水下中子活化分析的蒙特卡罗数值模拟

发布时间：2018-03-19 19:53

本文选题：水下中子活化元素分析仪　切入点：蒙特卡罗模拟　出处：《成都理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：根据初步调研显示海洋中蕴含着大量矿产资源,水下中子活化分析可以为海底金属矿产资源开发提供一种新的勘探方法。论文选题来源于863计划“资源与环境技术领域”主题项目课题“高精度能谱探测仪器研发”(课题编号:2012AA061803)和国家自然科学基金“地球和月球表面诱发辐射场及其地质响应研究”(项目批准号:41374136)。论文以水下中子活化元素分析仪为主体,以插入式模型和拖拽式模型为手段,以MCNP5软件为工具,以水下4000m处的污泥为研究对象,通过蒙特卡罗模拟数值分析研究对仪器内部结构参数的优化,两种不同模型下探测器计数随源距和孔隙度变化规律性所在,Na、Al、Si、Mn四种元素活化后感生特征γ射线计数对孔隙度的灵敏度,整个插入式模型感生特征γ射线能谱做了研究工作。本文的主要研究工作有:(1)调研了可控中子管的发展现状,选择适合当作水下中子活化元素分析仪的激发源,在MC模拟分析过程中激发源当作一个理想点源进行模拟研究。(2)在国内外多方学者所设计的仪器基础之上,利用MC模拟软件建立水下中子活化元素分析仪的整体结构,根据需要采用NaI(Tl)作为探测器,外围包有0.5cm厚的钆,防止热中子进入探测器,起到保护探测器的作用。在激发源和探测器之间设计三层复合体屏蔽结构,第一层研究了钨和钨镍合金两种屏蔽物质,第二层研究了石蜡和20%的含硼聚乙烯,第三层使用了屏蔽γ射线常用物质铅,得到三层屏蔽体的最佳厚度。(3)模拟分析了插入式模型和拖拽式模型探测器记录到感生γ射线总量随源距和孔隙度变化的规律,并且对探测器记录到Na、Al、Si、Mn四种元素的感生特征γ射线计数随孔隙度变化的灵敏度进行模拟分析研究。(4)对水下4000m下污泥所含65种元素中百分含量比较大的12种元素模拟分析了其感生特征γ射线谱;在此基础之上模拟分析了插入式模型源距为54cm时,在含水孔隙度为35%的水下污泥中,整体被中子活化产生的感生特征γ射线能谱。
[Abstract]:According to preliminary research, the ocean contains a lot of mineral resources. Underwater neutron activation analysis can provide a new exploration method for the exploitation of submarine metallic mineral resources. "(subject No. 2012AA061803) and National Natural Science Foundation of China" Research on Earth and Moon Surface induced radiation Field and its Geological response "(Project Grant No.: 41374136). The main body of the paper is the underwater neutron activation element analyzer. By means of plug-in model and towing model, with MCNP5 software as the tool and sludge at 4000m underwater as the research object, the optimization of the internal structure parameters of the instrument is studied by Monte Carlo simulation numerical analysis. The sensitivity of 纬 -ray counting to porosity after activation of four elements, NaAL-AlSiSi-Mn, is the regularity of detector counting with the variation of source distance and porosity under two different models. The main work of this paper is to investigate the development status of controllable neutron tube, and select suitable excitation source for underwater neutron activation element analyzer. In the process of MC simulation analysis, the excitation source is used as an ideal point source to simulate and study. (2) on the basis of the instruments designed by many scholars at home and abroad, the whole structure of underwater neutron activation element analyzer is established by using MC simulation software. According to the need to use NaIN Tl) as the detector, the peripheral is covered with 0.5 cm thick gadolinium, which prevents thermal neutron from entering the detector and plays the role of protecting the detector. A three-layer complex shielding structure is designed between the excitation source and the detector. The first layer studies tungsten and tungsten nickel alloy shielding materials, the second layer studies paraffin and 20% boron polyethylene, and the third layer uses lead, which is used to screen 纬 -rays. The optimum thickness of the three-layer shield is obtained. The law of the total amount of induced 纬 rays with the source distance and porosity recorded by the plug-in model and the drag model detector is analyzed. The sensitivity of 纬 -ray counting with porosity was simulated and analyzed. The sensitivity of 纬 -ray counting on 65 elements in sludge at 4000m underwater was simulated and analyzed. The results showed that the sensitivity of 纬 -ray counting to 65 elements in the sludge was higher than that of the other 12 elemental modes with a high percentage content of 65 elements in the sludge at 4000m under water. The 纬 -ray spectrum of its inductive characteristics is analyzed. On this basis, the inductive characteristic 纬 -ray energy spectrum produced by neutron activation in underwater sludge with water porosity of 35% was simulated and analyzed when the source distance of the plugged model was 54 cm.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.6;P744

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