Entergy's Pilgrim nuclear plant remained offline Monday after a weekend that brought extreme winter weather and two separate power outages at the Massachusetts nuclear plant.

On Friday, parts of the Northeast received as much as three feet of snow during a storm that knocked out electricity to 667,763 customers, according to the Department of Energy. Crews were able to bring that number down to about 136,000 by Monday morning.

At Pilgrim, a loss of offsite power shut the reactor down automatically from 80 percent power Friday night, according to a report filed with the Nuclear Regulatory Commission. A load reject caused the reactor to trip at 9:17 p.m., with offsite power available intermittently afterward, according to the report. Diesels and other emergency systems that included high pressure coolant injection and reactor core isolation cooling functioned as designed, and the plant issued an unusual event declaration that remained in effect until just before 11 a.m., Sunday, following restoration of an offsite power line.

Later that day, the plant lost offsite power again. Emergency diesels restarted at about 2 p.m. after ice is believed to have fallen on an insulator of a start-up transformer. The reactor was in cold shutdown at the time, and shutdown cooling was restored within minutes.

The DOE's report Monday morning indicated that offsite power had been restored, and an off-site grid operator was repairing two additional power sources to the plant.