A device and method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction

Abstract

The present invention belongs to the technical field of uranium hexafluoride production from natural uranium, and specifically relates to a device and method for preparing uranium hexafluoride from natural uranium by low-temperature plasma chemical reaction. The integrated device for preparing uranium hexafluoride by low-temperature plasma fluorination is developed, including: a gas supply system, a low-temperature plasma fluorination reaction system, a material collection system, a vacuum system and an exhaust gas treatment system. The method includes the following steps: preparation of the gas supply system, generation and regulation of low-temperature plasma, preparation of uranium hexafluoride by low-temperature plasma fluorination, system atmosphere replacement, unloading weighing, vacuum purification and calculation of uranium hexafluoride product yield. The device and method provided by the present invention effectively promote the ionization of fluorine gas through argon dielectric barrier discharge technology, providing a new technical solution for broadening the preparation path of uranium hexafluoride.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing uranium hexafluoride from natural uranium, and specifically relates to a device and a method for preparing uranium hexafluoride from natural uranium by low-temperature plasma fluorination reaction. Background Art

[0002] Uranium hexafluoride is one of the most important compounds in the nuclear fuel cycle and is also the most volatile uranium compound. Uranium hexafluoride is generally produced by fluorine gas at high temperature to fluorinate uranium tetrafluoride. Some countries also use uranium chemical concentrate (U3O8) as the starting material to produce uranium hexafluoride through hydrogen reduction, hydrofluorination and fluorination.

[0003] When uranium tetrafluoride is used as raw material to produce uranium hexafluoride, the reaction temperature is high and the process conditions are relatively harsh. In order to increase the conversion rate of uranium tetrafluoride, excessive use of fluorine gas is required. Fluorine gas accelerates the corrosion of equipment under high temperature conditions, seriously shortening the service life of the equipment. Summary of the invention

[0004] In order to circumvent the problems existing in the above-mentioned prior art, broaden the preparation methods of uranium hexafluoride, reduce the preparation temperature, slow down the corrosion rate of equipment, and extend the service life of equipment, it is urgent to carry out research on low-temperature preparation technology of uranium hexafluoride, design and develop an integrated device for preparing uranium hexafluoride by low-temperature plasma fluorination to meet actual production needs. This patent provides a specific method and device for preparing uranium hexafluoride by low-temperature plasma fluorination.

[0005] The technical scheme of the present invention is as follows: a method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction, which controls the low-temperature plasma concentration and the fluorination reaction process by regulating the voltage, current, duty cycle, and temperature of the reaction zone in a high-voltage power supply cabinet, thereby obtaining the best reaction conditions that meet the process requirements; the physical process of generating low-temperature plasma and the chemical engineering of the fluorination reaction are realized simultaneously and in the same area in a low-temperature plasma fluorination reaction integrated device.

[0006] A low-temperature plasma fluorination reaction integrated device, comprising: a gas supply system, a low-temperature plasma fluorination reaction system, a material collection system, a tail gas treatment system and a vacuum system;

[0007] The gas supply system, the low-temperature plasma fluorination reaction system, the material collection system and the tail gas treatment system are connected in series, and the tail gas treatment system and the vacuum system are connected in parallel.

[0008] The gas supply system includes a fluorine gas inlet, an argon gas inlet, a fluorine gas purification device a, a fluorine gas purification device b, a fluorine gas purification device c and a mixing tank;

[0009] A V1 stop valve is provided on the rear end pipeline of the fluorine gas inlet, which is then connected in sequence to fluorine gas purification device a, fluorine gas purification device b and fluorine gas purification device c;

[0010] The argon gas inlet is connected to the outlet of the fluorine gas purification device c through a pipeline, and a V2 stop valve is provided on the pipeline;

[0011] The two air intake lines converge in the mixing tank.

[0012] The low-temperature plasma fluorination reaction system includes a low-temperature plasma fluorination reaction generator;

[0013] The front end of the low-temperature plasma fluorination reaction generator is connected to the gas supply system through a mixing tank, and the rear end is connected to the cyclone filter and the material collection system through a V3 stop valve.

[0014] The material collection system includes a cyclone filter, a collection cold trap a and a collection cold trap b;

[0015] The cyclone filter is connected to the tail gas treatment system via the collecting cold trap a and the collecting cold trap b.

