ML20085G239

AO BFAO/50-260/7435W:on 741218,flow Control Valve 2-FCV-74-66 on RHR Sys Loop II Failed to Open.Caused by Loose Locknut Due to Missing Set Screws in Yoke Nut Bearing Locknut.Spare Motor Operator Installed

ML20085G239
Person / Time
Site:	Browns Ferry
Issue date:	12/27/1974
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085G245	List: ML20085G239 ML20085G256
References
NUDOCS 8308240719
Download: ML20085G239 (2)

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[A O e m NORI'AL OCCURPCIICE REKiiT j]

1 Report Ho.: BFAO-50-260/7435W Report Date: December 27, 1974 Occurrence Date: Decenter 18, 1974 Facility: Browns Ferry Nuclear Plant unit 2 Identification of Occurrence Failure of ficw control valve 2-FCV-74-66 on RHR system loop II to open.

Conditicas Pricr to Occurrence Reactor power was 3,117 a t and routine surveillance testing was being conducted.

Description of Cccurrence During the performance cf rcutine surveillance tests, f1cu control valve 2-FCV-74-66 cn the RER system was closed and cculd not be opened. Visual inspection revealed that the thrust bearing assembly was damaged.

Desirnaticn of Arparent Cause of Occurrence Set screws nissing; frca the ycke nut's upper bearing locknut allcwed the Iceknut to become loose and unscrew. This allowed the yoke nut to cove dcwrneard while the valve was attempting to open. The ycke nut moving dcwnward locked the operator and damaged the Iceknut, the upper bearings, the yoke nut key, and the yoke nut.

Analysis of Occurrence Both core spray lecps and F22 lcop I were availablr and could have provided emergency core eccling if required. There were no adverse effects to the public health or safety; and there was no dacage to other systems, components, or structures as a result of this cecurrence.

Corrective A:tien The valve motor operatcr and thrust bearing assembly were rencved. A spare tctor operater and bearirg asse bly were installed. Post-maintena6ce and functional tests were perforced satisfactorily. The yoke nut position en the vafve in a similar positica in lcop I was visually inspected and fcund satisfactcry.

Failure Data Manufacturer--Walworth Size--24" Body--WCB St en--CR-13 Code--655095724CCCA Humber--P3BS5C9WE USAS--6CO G 85G F.

l WOG--1,440 G 1C00 F.

See Abnormal Occurrence Report No. BFAO-50-260/7432W for valve disc failure.

l 8308240719 741227 PDR ADOCK 05000260 S PDR L

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.u Limes vP.,y g s2 > /aa0, m. na .-pJ, CCCUKZ:'E o TGPORT 321.0-50-260/743517 The enclo ed repart in to procide detailc concerning failure of flo control valve 2-FCV-Th-66 on F~:3 cystc= loop II to open e.nd is .nubmitted in Eccordance with Appendix I. to Regulatory Gaide 1.16, l'evision 1, October 1973 'Eric event occurred on Jrounc Ferry 1:uclear Pltnt unit 2 on Decerber 10, 1974 Ve:/ trcly yourc,

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