Development of visual inspection technique under sodium in FBR

The reactor vessel of a fast breeder reactor (FBR) is filled with optically opaque liquid sodium. Therefore, the ultrasonic imaging technique is useful for inspecting in-vessel structures in sodium. We have developed a high-speed and high-resolution three-dimensional image processing technique. For imaging in the sodium, a two-dimensional matrix transducer and the M-series transmitting signal were used. Cross-correlation processing between the transmitted signal and received signal was used to enhance the S/N ratio. Image synthesis also attempts enhancement of resolution by means of the synthetic aperture focusing (SAFT). It has been confirmed that clear and high-resolution three-dimensional ultrasonic images are acquired at a distance of 0.8m in the in-water visualizing test. (author)