Degradation processes of nuclear waste container materials

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Canada has employed nuclear reactors to generate large amounts of non-emitting electrical power for several decades, and maintaining a viable nuclear industry will be essential to meeting our collective commitment to decreasing greenhouse gas emissions, as outlined in the Pan-Canadian Framework on Clean Growth and Climate Change. The safe, permanent disposal of spent nuclear fuel is one necessary step in maintaining the viability of the nuclear industry in Canada and around the world. This research project, performed in partnership with the Nuclear Waste Management Organization (NWMO), will furnish a critical part of the required database for the development of the performance assessment models essential to achieving the safe disposal of Canada's high level nuclear waste. This project will investigate the fundamental processes that underlie the corrosion of nuclear waste container materials and the dissolution of the spent fuel. A wide range of electrochemical, spectroscopic, microscopic and surface analytical experiments will be conducted on copper-coated steel waste container materials and on uranium dioxide and simulated spent nuclear fuel specimens. On copper-coated steel specimens, the various corrosion processes that could occur as the conditions in a deep geologic nuclear waste repository evolve, as anticipated, from warm and oxidizing to cool and anoxic, will be evaluated. The aim will be to determine; (i) the copper corrosion allowance necessary to protect the underlying steel against exposure to groundwater during the short-term oxidizing period, (ii) the overall lifetime of the containers, and (iii) the consequences of container fabrication issues, such as hydrogen absorption and the presence of undetected through-coating defects. For the fuel, the rates of the various chemical processes occurring on the fuel surface will be examined, with the objective of understanding and quantifying the interactions between oxidants produced by radiolysis (e.g., hydrogen peroxide) and oxidant scavengers, such as hydrogen from radiolysis and the corrosion of the steel vessel. The work will be monitored by nuclear waste management authorities from Sweden and Switzerland, where similar issues are encountered.