The FirstEnergy Davis Besse nuclear plant in Ohio experienced an unplanned outage on Saturday, Sept. 10, according to a report filed with the Nuclear Regulatory Commission (NRC).
The facility was still listed at zero power early Sept. 12.
“At 0343 EDT, with the unit operating at approximately 100% full power, an automatic reactor trip occurred due to a Main Generator lock-out,” according to the NRC report.
“The cause of the generator lock-out is being investigated at this time. All control rods fully inserted. Post trip, the Steam Feedwater Rupture Control System was actuated due to high Steam Generator 1 level. The cause of the high Steam Generator 1 level is being investigated at this time.
“Operators identified that water from heavy rains moving through the area entered the turbine building through a roof vent that didn’t fully close,” the spokesperson said in an email. “Some of the water ran to an expansion joint on the turbine deck floor, where it dripped onto an electrical cabinet containing turbine controls, causing a short that shut down the turbine,” the FirstEnergy spokesperson added.
The company representative said plant workers have dried out the electrical cabinet and replaced and tested affected components. While the plant is offline, FirstEnergy will also take the opportunity to replace a valve on the pressurizer, which is part of the reactor coolant system.
“Replacing this component requires that part of the system to be drained, so this work will occur over the next few days,” the spokesperson added. “We will restart once that work has been completed and don’t expect a lengthy outage. For competitive reasons, we don’t share expected return to service dates.”
Davis-Besse is a roughly 900 MW pressurized water reactor (PWR) located in Oak Harbor, Ohio.