Atomic Energy Commission officials marveled at the simplicity of his design. In the late 1950s, Zippe worked as a researcher at the University of Virginia, where he built a centrifuge largely from memory. Though it took more research to adapt this to a scalable design, the basic design problems had been solved.Īfter release from the prisoner camp, Steeneck returned to East Germany, while Zippe traveled the world, marketing his centrifuge. The centrifuge rotor was made to spin on the tip of a needle, like a top, thus eliminating friction, while the centrifuge was spun via an electromagnetic field. Working in a POW camp, Steenbeck and Zippe made several improvements on Beam's design.
Max Steenbeck and Gernot Zippe, prisoners of war from Germany and Austria, were the next to tackle problem. All his designs, however, used a horizontal centrifuge, which would invariably break due to the pull of gravity on the underside. Fritz Lange, a German émigré working for the Soviet program, set to work on constructing a centrifuge. Soviet physicists felt, correctly, that gaseous diffusion did not make sense, since it would use more power than it could produce. While centrifuges were thought a lost cause in American nuclear engineering, scientists abroad continued to work on them. Because the centrifuge does not require massive capital investment or special equipment, it is the preferred method of separation today, and poses the biggest threat for proliferation. In the early 1950s, however, a German POW in the Soviet Union produced an efficient and durable centrifuge. Manhattan Project scientists opted to pursue gaseous diffusion over gas centrifuges as the primary method for uranium isotope separation, and in January 1944 Army support for the gas centrifuge method was dropped. The centrifuge Beams constructed could separate U-235 from U-238, but required huge amounts of energy and could only sustain a short run before breaking down in other words, it was not suited for industrial production. Beams pioneered this method and received much of the early funding.Ī high-speed centrifuge initially seemed promising for uranium enrichment, but the Manhattan Project failed to produce a workable model, and research stopped during the war. A cascade system composed of thousands of centrifuges could produce a rich mixture. This is because the lighter U-235 isotope would be less affected by the action and could be drawn off at the top center of the cylinder.
In 1940, American physicists thought that the centrifuge was the best possibility for large-scale enrichment, and Beams received government money to attempt uranium enrichment via centrifuge.Ĭentrifugal force in a cylinder spinning rapidly on its vertical axis would separate a gaseous mixture of two isotopes. Manhattan Project director General Leslie Groves wanted to investigate as many possibilities as possible, and had the resources to simultaneously pursue multiple speculative projects.Ī centrifuge was the first device to separate chemical isotopes, used by Jesse Beams of the University of Virginia to separate chlorine-35 from chlorine-37 in 1934. Nevertheless, scientists pressed forward on several complicated techniques of physical separation, all based on the small difference in atomic weight between the uranium isotopes. Furthermore, with their masses differing by less than 1 percent, separation by physical means would be extremely difficult and expensive. Since they were chemically identical, they could not be separated by chemical means. Uranium-235 occurred in a ratio of 1:139 in natural uranium ore. This required separating the two isotopes and discarding U-238. "Enrichment" meant increasing the proportion of U-235, relative to U-238, in a uranium sample.
Scientists had concluded that enriched samples of uranium-235 were necessary for further research and that the isotope might serve as an efficient fuel source for an explosive device. This question consumed thousands of hours and millions of dollars. Once the power that was hidden in uranium became evident, the emphasis shifted to methods to separate the much more potent U-235 from its abundant relative, U-238.