Several studies have evaluated the morphology of uranium compounds produced under controlled conditions at the laboratory scale, but it is unclear whether the morphological characteristics of these ...materials persist in commercially produced uranium ore concentrates (UOCs). To assess the morphology in “real-world” UOCs, we qualitatively evaluated the morphological profile of secondary electron images from over 100 commercial UOCs using a previously published lexicon. We observe differences between samples with differing chemical composition and samples with similar chemical composition and differing provenance. This work contextualizes morphology for commercially produced UOCs and will provide a basis for future machine learning efforts.
Northwest Africa (NWA) 8159 is an augite-rich shergottite, with a mineralogy dominated by Ca-, Fe-rich pyroxene, plagioclase, olivine, and magnetite. NWA 8159 crystallized from an evolved melt of ...basaltic composition under relatively rapid conditions of cooling, likely in a surface lava flow or shallow sill. Redox conditions experienced by the melt shifted from relatively oxidizing (with respect to known Martian lithologies, ∼QFM) on the liquidus to higher oxygen fugacity (∼QFM+2) during crystallization of the groundmass, and under subsolidus conditions. This shift resulted in the production of orthopyroxene and magnetite replacing olivine phenocryst rims. NWA 8159 contains both crystalline and shock-amorphized plagioclase (An50–62), often observed within a single grain; based on known calibrations we bracket the peak shock pressure experienced by NWA 8159 to between 15 and 23GPa. The bulk composition of NWA 8159 is depleted in LREE, as observed for Tissint and other depleted shergottites; however, NWA 8159 is distinct from all other martian lithologies in its bulk composition and oxygen fugacity. We obtain a Sm-Nd formation age of 2.37±0.25Ga for NWA 8159, which represents an interval in Mars geologic time which, until recently, was not represented in the other martian meteorite types. The bulk rock 147Sm/144Nd value of 0.37±0.02 is consistent with it being derived directly from its source and the high initial ε143Nd value indicates this source was geochemically highly depleted. Cr, Nd, and W isotopic compositions further support a unique mantle source. While the rock shares similarities with the 2.4-Ga NWA 7635 meteorite, there are notable distinctions between the two meteorites that suggest differences in mantle source compositions and conditions of crystallization. Nevertheless, the two samples may be launch-paired. NWA 8159 expands the known basalt types, ages and mantle sources within the Mars sample suite to include a second igneous unit from the early Amazonian.
A nuclear forensics investigation involving a uranium ore concentrate relies on accurate and precise analysis of impurities. Analytical data defensibility requires the use of reference materials as ...part of quality control. This study presents a compilation of trace element concentration results of the CUP-2 Uranium Ore Concentrate Standard measured by 11 different laboratories. The laboratories employed various dissolution methods, analytical preparation methods, and instrumental platforms. The data presented here contain concentrations of 66 impurities with up to 138 individual data points for each impurity. Consensus values have been assigned to each impurity following a statistical analysis of the data set.
In this study, data from thirteen laboratories from around the world are presented for a successful certification of uranium isotope ratios in uranium ore concentrate (UOC) certified reference ...materials from the National Research Council Canada. Different mass spectrometric measurement principles (including SF‐ICP‐MS, quadruple ICP‐MS, TIMS, MC‐ICP‐MS, SIMS and AMS) and measurement procedures were employed. In general, data from all sources exhibit good consistency with TIMS and MC‐ICP‐MS showing superior performance. The three candidate UOC CRMs (UCLO‐1, UCHI‐1 and UPER‐1) have natural uranium isotope ratios with certified values of 0.5304(7) × 10−4, 0.5475(2) × 10−4 and 0.5361(4) × 10−4 for n(234U)/n(238U) and 0.007 2563(13), 0.007 2563(10) and 0.007 2542(11) for n(235U)/n(238U), respectively, with expanded uncertainty (k = 2) applicable to the last digit of the value given in the parentheses. Information values for n(236U)/n(238U) in these three CRMs, measured by AMS, are also provided: 10 × 10−12, 200 × 10−12 and 22 × 10−12. The uncertainties of the proposed certified values of uranium isotope ratios in UOC CRMs are superior to available reference materials, and the values of n(234U)/n(238U) and n(236U)/n(238U) show significant variation among the three CRMs.
