METHOD FOR REASSEMBLING FUEL ASSEMBLY

PURPOSE:To decrease the pressure drop of a nuclear reactor core by exchanging spacers used from the initial period of loading with another spacers which are different in wall thickness at the time of reassembling a fuel assembly at the specific timing during in-pile loading period. CONSTITUTION:The honeycomb type spacers 52, which consist of 'Inconel(R)' having 0.35mm thickness and, the unit cells 503, 504 of which have a heaxagonal shape, are loaded into the high-conversion region fuel assembly A1 in the case of reassembling the fuel assembly A1 to the burner region fuel assembly B1. The honeycom type pacers 53, which consist of a zirconium niobium alloy of a different material having 0.50mm thickness and, the unit cells 505, 506 of which have a hexagonal shape, are used for the assembly B1 after the reassembly of the fuel. The thicknesses of these spacer structural materials are determined at the thicknesses at which the spacers withstand stresses at the time of earthquakes. The pressure drop of the reactor core is thus decreased by exchanging the spacers with another spacers having the different thickness in the case of reassembling the fuel assembly.