Improved Hydrothermal Corrosion Resistance of UN Fuel Forms via Addition of Metallic Constituents

Uranium mononitride (UN) continues to be an attractive alternative fuel form for use in light water and advanced technology nuclear reactors due to its high uranium density, high melting point, high thermal conductivity, and performance under irradiation, as compared to UO2. UN's susceptibility to oxidation and pulverization after exposure to water (or steam), similar to conditions experienced during a cladding failure or accident scenario, remains one reason UN has been inhibited from consideration for use as a LWR fuel type. A screening study will be presented that investigates various metallic additions to protect UN from corrosion degradation due to interactions with water or steam. The most desirable candidates will incorporate a material that can provide a barrier to the oxidation of UN and increase water corrosion resistance. The candidate materials were preliminarily screened based on thermophysical properties, neutronic properties that may enhance the fuel performance (e.g. thermal conductivity and irradiation resistance), and thermodynamic considerations. Samples consisting of UN and nominal additions of the candidate materials were synthesized, consolidated, and examined via X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Ab initio Molecular Dynamics was used to investigate bonding and electronic profiles of candidate metallic additions during the sintering process.