A method for separating and recovering a uranium-containing radioactive waste

Abstract

This application relates to the field of radioactive waste treatment technology in the nuclear industry, and more particularly to a method for separating and recovering uranium-containing radioactive waste. This application employs a combined vacuum sublimation and cryogenic distillation process. First, vacuum sublimation is used to vaporize the mixed working fluid under reduced pressure and heating. Then, a multi-stage condensation system separates the solid UF6 / BrF3. The uncondensed gas is passed into a cryogenic device for liquefaction and recovery of Br2. Finally, utilizing the vapor pressure difference between UF6 and BrF3, gradient depressurization distillation is used to achieve efficient purification of UF6 and BrF3. This application, through a fully sealed process design, avoids radioactive leakage and generates no secondary solid waste. The UF6 purity is ≥98.8%, making it suitable for the treatment of radioactive hazardous waste from uranium enrichment plants and the resource recovery of similar mixtures.

Description

Technical Field

[0001] This application relates to the field of radioactive waste treatment technology in the nuclear industry, and in particular to a method for separating and recovering uranium-containing radioactive waste. Background Technology

[0002] During the operation of a cascade system in a uranium enrichment plant, radioactive deposits generated in equipment and pipelines can lead to a decrease in production capacity. Some enrichment plants use BrF3 as a cleaning agent; the cleaning waste contains components such as UF6, BrF3, and Br2, which are highly corrosive, explosive, and radioactive. In existing technologies:

[0003] 1. Direct metal container temporary storage method: Waste is placed in metal containers for long-term storage, which leads to the occupation of factory space and the risk of Br2 leakage, UF6 and BrF3 reaction explosion, and cannot achieve resource recycling;

[0004] 2. Sodium fluoride adsorption method: BrF3 is solidified by chemical adsorption, but the reaction is violent and explosive, requiring high-temperature desorption (≥300℃), resulting in a uranium loss rate of >15% and generating radioactive solid waste, which requires secondary treatment;

[0005] 3. Single condensation process: Only a portion of Br2 is separated by low-temperature condensation, but UF6 and BrF3 are difficult to separate due to their similar vapor pressures, and the recovery rate is less than 80%.

[0006] The methods described above have failed to achieve effective separation and reuse of bromine compounds and UF6, and are characterized by high processing costs and significant environmental risks. Therefore, there is an urgent need to develop a safe, efficient, and low-consumption technology for the recovery of uranium-containing radioactive waste. Summary of the Invention

[0007] To address the aforementioned issues, this application provides a method for separating and recovering uranium-containing radioactive waste, enabling the classification, purification, and resource recycling of Br2, UF6, and BrF3, thereby reducing energy consumption and environmental risks.

[0008] To achieve the above objectives, this application adopts the following technical solution.

[0009] This application provides a method for separating and recovering uranium-containing radioactive waste, comprising the following steps:

[0010] (1) Vacuum sublimation process:

[0011] ① Reduced pressure heating: The mixed working fluid containing UF6, BrF3 and Br2 is vaporized in a container;

[0012] ② Multi-stage condensation: The generated gaseous mixture is fed into a multi-stage condensation system and condensed at a temperature ≤4℃ and a pressure ≤10kPa to condense solid BrF3 and UF6;

[0013] ③ Cold bromine recovery: Uncondensed gas is passed into a cryogenic device for liquefaction and recovery;

[0014] (2) Low-temperature distillation process:

[0015] ④ Fractional distillation: The UF6 and BrF3 mixture condensed in step (1) is subjected to gradient pressure reduction distillation. At 0℃ to -10℃, the pressure gradient is gradually reduced from 2.7kPa to 1kPa to separate UF6 gas and solid BrF3.

[0016] Furthermore, in step ①, the heating temperature is >75℃ and the pressure is controlled at ≤13.4kPa.

[0017] Furthermore, in step ①, the heating temperature is 60℃~80℃ and the pressure is 7kPa~13.4kPa.

[0018] Preferably, the heating temperature in step ① is 75°C and the pressure is 13.4 kPa.

