Development of Inspection System for Weld Joint between Steam Generator and Reactor Coolant Pump in Nuclear Power Plants

The reactor coolant pump casing of weld joint between steam generator outlet nozzle and reactor coolant pump is made by coarse-grain austenitic material. The weld joint is with thick wall, ultrasonic attenuation and grain scattering, the development of ultrasonic technique is very difficult. In this study, a special design is adopted to develop an automatic ultrasonic inspection system from inner surface of the steam generator outlet nozzle, and this system has been applied to the pre-service inspection of AP1000 Nuclear Power Plant in China. The results show that this system could fully meets the on-site inspection requirements, and the inspection results are in good agreement with the factory results.