An incident at the Prairie Island Nuclear Generating Plant Saturday caused operators to declare a Notification of Unusual Event at 6:34 p.m.
Operators made the notification after an external transformer malfunctioned, triggering a fire alarm at Plant Unit 2 that could not be verified within 15 minutes.
Operators confirmed there was no fire. The transformer malfunction caused the site's Unit 2 to shut down automatically. Unit 1 continues to operate normally.
Both Units are in stable condition and Xcel Energy customers' electric service is not expected to be impacted by this event.
Operators will investigate and resolve any issues with the transformer before returning Unit 2 to service.
A Notification of Unusual Event is the lowest of four emergency classifications established by the U.S. Nuclear Regulatory Commission.
The declaration indicates a potential reduction in Plant safety levels but no threat to public safety and it’s purpose is to have the Plants operating staff reach a state of readiness for emergency response if necessary.
The Plant was clear of the event at 11:04 p.m. the same day.