Genuine radioactive glass sampled from the vitrification plant Karlsruhe and actinide doped model 2 glasses are investigated by U/Pu/Np M4/M5 high energy resolution X‐ray absorption near edge structure (HR‐XANES), U L3 EXAFS and XPS spectroscopy techniques to characterize and compare the U, Pu and Np oxidation states and their local atomic environments. The importance of the results will be discussed in terms of the strategy of using simplified simulated waste glasses to understand more complex industrial glass samples. The final goal of these studies is to predict the long term behavior of vitrified nuclear waste stored in a nuclear waste repository.
Highly active waste concentrate (HAWC) from nuclear fuel reprocessing is immobilized in borosilicate glass matrices to generate a disposable waste form [1]. Between 2009 and 2010, the vitrification plant Karlsruhe (VEK) was operated for vitrification of liquid process residues left over from operation of the former reprocessing plant Karlsruhe (WAK). About 56 m3 HAWC were processed, resulting in 50 t of waste glass [2]. The long term radiotoxicity of U, Np, Pu and other actinide elements (An), minor constitute of the reprocessed waste, is of great concern in safety assessment studies of nuclear waste repositories. For example, in case of water intrusion and interaction with the glass matrix, corrosion processes will take place which might facilitate the release of radionuclides into the geosphere. The An redox state and bonding characteristics in the glass matrix determine their release mechanisms and retention processes taking place in near and far field of the repository [3]. Understanding the long term behavior of vitrified nuclear waste requires full and detailed characterization of the materials including their characteristics as synthesized and after exposure to
groundwater. Genuine radioactive waste glass has a complex chemical composition. Therefore we take a simplified approach by investigating and comparing the oxidation states of U, Pu and Np in high level waste (HLW) glass sampled from the VEK vitrification process (VEK glass) and in model glasses. The model glasses doped with U and Pu have the same borosilicate glass frit composition as the VEK glass, whereas the model glass doped with Np has a base glass composition (R7T7) typically used for
vitrification of HLW in France. U/Pu/Np M4/M5 edge high energy resolution X‐ray absorption near edge structure (HR‐XANES)
spectroscopy technique [4] is applied to characterize the An oxidation states
