A preliminary study on noncontact imaging inspection for internal defects of plate-type nuclear fuel by using an active laser interferometer

A non-contact optical imaging technique was preliminarily studied to detect internal defects of a plate-type nuclear fuel specimen by using an active laser interferometer. A sinusoidal and periodic thermal wave induced periodic micro deformation including internal defect information of the specimen. The laser interferometer acquired a micro deformation image for the specimen surface, the shape of which varied according to the energy of the thermal wave. An adopted flexible holder of the specimen increased the capability of defect detection by concentrating the strains at the defects. A real-time inspection image including internal defect information was produced after the signal processing to remove noises. As a nondestructive inspection system, the developed visual inspection technique using an active laser interferometer can be a valuable tool to detect the internal defects of plate-type nuclear fuel.

► An active laser interferometer was preliminarily studied to visually detect internal defects of plate-type nuclear fuel. ► The developed active optical interferometer system showed vivid defect images. ► The adopted flexible holder improved the detection efficiency for the internal defects by concentrating the strains. ► The filtering technique, which removes the whole-body variation, was effective in improving the defect detection capability. ► The developed noncontact imaging technique can be a useful nondestructive inspection tool for plate-type nuclear fuel.