Uranium ore concentrate (UOC) is a group of intermediate products widely used in the nuclear fuel cycle. Following the recent characterisation and classification of UOC industrial product powders for nuclear forensic analysis, this paper presents an experimental study of the hygroscopic properties of these UOC stockpile samples for long-term storage and the inhalation risk assessment of uranium particles. Two independent techniques, the density balance and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), were utilised to measure increases in sample weight and the infrared absorption peak of ten UOC samples, respectively, due to hygroscopic growth. Taking (NH4)4((UO2)2(SO4)O2)2(H2O) powder as an example, the hygroscopicity mechanism was investigated experimentally by monitoring hydration and dehydration processes using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and Thermogravimetric-Differential Thermal Analysis (TG-DTA), respectively. The hygroscopic growth factor of (NH4)4((UO2)2(SO4)O2)2(H2O) sample was determined using the above two techniques under precisely controlled temperature and humidity conditions. Screening results show significant differences in the hygroscopicity of sodium- and ammonium-containing UOC powders, despite their similar elemental composition, infrared functional groups, and crystal structures. The porous surface and hygroscopic component are beneficial for hygroscopic growth. Observation of the hydration and dehydration process confirms that the physical adsorption of water is the dominant mechanism. The hygroscopic growth factors of sample mass and infrared absorption peak increase with rising relative humidity above 80% RH. The hygroscopic growth curve of (NH4)4((UO2)2(SO4)O2)2(H2O) powder could be described using a simplified κ-Köhler equation. A dense surface, low RH (<80%) and an inert buffer gas are recommended for material processing and stable storage. For (NH4)4((UO2)2(SO4)O2)2(H2O) particles possibly inhaled in the respiratory tract, the effect of hygroscopic growth on the deposition profile is also discussed.

Atmospheric dispersion behavior of radioactive particles from nuclear facilities has attracted widespread attention due to their profound impacts on the environment and public health. The spatial variation of radioactive particle distribution could be mainly attributed to complex terrain. A simplification of complex terrain into idealized two-dimensional ridges and three-dimensional hills is a common methodological approach for investigating terrain effects. Here, an integrated approach employing both wind tunnel experiments and Computational Fluid Dynamics (CFD) simulations was used to investigate radioactive particulate dispersion trajectories over these typical idealized terrains. Key parameters, such as dimensions, types of terrain, release heights and positions of pollutants, were systematically varied. A comprehensive wind tunnel dataset was established using laser-sheet visualization to enrich high-fidelity validation data for particle dispersion model. Furthermore, the wind tunnel results indicated that the two-dimensional ridge enhanced plume rise relative to flat terrain, with the magnitude of enhancement dependent on its location and height. Conversely, lateral flow around the three-dimensional hill mitigated its influence on the plume trajectory, leading to negligible sensitivity to the hill height. However, large hills significantly blocked particle dispersion, resulting in a concentration decrease in the downwind area. Additionally, a higher release height and greater distance from the source diminished the influence of the complex terrain. In the CFD simulations, discrepancy of particle concentration was observed over the two-dimensional ridge when using various turbulent and dispersion model constants derived for flat terrain. A set of turbulent and dispersion constants of the CFD model (C1ε, C2ε, σk, σε, Cμ and cL) was optimized for application to complex terrain through validation against wind tunnel experimental data. The optimized values are 1.5, 1.92, 1.67, 3.25, 0.09 and 0.2, respectively.

This work details technical advancements in multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) for high-precision plutonium (Pu) isotope ratio analysis. Uranium (U) and Pu isotopes have been proven to exhibit similar mass fractionation effects, as measured using MC-ICP-MS, within analytical uncertainty. Herein, 233U-236U double spike method with IRMM3636 was developed to correct the mass fractionation while measuring Pu isotope measurement, achieving an RSD% of 0.0029 % for Pu isotope ratios at 10-2 level. This method was the first one to precisely measure low-abundance isotopes such as 241Pu and 242Pu via combining Faraday cup (1013 Omega amplifier) and secondary electron multiplier detector configuration. At trace levels (ng), long-term RSDs of 239Pu at a laboratory working standard reached 0.019 % (241Pu/239Pu) and 0.046 % (242Pu/239Pu) near the 10- 4 level, demonstrating exceptionally high precision in the isotope ratio analysis and representing the highest precision reported to date for these ratios. This state-of-the-art method maintained high sample throughput while delivering exceptional accuracy. Its robustness was confirmed through successful application to Pu isotope analysis in irradiated nuclear fuel samples, highlighting its broad applicability.

