Microanalytical X-ray Imaging of Depleted Uranium Speciation in Environmentally Aged Munitions Residues

Crean, Daniel E.; Livens, Francis R.; Stennett, Martin C.; Grolimund, Daniel; Borca, Camelia N.; Hyatt, Neil C.

doi:10.1021/es403938d

Cited by 25 publications

(24 citation statements)

References 34 publications

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“…We hypothesize that this short cooling time scale inhibits the expected Fe/U buffering effect by locking in the oxidation states of Fe and U before local oxygen fugacity can have any significant effect (as in the production of synthetic glasses under equilibrium conditions). Weathering driving U(IV) towards U(VI) [29] may be another explanation for the high U(VI) content of the Event 3 glass; we cannot rule out such effects based on the present data alone, but note that for similar melt glasses [18], reported step-heated gas extraction patterns are inconsistent with any significant disturbances due to weathering effects.…”

Section: Discussioncontrasting

confidence: 64%

“…This does not necessarily mean that the tetravalent ions are immobilized. Depending on the groundwater chemistry and the mineral and organic species present in the local environment, both U(IV) and Pu(IV) can be incorporated into aqueous colloids [5,27,28] or U(IV) may be con-3 verted into U(VI) by weathering [29]. In the case of bulk melt glass, the redox state of the material may impact the redox state of groundwater flowing through the test location [30,31], affecting, in turn, the solubility and transport properties of other materials.…”

Section: Introductionmentioning

confidence: 99%

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Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

Pacold

Lukens

Booth

et al. 2016

Journal of Applied Physics

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Nuclear weapons testing generates large volumes of glassy material that influence the transport of dispersed actinides in the environment and may carry information on the composition of the detonated device. We determine the oxidation state of U and Fe (which is known to buffer the oxidation state of actinide elements and to affect the redox state of groundwater) in samples of melt glass collected from three U.S. nuclear weapons tests. For selected samples, we also determine the coordination geometry of U and Fe, and we report the oxidation state of Pu from one melt glass sample. We find significant variations among the melt glass samples, and in particular, find a clear deviation in one sample from the expected buffering effect of Fe(II)/Fe(III) on the oxidation state of uranium. In the first direct measurement of Pu oxidation state in a nuclear test melt glass, we obtain a result consistent with existing literature that proposes Pu is primarily present as Pu(IV) in post-detonation material. In addition, our measurements imply that highly mobile U(VI) may be produced in significant quantities when melt glass is quenched rapidly following a nuclear detonation, though these products may remain immobile in the vitrified matrices. The observed differences in chemical state among the three samples show that redox conditions can vary dramatically across different nuclear test conditions. The local soil composition, associated device materials, and the rate of quenching are all likely to affect the final redox state of the glass. The resulting variations in glass chemistry are significant for understanding and interpreting debris chemistry, and the later environmental mobility of dispersed material.

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Section: Discussioncontrasting

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

Pacold

Lukens

Booth

et al. 2016

Journal of Applied Physics

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“…Uranium L III -edge (E 0 = 17.166 keV) µ-XANES (X-ray Absorption Near-Edge Structure) spectra were recorded in fluorescence mode by monitoring the U Lα 1 emission (13.614 keV). Two-dimesional micro-x-ray diffraction (µ-XRD) measurements were acquired using a CCD camera (Bruker SMART 1500) positioned 235 mm behind the sample and calibrated to an alumina Al 2 O 3 standard (NIST SRM676a) 25 . At a monochromatic beam energy of 17.200 keV, the wavelength was 0.7093 Å.…”

Section: µ-Xrf µ-Xrd and µ-Xanes Analysismentioning

confidence: 99%

“…At SLS, µ-XAS data were collected according to the methodology detailed by Crean et al 25,26 The monochromatic beam energy was identical to NSLS. Fluorescence µ-XANES spectra of uranium standards (UTi 2 O 6 , UO 2 , U 0.5 Y 0.5 Ti 2 O 6 , U 3 O 8 , UO 3 and CaUO 4 ) were measured to aid interpretation.…”

