Abstract: Manufacture of oxidic nuclear fuel bodies with oxygen-to-metal ratio of 2.0.+-.0.02 at relatively low sintering temperature in range of 1000.degree.-1400.degree. C. Nuclear fuel powder with an arbitrary oxygen-to-metal ratio is mixed with a grain-growth promoting additive (U.sub.3 O.sub.8) and pressed into blanks. The blanks are subjected to a two-stage operation in a furnace at 1000.degree.-1400.degree. C. - an oxidative-sintering stage in a carbon dioxide atmosphere and a reducing stage in a hydrogen containing atmosphere.

Abstract: The preparation of nuclear fuels such as uranium dioxide, carbide and nitride employing the ammonium urante, (NH.sub.4).sub.2 U.sub.2 O.sub.7, as starting material usually must undergo a series of chemical and metallurgical processes at relatively high temperature and under strictly controlled working condition.A simple method for the preparation of these nuclear fuels has evolved with respect to the electrolytic amalgamation of uranium ion directly from an aqueous solution. The thereby obtained uranium amalgam maybe thermally decomposed into a fine metallic powder which reacts readily with water vapor, methane and nitrogen gas to bring forth uranium dioxide, carbide and nitride, respectively.

Abstract: A method of treating a nuclear reactor fuel pellet which has been irradiated and is at least partially depleted of its initial fissile material content to substantially reduce the amount of fuel which would have to be reprocessed before it could be reused. The pellet is pulverized to a median particle size of less than about 300 microns and thereafter is separated into two fractions by size. In accordance with the present invention, it has been found that one of said fractions will contain a significantly greater proportion of the fissile content of the pellet than the other of said fractions. The fissile-rich fraction is suitable for reforming into pellets for use in a nuclear reactor with little or no further enrichment required. The method of the present invention is applicable to the metallic, oxide, and carboxide forms of nuclear reactor fuels such as uranium and thorium, which have been in service in a light water reactor or a fast breeder reactor.

Abstract: Sintered uranium dioxide pellets suitable for power reactor use are described, and a process for their manufacture. This process involves incorporating a small amount of sulphur into the uranium dioxide before sintering, as a consequence large grain sizes are found in the pellets. The increase in grain size results in an improvement in overall efficiency when such pellets are used in a power reactor.

Abstract: In a process for reducing the oxygen content of metal oxide material, particularly a nuclear fuel material, the metal oxide material is contained in a plurality of carbon crucibles which are moved through a heated zone in end-to-end contact counter current to a stream of hydrogen-containing gas.

Abstract: This information relates to the recovery of uranium from uranium peroxide yellowcake produced by precipitation with hydrogen peroxide. The yellowcake is calcined at an elevated temperature to effect decomposition of the yellowcake to uranium oxide with the attendant evolution of free oxygen. The calcination step is carried out in the presence of a reducing agent which reacts with the free oxygen, thus retarding the evolution of chlorine gas from sodium chloride in the yellowcake. Suitable reducing agents include ammonia producing compounds such as ammonium carbonate and ammonium bicarbonate. Ammonium carbonate and/or ammonium bicarbonate may be provided in the eluant used to desorb the uranium from an ion exchange column.

Abstract: In the production of UO.sub.2, ammonium uranyl carbonate is an intermediate product wet with water and contaminated with ammonium carbonate and is washed with methanol to remove water and ammonium carbonate. The spent methanol containing 50% water and up to 10% ammonium carbonate is subjected to rectification in a column under subatmospheric pressure with cooling the top of the tower to a low temperature to retard decomposition of ammonium carbonate and condense a liquid water fraction. Clogging of the column, vapor lines and condenser by recombination of the decomposition products is prevented. The purified methanol contains less than 5% water and may be returned for further washing of ammonium uranyl carbonate.

