高放废液总β放射性活度测量

方法采用塑料闪烁晶体β低本底测量装置直接测定了高放废液样品40 keV以上β射线的总β放射性活度。装置的β效率曲线采用与被测样品相同质量厚度、不同β能量的一系列标准源刻度。样品测量的β放射性对装置的总β效率是根据各个样品的放射性核素组成、各核素β射线能量对应于β效率曲线值以及各核素β放射性活度占样品总β放射性活度的比例加权平均计算求得。在测定样品各核素β放射性活度占总β放射性活度的比例时,方法对具有γ衰变的核素采用直接γ能谱法;对纯β衰变核~(90)Sr-~(90)Y,采用了半衰期近似法;对纯β衰变核~(147)Pm,采用了表观冷却时间近似替代法对高放废液样品测量的不确定度约为±15%。测量结果与化学分离各核素测得的结果在误差范围内符合。     

放射性污染源的调查和检测（四）

9 环境样品的总放射性测量 表征环境样品中核素含量的量是放射性活度,环境样品中的放射性活度是通过测量样品中核素在衰变过程中可能发射出的α、β或β射线获得.如果一个核素衰变过程中发射几种射线,用不同方法对各种射线的测量得到的放射性活度应该是一致的,并无α活度、β活度或β活度之分.不难理解,环境样品的放射性测量工作,除了选择测量仪器和测量方法外,应主要集中在如何把测量得到的信息转换为放射性活度.     

2012年度CTBT放射性核素实验室滤材样品能力验证

为检验核素实验室对大气颗粒物滤材样品中放射性核素的分析能力,全面禁止核试验条约筹委会临时技术秘书处从2000年开始每年组织一次能力验证活动。2012年度核素实验室能力验证活动中,参考样品中添加了24种放射性核素(其中主要核素11种,次要核素13种),北京放射性核素实验室使用相对效率为76%的HPGe?谱仪系统完成了样品的测量分析,准确识别出了11种主要核素和12种次要核素,主要核素活度测量结果准确,由95Nb/95Zr活度比推算的零时与参考值之间相差仅0.03 d。     

放射性核素γ谱分析方法探讨

在实验室仅存在混合刻度源条件下,探讨不同解谱方法对放射性核素活度估算的适用性。本文利用HPGe γ谱仪测量样品,并分别采用效率曲线法和相对比较法来分析样品中~(241)Am、~(60)Co、~(137)Cs、~(40)K核素活度。结果表明,若干扰核素对样品中待分析核素产生的影响可忽略,但对混合刻度源中相应的待分析核素影响较大时,经综合考虑,相对比较法所得结果优于效率曲线法;若干扰核素对样品中待分析核素产生的影响不可忽略,但对混合刻度源中相应的待分析核素影响不大时,与相对比较法相比,效率曲线法占优势。     

2010年度CTBT放射性核素实验室滤材样品国际比对

北京放射性核素实验室参加了全面禁止核试验条约（CTBT）筹委会临时技术秘书处（PTS）组织的2010年度放射性核素实验室气溶胶滤材样品国际比对,从参考样品中分析出20种相关放射性核素,计算得到了这些核素的活度及活度浓度,并推算了零时。PTS反馈结果表明,北京核素实验室核素识别准确,活度、活度浓度计算和零时推算与参考值一致,在此次比对中成绩优异。     

KD-402γ活度仪

随着核技术、核医学的发展,放射性核素应用越来越广泛。使用核素时必须及时而准确地测量其活度,特别是医院需要快速测量核素活度,为此,我们研制了一种操作方便、测量核素种类多、活度量程范围宽并能自动打印的KD-402γ活度仪。     

放射性惰性气体实时测量装置的设计与模拟研究

核反应堆在运行过程中或核应急情况下会产生~(85)Kr、~(133)Xe、~(135)Xe和~(41)Ar等放射性惰性气体,准确测量不同惰性气体的放射性活度对了解反应堆的运行状况和核应急预警均有重要意义。根据各种核素衰变发射的β、γ射线,设计并优化了可用于放射性惰性气体活度实时测量的4π双叠层闪烁体探测器。探测器的内层塑料闪烁体用于测量β射线,外层碘化铯闪烁体(CsI)用于测量γ射线,并通过β-γ的符合测量实现不同放射性核素的分辨及活度测量。针对核电放出的4种主要放射性惰性气体,基于GEANT4(GEometry ANd Tracking 4)模拟库包,研究了塑料闪烁体、CsI厚度及气体采样腔尺寸对不同核素发射的β、γ探测效率的影响;并给出该4π型双叠层闪烁体探测器的优化几何尺寸和相应探测器性能,为后续探测器的制作与测试提供参考。     

