In a last-ditch effort to stop a nuclear dump in Nevada, the state told a federal appeals court Wednesday the government has failed to ensure that thousands of years from now people will be protected from the waste's radiation.

Two of the three judges hearing the case asked government lawyers why the federal standards for radioactive releases for the Yucca Mountain (search) dump were pegged to 10,000 years into the future when scientists say the material will be most dangerous many thousands of years after that.

The 3 hours of arguments before the appeals court panel marked the first time a federal court has heard the merits of President Bush's decision in 2002 to select a ridge of volcanic rock 90 miles from Las Vegas as the place to entomb 77,000 tons of used rector fuel (search) from the nation's commercial power plants.

Congress affirmed Bush's decision in July 2002. Nevada officials argued Wednesday for the decision to be overturned, saying Congress violated the state's constitutional rights when it singled out Nevada.

The three-judge panel of the U.S. Court of Appeals (search) won't decide the case until later this year. Two of the judges made their views on several key issues clear during exchanges with Justice Department and Nevada lawyers.

They threw cold water on Nevada's hopes of challenging the way the Energy Department and later the White House decided to select Yucca Mountain.

Judge Harry Edwards, the senior jurist on the panel, said that's no longer an issue because Congress passed a law affirming Bush's decision.

But the judges accepted more openly some other arguments brought by opponents of the proposed nuclear waste site.

"All of the legal wrongs (in the government's decision) ... stem from the fact that the waste will not be isolated," Geoffrey Fettus, an attorney for the Natural Resources Defense Council (search), told the court. The NRDC filed one of the 13 lawsuits that have been consolidated by the court.

Opponents contend that the Environmental Protection Agency's (search) radiation standard for the site was inadequate because it would be applicable to only 10,000 years into the future. Critics cited a National Academy of Sciences (search) finding that said the peak radiation doses from some of the isotopes would be most dangerous up to 300,000 years.

Judge David Talen said the study clearly "rejected the 10,000 year limit" for radiation monitoring, but the EPA adopted it anyway.

The report is "absolutely clear ... that 10,000 years is incorrect," added Edwards. "`An agency does not have the authority to do whatever it wants to."

Christopher Vaden, representing the Justice Department, said the EPA selected the 10,000-year mark for its radiation exposure standard because of policy considerations as well as scientific issues.

The issue of time is important because the Energy Department acknowledges that it will rely on both the geology of the Yucca site and on engineered barriers to keep radioactivity from leaking into the environment. Scientists say that after 10,000 years, the performance of the engineered barriers is increasingly questionable.

After Wednesday's hearing, Joe Egan, the lead attorney for Nevada, said he thought the state had won on some issues and lost on others.

He described as "clear victories" an assertion that the government's environmental impact assessment would be subject to judicial review when it is considered by the Nuclear Regulatory Commission as part of the Yucca licensing process.

The judges' comments on EPA radiation standards were "encouraging," he said, noting that this was the first time a court has closely examined the legal merits of the waste dump, he said.

Energy Department spokesman Joe Davis said the department would go ahead as scheduled with a license application for the waste site toward the end of the year. "We're confident our science is sound," said Davis.

The Nuclear Regulatory Commission (search) permitting process could take three to four years. Plans call for the facility to begin accepting waste by 2010.

Congress in 1987 declared Yucca Mountain as the only site to be studied further for permanent waste repository.

Congress cannot single out a state .... in such a way," Charles Cooper, a lawyer for Nevada, told the panel on Wednesday. But the judges were far from impressed.

The waste site will be on federal land, noted Edwards. "It's their property." The argument would only hold if the decision to put the site there was found to be irrational, the judge said.

The court has consolidated 13 separate lawsuits, including nine filed by the state or other Nevada jurisdictions. The judges did not say when they will reach a decision.