bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional assessment of extreme sea levels and associated coastal flooding along the German Baltic Sea coast
Authors: Kiesel Joshua , Lorenz Marvin , König Marcel , Gräwe Ulf , Vafeidis Athanasios T.
Published: September 2023

Abstract. Among the Baltic Sea littoral states, Germany is anticipated to endure considerable damage as a result of increased coastal flooding due to sea-level rise (SLR). Consequently, there is a growing demand for flood risk assessments, particularly at regional scales, which will improve the understanding of the impacts of SLR and assist adaptation planning. Existing studies on coastal flooding along the German Baltic Sea coast either use state-of-the-art hydrodynamic models but cover only a small fraction of the study region or assess potential flood extents for the entire region but rely on global topographic data sources and apply the simplified bathtub approach. In addition, the validation of produced flood extents is often not provided. Here we apply a fully validated hydrodynamic modelling framework covering the German Baltic Sea coast that includes the height of natural and anthropogenic coastal protection structures in the study region. Using this modelling framework, we extrapolate spatially explicit 200-year return water levels, which align with the design standard of state embankments in the region, and simulate associated coastal flooding. Specifically, we explore (1) how flood extents may change until 2100 if dike heights are not upgraded, by applying two high-end SLR scenarios (1 and 1.5 m); (2) hotspots of coastal flooding; and (3) the use of SAR imagery for validating the simulated flood extents. Our results confirm that the German Baltic coast is exposed to coastal flooding, with flood extent varying between 217 and 1016 km2 for the 200-year event and a 200-year event with 1.5 m SLR, respectively. Most of the flooding occurs in the federal state of Mecklenburg-Western Pomerania, while extreme water levels are generally higher in Schleswig-Holstein. Our results emphasise the importance of current plans to update coastal protection schemes along the German Baltic Sea coast over the 21st century in order to prevent large-scale damage in the future.
Characterising a rock fracture rough surface using spatial continuity and kriging: a new approach to meshing coupled thermo–hydraulic–mechanical–chemical (THMC) models
Authors: Cunha Gonçalo B. , McDermott Christopher Ian
Published: September 2023

Abstract. Fluid flow through low permeability rocks is mainly accomplished through fractures. In order to model fluid flow, coupled thermo–hydraulic–mechanical–chemical (THMC) numerical models are used, which rely on fracture surface representations to construct a distribution model of the empty space (aperture) between the two fracture faces. The traditionally used statistical representations of fracture surfaces
often overlook spatial continuity (SC), i.e. how well correlated points are in direction and distance. Examples are the fractures' aperture distribution random sampling to the joint roughness coefficient. This may result in a poor representation of the aperture distribution and thus a poor model. The first aim of this study is to investigate the possibility of characterising a fracture surface roughness using its SC parameters, an upscaled fracture surface and ordinary kriging (OK) interpolation algorithm. This method provides better control over the aperture model creation, which will have implications for its complexity and computation times. The second aim is to utilise the SC information and the distribution of a fracture in order to extrapolate (i.e. blind predict) the distribution of the fracture where
no observations exist. A statistical analysis was performed in a greywacke
in order to acquire the parameters necessary to describe the SC of the
fracture surface topography. The surface was then interpolated using the OK
algorithm. These parameters and the surface distribution will be used to
inform the OK algorithm to extrapolate the fracture to where no data has yet
been acquired. A reasonable match between the kriged and original surfaces
has been achieved and the fit quantified by analysing the error between the
two and by R2, which offer positive measurements of methodological quality. The aperture can easily be calculated from the difference between both complementary surfaces. The aperture between the two original fracture surfaces versus the two kriged fracture surfaces was also quantified and compared, yielding good results. This method may provide a new alternative to current storing and computing solutions for fracture representation, especially in aperture distribution calculation for coupled THMC numerical models and simulations. To verify advances in accuracy and computing times for this method, results between models derived from the original versus kriging aperture data will have to be compared. Another potential applicability of the SC information is to know a priori from any modelling which directions are those of Darcy's flow and which are the directions of the highest and lowest dilation rates with shearing, which will have to be confirmed with future planned modelling work.
Feasibility studies of a continuum modelling approach using a ubiquitous-joint model in modelling fractured crystalline rock
Authors: Gafoor Ajmal , Müller Christian , Herold Philipp
Published: September 2023

