Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Hideaki Ishizaki

Hiromasa Hirakawa

Junjiro Nakajima

Masahisa Inagaki

Hideo Maki

Yasuhiro Aizawa

Nobukazu Yamamoto

Toraki Sakuma

Shozo Nakamura

Satoshi Kanno

Hajime Umehara

Iwao Takase

Norio Kawashima

Masayoshi Kanno

Takashi Fukumoto

Yoshihiko Yanagi

Kouichi Matsumoto

Nobuhiro Okazaki

Kenji Kanamori

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, where crystallographic orientations of a channel box are brought into a random distribution; and cladding tubes, spacers and a channel box are made from highly corrosion-resistant, Fe--Ni, zirconium-based alloy, hardened in the (.alpha.+.beta.) phase or .beta.-phase temperature region, has an average discharge burnup level of 50 to 550 GWd/t.

Fuel assembly, components thereof and method of manufacture

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

A control rod assembly for a boiling water reactor comprises a tie-rod of a cross-shaped section, and four sheaths. Each of the sheaths is of a U-shaped section and mounted to the respective arms of the tie-rod. One or more neutron absorber materials are disposed within a space defined by the arm and the sheath. The neutron absorber material is axially separated into two portions. One of two portions is supported by a supporting member. The other portion is suspended by a handle.

Control rod assembly for a boiling water reactor

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Mito, Japan

Hideaki Ishizaki