Abstract: A method for the non-destructive testing of an element for a nuclear reactor having the steps of: a) acquiring a radiographic digital image of at least one area in element, b) creating a reference image through the digital processing of the image obtained, and c) comparing the image obtained, processed if necessary, with the reference image to detect the presence of defects.

Abstract: A method of declogging at least one filter of a plant for manufacturing uranium oxide from uranium hexafluoride, including separating, from the wall of the filter, uranium oxyfluoride particles deposited, by a stream of inert gas such as nitrogen, injected into the filter, in a counter-currentwise direction to the flow of hydrofluoric acid.

Abstract: A substance in a condensed state, for example a powdered solid, is in continuous movement in the longitudinal direction (6) of a furnace (4, 5). A reactive gas mixture is brought into contact with the substance in the condensed state. A plurality of samples of the gaseous mixture are removed at a plurality of reference points (14) spaced apart from one another along the longitudinal direction (6) of the furnace (4, 5); each of the gas samples is analyzed outside the furnace to determine the composition of the gas mixture and for each point (14), the extent of a chemical reaction between the condensed substance and the reactive gas mixture is deduced from the composition of the gas mixture at each of the reference points (14). In particular, the apparatus comprises a sampling and injection rod (10) introduced into the furnace (4, 5) and disposed in its longitudinal direction (6).

Abstract: The installation provided includes at least one structure for receiving and holding guide tubes and structural elements; a carriage movable parallel to the guide tubes; at least one welding tool; and displacement means for moving the welding tool, the displacement means connecting the pincer to the carriage and presenting at least six degrees of freedom.

Abstract: A method of inspecting an operation of sealed closure by welding an end opening of a filling channel axially traversing an upper plug for closing the cladding of a fuel rod for a nuclear reactor, the cladding of the rod containing a plurality of pellets of nuclear fuel stacked in the axial direction of the cladding and two closure plugs, one of the plugs or the upper plug being traversed axially by the channel for filling the cladding of the rod with an inert gas and the sealed closure by welding of the filling channel of the upper plug being carried out after filling the cladding with inert gas, in a filling apparatus, by melting central part of the end of the upper plug adjacent to the opening of the filling channel, this method allowing for inspection of the conditions for implementing and carrying out the sealed closure of the upper plug by welding, efficiently and without extending the time needed for the manufacture of the fuel rod.

Abstract: Before welding, the plug and the sleeve of the fuel rod being in the welding position at the welding station, the sleeve and the plug of the fuel rod are rotated about their common axis with the aid of rotation means, images are taken along the periphery of the fuel element to obtain digitized images, the digitized images are analyzed to determine the position of the joint plane between the sleeve and the plug of the fuel rod, and the rotation of the fuel element is verified. It is deduced whether it is possible to perform the welding or not. If welding is performed, images are taken of the fuel element along the periphery of the fuel element, in the vicinity of a joint line between the sleeve and the plug, to obtain digitized images which are analyzed to check the conformance of a weld made along the joint line.

Abstract: The assembly apparatus comprises a frame for supporting the straps of the first set of straps in mutually parallel positions, clamping and engagement for clamping on each of the straps of a second set of straps in succession and for engaging them with the straps of the first set in position in the support frame, and at least one comb that is movable between a disengaged position and a position in which it engages each of the straps of the first set.

Abstract: The conversion apparatus comprises in succession: a reactor provided with injectors of UF.sub.6, steam, and nitrogen so as to cause UO.sub.2 F.sub.2 to be formed by hydrolysis; a rotary tubular pyrohydrolysis furnace for transforming UO.sub.2 F.sub.2 into uranium oxide, and provided with heaters distributed in at least five zones; and a tail end for conditioning the oxide powder. The injectors comprise three concentric nozzles connected respectively to inlets for UF.sub.6, nitrogen, and steam, UF.sub.6 being fed to the central nozzle and nitrogen being injected between UF.sub.6 and steam.

Abstract: A sinusoidal voltage is appied to a zirconium alloy clad fuel rod. The current is measured and the impedance is determined to provide a check for the compactness and adhesion of an oxide surface layer on the fuel rod.

Abstract: The spacer grid (20) is placed and held during welding in an arrangement such that its two opposite faces perpendicular to the edges (33) of the cells (34) are entirely accessible. At least four edge segments (33) of the grid (20) are welded simultaneously using two assemblies with at least two laser beam welding devices (25a, 25b, 25d) arranged on either side of the opposite faces of the spacer grid (20). Each of the welding devices directs a welding laser beam onto an edge (33) of the grid, via the exterior of the cells (34). After a welding operation, a relative displacement between the spacer grid (20) and the welding devices (25a, 25b, 25d) is produced so as to direct the welding laser beams (30a, 30b) of the welding device to at least four new edge segments (33) of the grid (20).

