The Calvert Board of County Commissioners yesterday urged a consortium of electric companies to choose Southern Maryland as the site of what could become the first nuclear power reactor built in the United States in 30 years.

The Calvert Cliffs nuclear power plant, 50 miles southeast of Washington, is one of six sites that the consortium, NuStart Energy Development LCC, is considering for a new type of reactor.

By a 5 to 0 vote, the commissioners expressed support for the addition of a third reactor to the Lusby plant, which is Calvert's largest taxpayer and private employer.

"Supporting the expansion of Calvert Cliffs was not a difficult decision," the commissioners wrote in a letter to NuStart, which includes the nation's largest nuclear power companies. "Calvert Cliffs plays a vital role in the County and State economy."

The nuclear plant, which produces 20 percent of Maryland's electricity, attracted national attention last month when President Bush spoke there to urge Congress to pass legislation encouraging the construction of nuclear reactors.

Local opposition to the power plant is almost nonexistent. At yesterday's meeting, every commissioner proudly expressed support for Calvert Cliffs, which is owned by Baltimore-based Constellation Energy. No one spoke out against the plant's expansion.

"You've been a great neighbor," board President David F. Hale (R-Owings) told Constellation officials. "We hope to keep you forever."

The commissioners said the nuclear plant, which went online in 1975, transformed Calvert from one of the state's poorest counties to one of the richest. Calvert Cliffs employs about 1,000 workers and pays about $15.3 million in property taxes.

Linda S. Vassallo, director of the county's department of economic development, said the county and state plan to put together a package of financial incentives to encourage NuStart to select Calvert County as a site for a new reactor.