最新刊期
      卷 45 ， 期 4 ， 2022

        SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS

      • “最新研究发现，人类头发中的黑素体赋予头发颜色，具有复杂生物学功能。利用光热诱导共振技术，研究了头发切片中的黑素体分布和化学性质，为理解黑素体在头发颜色和生物功能中的参与提供实验基础。”
        LU Yao,PENG Weiwei,JI Te,ZHU Huachun,WANG Jie,ZHAO Hongwei,LIAO Zekun,XUE Yanling,CHEN Min
        Vol. 45, Issue 4, Article number: 040101(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040101
        摘要：BackgroundAs one of the most visible organs, human hair has received intense attention in both basic and applied research. Melanin, produced by the melanosomes in human hair, imparts hair color while serving many complex biological functions. Due to the small size of human hair melanosomes, it is difficult to observe and study the chemical properties of melanosomes. In previous study on melanosome, chemical treatment methods were often used to extract melanosomes, which would affect their chemical properties and structures.PurposeThis study aims to apply infrared nano-spectroscopy to exploring the structure, distribution and chemical properties of melanosomes in hair.MethodsPhotothermal induced resonance (PTIR, also known as AFM-IR), a popular technique for infrared imaging and infrared spectroscopy measurements unrestricted by diffraction limit, was used to study melanosomes in hair slices. Synchrotron radiation infrared spectroscopy, together with AFM-IR were employed to characterize the distribution of melanosomes in the cortex in situ, and to measure the infrared characteristics and infrared chemical imaging of melanosomes spectroscopy at nanoscale spatial resolution.ResultsThe experimental results show that there are melanosomes in black hair but not found in white hair. Melanosomes are ellipsoidal, and the average lengths of long axis and short axis are 423 nm and 337 nm, respectively. The average length-to-short axis ratio is 1.26. The distribution of melanosomes in black hair gradually increases from the center to the outer layer.ConclusionsExploring the distribution and chemical information of melanosomes in hair carried out in this study provides an experimental basis for a better understanding of the involvement of melanosomes in hair color and biological function.  
        关键词：Infrared nano-spectroscopy;Chemical imaging;Melanosome;Hair   
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      • “全无机钙钛矿太阳能电池研究取得新进展，专家在CsPbI2Br衬底上真空蒸镀Spiro-OMeTAD分子，测定了界面电子结构，为提高器件性能提供新思路。”
        ZHANG Liujiang,WANG Chenyue,SU Zhenhuang,GAO Xingyu
        Vol. 45, Issue 4, Article number: 040102(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040102
        摘要：BackgroundAll-inorganic perovskite solar cells have been extensively studied for their phase and thermal stability. In perovskite solar cells, the interface energy level arrangement between the hole transport layer (HTL) and the perovskite layer plays a decisive role in the performance of the device. Suitable interfacial energy level alignment is essential to facilitate the injection of photogenerated holes from perovskite into the HTL simultaneously effectively block electron transport efficiently, thus suppressing the recombination of holes with electrons.PurposeThis study aims to precisely determine the interfacial energy level alignment between CsPbI2Br and Spiro-OMeTAD experimentally.MethodsFirst of all, the Spiro-OMeTAD was deposited on CsPbI2Br film, then the interfacial electronic structure between CsPbI2Br and Spiro-OMeTAD was investigated by in situ X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Finally, the fabricated CsPbI2Br film was characterized by synchrotron-based grazing incidence X-ray diffraction (GIXRD) and scanning electron microscope (SEM).ResultsExperimental results show that there is no detectable interaction observed at the Spiro-OMeTAD/CsPbI2Br interface where electrons accumulate due to the formed interfacial state. An interfacial dipole of 0.18 eV is formed at the interface with 0.13 eV and 0.27 eV upward energy band bending at the CsPbI2Br substrate side and the Spiro-OMeTAD side, respectively. The hole injection barrier at the interface as indicated by the gap between the CsPbI2Br valence band maximum (VBM) and the Spiro-OMeTAD highest occupied molecular orbital (HOMO) is determined to be 0.23 eV, which favours the hole injection and extraction. Meanwhile, the gap between the CsPbI2Br conduction band minimum (CBM) to the Spiro-OMeTAD lowest unoccupied molecular orbital (LUMO) known as the electron-blocking barrier is up to 1.25 eV, effectively blocking the electron transfer from CsPbI2Br to Spiro-OMeTAD with the interfacial recombination efficiently suppressed.ConclusionsIt is concluded that Spiro-OMeTAD is an excellent HTL material in CsPbI2Br-based all-inorganic perovskite solar cells. The present work also provides meaningful guidance for the tunning interfacial electronic structure between perovskite and HTLs for high-performance CsPbI2Br solar cells.  