[0019] Furthermore, step ② includes three stages of condensation:

[0020] First-stage condensation: Temperature 4℃, Pressure ≤10kPa;

[0021] Second-stage condensation: temperature -20℃, pressure ≤1.5kPa;

[0022] Third-stage condensation: temperature -40℃, pressure ≤0.693kPa.

[0023] Furthermore, the temperature for liquefaction recovery in step ③ is -105 to -115°C, and the pressure is ≤50Pa.

[0024] Preferably, the liquefaction recovery temperature is -110℃ and the pressure is 50Pa.

[0025] Furthermore, in the cold bromine recovery process of step ③, the unliquefied residual gas is treated by a gas absorption tower filled with sodium fluoride particles, and the gas residence time is ≥30 seconds.

[0026] Furthermore, step ④, segmented distillation, includes three stages of distillation:

[0027] First stage distillation: temperature 2 to -6℃, pressure 2.7 to 1.4 kPa;

[0028] Second stage distillation: temperature 0 to -10℃, pressure 1.8 to 1 kPa;

[0029] Third stage distillation: temperature 0 to -10℃, pressure 1.6 to 1kPa.

[0030] Furthermore, in step ④, the temperature of the fractional distillation is -2℃ to 0℃, and the pressure is controlled at 1.6kPa to 2kPa.

[0031] Preferably, step ④, fractional distillation, includes three fractional distillations:

[0032] First stage distillation: temperature 0℃, pressure 2kPa;

[0033] Second stage distillation: temperature 0℃, pressure 1.8kPa;

[0034] Third stage distillation: temperature 0℃, pressure 1.6kPa.

[0035] Furthermore, the low-temperature distillation process in step (2) further includes:

[0036] ⑤ UF6 collection: The gas produced by distillation is condensed and collected at -120℃ to -80℃ to obtain solid UF6;

[0037] ⑥ BrF3 collection: The solid mixture obtained from distillation is heated to 10℃~25℃ to obtain BrF3 liquid.

[0038] Furthermore, both the vacuum sublimation process and the cryogenic distillation process are carried out in a closed system, and the various devices are connected by pipelines.

[0039] This application employs vacuum sublimation to first convert the mixture into a mixed gas, then condenses bromine trifluoride and uranium hexafluoride into solids, while bromine remains gaseous. By controlling temperature and pressure, impurities are avoided from being trapped within the solid. Simultaneously, because bromine is separated from most substances at a higher temperature, the mass of substances requiring cooling is reduced, thus reducing energy consumption.

[0040] This application employs a cryogenic distillation method to separate bromine trifluoride and uranium hexafluoride, offering the following advantages: ① Bromine trifluoride and uranium hexafluoride in the system are chemically highly reactive and prone to explosion. This method does not introduce new substances into the system, and the separation is carried out at low temperatures, reducing the risk of leakage and explosion, thus ensuring the safety of the separation process; furthermore, it does not generate new radioactive waste; ② This method separates substances based on their physicochemical properties. Theoretically, the recovery rate of bromine trifluoride and uranium hexafluoride will be higher than that of traditional separation methods; ③ This method also reduces the difficulty of tail gas treatment, reduces the emission of tail gas and radioactive materials, and is more environmentally friendly; ④ The main instruments and devices in this method are all sealed, and the entire separation process system is in a sealed state, which reduces the risk of leakage of hazardous chemicals and radioactive materials, and also reduces the possibility of adverse reactions producing other impurities or even causing explosions.

[0041] Compared with existing technologies, the beneficial effects of this application are: ① High recovery efficiency: UF6 purity ≥ 98.8%; ② Strong safety: the pressure of the whole process is ≤ 13.4 kPa, and the operation is sealed to avoid the risk of UF6 decomposition and BrF3 explosion; ③ Excellent environmental protection: the whole process has no adsorbents or chemical additives and no new radioactive solid waste. Attached Figure Description

[0042] Figure 1 This is a flow chart of the separation process for uranium-containing radioactive waste according to Embodiment 1 of this application; Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0044] Example 1

[0045] like Figure 1 As shown, this embodiment provides a method for separating and recovering uranium-containing radioactive waste, including the following steps:

[0046] (1) Vacuum sublimation process:

[0047] ① Reduced pressure heating: Radioactive waste containing UF6, BrF3 and Br2 is introduced into a sealed container. The temperature of the cleaning mixture container is controlled at 75°C and the pressure at 13.4 kPa by electric heating and vacuum pump regulating valve. Reduced pressure heating causes the mixture in the container to gradually turn into gas.

