ENS 44094
ENS Event | |
|---|---|
23:49 Mar 25, 2008 | |
| Title | Loss of Offsite Power Due to Station Auxiliary Transformer Fault |
| Event Description | At 1835 on March 25, 2008, Unit 2 experienced a Loss of Offsite Power. At 1849, an Unusual Event was declared. Station Auxiliary Transformer (SAT) 242-2, Phase C, experienced a Phase Overcurrent. This resulted in an isolation of the SAT, a loss of offsite power, and an automatic Fire Protection deluge of the SAT. No fire was confirmed. All equipment responded as required. The appropriate abnormal operating procedure was entered for event mitigation and is in progress. The Unit 2 Emergency Diesel Generators are supplying required safety-related power. Unit 2 remains at power.
The plant is stable and all equipment is functioning as required. The licensee is assessing a cross-tie to Unit 1 which is unaffected by this event and in the refueling mode. The licensee notified the State and local authorities and the NRC Resident Inspector. Notified DHS (Greg Ray), FEMA (Erwin Casto), DOE (Sal Morrone), USDA (Timmons), HHS (Rick Turner), EPA/NRC (Petty Officer Thompson Report #866038).
The emergency buses on Unit 2 have been re-energized by offsite power supply sources via Unit 1 SAT. The Unit 2 EDGs have been secured and placed back in standby. The licensee is developing a recovery plan to restore a Unit 2 SAT to supply offsite power to Unit 2 loads. This will require such things as analyzing chemistry samples of the affected SAT transformers and assessing the protective relaying. In addition, some switchyard realignment will be necessary. The licensee is currently in a 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> LCO under Tech Spec 3.8.1 for the current electrical alignment. The NRC Resident Inspector is onsite and the NRC Region continues to monitor the situation.
At 2309 [hrs. CDT] on 3/27/08, Byron Unit 2 terminated an Unusual Event that was declared at 18:49 on 3/25/08, in accordance with EAL M.U.1 due to a loss of offsite power to transformers 242-1 and 242-2. Transformer 242-1has been energized from offsite power and is supplying Unit 2 ESF busses 241 and 242. The entry conditions for M.U.1 are no longer met. A press release will be issued. Transformer 242-2 is out of service and isolated for repairs. The licensee notified the NRC Resident Inspector. Notified R3DO (Hills), NRR EO (Ross-Lee), IRD (McDermott), DHS SWO (Doyle), FEMA (Liggett), DOE (Morrone), EPA (Allison), USDA (Timmon) and HHS (Dalziel). |
| Where | |
|---|---|
| Byron Illinois (NRC Region 3) | |
| Reporting | |
| Emergency class: | Unusual Event |
| 10 CFR 50.72(a) (1) (i), Emergency Class Declaration | |
| Time - Person (Reporting Time:+-3.42 h-0.143 days <br />-0.0204 weeks <br />-0.00468 months <br />) | |
| Opened: | Richard Williams 20:24 Mar 25, 2008 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Mar 28, 2008 |
| 44094 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (99 %) |