Sorption aspects for in situ matrix diffusion modeling at Palmottu natural analogue site, SW Finland

Concentration profiles in rock matrix around water-carrying fissures were measured at Palmottu U deposit. The profiles were interpreted by the classical matrix diffusion concept. Site-specific sorption studies were performed for U using standard batch experiments and surface complexation modeling; the response of sorption isotherms was also tested. Site-specific matrix properties as well as initial and boundary conditions were used in simulations. The results indicate that matrix diffusion alone cannot explain the observed enrichment of U and its daughters in the rock matrix