Ceramic membranes for processing plasma enhancement gases

Abstract

Fusion plasma exhaust is generally composed of unburned fuel (deuterium and tritium), helium and few impurities. However for a metal wall machine (like DEMO) that reaches elevated powers, a certain amount of plasma enhancement gas (nitrogen, Ar, Ne, etc.) could be used as seeding for enhancing the radiative power and decreasing the power load over the plasma facing components. The recovery of these Plasma Enhancement Gases (PEG) could be beneficial because of the high flow rates required, and to limit the load placed upon the exhaust detritiation system. In this work, the application of ceramic porous membranes for the separation of PEG from other plasma exhaust gases is studied. The gas permeability through porous media of hydrogen, helium and a number of inert gases of potential interest (N2, Ne, Ar, Kr, Xe) has been assessed via the models of Knudsen and Poiseuille. A parametric analysis taking into account the effect of temperature (20 and 300 °C), pressure (100 kPa and 1 MPa) and pore size of the membranes (0.1 nm, 10 nm, and 1 μm) has been undertaken to evaluate the capability of porous membrane systems to recover PEG from the exhaust gas in terms of separation factors. The preliminary design of a membrane module is also carried out.