device for kernreaktor for instellning and uppberning of brenslestavar

摘要

1374861 Fuel elements ATLANTIC RICHFIELD CO 10 March 1972 [18 March 1971] 11387/72 Heading G6C A nuclear reactor fuel assembly includes a frame and associated grid spacer for supporting fuel rods in a desired spaced relationship, the grid spacer including a grid having square openings and springs mounted on the grid to provide each rod with resilient supporting contacts on all four sides of the openings, through each of which a fuel rod extends. The spacer comprises a plurality of support strips B-C, B-R assembled in "egg-crate" fashion and secured to the frame F by tabs tb. The springs S each comprise one finger 15 integral with a support strip 17, the other spring of the pair being a similar finger 15 brazed at each end to the first finger. The fingers are of flared-base configuration and carry contact pads d against which the fuel rods (R) bear. Each fuel rod (R) is contacted by four of the springs S at right angles to each other. The frame and grid spacer may be of stainless steel or zirconium alloy, as may the cladding of the fuel rods (R). Each of the pairedbow springs provides a contact spring of a desired minimum stiffness to effectively eliminate all significant vibrational excursions of the rod. Each of the rods has a maximum anticipated lateral displacement and each of the springs is arranged to exhibit sufficient elastic springback to follow its associated rod without losing contact therewith and is also arranged to exhibit a "preset" capability, sufficient to accommodate this displacement, yet without affecting springback. The frame and grid spacer have sufficient strength that the grid system is incapable of being substantially distorted or weakend by rod elongation. A plurality of these frames and associated grid spacers is arranged in spaced relationship along the fuel rods, thereby dividing each rod into a number of spans and raising its natural vibrating frequency to increase its effective stiffness and resistance to vibration.