高温气冷堆球形燃料元件三维CT无损检测的伪像校正及统计评价方法研究

Spherical fuel elements are crucial for the safety of high-temperature gas-cooled reactor (HTGR).About ten thousand coated fuel particles containing UO2 core disperse in a graphite matrix., Good protection of fuel element safety requires good temperature distribution and gradient, which require good uniform dispersion, without contact and agglomeration..3D CT is an important tool for nondestructive evaluation of spherical fuel elements. But as a result of intense ray attenuation and scattering of UO2, stripes and cupping effect artifacts are unavoidable, hurt the details of image. Herein, it is difficult to effectively and reliably make quantitative statistical analysis because of its poor image quality..This paper intends to establish the spherical fuel elements non-destructive testing and quantitative statistical analysis methods of 3D CT. To improve image quality, studying the scattering effects and scattering correction of a large number of dispersed coated fuel particles are performed, which focus on the iterative algorithm’s effect on improving the metal artifacts with the input of digital phantom of particles random distribution. By extracting 3D position of coated fuel particles, quantitative index of distribution uniformity evaluation are calculated, such as the polyhedral occupation volume distribution, the nearest neighbor distance distribution, spherical coordinates radial distance distribution, polar angle.

球形燃料元件是高温气冷堆安全性的重要保障，约一万个包覆颗粒燃料弥散在石墨基体中，且必须分布均匀，不团聚，不理想分布导致不理想的温度分布、梯度和局部高温、应力等，进而导致放射性逸出或元件破坏。球形燃料元件的无损检测及均匀性评价采用三维CT很有价值，但由于包覆颗粒二氧化铀核心会引起强烈的射线衰减和散射，产生高强度的条纹和杯状伪像，难以进行有效可靠的自动定量统计分析。本课题拟研究用三维CT无损检测球形燃料元件和定量统计评价包覆颗粒均匀分布的方法，以颗粒随机分布数字模体为输入、重点研究优化迭代算法对大量散布式金属伪像的性能和参数，并校正大量散布式包覆颗粒的散射影响，使图像质量满足自动分析的要求。提取包覆颗粒的三维空间位置，建立颗粒的占据多面体体积分布，最近邻距离分布，球坐标径向距离分布、天顶角分布、方位角分布等均匀性评价定量指标，建立高温气冷堆球形燃料元件的三维CT无损定量评价方法。

球形燃料元件是高温气冷堆安全性的重要保障，约一万个包覆颗粒燃料弥散在石墨基体中，且必须分布均匀，不团聚，不理想分布导致不理想的温度分布、梯度和局部高温、应力等，进而导致放射性逸出或元件破坏。球形燃料元件的无损检测及均匀性评价采用三维CT很有价值，但由于包覆颗粒二氧化铀核心会引起强烈的射线衰减和散射，产生高强度的条纹和杯状伪像，难以进行有效可靠的自动定量统计分析。本课题拟研究用三维CT无损检测球形燃料元件和定量统计评价包覆颗粒均匀分布的方法，以颗粒随机分布数字模体为输入、重点研究优化迭代算法对大量散布式金属伪像的性能和参数，并校正大量散布式包覆颗粒的散射影响，使图像质量满足自动分析的要求。提取包覆颗粒的三维空间位置，建立颗粒的占据多面体体积分布，最近邻距离分布，球坐标径向距离分布、天顶角分布、方位角分布等均匀性评价定量指标，建立高温气冷堆球形燃料元件的三维CT无损定量评价方法。