ENS 47624
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ENS Event | |
|---|---|
16:01 Jan 30, 2012 | |
| Title | Unusual Event Due to Loss of Offsite Power Greater than 15 Minutes |
| Event Description | At 1101 EST, Byron Unit-2 experienced a reactor trip due to RCP undervoltage. All rods fully inserted, MSIV's were manually closed and decay heat is being removed by Auxiliary Feedwater pumps running and steam leaving via atmospheric relief valves. The unit is currently in a natural circulation cooldown with the diesels supplying station emergency loads. Licensee will be cooling the plant down to Mode 5.
At 1118 EST, Byron declared an Unusual Event due to a loss of offsite power on Unit 2 from a faulted Station Auxiliary Transformer (SAT). The faulted SAT caused both 6.9 kV and 4.1 kV bus voltage to drop. Smoke was observed coming from the SAT with no visible flames being apparent. This caused bus loads to trip without a complete loss of ESF busses 241 and 242. These buses were manually disconnected from the SAT, which transferred the load to the emergency diesel generators 2A and 2B. Both diesel generators started and loaded without incident. Offsite assistance was requested from the local fire department as a precaution. The licensee is also declaring notification for 10 CFR 50.72(b)(3)(v)(D) Unit 1 is not being affected by this event and remains at 100% power. The licensee has notified the NRC Resident Inspector.
At 2000 CST on 1/31/12, Byron terminated their Unusual Event due to the Loss of Offsite Power to Unit 2. Switchyard repairs were completed and offsite power has been restored to essential busses 241 and 242 thru System Auxiliary Transformers 242-1 and 242-2. Unit 2 Emergency Diesel Generators have been shutdown. The licensee is citing classification 10 CFR 50.72(c)(1)(iii) The licensee has notified the NRC Resident Inspector. Notified R3DO (James Cameron), NRR EO (Louise Lund), IRD MOC (Scott Morris), DHS (Konopka) and FEMA (Hollis). Licensee may issue a press release. |
| 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)(iv)(B), RPS Actuation 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+-4.37 h-0.182 days <br />-0.026 weeks <br />-0.00599 months <br />) | |
| Opened: | Leo Wehner 11:39 Jan 30, 2012 |
| NRC Officer: | John Knoke |
| Last Updated: | Jan 31, 2012 |
| 47624 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Byron with 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
WEEKMONTHYEARENS 540202019-04-22T18:24:00022 April 2019 18:24:00
[Table view]10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Initiation of the Auxiliary Feedwater System in Response to a Loss of Feedwater ENS 534912018-07-06T05:00:0006 July 2018 05:00:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Transformer Failure Causes Loss of Offsite Power to Unit 2 ENS 522952016-10-12T18:38:00012 October 2016 18:38:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Spurious Feedwater Isolation ENS 519312016-05-15T16:18:00015 May 2016 16:18:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to Excessive Unidentified Leakage During Plant Startup ENS 508592015-03-03T17:01:0003 March 2015 17:01:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Main Power Transformer Bushing Short ENS 499192014-03-15T16:02:00015 March 2014 16:02:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Momentary Loss of Shutdown Cooling Due to a Loss of Offsite Power ENS 488382013-03-21T00:51:00021 March 2013 00:51:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Loss of Generator Stator Cooling Water ENS 477082012-02-28T23:31:00028 February 2012 23:31:00 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 Unusual Event Due to Loss of Offsite Power ENS 476442012-02-06T23:19:0006 February 2012 23:19:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Rps Actuation Due to Turbine Trip ENS 476242012-01-30T16:01:00030 January 2012 16:01:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Unusual Event Due to Loss of Offsite Power Greater than 15 Minutes ENS 458672010-04-19T10:03:00019 April 2010 10:03:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Rps and Afw Actuation Signals While Shutdown in Mode 4 ENS 440942008-03-25T23:49:00025 March 2008 23:49:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Loss of Offsite Power Due to Station Auxiliary Transformer Fault ENS 438072007-11-27T15:15:00027 November 2007 15:15:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Alert Declared Due to Oxygen Deficient Atmosphere ENS 437352007-10-19T23:30:00019 October 2007 23:30:00 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown Tech Spec Required Shutdown Due to Ultimate Heat Sink Inoperability ENS 423742006-02-24T14:54:00024 February 2006 14:54:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Due to Fire in the Protected Area Not Extinguished within 15 Minutes ENS 420632005-10-19T05:57:00019 October 2005 05:57:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Low 2 Steam Generator Water Level 2019-04-22T18:24:00 | |
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