Supercritical carbon dioxide Brayton cycle system steady state modeling and analysis

超临界二氧化碳（Supercriticalcarbondioxide，S-CO2）布雷顿循环在中等温度条件下（450-700℃）循环热效率高于蒸汽朗肯循环和氦气布雷顿循环，并且其结构紧凑、受外部环境约束较小，是第四代反应堆系统推荐使用的新一代能量转换系统。进入21世纪以来，各国对该技术展开了一系列研究。 本文开发了S-CO2布雷顿循环稳态模拟计算程序，用于分析S-CO2布雷顿循环回热及再压缩循环的运行性能。计算程序核心模块采用Fortran语言构建底层计算模型，调用Python语言Numpy库完成数值求解，程序界面基于Cocoa框架，使用Objecitve-C语言编写。计算程序分别对S-CO...The efficiency of the supercritical carbon dioxide (S-CO2) power cycles are higher than steam Rankine cycle and helium Brayton cycle in the mild turbine inlet temperature region, and the compact structure and the less restraint of the environment make the S-CO2 a promising alternative power conversion system for next-generation nuclear reactors. Since the 21st century, many countries launched a se...学位：工学硕士院系专业：能源学院_核工程与材料学号：3242013115228

Modeling and Analysis of Nuclear Reactor System Using Supercritical-CO_2 Brayton Cycle

超临界二氧化碳(S-CO2)有可能作为循环工质应用于第四代核能系统中的3种快中子反应堆系统和当前常见商用反应堆系统内.使用工程等式求解器(EngInEErIng EQuATIOn SOlVEr,EES)工具,对S-CO2布雷顿循环进行了理论建模和分析.其中,针对系统中的重要部件换热器,进行了较为详细的建模.分析了S-CO2布雷顿循环系统的循环热效率,并与核工业中常用的循环工质进行对比.结果表明,S-CO2作为循环工质在特定的温度下具有较高的热转化效率.同时,针对不同的反应堆类型,对比分析S-CO2布雷顿循环与各种类型反应堆系统耦合时的热力循环效率与特性.结果表明,SCO2作为循环工质材料最适合在气冷快堆与液态金属快堆(钠冷快堆和铅冷快堆)中使用,具有热效率和铀资源利用率高等优势.The supercritical carbon dioxide(S-CO2)is considered as a potential working medium for the commercial nuclear reactor system and three types of Gen IV fast reactors.Engineering equation solver(EES)was introduced to set up a model for SCO2 Brayton cycle,and a detailed modeling for the significant components,such as heat exchanger,turbine and compressor,was carried out.After the analysis of thermal efficiency of the S-CO2 Brayton cycle system,results were compared with common mediums used in current nuclear industry,which shows the S-CO2 using as working medium has the highest thermal efficiency under the specific temperature.Meanwhile,thermal efficiencies and characteristics of the S-CO2 Brayton cycle system,coupling with various types of reactor systems,were analyzed.Preliminary analysis showed that S-CO2,using as cycle working fluid material,was most suitable for the gas-cooled fast reactor and the liquid metal-cooled fast reactor(the sodium-cooled fast reactor and the lead-cooled fast reactor),with the advantage of high thermal efficiency and high utilization of uranium resources.教育部重点实验室开发基金(ARES201402

Effect Factors of keffby Using Different Kinds of Materials in Travelling Wave Reactors

行波堆是一种趋近理想状态的先进核能系统,其焚烧策略可将铀资源利用率提高数十倍,废物量减至几十分之一.本文以蒙特卡罗程序为工具,设计了一个圆柱形行波堆堆芯物理模型,研究不同冷却剂、反射层厚度和燃料下行波堆几十年内的有效增殖因数(kEff)的变化情况.结果表明,当其他材料相同时,改变点火区的易裂变核素浓度对稳态时行波堆增殖和裂变的239Pu几乎没有影响,因此在平衡时kEff值保持稳定;增加反射层厚度、使用金属燃料和氦气冷却时反应堆的中子经济性较佳,此时kEff有较大值.Travelling wave reactor(TWR)is a type of ideal advanced reactor systems,of which burnup strategies can increase utilizing ratios of the uranium resources and decrease the nuclear waste by dozens of times.In this paper,we designed a cylindrical reactor core,as well as investigated changes of keffvalues with different coolants,reflector thickness,and fuels by using the Monte Carlo calculation procedure.Results showed that changing the concentration of fissile nuclide in the seed region exerted almost no effect on the breeding and fission of the 239 Pu in TWR during equilibrium states when other materials remained unchanged.As a consequence,the value of keffwas nearly a constant.Moreover,when increasing the thickness of reflectors,and using metallic fuels and helium as the coolant,we will be able to enhance the neutron economy of the TWR,yielding higher keffvalues.中央高校基本科研业务费专项(2012121034); 厦门大学校长基金(20720150095

