A preliminary report on a nuclear waste storage project in Nevada concludes that very little radiation would leak from the site and that a repository there would be as safe and much cheaper than securing the waste where it now collects, at dozens of sites around the nation.
The environmental impact statement, released Friday by the Energy Department, acknowledges that some key issues are not understood well enough to recommend Yucca Mountain, about 100 miles from Las Vegas.
The flow of water in the area is a major uncertainty. Opponents say assumptions used in the report about water flow are contradicted by other evidence.
Next week the Environmental Protection Agency plans to issue a draft of the rules that a repository would have to meet to be licensed.
The EPA will call for the repository to hold in the bulk of the radiation for 10,000 years, but the agency has not decided how many miles the radiation should be allowed to spread in that period.
The proposed site, which is 230 square miles, is controlled by the Energy Department, the Air Force or the Bureau of Land Management. Water flowing underground would eventually carry radioactive materials beyond the site's borders.
The statement evaluates the safety of leaving the waste at the current sites and finds little difference, if storage canisters at current sites can be replaced every century or so. But it finds that leaving the waste would be more expensive in the long run: hundreds of millions of dollars a year for thousands of years, while the repository would cost tens of billions of dollars.