Improvement of residual stress in reactor components by laser peening method

摘要

We have developed a laser peening method to prevent stress corrosion cracking (SCC) as a process for preventive maintenance of core components in nuclear reactors. This method, which utilizes the impulsive effect of underwater irradiation byintense laser pulses to improve residual stress on the material surface, requires no preconditioning of the material surface and is suitable for maintenance work in narrow spaces. Through experiments, we confirmed the effect of the laser peening method in improving the residual stress of stainless steel and suppressing SCC. A laser delivery system, remote maintenance equipment, and an on-line monitoring system were developed and the feasibility of the laser peening method was confirmed through full-scalemockup tests simulating maintenance work on the core shroud of a boiling water reactor (BWR).