In this study, we extend our previous high-speed photographic studies (Xie et al. 2022 and Han et al. 2025) to direct characterization of the central channel and its flow velocity distribution in an analytical inductively coupled plasma source. The strong plasma emission was successfully suppressed by optimising the high-speed camera's aperture size and shutter duration, allowing us to directly observe the central channel and the discrete ion cloud. The width of the central channel was determined from the luminance distribution rather than the analyte ion distribution, unlike the commonly used method. The effect of the addition percentage of oxygen and nitrogen to the sample flow on the channel width was investigated. By injecting and tracking five types of suspension particles with various inertial properties, the axial flow velocity in the central channel was determined using the time-of-flight method. The axial flow velocity distributions at varying r.f. power, sample flow rate, and addition fraction of oxygen and nitrogen in the sample flow were finally experimentally determined. Results show that the width of the central channel in pure Ar-ICP is 7.2 mm under the investigated operating conditions. The presented width value is comparable with the peak-to-peak distance of the plasma parameter distributions but about three times that determined from the analyte ion distribution. In the mixed-gas ICP, the width increases with increasing nitrogen addition percentage in the sample flow but is insensitive to the oxygen addition fraction. Compared with the flow velocity, no particle slipping or dragging was observed, indicating that the flow velocity was well represented by that of the suspension particles used. In pure Ar-ICP, Ar-O2 ICP and Ar-N2 ICP, the axial flow velocity tends to increase and then decrease with the axial position with respect to the torch outlet. In pure Ar-ICP, a cubic polynomial fitting of the axial flow velocity with the quadratic root of the axial position is proposed for velocity estimation. A velocity plateau is clearly observed in the normal analytical zone (NAZ). The present work provides detailed information on the central channel for pure argon, Ar-O2 ICP, and Ar-N2 ICP. Experimental data on the axial flow velocity distribution across a wide range in the ICP source are also presented.

Cross-matrix RSF calibration using bulk superalloy CRMs enables the determination of 63 elements in pressed IN718 superalloy powder pellets by pulsed GD-MS. Of the 16 independently validated elements, the majority were within 10% relative deviation.

Thermal ionization mass spectrometry (TIMS) is a widely used mass spectrometric technique for trace/ultra-trace isotopic analysis. For accurate isotope ratio determination, the detector dead time and ion counter efficiency have to be appropriately corrected for. Two methods of pulse counting detector dead time calculation were evaluated on a TIMS instrument. Both methods were based on the measurement of Sr isotope ratios in NIST standards and had similar performance in assessing the dead time for pulse-count detectors. In addition, one of the newly proposed methods in this manuscript can be used to simultaneously determine the dead time and ion counter efficiency of the pulse counting detector via the ratio measurement approach. The advantages of using the method presented here are firstly that both the detector dead time and the ion counter efficiency can be obtained simultaneously and secondly that the sampling time can be spent entirely on the isotopes of interest.

Resonance ionization mass spectrometry (RIMS) is a highly sensitive technique for isobar-free analysis of long-lived isotopes, leveraging its exceptional elemental selectivity. However, the inherent laser-induced isotopic discrimination (LIID) in RIMS has posed challenges for its application in high-precision isotope ratio analysis. To address this limitation, based on the experimental phenomena observed in the analysis of Sn isotope ratios using RIMS, we investigated how isotope mass and isotope shift affect ionization efficiency, and proposed a semi-empirical internal standard correction method for LIID. Additionally, the combination of the total evaporation method, which is commonly used in thermal surface ionization mass spectrometry (TIMS), with RIMS effectively corrects the influence of mass fractionation on ratio measurements, thereby decoupling the LIID from the mass fractionation. This novel internal correction model for LIID enables RIMS, for the first time, to perform isotope ratio measurements with internal calibration capabilities comparable to those of TIMS and inductively coupled plasma mass spectrometry (ICP-MS). The application of this correction method to Sn isotopes has led to a tenfold improvement in both precision and accuracy. Post-correction analyses demonstrated isotope ratio determinations with precision better than 0.05% and accuracy exceeding 0.1%. This advancement significantly expands the potential of RIMS in fields that demand strict isotopic fidelity, such as nuclear forensics, the nuclear industry, and environmental tracer studies.

