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Instrumentation effects on U and Pu CBNM standards spectra quality measured on a 500 mm <sup>3</sup> CdZnTe and a 2×2 inch LaBr <sub/>3</sub> detectors
摘要： Nowadays, there is interest in developing gamma-ray measuring devices based on the room temperature operated medium resolution detectors such as semiconductor detectors of the CdZnTe type and scintillators of the LaBr3 type. This is true also for safeguards applications and the International Atomic Energy Agency (IAEA) has launched a project devoted to the assessment of medium resolution gamma-ray spectroscopy for the verification of the isotopic composition of U and Pu bearing samples. This project is carried out within the Non-Destructive Assay Working Group of the European Safeguards Research and Development Association (ESARDA). In this study we analyze medium resolution spectra of U and Pu standards with the aim to develop an isotopic composition determination algorithm, particularly suited for these types of detectors. We show how the peak shape of a CdZnTe detector is influenced by the instrumentation parameters. The experimental setup consisted of a 500 mm3 CdZnTe detector, a 2x2 inch LaBr3 detector, two types of measurement instrumentation – an analogue one and a digital one, and a set of certified samples – a 207Bi point source and U and Pu CBNM standards. The results of our measurements indicate that the lowest contribution to the peak asymmetry and thus the smallest impact on the resolution of the 500 mm3 CdZnTe detector was achieved with the digital MCA. Analysis of acquired spectra allowed to reject poor quality measurement runs and produce summed spectra files with the least impact of instrumentation instabilities. This work is preliminary to further studies concerning the development of an isotopic composition determination algorithm particularly suited for CZT and LaBr3 detectors for safeguards applications.
关键词： LaBr3,isotopic composition,uranium enrichment,medium resolution,safeguards,CdZnTe
更新于2025-09-23 15:23:52
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Efficient and selective sensing of Cu2+ and UO22+ by a europium metal-organic framework
摘要： We report here the investigation of using a luminescent europium organic framework, [Eu2(MTBC)(OH)2(DMF)3(H2O)4]·2DMF·7H2O (denoted as compound 1), for detecting of both Cu2+ and UO2 2+ with high sensitivity. Based on the spectroscopy analysis, compound 1 could selectively respond to Cu2+ and UO2 2+ ions among other selected monovalent, divalent, trivalent metal cations based on a turn-off mechanism. The detection limit of compound 1 towards Cu2+ ion was as low as 17.2 μg/L, which is much lower than the maximum tolerable concentration of Cu2+ in drinking water (2 mg/L) defined by United States Environmental Protection Agency. On the other hand, the detection limit towards UO2 2+ ions is 309.2 μg/L, which could be used for detecting uranium in relative severely contaminated areas. The concentration-dependent luminescence intensity evolution process could be fully understood by the absorption kinetics and isotherm investigations. Furthermore, the quenching mechanism was elucidated by the UV-vis, excitation, luminescence, and lifetime studies. Compound 1, as the first MOF based luminescence probe for both Cu2+ and UO2 2+ ions, provides insight into developing MOF-based multifunctional sensors for both nonradioactive and radioactive elements.
关键词： Adsorption,Copper and uranium contamination,Luminescent metal organic frameworks,Detection
更新于2025-09-23 15:23:52
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Infrared Spectra of the HAnX and H <sub/>2</sub> AnX <sub/>2</sub> Molecules (An=Th and U, X=Cl and Br) in Argon Matrices Supported by Electronic Structure Calculations
摘要： Uranium and thorium hydrides are known as functional groups for ligand stabilized complexes and as isolated molecules under matrix isolation conditions. Here, the new molecular products of the reactions of laser-ablated U and Th atoms with HCl and with HBr, namely HUCl, HUBr and HThCl, HThBr, based on their mid and far infrared spectra in solid argon, are reported. The assignment of these species is based on the close agreement between observed and calculated vibrational frequencies. The H–U and U–35Cl stretching modes of HUCl were observed at 1404.6 and 323.8 cm?1, respectively. Using DCl instead to form DUCl gives absorption bands at 1003.1 and 314.7 cm?1. The corresponding bands of HThCl are 1483.8 (H–Th) and 1058.0 (D–Th), as well as 340.3 and 335.8 cm?1 (Th–35Cl), respectively. HUBr is observed at 1410.6 cm?1 and the BP86 computed shift from HUCl is 6.2 cm?1 in excellent agreement. The U–H stretching frequency increases from 1383.1 (HUF), 1404.6 (HUCl), 1410.6 (HUBr) to 1423.6 cm?1 (UH) as less electronic charge is removed from the U–H bond by the less electronegative substituent. These U–H stretching frequencies follow the Mayer bond orders calculated for the three HUX molecules. A similar trend is found for the Th counterparts. Additional absorptions are assigned to the H2AnX2 molecules (An = U, Th, X = Cl, Br) formed by the exothermic reaction of a second HX molecule with the above primary products.
