In multi-group deterministic neutron transport simulations for nuclear reactors, anisotropic scattering between neutrons and light nuclides is a common issue causing errors in eigenvalue and power distributions. Transport correction is the main approach for mitigating this error and it has advantages over high-order scattering due to higher efficiency in computational time and storage. The research on transport correction for light water reactors, in which hydrogen is the main nuclide for neutron slowing down, has been underway for more than 40 years. However, there is a lack of effort on transport correction for nuclear reactors using graphite as moderators, in which carbon is the main nuclide for neutron slowing down. Although neutron scattering with carbon is less anisotropic compared to hydrogen, previous tests have demonstrated significant errors resulting from anisotropic scattering. In this article, we focus on the transport correction for graphite-moderated reactors using the Cumulative Migration Method (CMM). Anisotropy in neutron scattering with graphite is examined and multi-group transport correction ratios for C-12 are evaluated using CMM with Monte Carlo code OpenMC. Numerical simulations are performed on the MIT Graphite Exponential Pile (MGEP) and HTR-10 models. The test results demonstrate that CMM achieves higher accuracy in computing the effective multiplication factor for transport cross sections on nuclear reactors involving graphite.
针对水下核爆炸和常规爆炸区分问题,开展了水下爆炸气泡脉动理论计算和数值模拟方法研究.基于气泡脉动能量守恒方程推导了水下爆炸气泡脉动最大半径理论计算公式,通过定义气泡脉动能量的传递因子,递推了后续气泡脉动周期和最大半径的计算公式.开展了水下常规爆炸的气泡脉动数值模拟方法研究,从状态方程、边界条件、人工黏性系数及计算网格设置等方面分析了关键参数设置对数值模拟结果的影响,提出了基于等效缩比定律的水下爆炸数值模拟方法,解决了水下千吨级常规爆炸气泡脉动数值模拟的问题.对WIGWAM试验的气泡脉动能量占比进行了理论计算,并开展了同等当量水下TNT爆炸气泡脉动的数值模拟,对比分析两者气泡脉动参数的结果表明,水下核爆炸第一次、第二次气泡脉动与等效TNT爆炸的差异并不明显,而第三次气泡脉动之间的差异较大,由此提出将第三次气泡脉动周期与第二次气泡脉动周期的比作为识别水下核爆炸的方法.
The thermodynamic properties of liquid deuterium under multi-shock compression have been calculated by using the coupled electron-ion Monte Carlo（CEIMC） method considering nuclear motion and selecting the appropriate standard model of Al substrate and sapphire window material. It is shown that the simulation data are in good agreement with the experimental and other ab-initio ones. The principal Hugoniot curve, which has a maximum compression of 4.48 at about 50.3 GPa, has passed through the error bars of various existing experiments generated via different high-pressure technologies. However, no apparent increase of the compression rate is found near 100 GPa. The re-shock and third-shock simulation results are also in excellent agreement with the existing principal Hugoniot, reverberating wave, and mechanical re-shock measurements of liquid deuterium using Z machine. The reverberation timing ratio has a maximum value of 3.34 when the first-shock pressure of liquid deuterium reaches 38 GPa. Moreover, we have investigated the change rules of states and its distribution of liquid deuterium under each shock. It is shown that the sixth-shock pressure will be higher than 96% of the final state pressure.
A commissioning method for the injection, capture, and acceleration processes of compact synchrotron rings is proposed and applied to the synchrotron commissioning of the Xi’an 200 MeV Proton Application Facility（XiPAF）. FCT is used to measure the current of injected beam, and closed orbit curve is used to correct RF frequency curve to improve acceleration efficiency. After injection bump curve optimization, closed orbit correction, tune adjustment, dual harmonic RF capture and acceleration, the maximum injection beam current of 47 mA is obtained, which corresponds to the particle number 2.5×10 11 . The maximum acceleration beam current of 53 mA is achieved, which corresponds to the number of particles 1×10 11 , and basically reach the design goal. By comparing the results of experiment measurement and simulation calculations, the deficiencies in the current commissioning are analyzed, and suggestions for the key tasks of future commissioning work are given.
电爆炸等离子体的光辐射特性对探究非理想等离子体性质及含能材料点火技术具有重要意义.在过去几十年,国内外学者对电爆炸物理与效应开展了广泛研究,明确了等离子体及可见光辐射效应的典型特征规律.近年来,随着电爆炸技术在国防、能源和材料领域的逐步应用,人们开始关注电爆炸等离子体光辐射现象中更多的物理细节,以期实现电爆炸负载光辐射效应的有效调控.本文简要回顾了电爆炸负载及其光辐射效应的研究历程,并介绍了相关实验手段及技术原理.从动力学角度系统介绍了电爆炸等离子体及光辐射的时空演化行为,从光谱学角度分析了放电不同阶段的辐射光谱特性,建立了电爆炸关键过程和光辐射物理机制的对应性,归纳了放电模式、金属材质、介质类型对负载光辐射特性的影响.最后,探讨了基于强光辐射效应的电爆炸技术的发展趋势.
