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Minerals
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Environmentally Sound In-Situ Recovery Mining of Uranium
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Environmentally Sound In-Situ Recovery Mining of Uranium

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Environmental Mineralogy and Biogeochemistry".

Deadline for manuscript submissions: closed (7 January 2022) | Viewed by 23118

Special Issue Editors

Dr. Paul Reimus

E-Mail Website
Guest Editor
Los Alamos National Laboratory, Los Alamos, NM 87545, USA
Interests: use of tracers to interrogate flow and transport properties of groundwater systems; chemical and biological methods of in situ groundwater restoration for uranium and hexavalent chromium; laboratory and field experiments to evaluate natural attenuation of contaminants in groundwater systems; integration of laboratory and field experiments with models to support optimal risk assessment and management of groundwater contamination
Dr. James Clay

E-Mail Website
Guest Editor
ISR Mining and Restoration, Helena, MT 59601, USA
Interests: maximizing efficiency and recovery for uranium ion exchange extraction circuits; data analysis and visualization techniques for optimizing ISR mining and restoration processes; improving restoration processes with a particular emphasis on geochemical stability of the restored zone; adjustments to the lixiviant chemistry with the goal of increasing the dissolution rate of uranium minerals during mining while minimizing the alteration of other aquifer minerals

Special Issue Information

Dear Colleagues,

Uranium in situ recovery (ISR) is economically competitive and offers more environmental, safety, and health advantages than conventional mining, but it leaves behind an altered geochemical environment that may pose long-term threats to downgradient aquifer water quality. In this Special Issue, we invite papers on innovative uranium ISR mining techniques that can more selectively extract uranium while minimizing adverse impacts on water quality, as well as on innovative post-ISR-mining restoration techniques that can reverse or negate the geochemical perturbations caused by mining. We also invite papers on the following topics related to the environmentally sound recovery of U:

  • Strategies for in situ remediation of shallow U contamination (e.g., biostimulation or chemical amendments) that have the potential for application in ISR settings;
  • Studies on U fate and transport in the subsurface (e.g., from contaminated sites or potential nuclear waste repositories) that can support a case for natural attenuation at ISR sites;
  • Innovative methods of assessing environmental impacts of ISR mining throughout its life cycle (e.g., through the use of geochemical, isotopic, or geophysical indicators);
  • Approaches to minimizing water usage and disposal in U ISR operations;
  • Innovative ISR mine unit designs that are amenable to environmentally sound U extraction;
  • Innovative approaches to extracting uranium from seawater.

Dr. Paul Reimus
Dr. James Clay
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Minerals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • uranium
  • in situ
  • mining
  • leach
  • lixiviant
  • oxidation
  • reduction
  • restoration
  • stability
  • aquifer

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Published Papers (8 papers)

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Editorial

Jump to: Research, Review

3 pages, 155 KiB  
Editorial
Editorial for Special Issue “Environmentally Sound In Situ Recovery Mining of Uranium”
by Paul Reimus and James Clay
Minerals 2023, 13(1), 100; https://doi.org/10.3390/min13010100 - 9 Jan 2023
Viewed by 1384
Abstract
This Special Issue features seven articles that cover a range of topics pertaining to the environmentally sound in situ recovery mining of uranium (U ISR) [...] Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)