Unlike traditional Thermal Ionization Mass Spectrometers (TIMS) with single-focusing magnetic mass analyzers (such as Triton, Phoenix, Nu TIMS, etc.), a newly developed Double-Focusing Thermal Ionization Mass Spectrometer (DF-TIMS) enhances the system stability by mitigating accelerating high-voltage noise and drift. Featuring a Nier-Johnson type double-focusing mass analyzer, the instrument includes a laminated magnet with a 250 mm radius and a cylindrical Electrostatic Analyzer (ESA) with a 350 mm radius, achieving a mass dispersion of 560 mm. It is equipped with of 16 Faraday cups and 4 full-size discrete dynode secondary electron multipliers (SEM), combined with variable dispersion double quadrupole zoom optics, allowing for multi- collection of isotopes with up to 20 % mass dispersion, such as isotopes of Lithium, Boron and Calcium. Additionally, a compact and advanced Retarding Filter enhances abundance sensitivity from < 2 ppm to < 5 ppb. Automated tuning and measurement improve efficiency for both positive and negative ions. With a 0.2 mm source slit and a 1 mm receiving slit, DF-TIMS achieves a resolution over 470 and a peak shape factor below 0.3. System stability is less than 15 ppm/30 min credit to the double-focusing design. Each Faraday cup operates with a dynamic range of 0-50 V, featuring Root Mean Square (RMS) noise (4s integration, 1011 Omega high resistance) under 20 mu V and baseline drift below 1 x 10(-16 )A/h. The instrument has been applied extensively, delivering internal precision and external precision for Strontium and Neodymium measurements under 5 ppm, meeting stringent isotopic ratio analysis requirements in nuclear science and geoscience.

Many numerical simulation models for analytical and industrial ICP sources have been developed; hence, experimental verification is essential. Compared with plasma temperature, the flow velocity profile is a direct and reliable criterion for model verification. In this paper, an experimental study on the dynamic properties of a home-made analytical ICP source and its tail flame is conducted using a high-speed colour camera and a high-speed fibre-optic spectrometer, and the spatially resolved pulsation frequency and flow velocity are presented. The pulsation frequencies of the plasma area and emission intensity were experimentally determined, respectively. The spatially resolved pulsation frequency indicates that pulsation of the normal analytical zone (NAZ) is very stable and synchronous, and the tail flame fluctuates due to ambient air entrainment. The flow velocity in the coolant gas was characterised by tracking the trajectories of injected alumina powder particles. After correcting for the velocity difference between the powder particle with high inertia and the surrounding flow, a plausible range of axial (Vz) and radial (Vr) velocity at the outer edge of the coolant gas is proposed. The flow velocity on the axis downstream of the NAZ was experimentally determined by tracking and interpolating the velocity of discrete erbium ion clouds originating from individual erbia suspension particles. By comparing the simulated profile of axial velocity with the experimental profile, the power coupling efficiency of the present ICP facility is estimated to be around 80%. A linear expression is presented to describe the variation of Vz with the axial position (z) in the range of 0 <= z <= 50 mm. Because erbium ion clouds were not distinguishable from the very bright emission background within the NAZ, a novel method is proposed to determine the flow velocity in the NAZ by combining the dependence of the audio frequency of plasma pulsation on the flow velocity profile, the simulated profile of axial velocity, and the experimental value of pulsation frequency. The determined value of axial velocity at the torch outlet axis operating at an r.f. power of 1200 W is in good agreement with the fitted value. This work presents complete experimental data on flow velocity in a single ICP facility and experimentally verifies the previously developed 2D numerical model.

