Nuclear decommissioning has often been overlooked in past literature but will gain relevance in future research as more and more NPPs reach the ends of their respective lifetimes.

Countries whose commercial reactors are currently undergoing decommissioning span a wide spectrum in terms of organization, regulation, financial provisions, and production of decommissioning services. This leads to most countries approaching decommissioning differently (to some extent), and poses questions of financial security and liability. Further, in this still relatively nascent industry, information on best practice approaches from a technical but also an organization perspective remains limited - as world-wide only a hand full of reactors have so far been fully decommissioned.

Additionally, due to unpredictability, lack of experience, and the long-term nature of operations, costs of nuclear decommissioning are seldom priced into economic analyses.

This session will attempt to shed light on some of these issues regarding decommissioning. Possible presentations could focus on various organization models in different countries, present more accurate cost data as is currently available in literature and provide insight into challenges faced by regulators.

This session offers the possibility to present talks and posters concerning all aspects of decommissioning and waste minimization not covered by session S1.

In this session, current studies regarding interim storage, conditioning as well as transport can be presented in general and will be discussed.

Presentations on the following topics could be submitted here:

• Modelling/presentation of the last ice ages as well as their future prognosis; how valid and meaningful is the view into the future?
• Current developments in permafrost areas (on land and under marine conditions); can these also play a future role in D?
• Threats due to sea-level rise, etc.

In repository concepts based primarily on engineered and geotechnical barriers, it must be ensured that the radioactive materials are contained and isolated within these barriers over the envisaged reference period. Corrosion from the outside and from the inside of a canister is an aspect that significantly influences the safety functions and the safety analyses in any repository concept and must be evaluated in a resilient manner over a very long period of time depending on national regulations.

The corrosion of the container and the processes at the external and internal interfaces must be well understood for integrating them in safety analyses. Modeling and evaluating the long-term stability of casing or canister materials is further part of the safety case.

Topics that can be discussed (non-exhaustive list) in this session include treatment of corrosion issues in national disposal programs, the corrosion behavior of disposal canister materials and its long-term consequences, microbial issues, in-situ experiments versus laboratory scale corrosion rate determination, material quality aspects and modeling on long time scales.

Criteria-driven site selection requires geoscientific data in a variety of geological situations. Which data sets are the most relevant? How can they be collected efficiently and reliably?

We want to discuss strategies and methods for the different host rock situations from data collection to integration into site descriptive models.

The use of the underground for a safe and permanent disposal of radioactive waste requires not only detailed knowledge of the host rock but also of the surrounding rock. This includes the structural setting, lateral variations in petrophysical rock properties as well as the impact of faults in the vicinity of the repository. All these factors play an important role not only for the site selection process and the construction phase of the repository, but also for its long-term safety.

The characterisation of the regional geological structures and the rock properties must be carried out in a timely and coordinated manner. Exploration of the subsurface by geophysical methods (in particular 3D seismic surveys), geophysical borehole measurements (e.g. present day stress state), determination of rock parameters based on cores, among others, are required.

All these methods provide the data base for a robust subsurface model which can estimate, for example the current stress state. Based on such models, the necessary safety assessments of the initial state of the repository can be carried out. In addition, the model results are valuable as initial conditions for forward simulations that can be used to investigate long-term safety scenarios addressing future tectonic deformation as well as exogenic processes like erosion and ice loading.

The aim of the session is to bring together researchers who are involved in the exploration of subsurface structures (seismology, structural geology, borehole geophysics), the determination of rock properties (petrophysics, rock mechanics), subsurface engineering (drilling technology), as well as the application of such data for geomechanical simulations.

Appropriate consideration and comprehensible assessment of uncertainties is a central aspect in conducting safety analyses for a geological repository for radioactive waste, including the preliminary safety analyses and their linkage with geoscientific considerations in the context of the German site selection procedure.

