Waterford – Unit 2 at the Millstone Power Station is back to 40 percent of its power-generating capacity this morning after being shut down since 7 a.m. Sunday.

Unit 3, the larger of the two nuclear reactors at Millstone, remains offline as evaluations and equipment repairs are completed.

Ken Holt, spokesman for Millstone, said Unit 2 will be brought back to 100 percent power over the next 24 to 48 hours.

Both units shut down Sunday after a short in electrical transmission lines that power operating systems for the plants. Unit 2 responded normally to the loss of power, with emergency diesel generators starting automatically to supply power to safety systems. Unit 3, however, experience an “unexpected loss of non-safety instrument air,” complicating the recovery actions, and as a result a rupture and leak from pressurized tanks that hold cooling water occurred, according to the Preliminary Notification of Unusual Event released by the Nuclear Regulatory Commission today.

The NRC said the Federal Emergency Management Agency and state Department of Energy and Environmental Protection officials have been informed of the event.