Pre-conceptual design of a PFC equipped with a W lattice armour for first wall limiters in the EU-DEMO fusion reactor

amongst the engineering challenges of power exhaust in DEMO and future reactors, an effective wall protection strategy is regarded as a crucial one. It aims at strongly mitigating the degradation of conventional plasma-facing components (PFCs) during plasma transients and disruptions [1]. amongst the solutions for the EU-DEMO reactor, sacrificial first wall limiters provided with innovative tungsten (W) lattices are envisaged as the last protection resource of the otherwise unshadowed wall during such extreme events. Their design must comply with conflicting requirements, e.g. adequate heat exhaust during normal operation but acceptable lifetime, i.e. vapour shielding and thermal insulation of the heat sink (HS), during transients. For this purpose, porous W lattices are preferred to dense armours, as the former provide larger design flexibility, pronounced HS insulation and promoted vapour shielding [2]. Additive manufacturing was employed to realize samples with the envisaged properties for material characterization and testing. In this work, we report on the recent research activities towards the development of a pre-conceptual design of a small-scale prototype of the sacrificial limiter. Above all, thermo-mechanical finite element (FE) analyses, implemented in support of the design phase, helped to assess and optimize parametrically the response of the lattice armour and component layout. In this context, an original MAPDL routine was employed to account for armour degradation and phase change of W during extreme events. Results suggest that a PFC provided with an optimized lattice armour could promote vapour shielding and prevent HS overloading during transients, at the same time ensuring adequate heat exhaust and acceptable thermal stresses during normal operation. Accurate measurements of thermo-physical and mechanical properties of W lattices helped improve our simulations. Dipping tests highlighted the technical viability of joining the lattice to copper-based substrates by infiltrating melt copper in the open pores of W lattices. This might significantly ease the mock-up and component fabrication, as one could rely on conventional joining methods, such as copper-copper brazing, industrially available and well-established for fusion applications.