Fabrication and Characterization of Uranium-based Nuclear Fuels

Nuclear energy continues to play a large role in the energy landscape of the world. Of particular interest is creating more resilient and efficient nuclear fuels such as uranium mononitride or large-grained uranium dioxide. Uranium dioxide feedstock powder was used to fabricate high density (>90% theoretical density) uranium mononitride (UN) and uranium dioxide (UO ₂ ) nuclear fuel pellets. A carbothermic reduction of UO ₂ and nitridation thermal process was used to convert the UO ₂ powder into phase-pure UN, which was confirmed through X-ray diffraction. The UN powder was cold pressed into green pellets (approx. 62% theoretical density) prior to sintering at 1900°C. UO ₂ pellets were pressed and sintered at 1500°C using a three step process (reducing-oxidizing-reducing atmospheres) to make high density, stoichiometric UO ₂ pellets. Scanning electron microscopy (SEM) was used for grain size analysis and energy dispersive x-ray spectroscopy (EDS) was used for chemical mapping on the sintered pellets. The fabrication and characterization of high quality nuclear fuels provides opportunities for further testing and optimization of high performance, accident tolerant fuels.