Abstract: A heat exchanger of the type incorporating an auxiliary cooling device includes an envelope with inlet and outlet windows for conducting a primary heat transfer medium through the envelope. A bundle of heat exchange tubes is mounted in the envelope with corresponding first ends of those tubes being located adjacent to the inlet window and corresponding second ends of the tubes being located adjacent to the outlet window. First and second collectors are in fluid communication with the tube ends for conducting a second heat transfer medium through the tubes. The auxiliary cooling device is positioned in the inlet window and surrounds the tube first ends and a ferrule projecting upwards from the envelope from the inlet window therein surrounds the cooling device to direct the primary heat transfer medium through the cooling device and into the inlet window of the envelope.

Abstract: Fast neutron nuclear reactor, which comprises a vessel containing a liquid cooling metal, a core immersed in this metal, the vessel having a flooring on which rests a structure for the core, said core being constituted by a juxtapositioning of assemblies fixed into the structure, the liquid cooling metal circulating in an upwards manner in the core, the liquid metal being called "cold liquid metal" before its circulation in the core and "hot liquid metal" after it has passed into the latter, wherein it comprises a fuel element storage structure, which is independent of the core structure and is arranged concentrically with respect to the latter and rests on the flooring, a circulation of cold liquid metal being ensured in the assembly by recovering leaks of the core structure.

Abstract: A steam generator for transferring the heat carried by a liquid metal to a water - steam circuit. It comprises a drainage tank directly suspended at the lower end of the envelope. A drainage tube connected to the bottom of the envelope is disposed within the tank and carries a burster disk at its end. This disk is placed behind a detachable observation window, fixed to the drainage tank and permitting the replacement thereof.

Abstract: Liquid metal-cooled nuclear reactor incorporating a main vessel sealed by a slab and containing the reactor core, an inner vessel placed within the main vessel and defining in the latter a hot zone filled with relatively hot liquid metal and a cold zone filled with relatively cold liquid metal, at least one pump for circulating the liquid metal between the cold zone and the hot zone across the core and at least one heat exchanger disposed between the hot zone and the cold zone, wherein the inner vessel comprises two truncated cone-shaped ferrules opposed by their large bases and a small diameter cylindrical ferrule extending the small base of the upper truncated cone-shaped ferrule, the reactor core resting on the small base of the lower truncated cone-shaped ferrule by means of a support structure, the hot zone being formed within the inner vessel, while the cold zone is formed between the main vessel and the inner vessel.

Abstract: The invention relates to a nuclear reactor cooled by a liquid metal contained in a vessel obturated by upper closing means, said latter essentially being constituted by a slab and rotating plugs. The upper closing means comprise at least one circuit for circulation of a cooling gas or liquid, this circuit being provided with means for maintaining the closing means at a homogeneous temperature at least equal to 100.degree. C. and preferably close to 120.degree. C. The invention is applicable to the production of less cumbersome and less expensive fast neutron nuclear reactors.

Abstract: Heat exchanger for a nuclear reactor of the type in which the main vessel is sealed by an upper slab, comprises a plurality of substantially straight exchange tubes mounted between on the one hand an upper annular tube plate associated with a secondary fluid discharge chamber and on the other a lower annular tube plate associated with a supply chamber, a ferrule surrounding the said tubes and provided with a discharge orifice for the primary fluid, a central shaft which communicates with the supply chamber, and a supply manifold and a discharge manifold for the secondary fluid, wherein it comprises a supporting ferrule fixed to the periphery of the upper tube plate and sealed at its upper end by a dome, said ferrule having on its outer periphery a supporting flange by the said slab, the manifolds being superimposed in the supporting ferrule and fixed to a horizontal plate, which is itself fixed to the supporting ferrule, the supply manifold being connected by at least one pipe to the upper end of the shaft, t

Abstract: Fast neutron nuclear reactor cooled by a liquid metal, comprising a main vessel sealed by an upper slab and within said main vessel at least one heat exchanger between the said liquid metal and a second fluid, at least one pump for circulating the liquid metal, a cylindrical inner vessel with a vertical axis and placed on flooring resting on the bottom of the main vessel, the inner vessel containing the reactor core which rests on a support bearing against the bottom of the main vessel by means of the said flooring, the liquid metal circulating from bottom to top through the reactor core, wherein the said inner vessel incorporates an internal baffle which revolves about the vertical axis of the inner vessel, said baffle comprising an upper cylindrical part adjacent to the inner vessel and arranged above the core, and a lower cylindrical part surrounding the core and having a smaller diameter than the upper part, said lower part being connected to the upper part by a frustum-shaped part, whereby the baffle con

Abstract: Heat exchanger of a nuclear reactor, whose vessel is sealed by a slab, the exchanger being of the type which has within a vertically axed outer ferrule a plurality of heat exchange modules with substantially straight tubes, each of the said modules having a secondary fluid inlet chamber and a secondary fluid outlet chamber and means for introducing and removing the primary fluid with respect to the exchange modules, wherein it comprises a base plate peripherally fixed to the said outer ferrule, means for supporting the outer ferrule by the slab, supporting ferrules for the modules, each ferrule traversing the base plate and being connected on the one hand to the upper end of the module and on the other to the said base plate, a plurality of pipes for the supply and removal of the secondary fluid sealingly traversing the base plate, a supply manifold and a discharge manifold for the secondary fluid positioned within the outer ferrule above the base plate, said manifolds being respectively connected to the supp

Abstract: In a first step, uranium hexafluoride gas is reacted with steam in a first region of a vessel. In a second step, the oxyfluoride UO.sub.2 F.sub.2 obtained in the first step is converted to UO.sub.2 in a two-stage reduction process in which it is first contacted with a mixture of hydrogen gas and steam in one zone of the second region of the vessel, then contacted with the hydrogen gas in another zone of the second region.