ML20084S070

Provides Addl Info Re Disassembly Insp & Final Corrective Action for Failed HPCI Steam Supply Valve 3-2301-3 Reported on 730614.All Damaged Parts Replaced to Return Valve to Operational Status

ML20084S070
Person / Time
Site:	Dresden
Issue date:	03/22/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084S074	List: ML20084S070 ML20084S086 ML20084S091 ML20084S094
References
218-74, NUDOCS 8306160135
Download: ML20084S070 (2)

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1 --- 7- Adoress Reply to: Post Office Box 767

. -j' Chicago. Ill.nois 60690 BBS Ltr #218-7h Dresden Iluelear Power Station R. R. #1 Morris, Illinois 60h50 March 22, 197h gg c '[."'.;,/,, '

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~ Mr. J. F. O' Leary, Director 50-249 i., /g,) , -

Directorate of Licensing 3 .

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U. S. Atonic Energy Connission Washington, D. C. 205h5 $,

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SUBJECT:

LICE'ISE DPR-29, DRESDKI NUCLMR PC.ER STATIC'! .__U !IT 3 ' ' \. '

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AD_illTIU aL L .~0R hTIO.1 Cl riiC1 STx SUPrM hLL 1UJRE -

Reference:

Dresden ;!uclear Power Station, Unit 3 Letter to Mr. A. Gianbusso, dated June lh,1973

Dear Mr. O' Leary:

This letter is to furnish additional information concerning the disassenbly inspection and final corrective action for the failed HPCI stean supply valve, 3-2301-3, as reported June lh,1973.

Prior to the disassembly and inspecticn of the HPCI stean supply valve, a reprerontative of Linitoroue of Philadc]phia Gear Corp.

unc centceted fer assistance in the deternination of nede of failure.

A necting uas held between Station Slectrical Zngineering and Limitorque to discuss the problen. The details of the failura vere discussed c.nd the cause of the problem was then found to be re3ated to the gearing ratio of the valve.

Because the HPCI stean supply valve is one requiring rapid operation, the gear ratio used is high. Due to the high gear ratio, there exists a lessening of the tolerances botueen gears, and a sl$ght shift of the valve sten is therefore possible. In this situation, it is pc rsible T,o over torque the valve sten by holding the valve control in the closed position. Once the valve has reached the closed position and the torque suitch opens, valve travel is stopped. However, with a slight shifting of the valve sten possible, the torque switch could reset, allcuing further closing torque to be applied. This condition would result in a bent or broken sten if the control suitch were held in the closed position longer than necessary.

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O C; P O 1,, Ju COPY SENT REGION M _

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! Mr. J. F. O' Leary, Director March 22, 197h i

I In regard to corrective measures, it would be possible to '

reduce the anount of sten shift by changing the gear ratio. The change,

however, would decrease the operational speed of the valve, since a lower gear ratio would be required. Since the HPCI systen response time

yould be decreased, the change was considered to be unacceptable.

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Upon disassenbly of the valve, it was found that the sten was indeed bent. The inspection of all conponent parts failed to reveal i other possible causes for the problen. It is therefore believed that the cause of the problen is inherent to the high gear ratio used, and that caution in operation is the only corrective action possible. An operating order to cautica valve operation has been issued by the i operating department.

To return the valve to an operaticnal status, all danaged i parts were replaced. In addition, Operations has been inforned of the need to release the control switch once the valve has reached its intended position.

Sincerely, , 7-~

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s-y '. ,St9pnenren f-,L/ (:s / W  %

)v 1 Superint'cndent EBS:TEL:ls J

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