A small scale first wall mock-up fabricated by HIP bonding of DS-Cu plates, internal SS cooling tubes and a SS base plate has been tested with heat fluxes of 5–7 MW/m2 up to 2500 cycles in total resulting in no identification of exfoliation at the joints and no degradation of heat removal performance. Post-mortem observations of the HIP bonded interfaces and hardness tests around the bonded interface were performed. With these detailed observations and tests, the high integrity of the HIP bonded interfaces was confirmed.