AbstractThe semi-scale mock-up (SSM) is an integral demonstration of the ability to manufacture the structural parts of a helium-cooled pebble-bed blanket segment according to the reference manufacturing procedure. In addition, building of a mock-up with significant dimensions allows one to quantify the precision achievable in the sequence of almost 100 manufacturing steps. The mock-up represents a section from the blanket segment with the dimensions 500 mm (toroidal), 280 mm (poloidal), and 300 mm (radial). The mock-up box includes a first wall (FW) with eight cooling channels and five dummy cooling plates. The manufacturing steps to be demonstrated with the mock-up are as follows: fabrication of a plane FW plate with integrated cooling channels by diffusion bonding of two grooved half-plates; bending of the FW plate into the U-shape of the box; machining of the bent FW plate to the final shape, including the welding ribs; and welding of the cooling plates to the FW box. The present contribution describes the design of the SSM, the status of manufacturing, and the results obtained so far.