Characterization of ITER tungsten qualification mock-ups exposed to high cyclic thermal loads

High heat flux tested small-scale tungsten monoblock mock-ups (5000 cycles at 10 MW/m2 and up to 1000 cycles at 20 MW/m2) manufactured by Plansee and Ansaldo were characterized by metallographic means. Therein, the macrocrack formation and propagation in tungsten, its recrystallization behavior and the surface response to different heat load facilities were investigated. Furthermore, debonding at the W/Cu interface, void formation in the soft copper interlayer and microcrack formation at the inner surface of the CuCrZr cooling tube were found.