|Columbia Generating Station|
|Reporting criterion:||10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident|
|ENS 52510||10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident|
|3972017001R00 - NRC Website|
|Person / Time|
|From:||Javorik A L|
Document Control Desk, Office of Nuclear Reactor Regulation
|Download: ML17079A545 (4)|
comments regarding burden estimate to the FOLA, Privacy and Information CoPections Branch (T5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001 or by e-mai to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection 05000- NUMBER NO.
001 00 Columbia Generating Station 397 2017 - -
At the time of the event, the plant was operating in Mode 1 at 100% power. There were no structures, systems, or components that were inoperable at the start of the event that contributed to the event.
On January 25, 2017 at 1836 PST, with the High Pressure Core Spray (HPCS) System [BG] declared inoperable in accordance with plant Technical Specifications for planned maintenance, the Diesel Mixed Air (DMA) Fan [FAN] was in normal operation with the fan running continuously, supplying air to the HPCS diesel room. The control room received a loss of power alarm for the fan's motor starter [MSTR], which was then followed by notification of smoke in the HPCS diesel room. The Operator at the motor control center [MCC] for the motor starter opened the disconnect and the smoke dissipated. Inspection of the motor starter found that the contactor coil [CNTR] had overheated.
This event is reportable as an event that could have prevented fulfillment of safety functions needed to mitigate the consequences of an accident per 10 CFR 50.73(a)(2)(v)(D), should the HPCS diesel have received a start signal during a design basis event. This condition was reported under 10 CFR 50.72(b)(3)(v)(D) via Event Notification #52510 for an event or condition that, at the time of discovery, could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident; however, the Event Notification was retracted on February 3, 2017, based on the determination that the HPCS System had been declared inoperable prior to the smoke incident in accordance with plant Technical Specifications.
Immediate Corrective Actions
Operations personnel opened the disconnect for the affected motor starter, at which point the smoke dissipated.
Assessment of Safety Consequences
There were no actual safety consequences associated with this event, as there was no loss of safety function. There was no change in plant status or operating condition, and there was no risk to the public at any time due to this event. At the time of the event, work on the HPCS Service Water System was being performed in accordance with 10 CFR 50.65(a)(4) for managing risk. In emergency conditions, the HPCS System is used to provide core cooling and, during a loss of coolant accident, maintains reactor inventory. The DMA fan maintains suitable temperatures within the HPCS diesel generator room to ensure equipment operability temperature limits are not exceeded during an emergency. Had the HPCS System been in service and credited for accident mitigation, this event could have challenged the ability of the HPCS System to perform its safety function.
Cause of Event
The investigation into the apparent cause of the unexpected fan failure determined that the contactor coil for the fan's motor starter had overheated. The cause evaluation determined that the premature coil failure was likely caused by two contributing factors: increased coil operating currents and heating caused by elevated system voltages, and increased heating of the coil assembly caused by high magnet assembly temperatures due to loose shading coils.
Est mated burden per response to comply with th s mandatory collection request:80 hours
. Reported lessons teamed are incorporated into the licensing process and fed back to industry. Send comments regarding burden estimate to the FOIA Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person Is not required to respond to, the information collection.
05000- NUMBER NO.
.001 00 Columbia Generating Station 397 2017 - Similar Events A review of Corrective Action Program documents did not identify any previous starter coil failures for this particular manufacturer. Similar equipment from a different manufacturer recently experienced coil failures; Energy Northwest is working to identify the cause and develop a corrective action plan. Neither of the previous coil failures in the equipment has resulted in a loss of safety function or required an LER.
Further Corrective Actions The contactor coil, magnet assembly, and upper contactor assembly were replaced. The starter was retested and returned to service. For critical starters from this manufacturer the frequency of the inspection maintenance will increase, and plant procedures w;11 be revised to ensure adequate inspection of all magnet assemblies and coils.
Energy Industry Identification System (EDS) Information codes from IEEE Standards 805-1984 and 803-1983 are represented in brackets as [XX] and [XXX] throughout the body of the narrative.