Thermo-Hydro-Mechanical-Chemical processes in geological disposal of radioactive waste – An example of regulatory research

Abstract

Deep geological disposal is being considered in Canada and many other countries as the most viable option for the long-term management of radioactive waste. The disposal method consists of emplacing the waste in a repository built at hundreds of metres depth in a suitable host rock. A multi-barrier system, that includes the host rock formation as a major component, would be provided in order to protect humans and the environment from the harmful effects of the waste for very extensive time periods. Many events and processes are expected to occur during the lifetime of the repository, such as heat generation from the waste, seismicity and glaciation. As a result of those events and processes the Thermal-Hydraulic-Mechanical-Chemical (THMC) regimes in the natural and engineered components of the multi-barrier system will be perturbed, and the evolution of the THMC regimes and how this evolution affects the multi-barrier performance need to be understood. The Canadian Nuclear Safety Commission (CNSC), Canada’s nuclear regulator, has been conducting independent experimental and theoretical research on coupled THMC processes for several decades. As part of this research, the CNSC used experimental data from laboratory tests and large-scale experiments at underground research laboratories (URL) in order to develop a mathematical framework for the simulation of coupled processes in engineered and natural barriers for geological disposal. In this paper, we describe that mathematical framework and show examples of how it was adapted and applied to several situations: water and gas injection experiment at an URL, a heater experiment at an URL, and the effects of nine glacial cycles in a sedimentary rock formation. Cited as : Nguyen, T.S. Thermo-Hydro-Mechanical-Chemical processes in geological disposal of radioactive waste – An example of regulatory research. Advances in Geo-Energy Research, 2018, 2(2): 173-189, doi: 10.26804/ager.2018.02.06