Development of Multifunction Laser Welding Head as Maintenance Technologies Against Stress Corrosion Cracking for Nuclear Power Reactors

Multifunction laser welding head has been developed. The head is able to perform not only underwater laser welding as repair, but also laser peening as preventive maintenance and laser ultrasonic testing as inspection. By using the effect of color aberration with optics, laser beam was focused to the ideal spot size on each process. Underwater laser welding was carried out onto EDM slit with the developed head and sealing ability with deposited weld metal was confirmed. As preventive maintenance, laser peening was also performed on the material surface with the developed head, and stress improvement ability was confirmed. For inspection with the developed head, a new method of visualizing weld defects in water by laser-ultrasonics has developed. Furthermore, developing synthetic aperture focus technique for visualized inspection surfaces 2-dementionally, the inspection result like penetrant testing despite underwater environment was achieved. Therefore, practicality of the developed head on each process was confirmed.