关键词： infrared,matrix isolation,thorium,uranium,density functional calculations
更新于2025-09-23 15:22:29
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Spatially-resolved uranium isotopic analysis of contaminated scrap metal using laser ablation multi-collector ICP-MS
摘要： Laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) was applied to the detailed investigation of the uranium (U) isotopic composition (234U, 235U, 236U, and 238U) of five contaminated scrap metal samples found within the European Union. Pressed pellets of the two certified U isotopic reference materials CRM U-020 and CRM U-030 were included in the measurement protocol for mass bias correction, calculation of the ion counter gains and for quality assurance. Since the investigated samples had low U content (0.15–14.3 wt%) compared to typically analysed pure U compounds (>60 wt%), the applied experimental parameters had to be adjusted. Spatially-resolved U isotopic information was obtained by line scan analysis of each sample. While other analytical techniques used typically in nuclear forensic investigations, such as g-spectrometry and thermal ionisation mass spectrometry (TIMS) yielded average U isotopic compositions of the entire sample, LA-MC-ICP-MS provided substantial added value, highlighting the inhomogeneous distribution of U isotopes within various scrap metal samples. Analysis of individual particles via secondary ion mass spectrometry (SIMS) confirmed the large range of 235U enrichment levels in heterogeneous scrap metal samples. Four out of five scrap metal samples contained 236U ((cid:1)0.05–(cid:1)0.11 wt%), indicating the presence of reprocessed U. Taken together, LA-MC-ICP-MS analysis provided fast and accurate spatially-resolved U isotopic information without consuming or altering the scrap metal samples, a key feature for nuclear forensics investigations.
关键词： nuclear forensics,Laser ablation,multi-collector ICP-MS,uranium isotopic analysis,scrap metal
更新于2025-09-23 15:21:01
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Photocatalytic reduction of U(VI) in wastewater by mGO/g-C3N4 nanocomposite under visible LED light irradiation
摘要： Efficient elimination of U(VI) from uranium wastewater is an urgent task for sustainable nuclear energy and environmental protection. In this study, magnetic graphene oxide decorated graphitic carbon nitride (mGO/g-C3N4) nanocomposite was prepared and used for photocatalytic reduction of U(VI) in wastewater under visible LED light irradiation for the first time. The batch experiments indicated that the mGO/g-C3N4 (mGCN) nanocomposite could efficiently reduce U(VI) under visible LED light, and a high U(VI) extraction capacity of 2880.6 mg/g was obtained with an extraction efficiency of 96.02 %. The transmission electron microscopy (TEM) elemental mapping, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses demonstrated that the soluble U(VI) was immobilized by transforming it to metastudtite ((UO2)O2?2H2O) by mGCN nanocomposite under visible LED light irradiation. This work indicated that the mGCN is a promising visible light catalyst for treatment of uranium wastewater.
关键词： removal,photoreduction,wastewater,uranium
更新于2025-09-23 15:21:01
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Determination of uranium in ores using laser-induced breakdown spectroscopy combined with laser-induced fluorescence
摘要： The plasma emission spectrum of uranium in laser-induced breakdown spectroscopy (LIBS) is weak and susceptible to spectral interference, especially in a complex ore matrix. In this study, laser-induced breakdown spectroscopy combined with laser-induced fluorescence (LIBS-LIF) technology was proposed to enhance the spectral intensity of uranium in ores and eliminate spectral interference. Different combinations of excitation lines and analytical lines of the U element were investigated. In contrast with atomic lines, uranium ion lines are more suitable for determination of uranium. The relative number of U ions in plasma was studied for the best selection of excitation lines and analytical lines. The analytical performance of LIBS-LIF and LIBS for U determination in ores was compared. The results showed that all indicators had been significantly improved by LIBS-LIF. The slope, R2, LoD, RMSECV, ARE, and ARSD values of LIBS-LIF were 1.1 (cid:1) 105 counts per wt%, 0.998, 35 mg g(cid:3)1, 0.05 wt%, 6.69%, and 6.37%, respectively. This work demonstrates that LIBS-LIF has excellent potential in the exploration of uranium resources.
关键词： laser-induced breakdown spectroscopy,uranium,spectral interference,laser-induced fluorescence,ore matrix
更新于2025-09-23 15:19:57
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a??Blind timea?? a?? current limitations on laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) for ultra-transient signal isotope ratio analysis and application to individual sub-micron sized uranium particles
摘要： The application of laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) to the isotope ratio analysis of UOx particles has the potential to improve the isotopic determination of these particles when compared to currently utilised ICP-MS techniques. To investigate this a high-speed, integrated ablation cell and dual concentric injector design, was tested in the expectation that the resulting increase in signal to noise ratio and sample ion yield would improve the determination of 234U/238U, 235U/238U and 236U/238U for such materials. However, when compared to a slower washout, more established low-volume cell design, the highly transient signals of the new design proved challenging for the mixed detector array of the multi-collector mass spectrometer, introducing a new bias. We describe a major component of this bias, referred to as ‘blind time’, and model its impact on UOx particle analysis. After accounting for blind time, average precisions for the uranium isotopic composition of sub-micron sized UOx particles using LA-MC-ICP-MS were 3 % 1RSD for 235U/238U and 8 % 1RSD for 234U/238U. When ablating a glass rather than a UOx particle, uncertainties of 1.3 % 1RSD for 235U/238U were achieved for 150 nm equivalent particle sizes using LA-MC-ICP-MS.
