Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Kenji Kanamori

Junjiro Nakajima

Hajime Umehara

Hiromasa Hirakawa

Yasuhiro Aizawa

Hideaki Ishizaki

Yoshihiko Yanagi

Toraki Sakuma

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

Kenji Kanamori