ML20084J162

Ao:On 721115,following Actuation of Test Switch for MSIV 20, Approx 25 Elapsed Before Valve Movement Detected by Indicating Lights on Control Room Panel 901-3.Caused by Faulty Operating Pilot Valve.Valve Replaced

ML20084J162
Person / Time
Site:	Quad Cities
Issue date:	11/24/1972
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
BBS-72-7, NUDOCS 8305120209
Download: ML20084J162 (2)

Text

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s Nuct:ar Pow:r St: tion Post Of a Box 216

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November 24, 1972 s 9,N':\ 33 l~,

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Mr. A. Giambusso Denuty Director for Reactor Projects Directorate of Licensing U.S. Atomi c Energy Commission

{ f' f) ,.,/ ' g p Washington, D. C. 20545

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Reference:

Quad-Cities Nuc1 car Power Station Unit 1 License DPR 30, Annendix A Sections 1.0.A.2, 3.7.D.2, and 6.6.B.3 L0

Dear Mr. Giambusso:

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The purpose of this letter is to inform you of the Ch

" detailsJngarding an incident._ involving.an outboard main steam isolation salve, A03 ;20 M a t_Ruad, j,k ]Citiesunit 1 Tris abnormal occurrence was renorted al to you by teleg' am on November 16, 1972.

w DESCRIPTION OF INCI DENT At 0030 on November 15, 1972 vi th the Unit I reactor at 90 percent power, partial closure surveillance was being nerformed on the main steam line isolation valves as requi red by Technical Snecification 4.7.D.I.d.

W A for MSIV-2D was actuated, annroximately 25 seconds clansed before any valve movement was ~~

Me c t e d_byJh e_I n d i_ca tTn~g!hih ts_o n con t to Lrcom na W 901-3. All other valves including the other

-71s I V in the D steam line tested satisfactorily, thus if an isolation signal hed been received, the steam lines vould have isolated.

INVESTIGATION AND REPAIR Due to the nrobability of receiving a High Steam Line Flow isolation and scram if an MSIV were fully closed while at 90% never, load had to be reduced before the 2D valve could be exercised and timed. As povert ias y

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being reduced at 1418, a pressure snike occurred while '

valving out the pressure regulator and the reactor scrammed on high neutron flux. An attempt was then made to exercise HSIV-2D with its control switch and the vaive would not move. The inboard valve, A0-1-203-ID was put in the closed position for the subsequent reactor startup. Initial trouble shooting indicated that the operating pilot valve was not moving. The pilot valve was replaced and the MSIV was satisfactorily tested by cycling it four times.

The defective operating pilot was carefully disassembled and inspected in an attempt to determine the exact cause of failure. Considerable effort was required to free the piston and remove it from the pilot cylinder. When the niston was examined, .it appeared to be clean exceot .

for a small amount'of a light colored residue which could not be identified. Efforts were made to scrape off an analytical quantity, but this could not be done.

The pilot piston was thoroughly cleaned and notished and the valve was reassembled. Cleaning the piston corrected the problem and the valve now onerates freely.

CONCLUSIONS AND CORRECTIVE ACTION The failure of the _MSIV onerating nilot was anparently caused by some contaminant from the Instrument Air-System. The valve had been successfully cycled and timed four days nrior to the failure. The fact that the steam.

lines vould have-isolated if required vas nroven by the demonstrated enerability of the other seven valves at'the time of the failure. Thus the niant was not operated at any time in an unsafe condition.- This is the first occurrence at this station where an MSIV has been rendered. inoperable by contamination from the'~ ~ ~

air system.. If trends develop unich indicate thls to 4: bWorablem, consideration vill be _given_ to a chemical .

flushing of the instrument alr.headersLduring the next major outage. ! Also as corrective action, an Operating Memo'has-been issued to all; shift engineers to 1nsure that

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they are aware pf this potential problem with the MSlV's. -

This should- assist them in detecting' the problem immediately based on the valve , behavior during partial closure survelliar.ce testing.

Very truly yours,'-

gj ( $ "

i 4 d B.'B. Stephenson '

- Superintendent

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