Research

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21 pages, 2913 KiB  
Article
A Novel Method for Conducting a Geoenvironmental Assessment of Undiscovered ISR-Amenable Uranium Resources: Proof-of-Concept in the Texas Coastal Plain
by Tanya J. Gallegos, Victoria G. Stengel, Katie Walton-Day, Johanna Blake, Andrew Teeple, Delbert Humberson, Steven Cahan, Douglas B. Yager and Kent D. Becher
Minerals 2022, 12(6), 747; https://doi.org/10.3390/min12060747 - 12 Jun 2022
Cited by 2 | Viewed by 2257
Abstract
A geoenvironmental assessment methodology was developed to estimate waste quantities and disturbances that could be associated with the extraction of undiscovered uranium resources and identify areas on the landscape where uranium and other constituents of potential concern (COPCs) that may co-occur with uranium [...] Read more.
A geoenvironmental assessment methodology was developed to estimate waste quantities and disturbances that could be associated with the extraction of undiscovered uranium resources and identify areas on the landscape where uranium and other constituents of potential concern (COPCs) that may co-occur with uranium deposits in this region are likely to persist, if introduced into the environment. Prior to this work, a method was lacking to quantitively assess the environmental aspects associated with potential development of undiscovered uranium resources at a scale of a uranium resource assessment. The mining method of in situ recovery (ISR) was historically used to extract uranium from deposits in the Goliad Sand of the Texas Coastal Plain. For this reason, the study’s methodology projected the following types of wastes and disturbances commonly associated with ISR based on historical ISR mining records: the mine area, affected aquifer volume, mine pore volume, water pumped and disposed during uranium extraction and restoration, and radon emissions. Within the tract permissive for the occurrence of undiscovered uranium resources, maps and statistics of factors were derived that indicate the potential contaminant pathways. The percentage of days meeting the criteria for air stagnation indicate the potential for radon accumulation; the geochemical mobility of COPCs in groundwater in combination with effective recharge indicates the potential for infiltration of surface-derived COPCs; the geochemical mobility of COPCs in groundwater combined with hydraulic conductivity indicates the propensity for transmitting fluids away from contaminated or mined aquifers; and finally, geochemical mobility of COPCs in surface water combined with the factor for climatic erosivity (R factor) indicates the potential for COPCs to persist in surface waters due to runoff. This work resulted in a new methodology that can be applied to any undiscovered mineral resource to better understand possible wastes and disturbances associated with extraction and identify areas on the landscape where COPCs are likely to persist. Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)
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47 pages, 12420 KiB  
Article
Restoration Insights Gained from a Field Deployment of Dithionite and Acetate at a Uranium In Situ Recovery Mine
by Paul Reimus, James Clay and Noah Jemison
Minerals 2022, 12(6), 711; https://doi.org/10.3390/min12060711 - 2 Jun 2022
Cited by 5 | Viewed by 2718
Abstract
Mining uranium by in situ recovery (ISR) typically involves injecting an oxidant and a complexing agent to mobilize and extract uranium in a saturated ore zone. This strategy involves less infrastructure and invasive techniques than traditional mining, but ISR often results in persistently [...] Read more.
Mining uranium by in situ recovery (ISR) typically involves injecting an oxidant and a complexing agent to mobilize and extract uranium in a saturated ore zone. This strategy involves less infrastructure and invasive techniques than traditional mining, but ISR often results in persistently elevated concentrations of U and other contaminants of concern in groundwater after mining. These concentrations may remain elevated for an extended period without remediation. Here, we describe a field experiment at an ISR facility in which both a chemical reductant (sodium dithionite) and a biostimulant (sodium acetate) were sequentially introduced into a previously mined ore zone in an attempt to establish reducing geochemical conditions that, in principle, should decrease and stabilize aqueous U concentrations. While several lines of evidence indicated that reducing conditions were established, U concentrations did not decrease, and in fact increased after the amendment deployments. We discuss likely reasons for this behavior, and we also discuss how the results provide insights into improvements that could be made to the restoration process to benefit from the seemingly detrimental behavior. Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)
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27 pages, 11053 KiB  
Article
Column-Test Data Analyses and Geochemical Modeling to Determine Uranium Reactive Transport Parameters at a Former Uranium Mill Site (Grand Junction, Colorado)
by Raymond H. Johnson, Aaron D. Tigar and C. Doc Richardson
Minerals 2022, 12(4), 438; https://doi.org/10.3390/min12040438 - 31 Mar 2022
Cited by 7 | Viewed by 2349
Abstract
The long-term release of uranium from residual sources at former uranium mill sites was often not considered in prior conceptual and numerical models, as contaminant removal focused on meeting radiological standards. To determine the reactive transport parameters, column tests were completed with various [...] Read more.
