Simulation of radionuclides 99Tc and 243Am migration in compacted bentonite

The distribution coefficients of radionuclides derived from batch experiments are used to evaluate the migration behavior of radionuclides 99Tc and 243Am in compacted bentonite after different times. The effects of times, dispersion coefficient, distribution coefficient and pore water velocity on the concentration distribution of 99Tc and 243Am in the environment are also calculated from the theoretical migration equation. 99Tc is poorly sorbed to bentonite and moves quickly into the environment. Migration of radionuclide increases with increasing dispersion coefficient and decreasing distribution coefficient. The effects of water velocity on the migration of Tc and Am are obvious. Most 243Am is retained in the first several meters, and 20 m of the backfill-compacted bentonites are sufficient to prevent the migration of radionuclide Am from the repository to the environment.