Key Points
Collaboration involving 13 international laboratories employing different mass spectrometric measurement principles (SF‐ICP‐MS, Q‐ICP‐MS, TIMS, MC‐ICP‐MS, SIMS, AMS) and measurement procedures.
Successful certification of uranium isotope ratios in uranium ore concentrate CRMs UCHI‐1, UCLO‐1 and UPER‐1 from the National Research Council Canada.
Suitable for validation of methods used for uranium isotope ratio measurements.
This interlaboratory study measured thorium concentrations and isotope compositions in uranium ore concentrates from different geographical locations to examine whether thorium impurities may be ...useful forensic signatures for uranium ore concentrates found out of regulatory control. Measured
230
Th/
232
Th in fifteen uranium ore concentrates record over three orders of magnitude of compositional variation. Results demonstrate that
230
Th/
232
Th used in combination with U/Th ratios resulted in a unique signature for individual uranium ore concentrates from different processing locations. Data presented here suggest potential for
230
Th/
232
Th and U/Th to be used as comparative signatures to investigate the provenance of seized uranium ore concentrates.
Radiochronometric data, a key signature in evaluating the provenance and process history of nuclear material out of regulatory control, are conventionally acquired via multi-collector mass ...spectrometry. Here we explore the potential of age-dating by single-collector mass spectrometry. To evaluate model age accuracy/precision across different instrument designs, we performed
230
Th–
234
U and
231
Pa–
235
U radiochronometry of CRM 125-A using two single-collector and one multi-collector plasma source mass spectrometers. Single-collector instruments produce accurate model ages for this uranium standard and thus hold promise for nuclear forensics radiochronometry. Increased acquisition of age information via multiple instrument designs will bolster the global response to nuclear interdictions.
Uranium ore concentrates (UOCs) are produced at mining facilities from the various types of uranium-bearing ores using several processes that can include different reagents, separation procedures, ...and drying conditions. The final UOC products can consist of different uranium species, which are important to identify to trace interdicted samples back to their origins. Color has been used as a simple indicator; however, visual determination is subjective and no chemical information is provided. In this work, we report the application of near-infrared (NIR) spectroscopy as a non-contact, non-destructive method to rapidly analyze UOC materials for species and/or process information. Diffuse reflectance spectra from 350 to 2500 nm were measured from a number UOC samples that were also characterized by X-ray diffraction. Combination and overtone bands were used to identify the amine and hydroxyl-containing species, such as ammonium uranates or ammonium uranyl carbonate, while other uranium oxide species (e.g., uranium trioxide UO3 and triuranium octoxide U3O8) exhibit absorption bands arising from crystal field effects and electronic transitions. Principal component analysis was used to classify the different UOC materials.
► We studied the effect of dissolved organic matter (DOM) on actinide retardation. ► Am/Pu
K
ds
were ∼100 times lower in DOM-rich Nevada Test Site (NTS) waters. ► U
K
ds
decreased due to high ...dissolved inorganic carbon (DIC). ► Thermodynamic model predictions generally agreed with DIC and DOM effects. ► Reduced Am/Pu retardation in DOM-rich NTS waters may affect contaminant distribution.
