Gas- and plasma-driven hydrogen permeation through a reduced activation ferritic steel alloy F82H

The first wall of a magnetic fusion power reactor will be subjected to hydrogen isotope permeation by the two mechanisms: one is gas-driven and the other is plasma-driven. Hydrogen transport through a reduced activation ferritic steel alloy F82H has been investigated using a steady-state laboratory-scale plasma device. Permeation parameters including permeability, solubility and diffusivity have been measured in the temperature range from 150 to 520 °C. The surface recombination coefficient for hydrogen has also been estimated by a one-dimensional steady-state permeation model with the input data taken from experiments. Using these parameters, the hydrogen plasma-driven permeation flux and inventory for a 0.5 cm thick first wall around 500 °C are estimated to be ∼1.0 × 10¹³ atom cm⁻² s⁻¹ and ∼2 × 10¹⁶ atom cm⁻³, respectively. Also, the implications of all these data on reactor operation are discussed