Abstract: An elongate fuel element is described that has a silicon carbide cladding enclosing a fuel, such as UO2, wherein the fuel is dimensioned relative to the cladding to define gaps at each lateral end of the enclosure sufficiently large such that upon swelling in use, the fuel does not increase the strain on the cladding beyond the limits of the claddings strain tolerance. The lateral gaps at the ends of the fuel allow lateral expansion during swelling that reduces the strain on the cladding.

Abstract: 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.

Abstract: Process for manufacturing a nuclear component comprising i) a support containing a substrate based on a metal (1), the substrate (1) being coated or not coated with an interposed layer (3) positioned between the substrate (1) and at least one protective layer (2) and ii) the protective layer (2) composed of a protective material comprising chromium; the process comprising a step a) of vaporizing a mother solution followed by a step b) of depositing the protective layer (2) onto the support via a process of chemical vapor deposition of an organometallic compound by direct liquid injection (DLI-MOCVD).

Abstract: An annular nuclear fuel pellet in combination with an inserted discrete neutron absorber. The pellet/absorber may be compatible with existing or future nuclear fuel assembly designs. The concept involves the use of nuclear fuel (e.g., uranium dioxide or uranium silicide) formed into annular fuel pellets which can then have a discrete absorber material inserted into the center of the pin. Preferably, the discrete absorber is a non-parasitic absorber. The resulting pellet/absorber can then be stacked into a fuel rod which is arranged in a nuclear fuel assembly. Dimensioning of the annular pellet and absorber and selection of the absorber material and density can allow the concept to be tailored for various nuclear fuel applications.

Abstract: A fuel assembly for a nuclear reactor, a fuel rod of the fuel assembly, and a ceramic nuclear fuel pellet of the fuel rod are disclosed. The fuel pellet includes a first fissile material of UB2, The boron of the UB2 is enriched to have a concentration of the isotope 11B that is higher than for natural B.

Abstract: Disclosed is a nuclear fuel rod including at least one or more fuel pellets, a cladding tube surrounding the fuel pellets, and burnable absorber inside the cladding tube. The burnable absorber comprises a burnable absorber material and a cladding material surrounding the burnable absorber material. The burnable absorber has a disk shape, and the cladding material is an alloy comprising zirconium.

Abstract: The present invention relates to a sintered nuclear fuel pellet wherein one or more consolidated bodies of a burnable absorber are inserted inside, wherein the one or more consolidated bodies of the burnable absorber do not include nuclear fuel which includes UO2, and the one or more consolidated bodies of the burnable absorber are inserted into a radially central region of the sintered nuclear fuel pellet, such that the one or more consolidated bodies are surrounded by the nuclear fuel pellet without being exposed to an outside of the sintered nuclear fuel pellet. The present invention can optimize the regulation of excess reactivity by optimizing the self-shielding and the burning speed of the burnable absorber using one or more consolidated bodies the burnable absorber.

Abstract: A fuel assembly, which linearizes change of an infinite multiplication factor of a fuel and flattens excess reactivity while increasing average fissile plutonium enrichment of a MOX fuel, and a reactor are provided. The fuel assembly includes first fuel rods containing Pu and not containing burnable poison, a second fuel rod containing uranium and burnable poison and not containing Pu, a water rod, and a channel box accommodating the first and second fuel rods and the water rod in a bundle. The second fuel rod is disposed on an outermost periphery and/or adjacent to the water rod, of a fuel rod array in a horizontal section, and N2<N1 (N2 is a positive integer or zero) is satisfied where the number of second fuel rods arranged on the outermost periphery is N1 and the number of second fuel rods arranged adjacent to the water rod is N2.

Abstract: According to an embodiment, a design method for a light-water reactor fuel assembly comprises: accumulating a determined fuel data, showing that each of a combination of p·n/N and e is feasible as the core or not, wherein N is a number of the fuel rods in the fuel assembly, n is a number of the fuel rods containing the burnable poison, p is a ratio wt % of the burnable poison in the fuel, and e is an enrichment wt % of the uranium 235 contained in the fuel assembly; formulating a criterion formula which determines whether a combination of p·n/N and e is feasible as a core or not and is formulated based on the determined fuel data; and determining whether a temporarily set composition of the fuel assembly is approved as a core or not based on the criterion formula.

