Diffusive Transport of Dissolved Gases in Potential Concretes for Nuclear Waste Disposal

Jacops, Elke; Phung, Quoc Tri; Frederickx, Lander; Levasseur, Séverine

doi:10.3390/su131810007

Cited by 13 publications

(5 citation statements)

References 25 publications

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“…Gas pressure build-up due to H 2 release might lead to gas migration in the geotechnical and geological barrier [23]. In the initially partially liquid saturated repository where a distinct gaseous phase is present, gas migration will likely occur via advection whereas in the fully liquid saturated host rock (and after the re-saturation of the backfilled repository, in the saturated bentonite), dissolved gas will be transported diffusively, driven by dissolved gas concentration gradients [18,29]. The transport of gas, be it by diffusion or advection in the liquid or gaseous phase, can imply the transport of radio nuclides [30].…”

Section: Relevant Thm-coupled Processes In Hlw Repositoriesmentioning

confidence: 99%

Benchmarking a new TH2M implementation in OGS-6 with regard to processes relevant for nuclear waste disposal

Pitz

Grunwald

Graupner

et al. 2023

Preprint

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In this paper, thermo-hydro-mechanically (THM) coupled processes triggered during the construction, operation and closure of a deep geological repository for heat generating, high level radioactive waste are discussed based on a generic disposal concept.For this purpose we are using the numerical non-isothermal two-phase-two-component flow in deformable porous media (\th2m) implementation \cite{Grunwald2022} in the open-source software OpenGeoSys \cite{Bilke2019337}.THM coupled effects covered in this work focus on single and two-phase-flow phenomena, gas and heat generation as well as poro-elastic medium deformation.A suitable set of benchmarks covering aforementioned THM-effects, devised in the scope of the BenVaSim benchmarking project \cite{Lux2022} is chosen and one additional benchmark is presented, allowing for the demonstration and comparison of the OGS-6 \th2m implementation against results obtained by other well-established codes used in the field.Apart from the code comparison, the benchmarks also serve as means to analyize THM coupled processes in a repository based on very simplified geometries. Therefore, they can help to improve the process understanding, but any quantitative results should not be interpreted as predictions of the behaviour of a real repository.The results obtained in this work agree well with the results presented by the project partners in BenVaSim -- both in single phasic, fully liquid saturated cases and in partially saturated two phase regions.Hence, the suitability of the OGS-6 \th2m implementation for the application in the field of radioactive waste management, supporting the safety case and analyzing the integrity of the geological and geotechnical barrier systems is demonstrated.Finally, a detailed discussion of observed phenomena in the benchmarks increases our understanding and confidence in the prediction of the behaviour of \th2m coupled systems in the context of deep geological radioactive waste disposal.

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Section: Relevant Thm-coupled Processes In Hlw Repositoriesmentioning

confidence: 99%

Benchmarking a new TH2M implementation in OGS-6 with regard to processes relevant for nuclear waste disposal

Pitz

Grunwald

Graupner

et al. 2023

Preprint

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“…The experimental setup for measuring permeability is the same as the one used on a similar sandy clay sample in a previous study [17]. This setup has not been modified because it is highly reliable and has been used to make K measurements for different samples [17]. Hydraulic conductivities are generally measured by imposing constant pressure gradients across the faces of the sample.…”

Section: Water Permeability Measurementsmentioning

confidence: 99%

An experimental methodology to assess the impact of desaturation on gas diffusion in clay based materials

et al. 2023

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The transport of gas in clay-based materials is dominated by diffusion. SCK CEN has studied and recorded an extensive data set of diffusion coefficients of gases in various saturated clays (Boom Clay, Opalinus Clay, Callovo-Oxfordian claystone and bentonites) used in Europe as host formations or in engineered barrier systems in the context of deep geological disposal of high and intermediate level nuclear wastes. However, partially saturated conditions may exist during the life cycle of a radioactive waste repository. The current study aims at establishing an experimental method to measure the diffusion coefficients of various gases in partially saturated clay-based materials by means of double through diffusion tests (cross diffusion of gases across the porous sample, driven by concentration gradients) and to assess the impact of desaturation on gas diffusivity. Historically, gas diffusion measurements have been performed under dissolved conditions with continuous water and dissolved gas flow around the clay sample. However, since the saturation degree of the sample has to be constant, a novel setup has been designed and optimized to operate under a pure gas phase under controlled relative humidity (RH). The experimental concept consists of cross diffusion of gas mixtures from two reservoirs at a fixed relative humidity on either side of the sample cell, namely, the upstream and downstream reservoirs. The RH is controlled using the same saturated salt solutions in both reservoirs. During the experiment, gases will diffuse from the upstream to the downstream reservoir. By measuring the change in gas composition in the downstream reservoir with a gas analyzer equipped with a mass spectrometer (which expresses the gas composition in terms of partial pressure), the gas flux and hence the diffusion coefficient is estimated by applying steady state Fick’s first law. The experimental methodology has been validated by performing an experiment on a sandy-clay sample of known petrophysical properties, at full saturation.

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“…The diffusion coefficients of initial materials were determined before and after a given time of interaction, similar to permeability. As presented in (Jacops et al 2021), a through-diffusion methodology was used to determine the diffusivities of two dissolved gases (He and CH4) in a single experiment. It is worth noting that the permeability/percolation cell can be readily detached and then rejoined to the diffusion setup due to its compatibility.…”

Section: Diffusivitymentioning

confidence: 99%

Degradation of Cement Pastes Subjected to Combined Carbonation and Leaching

Phung,

Fredericx,

Maes

2023

16th International Conference on Durability of Building Materials and Components

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Carbonation and leaching are likely to be the primary concrete degradation mechanisms for concrete utilized in geological repositories when the concrete is fully saturated and in contact with host rock pore water containing increased CO2 content. This work describes the changes in the microstructure and transport properties of cement pastes caused by coupled chemical degradation processes that occur at the cement paste-clay interface. In the laboratory, an experimental program was designed to accelerate the interface interaction under carbonation and leaching by bringing highly porous cement pastes (to mimic backfill materials used in geological disposal) and Boom Clay into contact in either accelerated percolation or batch-type experiments. Mercury intrusion porosimetry (MIP) was used to investigate the microstructural alteration. Inductively coupled plasma optical emission spectrometer (ICP-OES) and permeability, diffusion measurements were used to determine the evolution of chemical and transport properties, respectively. The results of the porosity change at the interface demonstrate an increase in porosity of the cement paste interface due to Ca leaching, which overwhelms the carbonation. As a result, the transport properties increase. This suggests that clogging of the cementitious material side is unlikely.

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Diffusive Transport of Dissolved Gases in Potential Concretes for Nuclear Waste Disposal

Cited by 13 publications

References 25 publications

Benchmarking a new TH2M implementation in OGS-6 with regard to processes relevant for nuclear waste disposal

Benchmarking a new TH2M implementation in OGS-6 with regard to processes relevant for nuclear waste disposal

An experimental methodology to assess the impact of desaturation on gas diffusion in clay based materials

Degradation of Cement Pastes Subjected to Combined Carbonation and Leaching

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