Abstract: The internal shell (6) of the nuclear reactor comprises at least one cylindrical sleeve (10) with a vertical axis. An annular enclosure (20) is arranged on the internal periphery of the cylindrical sleeve (10), at the top part thereof. The enclosure (20) is open upwards and delimited by a cylindrical secondary sleeve (21) arranged coaxially and inside the cylindrical sleeve (10) of the internal shell. The top end of the secondary sleeve (21) is located below the high level (14a) of the liquid metal inside the internal shell (6). An annular base (22) is fixed to the bottom end of the secondary sleeve (21) and onto the internal surface of the cylindrical sleeve (10) of the internal shell (6), below the low level (14b) of the liquid metal.

Abstract: The device includes a main receptacle (1) having an overflow pipe (2) and a secondary receptacle (9) mounted so as to be freely movable in the vertical direction inside the main receptacle (1). The inner space of the secondary receptacle (9) communicates with a drainage pipe (8) for fluid lost by the hydraulic installation. The secondary receptacle (9) floats in the fluid contained in the main receptacle (1). The immersion level of the secondary receptacle (9) increases, depending on the amount of lost fluid received by the secondary receptacle (9), and the supply of fluid from the main receptacle (1) is caused by the immersion of the secondary receptacle (9).

Abstract: The upper part of the vessel (3) is cooled as a result of the circulation of cooled sodium (27). The cooled sodium coming form the lower part of the reactor core is introduced into a first collector (15) via pipes (17) and then overflows into a second collector (16). The second collector (16) or return collector is delimited by an overflow sleeve (18) and by an inner sleeve (21), the height of which is substantially less than the height of the overflow sleeve (18). The lower part of the inner sleeve (21) is connected to the overflow sleeve (18) by an annular plate (22) ensuring the stiffening of the sleeve (18). The height of the sleeve (21) is preferably between one-third and third of the height of the sleeve (18). This prevents vibrations from being generated during the circulation of the sodium.

Abstract: The core is constituted by detachable assemblies (21) disposed vertically and maintained in position by a support or bolster (22) receiving the lower part or foot (21a) of the assemblies (21) inside sleeves having a vertical axis (25). Each of the sleeves (25) includes at least one orientation configuration (31) for the assembly (21) and each of the assemblies (21) includes on its foot (21a) at least one orientation configuration (30) adapted to cooperate with the orientation configuration (31) of the sleeve (25). The charging of the first core of the reactor may be carried out in a simple operation without a prior charging of false assemblies in an air atmosphere.

Abstract: The cooling device comprises a heat exchanger (7) immersed in the hot header (4) of the nuclear reactor vessel, a substantially vertical tubular conduit (14) passing through the stepped wall (2) vertically below the exchanger (7), a bell (16) fixed under the exchanger (7) in the extension of its lower part and a mechanism for compressing inert gas and relieving pressure in the internal space of the bell (16). The inert gas compressed in the bell (16) enables the liquid metal in the hot header (4) to be completely separated from the liquid metal in the cold header (5). When the pressure in the bell (16) is relieved, the outlets (10) for the cooled liquid metal in the exchanger (7) are brought into communication with the cold header (5) through the bell (16) and the conduit (14).

Abstract: The pump (8) comprises a vertical body (8a) and a discharge sphere (10) in its lower part. Discharge pipes (14) are connected to the sphere (10). The sphere (10) is suspended from the plating (4) of the reactor through a flexible metal strip (20). The sphere (10) is connected to the strip (20) in a region located below the region of connection between the strip (20) and the plating (4). The invention is in particular applicable to the primary pumps of fast neutron nuclear reactors of the integrated type.

Abstract: In order to multiply by three or four the combustion level of nuclear fuel pellets in fast neutron nuclear reactors, it is proposed that following a normal irradiation period of said pellets in the reactor core, that the irradiated can be replaced by a new can with an internal diameter slightly exceeding that of the first can. Thus, the pellets can undergo a new irradiation cycle in the reactor core. Preferably, the can is destroyed by progressive local melting over its entire length and the new can is preheated to facilitate the introduction of the pellets.

