Corrosion Resistant Cladding by YAG Laser Welding in Underwater Environment by Tsutomu Kochi, Toshio Kojima, Hirata Suemi, Ichiro Morita, Katsura Ohwaki.
It is known that stress-corrosion cracking (SCC) will occur in nickel-base alloys used Reactor Pressure Vessel (RPV) and Internals of nuclear power plants. A SCC sensitivity has been evaluated by IHI each part RPV Internals. There are several water level instrumentation nozzles installed domestic BWR RPV. In nozzles, 182 type were for the welding joint to estimated potential high this because a higher residual stress than yield strength (about 400MPa). This report describe preventive maintenance method these Heat Affected Zone (HAZ) welds corrosion resistant cladding (CRC) YAG Laser underwater environment (without draining reactor water). many kinds countermeasures SCC, example, Induction Heating Stress Improvement (IHSI), Mechanical Process (MSIP) so on. laser CRC one them. technology beam heat source irradiated through an optical fiber base metal material wires. After HAZ coated materials their surfaces improved. gas tungsten arc (GTAW) airenvironment had developed already applied couple operating plants (16 Nozzles). was course good but it spent much time perform installation some water-proof working boxes make TIG-weldability environment. superior features comparing conventional TIG as follows. At viewpoint environment, (1) outage term reduction (no drainage (2) radioactive exposure dose personnel. welding, narrower HAZ. smaller distortion. (3) few layers. test carried out different position, horizontal, vertical upward downward. The soundness layers 3 mm) confirmed visual penetration test, cross section observation. application actual plants, preferable reduce start end point numbers beads with which defect easy cause. Therefore special equipment could weld continuously developed.
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