Uranium nitride-silicide advanced nuclear fuel: higher efficiency and greater safety

As part of Accident Tolerant Fuel initiative for light water reactors, uranium silicide and silicide-nitride are being considered as fuels that can be combined with a more robust cladding such as a ferritic (FeCrAl) alloy. Although these materials have been studied in the past, uncertainties remain concerning the fundamental behaviour of these systems. In this study, four compositions between U₃Si₅ and USi₂ were fabricated by arc-melting. Additionally, in an effort to understand the UN–U₃Si₂ fuel system, an unidentified U–Si–N ternary was observed in samples fabricated by arc-melting U₃Si₂ in the presence of varied concentrations of N₂ in Ar. The analyses of compositions prepared to investigate these systems include structural characterisation using X-ray diffraction and compositional analysis employing scanning electron microscopy with energy dispersive spectrometry. Initial values of the Gibbs energy parameters via the CALPHAD (CALculation of PHAse Diagrams) method have been developed for the ternary phases observed upon U₃Si₂–FeCrAl interactions.