Abstract: The cover plug (4) comprises a cylindrical barrel (8), a support plate (10), a group of vertical tubes (12) for the control rods and for the instrumentation of the core, an apertured transverse plate (28) fixed to the lower end of the barrel (8) and a transverse deflection plate (32) located above the apertured plate (28). The transverse deflection plate (32) is suspended from the barrel (8) by substantially vertical elastically yieldable strips (34) evenly spaced apart on the periphery of the barrel (8). The strips (34) are welded to the barrel (8) by their upper end and to the edge of the deflection plate (32) by their lower end. They are located in the region of openings (35) in the barrel (8) which permit radial movement of the deflection plate. The deflection plate (32) is also integral with tubes (14b) receiving the control rods disposed in a single row coaxial with the barrel (8).

Abstract: A liquid metal cooled pool type nuclear reactor incorporates an emergency heat exchanger having a novel geometry. The heat exchanger comprises circular and annular tube plates coaxially aligned. The tube bundle has a vertical straight part connected to the central tube plate, a bent horizontal circular portion extending over one-third of the heat exchanger's circumference for returning the bundle, and a vertical straight return part joining the peripheral tube plate.

Abstract: A separator disposed in parallel relationship is provided for separating liquid particles entrained in a gas stream. It comprises zigzag walls (25) having fins (27) each covering each of the convex folds (28) of the walls while forming an open scoop (29) facing the gas flow. Each fin has a portion (27a, 27b) parallel to the wall (25) which supports it and which is spaced apart from said wall upstream and downstream of the fold (28). A rear connection zone (27c) gradually joins the wall and is connected along a line located substantially in the same plane orthogonal to the two walls defining a channel for the gas flow than the leading edge of the following fin (27).

Abstract: An ultrasonic beam is sent into liquid metal from a transmitting point (3) outside the enclosure (1) containing the liquid metal, the beam is detected outside the enclosure (1) after it has passed through the liquid metal, the amplitude of the ultrasonic waves detected is compared with the amplitude of the transmitted ultrasonic waves and the attenuation of the ultrasounds produced by the passage through the liquid metal which may contain gas bubbles (2) is determined. The device comprises a wave guide (4) metallurgically connected to the enclosure (1). A processing unit (10) connected to the ultrasonic transducers (3, 6) measures the attenuation.

Abstract: A steam generator in which the heat-carrying fluid is a liquid metal and the detection of leakages is carried out by sampling the liquid metal. The end of the steam generator through which the liquid metal enters comprises a tube plate (2), a thermal protection plate (10) and a hollow flow sill (22) constituting the end part of the bundle case (4). Tubes (20) for protecting the tubes (3) of the bundle are placed around each of the tubes (3) between the protection plate (10) and the tube plate (2), the space (17) between these two plates being closed on its periphery by a sleeve (15). The hollow sill (22) communicates with the space (17) through tubes (27) and with the inner volume or the bundle case (4). A liquid metal take-off device (31, 32) is placed in the hollow sill (22). The invention applies in particular to steam generators of fast neutron nuclear reactors cooled with liquid sodium.

Abstract: Anti-vibratory support device for a pipe whose thickness is small relative to its diameter, comprising a collar (2) formed by at least two rigid annular sectors (2a, 2b, 2c) which are articulated at at least one of their ends to the succeeding sector, to pivot about an axis parallel to the axis of the pipe (1). At least two successive sectors (2b, 2c) are interconnected by an elastic junction means (10, 11, 12) which enables the collar (2) to be closed. Parallelepipedic pads (18) made from knitted stainless steel wire disposed in cases (15) are interposed and put under compression between the collar (2) and the pipe (1). The invention is in particular applicable to pipes conveying liquid sodium of the secondary circuit of fast neutron nuclear reactors.

