System and method for recovering actinides from a fluorinated residue

Abstract

This application relates to recycling and processing technologies, and more particularly to a system and method for recovering actinides from fluorinated slag. The recovery system includes a raw material pretreatment unit, a fluorination conversion unit, a gas phase trapping unit, a gas phase conversion unit, and a product collection unit connected in sequence. This application provides a system and method for recovering actinides from fluorinated slag, which can efficiently recover actinides from fluorinated slag, further improving the recovery rate, and avoiding the secondary pollution problems caused by wet processes.

Description

Technical Field

[0001] This application relates to recycling and processing technologies, and more particularly to a system and method for recovering actinides from fluorinated slag. Background Technology

[0002] In the nuclear industry, actinide elements such as uranium (U) and plutonium (Pu) are key nuclear fuel materials. One of the mainstream preparation processes is the calcium thermal reduction method using the corresponding tetrafluorides. In this process, actinide tetrafluorides (such as UF4 or PuF4) react with metallic calcium at high temperatures to produce the target metal and a byproduct, fluorinated slag, primarily composed of calcium fluoride (CaF2). However, due to limitations in the reaction conditions, some tetrafluorides fail to react completely, and a small amount of the generated metal is entrained in the slag. When this slag comes into contact with air during processing, the metal within it may be oxidized (e.g., forming UO2, PuO2, etc.).

[0003] This not only wastes precious nuclide resources but also increases the complexity of waste disposal and environmental risks due to its radioactivity. Therefore, developing a technology that can simultaneously and efficiently recover actinide elements such as uranium and plutonium from this type of fluorinated slag is of great value for achieving a closed nuclear fuel cycle, reducing nuclear waste, and improving economic efficiency.

[0004] Existing treatment technologies mainly include physical methods and hydrometallurgical processes. Physical methods are not very effective at recovering actinides in the form of fine particles or oxides from slag. Although hydrometallurgy can recover nuclides through strong acid leaching, it generates a large amount of highly corrosive and radioactive acidic fluorine-containing wastewater. Its subsequent treatment process is extremely complex, costly, and causes serious secondary pollution problems.

[0005] Therefore, there is still room for improvement in the recovery of actinides from fluorinated slag.

[0006] Therefore, this application is hereby submitted. Summary of the Invention

[0007] This application provides a system and method for recovering actinides from fluorinated slag, which can efficiently recover actinides from fluorinated slag and avoid secondary pollution problems caused by wet processes.

[0008] The technical solution of this application is implemented as follows: This application, in its first aspect, provides a system for recovering actinides from fluorinated slag. The system comprises: a raw material pretreatment unit, a fluorination conversion unit, a gas phase trapping unit, a gas phase conversion unit, and a product collection unit connected in sequence. The raw material pretreatment unit includes a crushing device for crushing the fluorinated slag. The fluorination conversion unit includes a fluorination reaction device for converting actinides in the fluorinated slag into gaseous hexafluoride via a fluorination reaction. The gas phase trapping unit includes a gas-solid separation device and a condensation device. The gas-solid separation device separates the mixed gas and CaF2 residue generated in the fluorination conversion unit. The condensation device condenses the gaseous hexafluoride in the mixed gas into solid hexafluoride. The gas phase conversion unit includes a gas phase conversion device for sublimating the solid hexafluoride into gaseous hexafluoride. The product collection unit includes a reduction reaction device for reducing the gaseous hexafluoride into solid tetrafluoride.

[0009] In some embodiments, the recovery system further includes an exhaust gas treatment unit for treating the exhaust gases generated by the gas phase capture unit and the product collection unit.

[0010] A second aspect of this application provides a method for recovering actinides from fluorinated slag, the method using the aforementioned recovery system, comprising: S1: The fluorinated slag is crushed to obtain crushed slag material; the particle size of the crushed slag material is 50μm~1000μm; S2: The crushed slag and fluorine gas are subjected to a fluorination reaction to obtain a fluorination reaction product, wherein the fluorination reaction product includes a mixed gas containing gaseous hexafluoride and CaF2 residue; the hexafluoride includes UF6 and / or PuF6; S3: Perform gas-solid separation on the mixed gas and CaF2 residue, and condense the resulting mixed gas to collect the solid hexafluoride; S4: Sublimate the solid hexafluoride into a gaseous state, and reduce the obtained gaseous hexafluoride to obtain a solid tetrafluoride; the tetrafluoride includes UF4 and / or PuF4.

