Actinide and / or lanthanide trichloride and preparation method and application thereof

Abstract

The invention relates to the technical field of nuclear, and provides actinide and / or lanthanide trichloride and a preparation method and application thereof, and the preparation method comprises the following steps: placing ammonium chloride in a first container; placing a raw material containing actinide and / or lanthanide in a second container; placing the second container at the bottom in the first container; the molar ratio of the raw materials to the ammonium chloride is controlled to be 1: 5 or above according to the total amount of the actinide and lanthanide elements, the second container is heated to 300-600 DEG C, the pressure in the second container is normal pressure in the reaction process, and the trichloride is obtained after complete reaction. The preparation method disclosed by the invention is good in economical efficiency, high in safety, capable of realizing large-scale production of actinide and / or lanthanide trichloride, high in yield and high in product purity; the method is simple in process, high in practicability and low in equipment requirement, and has important significance on nuclear chemical engineering.

Description

Technical Field

[0001] This invention relates to the field of nuclear technology, and in particular to an actinide and / or lanthanide trichloride, its preparation method, and its application. Background Technology

[0002] Actinide trichlorides and lanthanide trichlorides are two important classes of inorganic compounds. Actinide trichlorides, in particular, are crucial nuclear chemical products with wide applications in the nuclear fuel cycle. For example, the molten salt electrolytic refining process requires the addition of approximately 10% uranium trichloride by mass to the lithium chloride-potassium chloride eutectic molten salt to sustain the spent fuel electrorefining reaction; the fuel for chloride molten salt fast reactors also requires large quantities of high-purity actinide trichlorides. Meanwhile, lanthanide trichlorides play a key role in applications such as catalysis, luminescent materials, and alloys, as well as in research on actinide analogs.

[0003] However, current methods for preparing trichlorides of actinides and lanthanides all suffer from technical bottlenecks. Taking uranium trichloride, an actinide, as an example, a common method involves reacting uranyl nitrate hydrate or uranium trioxide with hexachloropropylene, followed by reflux to obtain uranium tetrachloride, which is then reacted with high-purity hydrogen at 500°C to produce uranium trichloride. Alternatively, metallic uranium can be used as a raw material; the system is evacuated, hydrogen is introduced, and the temperature is raised to 250°C to produce uranium hydride, followed by the introduction of high-purity hydrogen chloride gas and maintaining the temperature at 250°C to produce uranium trichloride. These methods generally suffer from complex processes, high costs, and the need to use flammable and toxic gases (such as hydrogen and hydrogen chloride).

[0004] Therefore, existing technologies generally lack a method that is simple, low-cost, safe, applicable to a variety of actinide and lanthanide elements, and capable of producing high-purity trichlorides in large quantities. Summary of the Invention

[0005] This invention provides an actinide and / or lanthanide trichloride, its preparation method, and its application. By placing the actinide metal raw material and ammonium chloride in different positions to avoid direct contact between them, and by controlling the molar ratio of the actinide and / or lanthanide-containing raw material to ammonium chloride to be greater than 1:5 based on the total amount of actinide and lanthanide elements, and by making the reaction under normal pressure, the purity of the obtained product can meet the application requirements.

[0006] In a first aspect, the present invention provides a method for preparing actinide and / or lanthanide trichlorides, comprising: Place ammonium chloride in the first container; Place the raw materials containing actinides and / or lanthanides in the second container; Place the second container at the bottom inside the first container; Based on the total amount of actinides and lanthanides, the molar ratio of the raw material to the ammonium chloride is controlled to be 1:5 or higher. The second container is heated to 300~600°C. During the reaction, the second container is kept at atmospheric pressure. After the reaction is complete, the trichloride is obtained.

[0007] When the raw material contains only actinides, the total amount of actinides and lanthanides can be understood as the amount of lanthanides being 0, and only actinides are considered.

[0008] When the raw material contains only lanthanide elements, the total amount of actinides and lanthanides can be understood as the amount of actinides being 0, and only lanthanides are considered.

[0009] The reaction was carried out in an atmosphere in which both oxygen and water content were below 1 ppm in the second container.

[0010] In this invention, the molar ratio of the raw material to the ammonium chloride is any value or a range of any values ​​from 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, and 1:16.

