Abstract: High temperature moderators for nuclear reactors and processes for their production are disclosed. The moderators include at least one hydrided metal and/or hydride metal allow, such as yttrium hydride, thorium hydride, yttrium-cerium hydride, yttrium-gadolinium hydride, yttrium calcium hydride, cerium hydride, etc. Such metal hydrides and/or hydride alloys may have high thermal stability, a relatively low thermal neutron absorption cross section, the ability to retain hydrogen over a large temperature range, and have good mechanical properties. Such moderators may induce spectral shift in reactors which, in turn, magnifies the Doppler reactivity temperature coefficient. Such moderators to thermalize neutrons may also enhance fuel utilization and cost-effectiveness of the reactor while keeping the core portable.

Abstract: The present disclosure relates to a pellet containing an oxide additive to improve a nuclear-fission-gas-adsorption ability of a uranium-dioxide pellet used as nuclear fuel and increase the grain size thereof, and to a method of manufacturing the same. A La2O3—Al2O3—SiO2 sintering additive is added to uranium dioxide so that mass movement is accelerated due to the liquid phase generated during sintering of the uranium-dioxide pellet, which promotes the growth of grains thereof. Further, since less volatilization occurs during sintering due to the low vapor pressure of the liquid phase, efficient additive performance is exhibited, so the liquid phase surrounding the grain boundary effectively adsorbs cesium, which is a nuclear fission gas.

Abstract: An article formed of a metal alloy is covered at least partially with a metal hydride and a shell metal to form an assembly. Load is applied to the assembly and the assembly is heated. The shell metal deforms around the article and the metal hydride and forms a gas proof seal. The metal hydride thermally decomposes to form hydrogen gas. At least a portion of the hydrogen gas dissociates and moves as monoatomic hydrogen into the article. The metal alloy can be a zirconium metal alloy, the metal hydride can be a zirconium metal hydride, and the shell metal can be substantially copper.

Abstract: 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.

Abstract: A nuclear fuel pellet for a nuclear reactor is disclosed. The pellet comprises a metallic matrix and ceramic fuel particles of a fissile material dispersed in the metallic matrix. The metallic matrix is an alloy consisting of the principle elements U, Zr, Nb and Ti, and of possible rest elements. The concentration of each of the principle elements in the metallic matrix is at the most 50 molar-%.

Abstract: Systems and methods for manufacturing metal fuel are described. Methods for fabricating a metal-fuel-matrix cermet nuclear fuel may include crushed ceramic particles combined with metallic fast reactor fuel via bottom pour casting or injection casting, or a powdered metallurgical process. A maximum quantity of crushed ceramic particles added to the metallic fuel must not exceed that which would fail to yield a continuous matrix of metal fuel. After a short irradiation period, the microstructure of the fuel may be substantially identical to that of injection cast fuel, without crushed ceramic particles, irrespective of the fabrication process. Thus, the extensive existing database for injection cast fuel, without crushed ceramic particles, may be an excellent indicator of expected irradiation performance. Each of the processes may contribute to a solution of the spent nuclear fuel problem and may denature Pu239 during the process.

Abstract: The present invention relates generally to nuclear reactors, and more particularly, to nuclear reactors having fuel assemblies that employ support grids. A method of reducing friction and physical contact between a fuel rod and support grid in a nuclear fuel assembly is provided. The method includes applying a lubricant composition to the outer surface of the fuel rod during fuel assembly fabrication and removing the lubricant composition afterward.

Abstract: The present invention includes a composition of LiF—ThF4—UF4—PuF3 for use as a fuel in a nuclear engine.

Abstract: The present invention provides a nuclear fuel assembly, where a boron-containing compound is used as a burnable poison and is distributed in a majority of the rods in the assembly. The assembly comprises a plurality of fuel rods, each fuel rod containing a plurality of nuclear fuel pellets, wherein at least one fuel pellet in more than 50% of the fuel rods in the fuel assembly comprises a sintered admixture of a metal oxide, metal carbide or metal nitride and a boron-containing compound.

