Evaluating the microstructure and origin of nonmetallic inclusions in as-cast U-10Mo fuel

•Inclusions characterized on sub-nanometer to millimeter scale•Inclusions are hypostoichiometric oxides (UO2−x) and carbides (UC1−x)•Inclusions are 0.42 ± 0.25 % by area with average diameter of 4.6 ± 0.8 µm•~20 at. % 235U is measured for all carbide inclusions and the surrounding matrix, and higher 235U enrichment of ~25 - 27 at. % was measured in some oxide inclusions