Preliminary Test and Evaluation of Nondestructive Examination for ITER First Wall Development in Korea

ITER first wall (FW) includes a beryllium armour joined to a Cu heat sink with a stainless steel back plate. These FW panels are one of the critical components in the ITER tokamak with a maximum surface heat flux of 5 MW/m
²
. Therefore, a qualification test needs to be performed with the goal to qualify the joining technologies required for the ITER FW. Various mock-ups were fabricated to develop the manufacturing procedure of FW components. For the nondestructive examination of the fabricated mock-ups, an ultrasonic test (UT) was performed with optimized probes. The UT was performed by using a three-axis digital ultrasonic C-scan system and software. The system comprised an ultrasonic pulser and receiver, model Panametrics 5800PR; a personal computer having an internal analog/digital converter board and four-axis motion control board; and a three-axis scanning tank. Two types of transducers were used for this experiment. One was Panametrics V312-SU, having a center frequency of 10 MHz (nominal) and a piezoelectric element diameter of 0.25 in with a flat protective layer for the Be/Cu. The other was Panametrics V309-SU with a center frequency of 5 MHz and an element diameter of 0.5 in for the Cu/SS interface. Winspect software controlled all aspects of data acquisition, motion control, data archiving, and image display. Based on the acceptance criteria, the average amplitude of the interface signals, which have about 50% of the reference echo amplitude, was recorded and analyzed on each beryllium tile. An image-analysis software analyzed the statistics of amplitude distribution and calculated the unacceptable area. Each mock-up that passed these UTs was concluded to qualify the joining technologies required for an ITER FW by using a high-heat flux test facility. As a result of these qualification tests based on the acceptance criteria of an ITER FW, the fabrication technologies will be utilized to develop the FW of plasma-facing components.