ENS 45210
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ENS Event | |
|---|---|
21:42 Jul 17, 2009 | |
| Title | Actuation of Emergency Diesel Generators Due to Loss of Power to Safety Related Bus |
| Event Description | At 1742 EDT on July 17, 2009, while attempting to restore normal alignment providing offsite power following repair of the 'D' Common Station Service Transformer (CSST), the transfer from the alternate to the normal power supply for the 6.9kV Shutdown Board 2B-B failed because of an apparent failure of the interlock that should have prevented closing the normal breaker until an undervoltage condition existed on the alternate feed. The emergency diesel generators received a blackout signal and all four diesel generators started. Loads transferred and shed properly, and all systems functioned as expected.
WBN [Watts Bar Nuclear] had been in LCO 3.8.1 condition A since 0032 EDT on July 16, 2009 due to the outage of the D CSST. Because loads did not transfer to the offsite power source, WBN remains in LCO 3.8.1 A which requires restoration of the offsite power supply by 0032 EDT 7/19/2009. All systems are operating properly and the plant is stable. Troubleshooting and maintenance has begun and WBN anticipates return of the normal offsite power supply to the 2B-B Shutdown Board within the time required by technical specifications. This event is reportable under 10 CFR 50.72(b)(3)(iv) as an event or condition that resulted in valid actuation of the emergency diesel generators. The licensee has notified the NRC Resident Inspector The 6.9kV Shutdown boards at Watts Bar are safety related busses. The electrical configuration prior to the event had the 1A-A and 2A-A Shutdown Boards aligned to their normal offsite power source. The 1B-B and 2B-B Shutdown Boards were aligned to an alternate offsite power source because their normal source, the 'D' CSST had been out of service for repairs. Following completion of the repairs to the 'D' CSST, the licensee attempted to restore normal offsite power to the 2B-B Shutdown Board from the 'D' CSST using a fast transfer from the alternate power supply. For unknown reasons, the normal supply breaker attempted to close onto the 2B-B bus before the alternate supply breaker had opened. This, in effect, would have paralled both the primary and alternate sources of power to the 2B-B bus. An interlock prevents paralleling these two sources and resulting in both supply breakers tripping and the bus being de-energized. This generated a blackout signal that started all four emergency diesels generators (EDGs). All the EDGs started as required, only the 2B-B loaded onto its associated shutdown bus, as expected, because of the bus had been de-energized. The other busses (1A-A, 1B-B, and 2A-A) remained energized and the associated EDGs did not load. The 1A-A, 1B-B, and 2A-A EDGs were shutdown and returned to a standby condition. The 2B-B EDG continued to power the 2B-B Shutdown Board while the licensee investigated the fast transfer problem. All systems functioned as required during this event except for the 2B-B fast bus transfer from the alternate to normal offsite power supply. |
| Where | |
|---|---|
Watts Bar  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+2.73 h0.114 days <br />0.0162 weeks <br />0.00374 months <br />) | |
| Opened: | Greg Evans 00:26 Jul 18, 2009 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Jul 18, 2009 |
| 45210 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 570062024-03-05T06:32:0005 March 2024 06:32:00
[Table view]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 569702024-02-16T03:24:00016 February 2024 03:24:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Actuation of Emergency Diesel Generator System ENS 569352024-01-28T02:41:00028 January 2024 02:41:00 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 566602023-08-04T21:46:0004 August 2023 21:46:00 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 565932023-06-27T20:26:00027 June 2023 20:26:00 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 549972020-11-15T06:44:00015 November 2020 06:44:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of the Emergency Diesel Generators ENS 547202020-05-20T09:21:00020 May 2020 09:21:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of Emergency Diesel Generators ENS 542522019-09-01T00:55:0001 September 2019 00:55:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Trip Due to Loss of Steam Generator Level Control ENS 540772019-05-22T06:33:00022 May 2019 06:33:00 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 Failure of Main Feedwater Regulating Valve ENS 536972018-10-27T04:00:00027 October 2018 04:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Following Startup ENS 535572018-08-22T04:00:00022 August 2018 04:00:00 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 534672018-06-22T04:00:00022 June 2018 04:00:00 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 533272018-04-12T13:20:00012 April 