ML20085G661

AO BFAO-50-260/7432W:on 741204,shutdown Cooling Flow Control Valve FCV-74-66 Failed to Allow Waterflow Passage.Caused by Loosened Valve Disc.Valve Repaired

ML20085G661
Person / Time
Site:	Browns Ferry
Issue date:	12/13/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085G647	List: ML20085G661 ML20085G668 ML20085G683
References
NUDOCS 8308290266
Download: ML20085G661 (3)

Text

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s ABNORMAL OCCURRCCE RF20RT 1

Report No.: EFAO-50-260/7432W Report Date: December 13, 197h 2'

Occurrence Date: December 4, 1974 Facility: Browns Ferry Nuclear Plant unit 2 Identification of Occurrence

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Failure of shutdown cooling flow control valve FCV-74-66 to allow waterflow Passage.

Conditions Prior to Occu rence The unit was shut down and shutdown cooling loop 2 was being placed in service.

Descriution of Occurrence With the FCV-74-66 valve stem in the open position, flow could not be established" throu6h the valve.

i Desistnation of A :arent Cause of Occurrence The valve dise had become loose and was. stuck in the valve seat. Small tack welds between the valve disc and the sten guide ring, which are intended to prevent rotation, had broken. This allowed the disc to unscrew frc= the

stem guide ring and beco=e wedged in the seat opening.-

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. Analysis of Occurrence i

I Both core spray loops and EER loop 1 were available and could have provided emergency core cot ling if required. There were no adverse effects to the public health or safety; and there was no da= age to systems,. components, or structures as a result of this occurrence.

i Corrective Action .

The valve was disassembled and the disc found separated from the stem. The disc was renoved from the valve body; the valve body and seating surfaces were i visual 3y inspected; the mating threads on the disc and disc guide were cleaned,

inspected, and found satisfacto

/. The tack welds preventing rotation of the l -disc on the disc guide were found broken, and M1 parts were cleaned and l inspected. Repair was made by cutting a weld bevel on the; disc guide,

-reassembling the disc and guide, and applying a larger, stronger retaining weld to prevent separation of the parts.

The valve was reassembled and functionally tested satisfactorily.-

Valves in similar positions on both units 1 and 2 will be disassembled and.

inspected, and an additional weld will be adde'd to the disc and guide during unit outages when conditions permit.

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Failure Data .

Manufacturer--Walworth

, Size--24" h

Body--WC3

Stem-CR-13 i Code--655095724000A I Nu=ber--PSB5509'4 USAS--600 @ 850 F.

WOG--1,440 @ 100 F.

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Mr. Edson G. Case Acting Director of Licensing Office of Regulation '

U.S. Atonic Energy Co=nission Washington, DC 20545

Dear Mr. Case:

TEIEESSEE VALLEY AUTHORITY - BRO' INS FERRY UUCLEAR PIRIT UNIT 2 -

DOCKST NO. 50-260 - FACILITY OPERATING LICENSE DFR ABNORMAL OCCURRCCE REPORT EFAO-50-260/7h32W The enclosed report is to provide details concerning failure of shutdown cooling flow control valve FCV-74-66 to allow waterflow passage and is cub =itted in accordance with Appendix A to Regulator /

Guide 1.16, Revision 1, October 1973. This event occurred on Browns Ferry nuclear Plant unit 2 on December 4, 1974.

Very truly yours, TEICESSEE VALLEY AUTHORITY r , .- a k// -?

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, , E. F. Tho=as j Director of Power Production i

Enclosure -

CC (Enclosure):

Mr. Norman C. Moseley, Director Region II Regulator / Operations Office, USAEC 230 Peachtree Street, UW., Suite 818 .

Atlanta, Georgia 30303 12668 .

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ABNOIU'AL OCCUIiREGCE REPORT y

Rc'p ort No.: EFAO-50-260/7432W Report Date: Dece=ber 13, 1974

Occurrence Date

December 4, 1974 Facility: Browns Ferry Nuclear Plant unit 2 l Identification of Occurrence l

Failure of shutdown cooling flow control valve FCV-74-66 to allow waterflow passage.

Conditions Prior to Occu rence The unit was shut down and shutdown cooling loop 2 was being placed in service.

Description of Occurrence With the FCV-74-66 valve stem in the open position, flow could not be established" through the valve. i I i Desirmation of Arparent Cause of Occurrence h l The valve disc had become loose and was stuck in the valve seat. Small tack welds bet:een the valve disc and the stem p ide ring, which a.re intended t-prevent rotation, had broken. This allowed the disc to unscrew from the stem guide ring and beconc vedged in the seat opening.

Analysis of Occurrence Both core spray locps and RHR loop 1 were available end could have provided energency core cooling if required. Tnere were no adverse effects to the public health or safety; and there was no damage to systems, cocoonents, or structures as a result of this occurrence. -

Corrective Action .

8 The valve was disassembled and the dise found separated from the stem. The disc was recoved from the valve body; the valve body and seating surfaces were visunlly inspected; the rating threads on the disc and disc guide were cleaned, inspected, and found satisfactor/. The tack welds preventing rotation of the disc on the disc guide were found broken, and all parts were cleaned and inspected. Repair was cade by cutting a weld bevel on the dice guide, reassenbling the disc and guide, and applying a larger, stronger retaining weld to prevent separation of the parts.

The valve was reassembled and functionally tested satisfactorily.

Valves in similar positions on both units 1 and 2 will be disassembled and inspected, and an additional weld will be added to the disc and guide during unit outc6es when conditions permit, mw an0 '

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Failure Data

Manufacturer--Walworth Size--24"

• Body--WCB St'c=--CR-13 Code--65509572'4000A Hunber--PsB5509%'E USAs--600 0 850 F.

WoG--1,Wo ~@ loo F.

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Mr. Edson G. Case Acting Director of Licensing Office of Regulation - -

U.S. Atomic Energy Cornission '

Washington, DC 20545

Dear Mr. Case:

TEIINESSEE VALIZY AUTHORITY - BROWS FERRY I!UCLEAR PIRIT UIIIT 2 -

, DOCKET I!O. 50-260 - FACILITY OPERATIIIG LICEIiSE DPR ABliO?S.AL OCCURRE:!CEREPORTEFAO-50-260/7432W The enclosed report is to provide details concerning failure of shutdown cooling flow control valve FCV-74-66 to allow waterflow passage and is submitted in accordance with Appendix A to Regulator /

Guide 1.16, Revision 1, October 1973. This event occurred on Browns Ferry liuclear Plant unit 2 on December 4, 1974.

Very truly yours, TEITIIESSEE VALIZY AUTHORITY

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p.,(, E. F. Thomas y Director of Power Production Enclosure - -

CC (Enclosure): ,

Mr. Iiorcan C. Moseley, Director Region II Regulator / Operations Office, USAEC 230 Peachtree Street,liW., Suite 818 .

Atlanta, Georsia 30303 12868 e

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