RU2817671C2 - Preparation of metal fluorides and separation processes - Google Patents

Abstract

FIELD: chemical or physical processes; separation.

SUBSTANCE: invention relates to processes for preparing metal fluorides and to processes for separating or purifying metals and metal compounds, used for metal fluorides. Method of separating metal fluorides comprises a step of providing a mixture containing MoF₆ and UF₆. Then UF₆ is reduced to UF₅. At the next step, UF₅ and MoF₆ or the product of its conversion, which can be obtained by further conversion of molybdenum fluoride into another molybdenum compound, is separated.

EFFECT: invention provides fast separation of molybdenum or its compounds from uranium and reduces the amount of radioactive wastes compared to established wet chemical procedures.

19 cl, 1 dwg

Description

The present invention relates to processes for preparing metal fluorides and to processes for separating or purifying metals and metal compounds used for metal fluorides.

Nuclear medicine plays an important role in modern diagnostic and therapeutic strategies. An isotope widely used for imaging purposes is technetium-99m (Tc-99m). It is used, usually after combining with a target in a pharmaceutical compound, for example, to study the thyroid, lung, heart, liver, gallbladder or skeleton. Tc-99m is produced by the β-decay of its parent isotope molybdenum-99 (Mo-99), which in turn is predominantly produced by fission of uranium-235 (U-235) targets (Technische Universität München, Forschungs-Neutronenquelle Heinz Meier-Leibnitz; www.frm2.tum.de). As an alternative approach for the formation of Mo-99, US 8126104 B2 discloses alpha particle irradiation of zirconium-96.

Due to Mo-99's limited half-life of 66 hours, uranium targets used to provide the molybdenum isotope undergo a purification process immediately after irradiation to ensure separation of Mo-99 from the rest of the uranium and from other fission products. This process usually involves dissolving the target using an alkali or dilute nitric acid and can provide large quantities of molybdate with high specific activity. However, large volumes of acidic liquid radioactive waste are produced as an unwanted by-product. Thus, a process that allows rapid separation of molybdenum or its compounds from uranium and that allows for a reduction in the amount of radioactive waste compared to established wet chemistry procedures would be desirable.

In addition, uranium-molybdenum alloys are produced as fuel (U-Mo fuel) in high-flux neutron sources (research and test reactors). In the manufacture of such fuel, it is of interest to separate U and Mo, for example, to enable the reuse of unspent uranium enriched in uranium-235.

In the context of the present invention, it has been discovered that uranium and molybdenum can be efficiently separated by treating their fluorides as intermediates. In addition, the inventors have developed a convenient process for preparing these metal fluorides.

Thus, the present invention provides a process comprising

a step of providing a mixture containing MoF ₆ and UF ₆ ;

a stage in which UF ₆ is reduced to UF ₅ ; And

a step in which UF ₅ and MoF ₆ or its conversion product are separated, which can be obtained by further converting molybdenum fluoride into another molybdenum compound.

A first preferred aspect of the invention is a process that comprises the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides;

a dissolution step, which comprises dissolving MoF ₆ and UF ₆ in a liquid phase or a supercritical fluid phase to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form;

a precipitation step, which comprises a step of reducing the UF ₆ contained in the solution to UF ₅ and allowing it to precipitate out of the solution; And

a separating step, which contains a step in which

(i) separating the precipitated UF ₅ from the solution; or

(ii) removing the liquid phase or supercritical fluid phase of the solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separating UF ₅ and molybdenum fluoride or a conversion product thereof, which can be obtained by further conversion of molybdenum fluoride into another molybdenum compound.

According to a second preferred aspect, the invention provides a process comprising

a step of providing a gas-phase mixture containing MoF ₆ , UF ₆ and a fluorine atom scavenger mixed in gaseous form;

a step of irradiating UF ₆ in a gas-phase mixture in the presence of a fluorine atom absorber with light having a wavelength in the range from 340 to 410 nm to reduce UF ₆ to UF ₅ and to obtain a mixture containing UF ₅ and MoF ₆ ; And

the stage at which UF ₅ and MoF ₆ are separated.

Additionally, the invention relates to a process for providing metal fluoride, said process comprising the steps of:

providing fluorine radicals from a fluorine-containing parent compound using a plasma source;

reacting fluorine radicals with a solid material containing an elemental metal to produce a metal fluoride, or with a solid material containing an elemental semimetal to produce a semimetal fluoride; And

recovering metal fluoride or semi-metal fluoride;

wherein the metal is selected from molybdenum, technetium, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, gold and uranium, and the semi-metal is tellurium. This process is also referred to herein as the “metal fluoride production process” of the present invention.

The process according to the preferred first aspect of the invention set forth above will be described below. This process can be suitably used, for example, to produce molybdenum or a molybdenum compound, in particular to produce molybdenum or a molybdenum compound containing the molybdenum-99 isotope. Alternatively or additionally, it can be used to produce uranium or a uranium compound, in particular to produce uranium or a uranium compound enriched in uranium-235.

The process according to the first aspect includes the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides.

This process can be applied to mixtures containing molar ratios of MoF ₆ and UF ₆ varying over wide ranges, for example, from 1:400 to 100:1. Preferably, the molar ratios are in the range from 1:5 to 10:1.

As will be clear from the above, the uranium contained in UF ₆ may be uranium enriched in uranium-235. The molybdenum contained in MoF ₆ may contain molybdenum-99.

The step of providing a mixture containing MoF6 and UF6 as a starting mixture of metal fluorides preferably comprises a step of reacting a solid material that contains elemental uranium and elemental molybdenum with fluorine radicals to obtain a mixture containing MoF ₆ and UF ₆ . This reaction comprises the step of exposing the solid material to a gas stream containing fluorine radicals.

Also, the uranium contained in the solid material may be uranium enriched in uranium-235. Molybdenum contained in the solid material may contain molybdenum-99.

The weight ratio of elemental uranium and elemental molybdenum in the solid material is not particularly limited in connection with the separation of these two elements through their fluorides. Typical molybdenum content ranges from 0.01 to 12 wt. %, based on the total weight of uranium and molybdenum as 100 wt. %.

In the case of a solid material containing the isotope molybdenum-99, which reacts with fluorine radicals, the preferred elemental molybdenum content is in the range of 0.02 to 1.0 wt. %, more preferably from 0.05 to 0.2 wt. %, based on the total weight of elemental uranium and elemental molybdenum as 100 wt. %.

In the case of a solid material containing uranium and molybdenum, which can be used in the preparation of U-Mo fuel, and which can also react with fluorine radicals to obtain a mixture containing MoF ₆ and UF ₆ , the preferred elemental molybdenum content is in the range from 5 to 12 wt. %, more preferably from 7 to 10 wt. %, based on the total weight of elemental uranium and elemental molybdenum as 100 wt. %.

In addition to U and Mo, the solid material that reacts with fluorine radicals may contain other components including other metals, or it may be free of metals other than uranium and molybdenum. For example, aluminum may be present as a matrix material in combination with uranium in uranium targets that are irradiated with neutrons to convert the uranium to molybdenum-99.

The total content of elemental uranium and elemental molybdenum in the solid material that reacts with fluorine radicals is preferably in the range of 30-100 wt. %, more preferably 50-100 wt. %. In this context, the weight percentage is based on the total weight of the material that contains uranium and molybdenum, as 100%, not including the weight of the coating that may be applied to the material that contains uranium and molybdenum. As will be appreciated by those skilled in the art, the material which contains uranium and molybdenum and which is also referred to as "meat" may be provided as a dispersed phase in which the uranium and molybdenum are dispersed in a matrix material such as aluminum, or as a homogeneous or monolithic phase.

In the case of a solid material containing the isotope molybdenum-99, which reacts with fluorine radicals, the preferred total content of elemental uranium and elemental molybdenum is in the range of 30-100 wt. %, more preferably 50-100 wt. %, based on the total mass of meat, excluding any casing.

In the case of a solid material containing uranium and molybdenum, which is used in the preparation of U-Mo fuel, and which can also react with fluorine radicals to produce a mixture containing MoF ₆ and UF ₆ , the preferred total content of elemental uranium and elemental molybdenum is also is in the range of 30-100 wt. %, more preferably 50-100 wt. %, based on the total mass of meat, excluding any casing.

In a solid material containing elemental uranium and elemental molybdenum, these two elements may be combined, for example, in the form of a mixture or in the form of an alloy. Since, as noted above, additional components other than uranium and molybdenum may be present in the solid material, it is also possible for uranium, molybdenum, or both to form an alloy with one or more such other components. It should be noted that reference here to an alloy includes intermetallic phases, in the sense that such a phase is formed by the components of the alloy in question. Reference to an alloy also includes an alloy formed from one or more metals, such as uranium, and one or more semi-metals, such as silicon. As a preferred example of a solid material containing elemental uranium and elemental molybdenum, reference may further be made to a solid material containing uranium or a uranium alloy (for example, uranium silicide), in which molybdenum has been formed by neutron irradiation and dispersed in the uranium or uranium alloy .

The form in which the solid material reacts with fluorine radicals is not particularly limited. The solid material may have a compact shape, for example a regular compact shape such as a plate, cylinder or sphere. The solid material may also react with fluoride radicals in powder form. For example, in some applications, uranium and molybdenum may be encapsulated with another metal or dispersed in a matrix of another metal, so it may be useful to subject such encapsulated or dispersed starting material to mechanical disintegration to provide a powder that can be advantageously used as a solid material for the reaction with fluorine radicals.

The solid material that reacts with fluorine radicals, as a preferred embodiment of the process according to the first aspect of the invention, can be provided, for example, by irradiating the solid material that contains elemental uranium enriched in the isotope uranium-235 with neutrons. This provides a solid material containing elemental uranium and elemental molybdenum, in which the elemental molybdenum contains the isotope molybdenum-99. In other words, the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides may comprise the step of irradiating a solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons to produce a solid a material containing elemental uranium and elemental molybdenum, and in which the elemental molybdenum contains the isotope molybdenum-99. In this regard, established procedures for the formation of molybdenum-99 by fission of uranium-235 through neutron irradiation can be relied upon.

Alternatively, the solid material that reacts with fluorine radicals, as a preferred embodiment of the process according to the first aspect of the invention, can be provided by preparing an alloy containing elemental uranium enriched in the isotope uranium-235 and non-radioactive molybdenum. In this way, a solid material is obtained containing elemental uranium enriched in uranium-235 and molybdenum, which can be used, for example, as U-Mo fuel.

As mentioned above, uranium enriched in the uranium-235 isotope typically contains up to 50 weight percent uranium-235. % (based on the total weight of uranium as 100 wt.%).

The step of providing a mixture containing MoF6 and UF6 as a starting mixture of metal fluorides may further comprise, before reacting the solid material with fluorine radicals, reacting the solid material with hydrogen radicals to produce a solid material containing UH ₃ ; and reconverting the UH ₃ to elemental uranium by exposing the UH ₃ to elevated temperature. This reaction with hydrogen radicals may be particularly advantageous for a solid material produced by irradiating a solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons.

If, according to the preferred embodiment described above, a solid material containing elemental uranium and elemental molybdenum is produced by irradiating a solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons, the solid material may be reacted with hydrogen radicals for complete or partial conversion of uranium into UH ₃ . Accordingly, the reaction with hydrogen radicals can be carried out before the reaction with fluorine radicals. Molybdenum contained in solid material does not react with hydrogen. Such pre-reaction with hydrogen radicals to form UH ₃ may be useful, for example, to completely or partially disintegrate the metal matrix of a solid material containing uranium which has been irradiated with neutrons, whereby gaseous by-products, in particular Kr and Xe, may be formed during irradiation. Such gaseous by-products can be conveniently isolated and removed after conversion to UH ₃ . Also, before the solid material reacts with fluorine radicals, UH ₃ can be reconverted into elemental uranium. This can be accomplished, for example, by exposing the UH ₃ to elevated temperature, usually in a vacuum or in an inert atmosphere. This temperature is preferably in the range from 250°C to 500°C, more preferably 350°C.

Before subjecting a solid material that contains elemental uranium and elemental molybdenum to reaction with fluorine radicals, its surface may, if necessary, be cleaned, for example, to remove metal oxides. This can be done, for example, using an inorganic acid such as nitric acid.

Fluorine radicals that react with a solid material containing elemental uranium and elemental molybdenum according to the above embodiment are preferably generated from a fluorine-containing parent compound in a plasma source, more specifically, in a remote plasma source. Thus, the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides preferably comprises a step of generating fluorine radicals in a plasma source, more preferably in a remote plasma source.

In a plasma source, fluorine radicals are generated by applying energy to a fluorine-containing parent compound so as to dissociate the bond formed with a fluorine atom in the parent compound. Fluorine-containing starting compounds are usually gaseous compounds. Known starting compounds that may also be used in the context of the present invention include, for example, any of F ₂ , NF ₃ , SF ₆ and CF ₄ . Among them, F ₂ and NF ₃ are preferred, and NF ₃ is particularly preferred due to its less corrosiveness and its less toxicity compared to F ₂ .

In a plasma source, the plasma can be generated, for example, using microwave radiation. Commercially available plasma sources can be used for this purpose. The radiation frequency can be suitably adjusted, for example, depending on the fluorine-containing starting compound used, to achieve a high degree of dissociation.

The preferred use of a remote plasma source allows the reaction between the fluorine radicals and the solid material containing elemental uranium and elemental molybdenum to occur at a location that is remote from the actual plasma source. This makes it easier to control the reaction.

As noted above, reacting a solid material with fluorine radicals comprises exposing the solid material to a gas stream that contains fluorine radicals. The gas stream may further comprise a carrier gas. Typically, the carrier gas is a noble gas such as argon.

Typically, a gas stream that contains fluorine radicals is provided by directing a gas stream containing a gaseous fluorine-containing feed compound and preferably a carrier gas such as argon to a plasma source, preferably a remote plasma source. The solid material containing elemental uranium and elemental molybdenum can then be exposed to a gas stream containing fluorine radicals generated by the plasma source, and preferably containing a carrier gas. It should be understood that the gas stream into which the solid material is exposed may also contain residual feed compound.

Thus, the composition of the gas stream can be conveniently controlled by controlling the mass flow rate of the fluorine-containing feed compound and optional carrier gas in the plasma source. Typically, volume ratios of fluorine-containing feed compound and optional carrier gas are adjusted in the range of 10:1 to 1:10, preferably 2:1 to 1:2, more preferably 1:1.

For example, the mass flow rate of the fluorine-containing feed compound in the plasma source can be adjusted to values in the range of 10 to 50 cc. cm per minute, preferably from 15 to 35 cc. cm per minute The flow rate of the optional carrier gas may be adjusted accordingly based on the aforementioned typical/preferred volumetric ratios. As will be appreciated by those skilled in the art, standardized volumes are based on a temperature of 0° C. and a pressure of 1013.25 hPa.

If a carrier gas, in particular a noble gas such as argon, is present in the gas stream, it is advantageous to generate fluorine radicals in the plasma that burns in the immediate vicinity of the substrate, and thereby facilitate the reaction of the metals with the fluorine atoms.

The plasma may be ignited and maintained by generally known methods, such as direct current (DC), high frequency (HF), or microwave methods, or a combination of any of these methods. When a suitable potential of the substrate relative to the plasma is provided, and a floating potential is further applied to the solid material to be reacted with fluorine radicals, the plasma particles are accelerated towards the surface of the solid material. Thus, electrons allow for localized and targeted heating of the solid material, while ion bombardment results in the ejection of atoms of the solid material, which can further enhance the reaction with fluorine radicals.

