Comparison study of photon attenuation characteristics of Lead-Boron Polyethylene by MCNP code,XCOM and experimental data

The linear attenuation coefficient, mass attenuation coefficient and mean free path of various Lead-Boron Polyethylene (PbBPE) samples which can be used as the photon shielding materials in marine reactor have been simulated using the Monte Carlo N-Particle (MCNP)-5 code. The MCNP simulation results are in good agreement with the XCOM values and the reported experimental data for source Cesium-137 and Cobalt-60. Thus, this method based on MCNP can be used to simulate the photon attenuation characteristics of various types of PbBPE materials.     

Determination of mass attenuation coefficient of low-Z dosimetric materials

The mass attenuation coefficients of some low-Z dosimetric materials with potential applications in dosimetry, medical and radiation protection have been investigated using the Monte Carlo simulation code Monte Carlo N-Particle (MCNP). Appreciable variations are noted for the mass attenuation coefficient by changing the photon energy. The MCNP-simulated parameters are compared with the experimental data wherever possible and theoretical values through the WinXcom program. The simulated results obtained by MCNP generally agree well with the experiment and WinXcom predictions for various low-Z dosimetric and tissue substitute materials. In addition, the mass attenuation coefficients around the k-edges for low-Z dosimetric materials estimated from the MCNP code agree very well with WinXcom prediction. Finally, the results indicate that this simulation process can be followed to determine the interaction parameters of gamma rays in such low-Z materials for which there are no satisfactory experimental values available.     

Thermoluminescence energy response of TLD-100 subjected to photon irradiation using Monte Carlo N-particle transport code version 5

Useful TL properties of TLD-100 that is an excellent candidate for using in TL dosimetry of ionizing radiation are demonstrated. This study is focused on response of TLD-100 subjected to photon irradiation. The thermoluminescence (TL) response of TLD-100 subject to various photon energy, ranging from 20 keV to 6 MeV, was investigated as energy absorbed in the TL material using Monte Carlo N-Particle transport code version 5 (MCNP5). The input parameters included in this study are experimental geometry specification, source information, material information, and tallies. Tally F6 is used in this simulation. The results from MCNP5 simulation show good agreement with previous experimental data. However, the data obtained from the simulation are greater than the experimental data especially in lower energy ranges.     

Mass attenuation coefficients of composite materials by Geant4, XCOM and experimental data: comparative study

The main goal of this present study is focused on testing the applicability of Geant4 electromagnetic models for studying mass attenuations coefficients for different types of composite materials at 59.5, 80, 356, 661.6, 1173.2 and 1332.5 keV photon energies. The simulated results of mass attenuation coefficients were compared with the experimental and theoretical XCOM data for the same samples and a good agreement has been observed. The results indicate that this process can be followed to determine the data on the attenuation of gamma rays with the several energies in different materials. The modeling for photon interaction parameters was standard for any type of composite samples. The Geant4 code can be utilized for gamma ray attenuation coefficients for the sample at different energies, which may sometimes be impractical by experiment investigation.     

Calculation of gamma-ray mass attenuation coefficients of some Egyptian soil samples using Monte Carlo methods

Monte Carlo simulations, FLUKA and Geant4, were performed to study mass attenuation for various types of soil at 59.5, 356.5, 661.6, 1173.2 and 1332.5 keV photon energies. Appreciable variations are noted for all parameters by changing the photon energy and the chemical composition of the sample. The simulations parameters were compared with experimental data and the XCOM program. The simulations show that the calculated mass attenuation coefficient values were closer to experimental values better than those obtained theoretically using the XCOM database for the same soil samples. The results indicate that Geant4 and FLUKA can be applied to estimate mass attenuation for various biological materials at different energies. The Monte Carlo method may be employed to make additional calculations on the photon attenuation characteristics of different soil samples collected from other places.     

