British Energy Group Plc, whose nuclear reactors can produce about a fifth of the U.K.'s electricity, stopped Unit 2 at its Hartlepool atomic power plant today.
The generator, which has a capacity of about 605 megawatts, was taken off line at about 4:30 a.m. local time, according to data on the Web site operated by National Grid Plc. The other unit at the plant, located in northeastern England, was halted on Sept. 5.
British Energy officials weren't immediately available to comment.