Semantic search
Jump to navigation
Jump to search
| Entered date | Event description | |
|---|---|---|
| ENS 57083 | 20 April 2024 13:51:00 | 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 hour 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. |