[0016] The tail gas treatment system includes a sintered filter, a sodium fluoride trap, a charcoal trap and a complexing tank;

[0017] The sintered filter is connected to the jet pump via the sodium fluoride trap and the charcoal trap, one side of the jet pump is connected to the V4 stop valve, and the other side is connected to the complexing tank;

[0018] The exhaust gas treatment system is connected in parallel with the vacuum system through a jet pump.

[0019] A method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction comprises the following steps:

[0020] Step 1, gas supply system preparation:

[0021] Weigh uranium tetrafluoride and put it into a low-temperature plasma fluorination reaction generator; complete the assembly and air tightness test of the low-temperature plasma fluorination reaction integrated device; open the V2 stop valve, and introduce argon gas into the low-temperature plasma fluorination reaction integrated device from the argon gas inlet to replace the atmosphere; open the V1 stop valve and the V2 stop valve at the same time, and introduce fluorine gas and argon gas from the fluorine gas inlet and the argon gas inlet respectively, and the fluorine gas passes through the fluorine gas purification device a, the fluorine gas purification device b and the fluorine gas purification device c into the mixing tank to be mixed with the argon gas;

[0022] Step 2, low temperature plasma generation:

[0023] The fluorine-argon mixed gas produced in step 1 is introduced into a low-temperature plasma fluorination reaction generator, and the low-temperature plasma fluorination reaction generator is connected to a high-voltage alternating current. Under the action of a rapidly periodically changing electric field, the fluorine gas is continuously ionized to produce fluorine plasma;

[0024] Step 3, preparation of uranium hexafluoride by low temperature plasma fluorination and its collection:

[0025] The generated fluorine plasma contacts the uranium tetrafluoride material to undergo a fluorination reaction, generating uranium hexafluoride gas; the uranium hexafluoride gas is carried out of the low-temperature plasma fluorination reaction generator by the airflow, enters the material collection system through the V3 stop valve, and is collected and stored in the collection cold trap a and the collection cold trap b; the fluorine plasma that does not participate in the reaction is quenched or recombined into fluorine gas molecules, and the fluorine gas that is not completely ionized enters the tail gas treatment system and is burned in the charcoal trap; the uranium hexafluoride gas product that is not collected is complexed and captured by the sodium fluoride trap, and the uranium tetrafluoride raw material that does not participate in the reaction and is carried by the airflow is captured by the cyclone filter and the sintered filter;

[0026] Step 4, system atmosphere replacement:

[0027] Close the V1 stop valve, wait until the low-temperature plasma fluorination reaction integrated device cools to room temperature, open the V2 stop valve, and supply argon from the argon inlet to replace the atmosphere in the device. The replacement route is the gas supply system, the low-temperature plasma fluorination reaction system, the material collection system, and the tail gas treatment system.

[0028] Step 5, unloading weighing:

[0029] After the system atmosphere replacement is completed, close the V2 stop valve, V3 stop valve, and V4 stop valve in sequence; disassemble the low-temperature plasma fluorination reaction integrated device, unload the remaining solid raw materials in the device and weigh them;

[0030] Step 6, evacuate and purify and calculate the yield of uranium hexafluoride product:

[0031] After the unloading is completed, the collection cold trap a and the collection cold trap b are repeatedly heated and cooled, and evacuated with the vacuum system until the internal pressure of the collection cold trap a and the collection cold trap b is close to the saturated vapor pressure of uranium hexafluoride, and the evacuation and purification are completed. According to the ideal gas state equation, the amount of uranium hexafluoride collected in the cold trap is calculated;

[0032] In step 1, 50 g of uranium tetrafluoride is weighed and argon gas is introduced at a flow rate of 30 L / h to replace the atmosphere. The fluorine gas and argon gas introduced into the mixing tank can be in any ratio;

[0033] In step 2, the power supply parameters are 50V, 3.0A;

[0034] In step 3, the temperature of the low-temperature plasma fluorination reaction generator is controlled to be lower than 230° C., and the collecting cold trap a and collecting cold trap b have a collecting temperature of -70° C.; the pipelines from the low-temperature plasma fluorination reaction generator to the collecting cold trap a and collecting cold trap b are subjected to heat treatment;

