Patent Number: 049869531
Section: summary

The invention relates to a device for the support and positioning of means for checking and tools for working on fuel assemblies of a water nuclear reactor which are immersed in a pool. After a certain time of operation in the reactor, the fuel assemblies constituting the core of a reactor require examinations and checks in order to ensure that these assemblies have not suffered damage preventing their subsequent use in the core of the reactor. Dimensional checks may be performed in order to confirm the characteristics of an assembly after irradiation. If certain defects have been detected, it may be possible to perform certain repairs or certain work operations which make it possible to reuse the fuel assembly for refuelling the core of the reactor. These checking operations using visual means or a probe as well as the implementation of tools for working on the fuel assembly must be performed under a certain depth of water in the region of the minimum biological protection requirement of 3 metres, or slightly more, of water. These operations are performed in a pool where the assembly, whose height is in the region of 4 metres, is placed in a vertical position. These checks or work operations may thus be performed, in certain cases, under a depth of water which is far greater than 3 metres and in any position according to the height of the assembly. Among the work operations envisaged or in respect of which tools have already been designed, it is possible to mention the removal of foreign bodies or particles inside the fuel assembly, the straightening of the fins of the grids of fuel assemblies, the checking of the sliding of the fuel pencils in their structure and the removal of pieces of peripheral rods in the assembly which have suffered a breakage. In all cases, it is necessary to set in place visual checking means and a tool for working at a very precise location situated in the vicinity of the fuel assembly. It must also be possible to adjust, remotely and accurately and using a simple and rapid procedure, the positioning and the orientation of the work tool. No device was known hitherto which made it possible to perform the installation and accurate positioning of means for checking and tools for working on fuel assemblies immersed in a storage pool. The invention thus aims to propose a device for the support and positioning of means for checking and tools for working on fuel assemblies of a water nuclear reactor which are immersed in a pool under a certain depth of water, it being possible for this device to be implemented simply and rapidly, making it possible to obtain an extremely precise positioning of the means for checking and the work tools. To this end, the device according to the invention comprises: a control station having a support fixed on the edge of the pool, a rod of great length connected to the support of the control station at its upper end and disposed in a substantially vertical position inside the pool so as to present a part located opposite at least one fuel assembly disposed inside the pool, means for adjusting the inclination of the rod relative to the vertical direction and for immobilizing the rod in at least one inclined position, which means are fixed on the support of the control station, a carriage mounted so as to be movable along the length of the rod interacting with guide means carried by the rod, means for displacing the carriage which are controlled from the control station, at least one tool support intended to receive at least one means for checking and at least one work tool, an assembly for displacing the tool support in two different directions perpendicular to the axis of the rod, carried by the carriage, means for controlling the displacements of the tool support which can be activated from the control station, and means for controlling the work tool and the means for checking from the control station.