A novel approach was developed for the precise analysis of the 238Pu/239Pu ratio in plutonium using thermal ionization mass spectrometry (TIMS). This methodology was based on the difference in thermal evaporation behavior between U and Pu during the total evaporation (TE) process. By incorporating the U interference indicator into the Pu solution, a linear model that related the m/z 238 a.m.u. intensity changes to the isotope ratios of 238Pu/239Pu and 238U/235U was established. The ratios of 238Pu/239Pu and 238U/235U was determined by fitting the experimental data using multiple linear regression analysis. This method had been applied to analyze laboratory isotopic standard samples Pu(SO4)2.4H2O. Results showed that, even with extremely small sample size of 238Pu (picogram level), the relative standard deviation of 238Pu/239Pu ratio was less than 0.2 %. The approach was simple and would be an effective tool as a method for the characterization of 238Pu using TIMS.

This study addresses two persistent challenges in uranium fluoride chemistry: resolving decades-long spectral assignment conflicts across UF2, UF3, and UF4 species, and conclusively settling the symmetry controversy of UF4. By the cryogenic matrix isolation IR spectroscopy technique in combination with relativistic quantum chemical calculations, we experimentally tracked the stepwise formation of UF to UF6 in neon and argon matrices. Theoretical validation has led to a reassignment of the infrared absorption bands for UF2, UF3, and UF4, defining their molecular geometries. While UF2 exhibits a V-shaped C2v structure and UF3 has a pyramidal C3v configuration, UF4 adopts a D2d geometry rather than a Td symmetry, arising from the Jahn-Teller distortion, which was verified by complete active space second-order perturbation theory (CASPT2) calculations incorporating spin-orbit coupling, supporting predictions from relativistic density functional theory and BW-MRCCSD calculations by Johnson et al. Moreover, weak van der Waals interactions between UFn (n = 2-4) and argon atoms induced vibrational redshift. Bonding analyses revealed that U-F bonds in UFn (n = 1-6) possess dual ionic-covalent character, with ionic contributions of 78-88%. The covalent enhancement in fluorides arises from the overlap of U 5f/6d orbitals with F 2p orbitals and their near-degeneracy. These findings reconcile historical discrepancies, establish definitive benchmarks, and advance uranium fluoride chemistry for nuclear fuel applications.

Americium isotopes are crucial in various nuclear-related fields such as nuclear fuel cycle, nuclear forensics and nuclear safeguards. This study introduces enhanced methodologies for precise determination of 242Am/241Am and 243Am/241Am in trace americium by employing Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICP-MS) and Total Evaporation-Thermal Ionization Mass Spectrometry (TE-TIMS). We established a standard-sample bracketing (SSB) method with uranium-certified reference material (U CRM) to correct the mass fractionation and ion counter gain yield among different isotopes in MC-ICP-MS. The new methods were successfully applied to an aliquot of an 241Am progeny sample, an 241Am activity standard solution and an in-house Am isotopic working standard, achieving detection limits of 10- 7 for 242Am and 243Am. Analysis requires an aliquot containing about 1 ng of 241Am for MC-ICP-MS with a desolvation device for sample introduction and about 5 ng for TE-TIMS to determine 242Am/241Am ratios close to 10-5 and 243Am/241Am ratios close to 10-4, with observed relative standard deviations of 0.2 %. Comparative analysis of 242Am/241Am and 243Am/241Am using classical TE-TIMS and the newly developed MC-ICP-MS confirms their consistency within uncertainties, validating the precision of MC-ICP-MS in americium isotope ratio determination. These findings indicate that the 241Am activity standard sample was directly sourced from irradiated material rather than from a 241Pu solution, highlighting the methodology's applicability to nuclear forensics and nuclear fuel cycles.

