Present status and future of maintenance robots of nuclear power plants. Part 2. Toshiba Corporation's activity

Underwater remotely operated vehicle for inspection, repair and preventive maintenance in a narrow space had been developed with advanced robot technologies. Maintenance robot for core internals worked under high radiation environment and size limit of applied parts and passage space. Visual inspection (VT) and ultrasonic testing (UT) of welds using core shroud vehicle had been realized. Swimming type vehicle for VT and crawler type vehicle for cleaning was also prepared. Position measuring system for VT with image processing based on position information of movable joint axis and micro replica equipment to obtain microstructure image of structure surface could be combined. Underwater remotely operated maintenance and repair system was applied to improve surface stresses around welds to compression with laser peening technology and also to remove cracks with electric discharge machining for prevention of crack propagation. (T. Tanaka)