At the Bipartisan Policy Center, a nonprofit Washington group, Timothy Frazier, a former Energy Department official who heads the nuclear waste program there, said “it makes it hard, based on what they’ve written, for someone to say that Yucca Mountain is not technically acceptable.”

“If the Senate flips, you’re going to get money in the Senate appropriations bill to do something for Yucca Mountain,” he said. And there would probably also be money for temporary centralized storage of the waste now accumulating at more than 70 reactor sites around the country, he said. Congress has been stalemated on that point, with some proponents of Yucca Mountain trying to block any interim alternatives.

The stalemate, combined with delays because of technical problems, has become costly for taxpayers. Under the terms of a 1982 law, the Energy Department collected tens of billions of dollars in fees from reactor owners and was obligated to start taking the wastes in January 1998. Because it has not done so and has no prospect of taking wastes for years to come, the courts have assessed billions of dollars of damages against the Energy Department for the contract failure, and the potential liability runs well over $20 billion.

Yucca, a volcanic structure adjacent to what was formerly known as the Nevada Test Site, where the government exploded hundreds of nuclear bombs, was never described as the best place for burying nuclear waste, only an acceptable one about which a consensus could be achieved. The Energy Department selected Yucca Mountain as one of five candidate sites in 1986, under a procedure laid out by the Nuclear Waste Policy Act, which Congress passed in 1982. But in 1987, Congress amended the act to designate Yucca as the prime site, telling the department not to study anything else unless it found Yucca unsuitable.

In 1994, the Energy Department began drilling a five-mile tunnel through the mountain. By 1997, the department was burying metal containers in the rock, and heating them up to simulate nuclear waste, to study the effect on water and rock in the immediate area.