**2.8 Problem definition**

Modern projects of fast reactors with sodium and lead coolant have some disadvantages and, therefore, not yet used reserves in terms of increased safety. This is particularly evident in the transition to high-capacity power reactors (e.g., BN-1200, BREST-1200). There are opportunities to improve the fuel, coolant, and structural materials used. The greatest effect in improving the safety of the nextgeneration reactors should be expected with the complex (simultaneous) use of improved core materials.

This chapter offers some ideas for improving fuel, coolant, and structural materials to improve reactor self-protection.
