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

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 NaHCO3 solution where the actinides are present as carbonate or hydroxy–carbonate complexes. Effective diffusivity (De) values of (1.42±0.24)×10−13 m2 s−1 and (5.1±2.0)×10−14 m2 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 De value for uranyl carbonate species obtained in these experiments was found to be four times higher than the previously obtained De value for the uncomplexed uranyl ion.