On the optimization of the first wall of the DEMO water-cooled lithium lead outboard breeding blanket equatorial module

Within the framework of EUROfusion R&D activities a research campaign has been carried out at the University of Palermo in order to investigate the thermo-mechanical performances of the DEMO water-cooled lithium lead (WCLL) breeding blanket first wall (FW). The research campaign has been mainly focused on the optimization of the FW geometric configuration in order to maximize the heat flux it may safely withstand fulfilling all the thermal, hydraulic and mechanical requirements foreseen by safety codes. Attention has been focused on the FW flat concept endowed with square cooling channels and the potential influence of its four main geometrical parameters on its thermo-mechanical performances has been assessed performing a parametric analysis by means of a qualified commercial finite element method code. A set of 5929 different FW geometric configurations has been considered and the thermal performances of each one of them have been numerically assessed in case it undergoes 26 different values of heat flux on its plasma-facing surface. The resulting 154154 thermal analyses have allowed to select those cases fulfilling the adopted thermal-hydraulic requirements, whose thermo-mechanical performances have been numerically assessed under both normal operation and over-pressurization steady state loading scenarios to check whether they met the mechanical requirements prescribed by the pertaining SDC-IC safety rules. Four optimized FW configurations have been found to safely withstand a heat flux up to 2 MW/m2 fulfilling all the rules prescribed by safety codes. Finally, the thermo-mechanical performances of these FW optimal configurations have been further investigated under both normal operation and over-pressurization steady state loading scenarios setting-up more realistic 3D FEM models. Results obtained, herewith presented and critically discussed, have allowed to select one promising FW geometrical configuration.