Abstract: The steam generator includes a feedwater delivery device at an upper axial end of an annular space between an outer shell and a bundle wrapper of the steam generator. The feedwater, delivery device includes a header (11) having a shell of toroidal general shape, at least one feed pipe for the header and feedwater distribution means (14) in the upper part of the annular space of the steam generator. The feedwater distribution means (14) include a plurality of openings (17) that pass through the upper part of the shell of the toroidal header (11) and are distributed circumferentially on the wall of the header and a plurality of tubes (15) fixed via a lower end part at an opening (17) of the header (11). Each of the straight tubes (15) includes an upper end part through which openings (20), such as water passage slots, pass and a cap (16) fixed to the upper end of the tube (15) surrounding, with a radial clearance, the upper end part of the tube (15).

Abstract: A first coolant gas in contact with the core (5) of the high temperature nuclear reactor (1) is circulated in a closed circuit, a second heat-exchange gas is heated by heat-exchange with the first exchange gas or coolant gas and the second heat-exchange gas heated by the first coolant gas is used in an intermediate exchanger (7) to drive at least one gas turbine (2) coupled to an electric generator (4). The first exchange gas consists mainly of helium and the second exchange gas contains substantially 50 to 70% by volume of helium and 50 to 30% by volume of nitrogen. The second heat-exchange gas is circulated in a closed circuit so that the second heat-exchange gas at least drives the at least one gas turbine (2). Preferably, the device also comprises a tertiary circuit (10) in which there circulates water and steam formed by heating water from a fraction of the second exchange fluid and used to drive steam turbines (3a, 3b, 3c) preferably mounted on the shaft of the electric generator (4).

Abstract: A method for loading nuclear fuel assemblies inside a nuclear plant reactor core includes positioning at a second diagonal of a core plate, a triple guide module using an auxiliary mast of a loading machine or of a handling member designed therefor. Then, at least at each of the next diagonals of the core plate, positioning a guide module consisting of six consecutive guide tiles diagonally mounted so as to enable one to seven fuel assemblies to be installed one by one. Then, at an angle opposite to the initial angle for positioning the assemblies, positioning at the penultimate diagonal, the triple guide module, and two single-unit guide modules, so as to enable six fuel assemblies to be installed at the penultimate diagonal.

Abstract: A tool is provided for assisting the loading of nuclear fuel assemblies inside a reactor core. The assemblies have a prismatic shape and square cross-section, and are positioned on a plurality of adjacent locations, likewise with square cross-section, each comprising positioning blocks and orifices for circulating a liquid coolant and in particular water. The tool comprises an actuator which, in retracted positions, has a square requirement less than that of a fuel assembly. The actuator is provided with means for acting at the intermediate fuel assemblies and/or at the intermediate baffles of the reactor vessel of the location concerned at which it is being introduced. The actuator is provided with gripping means designed to cooperate with the grab of a handling mast enabling its insertion at the location concerned.

Abstract: The invention relates to a method for handling a nuclear reactor upper internals guide tube (15), in which method a gripper (30) equipped, at a first end, with two opposed arms (32) that can be moved between a retracted position and a deployed position and, a second end, with a control member (37) for controlling the said arms is introduced into horizontal guide plates (24) of the upper tube (16) of the guide tube (15), the first end of the gripper (30) is placed under one (25A) of the two upper guide plates of the lower tube, the two arms are deployed, the two arms are applied under this guide plate and the gripper (30) is used to simultaneously raise the two tubes of the guide tube (15).

Abstract: The steam generator (1) comprises an outer casing (2) with an axis (8) that is in a vertical disposition when the heat exchanger is in service, a bundle of tubes having straight portions that are parallel to one another and to the axis (8) of the heat exchanger (1) inside the outer casing (2), at least one tube plate (4) having through holes, each receiving the end of a tube of the bundle, and at least one water chamber having a wall (6) that is circularly symmetrical about the axis (8) of the heat exchanger (1), the water chamber being fixed to the tube plate (4) at the bottom of the heat exchanger. The surface (14a) of the solid bottom (14) of the heat exchanger includes at least one central point disposed substantially on the axis of the heat exchanger (1) at a highest level relative to the set of points constituting the inside surface (14a) of the bottom (14) of the heat exchanger.