Abstract: A method of forming a water resistant boundary on a fissile material for use in a water cooled nuclear reactor is described. The method comprises coating the fissile material, such as a pellet of U3Si2 and/or the grain boundaries, to a desired thickness with a suitable coating material, such as atomic layer deposition or a thermal spray process. The coating material may be any non-reactive material with a solubility at least as low as that of UO2. Exemplary coating materials include ZrSiO4, FeCrAl, Cr, Zr, Al—Cr, CrAl, ZrO2, CeO2, TiO2, SiO2, UO2, ZrB2, Na2O—B2O3—SiO2—Al2O3 glass, Al2O3, Cr2O3, carbon, and SiC, and combinations thereof. The water resistant layer may be overlayed with a burnable absorber layer, such as ZrB2 or B2O3—SiO2 glass.

Abstract: 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.

Abstract: Disclosed is a method of predicting, calculating, or analyzing the sintered density of uranium oxide (UOx) before uranium oxide is added in the pelletizing process during a process of manufacturing nuclear fuel, the method including measuring the chromaticity of ammonium diuranate using a spectrophotometer. The present invention provides a simple and highly reliable method of predicting the sintered density of uranium oxide (UOx), which overcomes the problem with a conventional technology where the sintered density of uranium oxide (UOx) can be analyzed only in a pellet state and a subsequent treatment process needs to be performed according to the analysis result.

Abstract: Disclosed is a uranium dioxide nuclear fuel pellet, which includes metallic microcell partitions having a high protection capacity for fission products and a high thermal conductivity simultaneously. These metal microcell partitions are arranged in the nuclear fuel pellet to trap fission products. Further disclosed is a method of making the uranium dioxide nuclear fuel pellet. The method includes providing a mixture of uranium dioxide powder and additive powder of Cr-containing compound or Mo-containing compound; compressing the powder mixture to form a green pellet; and then sintering the green pellet under reducing gas environment to form the metallic microcell partitions.

Abstract: A multi-layered cladding material including a ceramic matrix composite and a metallic material, and a tube formed from the cladding material. The metallic material forms an inner liner of the tube and enables hermetic sealing of thereof. The metallic material at ends of the tube may be exposed and have an increased thickness enabling end cap welding. The metallic material may, optionally, be formed to infiltrate voids in the ceramic matrix composite, the ceramic matrix composite encapsulated by the metallic material. The ceramic matrix composite includes a fiber reinforcement and provides increased mechanical strength, stiffness, thermal shock resistance and high temperature load capacity to the metallic material of the inner liner. The tube may be used as a containment vessel for nuclear fuel used in a nuclear power plant or other reactor. Methods for forming the tube comprising the ceramic matrix composite and the metallic material are also disclosed.

Abstract: Methods, processes, and systems of transportable nuclear batteries are provided. In one embodiment, the battery may comprise a sealed reactor shell, a reactor core, and a generator. In further embodiments, the transportable nuclear battery may comprise a nuclear fuel in the reactor core wherein the fuel comprises plutonium, carbon, hydrogen, zirconium and, thorium. In some embodiments, the fuel may comprise hydrogen-containing glass microspheres, wherein the glass microspheres, may be coated with a burnable poison, and other coating materials that may aid in keeping the hydrogen within the microsphere glass at relatively high temperature. The disclosed methods, processes and systems may aid in providing energy to remote areas.

Abstract: Disclosed are a fuel rod and a fuel bundle using the fuel rod. The fuel rod may include first enriched uranium in a boost zone of the fuel rod, wherein the boost zone may be arranged directly at a bottom of the fuel rod. The fuel rod may also include second enriched uranium in a second zone of the fuel rod, wherein the second zone is arranged over the boost zone. The fuel rod may also include natural uranium in a third zone of the fuel rod, wherein the third zone is arranged over the second zone. In this fuel rod, a percent of enrichment of the enriched uranium in the boost zone is at least one percent.

