the helikon vortex separation process is an aerodynamic uranium enrichment process designed around a device called a vortex tube. paul dirac thought of the idea for isotope separation and tried creating such a device in 1934 in the lab of peter kapitza at cambridge. other methods of separation were more practical at that time, but this method was designed and used in south africa for producing reactor fuel with a uranium-235 content of around 3–5%, and 80–93% enriched uranium for use in nuclear weapons. the uranium enrichment corporation of south africa, ltd. (ucor) developed the process, operating a facility at pelindaba (known as the 'y' plant) to produce hundreds of kilograms of heu. aerodynamic enrichment processes require large amounts of electricity and are not generally considered economically competitive because of high energy consumption and substantial requirements for removal of waste heat. the south african enrichment plant has apparently been closed.