Channel box for nuclear reactor

Purpose: To prevent the occurrence of creep deformation of materials constituting a channel box for use in fuels. Constitution: As the material for constituting a channel box, those materials with less circumferential irradiation growth at the outer surface of the channel box and with greater circumferential irradiation growth at the inner surface are used. This causes difference in the irradiation growth between the inner and the outer layers of the channel box to cause forces tending to cause distortion and deformation toward the inside of the channel box, which can offset the creep deformation force to the outside and substantially suppress the deformation of the channel box. Accordingly, it is possible to obtain a fuel assembly of high burnup degree used for a long period of time in a reactor, to reduce the fuel cycle cost and to decrease the radioactive wastes. (Takahashi, M.)