This session will delve into critical issues surrounding the very long-term safety of high-level nuclear waste (HLW). The discussion will focus on four key topics: (1) the relatively high level of hazard posed by HLW essentially indefinitely, (2) the foundations and limitations of the commonly used time horizon of up to one million years in safety assessments, (3) whether geology provides a permanent or merely temporary solution for long-term waste containment, and (4) the ethical considerations our societies must confront in addressing the environmental and human health implications of HLW indefinitely.

The session format can either consist of individual presentations addressing these topics or be structured around a keynote presentation followed by a panel discussion, with the audience having the opportunity to engage directly. In the event that no other presenters are available, I am willing to deliver the keynote presentation based on my own research, where the radiation hazard of both spent fuel and vitrified HLW is quantitatively assessed. This research, which will be published in a peer-reviewed journal by the end of this year, highlights the overlooked extended timescales in HLW management and challenges common comparisons of HLW radioactivity with that of the original uranium ore.

This session will be of particular interest to stakeholders in radioactive waste management, policymakers, researchers, and ethicists concerned with nuclear safety and sustainability.

This session shall cover all aspects on storage, final storage, transport and conditioning with their interrelationships to improve storage and final storage.

Other technical concepts than mining could accelerate site exploration and construction of final disposal. New hypothetical concepts and technologies can be presented here. Administrative and procedural processes for site selection are excluded.

Storing the radioactive waste in a deep geological repository (DGR) is considered a robust solution to minimize the risks to human health and the environment, even in the far future. However, how do we know it is truly safe? How can we manage uncertainties in an analysis extending up to 1 million years into the future? This session will focus on the methods used to assess post-closure safety of a DGR. We invite contributions related to all aspects of post-closure safety, from evaluating how the technical barriers contribute to the long-term safety of a DGR to calculating radiation doses to humans as well as non-human biota. Suggested topics may include (but are not limited to):
• Quantifying uncertainties related to long-term evolution of a DGR and its environment
• Defining scenarios for post-closure safety analyses, including different climate evolutions
• Evaluating how natural and technical barriers contribute to post-closure safety
• Determining representative persons and life habits over long timescales
• Evaluating radionuclide transport and dose to humans and non-human biota
• Assessing landscape development and identifying potential release areas
• Strategies for using generic versus site-specific data in post-closure safety analyses
• Methods for choosing and evaluating Features, Events and Processes (FEPs) of importance for post-closure safety
• Engineering and modelling perspectives on post closure safety
• Are there alternative waste-management solutions to DGRs?

Description

As a socio-technical endeavour, deep geological disposal of radioactive waste links to different aspects of sustainability – particularly concerning time. Due to its very long timeframe (several decades for implementation, operation and closure to hundred thousands of years for long-term safety) and scope, it is unique compared to other infrastructure projects: it is a clear transgenerational project, which automatically raises questions of sustainability. Not only waste management organisations (WMOs) - tasked with the implementation of radioactive waste disposal - but also other actors like regulators face sustainability challenges with regard to time-related aspects. This includes for example safety, intra- and intergenerational justice, endurance of institutions, participation of civil society, or knowledge management. However, is sustainability just a fashionable label in the discourse on geological disposal of radioactive waste? Is the discussion on sustainability even necessary? What are possible positive inputs of this discussion? In order to approach these questions, this session focusses on sustainability questions specifically related to the temporal aspects of final disposal of radioactive waste.

