行李放射性测控装置对~137Cs放射源活度响应及其非线性的测量与探讨

该文介绍了行李放射性测控装置对^137Cs放射源活度响应的校;隹方法,利用点状放射源的活度与照射距离的平方成反比的核物理特性,测量行李放射性测控装置对某指定探测点的活度响应,根据一系列的活度响应值计算出行李放射性测控装置对^137Cs放射源活度响应的非线性。试验结果表明,活度响应是反映探测器对放射性辐射探测能力的重要参数,必须在规定的测量条件下进行测量。     

车载式放射性探测系统的性能与检测方法

介绍了车载式放射性探测系统的主要类型及其性能特点,分析了IAEA技术报告与核工业行业标准提出的计算、标定方法及其关键因素和存在的问题,探讨了影响车载式放射性探测系统性能的主要参数及对检测设备的要求。     

不同能量放射性核素在井型电离室中轴向响应的实验

为了验证井型电离室对不同能量放射性核素溶液轴向响应及其对放射性活度测量的影响,利用CRC-25R型放射性活度计,将~(125)I、~(131)I、~(18)F、~(137)Cs四种不同能量的放射性核素溶液源在井型电离室内沿中心轴向上移动,测量其放射性活度值的变化,得到轴向位置不同处放射性活度计示值与井型电离室底部的参考示值之比的变化规律,分析轴向响应对不同能量放射性核素放射性活度测量的影响。实验结果表明,不同能量放射性核素溶液其井型电离室轴向响应有明显差异,γ射线能量越高,放射性核素的放射性活度示值极大值的轴向位置越接近井底参考位置;对于γ射线能量较低的~(125)I核素,放射性活度示值极大值的轴向位置接近于井型电离室中部,其示值极大值与参考示值的相对偏差达到了8%,而接近井口处位置时放射性活度计示值与井底参考位置的相对偏差仅-2.9%。     

日盲型紫外探测系统的探测距离模型及实验研究

日盲区的存在,给近地探测240～280 nm范围的紫外辐射提供了良好的背景.本文设计了一套成像型日盲紫外探测实验系统.从辐射能量传递的角度出发,借鉴凝视型红外搜索跟踪系统的分析方法,推导了紫外探测系统的探测距离模型.以氘灯为探测目标,在三种典型天气条件下对实验系统进行了探测距离实验.结果表明,采用探测距离模型的计算值和实验测量值有较好的吻合,为紫外探测系统的设计和性能评估提供了重要的理论和实验基础.     

井型电离室轴向响应对放射性活度测量的影响

用~(137)Cs核素溶液实验测量最常用两种型号放射性活度计的井型电离室轴向深度与活度测量示值的关系,从中反映响应灵敏度的轴向变化情况。CRC-25R型活度计响应最灵敏区域为井型电离室底部向上5 cm范围内,区域内活度计示值变化为0.3%;RM-905a型活度计响应最灵敏区域为井型电离室内距底面9～11 cm范围内,区域内示值变化小于1%。     

放射性薄层扫描仪检测用参考源研制与性能测试

采用半衰期较长、能量与PET-CT常用核素18F接近的137Cs核素,设计制作用于放射性薄层扫描仪检测的参考源,其中纯度检测参考源的活度量级为105 Bq,最小分辨距离检测参考源活度量级为104 Bq.实验表明:该参考源适用于检测放射性薄层扫描仪.检测结果显示,对于活度所占比例相差较大的样品,放射性薄层扫描仪的测量准确...     

测量β放射性活度的TDCR效率计算技术绝对测量方法

利用三管液闪探测系统实现ＴＤＣＲ计数效率计算技术,并完成２０４Ｔ１活度的绝对测量     

脉冲中子、伽马探测系统性能表征与设计技术

探测系统是获取辐射场特征信息的核心器件,是实施脉冲辐射探测的关键和技术基础,其性能直接决定测试数据的质量和测试方法的选择.对影响脉冲辐射探测的性能指标进行系统描述、表征是探测系统设计、研制、实际应用和综合性能评价的基础.用于复杂能谱脉冲中子、伽马混合辐射场时间谱、强度谱测量的探测系统,主要性能包括探测灵敏度、时间响应、能量响应、线性电流和中子、伽马分辨能力等指标参数,这些参数的获得与实现,需要根据中子、伽马射线与物质相互作用的基本原理,构建相应的探测结构和技术原理.在设计上,综合权衡能量收集和电荷收集方式选择、几何效率完备和高信噪比结合、信号响应和直照响应分离、探测效率与时间特性兼顾、综合性能与使用可靠性一致等设计原则,综合应用这些原则构成了探测系统设计方法.     

