Abstract: The invention concerns an alloy containing equally 0.02 to 0.07% wt. % of the total iron, of chromium or vanadium, 0.8 to 1.3 wt. % of niobium, 100 ppm or less of tin, 1100 to 1700 ppm of oxygen, less than 100 ppm of carbon, 10 to 30 ppm of sulphur and less than 50 ppm of silicon.

Abstract: A process in which isotopes of the same element belonging to the alkaline earth metals, transition elements and heavy metals having an atomic mass of less than 209, in particular lanthanide metals, are separated in an aqueous medium by treating an aqueous medium.

Abstract: A method to design a nuclear fuel assembly having the following steps including establishing the falling speed of the control rod upon entry into the lower damping portion when the control cluster falls in the event of a shutdown of the nuclear reactor, establishing, based on the falling speed established in step a), the progression of the falling speed of the control rod in the lower damping portion, establishing, based on the progression of the speed established in step b), a maximum elevated pressure produced in the liquid contained in the lower damping portion, and establishing, based on the maximum elevated pressure established in step c), a maximum circumferential stress produced in the lower damping portion.

Abstract: The invention proposes a zirconium-based alloy also containing, by weight, apart from unavoidable impurities, from 0.02 to 1% of iron, from 0.8% to 2.3% of niobium, less than 2000 ppm of tin, less than 2000 ppm of oxygen, less than 80 ppm of carbon, from 5 to 35 ppm of sulphur and less than 0.25% in total of chromium and/or vanadium, the ratio R of the niobium content less 0.5% to the iron content, optionally supplemented by the chromium and/or vanadium content, being lower than 3.

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: A method for designing a nuclear fuel assembly, including the steps of establishing a progression of a speed of the control cluster after the impact of the support against the upper end piece, establishing, based on the speed established in step a), a maximum longitudinal load for compression of the spring, and establishing, based on the maximum longitudinal load for compression, at least a maximum shearing stress in the spring.

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: 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: A control cluster for a pressurized water nuclear reactor comprising a bundle of neutron-absorbing rods each of which comprises a metal tube called cladding which is sealed off by a top end plug at its top end and by a bottom end plug at its bottom end and has a support, or spider, of radiating shape to which the absorber rods are attached through their upper end plugs, characterized in that the cladding of at least some of the absorber rods is weld-free hafnium tubes, the top end plugs of the absorber rods having hafnium cladding being of titanium-based alloy and being welded to the top end part of the hafnium cladding of the absorber rod, the bottom end plugs being of massive hafnium and being welded to the bottom.

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 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 invention relates to a process for treating alkali metals such as sodium charged with tritium or components contaminated with alkali metals such as sodium charged with tritium, in which the alkali metal is reacted with liquid water or water vapor, so as to obtain hydrogen and tritiated hydrogen, characterized in that the hydrogen and the tritiated hydrogen are subjected, in a recombiner (2) to a treatment of catalytic recombination by the addition of oxygen so as to obtain water and tritiated water, and in that the water and the tritiated water are treated so that they are not discharged into the environment. The invention also relates to a plant for carrying out the process.

Abstract: A process in which isotopes of the same element belonging to the alkaline earth metals, transition elements and heavy metals having an atomic mass of less than 209, in particular lanthanide metals, are separated in an aqueous medium by treating an aqueous medium.

Abstract: The invention relates to a process for treating alkali metals such as sodium charged with tritium or components contaminated with alkali metals such as sodium charged with tritium, in which the alkali metal is reacted with liquid water or water vapour, so as to obtain hydrogen and tritiated hydrogen, characterised in that the hydrogen and the tritiated hydrogen are subjected, in a recombiner (2) to a treatment of catalytic recombination by the addition of oxygen so as to obtain water and tritiated water, and in that the water and the tritiated water are treated so that they are not discharged into the environment. The invention also relates to a plant for carrying out the process.

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: 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: In an industrial installation equipped with a sensor, a method is provided for checking the sensor and providing a measurement sequence associated with the sensor. Monitoring occurs for a thermodynamic parameter of a monitored fluid circulating in the industrial installation, by sensing the fluid using the sensor while the industrial installation is operating and by collecting and processing an electric signal emitted by the sensor using the measurement sequence. A perturbation is produced of fluid origin of the thermodynamic parameter while the installation is operating and the fluid circulates in the installation in order to act on a sensitive element of the sensor and cause a modification of the electric signal emitted by the sensor. The method performs collecting and analyzing of the modified signal from the sensor using the measurement sequence.

Abstract: A device for handling a guide tube assembly. The assembly has an upper tube and a lower tube in each of which there are fixed horizontal guide plates arranged such that they are spaced apart in an axial direction. The handling device itself includes a gripper having a tubular body and two opposing arms located at one end of the tubular body and moveable between a retracted position and a deployed position, the arms bearing against a lower surface of a contacted guide plate when in the deployed position. A control member is located at an opposite end of the tubular body for controlling the arms. The length of the tubular body of the gripper selected to be: a) greater than the distance between an upper end of the upper tube and a first guide plate of the lower tube; and b) less than the distance between the upper end of the upper tube and a third guide plate of the second tube.

Abstract: A method of determining a threshold value of a nuclear reactor operating parameter having the steps of simulating at least a transient operational occurrence of the nuclear reactor, calculating the value reached by a physical quantity during the transient operational occurrence in at least a cladding of a fuel rod of the reactor and establishing, as a limit value of an operational parameter of the reactor, the value of the operational parameter when the value calculated the step of calculating the value reached by a physical quantity during the transient operational occurrence which corresponds to a value of the physical quantity which characterizes a failure of the cladding.

Abstract: Nuclear metal or alloy particle preparation method and device; said device comprising: means to prepare a fluid mass of the metal or alloy by melting; means to put the fluid mass of the metal or metal alloy in the form of a molten metal or alloy stream; means to impart a centrifugal rotation movement to a quenching fluid and carry out the atomisation of the molten metal or metal alloy stream particles and the quick quenching of the particles; means to melt the nuclear metal or metal alloy in an inert gas atmosphere, and means to surround the molten metal or metal alloy stream by a neutral gas envelope until quenching.