As the use of nuclear fuel skyrockets around the world, a team of MIT scientists led by Civil and Environmental Engineering Professor Franz-Josef Ulm has been asking a simple question: where is the waste going to go? Ulm and others have raised concerns about the ability of cement containers to hold nuclear waste over the long term.As the use of nuclear fuel skyrockets around the world, a team of MIT scientists led by Civil and Environmental Engineering Professor Franz-Josef Ulm has been asking a simple question: where is the waste going to go? Ulm and others have raised concerns about the ability of cement containers to hold nuclear waste over the long term.
But rather than watch potentially bad environmental policy take shape, Ulm and his colleagues took action by designing a test that allows them to observe in one day what weathering conditions nuclear waste containers will be exposed to over the next 300 years. Using a laboratory model based on miniaturized concrete slabs surrounded by a liquid bath, Ulm and his colleagues began to subject weathered materials to a variety of stresses and conditions to discover how the containers could be improved.
“Our goal is to go back to real-life structures, monitor the environment around them, and predict by model-based simulation what the concrete will do over extended periods of time,” Ulm said. And if a bad scenario plays-out, “we’ll be able to predict its eventual effect, and intervene in time to slow down or reverse the aging,” Ulm said.
Ulm is now attempting to export his model to those who need it most: the U.S. government. “When, and if, spent nuclear fuel from the U.S. is buried in the Department of Energy proposed repository at Yucca Mountain, it will be placed in concrete casks that are supposed to maintain integrity at least 300 to 1,000 years,” said Mujid Kazimi, an MIT professor of nuclear engineering. But what Ulm and others are finding is that the concrete containers can weaken over time, causing the concrete to dissolve. When Ulm applied a shear stress to his laboratory containers, slivers of the material slipped apart.
“So a material that is originally very strong ultimately ages to one that behaves like a weak low-friction soil, such as clay,” Ulm concluded. The findings may lead to a renewed emphasis to discover how the waste containers can be improved.
-- Sanjay Basu
Information provided by MIT News Office.