Non-destructive Evaluation of Nuclear Grade IG-110 Graphite Using Constant Potential X-Ray

Abstract

The main structures of the High Temperature Gas-cooled Reactor’s core are made of graphite material. High temperature and the high flux of neutron exposure in the HTGR reactor affects the integrity of graphite material. In order to ensure the integrity of the graphite materials, and in-service non-destructive inspection is needed. Commonly, prior to the operation, the radiography technique is conducted to evaluate the graphite material. The aim of this study is to develop a non-destructive inspection method in order to evaluate the quality of graphite materials. Five specimens made from nuclear grade graphite IG-110 produced by Toyo Tanso, Co. Ltd has been radiographically tested using X-ray constant potential machine to evaluate the graphite material. The parameter of the energy and intensity of X-ray has also been used in this computed radiography technique with a white type of phosphor imaging plate. A scanning machine of HD CR 35 NDT with 50 μm laser size and a 300 rpm scan rate equipped with a 16-bit system has been used to result in the digital image of the graphites. The results show that the increase of energy and intensity of the radiation to some extent produces better image contrast. The radiograph of the specimens also shows that there is no defect in the material. According to these results, it could be concluded that the digital radiography technique is appropriate for evaluating graphite material.