Activity Coefficients of Uranyl Nitrate and Nitric Acid in Aqueous Mixtures

The activity coefficients of nitric acid and uranyl nitrate in in aqueous mixtures are necessary to model the system H₂O-HNO₃-UO₂(NO₃)₂-TBP-diluent. Three methods have been compared in this work to determine activity coefficients based on experimental data, Pitzer's equation or Zdanovskiy's rule. Acid activities have been calculated from the data of two first methods. These results were compared with the data of third method. Errors were about 3.3.%. Activity coefficients of uranyl nitrate γ_U as a function of concentration of uranyl nitrate and nitric acid were determined in 76 mixed solutions. The equation to calculate γ_U was proposed.