ML20084K167

AO 50-237/1974-52:on 741018,during Run Mode,Recirculation Pump Suction Valve MO-2-0202-4B Failed to Close Completely. Caused by Open Torque Switch.Special Procedure Authorized to Bypass torque-limiting Switch

ML20084K167
Person / Time
Site:	Dresden
Issue date:	10/25/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084K170	List: ML20084K167 ML20084K177 ML20084K184
References
781-74, NUDOCS 8305190193
Download: ML20084K167 (2)

Text

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3' Comm crith Edison I) iM-95 one Fat m.anst Plaza. Chicaao. titinois D

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hcdress Reply to: Post OfficiBox 767 Chicago Illinois 60690 h-h3"7, BBM Ltr.#781 Dresden Nuclear Power Station R. R. #1 Morris, Illinois tS cv 6

October 25, 1c J f=ll ocru a NbMf Mr. Jcmes G. Keppler, Regional Director '05 "E A Directorate of Regulatory Operations-Region III U. S. Atomic Energy Cornission 799 Roosevelt Road g

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Glen Ellyn, Illinois 60137 4 -4

SUBJECT:

P2 FORT OF AENOFF1J, OCCURRENCE PER SECTION 6.6,A 0F TIIE TECIETICAL SPEIFICATIC"S.

NO-2-0202-4B (B RE IRCULATION PUMP SUCTION VALVE) FAILURE TO CLOSE.

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of AEC Regulatory Operations Telephone Mr. F. Maura, 1520 hours0.0176 days <br />0.422 hours <br />0.00251 weeks <br />5.7836e-4 months <br /> on October 18, 1974 Telegram Mr. J. Keppler, October 18, 1974 e 3) Drawing Number: M-26 Report Number: 50-237/1974-52

• Report Dato: October 25, 1974 e Occurrence Date: October 18, 1974 Facility: Dresden Nuclear Power Station, Morris, Illinois

-IDENTIFICATION OF OCCURRENCE ,

MO-2-0202-4B (B Recirculation Pump Suction Valve) failed to close on a signal from the control room. ,

CONDITIONS PRIOR TO OCCUP.RENCE At the time of the incident, Unit 2 was in the RUN mode and was at a thercal

_ power of 2085 megawatts with a corresponding electrical load of 640 megawatts.

--DFECRIPTION OF OCCUILE!CE s Valve MO-2-0202-4B,. the Unit 2 3 recirculation pump suction valve, failed to close completely while atter; ting to isolate the B rceirculation pump in pro-paration for replacing the leaking mechanical a m l.- At'0255 hours0.00295 days <br />0.0708 hours <br />4.21627e-4 weeks <br />9.70275e-5 months <br />'on October 8305190193 741025 g .g 7 gDRADOCK05000 . _

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Mr. James G K:pplw *' Octob:r 25, 1974 .

o 18, 1974, the-valve was assumed partially open because of a double indication of the position indicating lights. In addition, this determination was veri-fied by timing the interval betvicen the position indicator lights actuation.

DESIGNATIO'I OF APPARENP CAUSE OF OCCU3RE!CE (Other)

The valve apparently did not close completely because the torque switch opened.

The valve's torque switch was inspected during the subsequent reactor cutage.

No cause for the torque switch opening could be found. Tuo weeks prior to the occurrence, the valve operated satisfactorily during an outage.

ANALYSIS OF OCCURRSICE The health and safety of the plant personnel and the public were not jeopar-dized as a result of the valve failure. If a LOCA occurred and the failure was between the discharge and suction valves of the "B" recirculation pump, the partially opened suction valve would provide a flow path for the reactor water. Since the emergency core cooling systems (ECCS) were designed to main-tain the reactor water in the event of a maximum credible accident, these systems would be more than adequate to maintain the reactor water level in this condition.

e CORRECTIVE ifTION At 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />, a special procedure was authorized to bypass t,he torque-limiting switch and manually close the valve. T;is completely isolated the leaking pump seal.

A weekend outage was arranged to replace the pump seal and to examine the suction valve. The torque-limit switch has a relative adjustment from 0-5.

The existing valve closing setting of 15 was found to be inadequate and therefore, was increased to 2.0.

The manufacturer recommended a setting of 3 with a maximum of 5, which is within the allowable stress for which the valve was designed. The station revicu function performed an official on site review and approved this change.

FAILURE DATA

- To date, no previous malfunctic,ns or failurco of this nature have occurred on the recirculation pump suction valves. The valves are Crane 28" list 608 gate valves with design conditions of 1325 pai at 575*F.

Sincerely, j/

I Yl(

5. B. Staplcusonbnf Superintdndent BBS: GAR /RLW:do

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