Skip to main content

Lund University Publications

LUND UNIVERSITY LIBRARIES

Modeling uranium and 226Ra mobility during and after an acidic in situ recovery test (Dulaan Uul, Mongolia)

de Boissezon, H. ; Levy, L. LU ; Jakymiw, C. ; Distinguin, M. ; Guerin, F. and Descostes, M. (2020) In Journal of Contaminant Hydrology 235.
Abstract

This article presents the results of groundwater monitoring over a period of six years and the interpretation of these results by a reactive transport model, following an In Situ Recovery (ISR) test on the Dulaan Uul uranium deposit in Mongolia. An environmental monitoring survey was set up using 17 piezometers, from which it has been possible to describe the changes in the water composition before, during and after the ISR test. The water quality before the start of mining activities rendered it unfit for human consumption. During and after the test, a descent of the saline plume was observed, resulting in a dilution of the injection solutions. After a rapid decrease to pH = 1.13 during the production phase of the ISR test, the pH... (More)

This article presents the results of groundwater monitoring over a period of six years and the interpretation of these results by a reactive transport model, following an In Situ Recovery (ISR) test on the Dulaan Uul uranium deposit in Mongolia. An environmental monitoring survey was set up using 17 piezometers, from which it has been possible to describe the changes in the water composition before, during and after the ISR test. The water quality before the start of mining activities rendered it unfit for human consumption. During and after the test, a descent of the saline plume was observed, resulting in a dilution of the injection solutions. After a rapid decrease to pH = 1.13 during the production phase of the ISR test, the pH stabilized at around 4 in the production area and 5.5 below the production cell one year after the end of the test. Uranium and radium were being naturally attenuated. Uranium returned to background concentrations (0.3 mg/L) after two years and the measured 226Ra concentrations represent no more than 10% of the expected concentrations during production (75 Bq/L). The modeling of the contaminants of concern mobility, namely pH and concentrations of sulfate, uranium and 226Ra, is based on several key complementary mechanisms: density flow, cation exchange with clay minerals and co-precipitation of 226Ra in the barite. The modeling results show that the observed plume descent and sulfate dilution can only be predicted if consideration of a high-density flow is included. Similarly, the changes in pH and 226Ra concentration are only correctly predicted when the cationic exchanges with the clays and the co-precipitation reaction within the barite using the solid solution theory are integrated into the models. Finally, the proper representation of the changes in water composition at the scale of the test requires the use of a sufficiently fine mesh (1 m × 1 m cell) to take into account the spatial variability of hydrogeological (permeability distribution in particular) and geological (reduced, oxidized and mineralized facies distributions) parameters.

(Less)
Please use this url to cite or link to this publication:
author
; ; ; ; and
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Ra, In-Situ Recovery, Natural attenuation, Reactive-transport modeling, Uranium
in
Journal of Contaminant Hydrology
volume
235
article number
103711
publisher
Elsevier
external identifiers
  • pmid:32949982
  • scopus:85090897528
ISSN
0169-7722
DOI
10.1016/j.jconhyd.2020.103711
language
English
LU publication?
no
additional info
Publisher Copyright: © 2020 Elsevier B.V.
id
4e149aec-fcc5-4769-bab2-63f5098a39bf
date added to LUP
2024-05-26 11:07:03
date last changed
2024-06-23 12:43:12
@article{4e149aec-fcc5-4769-bab2-63f5098a39bf,
  abstract     = {{<p>This article presents the results of groundwater monitoring over a period of six years and the interpretation of these results by a reactive transport model, following an In Situ Recovery (ISR) test on the Dulaan Uul uranium deposit in Mongolia. An environmental monitoring survey was set up using 17 piezometers, from which it has been possible to describe the changes in the water composition before, during and after the ISR test. The water quality before the start of mining activities rendered it unfit for human consumption. During and after the test, a descent of the saline plume was observed, resulting in a dilution of the injection solutions. After a rapid decrease to pH = 1.13 during the production phase of the ISR test, the pH stabilized at around 4 in the production area and 5.5 below the production cell one year after the end of the test. Uranium and radium were being naturally attenuated. Uranium returned to background concentrations (0.3 mg/L) after two years and the measured <sup>226</sup>Ra concentrations represent no more than 10% of the expected concentrations during production (75 Bq/L). The modeling of the contaminants of concern mobility, namely pH and concentrations of sulfate, uranium and <sup>226</sup>Ra, is based on several key complementary mechanisms: density flow, cation exchange with clay minerals and co-precipitation of <sup>226</sup>Ra in the barite. The modeling results show that the observed plume descent and sulfate dilution can only be predicted if consideration of a high-density flow is included. Similarly, the changes in pH and <sup>226</sup>Ra concentration are only correctly predicted when the cationic exchanges with the clays and the co-precipitation reaction within the barite using the solid solution theory are integrated into the models. Finally, the proper representation of the changes in water composition at the scale of the test requires the use of a sufficiently fine mesh (1 m × 1 m cell) to take into account the spatial variability of hydrogeological (permeability distribution in particular) and geological (reduced, oxidized and mineralized facies distributions) parameters.</p>}},
  author       = {{de Boissezon, H. and Levy, L. and Jakymiw, C. and Distinguin, M. and Guerin, F. and Descostes, M.}},
  issn         = {{0169-7722}},
  keywords     = {{Ra; In-Situ Recovery; Natural attenuation; Reactive-transport modeling; Uranium}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Journal of Contaminant Hydrology}},
  title        = {{Modeling uranium and <sup>226</sup>Ra mobility during and after an acidic in situ recovery test (Dulaan Uul, Mongolia)}},
  url          = {{http://dx.doi.org/10.1016/j.jconhyd.2020.103711}},
  doi          = {{10.1016/j.jconhyd.2020.103711}},
  volume       = {{235}},
  year         = {{2020}},
}