Hitachi, Ltd.

Toshimi Yoshida

Isao Masaoka

Iwao Takase

Masahisa Inagaki

Hideo Maki

Hajime Umehara

Tetsuo Yasuda

Keiichi Kuniya

Ryutarou Jimbow

Junjiro Nakajima

Jiro Kuniya

Masayoshi Kanno

Shinzo Ikeda

Kiyotomo Nakata

Hisawo Itow

A channel box and/or a spacer of a fuel assembly is a welded construction and made of a Zr-Nb-Sn alloy comprising 0.5-2.2 wt % Nb, 0.5-1.5 wt % Sn contained so as to satisfy the relation of Sn(wt %) 22.times.Nb(wt %)--3.0, and balance Zr or a Zr-Nb-Sn-Mo alloy comprising 0.5-2.2 wt % Nb, 0.5-1.5 wt % Sn contained so as to satisfy the relation of Sn(wt %).gtoreq.2.times.Nb(wt %)--0.3, 0.1-0.8 wt % Mo, and balance Zr. The welded portion, its heat affected zone and the unwelded portion of the channel box and/or the spacer have substantially the whole equilibrium phase structure.

Nuclear reactor fuel assembly

A method of producing cladding tube comprises a step of temperature-gradient annealing in which the inner surface of the tube is heated to a temperature higher than the recrystallization temperature thereof, while the outer surface of the tube is cooled, after the tube has been hot-extruded. The temperature-gradient annealing is effected while a temperature gradient is maintained between the inner surface and the outer surface of the cladding tube. While keeping the inner surface at a temperature higher than the recrystallization temperature, and the outer surface at a temperature lower than the recrystallization temperature. The cladding tube is obtained with the outer surface which has an excellent resistance to nodular corrosion and a soft inner surface which has an excellent resistance to stress corrosion cracking.

Method of producing a cladding tube for reactor fuel

In a process for producing a zirconium-based alloy in which after the zirconium-based alloy is subjected to hot plastic working, it is subjected to cold plastic working and then to annealing and these steps are repeated at least twice, the present invention provides a process for producing a zirconium-based alloy characterized in that after the alloy is subjected to solid solution treatment in which it is heated to a temperature within the range including the .alpha. phase and the .beta. phase of the alloy, or within the range of the .beta. phase and is then quenched, cold plastic working is effected at least twice.

Process for producing zirconium-based alloy

Process for producing zirconium-based alloy and the product thereof

An alloy for use in an environment exposed to neutron rays consists principally of Cr-Ni austenite stainless steel containing nitrogen in an amount exceeding the amount of an impurity and having principally an austenite structure. The alloy is used for reactor core members such as a core shroud, core supporters, control rods, etc. which are exposed to the neutron radiation but prevented from being embrittled by the radiation.

Alloy for use in a radioactive ray environment and reactor core members

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Katsuta, Japan

Toshimi Yoshida