CRUSH RESISTANT NUCLEAR FUEL ASSEMBLY SUPPORT GRID
A spacer grid design for a nuclear fuel assemblies that exhibits increased crush strength. The walls of the grid straps that surround the fuel elements have a number of dimples and/or springs with the flat surfaces of those walls formed with a plurality of emboss geometries that are formed in a symmetrical pattern with the pattern covering substantially an entire area of the wall except for the contact surfaces of the dimples and springs that interface with the fuel rods.
1 . A nuclear fuel assembly comprising:
a parallel array of elongated fuel elements;
a support grid for supporting the elongated fuel elements along their longitudinal dimension, the grid having a lattice structure which defines a plurality of cells, some of through which the fuel elements are respectively supported, others of which respectively support a guide tube for a control rod, each of the cells having a plurality of walls which intersect at corners and surround the corresponding fuel element or a guide tube at the support locations; and
wherein each of the walls that supports the fuel elements has a number of dimples and/or springs and the walls that support the fuel elements are embossed with a plurality of emboss geometries that are formed in a symmetrical pattern with the pattern covering substantially an entire area of the wall except a contact surface of the dimples and springs that interface with the fuel elements.
2 . The nuclear fuel assembly of claim 1 wherein the emboss geometry is generally circular in cross-section.
3 . The nuclear fuel assembly of claim 1 wherein the emboss geometry is generally hexagonal in cross-section.
4 . The nuclear fuel assembly of claim 1 wherein the emboss geometry is generally rectangular in cross-section.
5 . The nuclear fuel assembly of claim 4 wherein the cross-section has rounded corner.
6 . The nuclear fuel assembly of claim 3 wherein the geometry has a width and a length, with the ratio of width to length greater than or equal to 1/10 and less than or equal to 1.
7 . The nuclear fuel assembly of claim 1 wherein the emboss geometries are arranged in alternate, staggered rows.
8 . The nuclear fuel assembly of claim 1 wherein the emboss geometry has a height and a wall thickness, with the ratio of the height to wall thickness greater than or equal to ¼ and less than or equal to 4.
9 . The nuclear fuel assembly of claim 1 wherein the plurality of emboss geometries has a diameter and a wall pitch, with the ratio of the diameter to the wall pitch greater or equal to ⅛ and less than or equal to 1.
10 . The nuclear fuel assembly of claim 1 wherein the plurality of emboss geometries have a width and the watts that support fuel elements have a pitch and the ratio of the width to the pitch is greater than or equal to ⅛ and less than or equal to 1.
11 . The nuclear fuel assembly of claim 1 wherein adjacent emboss geometries extend on opposite sides of the wall.
12 . The nuclear fuel assembly of claim 1 wherein adjacent geometries extend on the same side of the wall.
13 . A nuclear fuel assembly nuclear fuel element support grid comprising:
a lattice structure which defines a plurality of cells, at least some of which are configured to respectively support a nuclear fuel element, each of the cells that support the fuel element having a plurality of walls which intersect at corners and surround the corresponding fuel element; and
wherein the walls that support the fuel element has a number of dimples and/or springs and are embossed with a plurality of emboss geometries that are formed in a symmetrical pattern with the pattern covering substantially an entire area of the wall except a contact surface of the dimples and springs that interface with the fuel element.
14 . The nuclear fuel element support grid of claim 13 wherein the emboss geometries are arranged in alternate, staggered rows.
15 . The nuclear fuel element support grid of claim 13 wherein the emboss geometry has a height and a wall thickness, with the ratio of the height to wall thickness greater than or equal to ¼ and less than or equal to 4.
16 . The nuclear fuel element support grid of claim 13 wherein the plurality of emboss geometries has a width and a wall pitch, with the ratio of the width to the wall pitch greater than or equal to ⅛ and less than or equal to 1.
17 . The nuclear fuel element support grid of claim 13 wherein the plurality of emboss geometries have a pitch and the walls that support fuel elements have a width and the ratio of the pitch to the width is greater than or equal to ⅛ and less than or equal to 1.