Thermo-hydro-mechanical analysis of the complete lifetime of the bentonite barrier in the FEBEX in-situ test

Bosch, Jose A.; Qiao, Yunfeng; Ferrari, Alessio; Laloui, Lyesse

doi:10.1016/j.gete.2023.100472

Cited by 6 publications

(2 citation statements)

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“…FEBEX is a research and demonstration project that lasted 18 years and has been reported in numerous technical reports [25,26] and papers [22]. The key experiment of the FEBEX is the in situ test at the Grimsel test site in Switzerland, which has been simulated by several models [13,19,20,22,27,28]. Here, in the following sections, we briefly describe the configuration, key dates, and available data to facilitate the presentation of model results.…”

Section: Febex In Situ Testmentioning

confidence: 99%

“…The test had run for 18 years with two dismantling events providing a unique set of chemical data that allows for studying chemical changes in bentonite. Throughout the in situ test, models have been developed for different stages and aspects of the test: THM modeling analysis [19,20] for the entire time span of the in situ test; THC model [15] for the data collected after the first dismantling event, reactive transport model for the intermediate time [21], and THMC model for the prediction of the geochemical changes at the second dismantling [22], reactive transport model just for concrete/bentonite interaction [13] and bentonite/canister interaction [23]. Modeling the geochemical changes for long-term, large-scale tests like the FEBEX in situ test has been challenging.…”

Section: Introductionmentioning

confidence: 99%

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Prediction of Long-Term Geochemical Change in Bentonite Based on the Interpretative THMC Model of the FEBEX In Situ Test

Zheng,

Fernández

2023

Minerals

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Since nuclear energy is crucial in the decarbonization of the energy supply, one hurdle to remove is the handling of high-level radioactive waste (HLW). Disposal of HLW in a deep geological repository has long been deemed a viable permanent option. In the design of a deep geological repository, compacted bentonite is the most commonly proposed buffer material. Predicting the long-term chemical evolution in bentonite, which is important for the safety assessment of a repository, has been challenging because of the complex coupled processes. Models for large-scale tests and predictions based on such models have been some of the best practices for such purposes. An 18-year-long in situ test with two dismantling events provided a unique set of chemical data that allowed for studying chemical changes in bentonite. In this paper, we first developed coupled thermal, hydrological, mechanical, and chemical (THMC) models to interpret the geochemical data collected in the in situ test and then extended the THMC model to 200 years to make long-term prediction of the geochemical evolution of bentonite. The interpretive coupled THMC model shows that the geochemical profiles were strongly affected by THM processes such as evaporation/condensation, porosity change caused by swelling, permeability change, and the shape of concentration profiles for major cations were largely controlled by transport processes, but concentration levels were regulated by chemical reactions, and the profiles of some species such as pH, bicarbonate, and sulfate were dominated by these reactions. The long-term THMC model showed that heating prolongs the time that bentonite becomes fully saturated in the area close to the heater/canister; however, once the bentonite becomes fully saturated, high concentrations of ions in bentonite near the heater, which was observed in the field test, will disappear; illitization continues for 50 years but will not proceed further.

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