(GRS 588) Benchmarking for Validation and Verification of THM Simulators with special Regard to Fluid Dynamic Processes in Repository Systems - Project BenVaSim

For the geological disposal of heat-emitting radioactive waste in Germany, the safe containment has to be demonstrated for a time period of one million years. For predicting the long-term behaviour of a repository and for making realistic statements about the long-term safety, various numerical simulations are needed. Independent of the host rock and repository concept, there are thermal-hydraulic-mechanical (THM) coupled basic processes forming the background of all numerical simulations. The aim of this THM-coupled simulator benchmarking project was to apply well specified and simplified modelling tasks to investigate basic processes, especially flow phenomena, which are included in mostly all THM-coupled simulations in porous media. Therefore, different modelling phases were planned, starting with single phase flow coupled with mechanics extending to two-phase flow and finally reaching a full THM-coupled model. To have a clear focus on the model evolution and the influences of the various processes, it was started with a very simple one-dimensional model. With time the geometry complexity was increased by simulating a backfilled drift seal and finally assuming a generic repository drift, still in one-dimension. During the modelling work it was shown that differences exist for the treatment of basic processes in the various simulators which are of importance for more complex numerical models. In frame of this project, a deepened understanding of the simulator itself and the numerical treatment of coupled processes was gained, and improvements of the simulators were achieved.