Gas generation and migration in Boom Clay, a potential host rock formation for nuclear waste storage

Ortiz, L.W.; Volckaert, G.; Mallants, Dirk

doi:10.1016/s0013-7952(01)00107-7

Cited by 134 publications

(79 citation statements)

References 4 publications

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“…Bonin et al, 2000;Environment Agency, 2008). After the thermal phase, water vapour will be limited due to high water saturation, and microbial activities may reduce the net amount of gases due to metabolic activities (Ortiz et al, 2002). Therefore hydrogen gas generation due to metallic corrosion is thought to be the dominant generation mechanism (Kursten et al, 2004), with iron being the dominant metal.…”

Section: Gas Generation Ratesmentioning

confidence: 99%

“…Other reactions occur, for example creating ferrous hydroxide (Fe(OH) 2 ) which then converts thermodynamically to magnetite, water and hydrogen (e.g. Ortiz et al, 2002).…”

Section: Gas Generation Ratesmentioning

confidence: 99%

“…Ortiz et al (2002) considered that, below the threshold pressure of gas entry, diffusion mechanisms play a dominant role in gas transport until a gas threshold pressure is exceeded and the clay fabric may deform. Rodwell et al (1999) predicted that increasing gas pressure would simply force the clay minerals apart at the mouth of the largest pathway or where discontinuities already exist.…”

Section: Introductionmentioning

confidence: 99%

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Simulation of repository gas migration in a bentonite buffer

Thomas¹,

Masum²,

Chen³

et al. 2014

Proceedings of the Institution of Civil Engineers - Engineering

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The inventory of high-level radioactive waste in the UK is likely to be disposed of in a geological disposal facility, which will generate gases due to processes such as anoxic metal corrosion and water radiolysis. Such gases have the potential to migrate through the repository system and may be detrimental to the engineered barrier system by damaging the physical fabric of the buffer material through the build-up of pressure. An investigation into the migration of gases and the ranges of gas pressures expected in such a repository is presented. A model of gas transport is presented to simulate the transport of gases in conjunction with coupled thermo-hydro-chemical-mechanical processes. This model includes a boundary condition linking the corrosion behaviour to gas generation and water supply. A realistic range of gas generation rates has been established from available data alongside realistic ranges of material properties of a bentonite buffer. Numerical simulations were then undertaken for a range of realistic scenarios considering the corrosion processes and buffer properties.It was found that in all realistic cases, including realistic maxima and minima considered, the risk of pneumatic fracture was negligible.

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Section: Gas Generation Ratesmentioning

confidence: 99%

“…Other reactions occur, for example creating ferrous hydroxide (Fe(OH) 2 ) which then converts thermodynamically to magnetite, water and hydrogen (e.g. Ortiz et al, 2002).…”

Section: Gas Generation Ratesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulation of repository gas migration in a bentonite buffer

Thomas¹,

Masum²,

Chen³

et al. 2014

Proceedings of the Institution of Civil Engineers - Engineering

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“…If the rate at which this gas is produced exceeds the diffusional capability of the clay-rich engineered barrier and/or host rock, a consequent build-up in pressure will occur. This increase in pressure over time may exceed a critical level, at which point gas enters the material, potentially also transporting harmful radionuclides (Weetjens and Sillen, 2006;Ortiz et al, 2002;Wikramaratna et al, 1993). The mechanism allowing gas flow, its potential spatial distribution and temporal evolution, will strongly control the likelihood of radionuclide transport.…”

Section: Introductionmentioning

confidence: 99%

The visualization of flow paths in experimental studies of clay-rich materials

et al. 2015

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One of the most challenging aspects of understanding the flow of gas and water during testing in clay-rich low-permeability materials is the difficulty in visualizing localized flow. Whilst understanding has been increased using X-ray Computed-tomography (CT) scanning, synchrotron X-ray imaging and Nuclear Magnetic Resonance (NMR) imaging, real-time testing is problematic under realistic in situ conditions confining pressures, which require steel pressure vessels. These methods tend not to have the nano-metre scale resolution necessary for clay mineral visualization, and are generally not compatible with the long duration necessary to investigate flow in such materials. Therefore other methods are necessary to visualize flow paths during post-mortem analysis of test samples. Several methodologies have been established at the British Geological Survey (BGS), in order to visualize flow paths both directly and indirectly. These include: (1) the injection of fluorescein-stained water or deuterium oxide; (2) the introduction of nanoparticles that are transported by carrier gas; (3) the use of radiologically tagged gas; and (4) the development of apparatus for the direct visualization of clay. These methodologies have greatly increased our understanding of the transport of water and gas through intact and fractured clay-rich materials. The body of evidence for gas transport through the formation of dilatant pathways is now considerable. This study presents observations using a new apparatus to directly visualize the flow of gas in a kaolinite paste. The results presented provide an insight into the flow of gas in clay-rich rocks. The flow of gas through dilatant pathways has been shown in a number of argillaceous materials (Angeli et al., 2009;Autio et al., 2006;Cuss et al., 2014;Harrington et al., 2012). These pathways are pressure induced and an increase in gas pressure leads to the dilation of pathways. Once the gas breakthrough occurs, pressure decreases and pathways begin to close. This new approach is providing a unique insight into the complex processes involved during the onset, development and closure of these dilatant gas pathways.

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“…In most cases, these numerical computations are achieved under the assumption of constant gas pressure. However, after the introduction of the waste canisters, different potential gas sources exist in the storage gallery (Volckaert et al 1994, Ortiz et al 2002. The main origin of the gas is the corrosion of canister steel component.…”

Section: Introductionmentioning

confidence: 99%

Numerical modelling of the resaturation of swelling clay with gas injection

Gérard¹,

Radu²,

Talandier³

et al. 2010

Unsaturated Soils

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During long-term storage of radioactive waste, steel containers are corroded and this process leads to hydrogen production. An in-situ experiment has been designed by Andra, in order to analyze the influence of gas migration on the dynamics of resaturation of the bentonite plug. The competition between liquid water coming from argillite and a gas injection at both ends of the plug is studied. Predictive numerical modelling of the experiment is performed in order to support the design, with a special emphasis on the coupling between the water and gas transfers and the mechanical behaviour.can alter the good confinement between the canisters and the access gallery.The paper deals with an in-situ experiment that is currently performed by Andra in its underground laboratory at Bure. The objective of the PGZ experiment is the analysis of the dynamic of the bentonite plug resaturation, studying the competition between the liquid water coming from the host formation and a gas injection at both ends of the plug. In order to support the design of the experiment, predictive numerical simulations of the gas migration in both the host formation and the swelling clay plug are achieved, with a special emphasis on coupling between the gas transfers and the mechanical strains and stresses. The influence of damage or plasticity on the fluid transfer parameters, which can explained the preferential pathways, are not taken into account in the modelling of the experiment.In this paper, the concept of the experiment and the boundary value problem of the simulations are described in section 2. The hydro-mechanical model is then defined in section 3. In section 4 the results of the modelling are presented and analyzed, before the conclusions (section 5). BOUNDARY VALUE PROBLEMThe general concept of the PGZ experiment is presented on Figure 1. A 25 m long horizontal borehole is drilled in the callovo-oxfordian argillite,

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Gas generation and migration in Boom Clay, a potential host rock formation for nuclear waste storage

Cited by 134 publications

References 4 publications

Simulation of repository gas migration in a bentonite buffer

Simulation of repository gas migration in a bentonite buffer

The visualization of flow paths in experimental studies of clay-rich materials

Numerical modelling of the resaturation of swelling clay with gas injection

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