Uranyl ammonium carbonate precipitation and conversion into triuranium octaoxide.

Uranyl ammonium carbonate (AUC), with the chemical formula UOCO·2(NH)CO, plays a crucial role in the wet conversion of uranium hexafluoride (UF) into uranium dioxide (UO) or triuranium octaoxide (UO) for nuclear fuel production, and is used in commercial and research reactors. In this study, the precipitation of AUC from uranyl fluoride (UOF) solution and its subsequent conversion into UO powder were investigated. AUC precipitation was performed at uranium concentrations in UOF solution of 80-120 gL, ammonium carbonate (NH)CO concentrations of 200-400 gL, and (NH)CO to U (C/U) ratios of 5-9. The conversion of AUC into UO powder was studied and sintering of the UO nuclear material derived from ammonium uranyl carbonate (ex-AUC UO) was conducted at temperatures of 1000-1800 °C. The kinetics of AUC precipitation from the UOF solution were studied using fundamental kinetic equations, and the kinetics of AUC conversion into UO were examined using an isoconversion method based on the thermogravimetric analysis of AUC. The final product of UO nuclear material was characterized using typical techniques, such as thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. This study provides valuable insights into the production and characterization of AUC and UO nuclear materials, which are key materials in the nuclear fuel industry.