A data base for thermodynamic modeling of +III actinide solubility in concentrated Na-Cl-SO4-CO3-PO4 electrolytes

The literature contains thermodynamic parameters for describing the chemical behavior of the following: Am(III) in dilute NaHCO3 media; Nd(III) in dilute to concentrated Na2CO3 and NaHCO3 media; Pu(III) in dilute to concentrated NaCl media; Nd(III)/Am(III) in dilute to concentrated Na2SO4 media; and Am(III) in NaH2PO4 media. We have combined this information into a thermodynamic data base for the general +III actinide, An(III), using the analogy for chemical behavior of f-elements in the same oxidation state. This internally consistent data base is based on equilibrium thermodynamics and the specific ion interaction activity coefficient formalism of Pitzer. This data base forms the basis for the prediction of potential Am(III) and Pu(III) dissolved concentrations in the concentrated natural brines associated with the Waste Isolation Pilot Plant (WIPP) in Southeastern New Mexico, USA