There are two technologies that have been used for aerodynamic isotope separation, the jet nozzle and the advanced vortex tube. They use similar principles to the gas centrifuge but in these cases the circular wall remains static while the gas travels in a circular path at very high speed.

The jet nozzle process was initially developed in Germany and then transferred to Brazil with continued German participation. A small demonstration plant was built before work ceased in 1994. The process fires UF6 in a hydrogen carrier gas through a slit-shaped nozzle at very high velocity towards a semicircular wall. The fast moving gas and the static wall have much the same effect as a centrifuge, with the heavier 238UF6 tending to stay closer to the wall than the 235UF6. As the gas leaves the wall the stream may be split into slightly enriched and slightly depleted streams, as illustrated in Fig. 7.6.

The principle of the jet nozzle process is simple but the radius of the semicircular wall must be small and the gas velocity must be very high to provide the acceleration forces needed to make it work effectively. The radius of the wall needs to be 0.1 mm or less and the slit width for the nozzle significantly smaller than that. Manufacturing robust, UF6 resistant equipment to the very fine tolerances required and in the quantity needed for an operational scale facility poses a major technological challenge. Furthermore, energy consumption is high and care must be taken to avoid the UF6 reacting with the hydrogen carrier gas. Development work showed that, in essence, the technology was inferior to the gas centrifuge and therefore not suitable for commercial exploitation.

The advanced vortex tube was developed in South Africa and uses similar principles to the jet nozzle, but in this case the UF6 carrier gas mixture is fired at high speed tangentially to a cone-shaped wall, creating a vortex. The circular motion again causes the heavier 238UF6 molecules to concentrate closer to the wall, while the 2 35UF6 becomes enriched further away from the wall. Careful positioning of splitters allows the feed gas to be separated into enriched and depleted components.

As with many enrichment technologies, each stage in the advanced vortex process produces modest levels of enrichment, so that many stages are required to

achieve the enrichment levels needed for practical use. The South African developers were able to combine multiple stages into a single unit known as a helikon, but even then the technology remains inferior to the gas centrifuge. The technology was abandoned in 1990.