Preliminary test and evaluation of non-destructive examination for ITER First Wall development in Korea

ITER First Wall (FW) includes beryllium armour joined to a Cu heat sink with a stainless steel back plate. These first wall panels are one of the critical components in the ITER tokamak with a maximum surface heat flux of 5 MW/m2. So, a qualification test needs to be performed with the goal to qualify the joining technologies required for the ITER first wall. Various mockups were fabricated to develop the manufacturing procedure of first wall components. For the non-destructive examination (NDE) of the fabricated mockups, an ultrasonic test (UT) was performed with optimized probes. The UT test was performed by using a three-axis digital ultrasonic C-scan system and software. The system is comprised of an ultrasonic pulser/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 type transducers were used for this experiment. One was Panametrics V312-SU, having a center frequency of 10 MHz (nominal), a piezoelectric element diameter of 0.25 inch 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 inch 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, average amplitude of the interface signals, which have about 50% of the reference echo amplitude, was recorded and analyzed on each beryllium tile. Image analysis software analyzed the statistics of amplitude distribution and calculated the unacceptable area. Each mockup that passed these UT tests was concluded to qualify the joining technologies required for an ITER first wall by using high heat flux test facility. As a result of these qualification tests based on the acceptance criteria of an ITER first wall, the fabrication technologies will be utilized to develop the first wall of plasma facing components.