bluuebunny/crossref_metadata_2025 huggingface dataset:
New particle formation in the tropical free troposphere during CAMP2Ex: statistics and impact of emission sources, convective activity, and synoptic conditions
Authors: Xiao Qian , Zhang Jiaoshi , Wang Yang , Ziemba Luke D. , Crosbie Ewan , Winstead Edward L. , Robinson Claire E. , DiGangi Joshua P. , Diskin Glenn S. , Reid Jeffrey S. , Schmidt K. Sebastian , Sorooshian Armin , Hilario Miguel Ricardo A. , Woods Sarah , Lawson Paul , Stamnes Snorre A. , Wang Jian
Published: September 2023

Abstract. Nucleation in the free troposphere (FT) and subsequent growth of new particles represent a globally important source of cloud condensation nuclei (CCN). Whereas new particle formation (NPF) has been shown to occur frequently in the upper troposphere over tropical oceans, there have been few studies of NPF at lower altitudes. In addition, the impact of urban emissions and biomass burning on the NPF in tropical marine FT remains poorly understood. In this study, we examine NPF in the lower and mid-troposphere (3–8.5 km) over the tropical ocean and coastal region using airborne measurements during the recent Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex). NPF was mostly observed above 5.5 km and coincided with elevated relative humidity (RH) and reduced condensation sink (CS), suggesting that NPF occurs in convective cloud outflow. The frequency of NPF increases with altitude, reaching ∼ 50 % above 8 km. An abrupt decrease in NPF frequency coincides with early monsoon transition and is attributed to increased CS resulting from reduced convective activity and more frequent transport of aged urban plumes. Surprisingly, a large fraction of NPF events in background air were observed in the early morning, and the NPF is likely made possible by very low CS despite low actinic flux. Convectively detrained biomass-burning plumes and fresh urban emissions enhance NPF as a result of elevated precursor concentrations and scavenging of pre-existing particles. In contrast, NPF is suppressed in aged urban plumes where the reactive precursors are mostly consumed, while CS remains relatively high. This study shows a strong impact of urban and biomass-burning emissions on the NPF in tropical marine FT. The results also illustrate the competing influences of different variables and interactions among anthropogenic emissions, convective clouds, and meteorology, which lead to NPF under a variety of conditions in tropical marine environments.
An extraction method for nitrogen isotope measurement of ammonium in a low-concentration environment
Authors: Lamothe Alexis , Savarino Joel , Ginot Patrick , Soussaintjean Lison , Gautier Elsa , Akers Pete D. , Caillon Nicolas , Erbland Joseph
Published: September 2023

Abstract. Ammonia (NH3) participates in the nucleation and growth
of aerosols and thus plays a major role in atmospheric transparency,
pollution, health, and climate-related issues. Understanding its emission
sources through nitrogen stable isotopes is therefore a major focus of
current work to mitigate the adverse effects of aerosol formation. Since ice
cores can preserve the past chemical composition of the atmosphere for
centuries, they are a top tool of choice for understanding past NH3
emissions through ammonium (NH4+), the form of NH3 archived
in ice. However, the remote or high-altitude sites where glaciers and ice
sheets are typically localized have relatively low fluxes of atmospheric
NH4+ deposition, which makes ice core samples very sensitive to
laboratory NH3 contamination. As a result, accurate techniques for
identifying and tracking NH3 emissions through concentration and
isotopic measurements are highly sought to constrain uncertainties in
NH3 emission inventories and atmospheric reactivity unknowns. Here, we
describe a solid-phase extraction method for NH4+ samples of low
concentration that limits external contamination and produces precise
isotopic results. By limiting NH3atm exposure with a scavenging fume
hood and concentrating the targeted NH4+ through ion exchange
resin, we successfully achieve isotopic analysis of 50 nmol NH4+
samples with a 0.6 ‰ standard deviation. This extraction
method is applied to an alpine glacier ice core from Col du Dôme,
Mont Blanc, where we successfully demonstrate the analytical approach
through the analysis of two replicate 8 m water equivalent ice cores
representing 4 years of accumulation with a reproducibility of ±2.1 ‰. Applying this methodology to other ice cores in
alpine and polar environments will open new opportunities for understanding
past changes in NH3 emissions and atmospheric chemistry.
Ideas and perspectives: Beyond model evaluation – combining experiments and models to advance terrestrial ecosystem science
Authors: Caldararu Silvia , Rolo Victor , Stocker Benjamin D. , Gimeno Teresa E. , Nair Richard
Published: September 2023

