Diploma & Master Thesis
Sorption of U(VI) and Np(V) on Äspö-granite under anaerobic conditions
One request to the host rock of a potential repository for radioactive waste in deep geologic formations is its function as geological barrier to decrease the mobility of actinides accidentally released. In addition to salt and argillaceous rock, granite as magmatic rock is considered as potential host rock for nuclear waste repositories. U and Np are constituents of the spent nuclear fuel and contribute to the radiotoxic and chemotoxic inventory of spent fuel elements and other nuclear waste intended for final disposal.
To study the retention of actinides by granite, the sorption of U(VI) and Np(V) on granite from the underground hard rock laboratory in Äspö (Äspö HRL, Sweden) will be studied in this diploma thesis. The interactions will be simulated and described by batch sorption experiments in the laboratory. According to the conditions at the final disposal site and the planned emplacement of heat developing, highly radioactive waste, the effect of the grain size of the granite, the effect of the ionic strength of the background electrolyte and the effect of temperature will be investigated under anaerobic conditions. Thereby, the U(VI) and Np(V) concentration in the aqueous phase will be determined by liquid scintillation counting. The oxidation state of the actinides will be identified by liquid-liquid extraction with 2-thenoyltrifluoroacetone in xylene. By means of ATR FT-IR spectroscopy the speciation of the surface complexes will be elucidated.
This work is part of the project „Crystalline Rock Retention Processes” (CROCK) within the 7th framework program of the European Atomic Energy Community (EURATOM).