WASHINGTON — Turns out, it's going to cost taxpayers $32 billion more than first thought to open and operate the nation's first nuclear waste dump at Yucca Mountain in Nevada.

And Utah and Nevada members of Congress are using that news to try to kill that project and replace it with storing waste in dry casks at nuclear power plants that produce it.

The Bush administration's latest calculation — made public Tuesday — is that the Yucca Mountain facility will cost more than $90 billion. It's the first official estimate since 2001, when the figure was $58 billion.

Ward Sproat, the Energy Department official in charge of managing the controversial Yucca Mountain repository project in Nevada, disclosed the new number to reporters after a House hearing Tuesday.

The estimate includes $9 billion already spent and covers about 100 years of operation until the dump, 90 miles northwest of Las Vegas, is sealed up forever.

"That's a lot of money," said Rep. Jim Matheson, D-Utah, a member of the House Subcommittee on Energy and Air Quality, where the news was delivered. "We need to look at whether proceeding (with Yucca Mountain) is really the most cost-effective alternative. I don't believe it is."

Matheson and other Utah and Nevada members are pushing a bill calling for storing nuclear waste on-site at nuclear power plants in "dry cask" storage. Matheson notes that technology had not been developed when Congress first passed legislation calling for the Yucca Mountain repository.

Matheson said dry-cask storage could store all the radioactive waste produced in the last four decades on a space about the size of a football field. He says using that would be safer than transporting nuclear waste across the country, through Utah and into Nevada.

"Utahns have a hard time understanding why the transportation risks associated with shipping waste to Yucca Mountain have never been fully studied," despite all the money spent on Yucca Mountain so far, Matheson told the committee. "Given that 95 percent of the waste would go through Utah if rail were used, and 87 percent if we truck this waste, this is a huge concern to my constituents."

Matheson added, "The West — whether it is Utah's Skull Valley (proposed as an interim storage site), or Nevada's Yucca Mountain — is not the de facto dumping ground for this lethal material. Storing nuclear waste on site is the safest, most reasonable and most effective way of allowing nuclear power plants to continue operating while we search for an appropriate long-term storage solution."

Sproat said some of the estimated cost increase comes from inflation. Also, Energy Department officials now expect the dump will hold more radioactive waste than the 77,000 tons initially approved by Congress.