Patent Number: 
Section: claims

1. A fuel rod support insert for connecting to interlaced straps of a nuclear fuel assembly spacer grid, the interlaced straps defining a lattice of cells for receiving fuel rods, the fuel rod support insert comprising:a first end portion and a second end portion, the first end portion and the second end portion configured for abutting the straps, the fuel rod support insert extending axially along an insert axis between first end portion and the second end portion, the fuel rod support insert being configured such that the insert axis is positioned parallel to a center axis of at least one of the cells when the fuel rod support insert is connected to the straps; andat least one spring extending axially with respect to the insert axis between the first and second end portions, the at least one spring being defined in part by at least one slot extending axially with respect to the insert axis, the at least one spring being configured for transversely abutting a fuel rod when the fuel rod support insert is connected to the straps, the fuel rod support insert being configured for extending in at least one of the cells when the fuel rod support insert is connected to the straps, the spring extending axially through planes perpendicular to the insert axis and radially away from the first end portion and the second end portion to define an apex configured for contacting the fuel rod when the fuel rod is inserted into one of the cells, the spring having a non-rectilinear cross-section in each of the planes perpendicular to the insert axis,wherein the spring comprises a contact wing and a lateral wing adjacent to each other and extending side-by-side along the insert axis, the contact wing and the lateral wing each including an inner surface facing the straps and an outer surface facing away from the straps, the outer surfaces of the contact wing and the lateral wing being inclined relative to each other, the contact wing being configured for contacting the fuel rod and the lateral wing extending laterally from the contact wing towards one of the straps. 2. The fuel rod support insert as recited in claim 1 wherein the outer surface of the lateral wing is flat. 3. The fuel rod support insert as recited in claim 1 wherein the outer surface of the contact is convex. 4. The fuel rod support insert as recited in claim 1 wherein the lateral wing extends along a length thereof between the first end portion and the second end portion axially with respect to the insert axis, the lateral wing extending along a width thereof between a first longitudinally extending edge and second longitudinally extending edge laterally with respect to the insert axis, the width of the lateral wing varying along the length thereof. 5. The fuel rod support insert as recited in claim 1 wherein the contact wing extends along a length thereof between the first end portion and the second end portion axially with respect to the insert axis, the contact wing extending along a width thereof between a first longitudinally extending edge and second longitudinally extending edge laterally with respect to the insert axis, the width of the contact wing substantially constant along the length thereof. 6. The fuel rod support insert as recited in claim 1 wherein the contact wing extends along a length thereof between the first end portion and the second end portion axially with respect to the insert axis, the contact wing being arched away from the insert axis along the length. 7. The fuel rod support insert as recited in claim 1 further comprising one contact wall, a first connection wall and a second connection wall, the first and second connection walls being connected by the contact wall, the at least one spring including a first spring and a second spring, the first spring being formed by the one contact wall and the first connection wall, the second spring being formed by the one contact wall and the second connection wall. 8. The fuel rod support insert as recited in claim 1 further comprising at least two walls extending longitudinally between the first end portion and the second end portion, the at least two walls inclined one relative to the other when viewed along the insert axis, the at least two walls including a contact wall and a first connection wall adjacent to the contact wall, the spring being at a junction between the contact wall and the adjacent connection wall with the contact wing formed by the contact wall and the lateral wing formed by the adjacent connection wall. 9. The fuel rod support insert as recited in claim 8 wherein the at least one spring includes a first spring and a second spring, the at least two walls including a second connection wall adjacent to the contact wall such that the contact walls is laterally between the first connection wall and the second connection wall with respect to the insert axis, the first spring having a first contact wing formed by the contact wall and first lateral wing formed by the first connection wall, the second spring having a second contact wing formed by the contact wall and a second lateral wing formed by the second connection wall. 10. The fuel rod support insert as recited in claim 1 wherein the insert is tubular and includes a plurality of walls defining a polygonal cross-section, the at least one spring including a pair of springs located at each corner of the polygonal cross-section. 11. The fuel rod support insert as recited in claim 1 wherein the at least one spring includes a pair of springs defined by three slots each having a length extending axially with respect to the insert axis, the three slots including one central slot and two lateral slots, the length of the one central slot being greater than the length of each of the two lateral slots. 