Abstract. Ecosystem manipulative experiments are a powerful tool to
understand terrestrial ecosystem responses to global change because they
measure real responses in real ecosystems and yield insights into causal
relationships. However, their scope is limited in space and time due to
cost and labour intensity. This makes generalising results from such
experiments difficult, which creates a conceptual gap between local-scale
process understanding and global-scale future predictions. Recent efforts
have seen results from such experiments used in combination with dynamic
global vegetation models, most commonly to evaluate model predictions under
global change drivers. However, there is much more potential in combining
models and experiments. Here, we discuss the value and potential of a
workflow for using ecosystem experiments together with process-based models
to enhance the potential of both. We suggest that models can be used prior
to the start of an experiment to generate hypotheses, identify data needs,
and in general guide experimental design. Models, when adequately
constrained with observations, can also predict variables which are
difficult to measure frequently or at all, and together with the data they can
provide a more complete picture of ecosystem states. Finally, models can be
used to help generalise the experimental results in space and time, by
providing a framework in which process understanding derived from site-level
experiments can be incorporated. We also discuss the potential for using
manipulative experiments together with models in formalised model–data
integration frameworks for parameter estimation and model selection, a path
made possible by the increasing number of ecosystem experiments and diverse
observation streams. The ideas presented here can provide a roadmap to
future experiment–model studies.
Shifts in organic matter character and microbial community structure from glacial headwaters to downstream reaches in Canadian Rocky Mountain rivers
Authors: Drapeau Hayley F. , Tank Suzanne E. , Cavaco Maria , Serbu Jessica A. , St.Louis Vincent , Bhatia Maya P.
Published: September 2023

Abstract. Climate change is causing mountain glacial systems to warm rapidly, leading to increased water fluxes and concomitant export of glacially-derived sediment and organic matter (OM). Glacial OM represents an aged, but potentially bioavailable carbon pool that is compositionally distinct from OM found in non-glacially sourced waters. Despite this, the composition of riverine OM from glacial headwaters to downstream reaches and its role in structuring microbial communities has yet to be characterized in the Canadian Rockies. Over three summers (2019–2021) we collected samples before, during and after glacial ice melt along stream transects ranging 0 – 100 km downstream of glacial termini on the eastern slopes of the Canadian Rocky Mountains. We quantified dissolved and particulate organic carbon (DOC, POC) concentration, and used isotopes (Δ14C-OC, δ13C-OC) and dissolved OM (DOM) absorbance and fluorescence to assess OM age, source, and character. Environmental data were combined with microbial 16S rRNA gene sequencing to assess controls on microbial community composition. From glacial headwaters to downstream reaches, OM showed a clear transition from being aged and protein-like with an apparent microbial source to being relatively younger and humic-like. Indicator microbial species for headwater sites included chemolithoautotrophs and taxa known to harbour adaptations to cold temperatures and nutrient-poor conditions, suggesting a role for glacial seeding of microbial taxa to headwaters of this connected riverine gradient. However, environmental conditions (such as deuterium excess, an indicator of water source; water temperature; POC concentration; and protein-like DOM) could only significantly explain ~9 % of the observed variation in microbial community structure. This finding, paired with the identification of a ubiquitous core microbial community that comprised a small proportion of all identified amplicon sequence variants (ASVs), but was present in large relative abundance at all sites, suggests that mass effects largely overcome species sorting to enable a connected microbial community along this strong environmental gradient. Thus, with a loss of novel glacial and microbial inputs with climate change, our findings suggest consequent changes in OC cycling and microbial community structure may lead to complex ecosystem responses across the evolving mountain-to-downstream continuum in small, glacierized systems.
A new approach to understanding fluid mixing in process-study models of stratified fluids
Authors: Hartharn-Evans Samuel George , Stastna Marek , Carr Magda
Published: September 2023

Abstract. While well established energy-based methods of quantifying diapycnal mixing in process-study numerical models are often used to provide information about when mixing occurs, and how much much mixing has occurred, describing how and where this mixing has taken place remains a challenge. Moreover, methods based on sorting the density field struggle with under resolution and uncertainty as to the definition of the reference density when bathymetry is present. Here, an alternative method of understanding mixing is proposed. Paired histograms of user selected variables (which we abbreviate USP) are employed to identify mixing fluid, and are then used to identify regions of fluid in physical space that are undergoing mixing. This paper presents two case studies showcasing this method: shoaling internal solitary waves and a shear instability in cold water influenced by the nolinearity of the equation of state. The USP method identifies differences in the mixing processes associated with different internal solitary wave breaking types, including differences in the horizontal extent and advection of mixed fluid. The method is also used to identify how density, and passive tracers are mixed within the core of the cold-water Kelvin-Helmholtz instability.
Stream water sourcing from high elevation snowpack inferred from stable isotopes of water: A novel application of d-excess values
Authors: Sprenger Matthias , Carroll Rosemary , Marchetti David , Bern Carleton , Beria Harsh , Brown Wendy , Newman Alexander , Beutler Curtis , Williams Kenneth
Published: September 2023

