新型放射性气溶胶连续监测仪的研制

针对环境低水平气溶胶连续监测中常常遇到的问题和难点,本项目采用自主研发的一种新型薄膜滤纸,及一种双工位取样测量装置(中国实用新型专利),并采用甄别能量的假符合方法(中国发明专利)等关键技术,研发了一种新型气溶胶连续监测仪。该仪器主要性能指标突出表现为其探测下限:当氡浓度最高为102~103Bq/m3时,对铀和钚的探测下限可达到0.05~0.08 Bq/m3,对β的探测下限为5~10 Bq/m3,最长测量时间为40~60 min,并且能实现实时在线连续监测。因此,该仪器可用于地下洞库或坑道内高氡环境中,快速准确并连续测量出低水平气溶胶浓度,也可用于核电站、放射性工作场所、核事故应急以及气态排出流中放射性气溶胶的快速连续监测。     

基于双闪烁体探测器的四路低本底αβ测量仪研制

介绍了一种基于双闪烁探测器的低本底αβ测量仪,该仪器可用于低水平αβ样品测量,并可区分αβ粒子。阐述了αβ双闪烁体探测器的主要参数和先进的数字化电路设计思路,给出了仪器αβ本底水平、串道比、αβ效率等物理性能的测试指标。描述了仪器软件自动坪曲线测量、自动刻度等功能的设计。     

低本底自动液体闪烁计数器

~(14)C年代测量法是同位素年代测量中精确性好的一种方法。目前~(14)C实验室广泛采用液体法。但国内外商品液体闪烁计数器由于本底高而不能直接用于低水平测量。经采用加厚屏蔽,线路改进等措施后的FJ-353液体闪烁计数器的本底为6cpm,效率70％,优值820。为适应地学、考古、环保、海洋等学科中探测低水平~3H、~(14)C的需要,我们参考YSJ-76液闪研制了YSJ-SH79低本底自动液体闪烁计数器。     

参加全国液体闪烁计数器测量~3H活度比对的结果

中国计量科学研究院于1988年11月至1989年10月组织了由国内28个实验室参加的液体闪烁计数器测量~3H、~(14)C 活度的比对活动,本文简要介绍本实验室参加该次比对中~3H 源活度测量的结果。采用的仪器为美国 Beckman 公司的 LS-9000型液闪仪和 Packard 公司的2250 CA 型液闪仪,用 Beckman~3H 淬灭系列校正源(简称 B 源)和 Packard ~3H 淬灭系列校正源(简称 P 源)分别采用 tSIE 法(在2250CA 型液闪仪上)、H~#法和 SCR 法(在 LS-9000型液闪仪上),测量了~3H 比对源的活度。结果表明,用 B源作淬灭校正时由三种不同方法所得的测量值与参考值(4933.5 Bq)的相对偏差分别为-0.89、-2.57和-0.83%;用 P 源作淬灭校正时所得的相应的相对偏差分别为-4.45、-5.75和-1.78%。     

ZF-102S工具污染监测仪的硬件设计

本文介绍了ZF—102S工具污染监测仪的组成、电路原理设计和主要性能测试。该仪表选用两套大面积塑料闪烁体+PMT作为探测器,采用智能单向测量流程,测量腔室外加铅屏蔽,可在复杂环境下有效测量待测工具的γ放射性水平。试验结果表明:在条件为本底0.2μGy/h,测量时间60 s,置信度为95%,仪器最低可探测限小于100 Bq(参考源~(60)Co)。仪表具有长短工具两种测量模式,大容量蓄电池在仪器断电后持续工作超过3 h。     

Hidex 300SL液闪装置测量低水平氚水活度的参数优化

Hidex 300SL是基于三管符合计数/两管符合计数(TDCR)方法绝对测量低水平氚水活度的液闪装置。本工作基于该装置对标准非淬灭氚水样品进行测量研究,明确了系统的探测效率与TDCR的关系;讨论了该装置的测量模式、符合时间等参数对计数率、衰变率和TDCR的影响;并对仪器的运行参数进行选择优化,在"H-3"测量模式及35ns的符合时间窗下,系统对3 H的探测效率达73.2%,衰变率稳定性好于0.47%;最后对空气本底样品进行测量,评估了该装置对氚水样品的探测下限,为后续环境低水平样品的精确测量提供有益参考。     

