High spin states in neutron-rich ~(106)Tc nucleus

The high spin states of the neutron-rich odd-odd 106Tc nucleus have been reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. A previously known collective band is confirmed and expanded, and a new collective band is newly identified. Several levels in previous report in 106Tc are reexamined and they belong to the members of a band in 107Tc. The total Routhian surface (TRS) calculations show that the 106Tc has triaxial shape. The spins and parities as well as the configurations f...     

CiADS带绕丝燃料棒束通道横流特性

CiADS次临界反应堆采用铅铋作为冷却剂,使用绕丝定位的闭式燃料组件。螺旋绕丝能够使流动工质发生横向交混,增强不同子通道间的动量交换。本工作使用ANSYS ICEM和STAR-CCM+软件划分了结构化网格和多面体网格,对CiADS燃料棒束通道横流特性进行研究,分析了结构化网格与非结构化网格对流动特性的影响。结果显示:相比于非结构化网格,结构化网格的子通道间横流量计算结果更接近LES的结果;结构化网格得到的摩擦因子系数与UCTD公式预测值最为接近,多面体网格的结果比经验公式的预测值小。同时,本研究对现有横流特性经验公式进行了改进,可更准确地预测带绕丝燃料棒束横流特性。上述研究成果提供了子通道程序优化的新思路,同时可为CiADS燃料组件热工水力设计与分析提供参考。     

Cluster dynamics modeling of niobium and titanium carbide precipitates inα-Fe andγ-Fe

Kinetic behaviors of niobium and titanium carbide precipitates in iron are simulated with cluster dynamics.The simulations,carried out in austenite and ferrite for niobium carbides,and in austenite for titanium carbide,are analyzed for dependences on temperature,solute concentration,and initial cluster distribution.The results are presented for different temperatures and solute concentrations,compared to experimental data available.They show little impact of initial cluster distribution beyond a certain relaxation time and that highly dilute alloys with monomers only present a significantly different behavior from denser alloys or ones with different initial cluster distributions.     

New band structures in ~（107）Ag

High spin states in ¹⁰⁷Ag are studied via the ¹⁰⁰Mo(¹¹B, 4n)¹⁰⁷Ag reaction at an incident beam energy of 60 MeV. Prompt γ-γ coincidence and DCO ratios are measured by the detector arrays in CIAE. The level scheme has been updated and a new negative band belonging to ¹⁰⁷Ag is identified. The new negative side band has been constructed and its configuration is tentatively assigned to πg_9/2 νh_11/2(g_7/2/d_5/2).     

奇A 核的多声子γ振动带实验研究进展

对于近年来清华大学与美国合作研究组在原子核结构实验研究中有关奇A 核的多声子 振动带方面的进展进行了评述。研究人员通过有效的国际合作,识别了质量数A = 100 丰中子核区的奇A核103Nb,105Mo,107Tc 和109Tc中的两声子 振动带,这是迄今为止国际上在奇A 核的结构研究中发现的仅有的4 例这样的结构。对于实验方法、研究结果以及这些多声子 振动带的特性进行了评述,并对目前在多声子带其他方面的研究及今后进一步的工作进行了概述。The experimental research on multi-phonon γ-vibrational bands in odd-A nuclei by our international collaboration has been reviewed. The two phonon -vibrational bands in 103Nb, 105Mo, 107Tc and 109Tc in the A = 100 neutron-rich nuclear region were identified, which are the only four such bands discovered in nuclear structure studies until now. The experimental methods and results are summarized, and the characteristics for these band structures are discussed. The other aspects for our research on the multi-phonon vibrational bands as well as our future research work are also briefly reviewed.     

体积填充率变化对球床钨颗粒散裂靶中子学特性影响的研究

应用MCNPX程序,构建质子束轰击球床钨颗粒散裂靶的物理模型,模拟散裂靶泄露中子产额、能谱、通量轴向分布以及散裂靶沉积能分布。针对不同钨颗粒直径和体积填充率,研究了不同钨颗粒直径下体积填充率变化对球床散裂靶中子学特性的影响。模拟结果表明,钨颗粒体积填充率增加,散裂靶的最大沉积能密度减小。在1～20 mm的范围内,钨颗粒的直径越小,散裂靶泄漏中子产额越大,散裂靶泄漏中子产额随钨颗粒体积填充率变化的波动越小,有利于维持CIADS系统反应堆功率稳定。The physical model of the high-energy proton bombarding the tungsten pebble bed spallation target is simulated by the MCNPX program. The effect of the filling rate on the neutronic characteristics with different particle diameters is studied, by calculating the leakage neutron yield, leakage neutron spectrum axial neutron flux distribution and the energy deposition of the target. The result shows that when the diameter increases from 1 to 20 mm,the maximum deposited energy density decreases in the target, but the leakage neutron yield increases. When the filling rate reaches 74%, leakage neutron yields are almost the same value with different particle diameters. When the target is piled up with 1 mm tungsten particles, neutron leakage yield changes smaller with the variation of the filling rate than the other diameter particles which is beneficial to maintain the reactor power stability in ADS.     

Search for chiral bands in A~110 neutron-rich nuclei

High spin states in A~110 neutron-rich ¹⁰⁶Mo, ¹¹⁰Ru and ¹¹²Ru nuclei have been reinvestigated by measuring the prompt γ-rays from the spontaneous fission of ²⁵²Cf. Two similar sets of bands are observed to high spins in each of three nuclei. Through analyzing of characters of the band structures, the chiral doublet bands are suggested in ¹⁰⁶Mo, ¹¹⁰Ru and ¹¹²Ru.     

Observation of a new rotational band in 104Nb nucleus

The high spin states in neutron-rich ¹⁰⁴Nb have been investigated from study of prompt γ-rays in spontaneous fission of ²⁵²Cf with the Gammasphere detector array. A new rotational band has been identified for the first time. This band is proposed as a semi-decoupled band based on the configuration π5/2^－[303]⊙ν1/2^－[541].     

铅基反应堆自然循环与应急余热排出研究

自然循环特性是铅基反应堆一回路的关键运行特性,对反应堆的非能动应急余热排出具有重要的影响,自然循环特性与余热排出能力是反应堆热工水力研究的重要内容。采用多孔介质方法,建立了CiADS铅基堆1/4三维计算模型,使用FLUENT程序对额定工况与低功率工况进行稳态计算。为了研究全厂断电事故下的余热排出过程,从热工水力的等效原则出发,尝试建立二维等效模型以提高瞬态计算效率。结果表明,CiADS铅基堆具备低功率自然循环运行能力和一定的事故容错能力;二维等效模型与三维模型计算结果吻合较好,可用于瞬态下的简化分析;CiADS铅基堆的非能动余热排出系统能够较好地应对全厂断电事故,反应堆具有良好的固有安全性。     

High spin states in neutron-rich 106Tc nucleus

The high spin states of the neutron-rich odd-odd ¹⁰⁶Tc nucleus have been reinvestigated by observing prompt γ-rays from the spontaneous fission of ²⁵²Cf. A previously known collective band is confirmed and expanded, and a new collective band is newly identified. Several levels in previous report in ¹⁰⁶Tc are reexamined and they belong to the members of a band in ¹⁰⁷Tc. The total Routhian surface (TRS) calculations show that the ¹⁰⁶Tc has triaxial shape. The spins and parities as well as the configurations for these bands have been tentatively assigned according to the analysis of the angular momentum alignments.