Patent Number: 041750047
Section: claims

1. In combination with a nuclear fuel assembly of the type having a plurality of vertically extending fuel elements and guide tubes maintained in a laterally spaced array by at least one cellular spacer grid assembly that is composed of a multiplicity of intersecting slotted grid plates disposed to form a plurality of cells through which the fuel elements and guide tubes extend; and, lower and upper end fitting assemblies, each being rigidly attached to the respective ends of the guide tubes, the improvement comprising a plurality of protuberancies integrally formed in the guide tubes in spaced relation, each guide tube having a cross-section at each protuberancy greater than a distance between the plates forming the cell through which the guide tubes extend, the protuberancies being longitudinally aligned with and spaced relative to at least part of of the plates such that the protuberancies engage the plates to restrain longitudinal movements of the spacer grid assembly relative to the guide tubes beyond the longitudinal spacing, and the spaced relation of the protuberancies being such that the guide tubes, including the protuberancies, may be inserted through a cell. 2. The improved nuclear fuel assembly of claim 1 further comprising saddles formed in the grid plates to project into the cells containing the guide tubes, said saddles generally conforming to the shape of the guide tubes, wherein said protuberancies are longitudinally aligned with the saddles such that the protuberancies engage the saddles to restrain movements of the plates. 3. The improved fuel assembly of claim 2 wherein at least two longitudinally spaced saddles are formed to project from each grid plate forming a guide tube cell and said protuberancies are spaced between said longitudinally spaced saddles. 4. The improved fuel assembly of claim 3 wherein groups of said longitudinally spaced protuberancies are equidistantly spaced about the perimeter of the guide tubes. 5. The improved fuel assembly of claim 4 wherein said guide tubes are cylindrical and groups of four protuberancies are equidistantly spaced about the circumference of the guide tubes at longitudinally spaced intervals. 6. The improved fuel assembly of claim 5 wherein said guide tubes protuberancies are cut to form a lip at the protuberance edge adjacent to the spacer grid plate saddle. 7. The improved fuel assembly of claim 2 wherein at least two longitudinally spaced saddles are formed to project from each grid plate forming a guide tube cell and said protuberancies are spaced to span the width of the spacer grid plates having the longitudinally spaced saddles. 8. The improved fuel assembly of claim 7 wherein groups of said longitudinally spaced protuberancies are equidistantly spaced about the perimeter of the guide tubes. 9. The improved fuel assembly of claim 8 wherein said guide tubes are cylindrical and groups of four protuberancies are equidistantly spaced about the circumference of the guide tubes at longitudinally spaced intervals. 10. The improved fuel assembly of claim 9 wherein each of said guide tube protuberancies are cut to form a lip at the protuberancy edge adjacent to the spacer grid plate saddle. 11. In combination with a fuel assembly of the type having a plurality of vertically extending fuel elements and at least one guide tube maintained in a laterally spaced array by at least one cellular spacer grid assembly that is composed of a multiplicity of intersecting slotted grid plates disposed to form a plurality of cells through which the fuel elements and guide tube extend; and lower and upper end fitting assemblies, each being rigidly attached to the respective ends of the guide tube, the improvement comprising a plurality of protuberancies integrally formed in the guide tube in spaced relation, the guide tube having a cross-section at each protuberancy greater than a distance between the plates forming the cell through which the guide tube extends, the protuberancies being longitudinally aligned with and longitudinally spaced relative to at least part of the plates such that the protuberancies engage the plates to restrain longitudinal movements of the spacer grid assembly relative to the guide tube beyond the longitudinal spacing, and the spaced relation of the protuberancies being such that the guide tube, including the protuberancies, may be inserted through cell through which the guide tube extends.