ML20090E184

AO 50-220/74-3:on 740402,both Inside MSIVs Failed to Meet Required Limit of 12.9 Std Cubic Ft Per Inch.Caused by Drift in Position Switch on Valve Controller.Valves Will Be Repaired & Retested

ML20090E184
Person / Time
Site:	Nine Mile Point
Issue date:	04/09/1974
From:	Burt P NIAGARA MOHAWK POWER CORP.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20090E186	List: ML20090E184 ML20090E187
References
33314, AO-50-220-74-3, NUDOCS 8303140097
Download: ML20090E184 (2)

Text

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e NIAGARA MOHAWK POWER CORPORATION NBAGARA MOHAWK 300 ERIE BOULEVARD WEST SVRACUSr.N.Y.83102 April 9, 1974 Mr. Donald J. Skovholt b $

Assistant Director for Reactor Operations Q [C gg &

Division of Reactor Licensing A#h United States Atomic Energy Commission g Washington, D. C. 20545 c 4d D IS/4 $ -

J Esa Re: Provisional Operating License: DPR-17  % S Docket No.: 50-220 g ,

Abnormal Occurrence 220-74-3 .,7.gg

Dear Mr. Skovholt:

On April 2,1974, in accordance with Technical Specification 4.3.3 e(4), v the four (4) Main Steam Isolation Valves were leak tested. The cutside MS1V's " '

in each line successfully passed the leak rate test, however the inside valves in both lines failed to meet the required limit of 12.9 SCFH. Noti fication ,

was made to RO:I on April 2 1974 in acenrdanc,= with Technical Specific: tier. g 1.13c. '

V' The Main Steam Flow from the reactor to the turbine is through two l' independent 24" lines. Each line contains two l' solation valves, one inside the containment and one immediately outside the containment. The two failed . ,

valves, one in each line, were the valve inside the containment.

Under containment design basis accident conditions, both main steam lines would be essentially leak tight with low leakage through the outside valves and no hazard would be presented to the plant or the general public.

The primary corrective measure taken will depend upon the cause of leakaRe.

It appears from preliminary results that one valve (#111) experienced a drift  !

in the position switch on the valve controller to cause the valve not to fully close. The other valve #121, appears to require machine lapping of the valve seat. Such repairs have been made in the past and this is not the first of a kind failure.1 The tabular results for each valve is indicated below:

1. 111 Inside 1400 SCFH

1. 1~2 Outside

. 7.85 SCFil ,.  ;

1. 121 Inside 120 SCFH ,

1. 122 Outside 0.24 SCFH #

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33 L'1 8303140097 740409

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- Mr. Conmid J. Skov - -2 -

April 9, 1974

, U.S. Atesic Energy mmissicn In the interest of maintaining an efficient refueling outage schedule, the repair and retesting of the inside valves has not been completed to this  ;

date, however, the results of the repair and retest will appear in the Semi- l Annual report published in July, 1974.

Very truly yours, h d*: O P. Allister Burt General Superintendent Nuclear Generation l TJD:cm I Ltr. P.A. Burt - Skovholt - June 6, 1973.

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