        关键词：All-inorganic perovskite solar cells;Photoelectron spectroscopy;Interfacial electronic structure;Energy level alignment   
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      • “在人脑组织染色领域，研究者通过模拟人脑PMD状态，验证了同步辐射X射线成像技术在研究PMD对小鼠脑组织高尔基染色影响中的应用，为建立人脑组织高尔基染色方法奠定了基础。”
        YAN Xin,CAI Xiaoqing,TANG Qiaowei,ZHOU Feng,ZHU Ying,WANG Lihua,HU Jun
        Vol. 45, Issue 4, Article number: 040103(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040103
        摘要：BackgroundHuman brain tissue is usually obtained by donating, and post-mortem delay (PMD) is one of the important factors affecting Golgi staining in human brain. However, currently there are relatively few studies on how PMD affects Golgi staining in human brain tissue.PurposeThis study aims to explore the changes in the morphology and structure of pyramidal neurons in the cerebral cortex of mice with PMD.MethodThe changes of human brain PMD were simulated by using mouse brain tissues placed in vitro for different times, and light microscope imaging data were obtained by Golgi staining and Nissl staining. At the same time, the synchrotron X-ray micro-CT imaging technology was used to realize neurons three-dimensional imaging visualization. The Sholl analysis was employed to study the Golgi-stained pyramidal neurons in the cerebral cortex.ResultsAnalysis results show that the completeness and complexity emerge a significant decreasing trend with the increase of PMD, and the statistical results of dendritic spines also show the same decrease trend. The three-dimensional neuron visualization results reconstructed by synchrotron radiation X-ray micro-CT technology confirm the above analysis results.ConclusionsThis study provides a research foundation for the establishment of Golgi staining method of human brain tissue and synchrotron radiation X-ray imaging.  
        关键词：Cortical pyramidal neurons;Neuron structure;Golgi staining;Synchrotron X-ray micro-CT technology   
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        发布时间：2024-10-25

        ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS

      • “在畜牧业养殖领域，科学家利用能量色散X射线荧光光谱仪，建立了一种新的饲料添加剂氯化钠中钠元素的检测分析方案。”
        JING Wei,DENG Yufu,MENG Dechuan,LI Ji,LI Yu,YU Guiying
        Vol. 45, Issue 4, Article number: 040201(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040201
        摘要：BackgroundSodium is one of the essential mineral elements necessary for metabolism in all animals. It is very important to accurately detect sodium content in feed additive for livestock and poultry breeding, which can greatly enhance the added value of farm-raising production.PurposeThis study aims to propose a new method for measuring the content of sodium in feed additives by energy dispersive X-ray fluorescence (EDXRF) analysis.MethodsThe method combined chemical methods with EDXRF to accurately detect the content of sodium in feed additive sodium chloride. Firstly, samples were treated to prepare test samples and standard samples, respectively. By means of chemical reaction, the content of sodium element in the sample was completely converted into iron element, and then precipitated. Secondly, based on the process, a group of standard samples with different iron contents were prepared to seek the net area of characteristic peaks of iron element for EDXRF analysis. The relation curve between iron content and the net area of characteristic peak was found and served as the standard curve. Then the net area of characteristic iron peaks in the test samples were measured by EDXRF. The measured values were substituted into the standard curve to obtain the iron content in the precipitation. The sodium content in the sample was determined by the precipitation mass, the iron content in the precipitation and the relationship between iron element and sodium element in the product precipitation. Finally, the best excitation conditions of iron element were determined by relationship curve between characteristic peak-to-back ratio of iron element and excitation conditions.ResultsObtained optimum tube voltage and current for best excitation conditions of iron element are 25 kV and 11 µA, respectively. The measuring accuracy of sodium content in feed additive sodium chloride is 39.02% with relative average deviation of 0.27% and relative standard deviation of 0.32%.ConclusionsThe measured results are basically in good agreement with that obtained by wavelength dispersive X-ray fluorescence. Proposed method in this study for the determination of sodium in feed additive sodium chloride has the characteristics of good repeatability and strong operability, providing a new method for the determination and analysis of sodium in feed additive sodium chloride.  