Abstract: A process for treating a particulate uranium oxide composition containing ammonium diuranate precursors such as uranyl fluoride and uranyl nitrate, along with possible impurities, is disclosed. The process comprises the steps of (a) contacting the composition with a sufficient amount of an ammonium hydroxide solution to convert the ammonium diuranate precursors to ammonium diuranate, and (b) heating the composition under a controlled atmosphere at a temperature sufficient to dry the composition, sublime any ammonium fluoride present, and convert the ammonium diuranate to uranium dioxide. In a first modification of the invention, there is practiced the additional step of moving the composition, preferably by mechanically agitating the composition, prior to the heating step, or during the heating step, or both prior to and during the heating step, for a sufficient time to produce rounded agglomerates in the form of a readily flowable powder.

Abstract: According to one embodiment of the present invention, the oxygen gas is introduced into a horizontal, unitary and totally-closed furnace shell, and nuclear fuel to be reprocessed is charged onto an oxidation and separation plate which is horizontally disposed for vibration within the furnace shell along the axis, so that the nuclear fuel may be reprocessed by oxidation in the oxygen atmosphere while the fuel is vibrated and transported on the oxidation and separation plate and the reprocessed nuclear fuel in the form of particles may be discharged. At the same time released volatile fission products from the pulverized fuel are isolated by means of a vacuum blower. According to another embodiment of the present invention, a reduction furnace which is substantially similar in construction to the oxidation furnace described above except that a reducing gas is supplied by an independent source.

Abstract: This invention is a process for decomposing ammonium nitrate and/or selected metal nitrates in an aqueous solution at an elevated temperature and pressure. Where the compound to be decomposed is a metal nitrate (e.g., a nuclear-fuel metal nitrate), a hydroxylated organic reducing agent therefor is provided in the solution. In accordance with the invention, an effective proportion of both nitromethane and nitric acid is incorporated in the solution to accelerate decomposition of the ammonium nitrate and/or selected metal nitrate. As a result, decomposition can be effected at significantly lower temperatures and pressures, permitting the use of system components composed of off-the-shelf materials, such as stainless steel, rather than more costly materials of construction. Preferably, the process is conducted on a continuous basis. Fluid can be automatically vented from the reaction zone as required to maintain the operating temperature at a moderate value--e.g., at a value in the range of from about 130.

Abstract: Low density, porous, metal oxide microspheres are prepared from metal salt solutions by sol-gel technique followed by ammonia treatment of the green microspheres, drying, impregnation with fugitive organic material and heat temperature under controlled conditions of temperature and atmosphere. The product metal oxide microspheres have a density of below 70% of their theoretical maximum density and a porosity of at least 0.04 cubic centimeters per gram as measured by mercury penetration technique. Microspheres of hematite, magnetite, and other metal oxides useful as catalysts or as purifying agents to remove contaminants from liquid or gaseous streams may be produced.

Abstract: Uranium oxide is recovered from an aqueous solution of uranyl halides by extracting uranyl halide from the aqueous solution with an organic liquid, forming a crown ether uranyl halide complex in the organic liquid, and then contacting the uranyl halide crown ether complex with water, carboxylate ion, and light under suitable conditions. Also disclosed are certain novel crown ether uranyl halide complexes and their preparation. Also disclosed is the use of 18-crown-6 to selectively recover uranyl halide from a solution thereof containing other metal salts.

Abstract: A mixture of powders, preferably UO.sub.2 powders, is blended to complete homogeneity in a nuclear-safe, bubbling-bed fluidized bed blender. The blender includes a generally vertically-oriented, slab-shaped, nuclear-safe mixing vessel having a fluidizing grid disposed on the bottom of the vessel. The fluidizing grid comprises a linear array of generally downwardly-directed pyramidal-shaped hoppers each having walls converging into a conically-shaped closable opening. A plurality of gas orifices is provided for directing a flow of fluidizing gas downwardly into the bottom of each of the hoppers and fluidizing gas is supplied to the orifices at a velocity sufficient to cause bubbles of fluidizing gas to rise through and emerge from the mixture of UO.sub.2 powders until a homogeneous blend of solid UO.sub.2 powders is achieved. The apparatus eliminates dead-zones normally present near the bottom of prior art fluidized bed blenders.

