Abstract: A nuclear fuel rod comprises nuclear fuel contained in a cladding, the cladding comprising a tube and two plugs, the tube extending along a central axis and having two ends, each plug being attached to a corresponding end of the tube by sealing the end of the tube. The tube is covered by a tube coating extending over the entire length of the tube from one end of the tube to the other.

Abstract: The absorber rod comprises cladding (12) of stainless steel closed by plugs (14, 16) and containing a column of absorber pellets (24) e.g. of boron carbide. It also has an end bar (26) of hafnium secured to the bottom plug by a purely mechanical connection.

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: 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.