Abstract. About 80 % of the precipitation in the Colorado River’s headwaters is snow, and the resulting snowmelt-driven hydrograph is a crucial water source for about 40 million people. Snowmelt from alpine and subalpine snowpack contributes substantially to groundwater recharge and river flow. However, the dynamics of snowmelt progression are not well understood because observations of the high elevation snowpack are difficult due to challenging access in complex mountainous terrain as well as the cost- and labor-intensity of methods. We present a novel approach to infer the processes and dynamics of high elevation snowmelt contributions predicated upon stable hydrogen and oxygen isotope ratios observed in stream discharge. We show that d-excess values of stream water can serve as a comparatively cost-effective proxy for a catchment integrated signal of high elevation snow melt contributions to catchment runoff. We sampled stable hydrogen and oxygen isotope ratios of the precipitation, snowpack, and stream water in the East River, a headwater catchment of the Colorado River and the stream water of larger catchments at sites on the Gunnison River and Colorado River. The d-excess of snowpack increased with elevation; the upper subalpine and alpine snowpack (>3200 m) and had a substantially higher d-excess compared to lower elevations (<3200 m) in the study area. The d-excess values of stream water reflected this because d-excess values increased as the higher elevation snowpack contributed more to stream water generation later in the snowmelt/runoff season. Endmember mixing analyses based on the d-excess data showed that the share of high elevation snowmelt contributions within the snowmelt hydrograph was on average 44 % and generally increased during melt period progression, up to 70 %. The observed pattern was consistent during six years for the East River, and a similar relation was found for the larger catchments on the Gunnison and Colorado Rivers. High elevation snowpack contributions were found to be higher for years with lower snowpack and warmer spring temperatures. Thus, we conclude that the d-excess of stream water is a viable proxy to observe changes in high elevation snowmelt contributions in catchments at various scales. Inter-catchment comparisons and temporal trends of the d-excess of stream water could therefore serve as a catchment-integrated measure to monitor if mountain systems increasingly rely on high elevation water inputs during snow drought.
Understanding representations of uncertainty, an eye-tracking study – Part 2: The effect of expertise
Authors: Williams Louis , Mulder Kelsey J. , Charlton-Perez Andrew , Lickiss Matthew , Black Alison , McCloy Rachel , McSorley Eugene , Young Joe
Published: September 2023

Abstract. As the ability to make predictions regarding uncertainty information
representing natural hazards increases, an important question for those
designing and communicating hazard forecasts is how visualizations of
uncertainty influence understanding amongst the intended, potentially
varied, target audiences. End-users have a wide range of differing expertise
and backgrounds, possibly influencing the decision-making process they
undertake for a given forecast presentation. Our previous, Part 1 study
(Mulder et al., 2023) examined how the presentation of uncertainty
information influenced end-user decision making. Here, we shift the focus to
examine the decisions and reactions of participants with differing areas of expertise
(meteorology, psychology, and graphic-communication students) when presented
with varied hypothetical forecast representations (boxplot, fan plot, or
spaghetti plot with and without median lines) using the same eye-tracking
methods and experiments. Participants made decisions about a fictional
scenario involving the choices between ships of different sizes in the face
of varying ice thickness forecasts. Eye movements to the graph area and key
and how they changed over time (early, intermediate, and later viewing
periods) were examined. More fixations (maintained gaze on one location)
and more fixation time were spent on the graph and key during early and
intermediate periods of viewing, particularly for boxplots and fan plots.
The inclusion of median lines led to less fixations being made on all graph
types during early and intermediate viewing periods. No difference in eye
movement behaviour was found due to expertise; however, those with greater
expertise were more accurate in their decisions, particularly during more
difficult scenarios. Where scientific producers seek to draw users to the
central estimate, an anchoring line can significantly reduce cognitive load,
leading both experts and non-experts to make more rational decisions. When
asking users to consider extreme scenarios or uncertainty, different prior
expertise can lead to significantly different cognitive loads for processing
information, with an impact on one's ability to make appropriate decisions.
Understanding representations of uncertainty, an eye-tracking study – Part 1: The effect of anchoring
Authors: Mulder Kelsey J. , Williams Louis , Lickiss Matthew , Black Alison , Charlton-Perez Andrew , McCloy Rachel , McSorley Eugene
Published: September 2023