[0048] ② Multi-stage condensation: The generated gaseous mixture is condensed using a vacuum pump through a three-stage condensation system; wherein,

[0049] First-stage condensation: temperature is 4℃ (ethylene glycol cooling), pressure is 10kPa, residence time is 20 minutes, and condensate is collected; at this time, UF6 and BrF3 are condensed into solids after cooling, while bromine remains in a gaseous state and does not remain; in addition, at this temperature, there will be no eutectic phenomenon between uranium hexafluoride and bromine trifluoride, which is beneficial to the subsequent separation between uranium hexafluoride and bromine trifluoride;

[0050] Second-stage condensation: temperature -20℃ (ethylene glycol cooling), pressure 1.5 kPa, residence time 30 minutes, and collection of condensate;

[0051] Third-stage condensation: temperature -40℃ (liquid nitrogen cooling), pressure 0.693kPa, residence time 50 minutes, and collection of residue;

[0052] ③ Cold bromine recovery: After the uncondensed gas is passed into the cryogenic device, it is liquefied at -110℃ and 50Pa, and Br2 is collected. At this time, the saturated vapor pressure of bromine is 0Pa, and the gaseous bromine separated in the above process is completely condensed. After the container is completely empty (judged by a pressure gauge), the valve of the input pipe of the cryogenic device is closed, and other impurity gases (such as HF and O2) are evacuated and discharged into the gas absorption tower by a vacuum pump.

[0053] (2) Low-temperature distillation process:

[0054] ④ Segmented distillation: The condensed product from step (1) is subjected to gradient depressurization distillation. First, the vacuum pump is stopped and the pressure of the three-stage condenser is restored to atmospheric pressure. Then, the material from the first stage of condensation is cooled to 0°C, while the material from the second stage of condensation is heated to 0°C. The vacuum pump is then started, and the gas pressures of the containers are adjusted to 2 kPa, 1.8 kPa, and 1.6 kPa, respectively. UF6 in the container will sublimate into a gas due to the vacuum, while BrF3 remains a solid powder.

[0055] ⑤ UF6 collection: Collect the UF6 gas produced by the three-stage distillation into a UF6 collector at -120℃. Then, pass the UF6 gas from the two-stage distillation through the three-stage distillation and collect it into a uranium hexafluoride collector at -120℃. Finally, collect the UF6 gas from the first-stage distillation in the same way.

[0056] The mass percentage of UF6 increases progressively in the three-stage distillation, which means that the content of BrF3 gas in UF6 gas gradually decreases; at the same time, reducing the pressure also helps to reduce the volatility of BrF3 solid.

[0057] ⑥ BrF3 collection: The material after three-stage distillation is heated to 10°C to convert BrF3 from solid to liquid, and then collected into a BrF3 collector by pump.

[0058] Example 2

[0059] This embodiment provides a method for separating and recovering uranium-containing radioactive waste, including the following steps:

[0060] (1) Vacuum sublimation process:

[0061] ① Reduced pressure heating: Radioactive waste containing UF6, BrF3 and Br2 is introduced into a sealed container. The temperature of the cleaning mixture container is controlled at 80°C and the pressure at 11.5 kPa by electric heating and vacuum pump regulating valve. Reduced pressure heating causes the mixture in the container to gradually turn into gas.

[0062] ② Multi-stage condensation: The generated gaseous mixture is condensed using a vacuum pump through a three-stage condensation system; wherein,

[0063] First-stage condensation: The temperature is 4℃ (ethylene glycol cooling), the pressure is 5kPa, and the residence time is 20 minutes. The condensate is then collected. At this time, UF6 and BrF3 are condensed into solids after cooling, while bromine remains in a gaseous state and does not remain. Furthermore, at this temperature and below, there will be no eutectic phenomenon between uranium hexafluoride and bromine trifluoride, which is beneficial for the subsequent separation of uranium hexafluoride and bromine trifluoride.

