Post examination of tungsten monoblocks subjected to high heat flux tests of ITER full-tungsten divertor qualification program

In 2015, as part of ITER Full-Tungsten Divertor Qualification Program, Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) manufactured six small-scale Tungsten (W) monoblock mock-ups that were tested at the electron beam facility, ITER Divertor Test Facility (IDTF, St Petersburg, RF). The high heat flux (HHF) tests consisted of 5000 cycles at 10 MW/m2, followed by 300 cycles at 20 MW/m2 and additional 700 cycles at 20 MW/m2. All mock-ups fulfilled the requirements of high heat flux performance successfully. One (WTC-5) of the six mock-ups was then selected to carry out critical heat flux (CHF) test with local heat flux up to 37-39 MW/m2. After HHF test, ultrasonic test (UT) and destructive tests were performed to characterize the damages of monoblocks. The debonding of the Cu/CuCrZr interface was detected by both nondestructive and destructive tests. Intergranular rupture of W was observed by Scanning Electron Microscope (SEM). The recrystallization was found in the W monoblocks and the recrystallized depth were analyzed by metallography and Vickers hardness measurement.