Abstract: Nuclear fuel assemblies include non-symmetrical fuel elements with reduced lateral dimensions on their outer lateral sides that facilitate fitting the fuel assembly into the predefined envelope size and guide tube position and pattern of a conventional nuclear reactor. Nuclear fuel assemblies alternatively comprise a mixed grid pattern that positions generally similar fuel elements in a compact arrangement that facilitates fitting of the assembly into the conventional nuclear reactor.

Abstract: Systems for treating material are provided that can include a vessel defining a volume, at least one conduit coupled to the vessel and in fluid communication with the vessel, material within the vessel, and NF3 material within the conduit. Methods for fluorinating material are provided that can include exposing the material to NF3 to fluorinate at least a portion of the material. Methods for separating components of material are also provided that can include exposing the material to NF3 to at least partially fluorinate a portion of the material, and separating at least one fluorinated component of the fluorinated portion from the material. The materials exposed to the NF3 material can include but are not limited to one or more of U, Ru, Rh, Mo, Tc, Np, Pu, Sb, Ag, Am, Sn, Zr, Cs, Th, and/or Rb.

Abstract: The invention relates to a new and unique light water reactor (LWR) nuclear fuel pellet configuration formed using tri-isotropic (TRISO) fuel particles suspended in a metal, metal alloy, or ceramic matrix. The new TRISO LWR pellet would have the same dimensions as those of the standard uranium oxide pellet allowing its use without any change to the physical configuration of the reactor vessel, core internals or fuel assemblies. TRISO type fuels have a proven capability for retaining fission products within the confinement boundary created by the coating material. This robustness is expected to reduce or eliminate fuel failure risk and cost. Replacing standard pellets with TRISO LWR fuel pellets with the same, or higher, energy density can potentially extend the operating cycles of LWRs, reduce the number of fuel assemblies replaced in each refueling, reduce the quantity of spent fuel discharged from reactors, lower operating costs, and reduce radioactive waste.

Abstract: A reactor core is immersed in a liquid metal coolant in a core barrel of a liquid metal cooled reactor. The reactor core includes a plurality of fuel assemblies contained in the core barrel, a neutron absorber that absorbs a neutron in the reactor core, and a neutron moderator that moderates a neutron therein so as to control a reactivity of the reactor core. The neutron absorber and the neutron moderator constitute a mixture contained in reactivity control assemblies of the reactor core in the liquid metal coolant prior to immersion of the reactor core. The neutron moderator is composed of zirconium hydride.

Abstract: An article made by applying a burnable poison onto the cladding of a nuclear fuel rod, which involves providing a nuclear fuel rod and at least one application device, rotating the nuclear fuel rod, optionally removing one or more oxides and/or surface deposits on the outer surface of the nuclear fuel rod by spraying an abrasive material onto the nuclear fuel rod via the application device while adjusting the position of the application device in relation to the nuclear fuel rod, and applying burnable poison particles onto the outer surface of the nuclear fuel rod by spraying the burnable poison onto the nuclear fuel rod via the application device while adjusting the position of the application device in relation to the nuclear fuel rod, where the burnable poison particles are applied at a velocity sufficient to cause adhesion to the outer surface of the cladding.

Abstract: A 12×12 fully ceramic micro-encapsulated fuel assembly for a light water nuclear reactor includes a set of FCM fuel rods bundled in a square matrix arrangement. The fully ceramic micro-encapsulated fuel is comprised of tristructural-isotropic particles. Each tristructural-isotropic particle has a kernel that is comprised uranium nitride. The kernel diameter is 400 or more micrometers. The fully ceramic micro-encapsulated fuel is further mixed with a burnable poison material.

Abstract: Nuclear fuels for nuclear reactors are described, and include nuclear fuels having a first fuel component of recycled uranium, and a second fuel component of depleted uranium blended with the first fuel component, wherein the blended first and second fuel components have a fissile content of less than 1.2 wt % of 235U. Also described are nuclear fuels having a first fuel component of recycled uranium, and a second fuel component of natural uranium blended with the first fuel component, wherein the blended first and second fuel components have a fissile content of less than 1.2 wt % of 235U.

