Low and medium level waste forms: Guidelines and related research

A quality assurance policy has been elaborated, based on waste acceptance criteria and control measures for the verification of the quality achieved during conditioning. The implementation of this policy is being discussed. The research programme performed thus far has focused on two major items: (1) Characterization of waste forms, such as bituminized reprocessing sludges (simulated bituminizates from Cogema and real and simulated bituminizates from BELGOPROCESS) and real high temperature incinerator slags. Composition, physical properties (including ageing) and chemical stability were determined and compared with product specifications. (2) Evaluation of the compatibility of these waste forms with the expected repository environment (clay). Corrosion tests in static conditions in clay containing solutions of bituminizates show that whereas the soluble salts leach readily (as much as 5 mm equivalent leached thickness after six months), the immobilization of actinides is quite satisfactory (about 3 μm equivalent leached thickness after one year). For the incinerator slags, corrosion increases strongly with the clay concentration in solution, but remains below 0.1 mm equivalent leached thickness per year (based on bulk corrosion, at 90 deg. C.). Validation of the laboratory data is attempted through in situ experiments in an underground laboratory in clay. (author). 9 refs, 3 figs, 6 tabs