球形~(124)Sb-Be,~(24)Na-D_2O,~(24)Na-Be光中子源

为满足核物理实验测量的需要,我们设计制备了~(124)Sb-Be,,~(24)Na-D_2O,~(24)Na-Be球形光中子源,这种源的源强的角分布近于各向同性。下面简述中子源强度的估算及其结构,各向异性的测量和中子能谱的计算。一、光中子源的强度估算及其结构     

锰浴法绝对测量中子源发射率

锰浴法是目前绝对测量中子源发射率（中子源强度）最广泛、精度最高的方法之一。将已知活度的⁵⁶Mn溶液倒入锰池中,通过两路NaI(Tl)探测器测量锰液中⁵⁶Mn的γ计数,确定系统效率,然后通过锰液饱和活化计数得到中子源强度。利用锰浴法中子源强度标准装置绝对测量了标准²⁴¹Am-Be(α, n)中子源的强度。该中子源是国际电离辐射咨询委员会组织的国际比对CCRI(Ⅲ)-K9.AmBe的传递标准源。测量结果与比对平均值在不确定度范围内一致,验证了本标准装置的可靠性。     

反应性加入速度和中子源强度对临界事故规模的影响

在没有中子源或中子源强度很弱的核系统中,由于意外发生的临界事故(核闪变)释放的能量远大于反应堆动力学的预估值,为了给反应堆运行启动程序的制定和减小临界事故规模提供参考,本文建立了核闪变能量释放模型.在引发第一个持续裂变链的时间分布的基础上,从理论上推导出核闪变峰内能量释放与中子源强度.反应性加入速度的关系.结果表明:中子源强度越小,反应性加入速度越大,事故规模越大.     

CFBR-Ⅱ堆自发裂变中子源有效系数计算

为计算CFBR-Ⅱ堆自发裂变中子源的有效强度,建立了有效系数的蒙特卡罗算法。分别抽样模拟自发裂变中子源与本征分布中子源的产生及其在系统内的输运过程,统计二者引起的泄漏中子计数,其比值即为该自发裂变中子源的有效系数。考虑到CFBR-II堆体结构的特殊性,对上下半球分区处理,采用栅元舍弃技巧计算得到堆体各处自发裂变中子源的有效系数,为堆体总的自发裂变中子有效强度计算提供了依据。     

~(241)Am-Be中子源发热率和氦气生成量计算公式的导出

本文导出~(241)Am-Be中子源在堆中发热率和氦气生成量的计算公式。依据这些公式和必要的热工、强度计算,可以判断~(241)Am-Be中子源能否在铀氢锆堆中随堆运行。     

秦山核电厂反应堆无源装料及启动

秦山核电厂的第5燃料循环和第11燃料循环,分别由于中子源强度衰减过多和没有外加的次级中子源,在反应堆装料和启动过程中存在堆外核测仪表的部分监测盲区。介绍了我国法规的相关要求以及秦山核电厂实现无源启动所采取的应对措施,结果表明,无外加中子源时反应堆启动的安全性能够得到保证。     

水中氘成分对锰浴法测定光中子源强度的影响

锰浴法是绝对测定中子源源强比较准确的方法之一,因此它被广泛地用来刻度各种类型的中子源强度。当用天然水锰浴测定某些光中子源(例如~(24)Na-D_2O,~(24)Na-Be源)的强度时,除了要做中子源自吸收、中子洩漏等修正外,还必须考虑水中氘成分(氢中含氘0.015%)的影响。这是因为,这些光中子源γ射线的能量已超过D(γ,n)反应阈能(2.225     

计量与校准技术国防科技重点实验室电离辐射分室项目测试

本次中子源强比对由国际电离咨询委员会第三分部（CCRI（Ⅲ））组织,目的是通过测量214HAm-Be中子源强度,比较国际问初级标准的状态。214HAm—Be中子源由英国国家物理实验室（NPL）提供,在参加比对的实验室间传递。     

