Institute for Nuclear Waste Disposal. Annual report 2005 [report]

H. Geckeis
This section reports fundamental studies on the chemistry of dissolved actinide species in aqueous solutions, their interaction with minerals and colloid formation processes. Research on plutonium geochemistry still represents a challenge mainly due to the complex Redox chemistry. The first contribution describes the consistent thermodynamic description of Pu solubility data and measured Redox potentials. The structure of actinide aquo ions is subject of ongoing spectroscopic studies. A
more » ... studies. A thorough understanding of those species is a prerequisite for the straightforward interpretation of spectroscopic data as e.g. derived for curium ions by laser fluorescence. First experiments reveal structural changes in the actinide aquo ions at temperatures up to 200 o C -a relevant temperature range in a repository for heat producing high level nuclear waste. Sorption at mineral surfaces and incorporation into secondary mineral phases represent important geochemical mechanisms governing the radionuclide retention in the vicinity of a repository. INE studies concentrate on the elucidation of sorption and incorporation mechanisms, the characterization and quantification of formed species and the implementation of this information into geochemical models. Colloids on the other hand side are known to promote radionuclide mobility under certain geochemical conditions. Studies on different colloid generation mechanisms: actinide coprecipitation with colloidal alumosilicates and sorption to clay colloids are investigated by various techniques.
doi:10.5445/ir/270065515 fatcat:3ehqhfpbcrfwxgw7ivwp2wu4u4