Investigation of the applicability of the model based on the ion exchange reaction for the cesium sorption onto Horonobe sedimentary rocks

Doi, Reisuke  ; Xia, X.*; Shibata, Masahiro ; Kitamura, Akira  ; Yoshikawa, Hideki

Assessment for radionuclides sorption onto a rock in deep underground is important for the safety assessment of HLW geological disposal. Distribution coefficient, K is an available parameter to assess the sorption in the current safety assessment. We applied a model that the sorption of Cs is dominated by the ion exchange reaction on illite to experimental results of Cs sorption onto Horonobe sedimentary rocks. The equilibrium concentration of Cs was calculated under the conditions same as those adopted in the experiment to estimate the K value. Comparing the calculated results with the experimental data, the model could explain well the dependence of K values on Cs equilibrium concentration. By using the model, it is possible to assess Cs sorption onto a sedimentary rock. However, some differences were also obtained between the experimental data and the calculated one.