Contaminant Transport from a Deep Geological Repository: Lumped Parameters Derived from a 3D Hydrogeological Model

A model of contaminant transport from a repository to the biosphere is one of the major needs in the safety assessment of the geological disposal of spent nuclear fuel. This work deals with the development of a procedure that obtained characteristic data from the transport path by postprocessing the results of the 3D flow and transport models, according to the repository concept for the Czech Republic. Postprocessing was used to map the entire transport pathway, which included the smallest tracer flows; therefore, it is called the “integral method”. The results are the characteristics of the storage system, such as: transport path length, flow time, total dilution, groundwater flow, longitudinal dispersivity, porosity, etc. These acquired characteristics can be used directly in safety analyses or to narrow the selection of candidate sites. Furthermore, these parameters were used to set up a model with lumped parameters (in this case, created in the GoldSim SW environment). Even only one “Pipe” component, after being properly set up, shows almost identical results to the entire 3D model. Based on the results of the 3D model, it is possible to set up a lumped parameter model that accurately simulates the transport path and can perform further calculations of a larger number of contaminants in repeated runs, e.g., with stochastic input data, which would be very laborious (or not possible at all) with the 3D model.