52results about "Uranium fluorides" patented technology

Fluorine or a fluorine compound is subjected to a reaction with a spent oxide fuel to produce fluorides of uranium and plutonium, and recovering the fluorides using a difference in volatility behavior. The method includes steps of: subjecting a mixture of UO₂ and PuO₂ with hydrogen fluoride mixed with hydrogen to HF-fluorinate uranium and plutonium into UF₄ and PuF₃; subjecting UF₄ and PuF₃ with a fluorine gas to F₂-fluorinate uranium and plutonium into UF₆ and PuF₆; and fractionating UF₆ and PuF₆ using a difference in phase change of obtained UF₆and PuF₆, removing a part of UF₆, and volatilizing the remaining UF₆ and PuF₆ at the same time. By such a reprocessing method, PuF₄ hard to undergo a reaction is prevented from being formed as an intermediate fluoride, the material of a reactor is hard to be corroded, and a consumption of expensive fluorine gas is reduced.

The invention provides a method of separating uranium from at least fission products in irradiated nuclear fuel, said method comprising reacting said irradiated nuclear fuel with a solution of ammonium fluoride in hydrogen fluoride fluorinating said reacted irradiated nuclear fuel to form a volatile uranium fluoride compound and separating said volatile uranium fluoride compound from involatile fission products. The invention thus provides a reprocessing scheme for irradiated nuclear fuel. The method is also capable of reacting, and breaking down Zircaloy cladding and stainless steel assembly components. Thus, whole fuel elements may be dissolved as one thereby simplifying procedures over conventional Purex processes.

A method of declogging at least one filter of a plant for manufacturing uranium oxide from uranium hexafluoride, including separating, from the wall of the filter, uranium oxyfluoride particles deposited, by a stream of inert gas such as nitrogen, injected into the filter, in a counter-currentwise direction to the flow of hydrofluoric acid.

A method of preparing an actinide nitride fuel for nuclear reactors is provided. The method comprises the steps of a) providing at least one actinide oxide and optionally zirconium oxide; b) mixing the oxide with a source of hydrogen fluoride for a period of time and at a temperature sufficient to convert the oxide to a fluoride salt; c) heating the fluoride salt to remove water; d) heating the fluoride salt in a nitrogen atmosphere for a period of time and at a temperature sufficient to convert the fluorides to nitrides; and e) heating the nitrides under vacuum and/or inert atmosphere for a period of time sufficient to convert the nitrides to mononitrides.

A method for producing uranium oxide includes combining uranium oxyfluoride and a solid oxidizing agent having a lower thermodynamic stability than the uranium oxide after "oxide"; heating the combination below the vapor point of the uranium oxyfluoride to sufficiently react the uranium oxyfluoride and the oxidizing agent to produce uranium oxide and a non-radioactive fluorine compound; and removing the fluorine compound after "compound".

The invention relates to a process for treating uranium and fluorine-containing tail gas and waste liquid in the field of uranium chemical industry, in particular to a uranium- and fluorine-containing tail gas leaching and eluent regeneration process, which is carried out in sequence as follows: (1) K2CO3 solution is used for leaching Tail gas containing uranium and fluorine; (2) Potassium uranyl tricarbonate is separated by sedimentation. If the mass percentage concentration of K2CO3 in the resulting clear liquid is ≈0 and the concentration of KF is >8mol/l, add KOH to the clear liquid to generate diuranic acid Potassium precipitation; (3) Potassium diuranate precipitate is separated by filtration, and the obtained clear liquid is crystallized, and the crystal is KF crystal. The process of the invention can reduce the impact of radioactive waste on the environment, and has good social benefits; the closed loop of the eluent avoids the loss of uranium elements, saves resources, and recycles fluorine ions in the form of KF by-products to achieve It achieves the purpose of "turning waste into treasure" and has certain economic benefits.

Fluorine or a fluorine compound is subjected to a reaction with a spent oxide fuel to produce fluorides of uranium and plutonium, and the fluorides are recovered using a difference in volatility behavior. The spent oxide fuel is subjected to a reaction with an HF gas, whereby uranium, plutonium and most impurities are converted into solid fluorides having low valences or remained as oxides to inhibit volatilization thereof, and then in an F₂ fluorination step, the HF fluorination product is subjected to a reaction with a fluorine gas in two stages: one at a low temperature and the other at a high temperature, whereby a certain amount of gaseous uranium and volatile impurities are separated with plutonium kept in a solid form in the first stage, and mixed fluorides of remaining uranium and plutonium are fluorinated into hexafluorides at the same time in the second stage. By such a reprocessing method, plutonium enrichment can be adjusted, uranium and plutonium can be purified, and steps are simplified as well. In addition, reactors are hard to be corroded or deteriorated.