Abstract: A fabrication method of burnable absorber nuclear fuel pellets and burnable absorber nuclear fuel pellets fabricated by the same are provided, in which the fabrication method includes adding boron compound and manganese compound to one or more type of nuclear fuel powders selected from the group consisting of uranium dioxide (UO2), plutonium dioxide (PuO2) and thorium dioxide (ThO2) and mixing the same (step 1), compacting the mixed powder of step 1 into compacts (step 2), and sintering the compacts of step 2 under hydrogen atmosphere (step 3). According to the fabrication method, sintering can be performed under hydrogen atmosphere at a temperature lower than the hydrogen atmosphere sintering that is conventionally applied in the nuclear fuel sintered pellet mass production, by adding sintering additives such as manganese oxide or the like.

Abstract: A fully ceramic micro-encapsulated fuel assembly for a light water nuclear reactor includes a set of FCM fuel rods bundled in a square matrix arrangement. Fully ceramic micro-encapsulated fuel assemblies replace standard reference solid fuel assemblies with smaller number of FCM fuel rods that have a larger diameter than the diameter of the solid standard reference fuel rods, while keeping similar amounts of fissile material in the fuel assembly and maintaining comparable rates of burnup and number of EFPDs, and compatible power production, heat transfer and thermo-hydraulic features. A fully ceramic micro-encapsulated fuel rod includes multiple fully ceramic micro-encapsulated fuel pellets, which are comprised of tristructural-isotropic particles. In order to obtain compatible burnup rates with the standard reference fuel, the tristructural-isotropic particles have preferentially large diameter and packing fraction.

Abstract: A fuel assembly, comprising: a plurality of first fuel rods including uranium and not including a burnable poison; a plurality of second fuel rods including said uranium and said burnable poison; and a water rod; wherein said second fuel rods are placed at corners of an outermost layer of a fuel rod array; other second fuel rods are placed, in said outermost layer, adjacent to said second fuel rods placed at said corners; and other second fuel rods are placed adjacent to said water rod.

Abstract: A compressed powder composite (CPC) material for absorbing neutrons emitted from spent nuclear fuel thereby preventing the initiation of a chain reaction. The CPC material is typically provided as a substantially insoluble cylindrical pellet that is highly resistant to corrosion and is not subject to the failure modes associated with the alloy materials typically used in neutron absorption materials. The pellet preferably includes a dendritic nickel powder substantially uniformly mixed with a neutron absorber powder material, preferably boron carbide. Tubes filled with CPC materials, such tubes for replacing control roads so that a spent nuclear fuel assembly may be disposed of substantially indefinitely.

Abstract: A method is provided for operating a nuclear reactor. The method includes operating the nuclear reactor for at least one plutonium equilibrium cycle during which the core contains plutonium-equilibrium nuclear fuel assemblies; subsequently, operating the reactor for transition cycles, at least some of the plutonium-equilibrium nuclear fuel assemblies being progressively replaced with transition nuclear fuel assemblies and then with uranium-equilibrium nuclear fuel assemblies; and then operating the nuclear reactor for at least one uranium equilibrium cycle.

Abstract: [Problem to be Solved] To provide a fuel rod and a fuel assembly that can make thermal power uniform along an axial direction and lengthen an operation cycle. [Solution] In a first fuel rod 41 and a second fuel rod 42 each containing nuclear fuel and burnable poison for reducing a nuclear reaction of the nuclear fuel to be loaded in a pressurized water reactor, the gadolinium content rate of the first fuel rod 41 and the second fuel rod 42 is increased from both end portions toward a center portion in an axial direction. In a fuel assembly including the first fuel rod 41 and the second fuel rod 42, the first fuel rod 41 and the second fuel rod 42 are loaded in such a manner that a large percentage of the second fuel rod 42 that is a low-gadolinium fuel rod is arranged on an outer side than the first fuel rod 41 that is a high-gadolinium fuel rod.

