Experimentally determined swelling pressures and geochemical interactions of compacted Wyoming bentonite with highly alkaline solutions

Karnland, Ola; Olsson, Siv; Nilsson, Ulf J.; Sellin, Patrik

doi:10.1016/j.pce.2006.01.012

Cited by 145 publications

(62 citation statements)

References 11 publications

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“…It is also well established that bentonite displays a high swelling characteristic that is a function of the aforesaid physicochemical properties related to the montmorillonite mineral [3,[11][12][13][14]. The high swelling capacity provides an effective mechanism for the barrier to retard and adsorb radionuclides as well as the ability to self-heal to ensure fissure closure.…”

Section: Introductionmentioning

confidence: 99%

Physicochemical and Geotechnical Alterations to MX-80 Bentonite at the Waste Canister Interface in an Engineered Barrier System

Davies¹,

Davie

Edward

et al. 2017

Geosciences

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Abstract:The study investigated the basic geomechanical and mineralogical evolution of the bentonite barrier under various experimental boundary conditions which replicated the near-field Thermo-Hydro-Chemico (THC) conditions in a repository. The relationships between the physicochemical alterations and changes in the geotechnical properties have seldom been studied, especially on a consistent dataset. This paper attempts to link the physicochemical properties of Na-bentonite (MX-80) to the macro-scale engineering functionality of the bentonite post THC exposure. Experiments investigated the impact of THC variables on the engineering and physicochemical functionality of the bentonite with respect to its application within a High-Level Waste (HLW) engineered barrier system. Intrinsic alterations to the MX-80 bentonite under relatively short-term exposure to hydrothermal and chemical conditions were measured. Additionally, two long-term tests were conducted under ambient conditions to consider the impact of exposure duration. The intrinsic measurements were then related to the overall performance of the bentonite as a candidate barrier material for application in a UK geological disposal facility. Findings indicate that exposure to thermo-saline-corrosion conditions (i.e., corrosion products derived from structural grade 275 carbon steel) inhibits the free swell capacity and plasticity of the bentonite. However, the measured values remained above the design limits set out for the Swedish multi-barrier concept, from which the UK concept may take a lead. Corrosion alone does not appear to significantly affect the geotechnical measurements compared with the influence of thermal loading and high saline pore water after relatively short-term exposure. Thermal and corrosion exposure displayed no impact on the intrinsic swelling of the smectite component, indicating that no significant structural alteration had occurred. However, when exploring more complex saline solutions i.e., mixed Na, K and Ca, rather than the reference NaCl, divalent cation replacement was observed within the interlayer exchange site. This was accelerated in higher thermal loading conditions.

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Section: Introductionmentioning

confidence: 99%

Physicochemical and Geotechnical Alterations to MX-80 Bentonite at the Waste Canister Interface in an Engineered Barrier System

Davies¹,

Davie

Edward

et al. 2017

Geosciences

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“…This property, along with others, made bentonite a candidate material for the safe disposal of high-level radioactive waste (HLRW). Therefore, numerous publications on the swelling pressure of bentonites are available (Pusch et al, 1995;Lee et al, 1999;Herbert and Moog, 2002;Komine, 2004;Karnland et al, 2007;Agus and Schanz, 2008;Villar and Lloret, 2008). The swelling results from the hydration of the exchangeable cations resulting in expansion.…”

Section: Introductionmentioning

confidence: 99%

“…This means that despite a given dry density was reached compaction was less efficient with respect to increasing the swelling pressure if water was present. Furthermore, the swelling pressure significantly depends on the type of water the bentonite is exposed to (Karnland, 1997;Xie et al, 2007;Karnland et al, 2007;Herbert et al, 2008;Lee et al, 2012). Lloret (2004, 2008) and Lee et al (2010) reported decreasing swelling pressure with increasing temperature while Shirazi et al (2010) and Ye et al (2013) found increasing swelling pressure with increasing temperature.…”

Section: Introductionmentioning

confidence: 99%

About differences of swelling pressure — dry density relations of compacted bentonites

Kaufhold

Baille

Schanz

et al. 2015

Applied Clay Science

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“…The heater power was 1800 W and the instrumentation similar to that of the Prototype [1,7]. Figure 7 illustrates the recorded evolution of the total pressure, which includes the 100 kPa water pressure.…”

Section: Field Tests -The äSpö Retrieval Testmentioning

confidence: 99%

“…Figure 7: Evolution of total pressure at mid-height of the buffer in the wettest hole. The highest pressure, about 6.7 MPa, was reached after about 2 years while the lowest (4 MPa) appeared close to the canister [1,7].…”

Section: Field Tests -The äSpö Retrieval Testmentioning

confidence: 99%

The predicted and actual wetting rate of the buffer in repositories for high-level radioactive waste

Pusch¹,

Ramqvist²,

Knutsson³

2014

WIT Transactions on Ecology and the Environment

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Underground test sites for disposal of high-level radioactive waste (HLW) are commonly equipped with instrumentation for documentation of the evolution of engineered barriers and of changes in the physical state of the host rock. The rate of hydration of the clay buffer surrounding waste canisters determines the physical interaction with the rock and waste canisters and is recorded by use of RH meters and by measuring the swelling pressure exerted on cells installed in the clay. They are connected to cables and tubings extending to the recording units placed in room atmosphere. If they pass from the rock through the buffer groundwater under pressure can migrate through or along bunches of cables and tubings and reach the points of measurement earlier than in clay without instrumentation. The inconvenience is avoided by tight embedment of individual cables and tubings and placement of the pressure gauges such that they do not pass through the clay. Incorrect rates of hydration has led to the inadequate conclusion that water flows in unsaturated parts of the buffer according Darcy's law while it is in fact migrating by coupled diffusion processes.

show abstract

Experimentally determined swelling pressures and geochemical interactions of compacted Wyoming bentonite with highly alkaline solutions

Cited by 145 publications

References 11 publications

Physicochemical and Geotechnical Alterations to MX-80 Bentonite at the Waste Canister Interface in an Engineered Barrier System

Physicochemical and Geotechnical Alterations to MX-80 Bentonite at the Waste Canister Interface in an Engineered Barrier System

About differences of swelling pressure — dry density relations of compacted bentonites

The predicted and actual wetting rate of the buffer in repositories for high-level radioactive waste

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