Ameren Missouri's Callaway Energy Center is back online after an electrical problem caused a turbine trip and a reactor trip that shut the plant down on Dec. 2.
An Ameren release attributed the non-emergency shutdown in part to a damaged electrical cable running to one of the facility's transformers. The cable has been repaired.
"We are still in the process of determining the cause of the electrical problem," the release stated. "Our goal is to ensure the continued safe and reliable operation of Callaway."
The release further states that all nuclear systems are safe and that the Callaway plant has returned to service.
The Callaway Energy Center generates about 20 percent of the electricity for Ameren Missouri's 1.2 million customers. The shutdown did not affect service to those customers.