[0064] Second-stage condensation: temperature -20℃ (ethylene glycol cooling), pressure 1kPa, residence time 30 minutes, and collection of condensate;

[0065] Third-stage condensation: temperature -40℃ (liquid nitrogen cooling), pressure 0.35kPa, residence time 50 minutes, and collection of residue;

[0066] ③ Cold bromine recovery: After the uncondensed gas is passed into the cryogenic device, it is condensed at -115℃ and 50Pa, and Br2 is collected. At this time, the saturated vapor pressure of bromine is 0Pa, and the gaseous bromine separated in the above process is completely condensed. After the container is completely empty (judged by a pressure gauge), the valve of the input pipe of the cryogenic device is closed, and other impurity gases (such as HF and O2) are evacuated into the gas absorption tower by a vacuum pump.

[0067] (2) Low-temperature distillation process:

[0068] ④ Segmented distillation: The condensed product from step (1) is subjected to gradient depressurization distillation. First, the vacuum pump is stopped and the pressure of the three-stage condenser is restored to atmospheric pressure. Then, the material from the first stage of condensation is cooled to -5°C, while the material from the second stage of condensation is heated to -5°C. The vacuum pump is then started, and the gas pressure of the container is adjusted to 1.7 kPa, 1.5 kPa, and 1.3 kPa, respectively. UF6 in the container will sublimate into a gas due to the vacuum, while BrF3 remains a solid powder.

[0069] ⑤ UF6 collection: Collect the UF6 gas produced by the three-stage distillation into a UF6 collector at -120℃. Then, pass the UF6 gas from the two-stage distillation through the three-stage distillation and collect it into a uranium hexafluoride collector at -120℃. Finally, collect the UF6 gas from the first-stage distillation in the same way.

[0070] The mass percentage of UF6 increases progressively in the three-stage distillation, which means that the content of BrF3 gas in UF6 gas gradually decreases; at the same time, reducing the pressure also helps to reduce the volatility of BrF3 solid.

[0071] ⑥ BrF3 collection: The material after three-stage distillation is heated to 10°C to convert BrF3 from solid to liquid, and then collected into a BrF3 collector by pump.

[0072] Example 3

[0073] This embodiment provides a method for separating and recovering uranium-containing radioactive waste, including the following steps:

[0074] (1) Vacuum sublimation process:

[0075] ① Reduced pressure heating: Radioactive waste containing UF6, BrF3 and Br2 is introduced into a sealed container. The temperature of the cleaning mixture container is controlled at 60°C and the pressure at 7 kPa by electric heating and vacuum pump regulating valve. Reduced pressure heating causes the mixture in the container to gradually turn into gas.

[0076] ② Multi-stage condensation: The generated gaseous mixture is fed into a three-stage condensation system using a vacuum pump for segmented condensation; wherein,

[0077] First-stage condensation: Temperature is 4℃ (No. 1 hot and cold box), pressure is 10kPa, residence time is 20 minutes, and condensate is collected; at this time, UF6 and BrF3 are cooled and condensed into solids, while bromine remains in a gaseous state and will not remain; furthermore, at this temperature and below, there will be no eutectic phenomenon between uranium hexafluoride and bromine trifluoride, which is beneficial for the subsequent separation between uranium hexafluoride and bromine trifluoride;

[0078] Second-stage condensation: temperature -20℃ (No. 2 hot and cold box), pressure 1.5kPa, residence time 30 minutes, collect condensate;

[0079] Third-stage condensation: temperature -40℃ (No. 1 cryogenic chamber), pressure 0.693kPa, residence time 50 minutes, and collection of residue;

[0080] ③ Cold bromine recovery: After the uncondensed gas is passed into the No. 2 cryogenic chamber, it is condensed at -105℃ and 50Pa to collect Br2. At this time, the saturated vapor pressure of bromine is 0Pa, and the gaseous bromine separated in the above process is completely condensed. After the container is completely empty (judged by a pressure gauge), the valve of the input pipe of the cryogenic chamber is closed, and other impurity gases (such as HF and O2) are evacuated and discharged into the gas absorption tower by a vacuum pump.

