Abstract: A double strip mixing grid for nuclear reactor fuel assemblies is disclosed. This grid is fabricated by intersecting at right angles a plurality of double strips, each fabricated by welding two thin sheets together into a single structure with coolant channels. The mixing grid, having the channels, effectively mixes low temperature coolant with high temperature coolant within a fuel assembly, thus improving the thermal efficiency of the fuel assemblies. This mixing grid also effectively prevents the coolant from being partially overheated, thus improving the soundness of nuclear reactors. This mixing grid also has swirling flow blades and/or lateral flow blades to further improve the thermal efficiency of the fuel assembly. This mixing grid elastically supports the fuel rods by the sheets of the double strips, collaterally acting as positioning springs.

Abstract: A spacer grid for nuclear fuel assemblies is disclosed. This spacer grid has a plurality of side weld supports, that is, main supports, upper sub-supports and lower sub-supports, on its interlaced inner straps, with two flow mixing vanes integrally extending upward from each of the main supports. This spacer grid is fabricated by seam-welding the interlaced first and second inner straps to each other along the upper axial junction lines of the crossing main and upper sub-supports at the top of the intersections, and along the lower axial junction lines of the crossing lower sub-supports at the bottom of the intersections, thus forming side weld lines at the intersections.

Abstract: A spacer grid with hybrid flow-mixing devices for nuclear fuel bundle is made up of an intersection of a plurality of thin straps at right angles to form a plurality of cells for receiving and supporting fuel rods. Each strap is composed of two types of strap units, called a primary strap unit and a secondary strap unit, which are alternately arranged along the strap. The primary strap unit is a strap section having a primary vane set, and a secondary strap unit is a strap section having a secondary vane set. The straps intersect such that, by primary and secondary strap units, each intersection forms a hybrid flow-mixing device around the top of each junction. The primary vane set, consisting of a trapezoidal primary vane stand and two bent primary mixing vanes on both sides, protrudes upwardly from the strap and is primarily for generating cross flow between channels.