The expressions for the exergetic losses of the two most used methods of separating isotopes of uranium - the diffusion and centrifuge. Calculation of exergetic losses for different ways to enrich fuel for reactors of different types of evidence of the undoubted advantages exergetic centrifuge method of enrichment, virtually no influence on the exergy efficiency steam-turbine cycle nuclear power plant, in contrast to the diffusion method of isotope separation.