The safety case for a deep geological repository (DGR) for high-level radioactive waste (HLW) requires a detailed knowledge about retention and transport processes. Argillaceous rock is considered as a potential host rock, with Opalinus Clay (OPA) as a reference material for a natural clay rock. This natural material is characterized by a multiscale structural and compositional heterogeneity.
In previous studies applying synchrotron-based multimodal chemical imaging on compacted OPA samples in sorption and diffusion experiments with Np and Pu, a significant role of pyrite (FeS2) was identified in the retention of the studied radionuclides. Extending these studies in a continued collaboration between Johannes Gutenberg University Mainz (JGU, Mainz, Germany) and the Swiss Light Source (microXAS beamline project, Paul Scherrer Institute, Villigen, Switzerland) sub-mm-sized pyrite composites were isolated from OPA, subjected to sorption experiments with Np and Pu and studied by multimodal chemical tomography, gaining structural, elemental, mineralogical and chemical information in three dimensions.
Results of this study were presented at the ATAS-AnXAS 2022 – Joint Workshop (5th International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS) & 9th Workshop on Speciation, Techniques and Facilities for Radioactive Materials at Synchrotron Light Sources (AnXAS)), jointly organized by the European Synchrotron Radiation Facility (ESRF, Grenoble, France), also serving as the venue of the workshop, and Helmholtz-Zentrum Dresden-Rossendorf (HZDR, Dresden-Rossendorf, Germany). The workshop covered topics concerning research on actinides and radioactive materials with spectroscopy and synchrotron-based techniques, also comprising topical sessions on radioactive waste disposal, actinides-related bio-geochemistry and nuclear materials. The workshop provided an opportunity for presenting the work and results of our collaboration, scientific exchange and learning about new studies and techniques related to actinides and radioactive waste disposal.