Abstract: A method for fabricating a sintered annular nuclear fuel pellet includes: molding nuclear fuel powder or granules to fabricate an annular nuclear fuel green body; inserting a rod-like shaped structure into the annular nuclear fuel green body; sintering the rod-like shaped structure-inserted annular nuclear fuel green body in a reductive gas atmosphere; and separating the sintered annular nuclear fuel pellet from the rod-like shaped structure.

Abstract: A method for transmuting spent fuel from a nuclear reactor includes the step of separating the waste into components including a driver fuel component and a transmutation fuel component. The driver fuel, which includes fissile materials such as Plutonium239, is used to initiate a critical, fission reaction in a reactor. The transmutation fuel, which includes non-fissile transuranic isotopes, is transmuted by thermal neutrons generated during fission of the driver fuel. The system is designed to promote fission of the driver fuel and reduce neutron capture by the driver fuel. Reacted driver fuel is separated into transuranics and fission products using a dry cleanup process and the resulting transuranics are mixed with transmutation fuel and re-introduced into the reactor. Transmutation fuel from the reactor is introduced into a second reactor for further transmutation by neutrons generated using a proton beam and spallation target.

Abstract: A method for production of a nuclear fuel element with oxide base, in which the nuclear fuel with oxide base is mixed with Cr and sintered to a solid body. The amount of chrome oxide added is =>50 and <100 ppm with respect to the amount of nuclear fuel with oxide base added.

Abstract: The invention relates to a process for preparing a castable powder of uranium dioxide UO2, for use in the manufacture of MOX fuel. This process comprises the following stages: 1) to prepare an aqueous suspension of a powder of UO2 obtained by dry process from uranium hexafluoride, said suspension comprising 50 to 80% by weight of UO2 and at least one additive chosen among deflocculation agents, organic binders, hydrogen peroxide H2O2 and a powder of U3O8, in such a quantity that the viscosity of the suspension does not exceed 250 mPa.sec, and 2) to atomise this suspension and dry it in a hot gas, at a temperature of 150 to 300° C., to obtain a castable powder of UO2 with an average particle size of 20 to 100 &mgr;m.

Abstract: A nuclear fuel based on UO.sub.2, ThO.sub.2 and/or PuO.sub.2 having improved retention properties for fission products. The fuel comprises a metal such as Cr or Mo able to trap oxygen in order to form an oxide having a free formation enthalpy equal to or below that of the superstoichiometric oxide or oxides (U, Th)O.sub.2+x and/or (U, Pu)O.sub.2+x (O<x.ltoreq.0.01). Thus, it is possible to trap oxygen atoms released during the fission of U, Th and/or Pu. This leads to an increase in the retention level of the fission products and a possibility of obtaining a high burn-up of nuclear fuel elements.

Abstract: The invention is directed to a high-density dispersion nuclear fuel having spherical particles of an uranium alloy dispersed in a nonfissionable matrix. The alloy includes uranium and 4-9 wt % Q, wherein Q is selected from the group consisting of Mo, Nb, and Zr. A process of manufacturing the spherical particles is also disclosed.

Abstract: An improved test for determining densification characteristics of nuclear fuel including a fissionable ceramic material is disclosed. The test includes controlling the testing atmosphere to impede loss through vaporization of silica and in turn density reduction due to compositional changes.

Abstract: A sintered nuclear fuel body includes (U, Pu)O.sub.2 mixed crystals having a mean particle size in a range from 7.5 .mu.m to 50 .mu.m. This sintered nuclear fuel body has a high retention capacity for fission gas in a power reactor. In order to produce the sintered nuclear fuel body by sintering a body in a hydrogen-containing sintering atmosphere, a powered substance selected from the group consisting of aluminum oxide, titanium oxide, niobium oxide, chromium oxide, aluminum stearate, aluminum distearate and aluminum tristearate is added to the starting powder for the body. As an alternative or in addition, the body made from the starting powder is sintered during a holding period of 10 minutes to 8 hours at a sintering temperature of 1400.degree. C. to 1800.degree. C. in a hydrogen-containing sintering atmosphere, initially with an oxygen partial pressure of 10.sup.-10 to 10.sup.-20 bar and then from 10.sup.-8 to 10.sup.

