Solubility and speciation of radioactive elements of high-level radioactive waste disposal system

not registered; Shibata, Masahiro ; Yoshida, Yasushi*; not registered; Notoya, Shin ; Yui, Mikazu

The solubilities and speciation dataset for the selected safety-relevant elements in the second progress reports (H12), except for a soluble element (Cs), in the porewater compositions of the compacted bentonite, which are used in the H12 assessments, are provided in this report. The solubilities and speciation were basically determined by thermodynamic calculation using thermodynamic database of the radioactive elements, assuming chemical equilibrium with simple solubility limiting solid phase. For some elements, the solubilities were determined by comparing experimental solubility data, considering the conservatism of the solubility dataset. For radium, the solubility was determined based on simple co-precipitation model with alkaline earth elements. The variation of solubilities and speciation were also examined and discussed, considering the uncertainty of porewater chemistry, assumption of solubility limiting solid phase, and thermodynamic data.