During incorporation of radionuclides into solid-solutions, the whole mineral volume can be effective towards radionuclide sequestration. Compared to surface adsorption, solid-solution formation has, thus, an even higher potential to immobilize radionuclides in the confinement providing rock zone around a repository for high level nuclear waste. Nevertheless, simulations for long-term safety-assessments for waste repositories rarely consider solid-solution formation processes. Reason for this is the lack of necessary parameters to describe the thermodynamics and especially also the formation-kinetics of solid-solutions. In KRIMI we perform fundamental investigations on the formation kinetics and thermodynamics of radionuclide incorporation into the mineral-phases barite, calcite and magnetite. The goal is to enable quantification of radionuclide retention by incorporation into these mineral-phases on the basis of reliable mechanistic models.