The diffusion of water into epoxide composites containing sand or glass beads has been studied as a function of temperature, type of filler and its surface treatment. This investigation falls within a broader context whose aim is to assess the possibility of embedding nuclear wastes into polymer matrices. The quality of polymer-filler adhesion was checked by scanning electron microscopy. The best filler was found to be siliceous sand in particles of about 30 p m diameter, which could be added to epoxide networks in large proportions and provide a better material than the polymer alone.

The diffusion of water into typical epoxide and polyester materials has been studied as a function of temperature, temperature cycles and polymer structure. A reversible uptake characterised by a diffusion coefficient and an equilibrium absorption was accompanied by an irreversible water uptake due to hydrolysis. Polyesters showed a pronounced tendency to degradation, particularly above room temperature. This preliminary investigation was conducted within the broader scope of a study dealing with the feasibility of embedding nuclear wastes in polymer matrices. The results obtained thus far are encouraging, notably with epoxide networks.

The diffusion of cesium and chloride ions through epoxide membranes was studied under a variety of conditions including self-diffusion, the presence of other salts in the aqueous solution, an excess of either reagent used in the manufacture of the membrane, the addition of various fillers in the epoxide network and two temperatures. At 23°C, the diffusion coefficient D was (2-6) x 10-1 3 em? s -1 for most systems, except when the epoxide was prepared with an excess of the dioxirane component or when untreated glass beads were added to the network. In the latter instance D increased and most notably with glass beads. On the contrary, addition of sand to the epoxide resulted in a more effective barrier against diffusion as shown by a decrease in D. It is concluded that most of these materials should be suitable for the confinement oflow and medium activity nuclear wastes.