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Centrifugation (Isotope Separation) Kristine Gonzales Amardeep Kaur Yangzhong Li Shaun Beall Aaron Sellers
Introduction • What is a centrifuge? • How is centrifugation classified? • Why is it useful?
Origin of Gas Centrifugation • Bredig - introduced idea, 1895 • Aston and Lindemann - suggested method, 1919 • Beams and co-workers - first successful separation, 1934
Applications • Role of Centrifugation - Purifying industrial waste and sewage - Production of raw materials - Mineral extractions - Food products - Chemical industry
Applications (cont.) • Uranium/Plutonium Separation - Department of Energy (DOE) implemented a program to turn highly-enriched uranium weapons into low-enriched uranium and plutonium metal - Low-enriched uranium will be turned into fuel feed in nuclear plants to generate electricity - Pure safe plutonium is recovered and used in power plants as well
Main Principles • Separates in the radial direction • Separation occurs at equilibrium • Description of separation - enrichment of components - circulation flow
Flow Description and Zone Outline • viscous flow near the side-wall • transient flow area • strongly rare gas • Three boundary conditions • - no-slip condition • - boundary temperatures are given • - parameters of external flows entering into the centrifuge rotor
Governing Equations General Partial Differential Equation N (concentration) is a function of • Property of the gas, D (coefficient of self-diffusion), ΔM (M2 – M1 ) • Property of the centrifuge, z (height), a (radius) • Physical condition, p (pressure), T (temperature), w (angular velocity), u (radial velocity)
Concurrent Centrifuge • enrichment factor, Nout / Nin α0 = exp( ΔM V2 / 2RT ) • The concurrent centrifuge has the following disadvantages: 1. the take off pressures for the light fractions might be low and is different with that of the heavy fractions (hard to suck gas out). 2. the stage enrichment is small (α0 is small).
Countercurrent Centrifuge • maximum theoretical separation factor • The advantages of the countercurrent centrifuge are: 1. since a high separation factor can be obtained in a single unit (efficient); 2. both fractions can be extracted from the periphery, where the pressure is high, (no take off problems);
Uranium Isotope Separation • Only 0.71% of Uranium-235 is present in the nature • U-235 cannot be separated by chemical separation methods • Gas centrifuge is used to separate the uranium isotopes on the basis of different masses. • The lighter isotope (U-235)moves faster than the heavier isotope(U-238).
Competing Methods • Electromagnetic Isotope Separation • Laser Isotope Separation (L.I.S.) -Atomic Vapor L.I.S. -Molecular L.I.S. • Diffusion • Distillation and Chemical Exchange • Density Difference
Conclusion • Past/Present : generated things from common household products to nuclear weapons. • Future: Centrifugation will show the diversity with which respondents will separate the whole cells/viruses, subcellular organelles, nucleic acids, proteins and organic phases.
Acknowledgments • Borisevich, Valentin D, Levin,Eugene V. Separation of Multicomponent Isotope • Mixtures by Gas Centrifuge’: Separation Science and Technology. New York • Rensselaer Polytechnic Institute (2002): 1697-1735. • Conway, John T. “DNFSB Letterhead.” October 27, 1993. Defense Nuclear Facilities Pike, John. Nuclear Weapons: Uranium Production. Global Security Organization in the • News.17:20. February 23, 2003. http://www.globalsecurity.org/wmd/intro/uranium.htm • Records, Alan, and Ken Sutherland. Decanter Centrifuge Handbook. New York: Elsevier Advanced Technology, 2001. • Uranium Enrichment/Fuel Fabrication. November 13, 2003. Online. Internet. Available http://www.antenna.nl/wise/uranium/epusa.html. • McCall, J.S., Potter B.J. Ultracentrifugation. Baltimore: Williams & Wilkins Company, 1973. • Avery , Davies. Uranium Enrichment by Gas Centrifuge. Great Britain: The Pitman press, 1973.