Patent Number: 
Section: claims

1. A device for inspecting a fuel assembly containing a plurality of fuel rods in a pool of a nuclear plant equipped with a grapnel for displacing and suspending the assembly in the pool, comprising:a moveable image sensor including a field of observation, anda boom including a reference graduation extending along an axis parallel to a longitudinal axis of a fuel assembly containing a plurality of fuel rods, so that upon suspending the fuel assembly in the pool by the grapnel, the image sensor may observe in its field both the boom and the assembly, and the boom hangs in the pool beside the fuel assembly so as not to occupy the bottom of the pool, removable fastening means for fastening the boom on the assembly so as to maintain the assembly at a stationary position, wherein the assembly is supported and suspended in the pool by the grapnel at a stationary position while the image sensor is moving. 2. A device according to claim 1, wherein the boom comprises two ends, and the removable fastening means comprises a receptacle of a base of the assembly, connected to at least one end of the boom. 3. A device according to claim 2, wherein another end of the boom is fastened to a float. 4. A device according to claim 2, wherein the fastening means comprises a fork capable of being removably fastened to a top of the assembly. 5. A device according to claim 1, wherein the graduation comprises a tape measure ballasted with a weight. 6. A device according to claim 1, wherein the image sensor is a still camera. 7. A device according to claim 6, wherein the still camera is a high definition digital still camera provided with a motorized telephoto lens. 8. A device according to claim 6, further comprisingmeans for processing and controlling the images acquired by the image sensor, anda digital transmission chain between the still camera and the processing and control means. 9. A device according to claim 1, wherein the image sensor is mounted on a table capable of displacing the sensor in a plane perpendicular to the axis parallel to the longitudinal axis of the assembly on the one hand, and around an axis perpendicular to the axis parallel to the longitudinal axis of the assembly, on the other hand, in order to be able to adjust horizontality of the sensor. 10. A device according to claim 1, wherein the image sensor is mounted on a basket mounted on a rail parallel to the longitudinal axis of the assembly, the basket being capable of displacing the sensor parallel to the longitudinal axis of the assembly. 11. A device according to claim 10, wherein the basket and the rail are part of a lowerator. 12. A method for inspecting at least one fuel assembly in a pool of a nuclear plant, equipped with a grapnel for displacing and suspending the assembly in the pool, comprising:mounting a moveable image sensor including a field of observation, in proximity to the assembly containing a plurality of fuel rods, said method being characterized in that it further includes steps according to which:removably fastening a boom including a reference graduation and extending along an axis parallel to a longitudinal axis of the assembly to the assembly, such that when the assembly is suspended in the pool by the grapnel, the boom hangs in the pool beside the fuel assembly so as not to occupy the bottom of the pool, andobserving via the image sensor both the boom and the assembly in its field while the assembly is suspended by the grapnel.