ENS 45986
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ENS Event | |
|---|---|
13:48 Jun 8, 2010 | |
| Title | Automatic Reactor Trip with Safety Injection Due to Loss of Vital Ac Bus |
| Event Description | At 0948 hours0.011 days <br />0.263 hours <br />0.00157 weeks <br />3.60714e-4 months <br /> [EDT] on 6/8/10, a Unit 1 vital AC bus was lost when the uninterruptible power supply inverter failed while the alternate AC source was out of service for scheduled maintenance. The loss of the vital bus inverter caused a loss of 120 VAC vital bus 1-III. The loss of this vital bus caused the 'A' main feed pump recirculation valve to fail open and also caused 2 of the 3 main feedwater regulating valves to fail to automatic-hold mode of operation. This combination of as designed failures resulted in a reduction in main feedwater flow and resulted in an automatic reactor trip due to a feed flow steam flow mismatch in conjunction with low steam generator level.
The loss of vital bus 1-III also resulted in initiation of safety injection due to loss of vital bus 1-III instrumentation in conjunction with the expected momentary RCS cooldown below 543 DEG-F. The safety injection resulted from the high steam flow in conjunction with low RCS T-ave actuation signal. The safety injection actuation also resulted in automatic start of the #1 Emergency Diesel and the #3 Emergency Diesel Generators. Neither EDG was required to load since off-site power remained operable. The loss of vital bus 1-III also resulted in loss of numerous field inputs to the Plant Computer System [PCS] and resulted in non-functionality of the SPDS [Safety Parameter Display System]. The PCS itself remains functional along with MCR [Main Control Room] annunciators and sufficient MCR instrumentation to monitor critical safety functions. All three auxiliary feedwater pumps automatically initiated as designed on low-low steam generator level following the trip. Currently, RCS temperature is being maintained stable at 547 degrees. All systems functioned as required following the reactor trip. During the post-trip transient, pressurizer PORV [Power Operated Relief Valve], PCV-1455C, cycled as required to maintain RCS pressure due to the safety injection and the loss of normal letdown. There were no radiation releases due to this event, nor were there any personnel injuries or contamination events. This event is being reported in accordance with 10CFR50.72(b)(2)(iv)(B), 10CFR50.72(b)(2)(iv)(A), 10CFR50.72(b)(3)(iv)(A), and 10CFR50.72(b)(3)(xiii). The NRC Resident Inspector was notified of this event. During the trip, all rods inserted into the core. In addition to the pressurizer PORV lifting, a secondary main steam relief valve lifted. All relief valves properly reseated and there is no known primary to secondary leakage. The plant is in its normal shutdown electrical lineup. Main steam trip valves were isolated during the transient. Decay heat is being removed via main steam bypasses to the condenser and steam generator power operated relief valves. |
| Where | |
|---|---|
Surry  Virginia (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(iv)(B), RPS Actuation 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge 10 CFR 50.72(b)(3)(iv)(A), System Actuation 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness | |
| Time - Person (Reporting Time:+-1.8 h-0.075 days <br />-0.0107 weeks <br />-0.00247 months <br />) | |
| Opened: | Alan Bialowas 12:00 Jun 8, 2010 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Jun 8, 2010 |
| 45986 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Surry with 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)(3)(xiii), Loss of Emergency Preparedness, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge | |
WEEKMONTHYEARENS 571582024-06-02T21:08:0002 June 2024 21:08:00
[Table view]10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Automatic Reactor Trip ENS 537362018-11-12T05:00:00012 November 2018 05:00:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation ENS 536622018-10-11T04:00:00011 October 2018 04:00:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Actuation of Emergency Diesel Generator Due to Transformer Trip ENS 531702018-01-17T14:52:00017 January 2018 14:52:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Auto-Start of Emergency Diesel Generator Due to Transformer Fuses Being Disconnected ENS 522922016-10-09T06:54:0009 October 2016 06:54:00 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 Main Generator Differential Lockout Turbine Trip ENS 514672015-10-13T22:15:00013 October 2015 22:15:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip After a Turbine Trip ENS 514022015-09-17T00:14:00017 September 2015 00:14:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Start and Loading of the #2 Emergency Diesel Generator ENS 512442015-07-21T09:04:00021 July 2015 09:04:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Surry Unit 2 Trip During Reactor Startup ENS 505292014-10-13T11:58:00013 October 2014 11:58:00 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 a Spurious Overpower / Delta Temperature Signal ENS 496732013-12-23T13:28:00023 December 2013 13:28:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Communications with Virginia State Eoc Due to Power Outage ENS 486382012-12-29T13:03:00029 December 2012 13:03:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Emergency Diesel Generator Auto-Start and Load Upon Trip of Reserve Station Transformer ENS 469052011-05-30T12:08:00030 May 2011 12:08:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation - Afw Initiation ENS 467612011-04-16T22:55:00016 April 2011 22:55:00 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 Loss of All Offsite Power from Tornado Damage ENS 465842011-02-02T10:33:0002 February 2011 10:33:00 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 Loss of Rcs Coolant Flow in One Loop ENS 459862010-06-08T13:48:0008 June 2010 13:48:00 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)(3)(xiii), Loss of Emergency Preparedness, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge Automatic Reactor Trip with Safety Injection Due to Loss of Vital Ac Bus ENS 455282009-11-29T15:45:00029 November 2009 15:45:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation Trip from Intermediate Range Due to Rod Group Demand Counter Discrepancy ENS 442212008-05-17T13:04:00017 May 2008 13:04:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Failed Relay Causes Emergency Diesel Generator to Start ENS 441522008-04-21T02:16:00021 April 2008 02:16:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unit 1 Manual Reactor Trip Due to Main Turbine Vibrations ENS 440542008-03-12T09:00:00012 March 2008 09:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Interruption to Ens Telephone Service ENS 428852006-10-07T17:40:0007 October 2006 17:40:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Site Access Road Flooded ENS 428712006-10-02T04:00:0002 October 2006 04:00:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Offsite Sirens Inoperable for Planned Maintenance ENS 415332005-03-28T19:21:00028 March 2005 19:21:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Planned Outage of Spds Due to System Upgrade ENS 413832005-02-08T01:23:0008 February 2005 01:23:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip During Startup Due to Indication of Misaligned Rod ENS 407692004-05-22T01:08:00022 May 2004 01:08:00 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 Leads Failure ENS 406982004-04-22T14:45:00022 April 2004 14:45:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Safety Parameter Display System (Spds) Declared Inoperable ENS 401812003-09-19T15:30:00019 September 2003 15:30:00 10 CFR 50.72(b)(3)(xiii), Loss of Emergency Preparedness Loss of Sirens ENS 401682003-09-18T13:00:00018 September 2003 13:00:00 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 Expected Severe Weather 2024-06-02T21:08:00 | |
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