Simulations

Simulations were conducted for several test cases. 1D test cases are used to check the plausibility of the development in a relatively simple system, where temporal chemical changes cause dissolution or precipitation of calcite, which in turn affect the pH-value, the DIC and Ca concentrations. In consequence the Kd-value and therewith the transport of the radionuclides is impacted. The results of the 1D calculations are plausible showing the applicability of this approach to implement the smart Kd-concept.

Verification calculations are conducted using the code PHAST, a program for simulating groundwater flow, solute transport and multicomponent geochemical reactions. A simple box model was chosen for the comparative verification calculations with variations of the heterogeneity, chemical environment, complexity of the flow field, and model geometry.

Full scale applications were realized for the Gorleben reference site in Northern Germany. A simple 2D model was considered and results show that the method is able to describe long-term chemical changes in large model areas including their impact on radionuclide sorption.