[0011] In some embodiments, in S1, the specific surface area of ​​the crushed slag is 0.05 m². 2 / g~5.0m 2 / g.

[0012] In some embodiments, in S2, the fluorination reaction is carried out at a temperature of 300°C to 600°C; and / or, The pressure of the fluorination reaction is -0.05 MPa to 0.05 MPa; and / or, The flow rate of the crushed slag is 0.05 m³ / g. 3 / h~3m 3 Fluorine gas per hour.

[0013] In some embodiments, in S3, the temperature of the gas-solid separation is 50°C to 70°C.

[0014] In some embodiments, in S3, the mixed gas is subjected to multi-stage condensation, first condensing the mixed gas at 50°C to 70°C, and then condensing it at 30°C to 50°C.

[0015] In some embodiments, in S4, the sublimation temperature is 60°C to 100°C.

[0016] In some embodiments, in step S4, the reduction reaction includes: reducing the gaseous hexafluoride and hydrogen at 300°C to 600°C, wherein the flow rate of the hydrogen is 0.5 m³ / h to 2 m³ / h.

[0017] In some embodiments, the actinides in the fluorinated slag account for 0.5% to 5% by mass.

[0018] This application has the following beneficial effects: This application provides a system and method for recovering actinides from fluorinated slag, which can efficiently recover actinides from fluorinated slag and avoid the secondary pollution problems caused by wet processes. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of the method for recovering actinides from fluorinated slag provided in Embodiment 1 of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limitations on this application. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Fluorination volatilization utilizes strong fluorinating agents such as fluorine gas to convert different forms of actinides in materials into easily volatile fluorides (such as UF6 and PuF6), achieving effective separation from the matrix material through gas-phase separation. However, for materials with complex compositions and relatively low content of target elements, actinides such as uranium and plutonium exist in various chemical forms, including metallic, oxidized, and fluorinated states. Furthermore, these target elements are often tightly coated by the main byproduct, calcium fluoride (CaF2), making separation difficult. In addition, because the content of target actinides in the slag is relatively low, if a hydrometallurgical process is used, strong acid leaching must be employed. This generates a large amount of highly corrosive and radioactive acidic fluorine-containing wastewater, resulting in extremely high subsequent treatment costs and serious environmental risks.

[0022] Therefore, there is still room for improvement in the recovery of actinides from the fluorinated slag produced by current calcium thermal reduction.

[0023] Accordingly, this application employs a fully dry process flow. First, the raw material pretreatment unit crushes the slag, effectively disrupting the coating of the calcium fluoride matrix and increasing the specific surface area, thereby improving the efficiency of subsequent gas-solid reactions and facilitating the efficient recovery of uranium and plutonium from the fluorinated slag. Subsequently, in the fluorination conversion unit, fluorine gas is used to uniformly convert different forms of actinides into volatile hexafluoride gases (UF6, PuF6). Gas-phase separation completely eliminates solid-phase impurity interference, achieving a high recovery rate of over 97%. Finally, through condensation capture and hydrogen reduction technology, the nuclides are converted back into stable solid tetrafluoride. The entire process requires no liquid-phase reagents, fundamentally eliminating the generation of radioactive acidic waste liquid.

[0024] Specifically, this application has the following technical solution: This application, in its first aspect, provides a system for recovering actinides from fluorinated slag. The system comprises: a raw material pretreatment unit, a fluorination conversion unit, a gas phase trapping unit, a gas phase conversion unit, and a product collection unit connected in sequence. The raw material pretreatment unit includes a crushing device for crushing the fluorinated slag. The fluorination conversion unit includes a fluorination reaction device for reacting the actinides in the fluorinated slag into gaseous hexafluoride. The gas phase trapping unit includes a gas-solid separation device and a condensation device. The gas-solid separation device separates the mixed gas and CaF2 residue generated in the fluorination conversion unit. The condensation device condenses the gaseous hexafluoride in the mixed gas into solid hexafluoride. The gas phase conversion unit includes a gas phase conversion device for sublimating the solid hexafluoride into gaseous hexafluoride. The product collection unit includes a reduction reaction device for reducing the gaseous hexafluoride into solid tetrafluoride.

