Nuclear fuel assembly with a lock-support spacer grid
AssigneeWestinghouse Electric Corp.
InventorsYong LU, Xiaoyan Jiang
Life of this patent
Estimating the term…
Abstract
An improved grid for a nuclear reactor fuel assembly that has an egg-crate base grid as the primary support structure with each support cell of the base grid that supports a fuel rod having a lock-support sleeve that is rotatable within the support cell between a first and second orientation. In the first orientation the lock-support sleeve fits loosely within the support cell of the base grid and respectively, loosely receives the fuel rods that are loaded therein. The lock-support sleeves are then rotated to a second orientation that locks the fuel rods axially within the support cells.
Claims20
A fuel assembly for a nuclear reactor:
- a parallel array of a plurality of elongated nuclear fuel rods supported between a lower nozzle and an upper nozzle and having an axial length along the elongated dimension of the nuclear fuel rods;
- a plurality of spaced support grids arranged in tandem along the axial length of the fuel rods, between the upper nozzle and the lower nozzle, at least partially enclosing an axial portion of the circumference of each fuel rod within a support cell of the support grids to maintain a lateral spacing between fuel rods, at least one of the support grids comprising;
- an egg-crate base grid having a plurality of orthogonal intersecting straps that define the support cells at the intersection of each four adjacent straps that surround the nuclear fuel rods, a length of each strap between the intersections of the four adjacent straps forming a wall of the corresponding support cell, and
- a lock-support sleeve adapted to fit within at least one of the support cells and in a first orientation loosely receive the nuclear fuel rod therethrough and in a second orientation place a transverse pressure on the fuel rod to restrain the fuel rod axially, the lock-support sleeve being rotatable between the first orientation and the second orientation.
A method of loading a fuel rod into an elongated nuclear fuel assembly skeleton having an axial direction along a longitudinal dimension of the fuel assembly, a bottom nozzle. a plurality of transversely spaced thimble tubes attached at one end to the bottom nozzle and extending up axially toward a top nozzle that will be attached at the other end of the thimble tubes once an array of fuel rods are inserted into the fuel assembly skeleton, and a plurality of spaced support grids arranged in tandem along the axial length of the thimble tubes and attached to at least some of the thimble tubes, the support grids being designed to at least partially enclose an axial portion of the circumference of each fuel rod within a support cell of the support grids to maintain a lateral spacing between fuel rods, wherein at least one of the support grids comprise an egg-crate base grid having a plurality of orthogonal intersecting straps that define the support cells at the intersection of each four adjacent straps that surround the nuclear fuel rods, a length of each strap between the intersections of the four adjacent straps forming a wall of the corresponding support cell, and a lock-support sleeve adapted to fit within at least one of the support cells and in a first orientation loosely receive the nuclear fuel rod therethrough and in a second orientation place a transverse pressure on the fuel rod to load and restrain the fuel rod axially, the lock-support sleeve being rotatable between the first orientation and the second orientation, the method comprising the steps of:
- maintaining all the lock-support sleeves that are in axial alignment, in the first orientation;
- completely inserting a fuel rod into the fuel assembly through each of the lock-support sleeves in the axially transverse position in the fuel assembly skeleton in which the fuel rod is inserted;
- and
- loading the fuel rod to place a transverse pressure on the fuel rod after the fuel rod is completely inserted into the fuel assembly skeleton. by moving the lock-support sleeve surrounding the fuel rod to the second orientation.
Dependencies are inferred from the claim text.