[0011] In this invention, heating the second container to 300~600℃ can be any value or a range of any values ​​from 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃, and 600℃.

[0012] like Figure 1 As shown, this invention uses ammonium chloride as a chlorinating agent, which begins to decompose into ammonia and hydrogen chloride at around 200°C, reaching its fastest decomposition rate at around 330°C. The hydrogen chloride produced by decomposition reacts with actinide metals under heating conditions (above 300°C), generating actinide and / or lanthanide trichlorides when there is sufficient hydrogen chloride (i.e., sufficient ammonium chloride). The applicant found in experiments that if there is insufficient hydrogen chloride (i.e., insufficient ammonium chloride), a mixture of actinide and / or lanthanide chloride nitrides and trichlorides is easily formed, reducing the purity of the obtained product. Furthermore, experiments have shown that if the gas generated during the decomposition of ammonium chloride causes excessively high system pressure, the purity of the resulting product will decrease significantly. Based on this, the present invention, through extensive experimental research, has found that placing the raw material containing actinides and / or lanthanides and ammonium chloride in different locations to avoid direct contact between the two, and controlling the molar ratio of the raw material to the ammonium chloride to be greater than 1:5 based on the total amount of actinides and lanthanides, and heating the second container to 300~600℃, while maintaining atmospheric pressure inside the second container during the reaction, can ensure that the purity of the resulting product meets application requirements.

[0013] The raw materials containing actinides and / or lanthanides can decompose into actinides and / or lanthanides during the reaction. For example, hydrides of actinides and / or lanthanides. Considering that hydrides of actinides and / or lanthanides are too dangerous, the present invention preferably places actinides and / or lanthanides directly as raw materials in a second container for reaction.

[0014] According to the preparation method of actinide and / or lanthanide trichlorides provided by the present invention, the mass of the raw material is 4g or more; Preferably, the raw material is in block form.

[0015] To improve the reaction rate, actinide metals in powder form are generally used, but powder is very dangerous (radioactive contamination and flammability in air). Research has found that the method of this invention can directly use blocky actinide metal raw materials for the reaction, such as cylindrical metallic uranium with a diameter of 6 mm and a height of 8 mm, which can achieve a complete chlorination reaction.

[0016] To improve the success rate of the chlorination reaction, it is preferable to slow down the decomposition rate of ammonium chloride and delay its depletion; therefore, the reaction temperature does not need to be too high. The reaction temperature is 300~600°C, preferably 400~500°C. The reaction between hydrogen chloride and actinide metals releases a large amount of heat, so the heating rate should be slow to prevent the temperature from becoming too high. According to the method for preparing actinide and / or lanthanide trichlorides provided by the present invention, the second container is heated from T1 to T2 at a heating rate v1, and then held at T2 until the reaction ends. v1 is below 10℃ / h; T1 is below 300℃, and the temperature difference between T1 and T2 is greater than 100℃.

[0017] According to the method for preparing actinide and / or lanthanide trichlorides provided by the present invention, the heating parameters include: first heating to 280°C at a heating rate of 1°C / min, then heating to 400°C at a heating rate of 10°C / h, holding at this temperature for more than 24 hours, and then the reaction is completed.

[0018] According to the method for preparing actinide and / or lanthanide trichlorides provided by the present invention, the actinide metal is selected from one or more combinations of uranium, neptunium, plutonium, americium, and curium; And / or, the lanthanide elements are selected from one or more combinations of Nd, Sm, La, and Ce.

[0019] According to the method for preparing actinide and / or lanthanide trichlorides provided by the present invention, the water content of the ammonium chloride is less than 1 ppm.

[0020] Preferably, the ammonium chloride raw material is dried at 100°C for 48-72 hours, cooled, and then ground into powder under conditions of isolation from water and oxygen before the reaction is carried out.

[0021] According to the method for preparing actinide and / or lanthanide trichlorides provided by the present invention, the preparation method is carried out in a reactor; the reactor includes... A housing includes an opening, a cover a, an asbestos rubber gasket, and a plurality of bolts; the cover a completely covers the opening, the asbestos rubber gasket is located between the cover a and the opening, and the plurality of bolts are used to fasten the cover a and the asbestos rubber gasket to cover the opening. A suspended basket is located inside the housing; the material of the suspended basket is resistant to hydrogen chloride corrosion; the material of the suspended basket may be, for example, pure nickel, Hastelloy, etc.