Abstract. Geoscience communicators must think carefully about how
uncertainty is represented and how users may interpret these
representations. Doing so will help communicate risk more effectively, which
can elicit appropriate responses. Communication of uncertainty is not just a
geosciences problem; recently, communication of uncertainty has come to the
forefront over the course of the COVID-19 pandemic, but the lessons learned
from communication during the pandemic can be adopted across geosciences as
well. To test interpretations of environmental forecasts with uncertainty,
a decision task survey was administered to 65 participants who saw different
hypothetical forecast representations common to presentations of
environmental data and forecasts: deterministic, spaghetti plot with and
without a median line, fan plot with and without a median line, and box plot
with and without a median line. While participants completed the survey,
their eye movements were monitored with eye-tracking software. Participants'
eye movements were anchored to the median line, not focusing on possible
extreme values to the same extent as when no median line was present.
Additionally, participants largely correctly interpreted extreme values from
the spaghetti and fan plots, but misinterpreted extreme values from the box
plot, perhaps because participants spent little time fixating on the key.
These results suggest that anchoring lines, such as median lines, should
only be used where users should be guided to particular values and where
extreme values are not as important in data interpretation. Additionally,
fan or spaghetti plots should be considered instead of box plots to reduce
misinterpretation of extreme values. Further study on the role of expertise
and the change in eye movements across the graph area and key is explored in more detail in the companion paper to this study (Williams et al., 2023; hereafter Part 2).
El Niño–Southern Oscillation (ENSO)-driven hypersedimentation in the Poechos Reservoir, northern Peru
Authors: Foucher Anthony , Morera Sergio , Sanchez Michael , Orrillo Jhon , Evrard Olivier
Published: September 2023

Abstract. Although extreme El Niño events (EENEs) have always impacted
hydrological anomalies and sediment transport in South America, their
intensification by global warming and their association with changes in
human activities and land cover after humid periods may lead to the
acceleration of sediment transfers in river systems and dam reservoirs. This
situation may threaten soil and water resources in arid and semiarid regions
highly dependent on water originating from large dams. In this study, we
investigated the sediment sequence accumulated in the Poechos Reservoir
(northern Peru) and provided a retrospective reconstruction of the
interactions of El Niño–Southern Oscillation (ENSO), agricultural
practices and vegetation cover changes with sediment dynamics (1978–2019). To
this end, a sediment core was dated and characterized by physical and
chemical analyses (e.g., scanner tomography, X-ray fluorescence, particle
size analysis) to estimate the evolution of sedimentation rates and
changes in sediment sources during the last 5 decades. Sediment tracing results indicated the occurrence of changes in sediment
sources associated with positive and negative phases of the Eastern Pacific
index with a greater contribution of the lowland dry-forest area in
comparison to that of the Andean area to sediment during the El Niño
events (mean contribution of 76 %; up to 90 % during the coastal El
Niño events (CENEs) of 2016–2017). This source contribution was mostly
controlled by the stationary rainfall occurring during the EENEs in the lowland dry-forest area characterized by a low vegetation cover. Overall, after an extreme phase of ENSO, like after the
EENE 1982–1983, the normal discharges and persistent sediment supplies from
the middle- and upper-catchment parts led to river aggradation and the
storage of substantial amounts of sediment in alluvial plains. In the
absence of a significant EENE between 1983 and 1997, the large volume of
sediment stored in the alluvial plains was exported by the EENE 1997–1998
resulting in an increase in sedimentation rate of 140 % after 1997 with
a significant aggradation of the deltaic zone of the reservoir. In addition
to the impact of extreme climate events on sediment dynamics, the
development of agriculture along the riverine system after an extreme phase
of ENSO increased the availability of sediments in the main channel of the
rivers, easily transported by the next EENE. This study suggests that
intensification of human activities associated with a higher frequency of
extreme rainfall events amplified the quantity of sediment transported by
the river system, which will significantly decrease the lifespan of the
reservoir, which is essential to meeting the freshwater demands of the farmers and the
populations living in this arid and semiarid region.
Multi-objective optimization design of parallel manipulators using a neural network and principal component analysis
Authors: Yang Chao , Li Peijiao , Wang Yang , Ye Wei , Sun Tianze , Huang Fengli , Zhang Hui
Published: September 2023

Abstract. In this work, a multi-objective optimization design method is proposed based on principal component analysis (PCA) and a neural network to obtain a mechanism's optimal comprehensive performance. First,
multi-objective optimization mathematical modeling, including design
parameters, objective functions, and constraint functions, is established.
Second, the sample data are obtained through the design of the experiment
(DOE) and are then standardized to eliminate the adverse effects of a
non-uniform dimension of objective functions. Third, the first k principal components are established for p performance indices (k<p) using the
variance-based PCA method, and then the factor analysis method is employed
to define its physical meaning. Fourth, the overall comprehensive
performance evaluation index is established by objectively determining
weight factors. Finally, the computational cost of the modeling is improved
by combining the neural network and a particle swarm optimization (PSO)
algorithm. Dimensional synthesis of a Sprint (3RPS) parallel manipulator (PM) is taken as a case study to implement the proposed method, and the
optimization results are verified by a comprehensive performance comparison of robots before and after optimization.
How do uncertain parameters affect the analysis of host rock integrity? Methods and preliminary results for a generic clay rock site
Authors: Thiedau Jan , Bittens Maximilian , Maßmann Jobst , Mayr Sibylle
Published: September 2023

