UPDATE 1-Dominion shuts Wisconsin Kewaunee reactor for refuel

(Updates with company comment)

NEW YORK, March 31 (Reuters) - Dominion Resources Inc (D.N: Quote, Profile, Research) shut the 556-megawatt Kewaunee nuclear power station in Wisconsin on Friday for planned refueling and maintenance, a spokesman said Monday.

He could not say when the unit would likely return to service, due in part to competitive reasons, but he noted that during the outage the company would replace the plant's three main transformers. Each transformer is about the size of a small house.

Electricity traders guessed the unit would return in about a month.

The unit last shut for refueling from Sept. 2 to Oct. 26, 2006.

The Kewaunee station, which entered service in 1974, is located in Kewaunee, in Kewaunee County, about 30 miles from Green Bay, Wisconsin.

Dominion told the NRC it plans to file in the second quarter of 2008 for a 20-year extension of the plant's original 40-year operating license.

It usually takes the NRC about 22 months to make a decision on a license renewal without a hearing and about 30 months with a hearing.

One MW powers about 800 homes in Wisconsin.

Dominion, of Richmond, Virginia, owns and operates about 28,000 MW of generating capacity, markets energy commodities, and transmits and distributes electricity and natural gas to customers in 11 states. (Reporting by Scott DiSavino; Editing by Walter Bagley)