Waterford - The Unit 2 reactor at Millstone Power Station was at half-power over part of the weekend and on Monday, so a leak in tubes on a feedwater heater can be repaired.

A series of feedwater heaters are used to heat up water that is fed back into a steam generator to create steam, which is then piped to a turbine that is turned to generate electricity, said Neil Sheehan, a spokesman for the Nuclear Regulatory Commission.

The water circulates through the tubes as it is being heated.

Dominion, the owner of Millstone, identified leaks in two tubes Saturday afternoon, said company spokesman Ken Holt. Around 8 p.m. Saturday, the company night notified the NRC that the plant would have to be powered down for repairs, he said.

Those two tubes will be plugged. In addition, there are thousands of tubes in each heater, so operators are also evaluating and possibly strengthening other nearby tubes, he said.

"When you have a tube leak the water's at a high enough pressure that it can wear away on the tubes that are next to it," Holt said.

The water passing through the tubes is not on the radioactive side of reactor operation, but there are sometimes very low, minute levels of radioactivity in it, Sheehan said, even though the water never comes in contact with reactor.

It would be captured by plant systems, and workers would exercise certain precautions to make sure there's no harmful radioactivity exposure, Sheehan said.

There were no harmful releases in this instance, he added.

"We're still in the process of making the repairs," Holt explained Monday. "Once repairs are complete, we will return reactor to full power."

p.daddona@theday.com