Fuel assemblies

Purpose: To prevent failures in fuel elements loaded with fuel pellets containing burnable poisons such as gadolinium. Constitution: A fuel assembly comprises a plurality of fuel elements loaded with fuel pellets consisting only of uranium dioxide and plurality of hollow gadolinium-containing fuel elements loaded with gadolinium-containing fuel pellets prepared by adding gadolinium oxide as burnable poisons to uranium dioxide and formed into hollow cylinder in a fuel can, each disposed in a channel box. Since gadolinium is not contained in the center of the gadolinium-containing fuel pellet, the maximum power for the fuel elements is resulted at an earlier time than that for the solid gadolinium-containing pellets. Since the fuel can rapture distortion is greater as the reactor staying time is shorter, the risk of failures in the gadolinium-containing fuel elements can be reduced as the result. (Horiuchi, T.)