Laboratory Experiments and Modeling on Bi-Directional Hydrogen Isotopes Permeation Through the First Wall of a Magnetic Fusion DEMO Reactor

The first wall of a magnetic fusion DEMO reactor serves to separate the edge plasma from breeding blanket, the latter of which is required to operate at elevated temperatures. To minimize the thermo-mechanical stress, the wall thickness is often limited to be less than 1 cm. As a result, the first wall is subjected to hydrogen isotopes permeation in the two opposite directions via plasma-driven permeation (PDP) by D⁺ (or D⁰) and T⁺ (or T⁰) in the edge plasma region and via gas-driven permeation (GDP) by T₂ bred in the blanket. In the present work, the bi-directional hydrogen permeation behavior through a candidate first wall material, F82H, has been studied, using a laboratory-scale plasma device. Experimental data indicate that GDP tends to dominate the overall hydrogen isotopes transport. The effects of surface roughness and contamination on PDP have been investigated. Also, a one-dimensional diffusion code has been used to simulate bi-directional PDP and GDP under reactor-relevant conditions where multiple hydrogen isotopes flow through the first wall.