Analysis of the porewater chemical composition of a Spanish compacted bentonite used in an engineered barrier

Fernández, Ana María; Baeyens, Bart; Bradbury, Michael E.; Rivas, Pedro José

doi:10.1016/j.pce.2003.12.001

Cited by 141 publications

(92 citation statements)

References 23 publications

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“…Much effort has been made during recent years to improve the water extraction methods, develop numerical interpretation methods and achieve consistency of experimental data and geochemical modeling (Sacchi et al, 2001;Bradbury and Baeyens, 2003;Pearson et al, 2003;Fernández et al, 2004). Preserving in situ conditions of core samples is difficult.…”

Section: Inference Of Pore Water Composition From Aqueous Extract Datamentioning

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: Inference Of Pore Water Composition From Aqueous Extract Datamentioning

confidence: 99%

mentioning

confidence: 99%

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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“…Note that Hardin et al (2013) determined drift and waste package spacing based on a thermal limit at the rock wall of 100 o C. In this report smaller spacing is used based on the scoping calculation by Greenberg et al (2013) Table 4. Mass fraction (%) of minerals for FEBEX (ENRESA 2000;Fernández et al 2004) and MX-80 bentonite (Börgesson et al 2006 Table 5. Pore-water composition of FEBEX bentonite (Fernández et al 2001) and MX-80 bentonite (Curtis and Wersin 2002 Table 6.…”

Section: Figuresmentioning

confidence: 99%

“…Squeezing is a straight forward method -pore-water is squeezed out and concentrations are measured. However, squeezing does not allow extracting of pore-water from clay samples with gravimetric water contents less than 20% (Fernández et al 2001(Fernández et al , 2004, which means that squeezing cannot be done for FEBEX bentonite blocks, which initially have a water content 14% (ENRESA 2000). In an aqueous extract test, a crushed sample is placed in contact with water at a low solid/liquid ratio (ranging from 1:16 to 1:1).…”

Section: Mineralogical Compositionmentioning

confidence: 99%

Generic Argillite/Shale Disposal Reference Case

Zheng¹,

Colon²,

Bianchi³

et al. 2014

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“…Among all chemical processes, cation exchange (Reardon, 1981), surface complexation (Glynn, 2003) and the formation of solid solutions (Zhu, 2004) are considered to contribute most significantly to the retardation of radionuclides. Cation exchange reactions in bentonite, and in more general form, on clay minerals, have been well investigated (Bradbury and Baeyens, 1997;Huertas et al, 2001;Fernandez et al, 2004). The effect of solid solutions has also attracted some recent attention.…”

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confidence: 99%

Modeling the competition between solid solution formation and cation exchange on the retardation of aqueous radium in an idealized bentonite column

et al. 2009

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Clays and clay rocks are considered viable geotechnical barriers in radioactive waste disposal. One reason for this is the propensity for cation exchange reactions in clay minerals to retard the migration of radionuclides. Although another retardation mechanism, namely the incorporation of radionuclides into sulfate or carbonate solid solutions, has been known for a long time, only recently has it been examined systematically. In this work, we investigate the competitive effect of both mechanisms on the transport of radium (Ra) in the near-field of a low-and intermediate level nuclear waste repository. In our idealized geochemical model, numerical simulations show that barium (Ba) and strontium (Sr) needed for Ra sulfate solid solutions also partition to the cation exchange sites of montmorillonite (Mont), which is the major mineral constituent of bentonite that is used for tunnel backfill. At high Mont content, most Ra tends to attach to Mont, while incorporation of Ra in sulfate solid solutions is more important at low Mont content. To explore the effect of the Mont content on the transport of radium, a multi-component reactive transport model was developed and implemented in the scientific software OpenGeoSys-GEM. It was found that a decrease of fixation capacity due to low Mont content is compensated by the formation of solid solutions and that the migration distance of aqueous Ra is similar at different Mont/ water ratios.

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Analysis of the porewater chemical composition of a Spanish compacted bentonite used in an engineered barrier

Cited by 141 publications

References 23 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

Generic Argillite/Shale Disposal Reference Case

Modeling the competition between solid solution formation and cation exchange on the retardation of aqueous radium in an idealized bentonite column

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