Thermomechanical simulation of flat tiles mock-ups under high heat flux

Abstract

In the WEST (W -for tungsten- Environment in Steady-state Tokamak) tokamak, an actively cooled tungsten divertor for testing high heat flux technology is implemented. Beside the presently tested ITER divertor technology (i.e. W-monoblock), the WEST team in collaboration with ASIPP (China) worked on the development of an alternative design for actively cooled W/Cu plasma facing components capable to sustain heat loads close to monoblock design. Within this framework, two small-scale mock-ups based on the W-armoured flat-tile concept were produced by ASIPP and successfully tested in the electron beam facility JUDITH-1 (FZ-Jülich, Germany) under successive thermal cycling at 10, 15 then 20 MW/m². These results showed the capacity of this technology to remove heat loads over several hundreds of cycles at 20 MW/m2 without obvious indication of damage impacting the heat exhaust capability. However, the post-mortem analysis showed crack formation perpendicular to the loaded surface proceeding into the pure Cu interlayer for those tiles tested at 20 MW/m². This contribution focuses on the thermal and structural analysis performed with ANSYS for these components. The convective heat transfer coefficients were calculated using the Nukiyama model and the mechanical properties of pure copper at high temperature were extrapolated using the Ramberg-Osgood model. The thermal results are in good agreement with the experiments. The thermo-mechanical simulation explains partially the defects observed on the mocks up with the selected approach, which leads to suggest improvements for further study by modelling kinematic hardening for tungsten and creep for oxygen-free copper.