液闪测量低能β核素的放射性活度

为了测量缺乏标准溶液的低能弱β放射性样品的活度,采用分布在低能区(0~150 keV)的6种β核素(3H、241Pu、106Ru、63Ni、151Sm和14C)的标准溶液刻度低本底液闪谱仪(Tricarb-3170)的探测效率。在此基础上,拟合出探测效率随淬灭指数和核素平均能量变化的三维曲面。对影响液闪测量的主要因素,如闪烁液、淬灭剂、介质、样品瓶、体积等进行了研究,确定了最佳测量条件。该方法刻度了仪器在整个低能区的探测效率,适用于所有低能β核素活度的快速准确测定。     

内充气正比计数管系统绝对测量^135Xe活度

1996年9月10日联合国大会通过了全面禁止核试验条约(CTBT),稀有气体氙放射性监测是条约国际监测系统中的重要内容,国内外通常采用平面HPGeγ谱仪系统或β-γ符合系统进行监测样品的测量,如何准确刻度系统的探测效率是放射性氙同位素测量的难点.本文阐述了内充气正比计数管系统绝对测量放射性氙活度的原理和方法,在仔细测试内充气正比计数管系统性能基础上,绝对测量了135Xe活度,测量结果为38.87(1±1.0%)Bq/ml.实验证明用内充气正比计数管测量惰性气体氙的绝对活度是可行的,可为放射性核素实验室探测系统提供准确的绝对刻度标准.     

非人类生物辐射剂量评估技术中相关性分析方法的应用

<正>生物辐射剂量评估取决于生物所处环境中放射性核素活度浓度和生物体内核素活度浓度的具体数值和分布状态,这些浓度是由核素在生态环境中沉积、转移、积累所导致的,不同生物、不同核素、不同环境都会产生不同的放射性核素沉积。通过对公开发表的环境测量数据以及研究结果进行分析处理,对某生态环境区域中存在的动植物样品以及环境介质样品中的不同放射性核素活度浓度之     

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.     

Characteristics of pulsed photo-stimulated luminescence and thermoluminescence for the identification of gamma irradiated poultry eggs

Pulsed photo-stimulated luminescence (PPSL) is a simple screening method that can be employed qualitatively at the spot for the detection of eggs treated with ionizing radiation.Due to the variations in the results during storage,the eggs of ostrich,duck,hen,and quail were irradiated to doses of 0,1,2,and 3 kGy.Most of the samples were incorrectly identified during storage after four months of irradiation.Thermoluminescence (TL) technique was also tried by using egg shells in order to confirm the irradiation treatment in eggs.TL glow curves were recorded between the temperatures 50℃to 400℃at the rate of 5°/s for all the control and irradiated samples.On the basis of integrated areas of first glow curves (TL1),the glow curve ratios (TL1/TL2) and the shapes of maxima of TL1, the irradiation treatment of all the eggs was confirmed.Furthermore,the presence of calcite and aragonite minerals that cause the TL signal in the egg shells were studied using X-ray diffraction spectrometry.     

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.     

数字射线扫描成像系统MTF的测试分析

为有效实现数字射线扫描成像检测系统性能的定量分析评价,据此进行检测工艺参数的优化,对数字射线扫描成像检测系统调制传递函数(Modulation transfer function,MTF)进行了测试分析。采用刀口工具、双线型像质计、分辨率测试卡,对系统在不同焦点大小、放大倍数、运动方向的检测情况,分别进行了MTF的测试并进行了比较。结果表明,双线型像质计与分辨率测试卡的测试结果基本一致,但双线型像质计更便于对比度的定量计算;双线型像质计的对比度传递函数近似符合二次曲线,经转换得到的调制传递函数值高于刀口法的测试值,刀口法计算数值偏低的原因在于运动不平稳所带来的不利影响。分析表明,数字射线扫描成像系统性能受到多个因素的共同影响,MTF测试结果可较全面地对影响因素进行定量评价,可用于确定最佳的检测参数或找出等价的参数组合。     

基于物理体模CT图像的1岁儿童体素体模构建

本文介绍了基于1岁儿童物理体模（Model 704-D）的CT图像和中国成年男性参考人体素体模(CRAM)的1岁儿童体素体模（CPP01）的构建,包括通过对物理体模扫描得到OCP01体模（基于儿童物理体模的CT图像建立的一粗略的体素体模）,进而构建和优化CPP01。该体素体模的各器官组织的质量与GBZ/T 200.2-2007所给数据的相对偏差约在5%以内,且其外部轮廓和主要器官的位置与Model 704-D相匹配。