During its latest refueling outage, members of the Missouri General Assembly went behind the scenes at the Callaway Energy Center to learn more about the plant and its role in Ameren Missouri's generation fleet. The only nuclear power plant in Missouri, the 1,284 MW-generating energy center was declared operational in 1984. Every 18 months, the nuclear plant undergoes a refueling outage, allowing crews to complete preventative and corrective maintenance on the reactor, refuel the unit and carry out other tasks intended to ensure the plant runs as efficiently as possible.