Embodiments of a series-coupled fluidized bed reactor unit are provided. In one embodiment, the reactor unit includes primary and secondary reactors. The primary reactor includes a reaction vessel, a gas distributor fluidly coupled to the reaction vessel, and a cyclonic plenum assembly. The cyclonic plenum assembly includes a plenum assembly housing, which is fluidly coupled to the gas distributor and which has an annular sidewall; and a gas/solids inlet pipe, which fluidly couples a partially-reacted gas outlet of the secondary reactor to the plenum assembly housing. The gas/solids inlet pipe is tangentially positioned with respect to the annular sidewall of the plenum assembly housing to induce vortex flow within the plenum assembly housing of the partially-reacted gas received from the secondary fluidized bed reactor through the gas/solids inlet pipe to promote the cyclonic separation of entrained solids from the partially-reacted gas prior to entry into the gas distributor.

The invention belongs to a nuclear fuel preparation method, and specifically discloses a method for collecting UF6, which includes: inputting the UF6 gas mixture obtained by the gas-solid reaction of UF4 and F2 in a vertical fluorination furnace into a first-stage internal cooling and internal heating UF6 condenser, and passing through After condensing and separating most of the UF6, it is then input into the secondary internal cooling and internal heating UF6 condenser to condense and collect the remaining UF6, and the residual gas enters the exhaust gas treatment system to be purified and then emptied; among them, the refrigerant in the internal circulation pipe of the primary condenser is demineralized water , The temperature for receiving UF6 gas is 5-10°C. The present invention adopts demineralized water with low corrosion and no scaling as the secondary refrigerant of the first-stage internal cooling and internal heating type UF6 condenser, which reduces the corrosion of the internal circulation pipe of the internal cooling and internal heating type condenser; the temperature of the receiving gas is changed to 5-10 ℃, reduce the working temperature difference of the internal circulation pipe and reduce the stress corrosion of the internal circulation pipe. The working life of the condenser is extended to more than 1238tU, and the service life can reach more than 10 years; and the UF6 collection rate can still reach more than 99.6%.

A method for converting UO₃ and/or U₃O₈ into hydrated UO₄ of formula UO₄.nH₂O wherein n is 2 or 4, comprising the following successive steps:

• • a) preparing an aqueous suspension of a UO₃ powder and/or a U₃O₈ powder;
  • b) adding hydrogen peroxide H₂O₂ to the aqueous suspension of a UO₃ and/or U₃O₈ powder, converting the UO₃ and/or U₃O₈ into hydrated UO₄ and precipitating, crystallizing the hydrated UO₄ in the suspension;
  • g) recovering the precipitate, crystals of UO₄ hydrate;
  • h) optionally, washing the recovered UO₄ hydrate precipitate, crystal(s);
  • i) optionally, repeating step d);
  • j) optionally, drying the precipitate, the crystals;

wherein the addition of H₂O₂ to the aqueous suspension is carried out so that the suspension contains a stoichiometric excess of H₂O₂ relatively to the stoichiometry of the reaction from UO₃:

UO₃+nH₂O+H₂O₂→UO₄.nH₂O+H₂O  (1)

or of the reaction from U₃O₈

UO_2.67+1.33H₂O₂+nH₂O→UO₄.nH₂O+H₂O  (2)

• • and the pH of the suspension is maintained in steps a) and b) at a value comprised between 2 and 3.

The invention relates to a particle blend comprising mainly or consisting of an oxide phase of the pseudo-brookite type comprising at least titanium and aluminum, said blend being obtained from at least two particle size fractions, namely a coarse particle size fraction, the median diameter d₅₀ of which is greater than 12 microns, and a fine particle size fraction, the median diameter d₅₀ of which is between 0.5 and 3 microns, the mass ratio of said coarse fraction to said fine fraction being between 1.5 and 20, limits inclusive, and the ratio of the median diameter of the coarse fraction to that of the fine fraction being greater than 12.

A method for cleaning the filtering tube of a hydrofluorination fluidized bed in uranium conversion comprises the following steps: (1) removal of surface dirt; (2) removal of internal dirt; and (3) passivation and drying. A chemical medicament is prepared for cleaning of the blocked filtering tube of the hydrofluorination fluidized bed. the dirt inside the filtering tube can be effectively removed. The dirt in the filtering tube is further removed through chemical medicament immersion, bubbling and other processes after the dirt on the surface of the filtering tube is washed out. The passivating and drying process is used after the removal of the dirt in the filtering tube in order to ensure the anticorrosion performance of the filtering tube. The filtering tube cleaned with the cleaning method can meet the process requirements of the hydrofluorination fluidized bed to achieve the purpose of repeated use, has certain economic benefits, and reduces the production cost.

