BioEd Online

Twenty years ago an act of Congress put forward Yucca Mountain as a possible repository for the nation's nuclear waste - but fierce disputes over whether the site might leak radioactive material have held up its construction ever since. Now the mountain, in the political swing state of Nevada, has emerged as a hot campaign issue in the US presidential race, and both candidates claim that sound science is on their side.

George Bush has been a strong supporter of Yucca since the beginning of his term in office. In 2002, he signed a joint congressional resolution that approved the Yucca site, and paved the way for the Department of Energy to file a licence application - the final step before work on the project could begin. Bush points to studies indicating that the repository could contain the waste securely for up to 10,000 years. "I said I would make a decision based upon science, not politics," he said in a 13 August campaign speech in Las Vegas, Nevada.

But Democratic presidential hopeful John Kerry opposes the Yucca site, and uses other scientific reports to back his position. Kerry highlights a recent investigation by a board of scientists showing that storage canisters at the site could become corroded and spring leaks - a potential threat to local residents. Yucca's location atop an aquifer and its proximity to a major fault line reinforce the idea that it might be insecure. "I can sum up my stance on the Yucca Mountain plan in four words: not on my watch," Kerry said, also at a Las Vegas campaign stop in August.

The scientific truth lies somewhere between the two candidates' positions, according to Paul Craig, a physicist emeritus at the University of California, Davis, who served for seven years on one Yucca review board. In moving ahead with the plan, the Bush administration has ignored a 1995 National Academy of Sciences study which advised that, in order for the repository to be considered safe, it must be stable for 100,000 years or more, not 10,000 years as the president has advocated. "He ignored sound science," Craig says.

On the other hand, Kerry's chief criticism of Yucca, that corrosion could cause the canisters to leak, has largely been discounted by scientists who reviewed the site and concluded that it was unlikely to be a significant problem. But because there is no strong scientific consensus about whether to proceed with the site - and no clear alternative fate for the waste - the issue looks set to rumble on.