核电站滞留床用活性炭的性能研究和选择

建立可模拟核电站不同气流参数条件下的活性炭吸附剂性能评价系统,对不同活性炭样品分别进行了物理性能表征测试和放射性氪与氙滞留性能实验。同时针对不同影响因素条件下活性炭滞留惰性气体性能的影响进行了研究,包括系统气流压力、温度、气流比速及辐照强度。试验结果显示系统气流压力越高、温度越低,氪动态吸附系数越大;一定范围的气流比速、辐照强度对活性炭动态吸附系数的影响可以忽略。得到的活性炭吸附剂样品具有良好的物理性能与惰性气体滞留性能,可应用于核电站废气处理系统活性炭滞留单元。     

活性炭对惰性气体动态吸附影响因素的讨论

探讨了活性炭对惰性气体的动态吸附系数的多种影响因素。由文献调研可知,一定范围的气流比速与一般应用环境的CO2浓度对动态吸附系数的影响可以忽略;系统压力越高动态吸附系数越大;温度越高、环境相对湿度越大动态吸附系数越小;在不能达到吸湿平衡的情况下,用活性炭含水量代替相对湿度作为活性炭吸附惰性气体的影响因素更符合实际。     

不同工况下活性炭吸附放射性惰性气体性能的初步研究

活性炭吸附滞留工艺是核电站处理放射性惰性气体的技术发展方向之一。本文介绍了活性炭吸附放射性惰性气体Kr和Xe的原理及其主要物理参数。通过不同运行条件下对活性炭的吸附性能进行测试,结果表明活性炭的吸附性能受到气流温度、压力、流速和湿度等多方面因素影响。过高气体温度、湿度和过低的流速导致活性炭吸附性能下降,适当提升系统运行压力有利于提高活性炭的吸附能力。研究结果可指导核电站项目中废气处理系统的设计,通过合理控制滞留系统的运行条件可以保障活性炭的吸附性能和使用寿命。     

工程条件下椰壳活性炭吸附放射性惰性气体性能研究

在某一代表性工程条件下, 研究一种椰壳活性炭(YK型)对放射性惰性气体吸附能力.结果表明:在温度40 ℃、压力0.02 MPa、气流比速0.05 cm/s、气流相对湿度25%的工程条件下,YK型活性炭对惰性气体氙、氪的吸附系数分别为400 mL/g和28.8 mL/g.在30 ℃～40 ℃范围内,温度每升高1 ℃,氪在活性炭上的吸附系数下降约2%;活性炭对惰性气体吸附系数还受到湿度和压力的不同程度影响.根据实验测得的吸附系数可以推算出,在试验所用的工程条件下,如果要求对133Xe净化系数达到2 500(133Xe需经过60 d的衰变),用YK活性炭滞留床时体积只需6.514 m3,较压缩罐体积减少大约95%(压缩贮存衰变罐的贮存压力为1.0 MPa时,压缩罐体积需130 m3).     

氙在活性炭和碳分子筛上的动态吸附性能

为筛选氙的吸附剂,研究了氙在活性炭和碳分子筛(CMS)上的动态吸附性能,探讨了氙浓度、气流比速、温度、载气、压力和CO2等对氙动态吸附系数的影响。结果表明,CMS1对氙的吸附能力最强,其次为CMS2;低于10-5mol/L的氙浓度、实验气流比速以及5×10-5mol/L以下的CO2浓度对氙动态吸附系数影响不明显;载气种类和高于5×10-5mol/L的CO2浓度对氙的动态吸附系数有一定影响;吸附温度和吸附压力对氙动态吸附系数影响较大。提高吸附剂吸附氙能力的方法主要是降低吸附温度和增加吸附压力。     

放射性废气处理系统活性炭滞留单元工程规模装置性能研究

设计了放射性惰性气体滞留单元工艺流程,建立可模拟核电站不同气流参数条件下的活性炭滞留单元工程样机系统。对主要单元模块进行了性能实验,包括气体冷却器冷凝除湿性能、吸附剂装填实验、干燥单元除湿与再生性能以及活性炭滞留时间测试实验。结果表明:气体冷却器满足除湿性能要求,硅胶干燥单元除湿与再生性能优异,活性炭滞留单元具有良好的惰性气体滞留性能。研制的工程样机满足工程应用要求,具备实际工程应用条件。     