Objectives and scope

This session discusses various topics connecting time and sustainability in the implementation of geological disposal of radioactive waste. It focusses on the institutions involved, public participation and empowerment of society as well as preserving expertise and knowledge. In this context, it addresses the following general questions: What does sustainability mean regarding implementing final disposal of radioactive waste – especially for the WMOs? How can WMOs respect sustainability aspects and meet the respective challenges? Time is a safety factor: no compromise to the best possible safety shall be made but WMOs have to implement the geological disposal efficiently with reaching milestones and goals within a certain time. The relationship between safety and sustainability should be discussed, i.e. aspects of reciprocity, dependency or mutual exclusion. Moreover, aspects of justice, responsibility and fairness towards current and future generations as well as in the corresponding processes are relevant. Difficulties in predicting long-term future social, political, economic and environmental developments lead to the question of sustainability of the involved institutions. In view of the time scales, institutions are required that are able to act over long periods and to develop in line with changing boundary conditions. From the perspective of time and sustainability, questions of securing institutions as well as institutional embedding of the task are relevant. This includes additional aspects: transparent knowledge transfer and participation of the civil society and further stakeholder raise the question of whether and how corresponding formats are received and perceived. The task of transferring knowledge to future generations with changing social conditions and structures is challenging which requires a successful interaction between civil society and WMOs. In the field of knowledge management, it is and will be relevant to enable sustainable preservation of expertise - both now and in the future. In this context, retrospective considerations and evaluations of sustainability aspects in earlier approaches and programs can also be helpful (e.g. the relation of time planning and progress in reality as a permanent dilemma). Even before the forthcoming and popularization of the term ‘sustainability’, there was a discussion how to realize geological disposal of radioactive waste in a safe but economically efficient manner.

Contributions

Contributions with a socio-technical focus from all disciplines on national and international perspective are welcome and can address but are not limited to the following topics in context of time and sustainability:
• Safety and sustainability: aspects of reciprocity, dependency, exclusion
• Intra- / intergenerational and procedural aspects: responsibility, justice
• Endurance of institutions: resilient systems, long-term governance, organisational learning, aspects of error and safety culture, development of political landscape (e.g. relationship between the executive and legislative power, changing political majorities or public opinion)
• Participation of civil society: evaluation and results of formats of stakeholder involvement, models for evaluating participation formats
• Knowledge management: processes of preservation of knowledge and expertise, digital systems
• History: lessons learned from former approaches, programs and projects

In the multi-barrier concept for the safe long-term storage of high-level nuclear waste in deep geological repositories, the stability of the individual barriers is a key factor.
The stability of the individual barriers, such as the outer and inner canister materials, and the buffer materials (clays, cementitous materials), depend on a variety of hydro-bio-geochemical factors, but also on the materials used in each case. Material stability and forecast of material degradation phenomena in the long-term are important aspects to be adressed in the safety case and the design of a deep geological repository. This session adresses the interplay between timely and rapid research and development of canister and disposal concepts versus the reliable assesment of the long-term material behavior used in a multi-barrier concept, with a special focus on corrosion issues. Topics of interest are:
- Corrosion studies on potential canister materials
- Application orientied material and canister development and testing
- Stability and degradation of buffer and filler materials affected by corrosion
- Modelling of material behavior on long time-scales with respect to hydro-bio-geochemical induced corrosion phenomena
This session covers by an interdisciplinary approach the challenge to adress and forecast material behavior for the timely implementation of a safe deep geological repository.

Characterising spent nuclear fuel (SNF) and radioactive waste is essential for ensuring safe and efficient interim and final disposal. Precise knowledge of waste properties, including radionuclide composition, decay heat, reactivity, gamma-ray and neutron emission, allows for informed decision-making in storage, transport and disposal. Proper characterisation reduces uncertainties in safety assessments and helps optimise SNF and waste management. This session would explore advancements in characterisation methods and their critical role in the SNF and waste management.

