Steam generators are in the form of tubular heat exchangers in which molten lead coolant flows within the pipes, while the water-steam flows in a space between the pipes, the steam generators are arranged in separate boxes and communicate with the reactor cavity by means of circulation conduits for raising and discharging the lead coolant, the steam generators and most of the circulation conduits and are arranged higher than the level of the lead coolant within the reactor cavity, and the circulation pumps are arranged within the reactor cavity on the circulation conduits and for raising the “hot” lead coolant, and a technical means is provided for ensuring natural circulation of the lead coolant through the reactor core when the circulation pumps are switched off. The specific volume of lead coolant per unit of power of the reactor is reduced and the safety of the reactor is increased.