Qualification and post-mortem investigation of actively cooled tungsten flat-tile mock-ups for WEST divertor

Abstract

The WEST (W – for tungsten – Environment in Steady-state Tokamak) project has provided the opportunity of to developing and qualifying, in collaboration with ASIPP (China) and FZJ (Germany) a newly attractive W/Cu actively cooled PFCs technology able to sustain high heat loads close to ITER divertor ones.Within this framework, ASIPP has produced two small-scale mock-ups based on the W-armoured flat-tile concept. The results presented herein focus on the qualification program, performed by CEA, which consisted in a preliminary non-destructive testing (NDT) control based on infrared thermography to assess the joint interface quality followed by cyclic high heat flux (HHF) testing performed at FZJ. The HHF testing, performed by successive thermal cycling, allowed demonstrating the thermal performance 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 for both mock-ups.Furthermore, the subsequent post-mortem microstructural analysis allowed confirming the issues regarding the induced fatigue damages, especially the tungsten crack formation perpendicular to the incident surface appeared during cycling at 10 MW/m2 and plastic deformation inducing microstructure evolution in the pure Cu-interlayer during cycling beyond 10 MW/m2 for both mock ups.