Some aspects on colloids as a means for transporting radio nuclides

The diffusivity of a macromolecule through a compacted clay layer was measured. The results indicate that molucules and thus colloids of this size - M = 24 000 - will not diffuse through the clay barrier in any appreciable amount. Another set of experiments indicate that the clay will not be a source of colloids as the montmorillonite particles form a stable gel in groundwater with its rather high Ca2+ content. Transport of radionuclides from the repository by adsorption on colloids coming from the clay will thus be small. The colloid content of groundwater from Finnsjoen was measured. This was less than 1 mg/l, so low a colloid content is of little importance. Experiments designed to observe the adsorption of colloidal particles from the clay on rock surfaces were inconclusive