分类： 核科学技术 >> 核科学与技术 提交时间： 2024-04-14
摘要： 不确定度量化已经成为反应堆物理分析的普遍需求，核数据的协方差数据是开展不确定度量化的基础数据。在核数据处理程序NECP-Atlas中开发了协方差数据产生模块covar_calc，产生适用于蒙特卡罗程序的连续能量协方差数据库与确定论程序的多群协方差数据库。covar_calc可根据不同核数据在评价核数据库中的存储格式及不同的计算方法，分别处理评价核数据库给出的所有协方差数据，包括：平均裂变中子数、截面、次级粒子角度分布、裂变谱、共振参数、中子活化截面等数据的协方差数据。通过与核数据处理程序NJOY21中协方差数据制作模块的对比验证，表明NECP-Atlas制作的多群协方差数据库的精度与NJOY21相当,最大偏差小于0.1%。在此基础上使用蒙特卡罗计算程序NECP-MCX和不确定度量化程序NECP-UNICORN分别计算得到不同基准题的灵敏度系数，并分别结合连续能量协方差数据库和多群协方差数据库，利用“三明治公式”计算得到最终的不确定度。结果表明，基于NECP-Atlas制作的多群协方差数据库计算得到的不确定度具有与NJOY21相当的精度。连续能量协方差和多群协方差制作精确，满足蒙特卡罗程序和确定论程序使用需求。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-12
摘要： A microscopic method for calculating nuclear level density (NLD) based on the covariant density functional theory (CDFT) is developed. The particle-hole state density is calculated by combinatorial method using the single-particle levels schemes obtained from the CDFT, and then the level densities are obtained by taking into account collective effects such as vibration and rotation. Our results are compared with those from other NLD models, including phenomenological, microstatistical and non-relativistic HFB combinatorial models. The comparison suggests that the general trends among these models are basically the same, except for some deviations from different NLD models. In addition, the NLDs of the CDFT combinatorial method with normalization are compared with experimental data, including the observed cumulative number of levels at low excitation energy and the measured NLDs. Compared with the existing experimental data, the CDFT combinatorial method can give reasonable results.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-11
Xian-Lin Yang
Chang-Lin Lan
Yu-Ting Wei
Yi Zhang
Gong Jiang
Bo Xie
Yu Liu
Hong-Tao Shen
Xiao-Jun Sun
摘要： Aluminum is the primary structural material in nuclear engineering, and its cross-section induced by 14 MeV neutrons is of great significance. To address the issue of insufficient accuracy for the 27Al(n,2n)26Al reaction cross-section, the activation method and accelerator mass spectrometry (AMS) technique were used to determine the 27Al(n,2n)26Al cross-section, which could be used as a D-T plasma ion temperature monitor in fusion reactors. At the China Academy of Engineering Physics (CAEP), neutron activation was performed using a K-400 neutron generator produced by the T(d,n)4He reaction. The 26Al/27Al isotope ratios were measured using the newly installed GYIG 1 MV AMS at the Institute of Geochemistry, Chinese Academy of Sciences. The neutron flux was monitored by measuring the activity of 92mNb produced by the 93Nb(n,2n)92mNb reaction. The measured results were compared with available data in the experimental nuclear reaction database, and the measured values showed a reasonable degree of consistency with partially available literature data. Thenewly acquired cross-sectional data at 12 neutron energy points through systematic measurements clarified the divergence, which has two different growth trends from the existing experimental values. The obtained results are also compared with the corresponding