【作者】 王辉东；

【导师】 陆景彬；

【作者基本信息】 吉林大学 ， 粒子物理与原子核物理， 2012， 博士

【摘要】 21世纪随着核科学的发展及相关材料科学、制造工艺的进步，核技术应用在我国得到快速的发展，目前在国防、工业、农业、材料、生命、信息科学、环保和人类健康等方面核技术应用发挥着重要的作用。核技术总体分为两大类：核能利用类和非核能利用类。核能利用主要有核电、核武、核动力、核电池等。非核能利用主要有核分析技术、核成像技术、放射性药物、辐射加工、辐射检查、放射性示踪等。本论文课题方向为核技术应用，具体研究内容有两部分：核分析技术应用于煤质在线分析的课题：中子活化煤质在线分析研究；核电源应用于MEMS能源的课题：β辐射伏特核电池能量输运研究。一、中子活化煤质在线分析研究本论文针对国内燃煤电厂煤质成分实验室分析存在的不足，调研了国内外中子活化煤质在线分析设备，分析其性能、工业化等方面的优、缺点，研制了中子活化煤质在线分析系统。首先，对中子活化煤质在线分析测量系统进行设计：（1）增加了平煤器，减少煤流波动过大对测量稳定性的影响，同时防护煤流过高对系统的损伤；增加水份仪，直接测量煤质水份,解决在煤质工业指标计算过程中由氢元素到水份含量计算时存在的问题。（2）采用大体积BGO探测器，提高探测效率，同时为BGO探测器安装温控系统，减小温度变化对BGO性能的影响，提高系统的稳定性和测量精度。（3）采用了反射式的测量模式，与透射式测量模式相比，能有效消除煤流厚度对测量结果的影响；（4）采用蒙卡模拟方法，设计测量系统的辐射防护单元。本工作的核心是建立了一种新的实验谱库最小二乘法，该方法用于热中子俘获和快中子非弹的煤质在线分析，能有效降低谱库非线性的影响。在这种方法中，首先根据我国各大矿区煤种的元素含量，设置60个能代表全国煤种的煤样，通过这60个煤样的中子活化测量谱，采用最小二乘法建立20套单元素谱库，每套单元素谱库对应一个常见煤种。基于以上的20套单元素谱库，采用最小二乘法分析一个未知煤样，获得该煤样的初始估值。以初始估值为基础，采用谱库创建和样品分析的迭代方法建立一个新单元素谱库，建立该谱库的煤样与分析煤样的元素含量非常接近。因此这种实验谱库最小二乘法能尽可能的降低谱库非线性的影响。建立的实验谱库最小二乘法使用在本论文设计的煤质在线分析测量系统上，系统测量精度达到：灰份、水份、挥发、分热值分别为1.0wt%,0.5wt%,1.0wt%,350KJ/Kg。二、β辐射伏特核电池能量输运研究近年来，国内外对β辐射伏特核电池进行了大量研究，主要集中于换能器件的三维结构和新型半导体材料方面。β辐射伏特核电池的能量输运是电池设计、优化的重要依据之一。本文采用蒙特卡罗模拟程序Geant4，研究了β粒子在辐射伏特核电池中的能量输运,模拟分析主要为五个方面：（1）研究了单能电子在靶材料中的射程。分析得到了射程与能量、靶材料的经验公式。研究结果为设计核电池换能器件敏感区域厚度及核电池防护材料的最低厚度提供指导。（2）研究单能电子在靶材料表面的能量反散射系数与电子能量、入射角和靶材料的关系。结果表明①能量反散射系数随电子能量的增大而缓慢减少，核电池设计中以增大β源能量来减少反散射引起的能量损失是有限的；②能量反散射系数随入射角的增大而增大，入射角在00到250之间，能量反散射系数较小，增速也很慢，因此在核电池源的设计时，可以通过控制β粒子在换能器件表面的入射角尽可能的小，这样使更多的能量进入换能器件；③能量反散射系数随靶材料的平均原子序数增大而增大，在换能器件的材料选择时，低原子序数的靶材料更能获得较高的能量转换效率。（3）研究了放射源的自吸收。①给出了³H（1.2、1.8、2.0吸氚比的钛化氚）、⁶³Ni(20%、80%、100%的⁶³Ni丰度)、¹⁴⁷Pm（100%的147Pm丰度）β面源的表面最大活度、表面最大输出功率；②给出了以上源的最佳质量厚度及相应的表面出射活度和表面出射功率；③研究结果表明随源质量厚度的增加，表面出射粒子能谱中心向高能偏移。以上结果有助于核电池放射源的制备以及换能器件设计。（4）研究了单能电子在靶材料中的能量沉积规律。结果表明：①单能准直电子在材料中的能量沉积率随入射深度先增大后减少，有一个明显的能量沉积主要区域；②随电子能量增加，电子能量沉积的主要区间所在的深度增大；③随电子能量增加，电子在材料中的能量沉积率降低。该结果能指导核电池换能器件的几何尺寸设计，让电子能量沉积的主要区域与换能器件敏感区域尽量吻合。（5）研究了³H（1.8吸氚比的钛化氚）、⁶³Ni(80%的⁶³Ni丰度)和¹⁴⁷Pm(100%的¹⁴⁷Pm丰度)β面源在半导体材料（Si、SiC、GaAs）中的能量沉积。①结果表明随靶材料的深度增加，β射线的能量沉积率下降，源平均能量越低下降越快；②三种源在Si材料中的能量沉积表明：在常规核电池几何设计下⁶³Ni有最高的能量沉积率；③³H在三种材料中的能量沉积表明：SiC较适合作为³H的换能器件材料。本工作系统地从粒子输运和能量沉积的角度对辐射伏特核电池的几何尺寸、转换效率和输出功率进行详细研究。得到常规β辐射伏特核电池的理论参数和β粒子能量损失分布，总结出β辐射伏特核电池在结构和材料方面的一些优化方向。更多还原

【Abstract】 In the21st century, along with the development of nuclear science and theimprovement of materials science and the manufacturing technology, nucleartechnique has been quickly developed and plays a vital role in industry, agriculture,national defence and science-technology. Nuclear technique belongs to twomaincategorises: the utilization of nuclear energy and the utilization of non-nuclear energy.The utilization of nuclear energy consists mainly of nuclear power, nuclear weaponand nuclear battery. The utilization of non-nuclear energy consists mainly of nuclearanalysis technique, nuclear imaging system, radiopbarmaceutical etl.The main purpose of this thesis is to study nuclear technique application, which isspecifically the research on the on-line coal analysis based on neutron activation andthe β-voltaic nuclear battery.1. The research on the on-line coal analysis based on neutron activation:We have studied the development of the on-line coal analysis system and havedeveloped the on-line coal analysis system based on neutron