标准测氡仪的量值溯源方法研究

研究了利用氡活度绝对测量装置制备高准确度标准氡源的方法,得到了活度扩展不确定度为0.8%(k=2)的量传用氡源。依据计算标准氡体积活度的基本原理,对用于氡源活度量传所配套的小氡室的有效体积进行了校准,其有效体积的扩展不确定度为0.46%(k=2),对一般氡标准装置(标准氡室)所用的参考仪器(AlphaGUARD型标准测氡仪)进行校准,得到其平均体积活度响应为1.01,体积活度响应的扩展不确定度为3.2%(k=2)。     

基于静电感应的引信目标探测传感器研究

针对复杂干扰环境中传统引信目标探测系统无法稳定工作的问题,探讨了一种新型目标探测体制.基于静电感应基本理论,建立了静电引信探测传感器模型,设计和制作了高灵敏度的静电引信探测传感器和微弱信号检测电路.在实验室环境条件下对探测系统进行实验研究,结果表明:理论分析和实验结果趋于一致;输出电压与系统增益、目标电荷、相对速度和距离相关;所设计电路能够满足引信的探测要求,可对静电引信目标探测系统在复杂环境下的工程化设计提供参考.     

Lung counting: comparison of detector performance with a four detector array that has either metal or carbon fibre end caps, and the effect on mda calculation

This study described the performance of an array of high-purity Germanium detectors, designed with two different end cap materials-steel and carbon fibre. The advantages and disadvantages of using this detector type in the estimation of the minimum detectable activity (MDA) for different energy peaks of isotope (152)Eu were illustrated. A Monte Carlo model was developed to study the detection efficiency for the detector array. A voxelised Lawrence Livermore torso phantom, equipped with lung, chest plates and overlay plates, was used to mimic a typical lung counting protocol with the array of detectors. The lung of the phantom simulated the volumetric source organ. A significantly low MDA was estimated for energy peaks at 40 keV and at a chest wall thickness of 6.64 cm.     

Minimum detectable dose as a measure of bioassay programme capability

This paper suggests that minimum detectable dose (MDD) be used to describe the capability of bioassay programmes for which intakes are expected to be rare. This allows expression of the capability in units that correspond directly to primary dose limits. The concept uses the well established analytical statistic minimum detectable amount (MDA) as the starting point, and assumes MDA detection at a prescribed time post-intake. The resulting dose can then be used as an indication of the adequacy or capability of the programme for demonstrating compliance with the performance criteria. MDDs can be readily tabulated or plotted to demonstrate the effectiveness of different types of monitoring programmes. The inclusion of cost factors for bioassay measurements can allow optimisation.     

CsI(Tl)/plastic phoswich detector enhanced in low-energy gamma-ray detection

A phoswich detector composed of a thin plate CsI(Tl) scintillator and a plastic scintillator (BC-400) has been designed and evaluated in order to improve the sensitivity in the low-energy region of a large-area plastic scintillation detector. This newly designed phoswich detector can be applied to both gross gamma measurement and energy spectrometry for low-energy gamma-ray emitters. Judging by estimations of minimum detectable activity, the lower measurable energy of a large-area plastic scintillation detector can be expanded down to a few tens of keV by adding a thin plate CsI(Tl) scintillator.     

Sensitivity of a low energy Ge detector system for in vivo monitoring in the framework of ICRP 78 applications

In in vivo detection of internal contamination by actinides the minimum detectable activities (MDAs) correspond to significant doses, so the sensitivity of the detection system is the key to establishing adequate individual monitoring programmes for internal exposure to these radionuclides. The whole body counting (WBC) faculty at CIEMAT uses a low-energy Ge detector system with different available counting geometries to estimate the retention of actinides in the lungs and evaluate 125I in thyroid and 241Am in bone (skull and knee). A study of the factors and uncertainties involved in estimations of MDA is presented for lung and thyroid monitoring. The dependence of detection limits on counting efficiency in the measurement of low-energy emitters in the lungs has been carefully studied, carrying out a comparison among different biometric equations obtained by ultrasound techniques for estimations of chest wall thickness. Dosimetric implications of the estimated MDAs are taken into account in the framework of ICRP 78 application and considering Spanish regulations. The main interest in lung measurements is for the assessment of occupational exposure. This work confirms the low-energy Ge detector system to be an adequate in vivo technique for the routine monitoring of internal exposure to most insoluble uranium compounds (detection of 3% enriched uranium in lungs), and also to be useful in special monitoring programmes or in the case of incidents when the detection of 241Am is required.     

