ML20084D412

AO 50-237/75-31:on 750522,containment Cooling Svc Water Valve MO-1501-3A Failed to Control Flow During Scheduled Surverillance.Cause Not Determined.Design Mods for Valves Being Evaluated

ML20084D412
Person / Time
Site:	Dresden
Issue date:	05/30/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
334-75, 6044, AO-50-237-75-31, NUDOCS 8304110171
Download: ML20084D412 (4)

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SUBJECT:

REPORT 0? /MOR'ML OCCURRECE PER SFCTION 6.6.A 0F THE TECHNICAL SPECIFICATIONS VALVE FA1501-% PAILURE TO CON"'ROL FLOW

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Notification of Regicn III of U. S. Nuclear Regulatory Cornission Telophone:

Mr. Jchncon, 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on May 22, 1975 Telegram: Fr. Keppler, 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on May 22, 1975

3) Drawing Number P & ID M-29 Report Number:

50-237/75-31 Report Dates Ihy 30, 1975 Occurrence Date: May 22, 1975 Pacility: Dresden Nuclear Power Station, Morric, Illinois IDOTPIFIC/. TION OF OCCURREIE The contairment cooling service water valvo P0-1501-3A failed to control flow during a scheduled surveillanco.

_ CONK)ITICNS PRIOR TO CCCURPR;CE At the time of this occurrence, Unit-2 was operating at 890 ist and 252 ins.

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no@e DESCRIPTION OF OCCURRECE oo no At 0500 hours0.00579 days <br />0.139 hours <br />8.267196e-4 weeks <br />1.9025e-4 months <br />.on May 22, 1975 the Instrument Mechanico began LPCI/Contain=ent.

o Cooling logic testing. The MD-1501-3A valve ic throttled automt.tically to caintain n", g service water pressure 20 psig abovo LFCI/CC cystcm water pronouro to rainimize o"g the concoquences of a heat exchanser tube leak. When the 2A containment cooling wo corvice' water pump was started, MD-1501-3a continued to givo a closed indicatic:

whilo the pump flow indicator was rerfistering 3,000 gpa. The control room operator tried to increaso the containment cooling service water flow rato by adjusting

""gM the position nodulator referenco patentiornetor. Although thero was no i==ediate l

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responne, approximately one minute later the flow rapidly increased to 3600 gpn.

Repeated attempts by the operator to vary the flow by remotely operating the valve failed. A visual check of FO-1501-M verified that it was open. An the 2A containment cooling acrvice water pnp was occured, the mocor operator drove the valve closed as per design; however, the motor operator continued to run causing the valve stem to bcnd and disengage from the Limitorque. The valve had to be electrically racked out in crder to stop the motor.

DESIG!UsTIO:I 0F AppARE7P CAUSE (Equip::ent Failure)

Sinco the recent startup of Unib2, this particular type of failure has occurred on valvo 1:0-1501-3B. The actual cause has not yet been determined. A supplemcntary report identifying the causo vill be outclitted upon cor.pletion of the investigation.

ANALYSIS OP OCCURRFICE When the MO-1501-3A valve failcd, it was unable to control flow significantly; consequently the required 20 psig differential was not able to be maintained.

Houever, the coolin;; capability of the system was s,till effective since the valve was opened sufficiently to ensure adequate flow.

Despite the loso of differential precoure control, only a tubo leak in the heat exchanger could have resulted in a release of contaminated water to the river.

If a tubo leak had cecurred, the LTCI heat exchanger could have been manually icolated, diverting flow through the bypass lino. Therefore, the health and safety of the plant personnel and the public were not jeopardized no a result of this occurrence.

s CORRDCTIVE ACTIO?I The new 1" valve stems (previously decerited in report !!o. 50-237/75-28) have not yet crrived; concequently the valvo ctill utilized a 3/4" valvo atem.

At 0630 hours0.00729 days <br />0.175 hours <br />0.00104 weeks <br />2.39715e-4 months <br /> on Pay 25, 1975 the valve was placed back in service. At 1625 hours0.0188 days <br />0.451 hours <br />0.00269 weeks <br />6.183125e-4 months <br /> the LFCI/CC surveillance tect was succesantlly completed and the valve was declared operabic.

A dcaign modification for Unita 2 & 3 on valves M0-1501-3A & 33 is being evaluated.

A nu:Imary of this evaluation will be nut <nitted along with the results of the

Investigation to determine the cause of failure.

FAILUBE DATA The MO-1501-3A valvo io a 12"-300 pai stantard globe valve assembly manufactured by Copes-Vulcan, a division of Blaw-Knox Co. The operator is a Limitorque m

Mr. Jaraeo 0. Keppler

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c' One failur'c of this type has previously occurred for Unita 2 & 3 typo S!G-0.

On Vr.y 6,1975 M0-2-1501-3A & 33 failed in an identical raanner. For reference, ace report No. 50-237/75-28 no mentioned above.

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