Field analyses of 238 U and 226 Ra in two uranium mill tailings piles from Niger using portable HPGe detector

Déjeant, Adrien; Bourva, L.; Sia, R.; Galoisy, Laurence; Calas, Georges; Phrommavanh, Vannapha; Descostes, Michaël

doi:10.1016/j.jenvrad.2014.06.012

Cited by 39 publications

(32 citation statements)

References 27 publications

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“…Numerous studies have been conducted on the reactivity of U mill tailings (Fernandes et al, 1996;Abdelouas et al, 1998;Donahue et al, 2000;Martin et al, 2003;Moldovan et al, 2003;Landa, 2004;Scheinost et al, 2006;Essilfie-Dughan et al, 2010;Déjeant et al, 2014;Yan and Luo, 2015;Chautard et al, 2017;Liu et al, 2017). However, these studies are mostly specific to the sites considered and to the associated ores and processes.…”

Section: Introductionmentioning

confidence: 99%

A multi-scalar study of the long-term reactivity of uranium mill tailings from Bellezane site (France)

Ballini

Chautard

Nos

et al. 2020

Journal of Environmental Radioactivity

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The mill tailings from uranium mines constitute very low-level, long-lived, radioactive process waste. Their longterm management therefore requires a good understanding of the geochemical mechanisms regulating the mobility of residual U and 226 Ra. This article presents the results of the detailed characterization of the tailings resulting from the dynamic leaching processes used on the ore of the La Crouzille mining division and stored at the Bellezane site (Haute-Vienne, France) for over 25 years. A multi-scalar and multidisciplinary approach was developed based on a study of the site's history, on the chemical, radiological and mineralogical characterizations of the solid fraction of the tailings, and on porewater analyses. These were supplemented by thermodynamic equilibrium models to predict the long-term mobility of U and 226 Ra. Weakly acidic (pH = 6.35) and oxidizing (Eh = 138 mV/SHE) porewaters had a sulfated-magnesian facies ([SO4]tot = 43 mmol/L ; [Mg]tot = 33 mmol/L) with an accessory calcium bicarbonate component (TIC = 25 mmol/L ; [Ca]tot = 13 mmol/L) and dissolved concentrations of uranium and 226 Ra of 12x10-6 mol/L and 0.58 Bq/L respectively. Ultra-filtration at 10 kDa indicated the absence of colloidal phases. The characterization of the tailings confirmed their homogeneity from a radiological, chemical and mineralogical point of view. The residual U and 226 Ra concentrations measured in the solid were 160 ppm and 25 Bq/g respectively, in accordance with the initial ore grades and mill yields, or more than 99% of the total stock. In terms of chemical and mineralogical composition, the tailings were mainly composed of minerals from the granitic ore (quartz, potassium feldspar, plagioclases and micas) in association with their weathering products (smectite and ferric oxyhydroxides) and with neo-formed minerals following rapid diagenesis after neutralization of the tailings before their emplacement (gypsum and barite). All these minerals are effective traps for the retention of U and 226 Ra. The uranium is distributed partly in micrometer scale uraninite and coffinite refractory phases embedded in grains of quartz, and partly sorbed to smectite and ferric oxyhydroxides. The 226 Ra on the other hand is trapped mainly within the barite. The aqueous concentrations of U and 226 Ra could be described using a thermodynamic approach so that their long-term mobility can subsequently be assessed by modeling. The paragenesis of the tailings could be seen to be stable over time with the exception of neo-formed gypsum and calcite, which will gradually dissolve. The presence of retention traps offering surplus capacity, i.e. smectite, ferric oxyhydroxides and barite, will maintain the U and the 226 Ra at very low aqueous concentrations, even under oxidizing conditions. Moreover, the low permeability of the mill tailings leads, in the case of 226 Ra, to behavior dictated only by the radioactive decay. Highlights (no more than 85 characters, including spaces)  U mill tailings from Bellezane (France) were studied...

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Section: Introductionmentioning

confidence: 99%

A multi-scalar study of the long-term reactivity of uranium mill tailings from Bellezane site (France)

Ballini

Chautard

Nos

et al. 2020

Journal of Environmental Radioactivity

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“…Many analytical methods have been developed for UO 2 2+ detection such as electrochemical methods, 4 fluorescence spectroscopy, 5 UV–vis adsorption spectrometry, 6 ICP mass spectrometry (ICP-MS), 7 inductively coupled plasma atomic emission spectroscopy (ICP-AES), 8 and so on. Despite providing concentration information, those methods lack the capability of enforcing in situ analysis or require time-consuming sample preparation, sophisticated equipment, expert operators, and high cost, limiting their practical applications.…”

