Safety Assessment Of Repository Research Articles

A methodology for a risk-based approach to complex scenarios in a long-term safety assessment of a radioactive waste repository

A methodology for a risk-based approach to complex scenarios in a long-term safety assessment of a radioactive waste repository was developed using a Monte Carlo sampling method. The methodology consists of event characterization, influence evaluation, scenario combination, scenario assessment, and a convergence check. The methodology was applied to a hypothetical repository system considering earthquake events for illustration. Since two independent impacts by earthquakes were considered in the illustration, the complex scenarios could be categorized into 5 types including the simultaneous occurrence of impacts. From the assessment results, the total risk computed by the new methodology involved the occurrence probabilities of the complex scenarios, and these probabilities were reasonably converging to pseudo-theoretical probabilities. For further study, the characterizations of events and their impacts on a repository system must be preliminarily determined for a successful assessment.

Effects of matrix composition and sample preparation on instant release fractions from high burnup nuclear fuel

ABSTRACTThe rapid release of fission products segregated either to the gap between the fuel and the cladding or to the UO2grain boundaries from spent nuclear fuel in contact with water (often referred to as the instant release fraction - IRF) is of interest for the safety assessment of geological repositories for spent fuel due to the potential dose contribution. In September 2012 a study was initiated with the aim of comparing the instant release behavior of fuels with and without additives/dopants. Preliminary results from this (ongoing) study indicate that the release of uranium during the first contact periods was higher than during the tests with fuel segments, even though the fuel was cut open recently [1]. This could be due to the sample preparation method which included axial cutting of the cladding in order to remove the fuel fragments used in the study. In the present work, leaching data from both studies are presented and the releases are discussed comparing the two sample preparation methods and considering the effect of matrix composition. The leaching studies have been performed in air using 10 mM NaCl + 2 mM NaHCO3as leaching solution.

Äspö 원형 처분장에 대한 열-수리-역학적 모델링 연구: 열적 거동 해석

고준위폐기물처분장에 대한 열-수리-역학적 거동 모델링은 처분장의 성능 및 안전성 평가를 위해서 선행되어야 할 중요한 연구과제이다. 본 연구에서는 <TEX>$\ddot{A}$</TEX>sp<TEX>$\ddot{o}$</TEX> 원형처분장의 열적 거동을 해석하고, 현장 실험데이터와의 비교를 통해 모델 계산결과의 타당성을 검증하였다. 모델 시뮬레이션에서는 처분공과 처분터널 및 그 주변 암반에 대한 온도분포를 분석하였다. 현장 실험데이터와의 비교는 처분공 DH-6를 대상으로 수행하였다. 그 결과 모델 계산치는 측정위치에 따라 실험치 보다 약 2-<TEX>$5^{\circ}C$</TEX> 정도 높은 온도값을 보였으나, 온도변이 곡선은 비슷한 패턴을 보여 주었다. 실험치와 모델 계산치의 이러한 차이는 모델에 의한 열적거동 해석에서 암반을 제외한 완충재, 벤토나이트 펠렛, 뒷채움재 내의 수리학적 및 역학적 거동을 고려하지 않았기 때문으로 판단되었다. Thermal-hydro-mechanical (THM) modeling is a critical R&D issue in the performance and safety assessment of a high-level waste repository. With an <TEX>$\ddot{A}$</TEX>sp<TEX>$\ddot{o}$</TEX> prototype repository, its thermal behavior was analyzed and then compared with in-situ experimental data for its validation. A model simulation was used to calculate the temperature distributions in the deposition holes, deposition tunnel, and surrounding host rock. A comparison of the simulation results with the experimental data was made for deposition hole DH-6, which showed that there was a temperature difference of <TEX>$2{\sim}5^{\circ}C$</TEX> depending on the location of the measuring points, but there was a similar trend in the evolution curves of temperature as a function of time. It was expected that the coupled modeling of the thermal behavior with the hydro-mechanical behavior in the buffer and backfill of the <TEX>$\ddot{A}$</TEX>sp<TEX>$\ddot{o}$</TEX> prototype repository would give a better agreement between the experimental and model calculation results.

