ENS 52290
ENS Event | |
|---|---|
17:17 Oct 8, 2016 | |
| Title | Unusual Event Declared Due to Loss of Offsite Power |
| Event Description | UE SU1.1 declared due to momentary loss of power from the qualified off-site source. Both Emergency Diesel Generators started and loaded to supply power to both of the Emergency Buses.
'A' Service Water Pump did not start on Blackout sequencer. Sufficient Service Water flow is available from the other three operating pumps. All other systems operated as designed." At 1304 EDT Robinson Unit 2 experienced a momentary grid voltage drop that lowered the 4kV bus voltage and initiated an automatic reactor trip. All rods inserted and decay heat is being removed by steam generator PORVs. In response to the reduced bus voltage, the Emergency Diesel Generators (EDGs) automatically started and loaded onto the emergency busses. At 1317 EDT, the licensee declared an Unusual Event (EAL SU1.1) due to the loss of offsite power. The licensee is currently investigating the cause of the grid voltage instability. The emergency busses will continue to be powered by the EDGs until the licensee has determined the cause for the voltage drop. All offsite power sources and all equipment is available. The licensee has notified the state government and Darlington County. The NRC Resident Inspector has been notified. Notified DHS SWO, FEMA OPS Center, FEMA National Watch (email only), DHS NICC, Nuclear SSA (email only).
At 1303 EDT on 10/08/2016, a reactor trip occurred. The cause was under voltage to the plant 4kV buses due to an offsite grid disturbance. The cause of the disturbance is under investigation. Following the reactor trip, the Auxiliary Feedwater System actuated as expected on low steam generator level. At the time of the trip, the plant was in Mode 1. Currently, the Plant is in Mode 3. The current RCS Temperature is 550 degrees F (Average), and the Steam Generator Levels are in the range of 42 to 53% (normal range) with levels controlled by the Auxiliary Feedwater System. Decay heat removal is being controlled by the steam generator PORVs. 'A' Service Water Pump did not start on Blackout sequencer. Sufficient Service Water flow is available from the other three operating service water pumps 'B', 'C', and 'D'. All other systems operated as designed. Due to the Automatic Actuation of the Reactor Protection System, this event is being reported as a 4-hour Non-Emergency per 10 CFR 50.72(b)(2)(iv)(B). Due to the valid actuation of Auxiliary Feedwater System, this event is also being reported as an 8-hour Non-Emergency per 10 CFR 50.72(b)(3)(iv)(A)(B)(6). At no time during this occurrence was the public or plant staff at risk as a result of this event. The Resident Inspector has been notified.
At 2323 [EDT] Emergency Bus E-2 powered from off-site power." The NRC Resident Inspector will be notified. Notified R2DO (Bonser), IRD (Grant), NRR EO (Miller).
At 0011 [EDT] Robinson Nuclear Plant has terminated the Unusual Event. Basis for the Unusual Event termination was restoration of power to Emergency Bus E-2 from off-site power. The licensee has notified the NRC Resident Inspector. Notified R2DO (Bonser), NRR EO (Miller), IRD (Grant), DHS SWO, FEMA OPS Center, FEMA National Watch (email only), DHS NICC, Nuclear SSA (email only).
