Abstract: A reactor that is operable to produce an isotope includes a region for containing a controlled nuclear fission reaction, the region segmented into a plurality of independent compartments, each of the compartments for containing a parent material in an aqueous solution that interacts with neutrons to produce the isotope via a fission reaction. Also provided are methods of producing an isotope using the same.

Abstract: A reactor that is operable to produce an isotope includes a region for containing a controlled nuclear fission reaction, the region segmented into a plurality of independent compartments, each of the compartments for containing a parent material in an aqueous solution that interacts with neutrons to produce the isotope via a fission reaction. Also provided are methods of producing an isotope using the same.

Abstract: The fuel element of the present invention includes a cladding tube and a metal fuel contained in the cladding tube, in which a gas plenum region is formed above the metal fuel and inside the cladding tube and has a small-diameter portion in the gas plenum region. Further, the fuel assembly of the present invention includes the fuel element of the present invention and a wrapper tube surrounding the fuel element, in which a coolant material passage is formed between the fuel element and the fuel element. Further, the core of the present invention includes an inner core fuel region loaded with the fuel assembly according to the present invention, and an outer core fuel region loaded with the fuel assembly of the present invention.

Abstract: A molten salt reactor includes a nuclear reactor core for sustaining a nuclear fission reaction fueled by a molten fuel salt. A molten fuel salt control system removes a volume of the molten fuel salt from the nuclear reactor core to maintain a reactivity parameter within a range of nominal reactivity. The molten fuel salt control system includes a molten fuel salt exchange system that fluidically couples to the nuclear reactor core and exchanges a volume of the molten fuel salt with a volume of a feed material containing a mixture of a selected fertile material and a carrier salt. The molten fuel salt control system can include a volumetric displacement control system having one or more volumetric displacement bodies insertable into the nuclear reactor core. Each volumetric displacement body can remove a volume of molten fuel salt from the nuclear reactor core, such as via a spill-over system.

Abstract: A reactor that is operable to produce an isotope includes a region for containing a controlled nuclear fission reaction, the region segmented into a plurality of independent compartments, each of the compartments for containing a parent material in an aqueous solution that interacts with neutrons to produce the isotope via a fission reaction. Also provided are methods of producing an isotope using the same.

Abstract: Systems for controlling and protecting nuclear reactors. A drive of an emergency safety rod of a nuclear reactor includes an electric drive, a reduction gear, and a rack-and-pinion gear. The electric drive contains a contactless electric motor based on permanent magnets, which is installed in the housing of the electric drive with a motor rotor position sensor, and a reduction gear for changing the rate of rotation of the electric drive. A toothed rack is installed along the axis of the rack-and-pinion gear in order to provide for the reciprocating motion of a system absorber rod connected thereto. A toothed electromagnetic clutch having a contactless current supply is installed on an inner shaft of the rack-and-pinion gear, enabling the rigid and simultaneous mechanical coupling of half-couplings, and the drive contains a reverse-motion coupling, a rack-separation spring and toothed rack position sensors.

Abstract: A molten salt reactor includes a nuclear reactor core for sustaining a nuclear fission reaction fueled by a molten fuel salt. A molten fuel salt control system removes a volume of the molten fuel salt from the nuclear reactor core to maintain a reactivity parameter within a range of nominal reactivity. The molten fuel salt control system includes a molten fuel salt exchange system that fluidically couples to the nuclear reactor core and exchanges a volume of the molten fuel salt with a volume of a feed material containing a mixture of a selected fertile material and a carrier salt. The molten fuel salt control system can include a volumetric displacement control system having one or more volumetric displacement bodies insertable into the nuclear reactor core. Each volumetric displacement body can remove a volume of molten fuel salt from the nuclear reactor core, such as via a spill-over system.

Abstract: A block-type movable reflector/moderator (RM) for nuclear reactor control is disclosed. This reactor control system can be applied to all types of reactors regardless of design. This design for reactor control is used in addition to the necessary rod control system in accordance with the 10CFR50 design criteria. This allows for the requirements of the NRC to be met along with the ability for dual control on power control of any type reactor regardless of process output from the secondary plants.

Abstract: A Single Fluid Reactor with an inner zone that includes a solid neutron moderator, which can have through holes defined therein. This solid neutron moderator can have a relatively small diameter, which can range, in some embodiments, from less than one meter to about 1.5 meter. The solid neutron moderator effectively creates an inner zone with a neutron profile that is far more thermalized than if the solid neutron moderator were absent. The surrounding layer of salt surrounding this inner zone has a much harder neutron spectrum.

