Pumping Helium Out of Fusion Devices Using Membranes Superpermeable to Hydrogen

Superpermeable membranes (SPM) are able to let through suprathermal hydrogen particles with the probability comparable to 1, while being absolutely impermeable to particles of other gases including He. The SPM’s are proposed for separating from He and pumping deuterium/tritium (D/T) fuel out of fusion reactor exhaust to return the purified fuel to the reactor via the shortest possible recirculation loop, bypassing the tritium plant. Although this may seem somewhat unexpected, it turns out that when the SPM is pumping hydrogen isotopes, it is also capable of pumping and compressing He. A necessary condition for this is a viscous or transitional flow of the exhaust mixture, blocking the He flow back into the divertor.Due to precompression by the SPM, the pumping speed of the general-purpose (GP) pump required to evacuate He, multiple reduces, and thus, the SPM not only selectively evacuates D/T, but also serves as a first stage for He pumping. When the pumping speed of the GP pump is reduced, it evacuates with a lower speed not only He but also D/T. Since the SPM and GP pumps compete for D/T pumping, this allows for greatly reducing also the SPM pump, and therefore, the entire pumping system.