At approximately 2323 EDT on 10/08/2016, an auto-start of the Auxiliary Feedwater (AFW) Motor-Driven pumps occurred during the transfer of Emergency Bus power from the 'B' Emergency Diesel Generator (EDG) to offsite power. AFW system auto-start logic associated with Main Feed Pump (MFP) breakers being open is defeated when the EDG output breaker is closed. As such, when the EDG output breaker was opened during the power transfer while the MFP breakers were open, the auto-start logic was thereby met causing the AFW auto-start. Due to the valid actuation of the AFW System, this event is being reported as an 8-hour Non-Emergency per 10 CFR 50.72(b)(3)(iv)(A). At no time did this occurrence pose undue risk to the health and safety of the public. The NRC Senior Resident Inspector has been notified of this event. H.B. Robinson Unit 2 was in Mode 3 during this event. Notified R2DO (Bonser). |
| Where | |
|---|---|
Robinson  South 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)(B), RPS Actuation 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000261/LER-2016-005 |
| Time - Person (Reporting Time:+-3.55 h-0.148 days <br />-0.0211 weeks <br />-0.00486 months <br />) | |
| Opened: | Martin Bowskill 13:44 Oct 8, 2016 |
| NRC Officer: | Daniel Mills |
| Last Updated: | Oct 9, 2016 |
| 52290 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | A/R |
| Before | Power Operation (100 %) |
| After | Hot Standby (0 %) |
Robinson 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 | |
WEEKMONTHYEARENS 565852023-06-22T14:35:00022 June 2023 14:35:00
[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 Occured During Protection System Testing ENS 542122019-08-11T12:40:00011 August 2019 12:40:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Turbine Trip ENS 537452018-11-19T05:00:00019 November 2018 05:00:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Emergency Diesel Generator Actuation Due to Low Voltage Signal ENS 526622017-04-04T01:55:0004 April 2017 01:55:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of Auxiliary Feedwater System During Surveillance Testing ENS 522902016-10-08T17:17:0008 October 2016 17:17:00 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 Loss of Offsite Power ENS 521982016-08-24T17:38:00024 August 2016 17:38:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip Due Automatic Turbine Trip from 100 Percent Power ENS 501782014-06-06T20:22:0006 June 2014 20:22:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Notification of Unusual Event Due to a Fire Alarm Inside Containment ENS 497082014-01-10T03:34:00010 January 2014 03:34:00 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 495062013-11-05T23:00:0005 November 2013 23:00:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Due to Momentary Loss of 4 Kv Buses and Safety System Actuation ENS 495022013-11-05T05:41:0005 November 2013 05:41:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of the Auxiliary Feedwater System Due to Main Feed Pump Trip ENS 481992012-08-17T09:52:00017 August 2012 09:52:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to the Unplanned Loss of Annunciators > 15 Minutes ENS 477812012-03-28T19:03:00028 March 2012 19:03:00 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 Steam Generator High Water Level Condition ENS 476182012-01-23T23:04:00023 January 2012 23:04:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unsual Event Declared Due to Fire Inside Containment Lasting > 15 Minutes ENS 475512011-12-23T21:20:00023 December 2011 21:20:00 10 CFR 50.72(b)(2)(xi), Notification to Government Agency or News Release, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Alert Declared Due to Halon Discharge During Testing ENS 473022011-09-29T10:02:00029 September 2011 10:02:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to Fire Alarm in the Containment ENS 472932011-09-26T15:45:00026 September 2011 15:45:00 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 One Loop Low Flow Signal ENS 463132010-10-07T04:13:0007 October 2010 04:13:00 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 a One Loop Reactor Coolant Low Flow ENS 462382010-09-09T18:37:0009 September 2010 18:37:00 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 Overtemperature Delta-T Signal ENS 457992010-03-28T22:52:00028 March 2010 22:52:00 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 Alert Declared Due to Fire Affecting Safety Related Equipment ENS 454832009-11-07T03:02:0007 November 2009 03:02:00 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 Feed Reg Valve Closure ENS 446602008-11-17T10:51:00017 November 2008 10:51:00 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 Turbine Vibration ENS 433642007-05-15T15:16:00015 May 2007 15:16:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip on Turbine Trip Due to Differential Generator Protection ENS 429332006-10-25T06:48:00025 October 2006 06:48:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Manual Reactor Trip After a 100% Load Rejection ENS 412962004-12-27T05:31:00027 December 2004 05:31:00 10 CFR 50.72(a)(1)(i), Emergency Class Declaration Unusual Event Declared Due to Fire Inside Protected Area Lasting Greater than 10 Minutes 2023-06-22T14:35:00 | |