Abstract: An apparatus admits gas into the primary coolant of a pressurized water nuclear reactor having a coolant loop for a liquid coolant, in particular water, to which hydrogen is to be added. The coolant loop preferably includes a volume control tank for the coolant as well as at least one high-pressure pump which admits coolant that has been extracted from the coolant loop back into the coolant loop again. An admission point for the hydrogen is located in a suction line on the suction side of the high-pressure pump. A measurement line on the pressure side of the high-pressure pump communicates with the volume control tank or with a dewatering system. A device for measuring the hydrogen content in the coolant is incorporated into the measurement line. The measuring device is connected through a control device to a control valve, with which the delivery of hydrogen to the admission point can be controlled. The gas admission apparatus assures a definite, precisely maintained hydrogen content in the coolant.

Abstract: The invention relates to an inspection probe for an internal wall of a duct, comprising at least one sensor mounted in a support adapted to be moved inside the duct while pressing said sensor flat against said internal wall. The support is formed by a shell which is molded onto the sensor and comprises a body provided with a window for positioning said sensor and means for attaching said sensor flat against the internal wall of the duct, said means being integrally molded with the body. The invention has applications in the non-destructive testing of ducts in nuclear power plants.

Abstract: A fuel element for a nuclear reactor has fuel rods with nuclear fuel guided through spacers. The spacers are equipped with devices that exert a swirling impulse upon a coolant flowing along the fuel rods. In order to present as little flow resistance as possible for the coolant, these swirl-introducing devices have the form of a vane with a spoonlike or bladelike shape and they extend into the coolant flow. Owing to the shape—here the vane is curved in the longitudinal and in the transverse directions—practically all cross sections of the vane have such a high geometrical moment of inertia that even a vane made of a thin sheet metal is sufficiently rigid. Fuel elements configured according to the invention are particularly suitable for use in boiling water nuclear reactors.

Abstract: At least one injector condenser (20) is used to supply secondary feedwater to the steam generator (1) during a phase in the course of which the temperature and the pressure of the coolant of the reactor coolant system (2) of the nuclear reactor are varied between hot shutdown conditions of the nuclear reactor and conditions making it possible to bring into service the residual heat cooling system (RRA). The injector condenser (20) is fed with steam withdrawn from an upper part of the steam generator (1), at a first inlet, and with feedwater from a storage tank (10), at a second inlet. High-temperature pressurized feedwater is supplied to the steam generator (1) by means of one injector condenser (20) outlet. The steam generator (1) is fed without using an additional pump for withdrawing feedwater from the storage tank (10) and for injecting feedwater into the secondary part (3) of the steam generator (1).

Abstract: The invention relates to a method for handling a nuclear reactor upper internals guide tube (15), in which method a gripper (30) equipped, at a first end, with two opposed arms (32) that can be moved between a retracted position and a deployed position and, a second end, with a control member (37) for controlling the said arms is introduced into horizontal guide plates (24) of the upper tube (16) of the guide tube (15), the first end of the gripper (30) is placed under one (25A) of the two upper guide plates of the lower tube, the two arms are deployed, the two arms are applied under this guide plate and the gripper (30) is used to simultaneously raise the two tubes of the guide tube (15). The invention also relates to a handling device for implementing this method.

Abstract: A method and device for detection of a pulsed mechanical effect on a plant component includes continuously recording an operating noise in the plant component with a sensor disposed on the plant component and converting the recorded noise into a measured signal with the sensor. Then, the measured signal is subjected to a Fourier transformation. An evaluation function is derived from a number of value spectra determined in the above manner, which gives the onset of a pulsed mechanical effect on the plant component.

Abstract: Marking of the cuts which have to be made, cutting of the section at two ends, removal of the section which has to be replaced, bevelling of the joint ends of the parts remaining after the section has been cut out from the pipe, adjustment of a new or replacement section for length and bevelling of its joining ends and positioning and narrow bevel welding of the ends joining the replacement section to the ends of the remaining parts of the pipe are performed outside the pipe. Within the pipe operations of machining and inspecting an internal part of the joining ends welded together are performed by remote control in a programmed way by introducing and positioning means for working within the pipe from a component of the primary circuit.

