Effects of changing boundary conditions on the development of hydrogeological systems: Long-term numerical modeling considering thermal-hydraulic-mechanical (chemical) coupled effects (AREHS).
According to the "Law for the Search and Selection of a Site for a High-level Waste Repository (Site Selection Act - StandAG)", a site is to be identified which offers the best possible security for the construction of a repository for high-level radioactive waste for 1 million years. The application of the minimum requirements, exclusion criteria and geoscientific weighting criteria (§§ 22 to 24 StandAG) requires the knowledge of numerous (petro) physical and hydrogeological parameters that characterize the geological units. However, during the 1 million year detection period, external events, such as future cold and warm periods and associated icing events, will have the above petro physical characteristics as well as the natural hydrogeological characteristics of the overall system, e.g. B. Reactivation of disturbances or change the hydraulic gradient and consequently change directions of flow. It is therefore expected that the future hydrogeological regime will be very different from that currently observed. The long-term safety assessment, and thus assessment and selection of a suitable site, requires not only a thorough understanding of the geological initial state of the potential repository site, but also the identification and assessment of such future external events and processes that may affect its development.
As a regulatory authority, the BfE must not only be able to assess the scientific and technical results of the BGE mbH in relation to the criteria and requirements and safety investigations stated in the StandAG, but also to be able to assess the chosen methodological approaches and their possible effects on the results achieved.
The research project is therefore pursuing two goals: First, the effects of changing external boundary conditions on hydrogeologically relevant parameters (eg hydraulic permeability, porosity, migration routes, fluid availability, hydraulic gradients) of a potential geological repository in Germany (clay rock, rock salt , Crystalline rock) and its surrounding rock units can be modeled using coupled THM (C) approaches. Particular attention is paid to the cyclic mechanical loading and unloading due to icing events and the resulting changes in stress (M) as well as induced temperature effects (T) due to permafrost and hot periods. On the other hand, the results should show which processes are already well understood with the existing THM (C) modeling approaches and codes, where there is a need for development and research, and how the choice of specific modeling approaches and codes affect the results of the modeling.