ENS 42955: Difference between revisions
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ENS Event | |
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23:37 Nov 1, 2006 | |
| Title | Unit 2 Declared An Unusual Event Due To Loss Of Offsite Power To The 4Kv Emergency Buses |
| Event Description | At 1823 EST, Unit 2 was manually scrammed due to a loss of offsite power from the Startup Auxiliary Transformer to both 4KV Emergency (E) buses. Both Emergency Diesel Generators (EDGs) 3&4 autostarted and re-energized the affected electrical buses. At 1823 EST, an Unusual Event was declared based on EAL 06.01.01, "Inability to power either 4KV E bus from offsite power."
Unit 2 is currently stable in mode 3, Hot Shutdown, with MSIVs closed and HPCI controlling pressure and RPV Water Level. All control rods fully inserted following the manual reactor scram. The licensee determined that no emergency facilities will be activated and that no offsite assistance is needed at this time. The licensee informed both state and local agencies and will inform the NRC Resident Inspector.
On 11/01/06 at approximately 18:23 (EST) Brunswick Unit 2 experienced a loss of the unit's Startup Auxiliary Transformer and a loss of reactor forced circulation. A manual reactor scram was performed as required by station Abnormal Operating Procedures. Due to the loss of the Startup Auxiliary Transformer and subsequent manual reactor scram, a loss of Offsite Power resulted to the unit's power buses when unit shutdown was completed. All control rods properly inserted when the manual reactor scram was performed. All four site emergency diesels started and diesels 3 and 4 are supplying the Unit 2 emergency buses. Reactor water level reached low level 1 (LL1) and low level 2 (LL2) as result of the reactor scram and loss of offsite power. The LL1 signal resulted in Group 2 (floor and equipment drain isolation valves), Group 6 (monitoring and sampling isolation valves) and Group 8 (shutdown cooling isolation valves) isolation signals. All low level 1 isolations occurred as designed. The LL2 resulted in a Reactor Core Isolation Cooling (RCIC) system actuation, High Pressure Coolant Injection (HPCI) system actuation, Group 3 (reactor water cleanup valves) isolation signal, a secondary containment isolation signal, a Standby Gas Treatment (SBGT) initiation signal, a Control Room Emergency Ventilation (CREV) initiation signal, and an Alternate Rod Insertion (ARI) actuation signal. All isolation and actuations occurred as designed with the exception the CREV initiation and ARI actuation. CREV initiation and ARI actuations were performed by manual actions. The failure of the CREV and ARI initiation/actuations are under investigation. The RCIC and HPCI systems were used to restore reactor water level to the normal operation band. Reactor vessel pressure is being controlled in the normal band with manual operation of Safety Relief Valves (SRV), and HPCI/RCIC in pressure control mode. The Main Steam Isolation Valves (MSIVs) (Group 1) and the drywell pneumatic isolation valves (Group 10) closed on the loss of power. The plant is a stable condition. Troubleshooting activities are in progress to determine the cause of the event. At 1910, the NRC was previously notified of the Unusual Event declaration. Initial Safety Significance Evaluation: The safety significance of this event is minimal and Unit 2 is in a stable condition. All control rods properly inserted when the manual scram was performed. Plant safety systems responded as required with the exception of the CREV and ARI systems which did not automatically initiate but functioned properly when manually actuated. All four emergency diesels started and Unit 2 diesels 3 and 4 are supplying the Unit 2 emergency buses. Reactor pressure and level are being controlled per procedure, with HPCI and RCIC. Actions are in progress to re-establish off site power supply to emergency buses 3 and 4 via backfeed through the Unit Auxiliary Transformer (UAT). Corrective Actions: Actions are in progress to re-establish offsite power supply to emergency buses 3 and 4 via backfeed through the UAT. Investigations are in progress to determine the cause of the SAT failure and the failure of CREV and ARI to auto-initiate. The licensee has notified the NRC Resident Inspector and the State and local emergency agencies. Update provided also added the following reportable notifications due to the event: 10CFR50.72(b)(2) (iv)(A) and(iv)(B) and 10CFR50.72(b)(3)(iv)(A). Notified R2DO (Evans).
