Abstract: The invention relates to the use of thioether ligands in accordance with the formula: ##STR1## in which R.sup.1 and R.sup.2, which can be the same or different, represent alkyl radicals, R.sup.3 is an alkyl radical and A represents a divalent radical chosen from among the radicals of formula:--(CH.sub.2).sub.m ----(CH.sub.2).sub.n --X--(CH.sub.2).sub.p -- ##STR2## in which m is equal to 0 or is an integer from 1 to 6, n and p are integers between 1 and 6 and X represents O or S, for recovering the palladium present in a nitric aqueous solution (A.sub.0) for dissolving irradiated nuclear fuel elements.For example, it is possible to use the ligand of formula (I) with A representing CH.sub.2 --S--CH.sub.2 and R.sup.1 and R.sup.2 representing C.sub.10 H.sub.21.

Abstract: A cardiac valve comprises a ring, one or more flaps, the pivoting axis of the latter including two balls partly extending into a ring cavity and a conical flap cavity. This arrangement improves the life of the valve by reducing wear, stresses, friction and facilitates the assembly thereof if the ring is constituted by two concentric members and if the ring cavity extends on either side of the inner member. The invention more particularly applies to artificial valves installed in the heart in place of defective natural valves.

Abstract: So as to be able to carry out various operations, especially for cleaning observation and simple interventions, on an installation placed in an active cell, the present invention provides a mobile intervention chamber including a caisson (40) adapted to be docked on an access orifice formed in an upper horizontal partition of the cell. The caisson (40) contains the modular elements (88) of an intervention pole (94), these elements being placed on a tool holder barrel (78). With the aid of auxiliary handling arms and a retractable support (110), a pole (94) of a suitable type and length is long-distance constructed on a mechanism (128) mounted on a rotary plate (120) integrated in the ceiling of the caisson (40). Shielding windows (232, 236) and lighting and display systems facilitate the carrying out of intervention operations.

Abstract: A high pressure cleaner comprises a cleaning device (10) and an effluent recovery device (12). The cleaning device (10) is mainly constituted by a cleaning head (20) having a central chamber (44) into which a nozzle (26) sprays a high pressure cleaning liquid, the effluents being recovered in a peripheral chamber (46) connected to a decanter (54) of the recovery device (12). The actual decanter (54) is connected to an exhauster (72) across a liquid-gas separator (60) and filters (70). The liquid phase of the effluents is periodically recovered by a tube (80) immersed in the decanter (54) and connected to a hydroejector (82). The solid phase of the effluents is held back by a filter (92) surrounding the tube (80).

Abstract: The distance between substantially parallel metal tubes forming a flat sheet and the thicknesses of oxide layers covering the tubes are simultaneously measured. The tubes may particularly be sheaths of a nuclear fuel assembly.

Abstract: A spacer grid for a nuclear fuel assembly comprises a plurality of sets of plates which are interleaved and mutually interconnected to define cells each for receiving a fuel rod and further comprising a plurality of hairpin springs each carried by and retained on a respective one of the plates and each projecting into at least one respective cell when in released condition. Each spring is provided with one or two retention spurs arranged for retaining it temporarily in a retracted condition with respect to the respective plate. The retention spurs are releasable by a force of predetermined direction applied on the spring.

Abstract: A bracing grid suitable for use in a light water reactor has a plurality of mutually intersecting sets of plates defining cells which receive fuel rods. The plates carry springs for retaining the rods by friction. Each spring is formed has a U legs located each on one side of a plate, the branch being for contact on the elements in two mutually adjacent cells separated by the plate. The two legs are connected by a loop straddling the plate and are connected to each other by a weld at the base of the loop, through a window formed through the plate. The legs of each spring are also mutually connected by mechanical locking means which retain the two legs with respect to each other and with respect to the respective plate.

Abstract: A device for damping the fall of a neutron absorbing bar on the upper end piece of a nuclear fuel assembly, typically a PWR, comprises at least one pair of cylinder-piston sets which are located symmetrically with respect to the vertical axis of the fuel assembly. One of the cylinder and piston in each set is carried by a fixed plate secured to the upper end piece. The other of the cylinder and piston is fixed to a movable plate arranged to receive the bar upon fall thereof and to move vertically toward the fixed plate, damping being achieved by the head loss impressed to the fluid forced out of the cylinders.

