Progresses in researches on adsorption and migration properties of bentonite colloids and their co-migration with nuclide in repository

On the basis of elaborating the adsorption and migration properties of bentonite colloids in deep geological repository of high-level radioactive waste, a comprehensive review and summary of the co-migration experiments, interaction mechanisms and simulations of bentonite colloids and nuclides are summarized. The results show that the adsorption and mobility of the bentonite colloids are significantly affected by the concentration of the colloids, the ionic strength of groundwater and pH. The existing studies are difficult to evaluate the adsorption capacity of the bentonite colloids for nuclides and the migration capacity of the colloids themselves. The laboratory dynamic column tests and the in-situ dipole flow field tests both focus on the promotion of the mobile colloids and the blocking effects of filter colloids on the migration of the nuclide. There is a lack of examples of the co-migration of long-distance colloids and nuclides. The co-migration effects of the bentonite colloids and nuclides are controlled by the adsorption-desorption effect of the colloids and the filtering effect of the colloids, rarely considering the blocking effect of the medium. The dual permeability model and double-porosity model can simulate the co-migration breakthrough curves of the bentonite colloids and nuclides under specific conditions, but the fracture system considered is simple, and the competitive adsorption effect of the nuclides is not considered. For this reason, some suggestions for further experimental and theoretical researches are put forward.