The large temporal and spatial scales of the systems investigated as well as their heterogeneity and the complexity of the safety-relevant thermal, hydraulic, mechanical and chemical (THMC) processes imply various sources of uncertainties. These result, for example, from the restricted ability to characterize the geological barrier and its future evolution under internal and external impacts as well as from inaccuracies and difficulties in measurements

Additionally, the analysis of complex repository systems requires the use of abstracting models, which introduces further uncertainties connected to the judgements and simplifications made by the modelers. This session provides the opportunity to present and discuss advances on the following and related topics concerning uncertainties in safety investigations:

• Characterization and quantification of uncertainties in the geology and geophysical rock properties,
• Methods for reduction of uncertainties, for example through optimization of data acquisition and sampling,
• Dealing with scenarios uncertainties, like future climate conditions and glacial cycles,
• Model based probabilistic methods for analysis of impact of uncertainties on repository safety related quantities,
• Methodological and regulatory issues,
• Uncertainties related to human factors, and
• Adequate communication of methods and results to various stakeholders (reviewers, scientists with different backgrounds, interested public).

The disposal of heat generating radioactive waste is a worldwide concern. While each country has different regulations and available host rocks, the meshing, modeling, and assessment of disposal scenarios is required for both regulatory and planning side of commissioning a radioactive waste repository.

As a result, numerical methods play a key role in the understanding and assessment of disposing of low- to high-level radioactive waste in deep geologic formations. As numerical methods continue to advance, so does our understanding of final disposal of waste.

The aim of this session is to discuss recent and continued advances in numerical methods including but not limited to analytical methods, visualization, simulator development/capabilities, and meshing techniques aimed at untangling the complexities of the thermal, hydrological, mechanical, chemical, and biological processes associated with radioactive waste disposal in porous and fractured materials from the meter- to km-scale.

High level and long-lived radioactive waste, here referred to as nuclear waste (NW), are best disposed of in deep geological repositories (DGR). A DGR is a multi-barrier system of engineered and natural barriers (NB) that ensure long-term isolation of NW from the biosphere. NB comprise the host rocks and, depending on regulations, may include the surrounding geological formations.

An important aspect in the development of DGR is the selection of a site where the geological characteristics of the NB and the hydrogeological conditions of the site allow waste isolation.

National programs are developed to gather the geological information needed to design and construct a safe DGR. This data will then be used for supporting decisions at each DGR stage, notably about concept choices, site selection, licensing procedures for construction, waste emplacement and closure of DGRs. Technical designs, regulatory frameworks, evaluation and safety criteria are still evolving and differ from country to country.

Additionally, every stage of the DGR procedure must be transparent and comprehensible for the public. Accordingly, social acceptance and public involvement strongly contribute to the complex process of DGR disposal.

A collection of measurements should be available before and while nuclear waste is conditioned and stored at all locations where this happens:

1) geothermic drills near the storage facility should detect increase in radiation,
2) earth quake detection should start long before the nuclear waste arrives,
3) air pollution should be part of the collection of environment conditions to be measured as well,
4) other indicative numbers for reliability??

All these values should be

A) permanently,
B) public,
C) high available (no downtime),
D) as long as nuclear waste is dangerous

As we have learned from the Ukraine war, nuclear installations are sensible objects under the threat of warfare. This session deals with all aspects concerned with the safety of nuclear waste installations subjected to armed conflicts.

Open session for all types of contributions within the topic framework of the topic, which are not covered by session S12.

Current narratives of nuclear waste disposal are strongly influenced by future visions of nuclear reactors in a country or a region. Thus, some SMR-concepts (“small modular reactors”) suggest a decreasing production of waste for storage, and some reactor concepts are designed specifically to “burn” spent fuel. This covers mainly non-light water-cooled reactor types, which have not yet been developed commercial but are supposed to play an important role in many future energy and climate scenarios (e.g. the Russian fast reactors).

The objective of this session is to bring together papers that assess the technical and economic feasibility of “new” reactor concepts, to explore international experience in the field, and to relate this discussion to the core topic of safe-ND, i.e. nuclear disposal practices. We will seek both technical papers, but also economic assessments of nuclear future. The objective will be to link these developments to narratives of the nuclear fuel challenge.

Disposal of radioactive waste in a deep geological repository is considered the preferred disposal option in most countries worldwide. An alternative disposal option is to modify the quantity and composition of the radioactive waste using reactors to enhance the safety of a repository.

