Patent Number: 061545147
Section: claims

1. A structure of an upper hold-down spring of a fuel assembly for a nuclear reactor, the fuel assembly comprising: an upper and lower nozzle spaced apart form and facing each other;  a plurality of hollow guide tubes each extending parallel to and spaced apart from each other between the nozzles and secured at both ends thereof to the nozzles;  a plurality of fuel rod support grids each firmly mounted at the hollow guide tubes and spaced apart from each other in the lengthwise direction; and  a plurality of fuel rods each extending through and supported by the fuel rod support grids, each of the fuel rods extending in parallel to and spaced apart from each other,  wherein the upper hold-down spring which is mounted on an upper surface of the upper nozzle comprises one upper plate spring with plastic spring characteristics and one lower plate spring, said plate springs having base ends, said base ends of the plate springs being fastened at a common position, in which both of the plate springs are made of a precipitation hardened nickel base alloy and a thickness of the plate springs is between 4.6 to 5.2 mm in order to provide a stress value which is less sensitive to stress corrosion cracking. 2. The structure of an upper hold-down spring of a fuel assembly for a nuclear reactor as described in claim 1, wherein the lower plate spring has a slot extending in a lateral direction at a distal end portion thereof, the upper plate spring has a bent portion and a vertically oriented portion with an abutting ledge, and the upper and lower plate spring are assembled such that the vertically oriented portion extends through the slot below the abutting ledge.