Abstract
Dissolved nuclear wastes (Am, Cm, Pb, Np, Pu, Ra, Th, and U) can be affected by the composition of natural waters. Natural waters can have different values of pH, composition, ionic strength, temperature, and pressure. The solubility of these elements in natural waters can be determined experimentally or by modeling. Since direct measurements are not presently available for many metals of interest, it is important to develop methods that can be used to estimate the solubilities in natural waters of known composition. In this paper, one approach that can be used to estimate the solubilities using Pitzer’s equations is discussed. For some metals (i.e., Pb and U) the effect of composition can be directly calculated using existing data. While, for others (i.e., Am and Cm) limited data is available and one must use model compounds (rare earths) as analogs. The solubility of Fe(III) in seawater as a function of pH is used to demonstrate how the model can be used. The model has also been used to estimate the speciation and solubility of a number of radionuclides in WIPP brines.