Investigation of far-field processes in sedimentary formations at a natural analogue site - Ruprechtov

The analogue study at Rurpechtov site aimed at in-depth understanding of the behaviour of uranium and organic matter in a natural sedimentary system similar to overlying strata of salt domes but also other host rock formations for radwaste disposal. By application of a set of different microscopic and macroscopic analytical methods the complex immobilisation mechanism for uranium and the long-term stability of the immobile U(IV) phases were shown. Sedimentary organic carbon (SOC) is microbially degraded in the lignite rich layers, but DOC concentrations are relativley low, since only a very small fraction of SOC seems to be accessible. Beside increase of process understanding another important contribution of this study to the Safety Case consists in further development and testing of methods for colloid analysis, sample characterisation on μ-scale, and evaluation of environmental isotope signatures.