As will be appreciated by those skilled in the art, fluorine radicals are typically provided and the reaction of the solid material with the fluorine radicals is typically carried out in a reaction system that can be subjected to a vacuum and is suitable for introducing a controlled gas stream at pressures below atmospheric pressure. An exemplary diagram of a suitable reaction system is shown schematically in FIG. 1.

The pressure within the reaction system in which the solid material reacts with the fluorine radicals can be controlled by a selected mass flow rate of gases, preferably gases consisting of a fluorine-containing feed compound and optionally a carrier gas such as argon.

Typically, the pressure inside the reactor in which the solid material that contains elemental uranium and elemental molybdenum reacts with fluorine radicals is in the range of 10 Pa to 3000 Pa, preferably in the range of 10 Pa to 2000 Pa.

The reaction of the solid material, which contains elemental uranium and elemental molybdenum, with fluorine radicals occurs without the need to heat the solid material. However, due to the exothermic nature of the reaction, heat can be generated and can be controlled, for example, by adjusting the gas flow rate and/or the concentration of fluorine radicals contained therein.

Those skilled in the art will also appreciate that the reaction chamber in which the solid material is provided to react with fluorine radicals must be inert to fluorine radicals. For example, the reaction chamber may have a passivated nickel or monel metal surface. Due to the high reactivity of fluorine radicals, the distance between the plasma source and the solid material in the reactor must be kept short even when using a remote plasma source. By this means, the loss of fluorine radicals due to bulk and surface recombination can be minimized.

If the step of providing the mixture containing MoF ₆ and UF ₆ involves reacting the solid material with hydrogen radicals to produce a solid material containing UH ₃ and reconverting to elemental uranium, then this reaction/reconversion may be carried out as a preliminary reaction in the same reaction system in which the reaction with fluorine radicals can be carried out in a subsequent step. In particular, the solid material may be exposed to a gas stream containing hydrogen radicals and, optionally, a carrier gas. Hydrogen radicals are preferably generated in the plasma source, more preferably in a remote plasma source as described above. Hydrogen radicals can be generated from a hydrogen-containing parent compound in the plasma source. The hydrogen-containing starting compound may be, for example, H ₂ .

The mixture containing MoF ₆ and UF ₆ which is provided as the starting mixture of metal fluorides is preferably a gas phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form. The gas stream may further comprise a carrier gas. Typically, the carrier gas, if present, is a noble gas such as argon. For example, when a mixture containing MoF ₆ and UF ₆ is provided by exposing a solid material containing uranium and molybdenum to a gas stream containing fluorine radicals, the gas stream can be conveniently used after contact with the solid material to transport MoF ₆ and UF ₆ into as gaseous reaction products from the reaction chamber. Due to the relatively low boiling point or sublimation point of MoF ₆ and UF ₆ , respectively, the gas-phase mixture containing MoF ₆ and UF ₆ is provided at moderate temperatures, so that no special measures need to be taken to ensure that the fluorides pass into the gas phase.

In particular, the volatility of MoF ₆ and UF ₆ is higher than that of many other metal fluorides. Thus, the gas phase mixture containing MoF ₆ and UF ₆ can also be conveniently separated from other metal fluorides that may be formed during the reaction of solid material containing uranium and molybdenum with fluorine radicals. As described above, the solid material can be provided, for example, by irradiating the solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons. During the fission process initiated by irradiation, other metals can be formed as by-products. In addition, uranium targets may contain aluminum.

In view of the above, it should be understood that the process according to the first aspect of the invention preferably comprises:

a step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides, this step comprising steps of

form fluorine radicals in the plasma source, preferably in a remote plasma source,

reacting a solid material containing elemental uranium and elemental molybdenum with fluorine radicals, the reaction comprising the step of exposing the solid material to a gas stream containing fluorine radicals to produce a gas-phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form;

a dissolution step, which comprises dissolving MoF ₆ and UF ₆ in a liquid phase or a supercritical fluid phase to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form;

a precipitation step, which comprises a step of reducing the UF ₆ contained in the solution to UF ₅ and allowing it to precipitate out of the solution; And

separation stage, which contains stages in which

(i) separating the precipitated UF ₅ from the solution; or

(ii) removing the liquid phase or supercritical fluid phase of the solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separating UF ₅ and molybdenum fluoride or a conversion product thereof, which can be obtained by further conversion of molybdenum fluoride into another molybdenum compound.

The mixture containing MoF ₆ and UF ₆ , which is provided as a starting mixture of metal fluorides, can be subjected to a dissolution step of the process according to the first aspect of the invention, essentially, for example, by introducing a gas phase mixture containing MoF ₆ and UF ₆ into a liquid phase or into the supercritical fluid phase, or by first precipitating MoF ₆ and UF ₆ from the gas-phase mixture by cooling, and then dissolving the precipitated MoF ₆ and UF ₆ .

Alternatively, a portion of the UF ₆ contained in the initial fluoride mixture may be separated from the initial metal fluoride mixture in an additional processing step prior to the dissolution step. For example, if it is intended to recover a molybdenum compound using the process according to the first aspect of the invention, it may be desirable to reduce the UF ₆ content to optimize product yield during the separation step. Likewise, if it is intended to recover uranium or a uranium compound using the process of the first aspect of the invention, it may be effective to recover a portion of the uranium as UF ₆ directly from the feed fluoride mixture in such an additional processing step.

To carry out such recovery of UF ₆ , for the process according to the first aspect of the present invention, it is preferable that the mixture containing MoF ₆ and UF ₆ , which is provided as the starting mixture of metal fluorides, is a gas phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form and that the process comprises a step (also referred to herein as a "pre-deposition step") in which the gas-phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which a portion of the UF ₆ contained in the gas phase is precipitated and removed from the gas phase . This initial precipitation step produces a mixture containing MoF ₆ and UF ₆ in which the UF ₆ content is reduced and the ratio of MoF ₆ to UF ₆ is increased compared to the original metal fluoride mixture. Additionally, it produces precipitated UF ₆ which can be recovered. As will be understood, the initial precipitation step, if contained in the process according to the first aspect of the invention, is carried out before the dissolution step.

When the gas phase is cooled to a temperature at which the partial pressure of UF ₆ in the gas phase is higher than the saturated vapor pressure of UF ₆ at the temperature to which the gas phase is cooled, the UF ₆ precipitates, usually as a solid phase. It can thus be removed from the gas phase and separated from MoF ₆ . It should be noted in this regard that the vapor pressure of MoF ₆ at a given temperature is usually lower than the vapor pressure of UF ₆ . The vapor pressure of UF ₆ can be calculated between -15°C and 0°C using the equation:

mbar

(D.R. Llewellyn, J. Chem. Soc. (1953) 28).

For UF ₆ , this calculation can be done according to the following equation between -60°C and -8.7°C:

mbar

(G.H. Cady, G.B. Hargreaves, J. Chem. Soc. (1961) 1563).

Extrapolation of the calculated values allows us to estimate the following saturated vapor pressures, p _Vap , for MoF ₆ and UF ₆ depending on temperature:

Temperature (°C) p _Vap UF ₆ (Pa) p _Vap MoF ₆ (Pa) _pVap (UF _{6)/ pVap} (MoF ₆₎ -10 1042 12791 12.3 -thirty 157 2690 17.2 -50 17 428 25.8 -70 1 47 42.4

The partial pressures of MoF ₆ and UF ₆ in the gas phase mixture provided as the metal fluoride feed mixture can be adjusted, for example, by exposing a solid material that contains elemental uranium and elemental molybdenum to a gas stream containing fluorine radicals and by controlling the concentration and the mass flow rate of fluorine radicals or their parent compound in the gas stream and the concentration and mass flow rate of a carrier gas that may be contained in the gas stream. The total pressure in the reaction system in which the reaction between the solid material and the fluorine radicals occurs is typically in the range of 10 Pa to 3000 Pa, preferably in the range of 10 Pa to 2000 Pa. The partial pressure of UF ₆ is preferably in the range from 10 Pa to 500 Pa. The partial pressure of MoF ₆ is preferably in the range from 0.1 Pa to 5 Pa.

The initial deposition step is preferably carried out as part of the process according to the first aspect of the present invention in cases where the mixture containing MoF ₆ and UF ₆ , which is provided as the initial mixture of metal fluorides, is a gas-phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form, and the partial pressure of UF ₆ (p(UF ₆ )) in the gas-phase mixture is significantly higher than the partial pressure of MoF ₆ (p(MoF ₆ )), for example, in cases where the ratio p(UF ₆ )/p(MoF ₆ ) > 10.

During the initial deposition step, the gas phase mixture containing MoF ₆ and UF ₆ is typically cooled to a temperature of less than -10°C, preferably less than -50°C, and more preferably less than -70°C. A suitable temperature can be selected taking into account the partial pressure of UF ₆ in the gas phase mixture and the saturated vapor pressure of UF ₆ at various temperatures shown in the table above. As will be appreciated by those skilled in the art, the temperature must be such that the partial pressure of UF ₆ in the gas phase is above its vapor pressure at that temperature, but so that the partial pressure of MoF ₆ in the gas phase is below its vapor pressure at that temperature . A suitable temperature at which the cooling step is carried out can be determined taking into account the above together with the relative concentrations of MoF ₆ and UF ₆ in the gas phase mixture. In this way, UF ₆ can be precipitated, usually as a solid.

Cooling of the gas-phase mixture can conveniently be accomplished in one or more cold traps. Cooling media to achieve temperatures below the above preferred limits are known to those skilled in the art and can be provided separately, for example, using salt/ice mixtures or solvent/dry ice mixtures, or through the use of a cryostat.

Multiple cooling steps may be performed sequentially during the initial deposition step. If multiple cooling steps are to be carried out, for example two or three, this can conveniently be carried out using two or three cold traps. They can operate sequentially, at the same temperature or at decreasing temperatures.

In view of the above, it should be understood that the process according to the first aspect of the invention preferably comprises:

a step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides, this step comprising steps of

form fluorine radicals in the plasma source, preferably in a remote plasma source,

reacting a solid material containing elemental uranium and elemental molybdenum with fluorine radicals, the reaction comprising the step of exposing the solid material to a gas stream containing fluorine radicals to produce a gas-phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form;

a step in which the gas-phase mixture containing MoF ₆ and UF ₆ provided as the starting mixture of metal fluorides is cooled to a temperature at which a portion of the UF ₆ contained in the gas phase is deposited and removed from the gas phase;

a dissolution step, which comprises dissolving the remaining MoF ₆ and UF ₆ in a liquid phase or supercritical fluid phase to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form;

a precipitation step, which comprises a step of reducing the UF ₆ contained in the solution to UF ₅ and allowing it to precipitate out of the solution; And

separation stage, which contains

(i) a step of separating the precipitated UF ₅ from the solution; or

(ii) the step of removing a liquid phase or supercritical fluid phase from solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separating UF ₅ and molybdenum fluoride or a conversion product thereof that may be obtained by further converting molybdenum fluoride into another molybdenum compound.

Those skilled in the art will appreciate that the dissolution step of the preferred/more preferred embodiment of the process described above is carried out after the step in which the gas phase mixture containing MoF ₆ and UF ₆ provided as the starting mixture of metal fluorides is cooled to a temperature at in which a portion of the UF ₆ contained in the gas phase is precipitated and removed from the gas phase, and that reference to "remaining MoF ₆ and UF ₆ " in the context of the dissolution step refers to the MoF ₆ and UF ₆ that remain in the mixture after a portion has been removed from the mixture UF ₆ contained in the gas phase.

In the dissolution step of the process according to the first aspect of the present invention, MoF ₆ and UF ₆ are dissolved in a liquid phase or supercritical fluid phase to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form. As will be understood, the MoF ₆ and UF ₆ that are dissolved in this step are obtained from a mixture containing MoF ₆ and UF ₆ which is provided as a starting mixture of metal fluorides. However, the solution is not required to contain all of the MoF ₆ and UF ₆ that is contained in the original metal fluoride mixture. As described above, additional processing steps may be performed prior to the dissolution step specifically to separate a portion of the UF ₆ from the MoF ₆ in the initial metal fluoride mixture, such as the initial precipitation step described above.

Thus, in general, either the mixture of MoF ₆ and UF ₆ that is contained in the initial metal fluoride mixture is dissolved in a dissolution step, or the mixture of MoF ₆ and UF ₆ is dissolved in a dissolution step that follows the initial precipitation step in which the gas phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which part of the UF ₆ contained in the gas phase is deposited and removed from the gas phase.

If the MoF ₆ and UF ₆ to be dissolved in the dissolution step are contained in a gas phase, then the dissolution can be accomplished, for example, by introducing a gas-phase mixture containing MoF ₆ and UF ₆ into a liquid phase or a supercritical fluid phase.

Alternatively, if the MoF ₆ and UF ₆ to be dissolved in the dissolution step are contained in a gas-phase mixture, then the process may further comprise a step prior to the dissolution step in which the gas-phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which the MoF ₆ and UF ₆ contained in the gas phase are deposited as a mixture containing MoF ₆ and UF ₆ , this mixture is recovered and then subjected, optionally after re-evaporation to provide a gas phase mixture containing MoF ₆ and UF ₆ in gaseous form, to the step dissolution. If the recovered mixture is re-evaporated, the gas-phase mixture containing MoF ₆ and UF ₆ can be dissolved, for example, by introducing the gas-phase mixture into a liquid phase or into a supercritical fluid phase. If the recovered mixture is a solid mixture, it can be dissolved, for example, by adding it as such to a liquid phase or a supercritical fluid phase, or by adding a liquid phase or a supercritical fluid phase to a solid mixture.

If the process according to the first aspect of the invention comprises the initial deposition step described above and a step in which the gas-phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which the MoF ₆ and UF ₆ contained in the gas phase are deposited as a mixture containing MoF ₆ and UF ₆ , then the last step is carried out after the initial deposition step.

As will be appreciated by those skilled in the art, if a gas phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which the MoF ₆ and UF ₆ contained in the gas phase precipitate as a mixture containing MoF ₆ and UF ₆ , then The temperature for the cooling step is preferably chosen low enough that most of the metal fluorides are precipitated, or that precipitation occurs quantitatively. Typically, the gas phase is exposed to temperatures of -150°C or less, preferably -190°C or less. For example, a cold trap cooled by liquid nitrogen can be used for this purpose.

In the dissolution step, MoF ₆ and UF ₆ are dissolved in a liquid phase or supercritical fluid phase to produce a solution containing both MoF ₆ and UF ₆ in dissolved form. Thus, unless otherwise stated, reference to a solvent is intended to include a solvent in a liquid state as well as a solvent in a supercritical fluid state, and a reference to dissolution likewise includes the case in which dissolved fluorides are contained in a liquid solvent , and a case in which dissolved fluorides are contained in a supercritical fluid as a solvent. Preferably, MoF ₆ and UF ₆ are dissolved in a liquid phase to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form.

The liquid phase or supercritical fluid phase may contain a single solvent or a combination of solvents. Preferably they contain a single solvent.

As preferred examples of a suitable solvent, reference may be made to liquid SO ₂ and supercritical fluid CO. The most preferred solvent is liquid SO ₂ . Thus, it is preferable that MoF ₆ and UF ₆ be dissolved in a liquid phase containing or consisting of liquid SO ₂ as a solvent, or in a supercritical fluid phase containing or consisting of supercritical CO as a solvent. Most preferably, MoF ₆ and UF ₆ are dissolved in a liquid phase consisting of liquid SO ₂ as solvent.

