Patent ID: 7453972

Claim:
An elongated fuel assembly for a nuclear reactor having a longitudinal axis along its elongated dimension, the fuel assembly comprising: (a) a top nozzle; (b) a bottom nozzle axially spaced from the top nozzle; (c) a plurality of spacer grids stacked in tandem in a spaced array between the top nozzle and the bottom nozzle, each of said spacer grids being formed from an orthogonal arrangement of straps formed in a generally egg-crate shaped pattern to define a plurality of grid cells; (d) a plurality of elongated control rod guide thimbles disposed through specified locations of the grid cells and extending between and fixedly attached to the top nozzle and the bottom nozzle at a top end and a bottom end of the control rod guide thimble, respectively, at least one of the control rod guide thimbles having on an interior of its bottom end a female latch profile designed to receive a fastener; and (e) an elongated fastener bolt having a head and shank, with the shank extending from the head of the fastener bolt concentric with the axis of the elongated dimension of the fastener bolt and having a profile designed to engage the female latch profile of the control rod guide thimble, the fastener bolt head on a side opposite the shank, having a torque contour that can be engaged by a torque tool to place the shank in engagement with the female latch profile on the interior of the control rod guide thimble, and a raised, deformable rim, the shank being inserted through a hole in the bottom nozzle to engage the female latch profile in the control rod guide thimble and fasten the control rod guide thimble to the bottom nozzle, at least a portion of the deformable rim on the head of the fastener bolt being crimped outward of the central axis of the fastener bolt to engage a recess in the bottom nozzle that locks the fastener bolt from disengaging from the female latch profile of the control rod guide thimble.