Determining the gamma-ray parameters for BaO–ZnO–B2O3 glasses using MCNP5 code: a comparison study

Rapid technological advancement has multiplied people’s exposure to ionizing radiations greatly. Widespread applications of radiation in different fields (such as agriculture, radiation therapy and scientific research fields) require that humans be protected against unnecessary exposure. In this study, mass attenuation coefficient (μ_m), half-value layer, mean-free path, effective atomic number (Z_eff) and exposure buildup factor have been calculated for xBaO–20ZnO–(80???x)B₂O₃ (x?=?5, 10, 15, 20 and 25?mol%) glass systems. The mass attenuation coefficients of the selected glasses were calculated using simulation method of MCNP5 code. The simulation results have been compared with the experimental data and Xcom at the energies 223.02, 252.98, 287.28, 340.83, 398.97, 481.59, 562.68 and 662.00?keV. The agreement amounts of the mass attenuation coefficient values are from 0.2% to 2.8% and from 0.2% to 6.98% for MCNP5 and Xcom relative to experimental results, while the Monte Carlo program values are higher than that obtained by experimental data, using Xcom and MCNP5 code. The glass sample having the highest value of BaO content show high radiation shielding properties. It indicates that the MCNP5 code can be used for estimation of radiation interaction parameters where experimental results are not available.     

蒙特卡罗输运模拟软件JMCT的深穿透屏蔽计算

核设施辐射屏蔽计算,由于其大规模计算及深穿透等特性,一直是蒙特卡罗方法工程应用的难点之一。采用我国自主研发的三维中子-光子蒙特卡罗粒子输运模拟软件JMCT,结合可视化建模工具JLAMT,对OECD国际基准例题Winfrith Iron/Water Benchmark Experiment(ASPIS)两例实验装置进行建模与计算分析, 并将计算结果与实验值及MCNP计算值进行对比。结果表明,JMCT计算值与MCNP计算值符合较好,其中Winfrith Iron Benchmark Experiment(ASPIS)最大偏差不超过7%,平均偏差1.3%;Winfrith Water Benchmark Experiment(ASPIS)最大偏差小于20%,平均偏差小于10%,证明了JMCT在屏蔽计算以及深穿透问题的可靠性与工程应用性。     

临界-燃耗耦合计算方法

基于蒙特卡罗模拟方法,采用MCNP的多群计算程序模拟中子输运方程,并与栅元均匀化程序WIMS耦合,实现了临界-燃耗耦合计算。具体过程是:首先扩展MCNP的多群功能,将其能群扩展为69群;然后,由接口程序将WIMS程序产生69群共振、自屏宏观中子截面转化为ACE格式的多群截面;其次,将新产生的多群截面提供给MCNP,完成临界-燃耗计算;最后,利用此耦合程序进行了基准题校核计算以及实验对比。计算结果表明,此耦合程序是可靠和正确的。     

温度相关核截面数据库在MCNP计算中的必要性研究

MCNP程序由于其几何模拟和核数据上的优越性,现在在反应堆的研究分析中已经得到较多应用。通过基准题的计算,定量地说明MCNP通过其自带的常温（294K）下的核素截面数据库不能够对反应堆进行非常准确的计算（由于反应堆内各种材料／位置的温度不同）,而且,它也不能够计算反应堆中与温度相关的量,如反应性温度系数。选用了一个带有不同温度下核素截面数据的MCNP输入格式的数据库,使用MCNP-4C对基准题进行了计算,发现计算结果与基准值符合得非常好。这说明通过使用不同温度下的核素截面数据库,MCNP可以准确计算温度系数和增殖系数等,从而说明在反应堆设计计算中制作不同温度下的核素截面库的必要性。Due to the advantage of geometry simulation and nuclear data, the code MCNP is now widely used in the reactor analysis. Based on our calculation of the fuel temperature reactivity coefficient benchmark, it is quantificationally proved that MCNP with its own cross section library can＇ t be used to simulate the reactor accurately and to calculate the temperature reactivity coefficient. Furthermore, we use MCNP- 4C with a database that contains temperature dependent nuclear cross sections to calculate the benchmark. The results are well agreement with benchmark results. This means that, with the temperature dependent nuclear cross sections library, MCNP can calculate the temperature reactivity coefficient and reactor multiplication factor accurately. So the temperature dependent nuclear cross section library should be processed to meet the requirement of reactor calculation.     

