Ultrasonic Inspection Technique For The Sg/rcp Casing Weld Of AP1000 Plant

Compared to other types of nuclear power plants,the main features of AP1000 nuclear power plants are not only the canned motor Reactor Coolant Pump(RCP),but also the installation of RCP in the Reactor Coolant System(RCS).The RCP casing is directly connected to the primary side Outlet Nozzle of the Steam Generator(SG)by welding,while the RCP body is bolted below the casing.As a pressure boundary weld of RCS,it is of great importance to performe pre-and in-service inspection to ensure the safe operation of the AP1000 nuclear power plant.However,due to the special structure,dissimilar metal weld,coarse grains material,large thickness,it is difficult to install the inspection equipment and to perform the ultrasonic inspection.To solve the problem of SG/RCP casing weld inspection,mainly performed initial research of the automatic equipment,ultrasonic inspection techniques and ultrasonic data imaging characteristic etc.For the automatic equipment,designed and manufactured the special modular automatic scanning device,performed multi-point electric and pneumatic control via Ethernet distributed control structure,and designed the new telescopic positioning mechanism which can be mounted on a large diameter Outlet Nozzle by through a samll diameter SG manhole.For ultrasonic techniques,analyzed the automatic ultrasonic acquisition parameters and determined the specific parameters according to the test result,determined the probe specific parameters by the CIVA simulation and calibration block reflector test,and optimized automatic test processtion.For ultrasound imaging features of data analysis,classified signal display characteristics by a large number of simulated natural defects,summaried the judgment rules of signal,display characteristics,location and sizing method of defects with lots of examples.By the technique developing,it can be used for the inspection of AP1000 SG/RCP casing weld,meeting the pre-service requirements,and it can be used for other thick coarse grain dissimilar metal welds by applicability modification.