Section: Introductionmentioning

confidence: 99%

In Situ Surface-Enhanced Raman Spectroscopy Detection of Uranyl Ions with Silver Nanorod-Decorated Tape

et al. 2019

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Surface-enhanced Raman spectroscopy (SERS) has been utilized for rapid analysis of uranyl ions (UO 2 2+ ) on account of its fast response and high sensitivity. However, the difficulty of fabricating a suitable SERS substrate for in situ analysis of uranyl ions severely restricts its practical application. Hence, we proposed flexible and adhesive SERS tape decorated with silver nanorod (AgNR) arrays for in situ detection of UO 2 2+ . The SERS tape was fabricated through a simple “paste & peel off” procedure by transferring the slanted AgNR arrays from silicon to the transparent tape surface. UO 2 2+ can be easily in situ detected by placing the AgNR SERS tape into an aqueous solution or pasting it onto the solid matrix surface due to the excellent transparent feature of the tape. The proposed SERS tape with well-distributed AgNRs effectively improved the reproducibility and sensitivity for UO 2 2+ analysis. UO 2 2+ with concentration as low as 100 nM was easily detected. Besides, UO 2 2+ adsorbed on an iron disc and rock surface also can be rapidly in situ detected. With its simplicity and convenience, the AgNR SERS tape-based SERS technique offers a promising approach for environmental monitoring and nuclear accident emergency detection.

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“…Considerable large volumes of mill tailings are disposed every year near uranium mining sites (Abdelouas, 2006). Since most of the ore deposits have low uranium content, the mill tailings still comprise a small portion of the initial uranium and almost all of the daughter radionuclides of the 238 U decay series, including 226 Ra (Déjeant et al, 2014;Nirdosh et al, 1984). These decay products add to the environmental impactof uranium-waste, making the mill tailings to be considered low-level radioactive waste.…”

Section: Introductionmentioning

confidence: 99%

Study of uranium(VI) and radium(II) sorption at trace level on kaolinite using a multisite ion exchange model

Reinoso-Maset

2016

Journal of Environmental Radioactivity

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Uranium and the long-lived decay product radium-226 are abundantly present in mine wastes produced during uranium extraction activities. In the case of release to the surrounding environment, these radionuclides are at trace level compared to groundwater solutes, and the presence, content and properties of clay minerals in the host environment influence the extent of radionuclide sorption and, in turn, migration. Since clays are known to have the distinctive property of retaining ions, the aim of this work was to study the sorption of trace U(VI) and Ra(II) on a common phyllosilicate mineral, kaolinite, in the presence of excess K, a common groundwater cation, in order to obtain a thermodynamic database that describes the ion exchange equilibria occurring at the mineral-solution interface. Following a detailed experimental protocol using chemical and radiochemical analytical techniques, batch experiments over a wide pH range (from 2 to 11) and fixed concentration (ca. 10(-9) M), and additional adsorption isotherms at two different solution pH (6.2 and 10.4) over a concentration range (10(-10) to 10(-4) M) were carried out to measure the distribution coefficient (Kd) of U(VI) and Ra(II) sorption on kaolinite. The experimental sorption data was processed according to a general multisite sorbent/multispecies sorbate ion exchange model, which allowed deducing the charge of adsorbed species and the stoichiometry of the associated adsorption equilibria on kaolinite's surface sites. Aqueous speciation calculations predicted Ra(II) as Ra(2+) over the working pH range, and its adsorption curves and isotherms were explained using three sorption sites. Adsorption of U(VI) occurred on four sorption sites and was governed by its solution speciation, with positively charged hydroxylated (UO2(2+) and UO2(OH)(+)) and silicate (UO2(H3SiO4)(+)) species being adsorbed between pH 2 and 6, whereas its negatively charged forms (UO2(OH)3(-) and UO2(OH)4(2-)) dominated U(VI) sorption at pH > 7. Nonlinear fitting of the experimental data using the ion exchange model provided the associated equilibrium constants as corrected selectivity coefficients.

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Field analyses of 238 U and 226 Ra in two uranium mill tailings piles from Niger using portable HPGe detector

Cited by 39 publications

References 27 publications

A multi-scalar study of the long-term reactivity of uranium mill tailings from Bellezane site (France)

A multi-scalar study of the long-term reactivity of uranium mill tailings from Bellezane site (France)

In Situ Surface-Enhanced Raman Spectroscopy Detection of Uranyl Ions with Silver Nanorod-Decorated Tape

Study of uranium(VI) and radium(II) sorption at trace level on kaolinite using a multisite ion exchange model

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