Abstract: A nuclear reactor with juxtaposed prismatic fuel assemblies cooled by the flow of a liquid in a cylindrical jacket. A partitioning of the core between the peripheral assemblies and the jacket is constituted by rods parallel to the assemblies, guided laterally by bracing plates fast to the jacket in which the rods are free to slide longitudinally.

Abstract: The concentration of an acid in a weakly ionized aqueous solution, more particularly the concentration of boric acid in solution in demineralized water from the primary circuit of a pressurized water nuclear reactor, is modified by effecting simultaneously the dissociation of the acid and the electrodialysis of the solution using at least one electrodialysis membrane comprising a polymer support such as PTFE or FEP and having aminated groups introduced for example according to a process comprising a step of grafting.

Abstract: Process and apparatus for control of the heat transfer between a circulating bed of solid particles and a heat exchanger (6) located inside a fluidization enclosure (1) supplied with solid particles and connected to a device for recovering (4) and recycling (5) the particles into the fluidized bed. The heat exchange coefficient of the exchanger (6) is adapted at each moment to the heat transfer requirements of the plant by varying in the same sense the concentration of solid particles in the circulating bed, by increasing or reducing the quantity of circulating particles to increase or reduce, respectively, the exchange coefficient to the value required by the demand. The invention is particularly applicable to steam production boilers operating on coal.

Abstract: Autonomous assistance device for a safety valve protecting a vessel under pressure and comprising a hollow body (13), a seat cooperating with a movable closure member fixed to a rod (9), and a calibrated spring (7) bearing against the rod (9) and against the valve body (13) to hold the closure member against the seat. The closure member rod (9) is extended into a casing (19) fastened to the body (13) and receives the additional thrust of a spring (51). The casing (19) constitutes in addition a pneumatic ram whose piston (53) can apply to the rod (9) a thrust opposite to and greater than that of the spring (51). The device feeding the ram (19) comprises an autonomous reservoir (33), a three-way solenoid valve (24) for feeding the ram or connecting it to atmosphere, and a manometer contact (39) mounted on the wall of the pressure vessel and adjusted to close the solenoid valve supply circuit when the pressure in the vessel reaches the adjusted pressure.

Abstract: The invention relates to a fuel assembly with cooled guide tubes for a nuclear reactor.It consists of a bundle of parallel fuel tubes (1) held in a structure comprising spacer grids, guide tubes (6) and end plates. At least a part of the guide tubes (10) comprises a set of guiding surfaces (16) projecting towards the interior of the tubes (10) over the whole of their length. The projections (16) are formed by embossing of the wall of the tube (10) and permit the guidance of the rod of absorbing material which is moved in the tube and the provision of circulating spaces for the cooling fluid between the tube and the rod of absorbing material.The invention applies in particular to pressurized water reactors and to reactors with neutron spectrum variation.

Abstract: The device includes an electrode in the form of a cylindrical tube, an arrangement for causing an electrical discharge between the electrode and the workpiece, a support fixed to the workpiece and disposed at least partly inside the electrode for guiding the electrode in a direction perpendicular to the workpiece and electromagnetic structure placed inside the electrode to cause the electrode to vibrate.

Abstract: The invention relates to a core for a nuclear reactor cooled with water under pressure.The core comprises a first group of zones (1, 2) extending over its entire height and over a fraction of its transverse section where the fuel rods contain mainly enriched uranium oxide, and a second group of zones (3) inserted between the zones (1, 2) of the first group where the rods contain mainly plutonium. The rods of zones (1, 2) of the first group emit neutrons and maintain the neutron reactions. The energy spectrum of the neutrons is in the thermal region in the zones (1, 2). The rods of the zones (3) of the second group are spaced at a distance which is appreciably smaller than the distance separating the rods of the zones (1, 2) so that the neutrons produced therein are in the high energy region.The invention applies, in particular, to nuclear reactors with spectral shift control.

Abstract: Apparatus for the replacement of the guide pins of a guide tube of a pressurized water reactor. The apparatus consists of a rod with clamping means at each end which clamps the guide tube and holds the tube while the bolts connections are removed and then imparts a slight vertical movement to release the guide pins of the guide tube.

