高纯锗谱仪探测效率的实验刻度与MC模拟

利用低本底高纯锗谱仪测量了标准源(~(133)Ba、~(137)Cs和~(60)Co)的各特征γ射线,得到了各特征能量下的探测效率,并通过拟合给出了高能端的探测效率曲线。同时,利用MC模拟工具包Geant4,模拟了各单能γ射线在高纯锗探测器组件中的输运过程,得到了不同能量下的模拟探测效率。比对结果发现:实验值与模拟值能很好地符合,可为开展相关产品的设计和制造提供参考。     

石英β剂量的蒙特卡罗模拟

用蒙特卡罗方法对TL或OSL测定年代中用β源进行照射时石英样品的吸收剂量进行模拟,研究石英薄片样品厚度和石英单颗粒大小对吸收剂量的影响。模拟程序用EGSnrc/DOSRZnrc,圆柱形薄片样品直径0.97cm,厚度10–500μm,单颗粒大小60–300μm。结果表明,吸收剂量与薄片样品的厚度有关,相对剂量的最大差异达10%;石英单颗粒中相对剂量随颗粒变小而增大,最大差异达19%。这些因素在测定年代过程中需加以考虑。     

用蒙特卡洛方法计算砷化镓中的正电子迁移率

用计算机模拟的方法获得正电子在半导体材料的迁移率，讨论了正电子有效质量，杂质浓度和温度对正电子迁移率的影响。     

核技术应用研究中的蒙特卡罗计算问题

本文简单介绍了蒙特卡罗方法及其特点;重点叙述了蒙特卡罗方法在几个核技术领域中的应用;讲述了所使用的蒙特卡罗模拟方法;介绍了几个常用的蒙特卡罗方法的软件;给出了一个应用实例.     

Monte Carlo method for determining the response of portable gamma detector for in situ measurement of terrestrial gamma ray field

A Monte Carlo method to study the response of portable detector to terrestrial gamma ray is proposed. This method is based on two-stage Monte Carlo simulation.First, the probability distributions of the phase space coordinates of the events that are most likely to be detected are reconstructed at the phase space shell level. The phase space shell is a closed surface enclosing the detector. The detector response to events originating from the phase space shell is then studied. The full absorption spectra as well as the partial absorption spectra are obtained for natural radionuclides uniformly distributed in the ground. For validation, this method is applied to a Hp Ge portable detector previously studied. The previous study is based on a semiempirical model. Good agreement is achieved when we compare the full-energy peak efficiencies and the total in situ spectra obtained by the two methods. As an application, the effective depth of the activity of the~(137) Cs artificial radionuclide in the soil is determined from the low-energy part of the total in situ spectrum.     

BF3中子探测器阵列探测效率的蒙特卡罗计算

在用241Am-Be中子源对BF3中子探测器阵列探测效率标定的基础上,用蒙特卡罗方法对其探测效率进行了模拟计算,获得了比较满意的结果.然后用蒙特卡罗方法对BF3中子探测器阵列的探测效率进行了研究.研究结果表明,焦面探测器具有较好的探测效率.     

蒙特卡罗方法在反应堆物理计算中的应用

利用蒙特卡罗 (MonteCarlo简称MC)方法对高通量工程试验堆的堆芯物理进行了计算 ,计算了该堆的 5个临界装置的有效增殖系数keff以及一个实际运行的复杂堆芯中考验回路内的考验燃料元件的中子通量 ,计算结果与实验值符合得很好     

Monte Carlo estimation of average energy required to produce an ion pair in noble gases by electrons with energies from 1 keV to 100 MeV

This paper describes the results of Monte Carlo estimation of the average energy W required to produce an ion pair in five noble gases by fast electrons. The ENDF/B-VI.8 library was used as the source of electroionization and atomic excitation cross sections for electron energies above 1 keV, as well as the source of all other types of electron and photon interaction cross sections for all energies. The low-energy electroionization and atomic excitation cross sections were taken from three data-sets: ENDF/B-VI.8 and two data-sets posted on the LXCat website (www.lxcat.net), i.e., BIAGI-v8.9 and SIGLO. Calculations were done using MCNP6 and a similar open-source program MCNelectron (http://web.vu.lt/ff/a.poskus/mcnelectron/). By comparing the calculated W-values with experimental ones, it is shown that replacement of the low-energy part of ENDF/B-VI.8 electroionization and excitation cross section data by LXCat data causes a significant improvement of accuracy of the calculated W-value. This accuracy can be improved even more by interpolation between the low-energy LXCat cross sections and high-energy ENDF/B-VI.8 cross sections. It is concluded that the value of W obtained by Monte Carlo simulation using different sets of low-energy electron interaction cross sections can be used as one of the criteria for evaluating accuracy of those data-sets.     

