The results of systems studies of the coordinated development of nuclear and thermonuclear power generation to secure rapid growth of energy production in the current century are presented. Taking into consideration the increasing difficulties in meeting the required demand for energy, it is expedient to use thermonuclear reactors as high-power neutron sources for the production of nuclear fuel in a blanket. It is shown that in such a structural configuration of an energy system the fraction of thermonuclear sources can be relatively small. For sufficiently large scales of nuclear fuel production, even the paradigms for the development of nuclear power plants can change toward lower unit capacity in order to increase safety, simplify the fuel cycle, and do away with reprocessing of high-level spent fuel.