[0022] A corundum crucible A is located inside the basket; the first container is the corundum crucible A. A corundum crucible B is located at the bottom of the corundum crucible A; the second container is the corundum crucible B. A cover b, which completely covers the opening of the corundum crucible A; A heating device for heating the housing.

[0023] Ammonium chloride is volatile, and the reaction vessel with the above-described structure can slow down its volatilization. Furthermore, the reaction requires a large amount of ammonium chloride, ensuring that all the actinide metal raw materials can still react even if some of the ammonium chloride does not participate in the reaction and only volatilizes, yielding high-purity actinide and / or lanthanide trichlorides. Therefore, the specific reactor described above is used in this invention to meet the reaction requirements of this invention.

[0024] In addition, the present invention has an alumina lid on the alumina crucible A, which is to slow down the escape of hydrogen chloride gas from the alumina crucible A (reaction system), increase the contact probability between actinide metals and hydrogen chloride gas, and also to prevent condensed ammonium chloride and other impurities from mixing into the product during cooling.

[0025] Preferably, the diameter ratio of the corundum crucible A and the corundum crucible B is 1.7 or higher.

[0026] Considering that actinide metals are easily oxidized, flammable, and radioactive, and that ammonium chloride is hygroscopic, in the method for preparing actinide and / or lanthanide trichlorides provided by the present invention, the reactor is placed entirely within a containment space where both oxygen and water content are below 1 ppm.

[0027] Preferably, the containment space is inert, with both oxygen and water content below 1 ppm; for example, high-purity argon or high-purity helium.

[0028] Secondly, the present invention provides actinide trichloride products and / or lanthanide trichloride products obtained by the preparation method of actinide and / or lanthanide trichloride products as described above, wherein the purity of the actinide trichloride products is 95% or higher, and / or the purity of the lanthanide trichloride products is 95% or higher.

[0029] Thirdly, the present invention provides the application of the actinide trichloride products as described above in chloride molten salt fast reactor fuel.

[0030] This invention provides an actinide and / or lanthanide trichloride, its preparation method, and its application. By placing the actinide metal raw material and ammonium chloride in different positions to avoid direct contact between them, and by controlling the molar ratio of the actinide and / or lanthanide-containing raw material to the ammonium chloride to be greater than 1:5 based on the total amount of actinide and lanthanide elements, and by ensuring that the reaction is carried out under normal pressure, the purity of the obtained product can meet the application requirements.

[0031] Furthermore, the method for preparing actinide and / or lanthanide trichlorides provided by this invention is economical and safe, solving the problems of complex preparation processes, high costs, high risks, and low yields in existing technologies. It can also achieve large-scale production of actinide and / or lanthanide trichlorides with high yield and high product purity. The method is simple, practical, and requires low equipment. Actinide and / or lanthanide trichlorides can be prepared in a single reaction under mild reaction conditions, which is of great significance to the fields of nuclear chemical engineering and molten salt fast reactors and has good application prospects. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 This is a schematic diagram of the reaction process of the method for preparing actinide trichlorides provided by the present invention.

[0034] Figure 2 This is an X-ray diffraction pattern of the actinide trichloride product of Example 1 provided by the present invention.

[0035] Figure 3 X-ray diffraction pattern of the lanthanide trichloride product of Example 8 provided by the present invention.

[0036] Figure 4X-ray diffraction pattern of the lanthanide trichloride product of Example 9 provided by the present invention.

[0037] Figure 5 X-ray diffraction pattern of the lanthanide trichloride product of Example 10 provided by the present invention.

[0038] Figure 6 X-ray diffraction pattern of the lanthanide trichloride product of Example 11 provided by the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0040] The following is combined with Figures 1-6 This invention describes an actinide and / or lanthanide trichloride, its preparation method, and its application.

[0041] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0042] The commercial ammonium chloride used in this invention has a purity of 99.9% (commercially available high-purity product (Sigma-Aldrich)). In the following embodiments of this invention, the commercial ammonium chloride is dried in a drying oven at 100°C for 48 hours to remove residual moisture, and then transferred to a glove box where the oxygen and water content are both below 1 ppm, and ground into a fine powder using a mortar and pestle for later use.

