Initial assessment of first wall erosion and retention properties for the General Atomics fusion pilot plant

The tungsten first wall of the General Atomics Fusion Pilot Plant (FPP) will exhibit an average surface recession rate on the order of 0.03-0.05 mm/yr due to erosion by charge-exchange neutrals, corresponding to a total gross erosion rate of 180 kg/yr. First wall panels are made of 2 cm thick monoblocks that consist of a W/SiC functionally-graded composition and an embedded SiC_f/SiC coolant tube. The thickness of the pure W layer at the surface above the functionally-graded layer needs to be sufficient to survive one environmental cycle of erosion, thin enough for efficient heat removal, and optimized for neutron multiplication for tritium (T) breeding. The T accumulation rate in the wall also needs to be low enough to keep the total T inventory below any site-level regulatory limit. To ensure compliance with these requirements, initial estimates of first wall erosion and retention were made using reduced models based on existing literature at expected high first wall temperatures. The atomic D flux and impact energy for each wall element was determined using Eirene outputs from SOLPS-ITER simulations on a model equilibrium and wall geometry. These predictions of first wall material performance in FPP provide critical input on component-level engineering design that will satisfy system requirements.