ML19270F534

LER 79-011/03L-0:on 790115,reactor Coolant Pump 1-2-2 Started W/Incorrect Breaker Alignment,Causing Low Voltage Relays to Trip Which de-energized Both 4.16 Kv Essential Buses C1 & D1.Caused by Personnel Error

ML19270F534
Person / Time
Site:	Davis Besse
Issue date:	02/09/1979
From:	Marley J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19270F529	List: ML19270F528 ML19270F534
References
LER-79-011-03L, LER-79-11-3L, NP-33-79-14, NUDOCS 7902150389
Download: ML19270F534 (3)

Text

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NRC FORM 366 (7-77)

g. LICENSEE EVENT REPORT (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION)

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7 8 60 61 DOCKET NUVBER EVENT DESCRIPTION AND PROB ABLE CONSEQUENCES 10 o 2 l On 1/15/79 Reactor Coolant Pump (RCP 1-2-2 was started with an incorrect breaker l g 3  ; alignment which caused the low voltage relays to trip thus de-energizing both 4.16 KV l Both Emergency Diesel Generators (EDG) responded and ener-j g 4 l Essential Buses C1 and Dl.

The reactor was l g 3 g gized both buses and supplied power to the essential plant loads.

o e l shutdown at the time of the occurrence. Both buses were returned to the normal lineup l l o l 7 l [ within 12 minutes. (NP-33-79-14) l O 8 l 80 SUSC E COMPONENT CODE SUBC DE S ODE C DE CODE g lE Bj@ ]@ l A l@ lZ lZ lZ lZ lZ lZ l@ {@ [ Zl@

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, o l Starting a RCP required the intentional entry into the Action Statment of T.S. 3.8.2.1]

Personnel error in the alignment of

,,,,j ,by closing the tie breaker of the essential buses.

breakers caused the de-energization. A Facility Change Request was submitted to re- l g

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419-259-5000, Ext. 276 y DVR 79-01" James Marley PHONE *,

NAME OF PREPARER

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-79-14 DATE OF EVENT: January 15, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Loss of both 4.16 KV Essential Buses while start-ing Reactor Coolant Pump 1-2-2 Conditions Prior to Occurrence: The unit was in Mode 3, with Power (MWT) = 0, and Load (Gross MWE) = 0.

Description of Occurrence: On January 15, 1979 at 1118 hours0.0129 days <br />0.311 hours <br />0.00185 weeks <br />4.25399e-4 months <br />, the Reactor Operator was preparing to start Reactor Coolant Pump (RCP) 1-2-2 per Modification T-3444 to SP 1103.06, " Reactor Coolant Pump Operating Procedure", and closed the tie breaker AACD1 causing an intentional entry into the Action Statement of Technical Specifi-cation 3.8.2.1. Technical Specification 3.8.2.1 requires that the AC Electrical Buses Cl, Dl, El, F1, Yl, Y2, Y3, and Y4 be operable and energized with tie breakers open between redundant buses.

Due to personnel error, RCP l-2-2 was started with an incorrect breaker alignment which caused a low voltage condition to exist on both 4.16 KV Essential Buses C1 and Dl. This low voltage condition caused the low voltage relays to trip open the C1 and D1 Bus Feeder Breakers AC110 and AD110, thus de-energizing both 4.16 KV Essen--

tial Buses C1 and Dl. Both Emergency Diesel Generators responded and energized both C1 and D1 Buses and supplied power to the essential plant loads.

On January 15, 1979 at approximately 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br />, both 4.16 KV Essential Buses C1 and D1 feeds were returned to normal by switching from Emergency Diesel Generators 1 and 2 to the normal feeds from the C2 and D2 Buses, respectively. The normal breaker alignment for the 4.16 KV D2 Cus was re-established by closing Breaker ABDD2 and opening tie breaker AACD1, thus removing the unit from the Action State-ment of Technical Specification 3.8.2.1.

Designation of Aoparent Cause of Occurrence: The cause of the occurrence was per-sannel error. The operator was following an approved procedure modification (T-3444) which required the intentional entry into the Action Statement of Technical Specifi-cation 3.8.2.1 by closing the tie breaker of the redundant 4.16 KV Essential Buses.

Personnel error in the alignment of breakers prior to the starting of RCP l-2-2 resulted in the de-energization of both 4.16 KV Essential Buses when RCP 1-2-2 was started. When a 13.8 KV motor (RCP or Circulating Water Pump) is started, there is a prolonged voltage drop that carries through to the 4.16 KV Essential Bus Cl or D1 which causes undervoltage relays to initiate the start of an Emergency Diesel Generator.

LER #79-011

TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE PAGE 2 SUPPLEMENTAL INFORMATION FOR LER NP-33-79-14 Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. Both Emergency Diesel Generators 1 and 2 supplied energy to the essential plant loads. Plant conditions were such that the brief loss of both essential 4.16 KV Buses did not adversely affect plant equipment.

Corrective Action: Both 4.16 KV Essential Buses C1 and D1 were re-energized when The the Emergency Diesel Generators were transferred to the C1 and D1 Buses.

cperator restored the D2 Bus breaker alignment to normal by closing Breaker ABDD2 and opening the Breaker AACDl, thus removing the unit from the Action Statement of Technical Specification 3.8.2.1.

Facility Change Request (FCR)77-430 was submitted on October 28, 1977 to modify the existing situation and allow a Circulating Water Pump or Reactor Coolant Pump to be started without initiating an Emergency Diesel Generator startup by allowing the essential bus feeder low voltage breaker trip (90%) to be manually defeated during the starting of the RCP or Circulating Water Pump.

During the interim period until completion of FCR 77-430, Modification T-3444 to SP 1103.06, " Reactor Coolant Pump Operating Procedure" was written. This modifica-tion switches the normal feed of the affected 4.16 KV Essential Bus to its alternate feed prior to starting a RGP, thus preventing the inadvertent transfer of supply power of 4.16 KV Essential Bus C1 (D1) from the 4.16 KV Bus C2 (D2) to Emergency Diesel Generator 1 (2), resulting f rom a low voltage condition.

This incident will be reviewed with all operations personnel involved, and the importance of proper breaker alignment prior to starting the 13.8 KV equipment will be stressed.

Failure Data: Prior occurrences of a 4.16 KV Essential Bus being de-energized as a result of personnel error were previously reported in Licensee Event Reports NP-33-78-72 and NP-33-78-81.

LER #79-010