evaluated database, and the newly calculated excitation functions with TALYS-1.95 and EMPIRE-3.2 codes, the agreement with CENDL-3.2, TENDL-2021 and EMPIRE-3.2 results are generally acceptable. A substantial improvement in the knowledge of the 27Al(n,2n)26Al reaction excitation function was obtained in the present work, which will lay the foundation for the diagnosis of the fusion ion temperature, testing of the nuclear physics model, and evaluation of nuclear data, etc.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-10
摘要： 在核天体物理关心的热核反应中，有一些可以产生短寿命的正电子放射性产物，这些反应产物发射的正电子会在靶中与电子发生湮灭，继而产生一对能量为511 keV的γ射线，可以通过测量这一对γ射线来得到反应产额，从而计算出核反应截面以及天体物理S因子。以往的实验通常将靶辐照后转移到屏蔽体内进行离线活度测量，近期有研究提出了在实验终端上原位测量正电子湮灭的方法，该方法主要是借助511 keV-511 keV γ射线对的方向相反特性，利用探测阵列的对向单元进行空间符合测量，压制本底干扰。本文基于近期自主研发的大型模块化BGO阵列LAMBDA-II，在地面实验室利用强流质子束打靶，对这一方法进行了实验研究和验证，为将来进一步将该方法应用到核天体物理研究中奠定了良好的基础。
分类： 核科学技术 >> 核科学与技术 提交时间： 2024-04-09
摘要： 特征线方法（Method of Characteristics，MOC）因其具备强大的几何处理能力，且在计算过程中亦能兼顾计算成本和计算精度，被广泛应用于高保真数值模拟计算中。常见的输运计算方法除MOC外，还包括碰撞概率法（Collision Probability Method，CP）和界面流法（Interface Current Method，IC）等。本文从方法理论以及数值计算上将MOC、CP和IC进行比较分析，对于评估其在pin-by-pin计算中的能力尤为重要。同时在MOC计算中，不同的参数选择会对计算成本和计算精度产生影响，因此有必要进行敏感性分析以寻求最佳参数。本文首先将三种计算方法从原理上进行比较分析，再基于2D C5G7-MOX基准题完成了数值计算及MOC参数敏感性初步分析。计算结果表明：MOC在计算精度、计算效率和内存开销上均优于CP和IC。MOC的计算耗时和内存开销分别为23.9min和37.5MB，与参考解的相对误差仅为6.04×10-4。而CP和IC的计算耗时分别为MOC的56.7倍和15.6倍，内存开销分别为MOC的407.7倍和32.8倍。进一步通过参数敏感性分析发现：网格划分对计算内存开销以及计算时间的影响最大，极角的选择对计算精度的影响最大，并且给出一组建议参数：网格划分6×6，极角为GAUS且数目为2，方位角个数为30。该组参数的计算耗时为45.4min，内存开销为264.7MB，相对误差为5.9×10-5，归一化后的栅元均方根误差为0.00255。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-09
摘要： 元素俘获测井可以获取地层中的岩石元素含量，为了查明页岩气储层发育和展布规律，以中扬子地区保靖区块寒武统牛蹄塘组首口页岩气参数井—BY2井为研究对象，通过对元素俘获测井资料的解释和处理，获取精准的页岩储层元素组成及含量，建立牛蹄塘组地球化学指标剖面，利用元素地球化学指标开展古沉积环境的辨识和反演。研究结果表明：牛蹄塘组页岩中元素以Si、Al、Fe为主，少量的K、Ca、Mg、S等，页岩中Si、Fe、S等元素含量较高，页岩可压性较好；牛蹄塘组页岩属活动大陆边缘沉积，沉积物源岩的原始物质应来自西北端康滇古陆，基本为活动大陆构造带、有热液参与的正常沉积，牛蹄塘组上段沉积期气候干燥，为缺氧的滞留盆地边缘缓坡沉积，水体盐度高，陆源供给充分，古生产力低下；牛蹄塘组下段沉积期气候湿润，为深水滞留型盆地沉积，陆源供给不足，水体盐度较高，具有较高的古生产力，有利于有机质的形成，水体环境以贫氧相为主，有利于有机质保存，为页岩气形成和富集的有利沉积环境。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-08
摘要： 中国加速器驱动嬗变研究装置(CiADS)的超导直线段运行在连续波模式下，4K液氦压强波动导致超导腔体产生形变而失谐是影响低β腔稳定运行的重要因素。针对半波长超导谐振腔受氦压波动影响而运行不稳定的问题，以CiADS超导直线段β=0.19的半波长超导谐振腔（HWR019）为例，采用数值模拟的方法对液氦压强波动与该腔的频率变化规律进行仿真研究。通过对腔液氦接触区域、腔体的壁厚、液氦冷却流道的形状与腔体氦压敏感系数(KPrees)之间的关系进行计算分析，实现了将HWR019超导腔KPress值降为接近0的目的；同时通过对腔体进行热力学计算，提供了相应的强化传热方案，有效地降低了超导腔在运行过程中的最高温度，保证了CiADS装置对超导腔稳定运行的需求，其分析优化方法对同类型的低β超导腔也具有借鉴意义。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-08
摘要： 超薄壁钛合金内衬不锈钢真空管道以其结构强度高，横向孔径小，适合于极高真空环境，在快上升磁场中的涡流效应处于可接受范围内，与其他类型的磁场快变化磁铁的真空管道相比成本较低等原因，已经成为HIAF-BRing二极磁铁和四极磁铁真空管道方案的首选。二极铁和四极铁钛合金内衬真空管道是BRing中重要的束流耦合阻抗源。其中，四极铁钛合金内衬的阻抗及其减小措施尚未研究过。在模拟软件CST studio suite中使用传输线法和尾场法分别对各种规格的四极铁钛合金内衬真空管道进行模拟，模拟结果表明1—500 MHz频段内钛合金内衬真空管道主要引入宽带阻抗，且钛合金内衬内表面加薄板的阻抗减小措施同样适用于四极铁真空管道。利用模拟结果计算全环阻抗，发现在106—5x108Hz频段内，钛合金内衬真空管道采取阻抗减小措施能将全环横向宽带阻抗虚部从0.70MΩ/m(水平)和0.82MΩ/m(垂直)减小到0.33MΩ/m(水平)和0.43MΩ/m(垂直)，将此结果代入DELPHI中计算78Kr19+单个束团在不同流强下的模式频率移动，发现BRing中Kr束发生横向模耦合不稳定性的流强阈值从2.7x1011 ppp提升到4.4x1011ppp.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-08
