Unit 2 of the D.C. Cook nuclear power plant in Michigan, which had been knocked offline a week earlier, was back to 47% power early July 13, according to reactor status data from the Nuclear Regulatory Commission (NRC).
The unit, operated by American Electric Power (AEP) utility Indiana Michigan Power, had gone offline after a piece of equipment in the turbine building ruptured on July 6.
The Cook nuclear plant, located in Bridgman, Michigan, consists of two pressurized water reactors (PWRs) that each has a capacity rating of roughly 1,100 MW. Unit 1 continued to run at full power.
NRC is looking into the accident that was initially described as an “unanticipated explosion.” No one was in the area at the time and there were no injuries, the utility has said.
Indiana Michigan reported said the reactor returned to service at about 6 p.m. on July 12. The company also released additional information in a July 13 news release.
“The cause of the failure is believed to be vibration-induced metal fatigue,” the utility said. “During the repairs, improvements were made to the expansion joint to ensure reliability until the unit is taken off line this fall for refueling. More comprehensive design change improvements will be made then.”
Plant operators manually shut down the reactor immediately following the rupture and briefly entered the site’s emergency plan at the lowest level following the incident, the utility went on to say.
The Cook station had a capacity factor of 88% during 2014, according to GenerationHub data.