Plasma enhancement gases (PEGs) separation using a carbon molecular sieve (CMS) membrane

Plasma enhancement gases (PEGs) (such as: N-2, Ne, Ar and other inert gases) are injected into the plasma of several tokamaks in order to reduce the power load over the plasma facing components. The exhaust gas in the tokamak demonstration reactor (DEMO) consists of more than 90% of unburned fuel gas (D and T) and the remaining part will be He, PEGs and impurities. In DEMO reactor it is foreseen to recover the fuel gas and PEGs. For this purpose in this study a carbon molecular sieve (CMS) membrane and its precursor substrate have been tested at a permeation apparatus built at ENEA Casaccia laboratories. Single gas permeances for H-2, He, N-2 and Ar were measured with a pressure drop across the membranes between 10 Pa up to 140 kPa at room temperature, 144 degrees C and 250 degrees C. We found that H-2 to N-2 selectivity at 250 degrees C is equal to 47.68 while for H-2 to Ar is equal to 35.05.