Waterford — The Nuclear Regulatory Commission announced Monday that it has begun a special inspection at the Millstone Unit 3 nuclear power plant "to further review repetitive problems involving a pump that is part of a reactor safety system."

The inspection by a four-member team began Monday, according to the NRC. The press release said it will focus on a turbine-driven auxiliary feedwater pump for the plant, which is owned by Dominion Nuclear Connecticut Inc. The back-up system is one of several that can be used to help cool down the reactor following a shutdown by pumping water into the secondary side of the plant's steam generators.

The steam generators are essentially large heat exchangers that convert heat produced by the reactor into steam, which in turn is used to spin the plant's turbine and generate electricity.

Among the areas to be reviewed are "Dominion's responses to the issues, including the adequacy and completeness of testing on the pump and root-cause evaluations of the problems," the release states. The purpose is to expand on earlier assessments by the NRC resident inspectors and NRC specialist inspectors.

NRC Region I Administrator Bill Dean said repeated problems since last May, despite attempts to make repairs, prompted the special inspection. Starting last May and as recently as Jan. 23 the auxiliary feedwater pump has had problems including oscillations and over-speeding, the release states.

The NRC said follow-up by resident inspectors and other NRC staff found, in an inspection for the third quarter, "an inadequate operability determination by the company related to the performance of the speed-controller for the pump."

The inspection team will document its findings in a report within 45 days of the end of the review.

Millstone spokesman Ken Holt confirmed that the plant has been experiencing issues with the pump and said the company is conducting its own investigation. They have brought in outside experts to examine the issue, including employees of other Dominion nuclear power stations, he said.

In November, the NRC cited Millstone for a safety violation on the same piece of equipment that prompted this month's special inspection. That was a "green" violation, the lowest level violation in the NRC's four-tiered ranking system, indicating that the NRC did not consider it a very serious safety risk.

Holt said that although the November violation involved the same equipment, more analysis is necessary to determine whether or not the oscillation and over-speeding issues are related.

k.catalfamo@theday.com