辐射工作场所改造中的辐射防护与质量控制

在辐射工作场所改造的基础上，总结了改造过程中不同阶段的辐射防护监测、辐射安全管理和质量控制的经验。     

辐射工作场所监督性监测

1 监测内容及方法 2003年对辐射工作场所进行了监督性监测。根据中国原子能科学研究院常规监测计划要求,对我院科研、生产、运行及技术服务过程中一切产生辐射的工作场所进行监督性测量。监测的主要内容有:辐射工作场所中X、γ及中子剂量率的监测;α、β表面污染的监测;气溶胶     

2008年度中国原子能科学研究院辐射工作场所监督性监测

1监测目的和内容 2008年度,根据中国原子能科学研究院常规监测计划要求,辐射安全研究部辐射监测与评价研究室现场辐射监测组对我院的辐射工作场所（监督区）进行了监督性监测。     

2007年度全院辐射工作场所监督性监测

1监测目的和内容 2007年度，根据中国原子能科学研究院常规监测计划要求，辐射安全研究部辐射监测与评价研究室现场辐射监测组对我院的辐射工作场所（监督区）进行了监督性监测。     

2005年度辐射工作场所监督性监测

1监测目的和内容2005年度,根据中国原子能科学研究院常规监测计划要求,保健物理部监测中心现场监测组对我院科研、生产、运行及技术服务辐射工作场所进行了监督性监测。监督性监测的主要内容:辐射工作场所中X、γ及中子剂量率;α、β表面污染;放射性气溶胶总α、总β或相关核素。监督测量的周期为每年2次。2监测结果与分析2.1X、γ剂量率监测全年监测了7个院属二级单位的193个辐射工作场所,共731个监测点。监测结果列于表1。由表1可以看出,2005年我院监督区工作场所的X、γ剂量率平均值为0.89μGy/h,最大值为204.75μGy/h。从辐射水平分布…     

2006年度辐射工作场所监督性监测

1监测目的和内容 2006年度，根据中国原子能科学研究院常规监测计划要求，辐射安全研究部辐射监测与评价研究室现场辐射监测组对我院科研、生产、运行及技术服务过程中产生辐射的工作场所进行了监督性监测。     

核聚变装置辐射监控系统研究

核聚变装置在放电实验期间会产生高能中子和γ射线等辐射,部分辐射会通过生物屏蔽物透射或天空反散射而到达工作场所或者环境。设计并实现了可用于全范围(近、中、远程三种应用条件)中子和光子辐射、计算机集中监控系统(RMS),包括对工作场所进行监测的CAN系统、基于一种新的TRP蓝牙树型拓扑Ad Hoc网络的形成机制和路由协议在装置周围区域内移动状态下进行环境辐射监测的无线网络系统、对远程环境进行监测的移动GPRS无线网络系统。     

2004年度辐射工作场所监督性监测

1监测目的和内容2004年度,根据中国原子能科学研究院常规监测计划要求,保健物理部常规监测中心现场监测组对我院科研、生产、运行及技术服务过程中产生辐射的工作场所进行监督性测量。监督性监测的主要内容为:辐射工作场所中X、γ及中子剂量率的监测;α、β表面污染的监测;气溶     

核电厂辐射监测系统总体结构优化过程及改进方案

核电厂辐射监测系统用于对电厂工艺、流出物及工作场所的辐射监测,确保电厂的安全运行及保护工作人员和周围群众的健康。计算机技术的快速发展,为电厂辐射监测系统实现全数字化创造了条件。从岭澳核电一期、岭澳核电二期到宁德核电,电厂辐射监测系统总体结构发生了巨大的变化。本文针对核电厂辐射监测系统在优化过程中遇到的技术问题及改进方案进行分析讨论。     

兰州重离子研究装置的辐射监测系统

介绍了兰州重离子研究装置工作场所辐射监测系统的组成及性能,通过多年的现场使用,具有良好的稳定性和抗干扰能力,可以满足大型加速器或其他核装置的现场辐射剂量监测的需要。     

