The Callaway Energy Center resumed generating electricity Monday after a 23-day outage caused by an electrical fault in the plant's main power line.
The plant's nuclear reactor was not involved in the incident, which occurred on the main electrical power cable leading from the plant.
Ameren Missouri officials reported the electrical fault in the plant's main electrical power cable leading from the plant was caused by a ventilation louver that had dislodged and came into close proximity of the main electrical cable, which carries current generated by the plant to power lines leading from the plant.
Metal from the ventilation louver was close enough to the generating cable to cause electricity to arc to the louver, creating a flash that resulted in temporary closure of the nuclear power plant.
After the power disruption, normal operating safety procedures caused the plant's nuclear reactor to shut down automatically.
Equipment near the flash incident, located near edge of the plant away from nuclear reactor, was disassembled and rebuilt. During an investigation of the incident, the cause of the arc was found to be the dislodged ventilation louver.
Ameren officials said inspections were performed on the cabling and transformers. It was determined the impacts were limited to the local arc flash. Major equipment replacements were not necessary, shortening the time of the plant's outage.
The plant has two full-time inspectors employed by the U.S. Nuclear Regulatory Commission who are stationed permanently at the Callaway Energy Center.
The plant is powered by a nuclear reactor, which heats steam that drives turbines generating about 20 percent of the electricity supplied to Ameren Missouri's 1.2 million customers.
While the nuclear plant was out of service, electrical power was provided to the grid by other electrical power plants within the Ameren Missouri system.