Stabilization of Research Reactor Spent Nuclear Fuels: Fuel Types and Oxidation in Air

After more than 70 years of research reactor operation in Canada, Atomic Energy of Canada Limited (AECL) has generated a spent fuel inventory of non-CANDU (CANada Deuterium Uranium) fuel types, including many non-oxide fuel forms, that will require disposal. Canada’s long-term spent fuel management strategy, which has been proposed by the Nuclear Waste Management Organization, involves the construction of a Deep Geological Repository (DGR). The DGR is primarily designed for disposal of CANDU bundles (i.e. uranium dioxide fuel) as these make up the largest fraction of spent fuel in Canada. One strategy that could enable disposal of non-oxide, research reactor spent nuclear fuel materials in the same DGR would be to stabilize it to a high-density oxide-equivalent form. This paper outlines the various research reactor fuel types that may be considered for disposal in the DGR and the feasibility of converting them to their oxide form using furnace oxidation in air. In addition, preliminary experimental efforts are discussed on the stabilization of unirradiated uranium metal, uranium carbide, uranium silicide, uranium zirconium alloy, and thorium metal to their oxide forms, which correspond to research reactor fuel types that may require disposal in the DGR. These activities directly support Canadian Nuclear Laboratories’ lifecycle fuel management strategy by advancing safe disposal solutions for AECL’s legacy research reactor fuel inventories.