The invention relates to the use of a compound of formula KMgF₃ to trap metals present in the form of fluorides and/or of oxyfluorides in a gaseous or liquid phase.

It also relates to a compound of formula KMgF₃ which has a surface specific area at least equal to 30 m²/g and at most equal to 150 m²/g and also to its methods of preparation.

The invention notably finds application in the nuclear industry, in which it can advantageously be used to purify uranium hexafluoride (UF₆) present in a gaseous or liquid stream, with regard to metal impurities which are also present in this stream.

The invention belongs to the technical field of natural uranium hexafluoride gas-phase transfer, in particular to a natural uranium hexafluoride gas-phase transfer system and a natural uranium hexafluoride gas-phase transfer method. A secondary condenser and a tertiary condenser are arranged above two electronic scales respectively, and ethylene glycol and steam serve as a cold medium and a heat medium respectively. The secondary condenser is provided with two outlets, one of the outlets is connected to an inlet of a primary condenser through a valve J1, and the other outlet is connected to an inlet of the tertiary condenser through a valve J2, a valve J3, a valve J4 and a valve J5. The tertiary condenser is provided with two outlets, one of the outlets is connected to the inlet of the primary condenser through the valve J5 and a valve J7, and the other outlet is connected to an external tail gas treatment process system through a valve J6 and a valve J8. By the system and the method, assistance in pressure-relieved purification and gas-phase transfer of UF6 products in a cold trap can be realized, purity of the natural UF6 products is improved, the metal direct recovery rate is increased, and safety risks in a transfer process are reduced.

The invention belongs to a treatment method, and particularly relates to a method for preparing uranium tetrafluoride through dry fluorination. The method comprises the following steps of 1, calcining metal uranium, a uranium compound, a uranium-silicon mixture and the like at high temperature to form oxides, 2, uniformly mixing the oxide obtained by calcining with fluorinating agents such as ammonium fluoride and ammonium bifluoride according to a certain proportion, and 3, putting the mixed materials into a muffle furnace or a converter with a heating function, introducing inert gases such as nitrogen, hydrogen and ammonia gas or reducing gases, and electrifying and heating until the oxides are completely converted into uranium tetrafluoride powder. The method has the remarkable effects that uranium-containing wastewater is prevented from being generated, and the cost is reduced. The method can be applied to preparation of uranium tetrafluoride by taking metal uranium, uranium compounds, uranium-silicon mixtures and the like as raw materials in the fields of nuclear chemical engineering and fuel element manufacturing and recovery treatment of unqualified uranium-silicon mixtures in the fuel element manufacturing process.

A method of synthesizing alkali uranium fluorophosphate crystals. The method includes combining a uranium-based feedstock with a mineralizer solution. The mineralizer solution includes an alkali nutrient, a phosphate, and a fluoride. The feedstock and mineralizer solution are pressurized and a thermal gradient applied thereto such that a first portion of the feedstock and the mineralizer solution is heated to a temperature that is greater than a temperature of a second portion of the feedstock and the mineralizer solution. Uranium nutrient enters the mineralizer solution from the feedstock in the first portion and uranium nutrient precipitates to spontaneously form crystals in the second portion.

A fluidized bed reactor comprising a reaction column having a fluid portion; a gas inflow means for flowing a gas upwardly from the fluid portion of the reaction column; a particle feed means for feeding particles to the fluid portion of the reaction column; a cyclone capable of separating particles from the gas flowing upwardly from the fluid portion of the reaction column, the cyclone being located within the reaction column and being in communication with the gas flowing upwardly, wherein the cyclone comprises a cyclone body having an inlet, a gas outlet, and a particle drop port; and a particle discharge pipe having an upper part connected to the particle drop port of the cyclone body, and a lower part, wherein the particle discharge pipe is located substantially outside of the reaction column.

A method for treating process distillate heavies produced during uranium fluoride purification is described. The heavies contain primarily uranium hexafluoride, UF₆, and molybdenum oxytetrafluoride, MoOF₄. The uranium hexafluoride is removed via distillation at reduced pressure leaving essentially MoOF₄ containing <0.1% of residual uranium hexafluoride. This mixture is hydrolyzed in water, then treated with a solution of sodium hydroxide until a pH of at least 7.5 is reached. The precipitated sodium diuranate and sodium fluoride are removed by filtration. The filtrate is reacted with calcium chloride to precipitate the molybdenum values as calcium molybdate containing trace quantities of calcium fluoride.

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