05000260/LER-1986-003, Corrected Page 2 to LER 86-003-00:on 860226,energized Isolation Logic Tripped.Caused by Personnel Error.Temporary Cover for Protection Against Accidental Bumping of Bus Transfer Switch Provided

Corrected Page 2 to LER 86-003-00:on 860226,energized Isolation Logic Tripped.Caused by Personnel Error.Temporary Cover for Protection Against Accidental Bumping of Bus Transfer Switch Provided

ML20141E817
Person / Time
Site:	Browns Ferry
Issue date:	04/10/1986
From:	Robert Lewis TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML20141E791	List: 05000260/LER-1986-003, Corrected Page 2 to LER 86-003-00:on 860226,energized Isolation Logic Tripped.Caused by Personnel Error.Temporary Cover for Protection Against Accidental Bumping of Bus Transfer Switch Provided
References
LER-86-003-04, LER-86-3-4, NUDOCS 8604220392
Download: ML20141E817 (1)

LER-2086-003, Corrected Page 2 to LER 86-003-00:on 860226,energized Isolation Logic Tripped.Caused by Personnel Error.Temporary Cover for Protection Against Accidental Bumping of Bus Transfer Switch Provided

Event date:
Report date:
2602086003R00 - NRC Website

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01 0 012 0F 012 rm n - . c ,.- mim nn Units 1 and 3 were in extended maintenance outages, and unit 2 was in a refueling outage. This event affected unit 2 and common ventilation systes.

On February 26,1986, at 2112, electrical modifications electricians were pulling cables in unit 2 battery board room when the workmen accidentally bumped the reactor protection syst s (RPS) (JE) bus 'A' transfer switch. Power to RPS bus 'A' is supplied from a motor generator (MG) set or an alternate transformer.

The transfer of power between the two sources momentarily interrupted power to the RPS bus. Emping the transfer switch deenergized RPS 'A,' which tripped the normally energized isolation logic and caused:

1. Group 2 (shutdown cooling) inboard isolation (BO)

2. Group 3 (reactor water cleanup) inboard isolation (CE)

3. Group 6 (purging and venting) isolation (VB) 4 Group 8 (traversing incore probe) isolation (IG)

5. Half-scram signal on RPS channel 'A'

6. Unit 1, 2, and 3 refuel zone isolation (VG)

7. Unit 2 reactor zone isolation (VA)

8. control rom mergency ventilation initiation (VI)

9. Standby gas treatment initiation (BH)

The operators reset the isolations and returned the actuated systes to nomal standby readiness by 2120.

Unit 2 was empletely defueled at the time, and the inadvertant trip was in the conservative direction.

Personnel error is involved in that the electricians did not exercise due caution while pulling cables in the unit 2 battery board room. The transfer switen, along with the voltage adjustment control knob are located on the battery board for each unit. The switch is a General Electric type SBM. The switch is physically located about four feet above the floor and is not protected against accidental contact. The voltage adjustment control knob on unit 3 had been previously bmped on January 1986 as described in LER BFRO-50-2%/86001. A temporary cover for protection against accidental bumping of unit 2 RPS bus transfer switches has been provided. Pemanent protection in the form of an enclosure over the switch is planned for recurrence control.

Resoonsible Plant Section - EM Previous Events - BFRO-50-296/86001 8604220392 860410 0 PDR ADOCK 0500 S

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