Laser technology for maintenance of nuclear piping

As a part of R and D technologies for maintenance of piping in nuclear power plants, a cutting and welding device which integrates a high power CO2 laser and a high power YAG laser were developed, and their characteristics and qualities have been studied. As a result, it was found that in case of welding O2 gas assisted laser-cut joint, porosities in the weld zone disappeared, but the mechanical properties also decreased. Also, it was found that lap welding from the inside of the narrow tube (inner diameter: 10 mm) caused no porosity when N2 gas was applied as a shielding gas and that its welding quality proved the joint to be sound. This indicates that the piping maintenance technique using this cutting and welding device has promise for practical use because of its usefulness and reliability