Duke Energy is investigating what caused a loss of offsite power Wednesday night that automatically shut down one unit of its Catawba nuclear plant 18 miles south of Charlotte.
Duke declared an “unusual event,” the lowest of four emergency levels and one not experienced at the S.C. plant, near York, since 2006.
“We’re going to complete the investigation and take steps to make sure it doesn’t happen again” before restarting Catawba’s Unit 1, Duke spokesman Tim Pettit said. The plant’s second unit already was shut down to refuel.
Electrical power from a switchyard feeding the plant was lost just after 8 p.m. Wednesday, Pettit said, but it is not clear where the problem occurred.
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“Everything worked as designed,” he said. “Unit 1 tripped and all four (backup) diesel generators started” to supply the plant with power.
The event was declared over at 1:38 a.m. Thursday.
Unusual events can be caused by a wide variety of situations. They pose no threat to public safety but trigger a heightened state of emergency response.
Catawba declared its last unusual event in December 2006 because of a leak in a reactor’s coolant system. In May 2006, an unusual event was declared after the loss of offside power from an electrical relay in the switchyard.
The Nuclear Regulatory Commission will follow-up on the cause of Wednesday’s power loss, spokesman Roger Hannah said, but doesn’t plan to send an inspection team to the plant.
The NRC says no radiation was released, and workers and the public weren’t in danger. Officials will review the outage and determine if additional inspections are needed.√