Patent ID: 7668280
Filing Date: 2010-02-23
Classification: G21C,Y02E

Abstract:
1. A nuclear reactor fuel assembly comprising: a top nozzle; a bottom nozzle; a plurality of elongated control rod guide thimbles respectively attached at a first end to the top nozzle and at a second end to the bottom nozzle; a plurality of elongated fuel rods supporting fissile material there within, the fuel rods extending parallel to the control rod guide thimbles, between the top nozzle and the bottom nozzle; a plurality of transverse grids arranged in a spaced tandem array between the top nozzle and the bottom nozzle, the grids respectively forming a lattice to latterly support the fuel rods in a spaced orderly array, the grids being attached to and supported axially by the control rod guide thimbles; at least one elongated instrumentation tube extending and captured between the top nozzle and the bottom nozzle, the control rod guide thimbles, fuel rods and the instrumentation tube having parallel axes extending along their elongated dimension, the instrumentation tube being adapted to receive an in-core instrumentation that extends along a substantial axial length of the instrumentation tube, the in-core instrumentation remaining fixed during reactor operation; and an instrumentation tube insert that extends within and substantially along the elongated dimension and over the substantial axial length of the instrumentation tube, the insert having an inside narrow-most diameter at a plurality of axial locations along the length of the insert that is adapted to closely approximate the outside diameter of the in-core instrumentation, the plurality of axial locations extending over the substantial axial length, so as to maintain the in-core instrumentation centered in the instrumentation tube when inserted, the inside narrow-most diameter being supported a fixed distance from an inside diameter of the instrumentation tube at spaced segmented locations along an interior and substantially along the elongated dimension of the instrumentation tube, the insert comprising a spiral spring and being adapted to center the in-core instrumentation over the substantial axial length of the instrumentation tube.