Radiation effects on clay mineral properties

Allard, T.; Calas, Georges

doi:10.1016/j.clay.2008.07.032

Cited by 74 publications

(42 citation statements)

References 52 publications

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“…For example, Canadian researchers predict the maximum dose rate to be 52 Gy h Ϫ1 at the surface of a waste container (9). Similarly, Allard and Calas (10) suggest that dose rates in silicate clays used for backfill material may be in the order of 72 Gy h Ϫ1 over the first 1,000 years of the repository lifetime. For Swedish spent fuel disposal, on the other hand, the maximum estimate of dose rate outside the canister is 0.5 Gy h Ϫ1 over the first 1,000 years, followed by significant decay after this (11).…”

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confidence: 99%

The Impact of Gamma Radiation on Sediment Microbial Processes

Brown

Boothman

Pimblott

et al. 2015

Appl Environ Microbiol

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cMicrobial communities have the potential to control the biogeochemical fate of some radionuclides in contaminated land scenarios or in the vicinity of a geological repository for radioactive waste. However, there have been few studies of ionizing radiation effects on microbial communities in sediment systems. Here, acetate and lactate amended sediment microcosms irradiated with gamma radiation at 0.5 or 30 Gy h ؊1 for 8 weeks all displayed NO 3 ؊ and Fe(III) reduction, although the rate of Fe(III) reduction was decreased in 30-Gy h ؊1 treatments. These systems were dominated by fermentation processes. Pyrosequencing indicated that the 30-Gy h ؊1 treatment resulted in a community dominated by two Clostridial species. In systems containing no added electron donor, irradiation at either dose rate did not restrict NO 3 ؊ , Fe(III), or SO 4 2؊ reduction. Rather, Fe(III) reduction was stimulated in the 0.5-Gy h ؊1 -treated systems. In irradiated systems, there was a relative increase in the proportion of bacteria capable of Fe(III) reduction, with Geothrix fermentans and Geobacter sp. identified in the 0.5-Gy h ؊1 and 30-Gy h ؊1 treatments, respectively. These results indicate that biogeochemical processes will likely not be restricted by dose rates in such environments, and electron accepting processes may even be stimulated by radiation. In many countries, including the United Kingdom, the current policy for the long-term disposal of intermediate-level radioactive waste is to a deep geological disposal facility (GDF). In UK disposal concepts for higher-strength rocks and lower-strength sedimentary rocks, much of the intermediate-level radioactive waste is immobilized with a cementitious grout in stainless steel containers that are then surrounded with a cementitious backfill prior to closure of the facility (1). The vicinity of a GDF will not be a sterile environment, and microbial activity in the surrounding geosphere could have important implications for the evolution of biogeochemical processes, including microbial gas generation and utilization, microbially induced corrosion of waste containers and contents, and the mobility of radionuclides (2). In addition, there will be elevated concentrations of potential electron donors in and around the repository, including organics from the degradation of cellulose in the waste (3), and also molecular hydrogen from the radiolysis of water and the anaerobic corrosion of steel drums (4). Indeed, the availability of alternative electron acceptors will likely not be limited, since nitrate can be present in nuclear waste materials (5), and Fe(III) will be present due to aerobic corrosion of waste components and engineered infrastructure during the operational phase of the GDF.The stimulation of an Fe(III)-reducing community due to an increase in electron donors and acceptors is of particular interest since this may promote the reduction and precipitation of redoxactive radionuclides via the production of biogenic Fe(II)-bearing phases (2, 6). Indeed, many key Fe(III)-reducin...

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confidence: 99%

The Impact of Gamma Radiation on Sediment Microbial Processes

Brown

Boothman

Pimblott

et al. 2015

Appl Environ Microbiol

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“…Consequently, they present excellent targets for radiation emitted by the radioactive elements transported in solution or trapped in closely associated solid phases. Thus, radiation-induced defects have already been characterized in quartz Pan et al, 2006) and in several clay minerals, including kaolin minerals (i.e., kaolinite, dickite), montmorillonite, illite, and sudoite; the existence of similar defects stable over very long geological periods (so-called A-centers) has been demonstrated (Allard and Calas, 2009;Morichon et al, 2008Morichon et al, , 2010.…”

Section: Introductionmentioning

confidence: 97%

“…A promising way to defi ne and trace ancient pathways of uraniumbearing fl uids is based on the detection of paramagnetic defects created in the structure of minerals by natural ionizing radiations, using electron paramagnetic resonance spectroscopy (EPR) (Allard and Calas, 2009;Botis et al, 2006;Hu et al, 2008). The α-particles are major ionizing radiations emitted by the 238 U, 235 U, and 232 Th decay chains, representing 90% of the absorbed energy in matter, in addition to gamma and beta rays (Aitken, 1985).…”

Section: Introductionmentioning

confidence: 99%

Tracing past migrations of uranium in Paleoproterozoic basins: New insights from radiation-induced defects in clay minerals

Morichon

Beaufort

Allard

et al. 2010

Geology

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Radiation-induced defects were identifi ed in kaolinite, illite, and sudoite by electron paramagnetic resonance spectroscopy of the alteration halo surrounding the uranium orebodies in the Athabasca Basin (Saskatchewan, Canada). Clay minerals are assumed to behave similarly under irradiation. In all samples, defects are similar in nature, but their concentrations can vary widely over several orders of magnitude. The maximum fl uctuations in defect concentrations are observed along the regional Paleoproterozoic unconformity between the lower sandstones and the metamorphic basement rocks and close to crosscutting brittle structures, both of which appear to be the main vectors of uranium-bearing fl uid transfer in the basin. In the basement, some Hudsonian faults connected to this unconformity also show high defect concentrations, attesting that uranium-bearing fl uids may have circulated in the fracture network. The proximity of mineralization can be revealed through defects that record the past presence of uranium in altered rocks at signifi cant distances from the mineralized bodies. The absence of correlation between defect concentrations and present dose rates indicates that migrations of uranium-bearing fl uids took place after the formation of clay minerals.

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“…Applied and basic sciences of bentonite mineralogy have played a significant role in radioactive waste disposal practices. Bentonite material is used because its high sorptivity, longevity and low permeability, making it a promising candidate for retaining most natural and anthropogenic long-lived radionuclides within the contaminated and engineered disposal sites (Allard 2009). …”

Section: Introductionmentioning

confidence: 99%

Discrete element modelling of conceptual deep geological repository for high-level nuclear waste disposal

Verma

Gautam

Singh³

et al. 2015

Arab J Geosci

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The long-lived high-level spent nuclear has to be isolated from environment for the protection of ecosystem. One of the methods suggested to isolate the nuclear waste from ecosystem is its burial in deep underground repository. In this paper, discrete element method is used to disposal of spent fuel on stability of underground space and its surrounding rock strata. Effect of temperature increment on stressesstrains and temperature variation of surrounding rockmass due to heat generated by nuclear waste is studied and discussed. Simulation was performed on both strong and jointed granite rock in which tunnel is excavated. Bentonite is used as buffer because of its high sorptivity, longevity and low permeability. It has been found that both temperature and stresses at any point in the rock mass is below the design criteria which are 100°C for temperature over a time period of 16 years.

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Radiation effects on clay mineral properties

Cited by 74 publications

References 52 publications

The Impact of Gamma Radiation on Sediment Microbial Processes

The Impact of Gamma Radiation on Sediment Microbial Processes

Tracing past migrations of uranium in Paleoproterozoic basins: New insights from radiation-induced defects in clay minerals

Discrete element modelling of conceptual deep geological repository for high-level nuclear waste disposal

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