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

The first results of sorption experiments of U(VI), U-234 (VI) and U-238(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 234U onto the clays was found. Finally, the sorption of U(VI) onto the clays was also modeled using a surface complexation model.