FUEL ASSEMBLY

PROBLEM TO BE SOLVED: To make the distribution of thermal neutron flux more uniform on the cross section of a fuel assembly by preventing fretting corrosion which water rods cause to each other. SOLUTION: The fuel assembly 1 has a plurality of fuel rods 2 arranged in the form of a square grid with nine rows and nine columns, and two water rods 3 arranged in the center area of the fuel assembly 1 in such a manner as to replace some of the fuel rods 2. The outside diameter of the water rod 3 is greater than the spacing between the fuel rods 2. The two water rods 3 are spaced apart from each other. The interval between the two water rods 2 is smaller than the interval between the water rod and the adjacent fuel rod. COPYRIGHT: (C)2003,JPO