Abstract: A laser-beam welding device forming part of a set of at least four welding devices (13a, 13b, 13c, 13d) is introduced into each of the cells of a set of at least four cells (36a, 36b, 36c, 36d), along the axis of the cell in such a way that the welding laser beam (38a, 38b, 38c, 38d) of the welding device is aligned with an edge of the cell (36a, 36b, 36c, 36d). A laser-beam weld is simultaneously produced along at least a part of the length of an edge of each of the cells (36a, 36b, 36c, 36d) of the set of cells and relative displacement between the grid (35) and the welding devices (13a, 13b, 13c, 13d) is carried out in order to introduce the welding devices into at least four new cells of the grid which are arranged in a square. The invention also relates to a device for welding a grid via the interior of the cells of the grid and to an installation for fast welding of a grid.

Abstract: The installation includes at least one loading line comprising a framework support, a magazine for storing fuel rods and a traction bench in an arrangement aligned along the longitudinal direction of the housings of the framework of the assembly. The traction bench includes a support having a fixed part and a movable part to be positioned in the loading line in longitudinal alignment with the framework support and the storage magazine, a carriage mounted for movement on the support in the longitudinal direction, a plurality of rod grippers, linkage between the grippers and the carriage, an arrangement selectively controlling displacement or retention of the grippers, a selection unit for selective activation of a subset of grippers and controls for gripping the grippers.

Abstract: In order to classify cylindrical nuclear-fuel pellets automatically, they are rotated about their axis. A flat beam is focused onto a nominal generatrix of the pellet. The returned light coming from an elongate zone, this being the zone illuminated on a defect-free pellet, is collected. The intensity is detected, point by point, along the zone and the defects are deduced from the variations in the intensity. To this end, the points of each zone are determined in which the intensity of the returned light lies between two adjustable normality thresholds, the transition points are stored in memory, and the limits of each defect and its type are determined by neighborhood analysis.

Abstract: A device for measuring the force exerted by a spring of a supporting grid on a fuel rod passing through the grid has an elongate body connected by two flexible blades that are parallel to the long direction to two respective beams insertable in a cell. At least one of the beams carries a force sensor designed to be pressed against the spring. A unit is slidable in the body along the body between a position in which it moves the beams apart while keeping them parallel to give them a spacing that corresponds to the nominal diameter of a fuel rod, and a position in which it allows the flexible blades to move the beams towards each other. The unit is movable at will between the two positions.

Abstract: The automatic sorting device allows nuclear-fuel pellets to be distributed into correct, acceptable or scrapped pellets.

Abstract: The apparatus enables rods to be installed in an assembly skeleton that does not include its end-fittings. The apparatus comprises reception means receiving the skeleton without end-fittings and enabling the skeleton to be interposed between a storage magazine storing rods in alignment with rod-receiving emplacements in the skeleton and with a longitudinal displacement mechanism for displacing drawbars that are terminated by rod-grasping clamps towards the magazine and away from the magazine. The apparatus also includes a cap-placing assembly interposed between the reception means and the longitudinal displacement mechanism. The cap-placing assembly has a fixed support and a removable receptacle pierced with cap-retaining housings in an array that reproduces the array of rod-receiving emplacements. The shape of the caps being such that they fit over the clamps of the drawbars while the drawbars are moving towards the magazine.

Abstract: This equipment comprises a housing (6) rigidly fixed to the welding enclosure (5) and in which are rigidly mounted the various optical components necessary for focusing the laser beam transported by means of an optical fiber (20) to the joint (1) to be welded. The reflecting mirror (16) allows a small fraction of the laser beam, which is measured by a detector of luminous energy (8), to pass. The present invention is applicable to the manufacture of fuel rods, guide tubes and attached rods used in nuclear reactors.

Abstract: A method and a device for manufacturing a grid for use in a nuclear reactor fuel assembly. A grid whose component parts are to be mutually welded is placed in a holding frame having passages for access to points to be welded on two major faces and on the sides. The frame containing the grid is gripped with a device in a chamber where an inert gas atmosphere is generated. Welding is carried out on one face of the grid at a time using a laser beam penetrating from outside the chamber and the welding operations are repeated on the other faces. During welding on one face, the laser beam is moved in two mutually orthogonal directions while the frame is held stationary. The apparatus may include two chambers each with a gripping device, one for welding the two major faces and the other for welding the sides.

Abstract: The fuel rod (3) is inserted into the enclosure (6) thorugh a gasket (30) until the rod faces a window (32). The outlet arm (16) of the housing (5) for focusing the laser beam, is fixed to the enclosure by way of the body (35) of a solenoid plug valve (36).Application to the plugging of the axial seal weld hole of fuel rods for nuclear reactors.