"It is an aggressive goal, but with presidential leadership it could happen," the third-ranking Senate Republican told an economic and technology conference at the Y-12 nuclear weapons plant in Oak Ridge.

"I am convinced it should happen because conservation and nuclear power are the only real alternatives we have today to produce enough low-cost, reliable, clean energy to clean the air, deal with climate change and keep good jobs from going overseas."

The country's 104 commercial nuclear reactors produce 20 percent of the nation's electricity, while most of its energy comes from carbon-producing coal. The last reactor to come online was the Tennessee Valley Authority's Watts Bar Unit 1 reactor in Spring City, Tenn., in 1996.

Steve Smith, director of the Southern Alliance for Clean Energy, called Alexander's proposal "reckless."

"Nuclear power is a problem, not a solution," Smith said. "New nuclear reactors are expensive, create significant water use and thermal pollution risks to our communities and produce radioactive waste that after 50 years we still have no long-term solution for."

Smith urged conservation and efficiency improvements instead, but Alexander said that they would not be enough to blunt growing energy demand.

Alexander said that he also backs renewable energy sources, notably solar power and biomass fuels, yet called those still too expensive and inefficient.

"Today there is a huge energy gap between the renewable electricity we would like to have and the reliable, low-cost electricity we must have," he said. *