Fabrication and Characterization of UN-USix Nuclear Fuel

Abstract: In this thesis, UN-U3Si2 nuclear fuel was fabricated using spark plasma sintering and characterized to analyze the microstructure and crystal structure of the resulting pellets. This work was done in collaboration with accident tolerant fuel research, an effort which aims at developing nuclear fuel with superior safety and performance compared to currently used oxide fuels. Uranium silicide was manufactured by arc melting to produce U3Si2 and uranium mononitride was synthesized by using the hydriding-nitriding method. They were mixed in varying compositions (5 wt%, 10 wt%, 20 wt%, and 25 wt% U3Si2) in order to create composite fuel pellets. Characterization of the resulting pellets showed an apparent ternary phase of U-N-Si, prompting fabrication of four more pellets at varying temperatures (1200 °C, 1300 °C, 1400 °C, and 1500 °C) to try and identify the temperature of phase formation. The presence of a probable ternary U-N-Si phase was confirmed to be present in all fuel pellets. Therefore, further investigation into the thermodynamic behavior of the ternary U-N-Si system is suggested before this fuel can be recommended for use in a reactor.