Trace concentration – Huge impact: Nitrate in the calcite/Eu(III) system

The interactions of trivalent lanthanides and actinides with secondary mineral phases such as calcite is of high importance for the safety assessment of deep geological repositories for high level nuclear waste (HLW). Due to similar ionic radii, calcium-bearing mineral phases are suitable host minerals for Ln(III) and An(III) ions. Especially calcite has been proven to retain these metal ions effectively by both surface complexation and bulk incorporation. Since anionic ligands (e.g., nitrate) are omnipresent in the geological environment and due to their coordinating properties, their influence on retentive processes should not be underestimated. Nitrate is a common contaminant in most HLW forms as a result of using nitric acid in fuel reprocessing. It is also formed by microbial activity under aerobic conditions. In this study, atomic force microscopy investigations revealed a major influence of nitrate upon the surface of calcite crystals. NaNO3 causes serious modifications even in trace amounts (<10−7M) and forms a soft surface layer of low crystallinity on top of the calcite crystal. Time-resolved laser fluorescence spectroscopy of Eu(III) showed that, within this layer, Eu(III) ions are incorporated, while losing most of their hydration shell. The results show that solid solution modelling for actinides in calcite must take into account the presence of nitrate in pore and ground waters.

Temperature-Dependent Hydrolysis Reactions of U(VI) Studied by TRLFS

Temperature-dependent hydrolysis behaviors of aqueous U(VI) species were investigated with time-resolved laser fluorescence spectroscopy (TRLFS) in the temperature range from 15 to 75°C. The formation of four different U(VI) hydrolysis species was measured at pHs from 1 to 7. The predominant presence of UO2 2+ , (UO2)2(OH)2 2+ , (UO2)3(OH)5 + , and (UO2)3(OH)7 - species were identified based on the spectroscopic properties such as fluores- cence wavelengths and fluorescence lifetimes. With an increasing temperature, a remarkable decrement in the flu- orescence lifetime for all U(VI) hydrolysis species was observed, representing the dynamic quenching behavior. Furthermore, the increase in the fluorescence intensity of the further hydrolyzed U(VI) species was clearly observed at an elevated temperature, showing stronger hydrolysis reactions with increasing temperatures. The formation constants of the U(VI) hydrolysis species were calculated to be log K0 2,2 = -4.0 ‚ 0.6 for (UO2)2(OH)2 2+ , log K 0 3,5 = -15.0 ‚ 0.3 for (UO2)3(OH)5 + , and log K 0 3,7 = -27.7 ‚ 0.7 for (UO2)3(OH)7 - at 25°C and I = 0 M. The specific ion interaction theory (SIT) was applied for the extrapolation of the formation constants to infinitely dilut- ed solution. The results of temperature-dependent hydrolysis behavior in terms of the U(VI) fluorescence were compared and validated with those obtained using computational methods (DQUANT and constant enthalpy equa- tion). Both results matched well with each other. The reaction enthalpies and entropies that are vital for the com- putational methods were determined by a combination of the van't Hoff equation and the Gibbs free energy equa- tion. The temperature-dependent hydrolysis reaction of the U(VI) species indicates the transition of a major U(VI) species by means of geothermal gradient and decay heat from the radioactive isotopes, representing the necessity of deeper consideration in the safety assessment of geologic repository.

Investigation and Study on Environmental Radioactive Background in Xinchang and Jijicao Rock of Beishan Preselected Region for HLW Disposal Repository in China

On the basis of field environmental investigation and monitoring, the environmental radioactivity background of Xinchang and Jijicao rock in Beishan preselected region has been preliminary investigated and studied, and the public dose from local natural background radiation is estimated which can provide basic data and information for environmental impact assessment and safety assessment of HLW(the high level radioactive waste) disposal repository in the future. From the result of investigation and study, the environmental radioactivity of Xinchang and Jijicao rock is generally within normal natural background. The effective dose to local resident from natural background radiation is 2.110 mSv/a by internal and external exposure.