Presentations in this session could be, but are not limited to, on the following topics:

• partitioning and transmutation;
• state of science and technology of reactor for waste management (e.g. Gen IV reactors and SMRs);
• impact of reactors on quantity and composition of nuclear waste;
• deployment scenarios focusing on nuclear waste management;
• state of science and technology of reprocessing and fuel fabrication technologies;

The disposal of radioactive waste in drilled boreholes has been in discussion for decades. Disposal has been applied for liquid wastes and spent sources in the past. Lately, it has re-entered discussion and developments have been made also for the disposal of highly active waste.

In this session, recent developments affecting long-term and operational safety and other open questions can be presented and discussed. This may include concepts, legal implications or detailed studies regarding (geo-)technical or natural barriers as well as implications for scenarios and FEPs or studies on THMCB processes.

What does the operator of a repository for highly radioactive waste plan for the near future in a repository site region? What happens in the decades until the first container is stored? What happens after the last container is stored?

These are questions that have occupied the interested public in Germany since the announcement of the potentially suitable subareas in 2020. Demanding timeframes raise fears, on the one hand, that not enough care will be taken. On the other hand, the idea that there is no alternative and that nuclear waste disposal is characterized by major path dependencies is often heard.

This session will address the question of how, between constraints and pragmatic narrowing, "thinking in alternatives" (Grunwald 2019) can help lead to a site selection process and subsequent operation of a deep repository.

Strategically, it is a matter of linking conceptual frameworks with narratives and ideas about the future that seem possible and plausible today. If this succeeds, it opens up the possibility of breaking away from simplified notions of circumstantial linearity and opening up spaces for reflection that promote thinking about expectable futures. Possibilities of acting on the basis of convincing arguments, as favored in technology assessment, provide opportunities to further develop the necessary long-term governance (Kuppler / Hocke 2019, Böschen et al. 2021) in the technology conflict over nuclear waste disposal in Germany.

The idea is to develop a resilient process that meets the requirements of safety and a learning process with substantial public participation (Smeddinck et al. 2022). According to initial agreements, the presentations are proposed in such a way that they can come from the transdisciplinary work package "Capacity to act and flexibility in a reversible process" of the research network TRANSENS (Transdisciplinary Research on the Management of High-Level Radioactive Waste in Germany; www.Transens.de) as well as from relevant research teams outside the network.

We propose a session with two of our project colleagues giving talks on our recent efforts to address a range of uncertainties within the theme of nuclear waste management. Additionally, we welcome three talks external to our group on the same topic. Transporting the message of scientific uncertainty to a general audience is delicate, because lay people usually lack the conceptual portfolio to capture uncertainties (e.g. quantification). Moreover, uncertainties can lead to mistrust and may be misused to inhibit or delay radioactive waste management. The public approaches the topic more intuitively and draws on experiential knowledge, prior attitudes and trust as heuristics.

Moreover, individuals differ in their conception of ‘science’ and valid scientific knowledge. Some acknowledge the stepwise process in science and the lack of certainty in various questions. Others expect that one must be sure of “facts” before decisions are made. However, we argue that decisions must be drawn from uncertain knowledge; otherwise, we will never meet the objective to dispose of high-level nuclear waste.

In one talk, we report results of an experimental study that investigated preferences for and trust in different visualizations of simulation results and tested different forms of communication (verbal, numeric, visual). The most salient result is that across all experimental conditions the attitude towards a deep ground repository for high-level nuclear waste is the decisive parameter.

A second talk deals with uncertainties and their communication concerning the deep disposal projects in Germany for low- and intermediate radioactive waste. It focuses on the lessons learned to help with the communication of uncertainties related to the repository for high-level radioactive waste, which has yet to be planned.

The session will include presentations on new insights concerning material properties of information carriers and considerations on Nuclear Cultural Heritage in general. It might also include a presentation on nuclear semiotics.

In this session, current studies regarding participation processes for projects involving nuclear safety and disposal can be presented in general and discussed.