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

The session will focus on the processes, their modeling and parameterization that are governing the radionuclide transport through the buffer, backfill and host rock / cap rock. Contributions providing thermodynamic data of (bio)geochemical systems and fundamental understanding of the underlying molecular processes relevant for the long-term safety assessment of nuclear waste disposal are welcome in this session. Presentations are invited on both numerical and analytical approaches to reactive transport processes at the pore scale and beyond.
Themes:
- Identification of significant deficits in process understanding and strategies for advancing the state of knowledge
- Gaps in thermodynamic databases: relevance, use of estimation methods (primarily related to speciation, solubility, sorption)
- Methodological developments (detection limits, data processing and interpretation, multilateral procedures, upscaling in complexity, time and space)
- Uncertainty and sensitivity analyses, geostatistics
- Analysis of material heterogeneities that critically control sorption processes in geomaterials
- Parameterization of reactive transport models, validation of numerical approaches
Goals:
The contributions shall focus on those phenomena that are either in general essential to the radionuclide transport or that have currently large uncertainties rendering them especially critical. Strategies and methodologies to treat them in a way to make safety assessments more realistic and less uncertain shall be derived and discussed.

While discussions about the nuclear industry’s material legacy often center on the long-term disposal of high-level waste, this focus represents merely a small fraction of the total waste that requires our attention. Eventually, the entire nuclear infrastructure, which has turned into cumbersome old machines and buildings that are too outdated to continue operating, will need to be cared for and turned into massive amounts of low- and mid-level nuclear waste. How do actors in the nuclear industry but also in diverse political arenas envision the future decommissioning of these installations?
Nuclear decommissioning illustrates that nuclear waste is not just an object waiting to be picked up and stored. Instead, it results from complex processes that transform the infrastructure, which has lost its initial purpose, into packages suitable for long-term storage. Decommissioning is, therefore, a process that must deal with the “nuclear residues,” i.e. entities in a transitional state no longer being a fit-for-purpose infrastructure and not yet having become waste. This transformation of residues into waste faces many challenges: the long-term irradiation of components and the ongoing degradation of buildings needing decommissioning require special care to avoid contaminating workers and the environment. Some nuclear installations were not designed with future decommissioning in mind, posing challenges for accessing structures and understanding materials. Additionally, as decommissioning often stretches over long time periods, the memory of the sites must be properly preserved and passed on from one generation of workers to the next.
The transformation of nuclear installations into waste is thus not a straightforward process. It gives rise to different strategies and regulatory frameworks depending on the countries and the kinds of reactors. Although some argue in favor of decommissioning as fast as possible in order to avoid the effects of material degradation and memory loss, others argue for a deferred decommissioning that would benefit from further innovations in robotics, digital twinning, and technologies of long-term disposal for the low and mid-level wastes produced by decommissioning processes. Finally, some argue in favor of entombment: instead of transforming the installations into waste to be transported elsewhere, why not reinforce their structure in order to transform them into long-term disposal sites?
This panel focuses on the technical and political issues related to nuclear decommissioning and the transformation of old and obsolete nuclear installations into storable nuclear wastes, specifically focusing on low- and mid-level wastes.

The participatory turn in radioactive waste management has manifested itself in many countries through a discursive and practical involvement of citizens in the long-term management of various waste categories. In most cases, such involvement has primarily focused on repository planning and siting. However, the lifetimes of repositories and radioactive waste extend far beyond these early implementation stages, which themselves often span various decades – or even longer. To seriously address civil society involvement in radioactive waste management, this means we also need to consider the ways in which civil society groups and individual citizens could be engaged in this management over longer periods of time. Some initial scholarly commitment with this topic is currently developing, with theoretical and empirical work being conducted around concepts such as stewardship, care and hosting. However, a range of questions remain to be further explored, such as; What does it mean to pass engagement on from one generation to the next, and how could/should such intergenerational involvement be facilitated?; What sort of consequences could long-term engagement with civil society have regarding institutional responsibilities ?; How can participatory structures be adapted in such ways that they remain both sufficiently durable and flexible?; What meaningful role(s) are envisaged or intended to be played by civil society actors at later stages of a repository lifetime, especially also post-closure?; How could the different roles of actors over time be considered meaningful?; How can repository projects enact future opportunities for civic engagement?; What kinds of socio-technical governance structures or systems might emerge from these long-term interactions?