基于蒙特卡罗的HPGe伽马谱仪无源效率刻度方法

采用MCNP5模拟与数学计算相结合,并利用探测器晶体几何的轴对称性,建立一种HPGe探测器的无源效率刻度方法。基于此方法的计算程序在使用过程中完全脱离MCNP5,运算时间为1~60 s,可实现点源和同轴圆柱体源的效率刻度,能量范围为50 keV~3 MeV。程序计算结果与实验数据以及MCNP5直接模拟结果比较,误差分别不超过12%和7%,证明方法可行。     

Comparative Study of Micro and Nano Size WO_3/E44 Epoxy Composite as Gamma Radiation Shielding Using MCNP and Experiment

The radiation shielding characteristics of 50 wt% WO_3/E44 epoxy composite in various gamma energies from80 keV to 1.33 MeV are investigated via the MCNP code. Thus two scales are considered for WO_3 filler particles:micro and nano with sizes of 1,um and 50 nm, respectively. The simulation results show that WO_3 nano particles exhibit a larger increase in linear attenuation coefficient in comparison with micro size particles. Finally, validation of simulation results with the published experimental data shows a good agreement.     

BNCT治疗规划系统MCDB算法及测试

给出BNCT治疗计划系统软件MCDB的算法及测试结果,通过使用材料矩阵描述BNCT的网格模型,配合快速径迹算法和计数矩阵,进行粒子输运模拟及计数,模拟结果显示,MCDB的计算精度与MCNP相当,计算速度较MCNP提高3.1~3.4倍.MCDB模拟1 000万粒子的时间不足2个CPU小时,可保证大部分网格剂量误差在5%以内,基本上达到了BNCT临床要求,可用于30 kW的医院中子照射器的临床治疗.     

Reverse Monte Carlo iterative algorithm for quantification of X-ray fluorescence analysis based on MCNP6 simulation code

Reverse Monte Carlo iterative algorithm has been developed for quantification of energy-dispersive X-ray fluorescence analysis in order to calculate the concentrations of the elementary composition in solid substances. The core of the simulation code was the MCNP6 that is a well-established and widely applied software package in the nuclear research and practice for simulation of nuclear systems or the full process of gamma- or X-ray spectrometry. The reverse Monte Carlo algorithm and the full analytical procedure was tested by quantitative XRF analysis of reference alloy samples. The atomic compositions of the reference samples were determined by reverse Monte Carlo technique and also fundamental parameter method and by spark emission atomic spectroscopy. The agreement between the results of these three analytical methods was found within the standard deviations of the major elements of the samples. The total duration of the reverse Monte Carlo numerical computation was minimized to a few minutes using the variance reduction procedures available in the MCNP6.     

等离子体中X射线透过率分析及潜在通信应用研究

X射线具有波长短、光子能量高等特点,有望在等离子体环境中实现信息的有效传输.本文首先采用基于连续介质中的WKB分层法,研究了黑障条件下, X射线在非均匀等离子体鞘套中的透过率特性,仿真了不同等离子体电子密度和碰撞频率下X射线信号的透过率,理论上证明了X射线可用于黑障区信息传输的可行性.其次通过搭建环形扩散辉光放电等离子体发生器及实验验证系统,进行了国内外首次X射线穿过等离子体鞘套的验证实验.实验结果表明,等离子体对X射线信号的透过率存在一定程度的衰减,透过等离子体前后的X射线信号能谱轮廓相似度优于95.5%,能谱峰值点的偏移量小于1.3%.此外,在原有理论模型的基础上,考虑等离子中的粒子与X射线的碰撞、吸收效应,优化了X射线在等离子体中的透过率模型,与传统的理论方法相比,该模型可对实验现象进行更好的解释.同时计算了X射线在临近空间的透过率,并分析了X射线通信所能达到的潜在指标.这些结果有望为解决黑障区信号传输提供一定的理论与实验依据.     

Analytical formulas for calculating photoelectric attenuation coefficients

Photoelectric absorption is an interaction in which an incoming gamma ray virtually transfers all of its energy to an atomic electron, usually the most tightly bound K-shell electron of an atom. This paper uses the Win XCOM computer code as a reference base. We found analytical photoelectric attenuation coefficients for researchers using the Monte Carlo simulation program for Z∈ [1; 100] and E∈[10 keV; 3 MeV]. We define a photoelectric effect operator and coefficient operators and a series for photoelectric absorption. We have calculated two polynomial coefficient operators for use with XCOM for photoelectric absorption. We determined 14 energies and atomic number limits for elements, and we find that they are accurate limits of photoelectric absorption for fitting with XCOM.     