[0043] The following embodiments of the present invention utilize the following types of equipment: Equipment 1 A reactor, comprising: A housing, wherein the housing is made of 316L stainless steel; The housing includes an opening, a cover a, an asbestos rubber gasket, and several bolts; The cover a completely covers the opening, the asbestos rubber gasket is located between the cover a and the opening, and the bolts are used to fasten the cover a and the asbestos rubber gasket to cover the opening.

[0044] A suspended basket located within the housing; the basket is made of Hastelloy (C276), a material resistant to hydrogen chloride corrosion.

[0045] A corundum crucible A is located inside the basket. Generally, a corundum crucible with an outer diameter of 60 mm and a height of 120 mm can be used as corundum crucible A.

[0046] A corundum crucible B is located at the bottom of the corundum crucible A. Generally, a corundum crucible with an outer diameter of 30 mm and a height of 25 mm can be used as the corundum crucible B.

[0047] A cover b, which completely covers the opening of the corundum crucible A.

[0048] A heating device for heating the housing.

[0049] Equipment 2 It is basically the same as device 1, except that the asbestos rubber gasket is replaced with a fluororubber sealing ring.

[0050] Equipment 3 It is basically the same as device 1, except that the material of the suspended basket is replaced with Hastelloy, which is resistant to hydrogen chloride corrosion, and stainless steel 316L, which is not resistant to hydrogen chloride corrosion.

[0051] Example 1 A method for preparing actinide trichlorides, using equipment 1, such as... Figure 1 As shown, the steps are as follows: (1) Place ammonium chloride powder into corundum crucible A.

[0052] (2) Place the bulk uranium metal into corundum crucible B, and then place corundum crucible B into corundum crucible A. The mass of the bulk uranium metal is 4.211 g, and the molar ratio of uranium metal to ammonium chloride is 1:13.304.

[0053] (3) Cover with lid b, put the corundum crucible A into the hanging basket, put in the asbestos rubber gasket, cover with lid a, and tighten lid a.

[0054] (4) Heating shell, heating parameters are: 1℃ / min to 280℃, 10℃ / h to 400℃, heat up for 24h and then cool down naturally.

[0055] The entire process of steps (1) to (4) above is carried out in a glove box where the oxygen and water content is below 1 ppm. Since asbestos rubber gaskets are used (which cannot achieve a seal and will leak air), the entire shell is kept at atmospheric pressure.

[0056] After the reaction is complete, the black block-shaped substance (i.e., the product) is removed.

[0057] Examples 2-4 The examples are essentially the same as in Example 1, except for the following differences: the mass m of the bulk uranium and the molar ratio x of uranium to ammonium chloride. Specifically, m and x in Examples 2-4 are shown in the table below: Table 1

[0058] Examples 5-7 The method is basically the same as Example 1, except that the mass m of the bulk metallic uranium, the molar ratio x of metallic uranium to ammonium chloride, and the heating parameters are: heating to 280°C at 1°C / min, heating to 450°C at 10°C / h, and holding at the temperature for 24 hours before natural cooling.

[0059] Specifically, m and x in Examples 5-7 are shown in the table below: Table 2

[0060] Examples 8-11 A method for preparing lanthanide trichlorides is basically the same as in Example 1, except that the bulk metal uranium is replaced with bulk metal Ln (specific types are shown in the table below), and its mass and molar ratio x with ammonium chloride are shown in the table below.

[0061] Table 3

[0062] Example 12 It is basically the same as Example 2, except that: device 1 is replaced with device 3, that is, the material of the hanging basket is replaced with stainless steel 316L which is not resistant to hydrogen chloride corrosion.

[0063] Comparative Example 1 It is basically the same as Example 1, except that the mass of the bulk metallic uranium is 4.243g and the molar ratio of metallic uranium to ammonium chloride is 1:3.050.

[0064] Comparative Example 2 It is basically the same as Example 6, except that the device 1 is replaced with device 2, that is, the asbestos rubber gasket is replaced with a fluororubber sealing ring. Therefore, during the reaction process, the shell is under high pressure at high temperature, with the highest pressure being 3.2 MPa.