activation. Ourdevelopment aims at the shortage of the laboratorial analysis in coal-powercompanies.1) We adopt the coal-smoothing device which smoothes coal on the conveyer beltand protects instrument from hitting by the coal and reduces the fluctuation of coalflow. This module helps keep the precision of the whole system. As a solution of theproblem that the moisture can not be calculated considering both water and alkenescontain the element hydrogen, the moisture meter is employed by the system.2）A Φ127mm*127mm BGO detector with a temperature controller is adopted bythe system, wich decreases the Influences of the Temperature Changes and increasesthe stability and measurement accuracy of the system.3）The system adopt the back-scattering measurement model. which can decreasethe effect of coal fluctuate compared with the transmission measurement model.4) The moderating and shielding system has been designed based on the MonteCarlo simulation. A new experiment-library least-squares (experiment-LLs) method used in theneutron inelastic-scattering and thermal-capture analysis (NITA) technique for on-linecoal analysis was developed, which has significantly decreased the non-linearradiation effects. In this method, sixty samples with preset elemental contents weremade, from whose experiment spectra twenty single-element spectrum librariescorresponding to twenty kinds of coal were built by least-squares method. Thespectrum of unknown sample was analyzed based on these twenty libraries to estimateits element contents. With the initial estimated result, the procedure of developinglibrary and analysis was iterated to build a new library with the closest elementcontents to the unknown sample. Hence the experiment-LLs method can reducesnon-linear radiation effects as possible. The experiment-LLs method was performedon an improved coal analysis system which was equipped with a long-life14MeVpulsed-neutron generator, a bulk BGO detector with a temperature controller, amoisture meter and coal-smoothing device. The precision of this system for ashcontent, water content, volatile content and calorific value have reached1.0wt%,0.5wt%,1.0wt%,350Kj/Kg, respectively.2. The research on the energy transport of β-voltaic nuclear battery:In recent years, the β-voltaic nuclear battery has been extensively investigated,mostly focusing on the new three-dimensional structure and material ofsemiconductor of the energy conversion device. In fact, the energy transportation ofthe β-particle in the battery is the foundation for the design and optimization of theβ-voltaic nuclear battery. This work employed the Monte Carlo method to simulatethe β-particle energy transportation using the Geant4program, which included fiveparts of work as below:1) Estimated the flight range of the single-energy electron in the battery materialand analyzed the relation between the flight range and the energy and battery materialusing the experience formula. The result would be helpful for the design of the depthfor both the sensitive area and the radioprotection material of the β-voltaic nuclearbattery.2) We have researched the dependence of the energy backscattering ratio on the energy, the injection angle and the material of semiconductor device for thesingle-energy