Abstract: A method of controlling the criticality of a nuclear fuel cycle facility includes steps of producing a reactor fuel by adding less than 0.1% by weight of gadolinia to a uranium dioxide powder with a uranium enrichment of greater than 5% by weight and controlling the effective neutron multiplication factor of a uranium dioxide system in a step of handling the reactor fuel to be less than or equal to the maximum of the effective neutron multiplication factor of a uranium dioxide system with a uranium enrichment of 5% by weight.

Abstract: A nuclear reactor comprises a fuel rod into which nuclear fuel is enclosed and a control rod that controls nuclear reactions of the nuclear fuel. A concentration of a neutron absorber in a primary coolant at a full power operation of the nuclear reactor, when an operation of the nuclear reactor is started, is set equal to or lower than a value that is obtained by adding a predetermined value to a value obtained by subtracting a concentration of the neutron absorber that is required for maintaining a cold shutdown state of the nuclear reactor when an operation of the nuclear reactor is started from a concentration of the neutron absorber that is required for maintaining cold shutdown of the nuclear reactor when an operation of the nuclear reactor is completed.

Abstract: Disclosed are a fuel rod and a fuel bundle using the fuel rod. The fuel rod may include first enriched uranium in a boost zone of the fuel rod, wherein the boost zone may be arranged directly at a bottom of the fuel rod. The fuel rod may also include second enriched uranium in a second zone of the fuel rod, wherein the second zone is arranged over the boost zone. The fuel rod may also include natural uranium in a third zone of the fuel rod, wherein the third zone is arranged over the second zone. In this fuel rod, a percent of enrichment of the enriched uranium in the boost zone is at least one percent.

Abstract: An article made by applying a burnable poison onto the cladding of a nuclear fuel rod, which involves providing a nuclear fuel rod and at least one application device, rotating the nuclear fuel rod, optionally removing one or more oxides and/or surface deposits on the outer surface of the nuclear fuel rod by spraying an abrasive material onto the nuclear fuel rod via the application device while adjusting the position of the application device in relation to the nuclear fuel rod, and applying burnable poison particles onto the outer surface of the nuclear fuel rod by spraying the burnable poison onto the nuclear fuel rod via the application device while adjusting the position of the application device in relation to the nuclear fuel rod, where the burnable poison particles are applied at a velocity sufficient to cause adhesion to the outer surface of the cladding.

Abstract: Example embodiments are directed to materials useable as burnable poisons in nuclear reactors, components using the same, and methods of using the same. Example embodiment burnable poison materials produce desired daughter products as they burn out, thereby permitting placement and use for neutronic characteristic improvement and/or neutron flux shielding in locations conventionally barred as uneconomical. Example embodiment burnable poison materials may include natural iridium and enriched iridium-193. Example embodiment components may be fabricated, shaped, and placed to provide desired burnable poison effects in the reactor core in conventional locations and locations not conventionally used due to economic infeasibility.

Abstract: A method for applying a burnable poison onto the cladding of a nuclear fuel rod (2) which comprises, providing a nuclear fuel rod (2) and at least one application device (8), rotating the nuclear fuel rod, optionally removing one or more oxides and/or surface deposits on the outer surface of the nuclear fuel rod (2) by spraying an abrasive material onto the nuclear fuel rod via the application device (8) while adjusting the position of the application device in relation to the nuclear fuel rod (2), and applying burnable poison particles (33) onto the outer surface (6) of the nuclear fuel rod (2) by spraying the burnable poison onto the nuclear fuel rod via the application device while adjusting the position of the application device (8) in relation to the nuclear fuel rod, where the burnable poison particles are applied at a velocity sufficient to cause adhesion to the outer surface (6) of the cladding.