[0035] In step 4, argon gas was introduced at a flow rate of 60 L / h to replace the atmosphere;

[0036] In step 6, the collection cold trap a and the collection cold trap b are repeatedly heated and cooled and evacuated in the following manner: the temperature of the cold trap is maintained at -70°C, and after stabilization for 2 hours, the cold trap is evacuated for 15 minutes, the temperature is raised to 20°C, the temperature is lowered to -70°C again after stabilization for 2 hours, and the cold trap is evacuated again after stabilization for 2 hours, and the evacuation and purification operation is repeated until the pressure in the cold trap is close to the saturated vapor pressure of uranium hexafluoride at the corresponding temperature;

[0037] In step 6, the total volume of the collection cold trap a and the collection cold trap b is V, the temperature of the cold trap when uranium hexafluoride is vaporized is T, the saturated vapor pressure of uranium hexafluoride under this temperature condition is P, and the purification is completed when the actual pressure in the cold trap is P; the amount of uranium hexafluoride collected in the cold trap is calculated according to the ideal gas state equation: n=PV / RT.

[0038] The remarkable effects of the present invention are as follows: a specific preparation method and device for preparing uranium hexafluoride by low-temperature plasma fluorination are provided, wherein the low-temperature plasma fluorination reaction integrated device comprises a gas supply system, a low-temperature plasma fluorination reaction system, a material collection system, a tail gas treatment system and a vacuum system; argon gas is introduced to promote ionization of fluorine gas, thereby reducing the amount of fluorine gas used, and the conversion rate of uranium tetrafluoride can be improved without excessive use of fluorine gas; the temperature of the low-temperature plasma fluorination reaction generator is reduced to below 230° C., thereby effectively avoiding the problems of accelerated equipment corrosion and shortened equipment service life caused by the preparation of uranium hexafluoride under high temperature conditions; the present invention innovatively applies argon dielectric barrier discharge technology to the preparation of uranium hexafluoride, thereby providing a new technical solution for broadening the preparation path of uranium hexafluoride. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0040] Figure 1 This is a schematic diagram of an integrated device for low-temperature plasma fluorination reaction;

[0041] Figure markings: 1-gas supply system; 2-low-temperature plasma fluorination reaction system; 3-material collection system; 4-tail gas treatment system; 5-vacuum system; 6-fluorine gas inlet; 7-argon gas inlet; 8-V1 stop valve; 9-V2 stop valve; 10-1-fluorine gas purification device a; 10-2-fluorine gas purification device b; 10-3-fluorine gas purification device c; 10-4-collecting cold trap a; 10-5-collecting cold trap b; 10-6-sodium fluoride trap; 10-7-charcoal trap; 11-mixing tank; 12-low-temperature plasma fluorination reaction generator; 13-V3 stop valve; 14-cyclone filter; 15-sintering filter; 16-complexation tank; 17-V4 stop valve; 18-jet pump. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0043] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1

[0045] like Figure 1 As shown, a low-temperature plasma fluorination reaction integrated device of this embodiment includes: a gas supply system 1, a low-temperature plasma fluorination reaction system 2, a material collection system 3, an exhaust gas treatment system 4 and a vacuum system 5.

[0046] The gas supply system 1 includes a fluorine gas inlet 6, an argon gas inlet 7, a fluorine gas purification device a10-1, a fluorine gas purification device b10-2, a fluorine gas purification device c10-3 and a mixing tank 11;

[0047] A V1 stop valve 8 is provided in the rear pipeline of the fluorine gas inlet 6, and then the fluorine gas purification device a10-1, the fluorine gas purification device b10-2 and the fluorine gas purification device c10-3 are connected in sequence;

[0048] The argon gas inlet 7 is connected to the outlet of the fluorine gas purification device c10-3 through a pipeline, and a V2 stop valve 9 is provided on the pipeline;

[0049] The two air intake lines converge in the mixing tank 11.

[0050] The exhaust pipeline of the mixing tank 11 is connected to the low-temperature plasma fluorination reaction system 2 .

