阅读说明：本技术 生产铀硅化物的方法 (Method for producing uranium silicide ) 是由 E·J·拉霍达 S·米德勒巴格 于 2018-06-14 设计创作，主要内容包括：本文所述方法的特征可以在于使二氧化铀与碳反应以产生碳化铀,以及,使碳化铀与硅烷、卤化硅、硅氧烷或其组合以及过量的氢气反应以产生硅化铀。(The methods described herein may be characterized by reacting uranium dioxide with carbon to produce uranium carbide, and reacting uranium carbide with a silane, a silicon halide, a siloxane, or a combination thereof, and an excess of hydrogen to produce uranium silicide.)

1, a method comprising:

forming uranium dioxide;

reacting uranium dioxide with carbon to produce uranium carbide; and the combination of (a) and (b),

uranium carbide is reacted with a silicon-based reactant consisting of a silane, a silicon halide, a siloxane, and combinations thereof, in the presence of an excess of hydrogen gas to form a uranium silicide product.

2. The method of claim 1 wherein the uranium dioxide is formed from uranium fluoride.

3. A process as claimed in claim 2 wherein the uranium fluoride is selected from uranium hexafluoride (UF)₆) Uranyl fluoride (UO)₂F₂) And uranium tetrafluoride (UF)₄)。

4. The method of claim 1 wherein the uranium dioxide is formed by a process selected from the group consisting of: an ammonium uranyl carbonate process, an ammonium diuranate process and an integrated dry process.

5. The method recited in claim 1 wherein the silicon-based reactant has 1 to 6 silicon atoms in its linear, branched, or cyclic configuration.

6. The method of claim 1, wherein the silicon-based reactant has the general formula Si_nX_2n+2Wherein n is an integer from 1 to 6, and X is selected from the group consisting of hydrogen, halides, and combinations thereof.

7. The method of claim 1 wherein the uranium silicide is U₃Si₂。

8. The method of claim 1 wherein the residual carbon is removed by reacting the residual carbon with a silicon halide and an excess of halide.

9. The method of claim 8, wherein the halide is selected from the group consisting of fluoride, chloride, bromide, iodide, and combinations thereof.

10. A process as claimed in claim 1 in which the ratio of uranium to silicon in the uranium silicide product is varied in accordance with the ratio of feed compounds used to form or more of uranium dioxide, uranium carbide and silicon based reactants.

11. The process as claimed in claim 1, wherein the process is carried out in a rotary kiln.

12. The method of claim 1 wherein each step is conducted at a temperature below the melting point of the reactant contributing to the target stoichiometry of the uranium silicide.

13. The method of claim 1 wherein the step of forming the uranium silicide is performed at a temperature between 500 and 800K.

14. The method of claim 1 further comprising step homogenizing the uranium silicide product at a temperature above the temperature at which the formation of the uranium silicide occurs and below the melting temperature of the uranium silicide.

15. a process for producing uranium silicide nuclear fuel, comprising the reaction represented by:

(1)UF₆+H₂+2H₂O→UO₂+6HF；

(2)(i)UO₂+3C → UC +2CO and (ii) UO₂+2C→UC+CO₂ or both, and

(3)3UC+2SiX₄or Si₂ +2X in O₂→U₃Si₂+3CX₄，

Wherein X is selected from the group consisting of H, Cl, F, Br and I and combinations thereof.

1. Field of the invention

The present invention relates to a method of manufacturing uranium silicide for use as nuclear fuel, and more particularly, to a method of producing uranium silicide using uranium carbide as an intermediate.

2. Description of the Prior Art

Commercial nuclear fuels are produced primarily by using as UF a feed rich in uranium and depleted in uranium (i.e., enriched or depleted in the isotope of uranium 235 compared to the uranium 235 content of naturally occurring uranium ore)₆The process of (a). Enriched UF₆Conversion to UO by selected processes₂To provide the ceramic sinterability required to prepare nuclear fuel pellets.

Early patents to Reese et al (U.S. patent No. 3,168,369 filed 1961) and to Blundell et al (U.S. patent No. 3,235,327 filed 1962) described all of the basic reactions and general techniques required to produce uranium dioxide nuclear fuel for nuclear reactors from uranium hexafluoride.

Subsequently to UF₆The process of conversion to uranium oxide has been granted a number of U.S. patents. See, for example, U.S. Pat. No. 4,830,841 and the various U.S. patents listed therein, which describe the use of UF in furnaces, rotary kilns, fluidized beds, and the like₆A method for conversion to uranium dioxide.