        关键词：Feed additive;Sodium;Energy dispersive X-ray fluorescence   
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        发布时间：2024-10-25
      • “在低能X射线放射治疗领域，专家通过蒙特卡罗模拟和电离室校准测量，揭示了辐射野变化对剂量测量的影响，为提高剂量准确性提供了重要参考。”
        LU Pingzhou,WU Jinjie,LI Mengyu,QU Bingbing,SONG Fei,FAN Song,ZHOU Jianbin,ZHAO Rui
        Vol. 45, Issue 4, Article number: 040202(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040202
        摘要：BackgroundLow energy X-rays are often used in superficial radiotherapy, its air kerma or absorbed dose to water is usually measured with a plane-parallel ionization chamber.PurposeThis study aims to investigate the response of the plane-parallel ionization chamber in the low energy X-ray calibration process and the scattering caused by the change of the radiation field.MethodsFirst of all, Monte Carlo simulation of four reference radiations (30 kV, 25 kV, 50 kV(b) and 50 kV(a)) was carried out in the low-energy X-ray standard radiation field. Then, two commonly used plane-parallel ionization chambers. i.e., PTW23344 and PTW23342, were calibrated and measured in air and phantom respectively by experiment, and the size of radiation field was changed by using different secondary apertures.ResultsThe readings of the two ionization chambers increase with the increase of the diameter of the radiation field, but the overall trend is gradually flattening. Ratios between chamber's readings in air and in phantom of the two ionization chambers decreases as the diameter of the radiation field decreases, and the overall trend gradually flattening. The average increase in the calibration coefficient of the absorbed dose to water in the radiation field of the PTW23344 ionization chamber in the range of 4.5 cm to 9 cm is 2.85 times that in the range of 9 cm to 13.5 cm whilst the average increase of the calibration coefficient of the absorbed dose to water in the range of 2.03 cm to 4.05 cm is 1.50 times that in the range of 4.05 cm to 6.08 cm in the radiation field.ConclusionsIt is necessary to make the radiation field completely cover the sensitive volume of the ionization chamber to achieve the condition of electron balance measurement, but not too large to cause too much scattering and damage.  