Abstract. The thermal, hydraulic, and mechanical effects of excavating the repository mine and the thermal loading of nuclear waste on the safety of the geological barrier system are addressed in the regulations as integrity analyses. For repositories in clay rock, a modelling and assessment methodology has been developed in the ANSICHT (Methodik und Anwendungsbezug eines Sicherheits- und Nachweiskonzeptes für ein HAW-Endlager im Tonstein) project based on thermo-hydro-mechanically (THM) coupled simulations using the open-source
software project OpenGeoSys and has been illustrated by its application to a generic clay rock site in northern Germany. However, the assessment can be significantly influenced by uncertainties in the model inputs, which result, on the one hand, from the limited ability to characterize the geological barrier and, on the other hand, from fundamental difficulties and inaccuracies in the measurements. Hence, the results of these established integrity analyses have to be
enriched by statistical information. The developed workflow comprises
different steps beginning with a realistic characterization of parameter
uncertainties. A surrogate model based on mathematically sound techniques is built to capture the propagation of these uncertainties through the THM
simulation and the integrity criteria evaluation. The model can then be
evaluated to obtain probabilistic results for rock integrity assessment and
a sensitivity analysis to identify the inputs that primarily impact the
results. In this contribution, we present preliminary results based on the generic
repository system from the ANSICHT project and the developed tools for
stochastic analyses. This work is done as part of the BGE-funded research cluster URS (Uncertainties and Robustness with regard to the Safety of a repository for high-level radioactive waste).
Cross-scale perspective on the Opalinus Clay: insights from the GeomInt2 project
Authors: Cajuhi Tuanny , Maßmann Jobst , Ziefle Gesa , Nagel Thomas , Yoshioka Keita
Published: September 2023

Abstract. Understanding complex systems, such as radioactive waste repositories,
involves the study of cross-scale coupled processes. We discuss some important concepts and their mutual interactions for interpreting such
systems based on complementary model-based analyses at various scales (Fig. 1). These points are linked with practical examples that pertain to the hydromechanical effects and cracking of the Opalinus Clay. In the
Federal Ministry of Education and Research (BMBF)-funded project “Geomechanical integrity of host and barrier rocks – experiment, modeling and analysis of discontinuities (GeomInt2)” (Cajuhi et al., 2023a in Kolditz et al., 2023), these effects have been investigated experimentally and numerically, both at laboratory and at field scales. While interpretation influences the conceptualization of experimental and/or numerical models, a clear goal definition is required to delimit the complex system. One goal statement in the context of this contribution is to explain the formation of drying cracks, where essential processes and boundary conditions must be pinned down. Monitoring data are critical for determining the correlation between experimental and numerical setups. This is achieved by quantifying and questioning the assignability of information derived from data obtained from core samples tested in the laboratory to field-scale analyses. Numerical modeling can help validate model ideas by reproducing measured data and making predictions beyond the experimentally observable range. The detailed information gained from these studies can be used for interpretation and simplification. In a recent study, we used the phase-field approach to model the formation and evolution of cracks and stated the conditions under which desiccation cracks will develop at the field scale as well as how deep they propagate into the rock (Cajuhi et al., 2023b). This information about the near field can be used to determine how detailed repository far-field models must be and, for example, whether cracks need to be taken into account. Consequently, the cross-scale study of complex systems can lead to more robust analysis results.
The use of digital twins for waste estimation in nuclear facilities' dismantling and decommissioning: the PLEIADES project
Authors: Jacques Marie-Bénédicte , Gentes Sascha , Ridao Cabrerizo Joseph A. , Daniška Dušan
Published: September 2023

