Efficient Multi-Scale, Thermo-Hydro-Mechnaical Numerical Model for Simulation of Long-Term Stability of Rooms for Nuclear Waste Disposal

This project will develop a state-of-the-art numerical modeling tool for accurate and efficient analysis of performance and design of emplacement rooms for geological disposal of high-level nuclear waste. The modeling tool will be capable of predicting long-term stability of the rooms and the evolution of damage and permeability in the surrounding rock formation, which are critical for understanding the transport of radionuclides and overall performance assessment of the natural barriers and repository. It will be applicable to different geological settings, including crystalline and sedimentary rocks. The physics-based numerical tool will simulate relevant processes occurring in a deep geological nuclear repository, including the effects of excavation of emplacement rooms and coupled thermo-hydro-mechanical effects occurring during the long-term emplacement of high-level nuclear waste. The simulator will provide an efficient and unique approach to modeling performance rooms for waste emplacement for millions of years by encompassing near-field and far-field effects in one model. It will include the capability of modeling thermo-hydro-mechanical (THM) processes in the materials close to the waste containers with detailed explicit representation of the fracturing process in the walls of the emplacement rooms while simultaneously evaluating the coupled THM effects in the surrounding geological environment on the scale of the entire repository and responding to the repository-induced and environmental perturbations. Itasca will develop a framework that would allow efficient and accurate numerical simulation of THM processes affecting rock damage and stability of the emplacement rooms over a wide range of length and time scales, enabling parametric studies and uncertainty quantification analysis. The near-field model, based on the Discrete Element Method (DEM), will predict deformation and damage coupled with a continuum model of far-field processes that will use efficient implicit solvers to simulate relevant diffusion processes for time scales of the order of one million years. The proposed tool will be an integral component of a general total performance assessment system providing evolving geometry of the emplacement rooms and distribution of the perturbed permeability field in the surrounding rock mass as inputs to more specialized transport models. Such a tool will be an important contribution to efforts to design, develop, and characterize the barrier systems and their performance and will improve the overall safety of the nuclear waste disposal.