ENS 57237
ENS Event | |
|---|---|
12:02 Jul 24, 2024 | |
| Title | Notification of Unusual Event Due to Loss of Offsite Power |
| Event Description | The following information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
A Notification of Unusual Event was declared by South Texas Project Unit 1 at 0718 CDT for emergency action level (EAL) SU.1, loss of all offsite power for greater than 15 minutes, following a fire in the switchyard. Unit 1 tripped following the loss of power and is stable in Mode 3. Unit 2 reduced power to 90 percent but was otherwise unaffected by this event. Offsite services responded to the switchyard fire. The fire was extinguished at 0925 CDT. There is no radioactive release and no threat to public safety. The licensee notified state and local authorities and the NRC senior resident inspector. Notified DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).
The following information was provided by the licensee via phone and email: At 0702 CDT on 7/24/2024, with Unit 1 in Mode 1 at 100 percent power, the Unit 1 reactor automatically tripped due to loss of offsite power. The trip was not complex, with all systems responding normally post-trip. No equipment was inoperable prior to the event that contributed to the event or adversely impacted plant response to the scram. Operations responded and stabilized the plant. Decay heat is being removed by steam generator power operated relief valves (PORV). Unit 2 was reduced in power to approximately 90 percent power due to conditions in the switchyard. Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B). There was no impact on the health and safety of the public or plant personnel. The NRC resident inspector has been notified. Notified R4DO (Azua)
The following is a summary of information provided by the licensee via phone: At 1146 CDT, South Texas Project Unit 1 terminated the previously declared Notification of Unusual Event due to restoration of an offsite source of electrical power. Notified R4DO (Azua), NRR EO (McKenna), IR MOC (Crouch), DHS SWO, FEMA Operations Center, CISA Central, FEMA NWC (email), CWMD Watch Desk (email), DHS NRCC THD Desk (email), and DHS Nuclear SSA (email).
The following information was provided by the licensee via phone and email: For the 10 CFR 50.72(b)(3)(iv)(A) reporting requirements: At 0702 CDT on 7/24/2024, with both Unit 1 and 2 in Mode 1 at 100 percent power, the South Texas Project (STP) north and south switchyard electrical buses were de-energized. In Unit 1, all emergency diesel generators (EDGs) 11, 12, and 13 automatically started in response to loss of offsite power on train `A', `B', and `C' engineered safety feature (ESF) buses. Also in Unit 1, trains `A', `B', and `C' of the auxiliary feedwater (AFW) system automatically started. In Unit 2, EDG 22 automatically started in response to loss of offsite power on the train `B' ESF bus. Also in Unit 2, train `B' of the AFW system automatically started. This event is reportable under 10 CFR 50.72(b)(3)(iv)(A) as an event that resulted in the valid actuation of a pressurized water reactor auxiliary feedwater system (50.72(b)(3)(iv)(B)(6)) and emergency alternating current (AC) electrical power system (50.72(b)(3)(iv)(B)(8)). There was no impact on the health and safety of the public or plant personnel. The NRC resident inspector has been notified. For the 10 CFR 50.72(b)(2)(xi) reporting requirement: A news release was completed at 1140 CDT on 7/24/2024, by South Texas Project on the declaration of the Unusual Event. This media release is being reported in accordance with 10 CFR 50.72(b)(2)(xi): Any event or situation, related to the health and safety of the public or onsite personnel, or protection of the environment, for which a news release is planned or notification to other government agencies has been or will be made. Notified R4DO (Azua)
The following information was provided by the licensee via phone and email: After a review of station logs, it was determined that there was not a loss of all offsite AC power to Unit 1 related to the event that occurred on July 24, 2024. An offsite AC power source was available through the 138 kV transmission line. The NRC Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: At this time the licensee is not retracting the declaration of emergency action level 'SU.1'. Notified R4DO (Werner) |
| Where | |
|---|---|
South Texas  Texas (NRC Region 4) | |
| 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)(xi), Notification to Government Agency or News Release 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000498/LER-2024-004 Loss of Offsite Power Resulting in Unit 1 Automatic Reactor Trip and Actuation of Emergency Diesel Generators and Auxiliary Feedwater Pumps 05000498/LER-2024-004-01 Loss of Offsite Power Resulting in Unit 1 Automatic Reactor Trip and Actuation of Emergency Diesel Generators and Auxiliary Feedwater Pumps |
| Time - Person (Reporting Time:+-2.52 h-0.105 days <br />-0.015 weeks <br />-0.00345 months <br />) | |
| Opened: | Chris Mccrary 09:31 Jul 24, 2024 |
| NRC Officer: | Adam Koziol |
| Last Updated: | Jul 29, 2024 |
| 57237 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (90 %) |
South Texas with 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 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 | |
WEEKMONTHYEARENS 580542025-11-21T18:08:00021 November 2025 18:08:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip ENS 579862025-10-15T04:05:00015 October 2025 04:05:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification ENS 579842025-10-14T00:00:00014 October 2025 00:00:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Notification of Unusual Event ENS 572372024-07-24T12:02:00024 July 2024 12:02:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 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 Notification of Unusual Event Due to Loss of Offsite Power ENS 572012024-06-30T17:22:00030 June 2024 17:22:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification ENS 571242024-05-12T21:41:00012 May 2024 21:41:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip ENS 568772023-12-02T12:10:0002 December 2023 12:10:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation - Auto Start of Emergency Diesel Generator ENS 564392023-03-30T06:03:00030 March 2023 06:03:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to ON-SITE Fatality ENS 559182022-05-25T18:54:00025 May 2022 18:54:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification for Inadvertent Discharge of Halon ENS 556922022-01-06T12:03:0006 January 2022 12:03:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation - Auto Start Emergency Diesel Generator ENS 551042021-02-15T11:26:00015 