Abstract: A device for identifying and locating leaks has a permeable collecting line, a pump provided for pumping a transport medium through the line, and at least one sensor for detecting a substance that escapes in the event of a leakage. There are provided sources of a detectable gas, which, as way-points, are located at a distance from one another at known locations along the collecting line. A sensor for detecting the gas is spatially assigned to each sensor that is provided for detecting the escaping substance.

Abstract: A fuel element for a pressurized water reactor is described. The fuel element contains a laterally open skeleton having control-rod guide tubes each with a first end and a second end, spacers fastened to the control-rod guide tubes, a fuel element head disposed at the first end of the control-rod guide tubes, and a fuel element foot disposed at the second end of the control-rod guide tubes. Gastight cladding tubes are inserted into the skeleton and each is filled with a column of fuel pellets. At least some of the gastight cladding tubes have a multilayer wall. The multilayer wall is formed of a mechanically stable matrix containing a first zirconium alloy disposed in a middle of the multiplayer wall; and a thinner protective layer of a second zirconium alloy alloyed to a lesser extent than the first zirconium alloy. The thinner protective layer is bound metallurgically to the matrix and is disposed on an inside of the matrix facing the fuel pellets.

Abstract: The corrosion of a component in a water-guiding loop of a nuclear facility is reduced. A protective layer is produced with a sol-gel process. Prior to the sol application, water that wettens the component is removed from the conduction system and the component is optionally dried in a separate step. After the sol-gel process has been carried out, the conduction system is again filled with water. A liquid sol film that is produced on the component is dried, especially by means of hot air. A component in the primary system of a boiling water reactor can especially be coated with a highly corrosion-resistant zirconium oxide protective layer according to the sol-gel process.

Abstract: In order, in a pressure accumulator, to generate a required operating pressure of a fluid situated in the pressure accumulator, a heater device is provided, disposed in an upper region of the pressure accumulator. The device generates a vapor cushion and the required operating pressure. Where necessary, when the fluid flows out, the pressure in the pressure accumulator is automatically reduced after the level has fallen below a defined filling level, as a result of the vapor condensing at a cold insulating device with a high heat-accumulation capacity. The pressure accumulator is preferably used as an emergency shut-down tank or as an emergency accumulator in a nuclear power plant.

Abstract: A method and apparatus is disclosed for smoothly inserting a fuel rod loader through the skeleton of a fuel cell and then for pulling an attached fuel rod into the fuel rod skeleton while keeping the fuel rod under constant tension and preventing the bowing of the fuel rod. The pulling mechanism comprises a smooth collet with a smooth bullet end cap for guiding the puller mechanism into and through the skeleton where the bullet end cap is removed and the fuel rod is attached with a unique ball and slide mechanism actuated by a long puller rod that grabs the end of the fuel rod by a forward motion of the puller rod and is easily removed from the fuel rod by reversing this motion once the fuel rod is in place.

Abstract: A measuring head is used in measuring an assembly part of a nuclear facility, such as a fuel rod, a fuel assembly box, or a spacer of the fuel assembly. The measuring head is capable of augmenting a comparatively large data base representing the overall aging state of the fuel elements in a simple manner and within a short measuring time. The measuring head has a probe tip on the sensor housing and a layer thickness measuring probe is integrated into said probe housing, said measuring probe working according to the eddy current principle. The contour or the diameter of the fuel rod can be determined by the measured deflection of the probe.

