Fuel assembly, spectral shift rod, nuclear reactor and power control method for nuclear reactor

摘要

A fuel assembly (1) comprises a plurality of fuel rods (4) which are respectively arrayed in first and second square lattices (7A, 7B). The fuel rods (4) included in the first square lattice array are arranged among the fuel rods included in the different or second square lattice array. Each of the fuel rods (4) has both its end parts supported by an upper tie plate (2) and a lower tie plate (3), respectively.A spectral shift rod (40) which is cruciform in cross section has its cruciform side ends opposed to the corner parts of the fuel assembly (1). The spectral shift rod includes a coolant raising path (41) which is open below the fuel holding portion of the lower tie plate, and a coolant lowering path (42) which is open above the fuel holding portion. The coolant lowering path (42) communi­cates at its upper end with the upper end of the coolant raising path (41).