Waterford - After an unplanned shutdown lasting less than 48 hours, Unit 2 at the Millstone Power Station began producing power again Feb. 1, and no issues of concern were identified by the Nuclear Regulatory Commission in the shutdown or the restart.

The plant, the smaller and older of the two working reactors at Millstone, shut down Jan. 31 because of an issue with the electrical supply for the heaters in its water pressurizer. The plant produces 869.5 megawatts of electricity.

As operations at Unit 2 returned to normal, Unit 3 came under added scrutiny last week from the NRC for ongoing problems involving a pump that is part of a reactor safety system. Unit 3 is continuing to generate 1,210 megawatts of electricity as Millstone completes its own investigation of the pump, spokesman Ken Holt said Monday. He expects that investigation will conclude in early March.

NRC spokesman Neil Sheehan said inspectors were on site at Millstone last week for the special inspection of the pump, and are now reviewing documents and awaiting the outcome of Millstone's own review. The pump is considered "an important safety system" to cool the plant when it is shut down, he said.

"There have been a whole series of issues with the pump that the company has not been able to resolve," Sheehan said. The NRC conducts about a dozen special inspections nationally each year, he said.

The last special inspection at Millstone took place in 2011, and resulted in a "white finding" by the NRC that turbine valve tests were not done properly, resulting in an unplanned 8 percent increase in power.

A white finding is the second-lowest of the NRC's five-level ranking system for license violations.