SCK•CEN R&D on the interaction between nuclear waste glass and clay near- and far-field materials

A large R&D programme has been performed to evaluate the chemical durability of candidate high-level waste glasses in clay environments considered in Belgium. This paper discusses the methodology followed and the main results obtained over the past years. The methodology involves laboratory test set-ups focusing on the interaction with solid clay, modelling, and tests in the underground research laboratory in clay. The results discussed include dissolution rates, mobile radionuclide concentrations in the interacting solutions, analytical modelling and results from an in situ test. The results show that HLW glass will act as a substantial barrier in such an environment. The paper also discusses the main dissolution processes involved and the remaining uncertainties.