Abstract: The present invention provides a nuclear fuel comprising an actinide nitride such as 233U, 234U, 235U, 236U, 238U, 232Th, 239Pu, 240Pu, 241Pu, 242Pu, 244Pu, 239Np, 239Am, 240Am, 241Am, 242Am, 243Am, 244Am, 245Am, 240Cm, 241Cm, 242Cm, 243Cm, 244Cm, 245Cm, 246Cm, 247Cm, 248Cm, 249Cm, 259Cm, 245Bk, 246Bk, 247Bk, 248Bk, 249Bk, 250Bk, 248Cf, 249Cf, 250Cf, 251Cf, 252Cf, 253Cf, 254Cf, 255Cf, 249Es, 250Es, 251Es, 252Es, 253Es, 254Es, 255Es, 251Fm, 252Fm, 253Fm, 254Fm, 255Fm, 256Fm, 257Fm, 255Md, 256Md, 257Md, 258Md, 259Md, 260Md, 253No, 254No, 255No, 256No, 257No, 258No and 259No, and optionally fission products such as 97Tc, 98Tc and 99Tc, suitable for use in nuclear reactors, including those based substantially on thermal fission, such as light and heavy water reactors, gas-cooled nuclear reactors, liquid metal fast breeders or molten salt fast breeders. The fuel contains nitrogen which has been isotopically enriched to at least about 50% 15N, most preferably above 95%.

Abstract: A zirconium alloy, comprising erbium as a burnable neutron poison, said alloy comprising, by weight: from 3 to 12% erbium; from 0.005 to 5% additional elements such as additives and/or manufacturing impurities; the remainder zirconium. A structural component comprising such a zirconium alloy. Processes for manufacturing and shaping the zirconium alloy by a powder metallurgy or a melting process.

Abstract: A method of controlling the criticality of a nuclear fuel cycle facility includes steps of producing a reactor fuel by adding less than 0.1% by weight of gadolinia to a uranium dioxide powder with a uranium enrichment of greater than 5% by weight and controlling the effective neutron multiplication factor of a uranium dioxide system in a step of handling the reactor fuel to be less than or equal to the maximum of the effective neutron multiplication factor of a uranium dioxide system with a uranium enrichment of 5% by weight.

Abstract: A method is provided for evaluating pellet-cladding interaction (PCI) in a nuclear core having a reactor protection system and a plurality of elongated fuel rods each having fuel surrounded by cladding with a gap therebetween. The method includes: selecting a number of core parameters to be analyzed; evaluating the selected parameters at a plurality of statepoints; generating a model of an operating space of the core based, at least in part, upon the statepoints; selecting a subset or loci of statepoints from the model wherein each of the statepoints of the loci of statepoints, when subjected to a predetermined transient, falls within the operational limits of the reactor protection system; and evaluating the loci of statepoints for PCI in response to the transient. In this manner, the potential for PCI can be accurately determined without requiring every statepoint for every fuel rod in the core to be individually analyzed.

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 reactivity control rod adapted to be used in a reactor core of a fast reactor and disposed at a substantially central portion of the reactor core for controlling a reactivity therein. The reactivity control rod includes a wrapper tube surrounded by a plurality of fuel rods in a reactor core, and a plurality of neutron absorber rods arranged in the wrapper tube. At least one of the plurality of neutron absorber rods includes a cladding tube and a mixture filled in the cladding tube. The mixture is composed of a neutron absorber that absorbs a neutron and a neutron moderator that moderates the neutron.

Abstract: The absorbing rods have a nearly the same shape as the shape of columnar control rods for PWR used in reactivity control of core in a reactor. The absorbing rods can shield neutrons, and are inserted in control rod guide pipes and measuring pipes in fuel assemblies.

Abstract: A reactor core (104) includes fuel assemblies (202) arranged in a loading pattern (1100) in response to corresponding power levels of the fuel assemblies (202). A crud deposition model (412) is used to predict crud deposition on the fuel assemblies (202) and fuel pins (300) within the fuel assemblies (202). The prediction of crud deposition enables generation of the loading pattern (1100) and design of lattice structures (1600) for the fuel assemblies (202) that results in the reduction of total crud deposition in the reactor core (104) and causes a substantially uniform crud deposition on the fuel assemblies (202) of the reactor core (104).

Abstract: A fuel assembly attains high burnup and increases reactor shut-down margin when loaded into a reactor core wherein a water gap width on a control rod side and a water gap width on a side opposite to the control rod side are almost equal to each other. The fuel assembly has a plurality of fuel rods arranged in a square lattice pattern, each fuel rod being filled with nuclear fuel pellets and also has at least one neutron moderator rod shifted toward one corner where a control rod is inserted, away from a cross sectional center of the fuel assembly.

