Design and Commissioning of a Superpermeation Test Stand

Impurity species (such as helium, argon, or nitrogen) in low pressure hydrogen isotope streams can be removed through the technique of superpermeation. In this process, hydrogen molecules are atomized prior to their arrival at an asymmetric metal membrane. These metal membranes contain a surface barrier on the feed side to allow thermal hydrogen atoms to absorb into the membrane while also blocking upstream recombination, thus facilitating unidirectional permeation. The surface barriers are created by depositing a thin, low permeability surface coating such as an oxide or low-solubility metal. A custom symmetric vacuum system has been developed to test permeation of these asymmetric membranes in both forward and reverse direction. Initial commissioning and permeation tests have been done using alpha-iron. Additional permeation measurements will be performed using other well-characterized materials as well as novel membrane materials.