Abstract. According to the Site Selection Act, crystalline rock – in addition to rock salt and claystone – is considered a potential host rock for the disposal of high-level radioactive waste in Germany. Crystalline rock formations are inherently anisotropic and heterogeneous due to the presence of discontinuities. Therefore, it is necessary to consider discontinuities in the modelling of rock behaviour. Different numerical approaches are available to stimulate the thermo-hydro-mechanical (THM) behaviour of the crystalline rock. On the one hand, DEM approaches allow high accuracy in the modelling of single and multiple fractures generally but offer low computational efficiency
the larger the models are. On the other hand, continuum-based approaches
provide high computational efficiency but less accuracy. There are also
different subtypes available in the literature. For example, the fracture
continuum approach can be used. We investigate the different approaches to identify the advantages and
limitations of each numerical approach in simulating mechanical deformation
processes in crystalline rock. To assess the integrity of the geological
barrier, the fluid pressure and dilatancy criteria are defined. The fluid
pressure criterion states that the expected fluid pressures do not exceed
the strength of the rock within the geological barrier. The dilatancy
criterion states that the induced mechanical stresses do not exceed the
strength of the rock within the geological barrier. The project proposes a
continuum modelling approach using a ubiquitous-joint model that enables the
modelling of the rock fractures in crystalline rock explicitly. In a first
step, preliminary studies were carried out on small-scale models such as
cylindrical specimens and plate-like specimens with deterministic single, parallel and two orthogonal fractures under uniaxial testing
conditions. The typical anisotropic compressive strength curves were
reproduced and compared with both analytical and observed results from
the literature. It can be shown that the influence of fracture orientations on
the strength properties of the rock can be captured well. In a second step,
the applicability of the model for large-scale analyses of anisotropic rock
masses is tested using predefined structural–geological information. The models considered for the large-scale analyses are a model with a borehole, a model with a tunnel and a model with an underground repository. The influence of fracture orientation on the large-scale models
and its impact on assessing the integrity of the geological barrier will be
investigated in the context of the safe disposal of high-level radioactive
waste in crystalline rock. The numerical approach and preliminary results of
the numerical tests will be presented in the planned poster presentation.
Reactive transport modeling for assessing coupled hydrogeochemical processes at interfaces in deep geological repositories: from the laboratory to the real world
Authors: Poonoosamy Jenna , Lönartz Mara I. , Yang Yuankai , Deissmann Guido , Kosakowski Georg , Bosbach Dirk
Published: September 2023

Abstract. Deep geological repositories with a multi-barrier concept are foreseen by various countries for the disposal of high-level radioactive waste. Simulation tools for a close-to-reality description of repository evolution scenarios are required, especially to resolve the challenging task of comparing and assessing the long-term safety of different repository concepts in different host rocks within the German site-selection process.
Chemical, thermal, and pressure gradients at the interfaces of the different barriers in a repository can lead to mineral dissolution and precipitation, generating non-linear responses in transport and mechanical properties of barrier materials and host rocks. Reactive transport modeling (RTM) can be applied to investigate these perturbations and processes across temporal and spatial scales to assess subsurface evolution. Nevertheless, implementing RTM at the continuum scale while accounting for pore-scale heterogeneities and geometry evolution remains a challenge. Pore-scale simulations offer the potential to capture the complex evolution of porous media over a broad range of Peclet and Damköhler numbers, and they can be utilized to improve the RTM by using upscaling methods (Prasianakis et al., 2020). In this context, we developed “lab-on-a-chip” experiments, combining time-lapse high-resolution optical microscopy and confocal Raman spectroscopy to test extended constitutive equations to classically employed Archie's law to improve the description of changes in transport properties (e.g., diffusivity) in evolving porous media in RTM. The 3D Raman tomography of the porous media combined with pore-scale modeling enabled the derivation of upscaled transport parameters. Our results highlight the importance of calibrating pore-scale models with quantitative experiments prior to simulations over a wide range of Peclet and Damköhler numbers, whose results can be further used for the derivation of upscaled modeling parameters. The derived and parameterized constitutive equations based on simple systems have been tested in reactive transport models as a sensitivity case study to evaluate uncertainties in the predictions of the evolution of real subsurface systems such as clay–cement interfaces in deep geological repositories.
Performance assessment of a generic repository in salt host rock based on Task F of DECOVALEX-2023 – BASE's lessons learnt and future work
Authors: Pekala Marek , Dietl Carl Rudolf , Magri Fabiano , Kock Ingo
Published: September 2023

