05000346/LER-1980-056-03, /03L-0:on 800709,while Performing ST 5030.09 in Reactor Protection Sys Channel 3,insulated Alligator Clip Slipped Off Terminal Stud Causing Short Circuit Between Terminals 3 & 4.Caused by Personnel Error

/03L-0:on 800709,while Performing ST 5030.09 in Reactor Protection Sys Channel 3,insulated Alligator Clip Slipped Off Terminal Stud Causing Short Circuit Between Terminals 3 & 4.Caused by Personnel Error

ML19331B671
Person / Time
Site:	Davis Besse
Issue date:	08/07/1980
From:	Werner J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19331B667	List: 05000346/LER-1980-056, Forwards LER 80-056/03L-0 05000346/LER-1980-056-03, /03L-0:on 800709,while Performing ST 5030.09 in Reactor Protection Sys Channel 3,insulated Alligator Clip Slipped Off Terminal Stud Causing Short Circuit Between Terminals 3 & 4.Caused by Personnel Error
References
LER-80-056-03L, LER-80-56-3L, NUDOCS 8008120568
Download: ML19331B671 (3)

LER-1980-056, /03L-0:on 800709,while Performing ST 5030.09 in Reactor Protection Sys Channel 3,insulated Alligator Clip Slipped Off Terminal Stud Causing Short Circuit Between Terminals 3 & 4.Caused by Personnel Error

Event date:
Report date:
3461980056R03 - NRC Website

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U.S. NUCLEAR REGULATCRY COMMISSION NRC Fuh?' 11 (7 7N LICENSEE EVENT REPORT CONTROL BLOCK: l l

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8 60 61 DOCKET NUMBER 66 ti9 EVENT OATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h l (NP-33-80-70) On 7/9/80 at 2325 hours0.0269 days <br />0.646 hours <br />0.00384 weeks <br />8.846625e-4 months <br /> while performing ST 5030.09 in Reactor Protec- [

O 2 [bT~1 l tion System (RPS) Channel 3, an insulated alligator clip slipped off the terminal studi l causing a short circuit between terminals 3 and 4.

This resulted in a loss of Y3 l

O 4 I which caused a loss of Safety Features Actuation System (SFAS) Channel 3 containment l 0 s 0 s l radiation, placing the unit in violation of T.S. 3.,3.2.1. (3 was swf eched to an alter-l 10171 l nate power supply and SFAS Channel 3 was operable within minutes.

RPS and SFAS Chan-l l 0 l8 l l nels 1, 2, and 4 were continuously available.

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42 44 47 CAUSE OESCRIPTION AND CORRECTIVE ACTIONS h l The cause was a personnel error in that the technician used the wrong type of insulatg i O ITTTl I alligator clips. Under MWO 80-2821, FiO1 was replaced. At 0145 hours0.00168 days <br />0.0403 hours <br />2.397487e-4 weeks <br />5.51725e-5 months <br /> on 7/10/80, Y3 l l was powered from its normal source. A memo was written by the Lead I&C Engineer, l

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TOLEDO EDICON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-80-70 DATE OF EVENT: July 9, 1980 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE:

Loss of Instrument Bus Y-3 Conditions Prior to Occurren~3* The unit was in Mode 6, with Power (MWT) = 0 and Load (Gross MWE) = 0.

Description of Occurrence: On July 9, 1980, at about 2325 hours0.0269 days <br />0.646 hours <br />0.00384 weeks <br />8.846625e-4 months <br /> while performing ST 5030.09, Reactor Protection System (RPS) Response Time Test in RPS Channel 3, a test connection was being made to terminal board 1-10-6, terminals 3 and 4 to monitor li3VAC to the undervoltage coil on the channel 3 control rod trip breaker.

While attempting to install one of the insulated alligator clips on the test lead, the clip slipped off the terminal stud, contacted the adjacent stud and clip and caused a short circuit between terminals 3 and 4.

The short circuit resulted in the RPS trip circuit fuse F2 and the YV3 inverter input fuse F101 blowing. The failure of YV3 fuse F101 caused a loss of power to the Y3 essential power bus de-energizing Safety Features Actuation System (SFAS) Channel 3.

Bus Y3 was manually transferred to its alternate source, and the SFAS and RPS channels were re-energized.

The loss of SFAS Channel 3 meant that Channel 3 (RE2006)CTMT radiation was not operabic. This caused the unit to be placed in the' action statement No. 9 of Technical Specification 3.3.2.1.

The action statement requires the channel be restored within one hour or placed in a tripped condition within one hour. Y3 was switched to an alternate power supply and SFAS Channel 3 returned to operable status within minutes of its initial loss of power.

Designation of Apparent Cause of Occurrence: The apparent cause of the occurrence is two-fold.

The short circuit was the result of personnel error in that the tech-nician failed to note that the insulated alligator clip being used was the type with a needle spike in one jaw which would not grip and hold on the terminal stud as would a conventional insulated alligator clip.

The second cause is in the design in that the 200 amp inverter output fuse blew, de-energizing the whole bus before a 30 amp RPS supply fuse and the 25 amp RPS l

circuit breaker did. However, this is a design to protect the inverter from a 200 amp surge.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel.

RPS and SFAS Channels 1, 2, and 4 were continually avail-able as were 120 VAC essential buses Y1, Y2, and Y4.

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR P06'ER STATION U'(IT ONE PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NT-33-80-70 I

Corrective Action

Maintenr.nce Work Order 80-2821 was issued to investigate the loss of the Y3 Bus.

F101 was found blown and was replaced. RPS trip circuit fuse i

F2 was found blown and was replaced. There was no apparent damage to the inverter.

Tha Y3 Bus was transferred back to its normal source. There was no other cause found for the blown fuse other than the short circuit in the RPS cabinet.

At 0145 houra on July 10,1980, Y3 was powered froci its normal source. RE2006 i

was returned to service. A memo was written by the Lead I&C Enginect and dis-tributed to the I&C technicians cautioning them of the importance of using the 1

correct style insulated alligator clip.

Failure Data: Previous failures of 120 VAC essential power inverters due to acci-dantal shorting were reported in Licensee Event Reports NP-32-79-09 (79-067) and 4

NP-33-79-13 (70-009).

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