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

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

Determination of Mercury in Chinese Medicinal Material and Biological Samples Using Pyrolysis Atomic Absorption Spectrometry

建立了一种采用固体热解塞曼原子吸收光谱快速测定中药和生物样品中痕量汞的方法,样品不需要经过消解即可直接测定。考察了样品颗粒大小对分析结果的影响,在优化的实验条件下,方法的重现性为2.1%(峰面积)和9.1%(峰高),检出限为6.3 ng.g-1(3σ),回收率为95%~105%。使用标准参考物质进行对照分析,通过与ICP-MS分析法的结果进行比较,结果令人满意。大鼠灌胃实验表明,长期灌胃较大剂量的朱砂对肾等组织有一定的毒害,而在部分传统中药中朱砂用量较高。文章对制定中药安全性标准具有参考意义。In this paper a rapid and simple method using pyrolysis coupled with atomic absorption spectrometry for the analysis of total mercury in Chinese medicinal material and biological samples is presented.No sample digestion was needed and this greatly simplifies the analytical procedure and minimizes potential sources of contamination.Under optimum conditions,the reproducibility of the method was 2.1% for peak area and 9.1% for peak height.The detection limit(3σ) was 6.3 ng·g~(-1),and the recovery was within the range of 95%-105%.Several standard reference materials were analyzed and the results were obtained with satisfaction.The performance of the method was compared with inductively coupled plasma-mass spectrometry(ICP-MS),and excellent agreements were observed(between) these two methods.国家自然科学基金(20175022);; 福建省科技攻关计划重大招标(2003Y005)资助项

川西周公山柳杉人工林群落的边缘效应

为研究人工林群落的边缘效应特征,本文以川西周公山森林公园的柳杉(Cryptomeria fortunei)人工林破碎化大斑块为对象,以植株平均胸径、平均高度、平均密度、丰富度指数(D)和Shannon-Wiener指数(H)来综合衡量边缘效应深度。在实地踏查的基础上,从林缘向林内(梯度1至梯度5)设置5条样带(宽度为10 m),在每条样带中设置4个10 m×10 m的小样方进行调查。结果表明:(1)从物种组成上看,在总面积为2,000 m~2的20个小样方中共记录到111个物种,隶属于54科96属,物种数从林缘至林内递减。(2)从群落结构上看,乔木层的平均胸径从林缘至林内呈减小趋势,平均密度则相反,平均高度无显著变化;灌木层的平均密度从林缘向林内减小,平均高度无显著变化;草本层的平均密度和平均高度均呈减小趋势。(3)从物种多样性上看,总体上各层次的丰富度指数和Shannon-Wiener指数均从林缘向林内呈减小趋势,其中灌木层和草本层的变化趋势最明显;同时,林内各梯度与梯度1(林缘)的共有种和相似性系数从林缘向林内递减。(4)分析各项群落特征发现,平均高度、平均密度和相似性系数的数值在梯度2向梯度3过渡时的起伏变化最明显,推断本研究中柳杉人工林斑块的边缘深度可达林内20 m

Determination of mercury in Chinese medicinal material and biological samples using pyrolysis atomic absorption spectrometry

In this paper a rapid and simple method using pyrolysis coupled with atomic absorption spectrometry for the analysis of total mercury in Chinese medicinal material and biological samples is presented. No sample digestion was needed and this greatly simplifies the analytical procedure and minimizes potential sources of contamination. Under optimum conditions, the reproducibility of the method was 2.1% for peak area and 9.1% for peak height. The detection limit (3 sigma) was 6.3 ng(.)g(-1), and the recovery was within the range of 95%-105%. Several standard reference materials were analyzed and the results were obtained with satisfaction. The performance of the method was compared with inductively coupled plasma-mass spectrometry (ICP-MS), and excellent agreements were observed between these two methods