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AssigneeHitachi, Ltd.
InventorsJunichi Koyama, Motoo Aoyama, Akinobu Nakajima, Yasunori Bessho, Junichi Yamashita, Sadao Uchikawa, Hiromi Maruyama, Michihiro Ozawa, Mitsunari Nakamura
Estimating the term…
A nuclear fuel assembly has an array of fuel rods comprising a plurality of first fuel rods each containing nuclear fuel material but not containing burnable poison and a plurality of further fuel rods each containing both nuclear fuel material and burnable poison. The further fuel rods comprise second fuel rods and third fuel rods, and each second fuel rod has at a lower region of the fuel assembly a burnable poison concentration which is a minimum burnable poison concentration in the further fuel rods. To increase the effectiveness of the second fuel rods in controlling axial power peaking, as seen in plan view on the array, the first fuel rods are the nearest neighbors of each further fuel rod.
A nuclear fuel assembly having upper and lower regions and an array of fuel rods extending through both said regions, said fuel rods comprising a plurality of first fuel rods each containing nuclear fuel material but not containing burnable poison and a plurality of further fuel rods each containing both nuclear fuel material and burnable poison, said further fuel rods comprising at least one second fuel rod and at least one third fuel rods, wherein said at least one second fuel rod has at a lower region of the fuel assembly a burnable poison concentration which is a lowest burnable poison concentration other than zero of said burnable poison concentration contained in said further fuel rods at said lower region of the fuel assembly, and said at least one third fuel rod has at said lower region of the fuel assembly a burnable poison concentration higher than said lowest burnable poison concentration of said at least one second fuel rod, and wherein as seen in plan view said first fuel rods are disposed nearer to said second and third fuel rods than said second and third fuel rods are disposed with respect to one another in said array, and the burnable poison concentration of said second and third fuel rods of said further fuel rods at the lower region of the fuel assembly is determined at the same horizontal section extending through said further fuel rods in said lower region of the fuel assembly average burnable poison concentration of said further fuel rods is equal or higher in said lower region than in said upper region.
A nuclear fuel assembly having a plurality of first fuel rods each containing nuclear fuel material but not containing burnable poison and a plurality of further fuel rods each containing both nuclear fuel material and burnable poison, said further fuel rods comprising (a) at least one second fuel rod having at a lower region of the fuel assembly a burnable poison concentration which is a lower burnable poison concentration other than zero in said further fuel rods, (b) a plurality of third fuel rods having at said lower region of the fuel assembly a burnable poison concentration higher than said lowest burnable poison concentration, the fuel rods being arranged so that said first fuel rods are adjacent fuel rods of each of said further fuel rods, and wherein the burnable poison concentration of said second and third fuel rods of said further fuel rods at said lower region of said fuel assembly is determined at the same horizontal section extending through said further fuel rods in said lower region of the fuel assembly the average burnable poison concentration of said further fuel rods is equal or higher in said lower region than in said upper region.
Dependencies are inferred from the claim text.