And Maryland-based USEC is building its American Centrifuge plant in the Ohio river town of Piketon and expects to enrich enough uranium there by 2012 to supply a quarter of existing U.S. demand.

"Multiple enrichment facilities provide customers with diversity of supply and competition," said Jeremy Derryberry, a USEC spokesman. "We believe the market can support all current planned enrichment capacity."

Yellowcake uranium is mined and milled at 20 sites in the United States, according to the Nuclear Regulatory Commission, as well as in Australia, Canada and Kazakhstan. In Utah, Toronto-based Denison Mines Corp. plans to reopen the Tony M Mine in Garfield County for production this year, and the company plans to process the ore at its White Mesa mill near Blanding. Denison also owns the Pandora mine in southeastern Utah.

Uranium One Inc., also based in Toronto, owns the Frank M Mine, located in the same canyon as the Tony M Mine, as well as the Shootaring Canyon processing mill, which the company bought last year. In October, Uranium One bought the entire town of Ticaboo to facilitate work in the area.

Once out of the ground, the ore is converted into uranium hexafluoride that's shipped in metal cylinders to an enrichment plant. Uranium pellets are then taken to a fabrication plant where they're put into fuel rods. Those fire reactors at nuclear power plants.

The United States' 104 nuclear power plants get about 85 percent of their uranium from other countries, including the Russian program "Megatons for Megawatts" program, a 15-year-old program in which warheads are converted in that country to nuclear fuel and then shipped to U.S. commercial reactors.

That program, however, is due to end in 2013. A replacement agreement would bring in only about half the enriched uranium of the existing deal.

What's more, once USEC's new Ohio plant is completed, it plans to close its aging facility in Kentucky, which is now the only operating enrichment plant in the United States.

"We do not have adequate enrichment capacity for the existing demand that there is," said Felix Killar, the senior director for fuel supply for the Nuclear Energy Institute lobbying group in Washington, D.C. "It's going to be a tight market for some period of time."

As enrichment fever grows, however, the Union of Concerned Scientists in Washington, D.C., is watching with unease, on grounds this activity undermines U.S. credibility with Iran. The United States and some of its allies oppose Iran's expansion of its enrichment facilities, saying it could lead to the development of nuclear weapons.