Abstract: The objective of the invention is a process for producing a rigidified structure, comprising at least one element with superconducting properties, and the means for rigidifying, this process comprising a stage of deposit by plasma spraying of a layer of material on a surface of said element.

Abstract: This subsea exploration apparatus comprises a ballast tank and a shuttle (7) with a watertight enclosure (10) which contains instrumentation for measurement, control and transmission of signals to a surface buoy. The enclosure is guided along a cable (1) fixed to the ballast tank and is provided with a chamber (26) whose lower opening is equipped with a hatch (29). When the shuttle is in high position, a load of ballast is transferred from the tank (5) into the chamber (26), causing the shuttle to descend. This load is jettisoned in a low position of the shuttle, by opening the hatch (29), in order to permit it to reascend.

Abstract: A device for detecting the presence of a gaseous phase in the tank of a nuclear reactor closed by a cover on which a plurality of vertical tubes are fixed for adapting the control rod actuating mechanism of the reactor, the adapter tubes not provided with mechanisms being closed by a plug. A plurality of ultrasonic emitter-receivers are fixed to the upper surface of the plugs of at least a part of the adapter tubes, so that each emitter-receiver directs an ultrasonic beam to the inside of the tank parallel to the axis of the corresponding tube, the latter being provided with at least one reflector placed inside the tube in the path of the ultrasonic beam. The invention is especially applicable to reactors cooled by pressurized water.

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 method of ultrasonic measurement of the ratio of the volume of gas present in an enclosure containing a diphase liquid-gas mixture to the volume of the enclosure, or void coefficient. Waves at different frequencies are propagated through the fluid filling the enclosure (1). The propagation times of the waves are measured and the difference between these propagation times is calculated. If the propagation times are identical, it is deduced that all the gas is in the form of a layer surmounting the liquid. The void coefficient is determined from the propagation velocities of the ultrasounds in the gas and the liquid and from the measured propagation time. If the propagation times are different, a part of the gas is in the form of bubbles in the liquid, the void coefficient due to the gas surmounting the liquid and the void coefficient due to the gas bubbles in the liquid are determined separately. The total void coefficient is determined by adding the two values obtained.

Abstract: Method and apparatus for monitoring the movement of the control rods of a nuclear reactor.The number of steps of movement in either direction of the rod from which the control rod is suspended is counted. According to the height of the step, an indication of the position of the suspension rod and of the control rod. The apparatus comprises devices for measuring the speed of movement of the control rod, for logging variations in speed higher than a given value, and for counting such variations according to their sign. The invention is particularly useful in pressurized water nuclear reactors.

Abstract: The present invention allows the position of a defect to be located when it emits acoustic waves into a closed structure. The waves travel around closed routes in a section of the structure.To this end, it comprises at least three acoustic sensors (22-24), uniformly distributed on the surface of the section of the structure monitored, connected to logic (26, 27) for encoding the order of arrival of the signals detected. Control means (16, 20, 35) for controlling display means and means (19) for controlling the writing means of the latter, which is preferably a conventional dual-trace oscilloscope are described. The image of the section monitored is traced by two beams rotating in opposite directions, only one of which is illuminated for a brief instant at the moment of detection of the acoustic emission, as it passes the image point identifying the defect.

Abstract: Method and apparatus for detecting defective fuel elements in a nuclear reactor assembly. The assembly (20) is kept entirely immersed in a liquid such as water, ultrasonic waves are propagated successively in each of the fuel elements of the assembly or rods (21), an ultrasonic sensor (25) is disposed near the assembly (20) and the waves which may be scattered into the protective liquid by the defects in the fuel rod are picked up to determine the presence of a defective assembly and locate the defective rod in the assembly. The invention is particularly applicable to fuel assemblies of a pressurized water nuclear reactor.

Abstract: An apparatus for measuring acoustic emission is activated only at critical periods which are determined by detection of the background noise from a reference level. An acoustic emission transducer continuously transmits a signal to a detection circuit which delivers the top modulation envelope of the background noise to a comparator at a reference level delivered by a control unit.When a mean level of the background noise does not exceed a threshold reference level the AE is sampled at a low rate, f. When the background noise exceeds the threshold reference level the data sampling unit is activated to sample AE at a much higher rate F. Therefore AE is sampled at a high rate only when the pump or other machine under test is running and at a low rate when the article under test is not operating. The AE testing device also includes a frequency spectrum correlator which allows background noise to activate the increased sampling rate only if the noise is in a given frequency range.

Abstract: Gases contained in the sheaths of the fuel elements are made to expand in order to cause the escape of gas bubbles in the protective liquid into which the fuel assemblies are immersed. The progress of the gas bubbles in the protective liquid is arrested by means of a screen (1) located above the assembly and an acoustic phenomenon associated with the impact of the gas bubbles on the screen or with the accumulation of gas below the surface of the screen is recorded. The appearance of this acoustic phenomenon permits the detection of defective assemblies.The invention applies in particular to pressurized water nuclear reactors.

Abstract: Sound monitoring device for an industrial installation to detect possible impacts of stray bodies including at least one set of two sound detectors arranged in contact with the wall of the installation or in its vicinity, and a measuring and alarm circuit. The detectors are connected to this measuring circuit which includes a device for measuring the separation in time between the reception of the sound waves at one and the other detector, a comparator for this separation with at least one set of two predetermined values, and an alarm which is triggered if the separation in time falls between the two predetermined values. The invention is particularly useful for surveillance of the primary circuit of a pressurized water nuclear reactor.

Abstract: A method of testing new fuel rods for assemblies for nuclear reactors.Ultrasonic waves are transmitted in the canning tube of the fuel element disposed in the open, with an oblique incidence with respect to the axis of the tube, from one region of the side wall of the tube. By reflection at the walls of the canning tube, these waves produce plate waves or Lamb waves. These Lamb waves are picked up after a certain distance has been covered along the length of the canning tube and the attenuation undergone by these Lamb waves is measured. From this, by comparison with the attenuation results obtained at another part of the length of the tube or with a standard tube, data on the possible presence of moisture in the fuel rod is deduced. The invention particularly applies to the testing of fuel rods of assemblies for a pressurized water nuclear reactor.