Abstract: The nuclear reactor includes a fuel core (5) inside a vessel (2) and a system (1) for cooling the core (5), in which a liquid metal circulates and on which is placed at least one steam generator (15). The steam generator includes a casing (15a) in which the liquid metal circulates, water-feed means (16) and means for heat exchange between the liquid metal and the feed water. The liquid metal is caused to circulate in the cooling system (1), the steam generator (15) not being fed with water and the liquid metal circulating in the steam generator (15) is cooled by the flow of a gas in contact with the casing (15a) of the steam generator (15). The cooling device includes a tubular element (25) placed around the casing (15a) of the steam generator and defining an annular space for a cooling gas to flow around the casing (15a).

Abstract: The tube (4) to be plugged is cut at its ends adjacent to the first and to the second branch (14, 15) and the metal of the junction zones (16, 16') of the tube (4) with each of the branches (14, 15) is eliminated. At least one portion of the tube (4) adjacent to at least one of the branches (14, 15) is cut and eliminated. Into each of the ends of the tube (4) in place inside the heat exchanger is introduced a plug (24, 30) of tubular shape, the diameter of which is smaller than the inside diameter of the tube (4), so that the plug has a closed end (24a, 30a) inside the tube (4) and an opposite end located inside the corresponding branch (14, 15). The plugs (24, 30) are fixed in place in the branches (14, 15), and a continuous sealing weld is made between each of the plugs (24, 30) and the corresponding branch (14, 15 ), the tube (4) having some freedom of movement in the longitudinal direction in relation to the plugs (24, 30).

Abstract: The invention relates to a device for thermal protection of a component of a fast-neutron nuclear reactor consisting of at least one shell (10, 11) of a diameter smaller than the diameter of the passage (2) for the component (4) but greater than the diameter of the component (4). The length of the shell (10, 11) fixed under the flange (5) of the component (4) is greater than the slab thickness (1). Circulation of blanket gas (13) is established in the annular space (7) between the component (4) and the passage (2).The invention applies in particular to nuclear reactors cooled with liquid sodium whose upper level is under an argon blanket.