[0065] The products of the examples and comparative examples were tested using the following methods: The product type was verified by X-ray diffraction, such as Figures 2-6 As shown.

[0066] The purity of the product was determined using inductively coupled plasma atomic emission spectrometry.

[0067] Inductively coupled plasma mass spectrometry was used to detect impurities in the product.

[0068] The yield is calculated using the weight loss method. By weighing the increase in weight of corundum crucible B before and after the reaction and combining this with the product purity analysis results, the actual yield of actinide trichloride or lanthanide trichloride is determined. This actual yield is then divided by the theoretical yield (the mass of the raw material containing actinides and / or lanthanides when all of it is converted into actinide trichloride or lanthanide trichloride).

[0069] The test results are as follows: Table 3

[0070] The test results above show that there are differences in the yield and purity of Nd, Sm and La, Ce. This may be because La and Ce only have a +3 valence, while Nd and Sm contain trace amounts of NdCl2 and SmCl2 products (which can be considered impurities compared to LnCl3), but the content is so low that it hardly affects the product quality.

[0071] The molar ratio of metal to ammonium chloride and the reaction pressure have a key impact on the yield and purity of the product.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing actinide and / or lanthanide trichlorides, characterized in that, include: Place ammonium chloride in the first container; Place the raw materials containing actinides and / or lanthanides in the second container; Place the second container at the bottom inside the first container; Based on the total amount of actinides and lanthanides, the molar ratio of the raw material to the ammonium chloride is controlled to be 1:5 or higher. The second container is heated to 300~600°C. During the reaction, the second container is kept at atmospheric pressure. After the reaction is complete, the trichloride is obtained.

2. The method for preparing actinide and / or lanthanide trichlorides according to claim 1, characterized in that, The raw material has a mass of 4g or more; Preferably, the raw material is in block form.

3. The method for preparing actinide and / or lanthanide trichlorides according to claim 1 or 2, characterized in that, The second container is heated from T1 to T2 at a heating rate v1, and then held at T2 until the reaction ends. v1 is below 10℃ / h; T1 is below 300℃, and the temperature difference between T1 and T2 is greater than 100℃.

4. The method for preparing actinide and / or lanthanide trichlorides according to claim 3, characterized in that, The heating parameters include: first heating to 280°C at a heating rate of 1°C / min, then heating to 400°C at a heating rate of 10°C / h, holding at that temperature for more than 24 hours, and then the reaction is complete.

5. The method for preparing actinide and / or lanthanide trichlorides according to any one of claims 1 to 4, characterized in that, The actinide elements are selected from one or more combinations of uranium, neptunium, plutonium, americium, and curium; And / or, the lanthanide elements are selected from one or more combinations of Nd, Sm, La, and Ce.

6. The method for preparing actinide and / or lanthanide trichlorides according to any one of claims 1 to 5, characterized in that, The ammonium chloride has a water content of less than 1 ppm.

7. The method for preparing actinide and / or lanthanide trichlorides according to any one of claims 1 to 6, characterized in that, The preparation method is carried out using a reactor; the reactor includes... A housing includes an opening, a cover a, an asbestos rubber gasket, and a plurality of bolts; the cover a completely covers the opening, the asbestos rubber gasket is located between the cover a and the opening, and the plurality of bolts are used to fasten the cover a and the asbestos rubber gasket to cover the opening. A suspended basket, the basket being located within the housing; the basket is made of a material resistant to hydrogen chloride corrosion; A corundum crucible A is located inside the basket; the first container is the corundum crucible A. A corundum crucible B is located at the bottom of the corundum crucible A; the second container is the corundum crucible B. A cover b, which completely covers the opening of the corundum crucible A; A heating device for heating the housing.

8. The method for preparing actinide and / or lanthanide trichlorides according to claim 7, characterized in that, The reactor is placed entirely within a containment space where both oxygen and water content are below 1 ppm.

9. The actinide trichloride product and / or lanthanide trichloride product obtained by the method for preparing actinide and / or lanthanide trichlorides according to any one of claims 1 to 8, characterized in that, The purity of the actinide trichloride product is above 95%, and / or the purity of the lanthanide trichloride product is above 95%.

10. The application of the actinide trichloride product of claim 9 in chloride molten salt fast reactor fuel.

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