Law is both catalyst and drive for safety. Different countries apply different legal approaches to safety. The goal of this session is to gain an overview on safety-related provisions and definitions in several countries and through a comparison provide some lessons-learnt that are useful for further enhancing safety related policy.

In this session, current studies about the historical research regarding nuclear waste management in general will be discussed. The topics should focus on learning from the past.

Deep geological repositories of nuclear waste are an intricate and contentious policy field with an impact up to a million years. This contribution aims to explore how society and technology can set up and implement sustainable ways – in the long run – to cope with the issue. It also requires long-term, decades long, institutional involvement of the technoscientific community, waste producers, public administrators, non-governmental organizations, and the public.

The demonstration of long-term safety is challenging and monitoring may contribute to substantiate evidence, support decision making and legitimize the programs. What, where and when to monitor is determined by its goal setting: It may be operational, confirmatory (in the near field) or environmental (far field).

As it is “difficult to make predictions, especially about the future” (Danish saying) , this contribution, too, does not pretend to present the silver bullet, but Strategic Monitoring as proposed contributes to process, implementation or policy and institutional surveillance to sustain a once launched program. It addresses not only the controversial long-lasting “problem” (of nuclear waste) but investigates some ways to approach for “solutions” or solution spaces, not just technical but also institutional and personal, and this for the long term. It includes the tailored transfer of knowledge, concept and system understanding, experience and documentation to various audiences above. It is an integrative tool of targeted yet adaptive management and may be applicable to other long-term sociotechnical fields.

We propose a workshop in two parts (each approx. 90 min) to discuss

1. general dilemmas due to the long time range until an operable solution for the waste problem is found and
2. the pressure put on communities hosting interim storage sites.

In a first part, we highlight the twofold responsibility concerning the current generation’s decision-making in perspective of living and coming generations. According to own survey data and debate with citizens, we see the need to discuss the relative relevance of directly affected generations during the next decades (until the repository’s closure, which affects about four to five generations) compared to justice for generations (five plus) in the following decades and centuries.

In the second part we explore the consequences of the delayed final storage in Germany upon the current interim storage sites. Following dialogs with citizens (in Brokdorf, Oct. 2022 and in Lubmin Mar. /Apr. 2023) we investigate trade-offs between guaranteeing the safety in these sites and developing and implementing new concepts for long-term storage at these or new sites before beginning with final storage.

In terms of safety and fairness, invasive monitoring of casks or storage in a new centralized interim repository would be welcomed by some. However, both possible measures stay in conflict with long-term practices (e.g. approving licenses for several decades or the long-term planning for the final repository). Important questions arise:

• How much time may current generations take to identify the most suitable site?
• How can addressing all three time horizons specified in the Site Selection Act help to contextualize delays in the initial steps?
• What are the risks and chances associated with delayed deep geological disposal (economic, social, political, etc.)?
• To what extent may intragenerational (current generations) justice discount for generations in the far future?
• How can the prolongation of interim storage be justified?

The geoscientific discourse shall use examples or scenarios from the international environment to highlight any given possibilities for prognosis; at best, it shall name aspects of delay in the procedure, and shed light on repository-related research. The aim of ensuring that the geogenic conditions in the repository-relevant underground guarantee safety for the radioactive waste and, consequently, for the biosphere and society, is to be presented and discussed from an international perspective. Geoscience-related strands of arguments that seem plausible for independent research as well as operators and supervision, in particular, should be subject to critical scrutiny.

When stresses yield a critical value, rock breaks or pre-existing faults are reactivated generating pathways for fluid migration. Thus, the stress state is a key parameter to assess the stability of deep geological repositories. The prediction of the 3D stress state is achieved with 3D geomechanical models based on the prediction of the 3D structure and distribution of rock properties. Furthermore, point-wise measurements of the stress state are needed to fit the model to these data.

