Аннотация:A set of Pitzer-Simonson-Clegg (PSC) parameters, along with the solubility products for the Ca(NO3)2·2H2O, Ca(NO3)2·3H2O, UO2(NO3)2·2H2O, UO2(NO3)2·3H2O, and UO2(NO3)2·6H2O hydrates, is proposed to accurately describe the properties of the solution and solid–liquid equilibria in the H2O–HNO3–Ca(NO3)2–UO2(NO3)2 system. Literature data on solid–liquid and, where possible, vapor–liquid equilibria were utilized in the course of this study. The PSC interaction parameters for the H2O–HNO3 and H2O–Ca(NO3)2 subsystems were taken from the literature. The proposed model is valid within a wide range of temperatures and concentrations.