The present invention relates generally to electric power and process heat generation using a modular, compact, transportable, hardened nuclear generator rapidly deployable and retrievable, comprising power conversion and electric generation equipment fully integrated within a single pressure vessel housing a nuclear core. The resulting transportable nuclear generator does not require costly site-preparation, and can be transported fully operational. The transportable nuclear generator requires an emergency evacuation area substantially reduced with respect to other nuclear generators as it may be configured for operation with a melt-proof conductive ceramic core which allows decay heat removal even under total loss of coolant scenarios.

A steam generator includes a shroud and an annular stepwise helical baffle extending along at least part of a length of the shroud. There is a riser located in a central region of the steam generator. The helical baffle is made up of at least one annuler sector of flat plates. The edges of the flat plates may be straight or corrugated.

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.