05000443/LER-2006-004

LER-2006-004, Technical Specification Violation Due to Inoperable Battery Charger

Docket Number
Event date:	06-22-2006
Report date:	07-19-2006
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
4432006004R00 - NRC Website

I. Description of Event

On June 22, 2006, at 0620, with the plant at 100% power, it was discovered that there was no battery charger [EJ, BYC] in service on one of the two Train B vital batteries [EJ, BTRY] in violation of Technical Specification 3.8.2.1, DC Sources. Further review determined that the battery charger had been disconnected from its associated battery bank since approximately 1858 hours0.0215 days <br />0.516 hours <br />0.00307 weeks <br />7.06969e-4 months <br /> on June 21 when alarms caused by the opening of the battery charger breaker [BKR] were received in the Control Room. While securing battery charger EDE- BC-1B [EJ, BYC] after capacity testing, Maintenance electricians opened breaker DN4, which isolated both the battery charger and the portable battery charger from 125 VDC Bus 11B [EJ, BU]. The maintenance activity should not have repositioned breaker DN4. The opening of the breaker resulted in two Control Room alarms which operators believed to be expected alarms associated with the maintenance activity. The condition went unrecognized for approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The cause of the event was personnel error by the electricians for opening the breaker when unsure of how to secure the charger and by the licensed Control Room Operator for incorrectly processing the alarms as expected. Additionally, subsequent Operations personnel failed to recoginize the meaning of the alarms or validate the status of the battery.

The oncoming Control Room day shift questioned the alarms and discovered that 125 VDC bus 11B was supplied by its battery and that battery charger EDE-BC-1B was out of service. The battery charger was declared inoperable and TS 3.8.2.1 entered. At 0722 on June 22, 2006 station personnel closed the battery charger breaker to 125 VDC Bus 11B and exited TS 3.8.2.1.

II. Cause of Event

The cause for the event is personnel error by the electricians for opening battery charger output breaker DN4 when unsure of how to secure the charger. The maintenance procedure lacked detailed steps for "securing the battery charger." Although other electricians have successfully used the procedure in past maintenance activities, in this event the electricians were unsure of how to secure the battery charger. Upon recognition of the inadequate procedural guidance, the electricians did not seek clarification of the instruction, but developed a plan based on their understanding of the assignment and system line up to secure the battery charger. They did not stop and process a procedure change to incorporate the plan into the procedure.

A personnel error was also committed by Licensed Control Room Operators who assumed the alarms were associated with maintenance activities. The cause for this personnel error is that a licensed operator incorrectly processed the alarms as expected for the maintenance activity being performed. The licensed operator discussed the maintenance activity with the electrician, but resultant alarms and expected durations were not identified. Based on the communication with the electrician, the licensed operator processed the alarms as "expected," which resulted in Operations personnel failing to validate the reasons for the alarms. In addition, subsequent Operations personnel failed to recognize the meaning of the alarms or validate the actual status of the battery.

III. Analysis of Event

Each Train of the safety related portion of the DC power system consists of two 125-volt batteries, battery chargers and distribution panels. The loads supplied by the distribution panels include inverters for redundant vital instrument busses, distribution panels for power to Class lE loads, power for control and operation of Class lE systems for Engineered Safety Features, and power for selected non-Class lE loads. There are two Trains of DC power system at Seabrook Station. Each Train is equipped with a spare battery charger that can be connected to either battery on that Train.

The event consisted of not having a battery charger connected to one of the four vital batteries (EDE-B-1B) for a period of time longer than allowed by Technical Specification 3.8.2.1. While a battery charger was not connected, the associated battery provided power to the associated loads. Analysis determined that EDE-B- 1B would have been able to supply the 2-hour and 4-hour load profiles if a loss of offsite power or station blackout had occurred during the 12-hour period that the battery charger was disconnected.

This event is of regulatory significance because it met the reporting criterion of 10 CFR 50.73(a)(2)(i)(B) for a condition prohibited by the TS. The event was reported to the NRC on June 22, 2006 at 1428 (event # 42260) in accordance with Seabrook Station operating license condition 2.G for a violation of the Technical Specifications.

The event had no adverse impact on the plant or on the health and safety of the public or plant personnel. No plant transients, system actuations, or consequences resulted from the event. No other inoperable structures, systems, or components contributed to this event. The condition did not involve a safety system functional failure.

IV. Corrective Action The corrective actions to address this event include:

1. The individuals involved were coached and mentored on Station expectations.

2. An Operations Department Improvement Initiative was issued that focused on reinforcing management's expectations regarding the conduct of operations including control board monitoring, alarm response, configuration control and the return of equipment to service.

3. Management on shift obervations were conducted with each operating crew for a minimum of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to ensure consistent adherence to Station standards for the Conduct of Operations.

4. The Operations Department Manager will walk down this event in the field with Operations shift personnel, highlighting the actual vs. expected performance, what information and indications should have been used and what the expectations are for the Department.�

• 5. The Maintenance Department Manager will walk down this event in the field with Mechanical, Electrical and MC Maintenance personnel, highlighting the actual vs. expected performance, what information and indications should have been used and what the expectations are for the Department.

V. Similar Events A review of LERs for the previous two years did not identify any similar events.