Light water reactor core and fuel assembly

A light water reactor core comprising fuel which is enriched by adding plutonium or plutonium and an actinide to a uranium containing at least one of a depleted uranium, natural uranium, a degraded uranium and a low enriched uranium, which further comprises;

• fuel assemblies having fuel rods arranged in a triangular lattice configuration;
• and
• large-diameter control rods to be inserted into said fuel assemblies, said large-diameter control rod comprising at least one absorption rod and guide tubes in which said large diameter control rods are inserted, each said guide tube being disposed in a region having an area equivalent to at least 7 fuel rod unit lattice cells, wherein
• a breeding ratio of the reactor core is near 1.0 or larger than 1.0, and a power coefficient of the reactor core is negative, and a void coefficient of the reactor core is positive or zero.

A fuel assembly comprising fuel which is enriched by adding plutonium or plutonium and an actinide to a uranium containing at least one of a depleted uranium, natural uranium, a degraded uranium and a low enriched uranium, which further comprises:

• fuel assemblies having fuel rods arranged in a triangular lattice configuration;
• and
• at least one guide tube to insert a large-diameter control rod thereinto, said guide tube disposed in a region having an area equivalent to at least 7 fuel rod unit lattice cells, wherein
• a breeding ratio of the fuel assembly is near 1.0 or larger than 1.0.

A light water rector core comprising fuel which is enriched by adding plutonium or plutonium and an actinide to a uranium containing at least one of a depleted uranium, natural uranium, a degraded uranium and a low enriched uranium, which further comprises:

• fuel assemblies having fuel rods arranged in a triangular lattice configuration;
• and
• large-diameter control rods to be inserted into said fuel assemblies, said large-diameter control rods each comprising at least one absorption rod having a transverse cross-sectional area larger than a cross-sectional area of a unit lattice cell of the fuel rod;
• and
• guide tubes in which said large-diameter control rods are inserted, said guide tubes each having water excluding rods outside for excluding light water between said guide tube and fuel rods adjacent to said guide tube and disposed in a region having an area equivalent to at least 7 fuel rod unit lattice cells, wherein
• a breeding ratio of the reactor core is near 1.0 or larger than 1.0, and a void coefficient of the reactor core is negative.