Tritium Pumping Based on Asymmetric Permeation

Institut fur Plasmaphysik, Kernforschungsanlage Julich GmbH, Association EURATOM-KFA, Julich, West Germany The variation in the steady state hydrogen permeation flux magnitude through composite metals under both molecular and atomic hydrogen upstream driving conditions is discussed. With molecular hydrogen upstream, the permeant flux magnitude does not depend on the permeant direction through the composite. Under atomic hydrogen bombardment conditions on the upstream side, however, this magnitude does depend on the permeant direction. In a two layer system, the permeant flux magnitude is enhanced by orienting the composite metal such that the layer with the higher product of solubility (S) with surface recombination rate constant (k_r) faces downstream. Furthermore, the degree of asymmetry in the hydrogen flow (forward permeation/reverse permeation) increases with decreasing upstream pressure. First measurements on a copper-clad mild steel membrane are presented and confirm the expected permeation performance.