With just 2 years to go before deciding whether Yucca Mountain in southern Nevada should be a permanent home for spent fuel from the country's nuclear power plants, the U.S. Department of Energy (DOE) has hit another snag. A new report from an expert panel says major questions about the controversial site are still unanswered and casts doubt on DOE's ability to make a final decision in 2001.
Congress chose Yucca Mountain as the sole site to be studied as a high-level radioactive waste repository in 1987, and DOE has spent $6 billion toward reaching that goal. Political and legal battles have pushed back its original start-up date of 1998 to the current target of 2010. In December, the department announced that the latest study, an assessment of the remote mountain's ability to entomb the waste safely for thousands of years, had identified "no show stoppers," and DOE officials were confident that the repository would be safe for public health and the environment.
But on 11 February, a blue-ribbon panel hired to peer review the study raised doubts about that conclusion. Its report faults the department's current model for predicting the repository's behavior, which takes into account everything affecting the movement of radioactive elements out of the fuel rods and into the distant environment over millennia. For example, the panel states that the cladding that encases the enriched uranium rods and provides the first line of defense may not hold up as well as assumed. The panel is especially concerned about the assumptions behind the repository's "hot" design, in which heat from the waste is supposed to keep temperatures well above boiling and, thus, initially keep out moisture that could corrode the rods. "We don't think anybody can model that convincingly," says panel chair Chris Whipple, a risk assessment engineer at ICF Kaiser Engineers Inc., in Oakland, California.
DOE is taking the panel's report in stride. "I think they overstated [the uncertainties] a bit, [but] it's what we paid for," says Abe Van Luik, senior technical adviser for performance assessment in the Yucca Mountain Project. Van Luik says he's "a tad surprised at the amount of material they think we need to do." DOE is still aiming for a decision in 2001, he says.