The invention relates to nuclear physics, and specifically to reactor fuel elements and units thereof, and particularly to the composition of solid ceramic fuel elements based on uranium dioxide, intended for and exhibiting characteristics for being used in variously purposed nuclear reactors. The result consists in a more reliable, special structure and a simple composition of uranium dioxide without heterogeneous fuel pellet additives, approaching the characteristics of a monocrystal having enhanced, and specifically exceeding reference data, thermal conductivity as temperature increases, and a simple production method thereof. The result is achieved in that pores of between 1 and 5 microns in size are distributed along the perimeters of grains in the micro-structure of each metal cluster in a nuclear fuel pellet, and in that located within the grains are pores which are predominantly nano-sized. In addition, the metal clusters comprise between 0.01 and 1.0 percent by mass. The invention provides for a method of preparing a nuclear fuel pellet, including precipitating metal hydroxides, in two stages, having different pH levels. Uranium metal is melted at a temperature exceeding 1150°C, sintering is carried out in an insignificant amount of liquid phase at a temperature ranging between 1600 and 2200°C in a hydrogen medium until forming uranium dioxide, the structure of which includes metal clusters dispersed therein. An X-ray photon spectroscope is used for identifying the new structure of the UO2 pellet and the additional U-U chemical bond.