Decisions associated with radioactive waste management are made in the presence of irreducible and reducible uncertainties. Here, the identification of such uncertainties (namely numerical ones), their ranking according to relevance, their categorization, the elucidation of internal dependencies and cross-interactions is addressed. Suitable methodologies to analyse and illustrate complex uncertainty patterns are discussed.

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.

The corrosion process of spherical graphite cast steel GGG40 bentonite saturated with Opalinus Clay pore water was investigated in a specially designed electrochemical cell, which allows the corrosion rate to be monitored in medium-term experiments. The morphology and chemistry of the interface was inspected by means of electron microscopy and surface chemical spectroscopy. This study supports the evaluation of this material's chemical and physical integrity for repository containers.

The immobilization of trivalent actinides (Am, Cm) and their less toxic homologue (Eu) in feldspar, a very common mineral in our earth crust, was studied by sorption experiments and spectroscopic studies. The speciation was identified and used to gain thermodynamic parameters to develop a surface complexation model. To sum up, feldspar, a main component of crystalline rock, is suitable for retaining radionuclides in a deep radioactive waste repository.

Capturing the state of knowledge in radioactive waste management is a very important activity for supporting member states with the implementation of their national programmes towards the safe and effective management of waste. This requires the involvement of experts sharing their expertise and knowledge with the wider community. During the past 3 years, we have gained valuable insights into the procedures of involving experts and knowledge sharing, and the lessons learnt are shown here.