Nuclear fuel structures and methods for fabricating are disclosed herein. The nuclear fuel structure includes a plurality of fibers arranged in the structure and a multilayer fuel region within at least one fiber of the plurality of fibers. The multilayer fuel region includes an inner layer region made of a nuclear fuel material, and an outer layer region encasing the nuclear fuel material. A plurality of discrete multilayer fuel regions may be formed over a core region along the at least one fiber, the plurality of discrete multilayer fuel regions having a respective inner layer region of nuclear fuel material and a respective outer layer region encasing the nuclear fuel material. The plurality of fibers may be wrapped around an inner rod or tube structure or inside an outer tube structure of the nuclear fuel structure, providing both structural support and the nuclear fuel material of the nuclear fuel structure.

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.

The invention relates to the nuclear industry and can be used for producing fuel pellets from uranium-molybdenum metal powders enriched to 7% uranium 235 for nuclear reactor fuel elements. The pellets are sintered in an inert atmosphere of argon at a temperature ranging from 1100° C. to 1155° C., and the initial powder is a uranium-molybdenum powder having a fraction size of 160 .Math.m and a molybdenum con¬tent of 9.0 to 10.5 wt%. The powder is pre-heated at a temperature of 500° C. for 10-20 hours (in an atmosphere of argon) and is subsequently cold pressed into pellets in a die under a force of up to 950 MPa. In an alternative emb¬odiment for producing uranium-molybdenum pellets with a binder (plasticizer), the step of sintering is preceded by heating the pellets in an atmosphere of argon at 300° C. to 450° C. for 2-4 hours to remove the binder. The invention makes it possible to increase the uranium intensity of the fuel, reduce the amount of heat buildup in a reactor core, and lower the amount of energy released in the event of abnormalities in the operation of a nuclear reactor, thus providing increased reactor safety and resilience to accidents.

A variable diameter fuel rod of a nuclear reactor assembly is disclosed. The variable diameter fuel rod includes an elongated cladding tube configured to house a plurality of fuel pellets including a fissile material arranged in a fuel stack orientation. The elongated cladding tube includes first and second axial reflector regions and a middle axial region therebetween. The middle axial region comprises an outer diameter defined as d.sub.1. The first and second axial reflector regions include an outer cladding diameter defined as d.sub.2 and d.sub.3, respectively. The variable diameter fuel rod further includes a transitional region between the diameter d.sub.1 of the middle axial region and the diameter d.sub.2 of the axial reflector region. The diameter d.sub.2 of the axial reflector region is greater than the diameter d.sub.1 of the middle axial region.

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.

Disclosed are a nuclear fuel pellet having enhanced thermal conductivity and a method of manufacturing the same, the method including (a) a step of manufacturing a mixture including a nuclear fuel oxide powder and a thermally conductive plate-shaped metal powder; and (b) a step of molding and then heat-treating the thermally conductive plate-shaped metal powder to have an orientation in a horizontal direction in the mixture, thereby forming a pellet.

A method of generating power using a Thorium-containing molten salt fuel is disclosed. One example of the disclosed method includes the steps of providing a vessel containing a molten salt fuel, the molten salt fuel comprising Thorium and at least one salt containing a nucleus capable of interacting with a proton of sufficient energy to produce a (p, n) reaction resulting in the generation of a neutron at a first energy level and generating a proton beam externally to the vessel, where the externally generated proton beam being of an energy level sufficient to interact with the at least one salt in the vessel to produce a (p, n) reaction resulting in the generation of a neutron at the first energy level. In the example, the externally generated proton beam is directed into the vessel such that at least some protons forming the beam will interact with an atom forming a part of the at least one salt contained in the vessel to causing interaction between the externally generated proton beam and the at least one salt contained in the vessel to produce (p, n) reactions resulting in the generation of neutrons within the vessel and an absorption reaction involving the generated neutrons and Thorium within the vessel. Neutrons generated within the vessel through the (p, n) reactions caused by the externally generated proton’s interaction with the at least one salt are utilized to produce a fission reaction where the fission reaction increases. the heat content of the molten salt within the vessel. In the example, a heat exchanger is used to extract heat from the molten salt within the vessel and power is generated from the extracted heat.

A nuclear fuel includes a net neutron-producing material, a neutron-consuming material, and a neutron-moderating material. Upon exposure of the net-producing material, the neutron-moderating material, and the neutron-consuming material to a neutron source, a ratio of the net neutron-producing material to the neutron-consuming material and a ratio of the net neutron-producing material to the neutron moderating material are operable to convert neutrons into charged particles without producing net neutrons.

A method for determining at least one threshold value of at least one operating parameter of a nuclear reactor is implemented by an electronic determination system and includes the steps of determining a first threshold value of a respective operating parameter for an operation of the reactor at a first power; and determining a second threshold value of said parameter for an operation of the reactor at a second power. The operation at the lower power of the first and second powers is an operation continued for a duration of at least 8 hours over a 24-hour sliding window. The method also includes determining a third threshold value of said parameter for an operation of the reactor at a third power between the first power and the second power.

Disclosed herein is a method comprising coating a fissile, uranium-containing ceramic material with a water-resistant layer, the layer being non-reactive with the fissile, uranium-containing ceramic material. The coating is applied to a surface of the fissile, uranium-containing ceramic material. Also disclosed is a fuel for use in a nuclear reactor.