关键词： isotope ratio analysis,UOx particles,uranium isotopic composition,LA-MC-ICP-MS,blind time
更新于2025-09-23 15:19:57
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Expansion dynamics and chemistry evolution in ultrafast laser filament produced plasmas
摘要： Laser ablation in conjunction with optical emission spectroscopy is a potential non-contact, standoff detection method for all elements in the periodic table and certain isotopes such as radionuclides. Currently, significant development efforts are on-going to use ultrafast laser filaments for remote detection of materials. The application of filaments is of particular interest in extending the range of stand-off capability associated with elemental and isotopic detection via laser-induced breakdown spectroscopy. In this study, we characterize the expansion dynamics and chemical evolution of filament-produced uranium (U) plasmas. Laser filaments are generated in the laboratory by loosely focusing 35 femtosecond (fs), 6 milli Joule (mJ) pulses in air. Two-dimensional spectrally-integrated and time-resolved imaging was performed to study hydrodynamics and evolution of U atomic and UO molecular emission in filament-produced U plasmas. Our results highlight that filament ablation of U plasmas gives a cylindrical plasma plume morphology with an appearance of plume splitting into slow and fast moving components at later times of its evolution. Emission from the slow-moving region shows no distinct spectral features (i.e. broadband-like) and is contributed in part by nanoparticles generated during ultrafast laser ablation. Additionally, we find U atoms and U oxide molecules (i.e. UO, UxOy) co-exist in the filament produced plasma, which can be attributed to the generation of low-temperature plasma conditions during filament ablation.
关键词： optical emission spectroscopy,Laser ablation,plasma chemistry,ultrafast laser filaments,uranium plasmas
更新于2025-09-23 15:19:57
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Laser-induced breakdown spectroscopy of uranium in the VUV range
摘要： Quantitative analysis of impurities in nuclear materials is necessary in a number of areas, including process control during manufacturing, quality control of products, or for nuclear forensics purposes. Due to the important handling constraints induced by the samples radioactivity and their containment inside airtight enclosures, optical analytical techniques have great advantages over standard ones that require sample preparation, like ICP-based techniques. Therefore, laser-induced breakdown spectroscopy (LIBS) is developed for fast quantitative analysis of impurities in uranium. Actinides are well-known to have a very large number of emission lines in the UV-visible spectral range, hence making the detection of trace or minor elements a real challenge. Therefore, in this study we explored the vacuum ultraviolet range (VUV), i.e. below 200 nm, in order to investigate if this spectral region is more favorable for elemental analysis of uranium by LIBS. As practically no data on VUV spectroscopy of uranium are available, we first analyzed the spectra obtained to assess the spectral density of uranium lines, both in the UV and VUV. Then, the detection limits of two elements, carbon and vanadium, were estimated. It was found that, in spite of a less dense and less intense uranium background in the VUV, this spectral region is not relevant for metal impurities whose spectra are marginally analytically useful in the VUV. Conversely, for non-metals having intense lines in the VUV, the detection limit can be significantly better than in the UV. This was already known for non-nuclear samples. This study extends that conclusion to nuclear materials and has important practical consequences on the implementation of a LIBS analyzer in a nuclear facility.
关键词： vanadium,uranium,Laser-induced breakdown spectroscopy,impurities detection,carbon,VUV range
更新于2025-09-23 15:19:57
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Hyperfine structures and isotopic shifts of uranium transitions using tunable laser spectroscopy of laser ablation plumes
摘要： We report isotopic shifts and hyperfine structures of selected U transitions employing tunable spectroscopy viz: laser-induced fluorescence and laser absorption spectroscopy of laser ablation plumes. The plasmas were produced during ns laser ablation on a natural U metal target which contains 0.73% 235U. Our results show that isotopic shifts between 238U and 235U are entangled with hyperfine structures of 235U. Measurements obtained using laser-induced fluorescence are affected by the high absorbance of 238U. Time-resolved laser absorption spectroscopy is carried out for evaluating the optical absorption and estimating the hyperfine constants.
关键词： LIBS,Hyperfine structure,Laser absorption spectroscopy,Isotopic analysis,Uranium,Laser-induced fluorescence,Laser ablation,Tunable laser spectroscopy
更新于2025-09-23 15:19:57