H2O2 and radiation induced dissolution of UO2 and SIMFUEL in [formula omitted] deficient aqueous solution

Understanding UO2 matrix dissolution is of major importance for the safety assessment of a future deep geological repository. Oxidative dissolution of UO2 and SIMFUEL pellets have been extensively studied in HCO3- solutions, while less is known about systems with no or very low HCO3- concentrations. The aim of this work is to elucidate the oxidative dissolution of UO2 and SIMFUEL pellets in HCO3- free solutions by studying the dissolution of U (VI) and consumption of H2O2 over time. The results are compared with previous experiments performed in HCO3- solutions. The oxidative dissolution rate is higher for the UO2 pellet in HCO3- compared to the other systems. It is evident that the kinetics of the reaction with H2O2 is qualitatively different for SIMFUEL in comparison with pure UO2. For the UO2 pellet in pure water, the presence of a secondary phase (meta) studtite, on the surface of the pellet is confirmed by Raman spectroscopy. The kinetic impact of the secondary phase is evaluated in separate UO2 powder experiments. The (meta) studtite (surface) precipitation leads to a slower release of uranium into the solution. Numerical simulations using experimentally determined rate constants are used to evaluate a simple mechanism of surface precipitation. The numerical results are in fair agreement with the experimental observations given certain criteria. In addition, the γ-radiation induced dissolution of UO2 and SIMFUEL pellets were investigated in pure water, and compared with HCO3- systems. Also here the dissolution rate of uranium is higher for UO2 in HCO3- compared to pure water, while for SIMFUEL longer irradiation times are needed to observe any difference between pure and HCO3- containing water.

A novel technique of in situ phase-shift interferometry applied for faint dissolution of bulky montmorillonite in alkaline solution

The effect of alkaline pH on the dissolution rate of bulky aggregated montmorillonite samples at 23 °C was investigated for the first time by using an enhanced phase-shift interferometry technique combined with an internal refraction interferometry method developed for this study. This technique was applied to provide a molecular resolution during the optical observation of the dissolution phenomena in real time and in situ while remaining noninvasive. A theoretical normal resolution limit of this technique was 0.78 nm in water for opaque material, but was limited to 6.6 nm for montmorillonite due to the transparency of the montmorillonite crystal. Normal dissolution velocities as low as 1 × 10−4 to 1 × 10−3 nm/s were obtained directly by using the measured temporal change in height of montmorillonite samples set in a reaction cell. The molar dissolution fluxes of montmorillonite obtained in this study gave considerably faster dissolution rates in comparison to those obtained in previous investigations by solution analysis methods. The pH dependence of montmorillonite dissolution rate determined in this study was qualitatively in good agreement with those reported in the previous investigations. The dissolution rates to be used in safety assessments of geological repositories for radioactive wastes should be obtained for bulky samples. This goal has been difficult to achieve using conventional powder experiment technique and solution analysis method, but has been shown to be feasible using the enhanced phase-shift interferometry.

Refined Oil Repository Safety Assessment Studies

The purpose of this study is how to evaluate the security problem of refined oil repository. This paper uses gray comprehensive evaluation method to structure mathematic model. At last simulation results show that the method is certain referential significance for the refined oil repository safety assessment.

Sulphide mineral reactions in clay-rich rock induced by high hydrogen pressure. Application to disturbed or natural settings up to 250 °C and 30 bar

As abiotic hydrogen redox reactivity is kinetically limited, most of the possible redox reactions induced by hydrogen remain insignificant at low temperature, even at a geologic time scale. This is the case for sulphate and carbonate reduction, but some H2 induced redox reactions may be significant at low temperature conditions, in particular the pyrite reduction into pyrrhotite. In this experimental study, the geochemical impact of hydrogen in a clay-rich rock containing 1–2wt.% framboidal pyrite is evaluated under mid-hydrothermal condition (90 to 250°C) and with hydrogen partial pressure ranging from 3 to 30bar. This study demonstrates that the main geochemical perturbation induced by hydrogen in a claystone host-rock formation is the destabilisation of pyrite, which leads to the production of sulphide. Two different reaction mechanisms can be distinguished as a function of temperature and hydrogen pressure. When temperature is lower than 150°C and the hydrogen partial pressure is below 6bar, pyrite solubility controls the sulphide concentration at low values. By contrast, at higher temperature or at higher hydrogen partial pressure, the rate and extent of the reaction are driven by pyrrhotite precipitation. A complete replacement of pyrite into pyrrhotite occurs within a short interval of time at T>90°C and P(H2)>10bar. The pH of the media is also a critical parameter controlling the extent of the reaction as alkaline conditions may promote pyrrhotite precipitation at lower temperature and hydrogen pressure. These conclusions have a direct application in the safety assessment of nuclear waste repositories, but may also be extended to other contexts such as the underground storage of hydrogen, and, given the wide range of temperatures used in the experiments, can even be applied to hydrothermal-hosted submarine systems where hydrogen is naturally produced by olivine serpentinization.

