Vorstellung und Diskussion der Untersuchungen des HZDR zur Rolle von Mikroorganismen bei der Endlagerung radioaktiver Abfälle.

In the underground rock characterization facility tunnel ONKALO in Finland massive biofilms were observed attached to the fractured bedrock at a depth of 70 m. Experiments were performed in the laboratory to study the effect on the behavior of uranium in biofilms by adding uranium to the fracture water with a final uranium concentration (4*10-5 M) relevant for what can be expected from an injured and leaking waste canister in the far-field during a nuclear event in a HLW repository. The results obtained by analysis, microsensor measurements, TRLFS investigation, EF-TEM/EELS studies and thermodynamic calculations clearly indicate that biofilms have to be considered as microenvironments, which differ significantly from the surrounding medium. Our studies clearly demonstrate that biological systems have to be considered as a part of natural systems that may have significant influence on the behavior of radionuclides. They are contributing to an improved understanding on the response mechanisms of biofilms towards radionuclides in respect to safety assessments of the radioactive waste repositories.