MODULAR FUEL ROD SPACER ASSEMBLY FOR NUCLEAR REACTOR FUEL ASSEMBLIES

摘要

1312739 Fuel elements UNITED NUCLEAR CORP 14 June 1971 [15 June 1970] 27811/71 Heading G6C A fuel rod spacer assembly comprises a cellular spacer for providing lateral support for the fuel rods of a fuel assembly intermediate the ends of the fuel rods, and a plurality of bearing clips for laterally spacing and longitudinally retaining the fuel rods in the cells of the spacer. Each bearing clip (Fig. 2) comprises a pair of resilient split rings 7, 8 embracing a fuel rod 6, a pair of linking members 14, 15 for joining the split rings 7, 8 together at their respective free ends, and means for releasably engaging the clip with the cellular spacer to prevent longitudinal displacement of the clip. The latter means may comprise spring tabs 17 on the upper edge of split ring 7 and the lower edge of split ring 8, located at positions about 90 degrees apart and adjacent pairs of bearing lands 11, 12. The lands 11, 12 are for resiliently engaging the cell walls of the spacer. Inward bends 13 in the split rings 7, 8 between the lands of each pair allow for the circulation of coolant and so prevent " hot spots " from developing in the regions of contact of the fuel rod 6 and dimples 10 formed in the split rings 7, 8 in the region of the lands. There are also dimples 10 adjacent the free ends of the split rings 7, 8. The linking members 14, 15 are made of a resilient material and are provided intermediate their ends with bearing sections 16 (for resiliently engaging the bearing sections of adjacent clips) extending radially outward beyond the peripheries of the split rings 7, 8. The bearing clips are assembled on to the individual fuel rods 6 by springing the clips slightly open so that the rods may be axially positioned without scraping against the dimples 10. The cellular (" egg-crate ") spacers are set up on their sides at the prescribed locations with their cells in alignment and the fuel rods with the bearing clips in place are passed longitudinally through the cells of the " foreign " spacers until each clip is positioned within the cell of its own particular " home " spacer. There is ample clearance for the passage of each of the clips if the rods bearing these clips are rotated 45 degrees about their longitudinal axes from their final positions in the fuel assembly. When in their correct longitudinal positions the rods are rotated back 45 degrees and snapped into position. Where there are four fuel rods in each cell of the spacer (Fig. 6), the bearing section 16 of the linking member 14 of each clip engages the bearing section 16 of the linking member 15 of an adjacent clip and the bearing lands 11, 12 engage the walls of the cell.