05000346/LER-1979-131-03, /03L-0:on 791212,steam & Feedwater Rupture Control Sys Channel 4x15-volt Dc Power Supply PS-4 Failed.Caused by Overvoltage Trip Setpoint Actuating at Lower Value than Initial Adjustment.Installed New Power Supply

/03L-0:on 791212,steam & Feedwater Rupture Control Sys Channel 4x15-volt Dc Power Supply PS-4 Failed.Caused by Overvoltage Trip Setpoint Actuating at Lower Value than Initial Adjustment.Installed New Power Supply

ML19257B338
Person / Time
Site:	Davis Besse
Issue date:	01/09/1980
From:	Trautman D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19257B332	List: 05000346/LER-1979-131, Forwards LER 79-131/03L-0 05000346/LER-1979-131-03, /03L-0:on 791212,steam & Feedwater Rupture Control Sys Channel 4x15-volt Dc Power Supply PS-4 Failed.Caused by Overvoltage Trip Setpoint Actuating at Lower Value than Initial Adjustment.Installed New Power Supply
References
LER-79-131-03L, LER-79-131-3L, NUDOCS 8001150582
Download: ML19257B338 (3)

LER-1979-131, /03L-0:on 791212,steam & Feedwater Rupture Control Sys Channel 4x15-volt Dc Power Supply PS-4 Failed.Caused by Overvoltage Trip Setpoint Actuating at Lower Value than Initial Adjustment.Installed New Power Supply

Event date:
Report date:
3461979131R03 - NRC Website

text

U. S. NUCLEAR REGULATOR o.uMlbu.

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REPOHT DAT E BJ EVENT DESCRIPTION AND PROBABLE CCNSEGUENCES h lOn 12/12/79, and again on 1/6/80, the Steam and Feedwater Rupture Control System l

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l (SFRCS) Chanel 4 +15 volt DC power supply PS-4 f ailed causing a Channel 4 half trip l

goj3; lin Channel 2/4. Technical Specification 3.3.2.2 requires all four channels operable 1 9

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The station was in !! ode 5 on 12/12/79 and in !! ode 1 on

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1 1/6/80. There was no danger to the health and safety of the public or station per-l l C l 7 l l sonnel. Loss of the power supply places the channel in the tripped (safe) position.

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43 41 42 43 44 47 33 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h l The cause of the initial occurrence was the overvoltage trip setpoint actuating at a l i

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g l: l gg l channel declared operable on 12/27/79. The power supply failed on 1/6/80 and will be [

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4 TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-53-79-148 DATE OF EVENT: December 12, 1979, January 6,1980 FACILITY: Davis-Besse Unit 1 Failure of +15 volt DC power supply PS-4 in Steam IDENTIFICATION OF OCCURRENCE:

and Feedwater Rupture Control System (SFRCS) Channel 4.

The unit was in Mode 5, with Power (MWT) = 0, Conditions' Prior to First Occurrence:

and Load (Gross MWE) = 0.

tlc unit was in Mode 1, with Power (MWT) = 27 Conditions Prior to Second Occurrence:

and Load (Gross MWE) = 0.

Description of Occurrence: On December 12, 1979 at 2030 hours0.0235 days <br />0.564 hours <br />0.00336 weeks <br />7.72415e-4 months <br />, the SFRCS Channel 4

+15 volt DC power supply PS-4 failed causing a Channel 4 half trip in Channel 2/4.

This did not place the unit in the action statement of Technical Specification 3.3.2.2 which requires all four channels to be operabic in Modes 1, 2, and 3 only.

This event is being reported The unit was in Mode 5 at the time of the occurrence.

to document a component failure.

On January 6, 1980 at 2039 hours0.0236 days <br />0.566 hours <br />0.00337 weeks <br />7.758395e-4 months <br />, the SERCS Channel 4 power supply PS-4 failed caus-This event did place the unit in Action in; a Channel 4 half trip in Channel 2/4.13 of Technical Specification 3.3.2.2 which re The channel Statement of the channel to be placed in the tripped condition within one hour.

was declared inoperable at 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> and maintained in the tripped condition.

Investigation has revealed that the Designation of Apparent Cause of Occurrence:

a lower cause of the first occurrence was in the overvoltage trip setting actuating at The reason for the value than the initial installation setpoint of October 4, 1979.

drif t in the overvoltage prntection setpoint is unknown at this time. The power will be returned to the vendor (Sorenson) for further supply PS-4 (Serial No. 01 analysis of the cause of the failure.

There was no danger to the health and safety of the public Analysis of Occurrence:

The SFRCS Channel 4 performed as designed in both occur-or to station personnel.

The power supply PS-4 caused a trip condition in Channel 4 of SFRCS rences.

Channel 2/4.

During the time interval between the initial occurrence and

Corrective Action

when power was restored to the power supply, the input and output December 26, 1979, No trips of the power supply occurred during this time of the supply were monitored.

period.

i747 004

TOLEDO ED1 SON COMPANY Di.VIS-BESSE NUCLEAR PO'4ER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-148 PAGE 2 On December 26, 1979 at 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br />, the 15 volt DC power supply Serial No. 0148 was removed from the SFRCS channel and bench tested. The overvoltage protection setpoint was re-adjusted to the value as required by the mcaufacturer's technical information.

The power supply (Scrial No. 0140) was reinstalled in the SFRCS Channel 4.

The channel was declared operable on December 28, 1979. At the time of the second occurrence on January 6,1980, the SFRCS Channel 4 power supply PS-4 (Serial No. 0148) was removed from the SFRCS Channel 4.and tested again.

The overvoltage trip setting was not the cause of this f ailure and no apparent cause for the failure was discovered at this time.

On January 7,1980 at 2130 hours0.0247 days <br />0.592 hours <br />0.00352 weeks <br />8.10465e-4 months <br />, a new 15 volt DC power supply (Serial No. 0345) was installed as PS-4 in SFRCS Channel 4.

The channel was declared operable on January 7, 1980 at 2230 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.48515e-4 months <br />.

Failure Data: There has been one previous failure of an SFRCS 15 volt DC power supply, see Licensee Event Report NP-33-79-113.

1747 005