Abstract: A mixture of fine and cohesive powders is blended to complete homogeneity in a nuclear-safe bubbling-bed fluidized bed blender having an improved fluidizing grid. The blender includes a generally vertically-oriented slab-shaped, nuclear-safe mixing vessel having a fluidizing grid disposed at one end of the vessel. The fluidizing grid comprises a linear array of generally downwardly-directed, pyramidal-shaped hoppers each having walls converging into a conically-shaped opening. A plurality of ball valves are employed, one such valve being disposed at the bottom of each hopper. The rotary closure member of each of the ball valves includes a first set of gas orifices for directing a flow of fluidizing gas upwardly in a divergent swirl-shaped pattern along the walls of each of the hoppers. In one embodiment a second set of fluidizing gas orifices for directing a flow of fluidizing gas downwardly into the apex of each of the hoppers is also provided.

Abstract: There is provided a process for the production of pourable, directly compactable uranium dioxide powder by continuous precipitation of uranium peroxide from a stirred uranyl nitrate solution at a pH of 1 - 2.5 with hydrogen peroxide, calcining of the peroxide at 500.degree.- 800.degree. C. and subsequent reduction at 550.degree.- 750.degree. C. The precipitation solution contains 70 - 150 g/l of uranium and 0.80 g/l of ammonium nitrate and is treated with 15 - 20% aqueous hydrogen peroxide solution in the ratio of U:H.sub.2 O.sub.2 from 1:1.5 to 1:3 and there is led through the solution a mixture of ammonia and air having an air-ammonia volume ratio of 1:0.3 - 0.6. An apparatus for carrying out the process is also described. SUBACKGROUND OF THE INVENTIONThe present invention is directed to a process and apparatus for the production of directly pressable (moldable) uranium dioxide powder from uranium peroxide (UO.sub.4.xH.sub.

Abstract: UO.sub.2 for nuclear fuel is made from UF.sub.6. The method involves injecting UF.sub.6, with or without a nitrogen carrier, into a solution containing 1) an inert reaction medium, 2) water, 3) a Lewis base. The precipitate from the above reaction is then reduced in H.sub.2 at a temperature below 750.degree. C. to give ceramic grade UO.sub.2.

Abstract: In a first step, uranium hexafluoride gas is reacted with steam in a first region of a vessel. In a second step, the oxyfluoride UO.sub.2 F.sub.2 obtained in the first step is converted to UO.sub.2 in a two-stage reduction process in which it is first contacted with a mixture of hydrogen gas and steam in one zone of the second region of the vessel, then contacted with the hydrogen gas in another zone of the second region.

Abstract: Conversion of gaseous uranium hexafluoride to a uranium dioxide rich composition in the presence of an active flame in a reactor defining a reaction zone is achieved by separately introducing a first gaseous reactant comprising a mixture of uranium hexafluoride and a reducing carrier gas, and a second gaseous reactant comprising an oxygen-containing gas, the reactants being separated by a shielding gas as introduced to the reaction zone. The shielding gas temporarily separates the gaseous reactants and temporarily prevents substantial mixing and reacting of the gaseous reactants. The flame occurring in the reaction zone is maintained away from contact with the inlet introducing the mixture to the reaction zone. After suitable treatment, the uranium dioxide rich composition is capable of being fabricated into bodies of desired configuration for loading into nuclear fuel rods.

Abstract: A gas transport system for powder has a delivery pipe having an end portion of porous material having a pore size smaller than the particles of the powder. The porous end portion is surrounded by a jacket in which a vacuum is drawn to draw off transport gas and reduce filter capacity which would otherwise be required to remove it. Pulses of pressure are periodically introduced into the jacket to clear particles from the inside of the porous end portion. The vacuum is drawn in the jacket through a vacuum line containing a constriction through which a nozzle discharges high pressure gas at intervals to provide the pulses of pressure in the jacket. This system is particularly effective when used in the production of uranium oxide.