Abstract. The evaluation of coupled effects of mechanical deformation, fluid and gas
flow, thermal loading, and chemical reactions is an important element of the
performance and safety assessment of disposal systems for high-level
radioactive waste and spent nuclear fuel in deep geological formations.
Early investigations showed that to be able to conduct such an evaluation
there was a need to enhance process understanding and to develop models
capable of simulating coupled thermal–hydro–chemical–mechanical processes
over relevant timescales and spatial scales. Recognising these challenges and
needs, the DECOVALEX (DEvelopment of COupled models and their VALidation
against Experiments) (https://decovalex.org, last access: 24 July 2023) was initiated in
1992 as an international cooperative project of nuclear waste organisations.
BASE is one of the funding organisations for the current phase of
DECOVALEX-2023 (running from 2020 to 2023) and actively contributes to Task F of the project (https://www.base.bund.de/DE/themen/fa/soa/projekte-aktuell/projekte-aktuell_node.html, last access: 24 July 2023, – “Beteiligung an der internationalen Forschungskooperation
DECOVALEX”). Task F (https://www.decovalex.org/D-2023/task-f.html, last access: 24 July 2023) of
DECOVALEX seeks to build confidence in the models, methods, and software
used for performance assessment of deep geologic repositories and to
highlight additional research and development needed to improve performance
assessment methodologies. The task focuses on two illustrative disposal
concepts for spent nuclear fuel: a generic repository in a fractured
crystalline host rock and a generic repository in a salt formation. For each
of the disposal concepts a reference case is defined that includes a set of
conceptual models and parameters describing features, events, and processes
that impact repository performance. Modelling teams work independently and
are responsible for determining how best to implement and couple the models.
Each team develops its own model(s), calculates agreed performance indicator
values, and performs uncertainty and sensitivity analysis. The comparison of
model results is conducted in stages, commencing with a comparison of key
outputs of individual process models, followed by a comparison of a single
deterministic simulation of the full reference case, and proceeding to
uncertainty and sensitivity analysis. The present contribution describes recent BASE activities within Task F
Salt of DECOVALEX-2023. Lessons learnt are discussed and possible future
steps are presented.
Mitigating uncertainty in the site selection process for a German deep geological repository through a risk-based and multi-criteria decision-making approach
Authors: El Fatihi Hajar , Fischer-Appelt Klaus , Charlier Frank
Published: September 2023

Abstract. The site selection for final disposal of high-level
radioactive waste is a complex process that requires careful considerations.
In Germany, the site selection procedure for a deep geological repository
occurs in multiple phases. Step one phase one involves the identification of
90 subareas of interest. In step two phase one, sub-regions are
selected for surface exploration. Consequently, several dilemmas arise, such as the necessity to screen through a considerable number of
subareas with large surfaces to select sub-regions that are most adequate
for further investigation. The associated subsurface uncertainty and
the high exploration and operational costs create an additional challenge
when planning such a campaign. To address these challenges, we propose a method of sub-region
prioritization that combines favourability indexes developed using host-rock
and subarea-specific criteria with the probability of success and risk of
failure estimates. This method considers not only geological factors but
also the heterogeneous nature of subsurface data quality and quantity. This
heterogeneity leads to uncertainties that may overshadow the advantages of
specific sub-regions at the expense of others. The method focusses only on
the geological barriers of the repository system: the containment providing the
rock zone, the surrounding host rock, and the overburden. The geological
barriers are dealt with as a multi-component, multi-physics system. For each
component, a risk matrix is generated; consequently, a risk estimation and a classification
are made. To estimate the risk of failure in selecting an adequate
sub-region prior to exploration, we propose the following formula based on
Aven and Krohn (2014), which is defined as follows: Risk=likelihood×consequence×knowledge. This formula evaluates risk based on three factors: the probability of a
specific event occurring that may jeopardize the integrity of the geological
barriers (likelihood), the potential impact of that event (consequence), and
the level of understanding or uncertainty associated with that event
(knowledge), which can influence the overall risk assessment. The method involves the identification and evaluation of subsurface risk
factors using the multiple-criteria decision-making approach and the
development of a risk matrix. The risk matrix is based on expert judgement
and existing data to quantify the relative importance of each risk factor. The method is evaluated by applying it to one of the subareas designated by
the German federal company for radioactive waste disposal for methodological
developments. The developed approach provides a valuable tool for enabling
stakeholders to consider a wide range of factors, including the level of
uncertainty and lack of knowledge associated with subsurface risk factors,
and make informed decisions during the site selection process.
Potential and challenges of applying artificial intelligence (AI) in geosciences to the search for a high-level waste repository in Germany
Authors: Magri Fabien , Kock Ingo , Krohn Judith , Krob Florian , Ustohalova Veronika , Wittek Stefan , Bratzel Dimitri
Published: September 2023