双标记样品液体闪烁测量法及使用电子计算机进行数据处理

本文报导了~3H和~(32)P、~3H和~(14)C双标记样品液体闪烁测量法,使用仪器为Beckman LS8100和NE8312液体闪烁谱仪。由双标记样品在仪器不同计数道中计数效率与H-数或外道比值R的关系,推导出计算双标记样品dpm的公式,所得数据用Wang 600型台式电子计算机处理,结果证明:这种测量和计算方法适用于双标记样品,并能得到满意的结果。     

液体闪烁核活度计量仪

本文描述用液体闪烁计数法直接测定α、β发射体溶液放射性活度的计量仪器。该仪器包括三个光电倍增管的符合探测器和三个输出计数道;以三重对两重符合计数率之比(TDCR)为猝灭参数,通过外推效率曲线至TDCR=1直接得到核素的活度。该仪器用于放射性活度绝对测量至少有两个突出的优点:1.精确度较高,对~3H、~(63)Ni和~(14)C等多种β、α核素其总测量不确定度(3σ)在0.5—1.5％;2.操作简便,测量迅速。     

时间间隔分析法低活度~(220)Rn测量装置设计

介绍了时间间隔分析法测量低水平活度~(220)Rn的装置的设计,该装置基于STM32,由FD-125闪烁室探测器、主放大器电路、信号整形电路及系统软件结构组成。仪器设计根据~(220)Rn级联衰变特性,采用时间间隔分析法对采集到的核脉冲时间序列进行时间间隔分析。开展了对标准~(220)Rn源单独及混合场的测量实验研究,其结果相对偏差分别在5%、9%以内。     

探测超微发光的FJ—2115液体闪烁计数器

液闪是一种用于测量低能β(如~3H和~(14)C等核素)放射样品活度的仪器。具有4π空间探测能力,样品自吸收少、测量时间短、灵敏度高,样品制作方便及样品重复测量方便等优点。 放射性样品放出β射线与闪烁溶液作用,经溶剂、溶质分子的能量接收传递和激发闪烁体分子退激时产生荧光光子,它再由光电倍增管的换能与放大最后产生电脉冲,脉冲数与光量子的产量成正比,液闪仪器是用来分析记录这种成正比例关系物理量的核电子学系统。     

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.     

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.     

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。     

Activity level of gross α and gross β in airborne aerosol samples around the Qinshan NPP

The monitoring results of gross α and gross β activity from 2001 to 2005 for environmental airborne aerosol samples around the Qinshan NPP base are presented in this paper. A total of 170 aerosol samples were collected from monitoring sites of Caichenmen village, Qinlian village, Xiajiawan village and Yangliucun village around the Qinshan NPP base. The measured specific activity of gross α and gross β are in the range of 0.02 ～ 0.38 mBq/m3 and 0.10 ～ 1.81 mBq/m3, respectively, with an average of 0.11 mBq/m3 and 0.45mBq/m3, respectively. They are lower than the average of 0.15 mBq/m3 and 0.52mBq/m3, of reference site at Hangzhou City. It is indicated that the specific activity of gross α and gross β for environmental aerosol samples around the Qinshan NPP base had not been increased in normal operating conditions of the NPP.     

Simulation of the mixing process in FCIs with hydrodynamic fragmentation model

Fuel Coolant Interactions (FCIs) are important issues in nuclear reactor severe accident analysis. In FCIs, fragmentation model of molten droplets is a key factor to estimate degree of possible damage. In this paper, the mixing process in FCIs is studied by the simulation of MIXA experiment with hydrodynamic fragmentation model. The result shows that hydrodynamic fragmentation model underestimates the fragmentation rate of high temperature molten droplets under the condition of low Weber numbers. It is concluded that models based on thermal fragmentation mechanism should be adopted to analyze the FCI process and its consequence.     

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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NUCLEAR SCIENCE AND TECHNIQUES Volume 25,2014

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Probing stray surface electric patch fields using Rydberg atoms

The stray electric “patch” fields present at a Au(1 1 1) surface are investigated by studying the ionization of Rydberg atoms incident at near-grazing angles. Measurements of the threshold conditions required to observe the resulting ions are used to estimate how large such stray fields can be. The data show that the stray fields can be sizeable, as large as ∼10³ V cm⁻¹ 100 nm from the surface and ∼20 V cm⁻¹ 500 nm from the surface, and illustrate the potential of Rydberg atoms for detecting and characterizing surface electric fields.