In this workshop we present a range of methods that determine individual components of the stress state in the Earth’s crust. As example, we will use borehole image logs to identify borehole breakouts and drilling induced tensile fractures at the borehole wall. These are used to derive the orientation of the minimum and maximum horizontal stress. Furthermore, we will present methods for the estimation of stress magnitudes. These are essential data for the calibration of a 3D geomechanical model. We will give a brief overview on different methods and then focus on the analysis of mini-hydraulic fracture tests as well as on the sleeve fracturing and sleeve re-opening method. The combination of these are the only robust methods in a borehole to derive ranges of the magnitudes of the minimum and maximum horizontal stress.

Finally, we will show the usage of the estimated data for the prediction of the stress state in the subsurface. In particular, we will present and discuss the uncertainties of the results itself. As a major challenge, the uncertainty that results from the assumption that a data point taken from less than a cubic meter is a good representation for a large rock volume, i.e. a whole lithological layer, is addressed. We will show first results of a comprehensive borehole campaign in northern Switzerland where the location of the deep geological repository in Nördlich Lägern is proposed.

The primary goal of the management of radioactive waste is safety. On the disposal path leading to a repository for radioactive waste, Safety Cases for disposal facilities have an important function as a basis for management-related, licensing, and political decisions. In the German site selection process, the preliminary safety analyses play a central role: they have to inform siting decisions at three important steps of the process.

Many stakeholders therefore have high expectations of these safety assessments. Past experience suggests that their expectations are not always met by the current Safety Cases, which have grown historically and therefore follow internationally established conventions, are extensive, complex and difficult to comprehend.

Transdisciplinary research has the potential to provide the implementer BGE, the regulator BASE and other actors in waste management with valuable information for the design and review of safety analyses that better meet the expectations of different stakeholders and actors. It provides new impulses, opens up other perspectives on questions concerning the Safety Case and introduces novel proposals for solutions. In this way, it contributes to robust safety assessments and a resilient safety of repositories for radioactive waste.

On the basis of tangible results from the research project TRANSENS (Transdisciplinary Research on the management of high-level radioactive waste in Germany), we want to discuss how the Safety Case can be optimized in a transdisciplinary way.

At the same time, we will introduce and try out transdisciplinary tools and formats. The workshop offers the opportunity to exchange ideas on topics such as the design of a digital Safety Case, extensions of the FEP catalogue or the benefits of extended peer communities, as well as to experience transdisciplinary research first-hand.

Radionuclide mobility in a nuclear waste repository is strongly influenced by their chemical form (oxidation state, speciation), determining their solubility and chemical interactions with mineral surfaces. To date, significant efforts have been made to investigate mechanisms (e. g. sorption, diffusion) underlying radionuclide retention. However, knowledge gaps persist, especially under complex environmental conditions as may be expected in a deep geological repository (e.g. complexation of radionuclides with organic compounds, influence of elevated temperature, the effects of high ionic strength, etc.). In order to make reliable predictions about radionuclide mobility, and consequently about post-closure repository safety, it is necessary to identify, evaluate and, where necessary, close these knowledge gaps.

This workshop aims to bring together experts in both fundamental research and its applications to repository safety. It intends to facilitate knowledge exchange between the two fields, promoting a more coordinated and goal-oriented repository safety research. Participants are invited to share their knowledge about the need for further experimental and computational investigations on one hand and the data requirements for reliable transport models and implications for safety assessment on the other hand.

Draft for agenda:

I. Introduction

II. Impulse presentations (each 10+5 min.):
1) Fundamental research on radionuclide chemistry, solubility, complexation and sorption using wet chemistry, spectroscopy and modelling (invited speaker)
2) Safety assessment for nuclear waste repositories – selection of input parameters (invited speaker)

III. Discussion (each topic 20 min.)
1) Topic 1: Identification, evaluation and prioritization of knowledge gaps relevant for repository safety concerning radionuclide mobility
2) Topic 2: Interplay between fundamental research and application – how to enhance interconnectivity IV. Wrap-up

Interim storage of high-level radioactive waste will in several countries take much longer than the originally planned few decades. Does the extended timeline of interim storage significantly change the input parameters for final disposal? Does this affect the long-term safety of deep geological repositories? Are there aspects that could previously be neglected but need to be re-evaluated in order to not negatively affect planning and implementation of geological storage?

