A coupled THMC model of FEBEX mock-up test

Zheng, Liange; Samper, Javier

doi:10.1016/j.pce.2008.10.023

Cited by 54 publications

(26 citation statements)

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“…. (Wolery, 1992), selectivity coefficients for cation exchange reactions (ENRESA, 2006c;Samper et al, 2008a,c;Zheng and Samper, 2008), and protolysis constants for surface complexation reactions for a triple-site model (Bradbury and Baeyens, 1997) K Na-cation Na + + X-K  K + + X-Na 0.138 Na + + 0.5X 2 -Ca  0.5Ca 2+ + X-Na 0.2942 Na + + 0.5 X 2 -Mg- 0.5Mg 2+ + X-Na 0. Table 8.…”

Section: Mechanical Modelmentioning

confidence: 99%

“…These inferred data were compared to THC model predictions by Samper et al, (2008a) who found significant discrepancies for most chemical species, and especially for SO 4 2-and HCO 3 -. The limitations of the THC model of Samper et al (2008a) could be attributed to bentonite swelling and coupled phenomena such as chemical and thermal osmosis which were found to be relevant for reactive solute transport through FEBEX bentonite by Zheng and Samper (2008) for the FEBEX mock up test and Zheng et al (2010) for a small-scale (13 cm) heating and hydration lab test.…”

Section: Introductionmentioning

confidence: 99%

“…Relative permeability of the liquid Table 4. Initial chemical composition of the bentonite and granite pore waters (Samper et al, 2005), initial mineral volume fractions of the bentonite and the granite (Samper et al, 2008), cation exchange composition (Fernández et al, 2004) and site capacities for surface complexation for the triple-site (strong and two weak sites) model Baeyens, 2003, 2005 …”

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confidence: 99%

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A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

Zheng

Samper

Montenegro

2011

Journal of Contaminant Hydrology

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The performance assessment of a geological repository for radioactive waste requires quantifying the geochemical evolution of the bentonite engineered barrier. This barrier will be exposed to coupled thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes. This paper presents a coupled THC model of the FEBEX (Full-scale Engineered Barrier EXperiment) in situ test which accounts for bentonite swelling and chemical and thermal osmosis. Model results attest the relevance of thermal osmosis and bentonite swelling for the geochemical evolution of the bentonite barrier while chemical osmosis is found to be almost irrelevant. The model has been tested with data collected after the dismantling of heater 1 of the in situ test. The model reproduces reasonably well the measured temperature, relative humidity, water content and inferred geochemical data. However, it fails to mimic the solute concentrations at the heater-bentonite and bentonite-granite interfaces because the model does not account for the volume change of bentonite, the CO 2 (g) degassing and the transport of vapor from the bentonite into the granite. The inferred HCO 3 -and pH data cannot be explained solely by solute Page 2 of 54 transport, calcite dissolution and protonation/deprotonation by surface complexation, suggesting that such data may be affected also by other reactions.

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Section: Mechanical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

Zheng

Samper

Montenegro

2011

Journal of Contaminant Hydrology

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“…This may be caused either by inaccuracies in parameter values, or by a faulty conceptual model of the THM processes. Some proposed additional phenomena Li et al, 2009) that could be included in our understanding and modelling of the buffer include (a) the effect of microstructural evolution (Sanchez et al, 2005) (b) the existence of different states of water in the bentonite, (c) the existence of a threshold hydraulic gradient for water flow and (d) thermo-osmosis (Zheng and Samper (2008); Zheng et al, 2010). A proper inclusion of relevant THM processes, together with thermodynamical constraints, is needed for extrapolation of bentonite behavior over a long time frame.…”

Section: Thmc Processes In Buffer Materials (Bentonite)mentioning

confidence: 99%

Disposal systems evaluations and tool development : Engineered Barrier System (EBS) evaluation.