Abstract. Nowadays, a considerable number of nuclear power plants worldwide have reached or will reach the end of their lifespan and will need to be dismantled within the next few decades. Dismantling and decommissioning (D&D) of nuclear facilities is a challenging, complex, and hazardous task that was never foreseen before the first reactors' shutdowns. As part of D&D activities, the waste minimization and waste management have an essential interest. The EU-funded PLEIADES (PLatform based on Emerging and Interoperable
Applications for enhanced Decommissioning processES) project gathers 14
partners (academics and research organizations, small and medium-sized enterprises (SMEs) and industrial companies, and a Technical Safety Organization) representing different stakeholders and providers of the nuclear dismantling domain. Coming from seven European countries, they join forces to demonstrate an innovative digital approach and a new methodology for improving selected key tasks related to D&D. To achieve these goals, the project aims to develop digital twins (DTs)
through a BIM (building information modelling) technology-based platform. To
structure the data, PLEIADES proposes a decommissioning-oriented ontology
that provides a common understanding of the concept, with specific
decommissioning terminology. The developed platform provides the integration
of the different data and tools. In order to demonstrate the PLEIADES concept, six user stories have been
defined based on three real-life use cases from three different European countries, namely France, Norway, and Spain. They allow scenario studies and address application areas such as cost and planning, radiation exposure estimation, and waste assessment. Three of the user stories are directly linked to one use case and focus on comparing alternative scenarios to basic decommissioning activities such as radiological characterization or the decontamination of building surfaces. The other three focus on risk management, uncertainties, regulatory aspects, and waste management strategies. The data feeding the DTs are crucial and require data collection and
integration, data security assurance, and data completeness verification. The whole process is iterative until the DTs contain all the necessary information required to perform the user stories simulation. Among others, each simulation using a DT will consider a physical and radiological environment and estimate the waste produced, the waste management process, and the waste management cost. In real applications, the data constituting the DT will depend on each
D&D project, but the whole methodology is applicable. This may result in
the definition of best practices and the sharing of common processes.
AREHS: effects of changing boundary conditions on the development of hydrogeological systems: numerical long-term modelling considering thermal–hydraulic–mechanical (–chemical) coupled effects
Authors: Kahnt René , Konietzky Heinz , Nagel Thomas , Kolditz Olaf , Jockel Andreas , Silbermann Christian B. , Tiedtke Friederike , Meisel Tobias , Zill Florian , Carl Anton , Gabriel Aron D. , Schlegel Marcel
Published: September 2023

Abstract. The objective of the AREHS project, funded by BASE (FKZ 4719F10402), is to
model the effects of changing external boundary conditions on the
hydrogeologically relevant parameters and effects (e.g. hydraulic
permeability, porosity, migration pathways, fluid availability, hydraulic
gradients) of a generic geological repository in Germany in all three
potential host rocks (clay, salt, and crystalline rocks) in its hydrogeological setting. Special attention is paid to the cyclic mechanical
loading due to glaciation events. This results in stress changes (M – mechanical processes) as well as induced temperature effects (T – thermal processes) due to permafrost and warm periods. Since the thermal, hydraulic (H – hydraulic processes), and mechanical processes are strongly coupled, they have to be covered by state-of-the-art coupled thermal–hydraulic–mechanical (THM) (C) modelling. The presentation consists of a (a) presentation of important findings for all three host rock types and a (b) presentation of the overall workflow. Complex, time-varying boundary conditions have been formulated for modelling glacial cycles. Investigating the effects of these boundary conditions with THM simulation reveals a variety of coupling effects. To conduct the complex modelling workflow for claystone and salt rock
effectively, an automated workflow was developed and tested. It handles the
transformation from a simulator-independent geological model to a numerical
model specific to the simulator. This contains a suitable finite-element
mesh and a parameterization of the fully coupled or optionally isolated
thermal–hydraulic–mechanical processes, which are implemented and executed in the OpenGeoSys simulator. Simulation results are presented for selected physical quantities at characteristic local and temporal points with respect to the position of a migrating glacier. The investigation results are reproducible
through full automation, container deployment, and a continuous integration
process running on a GitLab instance (see Fig. 1a). To simulate the response of a fractured crystalline rock mass to THM impacts, the explicit integration of the fracture network in numerical models is necessary. The workflow couples the distinct element method (DEM) software “3DEC” and the discrete fracture network (DFN) software “DFN.Lab” automatically (Fig. 1b).
Multiphase flow modeling at the component level for the Swiss deep geological repository
Authors: Zbinden Dominik , Lengler Ursula , Luu Keurfon , Shabani Babak , Li Chao , Papafotiou Alexandros
Published: September 2023

Abstract. In a deep geological repository for radioactive waste,
anaerobic corrosion of various metals lead to the formation of hydrogen. In
Switzerland, the implementor (i.e., Nagra) is commissioned to describe and evaluate
safety-relevant processes related to gas that can affect the long-term
evolution of low- and intermediate-level waste (L/ILW), high-level waste
(HLW), and combined L/ILW and HLW repositories. Key tasks include the
evaluation of gas and radionuclide release pathways and the pressure and
temperature evolution in the repository using multiphase and
multicomponent flow and transport models. The Swiss repository design foresees the installation of multiple seals
(engineered barriers) in the repository: (i) the V1 seals next to the waste
emplacement caverns and tunnels, (ii) the V2 seals located in the access tunnels
toward the emplacement caverns and tunnels, and (iii) the V3 seals positioned in
the shafts of the repository. These seals are designed to satisfy a wide
range of requirements, including requirements related to the hydraulic
evolution of the repository and the associated transport of gas, water, and
radionuclides. A modeling workflow is currently being developed that integrates modeling
performed both at the repository scale using site-specific models and at the
component scale using semi-generic models. The repository-scale models are
built to assess the thermo-hydraulic evolution in the entire repository,
whereas the component-scale models allow for more detailed evaluations of
the gas and water flows in key structures of the repository, such as the V1,
V2, and V3 seals as well as the emplacement caverns and tunnels. This conference
contribution describes the methodology and workflow developed to integrate
these models, with a focus on the development and functionality of the
component-scale models.
Using a multi-criteria approach for a regional differentiation of the likelihood of future volcanic activity in Germany
Authors: Rummel Lisa , Bartels Alexander , May Franz
Published: September 2023

