Abstract: Marking of the cuts which have to be made, cutting of the section at two ends, removal of the section which has to be replaced, bevelling of the joint ends of the parts remaining after the section has been cut out from the pipe, adjustment of a new or replacement section for length and bevelling of its joining ends and positioning and narrow bevel welding of the ends joining the replacement section to the ends of the remaining parts of the pipe are performed outside the pipe. Within the pipe operations of machining and inspecting an internal part of the joining ends welded together are performed by remote control in a programmed way by introducing and positioning means for working within the pipe from a component of the primary circuit.

Abstract: The invention pertains to an electro-optical connector module comprising a connection part, at least one optical transmitter circuit and/or optical receiver circuit and at least one electro-optical converter for respectively converting electrical signals into optical signals or vice versa. The module further comprises at least two substantially flat and substantially parallel electrically insulating sheets on which the transmitter circuit and/or receiver circuit and the converter are mounted. It is preferred that the connector module according, comprises at least one optical transmitter circuit, at least one optical receiver circuit and at least two electro-optical converters for respectively converting electrical signals into optical signals and vice versa, wherein the optical transmitter circuit and a first converter are mounted on a first sheet and the optical receiver circuit and a second converter are mounted on a second sheet.

Abstract: The maintenance device comprises a robot (2) for carrying out maintenance work in a remote-controlled or programmed way in the maintenance region. The robot (2) comprises a supporting part (2a) connected to a clamping support (3) secured to a means (4) of transporting the maintenance device (1) between an introductory region and the maintenance region. The clamping support (3) comprises clamping shoes (11, 13a, 13b) which can be moved in roughly parallel and opposite directions so as to clamp the maintenance device (1) in the maintenance region. The transport means (4) may be constructed in the form of a carriage comprising two motorized wheelsets. The device and the method of the invention make it possible in particular to carry out machining or inspection work inside primary pipes of a pressurized water nuclear reactor.

Abstract: The present invention provides a motor signature measuring system comprising three current transformers which are placed around the power cables leading to the high voltage motor, an E-Plug module connected to the current transformers and located in a motor control case to reduce the motor voltage from 600V RMS to 5V RMS, jack connectors for connecting the 5V output of the module to a connector mounted through the door of the motor control enclosure, and a cable connector for connecting the door connector to a monitoring system conducting the motor signature testing operations.

Abstract: The maintenance device comprises a robot (2) for carrying out maintenance work in a remote-controlled or programmed way in the maintenance region. The robot (2) comprises a supporting part (2a) connected to a clamping support (3) secured to a means (4) of transporting the maintenance device (1) between an introductory region and the maintenance region. The clamping support (3) comprises clamping shoes (11, 13a, 13b) which can be moved in roughly parallel and opposite directions so as to clamp the maintenance device (1) in the maintenance region. The transport means (4) may be constructed in the form of a carriage comprising two motorized wheelsets. The device and the method of the invention make it possible in particular to carry out machining or inspection work inside primary pipes of a pressurized water nuclear reactor.

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 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 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 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.