A gas centrifuge is a device that performs isotope separation of gases. A centrifuge relies on the principles of centripetal force accelerating molecules so that particles of different masses are physically separated in a gradient along the radius of a rotating container. A prominent use of gas centrifuges is for the separation of uranium-235 from uranium-238. The gas centrifuge was developed to replace the gaseous diffusion method of uranium-235 extraction. High degrees of separation of these isotopes relies on using many individual centrifuges arranged in cascade, that successively achieve higher concentrations. This process yields higher concentrations of uranium-235 while using significantly less energy compared to the gaseous diffusion process.
The centrifuge relies on the force resulting from centripetal acceleration to separate molecules according to their mass, and can be applied to most fluids. The dense (heavier) molecules move towards the wall and the lighter ones remain close to the center. The centrifuge consists of a rigid body rotor rotating at full period at high speed. The Gas tube is located in the center of the rotor which is used to introduce feed gas into the rotor that removes the heavier product and waste streams in it. In addition, if one creates a thermal gradient in a perpendicular direction by keeping the top of the rotating column cool and the bottom hot, the resulting convection current carries the lighter molecules to the top while the heavier ones settle at the bottom, from which they can be continuously withdrawn.
In practice, several such centrifuges are connected in series. Each centrifuge receives one input and produces two output lines, corresponding to light and heavy fractions. The input of each centrifuge is the output (light) of the previous centrifuge and the output (heavy) of the following stage. This produces an almost pure light fraction from the output (light) of the last centrifuge and an almost pure heavy fraction from the output (heavy) of the first centrifuge.
Suggested in 1919, the centrifugal process was first successfully performed in 1934. American scientist Jesse Beams and his team at the University of Virginia developed the process by separating two chlorine isotopes through a vacuum ultracentrifuge. It was one of the initial isotopic separation means pursued during the Manhattan Project, but research was discontinued in 1944 as it was felt that the method would not produce results by the end of the war, and that other means of uranium enrichment (gaseous diffusion and electromagnetic separation) had a better chance of success in the short term. This method was successfully used in the Soviet nuclear program, making the Soviet Union the most effective supplier of enriched uranium.
In the long term, especially with the development of the Zippe-type centrifuge, the gas centrifuge has become a very economical mode of separation, using considerably less energy than other methods and having numerous other advantages. Effective usage of gas centrifuges were discovered by Pakistan which greatly enhances its capability to produce HEU fuels for both its commercial nuclear power plants and weapons. Pioneering research in physical performance of the centrifuges were studied by the Pakistani scientist Abdul Qadeer Khan in 1970s–80s, using the meaningful vacuum methods for advancing the role of the centrifuges for the development of nuclear fuel. According to one theoretical physicist involved in the program maintained that the centrifuge program was quite difficult, the most enduring, and challenging project that scientists were tackling and studying. Many of the theorists working with A.Q. Khan were unsure that either gaseous and enriched uranium would be feasible on time. The scientist recalled his memories: "No one in the world has used the [gas] centrifuge method to produce military-grade uranium.... This was not going to work. He [A.Q. Khan] was simply wasting time." Nonetheless and in spite of skepticism, the program was made feasible by Pakistan in the shortest time possible and enrichment by centrifuge has been used in physics experiments and effective physical use, particularly by Abdul Qadeer Khan in Pakistan, and the method was smuggled to at least three different countries by the end of the 20th century.
- Basics of Centrifuge - Cole Parmer
- Khan, Abdul Qadeer; Atta, M. A.; Mirza, J. A. (1 September 1986). "Flow Induced Vibrations in Gas Tube Assembly of Centrifuge". Journal of Nuclear Science and Technology 23 (9): 819–827. doi:10.1080/18811248.1986.9735059. Retrieved 10 December 2012.
- Gas Centrifuge Uranium Enrichment
- Khan, Feroz Hassan (November 7, 2012). "Mastering the Uranium Enrichment" (google book). Eating grass: the making of the Pakistani bomb (in English (Pakistan)). Stanford, California: Stanford University Press. p. 151. ISBN 978-0804776011. Retrieved 8 January 2013. More than one of