LAS VEGAS - Prominent scientists have shifted their stance on a key element of a national nuclear waste dump in Nevada, saying they no longer fear one type of corrosion would quickly weaken casks designed to contain radioactivity.
The new position by members of the Nuclear Waste Technical Review Board boosts plans for the Yucca Mountain repository while the Energy Department prepares to seek a crucial operating license from the Nuclear Regulatory Commission.
Board executive William Barnard attributed the shift to the evolution of understanding about the first-of-its-kind repository.
"It's a learning process for DOE," he said, "and a learning process for the board." Opponents downplayed the effect the finding would have on state efforts to block the federal government from burying the nation's most radioactive waste 90 miles northwest of Las Vegas.
Steve Frishman, a state consultant on Yucca Mountain, said that while it appeared the Energy Department had solved one corrosion problem, Yucca engineers had not addressed questions about other minerals that could create problems.
Sen. Harry Reid, D-Nev., insisted Friday that "overwhelming scientific evidence shows that Yucca Mountain is not safe."
"Deciding which type of corrosion is most dangerous will not change that underlying fact," he said.
The Energy Department maintains the Yucca project will be safe.
The board outlined its position in a four-page letter Wednesday to Margaret Chu, director of Energy Department's Office of Civilian Radioactive Waste Management, which directs the Yucca project. Chu did not plan to comment, a spokesman said.
Technical Review Board staff members said that while some concerns had been allayed, more needed to be known before scientists can be confident the Yucca Mountain repository would work the way the Energy Department expects.
Congress in 2002 picked Yucca Mountain as the site to bury 77,000 tons of highly radioactive waste from commercial nuclear reactors and military and industrial sites in 39 states.
The Energy Department wants to open the repository in 2010 and spend 24 years entombing the waste in casks made of nickel 22 metal alloy in tunnels 1,000 feet below ground.
The Technical Review Board threw a wrench into the plan last October, with a report based on Energy Department research that calcium chloride, a mineral compound, could react with moisture in the tunnels and form a brine that could corrode casks within 1,000 years. Such a finding would make it difficult for the repository to win an operating license.
The review board, created by Congress to evaluate Yucca science, convened a two-day seminar in May at which the Energy Department and other organizations presented updated analyses.