Abstract: Prior to the transportation to a discharge site of a casket or flask in which has been placed a container filled with radioactive waste, through a hole formed in the flask is introduced a probe holder (32) connected by electrical connectors (76,80) to an external measuring apparatus. The probe holder (31) is provided with a handle (68) making it possible, through a mechanism (66,56,54,50), to swing a door (42) to which a probe (34) is fixed between a retracted introduction position and a measuring position in which the probe can be oriented at 90.degree. relative to the probe holder axis. After the probe holder has been coupled by a nut (40) to a container carrier in which is located the container containing the waste, a precise, reproducible measurement of the dose rate within the transportation flask can be carried out.

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: A fuel assembly for a light water cooled and moderated nuclear reactor comprises a bundle of fuel rods and a structure for holding the bundle in position comprising upper and lower end pieces or nozzles joined together by guide tubes which support grids for maintaining the fuel rods at the nodal points of a regular array. The upper end piece comprises an adapter plate fixed to some at least of the guide tubes and having an upwardly directed shroud arranged to bear directly or indirectly on the upper core plate of the reactor and encircling a coolant passage defining an internal volume into which all guide tubes open. The adapter plate has coolant passages around the shroud. This arrangement makes it possible to direct an adjustable fraction of the cooling water flow outwardly of a cluster guide sleeve associated with the assembly and belonging to the upper internals of the reactor.

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: A method and device for enabling a molten radioactive glass to be cast from a crucible (2) situated in a top cell (1) and a container (4) situated beneath said crucible in a bottom cell (3), the radioactive glass flowing vertically downwards along a casting axis through an opening provided in a concrete slab (5) which separates said cells, said device being characterized in that it comprises the following components in succession going downwardly: a deformable guide tube (11) constituted by two housings (14, 15) slidably mounted in each other, with the inner walls (20, 21) thereof being frusto-conical in shape, and the apex of said frusto-conical shape being situated beneath said guide tube, the top housing (14) being fixed beneath said concrete slab, the bottom housing (15) having an end wall (22) in the form of a portion of a sphere, and said two housings being interconnected by a metal bellows (23); and a moving tube (12) constituted by an enclosure (32) whose inside wall extends downwardly so as to be cap

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: A grid for a nuclear fuel assembly comprises a common frame having an axis and a plurality of beds of plates distributed along the axis. Each bed has a plurality of plates which are mutually parallel and are directed transversely to the plates of the adjacent beds. All plates are secured to the common frame. The plates having a same direction are distributed between a plurality of said beds interleaved with other ones of said beds consisting of plates having another direction, and the plates of the beds placed in an upstream portion of the grid have fins oriented so as to deflect coolant inwardly whereas the plates placed in a downstream portion of the grid have fins oriented so as to deflect the flow coolant outwardly.

Abstract: This invention relates to a pusher placed in a magazine for irradiated fuel elements which allows displacement thereof for the cutting operations. The pusher according to the invention allows the displacement of elements of small section in a magazine of large section. At the end of a cutting operation, the pusher applies its blank against the auxiliary holding clamp forming a continuous surface and the element is pushed by a blade, the body of the pusher being immobilized.

Abstract: The device allows microsamples to be introduced into the ionization source of the spectrometer. It includes a reactor with means for introducing the microsample, means for heating the microsample, means for connection with a vacuum source and means for feeding an adjustable flow of reagent for transforming the microsample into gaseous compounds; a restricted and calibrated passage for flow of the gases from the reactor; and a sublimation tube connected on the one hand to the passage and, on the other, to the ion source of the spectrometer through a valve having means for bringing it to an adjustable cryogenic temperature.

Abstract: The invention has as its object a process for the purification of a uranium solution which is contaminated by zirconium. This process consists of bringing the pH of the solution to a value of 1 to 3, then adjusting the pH of the said solution to, and maintaining it at a value of 2.5 to 3 while raising the temperature to a value of around 30.degree. to around 60.degree. C. for a period sufficiently long that there occurs a selective precipitation of at least 70% of the zirconium while the uranium remains in the dissolved state.

Abstract: A device for measuring and remotely checking external dimensions of an external lateral face of a part of a work piece. The device comprises measuring means for measuring the length of the part and including a set of two ultrasonic transducers arranged to transmit and receive ultrasound pulses, a movable support for supporting the transducers, abutting means, first rotation means for rotating the supporting means about an axis parallel to the longitudinal axis of the workpiece, and second rotation means for rotating the supporting means between an initial position where the two transducers are substantially directed along a line perpendicular to the longitudinal axis of the workpiece and two predetermined angular positions symmetrical with respect to the initial position, and means for rectilinearly displacing the movable support for bringing the movable support into and out abutting contact with the lateral face to be measured.

Abstract: A sheath for a nuclear reactor control rod consists of chromium nickel stainless steel. It is protected against friction wear by nitridation over a depth of from 15 to 50 .mu.m obtained by an electric discharge in a nitrogen containing atmosphere.