The objective is to investigate the potential for conversion of clay organic matter into dissolved humicor humic alike substances under conditions relevant for nuclear waste disposal in the presence of cement. The project is based on preliminary investigations under aerobic conditions with clay rich inorganic matter that has not been consolidated under elevated temperatures. In the present project, investigations will be extended to anoxic conditions and clays with high temperature consolidated clay organic matter.
Two different clays are contacted with alkaline solution up to around 550 days. The alkaline solution reflects conditions resulting from cement dissolution. The generation of humic substances is monitored and important properties for radio nuclide complexation and mobility are determined. This includes determination of functional group content (proton exchange capacity), actinide complexation studies. molecular mass and size distribution. Simultaneously, the morphology of clay during the alkaline treatment is studied as well as the generation of new phases. Generation and characterization of clay mineral colloids is also studied. Results are interpreted in view of the potential: impact on actinide mobility in the near field of disposed radioactive waste.