Abstract: The invention relates to a method and a device for loading a fuel assembly into the core of a nuclear reactor. The inventive method consists in: inserting a dummy assembly (4) into the loading location (3) of the fuel assembly (5), said dummy assembly essentially having the same shape and dimensions as the loading location (3) and comprising smooth side walls; fixing the position of at least one fuel assembly (5) that is adjacent to the loading location (3), in the presence of the aforementioned dummy assembly (4), in relation to at least one second assembly (5) of the core, using at least one fuel assembly support tool (11); removing the dummy assembly (4) from the loading location (3); introducing the fuel assembly (5) which is being loaded into the loading location (3); and removing the fuel assembly support tool(s) (11).

Abstract: The liquid effluent from solvent extraction contains radioactive thorium Th-231 and Th-234. This invention uses an ion exchange process to remove and concentrate the thorium. The process is designed so that the thorium remains on the ion exchange column until it decays to uranium and protactinium. These decay products are subsequently replaced by additional thorium. Therefore, the thorium never reaches break-through and the column can be used continuously without regeneration.

Abstract: The device comprises a first valve (35a) and a second valve (35b) each comprising a chamber (13a, 13b) communicating via an admission orifice (19a, 19b) with a circuit or a receptacle containing a first or a second fluid, and via an exhaust orifice (18a, 18b) with exhaust means for the first or the second fluid, at least one valve member (20a, 20b) mounted to move within the valve chamber (13a, 13b) between a position for closing and a position for opening the exhaust orifice (18a, 18b), a piston (22a, 24a, 22b, 24b) connected to the valve member (20a, 20b) and resilient return means (32a, 32b) for returning the valve member (20a, 20b) to a closed position. Each of the first and second pistons (22a, 24a, 22b, 24b) has a first face exposed to one of the first and second fluids, and an opposite second face subjected to a force exerted respectively by the second fluid or by the first fluid.

Abstract: The wall of the water chamber is welded to the tube plate via a connection ring projecting from the tube plate. The wall of the water chamber is welded to the tube plate after the bundle of tubes has been secured to the tube plate. The connection ring presents a length in the axial direction that is equal to or greater than 250 mm.

Abstract: The apparatus for positioning a fuel assembly (10) comprises, on a respective side of the core support plate (19) and the upper core plate (9) directed towards an endpiece (15, 14) of the fuel assembly (10) at least two projecting positioning pins (16, 22) adapted to engage in openings in the lower endpiece (15) or upper endpiece (14). Each of the positioning pins (16, 22) is fixed in a blind opening (24) comprising a threaded bore and a support surface perpendicular to the axis of the blind opening (24) and comprises a flange adapted to come into contact with the support surface when the positioning pin (16, 22) is screwed into the threaded bore. A gudgeon enables the positioning pin to be locked to secure it against unscrewing. The invention also relates to a process and apparatus for replacing damaged positioning pins on the core support plate (19) or on the upper core plate (9).

Abstract: A nuclear power station includes a feedwater/steam circuit having a condensate-purification device and a feedwater pump connected upstream of a reactor pressure vessel. A branch line has a gas-injection device for introducing hydrogen into a coolant to ensure especially low maintenance and repair costs of the gas-injection device and an especially homogeneous distribution of hydrogen produced in the gas-injection device. The branch line branches off from the feedwater/steam circuit directly downstream of the condensate-purification device and discharges into the feedwater/steam circuit directly upstream of the feedwater pump.

Abstract: The apparatus for positioning a fuel assembly (10) comprises, on a respective side of the core support plate (19) and the upper core plate (9) directed towards an endpiece (15, 14) of the fuel assembly (10) at least two projecting positioning pins (16, 22) adapted to engage in openings in the lower endpiece (15) or upper endpiece (14). Each of the positioning pins (16, 22) is fixed in a blind opening (24) comprising a threaded bore and a support surface perpendicular to the axis of the blind opening (24) and comprises a flange adapted to come into contact with the support surface when the positioning pin (16, 22) is screwed into the threaded bore. A gudgeon enables the positioning pin to be locked to secure it against unscrewing. The invention also relates to a process and apparatus for replacing damaged positioning pins on the core support plate (19) or on the upper core plate (9).

