Patent Number: 054232198
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for ultrasonic detection techniques for the inspection of weld defects in a fuel rod weldment. 2. Technical Background In general, a fuel rod for use in a light water pressurized reactor is made by packing fuel pellets inside a fuel pipe, and the ends of the fuel pipe are fitted with end plugs and the end plugs are joined to the ends of the fuel pipe by means of joining techniques such as the tungsten inert gas (TIG) welding. Further, there is a (gas) seal opening disposed on one of the two end plugs for filling the fuel pipe interior with an inert gas under pressure. The gas seal opening is sealed off, by joining methods such as TIG welding, so as to maintain the interior of the fuel pipe at a certain inert gas pressure. Conventionally, the joints of the fuel rod welded as described above have been inspected non-destructively by X-ray transmission. However, the X-ray method is being superseded by the ultrasonic inspection method which is more compact in apparatus design and easier to handle. The ultrasonic inspection apparatuses which have been available to date are based on scanning the entire circumferential periphery of the weld by moving the detection probe linearly in the longitudinal direction while turning the fuel rod. When examining the weld by moving the detection probe in the longitudinal direction while rotating the fuel rod, there are no problems when the examination is being carried out at a rough scanning pitch or at low speeds. However, when it is desired to carry out inspection at a faster operating speed or at a finer scanning pitch, it was necessary to increase the rotational speed of the fuel rod, which lends to high loads on the rod and insufficient processing time for obtaining proper inspection results. SUMMARY OF THE INVENTION The present invention was made in view of the technical background presented above, and the objective of achieving efficient inspection of the weld with an inspection device comprising: a rotating member freely rotatable around its rotation axis having an inspection section formed within for holding said fuel rod in place during inspection; a liquid supplying means for filling said liquid medium in said inspection section; a plurality of ultrasonic probes disposed on said rotating member having said inspection section. According to the device of the above configuration, the fuel rod to be inspected is housed in the inspection section disposed in the rotating member which is filled with liquid, and the rotating member is rotated while ultrasonic inspection is being carried out with the probes disposed on the rotating member. Therefore, there is no need to rotate the fuel rod, and consequently, it is possible to inspect the welded section without imposing loads on the fuel rod, and the inspection process can be carried out more quickly and with higher resolution than with conventional inspection techniques. Furthermore, the inspection apparatus can be made compact, and automation of the inspection process is made easier. The maintenance operation can also be carried out easily. Another aspect of the invention is that the fuel rod is held firmly while being inspected. Still another aspect of the invention is that a transport device is provided to move the rotating member relative to the fuel rod along the rotation axis. Still another aspect of the invention is that the fuel rod is held stably during the inspection by an immobile or more particularly a non-rotating lid member provided opposite to and in sliding contact with an opening section of said rotating member for supporting the fuel rod which passes through a through hole disposed on the immobile on non-rotating lid member. Still another aspect is that the liquid is contained in the inspection section by a through hole provided with: a seal member which envelopes the fuel rod tightly; and a lid member which closes the through hole and is swingable inside the inspection section to open when a fuel rod is inserted through the through hole. Still another aspect is that the inspection is carried out while circulating the liquid from the bottom to the top by liquid supply means disposed on the lower part of the immobile lid member, and a liquid collection means for collecting liquid flowing out of the inspection section is disposed on the upper portion of the inspection section disposed on the upper portion of the immobile lid support member, Still another aspect is that the liquid is supplied to the rotating member through a plurality of liquid flow passages provided on the rotating lid member on the outer periphery; and liquid supply passages are provided opposite to each of the liquid flow passage disposed on the lower part of the immobile lid member for supplying liquid to the inspection section of the rotating member; and liquid collection passages are provided on the upper part of the immobile lid member opposite to each of the liquid flow passages for collecting liquid flowing out of the inspection section of the rotating member; wherein the diameters of each of the liquid supply passages and liquid collection passages are larger than the distance between the two adjacent liquid flow passages.