Abstract: Fast neutron nuclear reactor of the type comprising a primary circuit integrated into a liquid metal-filled vessel and containing the reactor core, as well as means for circulating the said liquid metal and means for transferring the heat carried by the liquid metal to the water circulating in a water/steam circuit, wherein the heat transfer means comprise at least one steam generator located in the reactor vessel and having at least one group of inner tubes in which circulates the water of the water/steam circuit, at least one group of outer tubes immersed in the primary liquid metal, the outer tube surrounding each of the inner tubes in order to define therewith an annular space under a neutral gas pressure, connected to secondary circuit with a low thermal power having means for circulating this pressurized neutral gas, such as helium in said annular space and ensure the heat exchange.

Abstract: A steam generator installation comprises an envelope, first and second tube plates defining an intermediate fluid discharge chamber; a bundle of external tubes connected to the tube plate, an internal tube being arranged within each external tube, a liquid metal circulating outside the external tube, an admission chamber for the water, which is introduced into the internal tubes, a discharge chamber for the steam and an admission chamber for the intermediate fluid. This fluid circulates between the internal tubes and the external tubes. The intermediate fluid discharge chamber is connected to the inlet of a heat exchanger, which cools it. The intermediate fluid admission chamber is connected to the outlet of this exchanger.