THREE-DIMENSIONAL X-RAY CT IMAGE OF AN IRRADIATED FBR FUEL ASSEMBLY

Three-dimensional X-ray computer tomography (CT) images were successfully taken of a fast breeder reactor fuel assembly that had been irradiated to high burnup. The interior and outside of the fuel assembly can be clearly observed on any cross section from any angle. These images make it possible to analyze deformations and microstructural changes in the fuel pins and abnormalities in the fuel assembly. An analysis was made for 12 7 central voids, i.e., one in each fuel pin of the traverse cross section, and the void sizes were tentatively related to the linear heat rating. Compared with conventional nondestructive and destructive postirradiation examinations (PIEs), this X-ray CT technique has great advantages including acquiring large numbers of PIE data in a short time, reducing PIE costs, reducing the amounts of radioactive waste generation, and physically protecting nuclear materials.