~(137)Cs示踪法研究黄土丘陵区坡面侵蚀空间变化特征

利用放射性同位素示踪技术,对黄土丘陵区不同坡长坡面土壤剖面中137Cs含量测定与分析,研究了坡面土壤侵蚀强度的空间变化特征.结果表明,坡长对坡面侵蚀强度的空间分布有重要影响,坡面侵蚀强度呈波动变化趋势.小流域全坡面水流汇集过程中,净泥沙流失强度随流程的增加先增加后减少.     

BGO矩形探测元探测效率的研究

理论计算了三种不同规格BGO晶体对于^137Cs0．662MeVγ射线的探测效率，并用GEANT4进行了Monte Carlo模拟，计算值与实验中光电倍增管测得的值进行了比较，给出了不同规格晶体对γ射线探测效率的区别，三者趋势基本一致。最后用^133Ba、^22Na、^137Cs和^60Co源测量了BGO探测元的能量线性，三种晶体对^137Cs0．662MeVγ射线的能量分辨分别为18．12％、18．08％和18．12％。     

不同孕期雌性大鼠受137Csγ射线照射后仔鼠脑发育的变化

用^137Csγ射线对孕期分别为第11天和第16天的雌性大鼠进行一次性全身照射,吸收剂量分别为0．2、0．4、0．9、2．0Gy,观察胚胎发育不同时期受^137Csγ射线照射后仔鼠条件饮水反应和大脑海马锥体细胞计数的变化。结果表明,不同孕期的孕鼠受^137Csγ射线照射均可导致仔鼠大脑海马锥体细胞计数和条件饮水反应达标率显著减少,两者的剂量效应关系均可表示为Y=a-b log10D(Y为效应,D为剂量);仔鼠的条件饮水反应达标率与其大脑锥体细胞计数显著相关,且孕期第11天受照射仔鼠的条件饮水反应达标率低于孕期第16天受照射的仔鼠。     

锗γ谱仪110mAg 657.8 keVγ射线符合相加修正因子与137Cs效率的相关性

本文主要介绍获得HPGe γ谱仪对^110mAg 657．8keV γ射线符合相加修正因子c与^137Cs全能峰效率ε的拟合直线回归方程的方法、结果及其验证。用标准^110mAg和标准^137Cs水溶液,各分别制成φ70mm10个不同高度(5～55mm)并保持相同活度的掺标源;根据^137Cs γ射线能量与^110mAg的657．8keV十分接近,利用在HPGe γ谱仪表面测量10个^110mAg掺标源657．8keV γ射线的净计数率n和10个^137Cs掺标源的探测效率ε的实验数据,计算不同源高度的c和ε,经拟合计算得到c=1．111 7．454ε(R^2=0．9915)。在与其他方法获得的c的比较和在比对(灰样)测量的应用中均获得较满意的结果;本拟合方程在一定的误差范围内,可以用到其他基质样品和其他HPGe γ谱仪上。     

压水堆核电站乏燃料元件γ扫描测量

在压水堆核电站乏燃料元件检验中,完成了4根完整元件棒、4根破损元件棒的γ扫描测量,元件燃耗分布在9 600～45 000 MW·d/t(U)之间,获得了完整元件轴向相对燃耗分布、破损元件~(137)Cs分布及迁移流失情况。结果显示,破损元件均存在不同程度的Cs迁移流失,破口处存在~(137)Cs计数突变(降低)。破损元件~(134)Cs/~(137)Cs原子比分布与相邻完整元件基本一致,表明~(134)Cs、~(137)Cs流失比例近似相等,可用~(134)Cs/~(137)Cs原子比表征其相对燃耗分布;破口处可通过低挥发性核素~(154)Eu计数水平判断燃料芯块是否缺失。检验结果可为燃料元件破损原因分析及堆内行为分析提供重要依据。     

用γ射线能谱法测量材料的吸收系数和厚度

采用NaI(T1)闪烁谱仪测全能峰的方法测量了^137Cs和^60Co的γ射线在铅、铜、铝材料中的吸收系数。对^137Cs(0．661MeV)分别为1．213、0．642、0．194cm^-1，与公认值相差均约1％；对^60Co分别为0．674、0．481、0．149cm^-1，与公认值相差均在5％以内。利用铁的吸收系数对其未知厚度进行测量，测量结果的误差均约2％。     

塑料闪烁探测器的γ灵敏度测定

利用^60Co和^137Cs γ辐射源测定了塑料闪烁探测器的γ灵敏度，给出了ST401、STl422和含^6Li(4％)塑料闪烁探测器的测定结果．获得了1．25和0．66MeV的γ灵敏度随闪烁体厚度的变化关系，实验结果与理论计算值在测量不确定度内一致。     

秦山核电基地外围环境水体放射性水平监测

自1992年，浙江省辐射环境监测站对秦山核电基地外围环境放射性水平进行了连续的监督性监测。1992～2004年，基地外围环境水体放射性水平的监测结果表明：秦山核电基地外围地区陆地环境淡水（饮用水、湖塘水、井水）中总α、总β、^90Sr、^137Cs平均浓度分别为67、157、4．4、0．3mBq／L，^3H为1．4Bq／L，雨水中^3H为2．0Bq／L；正常排放下，基地附近海域水样中^90Sr、^137Cs平均浓度分别为1．4、0．7mBq／L，^3H为I．0Bq／L；第一期核电厂三回路冷却水总β、^90Sr、^137Cs平均浓度分别为2．6、4．1、1．0mBq／L，^3H为2．IBq／L，排放口海水^3H平均浓度为1．4Bq／Lo与运行前本底值和对照点监测值相比，秦山核电基地外围环境水体放射性水平在正常波动范围内，基地外围环境陆地淡水和附近海域海水没有受到放射性污染。     

生物样中^90Sr、^137Cs及土壤样中天然铀含量分析对比

本文报道了有环保系统14个环境放射性实验室参加的生物样中^90Sr,^137Cs及土壤样中天然铀含量的分析对比方法及其结果。比对样品包括2种生物样和1种土壤样,其中1种生物样（生物粉碎样）和土壤样来自IAEA的标准参考样,有已知的标准参考值;另1生物样是来处杭州附近茶场真实的环境茶叶时,以各实验室分析的平均值为参考值。以与参考值的偏差范围表示的比对结果如下：1）生物粉碎样：对^90Sr和^137Cs,分别为－15．4％－26．5％和－15.0%--0.4%;2)土壤样;对天然铀为-25.5%-7.3%;3）茶叶样;对^90Sr为－22．7％－19．1％,对^137Cs分散性较大,最大与最小之比约为7。文中指出了一些可能存在明显系统误差的实验室的分析结果。     

γ能谱法分析土壤样品中几种人工放射性核素的活度

采用γ能谱法对一批放射性污染的环境土壤样品进行了定量分析。结果表明，不同磨样条件和样品放置方式对测量结果有一定影响，样品磨样过40目(0．42mm)筛子一般可满足均匀性要求；但^241Am核素在有些样品中的分布很不均匀，平行样品间的差异较大；^241Am主要分布在表面5cm的土层，而^137Cs、^152Eu在20～30cm深的土层仍可探测到。从不同地点所取的土样中^154Eu与^152Eu活度比基本一致，约0．07。     

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.