Abstract: This invention relates to an improved continuous calcining apparatus for consistently and controllably producing from calcinable reactive solid compounds of uranium, such as ammonium diuranate, uranium dioxide (UO.sub.2) having an oxygen to uranium ratio of less than 2.2. The apparatus comprises means at the outlet end of a calciner kiln for receiving hot UO.sub.2, means for cooling the UO.sub.2 to a temperature of below 100.degree. C and conveying the cooled UO.sub.2 to storage or to subsequent UO.sub.2 processing apparatus where it finally comes into contact with air, the means for receiving, cooling and conveying being sealed to the outlet end of the calciner and being maintained full of UO.sub.2 and so operable as to exclude atmospheric oxygen from coming into contact with any UO.sub.2 which is at elevated temperatures where it would readily oxidize, without the use of extra hydrogen gas in said means.

Abstract: A continuous, four stage fluidized bed process for converting uranium hexafluoride (UF.sub.6) to ceramic-grade uranium dioxide (UO.sub.2) powder suitable for use in the manufacture of fuel pellets for nuclear reactors is disclosed. The process comprises the steps of first reacting UF.sub.6 with steam in a first fluidized bed, preferably at about 550.degree. C, to form solid intermediate reaction products UO.sub.2 F.sub.2, U.sub.3 O.sub.8 and an off-gas including hydrogen fluoride (HF). The solid intermediate reaction products are conveyed to a second fluidized bed reactor at which the mol fraction of HF is controlled at low levels in order to prevent the formation of uranium tetrafluoride (UF.sub.4). The first intermediate reaction products are reacted in the second fluidized bed with steam and hydrogen at a temperature of about 630.degree. C. The second intermediate reaction product including uranium dioxide (UO.sub.

Abstract: Process for the preparation of fine particle size uranium dioxide from a uranium trioxide feed comprising the following steps:A. reacting solid uranium trioxide with aqueous ammonium nitrate to form an insoluble ammonium uranateB. neutralizing the thus formed slurry with ammonium hydroxide to precipitate out as an insoluble ammonium uranate the remaining dissolved uraniumC. recovering the thus formed precipitates in a dry state andD. reducing the dried precipitate to uranium dioxide.

Abstract: An improved process for the conversion of gaseous uranium hexafluoride to a uranium oxide rich composition in the presence of an active flame in a reaction zone is achieved by introducing a first gaseous reactant comprising a mixture of uranium hexafluoride and an oxygen-containing carrier gas and a second gaseous reactant comprising a reducing gas, the reactants being separated by a shielding gas as introduced to the reaction zone. The shielding gas temporarily separates the gaseous reactants and temporarily prevents substantial mixing and reacting of the gaseous reactants. The flame occurring in the reaction zone is maintained away from contact with the inlet introducing the mixture to the reaction zone.

Abstract: A three stage fluidized bed process for converting uranium hexafluoride (UF.sub.6) to a ceramic-grade uranium dioxide (UO.sub.2) powder by first, reacting hydrogen and steam with UF.sub.6 in a first fluidized bed in a temperature range of from about 475.degree. to 600.degree. C to form solid intermediate products UO.sub.2 F.sub.2 and U.sub.3 O.sub.8 ; second, reacting hydrogen and steam with the intermediate products in a second fluidized bed at a temperature ranging from about 575.degree. to about 675.degree. C to produce a second group of intermediate products including UO.sub.2 F.sub.2, U.sub.3 O.sub.8, and UO.sub.2 ; and, third, reacting hydrogen and steam with the second group of intermediate products in a third fluidized bed at a temperature of 575.degree. to 675.degree. C to produce ceramic grade UO.sub.2 powder having low residual content of fluorides and other foreign materials.