In this session we want to link discussions regarding extended interim storage to the long-term safety in geological depositories. Aspects of the discussion could be: Does the embrittlement of the fuel cladding lead to difficulties in transportation and conditioning of the inventory? Could the decreasing thermal power of the inventory lead to temperatures at the time of backfilling and closure of the final disposal site that will negatively affect safety relevant aspects, e.g. salt creep and compaction? We are looking forward to a multi-faceted, interdisciplinary discussion that may go well beyond the given examples.

This workshop is intended to provide an opportunity to present, share and learn from each other by selected GIS and web applications related to the site selection process (StandAV) in germany. In this context, BASE would also like to present and discuss selected own applications for its tasks in the site selection procedure. SafeND would be a good opportunity to present this application to a broader audience and to discuss opportunities and challenges of GIS and web applications. Who can be reached, who will not be reached?

Uranium mining is the very start of the nuclear fuel chain. In spite of this, it is the most neglected part of the entire chain, especially when considering sustainability and environmental protection. This workshop addresses this gap and links the lessons we can learn from uranium mining to nuclear waste disposal.

Uranium mining is a safety challenge from the first day a mine is in operation to the last day of land rehabilitation. Environmental and health issues are at stake during the entire lifetime of a mine. The remnants of the mining activities can be regarded as long-term liabilities, which must be monitored for many generations. Uranium mines are often contentious for the local population, specifically indigenous people. Their right of participation in the decision-making processes is often not given justice by mining companies and governmental authorities.

Participation, however, is crucial both for positive societal outcomes, such as development and low conflict levels, as well as for building of trust. This is also true for the quest for nuclear waste disposal sites. Based on insights from processes of uranium extraction we can draw conclusions for the site selection process of a final repository, specifically regarding licensing, operation and land rehabilitation processes. So, it is worth having a detailed look at the beginning of the nuclear fuel chain, as one moves forward to resolve the issues upcoming during nuclear waste disposal.

Safety and participation issues will be in the focus of this session. It will gather academics and practitioners from different fields in a transdisciplinary setting. Short inputs will introduce topics, followed by a structured discussion. The workshop is complemented by a post-conference field trip to Wismut facilities. This workshop will improve the transdisciplinary capabilities of the participants and will provide opportunities for exchange and networking.

The site selection act (StandAG) defines the selection of a repository as a learning process ("lernenden Verfahren") in § 1. Learning is also an essential aspect of transdisciplinary (td) research projects, besides capacity and network building as well as situation improvement. Learning can take place during all phases of the research process and at all levels (i.e., from the individual to the institution). However, how and what is learned is specific to the project context and topic (e.g. agriculture, urban planning, renewable energies).

TRANSENS is one of the few td-research projects internationally in the field of nuclear waste management. Therefore, we would like to identify the specific (learning) effects of stakeholder integration (e.g., public, practitioners) in the field of nuclear waste disposal. In an interactive workshop we will - taking into account the perspectives of citizens, practitioners and scientists - explore the following questions:

• What are the learning experiences of the td-approach in and around TRANSENS (i.e. of scientists and td-partners) so far?
• Which learning experiences are specific to nuclear waste management?
• Which learning experiences and insights can be transferred from TRANSENS to the site selection process in Germany and neighboring countries?

From the interaction we expect the identification of key experiences and their specific relevance for the nuclear waste management.

Germany is looking for a repository for high-level radioactive waste. This is a task for society as a whole, which requires a broad participation process and, above all, a scientific basis. The process is still at the beginning, but as the possible siting regions are being narrowed down, public attention will increase significantly in the years to come. The complex and scientific process must be transparent, comprehensible and understandable for everyone: Science communication is an essential factor for success.

In the workshop, we will discuss the role of science communication in the repository search procedure. How can scientific content be communicated? What formats should be adapted for science communication? A game plan that depicts the phases and sequence of the procedure and presents the most important information of the scientific process will form the basis for the workshop.

In the format of a World Café, the participants will experience to which extent their science communication plays a role as an essential factor in the procedure: There will be two scenarios – a failure and a success story – which will be influence by science communication. The player will go through each step on the search for a repository and discuss their influence as the communicating scientist on the success of the search. How can people be influence by communication of risk topics, do they trust science?