Caution when applying eddy current inversion to stress corrosion cracking

This study evaluates the applicability of computer-aided eddy current inversion techniques to the profile evaluation of stress corrosion cracking in Inconel welds. Welded plate specimens, which model head penetration welds of pressurized water reactors, are fabricated; notches and stress corrosion cracks are artificially introduced into the weld metal of the specimens. Eddy current inspections are performed using a uniform eddy current probe driven at frequencies of 10 and 40 kHz. Since weld noise is observed uniformly along the weld line, a simple signal processing is applied to eliminate it. First, the artificial notches are reconstructed and good agreements between reconstructed and true profiles are provided, which demonstrates that the computer-aided eddy current inversion technique can deal with defects in welds. Then, numerical simulations are performed to evaluate the profiles of the stress corrosion cracks. In the numerical simulations, the stress corrosion cracks are modeled as a conductive region with a fixed width of 0.3 mm. The cross-sectional profiles of the cracks are reconstructed from measured eddy current signals directly above and along a crack. Although eddy current signals calculated from the reconstructed profiles agree well with measured ones, the true profiles revealed by destructive testing are found to be very different from the reconstructed ones. Whereas the most plausible reason for the difference is the unexpectedly volumetric profile of the stress corrosion cracks, this study has revealed that computer-aided eddy current inversion techniques that have been used to consider cracks in thin structures would not at this point be directly applicable to those in thick structures. It is also important to know in advance those crack features that can adversely impact accurate crack sizing including whether a detected crack is volumetric or not, namely there are many parallel cracks in a cluster or not.     

Numerical Simulation and Experimental Identification of Divertor Configuration in the HL-2A Tokamak

Single- and double-null divertor configurations in HL-2A are simulated by SWEQU equilibrium code. Lower divertor discharges in the first physics campaign have been achieved by two kinds of power supply method of multipole-field coils. Single-null divertor configuration has been identified by visible photography, target probe arrays and the reconstructed magnetic surface. Magnetic separatrix and minor radius of plasma column are obtained by a reconstructed code of multiple current filaments using 18 Mirnov signals.     

Imaging performance evaluation in depth-of-interaction PET with a new method of sinogram generation:A Monte Carlo simulation study

In conventional PET systems,the parallax error degrades image resolution and causes image distortion.To remedy this,a PET ring diameter has to be much larger than the required size of field of view(FOV),and therefore the cost goes up.Measurement of depth-of-interaction(DOI)information is effective to reduce the parallax error and improve the image quality.This study is aimed at developing a practical method to incorporate DOI information in PET sinogram generation and image reconstruction processes and evaluate its efficacy through Monte Carlo simulation.An animal PET system with 30-mm long LSO crystals and 2-mm DOI measurement accuracy was simulated and list-mode PET data were collected.A sinogram generation method was proposed to bin each coincidence event to the correct LOR location according to both incident crystal indices and DOI positions of the two annihilation photons.The sinograms were reconstructed with an iterative OSMAPEM(ordered subset maximum a posteriori expectation maximization)algorithm.Two phantoms(a rod source phantom and a Derenzo phantom)were simulated,and the benefits of DOI were investigated in terms of reconstructed source diameter(FWHM)and source positioning accuracy.The results demonstrate that the proposed method works well to incorporate DOI information in data processing,which not only overcomes the image distortion problem but also significantly improves image resolution and resolution uniformity and results in satisfactory image quality.     

受压热冲击下反应堆压力容器内流动和传热研究综述

在发生反应堆失水事故（LOCA）时，紧急安注导致的受压热冲击（PTS）对反应堆压力容器（RPV）的安全有着重要影响，对于失水事故下反应堆压力容器内流动和传热的研究，发达国家已经进行了很年，在试验模拟和数值计算方面均取得了很多的成果，随着我国近年来核电技术的进步，对失水事故下RPV的完整性展开了研究工作，本文总结了国内外该方面研究工作，研究工作中存在的问题和发展的方向进行了探讨。     

