ML19345D445

LER 80-081/03L-0:on 801112,unit Experienced Loss of Essential Bus Y2.Caused by Use of Grounded Oscilloscope to Record Input Voltage Wave forms.YV2 Inverter Input Fuse Replaced & Essential 120-volt Ac Power Restored

ML19345D445
Person / Time
Site:	Davis Besse
Issue date:	12/10/1980
From:	Trautman D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19345D444	List: ML19345D443 ML19345D445
References
LER-80-081-03L, LER-80-81-3L, NP-33-80-105, NUDOCS 8012150118
Download: ML19345D445 (3)

Text

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O. S. NUCLE AR REGULATORY CoMMISSloN NPC FORM 3:36' LICENSEE EVENT REPORT CONTROL BLOCC l l l l l l o

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10141 I the Integrated Control System. The loss of flow indication started a series of event $

I c 151 I which resulted in a reactor trip on high RCS pressure. The Station entered the actio9 There was no danger to the health and l f Ts 1 I statement of TS 3.8.2.1 for the loss of Y2.

l iTT71 I safety of the public or to Station personnel. The three redundant safety circuits 1

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l li l o l l The cause was the use of a grounded oscilloscope by I&C personnel to record input f TT1 I voltage waveforms at the SFRCS Ch. 2 Cabinet. The ground fed back to the YV2 invertett The fuse l

, , l input fuse which took out the Y2 bus 9hich caused the loss of RPS Ch. 2.

3 3 l was replaced under FMO 80-3839 and essential 120 VAC power restored to Y2 at 1530 l Memorandum M80-2502 concerning oscilloscopes was issued. g 3 4 l hours. so IS O RY DISCOV E Rt' O ESCRIPTION StA S  % POWER OTHER STATUS Operator Observation l l

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-80-105 DATE OF EVENT: November 12, 1980 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of Essential Instrumentation Power Bus Y2 which resulted in a reactor trip Conditions Prior to Occurrence: The unit was in Mode 1 with Power (MWT) = 1092 and Load (Gross FME) = 330 Description of Occurrence: On November 12, 1980 at 1403 hours0.0162 days <br />0.39 hours <br />0.00232 weeks <br />5.338415e-4 months <br /> with the unit at approxi-mately 40 percent power, the unit experienced a loss of Essential Bus Y2. This bus powers the Reactor Protection System (RPS) Instrumentation Channel 2. This channel was providing Reactor Coolant System (RCS) flow indication to the Integrated Control System (ICS). When the bus was lost, ICS sensed a loss of flow indication and started running back feedwater flow on the secondary side. This loss of cooling to the RCS caused RCS pressure to go high, and the reactor tripp,ed on high pressure.

The loss of Y2 entered the station into the action statement of Technical Specification 3.8.2.1 which required the bus be restored to operable status within eight hours or be in at least hot standby (Mode 3) within the next six hours and in cold shutdown within the following thirty hours. Since the reactor tripped, and the station entered Mode 3, the conditions were met.

Designation of Apparent Cause of occurrence: The cause was determined to be a personnel error. An Instrument and Control apprentice overlooked a precaution written on a work order, and used a grounded oscilloscope to record input voltage waveforms at the Steam Generator Level Instrument Cabinet Channel 2 of the Steam and Feedwater Rupture Control System (SFRCS). These wr/eforms were being recorded as aWhen method of troubleshoot-the oscilloscope ing past difficulties experienced with Sorenson power supplies.

was connected, it caused a ground to feed back through the YV2 inverter and blew the inverter input fuse which caused the loss of Channel 2 of RPS, SFRCS, and Safety Features Actuation System (SEAS).

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The loss of essential bus Y2 disabled only one of four safety system circuits still allowing three redundant safety circuits to perform their function as designed.

Corrective Action: The I&C apprentice involved was given further guidance in performing proper test practices. The inverter input fuse was replaced under Maintenance Work Order 80-3839 and essential 120 VAC power restored to Y2 at 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br /> on November 12, 1980. Memorandum M80-2502 was issued to all 16C ap' prentices concerning the use of oscilloscopes in critical circuitry.

LER #80-081

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PAGE 2,*

SUiPLEMENTAL INFORMATION FOR LER NP-33-80-105 Failure Data: One previous similar occurrence has been reported, see Licensee Event Report NP-33-80-70 (LER 80-056)

LER #80-081 O

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