Review of sorption values for the cementitious near field of a near-surface radioactive waste disposal facility

This paper reports part of the documentation being assembled by ONDRAF/NIRAS to support the safety assessment of the near-surface disposal of short-lived low and intermediate level waste (LILW-SL) or category A waste at Dessel, Belgium. The aim of this study was to establish a sorption database of critical radionuclides and chemotoxic elements on concrete through literature review and data selection with the support of an international panel of experts. The database compiles sorption values in the form of distribution coefficients (Kd values) for radionuclides sorption on cementitious materials, which are utilized in safety assessment calculations to quantify the retardation of safety relevant radionuclides. Sorption values were critically reviewed and selected for both reducing and oxidizing conditions, making them applicable to geological disposal studies. The database encompasses sorption values for sixteen elements crucial for detailed impact calculations for the disposal facility in Dessel. A structured approach involving expert evaluation and estimation of sorption values was employed, alongside discussions on the effects of various components and the geochemical evolution of the cementitious near field. This study aims to provide a comprehensive framework for evaluating sorption data essential for ensuring safety in radioactive waste disposal.