Tritium discharge from the fusion system and its environmental impact receive wide attention. Considerable deviation exists in various atmospheric dispersion models for evaluating near-surface tritium concentration distribution. To quantitatively find out the diversity of these models, a performances comparison was performed based on the case of tritium discharge from the ITER site. Wind tunnel experiments were preliminarily performed to test the performances of these models. Annual average tritium concentration and individual radiation dose were assessed for some selected residential areas adjacent to the ITER site. It is indicated that atmospheric dispersion simulation by the CFD method is significantly influenced by the modeling of the turbulence. Atmospheric dispersion predicted by the CFD-RANS model with default parameters is weaker, resulting in higher downwind pollutant concentration, compared with the CFD-LES model, Gaussian plume model and Lagrangian puff model. Wind tunnel experimental results relatively support the CFD-LES model with strong turbulent dispersion. CFD-LES model is superior in reflecting the effects of complex topography in high resolution and shows strong turbulent dispersion. Individual radiation dose under normal operation at selected residential areas near ITER was estimated to be much lower than the natural radiation level and also the ITER dose limit even considering the uncertainty margin.

Gallium-72 is an important Comprehensive Nuclear-Test-Ban Treaty relevant radionuclide that arouses significant interest. However, the reported half-lives of Ga-72 are discrepant. In the current work, three solution samples of different concentrations were prepared and sequentially measured by a high-purity Germanium (HPGe) spectrometer. The count rates as a function of time of the 834.1 keV and 630.0 keV gamma-lines were followed for the half-life determination. Through mass normalization, the datasets of three samples are combined and the statistical uncertainties are reduced. Half-life values were derived from datasets of each sample and mass normalization and corresponding complete uncertainty budgets are presented. The final half-life determined for Ga-72 is 13.94 (2) h, showing a deviation of 1.12% from the last nuclear data sheets (NDS) recommended value. Comparing with the values of previous publications, the result from this work is smaller than most results and consistent with the latest value which has one large uncertainty. A recommended value of 14.07 (3) h is estimated using the power-moderated mean (PMM) method.

Uncovering the nature of dark matter microscopic particles is one of the most important disciplinary goals of physics and astronomy in the 21st century, and how to reduce background signals and environmental interference in dark matter experiments is one of the key factors to improve the sensitivity of the detector and to take the lead in obtaining significant detection results. High-purity nitrogen, as a crucial gas for detector purging, scintillator purification and pipe cleaning, among other things, contains the radioactive gases 85Kr and 81Kr in natural Kr, which emit beta-rays that can interfere with the detection of dark matter signals. Therefore, it is necessary to measure the concentration of ultra-trace level Kr in high-purity nitrogen, and screen high-purity nitrogen complying with the standard for use in dark matter experiments. This study develops a novel analytical method to determine ultra-trace level Kr in high-purity nitrogen using a static noble gas mass spectrometer coupled with a newly designed sample processing system. A large amount of reactive gases from the original sample are removed by the large-volume high-temperature purification device, and then we explore a simple and iterative trapping method for Ar-Kr separation. This method improves the noble gas separation factor with the promise of ensuring recovery. The separated Kr is fed into a static vacuum mass spectrometer. The detection limit of this method for natural Kr is as low as 10-14 L L-1 with an uncertainty of about 8%. This paper has developed newly an sample processing system combined with a static vacuum mass spectrometer to study how to measure 10-12 level krypton in high-purity nitrogen.

A study for atmospheric transport is essential for the consequence assessment of severe nuclear accidents since radionuclides could be released from the nuclear facility into the atmosphere and cause radioactive pollution in the environment. Atmospheric transport behaviors are strongly related with meteorological conditions, which can obviously influence the transport and diffusion characteristics of radioactive materials in the atmosphere; thus, it is meaningful to investigate the coupling effects between meteorological processes and transport behaviors of radioactive materials. To evaluate the influence of meteorological conditions on atmospheric transport, meteorological parameters for different seasons were first acquired by the weather research forecast model. Furthermore, atmospheric transport behaviors of radioactive materials were simulated by the meso-scale numerical model under different meteorological conditions, and numerical analyses were conducted toward transport and deposition behaviors of radioactive materials. In addition, the influence of FDDA (four-dimensional data assimilation) on meteorological parameters and atmospheric transport behaviors was researched. The present study is important for strengthening consequence assessment for severe nuclear accident and made it possible to apply the data assimilation technology in further research works.

