Patent Number: 052001431
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a fuel assembly 1 of PWR type. It is composed of fuel rods 2 (not shown in FIG. 1; see FIG. 4) and guide tubes 3 for control rods. Fuel rods 2 and guide tubes 3 are retained into an elongated bundle of a number of spacers 4 arranged across the bundle. The spacer 4 positioned at the bottom is named bottom spacer 5. The bundle is connected to a top nozzle 6 and a bottom nozzle 7 by means of the guide tubes 3. In the bottom spacer 5, bottom sleeves 8 for the guide tubes 3 are rigidly fixed. The bottom sleeves 8 rest against the bottom nozzle 7 and are provided with first locking members in the form of slots 9 for receiving second locking members, arranged at the end of a guide tube 3, in the form of tongues 10 (FIG. 2) whereby the guide tubes 3 are rigidly fixed. FIG. 2 shows in enlarged form how the bottom sleeve 8 is fixed in the bottom spacer 5. The bottom sleeve 8 has such a diameter that a guide tube 3 with an associated end plug 11 may be inserted into the bottom sleeve 8. The end plug 11 which is rigidly fixed to the guide tube 3 is provided with tongues 10 which fit into slots 9 provided in the bottom sleeve 8. Through the bottom nozzle 7, a guide tube screw 12 is screwed into the end plug 11 whereby the guide tube 3 is fixed to the bottom nozzle 7 without any torsional stresses being initiated in the guide tube 3. FIG. 3 shows how the tongues 10 fit into the slots 9. In FIG. 4, 2 designates a fuel rod and 3 guide tubes. The spacer 4 comprises a grid by means of which fuel rods 2 and guide tubes 3 are mutually fixed so as to form a bundle. 13 designates sleeves for the guide tubes 3 and 14 an instrumentation tube. The bundle is fixed between a top nozzle 6 and a bottom nozzle 7. The top nozzle 6 is provided at the top with a spring package 15 intended to keep the fuel assembly 1 in position in the reactor core. Bottom sleeves 8 are welded in the bottom spacer 5. The bottom sleeves 8 rest against the bottom nozzle 7. A guide tube screw for fixing a guide tube 3 to the bottom nozzle 7 is designated 12. FIG. 5 shows in enlarged form an end plug 11 intended to be screwed or welded to a guide tube 3. The end plug 11 is provided with tongues 10 intended to engage into slots 9 which are shown enlarged in FIG. 6. When a guide tube 3, with an end plug 11 fixed thereto, is inserted into the bottom sleeve 8, the tongues 10 of the end plug 11 slide into the slots 9 of the bottom sleeve 8, the guide tube 3 thus becoming rigidly fixed to the bottom sleeve 8. As mentioned before, the bottom sleeve 8 in its turn is rigidly fixed to the bottom space 5. The slots 9 and the tongues 10, respectively, in the bottom sleeve 8 and the guide tube 3 may, of course, be arranged in different ways--the main thing is that the guide tube is locked in a simple manner to the rigidly arranged bottom sleeve 8. The locking should be of such a nature that the guide tube 3 can be detached, without difficulty, when the guide tube screw 12 is removed.