2018 13:20:00 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 531322017-12-20T15:40:00020 December 2017 15:40:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation System Actuations Due to Opening of Feeder Breaker to Shutdown Board ENS 531122017-12-11T13:57:00011 December 2017 13:57:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip in Response to Indication of Multiple Dropped Control Rods ENS 529122017-08-17T16:05:00017 August 2017 16:05:00 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident, 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material Actuation of Turbine Driven Auxiliary Feedwater Pump Due to Loss of 6.9Kv Shutdown Board ENS 528722017-07-25T08:28:00025 July 2017 08:28:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Due to Rod Position Indication System Being Inoperable ENS 527322017-05-04T21:09:0004 May 2017 21:09:00 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 Failed Reactor Coolant Pump Power Transfer ENS 527252017-05-02T23:45:0002 May 2017 23:45:00 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 Failed Reactor Coolant Pump Power Transfer ENS 526302017-03-23T04:14:00023 March 2017 04:14:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Start of Auxiliary Feed Water ENS 526252017-03-20T12:13:00020 March 2017 12:13:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip as a Result of Secondary Plant Transient ENS 522102016-08-31T01:20:00031 August 2016 01:20:00 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 Notice of Unusual Event - Fire in a Main Bank Transformer ENS 521942016-08-23T17:56:00023 August 2016 17:56:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Trip Due to a Loss of Main Feedwater ENS 521772016-08-13T07:36:00013 August 2016 07:36:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Start of Turbine Driven Auxiliary Feed Water Pump ENS 520262016-06-20T19:40:00020 June 2016 19:40:00 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 519822016-06-05T16:27:0005 June 2016 16:27:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Reactor Trip and Eccs Actuation Caused by Turbine Governor Valve Failure ENS 519402016-05-17T20:30:00017 May 2016 20:30:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation - Loss of 1 B-B Electrical Buss ENS 518152016-03-22T15:31:00022 March 2016 15:31:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Watts Bar Automatic Reactor Trip ENS 508392015-02-21T15:32:00021 February 2015 15:32:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip Inserted Due to Rapid Loss of Main Condenser Vacuum ENS 502782014-07-13T23:37:00013 July 2014 23:37:00 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 Automatic Feedwater Heater Isolation ENS 491542013-06-28T17:30:00028 June 2013 17:30:00 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 Offsite Electrical Fault ENS 484142012-10-17T03:30:00017 October 2012 03:30:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation All Four Emergency Diesel Generators Auto-Start on Valid Undervoltage Signal ENS 482382012-08-28T07:32:00028 August 2012 07:32:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Following Failure of a Feedwater Regulating Valve ENS 469022011-05-29T05:55:00029 May 2011 05:55:00 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 ENS 464182010-11-14T11:52:00014 November 2010 11:52:00 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 Cooling to the 'A' Phase Main Bank Transformer ENS 461772010-08-15T19:24:00015 August 2010 19:24:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Aux Feedwater System Actuation During Power Reduction for Turbine Maintenance ENS 459442010-05-21T23:37:00021 May 2010 23:37:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip on Turbine Trip ENS 452102009-07-17T21:42:00017 July 2009 21:42:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Actuation of Emergency Diesel Generators Due to Loss of Power to Safety Related Bus ENS 445062008-09-20T13:06:00020 September 2008 13:06:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip Due to Turbine Trip ENS 443882008-08-07T06:28:0007 August 2008 06:28:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Trip from 50% Power Following Low Pressure Heater String Isolation ENS 427442006-07-31T16:13:00031 July 2006 16:13:00 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 Generator Trip ENS 426102006-05-30T21:00:00030 May 2006 21:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip on High Turbine Vibration ENS 410542004-09-19T08:56:00019 September 2004 08:56:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip in Response to Indication of Dropped Control Rods ENS 404542004-01-16T16:37:00016 January 2004 16:37:00 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 ENS 401002003-08-25T13:45:00025 August 2003 13:45:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Turbine Trip/Reactor Trip Due to a Sudden Pressure Relay Signal from Main Transformer Bank "1C 2024-03-05T06:32:00 | |
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