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.
A NanoSIMS 50 L was used to study the relationship between the 235U/238U atomic and 235U16O/238U16O molecular uranium isotope ratios determined from a variety of uranium compounds (UO2, UO2F2, UO3, ...UO2(NO3)2·6(H2O), and UF4) and silicates (NIST-610 glass and the Plesovice zircon reference materials, both containing µg/g uranium). Because there is typically a greater abundance of 235U16O+ and 238U16O+ molecular secondary ions than 235U+ and 238U+ atomic ions when uranium-bearing materials are sputtered with an oxygen primary ion beam, the goal was to understand whether use of 235U16O/238U16O has the potential for improved accuracy and precision when compared to the 235U/238U ratio. The UO2 and silicate reference materials showed the greatest potential for improved accuracy and precision through use of the 235U16O/238U16O ratio as compared to the 235U/238U ratio. For the UO2, which was investigated at a variety of primary beam currents, and the silicate reference materials, which were only investigated using a single primary beam current, this improvement was especially pronounced at low 235U+ count rates. In contrast, comparison of the 235U16O/238U16O ratio versus the 235U/238U ratio from the other uranium compounds clearly indicates that the 235U16O/238U16O ratio results in worse precision and accuracy. This behavior is based on the observation that the atomic (235U+ and 238U+) to molecular (235U16O+ and 238U16O+) secondary ion production rates remain internally consistent within the UO2 and silicate reference materials, whereas it is highly variable in the other uranium compounds. Efforts to understand the origin of this behavior suggest that irregular sample surface topography, and/or molecular interferences arising from the manner in which the UO2F2, UO3, UO2(NO3)2·6(H2O), and UF4 were prepared, may be a major contributing factor to the inconsistent relationship between the observed atomic and molecular secondary ion yields. Overall, the results suggest that for certain bulk compositions, use of the 235U16O/238U16O may be a viable approach to improving the precision and accuracy in situations where a relatively low 235U+ count rate is expected.
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.
Preparation of chromatographic columns requires considerable time during chemical separation procedures. Automated systems capable of repeatedly generating renewable, uniformly packed columns would ...find widespread use in analytical laboratories. Here, a fully automated commercial-off-the-shelf (COTS) system was utilized to pack and unpack 1 mL TEVA and UTEVA columns. To accurately determine the reproducibility of the resin load per column, studies were conducted over several weeks. Method optimization yielded an improvement in loading from 15-19% to 3-5% relative standard deviation. Availability of automated COTS equipment capable of reproducibly generating separation columns has the potential to reduce time and costs associated with column separation.
Rare earth elements such as neodymium and samarium are ideal for probing the neutron environment that spent nuclear fuels are exposed to in nuclear reactors. The large number of stable isotopes can ...provide distinct isotopic signatures for differentiating the source material for nuclear forensic investigations. The rare-earth elements were isolated from the high activity fuel matrix via ion exchange chromatography in a shielded cell. The individual elements were then separated using cation exchange chromatography. The neodymium and samarium aliquots were analyzed via MC–ICP–MS, resulting in isotopic compositions with a precision of 0.01–0.3%.
This work describes a streamlined approach to the separation and purification of trace uranium and plutonium in environmental swipe samples that contain a small amount of collected bulk material. We ...describe key modifications to conventional techniques that result in a relatively rapid, safe, cost-effective, and efficient U and Pu separation process. Simulated samples were produced by loading appropriate
235
U,
238
U, and
240
Pu onto high purity cotton swipes. Uranium concentration and isotopic composition were measured by multi-collector inductively coupled mass spectrometry. Corresponding plutonium measurements were conducted with a three stage thermal ionization mass spectrometer. Quantitative U and Pu recoveries were observed with this method.
Analysis of post-nuclear detonation materials provides information on the type of device and its origin. Compositional analysis of trinitite glass, fused silicate material produced from the above ...ground plasma during the detonation of the Trinity nuclear bomb, reveals gross scale chemical and isotopic heterogeneities indicative of limited convective re-homogenization during accumulation into a melt pool at ground zero. Regions rich in weapons grade Pu have also been identified on the surface of the trinitite sample. The absolute and relative abundances of the lanthanoids in the glass are comparable to that of average upper crust composition, whereas the isotopic abundances of key lanthanoids are distinctly non-normal. The trinitite glass has a non-normal Nd isotope composition, with deviations of −1.75 ± 0.60 ε (differences in parts in 10
4
) in
142
Nd/
144
Nd, +2.24 ± 0.75 ε in
145
Nd/
144
Nd, and +1.01 ± 0.38 ε in
148
Nd/
144
Nd (all errors cited at 2σ) relative to reference materials: BHVO-2 and Nd-Ames metal. Greater isotopic deviations are found in Gd, with enrichments of +4 ± 1 ε in
155
Gd/
160
Gd, +4.19 ± 0.75 ε in
156
Gd/
160
Gd, and +3.48 ± 0.52 ε in
158
Gd/
160
Gd compared to BHVO-2. The isotopic deviations are consistent with a
239
Pu based fission device with additional
235
U fission contribution and a thermal neutron fluence between 1.4 and 0.97 × 10
15
neutrons/cm
2
.
The determination of actinide (e.g., U and Pu) content and isotopics is of importance to the nuclear forensics and safeguards communities. However, in the analysis of environmental samples, such as ...those collected by the International Atomic Energy Agency, uranium measurements can be complicated by isobaric interferences from polyatomic variants of heavy elements (e.g., Pb). This leads to complex, time-consuming sample manipulations (i.e., separations) before determining isotope ratios. An alternative strategy to sample pretreatment is to use high-resolution mass spectrometric platforms during the analysis to fully resolve the uranium isotopes from potential polyatomic interferences, negating the need for prior chemical separation. The liquid sampling - atmospheric pressure glow discharge (LS-APGD) coupled with an Orbitrap mass spectrometer provides a high-resolution (>70,000 m/Δm at m/z 200) inorganic mass spectrometry platform. Further, as a demonstration of the power of this instrumental platform, and indeed, the high-resolution approach in general, uranium isotope ratios were determined in the presence of elemental impurities (e.g., Pb, Pt, Ta, W) commonly encountered with environmental sample swipe analysis, without any prior treatment. Even at elemental impurity concentrations of 1000–5000× relative to uranium, no interference was observed with the 235U or 238U signal. In addition, the 235U/238U isotope ratio for the samples with the concomitants present are within 2 standard deviations of the values obtained without their addition, indicating that these impurities do not impact the determined uranium isotope ratio. These findings represent a significant first step in leveraging the high resolution of the LS-APGD-Orbitrap-MS to overcome isobaric and molecular interferences instead of relying on chemical separations.
We report the first observation of the infrared spectrum of the free tert-butyl cation in the gas phase. This ion is produced in a pulsed supersonic expansion equipped with a pulsed electrical ...discharge. C4H9 + is detected with a time-of-flight mass spectrometer. Its infrared spectrum is recorded using infrared photodissociation spectroscopy and the method of rare gas tagging with argon. For this, the C4H9 +Ar complex is produced, mass selected, and studied with resonance-enhanced IR photodissociation spectroscopy using a tunable optical parametric oscillator laser system. Ab initio computations are employed at the MP2(fc)/6-311+G(2d,2p) level for various isomeric structures of C4H9 + and C4H9 +Ar, and for various configurations of the tert-butyl cation, to elucidate the spectra. We find that argon has a negligible effect on the IR spectra and that the patterns in the spectrum are consistent only with the tert-butyl cation in a C 1 or C s configuration.
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