As will be appreciated by those skilled in the art, it may be preferable to maintain the solvent at a reduced temperature to maintain it in the desired form, preferably in liquid form. If SO ₂ is used as a solvent in the dissolution step, it is usually maintained at a temperature of -45°C or less. If CO is used as a supercritical fluid solvent, it is usually maintained at a temperature between -140°C and 25°C and a pressure between 3500 kPa and 12500 kPa. Alternatively, a solvent such as SO ₂ which is in gaseous form at ambient temperature and atmospheric pressure can be used by condensing this gas at a sufficiently low temperature and by allowing the liquid phase thus provided to be heated under autogenous pressure conditions at a steady state. to the pressure of the vessel. Thus, the separation step can be carried out at room temperature.

Preferably, the liquid phase or supercritical fluid phase used for the dissolution step contains a fluorine atom scavenger, i.e., a compound that is configured to bind fluorine atoms that may be formed during or after the dissolution step in the solution, or that the liquid phase or supercritical fluid phase contained a solvent that functions as a scavenger for fluorine atoms. Also in this regard, liquid SO ₂ and supercritical fluid CO are preferred solvents, and liquid SO ₂ is a particularly preferred solvent because these solvents have the ability to bind fluorine atoms and act as a scavenger for fluorine atoms.

In view of the above, it will be understood that the process according to the first aspect of the invention preferably comprises:

a step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides, this step comprising steps of

form fluorine radicals in the plasma source, preferably in a remote plasma source,

reacting a solid material containing elemental uranium and elemental molybdenum with fluorine radicals, the reaction comprising the step of exposing the solid material to a gas stream containing fluorine radicals to produce a gas-phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form;

optionally, a step in which the gas-phase mixture containing MoF ₆ and UF ₆ provided as the starting mixture of metal fluorides is cooled to a temperature at which a portion of the UF ₆ contained in the gas phase is deposited and removed from the gas phase;

a dissolution step, which comprises dissolving the remaining MoF ₆ and UF ₆ in a liquid phase containing or consisting of liquid SO ₂ to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form;

a precipitation step, which comprises a step of reducing the UF ₆ contained in the solution to UF ₅ and allowing it to precipitate out of the solution; And

separation stage, which contains

(i) a step of separating the precipitated UF ₅ from the solution; or

(ii) a step of removing the liquid phase of the solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separating UF ₅ and molybdenum fluoride or a conversion product thereof, which can be obtained by further conversion of molybdenum fluoride into another molybdenum compound.

In the precipitation step of the process according to the first aspect of the present invention, the UF ₆ contained in the solution is reduced to UF ₅ , which precipitates out of the solution.

The reduction of UF ₆ to UF ₅ can conveniently be accomplished by photoreduction, ie, by irradiating a solution containing UF ₆ in dissolved form with light of a suitable wavelength. For example, photoreduction effectively occurs by irradiation with light having a wavelength in the range of 340 to 410 nm, preferably with a wavelength in the range of 380 to 400 nm, and most preferably at 395 nm. In this wavelength range, UF ₆ is efficiently converted to UF ₅ while MoF ₆ contained in solution does not show any significant absorption and remains unaffected by light.

As noted above, it is preferable that MoF ₆ and UF ₆ are dissolved in a dissolution step in a liquid phase or supercritical fluid phase that contains a fluorine atom scavenger. This fluorine atom scavenger is configured to bind a fluorine atom that is released from UF ₆ during its reduction.

Preferably, the solubility characteristics of UF ₅ differ significantly from the solubility characteristics of UF ₆ as well as from the solubility characteristics of molybdenum fluoride. Without wishing to be bound by theory, we note that this may be a consequence of the polymer solid structure of UF ₅ . Thus, UF ₅ that is formed as a result of reduction can be allowed to precipitate out of solution due to its limited solubility, ie, in general, precipitation of UF ₅ occurs spontaneously. For example, this precipitation occurs spontaneously during or after the formation of UF ₅ in a liquid phase containing or consisting of liquid SO ₂ as a solvent, in a liquid phase containing or consisting of liquid CO as a solvent, or in a supercritical fluid phase containing or consisting of CO as a solvent.

Thus, as will be understood from the above, the precipitation step of the process according to the first aspect of the present invention generally produces a combination of a liquid phase or supercritical fluid phase as a solution containing dissolved MoF ₆ and precipitated UF ₅ as a solid phase.

In the separation step of the process according to the first aspect of the present invention, the precipitated UF ₅ is separated from the molybdenum compound either in the presence or absence of a liquid phase/supercritical fluid phase. Thus, the separation step contains

(i) a step of separating the precipitated UF ₅ from the solution; or

(ii) a step of removing a liquid phase or a supercritical fluid phase of a solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separating UF ₅ and molybdenum fluoride or a conversion product thereof, which can be obtained by further conversion of molybdenum fluoride into another molybdenum compound.

If the precipitated UF ₅ is separated from the solution according to option (i), the separation step may further comprise a step of removing the MoF ₆ from the solution after separating the precipitated UF ₅ from the solution. Alternatively, the separating step may further comprise steps of

converting the MoF ₆ contained in the solution into another molybdenum compound before or after separating the precipitated UF ₅ from the solution, and

the molybdenum compound is removed from the solution after separating the precipitated UF ₅ from the solution.

Thus, the process according to the first aspect of the invention allows the production of a molybdenum compound from a mixture of MoF ₆ and UF ₆ , including in the case where MoF ₆ and UF ₆ are prepared by reacting a solid material (for example, an alloy) that contains elemental uranium and elemental molybdenum , with fluorine radicals. As a result, this process of the present invention can be advantageously used, for example, to provide a molybdenum-99 compound in which molybdenum-99 is formed by fission of uranium, or to recover uranium from uranium-molybdenum alloys used for the preparation of U-Mo fuel.

For example, if relying on option (i) above, the MoF ₆ contained in the solution can be recovered as such from the solution after separating the precipitated UF ₅ from the solution. Alternatively, the MoF ₆ contained in the solution can be converted to the molybdate ion MoO ₄ ^2- , preferably by reaction with hydroxy ions, which can be added to the solution, for example in the form of NaOH or KOH. The molybdate can then be recovered from solution, for example in the form of a sodium or potassium salt.

According to a further alternative, MoF ₆ can be reduced to MoF ₅ in solution and can be recovered as MoF ₅ after separating the precipitated UF ₅ from the solution. The reduction of MoF ₆ to MoF ₅ can be carried out, for example, by photoreduction, ie by irradiating a solution containing MoF ₆ in dissolved form with light of a suitable wavelength. For example, photoreduction occurs effectively by irradiation with light having a wavelength of 270 nm or less, preferably from 230 to 260 nm. Unlike UF ₅ , MoF ₅ exhibits significant solubility, for example, in a liquid phase containing or consisting of liquid SO ₂ as a solvent, in a liquid phase containing or consisting of liquid CO as a solvent, or in a supercritical fluid phase containing or consisting of CO in a supercritical state as a solvent. Thus, the conversion of MoF ₆ to MoF ₅ can be carried out before separating the precipitated UF ₅ from a solution containing molybdenum fluoride, or after separating the precipitated UF ₅ from a solution containing molybdenum fluoride.

Conventional solid/liquid separation techniques can be relied upon to separate precipitated UF ₅ from a solution containing molybdenum fluoride. For example, the solid precipitated UF ₅ can be separated from the solution by draining the solution or by filtering the solution.

Alternatively, also relying on option (i) above, the precipitated UF ₅ can be separated from the solution containing MoF ₆ by evaporation of the liquid phase or supercritical fluid phase along with the MoF ₆ followed by recovery of the MoF ₆ . For example, if precipitated UF ₅ is separated from a solution containing MoF ₆ dissolved in a liquid phase by evaporating the liquid phase along with MoF ₆ , then MoF ₆ may preferably be recovered by recondensing the liquid phase along with MoF ₆ to obtain a solution containing MoF ₆ , separated from the precipitated UF ₅ . Due to the relatively high vapor pressure/low boiling point of MoF ₆ , molybdenum fluoride can be conveniently vaporized in the form of MoF ₆ . According to another illustrative approach relying on option (i), if the precipitated UF ₅ is separated from the solution containing MoF ₆ by fractional distillation of MoF ₆ and fractional distillation of the liquid phase or supercritical fluid phase, then the MoF ₆ can be recovered separately.

Thus, according to a first preferred embodiment of the separating step, the separating step also comprises

a step of separating the precipitated UF ₅ from a solution containing MoF ₆ dissolved in a liquid phase by evaporating the liquid phase along with the MoF ₆ , and recovering the MoF ₆ by recondensing the liquid phase along with the MoF ₆ to obtain a solution containing MoF ₆ , separately from the precipitated UF ₅ , and

a solution containing MoF ₆ obtained after separation of precipitated UF ₅ is treated with OH ^- ions to obtain molybdate, which can then be extracted from the solution.

According to yet another preferred embodiment of the separating step, the separating step comprises steps in which

reducing the MoF ₆ contained in the solution by photoreduction to obtain a solution containing MoF ₅ , before or after separating the precipitated UF ₅ from the solution,

separating UF ₅ from the solution by draining or filtering the solution, and

MoF ₅ is recovered from solution by evaporating the solvent after separating the precipitated UF ₅ from the solution.

In view of the above, it will be understood that the process according to the first aspect of the invention preferably comprises:

a step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides, this step comprising steps of

form fluorine radicals in the plasma source, preferably in a remote plasma source,

reacting a solid material containing elemental uranium and elemental molybdenum with fluorine radicals, the reaction comprising the step of exposing the solid material to a gas stream containing fluorine radicals to produce a gas-phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form;

optionally, a step in which the gas-phase mixture containing MoF ₆ and UF ₆ provided as the starting mixture of metal fluorides is cooled to a temperature at which a portion of the UF ₆ contained in the gas phase is deposited and removed from the gas phase;

a dissolution step, which comprises dissolving the remaining MoF ₆ and UF ₆ in a liquid phase containing or consisting of liquid SO ₂ to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form;

a precipitation step, which comprises a step of reducing the UF ₆ contained in the solution to UF ₅ and allowing it to precipitate out of the solution; And

separation stage, which contains

(ia) a step of separating the precipitated UF ₅ from the solution, and

extract MoF ₆ from solution after separating precipitated UF ₅ from solution, or

(ib) a step of separating the precipitated UF ₅ from the solution,

converting the MoF ₆ contained in the solution into another molybdenum compound before or after separating the precipitated UF ₅ from the solution, and

the molybdenum compound is removed from the solution after separating the precipitated UF ₅ from the solution.

As noted above, the separation step may comprise, in accordance with option (ii), the step of removing a liquid phase or a supercritical fluid phase of a solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separating the UF ₅ and molybdenum fluoride.

According to this approach, the liquid phase or supercritical fluid phase of the solution is preferably removed by evaporation to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride.

As indicated generally by reference to molybdenum fluoride, the solid phase may comprise MoF ₆ , which is prepared from a starting mixture of metal fluorides, or MoF ₅ , which may be prepared by reducing MoF ₆ before removing the liquid phase or supercritical fluid phase. In addition, if SO ₂ is contained in the liquid phase during the dissolution step, then MoF ₆ can be allowed to react with SO ₂ to form MoOF ₄ by keeping MoF ₆ in contact with SO ₂ for a sufficiently long period of time.

If the solid phase obtained during the separation step contains precipitated UF ₅ and MoF ₆ , then the UF ₅ and MoF ₆ can be separated by evaporation of the MoF ₆ , for example by keeping the solid phase at a temperature in the range of -20°C to 100°C WITH. If necessary, MoF ₆ can be recondensed separately from UF ₅ . Thus, this approach allows the recovery of UF ₅ and/or MoF ₆ .

Alternatively, as noted above, the separation step may comprise the step of reducing the MoF ₆ contained in the solution to produce a solution containing MoF ₅ before removing the liquid phase or supercritical fluid phase of the solution. The resulting solid phase obtained by removing the liquid phase or supercritical fluid phase of the solution contains precipitated UF ₅ and MoF ₅ . Conversion of MoF ₆ to MoF ₅ prior to separation of UF ₅ and molybdenum fluoride can remove the liquid phase or supercritical fluid phase without significant loss of molybdenum fluoride since the vapor pressure of MoF ₅ is less than the vapor pressure of MoF ₆ .

As noted above, as a further alternative in the case where SO ₂ is contained in the liquid phase during the dissolution step, MoF ₆ can be converted to MoOF ₄ by reaction with SO ₂ and separation of the dissolved MoOF ₄ from the solid UF ₅ can be accomplished by filtration solution of SO ₂ containing dissolved MoOF ₄ from solid UF ₅ .

According to yet another alternative, a solid mixture of UF ₅ and MoOF ₄ can be obtained, and the MoOF ₄ can be removed by sublimation. Sublimation is carried out preferably between 60 and 160°C, more preferably between 70 and 120°C, most preferably at 90°C.

As described above, the reduction of MoF ₆ to MoF ₅ can be carried out, for example, by photoreduction, ie, by irradiating a solution containing MoF ₆ with light of a suitable wavelength. For example, photoreduction occurs effectively by irradiation with light having a wavelength of 270 nm or less, preferably from 230 to 260 nm.

The precipitated UF ₅ and MoF ₅ contained in the solid phase, which can be obtained in accordance with option (ii) of the separation step, can be effectively separated by sublimation of MoF ₅ , which can be carried out by precipitation of MoF ₅ separately from UF ₅ . In this way, UF ₅ and/or MoF ₅ can be recovered. This process is carried out preferably between 60 and 160°C, more preferably between 70 and 120°C, most preferably at 90°C.

According to a related approach that includes option (ii) of the separation step, UF ₆ and MoF ₆ can be reduced in the deposition step together by photoreduction to UF ₅ and MoF ₅ . In a subsequent separation step, the liquid phase or supercritical fluid phase of the solution can be removed in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and MoF ₅ , and UF ₅ and MoF ₅ can be separated by sublimation of MoF ₅ and its precipitation separately from UF ₅ .

Regardless of whether the separation step is based on option (i) or option (ii), it allows molybdenum to be recovered, for example, in the form of MoF ₆ , MoF ₅ , MoOF ₄ , or in the form of the compound to which molybdenum fluoride has been converted, for example, in the form of molybdate.

Likewise, the separation step allows UF ₅ to be recovered. The recovered UF ₅ can be reduced to uranium metal. It can also be reconverted to UF ₆ through a fluorination reaction, allowing the uranium-235 content to be adjusted using known isotope separation techniques. The fluoride can then be reduced to elemental uranium.

The following paragraphs provide a summary of important embodiments of the process according to the first aspect of the invention.

1. Process containing

a step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides;

a dissolution step, which comprises dissolving MoF ₆ and UF ₆ in a liquid phase or a supercritical fluid phase to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form;

a precipitation step, which comprises a step of reducing the UF ₆ contained in the solution to UF ₅ and allowing it to precipitate out of the solution; And

separation stage, which contains

(i) a step of separating the precipitated UF ₅ from the solution; or

(ii) a step of removing a liquid phase or a supercritical fluid phase of a solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separating UF ₅ and molybdenum fluoride or a conversion product thereof, which can be obtained by further conversion of molybdenum fluoride into another molybdenum compound.

2. The process according to paragraph 1, in which the molar ratio of MoF ₆ to UF ₆ in the initial mixture of metal fluorides varies from 1:400 to 100:1, more preferably from 1:5 to 10:1.

3. The process of claim 1 or 2, wherein the mixture containing MoF ₆ and UF ₆ which is provided as the starting mixture of metal fluorides is a gas phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form.

