Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Presently, argillaceous rock formations are under investigation as potential host rocks for nuclear waste repositories. In addition to the diffusion the sorption of radionuclides on mineral phases is an important physicochemical process in a nuclear waste repository in the case of a water inleakage. Concerning the required long-term safety and risk assessment of the storage of high-level radioactive waste the understanding of these processes is essential.
Opalinus Clay (OPA) is a complex composed argillaceous rock. This natural occurring clay rock is discussed as host rock formation for nuclear waste repositories.
In a repository based on argillaceous rock an initial temperature of around 100°C is expected due to the radioactive decay and the release of geothermal energy. But although elevated temperatures are able to influence the sorption behaviour of radionuclides on mineral phases the temperature effect is still investigated insufficiently.
The investigations concentrated on the sorption of Eu(III) on OPA under realistic OPA pore water conditions (pH 7.6, I = 0.4 mol•L-1) up to 50°C. In addition to the temperature dependent investigations the influence of organic matter (tartrate, citrate) on the Eu(III) sorption on OPA was studied up to 50°C.
The Eu(III) sorption is characterized by a very strong sorption to the clay surface. A significant temperature dependency of the Eu(III) sorption was observed. In the presence of tartrate or citrate the Eu(III) sorption decreases with rising ligand concentration. A surface species, most likely a EuCO3 surface species, was detected using TRLFS. The formation of a surface species containing tartrate or citrate was not observed with TRLFS.