摘要： In the framework of the Lanzhou Quantum Molecular Dynamics (LQMD) model, a possible probe to the neutron-skin thickness (δnp) of neutron-rich 48Ca is studied in 140A MeV 48Ca + 9Be projectile fragmentation reaction based on parallel momentum distribution (p//) of residual fragments.The Fermi-type density distribution is employed to initiate the neutron density distributions in the LQMD simulation. A combined Gaussian function with different width parameters for the left side (ΓL) and the right side (ΓR) in distribution are used to describe the p// of residual fragments. The value of ΓL, taking neutron-rich sulfur isotopes as examples, shows a sensitive correlation to δnp of 48Ca, which is suggested to be a probe to determine the neutron-skin thickness of the projectile nucleus.
分类： 核科学技术 >> 核科学与技术 提交时间： 2024-04-08
摘要： The safety assessment of high-level radioactive waste repositories requires a high predictive accuracy for radionuclide diffusion and a comprehensive understanding of the diffusion mechanism. In this study, a through-diffusion method and six machine-learning methods were employed to investigate the diffusion of ReO4– , HCrO4– , and I– in saturated compacted bentonite under different salinities and compacted dry densities. The machine-learning models were trained using two datasets. One dataset contained six input features and 293 instances obtained from the diffusion database system of the Japan Atomic Energy Agency (JAEA-DDB) and 15 publications. The other dataset, comprising 15,000 pseudo-instances, was produced using a multi-porosity model and contained eight input features. The results indicate that the former dataset yielded a higher predictive accuracy than the latter. Light gradient-boosting exhibited a higher prediction accuracy (R2= 0.92) and lower error (MSE = 0.01) than the other machine-learning algorithms. In addition, Shapley Additive Explanations,Feature Importance, and Partial Dependence Plot analysis results indicate that the rock capacity factor and compacted dry density had the two most significant effects on predicting the effective diffusion coefficient, thereby offering valuable insights.
分类： 核科学技术 >> 核科学与技术 提交时间： 2024-04-08
摘要： 无铅双钙钛矿Cs2AgBiBr6作为环境友好型材料受到了核辐射探测领域的广泛关注，实验上发现对Cs2AgBiBr6进行Cu+掺杂能够显著提高材料稳定性与光电转换率。目前Cu+掺杂Cs2AgBiBr6的影响还未得到理论系统研究，本文基于第一性原理，采用密度泛函，开展了Cu+掺杂Cs2AgBiBr6对结构和电学性能影响的模拟研究。研究结果表明，Cu+掺杂会提高Cs2AgBiBr6的稳定性。掺杂形成的Cs2Ag1-xCuxBiBr6与原始材料Cs2AgBiBr6皆为间接带隙半导体，并随着Cu+掺杂比例提高能带间隙会显著缩短。根据态密度图分析，能带间隙缩短是由于Cu+掺杂会导致由Bi6p轨道主导的导带底部下移。Cs2Ag1-xCuxBiBr6相比Cs2AgBiBr6具有更高的稳定性与更优的电学性能，可作为半导体辐射探测器的候选材料。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-08
摘要： 飞行时间（Time-Of-Flight, TOF）探测器是核与粒子物理实验的重要组成部分，多气隙电阻板室（Multi-gap Resistive Plate Chamber, MRPC）以其高时间精度的特点在TOF测量系统中被广泛应用，放大甄别结合时间数字变换是MRPC电子学读出的一种主流方案。为了满足MRPC读出电子学高时间精度、低功耗、高集成度的需求，设计了一款高速放大甄别原型芯片，该芯片集成了8个通道，通道内包含前置放大器、甄别器和输出驱动电路。前置放大器采用共栅极结构，这种低输入阻抗的结构有利于进行阻抗匹配设计；甄别器采用多级放大器级联的结构产生足够的增益，通过对信号进行饱和放大实现甄别功能；经过甄别后的脉冲波形信号由LVDS输出驱动器送到片外，其前沿和脉宽分别可以表征MRPC信号的到达时间和电荷量信息。基于180 nm的 CMOS 工艺完成了电路的设计、仿真和流片，并在实验室环境下完成了电子学性能测试。测试结果表明，在100 fC ~ 2 pC电荷量下，该芯片的时间精度好于10 ps (rms)，单通道功耗约为24 mW。
