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: 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: 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.

Abstract: A method of checking the dimensions of the extensions of control rods of a nuclear reactor when the extensions are located in a cooling pit or fuel storage pool under a safe depth of water, comprising placing each extension vertically on a reference support in the cooling pit, the support having a profile corresponding to that of the extensions, moving measuring pick-ups, calibrated by reference to the support, along the extension, measuring the distances between the pick-ups and the extension at a plurality of levels, and analyzing the measurements. An apparatus is also disclosed for performing the novel method of checking rod-extension dimensions in the nuclear reactor.

Abstract: Apparatus for visually examining the fuel rods of an assembly of fuel rods immersed in the tank of a nuclear reactor or in a deactivation tank, comprises an endoscope including a prism and an optical system of stabilized glass, and at least one arm supporting a mirror facing the prism and inclined relative to the plane defined by the axis of the tube of the endoscope and the arm, the thickness of the arm-mirror assembly being less than the free space between the rods of the assembly. In use the apparatus is mounted on a system of carriages which enable the apparatus to move in three perpendicular directions, the carriages being associated with rotatable means for supporting an assembly of rods to be examined.