Scientists said Tuesday they fear the metal selected to build nuclear waste storage casks could corrode much faster than expected under actual conditions at Yucca Mountain.
Aaron Barkatt of Catholic University in Washington, D.C., and Jeff Gorman of Dominion Engineering told the Nuclear Waste Technical Review Board the C-22 alloy is vulnerable to corrosion when exposed to heat and moisture containing traces of lead and mercury.
Both those metals are found in small amounts in the rocks of Yucca Mountain.
In their preliminary tests, Gorman said, a piece of the exotic alloy bent into a "U" shape was cracked nearly all the way through after just 15 days under temperatures of more than 400 degrees. Those are the kinds of temperatures that would be created by the radioactive waste in Yucca Mountain's storage vaults for thousands of years.
Barkatt showed coin-sized pieces of the metal also severely pitted after just 30 days in that environment.
They told the board that the corrosive effects on C-22 of naturally occurring metals such as lead and acids that will percolate out of Yucca Mountain's rocks has never been studied.
And they said that corrosion seems to be greatly speeded up by any dents, scratches or other damage to the containers that would happen naturally during installation and burial of the casks.
They urged a full scale study before containers are built from the metal and before a decision on Yucca Mountain is made by the federal government.
Barkatt said the results of that study may prove the metal safe but, "I don't think, at present, that we can say we know that."
He pointed out that the crack went through a piece of the metal an eighth of an inch thick in just 15 days.
"There needs to be enough time and enough resources to do the science before making irreversible decisions," he said after the meeting.
The report on C-22 was commissioned by Nevada's Nuclear Projects Agency. The scientists and agency director Bob Loux told the board it should recommend waiting on the decision to build at Yucca Mountain or not until that study is done.
"The problem is the Department of Energy wants to make a decision on Yucca Mountain within about a year," said Loux. "We need longer."
The two scientists told the board, which makes recommendations on scientific and technical matters at Yucca Mountain to the government, a full study would take three years.
They were joined by a third scientist hired by Nevada, consultant Roger Steahle, a professor at the University of Minnesota.
He said the C-22 alloy is susceptible to corrosion and unstable. A study of the actual chemistry of Yucca Mountain and its effect specifically on that metal must be done to see how long those casks would last, he told the board.
Loux said much of DOE's proposal to build the nuclear repository at Yucca Mountain is dependent on the storage casks because the mountain's ability to hold the poisonous waste naturally has been proven inadequate.
He said, however, even if C-22 is thrown out, political forces pushing for Yucca Mountain won't stop.
"Since the metal cask is 95 percent of the storage dump's performance, if this gets shot down I think in a couple of months a new magic metal will be discovered," he said.