Section: µ-Xrf µ-Xrd and µ-Xanes Analysismentioning

confidence: 99%

Multi-scale investigation of uranium attenuation by arsenic at an abandoned uranium mine, South Terras

et al. 2017

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Detailed mineralogical analysis of soils from the UK's historical uranium mine, South Terras, was performed to elucidate the mechanisms of uranium degradation and migration in the 86 years since abandonment. Soils were sampled from the surface (0-2 cm) and near-surface (25 cm) in two distinct areas of ore processing activities. Bulk soil analysis revealed the presence of high concentrations of uranium (<1690 p.p.m.), arsenic (1830 p.p.m.) and beryllium (~250 p.p.m.), suggesting pedogenic weathering of the country rock and ore extraction processes to be the mechanisms of uranium ore degradation. Micro-focus XRF analysis indicated the association of uranium with arsenic, phosphate and copper; µ-XRD data confirmed the presence of the uranylarsenate minerals metazeunerite (Cu(UO 2 ) 2 (AsO 4 ) 2 ·8H 2 O) and metatorbernite (Cu(UO 2 ) 2 (PO 4 ) 2 ·8H 2 O) to be ubiquitous. Our data are consistent with the solid solution of these two uranyl-mica minerals, not previously observed at uranium-contaminated sites. Crystallites of uranyl-mica minerals were observed to coat particles of jarosite and muscovite, suggesting that the mobility of uranium from degraded ores is attenuated by co-precipitation with arsenic and phosphate, which was not previously considered at this site.

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“…[14][15][16][17][18] While X-ray absorption spectroscopy has been applied to a limited number of materials of forensic interest. [19][20][21][22][23] The sensitivity of X-ray absorption near edge structure (XANES) to oxidation state lends itself to the observation of the gradual oxidation of nuclear material due to storage and environmental conditions, [23][24] and to studies of chemical signatures of post-detonation material. [25][26] This article describes the use of scanning transmission X-ray microscopy (STXM) in the soft X-ray region with methods optimized for nondestructive nuclear forensic analysis.…”

Section: Introductionmentioning

confidence: 99%

Development of small particle speciation for nuclear forensics by soft X-ray scanning transmission spectromicroscopy

Pacold

Altman

Knight

et al. 2018

Analyst

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Synchrotron radiation spectromicroscopy provides a combination of submicron spatial resolution and chemical sensitivity that is well-suited to analysis of heterogeneous nuclear materials. The chemical and physical characteristics determined by scanning transmission X-ray microscopy (STXM) are complementary to information obtained from standard radiochemical analysis methods. In addition, microscopic quantities of radioactive material can be characterized rapidly by STXM with minimal sample handling and intrusion, especially in the case of particulate materials. The STXM can accommodate a diverse range of samples including wet materials, complex mixtures, and small quantities of material contained in a larger matrix. In these cases, the inventory of species present in a sample is likely to carry information on its process history; STXM has the demonstrated capability to identify contaminants and sample matrices. Operating in the soft X-ray regime provides particular sensitivity to the chemical state of specimens containing low-Z materials, via the K-edges of light elements. Here, recent developments in forensics-themed spectromicroscopy, sample preparation, and data acquisition methods at the Molecular Environmental Science Beamline 11.0.2 of the Advanced Light Source are described. Results from several initial studies are presented, demonstrating the capability to identify the distribution of the species present in heterogeneous uranium-bearing materials. Future opportunities for STXM forensic studies and potential methodology development are discussed.

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Microanalytical X-ray Imaging of Depleted Uranium Speciation in Environmentally Aged Munitions Residues

Cited by 25 publications

References 34 publications

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

Chemical speciation of U, Fe, and Pu in melt glass from nuclear weapons testing

Multi-scale investigation of uranium attenuation by arsenic at an abandoned uranium mine, South Terras

Development of small particle speciation for nuclear forensics by soft X-ray scanning transmission spectromicroscopy

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