Fundamental Insights into Defect Generation and Transport Phenomena at Grain Boundaries in Nuclear Fuel

Nuclear power provides the only broadly deployable source of stable, 24/7, carbon-free energy and currently supplies 20% of electricity in the United States. Next-generation reactors such as small modular reactors, are expected to operate for longer time spans as well as under more extreme conditions regarding temperature and irradiation dose. The utilization of advanced fuels, such as doped UO₂ fuels is underway for the current reactor fleet, and highly likely to be implemented in advanced reactors. An in-depth understanding of how extreme conditions, e.g. radiation damage, effect the fuel properties will enable future mechanism-informed design of advanced nuclear fuel candidates. Combined experimental and computational results about fission gas diffusion at grain boundaries in surrogate materials, UO₂ and doped UO₂ will be presented. The effect of irradiation and fission gas accumulation in doped-UO₂ is analyzed by in-situ electrochemical impedance spectroscopy during Xe and Kr implantation at LANL's Ion Beam Materials Laboratory with a strong emphasis towards understanding grain boundary responses/alterations. These results are compared to irradiation experiments of doped UO₂ fuel candidates at UCI's TRIGA reactor with subsequent microscopic analysis of irradiation effects on defects in these complex oxides. Finally, new mechanistic insights from experimental and computational studies on diffusional creep models in UO₂ and doped UO₂ will be presented