Abstract. Future volcanic activity, which might influence the long-term stability of radioactive waste repositories, must be evaluated critically. In Germany, according to the Repository Site Selection Act (StandAG), areas in which Quaternary volcanism is either present or future volcanic activity is expected within the next 1 Ma must be excluded from the site selection process for a high-level radioactive waste repository. However, while regions with Quaternary volcanism are reasonably well known in Germany, forecasting volcanic activity in intraplate fields is difficult,
as many processes and their interaction control the spatial distribution of the volcanic centres. To develop an appropriate method to forecast possible
regions of volcanic activity, a semi-quantitative, multi-criteria approach
is used that combines a variety of indicators including, amongst others, seismic anomalies in the mantle, gravity data, tectonic activity, sutures,
ground motion, earthquakes, mantle degassing centres and the geochronological data of volcanic rocks. The used indicators provide possible information about the source of melting in the mantle, the ascent of melt through the lithosphere and the eruption process at the surface. In total, 30 indicators were defined and ranked according to their presumed relevance for the long-term prediction of volcanism, following the results of two expert surveys. Quantifiable parameters were selected for the individual indicators, and threshold values were assigned and related to levels of significance. The parameters were uniformly applied for Germany in order to enable a transparent and equal risk assessment of future volcanic activity in all of the federal states. To consider the uncertainties regarding the distribution and manifestation of parameters in addition to their mostly unknown underlying large-scale processes, buffer zones were defined in which the values of relevance decrease with increasing distance from the initial parameter extent. By combining all parameters into an overall index, the presented results allow the regional differentiation of the likelihood of future volcanic eruptions in Germany. The robustness of the results is shown by varying the weights of the used parameters in the Germany-wide risk map. Different categories for the probability of future volcanic activity can be defined and used, depending on the needs and assessment of the volcanic hazard potential.
Semi-analytical approach to modelling matrix diffusion in fractured media
Authors: Poller Andreas , Resele Georg , Missal Christian , Dahlhaus Nils , Voss Marie
Published: September 2023

Abstract. The German Site Selection Act (StandAG, 2017) mentions
crystalline rock as one of the candidate host rocks for the deep geological
disposal of high-level radioactive waste (HAW). Crystalline rock is
generally interspersed with fractures and other permeable structures, thus
allowing for substantial water flow even at depths of a few hundred metres,
where a deep geological repository for HAW may be situated. Radionuclides
that become mobile in case of disposal canister failure could then migrate
along fractures, thus potentially causing a relevant release of
radionuclides from the barrier system. Diffusion of radionuclides into the
rock matrix adjacent to the fractures, called matrix diffusion, has the
potential to markedly attenuate such release of radionuclides. Therefore, an
adequate conceptualisation and mathematical formulation of matrix diffusion
is key for the assessment of radionuclide release from a deep geological
repository in crystalline rock. Analytical solutions for contaminant transport along planar features with
matrix diffusion exist for some special cases. Generally, however, numerical
models are required to adequately address more realistic situations. In the
early phase of the site-selection process, when site-specific data are still
sparse and the goal is more to explore under which circumstances a
repository in crystalline rock could provide effective confinement of
radioactive substances, a modelling approach with intermediate complexity
may be best suited. In this talk, we present a semi-analytical approach to modelling the
transport of a single radionuclide along a fracture with diffusion into the
adjacent rock matrix. The approach has been implemented in an
Excel spreadsheet by using Visual Basic for Applications. Comparison of the
results of the semi-analytical approach with those of a numerical model
featuring the code AMBER has allowed us to determine the scope of application
of the semi-analytical approach.
Features, events and processes (FEP) analysis of the interactions between repository monitoring systems and multi-barrier systems
Authors: Parsons Sam , Haines Thomas , White Matthew , Norris Simon , Bertrand Johan , Griffault Lise , Hall Oliver , Sellin Patrik , Harbord Christopher
Published: September 2023