[0025] This application achieves highly efficient recovery of valuable nuclides (with a recovery rate exceeding 97%) by uniformly converting various forms of actinides in fluorinated slag into easily separable volatile fluorides. Furthermore, the method is applicable to fluorinated slag containing uranium and / or plutonium, demonstrating strong versatility. Simultaneously, the recovery system employed in this application is a completely dry process, fundamentally eliminating the problem of generating large amounts of radioactive acidic fluorine-containing wastewater associated with hydrometallurgy, significantly reducing environmental risks and treatment costs. Compared to hydrometallurgical processes, the recovery system of this application has a shorter process flow, consumes fewer chemical reagents, and uses relatively simpler equipment, reducing overall operational difficulty and operating costs.

[0026] In this application, the fluorinated slag is produced through a calcothermic reduction reaction. Its main component is a calcium fluoride (CaF2) matrix, which contains a random distribution of actinide elements in various chemical forms, including metallic, oxidized, and fluorinated states, which are residual due to incomplete reactions or high-temperature entrainment. This material is characterized by its extremely complex composition, relatively low content of the target nuclide, and tight coating by a dense matrix, making it difficult to effectively separate using traditional physical methods. Wet treatment, on the other hand, would generate serious radioactive acidic wastewater pollution.

[0027] In this application, the crushing equipment may be a jaw crusher, ball mill, or impact crusher, and the particle size is ensured to meet the standard through screening.

[0028] In this application, the fluorination reaction equipment and condensation equipment are corrosion-resistant reactors, which can be made of nickel-based alloys, tantalum or materials with fluorine-resistant coatings, and are equipped with precise temperature control and gas flow control systems to ensure stable reaction.

[0029] In some embodiments, the recovery system further includes an exhaust gas treatment unit for treating the exhaust gases generated by the gas phase capture unit and the product collection unit.

[0030] In this application, the tail gas generated throughout the process (mainly containing unreacted F2, reaction byproducts O2 and HF, etc.) is treated to render it harmless through a tail gas treatment unit. The tail gas can be passed into an alkaline scrubbing tower (such as NaOH solution) for neutralization and absorption, or treated by catalytic reduction or other methods to ensure that emissions meet environmental protection standards.

[0031] A second aspect of this application provides a method for recovering actinides from fluorinated slag, the method using the aforementioned recovery system, comprising: S1: The fluorinated slag is crushed to obtain crushed slag material; the particle size of the crushed slag material is 50μm~1000μm; S2: The crushed slag and fluorine gas are subjected to a fluorination reaction to obtain a fluorination reaction product, wherein the fluorination reaction product includes a mixed gas containing gaseous hexafluoride and CaF2 residue; the hexafluoride includes UF6 and / or PuF6; S3: Perform gas-solid separation on the mixed gas and CaF2 residue, and condense the resulting mixed gas to collect the solid hexafluoride; S4: Sublimate the solid hexafluoride into a gaseous state, and reduce the obtained gaseous hexafluoride to obtain a solid tetrafluoride; the tetrafluoride includes UF4 and / or PuF4.

[0032] This application achieves highly efficient recovery of valuable nuclides (with a recovery rate exceeding 97%) by uniformly converting various forms of actinides in fluorinated slag into easily separable volatile fluorides. Furthermore, the method is applicable to fluorinated slag containing uranium and / or plutonium, demonstrating strong versatility. Simultaneously, this recovery method is a completely dry process, fundamentally eliminating the problem of generating large amounts of radioactive acidic fluorine-containing wastewater associated with hydrometallurgy, significantly reducing environmental risks and treatment costs. Compared to hydrometallurgical processes, this recovery method has a shorter process flow, consumes fewer chemical reagents, and requires relatively simpler equipment, reducing overall operational difficulty and operating costs. For example, in S1, the particle size of the crushed slag can be 50μm, 70μm, 90μm, 110μm, 130μm, 150μm, 170μm, 190μm, 210μm, 230μm, 250μm, 270μm, 290μm, 310μm, 330μm, 350μm, 370μm, 390μm, 410μm, 430μm, 450μm, 470μm, 490μm, 510μm, 530μm, etc. The particle size ranges from 50 μm to 1000 μm, or any combination thereof. Optionally, the particle size of the crushed slag is 50 μm to 500 μm. Optionally, the particle size of the crushed slag is 50 μm to 150 μm.

