President Bush tours the control room of the Browns Ferry Nuclear Plant in Athens, Alabama Thursday.

(CNN) — President Bush used the reactivation of a long-closed nuclear reactor to plug his energy conservation proposals Thursday, urging Congress to ease the way for new power plants he said would produce carbon-free electricity.

“If you are interested in cleaning up the air, then you ought to be an advocate for nuclear power,” Bush said during a stop at the Browns Ferry nuclear plant near Athens, Alabama. “Without nuclear power here in the United States, there would be nearly 700 million additional tons of carbon dioxide in the atmosphere every year.”

No U.S. nuclear plant has been ordered since the 1978 accident at the Three Mile Island plant near Harrisburg, Pa. Critics say the dangers posed by radioactive waste and the cost overruns incurred by previous projects make the plants impractical and unsafe.

But because they produce none of the carbon emissions blamed for an increase in global temperatures, nuclear plants — which produce about 20 percent of U.S. electricity — have been getting a second look in recent years. Bush has pressed for more nuclear power since taking office and said the United States will need three new plants a year, starting in 2015, to keep pace with U.S. demand.

The Tennessee Valley Authority, which runs Browns Ferry, shut down the No. 1 reactor in 1985. The plant was the scene of a 1975 fire that damaged the plant’s electrical control system in what as the worst U.S. nuclear incident before the partial meltdown at Three Mile Island.

– From CNN News Editor Matt Smith