Fuel assembly, fuel channel box and method of manufacturing the same

A degree of heat treatment or rolling fabrication for a channel box made of a Zr-base alloy is changed in the longitudinal direction, and the direction of crystals of α phase Zr is changed to the longitudinal direction of the channel box. Especially, an orientation probability (Fr value) of the crystal direction <0001> of the α phase Zr in the direction of a surface normal line of the channel box in a region in the vicinity of a lower tie plate is controlled so as to be greater than the orientation probability (Ft, F1) in the lateral and longitudinal directions of the plate. Further, it is preferred that the orientation of the crystal direction in a longitudinal central region of the channel box is made at random. Bending of channel box along with irradiation growth is reduced by controlling the crystal direction of the channel box in the vicinity of the lower tie plate having the crystal direction formed at random, and relative lowering of the thermal margin of the fuels can be prevented. In addition, the amount of leakage can be reduced. (N.H.)