ENS 46298
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ENS Event | |
|---|---|
00:04 Oct 1, 2010 | |
| Title | Standby Diesel Generator Autostart Due to Loss of a Switchyard Bus During Maintenance |
| Event Description | At 1904 [CDT] on 9/30/2010, the South Texas Project (STP) North switchyard bus was lost due to a Transmission & Distribution Service Provider (TDSP) human performance error that occurred while performing maintenance on breaker Y-0530. This resulted in a loss of power to Standby transformer 1 which was supplying power to the Unit 1 B Train Engineered Safety Features (ESF) 4160v bus. The B Train Standby Diesel Generator automatically started due to the Loss of Offsite Power (LOOP) on its associated bus. The Mode II (LOOP) ESF loads sequenced onto the bus. All safety related equipment responded as expected. Action (e) of Technical Specification (TS) 3.8.1.1, 'AC Electrical Power Sources', was momentarily entered due to the loss of two independent offsite circuits while the North bus was de-energized. The North bus was de-energized for approximately 5 minutes. Action (a) of Technical specification (TS) 3.8.1.1, 'AC Electrical Power Sources', was entered due to the loss of one independent offsite circuit. All Technical Specification Limiting Condition of operation have been exited at this time.
An 8-hour notification is required for this event due to the valid actuation of safety related equipment as described in 10CFR50.72 (b) (3) (iv) (A). [A notification is required for] any event or condition that results in valid actuation of any of the systems listed in paragraph (b) (3) (iv) (B) of this section, except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation. The NRC Resident Inspector has been notified. Unit 2 briefly entered a Technical Specification Limiting Condition of Operation, while all electrical buses remained energized. |
| Where | |
|---|---|
South Texas  Texas (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+1.52 h0.0633 days <br />0.00905 weeks <br />0.00208 months <br />) | |
| Opened: | Brad Hardt 01:35 Oct 1, 2010 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Oct 1, 2010 |
| 46298 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 572372024-07-24T12:02:00024 July 2024 12:02:00
[Table view]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 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 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 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 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 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 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 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 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 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 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 2024-07-24T12:02:00 | |
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