WELCH, Minn. -- Xcel Energy said an "unusual event" caused a reactor at its Prairie Island nuclear plant to automatically shut down over the weekend, but there was "no threat to plant staff or to the public at any point."
Operators at the plant notified the U.S. Nuclear Regulatory Commission (NRC) of the event after an external transformer malfunctioned and set off a fire alarm at one of the plant's two reactors.
Operators confirmed there was no fire, Xcel said, but the malfunction automatically shut down the reactor at Unit 2. As of Wednesday, the reactor is still shut down, but Xcel said it plans to return it to service later this week.
"A notification of unusual event is the lowest of four emergency classifications established by the U.S. Nuclear Regulatory Commission," Xcel said. "The declaration indicates a potential reduction in the level of safety at the plant but no threat to public safety. The declaration's purpose is to have the plant's operating staff reach a state of readiness for emergency response if necessary."
In a statement sent to WCCO News Wednesday, NRC Public Affairs Officer Prema Chandrathil said in part:
The NRC Resident Inspectors responded to the site in response to the issue and verified that the plant was in a safe condition and that plant personnel were operating in a manner consistent with protecting the health and safety of the public. They will continue to monitor the licensee's investigation and repair efforts. The resident inspectors will also observe and monitor the reactor plant restart following completion of repair activities.
Last November, a faulty pipe at an Xcel nuclear plant in Monticello allowed water containing a radioactive isotope of hydrogen to leak. The leak wasn't publicly announced until months later, when a second leak occurred. Xcel said earlier this month.
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