4. The process according to paragraph 3, in which the gas-phase mixture containing MoF ₆ and UF ₆ additionally contains a carrier gas.

5. The process of claim 4, wherein the carrier gas is a noble gas and preferably is argon.

6. The process according to any one of paragraphs 3-5, which further comprises a step in which the gas-phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which the MoF ₆ and UF ₆ contained in the gas phase are deposited as a mixture, containing MoF ₆ and UF ₆ ,

this mixture is extracted, and

then subjected, optionally after re-evaporation to provide a gas-phase mixture containing MoF ₆ and UF ₆ in gaseous form, to a dissolution step.

7. The process of any one of claims 3 to 6, wherein MoF ₆ and UF ₆ are dissolved in a dissolution step by introducing a gas phase mixture containing MoF ₆ and UF ₆ into a liquid phase or supercritical fluid phase.

8. The process according to any one of claims 3-7, which further comprises, before the dissolution step, a step in which the gas-phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which part of the UF ₆ contained in the gas phase is deposited and is removed from the gas phase.

9. The process according to claim 8, in which the step in which the gas-phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which part of the UF ₆ contained in the gas phase is deposited and removed from the gas phase is carried out many times, preferably two or three times.

10. The process of any one of claims 3 to 9, which comprises the step of cooling the gas-phase mixture containing MoF ₆ and UF ₆ to a temperature at which a portion of the UF ₆ contained in the gas phase is precipitated and removed from the gas phase, and wherein this temperature is -10°C or less, preferably -50°C or less, more preferably -70°C or less.

11. The process according to item 10, in which the gas-phase mixture is cooled in a cold trap.

12. The process of claim 10, in which the gas-phase mixture is cooled in multiple cold traps that operate in series, at the same temperature or at decreasing temperatures.

13. The process of any one of claims 1 to 12, wherein MoF ₆ and UF ₆ are dissolved in a dissolution step in a liquid phase or supercritical fluid phase that contains a fluorine atom scavenger.

14. The process of any one of claims 1 to 13, wherein MoF ₆ and UF ₆ are dissolved in a liquid phase or supercritical fluid phase that contains a solvent that functions as a scavenger for fluorine atoms.

15. The process of any one of claims 1 to 14, wherein MoF ₆ and UF ₆ are dissolved in a dissolution step in a liquid phase that contains or consists of liquid SO ₂ as a solvent, or in a supercritical fluid phase that contains or consists of CO in a supercritical state.

16. The process according to claim 15, in which MoF ₆ and UF ₆ are dissolved in a dissolution step in a liquid phase that contains or consists of liquid SO ₂ .

17. The process of any one of claims 1 to 16, wherein the UF ₆ is reduced to UF ₅ in a deposition step by photoreduction.

18. The process according to claim 17, in which the photoreduction is carried out by irradiating the dissolved UF ₆ with light with a wavelength of 340 to 410 nm, preferably 395 nm.

19. The process of any one of claims 1-18, wherein the separation step comprises separating the precipitated UF ₅ from the solution.

20. The process of claim 19, wherein the separation step further comprises removing the MoF ₆ from the solution after separating the precipitated UF ₅ from the solution.

21. The process of claim 19, wherein the separating step further comprises steps in which

converting the MoF ₆ contained in the solution into another molybdenum compound before or after separating the precipitated UF ₅ from the solution, and

the molybdenum compound is removed from the solution after separating the precipitated UF ₅ from the solution.

22. The process of claim 19, wherein the separation step comprises separating the precipitated UF ₅ from a solution containing MoF ₆ dissolved in a liquid phase or a supercritical fluid phase by evaporating the solution containing MoF ₆ , followed by recovery of the MoF ₆ .

23. The process of claim 22, wherein the separation step comprises separating the precipitated UF ₅ from a solution containing MoF ₆ dissolved in the liquid phase by evaporating the solution containing MoF ₆ , and recovering the MoF ₆ by recondensing the solution containing MoF ₆ , separate from precipitated UF ₅ .

24. The process of claim 19, wherein the separation step comprises separating the precipitated UF ₅ from the MoF ₆ -containing solution by draining or filtering the solution to obtain a MoF ₆ -containing solution.

25. The process according to paragraph 23 or 24, in which the separation step further comprises a step in which the solution containing MoF ₆ obtained after separation of the precipitated UF ₅ is treated with OH ^- ions to obtain molybdate.

26. The process according to paragraph 25, in which the molybdate is recovered from solution.

27. The process of claim 19, wherein the separation step comprises reducing the MoF ₆ contained in the solution to produce a solution containing MoF ₅ before or after separating the precipitated UF ₅ from the solution.

28. The process according to paragraph 27, in which the reduction of MoF ₆ in solution is carried out by photoreduction.

29. The process of claim 28, wherein the photoreduction is carried out by irradiating MoF ₆ in dissolved form with light having a wavelength of 270 nm or less.

30. The process of any one of claims 27-29, wherein the separation step comprises separating the UF ₅ from the solution by draining or filtering the solution.

31. The process of any one of claims 27-30, wherein the separation step comprises removing MoF ₅ from solution by evaporating the solvent after separating the precipitated UF ₅ from the solution.

32. The process of any one of claims 1 to 18, wherein the separation step comprises (ii) a step of removing a liquid phase or a supercritical fluid phase of a solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separate UF ₅ and molybdenum fluoride.

33. The process of claim 32, wherein the liquid phase or supercritical fluid phase of the solution is removed by evaporation.

34. The process of claim 32 or 33, wherein the solid phase contains precipitated UF ₅ and MoF ₆ , and wherein the UF ₅ and MoF ₆ are separated by evaporating the MoF ₆ .

35. The process of claim 32 or 33, wherein the separation step comprises reducing the MoF ₆ contained in the solution to produce a solution containing MoF ₅ before removing the liquid phase or supercritical fluid phase of the solution, and wherein the solid phase, obtained by removing the liquid phase or supercritical fluid phase of the solution, contains precipitated UF ₅ and MoF ₅ .

36. The process according to item 35, in which the reduction of MoF ₆ in solution is carried out by photoreduction.

37. The process of claim 36, wherein photoreduction is carried out by irradiating MoF ₆ in dissolved form with light having a wavelength of 270 nm or less.

38. The process of any one of paragraphs 35-37, in which the precipitated UF ₅ and MoF ₅ are separated by sublimating the MoF ₅ and precipitating it separately from the UF ₅ .

39. The process according to any of paragraphs 1-16, in which

MoF ₆ and UF ₆ are reduced in the deposition step together by photoreduction to UF ₅ and MoF ₅ .

wherein the separation step comprises removing a liquid phase or a supercritical fluid phase of a solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and MoF ₅ , and

in which UF ₅ and MoF ₅ are separated by sublimating MoF ₅ and precipitating it separately from UF ₅ .

40. The process of claim 16, wherein MoF ₆ is allowed to react with SO ₂ to form MoOF ₄ , and separation of dissolved MoOF ₄ from solid UF ₅ is accomplished by filtering a solution of SO ₂ containing dissolved MoOF ₄ from solid UF ₅ , or by sublimation of MoOF ₄ from a solid mixture of UF ₅ and MoOF ₄ .

41. The process according to any one of paragraphs 1-40, in which the MoF ₆ contained in the initial mixture of metal fluorides contains the isotope molybdenum-99.

42. The process according to any of paragraphs 1-41, in which the UF ₆ contained in the initial mixture of metal fluorides is enriched in uranium-235.

43. The process of any one of paragraphs 1-42, which further comprises the step of recovering the precipitated UF ₅ .

44. The process of any one of claims 1 to 43, wherein the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides comprises the step of reacting a solid material that contains elemental uranium and elemental molybdenum, with fluorine radicals, and wherein the reaction comprises exposing the solid material to a gas stream containing fluorine radicals to produce a mixture containing MoF ₆ and UF ₆ .

45. The process of claim 44, wherein the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides comprises the step of irradiating a solid material that contains elemental uranium enriched in the isotope uranium-235 , neutrons to produce a solid material containing elemental uranium and elemental molybdenum, and in which the elemental molybdenum contains the isotope molybdenum-99.

46. The process of claim 44 or 45, wherein the solid material containing elemental uranium and elemental molybdenum contains molybdenum in a weight ratio ranging from 0.02 to 1.0 wt. %, more preferably from 0.05 to 0.2 wt. %, based on the total weight of uranium and molybdenum as 100 wt. %.

47. The process of claim 44, wherein the solid material that contains elemental uranium and elemental molybdenum is a mixture of uranium enriched in the isotope uranium-235 and molybdenum.

48. The process of claim 47, wherein the solid material containing elemental uranium and elemental molybdenum contains molybdenum in a weight ratio ranging from 5 to 12 weight. %, preferably from 7 to 10 wt. %, based on the total weight of uranium and molybdenum as 100 wt. %.

49. The process of any one of claims 44 to 48, wherein the step of providing a mixture containing MoF ₆ and UF ₆ as a metal fluoride feed mixture comprises the step of generating fluorine radicals from the fluorine-containing feed compound in the plasma source, more preferably at a remote plasma source.

50. The process of claim 49, wherein the fluorine-containing starting compound is selected from F ₂ and NF ₃ , and is more preferably NF ₃ .

51. The process of any one of claims 44-50, wherein the gas stream further comprises a carrier gas.

52. The process according to any one of paragraphs 44-51, in which the mixture containing MoF ₆ and UF ₆ , which is provided as the starting mixture of metal fluorides, is a gas-phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form.

53. The process according to any one of paragraphs 44-52, in which the reaction of the solid material with fluorine radicals is carried out under pressure in the range from 10 Pa to 3000 Pa.

54. The process of any one of claims 45-53, wherein the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides comprises, before reacting the solid material with fluorine radicals, the step of irradiating the solid material that contains elemental uranium enriched in the isotope uranium-235 with neutrons and reacting the irradiated solid material with hydrogen radicals to produce a solid material containing UH ₃ ; and reconvert UH ₃ to elemental U by exposing it to elevated temperature.

55. The process of claim 54, wherein hydrogen radicals are generated from a hydrogen-containing starting compound in a plasma source, more preferably in a remote plasma source.

The process according to the preferred second aspect of the invention set forth above will be described below. Similar to the process of the preferred first aspect, this process can be suitably used, for example, to produce molybdenum or a molybdenum compound, in particular to produce molybdenum or a molybdenum compound containing the isotope molybdenum-99. Alternatively or additionally, it can be used to produce uranium or a uranium compound, in particular to produce uranium or a uranium compound enriched in uranium-235.

The process according to the second aspect includes the step of providing a gas phase mixture containing MoF ₆ , UF ₆ and a fluorine atom scavenger mixed in gaseous form (ie, all three components are in gaseous form). Preferably, the gas phase mixture consists of MoF ₆ , UF ₆ , and a scavenger of fluorine atoms mixed in gaseous form.

This process can be applied to mixtures containing molar ratios of MoF ₆ and UF ₆ varying over wide ranges, for example, from 1:400 to 100:1. Preferably, the molar ratios are in the range from 1:5 to 10:1.

As will be clear from the above, the uranium contained in UF ₆ may be uranium enriched in uranium-235. The molybdenum contained in MoF ₆ may contain molybdenum-99.

The step of providing a mixture containing MoF ₆ and UF ₆ preferably comprises a step of reacting a solid material that contains elemental uranium and elemental molybdenum with fluorine radicals to produce a mixture containing MoF ₆ and UF ₆ . This reaction comprises the step of exposing the solid material to a gas stream containing fluorine radicals.

Also, the uranium contained in the solid material may be uranium enriched in uranium-235. Molybdenum contained in the solid material may contain molybdenum-99.

The weight ratio of elemental uranium and elemental molybdenum in the solid material is not particularly limited in connection with the separation of these two elements through their fluorides. Typical molybdenum content ranges from 0.01 to 12 wt. %, based on the total weight of uranium and molybdenum as 100 wt. %.

In the case of a solid material containing the isotope molybdenum-99, which reacts with fluorine radicals, the preferred elemental molybdenum content is in the range of 0.02 to 1.0 wt. %, more preferably from 0.05 to 0.2 wt. %, based on the total weight of elemental uranium and elemental molybdenum as 100 wt. %.

In the case of a solid material containing uranium and molybdenum, which can be used in the preparation of U-Mo fuel and which can also react with fluorine radicals to obtain a mixture containing MoF ₆ and UF ₆ , the preferred elemental molybdenum content is in the range of 5 to 12 wt. %, more preferably from 7 to 10 wt. %, based on the total weight of elemental uranium and elemental molybdenum as 100 wt. %.

In addition to U and Mo, the solid material that reacts with fluorine radicals may contain other components including other metals, or it may be free of metals other than uranium and molybdenum. For example, aluminum may be present as a matrix material in combination with uranium in uranium targets that are irradiated with neutrons to convert the uranium to molybdenum-99.

The total content of elemental uranium and elemental molybdenum in the solid material that reacts with fluorine radicals is preferably in the range of 30-100 wt. %, more preferably 50-100 wt. %. In this context, the weight percentage is based on the total weight of the material that contains uranium and molybdenum, as 100%, not including the weight of any coating that may be applied to the material that contains uranium and molybdenum. As will be appreciated by those skilled in the art, the material which contains uranium and molybdenum and which is also referred to as "meat" may be provided as a dispersed phase in which the uranium and molybdenum are dispersed in a matrix material such as aluminum, or as a homogeneous or monolithic phase.

In the case of a solid material containing the isotope molybdenum-99, which reacts with fluorine radicals, the preferred total content of elemental uranium and elemental molybdenum is in the range of 30-100 wt. %, more preferably 50-100 wt. %, based on the total mass of meat, excluding any casing.

In the case of a solid material containing uranium and molybdenum, which is used in the preparation of U-Mo fuel and which can also react with fluorine radicals to obtain a mixture containing MoF ₆ and UF ₆ , the preferred total content of elemental uranium and elemental molybdenum is also found in the range of 30-100 wt. %, more preferably 50-100 wt. %, based on the total mass of meat, excluding any casing.

In a solid material containing elemental uranium and elemental molybdenum, these two elements may be combined, for example, in the form of a mixture or in the form of an alloy. Since, as noted above, additional components other than uranium and molybdenum may be present in the solid material, it is also possible for uranium, molybdenum, or both to form an alloy with one or more such other components. It should be noted that reference here to an alloy includes intermetallic phases, in the sense that such a phase is formed by the components of the alloy in question. Reference to an alloy also includes an alloy formed from one or more metals, such as uranium, and one or more semi-metals, such as silicon. As a preferred example of a solid material containing elemental uranium and elemental molybdenum, reference may further be made to a solid material containing uranium or a uranium alloy (for example, uranium silicide), in which molybdenum has been formed by neutron irradiation and dispersed in the uranium or uranium alloy .

The form in which the solid material reacts with fluorine radicals is not particularly limited. The solid material may have a compact shape, for example a regular compact shape such as a plate, cylinder or sphere. The solid material may also react with fluoride radicals in powder form. For example, in some applications, uranium and molybdenum may be encapsulated with another metal or dispersed in a matrix of another metal, so it may be useful to subject such encapsulated or dispersed starting material to mechanical disintegration to provide a powder that can be advantageously used as a solid material for the reaction with fluorine radicals.

The solid material that reacts with fluorine radicals, as a preferred embodiment of the process according to the second aspect of the invention, can be provided, for example, by irradiating the solid material that contains elemental uranium enriched in the isotope uranium-235 with neutrons. This provides a solid material containing elemental uranium and elemental molybdenum, in which the elemental molybdenum contains the isotope molybdenum-99. In other words, the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides may comprise the step of irradiating a solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons to produce a solid a material containing elemental uranium and elemental molybdenum, and in which the elemental molybdenum contains the isotope molybdenum-99. In this regard, established procedures for the formation of molybdenum-99 by fission of uranium-235 through neutron irradiation can be relied upon.

