In this work, we study the diffusion characteristics and structure of the molten salt FLiNaK with dissolved CeF3 in the operating temperature range of the molten-salt reactor. The temperature dependence of the self-diffusion coefficients of the ions that make up the salt mixture is represented with good accuracy as a linear dependence, except for the case of self-diffusion of Ce ions. As a rule, Li and F ions are more mobile than Na and K ions and significantly more so than slow Ce ions. The coordination numbers and their increase upon dissolution of CeF3 in FLiNaK were determined based on the calculation of partial radial distribution functions. The detailed structure of the melt is studied based on the construction of Voronoi polyhedra. The obtained topological characteristics indicate a predominantly tetrahedral type of distribution of Ce ions over the bulk of the system. Rotational symmetry of the 5th order prevails in the structure of the Li and F subsystems, and symmetries of the 3rd and 4th orders prevail in the Na and K subsystems, respectively. The simulation results can be used to search for actinide, which can be replaced by cerium in real experiments. © 2023 by the author.