Additionally, to the personal experience, scientific questions regarding needed information during the phases of the search will be generated in that format. How can science of science communication support the different steps of the search?

Citizen science and other transdisciplinary approaches become more important in environmental policy and within academia. Scientists benefit from citizens’ to generate more societally robust knowledge. In the contested theme of nuclear waste management (NWM) such approaches can be particularly valuable but also face challenges. Within our transdisciplinary research project (www.transens.de) we work jointly with 14 citizens (Citizen Working Group = CWG), who are interested in the topic without being activists or carrying a specific agenda.

The CWG helps us enrich the research process with experiential knowledge. In parallel to gaining scientific knowledge, trust can be build due to the close collaboration. However, the CWG becomes more ‘scientific’ over time and does no longer resemble the general public. Moreover, we established a local measurement lab at the city of Remlingen near the Asse II site. This lab is open to the local public for measuring environmental samples using techniques such as gamma spectroscopy. One aim is to enable citizens to measure their samples in a scientifically sound way.

In the workshop, we would like to discuss the benefits and challenges of such collaborations going beyond the aforementioned examples. Potential key question are:

• Is there a possibility for multiplication/upscaling of small-scale approaches?
• How to assure the quality of the citizens’ work (measurements) and interpretation of results?
• Participation and in particular co-determination leads to a certain responsibility for the outcome. Are the citizens aware of it and willing to assume it?
• To what extent is extended participation with empowerment for decision making still in line with representative democracy?

No safe Nuclear waste disposal without interdisciplinarity, both in research and in practice. On this there seems to be growing consensus. But how to build and foster ‘true’ interdisciplinary programs?

In this workshop we will explore what interdisciplinary knowledge means and how it is obtained. How to get people with divers disciplinary backgrounds to work together and develop insights across disciplinary borders? How can compatibility between different, discipline-dependent research, communication and publication cultures be achieved and how necessary is such compatibility? Is it realistic to strive for such full integration, or is multidisciplinarity (representing loosely coupled disciplinary insights and views) the more likely outcome of any such attempt?

For that purpose, we will invite beforehand a number of people with varying disciplinary backgrounds and experience in interdisciplinary research settings to provide short (preferably rather provocative) testimonies, on which the participants can further reflect in a series of guided round table discussions. These will be set-up in ‘world café’ style: one plenary room with several tables (or flip chart ‘corners’), small groups moving from one table to another discussing a specific issue. Depending on the timeslots available that could be 3x 20 minutes, 4x 15 minutes, or variations of that.

We’d like to focus the discussions around criteria, best practices, challenges and pitfalls when venturing into or evaluating interdisciplinary projects and programs. Insights from the discussion rounds will at the end be presented (and again discussed) in plenary, with the aim to come to suggestions for realistic expectations regarding interdisciplinary approaches, including identifying key elements for breaking down disciplinary boundaries.

The concept of planetary boundaries provides a framework in which the finiteness of the planet is translated into boundaries in which human activities can thrive and thus generate transformation pathways for sustainable development. The boundary of climate change requires a strong decarbonization with large investments in low-carbon technologies.

Nuclear power is often classified internationally as a "clean" technology because of its low-emission operation. However, although no greenhouse gas emissions are produced during nuclear fission, radioactive waste is produced instead and must be stored safely for extremely long periods of time to avoid contact with humans and the environment. Surprisingly, radioactive waste is underrepresented in the concept of planetary boundaries.

In 2015, the German Advisory Council on Global Change (WBGU) recommended to establish fissile material as a part of global guard rails (a similar concept to planetary boundaries) and to stop production of new fissile material by 2070 as a new Sustainable Development Goal (SDG). These recommendations have not yet found their way into the international scientific discourse. Previous to the workshop it is envisaged to prepare a paper that provide arguments and possible indicators necessary to integrate nuclear waste into the concept of planetary boundaries taking the approach of WBGU guard rails into account. This preliminary work serves as a basis for discussion for the workshop.

