Bacterial Diversity in Clay and Actinide Interactions with Bacterial Isolates in Relation to Nuclear Waste Disposal

One potential source of radionuclides in the environment could be the accidental release from nuclear waste disposal sites. Hence the long-term safety of nuclear waste in a deep geological repository is an important issue in our society. Microorganisms indigenous to potential host rocks are able to influence the speciation and therefore the mobility of radionuclides and their retardation both by direct and indirect pathways. They can as well affect the conditions in a geologic repository (e.g., by gas generation or canister corrosion). The focus of this chapter lies on the influence of indigenous microbes on the speciation of Rn. Therefore, for the safety assessment of such a repository it is necessary to know which microorganisms are present in the potential host rocks (e.g., clay and salt) and if these microorganisms can influence the speciation of released Rn. Hence, dominant bacterial strains from potential host rocks for future nuclear waste deposition have to be investigated regarding their interaction mechanisms with soluble actinide (An) ions. This chapter will cover the following research areas. Gained knowledge concerning the bacterial diversity in e.g., Mont Terri Opalinus Clay by applying direct molecular culture-independent retrievals and cultivation experiments will be presented. Their influence on the geo-chemical behavior of selected An (e.g., uranium, and curium) will be highlighted. These investigations contribute to a better understanding of microbial interactions of An on a molecular level for an improved prediction of the safety of a planned nuclear waste repository.