Thorium-based fuel bundles are used in existing PHWR reactors (e.g., Indian 220 MWe PHWR, Indian 540 MWe PHWR, Indian 700 MWe PHWR, CANDU 300/600/900) in place of conventional uranium-based fuel bundles, with little or no modifications to the reactor. The fuel composition of such bundles is 60+ wt % thorium, with the balance of fuel provided by low-enriched uranium (LEU), which has been enriched to 13-19.95% .sup.235U. According to various embodiments, the use of such thorium-based fuel bundles provides (1) 100% of the nominal power over the entire life cycle of the core, (2) high burnup, and (3) non-proliferative spent fuel bundles having a total isotopic uranium concentration of less than 12 wt %. Reprocessing of spent fuel bundles is also avoided.

There is provided a core of a fast reactor including: a core fuel region in which core fuel assemblies loading a metal fuel are arranged on a central region in a radial direction of the core; an inner blanket fuel region in which blanket fuel assemblies loading another metal fuel are circumferentially arranged on an inner portion of the core fuel region; and an outer peripheral blanket fuel region in which the blanket fuel assemblies are circumferentially arranged on an outer periphery of the core fuel region, wherein the metal fuel is formed of a UPuZr alloy or an alloy of U, Pu, TRU other than Pu, and Zr, the other metal fuel is formed of an alloy of U and Zr, and the Zr content of the other metal fuel is lower than the Zr content of the metal fuel.

Thorium-based fuel bundles according to one or more embodiments of the present invention are used in existing PHWR reactors (e.g., Indian 220 MWe PHWR, Indian 540 MWe PHWR, Indian 700 MWe PHWR, CANDU 300/600/900) in place of conventional uranium-based fuel bundles, with little or no modifications to the reactor. The fuel composition of such bundles is 60+ wt % thorium, with the balance of fuel provided by low-enriched uranium (LEU), which has been enriched to 13-19.95% 235U. According to various embodiments, the use of such thorium-based fuel bundles provides (1) 100% of the nominal power over the entire life cycle of the core, (2) high burnup, and (3) non-proliferative spent fuel bundles having a total isotopic uranium concentration of less than 12 wt %. Reprocessing of spent fuel bundles is also avoided.

Nuclear fuel assemblies include fuel elements that are sintered or cast into billets and co-extruded into a spiral, multi-lobed shape. The fuel kernel may be a metal alloy of metal fuel material and a metal-non-fuel material, or ceramic fuel in a metal non-fuel matrix. The fuel elements may use more highly enriched fissile material while maintaining safe operating temperatures. Such fuel elements according to one or more embodiments may provide more power at a safer, lower temperature than possible with conventional uranium oxide fuel rods. The fuel assembly may also include a plurality of conventional UO2 fuel rods, which may help the fuel assembly to conform to the space requirements of conventional nuclear reactors.

In a pressurized water reactor operation method, a fuel assembly including first fuel rods that operates for a preset first operation time and second fuel rods that operates for a second operation time longer than the first operation time is prepared. An operation schedule of a pressurized water reactor is created by mixing the first operation time of the first fuel rods and the second operation time of the second fuel rods. The pressurized water reactor operates by repeating the operation schedule.

Disclosed are fuel assemblies that are loaded in the core of a fast reactor including first fuel assemblies and second fuel assemblies being different from the first fuel assemblies. The reactor core has an axially heterogeneous core structure in which an internal blanket region containing depleted uranium fuel is placed around an axially middle section of the core. The first fuel assemblies are loaded in an outer core fuel region extending toward the periphery of the reactor core in a radial direction and the second fuel assemblies are loaded in an inner core fuel region extending around the center of the reactor core in a radial direction. Thickness of an internal blanket in each of the first fuel assemblies in an axial direction of the reactor core is thicker than thickness of an internal blanket in each of the second fuel assemblies in the axial direction of the reactor core.

Thorium-based fuel bundles according to one or more embodiments of the present invention provide a fresh fuel bundle comprising a first ring of fuel pins and a second ring of fuel pins. Each ring fuel pin has a fuel composition comprising uranium and thorium. The first ring fuel pins differ from the second ring fuel pins in each of the thorium wt %, uranium wt %, and .sup.235U enrichment.

Thorium-based fuel bundles according to one or more embodiments of the present invention provide a fresh fuel bundle comprising a first ring of fuel pins and a second ring of fuel pins. Each ring fuel pin has a fuel composition comprising uranium and thorium. The first ring fuel pins differ from the second ring fuel pins in each of the thorium wt %, uranium wt %, and .sup.235U enrichment.

Nuclear fuel assemblies include fuel elements that are sintered or cast into billets and co-extruded into a spiral, multi-lobed shape. The fuel kernel may be a metal alloy of metal fuel material and a metal-non-fuel material, or ceramic fuel in a metal non-fuel matrix. The fuel elements may use more highly enriched fissile material while maintaining safe operating temperatures. Such fuel elements according to one or more embodiments may provide more power at a safer, lower temperature than possible with conventional uranium oxide fuel rods. The fuel assembly may also include a plurality of conventional UO2 fuel rods, which may help the fuel assembly to conform to the space requirements of conventional nuclear reactors.

Fuel bundles for a nuclear reactor are disclosed, and in some embodiments include a first fuel element including thorium dioxide; a second fuel element including uranium having a first fissile content; and a third fuel element including uranium having a second fissile content different from the first fissile content. Nuclear reactors using such fuel bundles are also disclosed, including pressurized heavy water nuclear reactors. The uranium having the different fissile contents can include combinations of natural uranium, depleted uranium, recycled uranium, slightly enriched uranium, and low enriched uranium.