This work presents the effects that produce the change in entropy during separation processes; it takes into account the dilution of UF6 in a carrier gas (H2, He, N2, Ar, Xe, SF6, etc.). Comparisons were made between two technologies: one a mature process currently used, i.e., centrifugation (process A), and the other in development, i.e., processes based on a laser [Condensation Repression Isotope Separation by Laser (CRISLA), Molecular Laser Isotope Separation (MLIS), etc.] (process B). The calculations were made using the principles of mix thermodynamics. The results indicate that entropy expenditure is two orders of magnitude higher than that necessary to separate isotopes when the amount (of isotopes) is the same in both process A and process B.