Alternatively, the solid material that reacts with fluorine radicals, as a preferred embodiment of the process according to the second aspect of the invention, can be provided by preparing an alloy containing elemental uranium enriched in the isotope uranium-235 and non-radioactive molybdenum. In this way, a solid material is obtained containing elemental uranium enriched in uranium-235 and molybdenum, which can be used, for example, as U-Mo fuel.

As mentioned above, uranium enriched in the uranium-235 isotope typically contains up to 50 weight percent uranium-235. % (based on the total weight of uranium as 100 wt.%).

The step of providing a gas phase mixture containing MoF ₆ and UF ₆ may further comprise, before reacting the solid material with fluorine radicals, reacting the solid material with hydrogen radicals to produce a solid material containing UH ₃ ; and reconverting the UH ₃ to elemental uranium by exposing the UH ₃ to elevated temperature. This reaction with hydrogen radicals may be particularly advantageous for a solid material produced by irradiating a solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons.

If, according to the preferred embodiment described above, a solid material containing elemental uranium and elemental molybdenum is produced by irradiating a solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons, the solid material may be reacted with hydrogen radicals for complete or partial conversion of uranium into UH ₃ . Accordingly, the reaction with hydrogen radicals can be carried out before the reaction with fluorine radicals. Molybdenum contained in solid material does not react with hydrogen. Such pre-reaction with hydrogen radicals to form UH ₃ may be useful, for example, to completely or partially disintegrate the metal matrix of a solid material containing uranium which has been irradiated with neutrons, whereby gaseous by-products, in particular Kr and Xe, may be formed during irradiation. Such gaseous by-products can be conveniently isolated and removed after conversion to UH ₃ . Also, before the solid material reacts with fluorine radicals, UH ₃ can be reconverted into elemental uranium. This can be accomplished, for example, by exposing the UH ₃ to elevated temperature, usually in a vacuum or in an inert atmosphere. This temperature is preferably in the range from 250°C to 500°C, more preferably 350°C.

Before subjecting a solid material that contains elemental uranium and elemental molybdenum to reaction with fluorine radicals, its surface may, if necessary, be cleaned, for example, to remove metal oxides. This can be done, for example, using an inorganic acid such as nitric acid.

Fluorine radicals that react with a solid material containing elemental uranium and elemental molybdenum according to the above embodiment are preferably generated from a fluorine-containing starting compound in a plasma source, more specifically, in a remote plasma source. Thus, the step of providing a gas phase mixture containing MoF ₆ and UF ₆ preferably comprises a step of generating fluorine radicals in a plasma source, more preferably in a remote plasma source.

In a plasma source, fluorine radicals are generated by applying energy to a fluorine-containing parent compound so as to dissociate the bond formed with a fluorine atom in the parent compound. Fluorine-containing starting compounds are usually gaseous compounds. Known starting compounds that may also be used in the context of the present invention include, for example, any of F ₂ , NF ₃ , SF ₆ and CF ₄ . Among them, F ₂ and NF ₃ are preferred, and NF ₃ is particularly preferred due to its less corrosiveness and its less toxicity compared to F ₂ .

In a plasma source, the plasma can be generated, for example, using microwave radiation. Commercially available plasma sources can be used for this purpose. The radiation frequency can be suitably adjusted, for example, depending on the fluorine-containing starting compound used, to achieve a high degree of dissociation.

The preferred use of a remote plasma source allows the reaction between the fluorine radicals and the solid material containing elemental uranium and elemental molybdenum to occur at a location that is remote from the actual plasma source. This makes it easier to control the reaction.

As noted above, reacting a solid material with fluorine radicals comprises exposing the solid material to a gas stream that contains fluorine radicals. The gas stream may further comprise a carrier gas. Typically, the carrier gas is a noble gas such as argon.

Typically, a gas stream that contains fluorine radicals is provided by directing a gas stream containing a gaseous fluorine-containing feed compound and preferably a carrier gas such as argon to a plasma source, preferably a remote plasma source. The solid material containing elemental uranium and elemental molybdenum can then be exposed to a gas stream containing fluorine radicals generated by the plasma source, and preferably containing a carrier gas. It should be understood that the gas stream into which the solid material is exposed may also contain residual feed compound.

Thus, the composition of the gas stream can be conveniently controlled by controlling the mass flow rate of the fluorine-containing feed compound and optional carrier gas in the plasma source. Typically, volume ratios of fluorine-containing feed compound and optional carrier gas are adjusted in the range of 10:1 to 1:10, preferably 2:1 to 1:2, more preferably 1:1.

For example, the mass flow rate of the fluorine-containing feed compound in the plasma source can be adjusted to values in the range of 10 to 50 cc. cm per minute, preferably from 15 to 35 cc. cm per minute The flow rate of the optional carrier gas may be adjusted accordingly based on the aforementioned typical/preferred volumetric ratios. As will be appreciated by those skilled in the art, standardized volumes are based on a temperature of 0° C. and a pressure of 1013.25 hPa.

If a carrier gas, in particular a noble gas such as argon, is present in the gas stream, it is preferable to generate fluorine radicals in a plasma that burns in the immediate vicinity of the substrate and thereby facilitates the reaction of the metals with the fluorine atoms.

The plasma may be ignited and maintained by generally known methods, such as direct current (DC), high frequency (HF), or microwave methods, or a combination of any of these methods. When a suitable potential of the substrate relative to the plasma is provided, and a floating potential is further applied to the solid material to be reacted with fluorine radicals, the plasma particles are accelerated towards the surface of the solid material. Thus, electrons allow for localized and targeted heating of the solid material, while ion bombardment results in the ejection of atoms of the solid material, which can further enhance the reaction with fluorine radicals.

As will be appreciated by those skilled in the art, fluorine radicals are typically provided and the reaction of the solid material with the fluorine radicals is typically carried out in a reaction system that can be subjected to a vacuum and is suitable for introducing a controlled gas stream at pressures below atmospheric pressure. An exemplary diagram of a suitable reaction system is shown schematically in FIG. 1.

The pressure within the reaction system in which the solid material reacts with the fluorine radicals can be controlled by a selected mass flow rate of gases, preferably gases consisting of a fluorine-containing feed compound and optionally a carrier gas such as argon.

Typically, the pressure inside the reactor in which the solid material that contains elemental uranium and elemental molybdenum reacts with fluorine radicals is in the range of 10 Pa to 3000 Pa, preferably in the range of 10 Pa to 2000 Pa.

The reaction of the solid material, which contains elemental uranium and elemental molybdenum, with fluorine radicals occurs without the need to heat the solid material. However, due to the exothermic nature of the reaction, heat can be generated and can be controlled, for example, by adjusting the gas flow rate and/or the concentration of fluorine radicals contained therein.

Those skilled in the art will also appreciate that the reaction chamber in which the solid material is provided to react with fluorine radicals must be inert to fluorine radicals. For example, the reaction chamber may have a passivated nickel or monel metal surface. Due to the high reactivity of fluorine radicals, the distance between the plasma source and the solid material in the reactor must be kept short even when using a remote plasma source. By this means, the loss of fluorine radicals due to bulk and surface recombination can be minimized.

If the step of providing a gas phase mixture containing MoF ₆ and UF ₆ involves reacting the solid material with hydrogen radicals to produce a solid material containing UH ₃ and reconverting to elemental uranium, then this reaction/reconversion may be carried out as preliminary reaction in the same reaction system in which the reaction with fluorine radicals can be carried out in a subsequent step. In particular, the solid material may be exposed to a gas stream containing hydrogen radicals and, optionally, a carrier gas. Hydrogen radicals are preferably generated in the plasma source, more preferably in a remote plasma source as described above. Hydrogen radicals can be generated from a hydrogen-containing parent compound in the plasma source. The hydrogen-containing starting compound may be, for example, H ₂ .

According to the above preferred approach, a gas phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form can be conveniently provided. This gas-phase mixture may additionally contain a carrier gas. Typically, the carrier gas, if present, is a noble gas such as argon. For example, when a mixture containing MoF ₆ and UF ₆ is provided by exposing a solid material containing uranium and molybdenum to a gas stream containing fluorine radicals, the gas stream can be conveniently used after contact with the solid material to transport MoF ₆ and UF ₆ into as gaseous reaction products from the reaction chamber. Due to the relatively low boiling point or sublimation point of MoF ₆ and UF ₆ , respectively, the gas-phase mixture containing MoF ₆ and UF ₆ is provided at moderate temperatures, so that no special measures need to be taken to ensure that the fluorides pass into the gas phase.

In particular, the volatility of MoF ₆ and UF ₆ is higher than that of many other metal fluorides. Thus, the gas phase mixture containing MoF ₆ and UF ₆ can also be conveniently separated from other metal fluorides that may be formed during the reaction of solid material containing uranium and molybdenum with fluorine radicals. As described above, the solid material can be provided, for example, by irradiating the solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons. During the fission process initiated by irradiation, other metals can be formed as by-products. In addition, uranium targets may contain aluminum.

To provide a gas phase mixture containing MoF ₆ , UF ₆ and a fluorine atom scavenger, the mixture of MoF ₆ and UF ₆ is typically subsequently combined and mixed with the fluorine atom scavenger. If the mixture of MoF ₆ and UF ₆ that is formed initially contains a carrier gas, then the MoF ₆ and UF ₆ can be separated from the carrier gas before mixing them with the fluorine atom scavenger.

In view of the above, it should be understood that the process according to the second aspect of the invention preferably comprises:

a step of providing a gas phase mixture containing MoF ₆ and UF ₆ and a fluorine atom scavenger mixed in gaseous form, the step comprising steps of

form fluorine radicals in the plasma source, preferably in a remote plasma source,

reacting a solid material containing elemental uranium and elemental molybdenum with fluorine radicals, the reaction comprising the step of exposing the solid material to a gas stream containing fluorine radicals to produce a gas-phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form, which is subsequently combined and mixed with a scavenger of fluorine atoms;

a step of irradiating UF ₆ in a gas-phase mixture in the presence of a fluorine atom absorber with light having a wavelength in the range from 340 to 410 nm to reduce UF ₆ to UF ₅ and to obtain a mixture containing UF ₅ and MoF ₆ ; And

the stage at which UF ₅ and MoF ₆ are separated.

The scavenger for fluorine atoms in gaseous form is preferably selected from CO, H ₂ , Xe and SO ₂ . More preferred are CO or H ₂ . The fluorine atom scavenger may be a single substance or a combination of two or more substances, and is preferably a single substance.

In a gas-phase mixture containing MoF ₆ , UF ₆ and a fluorine atom scavenger mixed in gaseous form, the fluorine atom scavenger is usually added in molar excess relative to UF ₆ , preferably in a molar amount that is 1.5 times or more the molar amount of UF ₆ . If necessary, irradiation and reduction of UF ₆ can be carried out many times, ie, two or more times to ensure quantitative conversion of UF ₆ to UF ₅ , and a fluorine scavenger can be added to the mixture before each repetition of irradiation and reduction. However, it is preferred that the process comprise a single step in which the UF ₆ is irradiated and reduced in the presence of a sufficient amount of fluorine atom scavenger.

The light used to irradiate the UF ₆ in the gas phase mixture has a wavelength in the range of 340 to 410 nm, preferably a wavelength in the range of 380 to 400 nm, and most preferably a wavelength of 395 nm. In this wavelength range, UF ₆ is efficiently converted to UF ₅ while MoF ₆ contained in solution does not show any significant absorption and remains unaffected by light.

After conversion of UF ₆ to UF ₅ , the reaction product of the fluorine and fluorine scavenger formed by the reduction of UF ₆ to UF ₅ in the gas phase mixture, and optionally the remaining fluorine scavenger, is preferably removed from the resulting mixture of UF ₅ and MoF ₆ . For example, this may conveniently be accomplished by cooling a reaction mixture containing UF ₅ , MoF ₆ , the reaction product of the fluorine scavenger and fluorine formed by the reduction of UF ₆ to UF ₅ in the gas phase mixture, and optionally the remaining fluorine scavenger to a temperature in which UF ₅ takes a solid form, MoF ₆ takes a liquid or solid form, and the reaction product of the scavenger of fluorine atoms and fluorine formed by the reduction of UF ₆ to UF ₅ can be removed, for example by pumping, in the gas phase.

The MoF ₆ and UF ₅ produced by the second aspect of the invention can be conveniently separated, for example by distilling the MoF ₆ , since MoF ₆ is a highly volatile substance while UF ₅ is not. The preferred temperature range for distillation of MoF ₆ is from 25 to 100°C. It should be understood that MoF ₆ is typically recondensed so that both UF ₅ and MoF ₆ can be recovered separately.

The following paragraphs provide the essence of important embodiments of the process according to the second aspect of the invention.

1B. Process containing

a step of providing a gas-phase mixture containing MoF ₆ , UF ₆ and a fluorine atom scavenger mixed in gaseous form;

a step of irradiating UF ₆ in a gas-phase mixture in the presence of a fluorine atom absorber with light having a wavelength in the range from 340 to 410 nm to reduce UF ₆ to UF ₅ and to obtain a mixture containing UF ₅ and MoF ₆ ; And

the stage at which UF ₅ and MoF ₆ are separated.

2B. The process of item 1B, in which the scavenger of fluorine atoms in the gas phase is selected from CO, H ₂ , Xe and SO ₂ .

3B. The process of item 1B or 2B, in which the fluorine atom scavenger is added to the gas-phase mixture in a molar amount that is at least 1.5 times the molar amount of UF ₆ contained in the gas-phase mixture.

4B. The process of any one of items 1B to 3B, wherein the light used for irradiation has a wavelength of 380 to 400 nm, more preferably 395 nm.

5V. The process according to any one of paragraphs 1B-4B, which further comprises the step of removing the reaction product of the scavenger of fluorine atoms and fluorine formed by the reduction of UF ₆ to UF ₅ .

6B. The process of any one of items 1B to 5B, wherein the MoF ₆ and UF ₅ produced in the process are separated by distillation of the MoF ₆ .

7B. The process according to any one of items 1B to 6B, wherein the molar ratio of MoF ₆ to UF ₆ in the gas phase mixture varies from 1:400 to 100:1, more preferably from 1:5 to 10:1.

8B. The process of any one of claims 1B to 7B, wherein the MoF ₆ contained in the gas phase mixture contains the isotope molybdenum-99.

9B. The process according to any one of paragraphs 1B-8B, in which the UF ₆ contained in the gas-phase mixture is enriched in uranium-235.

10V. The process of any one of claims 1B to 9B, wherein the step of providing a gas-phase mixture containing MoF ₆ , UF ₆ and a fluorine atom scavenger comprises the step of reacting a solid material that contains elemental uranium and elemental molybdenum with radicals fluorine, and wherein the reaction comprises exposing the solid material to a gas stream containing fluorine radicals to produce a mixture containing MoF ₆ and UF ₆ .

11B. The process of claim 10B, wherein the step of providing a gas-phase mixture containing MoF ₆ , UF ₆ and a fluorine atom absorber comprises the step of irradiating a solid material that contains elemental uranium enriched in the isotope uranium-235 with neutrons to produce a solid material containing elemental uranium and elemental molybdenum, and in which the elemental molybdenum contains the isotope molybdenum-99.

