ML20085G005

AO BFAO-50-260/756W:on 750221,120-volt Power Supply to RCIC Flow Controller & Suppression Pool Level & Drywell Pressure Indicators Lost.Caused by Mispositioning of 120-volt Selector Switch XS-57-170 to Off Position

ML20085G005
Person / Time
Site:	Browns Ferry
Issue date:	03/03/1975
From:	Eric Thomas TENNESSEE VALLEY AUTHORITY
To:	Case E Office of Nuclear Reactor Regulation
References
NUDOCS 8308240156
Download: ML20085G005 (3)

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. ABNORMAL OCCURREI!CE REI' ORT Report ITo. : BFAO-50-260/756W Report Date: March 3, 1975 Occurrence Date: February 21, 1975 Facility: Browns Ferry nuclear Plant unit 2 Identification of Occurrence Loss of 120-V power supply to RCIC flow centroller and suppression pool level and drywell presnure indicators due to selector switch XS-57-170 being incorrectly positioned.

Conditions Prior to Occurrence Unit was operating at 1,075 ige. .

Descriptien of Occurrence The operator on duty in the control room received the following alarms at approximately 2130.

1. Suppression pool level abnomal.

2. Containment spray initiation.

Follouing indications were lost.

1. Suppression pool level.

2. Drywell prc cure.

During nubsequent investication, it was found that power was also lost to the RCIC flow controller. Further invectigation revealed that colector switch XS-57-170 located on panel 25-32 in 4-kV chutdown board room C was in this OFF position. .

This cuitch in located in a " locked" room where access is not permitted without authorication of the shift engineer. No evidenco can be found that this room was unlocked and entered at the time of this occurrence. The time of the event is verified by recorder tracings, eliminating the possibility that the condition was existent before being noticed.

Apparent Cause of Occurrence Micpositioning of 120-V selector switch XS-37-170 to the OFF position.

A similar switch was tested to detemine possibility of self-movement from vibration or other means. The investigation revealed that there was no possibility of the switch to nisposition of its own accord.

8308240156 750303 PDR ADOCK 05000260 S PDR

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!!x. Edson G. Case (', [.' Td,

Acting Director of Licensing U.S. liuclear Regulatory Comission Ucchington, DC 205h5

Dear 1'x. Case:

TE:TITESSE3 VALLEY AUTHORITY - BROWS FERRY ITUCLEAR PLAllT UIIIT 2 DCCKET I!0. 50-260 - FACILITY OPERATII;G LICENSE DPR ABI!0FFAL OCCURRI!iCU PIPORT BFA0-50-260/756W The cuc20 sed report is to provide details conecrning loss of 120-V power cupply to the RCIC ficw controller and suppression pool level and dryuell prec. cure indicatore due to celector switch XS-57-170 being incorrectly pocitioned and is submitted in accordance with Appendix A to Regulatory Guide 1.16, Revision 1, October 1973 This event occurred on Browns Ferry I!ueleur Plant unit 2 on February 21, 1975.

Very truly yours, TE! iESSEE VALLEY AUTHORITY

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E. F. Thor.nc Director of Power Production Enclosure '.

CC (Enclosure):

l'r. I!ormen C. I'.oceley, Director U.S. Iiuclear Eegulatory Comission Regionel Office 230 Peachtree Street, IiW. , suito 818 Atlanta, Georgia 30303

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