The Y-12 Plant in Oak Ridge used the electromagnetic separation method, developed by Ernest Lawrence at University of California-Berkeley, to separate uranium isotopes.
The K-25 Plant in Oak Ridge used the gaseous diffusion process to enrich uranium.
Gaseous Diffusion Process
The K-25 plant was an enormously ambitious and risky undertaking. A mile-long, U-shaped building, the K-25 plant was the world’s largest roofed building at the time. British scientists working on the “tube alloy,” code for the atomic bomb project, first advocated the gaseous diffusion method in March 1941. Because of the Nazi bombing of England, any production plants had to be located elsewhere.
One of the most important branches of the Manhattan Project was the Metallurgical Laboratory (Met Lab) in Chicago. Using the name "Metallurgical Laboratory" as cover at the University of Chicago, scientists from the east and west coasts were brought together to this central location to develop chain-reacting "piles" for plutonium production, to devise methods for extracting plutonium from the irradiated uranium, and to design a weapon. In all, four methods of plutonium separation were considered, with the bismuth phosphate process displaying the most promise.