Sorption of 14C, 99Tc, 137Cs, 90Sr, 63Ni, and 241Am onto a rock and a fracture-filling material from the Wolsong low- and intermediate-level radioactive waste repository, Gyeongju, Korea

Sorption experiments for radionuclides such as C-14, Tc-99, Cs-137, Sr-90, Ni-63, and Am-241 were conducted using two different groundwaters (GM-1 and SS-5) and solid materials (granodiorite and fracture-filling material) sampled from the Wolsong low- and intermediate-level radioactive waste (LILW) repository, Gyeongju, Korea. The distribution coefficients of the radionuclides, K (d)'s, were obtained and their sorption properties were discussed for each radionuclide. For all sorbing radionuclides, the K (d) values for the fracture-filling material were observed to be higher than those for granodiorite regardless of the groundwater. The K (d) values were increased in the sequence Tc-99 < C-14 < Sr-90 < Cs-137 < Ni-63 < Am-241 regardless of sorbent types implying that the sorption of radionuclides onto geological media is affected by their chemical behavior in accordance with geochemical environments. Anionic radionuclides such as C-14 and Tc-99 showed very low K (d) values both for the granodiorite and fracture-filling material. The mineralogical composition of the geological media and groundwater conditions was also observed to be important in the sorption of sorbing radionuclides, especially in the case of strongly sorbing radionuclides.