基于CBS的人体安检图像组合增强方法

在X射线人体康普顿背散射(CBS)安检系统中,图像的清晰度对于识别隐匿在人体上的违禁品非常重要.根据人体CBS图像的特点,从人眼视觉感知的特点出发,提出了一种图像组合增强方法,明显改善了图像质量,获得了层次清晰、轮廓分明、背景均匀的CBS图像.     

阵列背散射成像中图像数据校正的仿真研究

阵列背散射成像是一种有发展潜力的辐射成像技术。与透射成像相比,阵列背散射图像数据校正较为复杂,涉及数据不一致性校正和系统响应曲线调整两个方面。基于阵列背散射成像系统的特点分析,应用蒙特卡罗仿真实验方法,归纳总结出1种增益归一化与斜率调整相结合的阵列背散射图像校正方法。利用该方法对仿真实验得到的数据进行校正,获得了较好的校正效果。     

秦山重水堆CPPF因子的修正

随着机组的老化,秦山重水堆堆芯燃料冷却能力下降,需要定期对区域超功率保护(ROP)停堆整定值(TSP)进行完整分析,以确保反应堆运行安全。分析结果通过修正用于停堆系统ROP探测器校正的通道功率峰值因子(CPPF)进行应用,并实现对热工水力、压力管蠕变等参数的持续跟踪。本文重点分析CPPF的ROP相关参数修正方法,并通过1号机组实际运行数据,分析修正前后相关参数的对比,以及修正后对换料等机组运行产生的影响,最后总结可以采取的运行优化和应对措施。     

热释光测量中的数据分散性

分析了热释光测量方法产生数据分散性的主要原因.选用一致性较好的GR200A型LiF(Mg,Cu,P)热释光探测器元件,在RGD3型热释光仪和BG2006释光仪上获取了测试数据并进行比较.针对因热传导差异产生的测量数据的分散性问题,提出了减小数据分散性的措施和建议.     

α能谱法测量222Rn/220Rn气体活度浓度过程中的拖尾修正

α能谱法是环境中²²²Rn/²²⁰Rn气体活度浓度测量的重要方法之一。吸收层及探测器能窗等导致的α能谱低能拖尾是影响²²²Rn/²²⁰Rn活度浓度准确测量的重要因素。为修正α能谱法对²²²Rn/²²⁰Rn气体活度浓度的测量结果,本文从原理上探讨了拖尾形成的原因及其对²²²Rn/²²⁰Rn气体活度浓度测量的影响。结合商用测氡仪,实验修正了²²²Rn/²²⁰Rn气体活度浓度的测量结果,对修正前后的结果进行了实验比对。研究表明,经准确刻度后的修正因子和刻度因子能很好地用于修正²²²Rn/²²⁰Rn气体活度浓度的测量结果,保证了测量结果的准确性。建议在对α能谱法测量²²²Rn/²²⁰Rn气体活度浓度的仪器进行刻度检定时,必要情况下需对拖尾修正因子和刻度因子进行适当刻度。     

蒙特卡罗方法在ADS屏蔽计算中的应用

利用蒙特卡罗方法计算了新一代核能系统加速器驱动系统(ADS)中质子束管内的中子归一化注量率分布以及通过质子束管入口和其它外表面逸出的归一化中子注量率,得出了一些对ADS系统的设计有重要意义的结论。     

Bootstrap非参数法在γ能谱处理中的应用

为减少统计涨落对能谱测量的影响-提高测量的精确性,利用数理统计理论,研究Bootstrap非参数法的基本原理及程序流程,并将其应用于实验室γ能谱数据处理中。用NaI(T1)探测器测量~(241)Am、~(137)Cs、~(60)Co的γ能谱,对短时间测量的γ能谱采用Bootstrap非参数法进行处理-与同样条件下长时间测量的γ能谱数据进行对比,吻合度较高,得到了满意的结果,为实现γ能谱在低活度水平的快速测量提供了可行的技术方案。     

