[en] A 3D model of large-power fast breeder power reactor is described in hexagonal geometry. A number of problems is formulated for carrying out test calculations: determination of 'wave-up' enrichments under steady-state refuelling conditions; temperature and power variations; determinations of reactivity effects depending on fuel burnup; determination of control rod efficiency; investigation of energy release field distribution at non-design position of burnup compensators. For the purpose of solving this problems, a 2D model of the reactor is presented in (R,Z) geometry which has been derived from the 3D model through homogenization of certain regions. The results of calculating for this model are presented. The calculations were performed in 2D (R,Z) geometry and in 2D and 3D geometry with hexagonal grid in few-group approximation. 8 refs.; 5 figs.; 18 tabs