Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Other

Toshiba Corporation

Yasuhiro Aizawa

Junjiro Nakajima

Hiromasa Hirakawa

Satoshi Kanno

Takashi Fukumoto

Koji Nishida

Norio Kawashima

Hideki Kurosaki

Hideaki Ishizaki

Yoshihiko Yanagi

Tadashi Mizuno

Makoto Irube

Atsuya Hirano

Motoo Aoyama

Shozo Nakamura

Masahisa Inagaki

Yasunori Bessho

Junichi Koyama

Masao Chaki

Katsumasa Haikawa

Hajime Umehara

Tetsuo Yasuda

Mikio Sakurai

Akira Maru

Takao Igarashi

Akira Koizumi

Yoshiharu Kikuchi

Yorihide Segawa

Yasuyuki Gotoh

Masana Sasaki

Kensuke Tokunaga

Kouichi Machida

Yoshishige Kawada

Masayoshi Ajima

Toraki Sakuma

Masafumi Imai

Mutsuo Konno

Mishihiro Ozawa

Toshimitsu Ishikawa

Kenji Kanamori

A fuel assembly having a plurality of fuel rods arranged in a square lattice array. The fuel rods include a plurality of short-length fuel rods each having a fuel active length shorter than that of each of remaining ones of the fuel rods. At least one water rod is arranged in a region in which one or more of the fuel rods are arrangeable in the array, and a plurality of fuel spacers are provided at a plurality of positions in the axial direction for holding the plurality of fuel rods and the at least one water rod, with mutual radial intervals therebetween being kept immovable. The plurality of short-length fuel rods include at least one first short-length fuel rod arranged in the outermost peripheral region of the square lattice array. Each of the plurality of fuel spacers include a plurality of cylindrical members.

Fuel assembly

A fuel assembly includes a plurality of fuel rods placed in a square lattice array of 9-rows/9-columns and at least one water rod. In this fuel assembly, the fuel rod pitch of the plurality of fuel rods is in a range of 14.15 mm to 14.65 mm, and means for offsetting and holding a fuel bundle composed of the fuel rods and the water rod is provided in such a manner that the center in a cross section of the fuel bundle is offset from the center in a cross section of the lower tie plate toward the channel fastener side. With this configuration, it is possible to provide a fuel assembly for a D-lattice core, which is capable of achieving the fuel economy comparable to that of a C-lattice core without reducing the thermal margin, and of using the existing fuel spacers.

Fuel assembly and reactor core and fuel spacer and channel box

A fuel assembly, particularly, a fuel assembly including short-length fuel rods and fuel spacers, is used for a boiling water reactor, which is capable of sufficiently reducing the pressure loss of at least one of the fuel spacers positioned above the upper ends of the short-length fuel rods, irrespective of the arrangement of the short-length fuel rods, and also ensuring the structural strength of the fuel spacer. The fuel assembly includes fuel rods located in a square lattice array, two water rods arranged in a region in which seven of the fuel rods are arrangeable, two fuel spacers for holding the fuel rods and the water rods with mutual intervals kept immovable. Each of the fuel spacers includes cells which are connected to each other and in which the fuel rods are to be inserted, respectively, and a band for surrounding the outermost peripheries of the cells. The short-length fuel rods include four first short-length fuel rods arranged in the outermost peripheral region of the square lattice array. One of the fuel spacers, positioned upward from the upper ends of the short-length fuel rods, is configured such that the cells located at lattice positions associated with the first short-length fuel rods are removed and instead supporting members, each being adapted to connect two of the cells adjacently located on both sides of each of the lattice positions in the outermost peripheral region to the band, are provided at the lattice positions.

To reduce the manufacturing processes of a control rod and shorten the time required for manufacturing a control rod, for the lower part support member,, the thin parts,A and,B are formed in the neighborhood of each of the left and right sides of the window,. In the left and right sides of the pull-up handle,, the grooves,A and,B are formed respectively. The groove,B is deeper than the groove,A. The thin part,A is fitted into the groove,A and the thin part,B is fitted into the groove,B. The gap formed between the end of the thin part,B and the bottom of the groove,B is larger than the gap formed between the end of the thin part,A and the bottom of the groove,A. Therefore, the thin part,A can be simply fitted into the groove,A.

Control rod and manufacturing method for the control rod

With an arrangement that the axial distance from the upper end of a first opening area to the upper end of the second opening area is equal to the axial distance from the upper end of a first coupling member to the upper end of a second coupling member, when a spring member is moved upwardly relative to round cells, the upper end of the second coupling member comes into contact with the upper end of the second opening area, and the spring members receives upwardly acting forces from fuel elements. The spring member is thereby prevented from inclining with respect to flow of a coolant. Simultaneously, the upper end of the first coupling member contacts the upper end of the first opening area, and the spring member is stably held in a condition where it is aligned with the direction of the coolant flow. Also, since the axial distance from the lower end of the first opening area to the lower end of the second opening area is smaller than the axial distance from the lower end of the first coupling member to the lower end of the second coupling member, the lower end of the first coupling member does not come into contact with the lower end of the first opening area when the fuel element is inserted. Thus, the friction force produced during passage of the fuel member along the spring member is small and the fuel element can be inserted more easily.

Fuel spacer and fuel assembly

A fuel assembly comprises a plurality of fuel rods, tie plates for holding both ends of these fuel rods, and spacers which support these fuel rods. The spacer comprises a plurality of cells into which the fuel rods are inserted respectively, the adjacent cells being joined to each other at axial ends thereof, whereby a space between these cells being held or retained, and a plurality of loop springs held respectively on the cells. Each of the loop springs has a pair of resilient members which are located within the pair of adjacent cells and which urge the fuel rods in a radial direction, and a pair of connections which connect axial ends of the resilient members to each other. Each of the connections have a passage through which coolant flows axially and which is defined by a closed peripheral wall. The closed peripheral wall is not uniform in thickness. The pair of adjacent cells have at axial end portions of peripheral walls openings for accommodating or receiving the connections of the loop spring.

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.

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

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

A fuel assembly has a fuel spacer consisting of a water rod having an outer diameter greater than that of fuel rods and a large number of circular sleeves into which the fuel rods are inserted. The fuel spacer has four bridge members. Both ends of these bridge members are fitted to two of eight circular sleeves which are adjacent one another in the diagonal direction of the fuel spacer. Both ends of each bridge member are bent so that its center projects outwardly away from the water rod.

Growing community of inventors

Hitachi, Japan

Yasuhiro Aizawa