Title: Rare-earth element fractionation in uranium ore and its U(VI) alteration minerals

Abstract

We developed a cation exchange chromatography method employing sulfonated polysterene cation resin (DOWEX AG50-X8) in order to separate rare-earth elements (REEs) from uranium-rich materials. The chemical separation scheme is designed to reduce matrix effects and consequently yield enhanced ionization efficiencies for concentration determinations of REEs without significant fractionation using solution mode-inductively coupled plasma mass spectrometry (ICP-MS) analysis. This method was then applied to determine REE abundances in four uraninite (ideally UO₂) samples and their associated U(VI) alteration minerals. In three of the samples analyzed, the concentration of REEs for primary uraninite are higher than those for their corresponding secondary uranium alteration phases. The results for U(VI) alteration minerals of two samples indicate enrichment of the light REEs (LREEs) over the heavy REEs (HREEs). This differential mobilization is attributed to differences in the mineralogical composition of the U(VI) alteration. There is a lack of fractionation of the LREEs in the uraninite alteration rind that is composed of U(VI) minerals containing Ca²⁺ as the interlayer cation (uranophane and bequerelite); contrarily, U(VI) alteration minerals containing K⁺ and Pb²⁺ as interlayer cations (fourmarierite, dumontite) indicate fractionation (enrichment) of the LREEs. Our results have implications for nuclear forensic analyses since a comparison is reported betweenmore » the REE abundances for the CUP-2 (processed uranium ore) certified reference material and previously determined values for uranium ore concentrate (UOC) produced from the same U deposit (Blind River/Elliott Lake, Canada). UOCs represent the most common form of interdicted nuclear material and consequently is material frequently targeted for forensic analysis. The comparison reveals similar chondrite normalized REE signatures but variable absolute abundances. Based on the results reported here, the latter may be attributed to the differing REE abundances between primary ore and associated alteration phases, and/or is related to varying fabrication processes adopted during production of UOC.« less

Authors:

Balboni, Enrica ^[1]; Spano, T ^[2]; Cook, N ^[2]; Simonetti, A ^[2]; Burns, P C ^[3]

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+ Show Author Affiliations

1. Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Science; Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Glenn T. Seaborg Inst.
2. Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Science
3. Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Science, Dept. of Chemistry and Biochemistry

Publication Date:

Fri Oct 20 00:00:00 EDT 2017

Research Org.:

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1416495

Alternate Identifier(s):

OSTI ID: 1549381

Report Number(s):

LLNL-JRNL-725124
Journal ID: ISSN 0883-2927

Grant/Contract Number:  

AC52-07NA27344

Resource Type:

Accepted Manuscript

Journal Name:

Applied Geochemistry

Additional Journal Information:

Journal Volume: 87; Journal Issue: C; Journal ID: ISSN 0883-2927

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; uranium ore; uranium ore alteration; extraction chromatography; ICP-MS; rare-earth elements fractionation