Spacer grid with mixing vanes and nuclear fuel assembly employing the same

A nuclear fuel assembly comprising:

• a plurality of elongated fuel rods;
• and
• a plurality of spacer grids for securing the elongated fuel rods in an organized array, at least one of the plurality of spacer grids comprising:
• a plurality of interlocking grid straps forming a plurality of four-walled cells for supporting the fuel rods therein, each of the four-walled cells including four cell walls having a longitudinal axis, and
• a plurality of mixing vanes extending from each of the grid straps, each of the mixing vanes including a middle ligament directly extending from a top portion of a corresponding one of the grid straps, an upper piece extending from an upper portion of the middle ligament, and a lower piece extending from a lower portion of the middle ligament,
• wherein each of the upper piece and the lower piece has at least one of a predetermined bend angle and a predetermined degree of twist, and the middle ligament has at least one of a predetermined rotation angle and a predetermined degree of twist, in order to provide a predetermined affect on a coolant as it flows over the fuel rods and through the fuel assembly.

A spacer grid for a nuclear fuel assembly including a plurality of elongated fuel rods and a coolant flowing over the fuel rods, the spacer grid comprising:

• a plurality of interlocking grid straps forming a plurality of four-walled cells structured to support the fuel rods therein, the four-walled cells each including four cell walls having a longitudinal axis;
• and
• a plurality of mixing vanes extending from each of the grid straps, each of the mixing vanes including a middle ligament extending from a top portion of a corresponding one of the grid straps, an upper piece extending from an upper portion of the middle ligament, and a lower piece extending from a lower portion of the middle ligament,
• wherein each of the upper piece and the lower piece has at least one of a predetermined bend angle and a predetermined degree of twist, the bend angle and/or the degree of twist of the upper piece being independent from the bend angle and/or the degree of twist of the lower piece, and the middle ligament has at least one of a predetermined rotation angle and a predetermined degree of twist, in order to provide a predetermined affect on the coolant as it flows over the fuel rods and through the fuel assembly.

A nuclear fuel assembly comprising:

• a plurality of elongated fuel rods;
• and
• a plurality of spacer grids for securing the elongated fuel rods in an organized array, at least one of the plurality of spacer grids comprising:
• a plurality of interlocking grid straps forming a plurality of four-walled cells for supporting the fuel rods therein, each of the four-walled cells including four cell walls having a longitudinal axis, and
• a plurality of mixing vanes extending from each of the grid straps, each of the mixing vanes including a middle ligament extending from a top portion of a corresponding one of the grid straps, an upper piece extending from an upper portion of the middle ligament, and a lower piece extending from a lower portion of the middle ligament,
• wherein each of the upper piece and the lower piece has at least one of a predetermined bend angle and a predetermined degree of twist, the bend angle and/or the degree of twist of the upper piece being independent from the bend angle and/or the degree of twist of the lower piece, and the middle ligament has at least one of a predetermined rotation angle and a predetermined degree of twist, in order to provide a predetermined affect on a coolant as it flows over the fuel rods and through the fuel assembly.

A spacer grid for a nuclear fuel assembly including a plurality of elongated fuel rods and a coolant flowing over the fuel rods, the spacer grid comprising:

• a plurality of interlocking grid straps forming a plurality of four-walled cells structured to support the fuel rods therein, the four-walled cells each including four cell walls having a longitudinal axis;
• and
• a plurality of mixing vanes extending from each of the grid straps, each of the mixing vanes including a middle ligament extending from a top portion of a corresponding one of the grid straps, an upper piece extending from an upper portion of the middle ligament, and a lower piece extending from a lower portion of the middle ligament,
• wherein each of the upper piece and the lower piece has at least one of a predetermined bend angle and a predetermined degree of twist, and the middle ligament has at least one of a predetermined rotation angle and a predetermined degree of twist, in order to provide a predetermined affect on the coolant as it flows over the fuel rods and through the fuel assembly, and wherein the upper piece and lower piece are structured such that the upper and lower pieces are not directly extending from a top portion of a corresponding one of the grid straps.