多群输运-燃耗耦合蒙特卡罗计算

介绍了三维多群中子输运-燃耗耦合P3近似蒙特卡罗程序MCMG-BURN，该程序是在连续截面蒙特卡罗程序MCNP和反应堆栅元均匀化程序WIMS基础上发展而来的，使用多群截面为模拟临界实验堆和高通量工程实验堆，取得与MCNP和实验一致的结果，MCMG-BURN具有与MCNP相同的精度，但计算时间较MCNP要少得多。     

Numerical simulation and experimental study of PbWO_4/EPDM and Bi_2WO_6/EPDM for the shielding of γ-rays

The MCNP5 code was employed to simulate the 7-ray shielding capacity of tungstate composites.The experimental results were applied to verify the applicability of the Monte Carlo program.PbWO_4 and Bi_2WO_6were prepared and added into ethylene propylene diene monomer(EPDM) to obtain the composites,which were tested in the 7-ray shielding.Both the theoretical simulation and experiments were carefully chosen and well designed.The results of the two methods were found to be highly consistent.In addition,the conditions during the numerical simulation were optimized and double-layer 7-ray shielding systems were studied.It was found that the 7-ray shielding performance can be influenced not only by the material thickness ratio but also by the arrangement of the composites.     

基于JLAMT可视化建模的JMCT模拟计算

JMCT是中国工程物理研究院高性能数值模拟软件中心粒子输运团队自主研发的三维蒙特卡罗模拟软件,JLAMT为其前处理可视化建模工具。使用JLAMT和JMCT程序对BW,KRITZ,BEAVRS等系列基准题进行了模拟,并对有效增殖系数及计数功能进行了对比分析。其中有效增殖系数计算结果与MCNP5的最大偏差为KRITZ2装载方案19基准题的89.1 pcm,除BEAVRS基准题外的计数结果与MCNP5的偏差基本小于2%,平均偏差在1%左右;BEAVRS基准题功率分布模拟结果与MCNP5及实测值最大偏差分别为7.06%,16.6%,控制棒价值计算与MCNP5及实测值均吻合较好。,     

Measurement of photon interaction parameters of high-performance polymers and their composites

In the present study, commercially important high-performance polymers and their composites have been investigated with respect to photon interactions as means of mass attenuation coefficient (μ/ρ), mean free path (MFP), half-value layer (HVL), effective atomic number (Z_eff), effective electron density (N_eff), and energy absorption and exposure buildup factors (EABF and EBF) at different photon energies. For this purpose, sample plates were prepared by extrusion and injection techniques using polyethersulfone, polyetherimide, acrylonitrile butadiene styrene copolymer, polyamide 66, polyphthalamide, and polypropylene copolymers as high-performance polymers and glass and carbon fibers as reinforcement. The (μ/ρ)s of the materials were measured at 81 and 356?keV photon energies to determine MFP, HVL, Z_eff, and N_eff. The theoretical values of these parameters were calculated via ZXCOM, WinXCom and Monte Carlo N-Particle simulation code (MCNP), and a good agreement was obtained between WinXCom–MCNP and MCNP–Exp. Finally, EABFs and EBFs of the samples were calculated up to around 40 MFP in the energy region 0.015–15?MeV and significant variations were observed in the continuous energy and MFP regions.     

基于MCNP计算结果的快速物理插值方法（英）

在核辐射科学研究中经常使用MCNP蒙卡计算程序,但其计算结果只是给定位置的物理量。为了快速获得计算点附近的感兴趣位置处的值,本研究建立了一种3点插值计算方法。首先分析了粒子在材料中输运的物理规律,给出了满足3点插值的空间范围,建立了插值计算模型。然后利用距离平方反比权重法,结合粒子衰减规律,推导了插值计算公式。最后设计了计算机程序,并用X射线屏蔽后注量的MCNP计算结果进行验证。通过和直接采用的距离平方反比权重法和克里金插值法对比,考虑物理作用机制的该计算方法精度更高,且误差在10%以内。