Element Mobility in Crystalline Rock around Open Fractures at Palmottu

摘要

The safe disposal of high-level radioactive wastes ultimately depends on the multibarrier concept, an understanding of the most important processes involved and a safety analysis of the potential repository candidates. Some elements in nature can be considered to behave exactly as in radioactive wastes, as for example natural uranium and thorium series members, while others are almost equivalent. Therefore it is possible to use natural analogues to assess these processes over long time scales. Rock specimens adjacent to two water conducting fractures at a depth of about 205 m from the Palmottu uranium deposit were studied in order to obtain information on element mobility. The drill core was sawn in such a way that a series of specimens perpendicular to the water conducting fracture were obtained for each of the fractures. Concentration profiles for a number of elements were determined. Uranium series disequilibrium studies as well as petrographic studies and porosity determinations were also performed.