The Role of Clays for Safe Storage of Nuclear Waste

Dohrmann, R.; Kaufhold, Stephan; Lundqvist, Björn

doi:10.1016/b978-0-08-098259-5.00024-x

Cited by 35 publications

(14 citation statements)

References 35 publications

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“…The properties of smectites are under extensive study due to their important role in a wide variety of technological and biochemical applications such as fluid filtration, catalytic processes and the disposal of high-level radioactive waste (Murray, 2000;Dohrmann et al, 2013). In the Finnish concept of geological disposal of nuclear waste, a multi-barrier system is planned to prevent/retard the release of radionuclides to the biosphere.…”

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confidence: 99%

Effect of layer charge on the crystalline swelling of Na⁺, K⁺ and Ca²⁺ montmorillonites: DFT and molecular dynamics studies

2016

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The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (−1.0, −0.66 and −0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the selfdiffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.

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Effect of layer charge on the crystalline swelling of Na⁺, K⁺ and Ca²⁺ montmorillonites: DFT and molecular dynamics studies

2016

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“…In many concepts for deep geological disposal of high-level nuclear waste in crystalline host rocks, the waste is emplaced inside a metal canister surrounded by a bentonite buffer [1,2]. The bentonite acts, inter alia, as a hydrogeological barrier delaying the contact of the canister with formation water and retarding the radionuclide release to the geosphere by means of its high sorption capacity and a diffusion-controlled transport.…”

Section: Introductionmentioning

confidence: 99%

Bentonite Nanoparticle Stability and the Effect of Fulvic Acids: Experiments and Modelling

Seher

Geckeis

Fanghänel

et al. 2020

Colloids and Interfaces

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In this study, the critical coagulation concentration (CCC) for FEBEX bentonite colloids is determined by colloid coagulation studies under variation of pH, electrolyte concentration, and fulvic acid (GoHy-573FA) content. For CaCl 2 electrolyte solution, a pH-independent Ca-CCC of 1 mmol L −1 is found. In the case of NaCl background electrolyte, a pH-dependent Na-CCC can be determined with 15 ± 5 mmol L −1 at pH 6, 20 ± 5 mmol L −1 at pH 7, 200 ± 50 mmol L −1 at pH 8, 250 ± 50 mmol L −1 at pH 9, and 350 ± 100 mmol L −1 at pH 10, respectively. The addition of 1 mg L −1 dissolved organic carbon in the form of fulvic acid (FA) increases the Ca-CCC to 2 mmol L −1 . An association of FA with FEBEX bentonite colloids as surface coating can clearly be identified by scanning transmission X-ray microscopy (STXM). The experimental bentonite stability results are described by means of an extended DLVO (Derjaguin-Landau-Verwey-Overbeek) approach summing up hydration forces, short-range Born repulsion, van der Waals attraction, and electrical double layer repulsion. The measured zeta (ζ)-potential of the bentonite colloids is applied as platelet face electrokinetic potential and the edge electrokinetic potential is estimated by the combination of silica and alumina ζ-potential data in the ratio given by the FEBEX bentonite structural formula. Adjusting the montmorillonite face electrokinetic potential by a maximum of ±15.9 mV is sufficient to successfully reproduce the measured stability ratios. Due to the uncertainty in the ζ-potential measurement, only semiquantitative calculations of the stability ratio can be given.

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“…These low-permeability rocks exhibit petrophysical, hydrogeologic, and geomechanical properties, among others, which allow them to behave as long-lived passive barriers to the movement of water and solutes on timescales relevant to the safety of a Deep Geologic Repository (i.e. 1 Ma) (Dohrmann et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Filling the Gaps – From Microscopic Pore Structures to Transport Properties in Shales

Schäfer¹,

Dohrmann²,

Greenwell³

et al. 2015

Fourth International Conference on Fault and Top Seals

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The Role of Clays for Safe Storage of Nuclear Waste

Cited by 35 publications

References 35 publications

Effect of layer charge on the crystalline swelling of Na⁺, K⁺ and Ca²⁺ montmorillonites: DFT and molecular dynamics studies

Effect of layer charge on the crystalline swelling of Na⁺, K⁺ and Ca²⁺ montmorillonites: DFT and molecular dynamics studies

Bentonite Nanoparticle Stability and the Effect of Fulvic Acids: Experiments and Modelling

Filling the Gaps – From Microscopic Pore Structures to Transport Properties in Shales

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The Role of Clays for Safe Storage of Nuclear Waste

Cited by 35 publications

References 35 publications

Effect of layer charge on the crystalline swelling of Na+, K+ and Ca2+ montmorillonites: DFT and molecular dynamics studies

Effect of layer charge on the crystalline swelling of Na+, K+ and Ca2+ montmorillonites: DFT and molecular dynamics studies

Bentonite Nanoparticle Stability and the Effect of Fulvic Acids: Experiments and Modelling

Filling the Gaps – From Microscopic Pore Structures to Transport Properties in Shales

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Product

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Effect of layer charge on the crystalline swelling of Na⁺, K⁺ and Ca²⁺ montmorillonites: DFT and molecular dynamics studies

Effect of layer charge on the crystalline swelling of Na⁺, K⁺ and Ca²⁺ montmorillonites: DFT and molecular dynamics studies