[0051] The low-temperature plasma fluorination reaction system 2 includes a low-temperature plasma fluorination reaction generator 12;

[0052] The front end of the low-temperature plasma fluorination reaction generator 12 is connected to the gas supply system 1 through the mixing tank 11, and the rear end is connected to the material collection system 3 through the V3 stop valve 13 and the cyclone filter 14.

[0053] The material collection system 3 includes a cyclone filter 14, a collection cold trap a10-4 and a collection cold trap b10-5;

[0054] The cyclone filter 14 is connected to the tail gas treatment system 4 via the collection cold trap a10-4 and the collection cold trap b10-5.

[0055] The tail gas treatment system 4 includes a sintered filter 15, a sodium fluoride trap 10-6, a charcoal trap 10-7 and a complexing tank 16, and the sintered filter 15 is connected to a jet pump 18 via the sodium fluoride trap 10-6 and the charcoal trap 10-7;

[0056] The tail gas treatment system 4 and the vacuum system 5 are connected in parallel via a jet pump 18; one side of the jet pump 18 is connected to a V4 stop valve 17, and the other side is connected to a complexing tank 16;

[0057] The exhaust gas treatment system 4 is connected in parallel with the vacuum system 5 via a jet pump 18 .

[0058] Based on the low-temperature plasma fluorination reaction integrated device provided in the above embodiment, the embodiment of the present application also provides a method for preparing uranium hexafluoride using the device, comprising the following steps:

[0059] Step 1: Preparation of gas supply system;

[0060] Weigh uranium tetrafluoride and spread it flat in the material boat of the low-temperature plasma fluorination reaction generator; complete the assembly and air tightness test of the low-temperature plasma fluorination reaction integrated device; open the V2 stop valve 9, and introduce argon gas from the argon gas inlet 7 to replace the atmosphere; open the V1 stop valve 8 and the V2 stop valve 9 at the same time, and introduce fluorine gas and argon gas from the fluorine gas inlet 6 and the argon gas inlet 7 respectively, and the fluorine gas passes through the fluorine gas purification device a10-1, the fluorine gas purification device b10-2 and the fluorine gas purification device c10-3 into the mixing tank 11 to mix with the argon gas;

[0061] In the specific implementation, 50 g of uranium tetrafluoride was weighed, and argon gas was introduced into the entire reaction system at a flow rate of 30 L / h to replace the atmosphere. The ratio of fluorine gas to argon gas introduced into the mixing tank 11 was 5:1.

[0062] Step 2: Low temperature plasma generation;

[0063] The low-temperature plasma fluorination reaction generator 12 is connected to a high-voltage alternating current, and the low-temperature plasma fluorination reaction generator 12 is in an electric field that changes rapidly and periodically. The argon gas in the low-temperature plasma fluorination reaction generator 12 performs dielectric barrier discharge. After the argon gas discharge is stable, the V1 stop valve 8 is opened, and the fluorine-argon mixed gas in step 1 is introduced into the gas cavity of the reaction device to maintain stable discharge for a certain period of time; the external electric field causes the fluorine gas molecules in the gas cavity of the low-temperature plasma fluorination reaction integrated device to be continuously ionized and generate fluorine plasma, and the voltage, current and duty cycle of the power supply are continuously adjusted to indirectly control the amount of fluorine plasma generated per unit time and the internal temperature of the low-temperature plasma fluorination reaction generator 12, so that the fluorine gas is continuously ionized to generate fluorine plasma;

[0064] The power supply parameters are adjusted to 50V and 3.0A. During the specific implementation, fine adjustments are made within a certain range to ensure stable discharge of the fluorine-argon mixed gas.

[0065] Step 3: Preparation of UF6 by Low-Temperature Plasma Fluorination and Its Collection

