Diffusion membrane is also called "separation membrane". A metal membrane with a fine porous structure. The micropores can restrict the ordinary air flow and allow the diffusion flow to pass, so the mass difference can be used for isotopic separation. For example, when the gas diffusion method separates uranium isotopes, the diffusion membrane is mostly made of sintered nickel (ceramics or polytetrafluoroethylene are also used).
There are hundreds of millions of micropores per square centimeter of the membrane, with a diameter of about 0.01-0.03 microns. They must meet the requirements of the separation process, and still maintain stability, reliability and certain mechanical strength in the hot and corrosive uranium hexafluoride process gas. Its development is the main technical key of the gas diffusion plant.