[0081] (2) Low-temperature distillation process:

[0082] ④ Segmented distillation: The condensed product from step (1) is subjected to gradient depressurization distillation. First, the vacuum pump is stopped and the pressure of the three-stage condenser is restored to atmospheric pressure. Then, the material from the first stage of condensation is cooled to 0°C, while the material from the second stage of condensation is heated to 0°C. The vacuum pump is then started, and the gas pressure of the container is adjusted to 2.0 kPa, 1.8 kPa, and 1.6 kPa, respectively. UF6 in the container will sublimate into a gas due to the vacuum, while BrF3 remains a solid powder.

[0083] ⑤ UF6 collection: Collect the UF6 gas produced by the three-stage distillation into a UF6 collector at -120℃. Then, pass the UF6 gas from the two-stage distillation through the three-stage distillation and collect it into a uranium hexafluoride collector at -120℃. Finally, collect the UF6 gas from the first-stage distillation in the same way.

[0084] The mass percentage of UF6 increases progressively in the three-stage distillation, which means that the content of BrF3 gas in UF6 gas gradually decreases; at the same time, reducing the pressure also helps to reduce the volatility of BrF3 solid.

[0085] ⑥ BrF3 collection: The material after three-stage distillation is heated to 10°C to convert BrF3 from solid to liquid, and then collected into a BrF3 collector by pump.

[0086] Comparative Example 1

[0087] This comparative example provides a method for separating and recovering uranium-containing radioactive waste. The difference between this method and Example 1 is that the first stage of condensation in step ②, the condensation temperature is 5°C and the pressure is 11 kPa; the rest of the preparation process and parameters are the same as in Example 1.

[0088] Comparative Example 2

[0089] This comparative example provides a method for separating and recovering uranium-containing radioactive waste. The difference between this method and Example 1 is that the temperature in step ④, the fractional distillation, is controlled at 5°C. The remaining preparation process and parameters are consistent with those in Example 1.

[0090] Comparative Example 3

[0091] This comparative example provides a method for separating and recovering uranium-containing radioactive waste. The difference between this method and Example 1 is that it does not use the vacuum sublimation process of (1) of this application to separate bromine. Instead, it uses a warm method to separate bromine trifluoride, uranium hexafluoride and bromine. First, the mixture is cooled to -110°C and then heated to -40°C. The bromine is converted into gas by controlling the pressure at 0.693 kPa to achieve bromine separation. Then, the low-temperature distillation process in step (2) is carried out. The rest of the preparation process and parameters are the same as those in Example 1.

[0092] Comparative Example 4

[0093] This comparative example provides a method for separating and recovering uranium-containing radioactive waste. The difference between this method and Example 1 is that the low-temperature distillation process in step (2) of this application is not used to separate bromine trifluoride and uranium hexafluoride. Instead, the separation of bromine trifluoride and uranium hexafluoride is achieved by using sodium fluoride adsorption. The remaining preparation process and parameters are consistent with those of Example 1.

[0094] Comparative Example 5

[0095] This comparative example provides a method for separating and recovering uranium-containing radioactive waste, including the following steps:

[0096] (1) Low temperature method to separate bromine trifluoride, uranium hexafluoride and bromine: first, the mixture is cooled to -110℃, then heated to -40℃, and the bromine is converted into gas by pressure control of 0.693kPa, thereby achieving the bromine separation effect;

[0097] (2) Then, the sodium fluoride adsorption method is used to separate bromine trifluoride and uranium hexafluoride.

[0098] Uranium-containing radioactive waste was treated using the methods of the embodiments and comparative examples of this application. The collected UF6 and BrF3 were detected by gravimetric method and indirect iodometric titration method according to ASTM C761-2011, "Standard Test Methods for Chemical, Mass Spectrometry, Spectrochemical, Nuclear and Radiochemical Analysis of Uranium Hexafluoride". The detection data are shown in Table 1.

[0099] Table 1. Detection data of embodiments and comparative examples of the present invention.

