Flow-Path Structure in Relation to Nuclide Migration in Sedimentary RocksAn Approach with Field Investigations and Experiments for Uranium Migration at Tono Uranium Deposit, Central Japan

摘要

The migration of natural uranium in geosphere has been studied at Tono uranium deposit, located in the Gifu Prefecture, central Japan. Geological and geochemical investigations have been carried out, as well as laboratory experiments, in order to characterize those structural and geochemical factors governing nuclide migration and to develop a conceptual nuclide migration model in sedimentary rocks. The results can be summarized as : (1) Micro-fractures within quartz grains, cleavages of detrital biotite flakes, and pores between detrital grains play an important role in nuclide migration, both as pathways and retention sites. Natural feature of uranium concentration in minerals and hydrogeological estimations suggest that diffusion may also exert a significant role on nuclide migration. (2) Flow-path structures, e.g. connectivity of pores, influence the sorption capacity of the host formation. Connectivity of pores probably change the number of accessible sorption sites along the flow-path in the sedimentary rocks.