Deep geological repositories (DGRs) remain the preferred option in many national programs for the long-term management of high-level radioactive waste (HLW). Their development requires studies of complex geological systems, processes over extended time scales, and assessments of uncertainties and safety. The results must then be translated into safety arguments and regulatory decisions that are transparent, robust, and understandable to the various stakeholders and to society.

In this session, we are particularly interested in how the results obtained from site characterization, geological and numerical modeling, uncertainty analysis, and long-term safety assessment are evaluated and used in site selection, safety cases, and the licensing. We seek contributions that address how different national programs and regulatory systems handle geoscientific evidence and uncertainty; how responsibilities and interactions are organized among implementing agencies, regulatory authorities, policymakers, scientists, NGOs, local communities, affected populations, and the general public; and how transparency, participation, communication, and differing perceptions of risk influence these processes.

Ethical and legal aspects of decisions with very long-term / intergenerational consequences are also welcome. Comparative perspectives and lessons learned from various national disposal programs are particularly encouraged.

DGRs remain the central theme of the session. However, we also welcome transferable lessons from other subsurface activities, including geological carbon storage, geothermal energy, and methane storage.

By bringing these perspectives together, the session aims to better understand how geoscientific evidence can support technically sound, transparent, and societally legitimate decisions for the long-term disposal of radioactive waste.