Management of sorption data to support radioactive waste disposal

Radioactive waste geological disposal is considered as a feasible and safe solution, but requires detailed understanding of the interactions between the radionuclides and the components of the disposal system. A key process limiting the mobility of radionuclides is sorption, which determines how these elements interact with solid phases such as clay and cement within geological and engineered barriers. Effective management of sorption data is required to improve traceability and confidence in safety analyses and to demonstrate the long-term safety of the repository. Sorption is classically determined by means of sorption experiments (e.g. isotherms, edges) and related thermodynamic sorption modelling. Extensive knowledge is already available in the scientific literature for the sorption of many radionuclides and toxic contaminants onto relevant solid phases. Sorption is known to be system specific and strongly dependent on the chemical conditions (e.g. ligand concentrations, redox conditions, pH). Sorption databases provide a sound framework for recording all relevant information and are expected to provide a robust basis for making good use of the knowledge in the safety case. This paper presents the development and current status of a sorption database system tailored to the specific needs of the Belgian programme, in particular disposal in poorly indurated clays (i.e. Boom Clay and Ypresian clays).