Patent ID: 6845138

Claim:
A spacer grid for nuclear fuel assembly, fabricated by an intersection of a plurality of thin inner straps, to form a plurality of cells for receiving and supporting fuel rods, and provided with a coolant flow-mixing device at its top: wherein each of said inner straps comprises a plurality of primary strap units and a plurality of secondary strap units being alternately arranged along each inner strap, and said inner straps are intersected with each other such that each intersection is formed by a primary strap unit of an inner strap and a secondary strap unit of another inner strap; the primary strap unit comprises a primary vane stand having an isosceles trapezoidal shape, the isosceles trapezoidal shape comprises non-parallel sides and a top edge extending therebetween, two primary mixing vanes extending from the non-parallel sides for creating cross flows of coolant to neighboring cells, wherein the top edge extends between the two primary mixing vanes and defines therewith a bubble outlet; and the secondary strap unit comprises a secondary vane stand having an isosceles trapezoidal shape, the isosceles trapezoidal shape comprises non-parallel sides and a top edge extending therebetween, two secondary mixing vanes extending from the non-parallel sides for creating swirl flows of coolant within the cells, wherein the top edge extends between the two secondary mixing vanes and defines therewith a bubble outlet.