[0100] UF6 purity (%) BrF3 purity (%) <![CDATA[UF6 loss rate (%)]]> Example 1 99.4 98.1 1.89 Example 2 98.8 97.0 2.95 Example 3 99.4 98.3 1.86 Comparative Example 1 99.1 97.5 3.54 Comparative Example 2 98.6 97.2 3.13 Comparative Example 3 96.7 95.2 3.96

[0101] The above testing process shows that the purity of the products obtained by the uranium-containing radioactive waste separation and recovery method of this application is as follows: UF6 purity ≥ 98.8%, which meets the purity standard of uranium hexafluoride for uranium enrichment and conversion production lines, realizing the recycling and reuse of uranium hexafluoride and reducing radioactive solid waste; BrF3 purity ≥ 97%, which can be reused as a cleaning agent for residual uranium hexafluoride solid waste in uranium enrichment and conversion production facilities, thereby reducing the management risk of hazardous chemicals and lowering costs; Br2, as an auxiliary solvent for bromine trifluoride cleaning agent, has a lower purity standard and does not require special testing, and generally the recovered liquid bromine will undergo further recycling treatment.

[0102] Compared to Example 1, in Comparative Example 1, the first stage condensation temperature in step ② of the segmented condensation was 5°C and the pressure was 11 kPa. The high heating temperature and pressure resulted in a small portion of bromine being liquid, dissolving some UF6 and BrF3, leaving residues in the container, affecting the separation effect and UF6 recovery rate in subsequent steps. In Comparative Example 2, the temperature in step ④ of the segmented distillation was too high, consistently controlled at 5°C, resulting in the ideal gas partial pressure ratio of UF6 and BrF3 being below 30, reducing the single-stage separation effect and ultimately leading to low purity UF6 product containing BrF3. In Comparative Example 3, the mixture was first cooled to -110°C and then heated to -40°C. The pressure control of 0.693 kPa converts bromine into gas, achieving bromine separation. Then, the low-temperature distillation process in step (2) is carried out, which makes it difficult to completely separate bromine from the mixture solids. There is a problem of solid impurities, which requires the addition of a solid crushing device. In addition, the presence of bromine will reduce the separation capacity of UF6 and BrF3, increasing the residual rate of solid waste. Comparative Example 4 uses sodium fluoride adsorption to separate bromine trifluoride and uranium hexafluoride, which requires the adsorbent to be replaced regularly, increasing the amount of radioactive solid waste. Moreover, due to the influence of sodium fluoride adsorbent, the purity of the product is difficult to control during the separation process, reducing the recovery rate of uranium hexafluoride.

[0103] Comparative Example 5 describes the separation of bromine trifluoride, uranium hexafluoride, and bromine from bromine using an existing low-temperature method. This process suffers from solid inclusions; some bromine is encapsulated by solid bromine trifluoride and uranium hexafluoride, making extraction difficult and resulting in poor bromine separation. Furthermore, the sodium fluoride adsorption method for separating bromine trifluoride and uranium hexafluoride also presents the following problems: ① The particle size distribution of sodium fluoride affects the adsorption effect. Small particles are compacted due to increased adsorption pressure and limited heat dissipation, hindering the reaction; large particles, on the other hand, cause uranium hexafluoride diffusion. The adsorption rate is lower than the reaction rate, resulting in a low adsorption rate. Furthermore, after the adsorption-desorption cycle, the particle size distribution of sodium fluoride changes; for example, particles become powder (potentially introduced into uranium hexafluoride), and the powder is compacted (resulting in residual uranium hexafluoride). To maintain separation efficiency, the adsorbent needs to be replaced periodically, increasing both cost and radioactive waste. Secondly, during high-temperature desorption, approximately 1.5% of the complex undergoes a decomposition reaction where U(VI) is reduced to U(V), leading to reduced adsorbent capacity and uranium loss. Therefore, this invention does not use sodium fluoride for direct adsorption and separation of the mixture, but rather treats it as an adsorbent for waste gas.