This session will delve into these questions and more, inviting contributions from diverse scientific disciplines. We particularly welcome insights related to intergenerational participation, stewardship, sociology of care, awareness preservation, youth involvement, innovative forms of civic participation and similar topics. By addressing these issues, we aim to build a deeper understanding of how long-term civil society involvement in radioactive waste management can be sustained and enriched over time.

Optimization will be in focus of advanced programmes as first repositories enter in construction and operation. Optimization provides benefits regarding technical, economical, long-term safety related aspects as well as flexibility and robustness. The need of optimization is justified by the long running character of repository projects and thus by expected changing boundary conditions (e.g. new waste types) or evolution of technology and/or the adaptations of processes due to operational experiences. Further, optimization is a process that shall involve all stakeholders of a RWM programme, including civil society and the regulatory bodies. Within the frame of the EURAD 2 program a work package “HLW Repository optimisation including closure – OPTI” was initiated. The objectives of the WP are to develop a mutual understanding and provide recommendations about methodologies and further activities for design and optimization of specific HLW deep geological repository systems, structures and components (SSCs) and procedures. Within the WP 23 parties from 11 European countries are involved. The participants represents waste management organizations (WMO), technical support organizations (TSO), research entities (RE) as well as representatives from the civil society. To open the discussion for additional representatives from the civil society as well as the regulatory body or other interested parties a session dealing with optimization is proposed. The session goal would be to open the discussion about optimization such as What is it? Why? When? Who is involved? etc.

The Covid-Pandemic as well as the war of Russia against Ukraine pointed towards blind spots in the safety assessment of nuclear and disposal facilities - disruptive events. This session will discuss the treatment of disruptive events at disposal facilities from an safety assessment and operational safety point of view.

Public opinion is often considered to be a key aspect for ensuring the long-term success of dealing with nuclear waste. Thus, it is of high relevance to collect robust empirical knowledge on how ordinary citizens perceive the current challenges of high-level radioactive waste, decommissioning of nuclear infrastructure as well as interim and long-term storage. In addition, regulators and operators must know what citizens expect from them and which role citizens want to play themselves in decision-making processes around nuclear waste management. Given the fragmentation of society, it is also important to answer these questions not only for the population as a whole but also separately for different strata. This also sets the foundation to provide explanations for current public opinion rather than just describing it.

This session aims to bring together public opinion research on nuclear waste management from all around the globe to learn from different perspectives and approaches. Submissions may address but are not limited to the following key areas and research questions:
• Knowledge and beliefs: What is the current level of knowledge in the population or specific groups on how nuclear waste is handled? Do citizens are aware who is responsible for dealing with the waste and were it is stored? What are beliefs in society on the risks around nuclear waste?
• Attitudes: Which strategies for dealing with radioactive waste do citizens support or oppose? How does the population judge the current work of regulators and operators? Which are the key dimensions citizens use to judge success and failure in dealing with nuclear waste?
• Needs: Which information needs around nuclear waste do citizens articulate? How much and in which ways does the population want to be actively involved in decision-making processes concerned with nuclear waste management?
• Antecedents: Which variables explain inter-individual differences in citizens’ attitudes, emotions, knowledge beliefs and/or needs around nuclear waste management? How can changes in these variables contribute to normatively desirable levels of knowledge in the population?
• Consequences: What consequences do have certain attitudes, knowledge and needs for potential actions of citizens towards nuclear waste? How do these individual level actions affect other individuals and/or society as a whole?
• Institutional reactions: Which conclusions can be drawn from public opinion data on how regulators and operators of nuclear waste management should adapt their policies? Which implications derive for their communicative and participatory practices?
• Conceptual: How does the relatively low issue salience of the topic in society affect the measurement of public opinion on nuclear waste on the individual level? Which degree of volatility in public opinion should be assumed? Which implications do both may have for conclusions drawn from public opinion data?
• Methodological challenges: How can be ensured that survey data remains representative for the population in times of decreasing response rates? Which actions can be taken to increase the validity of measurements of public opinion in society? How can computational methods contribute to better understand public opinion derived from digital trace data? Which new pathways exists to increase the comparability of studies across contexts, regions, and countries?
• Desiderata: What are the most important blind spots in recent public opinion research on nuclear waste? Which topics are overlooked that may are relevant to better understand public opinion on the topic, its antecedents or consequences?