分类： 核科学技术 >> 裂变堆工程技术 提交时间： 2024-04-07
摘要： 对于熔盐堆全堆高保真流体动力学计算，即使借助超级计算机的并行计算能力在面对快速甚至实时求解的问题仍然面临效率的巨大挑战，引入和采用模型降阶方法（Reduced Order Modeling，ROM），将能够有效解决这类问题。基于本征正交分解方法（Proper Orthogonal Decomposition, POD）与Galerkin投影法，引入基于有限体积的模型降阶方法（ROM based on Finite Volume approximation，FV-ROM）和上确界稳定模型降阶方法（ROM with supremizer stabilization，SUP-ROM），针对液态燃料熔盐堆(Liquid Fuel Molten Salt Reactor，LFMSR)层流和湍流瞬态工况开展适用性分析。结果表明，FV-ROM方法在速度误差和计算效率方面占有明显优势，层流和湍流瞬态速度平均L2相对误差低于0.5%和0.6%，且单步长的加速比分别为1500和1000倍左右；相比之下，SUP-ROM方法在压力预测方面表现出显著的优势，层流和湍流瞬态压力平均L2相对误差低至0.20%和0.38%。因此，通过FV-ROM和SUP-ROM两种方法相结合的方式进行熔盐堆流体动力学速度场和压力场预测，能够更加有效地提高流体动力学仿真的效率和确保瞬态模拟过程计算可靠性和精确度。
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2024-04-07
摘要： 在现场快速准确地实现放射性核素活度测量在放射性医学诊断中具有重要作用。本文采用电容积分式的电路结构，设计了低噪声前置放大器电路，并与高精度信号采集与处理电路相配合，成功研制了弱电流测量电路，实现了20 fA～10 μA弱电流测量。结合前端井型电离室，搭建了电容积分式放射性活度计的原型装置。测试结果表明：本文研制的放射性活度计重复性与商用RM-905A性能基本一致，本底小于0.065 MBq，重复性不超过0.84%，不稳定性为1.94%。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-07
摘要： Beams usually do not travel through the magnet centers due to errors in storage rings. The beam deviatingfrom the quadrupole centers is affected by additional dipole fields due to magnetic field feed-down. The beambased alignment (BBA) is often performed to find a golden orbit, on which the beam circulates around thequadrupole center axes. For storage rings with a large number of quadrupoles, the conventional BBA procedureis time-consuming, especially in the commissioning phase due to the necessary iterative process. Additionally,the conventional BBA method can be affected by strong coupling and nonlinearity of the storage ring optics.In this work, a novel method based on a neural network is proposed to find the golden orbit in a much shortertime with reasonable accuracy. This golden orbit can be directly used for operation, or can be adopted as thestarting point for the conventional BBA. The method is demonstrated in the HLS-II storage ring for the firsttime, through simulation and online experiments. The results of the experiments show that the golden orbitobtained using this new method is consistent with that from the conventional BBA. The development of thisnew method and corresponding experiments are reported in this paper.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-07
摘要： Room-temperature ferromagnetism is observed in the O+-implanted AlN films with O+ doses of 5 × 1016 cm-2 (AlN:O5×1016) and 2 × 1017 cm-2 (AlN:O2×1017). The observed magnetic anisotropy indicate that the ferromagnetism is attributed to the intrinsic properties of O+-implanted AlN films. The out-of-plane saturation magnetization (𝑀S) of the AlN:O5×1016 is about 0.68 emu/g, much higher than that of AlN:O2×1017, 0.09 emu/g, which is due to the excessively high O+ dose made more O+ ions occupy adjacent Al3+ positions in forms of antiferromagnetic coupling. Doppler broadening of positron annihilation radiation measurements demonstrate the existence of Al vacancies in the O+-implanted AlN films. The first-principles calculations suggest that the ferromagnetism originates mainly from the Al vacancies.
