A thermodynamic analysis is used to calculate the phase and component composition of uraniummolybdenum fuel with burnup 200 GW·days/ton. The equilibrium composition of the gas phase, consisting mainly of gaseous cesium whose pressure reaches 30 kPa, is determined more accurately. The quantitative composition of the phase of solid solutions of tellurides, whose formation degrades the structure of a fuel granule, is presented. Thermal tests of the fuel composition (U-Mo)-Al were performed. The investigation was performed in the presence of simulators of the chemically active fission products of cesium and iodine at different temperature. The interaction zone of (U-Mo)-Al is investigated by means of metallography and scanning electron microscopy. The data obtained on the composition of the indicated zone made it possible to conjecture the character of interaction between the fuel material and the aluminum matrix.The world is showing heightened interest in power reactor facilities of low and ultralow power and research nuclear reactors. These facilities use dispersion compositions in the form of UO 2 , UAl x , U 3 Si 2 , uniformly distributed in an aluminum matrix, as nuclear fuel. The 235 U enrichment often reaches >90% [1].When low (to 20%) enrichment fuel is used, the burnup decreases because of the lower volume content of 235 U [2]. As compensation it is suggested that fuel granules consisting of U-9%Mo (density 17.2 g/cm 3 ) in a matrix consisting of an aluminum alloy be used [3,4]. For example, if in the composition UO 2 -Al the uranium content is 3-3.5 g/cm 3 , then in the composition (U−9Mo)-Al it increases by a factor of 2. However, the use of the composition (U-Mo)-Al is held back by the interaction between uranium-molybdenum granules and an aluminum matrix with burnup 150-200 GW·days/ton [5]. This interaction is complicated. On the one hand, a chemical interaction is observed in the system U-Al at a temperature close to the melting temperature of aluminum. On the other hand, the effect of the fission products on the physicochemical and physical-mechanical characteristics of uranium-molybdenum alloy must be taken into account.The compatibility of the fuel with the matrix can be improved by introducing into the alloy a component, for example, silicon, that substantially lowers the interaction rate as well as by depositing a coating on the surface of the fuel particles [5][6][7][8].Even though from the technological point of view alloying with silicon is considered to be optimal, one should take note of the decrease of the stability of the γ-U-Mo phase. The introduction of silicon into an intermetallide does not exclude the focal interaction with aluminum; in addition, it can increase the temperature gradient at the boundary between a fuel granule and an aluminum matrix [6].Of special interest is the appearance of barrier coatings on the surface of uranium-molybdenum granules. Specifically, it is proposed that a layer of pure molybdenum be deposited on the fuel granules, which would then be protected from int...