Scientists trying to fine-tune estimates for when radioactive materials will escape containment at the planned Yucca Mountain repository said Wednesday corrosion will take its toll on waste packages between 40,000 years and 80,000 years after they are entombed in a maze of tunnels.
Water migrating down through the mountain, 100 miles northwest of Las Vegas, and dripping on metal shields covering the waste packages will at first be driven away by heat from the decaying waste.
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Eventually, however, moisture would condense and infiltrate the tunnels, gradually destroying the containers and carrying off deadly, long-lived radionuclides, they said.
The predictions of Tim McCartin, a senior adviser for the Nuclear Regulatory Commission, and others involved with researching safety standards beyond 10,000 years for the Yucca Mountain Project were presented to an independent board charged with ensuring the science is valid.
"We continue to look at the release rate," McCartin told the Nuclear Waste Technical Review Board, which met Wednesday at Desert Research Institute.
Board Chairman B. John Garrick said during a break in the meeting that the discussion on water infiltration, corrosion of waste packages and dose estimates was arranged "to be responsive to the 'so-what' question."
He said the panel wants to pin down how effective the mountain will be in protecting against materials escaping from the 77,000 tons of spent nuclear fuel and highly radioactive defense waste that will be buried there.
"The root issue is, 'What happens to the radioactive materials?' " Garrick said.
Some studies by the U.S. Geological Survey on water infiltration and climate models are swirled in controversy because of revelations last year in e-mails from USGS scientists that the quality of their work might be flawed.
When asked about the impacts of those studies on the project, Garrick said, "How they will affect the results, we don't know. ... We're interested in the truth there. Most of us don't think it's going to be a major impact, but we don't know."
