Abstract: Device for the remote control of the center distance of two bores or two cylinders with parallel axes in a structure with high dimensional accuracy, comprising a base plate (24) having a part (24a) for the accurate positioning of the device, two centering pins (26, 27), engageable in a perfectly coaxial position on the bores or cylinders (22, 23), two unit assemblies (33, 32') each carrying one of the pins (26, 27), articulated for moving the pins (26, 27) in any direction at right angles to the axes of the bores or cylinders (22, 23) and a distance detector transmitting transducer (50) fixed on a support (45) fixed integrally to one of the pins (26) and joined to the other pin (27) with some play in the direction of the center distance. The rod (51) of the detector (50) is directed along the direction of the center distance and its end is in contact with the pin (27). The device applies, particularly, to the control of the upper internal parts of a pressurized water nuclear reactor.

Abstract: Process and device for the detection of the variations, due to a fault in the position of the core control clusters, in the reactivity of the core of a reactor. A momentary value (6) representing the reactivity calculated directly from the core neutron power (2) is compared to a momentary value (30) representing the reactivity calculated from the momentary mean temperature (25) in the core and the mean boron concentration (29) in the primary fluid passing through the core. The invention applies to pressurized water nuclear reactors.

Abstract: Process and device for the detecting of faults in the distribution of the power of the core (2) of a pressurized water nuclear reactor, in which at least one parameter representing the power of the core (2) is measured, each parameter being measured at a determined number of points. For each parameter, the difference between the two extreme measured values and the ratio of this difference to the smallest measured value are determined, and this ratio is compared to a set value, a fault being detected if this ratio is greater than the set value. The sensors (4, 9) are arranged symmetrically close to the periphery of the core (2) and a further sensor (9) is placed close to the center of the core (2).

Abstract: A tightening wrench (5) carrying a measuring cell (8) freely mounted in the hollow part (4) of a wrench (5) and adapted to bear against an end of the pin (2) subjected to the pretension. A detector emitting and receiving ultrasounds (21) disposed inside the measuring cell (8) is made to bear against the end of the pin (2) by a spring (25) interposed between the cell (8) and the detector (21). The cell (8) itself bears against the end of the pin (2) through the action of a leaf spring (9) carried by the wrench (5).

Abstract: Process for corrosion protection of a steam generator tube, in which a metal layer (10) compatible with the material of the tube (1) is deposited by electrolysis on the inner surface of the tube (1) after it is fixed in the tube plate (2), on either side of the face of the plate (2) in contact with the water to be vaporized, over a length which is appreciably greater than the transition zone (5) between the crimped part and the uncrimped part of the tube (1). The outer surface of the tube (1) may also be covered with a metal layer (12) before it is fixed in the tube plate (2). The invention applies, in particular, to steam generators of pressurized water nuclear reactors.

Abstract: Device for fixing a fuel assembly to the lower core plate of a nuclear reactor, comprising a fastening element (23) fixed to the lower core plate (18), in the central part of the opening (19) in this plate (18) corresponding to the assembly, an expandable sleeve fixed to the lower end (3) of the assembly in its central part, a guide tube (10) passing through the assembly in its central part in the axial direction, a rod (25) mounted for sliding movement in the tube (10) and fixed to an oval locking knob (38), and a socket (26) fixed to the upper end of the bar (25) and having a gripping surface for a lifting tool. The fastening element has an axial opening (31) for engagement of the expandable sleeve. The bar (25) and the socket (26) allow displacement of the oval knob (38) between service and out-of-service positions in which the latter spreads the expandable sleeve inside the opening (31) in order to fix the assembly.

Abstract: Device for locating the position of a nuclear reactor control rod which is suspended from a shaft (12) sliding vertically inside an adaptor tube (10, 11) under the effect of a screw-nut mechanism which comprises a nut-forming rotor (14) mounted to rotate around the vertical axis of the tube (10) and provided with a threaded bore in which is engaged a corresponding threaded part (13) of the shaft (12).

Abstract: A complementary shutdown device for an undermoderated nuclear reactor, comprising, inside certain arrays (3) of the core, guide tubes (7) of which the cross-section is at least equal to the sum of the cross-sections of three rods (6), and which are surrounded by at least one row of fertile rods (8), and a set of shutdown rods, the cross-section of which matches the cross-section of the guide tubes (7). The shutdown is obtained by allowing the shutdown rods, containing a neutron-absorbing material, to fall into the arrays (3) of the core, in the position of maximum insertion. The invention applies, in particular, to pressurized water nuclear reactors.

Abstract: Upper internal equipment of a pressurized water nuclear reactor, comprising guide tubes containing guide plates and sleeves adapted to two different types of charge of the reactor core, one for obtaining a thermal neutron spectrum and the other for obtaining an epithermal spectrum. The plates (20) and the sleeves (33, 34) have, for each of the guide tubes, a first set of perforations (31, 36) and a second set of perforations (30,35) for guiding the control rods in either case. The invention applies to a pressurized water reactor operating either as a conventional reactor or as an undermoderated reactor.

Abstract: The device is disposed at the base of a fluidization chamber for the uniform distribution of a gaseous fluid throughout the section of the chamber, and comprises a multitude of small parallel tubes (12) provided with radial perforations and connected to manifolds (11a, 11b . . . ) for a looped supply of gaseous fluid to the tubes. The invention is particularly applicable to industrial fluidized beds for processing materials.