Monte Carlo法在检测浮选矿物品位中的应用

采用Monte Carlo法产生矿粉样品的XRF谱,对30个矿粉样品的品位进行了分析,结果表明该方法能够对浓度值为百分之几及其以上的元素进行有效分析。还对影响分析效果的各种因素进行了讨论,结果表明学习谱的个数越多,标准样品浓度分布范围越广,分析结果越精确可靠。此方法分析速度快,可以用于对矿物品位进行在线分析。     

Verification of modified sum-peak method in Monte Carlo simulationof full energy peak and sum-peak efficiencies of a HPGe detector

The modified sum-peak method estimates radioactivity by using only the peak and the sum-peak count rates.To verify the modified sum-peak method,the dependence of the full energy peak efficiency on the source-to-detector distance in a high-purity germanium detector system was studied using a Geant4 Monte Carlo simulation.The effect of the deadlayer in the germanium crystal was estimated by reference to experiments on ²⁴¹Am and the relative efficiency of the detector.The peak efficiency...     

蒙特卡罗模拟研究水平井密度测井中岩屑层的影响

利用蒙特卡罗方法,分别通过改变地层模型的岩性和水平井筒模型内岩屑层的厚度,研究了在多种地层中,水平井筒内0-5cm厚的岩屑层对密度测量的影响.为了保证模拟结果的可靠性,把模拟结果与前人实验数据进行了基准校正.研究表明,厚度在2cm以内的岩屑层对密度测量的影响是稳定的,可以用脊肋图的方式进行补偿校正,而岩屑层厚度大于2 cm之后,其对密度测量的影响不再容易校正.针对DSDL-8723双源距密度测井仪,初步给出了水平井中岩屑层对孔隙度影响的校正图版和公式.     

BNCT中载能粒子对肿瘤细胞损伤效应的Monte Carlo模拟及分析

为更好地了解硼中子俘获治疗(Boron neutron capture therapy,BNCT)中载能粒子穿过单个细胞引起的生物学效应以及理解在细胞或亚细胞水平上的微观剂量分布,采用Monte Carlo程序模拟载能粒子在人体细胞中的输运过程,给出了α粒子垂直细胞表面入射时的射程分布、径迹结构及靶损伤情况,同时模拟分析了^10B位于细胞中不同位置时主要载能粒子(α粒子和^7Li离子)在细胞中能量沉积情况和相应的细胞损伤与存活情况,为BNCT的微剂量研究提供了初步的理论依据。     

Benchmark Analysis of Criticality Experiments in the TRIGA Mark II Using a Continuous Energy Monte Carlo Code MCNP

The criticality analysis of the TRIGA-II benchmark experiment at the Musashi Institute of Technology Research Reactor (MuITR, 100kW) was performed by the three-dimensional continuous-energy Monte Carlo code (MCNP4A). To minimize errors due to an inexact geometry model, all fresh fuels and control rods as well as vicinity of the core were precisely modeled. Effective multiplication factors (k_eff) in the initial core critical experiment and in the excess reactivity adjustment for the several fuel-loading patterns as well as the fuel element reactivity worth distributions were used in the validation process of the physical model and neutron cross section data from the ENDF/B-V evaluation. The calculated k_eff overestimated the experimental data by about 1.0Δk/k for both the initial core and the several fuel-loading arrangements (fuels or graphite elements were added only to the outer-ring), but the discrepancy increased to 1.8Δk/k for the some fuel-loading patterns (graphite elements were inserted into the inner-ring). The comparison result of the fuel element worth distribution showed above tendency. All in all, the agreement between the MCNP predictions and the experimentally determined values is good, which indicates that the Monte Carlo model is enough to simulate criticality of the TRIGA-II reactor.     

Combining Monte Carlo simulations and dosimetry measurements for process control in the Tunisian Cobalt-60 irradiator after three half lives of the source

To check the dose uniformity and to determine the efficiency of medical devices sterilization by gamma irradiation after three half lives of the source,calculations of the absorbed dose were carried out.Monte Carlo simulations and dosimetry measurements,were established to study the radiation processing quality control.An isodose chart was created by GEANT4 Monte Carlo code to evaluate the absorbed dose rate uniformity inside the irradiation room from the year of the installation until the year of the source reload.The dose uniformity ratio (DUR) is deduced from maximum and minimum experimental doses in medical devices after three half lives of the source.     

Monte Carlo Analysis of Streaming Effect through Annular Gaps around Piping Legs in Sodium Pool to Secondary Sodium Activation of the Demonstration Fast Breeder Reactor

A top-entry loop-type reactor is one of the favorable options for Demonstration Fast Breeder Reactor (DFBR) which is now under development in Japan as a part of conceptual design study. Annular gaps around top-entry piping raise neutron streaming in upward direction in the sodium pool of reactor vessel. It enhances neutron flux level around decay heat exchangers (DHX's) in the pool and at the penetrations in primary biological shield for piping connecting to the vessels of intermediate heat exchangers (IHX's), and consequently enhance secondary sodium activations in these heat exchangers, which is one of the main issues for shielding design. In this study, three-dimensional Monte Carlo analysis method was applied to make precise evaluation of the neutron streaming effect with combination of some techniques for reduction of statistical error within reasonable CPU time. It is established that the contribution of neutron streaming to the secondary sodium activation in DHX's hardly reaches a level of 30% and that design analysis with two-dimensional discrete ordinates method gives conservative evaluation of the secondary sodium activations in DHX's and IHX's.