Abstract: A spacer grid for a fuel assembly in a light-water-cooled nuclear reactor, for providing the transverse retention of a bundle of fuel rods in mutually parallel arrangements, having an array of cells juxtaposed and placed in a regular lattice, each bounded and separated from neighboring cells by at least one peripheral wall which is open at two opposed ends, along the direction of an axis of the cell, so as to receive a fuel rod of cylindrical general shape passing along the cell along its axis parallel to the peripheral wall.

Abstract: An annular facing is machined in an inside surface of the spherical wall around the periphery of a zone where the wall has a bore for securing the tube passing therethrough. A first welding material is deposited in the facing, and the bore is made by drilling through a portion of the spherical wall that is surrounded by the facing. The tube is engaged tightly in the bore, and a second welding material is deposited in the facing at the periphery of the tube in order to weld the tube to the first welding material. At least one of the operations of depositing the first and second welding materials in the facing is performed automatically by causing a welding torch to turn around the axis of the bore while moving the torch in a direction that is parallel to the axis of the bore and while causing it to pivot about an axis that is orthogonal to the axis of the bore while rotation is taking place.

Abstract: The invention relates to a guide tube especially for an instrumentation lance extending into a reactor pressure vessel. The guide tube includes a lower tube section and an upper tube section that extends into the interior of the reactor pressure vessel. In order to prevent radioactively contaminated particles from reaching the lower tube section disposed outside the reactor pressure vessel from forming a source of radiation, a separator is arranged in the upper tube section. The separator has a separation chamber in which the particles are deposited and are removed from the water.

Abstract: Welding material is deposited automatically in the annular facing. A welding torch is causes to rotate about an axis of rotation that extends in a direction that is radial relative to the spherical wall and that passes through a point of the concave inside surface of the spherical wall in the central portion of the annular facing. Simultaneously with the welding torch being caused to rotate about the axis of rotation, it is displaced in a direction perpendicular to the axis of rotation in controlled manner, and the position of the welding torch in a direction parallel to the of rotation is also controlled so that the electrode of the welding torch describes an elliptical path and ensures that the welding material is deposited in the annular facing in the form of an elliptical bead.

Abstract: A recombination device (1, 1?) for catalytically recombining hydrogen and/or carbon monoxide with oxygen in a gaseous mixture comprises at least one catalyst system (2) in which a housing (4) is mounted through which the gaseous mixture can flow in free convection in the operational phase. According to the invention, said catalyst system (2) is provided with a plurality of sub-areas (T1, T2) in the direction of flow. A first sub-area (T1) comprises in the incoming direction a catalyst body (6) with a surrounding throttle layer (8) for inhibiting the diffusion of the incoming and/or discharged reaction gases. A second sub-area (T2) that adjoins the first sub-area (T1) comprises at least one catalyst body (6) that is directly accessible by the reaction gases.

Abstract: The steam generator (1) comprises a first normal feed water device (8) and a second emergency feed water device (16) of the steam generator, comprising, respectively, a first toroidal header (10) and a second toroidal header (17) arranged coaxially with respect to the outer jacket (2b) of the steam generator. The second toroidal header (17) of the second emergency feed water device (16) placed inside the upper cylindrical part (2b) of the outer jacket comprises, fastened to each of a set of openings penetrating an upper part of its toroidal wall, a water injection tube (22) having an open lower end part fastened to the opening of the toroidal wall, a straight part inclined with respect to the vertical axial direction in the direction of a central part of the steam generator and an open upper end at the end of the straight part of the tube (22) for injecting emergency water inside the steam generator.

Abstract: An fuel assembly with a connection between a fuel channel and a lower tie plate to allow the fuel channel to be removed from an internal fuel rod assembly without the necessity of moving interior fuel rods during removal of the fuel channel.