The Unit 2 reactor at the Millstone Power Station in Waterford, CT, shut down Friday morning because of an issue with the electrical supply for the heaters in its water pressurizer, the Nuclear Regulatory Commission (NRC) said.
The unit, a pressurized water reactor, experienced an electrical short in a breaker that supplies power that enables some of the heaters to open, NRC spokesman Neil Sheehan said. An emergency diesel generator that could provide backup power was out of service, so they had to shut down according to the plant’s technical specifications, Sheehan said.
Millstone spokesman Ken Holt said the emergency generator was undergoing routine maintenance. Plant operators began shutting the plant down manually at 3:30 a.m., and they removed the faulty heater from service.
“All systems operated normally,” Holt said.
The NRC inspector at the plan was aware of the shutdown. Unit 3 remains unaffected.
The last unplanned shutdown of Unit 2, the smaller of the two operating reactors at the power station, occurred in November. Built in 1975, it is the older of the two units and generates 869.5 megawatts of electricity. Unit 3, built in 1986, generates 1,210 megawatts.