Abstract: 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.

Abstract: An active zone includes a homogeneous uranium-plutonium nitride fuel, the mass fraction of which is a minimum 0.305, and consists of central, intermediate and peripheral parts which form fuel assemblies comprising fuel elements with geometrically identical shells but differing heights. The radial distribution of the fuel across the volume of the active zone has a stepped shape. The radius of the central part is from 0.4 to 0.5 of the effective active zone radius, while the height of the fuel column in the fuel elements in the central part is from 0.5 to 0.8 of the height of the fuel column in the peripheral part. The heights of the fuel columns forming a stepped intermediate part for diameters ranging from 0.5 to 0.85 of the effective active zone diameter are within the range from 0.55 to 0.9 of the height of the fuel column in the peripheral part.

Abstract: A lightly hydrided/deuterated metallic plutonium-thorium fuel for use in a fast fission pool-type nuclear reactor cooled with liquid metal coolants, including lithium-7 lead eutectic, lead bismuth eutectic or lead. When so used, plutonium-239 is consumed, and merchantable heat is produced along with fissile uranium-233, which can be denatured with uranium-238 and used in light water reactors as fuel.

Abstract: One use for irradiated graphite after remediation processing is to recycle it into a new graphite artifact. Examples of such artifacts include an electrode to be used for vitrification of radionucleotides, graphite or carbon articles for uranium processing, a moderator for a HTGR, in particularly a Gen IV HTGR, other types of graphite products for nuclear facilities, charcoal filters, silicon carbide applications, etc. Such graphite artifacts can be formed with up to 20 pph of carbon black, the carbon black is formed from vitrified irradiated graphite. Optionally the graphite artifact may be formed from up to 75 pph of pitch.

Abstract: A molten salt breeder reactor that has fuel conduit surrounded by a fertile blanket. The fuel salt conduit has an elongated core section that allows for the generation of electrical power on a scale comparable to commercially available nuclear reactors. The geometry of the fuel conduit is such that sub-critical conditions exist near the input and output of the fuel salt conduit and the fertile blanket surrounds the input and output of the fuel salt conduit, thereby minimizing neutron losses.

Abstract: The invention relates to light water reactor designs in which thorium is used as fuel and in particular to designs of jacketless fuel assemblies, which make up the cores of pressurized water reactors (PWRs) such as the VVER-1000. Nuclear reactor cores containing seed and blanket subassemblies that make up the fuel assemblies are used to burn thorium fuel together with conventional reactor fuel that includes nonproliferative enriched uranium, as well as weapons-grade and reactor-grade plutonium. In the first alternative, the reactor core is fully “nonproliferative,” since neither the reactor fuel nor the wastes generated can be used to produce nuclear weapons. In the second version of the invention, the reactor core is used to burn large amounts of weapons-grade plutonium together with thorium and provides a suitable means to destroy stockpiles of weapons-grade plutonium and convert the energy released to electric power.

Abstract: Disclosed is a breeding nuclear fuel mixture including metallic thorium useable in a nuclear power plant, prepared by mixing uranium dioxide (UO2) or plutonium dioxide (PuO2) having ceramic properties with metallic thorium (Th), in order to enable thorium breeding by neutrons released during nuclear fission of U or Pu and conversion of the bred thorium into a novel nuclear fissile material, i.e., U-233, thereby ensuring continuous nuclear fission. The foregoing nuclear fuel mixture may be burned at a reactor core of a nuclear power plant through thorium breeding over a long period of time. Therefore, when the inventive breeding nuclear fuel mixture is employed in a nuclear power plant, utilization of the nuclear power plant may be increased while maximizing conservation of limited uranium resources.

Abstract: The invention relates to the confinement of an alloy formed of actinide transuranic radioactive wastes and beryllium metal within a neutron moderating and reflecting apparatus to cause accelerated destruction (burning) of the actinide wastes. Waste actinides, including plutonium, neptunium, americium, and curium, emit alpha particles by radioactive decay. The alpha particles are converted into neutrons by the beryllium through an alpha-neutron (alpha, n) reaction. The neutrons developed by the alpha, n reaction are moderated by a surrounding layer of graphite, which allows the slowed neutrons to cause additional fission or decay events within the waste actinide alloy. This process is passive because the alpha particles that initiate the actinide burning are an intrinsic physical property of the actinides.

