Quantitative safety assessments for geologic disposal comprise an assessment of the overall level of performance of a repository and an analysis of the associated uncertainties. Such assessments rely on system-level models that are applied to predict the behavior of the whole system under consideration, which in turn are supported by process-driven submodels that assess individual components of the repository system. Many factors defining the evolution of a repository involve complex processes that are quite challenging to predict over short and long time scales, thus demonstrating model fidelity and accounting for prediction uncertainties is an unavoidable aspect of a safety case. Furthermore, results from uncertainty analyses need to be formulated in a clear way understandable to the public and other stakeholders.
This session seeks contributions on how model uncertainties of different nature - scenario uncertainty, conceptual and numerical model uncertainty, and parameter uncertainty – can be evaluated and potentially reduced, how they can be best incorporated in both system and submodels to avoid error propagation, and how uncertainty evaluations can be best communicated to achieve and maintain acceptance. Possible topics include:
• Model comparison against experimental data from lab- and field-based studies as well as natural analogs
• Benchmarking and model comparison studies
• Uncertainty quantification via probabilistic and deterministic approaches
• Transferring information from submodels to system-level models: Upscaling, simplifications, and abstractions
• Propagation of uncertainty between submodels and system-level models
• Assessing uncertainty over very long time frames
• Communicating model uncertainties to the public and other stakeholders
• Case studies from national and international programs and initiatives

Radioactive waste management combines technical as well as social, political, economic, and cultural challenges. It is an inherently socio-technical issue – as ongoing discussions surrounding countless societal facets like e.g. questions of justice in and justification of radioactive waste management programsthe acceptability of sites, compensation schemes for affected communities, or legacies of nuclear places demonstrate.

This session focuses on current research from the social sciences and humanities (SSH) that highlight important topics such as participation, regional development, heritage, and stakeholder engagement. The studies draw on a rich variety of European cases including Belgium, France, Finland, Germany, Italy, and Sweden.

Safeguards and non-proliferation are crucial to prevent the use of radioactive materials for military purposes. This session encompasses topics related to safeguards and non-proliferation issues in nuclear waste disposal. The scope of topics that could be placed in this session is intentionally broad. Possible topics are, e.g.,

1. Non-proliferation assessment of alternative disposal options such as reactor-based disposal and partitioning and transmutation;
2. Current, future, and long- term challenges and opportunities in safeguards implementation for disposal facilities (interim storage and geological disposal facilities);
3. Societal and political drivers in nuclear materials management with interconnections to safeguards and non-proliferation;
4. International safeguards, non-proliferation agreements and regulations in nuclear waste disposal, their technical requirements, and their impact on national regulations.
5. Material accountancy and disposal of waste containing fissile materials such as highly enriched uranium and plutonium.
6. Research and development of advanced and innovative methods and technologies for monitoring and verification such as satellite surveillance, on-site inspections, and nuclear material accountancy to ensure compliance with non-proliferation agreements in nuclear waste disposal.
7. Perspectives on the long-term evolution of the safeguards system and the non-proliferation regime, in particular with a view on nuclear disposal;
8. Safeguards and non-proliferation in crisis and incident situations;

The session is also intended to provide a platform for exchange between different scientific communities. It aims to foster interaction among groups that rarely have the opportunity to collaborate.