[0033] In this application, in S1, the fluorinated slag is mechanically crushed and ground to control the particle size within the above-mentioned range, which can increase the specific surface area of ​​the slag material, destroy the coating of uranium compounds on the CaF2 matrix, thereby improving the gas-solid phase contact efficiency and reaction rate in the subsequent fluorination reaction, and thus improving the recovery rate.

[0034] In this application, in S2, the metallic, oxidized, and fluorinated actinides in the crushed fluorinated slag react with fluorine gas to transform into volatile gaseous hexafluoride. The main chemical reactions of the uranium slag in the fluorinated slag are shown in chemical formulas (1) to (7): U+3F2→UF6 (1) UF4+F2→UF6(2) UO2+3F2→UF6+O2(3) U3O8+9F2→3UF6+4O2(4) The main chemical reactions of plutonium slag in fluorinated slag are as follows: Pu+3F2→PuF6 (5) PuF4+F2→PuF6(6) PuO2+3F2→PuF6+O2(7)

[0035] In this application, during step S3, the high-temperature mixed gas generated by the reaction (containing UF6, PuF6, excess F2, and O2, etc.) undergoes gas-solid separation with the non-volatile CaF2 residue. The separated gases (UF6 and PuF6) then enter a multi-stage condensation system (cold trap). By gradually cooling down, UF6 and PuF6 are condensed into solids for collection, which helps to improve the recovery rate. This process can efficiently collect UF6, while non-condensable gases such as oxygen enter the tail gas system.

[0036] In this application, in S4, the solid hexafluoride (UF6 and / or PuF6) collected by condensation is heated at a controlled temperature (60°C to 100°C) to sublimate it back into a gaseous state and transferred to a conversion reactor; then, the gaseous hexafluoride is reduced with hydrogen to convert it into a solid tetrafluoride that is more chemically stable, easier to store and use; wherein, the reduction reaction when the solid hexafluoride is UF6 or PuF6 is as shown in chemical formulas (8) to (9): UF6 + H2 → UF4 + 2HF (8) PuF6+H2→PuF4+2HF (9).

[0037] In some embodiments, in S1, the specific surface area of ​​the crushed slag is 0.05 m². 2 / g~5.0m 2 / g. For example, in S1, the specific surface area of ​​the crushed slag can be 0.05 m² / g, 0.15 m² / g, 0.3 m² / g, 0.5 m² / g, 0.7 m² / g, 0.9 m² / g, 1.1 m² / g, 1.3 m² / g, 1.5 m² / g, 1.7 m² / g, 1.9 m² / g, 2.1 m² / g, 2.3 m² / g, 2.5 m² / g, 2.7 m² / g, 2.9 m² / g, 3.1 m² / g, 3.3 m² / g, 3.5 m² / g, 3.7 m² / g, 3.9 m² / g, 4.1 m² / g, 4.3 m² / g, 4.5 m² / g, 4.7 m² / g, 4.9 m² / g, 5.0 m² / g, or a value within a range of any two of these values. Optionally, in S1, the specific surface area of ​​the crushed slag is 0.15 m². 2 / g~1.25m 2 / g. Optionally, in S1, the specific surface area of ​​the crushed slag is 0.85m². 2 / g~1.25m 2 / g.

[0038] In some embodiments, in S2, the temperature of the fluorination reaction is 300°C to 600°C; exemplaryly, the temperature of the fluorination reaction can be a value within a range of 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, or any combination thereof. By controlling the temperature of the fluorination reaction within the above range, it is helpful to improve the selectivity of the target hexafluoride, thereby improving the final recovery rate.

[0039] In some embodiments, during S2, the pressure of the fluorination reaction is -0.05 MPa to 0.05 MPa; exemplaryly, the pressure of the fluorination reaction is a value within a range of -0.05 MPa, -0.04 MPa, -0.03 MPa, -0.02 MPa, -0.01 MPa, 0 MPa, 0.01 MPa, 0.02 MPa, 0.03 MPa, 0.04 MPa, 0.05 MPa, or any combination thereof. By controlling the pressure of the fluorination reaction within the above range, it is helpful to improve the selectivity of the target hexafluoride, thereby improving the final recovery rate.