[0066] A fluorine-argon mixed gas is continuously introduced into the low-temperature plasma fluorination reaction generator 12, and the generated fluorine plasma contacts the uranium tetrafluoride material, and a fluorination reaction occurs to generate uranium hexafluoride gas; the uranium hexafluoride gas is carried out of the low-temperature plasma fluorination reaction generator 12 by the airflow and enters the collecting cold trap a10-4 and the collecting cold trap b10-5; the collecting temperature of the collecting cold trap a10-4 and the collecting cold trap b10-5 is set to -70°C, and the pipelines from the low-temperature plasma fluorination reaction generator 12 to the two-stage collecting cold traps are subjected to heat treatment, so that the uranium hexafluoride gas smoothly enters the cold trap without condensing in the pipe wall; the fluorine plasma that does not participate in the reaction is quenched or recombined into fluorine gas molecules, and the fluorine gas that is not completely ionized enters the tail gas treatment system 4 through the collection system 3, and is burned in the charcoal trap 10-7; the uranium hexafluoride product that is not collected is complexed and captured by the sodium fluoride trap 10-6, and the uranium tetrafluoride raw material that does not participate in the reaction and is carried by the airflow is captured by the cyclone filter 14 and the sintering filter 15;

[0067] In the specific implementation, the temperature of the low-temperature plasma fluorination reaction generator 12 is maintained below 230° C., the gas path system is kept unobstructed, and the ionization fluorination is performed for 2 hours.

[0068] Step 4: System atmosphere replacement;

[0069] After the ionization fluorination is completed, the V1 stop valve 8 is closed, and after the temperature of the low-temperature plasma fluorination reaction generator 10 drops to room temperature, the V2 stop valve 9 is opened to introduce argon gas into the low-temperature plasma fluorination reaction integrated device system to replace the fluorine gas in the system. The replacement route is the gas supply system 1, the low-temperature plasma fluorination reaction generator 10, the collection cold trap a10-4, the collection cold trap b10-5 and the tail gas treatment system 4 in sequence; after the replacement is completed, the V2 stop valve 9, the V3 stop valve 13 and the V4 stop valve 17 are closed in sequence;

[0070] During the specific implementation, argon gas was introduced at a flow rate of 60 L / h to replace the atmosphere.

[0071] Step 5: Unloading and weighing

[0072] After the system atmosphere replacement is completed, the joints, connectors, outer electrodes, and inner electrodes of the low-temperature plasma fluorination reaction generator 12 are disassembled in sequence, and the remaining solid uranium tetrafluoride raw material in the reactor is unloaded and weighed.

[0073] Step 6: Evacuate and purify and calculate the yield of uranium hexafluoride product

[0074] After the collection is completed, the collection cold trap a10-4 and the collection cold trap b10-5 are repeatedly heated and cooled, and evacuated in cooperation with the vacuum system 5 until the internal pressure of the collection cold trap a10-4 and the collection cold trap b10-5 is close to the saturated vapor pressure of uranium hexafluoride and the evacuation and purification are completed. According to the ideal gas state equation, the amount of uranium hexafluoride collected in the cold trap is calculated;

[0075] In specific implementation, the method of repeatedly raising and lowering the temperature and coordinating with vacuuming is: the temperature of the cold trap continues to be maintained at -70°C, and after stabilizing for 2 hours, the temperature is evacuated for 15 minutes, the temperature is raised to 20°C, and after stabilizing for 2 hours, the temperature is lowered to -70°C again, and the temperature is evacuated again after stabilizing for 2 hours, and the vacuuming and purification operation is repeated until the pressure in the cold trap is close to the saturated vapor pressure of uranium hexafluoride.

[0076] Example 2

[0077] A low-temperature plasma fluorination reaction integrated device, the structure and function of the low-temperature plasma fluorination reaction integrated device are the same as those of Example 1.

[0078] The present application also provides a method for preparing uranium hexafluoride using the device, which is the same as that in Example 1, except that:

[0079] Step 1: Preparation of gas supply system;

[0080] In a specific implementation, the ratio of fluorine gas to argon gas introduced into the mixing tank 11 is 5:2.

[0081] Step 3: Preparation of uranium hexafluoride by low-temperature plasma fluorination and its collection;

[0082] In the specific implementation, the temperature of the low-temperature plasma fluorination reaction generator 12 is maintained below 210° C., the gas path system is kept unobstructed, and the ionization fluorination is performed for 1.5 hours.

[0083] This embodiment achieves better results based on the first embodiment: by increasing the proportion of argon in the mixed gas, the ionization of fluorine gas is promoted, the amount of fluorine gas used can be reduced, the reaction temperature can be lowered, and thus the corrosion of fluorine gas to the equipment under high temperature conditions can be avoided.