Minimum detectable annual dose calculation for routine individual monitoring programme in case of plutonium and uranium contamination of the workplace

An example of a numerical method application for minimum detectable annual dose calculation that can be guaranteed by the operating monitoring programmes for plutonium and uranium is presented. The method analyses the frequency distribution for a total number of counts obtained in n measurements performed during n monitoring intervals that are inside the calendar year. Urine sample radiometric measurement technique for plutonium and uranium operating monitoring programmes is investigated, showing dependences of the detection limits on the frequency of measurements, on number of calendar years under observation and on the activity median aerodynamic diameter (AMAD). Only a probability density function (PDF), for the background number of counts, stochastic variability of urine excretion and uncertainty of the intake pattern were taken into account as the main variables influencing the calculated detection limits. But there is no limitation for the proposed method to include the variability of other influencing model parameters in the calculation procedure.     

误差白化与Kalman滤波的微硅加速度传感器动态补偿

通过模型参考的系统辨识方法建立微硅加速度传感器的动态补偿器。由于测量噪声和补偿器对传感器的频带扩展,使得补偿器的输入/输出信号存在严重的噪声干扰。在噪声干扰下,采用均方误差为代价函数的系统辨识方法,无法得到补偿器参数的无偏估计。补偿器参数的偏差和传感器频带的扩展将会使补偿器的输出信号出现严重失真和高频噪声干扰。为解决噪声对硅加速度传感器的动态补偿的影响,研究了一种新的动态补偿方法,该方法采用误差白化为代价函数的系统辨识方法得到补偿器的参数,可消除补偿器的参数在估计中的测量噪声影响,并通过卡尔曼实时滤波减小因传感器频带扩展所产生的高频噪声干扰。     

气载放射性碘监测设备的校准

介绍一种气载放射性碘监测设备校准方法,用Na131I放射性溶液与硫酸铁反应产生气态碘,并采集至源载体内;在确定条件下以实验方法测定高纯锗γ谱仪对碘-131放射性参考源的探测效率,据此对碘-131标准源定值,用以校准气载放射性碘监测设备的参考响应。     

Estimation of measurement uncertainties using virtual fringe projection technique

One of the main tasks of the quality test is the inspection of all relevant geometric parts related to the predefined tolerance range, whereas the uncertainty of measurement has to be less than the tolerance range. The reachable uncertainty of measurement can be determined using method A of the ISO Guide to the Expression of Uncertainty in Measurement (GUM), which is expensive and time consuming and has to be carried out for each individual metrologic case. Furthermore, it is possible to check the suitability of the measurement system for the planned inspection using virtual measurement techniques and therewith to reduce the time and money spent. This means that the uncertainty of measurement is estimated using method B of the GUM. In this paper, a virtual fringe projection system is used for the estimation of the uncertainty of measurement, which is compared with the uncertainty of measurement determined with a real measurement system using method A of the GUM. With the presented method, it is possible to calculate an optimal measurement position within the measurement volume, based on a minimum uncertainty of measurement. Thereby, the influence of the operator related to the uncertainty can be significantly reduced.     

An optical fiber radiation sensor for remote detection of radiological materials

This paper demonstrates the feasibility of a portable radiation sensor system that uses the pulsed optically stimulated luminescence technique to remotely interrogate an aluminum oxide (Al/sub 2/O/sub 3/:C) radiation sensor via an optical fiber. The objective is to develop a system for applications requiring simple and inexpensive sensors for widespread monitoring of ionizing radiation levels, which can be remotely interrogated at regular periods with little or no human intervention and are easy to install, operate, and maintain. Results on the optimization and performance of the system are presented. The current minimum detectable dose is of the order of 5 /spl mu/Gy, which is already satisfactory for applications such as the monitoring of radioactive plumes from radioactive waste sites. We also discuss potential developments that could decrease the minimum detectable dose to allow radiation doses as low as the background level to be measured over short time intervals, making the system more versatile for detecting radiological materials.