[en] The direct and indirect energetic investments for the construction and maintenance of nuclear power plants as well as for the fuel cycle, were analysed. The existing data in the literature was applied to the brazilian nuclear programme with a special attention to those peculiar aspects, particularly the enrichment process and mining. The energetic investments required by the various systems, using the 626 MW nuclear power stations or the 1240 MW, were determined in function of the brazilian ore with 0.108% of U₃O₈ and of a mine with a stripping ratio (the ratio of tons of overburden to tons of ore) of 28/1. About the enrichment, two hypothesis were considered for the concentration of ²³⁵U in the enrichment plant tails - the tails assay (0.25 and 0.35% of ²³⁵U) and for the specific energy consumption per unit of separative work (3.60 and 4.40 MWh/UTS). The fuel cycles with and without recycling of uranium and plutonium were taken in consideration. During the lifetime of the plants and for the various cases considered there is a self-consumption between 10 and 16 percent of the produced energy. The cumulative energy requirements as a function of time, was made for individual plants and for the brazilian nuclear programme as a whole in its actual form (9 nuclear power plants). (E.G.)