超临界二氧化碳再压缩布雷顿循环变工况特性分析

超临界二氧化碳再压缩布雷顿循环是高效紧凑的能量转换方式。目前许多研究在分析循环的特性时,常假设压缩机和透平的效率为恒定,该假设与实际情况差别很大。本文使用MODELICA作为工具,建立了超临界二氧化碳再压缩布雷顿循环模型。对于压缩机和透平,加入了真实压缩机和透平的特性曲线模型。通过模拟计算发现,循环输入功率和循环流量的改变将对循环火用效率和各组件的火用损产生影响。循环偏离设计工况时,适当控制输入功率和循环流量可调节循环输出功率和火用效率。福建省自然科学基金资助项目(2016J05020,2016J05137

Lu2Ti2O7和Lu2TiO5陶瓷材料的Kr离子辐照损伤研究

钛酸盐因其优异的物理化学性能,可作为高放射性核废物（HLW）和锕系元素（钚）的重要候选固化材料之一。采用传统的陶瓷烧结工艺制备了多晶的Lu2Ti2O7和Lu2TiO5陶瓷材料。在室温下,用800 keV Kr2+对两种材料进行辐照,辐照后的样品采用GIXRD进行表征,观察到两种样品都经历了先肿胀、然后再发生非晶相变的过程。不同的是Lu2Ti2O7的晶格肿胀程度大于Lu2TiO5。另外,Lu2TiO5样品的辐照到2×1014ions/cm2时非晶含量达95.54%,而Lu2Ti2O7样品在此剂量下非晶含量只有74.66%。通过第一性原理计算了Lu2Ti2O7晶体的晶格肿胀随反位浓度的变化关系,结果表明,Lu2Ti2O7出现非晶前的晶格肿胀主要由阳离子反位导致,而Lu2TiO5是无序的萤石结构,其辐照所导致的晶格肿胀不含阳离子反位的贡献,晶格肿胀程度较低

Fast Reactor Fuel Cycles and Metal Fuels

快堆作为第四代先进核能系统中最重要的反应堆型,有望显著提高铀资源利用率和减少核废物量,快堆及与其密切相关的核燃料循环和金属燃料技术越来越受到人们的广泛关注.本文综述了快堆(特别是行波堆)、核燃料循环及金属燃料技术的研究进展,重点介绍了美国的行波堆和金属燃料技术,并阐述了行波堆初期采用“一次通过式“简化燃料循环对于快堆早日实现大规模商业化的重要意义.As the most important type of nuclear reactors in Generation IV nuclear systems,fast reactors are expected to significantly improve the uranium resource utilization and reduce the amount of nuclear waste.Fast reactors,their associated nuclear fuel cycles,and metal fuel technologies have attracted increasing attention.This paper summarizes the research progress of fast reactors,nuclear fuel cycles,and metal fuel technologies,with focus on traveling wave reactors and metal fuel technologies,and expounds the significance of using the travelling wave reactor "once through" fuel cycle to realize the early large-scale commercialization of fast reactors and sustainable nuclear energy systems.中央高校基本科研业务费专项(2012121034

Analysis of Levelized Cost of Electricity for Travelling Wave Reactor

本文通过平准化发电成本的方法,以燃料循环作为研究对象,对行波堆一次通过式燃料循环和二次通过式燃料循环的经济性进行了研究,并选取10个重要的经济和技术参数进行成本敏感性分析。研究结果表明,行波堆的平准化发电成本低于现有压水堆和快堆,其中,行波堆一次通过式燃料循环方式的平准化发电成本最低。敏感性分析表明,贴现率、燃耗深度、隔夜价和反应堆热效率是影响行波堆经济性最重要的参数,而燃料价格和废物处置的价格由于占成本的比例较小,对行波堆经济性的影响不大。Based on levelized cost of electricity(LCOE)method,the fuel cycle was selected as the object of the study,the economics of once-through fuel cycle and twicethrough fuel cycle for travelling wave reactor(TWR)was studied.Ten important economic and technical parameters were proposed for the sensitivity analysis.The results show that the LCOE of TWR is lower than that of conditional light water reactor and fast reactor.Furthermore,the LCOE of once-through fuel cycle of TWR is lower than that of twice-through cycle.The sensitivity analysis indicates that the discount rate,burn-up,overnight cost and thermal efficiency impact the LCOE severely,while the price of uranium and the cost of waste disposal barely impact the LCOE.厦门大学校长基金资助项目(20720150095

Numerical Analysis of Reverse Flow in Inverted U-tube of Steam Generator Under Natural Circulation

在自然循环工况下,倒U型管蒸汽发生器(inverted U-tube steam; generator,UTSG)内有部分倒U型管会发生倒流现象,严重影响一回路系统的自然循环能力.采用计算流体力学(computational; fluid; dynamics,CFD)方法对自然循环工况下UTSG一次侧流体的流动特性进行三维数值模拟研究.结果表明:在低质量流量下,倒流集中发生在短管侧,; 而等长倒U型管中同时出现了倒流和正流的现象,这与入口腔室分配给各个倒U型管的初始质量流量有关.随着UTSG入口质量流量的增加,UTSG倒流管数减; 少;随着一次侧入口温度的升高,UTSG进出口压降为负值,压降绝对值逐渐增大,倒流管数增多.Under natural circulation condition,reverse flow occurs within some; tubes in inverted U-tube steam generator (UTSG), which can seriously; influence the capacity of natural circulation of primary loop system.In; this study,the computational fluid dynamics (CFD) method is used to; simulate the primary side, flow characteristics of UTSG under natural; circulation condition.The results show that at a low mass flow; rate,reverse flow mostly occurs at the short pipe side, while reverse; flow as well as normal flow simultaneously occur in equal length; U-tubes.This phenomenon is related to the initial mass flow rate; assigned to each inlet tube by the inlet chamber.The less the initial; mass flow rate is,the more likely the reverse flow occurs.With the; increase of the inlet mass flow rate of UTSG,the number of the reverse; flow pipes of UTSG is reduced.With the increase of the primary inlet; temperature,the pressure drop of UTSG is negative,the absolute value of; the difference of pressure increases gradually,and the number of the; reverse flow tubes increases.福建省自然科学基

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

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

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

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

轻、重离子辐照烧绿石Lu2Ti2O7导致的非晶结构变化

采用标准固相反应烧结法制备烧绿石结构的Lu2Ti2O7.在室温下,用800keV Kr2+和200keV He+进行辐照.辐照后的样品采用掠入式X射线衍射（GIXRD）表征.结果表明:用800keV Kr2+辐照样品时,辐照剂量达到2×1014cm-2（相应dpa（displacement per atom）为0.4）时,样品出现非晶化转变,并且随着辐照剂量的增加,非晶化转变量不断增加,增加至一定值后不再变化,未出现完全的非晶化转变;用200keV He+进行辐照时,即使辐照剂量增加至2×1017cm-2（dpa为1.25）,样品也没有出现非晶化转变.通过分子动力学模拟对结果进行分析后发现:重离子辐照时,样品在较小范围内产生较多的缺陷,且电子能损较低,样品温度增幅较小,缺陷复合率低,易导致非晶化转变;而轻离子辐照时结果相反.国家自然科学基金(11205128,11227804);;福建省自然科学基金(2017J01007