High-order cross-section homogenization method

A high-order cross-section homogenization method based on boundary condition perturbation theory is developed to improve the accuracy of nodal methods for coarse-mesh eigenvalue calculations. The method expands the homogenized parameters such as the cross-sections and the neutron flux discontinuity factor in terms of the node surface current-to-flux ratio. The expansion coefficients are evaluated during the nodal calculations using additional precomputed homogenization parameters. As a result, it is possible to correct (update) the homogenized parameters to arbitrary order of accuracy for the effect of reactor core environment (fuel assembly neutron leakage) with very little computational effort in the core calculation. The reconstructed fine-mesh flux (fuel-pin power) is a natural byproduct of the new method. A benchmark problem typical of a BWR core is analyzed in one dimension, monoenergetic diffusion theory by modifying a nodal method based on a bilinear, flat as well as a fine-mesh intranodal flux shape. The homogenized parameters are first computed using exact (fine-mesh) albedos and compared to those determined from a fine-mesh core calculation. Two nodal (coarse-mesh) examples are given to show how well this approach works as a higher-order perturbation method is utilized. The paper concludes by showing that this method succeeds in giving excellent results for cores that may be difficult to model using standard nodal methods.     

同步辐射X射线光斑信息对扫描相干衍射成像的影晌

本文采用拓展重叠关联迭代引擎算法,系统地模拟研究了x射线光斑尺寸、扫描点数及波前形貌对扫描相干衍射成像重建图像质量的影响。结果表明,在实际入射光斑尺寸不易确定时,算法中初始猜测光斑尺寸可以由模拟入射光斑最大光强值的1％对应边界确定。对物体进行扫描时,入射光斑个数大于7×7且重叠度优于70％可以重建出较好的图像。入射光斑的振幅和位相分布对重建图像质量也有着显著影响。     

The Effects of Incorrect Modeling on Noise and Resolution Properties of ML-EM Images

The effects of incorrect compensation for collimator blur in single-photon emission computed tomography (SPECT) images are studied in terms of the noise and resolution properties of the reconstructed images. Qualitative analysis of images of the Hoffman brain phantom reconstructed using nonlinear maximum-likelihood-expectation maximization (ML-EM) show the behavior of longer noise correlations for high-pass filtered images. These qualitative observations are confirmed with more quantitative noise measures. The differences also appear in images reconstructed using linear Landweber iteration. However, the signal-to-noise ratio, in terms of the noise-equivalent quanta, remains largely unchanged. We conclude that the compensation model affects SPECT image properties, though the effect on human task performance remains to be studied.     

A study of apparent apical defects in attenuation corrected cardiacSPECT

There are a number of factors that affect the intensity of the apical region in cardiac SPECT images, which sometime lead to apparent defects in this region. In some patient studies, images reconstructed with non-uniform attenuation correction appear to have a significant decrease of apical intensity, whereas images reconstructed without such correction have only a slight decrease. This phenomenon has been evaluated using a series of simulations, phantom experiments, and a patient study. The effects of a number of factors upon the severity of the apparent apical defects were studied, including: partial volume effect, non-uniform attenuation, and depth-dependent detector response. Simulation and phantom results indicate that (1) since the apex is generally less attenuated than the rest of the heart wall, attenuation correction boosts the intensity of non-apical regions more than that of the apex (by as much as 20%); and (2) partial volume effects due to discretization inadequacies and finite spatial resolution may cause as much as a 26% decrease in reconstructed intensity in the apical region. These two effects, in combination, may partially explain the presence of apparent apical defects when attenuation correction is performed. In addition, detector response compensation consistently reduced the severity of apparent apical defects. These results agree with and help to explain the occurrence of apparent apical defects observed in patient data     

Algorithm Validation of the Current Profile Reconstruction of EAST Based on Polarimeter/Interferometer

The method of plasma current profile reconstruction using the polarimeter/interferometer(POINT) data from a simulated equilibrium is explored and validated.It is shown that the safety factor(q) profile can be generally reconstructed from the external magnetic and POINT data.The reconstructed q profile is found to reasonably agree with the initial equilibriums.Comparisons of reconstructed q and density profiles using the magnetic data and the POINT data with 3%,5%and 10%random errors are investigated.The result shows that the POINT data could be used to a reasonably accurate determination of the q profile.     

工业CT散射校正方法的研究

在工业CT的扫描重建过程中，散射效应使得重建图像出现模糊，各点灰度值同实际物体的吸收系数之间出现偏差，需要进行校正。如果采用一般的卷积方法，则需要迭代多次才能收敛，所以在校正时间上不能达到要求。采用一种结合散射模型的Ordered Subsets Convex方法对散射效果进行校正，在校正速度和质量上都得到了很好的结果。