Abstract. In a science-based site selection procedure (StandAV), the Federal Republic of Germany is searching for a site with the best possible safety for a repository for high-level waste (HLW) over a period of 1 million years. This is a challenging task, given the size of Germany, its geological
variability and the verification period required to ensure the best possible long-term safety. In addition, an enormous amount of heterogeneous geodata has to be processed. The application of artificial-intelligence-based methods in geosciences has great potential for dealing with large heterogeneous data sets. In the German Federal Office for the Safety of Nuclear Waste Management (BASE)-funded project “Application of artificial intelligence (AI) in the site selection process for a deep geological repository (FKZ 4721E03210)”, an interdisciplinary assessment tool is being developed to evaluate the applicability of AI methods in the geosciences. This contribution focuses on the potential and challenges of applying AI in geosciences with respect to key geological activities in the StandAV. Limitations that may arise from the use of AI with respect to key activities in the StandAV are highlighted. The necessary conditions for its future applicability are proposed. The results show that AI methods offer clear advantages over conventional
methods for data management and handling large geological datasets and for
modelling complex long-term and coupled geological processes. However, AI
methods are generally only transferable to the geoscientific questions of
the StandAV with methodological and subject-specific adaptations. Furthermore, the use of AI requires sufficient data, both in terms of quality and quantity. The study also shows that AI should only be used in a
supportive way to address geological issues in key activities and should not have any decision-making power when used in StandAV. For example, AI can carry the risk of data and developer bias, which in turn can have serious consequences for the correct interpretation of results. High demands must be placed on the traceability of the AI methods used. AI
methods that do not meet the transparency requirements of the StandAV carry
a significant risk of jeopardising public confidence in the participation
process. This could increase the general mistrust and scepticism towards AI
in the public perception (Krob et al., 2023). It is strongly recommended that all methods should be evaluated and validated iteratively and that the results should be made available to the public when applied to the key activities of the StandAV.
The collection, digitisation, interpretation and publication of geological data in the German site selection procedure – status and challenges
Authors: Reiche Sönke , Schröder Lukas Alexander , Hermann Diana
Published: September 2023

Abstract. The German site selection procedure for a repository site for high-level nuclear waste is subdivided into three major phases. During the first phase, the subsurface of Germany is evaluated based on existing data,
with the aim of defining siting regions for surface-based underground
exploration. Although Germany is covered by large amounts of geoscientific
data – including ca. 50 000 boreholes deeper than 300 m and more than
340 000 km of reflection seismic lines – the legal obligation to make these data publicly available on a national scale is fairly new and dates back to the Geological Data Act of 2020 (GeolDG: Geologiedatengesetz vom 19. Juni 2020; BGBl. I S. 1387). However, significant amounts of data are available in analogue form only, posing a significant
challenge to the timeline of the site selection procedure. As the German
nuclear waste management organisation, the Federal Company for Radioactive
Waste Disposal (BGE) is in charge of collecting, interpreting and publishing geoscientific data that are relevant to the decisions made within the site selection procedure. In this contribution, we outline the path of data within the first phase of
the site selection procedure. We start with an overview of the BGE's current and past activities related to data collection and digitisation, focussing on a major campaign through which more than 16 000 drilling reports are being digitised in cooperation with the State Office for Mining, Energy and Geology in Lower Saxony (LBEG). We then report on the different approaches of data quality control, processing and supply, highlighting challenges related to the federal organisation of geodata storage in Germany. We present selected examples of how data are used for evaluating the subsurface in terms of suitability as a potential repository site. Finally, we give an outlook of how data could be integrated into a web application that is currently being developed as an interactive tool for the public presentation of results and underlying decisions.
Retention of trivalent actinides (Am, Cm) and lanthanides (Eu) by Ca feldspars
Authors: Lessing Jessica , Neumann Julia , Bok Frank , Lützenkirchen Johannes , Brendler Vinzenz , Schmidt Moritz , Stumpf Thorsten
Published: September 2023

Abstract. The transport of radionuclides in the environment is a
major problem for the safety assessment of radioactive waste repositories.
Storage in deep geological repositories is considered a safe disposal
strategy because of their ability to isolate hazardous components from the
biosphere for hundreds of thousands of years. Minor actinides (i.e. Am, Cm
and Np) dominate the radiotoxicity of spent nuclear fuel over geological
timescales. In underground repositories, reducing conditions are expected,
and therefore the trivalent oxidation state is dominant for Am and Cm as
well as possibly for Pu. For investigations of the mobility of the trivalent
actinides Am3+ and Cm3+, the less toxic trivalent rare earth
elements, in particular Eu3+, are commonly used. Besides clay and salt, crystalline rock is considered a possible host rock for deep geological repositories. Crystalline rock (e.g. granite) consists mainly of quartz, mica and feldspar. The latter forms common aluminosilicates making up ∼60 vol. % of the earth's crust, but
their sorption behaviour is not well understood, especially for the
Ca-bearing members of the group. Here, we study the sorption of trivalent actinides and their rare earth element homologues on plagioclase which are Ca-bearing feldspars, quantitatively and mechanistically. Zeta potentials of various Ca feldspars show an unexpected increase at pH 4–7, which becomes more pronounced as the amount of Ca in the
crystal lattice increases. This can be interpreted by assuming uptake of
Al3+ and/or the precipitation of an Al phase, where Al originates from
feldspar dissolution at different pH values. Nevertheless, only minor differences were found in the retention and surface speciation of Cm3+ on Ca and K feldspars (Neumann et al., 2021). Ca feldspar has a slightly higher potential to retain trivalent metal ions
compared to K feldspar. An inner-sphere (IS) complex and its two
hydrolysis forms have been identified on both minerals, but the hydrolysis
of the IS complex is stronger in the Ca-rich mineral. A surface complexation model for Ca feldspar was developed by combining the
batch sorption data and the spectroscopically identified surface complexes
to describe the experimental data. These data will be the basis for the
improvement of transport simulations for a reliable safety assessment of
potential radioactive waste repositories in crystalline rock.
Investigations of aged metal seals for interim storage
Authors: Jaunich Matthias , Goral Milan , Wolff Dietmar , Völzke Holger
Published: September 2023

