FAIL-FREE FUEL BUNDLE ASSEMBLY

PROBLEM TO BE SOLVED: To provide a fuel assembly (14) for a reactor core (10). SOLUTION: The fuel assembly (14) may include a plurality of rods (18/20) consisting of a fuel rod (18) and/or an isotope production rod (20). Each of the rods (18/20) contains a plurality of interconnected rod segments (40), and at least two of the rod segments (40) of at least one of the rods (18/20) have outer diameters (D) different from each other. The fuel assembly (14) may include a plurality of rod spacer grids (34) surely held between the interconnected rod segments (40) adjacent from each other in the axial direction. The rod spacer grids (34) connected with each other between the rod segments (40) adjacent to each other in the axial direction form an array of the rods (18/20) substantially equally spaced apart from each other. Further, the fuel assembly (14) may include an elongate tubular channel (22) for housing the arrayed rods (18/20). COPYRIGHT: (C)2009,JPO&INPIT