Arkansas Nuclear One Unit 2 was taken offline the morning of Dec. 9 due to a transformer fire in the site switchyard.

Operators at the plant declared an “Unusual Event” at 8 a.m. CST and notified the Nuclear Regulatory Commission (NRC) of the situation. An Unusual Event is the lowest of four nuclear emergency classifications and means events indicate a potential degradation of the level of safety of a plant. The NRC’s senior resident inspector assigned to the site reported to the plant’s control room to monitor the licensee’s response to the event.

The plant, operated by Entergy Operations Inc., is located in Russellville, Ark. The company reported that there were no injuries or threats to public health or safety resulting from the event. During the incident, interruption of electrical power to Unit 2 caused protective systems to shut down the reactor. Operators will keep the Unit 2 reactor offline while the cause of the explosion is investigated and a determination is made on what repairs are necessary. Unit 1 was unaffected and continued to operate at about 95% power.

—Aaron Larson, associate editor (@AaronL_Power, @POWERmagazine)