RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

Sorption parameters for Olkiluoto far-field conditions for the safety case were derived from source sorption values using conversion factors due to differences in water compositions, pH and the speciation of nuclides in the source data conditions and the reference waters. Estimation of sorption in evolving geochemical conditions urges for thermodynamical sorption models and their parameter to enable calculation of sorption. To start the developing of sorption models, in this report, the experimentally determined sorption of molybdenum, niobium, protactinium, selenium, tin, thorium and uranium on the illite and kaolinite in the groundwater simulants is modeled. In addition, the sorption of Eu and Ni on kaolinite in electrolyte solutions is modeled. The non-electrostatic approach to surface complexation was adopted for the sake of simplicity. The basic parameters of the solids needed were in-house values or adopted from literature. The surface complexation reactions and the cation exchange reaction selectivities of the main groundwater cations given in literature for illite and kaolinite were applied.