Hitachi, Ltd.

Jun Takamatsu

Junichi Yamashita

Masaaki Yamamoto

Sadao Uchikawa

Renzo Takeda

Kunitoshi Kurihara

Michiro Yokomi

Toshio Kawai

The core of a nuclear reactor is constituted by two sorts of fuel assemblies: first fuel assemblies each of which contains both fissile material and gadolinea and second fuel assemblies each of which contains only the fissile material. The ratio of the number of the first fuel assemblies to that of the second fuel assemblies are selected to be 1:3. The enrichment of the fissile material is larger at the upper part of the reactor core than at the lower part of the same. The fuel assembly containing both of the fissile material and the gadolinea includes first fuel rods each of which contain both the fissile material and the gadolinea, and second fuel rods which contains only the fissile material. The number of the first fuel rods and the concentration of gadolinea are substantially in proportion to the power density at positions in the reactor core where the fuel assembly is placed.

Nuclear reactor core structure with zones of varying enrichment

A fuel assembly suitable for use in boiling water reactor. The fuel assembly has a specific pattern of distribution of enrichment, so that the upper region of the assembly has a larger infinite multiplication factor than that of the lower region. In an example, the distribution of enrichment is such that the upper region has a mean enrichment larger than that of the lower region, while, in another example, the mean enrichment is maintained constant over the length of the assembly but the difference of enrichments between the central and peripheral portions of a plane normal to the axis of the assembly is made smaller at the upper region than at the lower region.

Fuel assembly

Growing community of inventors

Hitachi, Japan

Jun Takamatsu