Characterization of transport of caesium, strontium, cobalt and iron ions Tthrough concrete by steady-state migration and natural diffusion tests

immobilization of wastes in cement-based matrices is being increasingly used, Aparticularly in the case of elements of medium and low activity. Therefore, characterization of the system in Arelation to the release of ionic wastes through the cement, and consequently the determination of their diffusion Acoefficients, becomes of strategic importance. Nowadays, diffusion coefficients of some radioactive elements A(mainly of Cs+) can be found in the literature, obtained by natural diffusion tests that are very time-consuming. AIn the present paper, the calculation of steady-state diffusion coefficients of Cs+ , Sr2+ , Co2+ and Fe3+ through Aconcrete has been done by migration experiments. The mutual influence of the diffusion coefficients has also been Astudied, and transference numbers of the different ions have been calculated. The results have been compared with Athose obtained by natural diffusion tests, having found for Cs+ and Sr2+ that there is a very good accordance Abetween diffusion and migration tests. In contrast for Co2+ and Fe3+ the accordance is not so good, because at Amigration working conditions they are able to form complex compounds. In consequence, migration tests are reliable Afor obtaining diffusion coefficients of different elements through concrete, always taking into account the nature Aof the species that are present at working conditions.