Fabrication and thermal cycle testing of a first wall mock-up for ITER baffle blanket module

The objective of this study is to develop joining technology of a plasma facing CFC armor and DSCu heat sink by means of Ag-free brazing and to evaluate its performances under repeated high heat flux. For fabrication of a baffle first wall (FW) composed of dispersion strengthened copper (DSCu) as heat sink and carbon fiber composite (CFC) as amor material, a two-step brazing has been proposed. CFC armor tiles were joined to an oxygen free copper (OFCu) plate in the first step and the OFCu plates joined, in turn, to the DSCu heat sink in the second step. After screening tests, brazing materials of Cu-Mn and Al were selected for the first and the second steps, respectively. A small scale baffle FW mock-up of 400 mm in length, 49 mm in width and 52 mm in thickness was successfully fabricated. By destructive test of a piece with the same materials bonded under the same condition as the mock-up, bondability at each brazing interface was confirmed. Thermal cycle tests were performed with the fabricated mock-up. Test conditions were selected based on thermo-mechanical analyses to simulate the temperature at the brazing interface under ITER operation condition and also higher temperatures with higher heat fluxes for acceleration of thermal cycle tests. The mock-up withstood more than 4600 cycles with heat fluxes of 5-10 MW/m(2). From results of the thermal cycle tests, the integrity of CFC/DSCu interface was demonstrated.