Abstract: An actinide dioxide, e.g., uranium dioxide, plutonium dioxide, neptunium dioxide, etc., is prepared by reacting the actinide nitrate hexahydrate with sodium dithionite as a first step; the reaction product from this first step is a novel composition of matter comprising the actinide sulfite tetrahydrate. The reaction product resulting from this first step is then converted to the actinide dioxide by heating it in the absence of an oxygen-containing atmosphere (e.g., nitrogen) to a temperature of about 500.degree. to about 950.degree. C. for about 15 to about 135 minutes. If the reaction product resulting from the first step is, prior to carrying out the second heating step, exposed to an oxygen-containing atmosphere such as air, the resultant product is a novel composition of matter comprising the actinide oxysulfite tetrahydrate which can also be readily converted to the actinide dioxide by heating it in the absence of an oxygen-containing atmosphere (e.g., nitrogen) at a temperature of about 400.degree.

Abstract: Uniform microspheres substantially or completely free from internal cavities and voids are prepared by spraying an aqueous hydrated metal oxide solution onto the surface of a water-immiscible organic liquid containing from 0.04 to 2.0 percent by volume of a surface active agent, the viscosities of each of the organic and inorganic phases plus the amount of surface active agent within the above range being selected such that there is sufficient surface active agent present to prevent the globules from adhering to each other yet an insufficient amount to prevent deformation from the substantially spherical shape.

Abstract: An improved process for the conversion of gaseous uranium hexafluoride to a uranium oxide rich composition in the presence of an active flame in a reaction zone is disclosed and comprises introducing a first gaseous reactant comprising a mixture of uranium hexafluoride and an oxygen-containing carrier gas and a second gaseous reactant comprising a reducing gas, the reactants being separated by a shielding gas as introduced to the reaction zone. The shielding gas temporarily separates the gaseous reactants and temporarily prevents substantial mixing and reacting of the gaseous reactants. The flame occurring in the reaction zone is maintained away from contact with the inlet introducing the mixture to the reaction zone.

Abstract: An actinide dioxide, e.g. uranium dioxide, is prepared by reacting an actinide nitrate or hydrate or tetrahydrofuranate thereof, e.g. uranyl nitrate, a hydrate of uranyl nitrate or a tetrahydrofuranate of uranyl nitrate with an alkali or alkaline earth metal adduct of a monocyclic or polycyclic hydrocarbon in the presence of an inert organic solvent. Typically, the starting material may be uranyl nitrate dihydrate or uranyl nitrate ditetrahydrofuranate (the latter material is a novel composition of matter) with a reactant such as the sodium adduct of naphthalene in the presence of a solvent such as tetrahydrofuran. The resultant uranium dioxide may be further purified by heating it in the presence of hydrogen.

Abstract: Process and apparatus for producing ammonium diuranate (ADU) from uranium hexafluoride (UF.sub.6) wherein gaseous UF.sub.6 is first hydrolyzed, then partially neutralized with aqueous ammonium hydroxide to a pH of from 5 to 6, the resultant solution is conveyed to a precipitation vessel wherein it is admixed with additional aqueous ammonium hydroxide to a pH of from 9.8 to 10.

Abstract: Process for dehalogenation of particulate compositions containing halide impurities including metallic oxides and metallic halides such as metallic fluorides to produce metallic oxides by contacting the compositions in a heated atmosphere containing vaporized alcohol. A second gas including inert gases and active dehalogenating gases can be mixed with the vaporized alcohol. A preferred practice has agitation of the particulate compositions containing halide impurities during the dehalogenation process. The metallic oxide produced by dehalogenation can be freed from any hydrocarbon residues where desired by a subsequent heating step in a reducing atmosphere. The halide ions from the dehalogenation can be recovered as an acid by passing the dehalogenation atmosphere through water. A preferred practice of this invention uses propyl alcohol as no hydrocarbon residues are found in the dehalogenated powder.

