An efficient turbine system that preferably utilizes nuclear thermal energy in a unique combined Carnot cycle and Rankine cycle in a closed cogenerative and regenerative cycle with a condensible working fluid heated by the nuclear thermal energy and delivered to each stage of a multiple-stage gas turbine for isothermal expansion with a portion of the spent working fluid condensed and injected onto stators before and between the turbine blade stages and onto the turbine blades for a regenerative cogeneration expansion that supplements and combines with the primary working fluid in the staged gas turbine and in a final adiabatic expansion in a staged recovery turbine with work extracted by electric generators.