Diffusivity of U, Pu and Am carbonate complexes in a granite from Inada, Ibaraki, Japan studied by through diffusion

Abstract The diffusivities of uranium, plutonium and americium in Inada granite have been determined using through-diffusion method. Experiments were performed at (25±1)°C in a 0.1 mol l −1 NaHCO 3 solution where the actinides are present as carbonate or hydroxy–carbonate complexes. Effective diffusivity ( D e ) values of (1.42±0.24)×10 −13 m 2 s −1 and (5.1±2.0)×10 −14 m 2 s −1 were obtained for uranium and plutonium, respectively. Diffusion through 5 mm thick granite was not observed for americium within the experimental period of 366 days. The D e value for uranyl carbonate species obtained in these experiments was found to be four times higher than the previously obtained D e value for the uncomplexed uranyl ion.