Unit 1 at Maryland's Calvert Cliffs nuclear plant returned to service over the weekend following an automatic reactor trip Thursday.
Safety systems shut the unit down from full power on a signal from the reactor protection system, according to a report filed with the Nuclear Regulatory Commission. No other engineered safety features actuated, and unit 2 continued to operate normally.
Unit 1 returned to full power Sunday morning, according to Exelon. The Baltimore Sun reported that the trip occurred during circuit breaker testing. It was the second unplanned outage at the site this year. In late January, both units tripped automatically following a partial power loss at the plant.
Located on Chesapeake Bay southeast of Washington, D.C., Calvert Cliffs generates 1,937 megawatts using two Combustion Engineering pressurized water reactors. They are jointly owned by Exelon and EDF.