气流比速对活性炭氡吸附影响研究

为提高活性炭的氡吸附效率以及为降低氡净化成本提供参考,研究了在主动吸附模式下,设置活性炭在不同气流比速的条件下进行氡吸附实验,测量活性炭的氡吸附量。杏壳活性炭与煤质活性炭的氡吸附量随气流比速度的增加,没有较大变化;气流比速在0.9~2.0 cm/s依次增大时,椰壳活性炭的氡吸附量没有较大变化。气流比速在2.0~3.1 cm/s依次增大时,椰壳活性炭的氡吸附量呈先增加后降低的趋势,当气流比速为2.7 cm/s左右时,椰壳活性炭氡吸附量达到峰值,可选取2.7 cm/s作为椰壳活性炭氡吸附的最佳气流比速。     

“华龙一号”废气处理系统活性炭延迟衰变工艺研究

为提高放射性废气处理的安全性,推动"华龙一号"走出去的国家战略以及打破国际市场一些国家的政策限制,对"华龙一号"废气处理系统采用活性炭延迟衰变工艺进行研究。"华龙一号"废气主要来源于一回路裂变产物氪(Kr)和氙(Xe)等放射性惰性气体。目前,AP1000和EPR等三代核电站对其采用活性炭延迟衰变。通过研究温度、压力、相对湿度、流速以及活性炭床长径比等参数对活性炭动态吸附性能的影响,并设计"华龙一号"废气处理系统活性炭延迟衰变处理的工艺流程。     

活性炭对氙的动态吸附性能及其结构表征分析

近年来,活性炭吸附放射性氙被越来越广泛应用于核电项目的尾气处理中。活性炭对氙的动态吸附系数与其孔结构关系甚大,而相关研究却很少,因此有必要研究二者的关系,为活性炭的选择与开发提供参考。本研究通过动态吸附平台测定温度为25C、表压为0时的四利活性炭对氙的动态吸附系数,并利用氮气吸附以及扫描电镜对活性炭进行分析表征。结果表明,比表面积为991.9 m~2/g的JH12-16活性炭对氙的动态吸附数最大,且活性炭对氙的动态吸附系数不和比表面积或孔容成正比关系。中孔和大孔对吸附氙只是起着通道作用,最佳吸附氙的孔径在0.55-0.60 nm。     

用于核电站放射性惰性气体处理的常温活性炭滞留床研究

本文介绍了用于核电站放射性惰性气体处理的常温活性炭滞留床，试验结果表明，１１种市售国产活性炭大多数可用于常温活性炭滞留床，其中椰壳０１、０２炭，果壳１１、１２炭较好，滞留床吸附性能的主要影响因素包括：气流比速、压力、温度、活性炭含水量。设计的滞留床具有以下特点；常温操作，设备与操作过程较简单，操作压力低，比较安全；炭床体积小，活性炭更换次数少。     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

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Radioactivity levels in soil of salt field area,Kelambakkam,Tamilnadu,India

Soil samples in and around salt field area have been analyzed for natural radioactivity concentration using gamma ray spectrometer.The activity concentration for ~(232)Th,~(238)U and ~(40)K are ranged from 27.88 to 45.27 Bq/kg, from BDL to 13.30 Bq/kg,and from 135.54 to 381.28 Bq/kg,respectively.The measured activity concentrations for these radionuclides were compared with world average activity of soil.The average activity concentration of ~(232)Th in the present study is 1.19 times higher than world median value while the activity of ~(238)U and ~(40)K is found to be lower. The absorbed dose rates due to these radionuclides were calculated.The average absorbed gamma dose rate due to the presence of ~(232)Th,~(238)U and ~(40)K in soil samples is 36.99 nGy·h~(-1).These results indicate no radiological anomaly. The data presented in this study will serve as a base line survey for primordial radionuclides concentration in the study area.     

Non-FDG PET imaging of brain tumors

Due to relatively high uptake of glucose in the brain cortex, the use of FDG PET imaging is greatly limited in brain tumor imaging, especially for low-grade gliomas and some metastatic tumours. More and more tracers with higher specificity were developed lately for brain tumor imaging. There are 3 main types of non-FDG PET tracers： amino acid tracers, choline tracers and nucleic acid tracers. These tracers are now widely applied in many aspects of brain tumor imaging. This article summarized the general use of non-FDG PET in different aspects of brain tumor imaging.     

