Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Toraki Sakuma

Junjiro Nakajima

Hiromasa Hirakawa

Hideaki Ishizaki

Masahisa Inagaki

Hideo Maki

Hajime Umehara

Yasuhiro Aizawa

Iwao Takase

Yoshihiko Yanagi

Kouichi Matsumoto

Nobukazu Yamamoto

Kenji Kanamori

Nobuhiro Okazaki

In a method of fabricating a channel box for use in a nuclear reactor, Zr-alloy sheet material is formed into a tubular channel box. The method includes solution heat treatment of the Zr-alloy sheet material including quenching from a temperature at which .beta.-phase is present. After the solution heat treatment, portions of the Zr-alloy sheet are thinned relative to other portions by a non-stressing thinning process, such as chemical etching in a bath. The corrosion resistance imparted by heat treatment is retained, and the heat treatment itself is easily performed on material of uniform thickness.

Method of fabricating a channel box or other part for a nuclear reactor

A fuel assembly comprises a plurality of fuel rods supported by an upper tie plate and a lower tie plate respectively at each of upper end portion ad lower end portion, and a channel box surrounding a bundle of the fuel rods and the lower tie plate. The fuel assembly forms a natural uranium region at lower end portion of effective fuel length portion. A wall thickness at a lower thick wall region of the channel box is thicker than the wall thickness at a region disposed upwardly from the lower thick wall region and between corner portions of the channel box. An upper end of the lower thick wall region is disposed from an upper side of the lower tie plate and downwardly from an upper end of the natural uranium region. A wall thickness at the corner portion of the channel box is thicker than the wall thickness at a middle portion of the side wall between the corner positions at the region locating upward from the lower thick wall region. The fuel assembly is able to reduce stresses caused in the channel box during an earthquake, and, is able to improve fuel economy.

Fuel assembly

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Hitachi, Japan

Toraki Sakuma