Study of nuclide migration in sedimentary rocks at the Tono uranium deposit. Characteristics of flow-path structure in relation to nuclide sorption and retardation

The migration of U in sedimentary rocks has been studied at the Tono uranium deposit in Japan. Detailed investigations with rock specimens taken from two boreholes have been carried out to achieve a better understanding of the importance of microtexture in relation to nuclide migration. Present flow-paths for U migration are identified within, and between, detrital grains such as quartz and biotite, by the combined use of dye-impregnation, α-autoradiography, cathodoluminescence, EPMA and SEM techniques. The 238U-decay series disequilibria in the constituent minerals reveal that recent U migration on a microscale has occurred, and is different in each of the minerals in which the flow-paths are identified. The differences are due to the textural features of the minerals and mineral/water interactions. (author)