Other U.S. patents disclose single step processes for producing nuclear reactor fuel, such as U.S. patent No. 4,397,824 and U.S. patent No. 5,875,385, U.S. patent No. 5,752,158, which describe an exemplary single step process for producing solid uranium oxide powder by pooling two gaseous reactant streams at from UF₆A single step improved direct Process (MDR) process for producing uranium oxide powder in solid form and gaseous HF, with of the reactant stream containing optionally O₂Form of oxygen mixed UF₆The second reactant stream comprises H₂Or as a mixture of hydrogen in the form of a hydrogen-containing compound and oxygen in the form of an oxygen-containing compound the gaseous reactant streams are brought together at at a temperature and composition of to allow UF₆Rapidly converted by flame reaction into solid uranium oxide and gaseous HF products which are easily separated.

Including intermediate drying processesAn additional single-step drying process for obtaining uranium dioxide powder (i.e. by subjecting UF to UF)₆Direct reduction to UO₂) Has been used extensively at and is described, for example, in U.S. Pat. No. 4,889,663 and U.S. Pat. No. 4,397,824 conversion processes by drying (involving steam hydrolysis followed by the uranyl fluoride UO obtained₂F₂Thermal hydrolysis) has the advantage of being easy to sinter. The resulting powder has high activity but is difficult to handle and produces very weak green pellets. Therefore, they are fragile to handle and, if not noticed, very high in waste.

U.S. patent No. 6,656,391 discloses the use of a wet ammonium diuranate process (ADU) to remove Uranyl Nitrate Hexahydrate (UNH) and UF₆Production of UO₃/U₃O₈And both. In particular, the UO that will then result from this process₃/U₃O₈Treatment in a calciner to produce UO₂. The ADU process produces a stable but only moderately active UO (i.e., only on a constant basis to a final particle density of about 97.5%)₂And (3) powder.

Uranium silicide fuel (such as U)₃Si₂) UF is typically produced by mixing uranium with silicon metal at deg.C and melting them at a temperature above 1665 deg.C₆Is the most common commercial uranium feedstock. In the manufacture of U₃Si₂When UF must first be treated in a multi-step process that is expensive and difficult to manufacture on a large scale₆To uranium metal.

For example, high temperature processes, UF₆+H₂→2HF+UF₄A highly corrosive HF atmosphere is generated. Dependent on high temperature processes and uranium metal production, e.g. UF₄+2Mg→U+2MgF₂In the step (2), uranium is separated. Mixing the obtained uranium metal with silicon metal at a temperature higher than 1652 ℃ to make U₃Si₂3U +2Si → U₃Si₂The uranium metal is very dense, only a small amount of U metal is used in any batch because a larger amount can initiate the uranium fission process, therefore, each of these steps have critical conditions for large scale manufacturing and batch processingTo a problem of (a).

There is a need for safer and more cost-effective methods.

Background

Disclosure of Invention

The methods described herein address the problems associated with the use of uranium and silicon metals in the production of uranium silicides.

In various aspects, methods are described herein, the methods comprising forming uranium dioxide, reacting the uranium dioxide with a carbon source to produce uranium carbide, and reacting the uranium carbide with a silicon-based reactant consisting of a silane, a silicon halide, a siloxane, and combinations thereof, in the presence of an excess of hydrogen to produce uranium silicide.

The uranium dioxide may be formed by a process selected from: an ammonium uranyl carbonate process, an ammonium diuranate process, and an integrated dry process or any other suitable known process.

The uranium dioxide may be formed from uranium fluoride. In various aspects, the uranium fluoride may be selected from uranium hexafluoride (UF)₆) Uranyl fluoride (UO)₂F₂) And uranium tetrafluoride (UF)₄)。

In various aspects, steps of the methods described herein or the methods may be performed in a rotary kiln steps of the methods for forming uranium silicide may be performed at less than the reported SiH₄The decomposition temperature is, for example, at a temperature of more than about 623K to 673K (about 350 to 400 ℃). However, the temperature for the uranium silicide formation step may be between about 500K and 800K (about 227 ℃ to 527 ℃), and preferably may be between about 500K and 700K (about 227 ℃ and 427 ℃). The foregoing steps of the method may be carried out at a temperature below the melting point of the reactants, and may for example be carried out at a temperature below the melting point of the target uranium silicide of the target stoichiometry.

The target uranium silicide may be U₃Si₂However, the ratio of uranium to silicon in the uranium silicon product can be varied by varying the ratio of of the feed compounds used to form uranium silicide, uranium carbide, and silicon hydride and silicon halide.

once the uranium silicide forming reaction has been completed, a homogenization step at high temperature may be required,to reduce the interaction with the target U₃Si₂Compared to the content of the different phases in stoichiometric ratio. This may be at a temperature below the melting point of the target material (e.g., for U)₃Si₂1665 ℃ C.).

Drawings

The features and advantages of the present disclosure may be better understood with reference to the accompanying drawing, which provides a graph showing gibbs free energy (eV) values for several reactants (H, Cl, F and Br) over a temperature range from 0 to 2000K.