水平衡法与高温转化法在矿泉水氢氧稳定同位素测定中的应用

为了鉴别不同品牌矿泉水标注水源地信息真伪,对11种不同品牌饮用水的氢氧稳定同位素(δD和δ¹⁸O)进行测定。结果表明,水平衡法(GasBench-IRMS)和高温转化法(TC/EA-IRMS)的测定结果一致性较好,两种方法测定6种不同饮用水的δD和δ¹⁸O的平均差异分别为(0.6±1.59)‰和(0.02±0.13)‰。水平衡法需要较长的制备和测定时间,但δD和δ¹⁸O的测定精度明显优于高温转化法。11种饮用水δD和δ¹⁸O变化范围较大,其δD和δ¹⁸O受不同品牌饮用水的水源地降水影响形成明显的地域性。虽然无法区分矿泉水是否由其他类别饮用水伪造,但δD和δ¹⁸O可以为特定区域(如高海拔与沿海地区)以及产地相近的矿泉水水源地鉴别提供依据。     

水平衡法与高温转化法在矿泉水氢氧稳定同位素测定中的应用

为了鉴别不同品牌矿泉水标注水源地信息真伪,对 1 1 种不同品牌饮用水的氢氧稳定同位素(δD和δ18 O)进行测定.结果表明,水平衡法(GasBench-IRMS)和高温转化法(TC/EA-IRMS)的测定结果一致性较好,两种方法测定 6 种不同饮用水的δD 和δ18 O的平均差异分别为(0.6 ± 1.5 9 )‰和...     

中国实验快堆k_(eff)计算值对核数据的灵敏度和不确定度分析

为分析核数据引起的中国实验快堆(CEFR)keff计算值的不确定度,推导出基于一阶微扰方法的keff灵敏度计算式,基于多群节块扩散理论对keff的灵敏度计算式进行离散求解,并在快堆中子学分析系统(NAS)的基础上开发不确定度分析程序SUAPH,并对程序进行验证。根据现有协方差数据,采用SUAPH完成CEFR首炉堆芯keff的灵敏度和不确定度分析,由核数据引起的CEFR首炉堆芯keff的不确定度约为2.02%。     

Performance evaluation of the backprojection filtered （BPF） algorithm in circular fan-beam and cone-beam CT

In this article we introduce an exact backprojection filtered （BPF） type reconstruction algorithm for cone-beam scans based on Zou and Pan＇s work. The algorithm can reconstruct images using only the projection data passing through the parallel PI-line segments in reduced scans. Computer simulations and practical experiments are carded out to evaluate this algorithm. The BPF algorithm has a higher computational efficiency than the famous FDK algorithm. The BPF algorithm is evaluated using the practical CT projection data on a 450 keV X-ray CT system with a flat-panel detector （FPD）. From the practical experiments, we get the spatial resolution of this CT system. The algorithm could achieve the spatial resolution of 2.4 lp/mm and satisfies the practical applications in industrial CT inspection.     

近场编码孔径成像的数据校正

介绍了修正的均匀冗余阵列(MURA)编码孔径成像及其图象重建的基本原理.从理论上分析和探讨了编码孔径应用在近场核医学成像时,cos3 θ项带来的近场效应及其校正方法,并通过计算机模拟实验验证了这种矫正方法的正确性和可靠性.     

Pulse pileup correction in the presence of a large low-energy background

Pulse pileup correction is required for high count rate experiments. Spectral distortion due to pileup is strongly affected by the distribution of pulse heights. Methods used to limit the digitization rate – including energy thresholds and coincidence requirements – adversely affect attempts to correct the pileup-induced distortion. A simplified method for correcting the spectral distortion using a general pileup function can be used when the spectrum is dominated by a low-energy background. This method has particular relevance for nuclear resonance fluorescence experiments.     

射线检测技术在石油化工装置中的应用

对γ射线扫描技术和中子背散射技术的基本原理以及在石油化工装置中的主要应用进行了简要介绍。重点介绍了γ射线扫描技术在塔器操作上的典型工业应用，和中子背散射技术在测量工业气液分离器、加氢反应器料位的应用。这些应用情况表明，利用射线检测技术不仅可以准确诊断石油化工设备的故障，还可以用于装置的运行状况评价、操作优化、挖潜增效以及实现预测维修等多个方面。因此，该技术在石油化工领域具有广泛的应用前景。     

Accurate quantitative CF-LIBS analysis of both major and minor elements in alloys via iterative correction of plasma temperature and spectral intensity