Climate Considerations in Long-Term Safety Assessments for Nuclear Waste Repositories

For a deep geological repository for spent nuclear fuel planned in Sweden, the safety assessment covers up to 1 million years. Climate scenarios range from high-end global warming for the coming 100 000 years, through deep permafrost, to large ice sheets during glacial conditions. In contrast, in an existing repository for short-lived waste the activity decays to low levels within a few tens of thousands of years. The shorter assessment period, 100 000 years, requires more focus on climate development over the coming tens of thousands of years, including the earliest possibility for permafrost growth and freezing of the engineered system. The handling of climate and climate change in safety assessments must be tailor-made for each repository concept and waste type. However, due to the uncertain future climate development on these vast time scales, all safety assessments for nuclear waste repositories require a range of possible climate scenarios.Electronic supplementary materialThe online version of this article (doi:10.1007/s13280-013-0406-6) contains supplementary material, which is available to authorized users.

Radionuclide Transport and Uptake in Coastal Aquatic Ecosystems: A Comparison of a 3D Dynamic Model and a Compartment Model

In safety assessments of underground radioactive waste repositories, understanding radionuclide fate in ecosystems is necessary to determine the impacts of potential releases. Here, the reliability of two mechanistic models (the compartmental K-model and the 3D dynamic D-model) in describing the fate of radionuclides released into a Baltic Sea bay is tested. Both are based on ecosystem models that simulate the cycling of organic matter (carbon). Radionuclide transfer is linked to adsorption and flows of carbon in food chains. Accumulation of Th-230, Cs-135, and Ni-59 in biological compartments was comparable between the models and site measurements despite differences in temporal resolution, biological state variables, and partition coefficients. Both models provided confidence limits for their modeled concentration ratios, an improvement over models that only estimate means. The D-model enables estimates at high spatio-temporal resolution. The K-model, being coarser but faster, allows estimates centuries ahead. Future developments could integrate the two models to take advantage of their respective strengths.Electronic supplementary materialThe online version of this article (doi:10.1007/s13280-013-0398-2) contains supplementary material, which is available to authorized users.

Conceptual and Numerical Modeling of Radionuclide Transport and Retention in Near-Surface Systems

Scenarios of barrier failure and radionuclide release to the near-surface environment are important to consider within performance and safety assessments of repositories for nuclear waste. A geological repository for spent nuclear fuel is planned at Forsmark, Sweden. Conceptual and numerical reactive transport models were developed in order to assess the retention capacity of the Quaternary till and clay deposits for selected radionuclides, in the event of an activity release from the repository. The elements considered were carbon (C), chlorine (Cl), cesium (Cs), iodine (I), molybdenum (Mo), niobium (Nb), nickel (Ni), radium (Ra), selenium (Se), strontium (Sr), technetium (Tc), thorium (Th), and uranium (U). According to the numerical predictions, the repository-derived nuclides that would be most significantly retained are Th, Ni, and Cs, mainly through sorption onto clays, followed by U, C, Sr, and Ra, trapped by sorption and/or incorporation into mineral phases.

Impact of stress on solute transport in a fracture network: A comparison study

This paper compares numerical modeling of the effect of stress on solute transport (advection and matrix diffusion) in fractured rocks in which fracture apertures are correlated with fracture lengths. It is mainly motivated by the performance and safety assessments of underground radioactive waste repositories. Five research teams used different approaches to model stress/deformation, flow and transport processes, based on either discrete fracture network or equivalent continuum models. The simulation results derived by various teams generally demonstrated that rock stresses could significantly influence solute transport processes through stress-induced changes in fracture apertures and associated changes in permeability. Reasonably good agreement was achieved regarding advection and matrix diffusion given the same fracture network, while some observed discrepancies could be explained by different mechanical or transport modeling approaches.

