Nitrate ion effects on uranium chemistry in the tributylphosphate-dodecane system

Understanding the role of nitrate in the speciation of actinides is important in order to determine the necessary data for extraction modeling of the UREX process. The focus of this project is on the fundamental chemistry of uranium (U) in the tributyl phosphate (TBP) extraction system, with emphasis on the effect of nitrate on actinyl speciation. Speciation calculations can be performed if stability and solubility constants for the chemical species formed under the examined conditions are known. The stability constant of the uranyl-TBP complex was evaluated under a variety of conditions. The variables were nitric acid, uranyl, total nitrate concentration, and ionic strength. The thermodynamic data collected can be incorporated into extraction modeling codes used to predict distribution in reprocessing. The methods used in this research will be modified for corresponding experiments with plutonium and provide necessary data for optimizing the modeling codes.