Patent Number: 053234324
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for assembling a nuclear fuel assembly for nuclear reactors, and in particular to a simple apparatus for loading fuel rods into the fuel assembly efficiently. 2. Background Art A conventional fuel assembly such as the one disclosed in a U.S. Pat. No. 5,068,081, shown in FIG. 2, is known. In this figure, the numerals 1 and 2 refer to top and bottom nozzles, respectively, which are disposed vertically and oppositely spaced apart, and having a plurality of rigidly fixed control-rod guide pipes 3 (hereinbelow referred to as guide pipes 3) between the top nozzle 1 and the bottom nozzle 2. In the mid section of the guide pipes 3 are a plurality of grids 4 disposed vertically and spaced apart from each other. The grids 4 are, as shown in FIGS. 3 to 5, constructed of a plurality of straps 7 made of thin metal strips having slits 8 formed in the longitudinal direction thereof, and by interlocking the slits 8 to form lattices. The structure formed by the lattices is known as the grid cells 5, and a dimple 9 and spring 10 are formed on each of the opposing walls of the grid cells 5. A fuel rod 6 inserted into a grid cell 5 is pressed against the dimple 9 by the spring 10, thereby holding the fuel rod 6 firmly in the grid cell 5 therebetween. A method of inserting a fuel rod 6 in a grid cell 5 is known, for example, in Japanese Patent Application, Laid-open publication (Kokai) H2-181,699 which involves the use of a key device to deactivate the spring 10, and gripping the tip of a fuel rod 6 by means of a pull-in device, which then enables the fuel rod 6 to be pulled into the grid cell 5. However, such methods presented problems because of the necessity of pull-in device and other ancillary control devices, and the complexities of the devices mean that the operations become cumbersome and lengthy. SUMMARY OF THE PRESENT INVENTION The present invention was made to resolve the above mentioned problems associated with the conventional assembling apparatus, by providing an apparatus of a simple mechanical construction, enabling the insertion of fuel rods into the grids efficiently and without causing surface damages on the fuel rods. An apparatus for assembling a fuel assembly containing longitudinally extending fuel rods comprises: (a) a longitudinally extending fuel rod magazine containing a plurality of fuel rods; PA1 (b) a plurality of fluid-pressure operated loading cylinders provided on the fuel rod magazine, for pushing specific fuel rods of the plurality of fuel rods in a longitudinal direction into the grid cells, wherein each of the loading cylinders are disposed coaxially with corresponding ones of the plurality of fuel rods contained in the fuel rod magazine; PA1 (c) a plurality of grid support frames spaced apart and disposed in the longitudinal direction of the assembly so as to vertically support the plurality of fuel rods being loaded into the grid cells of the grids. According to the present invention, it becomes possible to insert the fuel rods into the grids by first placing the grids in the grid support frames, and simply by operating the fluid-driven loading cylinders provided on the invented assembling apparatus, it becomes possible to push the specified fuel rods out of the fuel rod magazine towards the grids, and inserting the fuel rods into the corresponding grid cells. Therefore, the assembly operation involves only the operation of the pressure-driven loading cylinders in association with a fuel rod magazine which hold the plurality of fuel rods. Therefore, the construction of the assembling apparatus is simplified significantly in comparison to the conventional apparatus such as the pull-in rods system. The operational procedure is correspondingly simplified because the necessity of complex operations such as gripping of the fuel rods has been eliminated.