b'Progress Towards Waterproofing Uranium NitridePrincipal Investigator: Aditya P. Shivprasad, LANLTeam Members/Collaborators: Joshua T. White and Amber C. Telles (LANL)U ranium mononitrideoccurred over the course of (UN) is a promising,minutes, though the addition of high-uranium-densityUO 2significantly delayed the onset fuel because of its good thermalof oxidation. Similarly, during properties and performance duringtemperature ramps in steam, the irradiation and has been consid- addition of UO 2appeared to delay ered as a potential replacementthe onset of oxidation, though for uranium(IV) oxide (UO 2 ) inpulverization occurred for pellets commercial light water reactors.containing more than 10 volume Despite these advantages, limita- percent UN. This work showed that tions are observed when the coolantwaterproofing effects are noticeable comes in contact with the fuel, e.g.,with compositing with oxidation-breach of cladding, resulting inresistant materials.degradation of the fuel. ResearchIn FY19, compositing efforts focused on continuing work fromfocused on evaluating UN cermets fiscal year (FY)18 that examined thewith metals that exhibit resistance to feasibility of UN-UO 2compositessteam corrosion, such as chromium for UN waterproofing purposes.(Cr), silicon (Si), and yttrium Steam oxidation testing of candidate(Y). UN-SiC composites were also waterproofing additive materials wasexamined for feasibility given the performed to evaluate the corro- interest within the Accident Tolerant sion resistance of these materials.Fuel (ATF) campaign. Materials Composite pellets were also pressedtested for steam oxidation were and heated to examine chemicalassessed for corrosion resistance compatibility with UN. based on the percentage of the Project Description: material oxidized (a reaction Previous work in FY18 evaluatedcoordinate) in steam. Chemical UN and UN-UO 2composites forcompatibility between UN and resistance to oxidation in steam.additive materials was also assessed During isothermal oxidationusing X-ray diffraction aftertests, mass gain and pulverizationthermal treatment.54 2019|AFC ACCOMPLISHMENTS'