[0040] In some embodiments, in S2, the flow rate per gram of the crushed slag is 0.05 m³ / s. 3 / h~3m 3 Fluorine gas per hour. For example, it could be 0.05 m³ / h. 3 / h, 0.08m 3 / h, 0.1m 3 / h, 0.3m 3 / h, 0.5m3 / h, 1.0m 3 / h, 1.5m 3 / h, 2.0m 3 / h, 2.5m 3 / h, 2.8m 3 / h, 3.0m 3 / h, or a value within a range of any two of these ranges. Controlling the temperature of the fluorination reaction within the above range helps to improve the stability of the reaction and the selectivity of the target hexafluoride, thereby increasing the final recovery rate.

[0041] In some embodiments, in S3, the temperature for gas-solid separation is 50°C to 70°C. Exemplarily, it can be a value between 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, or any combination thereof.

[0042] In this application, to ensure that the actinide hexafluoride remains in a gaseous state in the separation zone, the temperature of this zone is maintained within the aforementioned range. This temperature is higher than the sublimation point of UF6 (56.5°C) and close to the sublimation point of PuF6 (62.1°C), which ensures that both can migrate effectively, thereby improving the selectivity of the target hexafluoride.

[0043] In some embodiments, in step S3, the mixed gas undergoes multi-stage condensation. First, the mixed gas is condensed at 50°C to 70°C. For example, the condensation temperature can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, or any combination thereof. Then, condensation is performed at 30°C to 50°C. For example, the condensation temperature can be 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, or any combination thereof. By controlling the condensation method to be multi-stage condensation and further controlling the multi-stage condensation temperatures within the aforementioned ranges, the amount of hexafluoride solids collected can be further increased, thereby improving the final recovery rate.

[0044] In some embodiments, in S4, the sublimation temperature is 60°C to 100°C. Exemplarily, the sublimation temperature can be 60°C, 62°C, 64°C, 66°C, 68°C, 70°C, 72°C, 74°C, 76°C, 78°C, 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, 94°C, 96°C, 98°C, 100°C, or a value within a range of any two of these.

[0045] In some embodiments, in step S4, the reduction reaction includes: reducing the gaseous hexafluoride and hydrogen at a temperature of 300°C to 600°C, wherein the flow rate of the hydrogen is 0.5 m³ / h to 2 m³ / h. Exemplarily, the temperature of the reduction reaction can be a value within a range of 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, or any combination thereof. For example, the flow rate of hydrogen can be 0.5 m³ / s. 3 / h, 0.6m 3 / h, 0.7m 3 / h, 0.8m 3 / h, 0.9m 3 / h, 1.0m 3 / h, 1.1m 3 / h, 1.2m 3 / h, 1.3m 3 / h, 1.4m 3 / h, 1.5m 3 / h, 1.6m 3 / h, 1.7m 3 / h, 1.8m 3 / h, 1.9m 3 / h, 2.0m 3 / h, or a value between any two of them.

[0046] In some embodiments, the actinides in the fluorinated slag constitute 0.5% to 5% by mass. For example, the mass percentage of actinides in the fluorinated slag can be 0.5%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, 2.1%, 2.3%, 2.5%, 2.7%, 2.9%, 3.1%, 3.3%, 3.5%, 3.7%, 3.9%, 4.1%, 4.3%, 4.5%, 4.7%, 4.9%, 5%, or any combination thereof. The recovery system and method of this application are applicable to both high and low actinide content in the recovered raw materials, and exhibit particularly good recovery performance even when the actinide content in the recovered raw materials is low.

[0047] To further illustrate the technical solution of this application, the following embodiments are provided: In the following embodiments, the recovery rate of actinides is calculated as follows:

[0048] : Indicates the recovery rate of actinides; m1: indicates the mass of the solid tetrafluoride product collected after the reduction reaction; : Indicates the mass fraction of actinides in solid tetrafluoride products; : Indicates the original mass of the fluorinated residue entering the raw material pretreatment unit; : Indicates the total mass fraction of actinides in the original fluorinated slag.

[0049] Example 1 This application provides a system for recovering actinides from fluorinated slag. The recovery system includes: a raw material pretreatment unit, a fluorination conversion unit, a gas phase capture unit, a gas phase conversion unit, and a product collection unit connected in sequence.