The effect of dissolved organic matter (DOM) on Am(III), Pu(IV), Np(V), and U(VI) sorption was investigated with natural water (pH ∼8) and zeolitized tuff samples collected from the Rainier Mesa tunnel system, Nevada Test Site, where the USA detonated underground nuclear tests prior to 1992. Perched vadose zone water at Rainier Mesa has high levels of DOM as a result of microbial degradation of mining debris (diesel, wood, etc.). The Am and Pu sorption
K
ds
were up to two orders of magnitude lower in water with high DOM (15–19
mg C/L) compared to the same water with DOM removed (<0.4
mg C/L) or in naturally low DOM (0.2
mg C/L) groundwater. In contrast,
K
ds
of Np and U were less affected by DOM at these solution conditions. Uranium sorption decreased as a result of high dissolved inorganic C (DIC) resulting from microbial degradation of DOM. Thermodynamic model predictions, based on actinide–humic acid stability constants available in the literature, are in general agreement with measured
K
d data, correctly predicting the effects of DIC and DOM on actinide retardation. This agreement is encouraging to future modeling efforts and suggests that effects of DOM and DIC can be incorporated into reactive transport modeling predictions. The Am and Pu transport rates in Rainier Mesa tunnel waters will be substantially faster as a result of the elevated DOM levels. Low diffusion rates of actinide–DOM macromolecular complexes may focus Pu and Am transport into fractures and minimize retardation via matrix diffusion. The resulting transport behavior will affect actinide distribution patterns and associated risk estimates.
An international group of laboratories participating in CMX-4 subjected three samples to comparative nuclear forensic analysis using uranium assay and trace element analysis techniques to determine ...if the samples had similar or different origins. Uranium assay indicated that two pellet samples (ES-2 and ES-3) were nearly pure UO
2
while the black powder sample ES-1 was primarily UO
2
with UO
3
and/or U
3
O
8
forms present as impurities. Trace element analysis by five of the six participating laboratories reported molybdenum concentrations below 10 µg/g U in all of the exercise samples, suggesting the same likely facility of origin for all three samples.
Beryllium has been historically machined, handled and stored in facilities at Lawrence Livermore National Laboratory (LLNL) since the 1950s. Additionally, outdoor testing of beryllium-containing ...components has been performed at LLNL's Site 300 facility. Beryllium levels in local soils and atmospheric particulates have been measured over three decades and are comparable to those found elsewhere in the natural environment. While localized areas of beryllium contamination have been identified, laboratory operations do not appear to have increased the concentration of beryllium in local air or water. Variation in airborne beryllium correlates to local weather patterns, PM10 levels, normal sources (such as resuspension of soil and emissions from coal power stations) but not to LLNL activities. Regional and national atmospheric beryllium levels have decreased since the implementation of the EPA's 1990 Clean-Air-Act. Multi-element analysis of local soil and air samples allowed for the determination of comparative ratios for beryllium with over 50 other metals to distinguish between natural beryllium and process-induced contamination. Ten comparative elemental markers (Al, Cs, Eu, Gd, La, Nd, Pr, Sm, Th and Tl) that were selected to ensure background variations in other metals did not collectively interfere with the determination of beryllium sources in work-place samples at LLNL. Multi-element analysis and comparative evaluation are recommended for all workplace and environmental samples suspected of beryllium contamination. The multi-element analyses of soils and surface dusts were helpful in differentiating between beryllium of environmental origin and beryllium from laboratory operations. Some surfaces can act as “sinks” for particulate matter, including carpet, which retains entrained insoluble material even after liquid based cleaning. At LLNL, most facility carpets had beryllium concentrations at or below the upper tolerance limit determined by sampling facilities with no history of beryllium work. Some facility carpets had beryllium concentrations above the upper tolerance limits but can be attributed to tracking of local soils, while other facilities showed process-induced contamination from adjacent operations. In selected cases, distinctions were made as to the source of beryllium in carpets. Guidance on the determination of facility beryllium sources is given.
► We examined beryllium concentrations in historical on-site soil samples and local air particulates. ► We evaluated beryllium-to-metal ratios for soil and air filter samples and applied results to samples from facility carpets. ► Localized areas of contamination were identified, but operations do not appear to have increased Be in local air and water. ► Variation in airborne beryllium correlates to local weather patterns and PM10 levels and not to operational activities. ► Multi-element analysis provided information to determine whether the source of Be was natural or anthropogenic.
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