Development of the safety assessment technology for the radwaste disposal

Experiments and the model construct of the sorptive and/or diffusive behavior of the radionuclides were conducted to elucidate the migration phenomena of the radionuclides in the subsurface environments, and to provide the input data for the safety assessment of the nuclearwaste disposal. Sorption characteristics of the uranium and iodine onto the granite, tuff, and some clays were studied, and the sorption database was completed under limited but representative geochemical conditions. The surface complexation model (SCM) was studied for the radionuclides partitioning in geochemical settings; as a more conceptually satisfying alternative to the Kd approach which has been exclusively used to estimate radionuclide retardation factors in performance assessment calculations for the repository site. Diffusion experiments of sorptive and nonsorptive nuclides were conducted to determine effective diffusivity, geometric factor, and to propose the diffusion model by the through-diffusion method. (Author)