SPACER GRID WITH M-SHAPE DIMPLE FOR THE DEBRIS FILTERING

摘要

A spacer grid with an M-shaped dimple for filtering a debris is provided to minimize a cross section in a horizontal direction and reduce a maximum diameter for inflow of the debris. A spacer grid divides a plurality of unit grid cells by reciprocally crossing strips with slots formed at predetermined intervals horizontally and vertically and reciprocally inserting the slots. A dimple(21) includes a depressed unit(211) by bending the strip in a M shape, is projected from a center of a grid surface(20) of the spacer grid in both perpendicular directions, and is installed on the grid surface in a direction to have a minimum cross section for an axial direction of the spacer grid to support a lower rod short stopper(14) of a fuel rod through two line contacts between the depressed unit of the dimple and the lower rod short stopper. An arch(22) is formed by bending the strips to be projected by one pair from each of the grid surfaces in an orthogonal direction to the grid surface where the dimple is formed to the both perpendicular directions and limits a maximum diameter at which a debris is inputted in the axial direction of the spacer grid by less than a half compared when the dimple and the arch do not exist in charging the fuel rod to the spacer grid by being installed on the spacer grid in a direction to have the minimum cross section for the axial direction of the spacer grid.