ENS 47708
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ENS Event | |
|---|---|
23:31 Feb 28, 2012 | |
| Title | Unusual Event Due to Loss of Offsite Power |
| Event Description | Byron Unit 1 declared an Unusual Event due to a loss of offsite power for greater than 15 minutes (EAL MU-1). The 1A and 1B emergency diesel generators auto-started and automatically restored power to ESF (Engineered Safety Feature) Busses 141 and 142. The 1A Auxiliary Feedwater pump auto-started due to an undervoltage signal to ESF bus 141. The 6.9 KV Busses (Non-ESF) and 4.16 KV Busses (Non-ESF) auto transferred to the Unit Auxiliary Transformers and Unit 1 remained online. The ESF reserve feed breakers are available and in the process of transferring ESF loads over to Unit 2 via the ESF cross-ties. This will allow shutdown of the 1A and 1B diesel-generators and allow alignment to standby status. Switchyard repairs are being initiated.
The licensee notified the State of Illinois, Ogle County, Oregon and Byron municipalities and the NRC Resident Inspector. The licensee plans on issuing a news release. Unit 2 remained online and was unaffected throughout the event. Notified Nuclear SSA and NICC vie email.
Termination of Unusual Event. Repairs to switchyard components are complete. Offsite power has been restored to Unit One System Auxiliary Transformers. Unit One 4 KV ESF busses have been re-energized from Unit One System Auxiliary Transformers and are no longer cross tied to Unit Two System Auxiliary Transformers. This restores the normal electrical lineup to the ESF busses. The entry conditions for MU-1 are no longer met. The licensee has notified the NRC Resident Inspector, the State of Illinois, Ogle County, Oregon and Byron municipalities. Notified R3DO (Stone), NRR EO (Lee), IRD (Morris), and other FEDS (DHS SWO, DHS NICC, FEMA, and NuclearSSA via email). |
| Where | |
|---|---|
Byron  Illinois (NRC Region 3) | |
| Reporting | |
| Emergency class: | Unusual Event |
| 10 CFR 50.72(a) (1) (i), Emergency Class Declaration 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+-4.47 h-0.186 days <br />-0.0266 weeks <br />-0.00612 months <br />) | |
| Opened: | Chris Cote 19:03 Feb 28, 2012 |
| NRC Officer: | Charles Teal |
| Last Updated: | Feb 29, 2012 |
| 47708 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (99 %) |
Byron with 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
WEEKMONTHYEARENS 572112024-07-07T19:40:0007 July 2024 19:40:00
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