Licensee reported that the Unusual Event was terminated at 1745 EST on 11/02/06 after Offsite power was restored to both 4 KV E Buses from the Unit Auxiliary Transformer (UAT) on Unit 2. The #3 and #4 EDGs have been secured and are in Standby. #1 EDG remains inoperable and #2 EDG is presently being Load Tested. The licensee will be notifying the NRC Resident Inspector and the State and local emergency agencies. Notified R2DO (Evans), NRREO (Richards), IRD Manager (Leach), DHS (Barnes), and FEMA (Kuzia). |
| Where | |
|---|---|
Brunswick  North Carolina (NRC Region 2) | |
| Reporting | |
| Emergency class: | Unusual Event |
| 10 CFR 50.72(a) (1) (i), Emergency Class Declaration 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+-4.45 h-0.185 days <br />-0.0265 weeks <br />-0.0061 months <br />) | |
| Opened: | Shawn Zander 19:10 Nov 1, 2006 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Nov 2, 2006 |
| 42955 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | Yes, Manual Scram |
| Before | Power Operation (100 %) |
| After | Hot Shutdown (0 %) |
Brunswick 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)(iv)(A), System Actuation - ECCS Discharge | |
WEEKMONTHYEARENS 576362025-03-28T18:09:00028 March 2025 18:09:00
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of Emergency Preparedness Unusual Event for a Halon Release Near the Tsc and Eof ENS 497882014-02-03T15:03:0003 February 2014 15:03:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to Toxic Gas Release That Could Affect Normal Operation ENS 497132014-01-11T00:48:00011 January 2014 00:48:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to Explosion within Protected Area Boundary ENS 488902013-04-05T10:24:0005 April 2013 10:24:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to a Fire Alarm in the Stack Filter House ENS 487832013-02-26T14:00:00026 February 2013 14:00:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to Toxic Gas Leak ENS 478172012-04-09T09:29:0009 April 2012 09:29:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Emergency Diesel Generator Actuation ENS 476972012-02-24T05:37:00024 February 2012 05:37:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Reactor Protection System Actuation During Neutron Instrument Testing ENS 476902012-02-23T04:19:00023 February 2012 04:19:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram Due to High Delta-P Across Circulating Water Pump Traveling Screens ENS 474442011-11-16T08:01:00016 November 2011 08:01:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Due to Drywell Leakage Greater than 10 Gpm ENS 468732011-05-23T19:35:00023 May 2011 19:35:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Alert Declared Due to Halon Discharge in Emergency Diesel Generator Building ENS 459802010-06-06T15:37:0006 June 2010 15:37:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Brunswick Declared Alert Due to Halon Discharge in Emergency Diesel Generator Building ENS 459022010-05-05T15:44:0005 May 2010 15:44:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram Due to Reactor Feed Pump Trip ENS 457962010-03-27T02:45:00027 March 2010 02:45:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Dut to Fire Greater than 15 Minutes in Turbine Building ENS 457322010-02-27T06:58:00027 February 2010 06:58:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Core Isolation Cooling (Rcic) System Manually Started to Maintain Reactor Pressure Vessel Level Following a Pre-Planned Reactor Scram ENS 457112010-02-19T16:11:00019 February 2010 16:11:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unsual Event Due to Carbon Dioxide Discharge in the High Pressure Coolant Injection (Hpci) Room ENS 453752009-09-21T18:46:00021 September 2009 18:46:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Protection System and Primary Containment Isolation System Actuation After Placing Hpci System Inservice ENS 451902009-07-08T14:13:0008 July 2009 14:13:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Valid Emergency Diesel Generator Actuation ENS 446852008-11-26T17:00:00026 November 2008 17:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram Due to Ehc Malfunction ENS 446472008-11-09T16:08:0009 November 2008 16:08:00 Other Unspec Reqmnt, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Scram Due to Spurious Srv Opening ENS 444532008-08-30T19:03:00030 August 2008 19:03:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Turbine Electro-Hydraulic Control Malfunction Leads to Reactor Scram ENS 430622006-12-25T10:39:00025 December 2006 10:39:00 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 Scram Due to Trip from Neutron Monitoring System ENS 429862006-11-11T17:43:00011 November 2006 17:43:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Scram Due to Conductivity Excursion ENS 429552006-11-01T23:37:0001 November 2006 23:37:00 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)(iv)(A), System Actuation - ECCS Discharge Unit 2 Declared an Unusual Event Due to Loss of Offsite Power to the 4Kv Emergency Buses ENS 419832005-09-13T03:14:00013 September 2005 03:14:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to Hurricane Ophelia Warning ENS 418372005-07-13T13:17:00013 July 2005 13:17:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Turbine Trip/Reactor Trip ENS 415822005-04-09T05:50:0009 April 2005 05:50:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Scrammed from 61% Power Due to Low Reactor Water Level ENS 409532004-08-14T17:08:00014 August 2004 17:08:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Notice of Unusual Event Emergency Declared Due to Loss of Offsite Power ENS 409542004-08-14T16:59:00014 August 2004 16:59:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Rps Actuation Due to Loss of Offsite Power ENS 409512004-08-13T22:20:00013 August 2004 22:20:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Notice of Unusual Event Declared Due to Hurricane Warning ENS 402972003-11-04T22:32:0004 November 2003 22:32:00 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 Brunswick Unit 2 Scram Due to Generator/Turbine Trip ENS 401642003-09-17T02:40:00017 September 2003 02:40:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event at Brunswick Due to Hurricane Warning 2025-03-28T18:09:00 | |