Diffusion is the dominant process involved in the transport of 129I through geological media; therefore, the evaluation of the experimental results on the diffusion of I− through compacted bentonite was performed by three diffusion models, CC-CC, CC-VC, and VC-VC. Multiple experiments were cross-checked to verify internal consistency and thereby obtain reliable diffusion parameters. The results showed that I− diffusion coefficients ranged from 1.15 × 10–12 to 4.67 × 10–12 m2/s, which were consistent with those of the literature. These techniques could potentially be performed to measure the diffusion coefficients of non-sorbing or weakly sorbing radionuclides onto compacted bentonite in radioactive waste repositories. [ABSTRACT FROM AUTHOR]