12V. The process of claim 10B or 11B, wherein the solid material containing elemental uranium and elemental molybdenum contains molybdenum in a weight ratio ranging from 0.02 to 1.0 wt. %, more preferably from 0.05 to 0.2 wt. %, based on the total weight of uranium and molybdenum as 100 wt. %.

13V. The process of claim 10B, wherein the solid material that contains elemental uranium and elemental molybdenum is a mixture of uranium enriched in the isotope uranium-235 and molybdenum.

14V. The process of claim 13B, wherein the solid material containing elemental uranium and elemental molybdenum contains molybdenum in a weight ratio ranging from 5 to 12 weight. %, preferably from 7 to 10 wt. %, based on the total weight of uranium and molybdenum as 100 wt. %.

15V. The process of any one of claims 10B to 14B, wherein the step of providing a mixture containing MoF ₆ and UF ₆ as a metal fluoride feed mixture comprises the step of generating fluorine radicals from the fluorine-containing feed compound in the plasma source, more preferably in a remote plasma source.

16V. The process of item 15B, wherein the fluorine-containing starting compound is selected from F ₂ and NF ₃ , and is more preferably NF ₃ .

17V. The process of any one of claims 10B-16B, wherein the gas stream further comprises a carrier gas.

18V. The process according to any one of paragraphs 10B-17B, in which the reaction of the solid material with fluorine radicals is carried out under a pressure in the range of 10 Pa to 3000 Pa.

19V. The process of any one of claims 11B-18B, wherein the step of providing a gas-phase mixture containing MoF ₆ , UF ₆ and a fluorine atom scavenger comprises the step of irradiating the solid material that contains elemental uranium enriched in the uranium-235 isotope with neutrons and reacting the irradiated solid material with hydrogen radicals to produce a solid material containing UH ₃ ; and reconvert UH ₃ to elemental U by exposing it to elevated temperature.

20V. The process of claim 19B, wherein hydrogen radicals are generated from a hydrogen-containing starting compound in a plasma source, more preferably in a remote plasma source.

As noted above, the invention further relates to a process for providing metal fluoride, said process for producing metal fluoride comprising the steps of:

forming fluorine radicals from a fluorine-containing starting compound using a plasma source;

reacting fluorine radicals with a solid material containing an elemental metal to produce a metal fluoride or with a solid material containing an elemental semimetal to produce a semimetal fluoride; And

recovering metal fluoride or semi-metal fluoride;

wherein the metal is selected from molybdenum, technetium, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, gold and uranium, and the semi-metal is tellurium.

The solid material to be reacted with fluorine radicals contains a metal selected from molybdenum, technetium, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, gold and uranium, or tellurium as a semi-metal.

A solid material containing an elemental metal or semi-metal may contain one or more of the elements listed above. Additionally, one or more of the elements listed above may be combined in a solid material with another component, for example, an elemental metal or an elemental semi-metal not selected from molybdenum, technetium, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum , gold, uranium, and tellurium. For example, two elements may be combined in a solid material in the form of a mixture or in the form of an alloy. It should be noted that reference here to an alloy includes intermetallic phases, in the sense that such a phase is formed by the components of the alloy in question. Reference to an alloy also includes an alloy formed between one or more metals, such as uranium, and one or more semi-metals, such as silicon.

Preferably, the solid material contains a single elemental metal (i.e., only one elemental metal component is present), and this single metal is selected from molybdenum, technetium, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, gold and uranium. The solid material may also consist of a single elemental metal.

Preferably, the elemental metal is selected from molybdenum, ruthenium, rhodium, tungsten, rhenium, osmium, iridium, platinum and uranium.

The form in which the solid material reacts with fluorine radicals is not particularly limited. The solid material may have a compact shape, for example a regular compact shape such as a plate, cylinder or sphere. The solid material may also react with fluoride radicals in powder form.

Before subjecting a solid material to reaction with fluorine radicals, its surface may, if necessary, be cleaned, for example, to remove metal oxides. This can be done, for example, using an inorganic acid such as nitric acid. Possible oxide layers on platinum metals, tungsten or molybdenum can also be removed by exposing the material to hydrogen radicals before the fluorination process. Hydrogen radicals are generated from hydrogen gas using a plasma source, more preferably a remote plasma source.

Fluorine radicals that react with the solid material are generated from a fluorine-containing parent compound using a plasma source, more preferably a remote plasma source.

In a plasma source, fluorine radicals are generated by applying energy to a fluorine-containing parent compound so as to dissociate the bond formed with a fluorine atom in the parent compound. Fluorine-containing starting compounds are usually gaseous compounds. Known starting compounds that may also be used in the context of the metal fluoride production process of the present invention include, for example, any of F ₂ , NF ₃ , SF ₆ and CF ₄ . Among them, F ₂ and NF ₃ are preferred, and NF ₃ is particularly preferred due to its less corrosiveness and its less toxicity compared to F ₂ .

In a plasma source, the plasma can be generated, for example, using microwave radiation. Commercially available plasma sources can be used for this purpose. The radiation frequency can be suitably adjusted, for example depending on the starting compound used, to achieve a high degree of dissociation.

The preferred use of a remote plasma source allows the reaction between the fluorine radicals and the solid material containing the elemental metal to occur at a location that is remote from the actual plasma source. This makes it easier to control the reaction.

The reaction of fluorine radicals with a solid material containing an elemental metal typically comprises the step of exposing the solid material to a gas stream that contains fluorine radicals. The gas stream may further comprise a carrier gas. Typically, the carrier gas is a noble gas such as argon.

Typically, a gas stream that contains fluorine radicals is provided by directing a gas stream containing a gaseous fluorine-containing feed compound, and preferably a carrier gas such as argon, to a plasma source, preferably a remote plasma source. The solid material containing the elemental metal can then be exposed to a gas stream containing fluorine radicals generated by the plasma source, and preferably containing a carrier gas. It should be understood that the gas stream into which the solid material is exposed may also contain residual feed compound.

Thus, the composition of the gas stream can be conveniently controlled by controlling the mass flow rate of the fluorine-containing feed compound and optional carrier gas in the plasma source. Typically, volume ratios of fluorine-containing feed compound and optional carrier gas are adjusted in the range of 10:1 to 1:10.

For example, the mass flow rate of the fluorine-containing feed compound in the plasma source can be adjusted to values ranging from 1 to 100 cc. cm per minute The mass flow rate of the carrier gas, if available, is preferably in the range of 1 to 150 cc. cm per minute As will be appreciated by those skilled in the art, standardized volumes are based on a temperature of 0° C. and a pressure of 1013.25 hPa.

If a carrier gas, in particular a noble gas such as argon, is present in the gas stream, it is preferable to generate fluorine radicals in a plasma that burns in the immediate vicinity of the substrate and thereby facilitates the reaction of the metals with the fluorine atoms.

The plasma may be ignited and maintained by generally known methods, such as direct current (DC), high frequency (HF), or microwave methods, or a combination of any of these methods. When a suitable potential of the substrate relative to the plasma is provided, and a floating potential is further applied to the solid material to be reacted with fluorine radicals, the plasma particles are accelerated towards the surface of the solid material. Thus, electrons allow for localized and targeted heating of the solid material, while ion bombardment results in the ejection of atoms of the solid material, which can further enhance the reaction with fluorine radicals.

As will be appreciated by those skilled in the art, fluorine radicals are typically provided and the reaction of the solid material with the fluorine radicals is typically carried out in a reaction system that can be subjected to a vacuum and is suitable for introducing a controlled gas stream at pressures below atmospheric pressure. An exemplary diagram of a suitable reaction system is shown schematically in FIG. 1.

The pressure within the reaction system in which the solid material reacts with the fluorine radicals can be controlled by a selected mass flow rate of gases, preferably gases consisting of a fluorine-containing feed compound and optionally a carrier gas such as argon.

Typically, the pressure inside the reactor in which the solid material reacts with fluorine radicals is in the range of 10 Pa to 3000 Pa, preferably in the range of 10 Pa to 2000 Pa.

The reaction of the solid material with fluorine radicals can occur without the need to heat the solid material, but it is also possible, if necessary, to heat the solid material, for example, to speed up the reaction. Since the reaction with some metals can produce heat, it may be desirable to control the reaction, for example, by adjusting the gas flow rate and/or the concentration of fluorine radicals contained therein.

Those skilled in the art will also appreciate that the reaction chamber in which the solid material is provided to react with fluorine radicals must be inert to fluorine radicals. For example, the reaction chamber may have a passivated nickel or monel metal surface. Due to the high reactivity of fluorine radicals, the distance between the plasma source and the solid material in the reactor must be kept short even when using a remote plasma source. By this means, the loss of fluorine radicals due to bulk and surface recombination can be minimized.

The metal fluoride produced from this reaction can be recovered from the reactor after completion of the reaction. Depending on the vapor pressure of the metal fluoride, it is also possible to recover the metal fluoride from the gas phase. For example, when the reaction of fluorine radicals and a solid material is carried out by exposing the solid material to a gas stream containing fluorine radicals, the gas stream can conveniently be used after contact with the solid material to transport the metal fluoride as a reaction gas out of the reaction chamber. The metal fluoride may then be recovered from the gas phase, for example by cooling the gas phase to an appropriate temperature at which the metal fluoride precipitates.

The structure of the metal fluoride that is produced through this reaction depends on the type of metal that reacts with the fluorine radicals. As will be understood, when the solid material reacting with fluorine radicals contains molybdenum, the recovered metal fluoride contains molybdenum fluoride, i.e., for each of the elemental metals or elemental semi-metals selected from molybdenum, technetium, ruthenium, rhodium, palladium , tungsten, rhenium, osmium, iridium, platinum, gold, uranium, and tellurium present in the solid material, the corresponding metal or semi-metal fluoride will be formed by this reaction. The following table provides an overview of the metals and fluorides that can be produced by reacting them with fluorine radicals using the metal fluoride production process of the present invention.

Metal The resulting metal fluoride Mo MoF ₆ Te TeF ₆ Ru RuF ₅ , RuF ₆ Rh RhF ₃ , RhF ₆ Pd PDF ₆ W WF ₆ Re ReF ₆ , ReF ₇ Os OSF ₆ Ir IrF ₆ Pt PtF ₄ , PtF ₆ Au _AuF3 , _AuF5 U UF ₆

The following paragraphs provide the essence of important embodiments of the metal fluoride production process according to the present invention.

1C. A process for providing metal fluoride, said process comprising the steps of:

forming fluorine radicals from a fluorine-containing starting compound using a plasma source;

reacting fluorine radicals with a solid material containing an elemental metal to produce a metal fluoride or with a solid material containing an elemental semimetal to produce a metal fluoride or a semimetal fluoride; And

metal fluoride is recovered;

wherein the metal is selected from molybdenum, technetium, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, gold and uranium, and the semi-metal is tellurium.

2C. The process of claim 1C, wherein the solid material contains a single elemental metal, and wherein the metal is selected from molybdenum, technetium, ruthenium, rhodium, palladium, tungsten, rhenium, osmium, iridium, platinum, gold and uranium.

3C. The process of item 1C or 2C, in which the metal is selected from molybdenum, ruthenium, rhodium, tungsten, rhenium, osmium, iridium, platinum and uranium.

4C. The process of any one of paragraphs 1C-3C, in which the plasma source is a remote plasma source.

5C. The process of any one of claims 1C-4C, wherein the fluorine-containing starting compound is selected from NF ₃ , F ₂ , SF ₆ and CF ₄ .

6C. The process of 5C, wherein the fluorine-containing starting compound is NF ₃ .

7C. The process of any one of claims 1C to 6C, wherein the reaction of fluorine radicals with a solid material containing an elemental metal comprises exposing the solid material to a gas stream that contains fluorine radicals.

Fig. 1 shows a schematic diagram of an exemplary reaction system that can be used to react a solid material with fluorine radicals in the context of two aspects of the present invention. The gases provided are a fluorine-containing feed compound (1), hydrogen (optional, (2)), and a (noble) carrier gas (optional, (3)). The composition of the gas stream can be controlled by mass flow controllers (4), one each for argon (optional), hydrogen (optional), and fluorine-containing feed compound. The process gas reaches a remote plasma source (5) where fluorine radicals are generated. Optionally, hydrogen radicals may be generated prior to the reaction to hydrogenate a possible oxide layer on the platinum metals, molybdenum, or tungsten. Fluorination takes place in a reaction tube (7), which can be heated by an oven (6). The reaction product can be deposited in subsequent cold traps and can be removed through extraction ports located behind each cold trap. After the cold traps, two fluorine absorbers (8) can be located, which bind unconsumed reactive fluorine particles and thereby protect the pump unit (9).

EXAMPLES

Example 1 - preparation of a mixture of uranium fluoride and metal fluoride

a) Reaction system for the preparation of uranium and molybdenum fluorides

A mixture of UF ₆ and MoF ₆ was prepared using a reaction system which is schematically shown in the schematic diagram in FIG. 1.

This system (hereinafter called the fluoridation line) consists of the following subsystems: gas supply devices (1), (2), (3), (4), remote source (RPS, (5)) of plasma, reaction tube (6), ( 7), pipelines and cold traps, absorption system (8) and pumping station (9). Additionally, several peripheral devices provide process control. They include control units for mass flow controllers (MFC), a readout device for pressure sensors, a control unit for the oven, a power supply for the microwave device, as well as a PC, keyboard and screen, which are necessary for the operation of the control software funds for RPS. The system wiring is located in a separate control rack.

The use of three MFCs (4) allows the gas flow rate and thus the precise composition of the process gas to be controlled. The process gas is fed into the RPS (5), where fluorine, hydrogen and oxygen radicals are generated, depending on its exact composition. The (optional) use of oxygen allows for the synthesis of oxyfluorides, while the (optional) use of hydrogen allows for the removal of possible oxide layers on the substrate.

The actual fluorination occurs in a heated reaction tube (7). Cold traps are located downstream and allow precipitation of the reaction product. Thus, the use of the last cold trap as a "getter" has proven to be preferable for removing residues and impurities from the system. Further downstream are fluorine absorbers (8), which preferentially bind unconsumed reactive fluorine species and thus protect downstream pumps (9).

The use of a remote plasma source preferably allows fluoride synthesis to occur under low vacuum. Thus, the use of autoclaves, high pressure and/or high temperatures is not required.

Gas supply using MFC

The supply of process gases is controlled by three MFCs (mass flow controllers) manufactured by Bronkhorst. They are controlled via RS232 interface by the E-8501-0-2A control and readout system, also manufactured by Bronkhorst. MFCs are also equipped with an EtherCAT port. Pressure reading occurs via two Oerlikon Leybold CERAVAC Transmitter CTR100N capacitive sensors with a maximum pressure range of 100 Torr and 10 Torr, respectively. Thus, the 100 Torr sensor is located directly downstream of the RPS, while the 10 Torr sensor is located downstream of the third cold trap. The use of capacitive sensors offers the advantage of being independent of the supply gas.

MFC 1 supplies the RPS with fluorine-containing process gas (fluorine-containing feed compound). In this example, NF ₃ was used, but this system also allows the use of other process gases. To ensure long service life, MFC 1 is equipped with FFKM (Kalrez) gaskets.

The MFC 2 supplies the RPS with argon, which can be used as a carrier gas and/or to purge the line after the fluorination process and to provide a backflow when opening the extraction ports (minimizing the ingress of oxygen and moisture). MFC 2 gaskets are made of Viton.

MFC 3, if necessary, supplies either oxygen (synthesis of oxyfluorides) or hydrogen (removal of possible oxide layers on the substrate) into the line.

