ENS 50221
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ENS Event | |
|---|---|
16:07 Jun 23, 2014 | |
| Title | Emergency Diesel Generator Auto Start Due to Degraded Bus Voltage Signal |
| Event Description | At 1107 [CDT] on 6/23/14, Safeguards Bus 15 received a degraded voltage signal that resulted in the bus load shed and the automatic start of the D1 Emergency Diesel Generator (EDG). Bus 15 re-energized to normal voltage after the source breaker from D1 [EDG] automatically closed. This event is reportable under 10 CFR 50.72(b)(3)(iv)(A) for valid actuation of the D1 EDG.
The initiating condition appears to be a failure of the automatic voltage tap changer on the 10-Bank transformer which affected voltage to the normal offsite power supply to the 1R transformer and Safeguards Bus 15. Currently Bus 15 is powered from offsite via the CT-11 transformer and D1 [EDG] has been shutdown. When Bus 15 power supply was transferred from D1 [EDG] to CT-11 transformer, a lockout was received on D1 [EDG] due to reverse power. Unit 1 is in TS [Technical Specification] 3.8.1 Condition D for one path inoperable and one EDG inoperable. At no time during the event were the health and safety of the public challenged. The redundant AC power supply train (Bus 16 and D2 EDG) remained operable and Bus 16 remained powered from offsite power. The Senior Resident Inspector has been notified. TS 3.8.1 Condition D requires that the one inoperable offsite power path or the D1 EDG be returned to operable status by 2334 CDT or be in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. Unit 2 is not affected by this issue. |
| Where | |
|---|---|
Prairie Island  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| Time - Person (Reporting Time:+0.92 h0.0383 days <br />0.00548 weeks <br />0.00126 months <br />) | |
| Opened: | Brain Johnson 17:02 Jun 23, 2014 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | Jun 23, 2014 |
| 50221 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 570032024-03-03T17:42:0003 March 2024 17:42:00
[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 Due to Loss of Main Feedwater Pump Suction ENS 568032023-10-19T16:10:00019 October 2023 16:10:00 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 565432023-05-27T23:34:00027 May 2023 23:34:00 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 Notification of Unusual Event Due to Multiple Fire Alarms in Containment Not Verified within 15 Minutes ENS 555032021-10-03T20:25:0003 October 2021 20:25:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation ENS 548592020-08-26T18:19:00026 August 2020 18:19:00 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 Flux Rate ENS 534082018-05-17T16:15:00017 May 2018 16:15:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of Emergency Diesel Generator ENS 516092015-12-17T19:18:00017 December 2015 19:18:00 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 Fire Alarm in Containment Not Verified within 15 Minutes ENS 511362015-06-07T12:35:0007 June 2015 12:35:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Resulting from Turbine Trip on Low Oil Pressure ENS 511072015-06-01T03:20:0001 June 2015 03:20:00 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 Trip of Condensate and Main Feedwater Pump ENS 509502015-04-03T11:52:0003 April 2015 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 Scram Due to Loss of Main Feedwater Pump ENS 502212014-06-23T16:07:00023 June 2014 16:07:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Emergency Diesel Generator Auto Start Due to Degraded Bus Voltage Signal ENS 481862012-08-14T08:12:00014 August 2012 08:12:00 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)(2)(i), Tech Spec Required Shutdown Technical Specification Required Shutdown Based on Both Emergency Diesels Being Declared Inoperable ENS 470172011-07-01T20:52:0001 July 2011 20:52:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unit 1 Manual Trip Due to Electro-Hydraulic Control Fluid Leak on Turbine Stop Valve ENS 468302011-05-09T12:22:0009 May 2011 12:22:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Trip Upon Turbine Trip Due to Main Generator Lockout ENS 459522010-05-25T08:14:00025 May 2010 08:14:00 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 450772009-05-18T18:05:00018 May 2009 18:05:00 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 Due to Condenser Vacuum ENS 449202009-03-19T20:32:00019 March 2009 20:32:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Unplanned Start of a Cooling Water Pump During Testing ENS 443772008-07-31T13:17:00031 July 2008 13:17:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Reactor Trip During Testing ENS 425042006-04-14T19:25:00014 April 2006 19:25:00 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 Condensate Pump and Feedwater Pump Trip 2024-03-03T17:42:00 | |
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