Preface: Hydrogeology of cold regions

Almost half a century ago, Williams (1970) compiled an annotated bibliography of published materials (up to 1960) on permafrost groundwater in the former Soviet Union, United States and Canada, and Scandinavia. That comprehensive survey encompassed literature on permafrost and related temperature and hydrological phenomena, and scientific and applied aspects of groundwater in permafrost terrain. In the intervening years, there have been major advances in permafrost hydrogeology, accompanied by shifts in research emphasis driven by scientific, environmental and societal demands. The present theme issue of Hydrogeology Journal presents a collection of articles that reflect the current status of progress in research on the hydrogeology of cold regions. Several of the papers in this theme issue describe current conditions of resources and processes in different specific regions of the world. Overall, the studies address conditions across different parts of Alaska (USA), Canada, Siberia, China, Fennoscandia and other parts of Europe, and Antarctica. Although snow and seasonally or permanently frozen ground recurs as a common consideration, each paper presents a unique perspective on widely varying conditions. Greater understanding of polar and sub-polar processes may be gleaned from a comparison among these results. With the focus of this thematic issue being on the hydrogeology of cold regions, all the papers in the issue discuss important elements of subsurface hydrology, and there is particular emphasis on ground ice and permafrost interactions with groundwater. However, the studies also deal with externalities that impact the subsurface such as surface energy budget, snow hydrology or glaciers, and groundwater below ice sheets, and some contributions address subsurface controls on the surface conditions via interaction with surface water or ecology. With regard to investigation approaches, the studies deal with interpretation of field or remotely sensed data, theory of ice-impacted hydrologic processes, field techniques, and modeling of groundwater systems in cold regions. Some of themodeling papers combine in pointing at safety assessment of nuclear waste repositories under climate-cooling scenarios as an important motivation for development and application of numerical simulation approaches for the hydrogeology of cold regions. Some articles are about management of groundwater resources, and there is also some discussion on societal aspects of cold-regions hydrology, for example, impacts of climate warming in these regions. In summary, the range of investigations presented in this thematic issue constitutes a valuable compilation of the state of knowledge of cold region hydrogeology. This contribution is timely, with groundwater resources in cold regions facing immediate or impending changes as a consequence of the ongoing climate change, the intensification of the hydrologic cycle, and in response to increased demands from communities and industry.

Effects of matrix composition on instant release fractions from high burn-up nuclear fuel

ABSTRACTThe release of radionuclides from spent nuclear fuel in contact with water is controlled by two processes – the dissolution of the UO2grains and the rapid release of fission products segregated either to the gap between the fuel and the cladding or to the UO2grain boundaries. The rapid release is often referred to as the Instant Release Fraction (IRF) and is of interest for the safety assessment of geological repositories for spent fuel due to the potential dose contribution.Previous studies have shown that the instant release fraction can be correlated to the fission gas release (FGR) from the spent fuel. Studies comparing results from samples in the form of pellets, fragments, powders and a fuel rodlet have shown that the sample preparation has a significant impact on the instant release, indicating that the differentiation between gap release and grain boundary release should be further explored.Today, there are trends towards power uprates, longer fuel cycles and increasing burn-up putting additional requirements on the nuclear fuel. These requirements are met by the development of new fuel types, such as UO2fuels containing dopants or additives. The additives and dopants affect fuel properties such as grain size and fission gas release. In the present study we have performed experimental leaching studies using two high burnup fuels with and without additives/dopants and compared the fuel types with respect to their instant release behavior. The results of the leaching of the samples for the 3 initial contact periods; 1, 7 and 23 days are reported here.

On persistent primary variables for numerical modeling of gas migration in a nuclear waste repository

Numerical simulation of gas migration driven by compressible two-phase partially miscible flow in porous media is of major importance for safety assessment of deep geological repositories for long-lived high-level nuclear waste. We present modeling of compositional liquid and gas flow for numerical simulations of hydrogen migration in deep geological radioactive waste repository based on persistent primary variables. Two-phase flow is considered, with incompressible liquid and compressible gas, which includes capillary effects, gas dissolution, and diffusivity. After discussing briefly the existing approaches to deal with phase appearance and disappearance problem, including a persistent set of variables already considered in a previous paper (Bourgeat et al., Comput Geosci 13(1):29–42, 2009), we focus on a new variant of the primary variables: dissolved hydrogen mass concentration and liquid pressure. This choice leads to a unique and consistent formulation in liquid saturated and unsaturated regions, which is well adapted to heterogeneous media. We use this new set of variable for numerical simulations and show computational evidences of its adequacy to simulate gas phase appearance and disappearance in different but typical situations for gas migration in an underground radioactive waste repository.

