Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Akira Maru

Shozo Nakamura

Junjiro Nakajima

Tetsuo Yasuda

Yoshihiko Yanagi

Tadashi Mizuno

Junichi Yamashita

Masahisa Inagaki

Katsumi Ohsumi

Yamato Asakura

Jiro Kuniya

Hideo Maki

Naohito Uetake

Yuichiro Yoshimoto

Hajime Umehara

Tatsuo Hayashi

Yasuhiro Aizawa

Iwao Takase

Hiromasa Hirakawa

Masayoshi Kanno

Masayoshi Kondoh

Masaomi Oguma

Yorihide Segawa

Yoshishige Kawada

Tetsuro Yasuda

Eiichi Sagi

Seiji Kawahara

In a nuclear fuel rod having a zirconium liner and a method of manufacturing the same, the outer surface of a zircaloy cladding tube in which fuel pellets are filled has an oxide film having fine irregularities of which the pitch is 1 .mu.m or less. The fine irregularities are formed by oxidizing the surface in high temperature steam or polishing the surface of the cladding tube. The surface of the fuel rod can effectively trap radioactive substances in the reactor water.

Nuclear fuel rod and method of manufacturing the same

A fuel assembly for a nuclear reactor comprising a fuel cladding tube of three-layer structure having an outer surface in contact with reactor water of the nuclear reactor, an inner surface layer in contact with the nuclear fuel, and an intermediate layer interposed between the outer surface layer and the inner surface layer. the outer surface layer is made of a Zr-based alloy containing Nb, Sn and Mo. The inner surface layer is made of pure zirconium. The intermediate layer is made of a high ductility alloy which is higher in ductility than the outer surface layer and is higher in strength than the inner surface layer.

Fuel assembly for nuclear reactor, method for producing the same and

A fuel assembly comprises a plurality of fuel rods, a lower tie plate for supporting lower ends of the fuel rods, and a channel box surrounding a bundle of the fuel rods and the circumference of the lower tie plate to thereby define a cooling water leak passage between the lower tie plate and the channel box. The fuel assembly includes a venturi provided in the lower tie plate for generating a force tending to attract the channel box toward the lower tie plate under the action of a leak stream of the cooling water passing through the cooling water leak passage. The fuel assembly also includes an arrangement provided in the lower tie plate for suppressing vibrations of the channel box caused upon an influence of the venturi.

Fuel assembly

A nuclear fuel assembly has a plurality of fuel rods and a lower tie plate supporting their lower ends. Coolant apertures extending through the lower tie plate. A channel box surrounds the fuel rods and receives the lower tie plate, to confine the coolant. To restrict leakage of coolant between the tie plate and the channel box, the coolant apertures include, adjacent the periphery of the lower tie plate, a plurality of peripheral apertures which are located at least partly outside the outermost fuel rods. The peripheral apertures each provide a coolant velocity peak located further from the axial center line of the tie plate than the axial center lines of the closest neighboring fuel rods. The invention also provides venturis in the leakage path between the channel box and the tie plate, to restrict deformation of the tie plate.

Nuclear fuel assemblies

The vented nuclear fuel element comprises a cladding tube containing nuclear fuel therein and a device disposed in the upper portion of the cladding tube for venting gaseous fission products released from the nuclear fuel. The venting device comprises a porous plug for closure of the top end of the venting tube, which plug has the property of getting wet with the surrounding coolant, two plates that in cooperation with the cladding tube define a chamber for holdup of the gaseous fission products, a capillary tube for introducing the gaseous fission products from the nuclear fuel into the upper portion of the chamber, another capillary tube for introducing the gaseous fission products from the lower portion of the chamber to the porous plug, and a check valve for preventing the gaseous fission products within the chamber from flowing back into the interior of the cladding tube. Upon operation of the nuclear reactor, the gaseous fission products released from the nuclear fuel will pass through the check valve and the first mentioned capillary tube to reach the chamber, and from the chamber the gaseous fission products will pass through the second mentioned capillary tube and be vented through the porous plug to the coolant surrounding the nuclear fuel element.

Vented nuclear fuel element

Growing community of inventors

Ibaraki, Japan

Akira Maru