Description of the preferred embodiments

As used herein, the singular forms "," "," and "the" include the plural forms unless the context clearly dictates otherwise.

In the present application, including the claims, all numbers expressing quantities, values, or characteristics are to be understood as being modified in all instances by the term "about" unless otherwise indicated, and thus, even though the term "about" may not expressly appear with the number , the number may be read as if the word "about" preceded it.

Any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

The term "rotary kiln" or alternatively "calciner" refers to a rotary tubular pyrohydrolysis (pyrohydrolysis) furnace, for example, a powder feed device at the inlet end with a heating device as outlined in U.S. patent No. 6,136,285Near the outlet of the reaction products for injecting, for example, steam, gaseous H₂O and H₂ or more, a rotary tube pyrohydrolysis furnace or other commercially available equivalent furnace.

The methods described herein may be characterized by reacting uranium dioxide with carbon to produce uranium carbide, and reacting uranium carbide with a silicon-based reactant consisting of a silane, a silicon halide, a siloxane, and combinations thereof, and excess hydrogen to produce uranium silicide.

In various aspects, the method may be characterized by forming uranium dioxide, reacting the uranium dioxide with carbon from any suitable carbon source, such as graphite or carbon black, to produce uranium carbide, and reacting the uranium carbide with a silicon-based reactant in the form of a linear, branched, or cyclic configuration. In excess of hydrogen (H)₂) The silicon-based reactant may be selected from silanes (e.g., SiH) in the presence of₄、Si₂H₆、Si₃H₈、Si₄H₁₀、Si₅H₁₂Or Si₆H₁₄) Silicon halides (e.g., SiF)₄、SiH₃F、Si₂H₅F、Si₃H₆Cl₂、Si₄H₈Br₂、Si₅H₈I₄Or Si₆H₁₀Cl₄Etc.) or siloxanes (e.g. Si₂O) to produce uranium silicide. In various aspects, the silicon-based reactant can have the general formula Si_nX_2n+2Wherein n is 1 to 6 and X is selected from the group consisting of hydrogen, halides, and combinations thereof. In other aspects, the silicon-based reactant can be in a cyclic configuration having less than 2n +2X molecules.

An exemplary representation of the method may be shown as:

UF₆+H₂+2H₂O→UO₂+6HF

or any suitable known method for producing uranium dioxide. The conversion of uranium dioxide to uranium carbide may be carried out as follows:

UO₂+3C→UC+2CO

or

UO₂+2C→UC+CO₂。

The uranium carbide reacts with stoichiometric silicide, which in an exemplary reaction proceeds as follows:

3UC+2SiX₄+2X₂→U₃Si₂+3CX₄，

wherein X is preferably H, such that the reaction can be represented as follows:

3UC+2SiH₄+2H₂→U₃Si₂+3CH₄。

x may also be a halide selected from F, Cl, Br and I, or a mixture of H and a halide. If X is a halide, the reaction has been determined thermodynamically to be more difficult due to the high Gibbs free energy in the halide system, as shown in the drawing.

Suitable known methods for producing uranium oxide include, for example, Ammonium Uranyl Carbonate (AUC), Ammonium Diuranate (ADU), and integrated dry process (IDR) processes. One skilled in the art will recognize that any source or method of producing uranium dioxide may be used.

In various aspects, an exemplary uranium ammonium carbonate (AUC) process can be a two-step process, which proceeds as follows:

UF₆+5H₂O+10NH₃+3CO₂→(NH₆)₄(UO₂(CO₃)₃)+6NH₄F

(NH₄)₄(UO₂(CO₃)₃)+H₂→UO₂+4NH₃+3CO₂+3H₂O。

the chemical composition of the AUC precipitate varied depending on the C/U ratio of the precipitation solution. A C/U ratio greater than or equal to 7.5 results from (NH)₄)₄(UO₂(CO₃)₃) Indicated precipitate composition. UO₂The conversion is characterized by the formation of discrete particles with a size of 40 to 300 μm, which allows direct granulation.

In various aspects, an exemplary Ammonium Diuranate (ADU) process may be carried out by passing UF through₆Reacting with water to form a uranyl fluoride solution or a uranyl nitrate solution and hydrogenOxidizing the ammonium solution to produce an ADU precipitate. After calcination of the ADU precipitate in nitrogen and reduction with a steam-hydrogen mixture, the reaction product is converted to UO₂And (3) powder. This reaction can be generally represented as follows:

UF₆+2H₂o (e.g. UF)₆Aqueous solution of (b) → UO₂F₂+4HF，

(at about 120 ℃ F. (about 48.9 ℃ C.))

UO₂F₂+2NH₄OH→UO₂(NH₄)₂+2HF

(at about 70 ℃ F. (about 21 ℃ C.))

