The Nuclear Regulatory Commission sent inspectors to Calvert Cliffs Nuclear Plant in Lusby to review problems related to an unplanned shutdown of both reactors last week, the federal agency said Monday.
The reactors automatically shut down, as designed, in response to a power grid disturbance, caused by the failure of a transmission line in Southern Maryland on April 7, the NRC said. Power company Exelon operates the plant.
An emergency diesel generator, which powers safety systems when off-site power is lost, started but tripped off after 11 seconds. The same generator had failed to start in 2010 after a loss of off-site power. Additionally, one of three saltwater pumps on the unit failed to automatically restart when power was switched to emergency diesel generators. Plant operators had to manually start the pump, which cools plant equipment.
"While there was no impact on public health and safety, the issues with the emergency diesel generator and the saltwater pump warrant a closer look," said Dan Dorman, region 1 administrator for the NRC.
A three-member team will develop a sequence of events, review and assess the equipment response, look into operator performance and assess Exelon's response. A report showing findings will be issued within 45 days after the inspection is completed.