Diffusion of La3+ in Compacted GMZ Bentonite Used as Buffer Material in HLW Disposal

It has been studied that the GMZ bentonite which has a chemical barrier property can play an important role in retarding the migration of radioactive nuclide. In order to understand the diffusion properties of nuclide in GMZ bentonite, a series of experiments were conducted to obtain the apparent diffusion coefficient of La3+ in GMZ bentonite under different dry density and pH value conditions using a autonomous ion diffusion instrument. The results show that the apparent diffusion coefficient of La3+ decreases significantly with the increasing dry density or pH value. The influence of dry density on the diffusion is very apparent for a low dry density, and the influence gradually slow down with the increase of dry density. At last the influence mechanism of the dry density and pH value on diffusion coefficient was also analyzed.