INFLUENCE OF IMPACTS ON THE SAFETY OF A GEOLOGICAL REPOSITORY

The influence of impacts on the long-term safety of the radioactive waste geological disposal system was considered, and also the probability of such effects was assessed. It was analyzed and generalized information in relation to: frequencies of impacts and processes within geological environment and biosphere, which accompany formation of craters; scales of these processes depending on energy of projectiles, which encounter with the Earth; possible ecological and social consequences of impacts. Based on these data certainly scenarios of impacts influence on geological repository safety were determined; scenarios probabilities and maximum ranges of the corresponding projectile were estimated, and also some conclusions concerning the account of impacts at safety assessments of geological repositories were formulated. In particular, it was shown that there is an impacts energy class (102…105 Mt), the radiological consequences of which can jeopardize greater territory than the non-radiological one. The probability of such scenario is low (10-10…10-9 y-1). However, the risk of this scenario can exceed the level of acceptable risk determined by the radiation safety norms. Thus, such scenario should be examined at the safety analysis of geological repository. Recommendations were also given in relation to the decreasing of probability of the geological repository destruction.

Immobilization of uranium in biofilm microorganisms exposed to groundwater seeps over granitic rock tunnel walls in Olkiluoto, Finland

In an underground rock characterization facility, the ONKALO tunnel in Finland, massive 5–10-mm thick biofilms were observed attached to tunnel walls where groundwater was seeping from bedrock fractures at a depth of 70m. In laboratory experiments performed in a flow cell with detached biofilms to study the effect of uranium on the biofilm, uranium was added to the circulating groundwater (CGW) obtained from the fracture feeding the biofilm. The final uranium concentration in the CGW was adjusted to 4.25×10−5M, in the range expected from a leaking spent nuclear fuel (SNF) canister in a future underground repository. The effects were investigated using microelectrodes to measure pH and Eh, time-resolved laser fluorescence spectroscopy (TRLFS), energy-filtered transmission electron microscopy (EF-TEM), and electron energy-loss spectroscopy (EELS) studies and thermodynamic calculations were utilized as well. The results indicated that the studied biofilms constituted their own microenvironments, which differed significantly from that of the CGW. A pH of 5.37 was recorded inside the biofilm, approximately 3.5units lower than the pH observed in the CGW, due to sulfide oxidation to sulfuric acid in the biofilm. Similarly, the Eh of +73mV inside the biofilm was approximately 420mV lower than the Eh measured in the CGW. Adding uranium increased the pH in the biofilm to 7.27 and reduced the Eh to −164mV. The changes of Eh and pH influenced the bioavailability of uranium, since microbial metabolic processes are sensitive to metals and their speciation. EF-TEM investigations indicated that uranium in the biofilm was immobilized intracellularly in microorganisms by the formation of metabolically mediated uranyl phosphate, similar to needle-shaped autunite (Ca[UO2]2[PO4]2·2–6H2O) or meta-autunite (Ca[UO2]2[PO4]2·10–12H2O). In contrast, TRLFS studies of the contaminated CGW identified aqueous uranium carbonate species, likely (Ca2UO2[CO3]3), formed due to the high concentration of carbonate in the CGW. The results agreed with thermodynamic calculations of the theoretically predominant field of uranium species, formed in the uranium-contaminated CGW at the measured geochemical parameters.This investigation clearly demonstrated that biological systems must be considered as a part of natural systems that can significantly influence radionuclide behavior. The results improve our understanding of the mechanisms of biofilm response to radionuclides in relation to safety assessments of SNF repositories.

Importance of thermo-osmosis for fluid flow and transport in clay formations hosting a nuclear waste repository

Three osmotic processes have been identified in clay-rich media. Electro- and chemo-osmosis – flows of water caused by salinity and electrical potential gradients – have so far attracted almost exclusive attention. But, despite the recurring concern about the importance of thermo-osmosis – a flow of water driven by a temperature gradient – in argillaceous media, it remains largely neglected. Here we propose a new formalism for estimating the thermo-osmotic permeability based on a theoretical analysis at the molecular and pore scale, then upscaled. We show that the thermo-osmotic permeability can be estimated only from surface-charge density, temperature, pore size and salinity. The possible prominent role of thermo-osmosis in compacted shale layers with a temperature gradient is then exemplified. This first general estimate of the thermo-osmotic permeability can be used to improve our understanding of the influence on fluid flow and pressure fields of the natural geothermal gradient in sedimentary basins, which is required, e.g., for safety assessments of nuclear-waste repositories in shale layers.