Abstract. The storage of spent fuel and high-level radioactive waste in
Germany is performed in interim storage containers with double-lid systems.
The lids are bolted and equipped with metal seals (e.g.
Helicoflex®) to ensure the safe containment of the inventory. The used metal seals have a layered structure consisting of three components as can be seen schematically in the cross-sectional view in Fig. 1. In the centre, a helical spring is positioned that is surrounded by two
C-shaped jackets and is mainly responsible for generation of the required
restoring force. The inner jacket is made of stainless steel and homogenises
the restoring force of the helical spring. The outer jacket is made of
silver or aluminium which are both soft metals in comparison to the contact
partners (lid and container body). During bolting of the lid to the
container body, the seal is compressed. The generated restoring force of the
helical spring causes a plastic deformation of the outer jacket and adapts
to the surfaces of the lid and the container body. Hence, leakage paths are
closed, and the sealing function is generated. Typical durations for existing interim storage licenses in Germany are
40 years, but it can be expected that they have to be extended to longer
periods as a final repository will not be available before the end of the
running licence periods. This extension of licence periods requires a solid
understanding of the long-term behaviour of the seals under storage
conditions. To meet this challenge, long-term investigations were
started at the Bundesanstalt für Materialforschung und -prüfung (BAM)
in 2009. These tests focus on seals assembled in test flanges which are
stored at temperatures ranging from room temperature to 150 ∘C
for accelerated ageing. The aged seals are tested repeatedly after certain
ageing steps, and the leakage rate (as indicator for sealing performance), the
remaining seal force, and the useable resilience upon decompression are
determined. An update on the performed investigations with respect to
earlier publications (Grelle et al., 2019; Goral et al., 2023) will be given,
and the implications of the results for resilient, long-term safety will be
presented. Additionally, there will be a focus on the currently planned
further investigations, and the following question will be addressed. What is additionally needed for
evaluation of an interim storage period extension in regard to the used
metal seals?
Discourse on deep geological repositories – defining retardation moments and questioning the feasibility of prognostic approaches
Authors: Wartenberg Wolfram
Published: September 2023

Abstract. On the basis of the German site selection procedure and
the geoscientific suitability of a designated repository site an open
discourse on process approaches for the realization shall be implemented as
a workshop in the scope of the 2023 SafeND. The geoscientific open discourse
should use examples or scenarios from the international professional circles
to emphasize which site description options are available at best; it should
name moments of retardation in the process and illuminate research related to deep geological repositories. The goal that is to be presented and discussed from an
international perspective relates to geogenic conditions in the repository-relevant
subsurface providing safe confinement for radioactive waste and
consequently protecting people and the environment from ionizing radiation
and other harmful effects. Particularly desired is the critical questioning of geoscience-related lines
of argument that seem plausible for stakeholders. For this reason, the
workshop intends to bring together researchers and stakeholders from, e.g., universities and institutions that have not necessarily been involved in
deep geological disposal so far. This is an occasion to reflect on knowledge
and concepts established by stakeholders from the point of view of
universities and research institutions.
Time to change the geoscientific perspective!?
Authors: Kühn Michael , Bosbach Dirk , Geckeis Horst , Brendler Vinzenz , Kolditz Olaf
Published: September 2023

