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Groundwater restoration following in-situ recovery (ISR) mining of uranium

Lookup NU author(s): Dr Lucia Rodriguez Freire

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Abstract

From 1950 through the early 1980's New Mexico accounted for roughly half of domestic uranium (U) production for the nuclear power industry and the nation's weapon programs. Increased interest in nuclear energy has led to proposals for renewed development using both underground mining and uranium in situ recovery (ISR). When feasible, ISR greatly reduces waste generated by the mining and milling processes, however, the ability to restore ground water to acceptable quality after ISR ends is uncertain. This research investigated two methods of stabilizing an aquifer following ISR. Batch and column studies were performed to evaluate chemical and biological methods of stabilization. Columns packed with ore were first leached with an aerated NaHCO₃ ground water solution to simulate ISR. Constituents present at elevated concentrations after leaching included molybdenum (Mo), selenium (Se), U, and vanadium (V). Chemical stabilization was studied by passing a phosphate (PO₄^3-) amended solution through the ore to achieve passivation of mineral surfaces by P precipitates. Microbial stabilization was studied by passing a lactate solution through the ore to stimulate growth of anaerobic metal- and sulfate-reducing organisms to reduce U and other elements to less soluble phases. Analyses of the solids from the columns after completion of these experiments by X-ray photo electron spectroscopy (XPS) identified phosphate on samples near the column inlet of the chemically stabilized columns. Microbial populations were characterized by Illumina DNA sequencing and confirmed the presence of metal- and sulfate-reducing organisms. Neither chemical nor microbial stabilization method achieved contaminant immobilization, which is believed due to limited mixing of the stabilization solutions with the contaminated leach solutions. These results emphasize that ground water hydrodynamics, especially mixing, must be considered in aquifer restoration of soluble constituents.

Publication metadata

Author(s): Ruiz O, Thomson B, Cerrato JM, Rodriguez-Freire L

Publication type: Article

Publication status: Published

Journal: Applied Geochemistry

Year: 2019

Volume: 109

Print publication date: 01/10/2019

Online publication date: 03/09/2019

Acceptance date: 01/09/2019

ISSN (print): 0883-2927

ISSN (electronic): 1872-9134

Publisher: Elsevier Ltd

URL: https://doi.org/10.1016/j.apgeochem.2019.104418

DOI: 10.1016/j.apgeochem.2019.104418

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