Precise and accurate analysis of 235U/238U, 234U/238U, 230Th/234U and 230Th/232Th in 15 uranium ore concentrates (UOCs) was achieved using ICP-MS for nuclear forensic applications. A novel method was developed to dating UOCs.

Isotope analysis of Sn plays a crucial role in geochemical studies and in monitoring nuclear contamination. Nevertheless, prevalent analytical techniques for examining Sn isotopes encounter the issue of isobaric interference, markedly impacting the accuracy of the test results. Laser resonance ionization mass spectrometry (LRIMS) can effectively overcome the difficulties associated with the isobaric interference inherent in commercial mass spectrometry. In this paper, different amounts of Sn were prepared on Re filaments by electrodeposition and tested via LRIMS. The results showed that the average detection efficiency of LRIMS decreased with increasing total Sn content from 1 μg to 4 μg, and the fluctuations in the test results among the samples increased significantly. Therefore, the electrodeposition process, as well as the composition and morphology of the deposits were characterized by SEM, EDS and XPS; results showed that the degradation of the samples with increasing Sn content was attributed to the complexity of the composition, micro-structure, valence of the deposits, and the interference of various elements. To cope with the anomalies encountered above, the deposits were heat-treated at 600 °C in a hydrogen atmosphere to eliminate detrimental impurities, like Cl, and Sn was effectively reduced to an almost singular atomic state. Furthermore, a titanium layer was covered on the surface of the heat-treated deposit by magnetron sputtering. Ultimately, a highly efficient and stable Sn atomic beam source with a sandwiched structure has been successfully developed and exhibits broad application prospect.

The characteristics of enriched uranium materials are very important for nuclear fuel cycle and nuclear forensic analysis.Among all those fingerprints,the urani-um isotope ratios and the uranium age are considered to be of major parameters for trac-ing the sources and process conditions.To the best of our knowledge,there are only a few relevant articles focusing on the analysis of 233 U isotope abundance.In most of the published literatures subjected to uranium age dating,either 230Th-234 U chronometer or 231 Pa-235 U chronometer was employed to determine the age of enriched uranium materials with the isotope dilution mass spectrometry and anion exchange separation procedure,where the most time-consuming step was the sample preparation.Hence,this project aimed to develop a fast and flexible method for the determination of the uranium isotope ratios,230Th/234 U and 231 Pa/235 U atom ratios of the enriched uranium samples by the combination of multiple collector inductively coupled plasma mass spectrometry(MC-ICP-MS)and triple quadrupole inductively coupled plasma mass spectrometry(ICP-QQQ-MS).The results showed that the limits of detection(LODs)of 233 U by Neptune XT MC-ICP-MS and Agilent 8800 ICP-QQQ-MS were 3 × 10-9 and 6 × 10-10,respec-tively,and the relative standard deviations(RSDs)of 233 U/235 U isotope ratios at the level of 10-7 by MC-ICP-MS and ICP-QQQ-MS were 1.0％(2a)and 4.8％(2a),respectively.The standard sample bracketing(SSB)method of ICP-QQQ-MS based on the calibration of GBW04240 reference material was established to correct the mass fractionation of 230Th/234 U and 231 Pa/235 U atom ratios simultaneously.The ages of the uranium materials were diagnosed by the two parent-daughter relations of 234 U-230 Th and 235 U-231 Pa,indicating that the LODs of age dating were 0.2 a and 0.5 a,respectively.Meanwhile,the isotope ratios of 234 U/235 U,235 U/238 U and 236 U/235 U were determined by MC-ICP-MS.The fingerprints showed that the last purification time of the enriched uranium samples were around 2009 and the samples had been irradiated by the nuclear reactor.Overall,this method can reveal precise and accurate genetic signatures within one week,providing rapid technical supports for nuclear forensics,certification of nuclear reference materials and nuclear safeguards.