Contributions are welcome that employ quantitative methods of the social sciences such as:
• Surveys
• Lab, survey, or field experiments
• Quantitative text analyses
• Network analyses
• Observational studies

Site selection procedures for deep geological repositories (DGRs) that aim to find the site with the best possible safety, out of a set of possible sites, will face one challenge: To compare the safety of two sites. While at the beginning of the selection process, it may be possible to reduce the number of sites by means of indicators that map geoscientific parameters against some agreed indicator standard, sooner or later, when the number of potentially best possible sites becomes smaller, safety needs to be compared between two (or more) sites.

This session solicits oral presentations by (safety) scientists whose research contributes to the challenge of determining the safer site of two.

The session goals:

To provide a platform for scientific exchange in this field, which has not experienced abundant scientific exchange so far.

To raise awareness in the wider community for the challenge under focus in this session.

To discuss the opportunities for increasing the efficiency of site selection procedures by addressing the issue early.

Events and processes due to climatic developments are relevant for assessing the safety of a repository for nuclear waste including operational safety of e.g. surface installations and long-term safety of a deep geological repository (DGR). Short-term events, such as floods or storms, may impact transport infrastructure and surface installations. Long-term processes, such as glacial erosion, subglacial valley formation or permafrost thawing/freezing as results of certain climate states modify the setting of the overburden and can potentially even impact the geological barrier of a DGR. The investigation of the impact of such events and processes on the safe containment of the radioactive waste when describing the safety case is paramount and ongoing in the international context but still challenging due to uncertainties regarding the future climate evolution. Nevertheless, such future climate scenarios are required as part of the FEP analysis (Features, Events and Processes) for estimating the performance of a repository. Research is also being undertaken to better understand the influence of recent (anthropogenic) climate change on the long-term evolution of expected climate patterns as a basis for estimating future climate scenarios and their impact on repository safety.
This session shall combine a broad array of presentations on the effects of climate events and processes of relevance to the safety of radioactive waste management on all relevant timescales – from operational safety to long-term safety, for all waste types, and for all disposal concepts. Theoretical and experimental or field based works are equally welcome in this session.

The second European Programme on Radioactive Waste Management EURAD-2 has been launched in October 2024. Under the umbrella of this international cooperation in the field of RWM, more than 100 organisation from 52 countries conduct ten R&D projects, a valuable range of Knowledge Management activities and six Strategic Studies.
For the symposium the outcomes of EURAD-2 would be very valuable with respect to the scientifically excellent works and further development of the state of the art throughout all phases of a RWM programme and covering the broad scope of our EURAD-2 roadmap. All this within a unique international cooperative framework bringing together the different key actors and stakeholder in the field of RWM plus civil societal representatives. Whereas the R&D and KM activities have a duration of five years, all Strategic Studies will be finished after two years by september 2026. One year in future all StS will already have produced relevant and interesting results within their gap analyses, white or green papers.
It is proposed to have a few detailed talks from interested and selected work packages, supplemented by an overview talk about the rest of the EURAD-2 strategic studies, e.g.
1. EURAD-2 – programme overview and mission of the conducted strategic studies
2. Presentation of objectives and results/recommendations from WP FORSAFF (Waste management for SMRs and future fuels), WP CLIMATE (Impact of climate change on nuclear waste management), WP DITUSC (Development and Improvement of Quality Assured Thermodynamic Understanding for use in Nuclear Waste Disposal Safety Case)
3. WP ASTRA (Alternative RWM strategies)
4. WP DITOCO2030 (Next generation Digital Twins to support Optimisation, Construction and Operation of surface and subsurface radioactive waste management facilities)
5. WP OPTI (HLW repository optimisation including closure)

As siting processes for large-scale infrastructures move further along the timeline, the relevance of potential siting regions increases as it becomes clearer where they could be located. As potential locations for large-scale infrastructures, regions consequently take on a central role in the process. This session thus explores the nexus of regions and the siting of large-scale infrastructures such as final repositories for nuclear waste, power plants, dams, and other examples.

