Speaker
Description
A reliable understanding of radionuclide (RN) migration in potential host rock formations is essential for the long-term safety assessment of radioactive waste disposal. During recent decades, major progress has been achieved in this field. Nevertheless, relevant knowledge gaps remain, especially for complex and transient systems at close to nature boundary conditions. The transfer of parameters from simplified batch experiments to dynamic transport systems is still associated with considerable uncertainty.
Within the ongoing research project SPIEG3L, an integrated experimental and analytical approach is developed to investigate RN retention processes in situ. Column experiments are performed under saturated, artificial natural conditions. The focus lies on the trivalent f-element Eu, which serve as chemical analogues for actinides. An innovative combination of state-of-the-art spectroscopic methods is applied directly to the transport experiments. This approach allows the identification and differentiation of surface processes such as sorption, incorporation, surface precipitation, and changes in speciation.
The column experiments are to be coupled to logging systems. These systems enable continuous monitoring of pH, electrical conductivity, and tracer concentrations. Embedded markers that can be retraced ensure that each following analytical technique is applied to the identical sample locations. This multilevel analytical concept allows the identification of surface complexes and high-affinity sorption sites.
The experimental results will be used to develop surface complexation models. These models are subsequently implemented and verified in one-dimensional reactive transport simulations. The derived parameters support the linkage between laboratory-scale experiments and large-scale safety assessment calculations. Overall, SPIEG3L contributes to an improved process-based understanding of RN transport under artificial natural conditions.