Calvert Cliffs Reactor Shut Down Unexpectedly

Unit 2, one of the two nuclear reactors at the Calvert Cliffs nuclear power plant in Maryland, shut down unexpectedly on Wednesday May 8th. Spokesperson for Constellation Energy Nuclear Group, Kory Raftery, confirmed that at 9:47 pm, the reactor was automatically shut down due to a malfunction of the valves feeding steam to the turbine. The valves, when working properly, prevent steam pressure from building up in the cooling system.

The Constellation Energy Nuclear Group, the owner and operator the plant, claimed that this was the first unplanned shutdown or "scram" of Unit 2 since 2010. However, Unit 1, which remained operational throughout this disruption, had to be shut down in 2012 after a control rod unexpectedly dropped into the reactor core.

Unit 2 uses a Pressurized Water Reactor (PWR), also known a generation II reactor design classification. This generation unit was designed by Westinghouse and began commercial operation on April 1, 1977. It is licensed to operate through August 13, 2036.

Unit 2 remained shut down until through May 11, 2013. The Nuclear Regulatory Commission (NRC) released a statement indicating that they had inspectors on site assisting with troubleshooting and developing repair plans. According to the NRC website, Unit 2 was back online on May 12th at 30% power and at full power on May 13th. Exact cause of the malfunction has yet to be determined at this time.

The NRC Event Text Can be found here:
Event Number: 49012