Abstract. The Repository Site Selection Act (StandAG) explicitly emphasises that targeting the disposal of high-level radioactive waste is a so-called learning process. For example, progress in scientific knowledge, in the methodological approach or in new data should be accounted for. We believe that now is a good time to reflect on what we have learned so far and to put the methodological approach to the test. Therefore, we need to question the perspective of the problem: is the bottom-up strategy (data-based), which reduces the remaining search area more and more, objectively feasible enough, or is there a complementary methodological approach? We are of the opinion that the procedure and the available data should be combined with geoscientific knowledge in a top-down (knowledge-based) manner to support the identification of siting regions. The current bottom-up strategy of continually narrowing down the areas can
be purposeful, but it postpones a fundamental problem to a later point in
time: how do we compare host rock types? So far, this question has only been
addressed qualitatively (BGR, 2007). If this approach were to be developed
intellectually and quantitatively, then the following fundamental question
could be addressed: does one type of host rock in Germany generally always
perform better or worse than another? If these questions could be answered on the basis of data and knowledge and
if a clear result were to emerge, then numerous sub-areas could possibly be
excluded at this stage. In order to pursue such a complementary approach,
the following points need to be examined:
a. quantitative ranking of properties for different host rock types is required for assessments;b. geoscientific knowledge to be used, not only pure data, but also basic findings and expert knowledge;c. synthetic, idealised sites must be defined with the best possible parameters according to the state of science.
We propose this workshop based on the questions outlined above and invite all
experts who have dealt with the search for a repository site from a geoscientific perspective. The aim of the workshop is to start the exchange
of previous experiences and what has been learned, to discuss alternative or
complementary approaches scientifically, and thus to further develop the
investigation of the remaining sub-areas.
Future nuclear fission reactors – uncertainties, the effect of parameter choice and an application to small modular reactor concepts
Authors: Steigerwald Björn , Weibezahn Jens , Slowik Martin , von Hirschhausen Christian
Published: September 2023

Abstract. Today, steep declines in the generation costs of renewable energy systems, particularly solar photovoltaic and wind, combined with a recent spur in storage and flexible technologies mainly driven by batteries and renewable-energy-generated hydrogen are driving a paradigm shift in energy systems across the world, and renewable energy dominates investments in installed electricity generation systems (Ram et al., 2022). In contrast, in 2022 USD 4.8 billion (ca. 21 %) of the total spending in research and development expenditures by countries within the Organisation for Economic Co-operation and Development (OECD) was still spent on nuclear development alongside the current discussion in recent literature about the role of new nuclear developments in combating the recent energy crisis and climate change (Asuega et al., 2023; Ingersoll et.al., 2020; IEA, 2023). Since predicting future costs of technologies not yet developed is a complex exercise, we start this paper with a comparison of two different approaches from production theory and show that they have a theoretically equal structure (Steigerwald et al., 2023). This we then apply to estimate a range of potential production costs for 15 so-called small modular reactor (SMR) concepts for which sufficient data are available. These include light-water, high-temperature and fast reactors. In a third step, we apply the Monte Carlo method to benchmark the cost projections assumed by the manufacturers by varying production parameters in simulations of the net present value (NPV) and the levelized cost of electricity (LCOE). Besides this, we test whether the differences between the manufacturer estimates and ours differ between technology families of SMR concepts and apply a sensitivity analysis. This contributes to an intensifying debate in the literature on the economics and finance of SMR concepts (Steigerwald et al., 2023). In a final step we compared our results with current costs of renewable energy technologies and could conclude that none of the tested concepts is able to compete economically with existing renewable technologies, not even when taking their variability and necessary system integration costs into account. We conclude that any technology foresight has to take the case specifics into account as much as possible, including technological and institutional specifics; this also holds for SMR concepts.
Solving problems collectively in nuclear waste governance
Authors: Enderle Stefanie , Bechthold Elske
Published: September 2023

Abstract. Nuclear waste governance is a technical and societal task with numerous and complex challenges. The goal is generally accepted and clearly defined, which is that high-level waste is to be stored in a deep geological repository. The path to this goal is determined by the site selection procedure outlined in the Repository Site Selection Act (StandAG). Today (2023), we are in the phase of moving from potentially suitable areas in Germany to a limited number of siting regions. However, selecting a repository site with the best possible safety is only one of the challenges on the way to the final storage of nuclear waste. It can be assumed that the conditions of the social and political framework will change during the decade-long process of site selection, construction, and storage in a repository (Hocke et al., 2021). It is highly probable that unforeseen developments will occur and that a response will be necessary. The entire disposal process must be designed to be flexible so that the central players can remain capable of acting. At the same time, however, it must also be sufficiently robust to allow the process of emplacement in a repository to be completed with as little delay as possible. What precautions need to be taken so that, from the current perspective, the best possible response can be made to unforeseen developments? What decisions will have to be made, and what consequences can be expected? How can path dependencies be avoided (Scheer et al., 2023)? These and other questions were the subject of the 2 d workshop “Nuclear Waste Disposal – Possible Paths, Directional Decisions, Future Challenges”, which was held with a selected group of stakeholders from the field of nuclear waste governance in May 2023. In our contribution, we will present key results of the workshop. The focus of our attention is on the question regarding which problems and perceptions the central actors represented in the workshop focus on and to what extent the experimental setting of the workshop is suitable for promoting collective problem-solving (Werle and Schimank, 2000).
Performing science, performative science: a science and technology studies (STS) reflection on the pioneering pathways of the HADES underground research laboratory (URL)
Authors: Geysmans Robbe , Silvikko de Villafranca Marika , Meskens Gaston
Published: September 2023

