Sodium nitrate release from EUROBITUM bituminised radioactive waste. Scoping calculations

Eurobitum intermediate level bituminised radioactive waste has been produced at the EUROCHEMIC/BELGOPROCESS reprocessing facility (Mol-Dessel, Belgium) and it is destined for geological disposal in Boom Clay. Owing to the importance of the clay host formation in the overall repository safety, it is important to verify whether the processes induced by the emplacement of Eurobitum will significantly affect the safety-relevant properties of this barrier. The Belgian research program therefore focuses on the compatibility of Eurobitum with the Boom Clay. This report is concerned with the impact of the leaching of NaNO3 on the safety functions of the Boom Clay. A first step in this assessment is investigating the migration of Na+ and NO3- through the engineered barrier system (EBS) and Boom Clay and to calculate potential maximum concentrations of Na+ and NO3- in the repository near field (NF). This report is complementary to a former assessment of nitrate release reported in SCK•CEN report R-3767 (Weetjens, 2003), taking into account the modification in disposal concept and (re-)interpretation of the laboratory tests.