Studies on the Small Pressurized Water Reactor Based on TRISO Fuels

目前世界上运行的大部分压水堆都采用二氧化铀(uO2)作为核燃料,锆合金作为包壳.该技术虽然成熟,但在高温下仍存在一定缺陷.新开发的TrISO(TrISTruCTurAl-ISOTrOPIC)燃料可以长时间在1 600℃的温度下保持燃料和包壳的完整性,防止裂变产物释放到环境中,在压水堆中使用TrISO燃料替代常规uO2芯块燃料可以大大提高反应堆的安全性.本研究使用TrISO包覆颗粒燃料的小型压水堆,对不同富集度组件排列下的有效增殖系数、堆芯换料周期、中子通量分布等进行分析讨论,并比较2种燃料棒在反应堆正常运行环境下的温度分布.计算结果表明,从换料周期、通量展平、燃料的中心最高温度这3个方面看,在小型压水堆中采用TrISO燃料棒替代常规uO2燃料棒是可行的,使用TrISO燃料的堆芯具有更优异的安全性.At present,most of pressurized water reactors(PWR)use UO2 fuel pellets as nuclear fuels in the world.Although fuel pellets are utilized widely,they suffer from some defects under high temperature.The newly developed tristructural-isotropic(TRISO)fuel can maintain the integrity of the fuel and cladding,which is able to prevent the fission products from being released to the environment at a temperature of 1 600 ℃for a long time.Therefore,the safety of the reactor can be significantly improved by using TRISO fuel instead of the conventional UO2 pellet fuel in PWR.In this paper,a small pressurized water reactor using TRISO fuel was considered.The effective multiplication factor under different uranium enrichment,the refuel cycle,and the neutron flux distribution were discussed.The temperature distributions for two kinds of fuel rods in the reactor were compared.Calculation results show that,according to the fuel reloading length,flux flatted,and temperature distribution,using TRISO instead of conventional UO2 fuel rods is feasible and safer in the small pressurized water reactor.厦门大学校长基金(2012121034;20720150095

Influence of pressure on the thermal performance of the S−CO2{\rm{S}} - {\rm{C}}{{\rm{O}}_2} Brayton cycle

为了研究${\rm{S}} -; {\rm{C}}{{\rm{O}}_2}$布雷顿循环中工作温度、压力以及换热器的换热能力对系统的热效率的影响。通过计算机数值模拟的方法,建立了; ${\rm{S}} -; {\rm{C}}{{\rm{O}}_2}$闭式再压缩布雷顿循环的热力模型。在换热器换热能力一定的条件下,通过调整压缩机出口压力、压比以及换热器压; 降等参数,研究系统循环最大热效率的变化。计算结果表明,压缩机出口压力以及压比均存在最优值,当压力超过一定数值后,增大系统压力并不能提高热效率。换; 热器的压降对系统热效率影响显著,并影响系统最大热效率情况下的再压缩份额。To study the effects of the working temperatures and pressures, and heat; exchanger (HX) characteristics on the thermal efficiency of the cycle,; an ${\rm{S}} - {\rm{C}}{{\rm{O}}_2}$ recompression closed cycle model; was established using numerical simulation. By adjusting the outlet; pressure of the compressor, and the pressure ratio and pressure loss; inside the HXs, the maximum thermal efficiency of the ${\rm{S}} -; {\rm{C}}{{\rm{O}}_2}$ Brayton cycle was studied. Results show that both; pressure and pressure ratio have an optimal value. When the pressure; exceeds a certain value, the thermal efficiency of the cycle cannot be; improved by further pressure enhancement. Pressure loss significantly; affects the thermal efficiency of the cycle and,at the same time,affects; the re-compression ratio of the cycle for maximum thermal efficiency.教育部重点实验室开发基金项