to the service, there is little opportunity for leakage b_) in this application.

[ The leakage is known to have been caused by the failure of the soft h)'j)' -

seats in the valves. The soft seats consist of a ring of ethylene f propylene (a rubber compound), with the trade name Nordell, installed a O' in the form of an "0" ring around the valve plunger. The valve seats

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hr. John F. O'L cy, Dir:ctor g

(; May 18, 1973 are stellite. The "O" rings were missing when the valves were disassembled.

The valves were rated at 200*F. These valves had been installed around March, 1971, during plant construction after the original design valves failed to pass the containment leak tests, specifically the air leak rate test.

The permanent corrective action will be to replace the curr2ntly installed soft seat valves with valves meeting the original design rpecifications.

This apparently contradictory step is, in fact, satisfactory because it is now felt that the original design valves failed the air test because their seats were not lapped properly after the valves were installad. The re-placement valves are of the hard seat type, with all seating surfaces of stellite. The job of replacing the soft seat valves is presently in pro-gress and is scheduled for completion on or before May 26, 1973.

These valve problems constitute an abnormal occurrence because of the generic nature of the problem and because the valves are in a safety system.

The backleakage would not, of course, have prevented or impeded design high head safety injection flow through the valves in case of an accident re-quiring high head safety injection. Backleakage in case of a loss of coolant accident in conjunction with a safety injection piping break outside contain-ment would have posed no problem because the reactor has never been critical and RCS gross B-y activity was below minicum detectable. Therefore, the health and safety of the public was not adversely affected by the valve problem.

Very truly yours, h'

A. D. Schmidt Director of Power Resources cc: Norman C. Moseley, Director Region II, Directorate of Regulatory Operation U.S. Atomic Energy Commission Suite 818,230 Peachtree Street, N. W.

Atlanta, Georgia Mr. G. A. Olson Edison Electric Institute 90 Park Avenue New York, N. Y. 10016 Dr. James Coughlin J. W. Williams, Jr.

J. R. Bensen J. B. Olmstead W. H. Rogers, Jr. S. G. Brain G. E. Liebler Plant Superviscrs J. K. Hays Plant Nuclear Safety Committee C. E. Branning Documentary Files D. W. Jones