Abstract. Developing and implementing a project for managing high-level
radioactive waste over extensive periods of time is a multifaceted
challenge. Among others, it entails demonstrating the feasibility, safety
and overall performance of the proposed waste management strategy. However, how to tackle such a demonstration when the periods over which the waste needs to be isolated and contained extend over thousands of years? In the development
of geological disposal facilities, a key role in this matter is played by
underground research laboratories (URLs), which aim to provide a setting to
study how different techniques and materials perform in a realistic
environment. Insights gained into URLs are expected to be translatable to the performance and timescales of an actual repository, hence offering a tool to make a seemingly distant future comprehensible today. In this contribution, we use the HADES (High-Activity Disposal Experimental Site) URL in Mol, Belgium, as an example to illustrate how URLs are producing knowledge and insights, and how in this way they are also actively
performing the possible future(s) of radioactive waste management. Building
on insights gained in the field of science and technology studies (STS),
this paper emphasizes how knowledge production is a complex process
characterized by the interplay of heterogeneous – and sometimes rather
trivial – elements and actors interlinked through a range of explicit and
implicit decisions. We argue that tracing these elements and decisions,
making them explicit and reflecting upon them are of key importance, as
knowledge production not only describes a possible future but also actively contributes to “making the future” by emphasizing what is considered possible and imaginable – and what is not. This paper will therefore also focus on what the implications of making the future could entail from an ethical perspective, with a particular focus on deliberation and intergenerational justice.
Corrosion evaluation for engineered barriers in crystalline host rock – challenges for container development in the German site selection process
Authors: Stephan-Scherb Christiane , Philipp Thimo , Weyand Torben , Fass Thorsten , Maerten Lena
Published: September 2023

Abstract. Crystalline rock is being considered as a potential host rock
for a deep geological disposal facility for high-level radioactive waste in
the ongoing site selection process in Germany. As crystalline rock is
commonly highly fractured, the designation of a containment-providing rock
zone is potentially not possible. In this case, according to German law
(§ 23 (1) and (4) StandAG), the safe containment of the nuclear
waste for 1 million years must be guaranteed by engineered and
geo-engineered barriers. Therefore, it is of great importance to evaluate
and understand processes that might lead to corrosion of the canister from
the outside or from the inside. The long-term integrity of the waste
canister depends on various parameters such as the material, microstructure, and coating of the canister; the properties of the geo-engineered
barriers; the local pore water composition; the radiolysis on the inside of the
container; and the tectonic strain. In a recent project (Long-Term Integrity of Canisters in Crystalline Host Rock – LaKris), the challenges of determining the durability of waste canisters in crystalline host rock have been addressed by comparing and evaluating different international concepts for canister design and discussing their applicability to the requirements in Germany. Further focus lies on the
evaluation of predominant corrosion mechanisms while also considering the
geochemical environment of the crystalline host rock in Germany that the
canisters might be subjected to. This contribution will highlight the activities within the project with
regard to evaluating the corrosion properties of different potential
canister materials such as copper, cast iron, and stainless steel. The aim is
to deepen the understanding of individual processes and their combined effects as well as their classification into favourable or unfavourable processes and
conditions for the derivation or justification of requirements. It also
includes a review of the existing requirements on canister integrity
according to the regulatory framework as well as a discussion about
important hydrogeochemical parameters, which could influence the corrosion
of the canister, including the limited availability and uncertainty of such
data.
A note on the duration of claystone exploration programs
Authors: Mann Thomas , Schuck Bernhard , Kneuker Tilo , Pollok Lukas , Bornemann André , Erbacher Jochen
Published: September 2023

