A thermodynamic model of plutonium (IV) nitrate solutions

Plutonium nitrate solutions contain a large number of chemical species and they exhibit significant deviations from ideal behavior. Modeling this system is challenging. A model that includes all known chemical species and accounts for nonideal solution behavior could contain several hundred unknown parameters, but insufficient published data exists for evaluating large numbers of parameters. A practical model of plutonium nitrate solutions, therefore, must be a compromise between the number of chemical species included and the number of parameters that can be evaluated from available data. A practical model of acidic plutonium nitrate was developed. The model, which was based on an extended UNIQUAC-Debye-Huckel equation, captures the essential behavior of the system with a minimum number of chemical species. It is capable of representing the vapor-liquid equilibrium data for the nitric acid-water system, the activity of water in the plutonium nitrate-nitric acid-water system, the distribution of plutonium-nitrate complexes in aqueous nitric acid solution, and plutonium adsorption on an anion exchange resin.