Patent Number: 052746844
Section: abstract

The present invention presents a method and an apparatus for assembling a fuel assembly which is free of surface damage on the fuel rod surfaces, and of distortions caused by residual stresses. Such problems are introduced by the method of inserting the fuel rods into the grids, and the sequence of attaching the control rod guiding pipes. In the conventional method, the guiding pipes are attached to the respective grids first and the fuel rods are inserted in the grids while the holding mechanisms (such as spring force against a dimple formed on the grid wall) are active. In the invented assembling method, the sprigs are deactivated first and then the fuel rods are inserted into the grids. Once the assembly is made firm with all the fuel rods in place and fixed firmly to the grids, the control rod guiding pipes are inserted into the grids and the pipes are fixed rigidly to the respective grids. By performing the assembling operation in the above sequence, slight shifting of the grids which occurs on fixing the pipes to the grids, during the conventional method, is prevented. The final assembly produced according to the invented method is free of surface damage and the overall quality of alignment of the assembly is excellent.