The aim of the workshop is to discuss the provided arguments for their suitability to meet the criteria to establish nuclear waste as a control variable of the planetary boundary called “novel entities”. Furthermore, it shall be discussed which one of the possible indicators to quantify a control variable of planetary boundaries and what challenges need to be addressed in future work.

This two-part panel focuses on approaches, concepts, methods, and technologies for safeguarding nuclear waste management. The first part discusses the current state and challenges in safeguarding spent fuel storage facilities, encapsulation plants and geological repositories and elaborates the recent progress of safeguards developments and implementation, as well as existing gaps. The second part then looks at future challenges of safeguarding nuclear waste management in the medium and long term and develops some priorities in order to meet these challenges.
Both parts will be held as panels of 60 min, including three inputs of 10 min each (all speakers TBC) and a facilitated discussion of 30 min.

Part I: Status, progress, and gaps (60 min)

1. Input Inspectorate; IAEA or Euratom: Which safeguards approaches are currently developed for or implemented at spent fuel storage facilities, encapsulation plants and geological repositories?
2. Input National Safeguards Authority; STUK or SSM: How to make best use of safeguards concepts, such as Safety-Security-Safeguards (3S), Safeguards-by-Design (SBD), etc. in nuclear waste management?
3. Input research entity; JRC, VTT, or Jülich: What are the most important R&D activities regarding safeguards methods and technologies in nuclear waste management (TRL 4-8)?

Part II: Future challenges and priorities (60 min)

1. Input Inspectorate; IAEA or Euratom: Which challenges are on the horizon regarding safeguards implementation at spent fuel storage facilities, encapsulation plants and geological repositories in the medium and long term?
2. Input Operator; Posiva or SKB: What are medium- and long-term challenges of safeguards implementation from the operator's point of view?
3. Input research entity; NN: Technology foresight: What are the most promising methods and technologies for safeguarding nuclear waste management in the medium- and long-term future (TRL 1-3)?

States and private industries are researching and developing reactor concepts that are not based on the current light or heavy water cooled reactor technology. One important aspect of these so called novel or advanced nuclear reactor designs, both large gigawatt types and small modular reactors, is their potential for radioactive waste management. The prospects for their development and industrial use also largely depend on possible improvements to reactor safety, on the proliferation resistance of the fuel cycle and on the economics of those reactor concepts. The panelists will discuss chances and impediments to the implementation and use of advanced reactor concepts and their fuel cycles and their use as an alternative disposal option. The discussion will be open for the audience to participate.

Panelist can be experts on

• Reactor based nuclear waste management
• Nuclear safety and security
• State of science and technology of advanced nuclear reactors (technology readiness level)
• Nuclear power economics

A resilient system at social level can be understood as one where society, at any point in time, takes responsibility for the repository system and acts to preserve the basic conditions for future generations to take responsible decisions. The idea of societal responsibility is included in the notion of oversight, which has become a crucial ingredient of ICRP’s system of radiological protection where geological disposal is concerned. Oversight, after closure, is described as “‘watchful care’ and refers to society ‘keeping an eye’ on the technical system and the actual implementation of plans and decisions” (ICRP-122).

The concept of oversight has been further developed by the NEA in the context of exploring strategies for the preservation of Records, Knowledge and Memory (RK&M) across generations, which is generally seen as a precondition for exercising oversight in the future. While societal decisions on how to organise and exercise post-closure oversight may be decades away, the discussion on RK&M preservation strategies has started. At a recent conference in Dessel, Belgium, organised by NEA’s Expert Group on Awareness Preservation (EGAP), new ideas and aspects were presented. The discussions revealed, however, that participants felt that a “common vision” in the community (meaning both international expert community and any interested parties) would be beneficial to help focus discussions on RK&M preservation strategies later on.

Different states - different approaches. While there are countries that - following their traditions - form laws as binding manual for the regulator, there is also the approach to grant freedom of decision up to a certain distinct and legally discuss decisions afterwards. How do the approaches look alike? What is their difference - and, most important, what is the common ground of law concerning nuclear waste management? The goal of this session is to gain an overview on legal approaches for the same challenges in several countries and to understand procedures in other jurisdictions.