We invite contributions from the social sciences, humanities and related fields on this topic. Contributions that do not only address the siting of nuclear waste but that take a broader view and/or address comparable siting processes are explicitly welcomed. They can tackle the following four broad themes but are not limited to them:

• Regional Development: Large-scale infrastructures often bring economic benefits to regions, but at the same time also impose burdens like pollution, noise, and environmental changes. National governments and private corporations alike often attempt to address such issues through compensations with the goal of regional development. How can sustainable and successful regional development be achieved? What is the long-term impact of such interventions? How can ‘development’ be conceptualized and how could this differ between regions?

• Regional Discourses and Attitudes: Siting processes may prove controversial on the regional level. Diverging local interests can culminate around the topic. Understanding regional discourses and attitudes is thus essential for the overall siting process. This raises questions on how different regional actors perceive and evaluate issues, what might influence them but also how the regional, national, and even international level interact.

• Regional Participation: Siting decisions in democracies are nowadays almost always accompanied by formal and informal regional participation. The prospect of large-scale infrastructures close to one’s home presents a particularly pressing issue for many citizens and other local stakeholders. Here, participation can take on many forms, where major and minor design decisions sometimes greatly influence the results of deliberative and consultative procedures. This can for instance include the choice of instrument (mini-publics, “Planzellen”, conferences…), decision making power, eligibility, or agenda-setting. At the same time, involving marginalized groups remains a challenge.

• Relevance of Time: Large-scale siting processes such as the search for a final repository for nuclear waste often cover large timeframes. This comes with several challenges: How can participation be fostered and sustained over several decades? What is the role of changing regional identities, socio-economic factors, and perception of time scales?

A sudden focus on national energy independency following intensifying climate change mitigation efforts, geopolitical conflicts and reported breakthroughs in nuclear fusion seem to point in the direction of a nuclear renaissance. The state and corporate interest in so-called small modular reactors (SMRs) is reaching new peaks, and old promises of nuclear technology are being revived. Nuclear power is routinely portrayed as the source of limitless amounts of clean energy and as the stable source of carbon-free electricity. The rhetorical move from speaking about ‘renewable energy’ to ‘fossil-free energy’ is increasingly evident.

Amidst this prospective renaissance, the task of managing the radioactive leftovers from nuclear energy production becomes more pronounced. Whilst the immediate storage of highly radioactive matter has been in place for decades, the question of long-term storage has caused intense political debates and numerous cancelled construction projects. Not least are debates around how best to communicate memory of these nuclear waste leftovers thousands of years into the future.

In this session we gather research engaging critically with practices of this seeming nuclear renaissance. We invite papers engaging with topics including, but not limited to, the following:
- Critical readings of nuclear renaissance practices in historical and/or national contexts.
- Theorizations of nuclear energy cultures relating to nuclear matter, agencies, and powers.
- Archival and memory research into atomic heritage.
- Engagements with the institutional management and/or legitimization of nuclear power and/or weapons programs.
- Deep future and future studies engagements with the nuclear.

