LAB-LYSIMETER TRANSPORT MODELLING

High-level and long lived radioactive waste is planned to be stored for a safety assessment period of up to 1 Ma in deep geological repositories (POSIVA 2016; BGE). Although a safe multi-barrier system principle is generally accepted and conceptually designed, the potential pathway of radionuclides to the biosphere and into crop plants under different climatic scenarios have to be assessed.

In the framework of the Trans-LARA project, we aim to clarify some of the factors that affect the transport of radionuclides from the saturated zone (groundwater) via the unsaturated zone to the biosphere overcoming the simplifications of transfer factors. Consequently, we set up four lab-lysimeter experiments using different types of soils (FraunhoferIME). Numerical simulations of fluid flow, transport of contamintants and chemical interactions in 1D and 3D of the lysimeter column experiments have been carried out and compared against the actual data of the lysimeter column lab experiments (Böhm et al., 2022).

Wepeakt at different water saturation models (Wang, Jin, and Deng 2018; Too et al. 2014) and their influence on the transport and chemical system established, which is simplified by cation exchange and sorption/surface complexation reactions to a three component system (ferrihydrite, illite and humic substances) representing a simplified soil (Hormann and Fischer 2013). Furthermore, we explore implementation of alternative chemical models (Stockmann et al. 2017) and their reliability.  A comparison of the numerical and experimental results will be given under the systematic variation of model boundary conditions and potential ways of improvement discussed.