Abstract: A nuclear fuel assembly has fuel rods connected to the lower end plate of the assembly. The connecting structure comprises an attachment plate which is superimposed on the lower end plate and which is formed with openings corresponding to the rods. The openings lead out into parallel grooves machined on the lower surface of the plate. Each rod comprises a lower part having three radial branches at 120.degree., each formed with an end extension projecting radially outwardly from the outline of the rod. The extensions engaged in a groove have a height substantially equal to the depth of the groove. Axial fixing and locking against rotation of the rods are thus ensured.

Abstract: A steam generator incorporating a tube bundle (2) arranged in a bundle casing (5), in which the wall of bundle casing (5) incorporates openings each corresponding to a supporting component (20), openings along the edge of which are fixed sleeves (15) projecting radially into the space between the casing (5) and the outer wall (3) of the heat exchanger. Each of the supporting components (20) incorporates two cylindrical parts situated in extension of one another, a large-diameter part (20a) welded by its side surface inside the sleeve (15) and a small-diameter part (20b) abutting against the casing (3). Wedges (23) are inserted between the part (20a) of the supporting component (20) and a spacer plate (8) of the heat exchanger. The invention applies, in particular, to steam generators of pressurized water nuclear reactors.

Abstract: A tool for the manufacture of a fuel assembly, said tool comprising for each end of an assembly an inner metal plate which can be applied to the bottom of an end member, an outer metal plate which can be displaced, under the action of a jack, along sliding columns fixed to the inner plate, in longitudinal translation with respect thereto and threaded ties traversing corresponding openings in the end member and in the inner and outer plates, able to engage with the internal thread of the guide tubes, and each provided with a head on which is supported a spring for compensating the action of the jack. A method for utilizing the tool is set forth, also.

Abstract: A device and method for determining the power of a pressurized water nuclear reactor, comprising measurement of the neutron power (15) and of the temperature of the primary fluid in the cold branch (1) and in the hot branch (1'), computing (2, 4, 6, 8, 12) the thermal power of the reactor from these temperature measurements (1, 1'), comparing (14) the thermal power signal (13) and the neutron power signal (16) and correcting (22) the neutron power signal (16). The device in addition comprises means for fast and precise determination of the secondary power of the reactor by comparison of a first signal of the secondary thermal power (13) established by means of the temperature measurements (1, 1') and a second signal of the thermal power (16') established by means of a simplified secondary heat balance (25).

Abstract: Fuel assembly for a pressurized water nuclear reactor, comprising a peripheral zone (1) consisting of a first group of rods (2) containing mainly enriched uranium oxide and a central zone (4) consisting of a second group of rods (5) containing mainly plutonium or uranium depleted in fissile uranium. The rods of the first zone (1) are spaced sufficiently so that the neutrons are slowed down to the thermal region. The rods of the second zone (4) are spaced by a distance which is appreciably smaller so that the neutrons produced in this zone (4) are in the high-energy region. The invention applies, in particular, to nuclear reactors with spectral shift.

Abstract: A logic system of the type which has means for applying two-state logic testing signals to an input of a logic circuit to be tested is disclosed. A logic circuit to be tested has two output logic states. The system comprises control means for applying control signals having two logic states to the input of the logic circuit to be tested. The value of the two output logic states is dependent respectively on two input logic states of the control signals applied to the input of the logic circuit to be tested. Override means imposes each logic state of the test signals on the input of the logic circuit to be tested, independent of the logic state of the control signals.

Abstract: Device for calibrating a machine tool including a tool (32) rotating about its axis XX', comprising a tubular-shaped support with an annular fixing component (3) connecting it to the housing (1) of the machine tool so that its central opening forms an extension of the opening (2) of the housing (1) for the passage of the tool (32). The support also has at least one part (18) which is deformable under the action of twisting about the axis XX' and is provided with at least one strain gauge (19), and an end part (12) which is opposite the fixing component (3) and in which there is arranged, along the axis of the support, a component (20) for connecting the end of the tool (32), which component is provided with means (20') enabling locking of said tool in rotation with the connection component. The latter carries a disk (30) located between two annular components (31a and 31b) held against the disk (30 ) by adjustable means (22, 25).