[0050] The raw material pretreatment unit includes crushing equipment, which is a jaw crusher and a ball mill, used to crush fluorinated slag. The fluorination conversion unit includes a fluorination reaction device, which is a corrosion-resistant nickel-based alloy fluorination reactor used to react and convert the actinides in the fluorination slag into gaseous hexafluoride. The gas phase capture unit includes a gas-solid separation device and a condensation device; the gas-solid separation device is used to separate the mixed gas and CaF2 residue generated in the fluorination conversion unit; the condensation device is used to condense the gaseous hexafluoride in the mixed gas into solid hexafluoride; The gas phase conversion unit includes a gas phase conversion device, which is used to sublimate the solid hexafluoride into a gas phase hexafluoride. The product collection unit includes a reduction reaction device for reducing the gaseous hexafluoride to a solid tetrafluoride.

[0051] This embodiment further provides a method for recovering uranium fluoride from fluorinated slag using the above-described recovery system. A flowchart of the recovery method is shown below. Figure 1 The recycling method includes the following steps: The composition of the fluorinated slag sample after the calcium thermal reduction process is shown in Table 1. The slag was crushed using a jaw crusher and ball mill, and then sieved to collect powder with a particle size of 100 micrometers. The specific surface area of ​​this powder was 0.85 m². 2 / g~1.25m 2 / g.

[0052] Table 1

[0053] The powder was fed into a nickel-based alloy fluorination reactor and heated to 500°C. Then, 99.9% pure fluorine gas was introduced at a flow rate of 1.5 m³ / h, and the reaction was allowed to proceed for 2 hours. The resulting gas was then introduced into a gas-phase separation chamber (temperature maintained at 65°C). The separated UF6 gas entered a two-stage condensation system, with the first and second stages controlled at 60°C and 40°C respectively, yielding solid UF6. The collected UF6 was heated and sublimated, then introduced into a reduction reactor. Reduction was performed at 350°C with hydrogen gas at a flow rate of 1 m³ / h for 3 hours, yielding UF4 powder. The calculated uranium recovery rate reached 98%. All tail gases were treated in an alkaline scrubbing tower before being discharged in compliance with emission standards.

[0054] Example 2 This embodiment uses the recovery system of Example 1 to recover uranium fluoride from fluorinated residue. The recovery method includes the following steps: Take slag with the same composition as in Example 1, crush it, and collect powder with a particle size of 500 micrometers. The specific surface area of ​​this powder is 0.15 m². 2 / g~0.35m 2 / g. The reactor temperature was set to 450°C, the fluorine gas flow rate was 1 m³ / h, and the reaction time was extended to 3 hours. After UF6 gas separation, the condensation system temperature was set to 55°C. The collected UF6 was reduced to UF4 by hydrogen gas at 300°C for 3.5 hours. The final uranium recovery rate was 97%.

[0055] Example 3 This embodiment uses the recovery system of Example 1 to recover uranium fluoride from fluorinated residue. The recovery method includes the following steps: Take slag with the same composition as in Example 1, crush it, and collect powder with a particle size of 1000 micrometers. The specific surface area of ​​this powder is 0.08 m². 2 / g~0.15m 2 / g. The fluorination reaction was carried out in a reactor at 400°C with a fluorine gas flow rate of 0.8 m³ / h for 4 hours. After UF6 gas separation, the condensation temperature was controlled at 50°C. UF6 was then reduced to UF4 with hydrogen at 320°C. The final uranium recovery rate was 94%.

[0056] Example 4 This embodiment uses the recovery system of Example 1 to recover uranium fluoride from fluorinated residue. The recovery method includes the following steps: The plutonium-containing fluoride slag produced after the preparation of metallic plutonium by the calcium thermal reduction method is shown in Table 2. Table 2

[0057] The slag was pulverized using a pretreatment method similar to that in Example 1, and powder with a particle size of 100 micrometers and a specific surface area of ​​0.85 m² was collected. 2 / g~1.25m 2 / g. The powder was reacted in a reactor at 550°C with fluorine gas at a flow rate of 1.2 m³ / h for 2.5 hours to generate volatile PuF6. The gas then passed through a separation zone at 70°C and entered a condensation system to collect solid PuF6. Subsequently, hydrogen gas was introduced at 400°C to reduce PuF6 to stable PuF4 powder. The plutonium recovery rate was measured to be over 97%. All tail gas was treated in an alkaline scrubbing tower before being discharged in compliance with standards.