Abstract: A nuclear reactor core fuel element is composed of nanophase high temperature materials. An array of the fuel elements in rod form are joined in an open geometry fuel cell that preferably also uses such nanophase materials for the cell structures. The particular high temperature nanophase fuel element material must have the appropriate mechanical characteristics to avoid strain related failure even at high temperatures, in the order of about 3000.degree. F. Preferably, the reactor type is a pressurized or boiling water reactor and the nanophase material is a high temperature ceramic or ceramic composite. Nanophase metals, or nanophase metals with nanophase ceramics in a composite mixture, also have desirable characteristics, although their temperature capability is not as great as with all-ceramic nanophase material. Combinations of conventional or nanophase metals and conventional or nanophase ceramics can be employed as long as there is at least one nanophase material in the composite.

Abstract: A part of a light-water reactor, for example, a cladding for a light-water reactor has at least a portion made of an intermetallic compound, such as Ni.sub.3 Al, Ni.sub.2 Al.sub.3, TiAl, Ti.sub.3 Al, Pt.sub.2 Si, PtSi, FeAl.sub.2, CoAl, and MoSi.sub.2, thereby having limited irradiation degradation by fast neutrons, improved ductility and usability at high temperatures the intermetallic compound is produced by a process comprising a step of irradiating the intermetallic compound with at least one selected from the group consisting of a neutron, a light ion, and an electron. The intermetallic compound may contain a twin and a third additional element segregatedly present or forms a second phase at or near to a grain boundary.

Abstract: Plutonium is effectively and economically rendered unsuitable for employment in a device for creating a nuclear detonation. Weapons-grade plutonium is made into ceramic fuel in the form of spheroids of submillimeter size, coated with multi-layer fission-product-retentive coatings and disposed in sealed fuel chambers in graphite block fuel elements. These elements are used to form a core for a modular helium-cooled high temperature nuclear reactor which is operated to efficiently generate power by causing the hot high pressure helium coolant to drive a gas turbine directly connected to an electrical generator, which nuclear fuel core has about a 3-year lifetime. Spent nuclear fuel elements are removed at the end of 3 years and shifted to form the core for an accelerator-driven helium-cooled reactor wherein a subcritical core of spent fuel elements is safely caused to effectively continuously fission by a neutron flux created by a Linac which bombards a lead target with a beam of high energy protons.

Abstract: An accurate method for testing the strength of nuclear fuel particles. Each particle includes an upper and lower portion, and is placed within a testing apparatus having upper and lower compression members. The upper compression member includes a depression therein which is circular and sized to receive only part of the upper portion of the particle. The lower compression member also includes a similar depression. The compression members are parallel to each other with the depressions therein being axially aligned. The fuel particle is then placed between the compression members and engaged within the depressions. The particle is then compressed between the compression members until it fractures. The amount of force needed to fracture the particle is thereafter recorded. This technique allows a broader distribution of forces and provides more accurate results compared with systems which distribute forces at singular points on the particle.

Abstract: The invention provides a heterogeneously loaded type of fast reactor core in which a reduced number of target fuel assemblies containing minor actinide nuclides are heterogeneously dispersed and loaded. A wrapper tube for each of the target fuel assemblies is of the same shape and size as a hexagonal wrapper tube for an ordinary core fuel assembly. Each of target fuel rods within the wrapper tube contains 20 to 50% of minor actinide nuclides, and has a diameter more reduced than that of an ordinary core fuel rod. The number of the ordinary core fuel rods loaded in the ordinary core fuel assembly is 271 while the number of the target fuel rods loaded in the target fuel assembly is 331 or 397. Thirty to 50 such target fuel assemblies are heterogeneously dispersed and loaded in the fast reactor core.

Abstract: The present invention provides improved nuclear fuel pellets having high thermal conductivity for use in an LWR. This can be achieved by creating a continuous deposition phase of high-thermal conductivity substances in the grain boundaries in the pellets. As a result, the temperature in the center of the fuel rod can be significantly reduced, and the discharge amount of gases generated on the nuclear fission can be efficiently reduced.The present invention also provides a method of manufacturing the above-described nuclear fuel pellets.

