The main reasons for and the results of switching to uranium-erbium fuel in the units of the Lengingrad, Kursk, and Smolensk nuclear power plants are presented. It is shown that uranium-erbium fuel made it possible to regulate the steam coefficient of reactivity, upgrade the control rods, lower the power density in the core, increase the reliability of the fuel assemblies, increase burnup, decrease the volume of spent fuel, and improve the commercial indicators. The prospects for improving the characteristics of uranium-erbium fuel for RBMK-1000 reactors are also presented.Increasing the safety of nuclear power plants and improving the cost-effectiveness of power-generating units is a natural and stable trend in the modern stage of development of nuclear power. Safety analysis of nuclear power plants with RBMK-1000 reactors, performed by experts in this country and abroad, has shown that the improvements adopted after the Chernobyl accident substantially decrease the possibility of anticipated accidents developing into serious accidents. First and foremost, these improvements were directed toward eliminating the drawbacks of the construction of the control rods and the suboptimal uranium-graphite ratio, as a result of which the steam coefficient of reactivity was (4-5)β eff . It was decreased by loading additional boron absorbers and increasing the excess reactivity. The goal was achieved quickly, using means which the industry possessed during the mid-1980s.However, these measures were suboptimal, since at that time it was pointless to talk about the quality of the fuel cycle and certain other parameters, which do not directly determine the flow of accidents. Examples of the negative consequences are:• approximately a 25% decrease of fuel burnup, resulting in a higher fuel component of the intrinsic cost and sharpening of the problem of storing spent fuel, associated with an increase in the reloading rate;• increase of the operational excess reactivity, resulting in the appearance of a useless, for the purpose of controlling the distribution of energy release, part of the control rods (which are completely inserted), decrease of the efficiency of the