Preliminary investigation on W foams as protection strategy for advanced FW PFCs

As one among the core missions towards the realization of nuclear fusion, a future reactor must provide efficient and safe power exhaust through both divertor and first wall (FW). Recent studies have confirmed that the greatest challenges arise from the occurrence of plasma transients. Indeed, extensive damage of the plasma facing component (PFC) may occur during transients, with the risk of loss of coolant accidents (LOCA) that would hinder the safety of a future reactor as well as its prompt return to normal operation. Among the possible wall protection strategies, a sacrificial and micro-engineered surface made of porous tungsten (W) may promote the heat flux reduction while preventing the failure of the cooling pipe. As a preliminary step in this direction, the present study aims to investigate the possible application of W-based open cell foams as a sacrificial armor material. At first, an equivalent solid model, originally validated for Al open cell foams, was transferred to W foams. Then, a steady state thermal FEM analysis was carried out to evaluate the equivalent thermal conductivity provided by several foam configurations. Ultimately, a scaling law of the thermal response was developed as a function of the most influential foam parameters. As a future outlook with respect to DEMO-relevant transients scenarios, the scaling law will support design optimization and tailoring of an advanced FW PFC provided with a sacrificial W foam armor.