Calvert Cliffs Nuclear Power Plant in Lusby, MD, is back up and running after an automatic shutdown of both reactors, said officials at Constellation Energy Nuclear Group.
Units 1 and 2 shut down Jan. 21 at 9:25 p.m. when an electrical bus connected to components on both units tripped, or went offline, resulting in the automatic shutdown, Constellation officials said.
The units came back online and began sending electricity to the grid during the following weekend, according to Constellation. Unit 2 came online and connected at 11:54 p.m. Jan. 25, and Unit 1 went online and connected at 3:12 a.m. Jan. 26.
“We are currently performing a comprehensive review of our actions during the shutdown, and we welcome an independent review from the [U.S. Nuclear Regulatory Commission (NRC)], as well,” said Calvert Cliffs spokesman Kory Raftery. “These reviews are common after shutdown events, and we are committed to implementing any procedural or performance improvements identified during the review that might make our facility even safer moving forward.”
A three-member inspection team began a “Special Inspection” at the plant to further review the unplanned shutdown of both units Jan. 21, according to the NRC.
The review, the release said, will evaluate what happened during the event, including response by plant operators and safety systems, as well as the event’s cause and related issues.
“We want to gain a better understanding of the chain of events that caused both of the reactors to simultaneously shut down and equipment anomalies subsequent to the plant trips,” said NRC Region I Administrator Bill Dean. “This inspection is designed to shed additional light on not only why the outages happened but how the plant operators handled them.”
Raftery said when the shutdowns occurred, the operators followed their training and “performed well.”
On Jan. 21, there was a temporary interruption of an electrical supply system that distributes off-site power to the plant, according to the NRC’s initial report.
“At this point it appears that snow and ice affected a ventilation louver filter, causing an electrical fault, or short-circuit,” the NRC said. The breakers tripped as designed to clear the fault, shutting down the electrical supply system, the release said.
Several electric-powered plant systems and components shut down, including motors for moving control rods and circulating-water pumps for Unit 2, according to the release. The loss also caused the Unit 1 main turbine control circuit to malfunction.