In Germany, all nuclear power plants have been shut down and some are already in various stages of decommissioning. All waste volumes that are not deposited in a repository must pass through officially approved clearance procedures, which are regulated in the German Radiation Protection Ordinance (StrlSchV 2021). After clearance, the materials can be fed into further material cycles or disposed of in accordance with the type of release. The release values of the Radiation Protection Ordinance are based on the 10 µSv criterion. This criterion is intended to ensure the protection of the population from ionizing radiation.
Numerical groundwater models can be used to simulate the distribution of radionuclides and provide information on concentrations in space and time, which can be used as input parameters for calculating possible ingestion doses for different exposure paths.
The basic transport processes of advection, diffusion, dispersion, and sorption are implemented in the simulation codes "Simulation of Processes in Groundwater (SPRING)" (König et al. 2023), “DuMux – Dune for Multiphase flow and transport” (Koch et al. 2021) and "distributed density-driven flow (d3f++)" (Fein & Schneider 1999, Fein 2004). Decay chains can also be modeled in the codes.
The model area represents a simple 2D model and a generic landfill body with its various layer compartments and an associated aquifer. In a further model, the infiltration of precipitation water into contaminated soil with mass transport into the saturated zone is considered. This work presents the first results of the generic numerical groundwater models.