Abstract: A device for regulating the flow of a fluid comprising a series of gratings positioned perpendicularly to the fluid flow, wherein it is formed by a stack of identical, contiguous gratings, whereof each is constituted by identical meshes forming a flat system, said meshes being staggered from one grating to the following contiguous grating, and wherein the mesh is formed by two adjacent equilateral triangles, one corresponding to an orifice and the other containing a crosspiece with three branches.The invention also relates to a nuclear reactor fuel assembly incorporating such a device.