球形容器核材料滞留量探测器小角度转动发射层析测量方法

Small Angle-Rotated Detector Emission Tomography for Measuring Holdup in Spherical Container

核材料生产线上很多设备(如混合器、反应器)是球形结构,在生产过程中,内部会有核材料滞留。了解内部核材料滞留量,对核材料管理与衡算和核材料临界安全至关重要。本工作针对球形反应器内部核材料滞留量的测量,提出探测器小角度转动发射层析方法。认为球形容器内部的核材料近似球形分布,并按一定的方式将其分割为若干体素。探测器在有限小角度范围内转动,对球形容器进行分层扫描测量,获取投影数据。应用最小二乘法或最大似然法,对核材料分布进行重建计算。这样,不仅可给出较为准确的反应器内部核材料的总量,而且可给出核材料在内部的分布情况。采用蒙特卡罗模拟计算技术,对该方法进行了验证,证明该方法合理可行。

Some special nuclear material （SNM） is inevitably deposited in the facilities （mixer, reactor） of nuclear material process line. Exactly knowing the quantity of nuclear material holdup is very important for nuclear material accountability and critical safety. The small angle-rotated emission tomography method was presented for SNM holdup measurement of spherical container. Because of other equipments exist at the left, right and back side of the container, so that the detectors can be put only in front of container for measurement. The nuclear material deposited in the spherical container can be looked as spherical shell source, which is divided into many voxels. The detectors scanning spherical shell source are rotated around the container at small angle at each layer to obtain projection data, with which deposited material distribution can be reconstructed by using least square （LS） method or maximum likelihood （ML） method. Based on these methods accurate total holdup can be obtained by summing up all the voxel values reconstructed. The measurement method for holdup in the spherical container was verified with Monte-Carlo simulation calculation.