Figure 1. Diffusers set up in a cascade. Enriched uranium comes out of the upper pipes and is sent upward through the cascade while the depleted uranium comes out of the bottom pipes and is sent downward through the cascade.[1]

A Cascade process is used when purifying or enriching a desired substance and when one stage of enrichment is not enough to reach the target percentages. Since one stage isn't enough many stages together are put together in a sequence. The sequence uses the more enriched (or more pure) output from one stage as the input for the next stage. The depleted (or less pure) output goes back to a previous stage.[2]

Cascades are often used in the enrichment of uranium. See the gaseous diffusion page for an example of a cascade process detailed process explanation.

Figure 2. Three stages of a gaseous diffusion cascade.[3]

## References

1. U.S. Department of Energy (September 21, 2016). The Manhattan Project [Online]. Available: https://www.osti.gov/opennet/manhattan-project-history/Events/1942-1944_ur/k-25_working.htm
2. John R. Lamarsh, Anthony J. Baratta. (June 28, 2016). Introduction to Nuclear Engineering. Third Edition. Upper Saddle River, NJ, U.S.A:Prentice Hall, 2001.
3. Portsmouth Gaseous Diffusion Plant Virtual Museum (September 23, 2016). A Diffusion Cascade [Online]. Available: http://www.portsvirtualmuseum.org/history-process.htm