12. The fuel rod support insert as recited in claim 11 wherein the central slot has a width decreasing from axial ends of the central slot towards a middle of the central slot. 13. A spacer grid for a nuclear fuel assembly, the spacer grid comprising:interlaced straps defining a lattice of cells for receiving fuel rods; andsupport inserts provided at intersections of the straps for supporting the fuel rods which extend through the cells, the support inserts each comprising:a first end portion and a second end portion, the first end portion and the second end portion configured for abutting the straps, the fuel rod support insert extending axially along an insert axis between first end portion and the second end portion, the fuel rod support insert being configured such that the insert axis is positioned parallel to a center axis of at least one of the cells when the fuel rod support insert is connected to the straps; andat least one spring extending axially with respect to the insert axis between the first and second end portions, the at least one spring being defined in part by at least one slot extending axially with respect to the insert axis, the at least one spring being configured for transversely abutting a fuel rod when the fuel rod support insert is connected to the straps, the fuel rod support insert being configured for extending in at least one of the cells when the fuel rod support insert is connected to the straps, the spring extending axially through planes perpendicular to the insert axis and radially away from the first end portion and the second end portion to define an apex configured for contacting the fuel rod when the fuel rod is inserted into one of the cells, the spring having a non-rectilinear cross-section in each of the planes perpendicular to the insert axis,wherein the spring comprises a contact wing and a lateral wing adjacent to each other and extending side-by-side along the insert axis, the contact wing and the lateral wing each including an inner surface facing the straps and an outer surface facing away from the straps, the outer surfaces of the contact wing and the lateral wing being inclined relative to each other, the contact wing being configured for contacting the fuel rod and the lateral wing extending laterally from the contact wing towards one of the straps. 14. The spacer grid as recited in claim 13 wherein connection walls of each of the support inserts are inserted in connection slots provided on lower edges of the interlaced straps. 15. The spacer grid as recited in claim 13 wherein each of the inserts is secured to the straps by spot-welds. 16. A nuclear fuel assembly comprising:a bundle of fuel rods; andan armature for supporting the fuel rods, the armature comprising at least one spacer grid for a nuclear fuel assembly, the spacer grid comprising:interlaced straps defining a lattice of cells for receiving fuel rods; andsupport inserts provided at intersections of the straps for supporting the fuel rods which extend through the cells, the support inserts each comprising:a first end portion and a second end portion, the first end portion and the second end portion configured for abutting the straps, the fuel rod support insert extending axially along an insert axis between first end portion and the second end portion, the fuel rod support insert being configured such that the insert axis is positioned parallel to a center axis of at least one of the cells when the fuel rod support insert is connected to the straps; andat least one spring extending axially with respect to the insert axis between the first and second end portions, the at least one spring being defined in part by at least one slot extending axially with respect to the insert axis, the at least one spring being configured for transversely abutting a fuel rod when the fuel rod support insert is connected to the straps, the fuel rod support insert being configured for extending in at least one of the cells when the fuel rod support insert is connected to the straps, the spring extending axially through planes perpendicular to the insert axis and radially away from the first end portion and the second end portion to define an apex configured for contacting the fuel rod when the fuel rod is inserted into one of the cells, the spring having a non-rectilinear cross-section in each of the planes perpendicular to the insert axis,wherein the spring comprises a contact wing and a lateral wing adjacent to each other and extending side-by-side along the insert axis, the contact wing and the lateral wing each including an inner surface facing the straps and an outer surface facing away from the straps, the outer surfaces of the contact wing and the lateral wing being inclined relative to each other, the contact wing being configured for contacting the fuel rod and the lateral wing extending laterally from the contact wing towards one of the straps. 17. The nuclear fuel assembly as recited in claim 16 further comprising at least one intermediate mixing grid comprising interlaced straps provided with mixing vanes and defining a lattice of cells for receiving the fuel rods, the support inserts being tubular and each being provided around the intersection of two of the straps of the mixing grid for preventing contact between the fuel rods extending through the cells and the mixing vanes. 18. The nuclear fuel assembly as recited in claim 17 wherein the support inserts are secured to the straps of the mixing grid by at least one spot weld.