石墨构件和碳砖是构成高温气冷堆（high temperature gas-cooled reactor，HTGR）堆芯及反射层的重要材料，在其生产运输过程中，不可避免会出现缺陷，当使用了有较为严重的缺陷的石墨构件或碳砖进行建设时，将对反应堆造成重大安全隐患。目前传统检测方法主要是基于目视的表面检查，无法检测其内部缺陷。该文提出了一种基于螺旋CT的石墨构件及碳砖检测方案，并采用数值模拟的方式，对大尺寸碳砖模体进行了螺旋CT重建，研究了不同螺距、旋转速度及不同重建算法对重建图像质量的影响。结果表明，螺距对重建图像质量影响较大，在螺距为0.8时可基本满足检测需求；旋转速度对图像质量影响相对较小；在较优参数下，采用CGLS重建算法，最小可检测至φ2 mm的孔缺陷和宽1 mm的缝缺陷。该研究结果对螺旋CT石墨碳砖检测系统及检测方案的设计具有重要参考意义。
The graphite components and carbon bricks are essential materials for the core and reflector of the high temperature gas-cooled reactor (HTGR). However, production and transport create defects. Defective graphite components or carbon bricks can lead to serious safety hazards in the HTGR. The current defect detection methods are mainly based on visual inspections, which cannot detect internal defects. This paper describes a method to detect defects inside the graphite components and carbon bricks using helical CT. Numerical simulations of large carbon bricks were used to study the influence of pitch, rotational speed and reconstruction algorithm on the quality of the reconstructed images. The results show that the pitch greatly influences the reconstructed image quality with 0.8 as the optimal pitch for the best image quality. The rotational speed has less influence on the image quality. The CGLS reconstruction algorithm with the optimal parameters can detect holes as small as 2 mm and cracks as small as 1 mm. These results are important when designing defect detection systems for graphite components and carbon bricks.
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