ML19263B920

LER 78-125/03L-0 on 781104:personnel Started Reactor Coolant Pump 1-1-2 Instead of 1-1-1 Causing Loss of Power of Essential Bus D1.Caused by Personnel Error & Design Deficiencies.Facility Change Requests Prepared

ML19263B920
Person / Time
Site:	Davis Besse
Issue date:	01/19/1979
From:	David Brown TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19263B916	List: ML19263B915 ML19263B920
References
LER-78-125-03L, LER-78-125-3L, NP-33-78-148, NUDOCS 7901250140
Download: ML19263B920 (3)

Text

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FVENT DESCRIPTio'; A'.D PRC3 AELE CC',SE CUE *.'CES h

[ol2l At 02:54:03 hours, operatiens personnel intendine to start Peactor Coolant Pump _GCP) I o 3 l1-1-1, whose essential bus feed breaker undervoltage relays were disconnected for the i o a latart, started RCP 1-1-2 instead. Essential Bus D1 de-enereized at 02:54:03 hours. I 02 : 54 : 1f 8 o s [Energency Diesel Generater 1-2 started and Essential Bus D1 was re-enereized at It was also deter ined that disabling the esse:Tt al bus undervoltace relave. is l o c l hou rs.

l o l 7 l l contrary to Technical Specification 3.8.2.1. The total t~me in which Essential Eus D1 o a Iwas de-energized was ten seconds. The unit was subcritical at the Line of the inciden_tj. "4 7 8 9 (NP-33-78-148) sva E'.s c: % cAun cO ?P ve. tu C;;i S ?:COE C9 WANE *.T CODE SLBCCDE Ss0 CODE CCOE o 9 lE l Bj@ ]@ l Al@ l C IK l T l B l K I R lh lE lh Iz l h 13 M 14 .s 8 9 10 11 12

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g i g , y pas transf erred back to its normal power supply and Emergency Diesel Generator 1-2 uas I gre turned to normal standby status. Operations personnel vill now transfer the essen- t FCRs

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a TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION U'ilT ONE SUPPLE" ENTAL INFORMATION FOR LER NP-33-78-148 DATE OF EVENT: Nove=ber 4, 1978 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF CCCURRENCE: Loss of power to 4.16 KV Essential Bus D1 and remov-ing essential bus ondervoltage relays when starting Reactor Coolant Pumps Conditions Prior to Occurrence: The unit was in Mode 3, with Power (MWT) = 0, and Load (Gross MWE) = 0.

Description of Occurrence: Prior to starting Reactor Coolant Puaps (RCP) 1-1-1 and 1-2-2 on November 4, 1978, unit personnel temporarily disabled 4.16 KV Essential Bus "Cl" Feeder Breaker AC110 Undervoltage Relays 27A-1/C1 and 27A-4/Cl per Reactor Coolant Pu=p Operating Procedure SP 1103.06, Terporary Modification T-2937. This was done to elininate the post.ibility of tripping Essential Bus Cl on low voltage when RCP l-1-1 or RCP l-2-2 was s tarted. At 02:50:45 hours, RCP l-2-2 was successfully started.

At 02:54:03 hours, operations personnel intending to start RCP 1-1-1, started RCP l-1-2 instead. When RCP 1-1-2 was started, it depressed the voltage of its eupply bus, 13.8 KV Bus "B". The 4.16 KV Essential Bus "D1", which is also supplied from Bus "B" through Bus Tie Transforcer "BD", suffered a proportional voltage drop which caused Essential Bus "Dl" Feeder Breaker AD110 Undervoltage Relays 27A-1/D1 and 27A-4/D1 (still in service) to trip Feeder Breaker AD110 and de-energize Essential Bus D1 at 02:54:0S hours.

The loss of power initiated an c=ergen.y start of Emergency Diesel Generator 1-2. As a result, Essential Bus "Dl" was re .ncrgized, and its voltage was returned to normal at 02:54:18 hours.

The loss of power to Essential Bus "Dl" placed the unit in the Action Statement of Technical Specification 3.8.2.1, which states that 4.16 KV Essential Bus "Dl" must be operable and energized while it Mode 3.

The total time in which Essential bts "Dl" was de-energized was ten seconds. During an NRC Exit Interview on December 22, 1978, it was determined that this incident was reportable and that disabling the essential bus undervoltage relays as described in Mcdification T-2937 was contrary to Technical Specification 3.3.2.1.

Desitnation of Apparent Cause of Occurrence: This incident was caused by personnel error and by design deficiencies. Operations personnel started RCP l-1-2 instead of RCP l-1-1; Essential Bus "Dl" Feeder Breaker AD110 Undervoltage Relays were still in service and the start of RCP l-1-2 and the resultant voltage depression caused Essential Bus "Dl" to trip. Bus voltage depression caused by starting large motors LER #78-125

4 TOLEDO EDISON COMPANY DAV1S-BESSE NUCLEAR PO'..'ER STATION UNIT ONE PAGE 2 SUPPLDIENTAL I!:rOR'IATION FOR LER NP-33-78-148 such as the Reactor Coolant Pwmps necessitated the temporary removal of the essen-tial bus feeder breaker undervoltage relays. This action lef t the affected bus without undervoltage protection.

Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. The unit was subcritical at the time of the incident. There was only a brief interruption in essential equipment operation as Essential Bus "Dl" was re-energized within ten seconds.

Corrective Action: At 02:54:18 hours, the 4.16 KV Essential Bus "D1" was re-ener-gized. At 03:00:38 hours, Essential Bus "D1" was transferred back to its normal power supply and Emergency Diesel Generator 1-2 was returned to normal standby status. Operations personnel have been instructed to be more alert when starting unit equipment.

Modification T-2937 has been replaced by Modification T-3444. T-3444 transfers the affected essential bus's power supply from its normal 13.8 KV/4.16 KV bus tie transformer to the alternate 13.8 KV/4.16 KV bus tie transformer during the start of a Reactor Coolant Pump.

Facility Change Requests77-430 and 77-430 Supplement 2 were written to request provisions for momentary bypassing of the undervoltage relays when starting the Reactor Coolant Pumps and to change the Technical Specifications to allow the undervoltage relays to be momentarily bypassed when starting Reactor Coolant Pumps and Circulating Water Pumps.

LER #78-125

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