High-level and long-lived radioactive waste, referred to as nuclear waste (NW), are best disposed of in deep geological repositories (DGRs). A DGR is a multi-barrier system of engineered and natural barriers (NB) designed to ensure long-term isolation of NW from the biosphere. NB includes host rocks and, depending on regulations, may encompass surrounding geological formations.
An essential aspect of DGR development is site selection, where the geological characteristics of the NB and hydrogeological conditions of the site must support effective waste isolation. Timely implementation of DGRs is crucial due to the high current radioactivity of NW and the associated risks of above-ground storage, which is vulnerable to geopolitical threats and climate change impacts.
National programs gather geological information for designing and constructing safe DGRs, informing decisions at each stage, including concept choices, site selection, licensing, waste emplacement, and closure. However, the technical designs, regulatory frameworks, evaluation, and safety criteria are still evolving and vary by country. Additionally, each stage must be transparent and understandable to the public, making social acceptance and public involvement vital.
We seek contributions that address:
• The integration of timing as a safety factor in DGR projects, considering the current high radioactivity of NW and the risks associated with above-ground storage.
• Lessons learned from NW disposal projects, focusing on issues and solutions related to DGR site characterization and selection, with an emphasis on timely implementation.
• The strong link between safety in NW disposal and geoscience fundamentals, and insights from other geoscience applications (e.g., geothermal energy extraction, geological carbon sequestration) relevant to NW disposal.
• National and transnational public outreach, involvement programs, siting approaches, and regulatory frameworks, highlighting how these contribute to timely and safe NW disposal.
This session aims to:
• Promote the exchange of information on disposal concepts, site characterization, and the integration of timely implementation into safety evaluations.
• Provide key references on different national disposal programs, valuable for geoscientists, engineers, regulatory bodies, and NGOs involved in NW management. It will also be of interest to the public and decision-makers seeking an overview of advances in R&D related to DGR site characterization, selection, and timely implementation.

Final disposal containers for HLW like spent nuclear fuel and vitrified high-level waste from reprocessing are a crucial component both for the handling and emplacement of the waste and (depending on the safety concept) as a barrier for ensuring post-closure safety of the repository. As the inventory, geology and safety concept differs from country to country, various types of containers are being developed worldwide.

The session should provide insights to national and international developments in e. g., container design, material selection, safety and design requirements, both from the regulator’s and the implementer’s perspective, on the way to long-term safe HLW repositories worldwide.

Potential contributions:
- Presentations about research projects related to HLW final disposal containers in Germany, e.g. by BASE, BAM, BGE, GNS
- Presentations about international container concepts (e. g. from Switzerland, Sweden, Czech, EURAD-2 InCoManD)

This session is aimed towards different aspects of permeability, including its laboratory and in situ measurement and its critical upscaling required for modeling geological systems. We welcome keen laboratory and in-situ researchers as well as numerical modelers to discuss the challenges in and relevance of permeability assessment, regardless of the type of host rock or barrier material.

Key Laboratory Topics:
• Challenges in Measuring Low Permeability: Explore the pitfalls of measuring the lowest permeability values and how to overcome them.
• Unverified Method Comparability and Round-Robin Tests: Discuss the variability across measurement techniques and how collaborative round-robin testing can pave the way for greater comparability.
• Standardization Procedures for Site Selection: Debate the feasibility of developing standard procedures for permeability measurements, which are crucial for reliable evaluation and eventual site selection.
In Situ Measurement Topics:
• Distinguishing Flow Processes Across Scales: How to measure, distinguish and map fracture and matrix flow?
• Spatial and Volumetric Extrapolation: Discuss how to extrapolate localized permeability measurements to larger, reservoir or disposal-site scales, ensuring representativeness and reliability in assessments.
Numerical Modeling Topics:
• Upscaling Micro-Scale Processes: Delve into how small-scale measurements can be scaled to accurately represent larger geological systems.
• Fracture Networks to Equivalent Porous Media: Examine methods to modify discrete fracture networks into equivalent porous media to support the development of large-scale, realistic digital twins of geological systems.
• Future developments of barriers and geosphere: How to deal with changes of porosity due to mechanical load or precipitation of secondary phases, how (un)certain is pore-clogging?

The session will also provide room to discuss two-phase flow, relative permeability and the material dependency of environmental controls, which might dynamically change throughout the long-term evolution of a repository.