Appendix ADOE-HDBK-1015/1-93BASIC SEPARATION THEORYRev. 0CH-01Page A-1BASIC SEPARATION THEORYIntroductionThe fundamental principles upon which a gaseous diffusion plant is based are as follows.1.All the particles (atoms, molecules, or ions) which make up the gas arecontinuously moving in straight lines in all directions. The particles collidewith anything in their path (e.g., other particles or the walls of the container),thereby altering the course of moving particles but not their average velocities.2.All of the particles have the same average kinetic energy. Accordingly, if themasses of the particles are different, so must their velocities be different withthe lighter particles having the greater average velocities.On the basis of the two principles stated above, if a quantity of gas is confined by a porousmembrane or barrier, some of the gas will escape through the pores in the barrier. If theconfined gas is isotopic (a mixture of particles of different molecular weights), the lighterparticles of the gas will have a greater tendency to diffuse through the barrier because of theirgreater average velocities. Consequently, the gas which has passed through the barrier willbe enriched in the light constituent while that gas which has not diffused through the barrierwill be depleted in the light constituent.IsotopicSeparationThe isotopes with which we are concerned are those of uranium; namely Uand U. In235 238order that the isotopes of uranium may be separated by the gaseous diffusion process, it isnecessary that the uranium be in a gaseous state. This is accomplished by combining theuranium with fluorine to form uranium hexafluoride, which is a gas at workable temperaturesand pressures. Another advantageous quality of uranium hexafluoride is that fluorine has noisotopes to further complicate the separation process. In general, the following discussionis concerned with the separation of UF and UF .235 2386 6
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