分类： 核科学技术 >> 核科学与技术 分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-05
摘要： Space objects, such as spacecraft or missiles, might be exposed to intense X-rays in outer space, leading to severe damage. How to reinforce these objects to reduce damage from X-ray irradiation is a significant concern. Blow-off impulse (BOI) is a crucial physical quantity for investigating the material damage induced by X-ray irradiation. However, the accurate calculation of the BOI is a challenge, particularly for the large deformation of materials with complex configurations. In this paper, we develop a novel two-dimensional Particle-in-Cell (PIC) code, Xablation2D, to calculate the BOIs under far-field X-ray irradiation. This significantly reduces the dependence on grid shape for numerical simulation. The reliability of this code is verified by the simulation results from the open-source codes, and the calculated BOIs are consistent with experimental and analytical results.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-04-04
摘要： The High Energy Fragment Separator (HFRS), which is currently under construction, is a leading international radioactive beam device. Multiple sets of position-sensitive Twin Time Projection Chamber (TPC)detectors are distributed on HFRS for particle identification and beam monitoring. The twin TPCs’ readoutelectronics system operates in a trigger-less mode due to its high counting rate, leading to a challenge of handling large amounts of data. To address this problem, we introduced an event-building algorithm. This algorithmemploys a hierarchical processing strategy to compress data during transmission and aggregation. In addition,it reconstructs twin TPCs’ events online and stores only the reconstructed particle information, which significantly reduces the burden on data transmission and storage resources. Simulation studies demonstrated that thealgorithm accurately matches twin TPCs’ events and reduces more than 98% of the data volume at a countingrate of 500 kHz/channel.
分类： 能源科学 >> 能源（综合） 分类： 核科学技术 >> 核聚变工程技术 提交时间： 2024-04-02
摘要： 托卡马克等离子体破裂会产生逃逸电流，如不进行抑制，其携带的巨大能量将对设备造成严重破坏。本文使用DREAM程序中的流体模型，研究注入氘氩/氖混合气体对破裂逃逸电流的影响。研究表明，注入氘氩/氖混合气体可以抑制最终形成的平台逃逸电流。在讨论的破裂前等离子体电流Ip范围内，最优条件下氩/氖在混合气体中的含量应在0.50% ~ 0.70%，氘的注入量应在1020 m-3 ~ 1021 m-3。在这个范围外，氘氩/氖混合气体注入对逃逸电流的抑制效果都会减弱，甚至会增大逃逸电流。破裂前等离子体电流Ip是影响逃逸电流的关键因素。Ip越大，形成的逃逸电流越大，也需要注入更多的混合气体。在Ip高达10 MA的聚变堆级托卡马克装置上，注入混合气体的密度需要达到1022 m-3，这是目前大量气体注入（Massive Gas Injection, MGI）技术所不能达到的，通过散裂弹丸注入氘氩/氖混合物将是更加可行的方式。
分类： 核科学技术 >> 辐射防护技术 分类： 核科学技术 >> 核安全 分类： 核科学技术 >> 核聚变工程技术 提交时间： 2024-04-02
摘要： 聚变堆贮存及释放的气态氚的量远高于现行的裂变堆，氚是聚变堆潜在放射性的重要来源。因此，为未来实现聚变堆的安全性及环境友好性，需要研究聚变堆气态氚排放对环境的影响。基于使用高斯模型预测气态氚释放后的大气弥散规律以及氚气（HT）的干沉积、土壤氧化以及氚化水（HTO）的再蒸发效应，计算了聚变堆1g的HT在短期释放情况下对周围环境的公众所造成辐射剂量。计算结果显示：在10m高度处释放的HT对排放点W方位500-3000m处的成人造成的吸入内照射剂量在0.38~0.10mSv之间，不同距离HTO的再蒸发效应所造成的剂量都是气态氚剂量的主要来源，沉降至土壤中的HT被氧化成HTO的比例及气象条件是决定气态氚剂量的关键参数。研究表明聚变堆HT释放所造成公众剂量要高于现行的裂变堆，在后续开展聚变堆的相关研究过程中，需要进一步关注其释放的气态氚对环境的辐射效应。
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