Abstract: The steam generator (1) comprises an outer casing (2) with an axis (8) that is in a vertical disposition when the heat exchanger is in service, a bundle of tubes having straight portions that are parallel to one another and to the axis (8) of the heat exchanger (1) inside the outer casing (2), at least one tube plate (4) having through holes, each receiving the end of a tube of the bundle, and at least one water chamber having a wall (6) that is circularly symmetrical about the axis (8) of the heat exchanger (1), the water chamber being fixed to the tube plate (4) at the bottom of the heat exchanger. The surface (14a) of the solid bottom (14) of the heat exchanger includes at least one central point disposed substantially on the axis of the heat exchanger (1) at a highest level relative to the set of points constituting the inside surface (14a) of the bottom (14) of the heat exchanger.

Abstract: Transverse vibrations of the pellet columns included in the fuel rods of fuel elements are limited by elastically mounting the fuel rod jacket tubes in the mesh of spacer grids. When the fuel rods are supported in this way, flexural vibrations of a higher order occur that lead to damage to the jacket tubes caused by fretting. These vibrations are the less dampened the more rigid the fixture of the fuel rod is. These vibration conditions are more easily excited and more strongly dampened when the pellet columns are more mobile, thereby removing vibration energy from the fuel element and avoiding damage caused by fretting. The mobility of the columns can be increased by increasing the gap between the pellet and the jacket tube, or by using constructions in which a torque M?10 N mm on the fuel rod leads to a tilting angle ??0.1°.

Abstract: The apparatus for positioning a fuel assembly (10) comprises, on a respective side of the core support plate (19) and the upper core plate (9) directed towards an endpiece (15, 14) of the fuel assembly (10) at least two projecting positioning pins (16, 22) adapted to engage in openings in the lower endpiece (15) or upper endpiece (14). Each of the positioning pins (16, 22) is fixed in a blind opening (24) comprising a threaded bore and a support surface perpendicular to the axis of the blind opening (24) and comprises a flange adapted to come into contact with the support surface when the positioning pin (16, 22) is screwed into the threaded bore. A gudgeon enables the positioning pin to be locked to secure it against unscrewing. The invention also relates to a process and apparatus for replacing damaged positioning pins on the core support plate (19) or on the upper core plate (9).

Abstract: A module for controlling a drive is described. The module contains a terminal for connecting to a control system for operating tasks and a control system for safety tasks. Commands from the control system for safety tasks have priority over commands from the control system for operating tasks. A microprocessor is provided for processing the commands and is coupled to the terminal. A logic circuit is provided for prioritizing the commands from the control system for safety tasks, the logic circuit is connected to the microprocessor. At least one output is coupled to the microprocessor and/or the logic circuit. An interface is provided for connecting to the control system for operating tasks or a diagnostic device, the interface is connected to the microprocessor. A memory is provided for storing the commands and replies, the memory is connected to the microprocessor.

Abstract: The invention relates to a method for transferring an article from a fluid-filled first vessel into a fluid-filled second vessel or in the opposite direction. The vessel is connected by a connecting element, in which there is a transport device for moving the article. A fluid flow flowing out of the first vessel is maintained in one part of the connecting element, while the article is transported through the connecting element. An apparatus for transferring an article, in particular a nuclear fuel element, between the vessels is also described, in which an extraction device for the discharge of fluid is located on the connecting element.

Abstract: The diameter of a segment of a peripheral rod in a fuel assembly is measured between two successive spacer grids. A measuring tool is positioned at a level situated between the two successive spacer grids, the tool comprising two measuring fingers that are free to move relative to each other in a first horizontal direction and that are urged towards each other by a resilient return arrangement, and that extend in a second horizontal direction perpendicular to the first horizontal direction. The measuring fingers are moved in the second horizontal direction towards a rod so as to put two contact pieces of the measuring fingers into contact with two zones of the rod segment. The measuring fingers are moved in the vertical axial direction of the rod along its segment situated between the two spacer grids and an electromagnetic sensor is used to measure the distance between the measuring fingers in the first horizontal direction while the measuring fingers are being moved axially.

Abstract: A process for measuring the thickness of a layer of oxide on a rod cladding in a fuel assembly comprising a bundle of rods parallel to each other and held in a framework comprising spacer grids for transversely holding rods distributed in an axial direction of the bundle.