Patent Number: 
Section: claims

1. A nuclear fuel assembly comprising a plurality of fuel rods and a spacer grid having canoe-shaped springs for preventing fretting wear of the fuel rods, the spacer grid comprising:strips adapted to define a plurality of unit grid cells; anda plurality of springs each protruding in predetermined directions on a grid surface of a strip of the strips and supporting a nuclear fuel rod of the plurality of fuel rods with predetermined elasticity,wherein each spring of the plurality of springs comprising:a fuel rod-contacting part having a flat surface and two reinforcing portions, the flat surface comprising an upper end, a lower end, and two sides, wherein the flat surface has a predetermined length along a longitudinal direction of the fuel rod-contacting part from the upper end to the lower end, and a predetermined width in a direction transverse to the longitudinal direction from one of the two sides to the other of the two sides, wherein the flat surface is in linear contact with the nuclear fuel rod and wherein the two reinforcing portions are respectively located at the two sides of the flat surface so as to prevent the flat surface from getting distorted and are separated from the grid surface;legs installed between the fuel rod-contacting part and the grid surface, giving elastic force to the spring and supporting the spring on the grid surface,wherein each one of the two reinforcing portions is formed along the longitudinal direction of the fuel rod-contacting part and is bent toward the grid surface and has a shape of a curved surface extending from one of the two sides of the flat surface;an upper leg-connecting part and a lower leg-connecting part, wherein each of the upper leg-connecting part and the lower leg-connecting part is formed between two legs of the installed legs and connecting the two legs; andan upper curved surface-connecting part and a lower curved surface-connecting part,wherein the upper curved surface-connecting part is installed between an upper portion of the fuel rod-contacting part and the upper leg-connecting part and is connected to both the upper portion of the fuel rod-contacting part and the upper leg-connecting part, and the lower curved surface-connecting part is installed between a lower portion of the fuel rod-contacting part and the lower leg-connecting part and is connected to both the lower portion of the fuel rod-contacting part and the lower leg-connecting part, andwherein each of the upper curved surface-connecting part and the lower curved surface-connecting part has a gradually reduced width toward a corresponding leg-connecting part of the upper and lower leg-connecting parts from the fuel rod-contacting part, and an outer diameter and shape of the upper curved surface-connecting part are the same as an outer diameter and a shape of the fuel rod-contacting part at a contact portion between the upper curved surface-connecting part and the fuel rod-contacting part, and an outer diameter and a contour of the lower curved surface-connecting part are the same as an outer diameter and a contour of the fuel rod-contacting part at a contact portion between the lower curved surface-connecting part and the fuel rod-contacting part. 2. The nuclear fuel assembly according to claim 1, wherein two legs connected by the upper leg-connecting part are formed to be oblique with respect to the longitudinal direction of the fuel rod-contacting part in opposite directions to each other and two legs connected by the lower leg-connecting part are formed to be oblique with respect to the longitudinal direction of the fuel rod-contacting part in opposite directions to each other.