Application of sorption data to the evaluation of radioelement migration in the boom clay formation

An evaluation of effective diffusion coefficients, for the purpose of modelling the migration of Am, Pu, Np and Tc in the Boom Clay formation, has been obtained on the basis of three kinds of information. First, the largest organic molecules (OM) found in the pore water have a Mwt. of about 105 (most are under 4x104). Second, in the pore water, radionuclides are quantitatively in the form of OM complexes which therefore determine the mobility of these radionuclides in the formation. Finally, the sorption tests, conducted to determine the distribution of each radionuclide between the solids and the mobile fraction of OM, provides Kd values corresponding to the in situ conditions. (author)