        关键词：X-ray;Plane-parallel ionization chamber;Absorbed dose to water;Scatter radiation   
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        发布时间：2024-10-25

        NUCLEAR CHEMISTRY, RADIOCHEMISTRY, RADIOPHARMACEUTICALS AND NUCLEAR MEDICINE

      • “在肿瘤骨转移治疗领域，研究人员发现静脉注射EDTA可有效促进223RaCl2在胃肠道的清除，降低辐射损伤。”
        LI Danni,LI Xiao,YANG Jian,JIA Guorong,PENG Ye,ZUO Changjing
        Vol. 45, Issue 4, Article number: 040301(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040301
        摘要：Background223Ra dichloride (223RaCl2) is an α internal irradiation drug for the treatment of bone metastases. In addition to deposition in bone metastatic lesions, 223Ra is mostly enriched in the intestines, causing toxic and side effects.PurposeThis study aims to propose a strategy for promoting excretion of 223Ra deposited in the gastrointestinal tract to exploit ethylenediaminetetraacetic acid (EDTA) as a complexing agent for binding of Ra2+ ions in vivo.MethodsFirstly, the in vivo distribution of 223RaCl2 in rats was evaluated by SPECT/CT at different time points. Then the intravenous and gavage administration were compared side-by-side to determine whether the route of EDTA administration affected the capacity of promoting the excretion of 223Ra. At last, the effects of EDTA intervention on bone uptake and the protective effect on the gut were assessed by SPECT/CT imaging and quantitative analysis of radioactive counts.ResultsThe total counts of radioactive uptake in rat bone reach 86.3% of the peak at 2 h after 223RaCl2 injection, and reach the peak (1 405±21) at 12 h after injection. The intestinal clearance of 223Ra is increased from (21.3±5.6)% to (46.9±4.4)% at 6 h after EDTA intravenous dose of 1 mg∙kg-1 behind the EDTA administration at 2 h after 223RaCl2 injection, meanwhile, the bone-specific deposition is unaffected.ConclusionsThe in vivo complexation of intravenous EDTA administration appears to reduce the gastrointestinal radiation injury after 223RaCl2 injection.  
        关键词：223RaCl2;EDTA;Bone metastases;Gastrointestinal tracts;In vivo complexation   
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      • “在熔盐堆核能系统领域，专家利用自主研发装置，研究了熔盐中含氧杂质离子的去除，为实现熔盐高效纯化提供新方案。”
        ZHENG Xiaoqiang,DOU Qiang,CHENG Ming,LI Qingnuan,FU Haiying,LI Wenxin,YAN Liuming
        Vol. 45, Issue 4, Article number: 040302(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040302
        摘要：BackgroundIn molten salt reactor, the concentration of oxygen impurities in the molten salt should be strictly controlled to avoid the potential safety risks caused by the reaction of O2- in the carrier salt with UF4 fuel to generated UO2 precipitation.PurposeThis study aims to investigate the evaporation behavior of the main oxygen-containing impuritiy ions in carrier salt at high temperature and low pressure and the influence of process parameters such as temperature, pressure and initial oxygen content of molten salt on the removal of O2- in carrier salt.MethodsThe vacuum distillation method was employed and a vacuum distillation device were used to carried out experimental study of the separation behavior of the main oxygen-containing impurities NO3-, SO42-, PO43- and O2- in the carrier salt during vacuum distillation. The removal mechanism of the above ions was explored, and the specific influence of process conditions on the separation effect of O2- distillation was investigated.ResultsThe results show that the removal ability of oxygen-containing impurities by vacuum distillation is NO3-＞PO43-＞SO42-＞O2-. The removal capacity of O2- increases with the increase of temperature, and the recovered salt with a total oxygen content about 2.40×10-4 g·g-1 salt is obtained at 1 050 ℃. The phenomenon of oxygen with a total oxygen content about 2.50×10-4 g·g-1 salt is observed when the pressure is higher than 40 Pa. The oxygen entrainment is increased during the evaporation of molten salt with the decrease of pressure, and the recovered salt content in the recovered salt continued to decrease with the decrease of the initial content of O2- in the carrier salt, which confirmed the technical feasibility of melting salt multiple distillation to remove oxygen.ConclusionsIt is verified by study shows that vacuum distillation can remove oxygen-containing impurities from carrier salt effectively and achieve the rapid and efficient purification of the carrier salt.  