Abstract: A method and apparatus for eliminating leakage spaces between the partitions (1) surrounding the core of a pressurized water nuclear reactor, after it is brought into operation. Operations are carried out under water, during shutdown of the reactor. The defective joins (12) between the partitions (1) are identified. For each join, the partitions (1) are pierced, the hole inside a partition (1) is screw-threaded, the swarf is recovered, a screw with diametrical expansion is introduced and screwed into the hole and the screw is expanded by displacement of a rod in the longitudinal direction of the screw. Moving location, the operations are repeated for each defective join (12). The apparatus comprises a case (25) containing a drum (36) bearing tools for boring (54-65), screw-threading, and screwing, a cleaning tube and a punch for locking the screw.

Abstract: The invention relates to a process for monitoring leaks in the primary circuit of a pressurized water nuclear reactor.The primary circuit consists of the vessel (1), the primary part of the steam generators (6), pipework (3, 4), the pressurizer (10) and various stocktanks (20). Connected to the primary circuit is at least one auxiliary circuit such as the circuit for volumetric and chemical monitoring comprising a stocktank (17). A sectioning of the primary circuit and of the circuit for volumetric and chemical monitoring into volume elements, excluding the stocktanks (20, 17) is determined. At regular time intervals, or steps, the mass of water in each of the volume elements and in each of the stocktanks is determined from measurements of pressure, temperature and levels and then, by addition, of the total mass of water.

Abstract: The invention concerns a method and apparatus for eliminating leakage spaces between the partitions (1) surrounding the core of a pressurized water nuclear reactor, after it is brought into operation.Operations are carried out under water, during shutdown of the reactor. The defective joins (12) between the partitions (1) are identified. For each join, the partitions (1) are pierced, the hole inside a partition (1) is screw-threaded, the swarf is recovered, a screw with diametrical expansion is introduced and screwed into the hole and the screw is expanded by displacement of a rod in the longitudinal direction of the screw. Moving location, the operations are repeated for each defective join (12). The apparatus comprises a case (25) containing a drum (36) bearing tools for boring (54-65), screw-threading, and screwing, a cleaning tube and a punch for locking the screw.The invention is applicable to work on pressurized water nuclear reactors, after they have been brought into operation.

Abstract: Process and apparatus for testing a pilot-operated safety valve, applicable to (1) a safety valve composed of a body having an inlet branch connected to a pressurized fluid container, and an outlet branch, of a valve head cooperating with a seat for controlling fluid flow between these branches, of a control actuator consisting of a piston connected to the valve head and sliding in a cylinder, forming two chambers, the operative one of which is fed with fluid, and (2) a pilot apparatus controlling the valve and comprising a pressure detection actuator whose piston is subjected to the pressure of the fluid and to the action of a spring acting against the force developed by the pressure, and a hydraulic mechanism with two cocks whose closing contact portions (311, 321) are displaced via an operating rod carrying a disc displaced by the piston, and one of which controls the fluid pressure in the control actuator and the pressure detection actuator, while the other controls the discharge of the control actuator.

Abstract: The invention relates to a device for controlling the supply of fluid under pressure to a hydraulic circuit as a function of the state of locking or unlocking of two mechanical members.The device comprises two interconnected jacks (1,2), the rods (3,4) of which are integrally fixed to mechanical members. The piston (30) of the first jack (1) separates the chamber (35) of the latter into two parts (35a,35b). The piston (31) of the second jack (2) divides the chamber (35') of the latter into three parts (35'a,35'band 35'c). The inlet chambers (35a and 35'a) are connected to pipes for supplying fluid under pressure (10a,10b), and the outlet chambers (35b and 35'c) are connected to a depressurizing pipe (20). According to the position of the pistons (30 and 31), which itself depends on the state of locking or unlocking of the rods (3,4), an interconnecting pipe (23) and a pipe (25) supplying the hydraulic circuit with fluid under pressure communicate with one chamber or another.