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。     

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...     

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.     

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.     

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.     

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].     

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).     

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.     

High-spin states in neutron-rich ~(102)Mo nucleus

High-spin states in neutron-rich 102Mo nucleus have been studied by measuring the prompt γ-rays in the spontaneous fission of 252Cf. The previous level scheme has been updated and some new levels and transitions are identified. The one-phonon γ-band is expanded and a band head level of the two-phonon γ- band is proposed. The systematic characteristics of yrast bands, one-phonon γ-bands, two-phonon γ-bands and quasi-particle bands in 102Mo, 104Mo and 106Mo are discussed.     

Proposed Chiral Doublet Bands in ^98Tc

High spin states in odd-odd ^98 Tc nuclei are studied by in-beam γ-ray spectroscopy with the ^96 Zr（^6Li, 412） fusionevaporation reaction at a beam energy of 35MeV. The previous level scheme is updated. A band based on 1090.7keV is expanded, and another band based on 1920.6 keV is newly identified. The observed two negative parity bands in ^98 Tc are proposed to be a pair of chiral doublet bands with the configuration πg9/2 vh11/2. The evidence supporting the assignment of the chiral doublet bands is discussed. Signature splitting and signature inversion are observed in the πg9/2 vh11/2 band in ^98Tc.