Patent ID: 6707872
Filing Date: 2004-03-16
Classification: G21C,Y02E

Abstract:
A spacer grid for placing and supporting a plurality of longitudinal fuel rods in a nuclear reactor fuel assembly, comprising a plurality of inner strips arranged while intersecting each other at right angles prior to being encircled with four perimeter strips, thus forming an egg-crate pattern, said inner and perimeter strips each being fabricated with a plurality of unit strips arranged in parallel, and forming a plurality of unit rod cells for receiving and supporting the fuel rods therein while isolating the fuel rods from each other, each unit strip of said inner strips having one grid spring formed on a central portion of the unit strip while projecting in a direction, and two dimples formed on the unit strip at positions above and under the grid spring while projecting in a direction opposite to the grid spring, and each unit strip of said perimeter strips having one grid spring formed on a central portion of the unit strip while projecting in a direction, wherein said grid spring comprises:a vertical support part including: an opening formed at the central portion of the unit strip; upper and lower base parts extending downward and upward from central portions of top and bottom edges of said opening; and two bridge parts branched from the upper base part and extending symmetrically downward until they are united at the lower base part; and a fuel rod support part including: a conformal support part brought into surface contact with an external surface of a fuel rod; and two transverse connection parts extending outward from opposite outside edge of said conformal support part while being specifically bent, and integrated with the central portions of inside edges of said two bridge parts into a single structure, thus connecting the fuel rod support part to the vertical support part wherein said vertical support part including said upper and lower base parts and said two bridge parts has a strength which is lower than that of said fuel rod support part having said conformal support part wherein the vertical support part is elastically deformed before deformation of the conformal support part so as to allow the conformal support part to maintain a conformal contact with the fuel rod upon application of a force from the fuel rod to the grid spring.