Research On The On-line Coal Analysis Based On Neutron Activation And The Energy Transport Of β-voltaic Nuclear Battery

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.