[0084] The above description is only a preferred embodiment of this patent and is not intended to limit this patent. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this patent should be included in the scope of protection of this patent.

[0085] It should be noted that, for the above-mentioned method embodiments, for the sake of simplicity of description, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described action sequence, because according to the present application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required by the present application.

[0086] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0087] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The optional embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of the present application. The present application selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can understand and use the present application well.

Claims

1. A low-temperature plasma fluorination reaction integrated device, characterized in that: include: A gas supply system (1), a low-temperature plasma fluorination reaction system (2), a material collection system (3), an exhaust gas treatment system (4) and a vacuum system (5); The gas supply system (1), the low-temperature plasma fluorination reaction system (2), the material collection system (3) and the tail gas treatment system (4) are connected in series, and the tail gas treatment system (4) and the vacuum system (5) are connected in parallel.

2. The low-temperature plasma fluorination reaction integrated device according to claim 1, characterized in that: The gas supply system (1) comprises a fluorine gas inlet (6), an argon gas inlet (7), a fluorine gas purification device a (10-1), a fluorine gas purification device b (10-2), a fluorine gas purification device c (10-3) and a mixing tank (11); A V1 stop valve (8) is provided on the rear pipeline of the fluorine gas inlet (6), and then the fluorine gas purification device a (10-1), the fluorine gas purification device b (10-2) and the fluorine gas purification device c (10-3) are connected in sequence; The argon gas inlet (7) is connected to the outlet of the fluorine gas purification device c (10-3) through a pipeline, and a V2 stop valve (9) is provided on the pipeline; The two air inlet pipelines converge in the mixing tank (11).

3. The low-temperature plasma fluorination reaction integrated device according to claim 1, characterized in that: The low-temperature plasma fluorination reaction system (2) comprises a low-temperature plasma fluorination reaction generator (12); The front end of the low-temperature plasma fluorination reaction generator (12) is connected to the gas supply system (1) through a mixing tank (11), and the rear end is connected to the cyclone filter (14) and the material collection system (3) through a V3 stop valve (13).

4. The low-temperature plasma fluorination reaction integrated device according to claim 1, characterized in that: The material collection system (3) comprises a cyclone filter (14), a collection cold trap a (10-4) and a collection cold trap b (10-5); The cyclone filter (14) is connected to the tail gas treatment system (4) via the collection cold trap a (10-4) and the collection cold trap b (10-5).

5. The low-temperature plasma fluorination reaction integrated device according to claim 1, characterized in that: The tail gas treatment system (4) comprises a sintered filter (15), a sodium fluoride trap (10-6), a charcoal trap (10-7) and a complexing tank (16); The sintered filter (15) is connected to the jet pump (18) via the sodium fluoride trap (10-6) and the charcoal trap (10-7); one side of the jet pump (18) is connected to the V4 stop valve (17), and the other side is connected to the complexing tank (16); The tail gas treatment system (4) is connected in parallel with the vacuum system (5) via a jet pump (18).

