Migration of radionuclides from a high-level radioactive waste repository in deep geological formations

The paper presents the development of an analytical model to estimate the migration of radionuclides through a single fracture with right circular cylinder geometry from a high-level radioactive waste repository in deep geological structures. The processes considered are advection, dispersion, surface sorption and radioactive decay for transport in the fracture; diffusive loss to the host rock; radial diffusion, adsorption and radioactive decay for transport in the host rock. The model is applied to a typical case of high-level radioactive waste repository in deep geological rock formations. The concentrations showed an increasing trend with increasing dispersion in fracture or reducing dispersion in the host rock or reducing porosity. It is shown that the models which do not consider the dispersion of radionuclides within the fracture underestimate the radionuclide concentrations in the fracture water. Also, the effect of dispersion reduces with increase in fracture water velocity. The concentration of radionuclides in the fracture water in general increases with increase in fracture radius until a critical radius is reached. The model development is targeted for the performance assessment of high-level radioactive waste repositories.