electron. The energy backscattering ratio increases with the injectionangle and the increasing rate also increases with the injection angle. The energybackscattering ratio is12.34while the injection angle is from00to250and50.22from640to890. The energy backscattering ratio decreases with the electron energyslowly expert for the material Au. The result of decreasing the energybackscattering ratio is quit limited by increasing the energy of electron. Theenergy backscattering ratio increases with the average atomic number of devicematerial. The small average atomic number makes contribution to the highenergy conversion efficiency and the SiC is most suitable for the three materialsconsidering this aspect.3)①The research of the source absorption presents the suitable thickness and themaximum surface output power of β sources.②.The energy spectra of β particleemitted from the source surface are different to that of β particle emitted fromradioactive isotopes. The peak of spectrum is moving to the center and the electronwith low energy becomes less with the thickness of source. The self absorption ofthese three β sources are more than55%which affect seriously the energy utilizationefficiency and the maximum output power of the nuclear battery. Reduction the selfabsorption and improving the surface output power are important for optimization thenuclear battery.4) The relationship between the deposited energy and the depth in the nuclearbattery for the single-energy electron indicates that①.The deposited energy is afunction of the depth in the silicon. The energy deposition rate of the single energyelectron increases firstly and then decreases with the device depth. There is oneobvious region in which most energy of electron deposits.②.The higher the energy ofelectron, the deeper the region is. In design the nuclear battery, we should focuson the electron with energies more than5keV and the sensitive region of deviceshould fit to the energy deposition region.5) The distribution of deposited energy has been studied.The β sources are3H （the titanium-tritium ratio:1.8）、63Ni（the purity:80%）、147Pm（the purity:100%）.The materials are Si、SiC、GaAs.①.The energy deposition rate decreases with thedepth increasing. The lower the average energy of β source, the bigger the energydeposition rate and the decreasing rate.②.The deposited energy distribution of threeβ sources in the material Si indicates that63Ni is the suitable source and has thehighest utilization ratio of energy.③. The deposited energy distribution of3H βsources in three materials indicates that SiC is the suitablematerial and has the highestutilization ratio of energy.The energy transport of β particle in general β-voltaic nuclear batteries has beensimulated. Some theoretical parameters about these nuclear batteries has beenpresented, such as the suitable thickness and the maximum surface output power of βsources, the possible values of the deposited energy and the deposition ratio in thesensitive region of these batteries, etc.. Some advice about the optimization ofstructure and material of nuclear batteries has been summarized from these laws ofenergy transport. These parameters and advice are useful in the further study ofβ-voltaic nuclear batteries.更多还原