Radionuclide Retention in the Cementitious Near-field of a Repository for Low- and Intermediate-level Waste: Development of the Cement Sorption Database
Tits, J. & Wieland, E. (2023): Radionuclide Retention in the Cementitous Near-field of a Repository for Low- and Intermediate-level Waste: Development of the Cement Sorption Database. Nagra Technical Report NTB 23-07.
This report documents the cement sorption database (SDB) for the cementitious near-field of Switzerland’s future deep geological repository for low- and intermediate-level waste (L/ILW repository). The current update of sorption values is based on earlier SDBs prepared within the framework of the Swiss waste management programme. The updated cement SDB is intended for use in safety assessment calculations. Sorption values were selected based on the values and procedures reported in earlier SDBs, taking into account the results from in-house experimental studies and from work published in the open literature. In contrast to previous SDBs, sorption values were also assigned to the radionuclides considered for safety analysis in the fourth stage of the cement degradation process.
In addition to the sorption values, this report also includes a compilation of sorption reduction factors resulting from the presence of cement-derived colloids and important complexing ligands as well as from sorption competition with iron-corrosion products and stable isotopes present in the cementitious near-field. The sorption reduction factors linked to colloids and complexing ligands were assigned on the basis of information on their concentrations in the near-field and their complexing properties, while sorption reduction due to sorption competition was assessed by estimating the effect of the solubility-limited concentrations of key radionuclides on the sorption capacity of calcium silicate hydrates (C-S-H).