ENS 57083
ENS Event | |
|---|---|
12:04 Apr 20, 2024 | |
| Title | Automatic Actuation of Emergency Diesel Generators |
| Event Description | The following information was provided by the licensee via phone and email:
At 0704 CDT on 4/20/24 with Unit 1 in Mode 1 at 100 percent power, an actuation of the emergency AC power system, specifically the Division 1 and Division 3 emergency diesel generators (EDGs) occurred during an unexpected loss of the Unit 1 system auxiliary transformer (SAT). The cause of the emergency AC power system auto-start was an unexpected loss of the Unit 1 SAT during switchyard maintenance. Bus 141Y did not fast transfer as designed resulting in the actuation of the Division 1 EDG. Division 3 EDG actuation is expected for this condition. The Division 1 and Division 3 EDGs automatically started as designed when the emergency AC power system valid actuation signal was received. This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the emergency AC power system. There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified." The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Division 1 and Division 3 EDGs will remain in operation and loaded until the Unit 1 SAT is restored. This event resulted in the plant entering an unplanned 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> limiting condition for operation (LCO) in accordance with technical specification 3.8.1. The licensee is investigating the cause of the unexpected loss of the Unit 1 SAT and the failure of the bus 141Y fast transfer. |
| Where | |
|---|---|
Lasalle  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(iv)(A), System Actuation | |
| LER: | 05000373/LER-2024-004 Emergency Diesel Generator Auto-Start and Load Due to Loss of Station Auxiliary Transformer |
| Time - Person (Reporting Time:+1.78 h0.0742 days <br />0.0106 weeks <br />0.00244 months <br />) | |
| Opened: | Kelsey Smith 13:51 Apr 20, 2024 |
| NRC Officer: | Tenisha Meadows |
| Last Updated: | Apr 20, 2024 |
| 57083 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 570832024-04-20T12:04:00020 April 2024 12:04:00
[Table view]10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of Emergency Diesel Generators ENS 563892023-03-04T15:10:0004 March 2023 15:10:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Actuation of Reactor Protection System (RPS) ENS 539032019-03-01T04:17:0001 March 2019 04:17:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Specified System Actuation - Trip of Safety Related Bus ENS 503462014-08-05T22:34:0005 August 2014 22:34:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Automatic Reactor Scram ENS 489392013-04-17T20:11:00017 April 2013 20:11:00 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 Notification of Unusual Event Declared Due to Loss of Offsite Power from a Lightning Strike ENS 423482006-02-20T06:23:00020 February 2006 06:23:00 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition, 10 CFR 50.72(a)(1)(i), Emergency Class Declaration, 10 CFR 50.72(b)(3)(iv)(A), System Actuation Site Area Emergency - Reactor Scram ENS 417872005-06-22T04:40:00022 June 2005 04:40:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation Multiple Specified Systems Actuations Due to Loss of Ac Safety Related Buses ENS 404952004-02-02T04:34:0002 February 2004 04:34:00 10 CFR 50.72(b)(3)(iv)(A), System Actuation One Half Scram Signal Due to the Loss of the "B" Reactor Protection System Bus. 2024-04-20T12:04:00 | |