The long-term release of uranium from residual sources at former uranium mill sites was often not considered in prior conceptual and numerical models, as contaminant removal focused on meeting radiological standards. To determine the reactive transport parameters, column tests were completed with various influent waters (deionized water, site groundwater, and local river water) on sediment from identified areas with elevated uranium on the solid phase in (1) vadose-zone (VZ) sediments, (2) saturated-zone sediments with higher organic carbon content, and (3) both vadose- and saturated-zone sediments with additional gypsum content. The gypsum was precipitated when low-pH, high-sulfate, tailings fluids or acidic waste disposal water were buffered by natural aquifer calcite dissolution. In general, the resulting uranium release was higher in the sediments with greater uranium concentrations. However, the addition of deionized water (DI) to the VZ sediments delayed the uranium release until higher-alkalinity groundwater was added. Higher-alkalinity river water continued to remove uranium from the VZ sediments for an extended number of pore volumes, with the uranium being above typical standards. Thus, river flooding is more efficient at removing uranium from VZ sediments than precipitation events (DI water in column tests). Organic carbon provides a stronger uranium sorption surface, which can be explained with geochemical modeling or a larger constant sorption coefficient (Kd). Without organic carbon, the typical sorption in sands and gravels is easily measurable, but sorption is stronger at lower, water-phase uranium concentrations. This effect can be simulated with geochemical modeling, but not with a constant Kd. Areas with gypsum create situations in which geochemical sorption is more difficult to simulate, which is likely due to the presence of uranium within mineral coatings. All the above mechanisms for uranium release must be considered when evaluating remedial strategies. Column testing provides initial input parameters that can be used in future reactive transport modeling to evaluate long-term uranium release rates and concentrations. Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)
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29 pages, 4586 KiB  
Article
Development and Description of a Composite Hydrogeologic Framework for Inclusion in a Geoenvironmental Assessment of Undiscovered Uranium Resources in Pliocene- to Pleistocene-Age Geologic Units of the Texas Coastal Plain
by Andrew P. Teeple, Kent D. Becher, Katherine Walton-Day, Delbert G. Humberson and Tanya J. Gallegos
Minerals 2022, 12(4), 420; https://doi.org/10.3390/min12040420 - 29 Mar 2022
Cited by 4 | Viewed by 3201
Abstract
A previously completed mineral resources assessment of the Texas Coastal Plain indicated the potential for the future discovery of uranium resources. Geoenvironmental assessments that include the hydrogeologic framework can be used as a tool to understand the potential effects of mining operations. The [...] Read more.
A previously completed mineral resources assessment of the Texas Coastal Plain indicated the potential for the future discovery of uranium resources. Geoenvironmental assessments that include the hydrogeologic framework can be used as a tool to understand the potential effects of mining operations. The hydrogeologic framework for this study focused on the composite hydrogeologic unit of the tract permissive for the occurrence of uranium consisting of the upper part of the Miocene-age Fleming Formation/Lagarto Clay, Pliocene-age Goliad and Pleistocene-age Willis Sands, Pleistocene-age Lissie and Beaumont Formations, and Holocene-age alluvial sediments (fluvial alluvium and eolian sand deposits). This composite hydrogeologic unit, which contains the Chicot and Evangeline aquifers of the Gulf Coast aquifer system, is intended for inclusion in a regional-scale geoenvironmental assessment of as yet undiscovered uranium resources. This article provides (1) a brief literature review describing the geologic and hydrogeologic settings, (2) the methodology used to develop a composite hydrogeologic framework, and (3) descriptions and maps of the land-surface altitude, composite hydrogeologic unit base and midpoint depth, water-level altitude, depth of water, unsaturated and saturated zone thickness, and transmissivity and hydraulic conductivity. A composite hydrogeologic unit, created by combining geologic and hydrogeologic data and maps for individual geologic and hydrogeologic units, is intended for use as a tool in a geoenvironmental assessment to evaluate potential contaminant migration through various avenues. Potential applications include using the hydrogeologic framework as an input into a geoenvironmental assessment to help estimate the potential for (1) runoff of contaminants into surface water, (2) infiltration of contaminants into the groundwater (aquifers), or (3) movement of contaminants from the mining area through wind, groundwater-flow, or streamflow in a given permissive tract. The procedures outlined in this paper also provide a method for developing hydrogeologic frameworks that can be applied in other areas where mining may occur. Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)
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28 pages, 3800 KiB  
Article
