NUCLEAR FUEL ASSEMBLY FOR BOILING-WATER REACTOR

PROBLEM TO BE SOLVED: To increase concentration of fissile material for high burn up and long fuel cycles while securing a thermal margin even when setting end regions to a nuclear fuel assembly for a boiling-water reactor.SOLUTION: Cross-sectional mean fissile material concentration of end regions disposed at at least one of top ends and bottom ends of individual fuel effective portions of a nuclear fuel assembly is 3.0 wt.% or less. In individual selected fuel rods including corner fuel rods of all corner portions and fuel rods adjacent to the corner fuel rods out of fuel rods disposed at an outermost peripheral in the nuclear fuel assembly, fissile material concentration in at least one of the end regions is maximum in a fissile material concentration distribution in the fuel rods.