Integrated fast reactor of the liquid metal cooled type

A nuclear reactor comprising a main vessel, a reactor core within said main vessel, fuel assemblies in said core, a support structure in said main vessel supporting said fuel assemblies, a liquid metal coolant in said core which flows upwardly through said fuel assemblies and exiting said core as hot metal coolant, primary heat exchangers in said main vessel receiving said hot coolant from said core, cold liquid metal coolant exiting from said heat exchanges into an intervessel space in a bottom zone of said main vessel, a primary enclosing said vessel core and separating said intervessel space from the zone containing said hot metal coolant, pumps in said intervessel space withdrawing said cold liquid metal from said intervessel space and reinjecting said cold liquid metal under pressure into a lower portion of said fuel assemblies, a circuit for cooling said main vessel supplied with a fraction of said cold liquid metal, said coolant circuit including on one side said main vessel and a flow reversing baffle plate, said flow reversing baffle plate comprising a first shell within said main vessel said coolant circuit including on the other side at the top portion of said main vessel said flow reversing baffle plate and a counter baffle, said counter baffle comprising a second shell which surrounds said primary vessel, said first shell surrounding said second shell, an annular chamber above said cold liquid metal between said second shell and said primary vessel and an inert gas in said annular chamber forming a gas/liquid metal interface chamber at a pressure such that the gas/liquid metal interface within said chamber is located below the top of said flow reversin baffle plate.