        关键词：Molten salt reactor;Carrier salt;Vacuum distillation;Removal of oxide   
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        发布时间：2024-10-25

        NUCLEAR PHYSICS, INTERDISCIPLINARY RESEARCH

      • “在核电厂放射性废物桶测量领域，专家提出了基于深度神经网络的γ能谱解析方法，解决了核素误识别和峰面积计算精度较差的问题，为放射性废物桶的能谱解析提供解决方案。”
        WANG Jiangwei,GU Weiguo,YANG Hui,WANG Dezhong
        Vol. 45, Issue 4, Article number: 040501(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040501
        摘要：BackgroundIn the measurement of radioactive waste drums in nuclear power plants, the traditional analytical method of γ energy spectrum has the problems of nuclide misjudgment and poor accuracy of peak area calculation.PurposeThis study aims to evaluate the performance of an analytical method for γ energy spectrum based on deep neural network.MethodsThe whole data of γ energy spectrum were taken by the deep neural network model as the analysis object, hence no need of the traditional methods such as spectral line smoothing and peak searching. First of all, combinations of five different γ sources placed in different positions in the 200 L steel drum from Qinshan nuclear power plant-phase I, filled three different media (air, water and sand) were experimental measured by using digital γ-ray spectrometer and high purity germanium (HPGe) detector. Then the γ energy spectra obtained by Monte Carlo simulation using the model of the same experimental measurement system were used as the data set of the neural network training. Finally, γ energy spectra obtained by experiments were compared with simulated for verification.ResultsThe trained deep neural network converges quickly, both the nuclides identification and peak area calculation are fast with the accuracy of 96.47%. Hardly misidentification of nuclides is caused for the complex energy spectrum of multi-nuclide mixture, and less than 10% identification error for the peak area calculation of a weak peak in the γ energy spectrum.ConclusionsThe analytical method based on deep neural network is suitable for the analysis for γ energy spectrum of radioactive waste drums, and the spectrum resolution accuracy is better than the traditional method.  
        关键词：Deep neural network;Monte Carlo;γ energy spectrum;Nuclide identification   
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        NUCLEAR ENERGY SCIENCE AND ENGINEERING

      • “中国科学院合肥物质科学研究院核能安全技术研究所设计的中国双功能锂铅包层，通过一系列中子学实验，验证了聚变反应堆氚增殖包层设计中核数据库和仿真软件的准确性。”
        ZENG Zhengkui,CHEN Size,ZHANG Yong,WANG Haixia,XIONG Houhua
        Vol. 45, Issue 4, Article number: 040601(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040601
        摘要：BackgroundChina Dual Functional Lithium-Lead (DFLL) blanket is designed by the Institute of Nuclear Energy Safety Technology, Hefei Institutes of Physical Science, Chinese Academy of Sciences for fusion reactor. Since the designs of fusion reactor tritium breeding blankets are highly depended on neutronics calculation, nuclear data and simulation software used for DFLL cladding design is needed to be verified.PurposeThis study aims to evaluate the feasibility of nuclear data and code in DFLL cladding design by neutronics experiments.MethodsFirst of all, a DFLL mock-up was built and a series of neutronics experiments were performed on the D-T Fusion Neutron Generator. Then, a combination of Nb activated foil with reaction channel 93Nb(n,2n)92mNb and 238U fission chamber was chosen in this experiment for neutron yield measurement and relative neutron source intensity monitoring respectively. The Li2CO3 pellets and activation foils were used to measure the tritium production rates (TPR) and the multi-threshold reaction rates at different depths in the DFLL mock-up respectively. Finally, the measured TPR and reaction rates of the activation foils were compared with Monte Carlo simulation results coupled with JEFF3.2 nuclear data library.ResultsThe comparison results show that measurement uncertainty of neutron source intensity is within 4.2%, and the ratios of calculation results to experimental data (C/E) are 1.0~1.07 on TPRs and 0.77~1.1 on reaction rates.ConclusionsThe obtained results indicate that the tritium breeding ratio in neutronics design can be accurately evaluated.  
