THEREDA represents a web-based system of programs enabling access to thermodynamic reference data for the needs of the final disposal of radioactive waste in Germany. It is the only polythermal database worldwide that covers the entire system of oceanic salts, including acids, bases and carbonates. THEREDA aims at calculation of solubilities in high-saline solutions and uses the Pitzer approach.

In the past 2 decades, X-ray absorption spectroscopy (XAS) and related synchrotron-based radionuclide speciation techniques have become indispensable, supporting issues in fundamental radiochemistry and nuclear waste disposal alike. The KIT Institute for Nuclear Waste Disposal operates two highly versatile beamline stations dedicated to investigating radionuclide materials by X-ray absorption fine structure (XAFS) spectroscopy techniques for samples with activities above the exemption limit.

Stainless steel was exposed to highly saline brines under anoxic and elevated temperature conditions. Samples were analyzed by various techniques in order to identify the nature of the secondary phases present in the corrosion layer forming at the steel–brine interface. Outcomes suggest that the corrosion layer has duplex structure, with an inner layer mostly of chromium (hydr)oxides and an outer layer made of iron- and nickel-based spinel compounds with admixed nickel (hydr)oxides.

Our contribution focuses on the release of fission gases during the dissolution process of two different types of spent nuclear fuel, i.e. UO_X and (U, Pu)OX mixed-oxide fuels, in order to identify and quantify the role of fission gas release rates as an indicator of radionuclide source terms. Within our work, it is shown that, independent of the type of spent nuclear fuel, a comparable, fast initial release of fission gases is evident in all experiments.

This paper presents an experimental investigation of uranium release from spent nuclear fuels under conditions expected in a deep geological repository.