15 MeV电子束驱动中子源靶站模拟分析

电子轰击金属靶产生的中子源,可用于核素反应截面测量实验。为利用7.5 kW、15 MeV电子加速器作为驱动加速器,产生适用于核数据测量实验的中子源,相应开展了该功率下的中子靶站设计。研究中,依据蒙特卡罗程序MCNPX模拟计算的中子源数据,分析优化靶站结构;计算得到靶体能量沉积,导入商用CFD软件CFX中作为热源,模拟分析靶体对流传热性质,优化冷却通道模型,安全实现中子靶站冷却。本研究模拟设计的靶站,能产生强度为10¹²s^-1量级的中子源。     

简易旋转靶的研制

用高压倍加器加速能量为几百keV的氘离子,束流强度可达几十到几百mA量级。由于T(d,n)~4He反应在这一能区具有较高的反应截面,通常用它轰击氘钛靶产生中子作为强中子源。假定能量为400keV的氘离子束流强度为5mA,它打在靶上产生的热功率为2kW。如果靶子得不到有效的冷却,靶中吸附的氚将迅速地从钛层逸出,使中子源强度     

Stopping powers of Be,Al, Ti,V, Fe,Co, Ni,Cu, Zn,Mo, Rh,Ag, Sn,Ta, Pt and Au For 6.5 MeV protons

The stopping powers of Be, Al, Ti, V, Fe, Co, Ni, Cu, Zn, Mo, Rh, Ag, Sn, Ta, Pt and Au for 6.5 MeV have been measured using a surface barrier silicon detector. The accuracy of the results is ± 0.3%. The detail of the experimental procedures is described. The results have been compared with the Risø data and the Aarhus data of Andersen et al. The present results for Al, Cu and Ag agree very well with the Aarhus results at 6.5 MeV. The mean excitation energy has been extracted from the present results using the Bonderup shell correction, the Barkas correction and the Bloch correction. The parameters x and b which appear in the Bonderup shell correction and the Barkas correction have been newly determined as x = 1.358 and b = 1.3. The present mean excitation energy agrees very well with the I values obtained by other authors. It has been confirmed that the Bonderup shell correction is quantitatively correct for 6.5 MeV protons.     

Wavelengths,transition probabilities,and oscillator strengths for M-shell transitions in Co-, Ni-, Cu-, Zn-, Ga-, Ge-, and Se-like Au ions

Wavelengths, transition probabilities, and oscillator strengths have been calculated for M-shell electric dipole transitions in Co-, Ni-, Cu-, Zn-, Ga-, Ge-, and Se-like Au ions. The fully relativistic multiconfiguration Dirac–Fock method, taking quantum electrodynamical effects and the Breit correction into account, was used in the calculations. Calculated energy levels of M-shell excited states for Cu-, Zn-, Ga-, Ge-, and Se-like Au ions from the method were compared with available theoretical and experimental results, and good agreement with them was achieved.     

Gamma-Ray Production Cross Sections for Interactions of 14.8 MeV Neutrons with O,Na, Al,Cl, Cr,Fe, Ni,Cu and Pb

Production cross sections for 85 discrete γ-rays at 125° were measured with a Ge(Li) detector for interactions of 14.8 MeV neutrons with natural samples of O, Na, Al, Cl, Cr, Fe, Ni, Cu and Pb. The obtained cross sections were compared with the results of previous works. For O, Na, Al, Cr and Ni, the present results agree with the previous data measured with monoenergetic neutron sources; for Cl, Fe, Cu and Pb, the present results are larger than the previous data. In comparison between the present results shown by histograms of γ-ray energy and unfolded data, a considerable discrepancy is found from some of the previous data for Fe.     

Discovery of dysprosium,holmium, erbium,thulium, and ytterbium isotopes

Currently, thirty-one dysprosium, thirty-two holmium, thirty-two erbium, thirty-three thulium, and thirty-one ytterbium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.