The solving of ecological problems of future nuclear power is connected with the solving of long-lived radioactive waste utilization problems. This concerns primarily plutonium and minor actinides (neptunium, americium, and curium), accumulated in the spent fuel of nuclear reactors. One of the ways this can be solved is to use a fast reactor with uranium-free fuel. The physics of this type of reactor was widely investigated during the last year for the BN-800 reactor. The solutions of the most important problems were (a) a decrease in nonuniformity of the power distribution and (b) an increase of the Doppler effect. The next stage of such core investigations is an evaluation of self-protection to beyond-design accidents. Preliminary results show a high safety level of the BN-800 reactor with uranium-free fuel in unprotected loss-of-flow and unprotected transient overpower events.