초록 ▼

Zirconium alloy or Zircaloy grid straps in a fuel assembly grid have predetermined texture (or grain orientation) to offset stress relaxation which occurs upon irradiation of the grid. Particularly, by providing “f-factor”values of the material greater in generally orthogonal, longitudinal direction

Zirconium alloy or Zircaloy grid straps in a fuel assembly grid have predetermined texture (or grain orientation) to offset stress relaxation which occurs upon irradiation of the grid. Particularly, by providing “f-factor”values of the material greater in generally orthogonal, longitudinal directions of the straps than in the strap height direction, the grid strap material will undergo irradiation shrinkage in the longitudinal directions which will serve to offset stress relaxation and maintain sufficient spring force on the fuel rods extending through the cells formed by the grid straps.

대표청구항 ▼

In a fuel assembly support grid including interleaved straps fabricated from fully recrystallized material which upon irradiation grows differently in different directions depending on the texture of the material and defining a multiplicity of cells, each cell adapted to receive a fuel rod therethro

In a fuel assembly support grid including interleaved straps fabricated from fully recrystallized material which upon irradiation grows differently in different directions depending on the texture of the material and defining a multiplicity of cells, each cell adapted to receive a fuel rod therethrough in a direction generally along an axis of said cell and to exert a predetermined spring force on said fuel rod in a direction along a cross-section of said cell which is sufficient for holding the said fuel rod in a predetermined position, the improvement which comprises: said fully recrystallized material of said grid straps having respective predetermined “f-factor”values in said direction along said cross-section of said grid cell and in said direction along said axis of said grid cell such that upon irradiation of said grid any stess relaxation thereof in said direction along said axis of each of said grid cells will be substantially offset by shrinkage of said grid strap material in said direction along said cross-section of each of said grid cells and thereby maintain said predetermined spring force on each of said fuel rods.