Abstract: The present invention related to a novel process for accelerating the breeding and conversion of fissile fuel in various types of nuclear reactors. In said process a movable nuclear fuel ball bed filled with a coolant creeps through the reactor core. The said process could provide higher specific power per unit fuel volume inside the reactor core and proceed on-line refueling, thus requires much less initial fissile fuel inventory per unit power output as compared with the traditional breeding or conversion reactors. The said process has full inherent safety characteristics and could follow the external power demand with the inherent negative temperature coefficient of reactivity. The said process, therefore, is a more efficient and economic approach to meeting the enormous demand of fissile fuel for the forthcoming “second nuclear era”.

Abstract: A process to safely convert about 95% of the nuclear waste into a usable fuel source is disclosed. The process, involving a sub-critical power reactor and a proliferation-resistant fuel cycle, consumes depleted uranium or thorium fuel with fissionable fuel, including reactor or weapons-grade plutonium. The reactor is comprised of coaxial neutron and energy-amplifying regions separated by moderating and thermal neutron absorbing layers. Control of the water or gas-cooled reactor is provided by plutonium-helium loops with a variable volume flow rate and an external source of neutrons that quickly reacts to any fluctuations of the reactor parameters. A second embodiment of the invention is a compact sub-critical propulsion reactor utilizing fission electric cell and thermo-acoustic technology for electrical power generation.

Abstract: A method and apparatus for optimizing the production of Pu-238 in a nuclear reactor during normal reactor operation is disclosed wherein the production of Pu-238 is confined to one or more selectively replaced fuel cells with target cells located in the inside of the active volume of the reactor core to maximize the neutron flux for target irradiation. The target cells are modified existing nuclear fuel assembly cells having some fuel rods replaced with target rods of Np-237 forming a cluster array and having rings of water filled rods surrounding the target cluster to produce the desired optimal Pu-238 production.

Abstract: There are provided a light water reactor core which has the same levels in cost efficiency and degree of safety as those of an existing BWR under operation now, that is, which is oriented to plutonium multi-recycle having a breeding ratio near 1.0 or slightly larger and having a negative void coefficient with minimizing modification of the reactor core structure of the existing BWR under operation now, and to fuel assemblies used for the boiling water reactor. The light water reactor core having an effective water-to-fuel volume ratio of 0.1 to 0.

Abstract: A subcritical reactor-like apparatus for treating nuclear wastes, the apparatus comprising a vessel having a shell and an internal volume, the internal volume housing graphite. The apparatus having means for introducing a fluid medium comprising molten salts and plutonium and minor actinide waste and/or fission products. The apparatus also having means for introducing neutrons into the internal volume wherein absorption of the neutrons after thermalization forms a processed fluid medium through fission chain events averaging approximately 10 fission events to approximately 100 fission events. The apparatus having additional means for removing the processed fluid medium from the internal volume. The processed fluid medium typically has no usefulness for production of nuclear weapons.

Abstract: Seed-blanket type nuclear reactor cores are employed to burn thorium fuel with conventional reactor fuels, including nonproliferative enriched uranium, and weapons or reactor grade plutonium. In a first embodiment, the core is completely nonproliferative in that neither the reactor fuel, nor the generated waste material, can be used to manufacture nuclear weapons. In a second embodiment of the invention, the core is employed to burn large amounts of weapons grade plutonium with the thorium, and provides a convenient mechanism by which stockpiled weapons grade plutonium can be destroyed and converted into electrical energy. The cores of both embodiments are comprised of a plurality of seed-blanket unit fuel assemblies which have centrally located seed regions that are surrounded by annular blanket regions. The seed regions contain the uranium or plutonium fuel rods, while the blanket regions contain thorium fuel rods.

Abstract: A reactor core for a boiling water reactor, a fuel assembly and a control rod intended for Pu multi-recycling at a breeding ratio of about 1.0, or 1.0 or more while keeping the economical or safety performance to the same level as in a boiling water reactor now under operation. The reactor has an effective water-to-fuel volume ratio of 0.1 to 0.6 by the combination of a dense lattice fuel assembly constituted of fuel rods formed by adding Pu to degraded uranium, natural uranium, depleted uranium or low concentrated uranium, and having coolants at a high void fraction of 45% to 70% and a cluster-type, Y-type or cruciform control rod.