Abstract: During operation of a light water moderated and cooled nuclear reactor, rods varying the neutron energy spectrum are introduced into the core of the reactor in the course of a first phase of the cycle in order to reduce the ratio of the volume of moderator to the volume of fissile material in the core. In a second phase of the cycle the spectrum displacement rods are extracted. The rods are of a mixture of thorium energy neutrons. The rods may be of fertile material and--depleted uranium. The invention is of particular interest in PWRs.

Abstract: A process for the production of plutonium-containing mixed oxide nuclear fuel. The process comprises selecting a plutonium-containing solution, determining the plutonium isotopic composition of the solution, precipitating particulate plutonium oxide from the solution, forming a mixture comprising the plutonium oxide and a particulate uranium oxide, and forming nuclear fuel compacts from the mixture. The amount of plutonium in the mixture is controlled in accordance with a given equation.

Abstract: The present invention provides improved nuclear fuel pellets having high thermal conductivity for use in an LWR. This can be achieved by creating a continuous deposition phase of high-thermal conductivity substances in the grain boundaries in the pellets. As a result, the temperature in the center of the fuel rod can be significantly reduced, and the discharge amount of gases generated on the nuclear fission can be efficiently reduced.The present invention also provides a method of manufacturing the above-described nuclear fuel pellets.

Abstract: The present invention provides improved nuclear fuel pellets having high thermal conductivity for use in an LWR. This can be achieved by creating a continuous deposition phase of high-thermal conductivity substances in the grain boundaries in the pellets. As a result, the temperature in the center of the fuel rod can be significantly reduced, and the discharge amount of gases generated on the nuclear fission can be efficiently reduced.The present invention also provides a method of manufacturing the above-described nuclear fuel pellets.

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: To increase the operating temperature of a reactor, the melting point and mechanical properties of the fuel must be increased. For an actinide-rich fuel, yttrium, lanthanum and/or rare earth elements can be added, as stabilizers, to uranium and plutonium and/or a mixture of other actinides to raise the melting point of the fuel and improve its mechanical properties. Since only about 1% of the actinide fuel may be yttrium, lanthanum, or a rare earth element, the neutron penalty is low, the reactor core size can be reduced, the fuel can be burned efficiently, reprocessing requirements are reduced, and the nuclear waste disposal volumes reduced. A further advantage occurs when yttrium, lanthanum, and/or other rare earth elements are exposed to radiation in a reactor, they produce only short half life radioisotopes, which reduce nuclear waste disposal problems through much shorter assured-isolation requirements.

Abstract: An isotopic heat source is formed using stacks of thin individual layers of a refractory isotopic fuel, preferably thulium oxide, alternating with layers of a low atomic weight diluent, preferably graphite. The graphite serves several functions: to act as a moderator during neutron irradiation, to minimize bremsstrahlung radiation, and to facilitate heat transfer. The fuel stacks are inserted into a heat block, which is encased in a sealed, insulated and shielded structural container. Heat pipes are inserted in the heat block and contain a working fluid. The heat pipe working fluid transfers heat from the heat block to a heat exchanger for power conversion. Single phase gas pressure controls the flow of the working fluid for maximum heat exchange and to provide passive cooling.

Abstract: The disclosed invention consists of a ceramic form of fuel for a nuclear reactor comprising an oxide of a fissionable element and containing therein a consumable neutron absorbing agent. The ceramic fissionable fuel product provides longer fuel performance in nuclear reactor service.

Abstract: A blending/loading system wherein an elongated cylinder or fuel rod is positioned on a turntable underneath a series of hoppers containing the particulates to be blended/loaded. Separate transfer tubes from each hopper are aligned with the cylinder and are subsequently lowered into the cylinder. Upon lowering, the cylinder is rotated and nozzles at the ends of the transfer tubes are activated to discharge, disperse and mix the stored particulates into the rotating cylinder. As the cylinder fills up, the transfer tubes are withdrawn from the rotating cylinder until the desired amount of fill is reached. Afterwards, the nozzles block any additional flow from occurring as they are raised out of the cylinder.

