Patent Number: 047626690
Section: abstract

In a nuclear reactor, the core is composed of fuel assemblies disposed in side-by-side spaced relationships with an outer group thereof defining the periphery of the core and an inner group thereof positioned inwardly of the outer group. A baffle structure extends about the reactor core adjacent the fuel assemblies in the outer group. Any jetting of coolant fluid through the baffle structure will impinge upon fuel rods in the outer group of fuel assemblies so as to cause vibration of the fuel rods. To prevent such vibration, a plurality of annular anti-vibration grids are axially spaced along and connected to guide thimbles of the fuel assemblies in the outer group thereof between at least some of the support grids of such fuel assemblies. The annular grids are separate from and unconnected to the support grids. Each annular grid defines a plurality of cells being less in number than the multiplicity of fuel rods of each fuel assembly in the outer group but at least equal in number to the plurality of the fuel rods positioned about the periphery of each such fuel assembly. The cells receive respective ones of the peripheral fuel rods therethrough and engage them so as to dampen vibration thereof due to impingement by coolant fluid jetting from the baffle structure.