Patent ID: 6721384
Filing Date: 2004-04-13
Classification: G21C,Y02E

Abstract:
A spacer grid used in a nuclear fuel assembly such that a plurality of spacer grids are regularly and transversely arranged along the fuel assembly to support a plurality of fuel rods within the fuel assembly while maintaining a desired pitch of the fuel rods and promoting the mixing of a coolant flowing longitudinally upwardly along nuclear fuel rods, comprising:a plurality of first inner straps each having a rectangular-shaped first strap body, with a plurality of main supports and a plurality of upper sub-supports alternately formed along a top edge of the first strap body while being spaced apart from each other at regular intervals, a plurality of lower sub-supports formed along a bottom edge of the first strap body while being spaced apart from each other at regular interval, a pair of flow mixing vanes symmetrically formed along a top edge of each of said main supports, and a plurality of upper vertical slits extending from center of top edge of each said main supports and each upper sub-supports of the first strap body toward a middle of said first strap body; and a plurality of second inner straps each having a rectangular-shaped second strap body, with a plurality of main supports and a plurality of upper sub-supports alternately formed along a top edge of the second strap body while being spaced apart from each other at regular intervals, a plurality of lower sub-supports formed along a bottom edge of the second strap body while being spaced apart from each other at regular interval, a pair of flow mixing vanes symmetrically formed along a top edge of each of said main supports of the second strap body, and a plurality of lower vertical slits extending from center of bottom edge of each said lower sub-supports of the second strap body toward a middle of said second strap body; whereby said first and second inner straps are interlaced at right angles at the vertical slits such that the interlaced inner straps form a plurality of square cells for receiving the fuel rods, with the main supports of the first and second inner strap crossing the upper sub-supports of the second and first inner straps while forming a plurality of upper axial junction lines, and the lower sub-supports of the first and second inner straps crossing each other while forming a plurality of lower axial junction lines, said inner straps being seam-welded to each other along the upper and lower junction lines to form a plurality of side weld lines, and said flow mixing vanes of the interlaced inner straps guiding axial flows of coolant to gaps between the fuel rods, thus forming cross flows of coolant.