Abstract: The fuel rod comprises a sheath having an inner tubular layer and an outer surface layer composed of zirconium alloys which differ from each other. The surface layer, whose thickness is between 10 to 25% of the total thickness of the wall of the sheath, is constituted by a zirconium-base alloy containing by weight 0.35 to 0.65% tin, 0.20 to 0.65% iron, 0.09 to 0.16% oxygen and niobium in a proportion of 0.35 to 0.65% or vanadium in a proportion of 0.25 to 0.35%. The inner layer may be constituted by an alloy such as Zircaloy 4 or a zirconium-niobium alloy.

Abstract: A process for separating iron +3 from uranium +6 is an organic solution of a neutral phosphine oxide and an acid organophosphorus compound. The uranium-containing organic solution is contacted with aqueous oxalic acid or an aqueous mixture of phosphoric acid and sulfuric acid so that most of the uranium remains in the organic solution and most of the iron passes into the aqueous acid.

Abstract: The sleeve (20) for locking the guide tube has an outer surface comprising successivley a cylindrical and a frustoconical part in the axial direction, without any radially protruding part. The upper cylindrical part (25) of the sleeve constitutes a fastening shell of the sleeve (20) in the end fitting of the assembly and the lower frustoconical part (24) a ring for expanding the guide tube. The fastening shell (25) the thickness of which is substantially smaller than the thickness of the ring (24) can be distorted into cavities machined in the end fitting of the assembly. An annular interlocking groove (20) is machined in the upper part of the ring (24).

Abstract: The device comprises a vertical pole (11) having a manipulating handle (14) at its upper end and a gripper (22) fastened to one end of a gripper support (20) mounted pivotally about a horizontal axis (21) at the end of the pole (11). Springs (25, 29) make it possible to return the gripper into a grasping position distant from the vertical axis ZZ' of the pole (11). A mechanism (24) for controlling the gripper in order to open and close it is carried by the gripper holder (20). This mechanism is connected to a remote-actuation mechanism by a flexible transmission element (37).

Abstract: The guide tube (4) is fixed inside the adapter plate (10) of the demountable end block by a locking sleeve (20). The locking sleeve (20) comprises a part (24) ensuring expansion of the tube (4) and a ferrule (25) for fixing in the adapter plate (10). The fixing ferrule (25) consists of cylindrical segments separated by slits arranged in the direction of the generatrices of the ferrule (25). The cylindrical segments have deformations (29) inside cavities (22) radially directed relative to the through-hole (11) of the adapter plate (10), for ensuring fixing of the sleeve (20). The cylindrical segments of the ferrule (25) can be folded inwards so as to disengage the deformations (29) from the cavities (22), before extraction of the sleeve (20), in order to carry out demounting of the connection of the guide tube (4) and the adapter plate (10).

Abstract: In order to ensure a good seal and a good resistance to shocks and corrosion, without increasing their cost, radioactive waste storage containers are completely made from metal fiber-reinforced concrete. This material is used for producing by molding a drum (210) and a cover (212), as well as a keying joint (224) by which the cover is fixed to the drum. At least one dovetail keying groove is formed in the junction zone between the drum and the cover. Advantageously, a filling material of the same nature as that in which is formed the container is injected into the latter, so as to form a homogeneous block.

Abstract: The device comprises a rod (28) on which is mounted a means (30, 32, 33) for support and displacement which is movable in an axial direction of the rod (28) and in two directions perpendicular to this axial direction. The support (33) of the means for displacement carries a device for pushing axially on a longitudinal end of the pencil, which may be activated by a control means (35), one end of which is located in a control station (25) disposed above a fuel assembly storage pool. Means for measuring the axial pushing force on the pencil and the length of axial displacement of the pencil under the effect of the pushing are disposed in the control station (25). A video camera (34), carried by the support (33), makes it possible to provide an image of a zone in the vicinity of the end of the pencil.

Abstract: The device comprises a rod (20) on which is mounted a means (22, 24, 25) for the support and displacement of a work tool which is movable in an axial direction of the rod (20) and in two directions perpendicular to this axial direction. The tool comprises tongs consisting of two arms which are articulated together about a spindle fixed on the means (22, 24, 25) for support and displacement in a direction parallel to the axis of the rod (20). The tongs comprise end jaws which are capable of gripping a fuel rod. The gripping of the tongs is controlled remotely and the positioning of these tongs on a fuel rod to be removed is checked by means of a video camera (26).

Abstract: The device comprises a control station (2) fixed on the edge of the pool (3), a rod (4) connected to the support of the control station (2) at its upper end (5), means for adjusting the inclination of the rod (4) relative to the vertical direction, a tool support (12) and an assembly for displacing the tool support (12) in two directions perpendicular to the axis of the rod (4), carried by the carriage (10). Control means (14, 15) may be activated from the control station (2) in order to displace the tool support (12) by means of the displacement assembly.