Rutqvist¹,

Liu²,

Steefel³

et al. 2011

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Eric Sonnenthal (LBNL) Engineered Barrier System (EBS) Evaluation This page is intentionally left blank Engineered Barrier System (EBS) Evaluation 5 Executive SummaryKey components of the nuclear fuel cycle are short-term storage and long-term disposal of nuclear waste. The latter encompasses the immobilization of used nuclear fuel (UNF) and radioactive waste streams generated by various phases of the nuclear fuel cycle, and the safe and permanent disposition of these waste forms in geological repository environments. The engineered barrier system (EBS) plays a very important role in the long-term isolation of nuclear waste in geological repository environments. EBS concepts and their interactions with the natural barrier are inherently important to the long-term performance assessment of the safety case where nuclear waste disposition needs to be evaluated for time periods of up to one million years. Making the safety case needed in the decision-making process for the recommendation and the eventual embracement of a disposal system concept requires a multi-faceted integration of knowledge and evidence-gathering to demonstrate the required confidence level in a deep geological disposal site and to evaluate longterm repository performance.The focus of this report is the following:• Evaluation of EBS in long-term disposal systems in deep geologic environments with emphasis on the multi-barrier concept;• Evaluation of key parameters in the characterization of EBS performance;• Identification of key knowledge gaps and uncertainties;• Evaluation of tools and modeling approaches for EBS processes and performance.The above topics will be evaluated through the analysis of the following:• Overview of EBS concepts for various NW disposal systems;• Natural and man-made analogs, room chemistry, hydrochemistry of deep subsurface environments, and EBS material stability in near-field environments;• Reactive Transport and Coupled Thermal-Hydrological-Mechanical-Chemical (THMC) processes in EBS;• Thermal analysis toolkit, metallic barrier degradation mode survey, and development of a Disposal Systems Evaluation Framework (DSEF).This report will focus on the multi-barrier concept of EBS and variants of this type which in essence is the most adopted concept by various repository programs. Empasis is given mainly to the evaluation of EBS materials and processes through the analysis of published studies in the scientific literature of past and existing repository research programs. Tool evaluations are also emphasized, particularly on THCM processes and chemical equilibria. Although being an increasingly important aspect of NW disposition, short-term or interim storage of NW will be briefly discussed but not to the extent of the EBS issues relevant to disposal systems in deep geologic environments. Interim storage will be discussed in the report Evaluation of Storage Concepts FY10 Final Report (Weiner et al. 2010). Engineered Barrier System (EBS) Evaluation 6This page is intentionally left blank Engineered Barrier System (EBS) Eva...

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“…In such cases the numerical simulations are conducted linking the reactive transport simulator TOUGHREACT (Xu et al 2011) to FLAC3D. Currently there are also other codes that have some THMC capability such as CODE_ BRIGHT (Guimarães et al 2007) and FADES-CORE (Zheng and Samper 2008) and have been used to conduct THMC simulations (e.g., Gens et al 2010;Zheng et al 2010). However, in these simulations, while they demonstrated that THMC simulations can be done by one code simultaneously, how chemical and mechanical processes were coupled was not discussed.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Coupled Thermo-Hydro-Mechanical Processes with Links to Geochemistry Associated with Bentonite-Backfilled Repository Tunnels in Clay Formations

et al. 2013

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This paper presents simulation results related to coupled thermal-hydraulic-mechanical (THM) processes in engineered barrier systems (EBS) and clay host rock, in one case considering a possible link to geochemistry. This study is part of the US DOE Office of Nuclear Energy's used fuel disposition campaign, to investigate current modeling capabilities and to identify issues and knowledge gaps associated with coupled THMC processes and EBSrock interactions associated with repositories hosted in clay rock. In this study, we simulated a generic repository case assuming an EBS design with waste emplacement in horizontal tunnels that are back-filled with bentonite-based swelling clay as a protective buffer and heat load, derived for one type of US reactor spent fuel. We adopted the Barcelona basic model (BBM) for modeling of the geomechanical behavior of the bentonite, using properties corresponding to the FEBEX bentonite, and we used clay host rock properties derived from the Opalinus clay at Mont Terri, Switzerland. We present results related to EBS host-rock interactions and geomechanical performance in general, as well as studies related to peak temperature, buffer resaturation and thermally induced pressurization of host rock pore water, and swelling pressure change owing to variation of chemical composition in the EBS. Our initial THM modeling results show strong THM-driven interactions between the bentonite buffer and the lowpermeability host rock. The resaturation of the buffer is delayed as a result of the low rock permeability, and the fluid pressure in the host rock is strongly coupled with the temperature changes, which under certain circumstances could result in a significant increase in pore pressure. Moreover, using the BBM, the bentonite buffer was found to have a rather complex geomechanical behavior that eventually leads to a slightly nonuniform density distribution. Nevertheless, the simulation shows that the swelling of the buffer is functioning to provide an adequate increase in confining stress on the tunnel wall, leading to a stabilization of any failure that may occur during the tunnel excavation. Finally, we describe the application of a possible approach for linking THM processes with chemistry, focusing on the evolution of primary and secondary swelling, in which the secondary swelling is caused by changes in ionic concentration, which in turn is evaluated using a transport simulation model.

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A coupled THMC model of FEBEX mock-up test

Cited by 54 publications

References 49 publications

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

A coupled THC model of the FEBEX in situ test with bentonite swelling and chemical and thermal osmosis

Disposal systems evaluations and tool development : Engineered Barrier System (EBS) evaluation.

Modeling of Coupled Thermo-Hydro-Mechanical Processes with Links to Geochemistry Associated with Bentonite-Backfilled Repository Tunnels in Clay Formations

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