FUEL ASSEMBLY AND REACTOR CORE

摘要

PURPOSE:To achieve a smaller void coefficient without lowering reactivity and also an optimization of a cross-sectional area of a neutron moderation rod over a moderator by flattening a local peaking in a fuel assembly body aimed at higher degree of combustion. CONSTITUTION:Normal fuel rods 2 and partial-length fuel rods 3 are arranged in a square lattice of 10X10 and three large water rods 4 are arranged diagonally in an area which allows the setting of ten center fuel rods. The partial- length fuel rods 3 are arranged within a range of a projection area of the water rods 4 in the outermost layer of the fuel rod arrange in the square lattice an the normal fuel rods 2 alone are arranged in two layers inward from the outermost layer. With such an arrangement. the void coefficient is lowered while the value of a control rod is improved. In addition. a loss of reactivity and a local output peaking are both improved to upgrade fuel economy and thermal allowance as well. The internal cross-sectional area of the water rods is 9cm<2>. This also helps improve fuel economy and achieves higher channel stability and higher stability of a reactor core.