Comparison of modeling methods for the effective diffusivities of IO${}_3$${}^{-}$ estimated in compacted bentonite using through-diffusion tests under aerobic conditions

Diffusion is the predominant mechanism governing the transport of ${}^{129}$I through geosphere. Consequently, the assessment of the experimental findings on two-compartment diffusion reservoirs of IO${}_3$${}^{-}$ within compacted bentonite involved the application of three distinct diffusion models: CC-CC (constant concentration), CC-VC (variable concentration), and VC-VC. To ensure the reliability of the obtained diffusion coefficients, multiple laboratory tests were performed for internal comparison. The experimental results revealed that IO${}_3$${}^{-}$ diffusion coefficients were ranging from 3.83 × 10${}^{-13}$ to 1.91 × 10${}^{-11}$ m2/s. These techniques using three mathematical models could be conducted to estimate the diffusion coefficients of non- or weakly-sorbing radionuclides on compacted bentonite for safety assessment of radioactive waste final disposal.