This is a no A question , individual with detailed knowledge is advised to do so. The current underwater welding methods are wet welding, dry welding and local dry welding, where the local dry underwater welding is the welding area of the water discharge, for the welding area to create a similar to the dry welding environment. The repair of nuclear spent fuel pool has a high requirement for the quality of welding, the welding speed directly affects the quality of the weld when local dry automatic underwater welding is used to repair the damaged surface. Under the condition of the same condition, the local dry automatic underwater welding test was carried out under the condition of the same welding condition. Taking the 20cm as the experimental condition, after massive experiments show that when the welding speed is approximately 48cm/min the weld quality is high, meeting the design requirements, based on the double layer shrinkage nozzle chamber of local dry underwater automatic welding. A reinforced concrete slab with effective depth of 50 mm is simply supported at two opposite ends on 240 mm thick masonry walls. The centre to centre distance between the walls is 3.7 m. As per IS 456:2000, evaluate the effective span of the slab. . A special local dry underwater welding robot system was developed for the emergency rescue and repair of nuclear power plants. The system has dedicated underwater DSC full digital welding power supply, compact diving wire feeder and local dry underwater Drainage hood, integrated fault diagnosis system and other ancillary equipment