February 2021 11:26:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip Due to Low Steam Generator Level ENS 550532020-12-30T21:50:00030 December 2020 21:50:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Inadvertent Emergency Siren Activation ENS 547142020-05-14T21:10:00014 May 2020 21:10:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification for Hydraulic Oil Release ENS 546052020-03-24T15:46:00024 March 2020 15:46:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation - Auto Start Emergency Diesel Generators ENS 545872020-03-17T20:58:00017 March 2020 20:58:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Notification to Other Government Agency ENS 545612020-03-04T13:18:0004 March 2020 13:18:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release ENS 545292020-02-17T23:17:00017 February 2020 23:17:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Notification to Other Government Agency ENS 543512019-10-25T01:51:00025 October 2019 01:51:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Undervoltage Actuation During Edg Sequencer Maintenance ENS 541452019-07-03T15:26:0003 July 2019 15:26:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Offsite Notification Due to Radio Transmitter Out of Service ENS 540972019-06-01T21:18:0001 June 2019 21:18:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Gasoline Leakage to Site Drainage System ENS 534052018-05-17T03:02:00017 May 2018 03:02:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification of Fires in the Owner Controlled Area ENS 531412018-01-01T16:15:0001 January 2018 16:15:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification - Emergency Notification Siren Inadvertent Actuation ENS 531162017-12-12T21:19:00012 December 2017 21:19:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Inadvertent Actuation of Emergency Notification Siren ENS 529112017-08-17T19:42:00017 August 2017 19:42:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Non Work Related Onsite Fatality ENS 527332017-05-05T02:03:0005 May 2017 02:03:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Miscommunication During On-The-Job Training ENS 527162017-04-29T21:23:00029 April 2017 21:23:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Small Grass Fire in Owner Controlled Area ENS 521422016-08-01T20:18:0001 August 2016 20:18:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Unintentional Release of Halon ENS 521062016-07-13T16:00:00013 July 2016 16:00:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Exercise Press Releases Aired on Radio as an Actual Event ENS 519642016-05-28T01:46:00028 May 2016 01:46:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to an Inadvertent Actuation of One Emergency Siren ENS 518972016-05-02T01:21:0002 May 2016 01:21:00 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 Generator Lockout ENS 517872016-03-14T07:47:00014 March 2016 07:47:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Inadvertent Actuation of Offsite Emergency Notification Siren ENS 516872016-01-27T05:25:00027 January 2016 05:25:00 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 Feedwater to a Single Steam Generator ENS 516152015-12-21T21:33:00021 December 2015 21:33:00 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 Feedwater Isolation ENS 515362015-11-13T12:39:00013 November 2015 12:39:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Notification of Unusual Event Due to Unidentified Rcs Leakage Greater than 10 Gpm ENS 513392015-08-23T18:00:00023 August 2015 18:00:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Grass Fire in Owner Controlled Area ENS 510732015-05-15T22:53:00015 May 2015 22:53:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Inadvertent Siren Actuation ENS 507162015-01-05T23:45:0005 January 2015 23:45:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Death of Employee ENS 497402014-01-18T10:01:00018 January 2014 10:01:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Due to Fire in the Protected Area ENS 496662013-12-20T04:33:00020 December 2013 04:33:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Actuation of Main Steam Isolation Valves That Was Not Part of a Preplanned Sequence ENS 486592013-01-08T22:40:0008 January 2013 22:40:00 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 Unusual Event Declared Due to Main Transformer Fire ENS 486512013-01-04T15:41:0004 January 2013 15:41:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unit 2 Manually Tripped After Two Shutdown Control Rods Unexpectedly Dropped During Surveillance Testing ENS 474852011-11-29T09:29:00029 November 2011 09:29:00 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 Turbine Trip on Generator Lockout ENS 473622011-10-20T21:50:00020 October 2011 21:50:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to the Offsite Fatality of an Employee ENS 463872010-11-03T15:21:0003 November 2010 15:21:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 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 Unusual Event Declared Due to an Explosion in the Protected Area Which Affects Normal Operations ENS 462982010-10-01T00:04:0001 October 2010 00:04:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Standby Diesel Generator Autostart Due to Loss of a Switchyard Bus During Maintenance ENS 461912010-08-20T20:25:00020 August 2010 20:25:00 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 an Inadvertent Turbine Trip Signal During Testing ENS 452622009-08-13T20:41:00013 August 2009 20:41:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to a Grass Fire in the Owner Controlled Area ENS 446052008-10-26T04:42:00026 October 2008 04:42:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Safety Injection Signal Due to Maintenance Error ENS 436122007-09-01T21:58:0001 September 2007 21:58:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Related to Fatality ENS 427572006-08-08T20:43:0008 August 2006 20:43:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Inadvertent Emergency Notification Siren Activation ENS 423222006-02-08T22:30:0008 February 2006 22:30:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification ENS 415052005-03-19T14:27:00019 March 2005 14:27:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Injured Contract Employee ENS 413942005-02-10T02:20:00010 February 2005 02:20:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification Due to Press Release for Plant Shutdown ENS 406572004-04-08T14:44:0008 April 2004 14:44:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release Offsite Notification of a Fatality ENS 404732004-01-23T22:16:00023 January 2004 22:16:00 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 High-High Steam Generator Level 2025-11-21T18:08:00 | |