[0058] Comparative Example 1 This comparative example uses the recovery system of Example 1 to recover uranium fluoride from fluorinated slag. The difference between the recovery method and Example 1 is that the fluorinated slag is not crushed; the particle size of the fluorinated slag is 2mm~10mm, and the specific surface area is 0.01m². 2 / g~0.05m 2 / g. Measurements showed that the uranium recovery rate was below 60%.

[0059] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of this application are included within the scope of protection of this application.

Claims

1. A system for recovering actinides from fluorinated slag, characterized in that, include: The raw material pretreatment unit, fluorination conversion unit, gas phase capture unit, gas phase conversion unit and product collection unit are connected in sequence. The raw material pretreatment unit includes a crushing device, which is used to crush fluorinated slag. The fluorination conversion unit includes a fluorination reaction device, which is used to convert the actinides in the fluorination residue into gaseous hexafluoride through a fluorination reaction. The gas phase capture unit includes a gas-solid separation device and a condensation device; the gas-solid separation device is used to separate the mixed gas and CaF2 residue generated in the fluorination conversion unit; the condensation device is used to condense the gaseous hexafluoride in the mixed gas into solid hexafluoride; The gas phase conversion unit includes a gas phase conversion device, which is used to sublimate the solid hexafluoride into a gas phase hexafluoride. The product collection unit includes a reduction reaction device for reducing the gaseous hexafluoride to a solid tetrafluoride.

2. The system for recovering actinides from fluorinated slag according to claim 1, characterized in that, The recovery system also includes an exhaust gas treatment unit, which is used to treat the exhaust gas generated by the gas phase capture unit and the product collection unit.

3. A method for recovering actinides from fluorinated slag, characterized in that, The method uses the actinide element recovery system in the fluorinated slag as described in claim 1 or 2, comprising: S1: The fluorinated slag is crushed to obtain crushed slag material; the particle size of the crushed slag material is 50μm~1000μm; S2: The crushed slag and fluorine gas are subjected to a fluorination reaction to obtain a fluorination reaction product, wherein the fluorination reaction product includes a mixed gas containing gaseous hexafluoride and CaF2 residue; the hexafluoride includes UF6 and / or PuF6; S3: Perform gas-solid separation on the mixed gas and CaF2 residue, and condense the resulting mixed gas to collect the solid hexafluoride; S4: Sublimate the solid hexafluoride into a gaseous state, and reduce the obtained gaseous hexafluoride to obtain a solid tetrafluoride; the tetrafluoride includes UF4 and / or PuF4.

4. The method for recovering actinides from fluorinated slag according to claim 3, characterized in that, In S1, the specific surface area of the crushed slag is 0.05 m 2 / g ~ 5.0 m 2 / g.

5. The method for recovering actinides from fluorinated slag according to claim 3 or 4, characterized in that, In S2, the fluorination reaction is carried out at a temperature of 300°C to 600°C; and / or, The pressure of the fluorination reaction is -0.05 MPa to 0.05 MPa; 0.05 m 3 / h~3m 3 / h of fluorine gas.

6. The method for recovering actinides from fluorinated slag according to any one of claims 3 to 5, characterized in that, In S3, the temperature for gas-solid separation is 50℃~70℃.

7. The method for recovering actinides from fluorinated slag according to any one of claims 3 to 6, characterized in that, In step S3, the mixed gas is subjected to multi-stage condensation. First, the mixed gas is condensed at 50°C to 70°C, and then condensed at 30°C to 50°C.

8. The method for recovering actinides from fluorinated slag according to any one of claims 3 to 7, characterized in that, In S4, the sublimation temperature is 60℃~100℃.

9. The method for recovering actinides from fluorinated slag according to any one of claims 3 to 8, characterized in that, In S4, the reduction reaction includes: reducing the gaseous hexafluoride and hydrogen at 300℃~600℃, wherein the flow rate of the hydrogen is 0.5m³ / h~2m³ / h.

10. The method for recovering actinides from fluorinated slag according to any one of claims 3 to 9, characterized in that, In the fluorinated slag, the mass percentage of actinides is 0.5% to 5%.

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