UO₂(NH₄)₂+H₂+2H₂O (e.g. UO)₂(NH₄)₂With steam in a hydrogen atmosphere)

→UO₂+2NH₄OH

(at about 1100 ℃ F. (about 593.3 ℃ C.))

Integrated dry process (IDR) Process UF is typically mixed with hydrogen in stages in a kiln such as, for example, a rotary kiln₆To ceramic grade uranium dioxide (UO)₂) Powder to produce UO₂And HF gas. In an exemplary process, uranium hexafluoride gas is blown into a kiln or calciner and mixed with steam and excess hydrogen gas at atmospheric pressure at 1100 ° F (about 593.3 ℃). This reaction can be generally represented as follows:

UF₆+H₂+H₂O→UO₂+6HF。

excess hydrogen remaining after the reaction is burned off and HF gas is captured as an HF solution.

The uranium dioxide produced in any of of these or other reactions is in powder form₂The powder may be combined with solid carbon in a calciner or rotary kiln in a hydrogen atmosphere to create a reducing atmosphereAnd/or the carbon dioxide reaction product may be in gaseous form and burned off or removed by other suitable means. The uranium carbide reaction product is in the solid state.

advantages of uranium carbide are that uranium is highly covalent, having an effective valence close to zero₃Si₂The conversion of (b) involves replacing carbon with silicon. The silicon may be introduced in several ways, such as by reacting uranium carbide powder with, for example, an excess of silane gas (SiH) in a calciner₄) In excess of hydrogen (H)₂) In the presence of a catalyst. The powder and gas will be rotated in the calciner at atmospheric pressure at a temperature of between about 500 and 800K (about 227 ℃ to 527 ℃), preferably between 500 and 700K (about 227 ℃ and 427 ℃) to produce U₃Si₂And methane gas, which can be expressed as:

3UC+2SiH₄+2H₂→U₃Si₂+3CH₄。

excess silane and hydrogen will react towards U₃Si₂And (5) driving. The methane reaction product may be degassed, burned or removed by any suitable means.

In various aspects, the SiH can be varied₄And H₂The rate of addition of the gas to vary the ratio of reactants to form the divide-by-U₃Si₂And uranium silicide compounds other than uranium silicide. Examples of other uranium silicides include USi_1.78、U₃Si, USi and U₃Si₅. In practice, a combination of uranium suicides will be produced. One skilled in the art will appreciate that reactant ratio control can drive the reaction to produce more of the desired product.

Several reaction schemes are thermodynamically studied using silane and several silicon halides. Silane reaction 3UC +2SiH₄+2H₂Has a negative gibbs free energy, as shown by the diamonds in the figure. Silicon halides, usually by 3UC +2SiX₄+2X₂→U₃Si₂+3CX₄Wherein X is selected from the group consisting of Br, Cl, F and I, represented in the figure by × (Br), squares (Cl) and triangles (F), has a positive Gibbs free energy and is therefore less than the negative free energy of silaneThe desired reaction scheme. Iodine is not shown, but it is expected to have a positive free energy, falling above bromine in the figure.

Although preferred is the formula Si_nX_2n+2Silane reactions in which X is H, but silicon halide reactions in which X may be a halide or both H and halide may be used to react from U₃Si₂Removing trace residual carbon and other uranium silicide reaction products. The reaction using silicon halide will also be carried out in a rotary kiln in the same temperature range and at the same pressure as the reaction using silane. After formation of the uranium silicide, a homogenization step using a silicon halide may be performed to remove traces of residual carbon. This may be done at a temperature below the melting point of the target uranium silicide material.

The process described herein produces U than using silicon metal₃Si₂Is more cost-effective and can be carried out in a plant capable of operating at a temperature above 500 ℃ but below the melting point of the target uranium silicide, e.g. U, of the target stoichiometry₃Si₂、USi_1.78、U₃Si、USi、U₃Si₅Or combinations thereof, significantly improves safety since there is no need to handle corrosive molten materials.

All patents, patent applications, publications, and other publications mentioned herein are incorporated by reference in their entirety as if each individual reference were specifically and individually indicated to be incorporated by reference. All references cited herein, and any materials or portions thereof, are incorporated herein by reference to the extent that the incorporated materials do not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. To the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference, and the disclosure as explicitly set forth herein shall govern.

The embodiments described herein are to be understood as providing illustrative features of varying details of various embodiments of the disclosed invention, and therefore, unless otherwise specified, it is to be understood that or more features, elements, components, ingredients, structures, modules, and/or aspects of the disclosed embodiments can be combined, separated, interchanged, and/or reconfigured, within the scope of possibility, without departing from the scope of the disclosed invention, with or in relation to or more other features, elements, components, ingredients, structures, modules, and/or aspects of the disclosed embodiments.