Status of design and manufacturing qualification activities of the first wall of the Divertor Tokamak test facility

This paper gives an overview of the current design of the First Wall (FW) of the Divertor Tokamak Test facility (DTT) under construction at Enea Research Centre of Frascati (Rome), as well as the qualification activities related to the manufacturing process of the FW small scale mock-ups.

The main goal of the overview is to illustrate the latest release of the FW component’s design, in accordance with many constraints stemming from the Physics and DTT system interface, at both Inboard (IFW) and Outboard (OFW) side of the DTT device.

Concerning the qualification activities related to the manufacturing of FW preliminary small-scale mock-ups, different technologies were compared. Regarding the OFW plasma facing units (PFUs), the machining and welding processes – TIG, Laser and Electron Beam (EB) – are investigated as conventional manufacturing solutions. The additive manufacturing technology of selective laser melting is considered a valuable procedure that makes a as the best compromise between the manufacturability, performance and costs. Regarding the IFW, the small-scale mock-ups to be manufactured and qualified concern the limiter module. It will be adopted, other than the standard one, to cope with plasma limited phases, i.e. when the plasma interacts with the inner wall. The limiter layout is presented with the aim of discussing its manufacturability and performances.

The qualification activities related to the Copper-Chromium-Zirconium (CuCrZr)-Inconel weldings, by means of EB, were also performed and are discussed in this paper, in order to manufacture the transitions – up to the steel lids – located at the ends of the limiter modules – nearby the divertor region.

For the manufacturing solutions, destructive and non-destructive tests have been carried out on the mock-ups to assess the feasibility of the technological processes, and the results are presented in this contribution.