GRADUATE RESEARCH FELLOWSHIP PROGRAM (University of Michigan Ann Arbor)
New research by an NSF-funded graduate research fellow points to steel corrosion as a helpful process in efforts to safely dispose of nuclear waste.
Her work has implications for the safe geologic disposal of spent nuclear fuel. This research is essential if the United States expands its use of nuclear energy as it lessens reliance on fossil fuels.
Elizabeth Ferriss of the University of Michigan tested a hypothetical system in which fuel assemblies would be separated by steel supports inside large, stainless steel cylinders, forming "waste packages."
Ferriss assumed that after the outside steel layer ruptured and water seeped in, the spent fuel immediately would begin to oxidize and corrode, leading to the formation of potentially mobile ions.
She used a series of six miniature waste packages, two of which contained 0.1 g synthetic uranium dioxide (UO2), a material similar in structure and chemistry to spent nuclear fuel. She left half of the packages partially open, allowing access to the outside air. Water was injected regularly for up to two years, at which point Ferriss analyzed the solids and liquids.
Both modeling and previous experimental work suggest that the UO2 should have corroded. But UO2 oxidation and subsequent uranium release were much slower than expected, because simultaneous steel corrosion reactions used up the oxygen inside the waste package faster than the oxygen could be replenished from the outside air.
Ferriss' work shows that the positive effects of steel corrosion should be considered in the design of nuclear waste repositories.
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