Constellation Energy Nuclear Group said it has shut down one of two reactors at its Calvert Cliffs plant in southern Maryland after a malfunction caused a drop in power generation.
A spokesman said Monday that a control rod unexpectedly dropped into the reactor core. Control rods are used to regulate the pace of the nuclear reaction.
A Nuclear Regulatory Commission spokesman said such events are infrequent but do not pose a risk to the public. He said shutting down the unit for inspections and maintenance was a prudent decision.
Plant spokesman Kory Raftery said he can't predict when Unit 1 will return to operation. He said Unit 2 is running at full power.
The plant is located along the Chesapeake Bay near Lusby, about 70 miles south of Baltimore.