Investigation of Reactive Transport and Coupled THMC Processes in the EBS

Report on THMC Modeling of the Near Field Evolution of a Generic Clay Repository: Model Validation and Demonstration

“…While development of a more comprehensive and rigorous chemical-mechanical model is underway (Davis et al, 2013), in this report we use a linear elastic swelling model that is extended by incorporating the changes in the abundance of swelling clay to evaluate the consequence of illitization on stress in EBS bentonite. The mechanical model for the clay formation is the same as in Rutqvist et al (2013).…”

Laboratory Experiments on Bentonite Samples: FY15 Progress

“…A detailed description of the Na-montmorillonite purification procedure has been provided previously (Rutqvist et al, 2012;Davis et al, 2013). Briefly, pretreatment steps included: the removal of calcite impurities using a 1 M sodium acetate/glacial acetic acid solution (0.564 M) at pH 5; clay equilibration with a 1 M sodium chloride solution; removal of excess salts with Nanopure water; separation of quartz and feldspar impurities from the <2 µm clay fraction by centrifugation; and oven-drying of the purified clay at 45 °C.…”

“…As described in detail previously (Davis et al, 2013;Rutqvist et al, 2014), our first diffusion experiment focused on the diffusive transport of calcium bromide in purified Na-montmorillonite at a low degree of compaction (dry density of 0.79 kg/l). This experiment allowed us: (1) to test our experimental approach with non-radioactive solutes prior to uranium(VI) diffusion experiments; (2) to determine diffusion coefficients for calcium (and bromide) for their later incorporation in performance assessment models, which is motivated by the strong influence of Ca on uranium(VI) solution speciation; and (3) to examine the ability of existing pore-scale conceptual models to link molecular and macroscopic scale data on adsorption and diffusion in compacted smectite.…”

On the impact of temperatures up to 200 °C in clay repositories with bentonite engineer barrier systems: A study with coupled thermal, hydrological, chemical, and mechanical modeling

“…While development of a more comprehensive and rigorous chemical-mechanical model is underway (Davis et al, 2013), in this paper we use a linear elastic swelling model that is extended by incorporating changes in the abundance of swelling clay to evaluate the consequence of illitization on swelling stress in EBS bentonite. The mechanical model for the clay formation is the same as in Rutqvist et al (2014).…”