ML20084D441

AO 50-237/75-28:on 750506,containment Cooling Svc Water Valves MO-1501-3A & 3B Failed to Control Flow During Lpci/ Containment Cooling Logic Test.Caused by Bent Valve Stems. Increased Size Stem Valves on Order

ML20084D441
Person / Time
Site:	Dresden
Issue date:	05/23/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
322-75, 5942, AO-50-237-75-28, NUDOCS 8304110217
Download: ML20084D441 (3)

Text

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Comm rlth Edison p,

/ One Firs . anal Plaza, Chicago, lilinois i "

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} ~ 7 Address ly to: Post Othee Box 767

/ Chicago, Ilhaois 60690 EDS Ltr. ,4322-75 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 6C450 May 23, 1975 4 g kr o,

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Mr. James G. Keppler, Regional Director

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Directorate of Regulatory Operation-Region III k . gN l$[$ 5 Lj [

U. S. Nuclear Regulatory Co:anission u. "j**m, gy ,

M4 799 Roosevelt Road '/

Glen Ellyn, Illinois 60137 I$$

SUBJECT:

REPORT OF A? NORMAL CCCURR 2:CE PER SECTION 6.6. A 0F TFEK.OJ i' .

SFiX:IFICI,TIO::S FAILURE OF CONTADFFl:T COOLING ' DATER VALVES 1501-M & B

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Motification of Region III of U. S. Nuclear Regulatory Commission Telephone: Fr. Johnson, 1050 hours0.0122 days <br />0.292 hours <br />0.00174 weeks <br />3.99525e-4 months <br /> on Iay 16, 1975 Telegram: Mr. Keppler, 1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br /> on May 16, 1975

3) Drawing I! umber P & ID M-20 Report Number: 5c-237/75-28 Report Date: May 23, 1975 Occurrence Date: I'ay 6,1975 Facility: Drecden Nuclear Power Station, Morris, Illinois IDDC'FICATICM OF CCCURRD:CE The contaire.ent cooling service vater valves MD-1501-3A & 3R failed to control flow during a LFCI/Centainment cooling logic test. This problem was not reported at the time of the occurrence because the containment cooling system was nct required for operation and had not yet been declared operable following the heat exchanger cleaning. Subsequent review of the occurrence determined  ;

thht the incident was reportable. '

CO:IDITIONS PRIOR TO OCCURRD:CE l l

At the time of this occurrence, Unit-2 was in a refueling outage with the reactor mode switch in the SIRTfD0'<.N position.

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5942 8304110217 750523 PDR ADDCK 05000237 S PDR

!*r. James G. Keppler p q May 23, 1975

. U I G)

DESCRIPTION CP OCCURRE!CE .

At 0200 hours0.00231 days <br />0.0556 hours <br />3.306878e-4 weeks <br />7.61e-5 months <br /> on May 6,1975, the Instrument Mcchanics began LNI/ Containment ecoling logic testing. The 1501-3A & 33 valves are throttled automatically to maintain service water pressure 20 psig above LPCI/CC system water pressure.

The valves were found to be inoperabic.

DESIG"ATICN OF APPARE.~? CAUSE OF OCCURRE CE (Component Failure)

Upon inspection of the 1501-3A & 3B valves, both valve stems were found to be bent. The stems are made of 3/4" stainless steel and the motor-operators i are Limitorque type Sh~.d-0, which develop approximately 10,000 lbs of thrust, The brakes on both motor-operators were found to slip. Prior to the system j logic testing, routine maintenance was performed on both containment cooling heat exchangers. Ecth valves were manually closed after the motor-operators disengaged in order to minimize any leakage. It is assumed that botn the above conditions centributed to the bending of the valve stems.

ANAINSIS OF OCCURRE!CE The containment cooling system was not required since the reactor water temperature was below 212*F. If the system had been required, an inadvertent release of contaminated water would have occurred only if there were tube Ic s s in the heat exchangers. Therefore, the health and safety of the plant p'rsonnel and the public were not jeopardized as a result of this incident.

CORRECTIVE ACTICN The valve manufacturer uas consulted concerning these failures. It was decided to increase the size of the valve stems; consequently, new 1" dit=.eter stems are now on order. Pending the arrival of the new stems, another cet of 3/h" stems were temporarily installed. The Limitorque brakes were adjusted to provide minimum slippace. At 1812 hours0.021 days <br />0.503 hours <br />0.003 weeks <br />6.89466e-4 months <br /> on I~.ay 17, 1975 the valves were made operabic and the LNI/ Containment cooling logic testing was completed.

FAILURE 1TA A review of the history of these valves for Unit-2 & 3 reves1s no similar failures. The valves are 12"-300 PSI USA standard valve a w emblics manufactured-by Copes-Vulcan, a division of Elaw-Knox Co.

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G3s Bernned C. Rusche, Director Directorate of Licensing U.S. Nucient Regulatory Cocumission.

Washington, D.C. 20555 WRJECT: DPRa N . Dresden Nuclear Power Station. Ifnit2_

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