[0104] This invention utilizes vacuum sublimation and cryogenic distillation to separate and recover uranium-containing radioactive waste. First, bromine is effectively separated from the waste via vacuum sublimation. This leverages the higher melting point and saturated vapor pressure of bromine at low temperatures compared to uranium hexafluoride and bromine trifluoride. Uranium hexafluoride and bromine trifluoride are first condensed, and then the percentage of bromine is increased through staged condensation. Finally, bromine separation from the mixed waste is achieved at low temperatures. Second, uranium hexafluoride is separated from bromine trifluoride through staged cryogenic distillation, and bromine trifluoride is recovered separately. This utilizes the difference in saturated vapor pressure between uranium hexafluoride and bromine trifluoride. At low temperatures, the ideal gas partial pressure ratio of the two meets the separation requirements. By controlling the temperature and pressure during cryogenic distillation, separation from uranium hexafluoride and bromine trifluoride is achieved. This enables the classified recovery of uranium-containing radioactive deposit cleaning waste, ensuring that the materials and cleaning agents meet reuse requirements. This is beneficial for the sustainable development of uranium enrichment plants and the green development of the nuclear industry. This technology can also be applied to the recovery of similar mixed waste.

[0105] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific description herein should not be construed as limiting the nature and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for separating and recovering uranium-containing radioactive waste, characterized in that, Includes the following steps: (1) Vacuum sublimation process: ① Reduced pressure heating: The mixed working fluid containing UF6, BrF3 and Br2 is vaporized; ② Multi-stage condensation: The generated gaseous mixture is fed into a multi-stage condensation system and condensed at a temperature ≤4℃ and a pressure ≤10kPa to condense solid BrF3 and UF6; ③ Cold bromine recovery: Uncondensed gas is passed into a cryogenic device for liquefaction and recovery; (2) Low-temperature distillation process: ④ Fractional distillation: The UF6 and BrF3 mixture condensed in step (1) is subjected to gradient pressure reduction distillation. At 0℃~-10℃, the pressure gradient is reduced by 1 kPa from 2.7 kPa to separate UF6 gas and solid BrF3. In step ②, the multi-stage condensation includes three stages of condensation: First-stage condensation: Temperature 4℃, Pressure ≤10kPa; Second-stage condensation: temperature -20℃, pressure ≤1.5kPa; Third-stage condensation: temperature -40℃, pressure ≤0.693kP.

2. The method for separating and recovering uranium-containing radioactive waste according to claim 1, characterized in that, In step ①, the heating temperature is >75℃ and the pressure is controlled at ≤13.4kPa.

3. The method for separating and recovering uranium-containing radioactive waste according to claim 2, characterized in that, In step ①, the heating temperature is 60℃~80℃ and the pressure is 7kPa~13.4kPa.

4. The method for separating and recovering uranium-containing radioactive waste according to claim 1, characterized in that, The temperature for liquefaction recovery in step ③ is -105~-115℃ and the pressure is ≤50Pa.

5. The method for separating and recovering uranium-containing radioactive waste according to claim 1, characterized in that, In the cold bromine recovery process of step ③, the unliquefied residual gas is treated by a gas absorption tower filled with sodium fluoride particles, and the gas residence time is ≥30 seconds.

6. The method for separating and recovering uranium-containing radioactive waste according to claim 1, characterized in that, Step ④, fractional distillation, includes three stages of distillation: First stage distillation: temperature 2~-6℃, pressure 2.7~1.4kPa; Second stage distillation: temperature 0~-10℃, pressure 1.8~1kPa; Third stage distillation: temperature 0~-10℃, pressure 1.6~1kPa.

7. The method for separating and recovering uranium-containing radioactive waste according to claim 1, characterized in that, The low-temperature distillation process in step (2) further includes: ⑤ UF6 collection: The gas produced by distillation is condensed and collected at -120℃ to -80℃ to obtain solid UF6; ⑥ BrF3 collection: The solid mixture obtained from distillation is heated to 10℃~25℃ to obtain BrF3 liquid.

8. The method for separating and recovering uranium-containing radioactive waste according to claim 1, characterized in that, Both the vacuum sublimation process and the cryogenic distillation process are carried out in a closed system, and the various devices are connected by pipelines.

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