Abstract: For clearing or unblocking a pipe (10) filled with a liquid (12) and in which a plug (14) has formed, an apparatus (16) is connected to said pipe. This apparatus applies to the liquid harmonic-rich longitudinal pressure waves and which are preferably constituted by a pulse train. By means of a regulatable compliance volume (28), the harmonic n of the resonant frequency of the incompressible mode of the liquid (12)-pipe (10) system is adjusted, so that its frequency is equal to that of harmonic 1 of the resonant frequency of the compressible mode of the system (n preferably being equal to 1, 2 or 3). This makes it possible to take advantage of the resonances of the compressible and incompressible modes of the system by using a low exciting frequency (below 20 Hz), which reduces the risks of the pipe (10) fracturing or bursting.

Abstract: The spacer-grid comprises at least one single-piece plate (1) through which extend a group of openings (2) at least a part of which constitutes an even network of passages (2) for the fuel rods and the guide tubes of the fuel assembly. The spacer-grid may be formed by one single-piece plate (1) of great thickness or by the association of a plurality of parallel single-piece plates interconnected by an outer girdle element.

Abstract: The fuel element comprises a plurality of modular capsules (5) arranged in sequence axially within a sheath (2). Each of the capsules (5) comprises a tubular case (10) closed at both ends by a porous element (13, 14) and enclosing a stack of pellets (11) in contact with the inner surface of the case (10) without radial clearance. The outside diameter of the capsules (5) is such that a very small radial clearance exists between the outer surface of the capsule (5) and the inner surface of the sheath (2).

Abstract: A zirconium alloy sheet containing 2 to 3% of niobium is cooled at a controlled and moderate rate to the .alpha.+.beta. state. Plates (2, 2') are cut from the cooled sheet and cold-formed. The grid (1) is assembled from the plates (2, 2') which are welded together and the completed grid is then returned to the .alpha. phase by heating at a temperature of between 400.degree. and 550.degree. C. for a period of ten to thirty hours.

Abstract: For manufacturing uranium oxide based nuclear fuel pellets, a fine and reactive U.sub.3 O.sub.8 powder is mixed with a fine UO.sub.2 powder obtained by dry conversion. The U.sub.3 O.sub.8 is obtained by oxidation in air of UO.sub.2 obtained by a dry process, at a temperture less than 800.degree. C.

Abstract: For passing stepwise bottles (F, F') in front of different stations, in order to more particularly take liquid samples, the bottles are placed in receptacles formed on a plate (24). The rotation of the plate is ensured by a lifting support action using compressed air delivered by injectors (18). Immediate rotation stoppage is obtained when a hole (38) formed in plate (24) faces the end of an optical fiber, whereof the opposite end issues onto an optical detector. Associated with an automatic sampling and dilution system, the assembly can be advantageously installed in a glove box or shielded enclosure in the nuclear industry.

Abstract: Package for shipping dangerous materials to ensure the containment of these materials under conditions of severe accident. A containment enclosure of austenitic stainless steel, constituted by a single part devoid of orifices and of joints other than welds, has the shape of a cylinder of revolution closed at its two ends which are of convex shape. The wall of this enclosure is of a substantially uniform thickness without sudden variations including the area of the welds. Two axial shock absorbers, each formed by a section of metal tube preferably of the same cross-section as the above enclosure, are positioned on the end of the latter so that they are coaxial therewith. A support ensures the storage and the handling of the assembly are provided, as well as if necessary, removable means adapted to ensure the wedging of the dangerous materials inside the enclosure.

Abstract: During the dismantling of a nuclear reactor fuel assembly, there is a simultaneous gripping of all the rods (a) arranged in square grid form in said assembly using a device (10) which effects a clamping or locking at the end of the rows of rods. For this purpose, device (10) has passageways (26) penetrated by the ends of two adjacent rows of rods (a). In said passage ways are trapped mobile members (34, 34') arranged in such a way that each rod is placed between two adjacent members. By applying a locking force on the mobile end members in each passageway (26), each rod is gripped between two members (34, 34'). Preferably, the mobile members (34, 34') are provided with abutments limiting the locking or clamping force individually applied to each rod. For filling the gaps of the grid of rods (a) corresponding to the locations occupied by the guide tubes in the assemblies, rollers (78) are placed in the passageways (26) at the corresponding locations.

Abstract: In order to transfer a bundle of rods of or from a nuclear fuel assembly into a storage case, the bundle is placed in a waiting position above a cassette provided with recesses. The rods are then introduced into the recesses by lowering them by gravity. When the cassette is full, it is brought into the extension of the case by interposing a transformation member. By simultaneously exerting a thrust on all the rods, the latter are compactly transferred into the case.

Abstract: The device for coupling two pipes comprises a variable length assembly formed from two tubular parts, whereof the internal diameter corresponds to the internal diameter of the pipes. The tight coupling of this assembly to the ends of the pipes is brought about by compressing O-rings between a planar surface and a spherical surface by means of two nuts. The two tubular parts are then tightly joined by actuating a nut compressing a third O-ring.

Abstract: In order to seal an opening formed in a vertical wall, a removable partition is formed, which is constituted by at least two dry-stacked brick layers. Each layer is formed from several rows of bricks, each constituted by bricks which, in cross-section, are shaped like a parallelogram, arranged in opposite directions on either side of a central locking brick which, in cross-section, is shaped like an isosceles trapezium. Each row of bricks behaves like a fictitious funicular arc when exposed to a horizontal force normal to the partition. Thus, the earthquake resistance is ensured without adding a reinforcing framework to the two faces of the partition.