Discussion on aquifer restoration at uranium in situ leach sites

Anastasi, F. S.; Williams, Roy E.; Hancock, Stephen

doi:10.1007/bf02498192

Cited by 2 publications

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“…The presence of U(VI) sorbed onto ferric iron oxides that are formed during ISR-mining may present a special restoration challenge, as the re-establishment of reducing conditions could cause conversion of ferric solids to more soluble ferrous iron, thus resulting in dissolution of the solids and liberation of the sorbed U(VI) (Anastasi et al, 1985). The persistence of such labile uranium-rich sources coupled with the local redox poising provided by iron sulfides and organic carbon persisting after mining may help explain short-term "rebounding" of uranium concentrations following groundwater restoration that occurs at some ISR sites.…”

Section: Discussionmentioning

confidence: 99%

Persistent U(IV) and U(VI) following in-situ recovery (ISR) mining of a sandstone uranium deposit, Wyoming, USA

Gallegos

Campbell

Zielinski

et al. 2015

Applied Geochemistry

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Drill-core samples from a sandstone-hosted uranium (U) deposit in Wyoming were characterized to determine the abundance and distribution of uranium following in-situ recovery (ISR) mining with oxygen-and carbon dioxide-enriched water. Concentrations of uranium, collected from ten depth intervals, ranged from 5 to 1920 ppm. A composite sample contained 750 ppm uranium with an average oxidation state of 54% U(VI) and 46% U(IV). Scanning electron microscopy (SEM) indicated rare high uranium (~1000 ppm U) in spatial association with P/Ca and Si/O attributed to relict uranium minerals, possibly coffinite, uraninite, and autunite, trapped within low permeability layers bypassed during ISR mining. Fission track analysis revealed lower but still elevated

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Section: Discussionmentioning

confidence: 99%

Persistent U(IV) and U(VI) following in-situ recovery (ISR) mining of a sandstone uranium deposit, Wyoming, USA

Gallegos

Campbell

Zielinski

et al. 2015

Applied Geochemistry

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“…Oxidation of the deposit with the lixiviant may promote the formation of oxidized solids such as ferric hydroxides that have the potential for sequestering contaminants such as U, Ra, Mn and As. If reducing conditions return after mining, these iron hydroxides may reductively dissolve, providing a new source of contaminants (Anastasi and Williams, 1985). If the initial solid sulfide composition (e.g., as pyrite) exceeds 2-4%, the resulting sulfate concentration may precipitate gypsum (CaSO 4 Á2H 2 O), which can decrease the permeability of the mining zone.…”

Section: Heap Leaching and Bioleachingmentioning

confidence: 99%

Biogeochemical aspects of uranium mineralization, mining, milling, and remediation

Campbell¹,

Gallegos²,

Landa

2015

Applied Geochemistry

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aspects of uranium mineralization, mining, milling, and remediation" (2014 U is overwhelmingly the most abundant at greater than 99% of the total mass of U. Prior to the 1940s, U was predominantly used as a coloring agent, and U-bearing ores were mined mainly for their radium (Ra) and/or vanadium (V) content; the bulk of the U was discarded with the tailings (Finch et al., 1972). Once nuclear fission was discovered, the economic importance of U increased greatly. The mining and milling of U-bearing ores is the first step in the nuclear fuel cycle, and the contact of residual waste with natural water is a potential source of contamination of U and associated elements to the environment. Uranium is mined by three basic methods: surface (open pit), underground, and solution mining (in situ leaching or in situ recovery), depending on the deposit grade, size, location, geology and economic considerations (Abdelouas, 2006). Solid wastes at U mill tailings (UMT) sites can include both standard tailings (i.e., leached ore rock residues) and solids generated on site by waste treatment processes. The latter can include sludge or ''mud'' from neutralization of acidic mine/mill effluents, containing Fe and a range of coprecipitated constituents, or barium sulfate precipitates that selectively remove Ra (e.g., Carvalho et al., 2007). In this chapter, we review the hydrometallurgical processes by which U is extracted from ore, the biogeochemical processes that can affect the fate and transport of U and associated elements in the environment, and possible remediation strategies for site closure and aquifer restoration. This paper represents the fourth in a series of review papers from the U.S. Geological Survey (USGS) on geochemical aspects of UMT management that span more than three decades. The first paper (Landa, 1980) in this series is a primer on the nature of tailings and radionuclide mobilization from them. The second paper (Landa, 1999) includes coverage of research carried out under the U.S. Department of Energy's Uranium Mill Tailings Remedial Action Program (UMTRA). The third paper (Landa, 2004) reflects the increased focus of researchers on biotic effects in UMT environs. This paper expands the focus to U mining, milling, and remedial actions, and includes extensive coverage of the increasingly important alkaline in situ recovery and groundwater restoration.Ó 2014 Published by Elsevier Ltd.

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Discussion on aquifer restoration at uranium in situ leach sites

Cited by 2 publications

References 0 publications

Persistent U(IV) and U(VI) following in-situ recovery (ISR) mining of a sandstone uranium deposit, Wyoming, USA

Persistent U(IV) and U(VI) following in-situ recovery (ISR) mining of a sandstone uranium deposit, Wyoming, USA

Biogeochemical aspects of uranium mineralization, mining, milling, and remediation

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