Abstract: There is disclosed a process for fabricating UO.sub.2 pellets from highly active uranium dioxide powders, comprising the steps of (1) uniformly adding at least one pore-former agent in the range of 0.3 to 1.4% by weight to uranium dioxide powders as a starting material, the pore-former agent decomposing and sublimating below 600.degree. C. and having an average particle size in the range of 5 to 500 .mu.m, (2) compacting the uranium dioxide powders including the pore-former agent to form green pellets, and (3) sintering the green pellets to form sintered UO.sub.2 pellets having large grain size crystals. According to the present invention, UO.sub.2 pellets having the sintered density in the range of 94 to 97% TD are fabricated from highly active UO.sub.2 powder when the pellets have large crystalline grain sizes exceeding 20 .mu.m. Accordingly, the fission gasses generated during irradiation is restrained to the inside pellet thereof to enhance the safety of the irradiation.

Abstract: Nuclear fuel particles having fission-product-retentive characteristics are disclosed which are particularly adapted for the production of nuclear fuel compacts or nuclear fuel elements by combination with a matrix material having an acceptable nuclear properties and good thermal conductivity. Preferably, the outermost shell of the fission-product-retentive layer is formed of a refractory carbide, such as silicon carbide or zirconium carbide, and a thin overcoating material is applied thereto. When aluminum is employed as the matrix material, an overcoating of elemental silicon or elemental zirconium is used which is wet by the aluminum matrix. Silicon also forms a low melting eutectic alloy with the aluminum of the matrix that provides good lubricating properties--a particularly valuable feature when high pressure extrusion is used to form fuel elements.

Abstract: A high flux reactor is comprised of a core which is divided into two symetric segments housed in a pressure vessel. The core segments include at least one radial fuel plate. The spacing between the plates functions as a coolant flow channel. The core segments are spaced axially apart such that a coolant mixing plenum is formed between them. A channel is provided such that a portion of the coolant bypasses the first core section and goes directly into the mixing plenum. The outlet coolant from the first core segment is mixed with the bypass coolant resulting in a lower inlet temperature to the lower core segment.

Abstract: A flat or curved plate structure, to be used as fuel in a nuclear reactor, comprises elongated fissionable wires or strips embedded in a metallic continuous non-fissionable matrix plate. The wires or strips are made predominantly of a malleable uranium alloy, such as uranium silicide, uranium gallide or uranium germanide. The matrix plate is made predominantly of aluminum or an aluminum alloy. The wires or strips are located in a single row at the midsurface of the plate, parallel with one another and with the length dimension of the plate. The wires or strips are separated from each other, and from the surface of the plate, by sufficient thicknesses of matrix material, to provide structural integrity and effective fission product retention, under neutron irradiation. This construction makes it safely feasible to provide a high uranium density, so that the uranium enrichment with uranium 235 may be reduced below about 20%, to deter the reprocessing of the uranium for use in nuclear weapons.

Abstract: In a water-cooled nuclear reactor for producing energy and having seed and blanket zones, which reactor is cooled by pressurized water and contains fissile material of plutonium and uranium, the reactor is provided, in its seed zones and blanket zones, with a plutonium composition such as obtained from light water power plant reactors after a normal service life and recycle, and with fuel elements whose geometry in the seed and blanket zones, with respect to the coolant water, is selected to produce an epithermal neutron spectrum.

Abstract: A nuclear fuel cartridge comprises a sheath, and nuclear material inside the sheath. A continuous liquid permeable passageway extends from one end of the nuclear material to the other, and an annular end member is disposed at each end of the nuclear material. Inner spacing members also of annular form may be disposed in intermediate positions along the sheath between portions of the nuclear material.

Abstract: A nuclear fuel includes uranium dispersed within a thorium hydride matrix. The uranium may be in the form of particles including fissile and non-fissile isotopes. Various hydrogen to thorium ratios may be included in the matrix. The matrix with the fissile dispersion may be used as a complete fuel for a metal hydride reactor or may be combined with other fuels.