NOVEL AND PRACTICABLE APPROACH TO MODELLING RADIONUCLIDE TRANSPORT THROUGH HETEROGENEOUS GEOLOGICAL MEDIA

This paper describes a novel approach to modelling radionuclide transport through a heterogeneous geological medium. The objective is to provide a statistical description of the heterogeneity and develop a modeling framework that accounts for this variability. The methodology consists of three steps: firstly, sampling a large number of potential transport pathways; secondly, grouping these pathways to reflect their significance for radionuclide transport; and thirdly, modeling geosphere transport processes within these grouped pathways, termed 'legs'. Results indicate that only a small number of legs (5 in the Wellenberg case study) is needed to conservatively represent all transport pathways, thus enhancing computational efficiency in safety assessments where various parameter variations must be analyzed. The findings highlight the significance of properly selected pathways in representing transport and underscore the importance of incorporating heterogeneity into models for groundwater flow and contaminant transport in geological media. Future work will explore heterogeneity along pathways as well as the matrix diffusion in the rock structure. This study contributes to improving safety assessments for geological repositories by optimizing modeling approaches considering geological complexities.