WASHINGTON -- A North Carolina senator who voted for Yucca Mountain four years ago said Thursday he now believes the Nevada nuclear waste repository should be put on a back burner while scientists explore new ways to reprocess spent nuclear fuel.

Sen. Richard Burr, a Republican, called for a "pause" on the repository. He suggested federal spending on underground nuclear waste disposal be frozen or reduced for the time being, while the government prepares to spend new millions on research into potentially promising alternatives.

"Maybe it is time for us to rethink based on what we know today versus what we knew a number of years ago when we made the decision on Yucca Mountain," Burr said. "I believe we should explore whether reprocessing is a better route."

In the meantime, Burr said, "we might be able to store sweet potatoes at Yucca Mountain."

The Energy Department's bid to license a Yucca Mountain repository has stalled since President Bush and Congress gave the go-ahead in 2002.

Technological advances now being promoted by the Bush administration and key lawmakers like Sen. Pete Domenici, R-N.M., are refocusing nuclear waste strategy.

Burr's change in position is evidence of this shift taking place in Congress, Sen. John Ensign, R-Nev., said. Doubts about Yucca Mountain that used to be expressed only in cloakrooms now are becoming public, he said.

"I think it is significant anytime you have an original supporter of Yucca Mountain now coming and saying there are serious problems and we shouldn't look for more money," Ensign said, predicting more senators will follow suit.

As a House member, Burr worked on Yucca bills as a member of the Energy and Commerce Committee and voted to designate the Nevada site for nuclear waste in 2002. In 2004 he was elected to the Senate from a state where five nuclear reactors supply 32 percent of electricity.

More than 2,700 metric tons of used nuclear fuel is stored in water pools and dry cask vaults at North Carolina plants, according to the Nuclear Energy Institute.

But dozens of pending lawsuits against Yucca Mountain promise to "delay indefinitely any decisions on the movement of that waste," Burr said. "I try to be a realist.

"I think we need to make a decision whether we are going to go through a different course than Yucca for storage of current fuel," he said.

Sen. Harry Reid, D-Nev., "has said for decades that Yucca Mountain is never going to happen and we are very happy to see that other senators are starting to see that fact," spokeswoman Sharyn Stein said.

Burr became the second senator to rethink support for Yucca Mountain since September, when Sen. Robert Bennett, R-Utah, announced his position in favor of the project had changed. A majority of senators continue to publicly support the Nevada repository.

But with a growing emphasis on reprocessing, a Nevada repository as is presently being designed may not be the Nevada repository that is eventually put into use, Domenici, Senate Energy Committee chairman, said Thursday.

"Part of this is assuming that we are not going to be putting that same waste into Yucca," said Domenici. "We have to adjust but how much we would have to adjust I don't know yet."

Reprocessed nuclear waste is said to be volumes smaller and less toxic than the highly radioactive fuel rods planned to be buried at Yucca Mountain. France, Germany and Japan are among nations that currently reprocess.

Fuel rods now are removed from reactors and set aside after being utilized "once-through." Reprocessing proponents say fuel recycling technologies could wring up to 96 percent more energy.

Advanced reprocessing being studied in government laboratories may also be able to shape new fuel without producing plutonium byproducts capable of being used in nuclear weapons, they say.

Critics say reprocessing is prohibitively expensive and unproven for nuclear nonproliferation. But President Bush has gotten behind the effort, proposing $250 million to get started on a research and development initiative called the Global Nuclear Energy Partnership.

DOE officials have tied Yucca Mountain to the GNEP initiative, but have not explained how the projects would be harmonized. Talking to reporters on Thursday, Domenici also said that much is uncertain about how the two would fit together.

The Bush administration may provide more clues when it sends new legislation to Congress. DOE officials have briefed key senators and staffers but have not said when it will be introduced.

The Environment and Energy Daily, a Web-based publication, reported this week that industry officials expect the bill will authorize nuclear waste to be moved from reactor sites and stored on an interim basis at federal facilities possibly in Tennessee, Idaho, South Carolina, Washington or the Nevada Test Site.

DOE spokesman Craig Stevens said he would not confirm the report.

Appearing before the Senate Energy Committee on Thursday, Energy Secretary Samuel Bodman said GNEP could cost between $20 billion and $40 billion, and might rise to the $62 billion once estimated by the National Academies of Science in a 1996 study.

Domenici raised the idea that money the nuclear power industry has been gathering in a government fund to build Yucca Mountain might be redirected to fuel reprocessing research that would achieve the same result. About $20 billion sits in the fund.