Remote Plasma Source (RPS)

The plasma burns inside the remote plasma source. The plasma is created using microwave radiation with a frequency of 2.45 GHz. This radiation provides the energy to break fluorine bonds in the fluorine-containing process gas (fluorine-containing feed compound). In this case, a high concentration of fluorine radicals can be created (the degree of dissociation is greater than 95%), which allows for very effective fluorination.

Due to its relatively weak binding, NF ₃ is preferably used as a process gas. The RPS is a device model MA3000C-193BB from MUEGGE. According to the technical specifications, this model requires a high process gas flow rate of at least 500 cubic meters. cm per minute However, during operation it has been demonstrated that the RPS can operate reliably at significantly lower flow rates down to 2 cu. cm per minute The RPS is powered by the MX3000D-117KL Microwave Power Supply (MPS) with a maximum output power of 3000 W, also manufactured by MUEGGE. It is controlled by a PC, which runs a Windows-based control software. However, the input signal for the RPS is based on the CAN bus, so the signal converter is placed between the PC and the MPS.

Cooling water control for both components is automated. As soon as the temperature leaves a precisely defined window, or the cooling water flow becomes too low, the blocking device closes the MFC. If the cooling water pressure exceeds a threshold value, inlet solenoid valves turn off the cooling water to protect the system from damage and/or leakage.

Reaction tube

The actual fluorination occurs in the reaction tube. The reaction tube is made of nickel, which has previously been passivated. It is placed inside a furnace that can be heated up to 1000°C. Due to the high reactivity of fluorine radicals, the distance from the plasma to the substrate should be kept as small as possible to reduce losses due to recombination. Thus, only a short four-way crosspiece is placed between the RPS and the reaction tube. One of the pressure sensors is located here, as well as a viewing window equipped with a sapphire crystal window on the opposite side. The observation window, on the one hand, allows you to check whether the plasma is burning, and, on the other hand, allows you to directly evaluate the reaction process on the substrate.

Pipelines and cold traps with bypass

Piping runs from the reaction tube further downstream to cold traps where precipitation occurs.

The pipes are made of 1.4404 stainless steel with a diameter of ½ inch. All valves used are Swagelok Type 6L ELD8 77X-P diaphragm valves. These valves provide high corrosion resistance.

Cold traps are made of PFA and have a simple U-tube design. They are passivated before use at 1 bar for 24 hours with pure fluorine to remove non-fluorinated constituents and thus render the material chemically inert. Each cold trap can be bypassed. This allows the system to be purged with argon before the re-sublimation process, on the one hand, and, on the other hand, allows switching to another cold trap if the precipitated product negatively affects the gas flow, leading to an increase in pressure. Additionally, it has proven useful to use the cold trap furthest downstream as a “getter” to remove residues and residual moisture that remain after heating and vacuuming the system, and thus further increase the purity of the synthesized products. .

Absorption system

The absorption system consists of two tubes made of stainless steel 1.4435, filled with a fluorine absorbent. It can be soda lime, Al ₂ O ₃ or TiO ₂ . They protect the pump unit from non-precipitated reactive fluorine particles. The absorber tubes are connected to the valves in such a way that they can be used either in series or in such a way that the front tube can be bypassed. Three thermocouples on each tube allow monitoring the reaction front. Thus, they allow the level of depletion of the absorber material to be measured. Tubes with absorber are connected to the line via DN 40 CF flanges.

Pump block

The pumping system used was a TRIVAC D40BCS rotary vane pump with Leybold PTFE oil as the first stage, reinforced with a Roots vacuum pump RUVAC WSU 251 as the second stage. The SECUVAC valve is placed at this stage, which automatically vents the pumps and closes the system on the vacuum side when the rotary vane pump is turned off. The rotary vane pump is equipped with a chemical filter CFS 40-65, which consists of porous Al ₂ O ₃ and removes residues from the oil. It is also equipped with an ARS 40 65 exhaust filter with lubricant return.

Extraction of the synthesis product

The synthesis product is extracted from cold traps by re-condensing it in sampling cylinders. These cylinders are equipped with a diaphragm valve and are connected to extraction ports. The sampling cylinder is cooled with liquid nitrogen while the coolant in the cold traps is simultaneously removed. This recondensation step further increases the purity of the synthesis product.

b) Preparation of UF ₆ and MoF ₆

Using the reaction system described above, a mixture containing UF ₆ and MoF ₆ was provided in accordance with the following protocol.

- Cleaning a metal substrate containing 99 wt. % U and 1 wt. % Mo, 7 M HNO ₃ to remove the oxide layer, then remove HNO3 with decomposer (dest.) water and acetone (total weight after cleaning: 1504.8 mg).

- Placing the substrate on the monel carrier and inserting it under a countercurrent of argon into the reaction chamber.

- Purging the entire system with argon three times and then creating a vacuum to remove any oxygen or moisture that entered the system during the introduction of the carrier and substrate. During the purge process, the absorbers are bypassed to prevent the accumulation of unwanted dust from the absorber material in the downstream valves.

- Filling Dewar vessels of cold traps with different cooling mixtures (in the latest experiments, isopropanol dry ice at a temperature of -82°C for cold trap 1, isopropanol dry ice at a temperature of -85°C for cold trap 2 and liquid nitrogen at a temperature of -190°C for the third cold trap).

- Closing all MFC bypass valves.

- Closing all cold trap bypass valves.

- Closing the absorber bypass and opening the absorber valves.

- Turn on the cooling water for the RPS (Remote Plasma Source) and Microwave Power Supply (MPS), checking that the flow rate is greater than 4 l/min.

- Setting the value for MFC Ar on the MFC control panel to 20 cc. cm per minute

- Launch RPS on the control computer, setting it to 3000 W.

- Setting the value for MFC NF ₃ on the MFC control panel to 20 cc. cm per minute

- Control through the sapphire window whether the plasma has been ignited correctly.

- Fluoridation for 45 minutes until the target is dissolved (under control through a sapphire glass window).

- Pressure sensor 1: between 3.70 (start of process) and 4.15 mbar (end of process).

- Pressure sensor 2: between 3.04 (start of process) and 3.28 mbar (end of process).

- Maximum temperature of the reaction chamber is 74.6°C (no forced cooling of the tube is required).

- Closing cold traps by closing their valves.

- Removing cooling mixtures and allowing fluorides in cold traps to warm up.

- Extract fluorides through extraction ports and move them into FEP tubing cooled with liquid nitrogen. The highest concentration of MoF ₆ is provided in the cold trap 3, and therefore it will be extracted through port 3.

- The amount of MoF ₆ recovered from the cold trap 3 was about 35% of the total amount of MoF ₆ produced during the reaction and was increased from 1:99 to 3:2 (weight ratio of MoF ₆ to UF ₆ ). An additional 20% MoF ₆ was deposited in cold trap 1. The amount of UF ₆ that was recovered was not recorded.

Example 2 - Gas-phase separation by UV light using CO as a fluorine scavenger

A 1:1 mixture (by weight) of UF ₆ and MoF ₆ was placed in a quartz vessel. CO (gaseous) was added to this mixture at 100 kPa (1 bar) and the UF ₆ /MoF ₆ /CO mixture was irradiated with ultraviolet light having a wavelength of 395 nm for 12 hours. The following reactions occurred:

After 12 hours of irradiation, the reaction mixture was cooled using liquid nitrogen (-196°C) and the volatile COF ₂ was pumped off. Additional (gaseous) CO at 100 kPa (1 bar) was added to the quartz vessel and the mixture was again irradiated with light at 395 nm for an additional 12 to 24 hours.

After this additional irradiation cycle, the reaction mixture was cooled to -196°C and the volatile COF ₂ was pumped off. What remains is a mixture of UF ₅ (solid, non-volatile) and MoF ₆ (liquid, volatile). MoF ₆ was then separated from UF ₅ by distillation. Both UF ₅ and MoF ₆ were collected in quantifiable volumes at the end of the separation. Analysis using microwave plasma atomic emission spectroscopy (MP-AES) showed that the molybdenum sample was clean and there were no detectable amounts of uranium. Analysis of the UF ₅ sample showed that more than 99% of the molybdenum had been removed.

Likewise, this reaction can be carried out using hydrogen gas (H ₂ ). The separation was carried out in the same way as the separation with CO, except that the corresponding reactions were:

However, care should be taken to select an appropriate reaction vessel. Quartz should not be used as it will react with the HF gas produced. Perfluorinated plastics also cannot be recommended due to the solubility of MoF ₆ in such plastics.

Procedures

1. 200 mg UF ₅ and 200 mg MoF ₆ were distilled into a quartz vessel (which was previously flame dried; the volume of the quartz vessel was approximately 30 ml).

2. CO (gas) at 100 kPa (1 bar) was added to the vessel.

3. The UF ₆ /MoF ₆ /CO mixture was irradiated with light at 395 nm for 12 hours.

4. The mixture was cooled to -196°C (using liquid nitrogen) and the volatile COF ₂ was pumped off.

5. Fresh CO at 100 kPa (1 bar) was placed in the vessel and the mixture was again irradiated with light at 395 nm for an additional 12 to 24 hours.

6. The mixture was cooled to -196°C and the remaining CO and COF ₂ were pumped out. What remains is a mixture of MoF ₆ (liquid, volatile) and UF ₅ (solid, non-volatile).

7. MoF ₆ was then distilled into a new quartz vessel.

8. MP-AES analysis was performed on molybdenum-containing (MoF ₅ , see below) and uranium-containing (UF ₅ ) samples to check purity.

- To facilitate handling of the MoF ₆ sample for MP-AES measurements, MoF ₆ was reduced to MoF ₅ with light at 252 nm using the following reaction:

- The MP-AES measurement results for the uranium containing (UF ₅ ) sample can be found in Table 1. The MP-AES measurement results for the molybdenum containing (MoF ₅ ) sample can be found in Table 2.

results

Table 1: MP-AES results of a uranium sample (UF ₅ ) obtained after UV separation of MoF ₆ from UF ₆ using 395 nm light and carbon monoxide. All experiments were carried out in triplicate.

Experience 1 (U) Experience 2 (U) Experience 3 (U) Mo, mg/l 0.16±0.01 0.16±0.01 0.13±0.00 %Mo 0.30±0.01 0.32±0.01 0.26±0.00 U, mg/l 39.31±2.27 35.62±0.77 35.52±0.95 %U 73.52±1.41 68.61±1.70 68.89±1.05 Mo/U ratio
before separation 1.7 1.63 1.61 Mo/U ratio
after separation 0.01±0.00 0.01±0.00 0.01±0.00 % Mo removed 99.41±0.02 99.30±0.03 99.42±0.01

Table 1 shows the analysis of a UF ₅ sample obtained after gas phase separation using CO as a fluorine scavenger. The separation was carried out three times, Trial 1 to Trial 3. Measurements were carried out in triplicate and the mean of the results is reported along with the standard deviation. The amount of Mo is reported along with its percentage in the sample. Likewise, the amount of U is reported along with its percentage in the sample. Mo/U ratios before and after separation are given along with % Mo removed.

Table 2: MP-AES results of a molybdenum sample obtained after UV separation of MoF ₆ from UF ₆ using 395 nm light and carbon monoxide. A single sample was prepared for each experiment.

Experience 1 (Mo) Experience 2 (Mo) Experience 3 (Mo) Mo, mg/l 29.14 26.29 28.95 %Mo 39.99 36.34 40.02 U, mg/l Not found Not found Not found

Table 2 shows the analysis of the MoF ₅ sample obtained after separation with CO gas. Runs 1-3 in Table 2 correspond to runs 1-3 in Table 1. The entire MoF ₅ sample was dissolved for the MP-AES measurements, so only one sample was prepared for each measurement. The amounts of Mo found in the sample are reported along with the percentage of Mo. No uranium was discovered.

Example 3 - Separation Using Liquid Sulfur Dioxide (SO ₂ ) and UV light

A 1:1 (by weight) mixture of UF ₆ and MoF ₆ was placed in a FEP or PFA reaction vessel. 3-5 ml of (liquid) SO ₂ were distilled into this mixture. The reaction mixture was then irradiated with light at 395 nm. The irradiation time can be appropriately selected depending on how much UF ₆ is present in the sample. In the case of 200 mg UF ₆ , an irradiation time of 1 hour and 30 minutes was more than sufficient. The separation of MoF ₆ from UF ₆ is achieved through the following reactions/conditions:

Since MoF ₆ is not affected by UV light at this wavelength (395 nm) and since its reaction with SO ₂ is so slow, after irradiation a mixture of UF ₅ (solid, non-volatile), MoF ₆ (liquid, dissolved, volatile), SO ₂ (liquid, volatile) and SO ₂ F ₂ (gas, volatile). MoF ₆ and remaining SO ₂ +SO ₂ F ₂ were removed from UF ₅ by distillation. MoF ₆ can be extracted from the SO ₂ solution after a few days (4 to 7 days) as solid MoOF ₄ formed by the reaction of MoF ₆ with SO ₂ described above.

Analysis of the MoOF ₄ sample using MP-AES shows no detectable amounts of uranium. Measurement of the UF ₅ sample showed that more than 99% of the molybdenum had been removed.

Procedures

1. 200 mg UF ₆ and 200 mg MoF ₆ were distilled into a FEP or PFA reaction vessel. The reaction vessel contained a 1 cm stirrer coated with PTFE.

2. About 3-5 ml SO ₂ was distilled into the reaction vessel using liquid nitrogen as a coolant.

3. The reaction mixture was warmed to room temperature and stirred using a stirrer plate to ensure complete dissolution of MoF ₆ and UF ₆ in SO ₂ .

4. With constant stirring, the sample was irradiated with light at 395 nm for 1 hour and 30 minutes.

5. After irradiation, we obtained a mixture of UF ₅ (solid, non-volatile), MoF ₆ (liquid, dissolved, volatile), SO ₂ (liquid, solvent, volatile), and SO ₂ F ₂ (gaseous, somewhat dissolved, volatile) .

6. MoF ₆ was removed by distilling all volatile compounds (MoF ₆ , SO ₂ , and SO ₂ F ₂ ) into a new FEP or PFA reaction vessel.

7. Molybdenum can then be extracted from the SO ₂ solution (SO ₂ /SO ₂ F ₂ mixture) by allowing MoF ₆ to react completely with the SO ₂ solvent to form MoOF ₄ , see equation below.

This reaction is slow and takes about a week.

8. After one week, MoOF ₄ was extracted by pumping out the SO ₂ solution.

9. MP-AES analysis was carried out on uranium-containing (UF ₅ ) and molybdenum-containing (MoOF ₄ ) samples.

- The results of the MP-AES analysis of the uranium-containing (UF ₅ ) sample are shown in Table 3. The results of the MP-AES analysis of the molybdenum-containing (MoOF ₄ ) sample are given in Table 4.

results

Table 3: MP-AES results of uranium sample (UF ₅ ) obtained after SO ₂ /UV separation of MoF ₆ from UF ₆ using 395 nm light and SO ₂ as solvent. All experiments were carried out in triplicate.

Experience 4 (U) Experience 5 (U) Experience 6 (U) Mo, mg/l 0.08±0.00 0.283±0.03 0.10±0.01 % Mo 0.15±0.01 0.50±0.02 0.17±0.00 U, mg/l 37.44±0.25 34.78±2.54 36.22±3.77 %U 73.01±2.35 62.82±0.42 63.11±0.43 Mo/U ratio
before separation 1.64 1.68 1.65 Mo/U ratio
after separation 0.01±0.00 0.02±0.00 0.01±0.00 % Mo removed 99.69±0.02 98.81±0.04 99.58±0.01

Table 3 shows the analysis of the UF ₅ sample obtained after separation with liquid SO ₂ . This separation was carried out three times, Trial 4 - Trial 6. Measurements were carried out in triplicate and the mean of the results is reported along with the standard deviation. The amount of Mo is reported along with its percentage in the sample. Likewise, the amount of U is reported along with its percentage in the sample. Mo/U ratios before and after separation are given along with % Mo removed.

