Since the thermal loads causes deformation of the divertor plate, it is one of the critical issues to develop support structures which can suppress the deformation within an allowable tolerance. Slide support structures and rigid support structures have been proposed for the ITER divertor plate design. Advantage of the fully rigid support structure is 1) the thermal deformation can almost fully be suppressed, 2) the fabrication process becomes simpler than the slide support structures. However, stresses/strains of the divertor plate with the rigid support structure are seemed to be much higher than those of the slide support structures. To evaluate the thermal fatigue behavior for the rigid support structure, the authors have developed a 1 m long divertor mock-up and have performed the thermal cycling experiments of the mock-up. The mock-up consists of 36 armor tiles, a soft copper (OFHC-Cu) heat sink, and an OFHC-Cu cooling tube. The armor tiles were made of a unidirectional Carbon Fiber Reinforced Carbon composite material which has high thermal conductivity perpendicular to the coolant flow direction. The saddle-shaped armor tiles were brazed onto the heat sink with a silver braze. The thermal cycling experiment was performed in an area of 25 × 50 mm2 at an incident heat flux of 25 MW/m2 for a pulse duration of 10 s. As a result, a water leakage from the cooling tube between the heated armor tiles occurred at 1247th thermal cycle. In the scanning electron microscope (SEM) observation, the striation which is typical for fatigue cracking was clearly observed at the fracture surface of the cooling tube. The 3-D finite element analysis for the simulation of the experiment was also performed, and the large strain amplitude was found at the heated side of the cooling tube. Therefore, the fatigue cracking of the cooling tube could mainly be attributable to this large strain amplitude. To realize the rigid support structure, more stiffness is required for the structural material of the cooling tube.
