How is the separation achieved in the diffusion process of uranium enrichment?

The separation in the diffusion process of uranium enrichment is achieved by passing uranium hexafluoride gas through a semi-porous membrane. This method takes advantage of the slight mass difference between the isotopes of uranium, primarily uranium-238 and uranium-235. When the gas is forced through the membrane, the lighter uranium-235 isotopes pass through more readily than the heavier uranium-238 isotopes. As a result, the gas that emerges on the other side of the membrane has a slightly higher concentration of uranium-235, allowing for the enrichment of the desired isotope. This selective permeation method is crucial in achieving the necessary enrichment levels for use in nuclear reactors or nuclear weapons.