Table 4: MP-AES results of molybdenum sample (MoOF ₄ ) obtained after SO ₂ /UV separation of MoF ₆ from UF ₆ using 395 nm light and SO ₂ as solvent. All experiments were carried out in triplicate.

Experience 4 (Mo) Experience 5 (Mo) Experience 6 (Mo) Mo, mg/l 54.24±2.55 55.90±3.71 55.92±1.11 %Mo 54.65±1.23 50.59±1.33 49.96±0.83 U, mg/l Not found Not found Not found

Table 4 shows the analysis of the MoOF ₄ sample obtained after separation with liquid SO ₂ . This separation was carried out three times, Trials 4-6, which correspond to Trials 4-6 shown in Table 3. Measurements were carried out in triplicate, and the mean of the results is reported along with the standard deviation. The amount of Mo is reported along with its percentage in the sample. No uranium was detected in these samples.

Example 4 - Separation Using Liquid SO ₂ with filtration

A UF5/MoF5 mixture can be prepared based on the following reactions (using the specified wavelength):

This 1:1 (by weight) mixture of UF ₅ and MoF ₆ was then separated by placing the mixture in a filtration vessel (a glass H-tube was used, but any suitable filtration vessel is also suitable). 5-10 ml of SO ₂ (liquid) was distilled into the mixture. MoF ₅ is soluble in SO ₂ , while UF ₅ is insoluble in SO ₂ . Separation was then achieved by glass filtration. After filtration/separation, analysis of the MoF ₅ sample showed the presence of less than 0.25% uranium. Analysis of the UF ₅ sample showed that the sample contains about 2% molybdenum. The amount of molybdenum in a UF ₅ sample naturally depends on the quality of filtration and the number of filtration repetitions.

Procedures

1. 50 mg of UF ₅ and 50 mg of MoF ₅ were placed in a glass filtration device (H-tube was used).

2. 5-10 ml of SO ₂ were distilled into this mixture at -196°C. The mixture was then allowed to warm to -30°C. The UF ₅ -containing portion of the filtration device was maintained at -30° C. during the filtration procedure.

3. The solution was mixed manually by gentle shaking to dissolve the MoF ₅ in the SO ₂ solvent. Dissolving MoF ₅ in SO ₂ produces a yellow solution (SO ₂ itself is colorless).

4. The SO ₂ solution containing MoF ₅ was then filtered onto the other side of the filtration device using glass solder.

5. This side of the filtration device was maintained at -30° C. while the side containing the newly filtered SO ₂ /MoF ₅ solution was allowed to warm up. Then, SO ₂ was slowly distilled back to the original side (UF ₅ ) of the filtration device.

6. Steps 4 and 5 were repeated 7 to 10 times or until the SO ₂ solution above the UF ₅ sample became colorless.

7. SO ₂ was distilled from the filtration device. MoF ₅ was obtained on one side of the device, while UF ₅ was obtained on the other side.

8. Samples of MoF ₅ and UF ₅ were tested for purity using micro-X-ray fluorescence spectroscopy.

- The results are shown below. The uranium sample showed about 2% molybdenum impurity, while the molybdenum sample showed about 0.25% uranium impurity.

results

The above table shows the results of micro-X-ray fluorescence spectroscopy of a MoF ₅ sample. It shows that less than 0.25% of uranium remained in the sample after filtration.

The above table shows the results of micro-X-ray fluorescence spectroscopy of a UF ₅ sample. It shows that about 2% Mo remains in the sample.

Example 5 - separation using supercritical CO

Since the critical point of CO is determined by a pressure of 34.5 bar and a temperature of 132.9 K, all experiments with supercritical CO were carried out in a high-pressure vessel. The pressure-resistant body of the vessel contained a mixture of UF ₆ and MoF ₆ , which was cooled with a cold finger in its bottom. The bottom itself was tilted to ensure that there were no shadow areas that could remain unirradiated. The sapphire window allowed UV light to pass through and was sealed against the pressure-resistant case with an FFKM O-ring. The pressure required for a reliable seal was applied by a steel lid secured to the pressure-resistant housing by six screws. Both the pressure-resistant body and the cold finger have a hole for inserting thermocouples to measure temperature. The pressure-resistant housing was wrapped with heating tape to ensure that both MoF ₆ and UF ₆ actually condensed on the cold finger rather than on the walls of the pressure-resistant housing.

The high-pressure container was connected through a sealed bellows valve to a container for storing CO, as well as a pressure sensor. The pressure sensor and storage container were also connected through a bellows sealed valve. A third bellows sealed valve connected the high pressure section and the low pressure section. Two storage containers, one for UF ₆ and one for MoF ₆ , can be connected to one port of the low pressure section. They were added one after another. The measurement module for IR and UV/VIS spectroscopy was connected to another extraction port. The pressure in this part of the system was determined by a piezoresistive pressure sensor. This low pressure section can be sealed to the pumps, argon inlet and CO inlet with a bellows sealed valve.

For experiments, a mixture of MoF ₆ and UF ₆ was condensed into a measurement module and characterized by IR spectroscopy. In this way, the exact composition and ratio of MoF ₆ /UF ₆ were known before the experiment. After spectroscopic analysis, the measurement module was reconnected to the line and its contents were re-distilled into a high-pressure container, which was cooled with liquid nitrogen on a cold finger to a temperature of -33°C, while the wall temperature was maintained at 1°C by means of a heating tape. This ensured that MoF ₆ and UF ₆ only condensed on the cold finger. The pressure container was then sealed.

In the next step, the dried CO was condensed into a storage container using liquid nitrogen and then heated to room temperature, causing it to become supercritical. The CO was allowed to enter the pressure container by opening the connecting valve. The pressure gauge read 56 bar, so the CO in the high-pressure container was in a supercritical state. The high-pressure container was resealed by closing the connecting valve, heated to 20° C. and its contents were irradiated for 60 minutes with light at a wavelength of 395 nm. During this time, the storage container was pumped out again.

After this time, all components that were volatile at room temperature were condensed in a storage container using liquid nitrogen. The storage container was maintained at liquid nitrogen temperature and evacuated, removing CO and COF ₂ but leaving MoF ₆ and unreacted UF ₆ in the solid phase. The storage container was then disconnected from the line, vented and filled with water to dissolve the UF ₆ and MoF ₆ and the solution was analyzed using MP-AES.

The pressure chamber solids (mainly UF ₅ ) were dissolved in dilute HNO ₃ and also analyzed using MP-AES.

The results are shown in the following table:

Initial mixture Contents of the storage container Contents of the high pressure chamber U [mg] 26.8 2.98 20.96 Mo [mg] 8.5 7.35 0.08

In this way, the uranium content can be reduced by 89% and, at the same time, 86% of the molybdenum content can be recovered. Also important is that very little Mo remained in the pressure chamber, providing MoF ₆ that was essentially unaffected by the irradiation process.

Example 6 - preparation of OsF ₆

Using the reaction system described in Example 1, OsF ₆ was prepared using the following materials and reaction conditions.

- Placing osmium powder on a monel carrier (total weight 206.8 mg).

- Inserting the substrate under a countercurrent of argon into the reaction chamber.

- Slowly creating a vacuum in the system to prevent swirling of the powder and slowly filling it again with argon, repeating this process two or more times, the last time only creating a vacuum without refilling the chamber with argon.

- Heating the chamber to 100°C to remove moisture absorbed on the surface of the osmium powder (high temperature and low pressure effectively dry the powder).

- Turn off the heat and allow the chamber to cool down again to about 40°C.

- First filling the last Dewar flask with liquid nitrogen to bind the remaining moisture.

- Filling the first two Dewars with liquid nitrogen (only a cold trap one or two are used to recover the reaction product to increase its purity).

- Closing all MFC bypass valves.

- Closing all cold trap bypass valves.

- Closing the absorber bypass and opening the absorber valves.

- Turn on the cooling water for the RPS (Remote Plasma Source) and MPS (Microwave Power Supply), checking that the flow rate is greater than 4 l/min.

- Set the value for MFC Ar on the MFC control panel to 8 cc. cm per minute

- Launch RPS on the control computer, setting it to 3000 W.

- Setting the value for MFC NF ₃ on the MFC control panel to 2 cu. cm per minute

- Control through the sapphire window whether the plasma has been ignited correctly.

- Fluoridation for about 75 minutes after the osmium powder has been completely consumed.

- Pressure sensor 1: 1.60 mbar.

- Pressure sensor 2: 1, 242 mbar.

- Maximum temperature of the reaction chamber is 74.1°C (no forced cooling of the tube is required).

- Closing cold traps by closing their valves.

- Removing cooling mixtures and allowing fluorides in cold traps to warm up.

- Extract fluorides through extraction ports and move them into FEP tubing cooled with liquid nitrogen.

Examples 7-16

Using conditions similar to those set forth in Example 2, except for the modifications indicated in the table, the metal fluorides listed below were prepared:

Etc. Metal The resulting fluoride Heating the metal Mass flow rate of F-containing parent compound Carrier gas mass flow Note 7 Mo MoF ₆ No heating 35 cu. cm per minute 35 cu. cm per minute 8 Ru RuF ₅ 190°C 2 cu. cm per minute 14 cu. cm per minute 9 Rh RhF ₃ 2 cu. cm per minute 8 cu. cm per minute RhF ₃ requires rapid cooling 10 W WF ₆ No heating 60 cu. cm per minute 100 cu. cm per minute eleven Re ReF ₆
ReF ₇ No heating 60 cu. cm per minute 100 cu. cm per minute Both substances are formed simultaneously at given gas ratios. Separation is possible using cold traps at different temperatures. 12 Os OSF ₆ No heating 2 cu. cm per minute 8 cu. cm per minute 13 Ir IrF ₆ No heat (although heat may be preferable) 60 cu. cm per minute 0 cu. cm per minute 14 Pt PtF ₄ No heating 54 cu. cm per minute 10 cu. cm per minute The use of nickel/monel holder is preferred due to the effect of atomic fluorine redundancy; PtF ₄ requires rapid cooling 15 U UF ₆ No heating 25 cu. cm per minute 25 cu. cm per minute 16 Te TeF ₆ No heating 8 cu. cm per minute 8 cu. cm per minute

Claims (35)

1. A method for separating metal fluorides, containing a step of providing a mixture containing MoF ₆ and UF ₆ ; a stage in which UF ₆ is reduced to UF ₅ ; And a step in which UF ₅ and MoF ₆ or its conversion product are separated, which can be obtained by further converting molybdenum fluoride into another molybdenum compound. 2. The method according to claim 1, containing a step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides; a dissolution step, which comprises dissolving MoF ₆ and UF ₆ in a liquid phase or a supercritical fluid phase to obtain a solution containing both MoF ₆ and UF ₆ in dissolved form; a precipitation step, which comprises a step of reducing the UF ₆ contained in the solution to UF ₅ and allowing it to precipitate out of the solution; And a separating step, which contains a step in which (i) separating the precipitated UF ₅ from the solution; or (ii) removing the liquid phase or supercritical fluid phase of the solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separating UF ₅ and molybdenum fluoride or a conversion product thereof, which can be obtained by further conversion of molybdenum fluoride into another molybdenum compound. 3. The method according to claim 2, wherein the mixture containing MoF ₆ and UF ₆ , which is provided as the starting mixture of metal fluorides, is a gas phase mixture containing MoF ₆ and UF ₆ mixed in gaseous form. 4. The method according to claim 3, which further comprises a step in which the gas-phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which the MoF ₆ and UF ₆ contained in the gas phase are deposited as a mixture containing MoF ₆ and UF ₆ , this mixture is extracted, and then subjected, optionally after re-evaporation to provide a gas-phase mixture containing MoF ₆ and UF ₆ in gaseous form, to a dissolution step. 5. The method according to claim 3 or 4, which further comprises, before the dissolution step, a step in which the gas-phase mixture containing MoF ₆ and UF ₆ is cooled to a temperature at which part of the UF ₆ contained in the gas phase is deposited and removed from the gas phase. 6. The method according to any one of claims 2 to 5, wherein MoF ₆ and UF ₆ are dissolved in a dissolution step in a liquid phase that contains or consists of liquid SO ₂ as a solvent, or in a supercritical fluid phase that contains or consists of CO in a supercritical state. 7. The method according to any one of paragraphs 2-6, in which the dissolution step comprises a step in which the precipitated UF ₅ is separated from the solution. 8. The method according to claim 7, in which the separation step further comprises steps in which converting the MoF ₆ contained in the solution into another molybdenum compound before or after separating the precipitated UF ₅ from the solution, and the molybdenum compound is removed from the solution after separating the precipitated UF ₅ from the solution. 9. The method of claim 7, wherein the separation step comprises reducing the MoF ₆ contained in the solution to obtain a solution containing MoF ₅ before or after separating the precipitated UF ₅ from the solution. 10. The method according to any one of claims 2 to 9, wherein the separation step comprises (ii) a step of removing a liquid phase or a supercritical fluid phase of a solution in the presence of precipitated UF ₅ to obtain a solid phase containing precipitated UF ₅ and molybdenum fluoride, and separate UF ₅ and molybdenum fluoride. 11. The method of claim 10, wherein the separation step comprises reducing the MoF ₆ contained in the solution to obtain a solution containing MoF ₅ before removing the liquid phase or supercritical fluid phase of the solution, and wherein the solid phase obtained by removing the liquid phase or supercritical fluid phase of the solution, contains precipitated UF ₅ and MoF ₅ . 12. The method according to claim 11, in which the precipitated UF ₅ and MoF ₅ are separated by sublimating the MoF ₅ and precipitating it separately from the UF ₅ . 13. The method according to any one of claims 2 to 12, wherein the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides comprises the step of reacting a solid material that contains elemental uranium and elemental molybdenum, with fluorine radicals, and wherein the reaction comprises exposing the solid material to a gas stream containing fluorine radicals to produce a mixture containing MoF ₆ and UF ₆ . 14. The method according to claim 13, wherein the step of providing a mixture containing MoF ₆ and UF ₆ as a starting mixture of metal fluorides comprises the step of generating fluorine radicals from the fluorine-containing starting compound in a plasma source, more preferably in remote plasma source. 15. The method according to claim 1, containing a step of providing a gas-phase mixture containing MoF ₆ , UF ₆ and a fluorine atom scavenger mixed in gaseous form; a step of irradiating UF ₆ in a gas-phase mixture in the presence of a fluorine atom absorber with light having a wavelength in the range from 340 to 410 nm to reduce UF ₆ to UF ₅ and to obtain a mixture containing UF ₅ and MoF ₆ ; And the stage at which UF ₅ and MoF ₆ are separated. 16. The method of claim 15, wherein the light used for irradiation has a wavelength of 380 to 400 nm, more preferably 395 nm. 17. The method according to claim 15 or 16, wherein the scavenger for fluorine atoms in gaseous form is selected from CO, H ₂ , Xe and SO ₂ . 18. The method according to any one of paragraphs 15-17, which further comprises the step of removing the reaction product of the scavenger of fluorine and fluorine atoms formed by the reduction of UF ₆ to UF ₅ . 19. The method according to any one of paragraphs 15-18, in which UF ₅ and MoF ₅ are separated by distillation of MoF ₆ .

Images