WASHINGTON -- The planned Yucca Mountain repository could hold between four to nine times more nuclear waste if it were expanded and redesigned, according to an industry report previewed Wednesday.

Early results of an ongoing study indicate at least 286,000 tons and possibly as many as 628,000 tons of used nuclear fuel could be stored at the Nevada site, authors said at a briefing.

A reconfigured repository would dwarf the current legal limit of 77,000 tons. The study assumes the repository area could be doubled, and that storage tunnels could be grouped or carved into multiple levels of the mountain.

The study also is expected to stoke debate about a new Bush administration bill that seeks to lift the official capacity at Yucca Mountain and take other steps to speed repository development as a way to encourage construction of more nuclear power plants.

"These are numbers that are draining the blood from the faces of many people who say, 'Wow, that is a lot,' " lead author Mick Apted said at a briefing for members of the Nuclear Regulatory Commission's nuclear waste advisory board.

There are about 50,000 tons of nuclear waste stored at power plants in the United States, according to the Department of Energy. The Nuclear Energy Institute estimates about 313,000 tons of nuclear waste are stored worldwide. The World Nuclear Association reports high-level waste is accumulating at 12,000 tons a year.

The Yucca study is being performed by the Electric Power Research Institute, the research arm of the utility industry. A preliminary draft is expected to be published in May while analysts continue to delve into the topic, said John Kessler, the institute's high level waste manager.

Marty Malsch, an attorney who represents the state of Nevada in nuclear waste matters, said the capacities detailed in the presentation would position Yucca Mountain "to hold all the nuclear waste in the world."

Malsch questioned whether an expanded repository could comply with the federal nuclear waste law, principally requirements that limit the amount of decaying nuclear materials allowed to seep into groundwater.

Per Peterson, a nuclear engineering professor at the University of California at Berkeley, said he is skeptical of tiered designs for Yucca Mountain, as well as expanding the repository to a large capacity.

"DOE will be lucky to get together a baseline application for a 60 metric ton per acre repository for submission to NRC by 2008, and while there are maps showing up to 4,200 acres (at the site), only a tiny fraction of this area has been characterized to the level needed to verify that it is suitable for repository use."

Malsch said the study appears part of a nuclear industry drive to persuade Congress to lift the capacity limit at Yucca Mountain.

Industry officials have argued that at the current limits, Yucca Mountain would be fully subscribed by the time it is built, potentially holding up the development of new nuclear power plants.

Kessler told the NRC panel that researchers were conservative in their modeling, and assumed a "hot temperature" repository design, the same being considered by the Energy Department for Yucca Mountain.

DOE already has conducted limited studies on repository expansion, Kessler said. The department's environmental study for Yucca examined a 120,000 ton repository limit.

"We are not starting with a blank slate," Kessler said. "We think there is a good chunk of information available."

The Energy Department believes the 77,000 ton repository cap, which was set by Congress in 1982, is an "arbitrary limit," spokesman Craig Stevens said in an e-mail.

"We already know that the true capacity of Yucca Mountain is significantly greater, that's why we've asked for a change in the law," Stevens said. He did not comment on the research institute's study.

Rep. Shelley Berkley, D-Nev., thinks President Bush should be asked about expanding Yucca Mountain when he appears in Las Vegas on Monday, her spokesman David Cherry said.

"Congresswoman Berkley has already said that President Bush wants to make Nevada a global nuclear garbage dump and these findings only add fuel to the fire," Cherry said.