New Geochemical Framework and Geographic Information System Methodologies to Assess Element Occurrence, Persistence, and Mobility in Groundwater and Surface Water
by Johanna M. Blake, Katherine Walton-Day, Tanya J. Gallegos, Douglas B. Yager, Andrew Teeple, Delbert Humberson, Victoria Stengel and Kent Becher
Minerals 2022, 12(4), 411; https://doi.org/10.3390/min12040411 - 26 Mar 2022
Cited by 4 | Viewed by 2730
Abstract
This study presents a geochemical framework and geographic information system (GIS) method for assessing the intrinsic potential of surface water and groundwater to mobilize arsenic, molybdenum, selenium, uranium, and vanadium. The method was created using published groundwater and surface water geochemical data from [...] Read more.
This study presents a geochemical framework and geographic information system (GIS) method for assessing the intrinsic potential of surface water and groundwater to mobilize arsenic, molybdenum, selenium, uranium, and vanadium. The method was created using published groundwater and surface water geochemical data from the National Uranium Resource Evaluation database for 2302 groundwater and 915 surface water samples. The method was evaluated using published groundwater geochemical data from the Texas Water Development Board. Geochemical data were analyzed in GIS. Samples were categorized by environmental condition, which was determined by using reduction–oxidation—as indicated by pe—and pH ranges for each sample based on geochemical mobility frameworks developed by Smith (2007) and Perel’man (1986). Reduction–oxidation and pH influence the occurrence, persistence, and mobility of arsenic, molybdenum, selenium, uranium, and vanadium in groundwater and surface water. Reduction–oxidation categories were assigned to water samples using concentrations of redox-active constituents, including dissolved oxygen, iron, manganese, and sulfur. The presence of iron substrates and hydrogen sulfides were considered in relation to mobility mechanisms. Twelve-digit hydrologic unit code (HUC) boundaries were used in GIS as analysis areas to determine the most commonly occurring environmental condition in each HUC. The resulting maps identify the environmental conditions in different areas that can be used to identify where the elements are mobile. This methodology provides a systematic approach to identify areas where elements in groundwater and surface water may occur and persist and may be transferable to other locations. Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)
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29 pages, 5111 KiB  
Article
A Methodology to Assess the Historical Environmental Footprint of In-Situ Recovery (ISR) of Uranium: A Demonstration in the Goliad Sand in the Texas Coastal Plain, USA
by Tanya J. Gallegos, Anne M. Scott, Victoria G. Stengel and Andrew P. Teeple
Minerals 2022, 12(3), 369; https://doi.org/10.3390/min12030369 - 17 Mar 2022
Cited by 4 | Viewed by 3121
Abstract
In-situ recovery (ISR) has been the only technique used to extract uranium from sandstone-hosted uranium deposits in the Pliocene Goliad Sand in the Texas Coastal Plain. Water plays a crucial role throughout the ISR lifecycle of production and groundwater restoration yet neither the [...] Read more.
In-situ recovery (ISR) has been the only technique used to extract uranium from sandstone-hosted uranium deposits in the Pliocene Goliad Sand in the Texas Coastal Plain. Water plays a crucial role throughout the ISR lifecycle of production and groundwater restoration yet neither the water use nor other environmental footprints have been well documented. The goal of this study is to examine historical records for all six ISR operations completed in the Goliad Sand to identify and quantify parameters that indicate the surface and aquifer disturbances, water use, and radon emissions. Overall, the average mine area was 0.00023 ± 0.00006 acres per pound (ac/lb) U3O8. The average mine pore volume was 48.9 ± 50 gal/lb U3O8 with a minimum affected aquifer volume of 0.51 ± 0.08 cubic feet per pound (cu ft/lb) U3O8. An average of 258 ± 40 gallons (gal) of fluid were disposed per pound (lb) U3O8, with an average of 169 ± 26 gal/lb U3O8 attributed to restoration and 89 ± 36 gal/lb U3O8 attributed to the uranium production phase. The average radon emitted was 1.06 × 10−3 ± 7.4 × 10−4 curies per pound (Ci/lb) U3O8. Goodness-of-fit (R2) values are ≥0.79 for linear regressions of the amount of uranium produced versus mine area, mine pore volumes, mine aquifer volumes, water pumped, and total water disposed. The R2 value for radon emitted was 0.68. However, the water disposed only during the uranium production phase is more strongly correlated to the number of production days (R2 = 0.96) than to uranium production (R2 = 0.84), whereas the volume of water disposed during restoration is more strongly correlated to the “pore volume” (R2 = 0.97) than to uranium production (R2 = 0.90). Pore volume is an industry term used to describe the amount of fluid circulated through the aquifer during the uranium production period and stipulated in bond agreements in order to satisfy groundwater restoration requirements. Models constructed in this study can be used to estimate probable water use and the extent of surface and aquifer disturbances associated with ISR-amenable undiscovered uranium resources in the Goliad Sand. The historical perspective offered by the data compiled and correlations may prove useful to both industry and regulators. Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)
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Review

