"Enrichment" refers to raise a specific isotope abundance of elements of the isotope separation process, such as the production of enriched uranium from natural uranium or production of heavy water from ordinary water, enriched uranium is aimed at raising -235 as opposed to the abundance of uranium -238 or Concentration.

    In the enrichment process, a total of 7 kinds of methods, including gas diffusion, gas centrifuge, and gas dynamics of separation, laser enrichment method, electromagnetic isotope separation, chemical separation and plasma separation. Many countries have adopted gas diffusion. Carrying out uranium enrichment, the first uranium-containing uranium -238 and -235 of natural uranium into uranium hexafluoride gas, refining, after purification into the centrifuges, and through the porous membrane to carry out enrichment. On the membrane centrifuges for every 000 square centimeters of hundreds of millions of micro. These gases through the membrane, -235 uranium gas composed of molecules through the membrane than the proportion of uranium -238 composed of gas molecules to pass through some of the slightly larger proportion. After each level separated from the concentration of uranium -235 will increase 4.3 per thousand. After multi-stage separation, will be able to obtain enriched uranium. For example, to natural uranium to 3%, to go through thousands of such series of grade separation. If you want to more than 90% have been separated from a San Siqian level.