FUEL AGGREGATE AND CORE OF NUCLEAR REACTOR

PURPOSE:To suppress the output peaking in the axial direction and to improve the profitability of fuel by making a ratio occupied by a fuel rod in which an enrichment of the lower area is larger than an average enrichment of the lower area of a fuel aggregate smaller than a ratio of the same of the upper area. CONSTITUTION:Among 28 pieces of fuel rods 16 which have been placed in the peripheral part of a fuel aggregate 10, as for 16 pieces of fuel rods 16 (57% as a ratio), an enrichment of its upper area is larger than an average enrichment of the upper area of the fuel aggregate 10. Also, among 28 pieces of fuel rods which have been placed in the peripheral part of the fuel aggregate 10, the fuel rod in which an enrichment of the lower area is larger than an average enrichment of the lower area of the fuel aggregate 10 does not exist at all. That is, among the fuel rods which have been placed in the peripheral part of the fuel aggregate 10, a ratio occupied by the fuel rod in which an enrichment of the lower area is larger than an average enrichment of the lower area of the fuel aggregate does not exceed 20%.