The chemical composition of alloys directly determines their mechanical behaviors and application fields.Accurate and rapid analysis of both major and minor elements in alloys plays a key role in metallurgy quality control and material classification processes.A quantitative calibration-free laser-induced breakdown spectroscopy (CF-LIBS) analysis method,which carries out combined correction of plasma temperature and spectral intensity by using a secondorder iterative algorithm and two boundary standard samples,is proposed to realize accurate composition measurements.Experimental results show that,compared to conventional CF-LIBS analysis,the relative errors for major elements Cu and Zn and minor element Pb in the copperlead alloys has been reduced from 12％,26％ and 32％ to 1.8％,2.7％ and 13.4％,respectively.The measurement accuracy for all elements has been improved substantially.     

A novel algorithm for transmission image reconstruction of tomographic gamma scaners

<正>It is difficult to develop image reconstruction algorithms for tomographic gamma scanning based on drummed radioactive residues or wastes.In this paper,a novel reconstruction algorithm of transmission image for tomographic gamma scanning is proposed.It is based on the conventional transmission equation and equivalent gamma-ray track length modified by a Monte Carlo method.The algorithm is implemented by simulating the samples on the established platform.For the verification experiments of the algorithm,several cubic voxel samples were designed and manufactured.Experimental tests were conducted.The tomographic gamma scanning of transmission images is compared with the linear attenuation coefficients by the simulated values and experimental data with the algorithm and the reference values.The results show that the absolute relative errors of the reconstructed images are less than 5%.     

Availability of MCNP & MATLAB for reconstructing the water-vapor two-phase flow pattern in neutron radiography

The China Advanced Research Reactor (CARR) is scheduled to be operated in the autumn of 2008. In this paper, we report preparations for installing the neutron radiography instrument (NRI) and for utilizing it efficiently. The 2-D relative neutron intensity profiles for the water-vapor two-phase flow inside the tube were obtained using the MCNP code without influence of γ-ray and electronic-noise. The MCNP simulation of the 2-D neutron intensity profile for the water-vapor two-phase flow was demonstrated. The simulated 2-D neutron intensity profiles could be used as the benchmark data base by calibrating part of the data measured by the CARR-NRI. The 3-D objective images allow us to understand the flow pattern more clearly and it is reconstructed using the MATLAB through the threshold transformation techniques. And thus it is concluded that the MCNP code and the MATLAB are very useful for constructing the benchmark data base for the investigation of the water-vapor two-phase flow using the CARR-NRI.     

大型工业CT中X射线硬化校正的一种方案

介绍了大型工业CT的一种多色X射线硬化校正方法。该方法利用一个标准函数将多色投影值转化为单色投影值。定义了一些参数来证明该方法适用于大型工业CT的硬化校正,并对参数进行了优化。通过模拟实验,这种校正方法在不需要先验知识,使用单色重建算法的前提下,仍能大大减小CT重建图像的硬化伪像。     

An interpretation of Fukushima-Daiichi Unit 3 plant data covering the two-week accident-progression phase based on correction for pressure data

Water columns were adopted in the pressure measurement system of Fukushima-Daiichi Unit 3 to compensate for evaporation/condensation during normal operation. Some of these water columns evaporated partially during the accident condition jeopardizing correct understanding on actual pressure. Through inter-comparison of reactor pressure vessel (RPV) and suppression chamber (S/C) pressures with drywell (D/W) pressure, such water-column-change effect was evaluated. From this evaluation, correction for the specific effect was developed for RPV and S/C pressure data. With this corrected pressure, slight pressure difference among RPV, S/C, and D/W during the accident transient was evaluated. This information of pressure difference was then integrated with other available data, such as water level, containment atmosphere monitoring system, and environmental dose rate in the Fukushima-Daiichi site, into an interpretation of accident progression behavior focusing on RPV and primary containment vessel pressurization/depressurization and radioactive material release to environment. It is suggested that dryout of in-vessel and ex-vessel debris was likely causing pressure decrease on one hand, and S/C water poured into pedestal heated by relocated debris was a likely cause of pressurization on the other hand. Cyclic reflooding of pedestal debris and its dryout was likely leading to the cyclic pressure change lasting several times until the final debris reflooding.