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34 pages, 5813 KiB  
Review
Geoenvironmental Model for Roll-Type Uranium Deposits in the Texas Gulf Coast
by Katherine Walton-Day, Johanna Blake, Robert R. Seal II, Tanya J. Gallegos, Jean Dupree and Kent D. Becher
Minerals 2022, 12(6), 780; https://doi.org/10.3390/min12060780 - 20 Jun 2022
Cited by 7 | Viewed by 3737
Abstract
Geoenvironmental models were formulated by the U.S. Geological Survey in the 1990s to describe potential environmental effects of extracting different types of ore deposits in different geologic and climatic regions. This paper presents a geoenvironmental model for roll-front (roll-type) uranium deposits in the [...] Read more.
Geoenvironmental models were formulated by the U.S. Geological Survey in the 1990s to describe potential environmental effects of extracting different types of ore deposits in different geologic and climatic regions. This paper presents a geoenvironmental model for roll-front (roll-type) uranium deposits in the Texas Coastal Plain. The model reviews descriptive and quantitative information derived from environmental studies and existing databases to depict existing conditions and potential environmental concerns associated with mining this deposit type. This geoenvironmental model describes how features of the deposits including host rock; ore and gangue mineralogy; geologic, hydrologic, and climatic settings; and mining methods (legacy open-pit and in situ recovery [ISR]) influence potential environmental effects from mining. Element concentrations in soil and water are compared to regulatory thresholds to depict ambient surface water and groundwater conditions. Although most open-pit operations in this region have been reclaimed, concerns remain about groundwater quality at three of the four former mills that supported former open-pit mines and are undergoing closure activities. The primary environmental concerns with ISR mining are (1) radon gas at active ISR operations, (2) radiation or contaminant leakage during production and transport of ISR resin or yellowcake, (3) uranium excursions into groundwater surrounding active ISR operations, and (4) contamination of groundwater after ISR mining. Although existing regulations attempt to address these concerns, some problems remain. Researchers suggest that reactive transport modeling and a better understanding of geology, stratigraphy, and geochemistry of ISR production areas could minimize excursions into surrounding aquifers and improve results of groundwater restoration. Full article
(This article belongs to the Special Issue Environmentally Sound In-Situ Recovery Mining of Uranium)
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