Increasing understanding and confidence in THM simulations of Engineered Barrier Systems

Schäfers, A.; Gens, Antonio; Rodríguez-Dono, Alfonso; Baxter, S.; Tsitsopoulos, Vasileios; Holton, David; Malmberg, D.; Sawada, Masataka; Qiao, Yunfeng; Ferrari, Alessio; Laloui, Lyesse; Sjöland, Anders

doi:10.1680/jenge.18.00078

Cited by 13 publications

(3 citation statements)

References 10 publications

(14 reference statements)

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“…Post closure, however, this liquid influx will re-saturate the back-filled repository [22]. At the same time, water vapour transport in the gaseous phase driven by vapour mass fraction and temperature gradients created by the heat generation of the high-level-waste takes place, leading to a dry-out of the bentonite in the vicinity of the waste-containing canisters [46,13]. In the fully saturated host rock, temperature increase might lead to a pore liquid pressurization (due to the volumetric expansion of water with increasing temperature) which in turn could trigger liquid flow or, in the worst case could cause the loss of integrity of the host rock.…”

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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“…for swelling clay rocks (Graupner et al 2018;Schäfers et al 2020), which relates the swelling stress to the maximum swelling pressure sw max by saturation changes as follows:…”

Section: The Mechanical Processmentioning

confidence: 99%

Coupled Hydro-Mechanical Modeling of Swelling Processes in Clay–Sulfate Rocks

et al. 2022

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Swelling of clay–sulfate rocks is a serious and devastating geo-hazard, often causing damage to geotechnical structures. Therefore, understanding underlying swelling processes is crucial for the safe design, construction, and maintenance of infrastructure. Planning appropriate countermeasures to the swelling problem requires a thorough understanding of the processes involved. We developed a coupled hydro-mechanical (HM) model to reproduce the observed heave in the historic city of Staufen in south-west Germany, which was caused by water inflow into the clay–sulfate bearing Triassic Grabfeld Formation (formerly Gipskeuper = “Gypsum Keuper”) after geothermal drilling. Richards’ equation coupled to a deformation process with linear kinematics was used to describe the hydro-mechanical behavior of clay–sulfate rocks. The mathematical model is implemented into the scientific open-source framework OpenGeoSys. We compared the model calculations with the measured long-term heave records at the study site. We then designed a sensitivity analysis to achieve a deeper insight into the swelling phenomena. The synthetic database obtained from the sensitivity analysis was used to develop a machine learning (ML) model, namely least-squares boosting ensemble (LSBoost) model coupled with a Bayesian optimization algorithm to rank the importance of parameters controlling the swelling. The HM model reproduced the heave observed at Staufen with sufficient accuracy, from a practical point of view. The ML model showed that the maximum swelling pressure is the most important parameter controlling the swelling. The other influential parameters rank as Young’s modulus, Poisson’s ratio, overburden thickness, and the initial volumetric water content of the swelling layer.

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“…Moreover, regarding nuclear fission energy, uranium reserves are not sufficient to guarantee the supply for more than thirty years [68] and the issue of radioactive waste disposal is still not resolved [69,70]. As for nuclear fusion technology, it is at the level of research and far from being available at the operational level [71].…”

Section: Likert-type Questionsmentioning

confidence: 99%

Fostering Sustainability and Critical Thinking through Debate—A Case Study

Rodríguez-Dono

Hernández-Fernández

2021

Sustainability

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Transversal competences such as sustainability or critical thinking have become more important in the last decades in University teaching. The objective of this article is to assess the effectiveness of debate as a teaching method capable of fostering such competences in engineering students. To do this, a debate activity has been held facing two reasonable positions: Sustainable Development versus Degrowth. The research methodology consisted of performing this activity in the classroom (with 13 students in this particular case study), and conducting some tests before and after the debate that served as feedback to assess the effectiveness of the debate on the learning process. This feedback is composed of different documents, including a pre-post test, a specific survey about the debate, a pre-post knowledge survey and the Student Evaluation of Educational Quality (SEEQ) survey. A methodology for the organization of the debate is proposed and the answers of the students to these feedback documents are analyzed. As it can be inferred from the different surveys, the debate has been an efficient learning tool to acquire knowledge and to develop sustainability and critical thinking competences.

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Increasing understanding and confidence in THM simulations of Engineered Barrier Systems

Cited by 13 publications

References 10 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

Coupled Hydro-Mechanical Modeling of Swelling Processes in Clay–Sulfate Rocks

Fostering Sustainability and Critical Thinking through Debate—A Case Study

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