Abstract. In line with the European waste directive 2011/70/EURATOM, the European Joint Programme on Radioactive Waste Management (EURAD) was launched in June 2019. EURAD aims to make a step change in European collaboration between advanced and early-stage waste management programmes. Monitoring Equipment and Data Treatment for Safe Repository Operation and Staged Closure (MODATS) is Work Package (WP) 17 of the EURAD programme. This WP aims to address a range of research needs relating to repository monitoring data and technologies. This abstract summarises research relating to the interactions between
repository monitoring systems and the multi-barrier systems in which they
are emplaced. A detailed features, events and processes (FEP) analysis is
being undertaken to identify and describe the manner in which monitoring
systems may interact with multi-barrier systems. Monitoring system
components are generically considered in this research; they include data
acquisition technologies, power technologies, data transmission technologies and data loggers. No specific disposal concepts have been selected; however, a range of commonly engineered barrier system materials and typical host rocks are considered. This FEP analysis research will provide an understanding of the impacts of
monitoring systems, which could be used to aid monitoring system design
optimisation, for example by supporting the screening of monitoring
technologies (White and Scourfield, 2019). It may also provide evidence to
demonstrate that monitoring systems do not unacceptably impact the safety
functions of the multi-barrier system. Potential interactions may include the creation of gas migration pathways
along monitoring power or data transmission cables positioned in the
multi-barrier system. This process has been observed in underground research laboratory experiments, such as the Large Scale Gas Injection Test (LASGIT) experiment in the Äspö Hard Rock Laboratory, which involved a series of gas injection tests in a full-scale KBS-3V deposition hole. Other possible interactions could include (non-exhaustive) corrosion of metallic components, degradation of non-metallic components, microbial activity, gas generation, void introduction and formation and volume changes. The final output of this research will be a catalogue of FEPs describing the interactions between generic monitoring systems and multi-barrier systems. Similar to the Nuclear Energy Agency FEP lists, this FEP catalogue is intended to be a starting reference for waste management organisations to use to understand the potential interactions between their specific
monitoring systems and multi-barrier systems.
Workshop – impact of extended interim storage of high-level radioactive waste on the safety of final disposal
Authors: Borkel Christoph , Maerten Lena
Published: September 2023

Abstract. Interim storage of high-level radioactive waste
will in several countries take longer than the originally planned few
decades. Does the extended timeline of interim storage significantly change
the input parameters for final disposal? Are there aspects that could
previously be neglected but need to be re-evaluated for planning and
implementing a deep geological repository (DGR)? Interim storage is
structurally separated from the search for a deep geological repository in
Germany, and the waste acceptance criteria for waste canisters still have to
be defined. However, from the fundamental understanding of processes and
geoscientific understanding, it may be possible to identify positive or
negative aspects of inventory behaviour or technical measures during interim
storage. Taking the requirements of final storage into account when
considering extended interim storage offers the possibility of avoiding or
minimising developments or changes in high-level radioactive waste during
interim storage that may have negative influences on the safe confinement of the waste in a DGR. In this workshop we want to link discussions regarding extended interim
storage to the long-term safety of geological repositories. Aspects of the
discussion could be as follows: 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 that will
negatively affect safety-relevant aspects? We are looking forward to a
multi-faceted, interdisciplinary discussion that may go well beyond the
given examples. Confirmed talks related to the workshop's topic will be given by Volker Metz (KIT-INE), Benedict Bongartz (IW University Hanover) and Florence Sentuc (GRS gGmbH).
Following these introductory talks, we will discuss the given impulses and
evaluate possible outcomes.
“Key performance indicators” for environmental assessments in nuclear waste management
Authors: Geißler Gesa , Köppel Johann
Published: September 2023

Abstract. The planning and licensing processes for nuclear waste management
involve a variety of environmental assessments. Their obligatory public
participation and the possibility of judicial review place high demands on
the quality of these procedures and documents. In contrast to some other
countries (see Günther et al., 2017), no adequately formulated quality
assurance options for environmental assessments have been applied in Germany to date (ibid.). However, KPIs (“key performance indicators”) for
environmental assessment can certainly be presented and operationalised to
varying degrees (e.g. Geißler et al., 2019). On the one hand, this relates to procedural performance, such as how
carefully alternative solutions are investigated and how remaining
uncertainties are addressed. The other overarching set of KPI criteria
relates to substantial performance, i.e. the extent to which improvements
are achieved in the course of environmental assessments with a view to a
high level of environmental protection and the extent to which actors and
stakeholders involved may perceive preferred alternative solutions as fair.
Strategic environmental assessments (SEAs) for the search for a final repository site for high-level radioactive waste will have to meet high quality standards (see Rehhausen et al., 2018) because the process and task pose unique challenges. This includes the core question of whether the SEAs can be integrated early enough. The aim of the panel proposed here is to introduce relevant key performance
indicators for environmental assessments, especially at a high international level via short input statements. Secondly, we want to discuss and classify these KPIs provisionally regarding different operationalisation options in the field of nuclear waste disposal. On the one hand, there may be “low hanging fruit” as far as tangible KPIs are concerned, and on the other hand, there may be a need for further research and development which shall be identified in the panel.