6. A method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction, characterized in that: The following steps are involved: Step 1, gas supply system (1) preparation: Weigh uranium tetrafluoride and place it in a low-temperature plasma fluorination reaction generator (12); complete the assembly and airtightness test of the low-temperature plasma fluorination reaction integrated device; open the V2 stop valve (9), and introduce argon gas from the argon gas inlet (7) to replace the atmosphere; simultaneously open the V1 stop valve (8) and the V2 stop valve (9), and introduce fluorine gas and argon gas from the fluorine gas inlet (6) and the argon gas inlet (7), respectively, and the fluorine gas passes through the fluorine gas purification device a (10-1), the fluorine gas purification device b (10-2) and the fluorine gas purification device c (10-3) into the mixing tank (11) to be mixed with the argon gas; Step 2, low temperature plasma generation: The fluorine-argon mixed gas produced in step 1 is introduced into a low-temperature plasma fluorination reaction generator (12), and the low-temperature plasma fluorination reaction generator (12) is connected to a high-voltage alternating current, and under the action of a rapidly periodically changing electric field, the fluorine gas is continuously ionized to generate fluorine plasma; Step 3, preparation of uranium hexafluoride by low temperature plasma fluorination and its collection: The generated fluorine plasma contacts the uranium tetrafluoride material to undergo a fluorination reaction, thereby generating uranium hexafluoride gas; the uranium hexafluoride gas is carried out of the low-temperature plasma fluorination reaction generator (12) by the airflow, and enters the material collection system (3) through the V3 stop valve (13), and the uranium hexafluoride gas is collected and stored in the collection cold trap a (10-4) and the collection cold trap b (10-5); the fluorine plasma that does not participate in the reaction is quenched or recombined into fluorine gas molecules, and the fluorine gas that is not completely ionized enters the tail gas treatment system (4) and is burned in the charcoal trap (10-7); the uranium hexafluoride gas product that is not collected is complexed and captured by the sodium fluoride trap (10-6), and the uranium tetrafluoride raw material that does not participate in the reaction and is carried by the airflow is captured by the cyclone filter (14) and the sintered filter (15); Step 4, system atmosphere replacement: Close the V1 stop valve (8), wait for the low-temperature plasma fluorination reaction integrated device to cool to room temperature, open the V2 stop valve (9), supply argon gas from the argon gas inlet (7), and replace the atmosphere in the device. The replacement route is the gas supply system (1), the low-temperature plasma fluorination reaction system (2), the material collection system (3), and the tail gas treatment system (4); Step 5, unloading weighing: After the system atmosphere replacement is completed, the V2 stop valve (9), the V3 stop valve (13), and the V4 stop valve (17) are closed in sequence; the low-temperature plasma fluorination reaction integrated device is disassembled, and the remaining solid raw materials in the device are unloaded and weighed; Step 6, evacuate and purify and calculate the yield of uranium hexafluoride product: After the unloading is completed, the collection cold trap a (10-4) and the collection cold trap b (10-5) are repeatedly heated and cooled, and evacuated in cooperation with the vacuum system (5) until the internal pressure of the collection cold trap a (10-4) and the collection cold trap b (10-5) is close to the saturated vapor pressure of uranium hexafluoride, and the evacuation and purification are completed. According to the ideal gas state equation, the amount of uranium hexafluoride collected in the cold trap is calculated.

7. The method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction according to claim 6, characterized in that: In the step 1, 50 g of uranium tetrafluoride is weighed and argon gas is introduced at a flow rate of 30 L / h to replace the atmosphere. The fluorine gas and argon gas introduced into the mixing tank (11) can be in any ratio.

8. The method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction according to claim 6, characterized in that: In step 2, the power supply parameters are 50V, 3.0A.

9. The method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction according to claim 6, characterized in that: In the step 3, the temperature of the low-temperature plasma fluorination reaction generator (12) is controlled to be lower than 230°C, and the collecting cold trap a (10-4) and the collecting cold trap b (10-5) have a receiving temperature of -70°C; and the pipelines from the low-temperature plasma fluorination reaction generator (12) to the collecting cold trap a (10-4) and the collecting cold trap b (10-5) are subjected to heat treatment.

10. The method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction according to claim 6, characterized in that: In the step 4, argon gas is introduced at a flow rate of 60 L / h to replace the atmosphere.

11. The method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction according to claim 6, characterized in that: In step 6, the collection cold trap a (10-4) and the collection cold trap b (10-5) are repeatedly heated and cooled and evacuated in the following manner: the temperature of the cold trap is maintained at -70°C, and after stabilizing for 2 hours, the cold trap is evacuated for 15 minutes, the temperature is raised to 20°C, and after stabilizing for 2 hours, the temperature is lowered to -70°C again, and after stabilizing for 2 hours, the cold trap is evacuated again, and the evacuation and purification operation is repeated until the pressure in the cold trap is close to the saturated vapor pressure of uranium hexafluoride at the corresponding temperature.

12. The method for preparing uranium hexafluoride by low-temperature plasma fluorination reaction according to claim 6, characterized in that: In step 6, the total volume of the collection cold trap a (10-4) and the collection cold trap b (10-5) is V, the temperature of the cold trap when uranium hexafluoride is vaporized is T, the saturated vapor pressure of uranium hexafluoride under this temperature condition is P, and the purification is completed when the actual pressure in the cold trap is P; the amount of uranium hexafluoride collected in the cold trap is calculated according to the ideal gas state equation: n=PV / RT.

Images