Abstract: A process for converting uranium hexafluoride (UF.sub.6) to uranium dioxide (UO.sub.2) of a relatively large particle size in a fluidized bed reactor by mixing uranium hexafluoride with a mixture of steam and hydrogen and by preliminary reacting in an ejector gaseous uranium hexafluoride with steam and hydrogen to form a mixture of uranium and oxide and uranium oxyfluoride seed particles of varying sizes, separating the larger particles from the smaller particles in a cyclone separator, recycling the smaller seed particles through the ejector to increase their size, and introducing the larger seed particles from the cyclone separator into a fluidized bed reactor where the seed particles serve as nuclei on which coarser particles of uranium dioxide are formed.

Abstract: This invention presents a process for conversion of gaseous uranium hexafluoride to an oxide product of uranium by introducing to a reaction zone in the presence of an active flame maintained in the reaction zone a first gaseous reactant comprising a mixture of uranium hexafluoride and an oxygen-containing gas and a second gaseous reactant comprising a reducing gas and temporarily separating the first and second gaseous reactants with a shielding gas which temporarily prevents substantial mixing and reaction between these gaseous reactants. The first and second gaseous reactants ultimately react in a primary flame to give a particulate uranium dioxide rich composition and residual reducing gas. An oxygen-containing gas as a third gaseous reactant is introduced through multiple downstream inlets with the inlet closest to the primary flame being at a location in the reaction zone where the uranium hexafluoride conversion to the uranium dioxide rich composition is substantially complete.

Abstract: A method of dehalogenating a particulate composition in a calciner having a heating zone and a cooling zone is presented in which a dehalogenating atmosphere flows through the calciner, including a constricted zone in the calciner, countercurrent to the movement of the composition through the calciner. There is practiced a step of constricting the passage of the controlled atmosphere to a zone of greater flow velocity so that the flow of the dehalogenating atmosphere through the constricted zone substantially minimizes diffusion into the cooling zone of the gaseous impurities removed from the particulate composition in the heating zone.

Abstract: Uranium is separated from contaminating cations in an aqueous liquor containing uranyl ions. The liquor is mixed with sufficient recycled uranium complex to raise the weight ratio of uranium to said cations preferably to at least about three. The liquor is then extracted with at least enough non-interfering, water-immiscible, organic solvent to theoretically extract about all of the uranium in the liquor. The oganic solvent contains a reagent which reacts with the uranyl ions to form a complex soluble in the solvent. If the aqueous liquor is acidic, the organic solvent is then scrubbed with water. The organic solvent is stripped with a solution containing at least enough ammonium carbonate to pecipitate the uranium complex. A portion of the uranium complex is recycled and the remainder can be collected and calcined to produce U.sub.3 O.sub.8 or UO.sub.2.

Abstract: Uranium dioxide powder is prepared by the AUC (ammonium uranyl carbonate) method. Supplementing the known process steps, the AUC, after separation from the mother liquor, is washed with an ammonium hydrogen cabonate or an NH.sub.4 OH solution and is subsequently post-treated with a liquid which reduces the surface tension of the residual water in an AUC. Such a liquid is, for instance, alcohol.

Abstract: The production of UF.sub.6 in which UF.sub.4 is reacted with air or oxygen in the presence of a catalyst at 500.degree. to 700.degree.C. The solid byproduct of this reaction is reduced with hydrogen in the presence of a catalyst at 400.degree. to 600.degree.C. Fresh UO.sub.3 may also be reduced with hydrogen in the same reactor as UO.sub.2 F.sub.2. The reduction product or products are reacted with hydrogen fluoride at 400.degree. to 600.degree.C, producing UF.sub.4 which would be recycled for further reaction to produce UF.sub.6.

Abstract: A fluorine containing heavy-metal oxide powder, particularly UO.sub.2 powder, is subjected to a pyrohydrolysis treatment under the most complete exclusion of hydrogen.