        关键词：Fusion blanket;Neutronics experiment;Tritium production rate;Deuterium-tritium fusion neutron source   
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      • “在核反应堆领域，专家设计了锆合金包壳管二次氢脆模拟装置，成功模拟了包壳管内外壁氧化和氢化物生成过程，为解决二次氢脆问题提供解决方案。”
        MA Yan,ZHANG Zhixin,CHEN Jiawei
        Vol. 45, Issue 4, Article number: 040602(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040602
        摘要：BackgroundWhen the fuel zirconium cladding tube of pressurized water reactor (PWR) breaks, the water flowing into the cladding will flash into water vapor under the action of the pressure difference between the inner and outer surface. The inner surface of the tube is damaged due to a large amount of hydrogen absorption, which is known as secondary hydriding embrittlement.PurposeThis study aims to simulate the operating conditions of the first circuit of a PWR and the occurrence of secondary hydrogen embrittlement in zirconium clad tubes.MethodsThrough theoretical strength calculations and thermal engineering verification, a Zirconium alloy clad tube secondary hydrogen embrittlement experimental off-heap simulator was independently designed and implemented. Then the dual heat source simulation experiments ware conducted for ZIRLO alloy clad tube.ResultsUnit operation and experimental results show that unit achieves long-term stable operation at the one-loop condition level, and the inner and outer walls of ZIRLO alloy tubes oxidize and generate hydrides with increasing concentration along the axial direction from the bottom up.ConclusionsThe off-heap simulator device of study solves the impact of thermal delamination in narrow seam space, and can simulate the water loss in primary breach, cooling water flash and interstitial steam corrosion behavior in the secondary hydrogen embrittlement process of the pressurized water reactor cladding tube, which verifies the feasibility of the technical means of the device.  
        关键词：Zirconium cladding;Second hydrogen embrittlement;Off-heap simulator;Oxidation;Hydride   
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      • “离子回旋共振加热天线系统研究取得新进展，优化设计铁氧体长度及天线与单铁氧体调谐器之间的机械长度，结合频率反馈控制，可有效降低反射系数，增强阻抗匹配效果。”
        YANG Kaijian,DU Dan,TAN Qingyi,ZHOU Hua,PAN Guangzu,QIAO Guanjin,GONG Xueyu
        Vol. 45, Issue 4, Article number: 040603(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040603
        摘要：BackgroundIon cyclotron resonance heating (ICRH) is an important auxiliary heating method in tokamak. When fast plasma phenomena such as L-H mode transitions and edge localized modes (ELM), etc., happens, a large change in the antenna coupling impedance occurs. This causes the reflected radio frequency (RF) power of ICRH antenna system increases drastically, which is an urgent problem to be solved in ICRH experiment.PurposeThis study aims to reduce the reflected power of ICRH antenna system by an optimal design of the antenna impedance matching system.MethodsThe transmission line theory was employed to analyze the effect of frequency modulation on impedance matching of single ferrite in ICRH antenna system with varied coupling impedance in the range of 2~8 Ω. The ferrite length and the mechanical length between the antenna and single ferrite tuner (the normalized length is about 0.540) were optimized under certain conditions.ResultsSimulation results show that the reflection coefficient of the ICRH antenna system is reduced within 0~8.4% under optimized design through feedback adjustment, and the relative frequency shift is between 0.146%~0.134% whilst the system impedance matching response time is less than 1 ms.ConclusionsFrequency feedback control of single ferrite tuner, not only effectively reduces the space size of the matching network, but also enhances the impedance matching effect. The relevant research results may provide a certain reference for the design of the ICRH antenna system.  