Abstract: Device for purifying liquid metal coolant for a fast neutron nuclear reactor, comprising a pump (6) for circulating the liquid metal, the metal then being purified and heated after purification, as well as a filter (24) of metallic fibers. It consists of an assembly of annular chambers with a vertical axis, closed at their lower part by a base plate (10) and defined and separated from each other by an assembly of coaxial cylindrical metallic shells. The device comprises, from the exterior inwards, a degassing chamber (12), a chamber enclosing an economizer-exchanger (14, 16), a thermal insulation wall (18), a cooling chamber (20) and a purifying chamber (22) in the central part of which is a filter cartridge (24). In the central part of the cartridge (24) is a channel (25) for collecting the purified liquid metal in communication with a basin (44) for collecting the purified liquid metal rising above the device.

Abstract: A double-wall tube for a heat exchanger and method for producing same, the tube being formed by two tubular walls (1, 2) mounted one inside the other with a very small clearance (3)and then made to have a tight fit therebetween, the outer surface of the inner wall (2) and the inner surface of the outer wall (1) being interconnected by a thin layer of brazing metal in regions (4) which are discontinuous both in the circumferential direction and in the longitudinal direction of the tube. The brazed regions (4) represent 5 to 15% of the confronting surfaces of the inner wall (2) and outer wall (1) of the tube. The invention is in particular applicable to steam generators of fast neutron nuclear reactors.

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.

Abstract: Cover-plug for the core of a fast neutron nuclear reactor, comprising a support-plate (6), a cylindrical shell (8) having a vertical axis fixed integrally to the support plate (6) and braces (14) which are transverse relative to the shell (8). Vertical tubes fixed to the support plate (6) at their upper part are joined to the braces (14), which consist of at least two conical webs (14) having their axes coincident with the axis of the shell (8). These conical webs have a top angle greater than 120.degree. and a diameter which is slightly smaller than the diameter of the shell (8), at their base. The brace (14a) situated in the lowest position in the shell (8) ensures the deflection of the reactor cooling fluid. The invention applies, in particular, to fast neutron nuclear reactors of the integrated type.

Abstract: According to the invention, the central body (10) of the steam generator filled with liquid sodium in its upper and middle part comprises in its lower part, on one hand, a crowned end wall (23) under which an inert gas is injected for forming a pocket (24) which contains a small volume of gas and defines a gas-liquid separation surface (25) for the reflection and the attenuation of a pressure wave in the event of a sodium-water reaction, and, on the other hand, a spider element (11) which connects the lower end of the central body (10) to an end element (16) provided with a frustoconical portion (17) which extends with an annular clearance into the outlet pipe (5) for the liquid sodium which has travelled through the tube bundle (7). Application in particular to nuclear power stations.

Abstract: A steam generator for a nuclear reactor cooled with liquid metal, comprising a bundle consisting of double-walled tubes (20) arranged inside an enclosure in which the liquid metal circulates. The tubes (20) which are substantially straight and directed in the axial direction of the steam generator enclosure are each formed by at least two successive sections (20a and 20b) in the axial direction. Each section (20a or 20b) comprises an outer tube (27a or 27b) welded at one of its ends to at least one leakage collecting chamber (25) arranged wholly inside the enclosure. The adjacent sections of the outer tubes (27a, 27b) are not joined together. Each section also comprises an inner tube (28a or 28b) welded to the adjacent inner tube, inside the chamber (25). The leakage space between the tubes (27 and 28) communicates solely with the inner space of at least one collecting chamber (25). The invention applies in particular to fast neutron nuclear reactors cooled with liquid sodium.

Abstract: The invention relates to a secondary heat transfer circuit for a liquid metal-cooled nuclear reactor, as well as to a steam generator which can be used in such a circuit.According to the invention, a downstream buffer tank and an upstream buffer tank are arranged within the steam generator. The upstream buffer tank is annular and surrounds and communicates with an area of the generator by which the liquid metal flows downwards between the exchange zone and the discharge tube. The pressure of the neutral gas pocket in the downstream buffer tank is higher than that of the pocket of the upstream buffer tank.Application to fast neutron nuclear reactors.