Abstract: Acoustic waves are sensed in contact with or near the plant at at least two points (1, 2, 3, 4) whose position is accurately determined with respect to the monitored region. The order of arrival of the acoustic waves at the sensing points (1, 2, 3, 4) is determined and this order is compared with a predetermined order corresponding to a phenomenon occurring in the monitored region. An alarm is triggered if the order of arrival corresponds to the predetermined order. The apparatus includes an encoding logic (9), a comparator (10) and a monostable circuit (12) triggering the alarm. The invention is particularly applicable to monitoring nuclear reactors in operation.

Abstract: The invention relates to a temporary sealing obturation panel, inside a vessel accessible only through a manhole, of a passage provided on its periphery with a support collar. It is constituted by: panels articulated by flexible fluid-tight hinges, bordered by lines of latching pins, stiffeners comprising lines of holes conjugate with the lines of pins, a frame in at least two articulated parts, with means for gripping the ends of the panels and the stiffeners against the support collar. The invention is applicable to the closing of primary circuit ducts opening into the water box of a steam generator of a pressurized water nuclear boiler.

Abstract: Control cluster guide devices, for light water cooled nuclear reactors, including housings. The reactor includes means outside the core for guiding control clusters (7) during their movements.The housings (12) are associated respectively with the several control clusters (7) and comprise plates which ensure discontinuous guidance at intermediate levels for the individual pencils and an associated spider, each housing including for continuous of the individual pencils, tubes which connect two tube plates for the pencils to pass through, which are proper to the housing, the one terminating it and the other forming a positioning flange on the core plate.

Abstract: Telemanipulator for operation in a waterbox of a steam generator for attachment underneath the tubeplate of the latter. The device has expandable grippers mounted on arms carried by a bearer unit, for engaging and locking as required in the orifices in the tubeplate, with means enabling independent movement of the apparatus underneath the tubeplate while remaining always suspended by at least two grippers. The bearer unit has four independent arms each equipped with two expandable grippers, and on the portion of it opposite from the tubeplate it supports an arm having a number of members hinged together, the end member of the arm being equipped with tool attachment means, the whole of the arm being in turn revolvable about the axis of the unit perpendicular to the tubeplate, with remote-controlled means for adjusting and maintaining the angular position of the arm with respect to the bearer unit and the angular position of each of the members of the arm relative to one another.

Abstract: A thermal liquid level measuring system including a heat sensor with a sheathed heating resistor and a measuring resistor. Power is supplied to the heating resistor in a series of pulses. The measuring resistor is connected to two filters which extract the a.c. and d.c. components from the measuring signal. A temperature measuring device determines the difference in temperature of the liquid and the gas above the liquid. A computer receives signals from the filters and the temperature measuring device to determine the level of the liquid and its temperature.

Abstract: Sealing device for the drive shaft (27) of a high pressure fluid pump comprising a system of seals (33, 34, 35) at least one of which (33) is a hydrostatic seal. Between this hydrostatic seal (33) and the interior of the volute (21) is disposed an auxiliary seal (45) of the mechanical type. The auxiliary seal (45) separates two chambers (46a) and (46b) which can be brought into communication or isolated by a system of pipes (47) on which a valve (48) is disposed. The invention is particularly applicable to the primary pumps of a pressurized water nuclear reactor.

Abstract: The subject of the invention is a device for checking the disconnexion of the actuating rods of the control clusters before the removal of the internal equipment of a nuclear reactor, comprising, within a pit (10) forming a cooling pond, a vessel (1) closed by a removable cover and containing the core and a set of control clusters fitted slidably in the upper internal equipment forming a guide structure above the core, each cluster being fixed to the lower part (32) of an actuating rod (3) capable of being detached from the corresponding cluster, after opening the cover, by means of a disconnecting tool suspended from a charging crane (2) transportable above the cooling pond (10).

Abstract: The invention relates to a process for the replacement of guide pins of a guiding tube forming part of the top internal equipment of a pressurized water nuclear reactor.While the internal equipment is disposed under water in its storage bay, the two parts of the guiding tube (2) are fastened together by introducing a rod (50) along the axis of the tube and over its entire length, and effecting axial clamping of the tube by members (51, 52) each of which bears against one part of the guiding tube (2). The tube (2) is detached and extracted from the internal equipment, it is decontaminated and transported to a dry treatment zone in which the guide pins are replaced. The tube is transported to the internal equipment storage bay, it is placed back in position in this equipment, it is fastened and the connection between the two parts of the tube is detached. The invention also relates to apparatus for carrying out the process of the invention.

Abstract: Method of monitoring a nuclear power station by gathering information, called parameters, relating to the operation and state of the power station and its auxiliary equipment, comparing these parameters with reference data corresponding to normal operation, and signaling the differences, in order to permit an operator to evaluate the state of the power station very quickly, and to undertake any needed steps promptly.

Abstract: Device for detecting the operation of a valve, comprising a movable member (15) connected kinematically to a movable part (6) fastened to the closure member of the valve. A detector (24, 25, 26) makes it possible to monitor the displacements or the position of the detection member (15). The detection member (15) has at least one part provided with a predetermined breaking point (20). The kinematic connection between the valve and the detection member (15) can thus be interrupted by the breaking of the member (15) in the event of the jamming of the latter. The invention is in particular applicable to safety valves in nuclear power stations.