Diffusion of 3H, 99Tc, 125I, 36Cl and 85Sr in granite, concrete and bentonite

Understanding the characteristics of diffusion is essential in the assessment of radionuclide release through the backfill of waste repository. The diffusion behavior of ³H, ⁹⁹Tc, ¹²⁵I, ³⁶Cl and ⁸⁵Sr in granite, concrete and bentonite was studied in a specially designed diffusion cell. Diffusion coefficients (D, D_a) and time-lag (t_a) were measured, break-trough curves were plotted and experimental data were interpreted to predict diffusion rates. The results showed that tritium, iodine and chlorine could be considered as non-sorbing tracers, while technetium was weakly and strontium was strongly sorbed (no break-through was observed during the period of the experiments).