Sorption behavior of U(Ⅵ), ~(234)U(Ⅵ) and ~(238)U(Ⅵ) onto fracture-filling clays in Beishan granite, Gansu: Application to selecting the site of high-level radwaste repository in China

摘要

The first results of sorption experiments of U(Ⅵ), ~(234)U(Ⅵ) and ~(238)U(Ⅵ) onto original (unpurified) fracture-filling clays from No.1 monzonitic granite intrusion, Beishan area, Gansu Province, China are reported. The monzonitic granite intrusion is a potential location for a high-level radwaste (HLW) repository in China. The present experimental results show that the maximum U(Ⅵ) sorption reached 92% at near-neutral pH and the distribution coefficient (K_d) was 1226 mL/g. A high sorption capacity of the fracture-filling clays in host rock on radioactive elements is necessary for HLW deep geological disposal repository. No preferential sorption of ~(234)U onto the clays was found. Finally, the sorption of U(Ⅵ) onto the clays was also modeled using a surface complexation model.