基于NPL-NMC系统的γ测量子系统的建模与优化

在军控核查中,核部件的质量、丰度、年龄属性需采用无损方法进行核查,NPL-NMC系统是一套利用中子多重性测量核部件质量属性的装置,为建立完善的属性测量系统,还需在NPL-NMC系统的基础上建立γ测量子系统。本文通过设计γ测量子系统在NPL-NMC系统上的布局及对中子屏蔽的优化,使系统能对铀部件的丰度、年龄属性进行测量。模拟计算结果表明,该γ测量子系统能很好地满足军控核查对铀部件丰度、年龄属性测量的要求。     

Improvement of carbon fiber surface properties using electron beam irradiation

Carbon fiber-reinforced advance composites have been used for structural applications,mainly on account of their mechanical properties.The main factor for a good mechanical performance of carbon fiber-reinforced com- posite is the interfacial interaction between its components,which are carbon fiber and polymeric matrix.The aim of this study is to improve the surface properties of the carbon fiber using ionizing radiation from an electron beam to obtain better adhesion properties in the resultant composite.EB radiation was applied on the carbon fiber itself before preparing test specimens for the mechanical tests.Experimental results showed that EB irradiation improved the ten- sile strength of carbon fiber samples.The maximum value in tensile strength was reached using doses of about 250 kGy.After breakage,the morphology aspect of the tensile specimens prepared with irradiated and non-irradiated car- bon fibers were evaluated.SEM micrographs showed modifications on the carbon fiber surface.     

Measurement system for SSRF pulsed magnets

This paper describes the magnetic field measurement system for pulsed magnets in SSRF.The system consists of magnetic probes,analog active integrator,oscilloscope,stepper motor and a controller.An application pro- gram based on LabVIEW has been developed as main control unit.After the magnetic field mapping of a septum magnet prototype,it is verified that the test results accord with the results of theoretical calculation and computer simulation.     

旁路阀调节对高温气冷堆闭式布雷顿循环瞬态特性影响研究

闭式布雷顿循环是第4代高温堆核能系统的关键技术之一,其典型的动态过程是旁路阀调节。为分析这一过程,建立了循环中关键部件的动态模型,其中压气机在径向平衡模型基础上耦合了对附面层发展的预测,兼顾了计算效率与准确性;换热部件模型基于双曲型守恒律方程,对工质的热物性和参数的快速变化有较好的适应性。在此基础上根据回路的质量守恒和压力平衡原则将各部件的模型耦合,建立了系统的动态模型。由于旁路阀调节是氦气透平发电系统主要的功率快速调节手段,瞬态效应较为显著,以模块式高温气冷堆（HTR-10GT）旁路阀开启后的过渡过程作为算例,分析了主要循环参数的响应特性,并通过分析,给出了降低输出功率的机制。计算结果表明：系统的容积惯性对旁路阀调节的响应速度影响较大,而阀门的开度则决定了系统在末态的输出功率;回热器的温度冲击现象可能发生在调节过程中,但可通过两旁路阀联动的方式缓解;反应堆出口温度变化幅度很小,因此反应堆模型的准确程度对结果基本无影响。     

CEFR 100%额定功率运行汽轮机发电能力分析

中国实验快堆(CEFR)首次100%额定功率发电运行中,实际电功率较设计值相差较多。为判断影响机组实际发电能力的主要原因,以现场采集的运行数据和汽轮机厂商提供的设计资料为基础,进行了相应的计算分析。对汽轮机内效率进行修正,绘制汽轮机近似热力过程曲线,并通过实测的各段抽汽压力,在热力过程曲线上获得抽汽焓值;利用换热器的能量守恒和流量守恒的基本方程进行除氧器和各加热器的热平衡计算,获得各段抽汽的流量;利用汽轮机的功率计算方程,得到汽轮机发电功率的计算值。通过计算值与实际值的比较分析,得出主蒸汽参数不达标是影响CEFR汽轮机发电能力的主要因素。