Fuel assembly.

摘要

A fuel assembly of the present invention comprises a plurality of fuel rods (15) which are held by an upper tie plate and lower tie plate at the ends thereof and a moderating rod (17) which is arranged between the fuel rods (15) and held by the lower tie plate at its lower end. The fuel rods are arranged in a lattice form having 9 rows and 9 columns, and the moderating rod (17) contains a passage for a coolant and has a cruciate cross-sectional form. The ratio AM/AC of the area AM of a moderator region in the moderating rod in the cross-sectional plane in which the moderator is present to the area AC of the coolant passages in said fuel assembly (10) is within the range of 0.07 to 0.11, and the area AM is 75 % or more of the total area of the fuel lattice units in which none of the fuel rods (15) is arranged, but the moderating rod (17) is arranged.