[en] Purpose: To prevent meshing of the corner parts even when the side surfaces of fuel assemblies come into contact with each other by forming an internally curved portion by bending the edge part of the outer frame corner part of the lattice for the fuel assemblies which accommodate fuel rods. Constitution: At the upper edge of the outer frame of the lattice, an internally curved surface formed by bending a projection formed integrally with the outer frame is provided between the corner part and the vane adjacent thereto or over a cell closest to the corner part or a cell adjacent thereto. The quantity of bending of the internally curved portion is substantially equal to the thickness of the outer frame. This internally curved portion displays a guide function at the time of loading the fuel assemblies into the core, and even when the side surfaces of the fuel assemblies come into contact with each other, the corner parts of the lattice are prevented from developing into an enmeshed state. (Sekiya, K.)