A COOLANT FLOW MIXING GRID FOR A NUCLEAR REACTOR FUEL ASSEMBLY

摘要

The invention relates to a coolant-flow mixing grid for a nuclear-reactor fuel assembly. The mixing grid, which has essentially no fuelrod supporting function, is composed of straps (44) interleaved in egg-crate-like fashion to define cell openings (46, 60) for fuel rods, each of which cell openings has associated therewith at least one mixing vane (52) disposed on the downstream edge of one of the straps, and at least one impact-preventing protrusion (54) projecting from the side of the strap into the associated cell opening so as to protect the mixing vane associated therewith from impact when a fuel rod therein undergoes lateral motion. The mixing grid includes a peripheral strap (58) to which the interleaved straps (44) are connected and which lends added structural integrity. The inner straps (44) preferably are th of substantially lower height than the peripheral strap (58) in order to minimize coolant pressure drop through the grid as well as the amount of structural material capable of parasitically absorbing neutrons.