        关键词：Ion cyclotron resonance heating;Coupling impedance;Impedance matching;Single ferrite tuner;Frequency feedback   
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      • “在提高燃料热导率领域，研究人员采用放电等离子烧结工艺制备出高密度大晶粒UO2-SiC复合燃料芯块，有效避免了UO2-SiC界面反应，显著提高了热导率。”
        YAN Chao,YU Xiaohe,HUANG He,HOU Keke,CAO Changqing,LIN Jun,ZHU Zhiyong
        Vol. 45, Issue 4, Article number: 040604(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040604
        摘要：BackgroundThe Uranium dioxide (UO2) is currently the most widely used nuclear fuel for commercial nuclear reactors. However, the Fukushima Daiichi nuclear disaster revealed the primary safety risks of this fuel in an accident, so various international programs were launched to develop accident tolerant fuel (ATF), a new generation of fuel system developed to enhance the capability of nuclear fuel assemblies in severe accidents.PurposeThis study aims to improve the thermal conductivity of fuel pellets by adding a second material to the UO2 matrix, an important research direction for ATF.MethodsFirst of all, large-grain UO2 particles were used as raw materials, and the high-density large grain UO2-SiC composite fuel pellets were obtained by Spark Plasma Sintering (SPS) sintering process at lower sintering temperature. Then, the properties, such as microstructure and chemical composition, of the composite fuel pellets were characterized by using metallographic microscope (MM), scanning electron microscope (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). Finally, the high-temperature oxidation resistance in air environment was studied.ResultsThe results show that the UO2-SiC interfacial reaction can be avoided by the SPS sintering at lower temperature, and the density of the prepared pellets is more than 95% theoretical density (TD). Compared with traditional UO2 fuel pellets and SPS sintered UO2-SiC pellets using conventional UO2 powders, the thermal conductivity of large-grain composite fuel pellets is significantly improved. Oxidation tests results indicate that the oxidation weight gain of the composite fuel pellets is significantly weaker than that of traditional pellets when the temperature is lower than 350 ℃. However, when the temperature reaches 350 ℃, the oxidation of UO2 cannot be further prevented by SiC.ConclusionsThis study provides reference for improving the thermal conductivity of UO2 matrix by adding a second phase with high thermal conductivity.  
        关键词：Accident tolerant fuel (ATF);UO2;Composite fuel pellet   
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      • “在核反应堆安全分析领域，专家采用无需形成雅克比矩阵的牛顿-Krylov迭代法，提高了数值算法的稳定性，为两相流模型计算提供了解决方案。”
        FAN Jie,WU Hexin,GOU Junli,SHAN Jianqiang
        Vol. 45, Issue 4, Article number: 040605(2022) DOI: 10.11889/j.0253-3219.2022.hjs.45.040605
        摘要：BackgroundMost nuclear reactor safety analysis codes using the two-fluid three-field two-phase flow model are based on semi-implicit numerical algorithm. The stability of the numerical scheme is limited to the Courant value. Few codes based on two-fluid three-field model are solved by classic Newton iteration method, which needs a Jacobian Matrix. The writing of the Jacobian matrix is difficult.PurposeIn order to improve the stability of the numerical scheme and avoid writing the Jacobian matrix, JFNK (Jacobian-free Newton-Krylov) method is adopted to fully-implicitly solve the two-fluid three-field two-phase flow model.MethodsThe conservation equations of the two-fluid three-field two-phase flow model are discretized based on the staggered grid and finite volume difference. The equation set is solved by JFNK method. When one phase or two phases of the three-field model aren't existed, the fraction of the non-existent phase is assumed as a tiny value, which can avoid the Jacobian matrix and precondition matrix being singular.ResultsBy simulating the Ransom water faucet test, the accuracy of the numerical algorithm is verified. The numerical treatments for the non-existent phase are feasible. For the simulations of Barotolimei sub-cooled boiling experiments and dryout experiments, the performances of the developed numerical algorithm for the single-phase flow, two-phase flow and the transition from the single-phase flow to the two-phase flow are validated.ConclusionsBy simulating the water faucet test and pipe heat transfer experiments, the fully-implicit numerical algorithm based on JFNK method for two-fluid three-field two-phase flow model is successfully achieved. It lays a foundation for the advanced nuclear reactor safety analysis code based on the two-fluid three-field two-phase flow model and fully-implicit numerical algorithm.  
        关键词：Two-fluid three-field model;Fully-implicit numerical algorithm;JFNK;Semi-implicit precondition   
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        发布时间：2024-10-25
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