Hitachi, Ltd.

Hitachi Engineering Co., Ltd.

Michihiro Ozawa

Junichi Yamashita

Motoo Aoyama

Sadao Uchikawa

Yasunori Bessho

Junichi Koyama

Hiromi Maruyama

Takaaki Mochida

Akinobu Nakajima

Mitsunari Nakamura

Toshiro Yoshioka

Akira Nishimura

Yukihisa Fukasawa

Masaki Enomoto

Takao Igarashi

A nuclear fuel assembly has an array of fuel rods comprising a plurality of first fuel rods each containing nuclear fuel material but not containing burnable poison and a plurality of further fuel rods each containing both nuclear fuel material and burnable poison. The further fuel rods comprise second fuel rods and third fuel rods, and each second fuel rod has at a lower region of the fuel assembly a burnable poison concentration which is a minimum burnable poison concentration in the further fuel rods. To increase the effectiveness of the second fuel rods in controlling axial power peaking, as seen in plan view on the array, the first fuel rods are the nearest neighbors of each further fuel rod.

Nuclear fuel assemblies and reactor cores including them

Reactor core, fuel assembly and fuel spacer

A fuel assembly has a plurality of first fuel rods each of which contains nuclear fuel material but does not contain burnable poison, and a plurality of second fuel rods each of which includes nuclear fuel material and burnable poison. The amount of burnable poison in a lower region of the fuel assembly is smaller than that in an upper region thereof. When each of the second fuel rods is divided into an upper region and a lower region, a region of the divided regions in the second fuel rods containing a maximum burnable poison concentration Gmax and a region of the divided regions in the second fuel rods containing a minimum burnable poison concentration Gmin are located in the lower region of the fuel assembly. The burnable poison concentration of the upper region of each second fuel rod is between Gmax and Gmin. The fuel assembly may moderate a maximum linear heat rating with an increased spectral shift effect.

Fuel assembly

A fuel assembly including a channel box, upper and lower tie plates, fuel rods inserted in the channel box and held at upper and lower end portions by the upper and lower tie plates, a water rod disposed among the fuel rods and spacers for keeping the fuel rods and the water rod spaced from one another. The water rod has a diameter larger than that of each of the fuel rods and the upper end of the water rod has a height substantially as high as an upper end of an effective enriched fuel section of each fuel rod.

A nuclear fuel assembly has a plurality of fuel rods each containing a multiplicity of fuel pellets. The fuel rods include a plurality of first fuel rods and a plurality of second fuel rods. Each of the first fuel rods contains a burnable poison over substantially the entire axial length thereof. The first fuel rod also has a greater means enrichment in the upper axial region thereof than that in the lower axial region thereof. Each of the second fuel rods contains no burnable poison and has a uniform enrichment distribution over substantially the entire axial length thereof. In each cross-section of the fuel assembly perpendicular to the axis thereof, the outer peripheral portion has a greater mean enrichment than the central portion. The first fuel rods are disposed in the peripheral portion except the outermost peripheral portion of the cross-section of the fuel assembly.

Nuclear fuel assembly

A core construction of a nuclear reactor wherein the fuel charge in the core has 1/4 symmetry and fuel assemblies adjacent a control rod (10) constitute a core unit. In the central portion of the core, each core unit (12) is composed of one thrice burned fuel assembly (3), and three once (1) or twice (2) burned fuel assemblies. One of the two types of fuel assemblies which includes two fuel assemblies located on a diagonal line in the respective core unit. In the core as a whole, the fuel assemblies of the same type or the same burning cyclic period are located on a diagonal line (E,F,G).

Core construction of nuclear reactor

Growing community of inventors

Hitachi, Japan

Michihiro Ozawa