Research Of Phased Array Ultrasonic Testing Key Technology On Future Fusion Reactor Vacuum Vessel Complex Welds

The China Fusion Engineering Testing Reactor(CFETR)is the next generation Tokamak device for Chinese magnetic confinement fusion programme.The vacuum vessel(VV)facing high temperature plasma directly is one of the most critical components of CFETR facility.Supported by the National Magnetic Confinement Fusion Science Program under grant agreement No.2015GB107000,the Research and Development(R&D)of CFETR 1/8 VV mock-up have been carried out since 2015 by the Institute of Plasma Physics Chinese Academy of Science(ASIPP),for solving hot forming,welding,non-destructive testing(NDT)processing,and many other key technologies.Aiming at solving the technical problems of automatic NDT the above mentioned,based on technical experience of design,manufacture and scale production of ITER VV,combined with the operation experience of EAST project in China and the actual situation of industrial production,the key technology of phased array ultrasonic testing(PAUT)for CFETR VV complex welds was carried out.The main research work includes analyses of welded joint microstructure and properties,selection of phased array probe,optimization of detecting parameters,development of detecting system,verification of system capability.Firstly,the research status of ultrasonic testing(UT)of austenitic stainless steel welds at home and abroad was summarized through literature research,the problems of UT of the CFETR VV welds were pointed out.Based on metallographic analysis,microhardness test and acoustic property test,the structural characteristics and acoustic properties of CFETR VV welded joints were analyzed.Secondly,the theory of sound field and imaging quality of phased array probes were deeply studied by combining theoretical analysis,simulation and experimental verification.The selection of phased array probes and the optimization of detection parameters were completed.Finally,a phased array ultrasonic detecting system was developed for the manufacturing site of the CFETR 1/8 VV mock-up.UT blocks embedded with typical welding defects were designed and manufactured,and the capability verification test of the detection system was carried out.The results show that it is feasible to use PAUT technology for NDT of complex austenitic stainless steel welds in CFETR VV Furthermore,PAUT technology has advantages such as high welding defect detection rate,rich defect information and high testing efficiency.The research results of this paper could provide technical support for automated NDT of complex welds in CFETR VV in the future.