"The market is clearly looking ahead to what it perceives to be an obvious path of much more demand as this ebbs and another begins," he said.

Federal officials do not break down Utah uranium reserves separately from those in Arizona and Colorado. If uranium sold for $50 a pound, the Energy Information Administration says, the three states' combined reserves would amount to 45 million tons of ore containing 123 million pounds of uranium. Should the price drop to $30 a pound, the amount worth recovering would be only 8 million tons of ore with 45 million pounds of uranium.

"Utah used to have a lot of uranium mines, but the uranium deposits in Utah are low-grade and small" compared with worldwide resources, said Ken Krahulec of the Utah Geological Survey.

One mine in Canada is believed to have uranium reserves that are twice as large as the entire Utah production so far. "And the grade of that mine is 100 times the grade of our old mines. We have to compete with mine operations like that. In normal circumstances we just can't do that."

Then prices rose and Utah mines became economical again.

"The best of the old mines are going back into production" or are being reclaimed. "The mine with the largest uranium reserves in Utah, the Tony M, is being prepared for production in 2008." The Pandora Mine near Lake Powell is already producing, he said.

How long production continues is "a matter of how long the uranium price is going to be up like it is right now. Because if it goes back to the historic price, Utah's mines won't work."

China, France and Canada are part of the demand for uranium as a nuclear fuel, he said.

In October 2006 the Cameco Corp. of Saskatoon, Saskatchewan, announced that one of its best potential mines, the Cigar Lake Mine, had flooded. Production now is expected to begin in 2010, according to Cameco. With likely high demand for uranium in China, Nusbaum said, "this Cigar Lake issue to some degree alters supply."

Uranium One announced in April 2007 that it had acquired U.S. Energy Corp.'s Shootaring Canyon uranium mill near Tickaboo, Garfield County. The company also obtained 38,763 acres of uranium exploration properties in Utah, Wyoming, Arizona and Colorado, it said.

Denison Mines notes on its Web site that it has five uranium mines in the United States and two in Canada. It estimates that its North American production will reach 5 million pounds by 2011.

Denison received the go-ahead to operate a uranium mine in the Henry Mountains in September. To process ore it will use the White Mesa mill, which Denison owns, near Blanding.

The Energy Information Administration lists White Mesa as the only operating uranium mill in the United States, and it has the capacity to mill 2,000 short tons of ore per day.