Abstract: A fuel assembly in accordance with the present invention comprises a plurality of first fuel rods and a plurality of second fuel rods having a length shorter than a length of the first fuel rod, and these two kinds of fuel rods are arranged in a fuel rod array of 10 rows by 10 columns. Two water rods are arranged in regions capable of arranging 8 fuel rods. The second fuel rods are not arranged in the outermost tier of the fuel rod array. Which satisfies the following conditions, that is, B≧60  (Equation 1) 15≦n≦20(n: integer)  (Equation 2) Awr/Ach≦0.149  (Equation 3) Lp/Lf≧11/24  (Equation 4) Awr/Ach≧(3.00×10−4×n2+6.00×10−4×n−1.2×10−2)×(Lp/Lf−1)+1.75×10−1  (Equation 5) Awr/Ach≦(8.63×10−4×n2−6.09×10−2×n+1.33×10−1)×(Lp/Lf−8.

Abstract: A MOX nuclear fuel assembly employable either for a thermal neutron reactor employing UO2 as the nuclear fuel and light water as the moderator/coolant or for a thermal neutron reactor employing the MOX fuels as the nuclear fuel and light water as the moderator/coolant is provided with only one kind of MOX nuclear fuel rods each of which has relatively large magnitude of the enrichment grade of the fissionable Pu-s or Pu239 and Pu241, the quantity of the MOX nuclear fuel rods being relatively small.

Abstract: A fuel assembly comprises a plurality of fuel rods bundled in grid pattern, a part of the fuel rods containing gadolinium as a burnable poison. At least one of the fuel rod having gadolinium contains gadolinium enriched in at least one kind of isotope of odd mass number more than an isotopic abundance of natural gadolinium. In the enriched gadolinium, a ratio of a content of Gd-155 to that of Gd-157 is 0.1 or less. An average concentration (wt %) G0 of enriched gadolinia is, with M denoting the number of month under rated power operation per one cycle of an equilibrium core, P power density of a nuclear reactor (kw/l unit) and W a sum of isotopic composition, is set in the range shown by the following expression. G0<0.25·P·M/W. Thereby, in the fuel assembly, residual reactivity of a burnable poison at a cycle end can be decreased and thermal performance can be improved.

Abstract: An alloy of zirconium and niobium that includes erbium as a consumable neutron poison, its method of preparation and a component comprising said alloy are provided. This invention relates to an alloy of zirconium and niobium that includes erbium as a consumable neutron poison. The invention also relates to a method for the preparation and conversion of said alloy and a component comprising said alloy. Such an alloy is particularly intended for the manufacture of cladding and/or other elements or structural components of fuel assemblies for nuclear reactors using water as coolant.

Abstract: Each of short-length fuel rods 3 is arranged at a position other than in 3×3 corner regions 6 to 9 in such a manner as not to be simultaneously adjacent to a water rod 5 and others of the short-sized fuel rods. Gd fuel rods 4 are arranged at positions excluding the outer periphery, and the number of those of the Gd fuel rods 4 adjacent to the short-length fuel rods 3 is one-half or less the total number of the Gd fuel rods. At a transverse cross-section of a region upward from upper ends of the short-sized fuel rods 3, the amount of burnable poison contained in a polygonal region 10 whose vertexes are located at centers of those of the first fuel rods 3 arranged at the outermost layer is smaller than the amount of burnable poison outside the region 10. With this configuration, a critical power can be improved in consideration of both a distribution of the flow of coolant and a distribution of a thermal power in the fuel assembly.

Abstract: A fuel assembly for a boiling water reactor comprising a plurality of fuel units (3a, 3b, 3c, 3d), stacked on top of each other, each one comprising a top tie plate (5), a bottom tie plate (6) and a plurality of fuel rods (4a, 4b, 4c) arranged between the top tie plate and the bottom tie plate. The fuel units are surrounded by a fuel channel (9) with a substantially square cross section. At least some of the fuel units comprise fuel rods with different diameters and different fuel quantities. The fuel rods are adapted such that fuel quantity and lattice space are optimized laterally and axially in the fuel assembly.