Abstract: A fast reactor core in which a coolant flows comprises a plurality of fuel assemblies each loaded with a fissionable material and a plurality of gas sealed assemblies disposed between the fuel assemblies and sealed with a gas, wherein a surface level of the coolant in the gas sealed assembly changes from an axially upper portion including a core top level to an axially lower portion at a time of core power increase or a core coolant flow quantity decrease. Each of the gas sealed assemblies includes an inner cylindrical member for reducing a horizontal cross sectional area of the flow of the coolant at a portion in height corresponding to an axial central portion of the core and the cylindrical member includes a member for generating heat by radiation.

Abstract: Neptunium of minor actinide nuclides separated from spent fuel is added to fuel of reactor cores (inner reactor cores and/or outer reactor cores) of a fast reactor and americium of the separated minor actinide nuclides and rare earth elements are added to either or both of radial and axial blankets of the fast reactor for burning. Thus, the minor actinide nuclides with long half-lives can be burnt with the fast reactor core with the minimized effects of the rare earth elements. For a burner reactor, americium and rare earth elements may be added to shields for burning. Curium may be added together with americium and rare earth elements. Neptunium is added in amount of 2% to 5% by weight based on the weight of the fuel and the rare earth elements are added in an amount of 50% by weight or less based on the weight of the fuel. A Purex process is used to separate neptunium and a Truex process is used to separate americium and curium.

Abstract: A method and apparatus for improving the performance of a thermal breeder reactor having regions of higher than average moderator concentration are disclosed. The fuel modules of the reactor core contain at least two different types of fuel elements, a high enrichment fuel element and a low enrichment fuel element. The two types of fuel elements are arranged in the fuel module with the low enrichment fuel elements located between the high moderator regions and the high enrichment fuel elements. Preferably, shim rods made of a fertile material are provided in selective regions for controlling the reactivity of the reactor by movement of the shim rods into and out of the reactor core. The moderation of neutrons adjacent the high enrichment fuel elements is preferably minimized as by reducing the spacing of the high enrichment fuel elements and/or using a moderator having a reduced moderating effect.

Abstract: A fuel assembly for a nuclear reactor includes a number of fuel rods filled with a fuel material. A plurality of fuel rods have a partial effective fuel area filled with a fuel material and has a portion in which enrichment of a fissile nuclide is significantly reduced or the fissile nuclide does not exist at all on an axial level including a reactor shut-down zone at which subcriticality becomes small during a reactor operation period. The other fuel rods are filled with the fuel material throughout the entire axial length thereof. The first mentioned fuel rod may be provided with a partially interposed zone or may be constructed by a fuel rod having a length shorter than that of the other fuel rod. The tube means may be arranged in the fuel assembly so as to pass the moderator therethrough.

Abstract: A nuclear power plant that is of a walk-away type with an encapsulated reaction core in a glass matrix pool having a reactive Thorium/U.sup.233 composition in a containment structure that radiates thermal energy for use in a closed gas cycle with a split path having a common compressor with an output that divides into a first path communicating with the thermal source and a second path communicating with an intercooler, the two paths combining in a turbine with an expander that discharges to a common collector for return to the compressor.

Abstract: A light water cooled and moderated nuclear reactor for breeding fissile material on a uranium-plutonium cycle and also a method of operating a light water cooled and moderated reactor having a prebreeder section fueled from plutonium extracted from fuel discharged by a uranium burner or converter burner core. Subsequently, the prebreeder section, together with a breeder section, operated as coupled cores or modules, becomes self-sustaining and able to breed fissile plutonium fuels at a relatively high rate of gain.

Abstract: A nuclear reactor fuel core assembly comprises an array of sub-assemblies comprising a central zone of fuel/breeder sub-assemblies (20F) surrounded by an annular zone of shielding sub-assemblies (20S). The fuel/breeder sub-assemblies (20F) are flexibly mounted from the reactor diagrid top plate 26 while the shielding sub-assemblies (20S) are mounted as stiff cantilevers so as to provide resilient restraint against bow of the central sub-assemblies (20S) during reactor operation, the restraint being exerted via abutment pads (40) at the level of the tops of the sub-assemblies (20S, 20F). The central core sub-assemblies (20F) also have abutment pads (34) at a lower level to form a lower restraint plane at this level controlling sub-assembly bowing in the central core zone.