Abstract. In a recent report, the German Federal Company for Radioactive Waste Disposal (BGE) estimated the probable duration of exploration activities within potential siting regions (BGE, 2022). Based on many years of expertise regarding the exploration of the subsurface, we outline in this contribution that the BGE (2022) likely underestimates the time necessary to characterize claystones within potential siting regions. Our latest experience originates from two research projects that developed sequence stratigraphic frameworks for the largely homogenous claystone successions of the Lower Cretaceous in northern Germany (Thöle et al., 2020) and the Middle Jurassic in southern Germany, respectively. Although the specific study areas are not considered in the site selection procedure, both stratigraphic units are reviewed to potentially host a nuclear waste repository. Accordingly, our hands-on experience might constitute a highly relevant contribution to the ongoing debate. Within each study area, drill cores were extracted from four boreholes with a total length of ∼660 m (northern Germany) and ∼930 m (southern Germany). After the drilling campaigns, each having taken approx. 5–6 weeks, the cores were split, photographed in high resolution, lithologically described, scanned with an X-Ray fluorescence (XRF) core scanner (10 mm scan interval) to determine the elemental distribution, and sampled for lithological, mineralogical and geochemical analyses at a resolution of 1 m, which took approx. 12 months. However, the most time-consuming steps were the analysis and interpretation of the stratigraphy and particularly the mineralogical investigations. With a sampling resolution of 1 m, an analysis time of approx. 6 months per 250 core meters is a robust reference. We reckoned a total duration of 5 years for the workload in each of the abovementioned research projects. Obviously, the duration of claystone exploration will vary, depending on the number and length of the core drillings per siting region, in addition to the sampling resolution. However, if BGE aims to characterize claystones with a degree of detail comparable to our
projects, the estimated 42 months (see Table 3 in BGE, 2022) will likely be
insufficient.
The anisotropy of geomaterial granite
Authors: Müller Franz , Hallas Peter , Kroner Uwe
Published: September 2023

Abstract. Granites appear to be isotropic, which qualifies them as suitable
crystalline host rocks for nuclear waste repository sites. However, despite
their optical appearance, granites show a primary structural anisotropy
(Bouchez, 1997) that evolved during emplacement and
crystallization of the melt. The major processes involved are magmatic flow and
oriented crystal growth (Müller et al., 2011).
Hypothetically, it is expected that different tectonic environments, i.e.
different orientations of the stress tensor, cause significant differences
in the primary anisotropy, which is expressed by the crystallographic
preferred orientation (CPO) of the rock-forming minerals. It is likely that
primary anisotropic petrophysical properties control the orientation of
post-magmatic structural features like extensional fractures and thus shape potential fluid pathways. We present the first results of a systematic study of felsic plutonites,
i.e. the GAME project (Gefüge, Textur- und Anisotropie-Messungen von potenziell für die Endlagerung geeigneten Graniten zur Charakterisierung möglicher Fluidwegsamkeiten). The samples of syn-Variscan felsic plutons from two
sites (Erzgebirge and Fichtelgebirge) represent different tectonic settings
during intrusion: extension and compression. Furthermore, they depict
different stages of fractionation of the peraluminous granite suites. The
CPOs were analysed using the neutron time-of-flight (ToF) texture
diffractometer SKAT (Keppler et al., 2014; Ullemeyer et al., 1998) and
EBSD (electron backscatter diffraction). Using scanning electron microscope (SEM) automated mineral liberation analysis (Schulz et al., 2020), modal mineral compositions
are quantified. This enables us to model primary or “intrinsic”
petrophysical properties for these granites based on the elastic stiffness
tensor of the individual rock-forming minerals (Mainprice et al.,
2011). Main- and trace-element geochemical data (ICP-AES and ICP-MS) allow
for a characterization of the different magmatic settings of the samples. All granites show distinct preferred orientations of rock-forming
minerals. The quartz textures, for example, exhibit similar CPOs, with
point maxima of the positive rhombs in combination with small circles to
crossed-girdle c-axis distributions. However, the orientation with respect
to the geographic reference system strongly varies. We will discuss the
CPOs in relation to the stress tensor orientation during emplacement of the felsic plutons and compare the primary anisotropy with the post-magmatic fracture patterns of the particular granites.
Challenges for geomechanical laboratory analyses of claystones with regard to the time frame of the site selection process
Authors: Schumacher Sandra , Gräsle Werner
Published: September 2023

Abstract. The current programme for the site selection process in Germany schedules 11 months for geomechanical laboratory tests per potential future site (BGE, 2022). For the laboratory analysis of rock salt, this time frame seems realistic as no hydromechanical coupling has to be taken into account. In the case of a crystalline basement, the intact rock matrix is low permeable, but transport processes are dominated by ubiquitous fracture networks, which are hard to capture in laboratory settings. Thus, the effect that hydromechanical coupling in low permeable rock has on the speed of laboratory measurements will probably be no problem. However, for claystones, the geomechanical processes within the rock matrix strongly depend on the hydromechanical coupling, which thus determines the speed with which, for example, loading ramps can be applied in the laboratory. The need to maintain the pore pressure equilibrium during the experiments in order to know the acting effective stresses slows down the speed of the measurements significantly. Given the tight time frame of 11 months and the numerous parameters which have to be analysed according to law (StandAG, 2017), the low speed with which the experiments can be performed represents a severe hindrance. It is thus important to establish measurement protocols which enable the simultaneous determination of several parameters in order to save time. Based on our experience with experiments on Opalinus Clay, we offer a first idea of how such a measurement protocol could look and would like to invite a discussion on how to optimise experiments on claystones further in order to have a chance to meet the very tight time frame required by the site selection process.