Synthesis and sintering of UN-UO₂ fuel composites

The design and development of an economical, accident tolerant fuel (ATF) for use in the current light water reactor (LWR) fleet is highly desirable for the future of nuclear power. Uranium mononitride has been identified as an alternative fuel with higher uranium density and thermal conductivity when compared to the benchmark, UO₂, which could also provide significant economic benefits. However, UN by itself reacts with water at reactor operating temperatures. In order to reduce its reactivity, the addition of UO₂ to UN has been suggested. In order to avoid carbon impurities, UN was synthesized from elemental uranium using a hydride-dehydride-nitride thermal synthesis route prior to mixing with up to 10 wt% UO₂ in a planetary ball mill. UN and UN - UO₂ composite pellets were sintered in Ar - (0-1 at%) N₂ to study the effects of nitrogen concentration on the evolved phases and microstructure. UN and UN-UO₂ composite pellets were also sintered in Ar - 100 ppm N₂ to assess the effects of temperature (1700-2000 °C) on the final grain morphology and phase concentration.