Abstract: Fuel array for an undermoderated nuclear reactor, comprising rods (6) arranged in a prism-shaped casing (1) parallel to the height of this casing (1). The internal surface of each of the walls (2) of the casing (1) is provided with channels (5) each of the channels (5) is located opposite a rod (6) arranged at the periphery of the array. The projecting parts (9) of the walls (2), between two channels (5), occupy part of the space between two peripheral rods (6). In this way, the moderating level remains constant throughout the cross-section of the array.The invention applies, in particular, to pressurized water reactors.

Abstract: To provide a lithium-containing neutron target particle for breeding tritium within the core of a nuclear reactor, including a central core formed of a stable lithium-containing compound, a surrounding buffer layer, and an outer tritium-impermeable silicon carbide coating, the core is initially sealed with an inner sealing layer of pyrolytic carbon and an outer sealing layer of stoichiometric zirconium carbide. The pyrocarbon seal protects the lithium within the core from attack from the zirconium carbide coating atmosphere, and the zirconium carbide layer prevents loss of lithium from the core when the silicon carbide coating is deposited at elevated temperatures.

Abstract: A method for reducing thermal striping in liquid metal fast breeder reactors by reducing temperature gradients between adjacent fuel and blanket assemblies by shuffling blanket assemblies at each refueling outage so as to progressively shuffle the blanket assemblies to the core periphery through multiple moves and to generally locate fresh blanket assemblies adjacent to exposed fuel assemblies and exposed blanket assemblies adjacent to fresh fuel. Additionally, assembly orificing is altered to provide less flow to blanket assemblies needing less flow due to an otherwise decreased temperature gradient and providing additional flow to fuel assemblies which need more flow to sufficiently reduce temperature gradients to prevent thermal striping.

Abstract: A fast breeder has a driver core region enriched with a fissile material and a blanket core region containing mainly a fertile material. The driver core region includes an inner core region and an outer core region surrounding the inner core region. The volume of the inner core region is selected to range between 30 and 70% of the volume of the driver core region. The enhancement of the fissile material in the inner core region ranges between 30 and 80% of the fissile material in the outer core region.

Abstract: A blanket assembly for a nuclear reactor core perimeter region having at least two regions within the assembly of different H/U ratios and rod enrichments.

Abstract: An improved fuel rod for nuclear reactor fuel assemblies, said fuel rod having a region of relatively low density fuel pellets, causing the neutron-induced fission reaction to be more uniformly distributed along the rod.

Abstract: A fuel assembly for a liquid metal fast breeder reactor having an upper axial blanket region disposed in a plurality of zones within the fuel assembly. The characterization of a zone is dependent on the height of the axial blanket region with respect to the active fuel region. The net effect of having a plurality of zones is to establish a dispersal flow path for the molten materials resulting during a core meltdown accident. Upward flowing molten material can escape from the core region and/or fuel assembly without solidifying on the surface of fuel rods due to the heat sink represented by blanket region pellets.

Abstract: The production of a novel nuclear fuel utilizing clean uranium 233 in combination with other nuclear materials is made possible by utilization of an equally novel reactor configuration and method of operation. Clean uranium 233 is produced from thorium in a light water reactor while utilizing discrete separation of the thorium being irradiated from the fissile fuel. This clean uranium 233 is then incorporated directly as fissile isotope enrichment into a new nuclear fuel which may be done without encountering the usual difficulties and hazards in the handling of uranium 233 or the expense and delays associated with gaseous diffusion enrichment. The thorium from this process may be directly reprocessed for reactor charging without radiation hazard also.

Abstract: The production of a novel nuclear fuel, utilizing uranium 233 low in uranium 232 content in combination with other nuclear materials is made possible by utilization of an equally novel reactor configuration and method of operation. Uranium 233 is produced from thorium in a light water reactor (LWR) while utilizing discrete separation of the thorium being irradiated from the fissile fuel. This uranium 233 is then incorporated directly as fissile isotope enrichment into a new nuclear fuel which may be done without encountering the usual difficulties and hazards in the handling of uranium 233 or the expense and delays associated with gaseous diffusion enrichment. Thorium from this process may be directly reprocessed for reactor charging without radiation hazard also.