Research on Nondestructive Examination of Jacket Section for CFETR TF Coil

The Chinese Fusion Engineering Testing Reactor (CFETR) is aiming to bridge the gap between the International Thermonuclear Experimental Reactor (ITER) and the first commercial fusion power plant, a necessary complement of the ITER. The requirement for sustaining long burn duration as specified in the duty time CFETR mission necessitates the use of superconducting magnets. Totally 16 toroidal field (TF)D-shaped coils which are of cable-in-conduit conductor type are designed. All the subcomponents have very demanding requirement to withstand the severe environments. This paper gives the nondestructive examination (NDE) method developed for the jacket of TF conductor which is made of 316L stainless steel. Based on the linear elastic fracture mechanics, maximum acceptable defect sizes in the TF jacket material have been defined. Phased array ultrasonic testing(PAUT)method and eddy current test (ECT) method were developed for the circular-in-square jacket inspection. For PAUT method, focus laws were calculated and optimized. For ECT method, specific ECT probe was designed and manufactured. Benchmark experiments were carried out to study the NDE reliability.