Uranium isotope variation within vein-type uranium ore deposits

Anya C Keatley, James A Dunne*, Tomas L Martin, Dan C Nita, Morten B. Andersen, Thomas Bligh Scott , David A Richards, Roy Awbery

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

8 Citations (Scopus)
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Abstract

Isotopic composition of uranium has previously been used to infer the depositional redox environment of uranium ore concentrates and also provide a potential signature to inform nuclear forensic investigations. This study evaluates the diagnostic power of the U isotope signature by investigating (1) the heterogeneity of U isotope compositions in samples collected from the same mine and/or vein, and (2) the influence of U ore processing on 238U/235U and 234U/238U ratios. These characteristics are explored via high precision mass spectrometric measurement of vein type uranium ore samples collected predominantly from mines located in central Portugal and Southwest England. Samples collected from the same vein and mine exhibit δ238U values from −0.16 to +0.03 (±0.04) ‰ and −1.6 to −64.7 (±0.4) ‰ for δ234U (±2SD). These variations can be attributed to redox-driven isotope fractionation processes and/or U redistribution during localised leaching and re-precipitation. Analyses of residues and leachates from small-scale batch experiments designed to simulate industrial U ore leaching procedures reveal significant positive and negative changes in isotope composition in the leachate relative to the bulk material (up to 0.21 ± 0.06‰ for δ238U and 62.0 ± 0.6‰ for δ234U). These findings highlight the possibility of significantly different δ238U and δ234U of uranium ore concentrate from the same mine even if manufacturing processes remain unchanged.

Original languageEnglish
Article number104977
Number of pages10
JournalApplied Geochemistry
Volume131
Early online date12 May 2021
DOIs
Publication statusPublished - 1 Aug 2021

Bibliographical note

Funding Information:
The authors wish to extend thanks to the Cabot Institute, University of Bristol , for supporting this work and AWE plc for funding [contract reference: 30218761]. Additional thanks to Tim Elliott and Christopher Coath, Bristol Isotope Group, University of Bristol. The authors also wish to acknowledge Laboratório de Protecção e Segurança Radiológica at Unidade de Protecção e Segurança Radiológica for their assistance during fieldwork and sample collection. We are grateful to the two anonymous reviewers for their suggested improvements to this paper.

Funding Information:
The authors wish to extend thanks to the Cabot Institute, University of Bristol, for supporting this work and AWE plc for funding [contract reference: 30218761]. Additional thanks to Tim Elliott and Christopher Coath, Bristol Isotope Group, University of Bristol. The authors also wish to acknowledge Laborat?rio de Protec??o e Seguran?a Radiol?gica at Unidade de Protec??o e Seguran?a Radiol?gica for their assistance during fieldwork and sample collection. We are grateful to the two anonymous reviewers for their suggested improvements to this paper.

Publisher Copyright:
© 2021

Keywords

  • Nuclear forensics
  • Uranium
  • Isotopic fractionation
  • Uranium ore concentrates

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