? à BASIC SEPARATION THEORYDOE-HDBK-1015/1-93Appendix ACH-01Rev. 0Page A-2SeparationFactorThe ability of a barrier to separate isotopes is expressed by a value called the separationfactor. It is denoted by the Greek letter ?, and is defined as the mole ratio of lightcomponent to heavy component in the gas passing through the barrier at a given pointdivided by a similar mole ratio on the high pressure surface of the barrier at the samepoint. The separation factor can be expressed by the following equation.In this equation, y and x are the mol fraction of light component on the low and highpressure sides of the barrier respectively. It should be emphasized that ?, as shown inFigure A-1, is a point value, and that x and y are concentrations at a given point on thetwo surfaces of the barrier. In practice, point values are usually not determined. Theaverage ?'s of the surface of samples are calculated from experimental separation data.As previously stated, the separation of isotopes is dependent upon the difference in themass of the particles. Under ideal conditions, the separation factor would be equal tothe ratio of the square roots of the molecular weights. For a mixture of U F and2356U F , this value is 1.0043 and is commonly referred to as the ideal separation factor.2386In actual practice, however, these ideal conditions cannot be duplicated. For example,to approach the ideal separation factor, only a small fraction of the total gas involvedcould be diffused through the barrier. For such a process to be productive, the plant sizeand its power consumption would be too large to be economically feasible. Limitationsof plant size and power consumption have, necessitated a reduction in the separationfactor to a lower value. This lower value is called the actual separation factor.StageSeparationThe ratio of the total molar rate of flow through the barrier within a converter to thetotal rate of flow into the same converter is called the cutand is designated by the Greekletter à.In a production cascade, a cut of approximately 0.5 is the optimum value with respectto operating efficiency and production.