Nuclear fuel assembly with pivot dimpled grids

摘要

A soft pivot dimple nuclear fuel assembly grid that utilizes a “dog bone” shaped window cutout and radius coining of edges perpendicular to coolant flow, to reduce the susceptibility of fuel rod leaking during the reactor operation. Radius coining allows the fuel rod to smoothly transition over the radiused edge to the flat rod contact section of the dimple. The symmetric “dog bone” shape enables the dimple to pivot during rod loading resulting in improved alignment between the dimple and the fuel rod, thereby minimizing scratching. The “dog bone” shape also allows for a large contact area dimple to be softer than a typical dimple which reduces contact stresses and fretting wear during reactor operations.

主权项

1. A nuclear fuel assembly grid comprising:
a first plurality of spaced, parallel, elongated straps; a second plurality of spaced, parallel, elongated straps positioned orthogonal to said first plurality of spaced, parallel, elongated straps and aligned in a regular pattern so that the intersection of each set of four adjacent straps defines a cell, some of which are designed to support fuel rods, with an extent of each of the first and second straps that border each cell forming a wall of the cell; wherein at least one wall of the cells that are designed to support fuel rods has a dimple arrangement that extends from the wall into the cell from a “dog bone” shaped cutout in the wall of the cell and the dimple arrangement has a downstream edge that contacts the fuel rod when the fuel rod is loaded into the grid wherein the downstream edge, in relation to the flow of coolant when the nuclear fuel assembly grid is placed in the core of an operating nuclear reactor, is rounded in a direction away from the fuel rod.