A system and method for treating boron-containing radioactive waste liquid from a nuclear power plant

Abstract

The present invention relates to a system and method for treating boron-containing radioactive waste liquid from a nuclear power plant. The treatment system comprises a pretreatment unit, a main treatment unit, and a deep treatment unit. The pretreatment unit comprises an ultrafiltration system for separating particulate impurities and colloidal nuclides from the boron-containing radioactive waste liquid. The main treatment unit comprises a primary nanofiltration membrane system and a secondary nanofiltration membrane system. One end of the primary nanofiltration membrane system is connected to the pretreatment unit via a pipeline, and the other end of the primary nanofiltration membrane system is connected to the secondary nanofiltration membrane system via a pipeline. The primary and secondary nanofiltration membrane systems are used to separate ionic nuclides from the clear liquid output from the pretreatment unit. The deep treatment unit comprises an electro-desalination system. One end of the electro-desalination system is connected to the secondary nanofiltration membrane system via a pipeline. The electro-desalination system is used to deeply purify the boron solution containing a small amount of radioactive nuclides output from the main treatment unit.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment, and in particular to a system and method for treating boron-containing radioactive waste liquid from a nuclear power plant. Background Art

[0002] As an important component of clean energy, the safe and efficient development of nuclear energy has always been accompanied by the innovation of radioactive waste treatment technology. During the operation of nuclear power plants, boron-containing radioactive waste water has become a difficult problem to treat due to its complex composition characteristics. This type of wastewater not only contains high concentrations of boron, but also contains a variety of radioactive nuclides (such as 58 CO, 60 CO, 110m Ag, 54 Mn, 124 Sb and 137 Cs, etc.), its treatment needs to take into account the dual goals of deep purification of radioactive nuclides and resource utilization of boron.

[0003] At present, the treatment of boron-containing radioactive waste liquid usually adopts a combined process of ion exchange, membrane filtration and evaporation. Although this type of process can remove radionuclides, it still has defects: (1) Boron and radionuclides are treated together as source items. While achieving the removal of radionuclides, a large amount of radioactive concentrated boron-containing liquid is produced, resulting in solidified volume expansion; (2) The evaporation process has high energy consumption and is prone to crystallization and scaling, as well as the entrainment and release of radionuclides with steam; (3) The separation efficiency of reverse osmosis membranes for boron is limited by pH conditions. In most cases, in order to obtain higher boron separation efficiency, the pH needs to be adjusted, resulting in the introduction of other ions.

[0004] In addition, when using reverse osmosis membranes to concentrate and reduce boron-containing radioactive waste liquid, boron crystallization on the membrane surface is likely to occur, resulting in limited concentration.

[0005] Chinese patent CN110473644A discloses a device for removing boron from radioactive wastewater. The device comprises a raw water tank, a separation unit inlet pump, a separation unit membrane assembly, an intermediate water tank, a concentration unit inlet pump, a concentration unit membrane assembly, a fresh water tank, a continuous electro-desalination membrane assembly, a concentrate tank, and a product water tank. These components are connected to each other. The separation unit membrane assembly has a boron permeability greater than 90% and a radionuclide rejection greater than 95%, while the concentration unit membrane assembly has a boron rejection greater than 95%. This patent relies on a custom composite reverse osmosis membrane (including a special separation layer), which has a complex manufacturing process, high cost, and poor applicability. Summary of the Invention

[0006] The present invention aims to provide a system and method for treating boron-containing radioactive waste liquid from nuclear power plants. The system, described herein, is primarily designed to treat boron-containing radioactive waste liquid. While efficiently separating nuclides from boron, it achieves deep nuclide purification and boron recovery, concentrating and reducing the amount of the nuclide-containing concentrated solution, ultimately reducing the amount of radioactive waste produced.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A boron-containing radioactive waste liquid treatment system for a nuclear power plant includes a pretreatment unit, a main treatment unit and a deep treatment unit.

[0009] The pretreatment unit includes an ultrafiltration system, which is used to separate particulate impurities and colloidal nuclides in the boron-containing radioactive waste liquid;

[0010] The main treatment unit includes a primary nanofiltration membrane system and a secondary nanofiltration membrane system, one end of the primary nanofiltration membrane system is connected to the pretreatment unit through a pipeline, and the other end of the primary nanofiltration membrane system is connected to the secondary nanofiltration membrane system through a pipeline, and the primary nanofiltration membrane system and the secondary nanofiltration membrane system are used to separate ionized nuclides in the clear liquid output from the pretreatment unit;

[0011] The deep processing unit includes an electric desalination system, one end of which is connected to a secondary nanofiltration membrane system through a pipeline. The electric desalination system is used to deeply purify the boron solution containing a small amount of radioactive nuclides output by the main processing unit.

[0012] Furthermore, the ultrafiltration system has a boron transmittance greater than 99%;

[0013] The boron transmittance of the first-stage nanofiltration membrane system and the second-stage nanofiltration membrane system is greater than 99%;

[0014] The electro-desalination system has a boron recovery rate greater than 95%.

[0015] Furthermore, the pretreatment unit further comprises a raw water tank, and the ultrafiltration system comprises an ultrafiltration membrane, an ultrafiltration water inlet pump and an ultrafiltration concentrated water proportional valve.

[0016] One end of the raw water tank is connected to the waste liquid input pipeline, and the other end of the raw water tank is connected to the ultrafiltration membrane through a pipeline, and the pipeline is provided with an ultrafiltration water inlet pump.

[0017] The concentrated water produced by the ultrafiltration membrane flows back to the raw water tank through a pipeline, and the pipeline is provided with an ultrafiltration concentrated water proportional valve;

[0018] The ultrafiltration membrane is used to remove particulate impurities and colloidal nuclides in the boron-containing radioactive waste liquid, and plays a protective role for subsequent units.

[0019] As a preferred technical solution, the ultrafiltration membrane is any one of a hollow fiber membrane, a spiral membrane or a flat membrane, and the filtration pore size is 0.05 μm to 0.1 μm.

[0020] Furthermore, the main treatment unit further comprises a nanofiltration water tank, the first-level nanofiltration membrane system comprises a first-level nanofiltration membrane, and the second-level nanofiltration membrane system comprises a second-level nanofiltration membrane.

[0021] One end of the nanofiltration water tank is connected to the ultrafiltration membrane through a pipeline, and the other end of the nanofiltration water tank is connected to the first-level nanofiltration membrane through a pipeline. The pipeline is sequentially provided with a first-level nanofiltration booster pump and a first-level nanofiltration high-pressure pump.

[0022] The end of the first-level nanofiltration membrane away from the nanofiltration water tank is connected to the second-level nanofiltration membrane through a pipeline, and the pipeline is provided with a second-level nanofiltration high-pressure pump.

[0023] Furthermore, the concentrated water produced by the primary and secondary nanofiltration membranes is returned to the nanofiltration water tank through a pipeline.

[0024] The pipeline connecting the nanofiltration water tank and the first-level nanofiltration membrane is provided with a first-level nanofiltration concentrated water proportional valve.

[0025] A secondary nanofiltration concentrated water proportional valve is provided on the pipeline connecting the nanofiltration water tank and the secondary nanofiltration membrane.

[0026] Furthermore, the electro-desalination system comprises a desalted water tank, an electro-desalination water inlet pump and an electro-desalination system connected in sequence by pipelines, wherein one end of the desalted water tank away from the electro-desalination water inlet pump is connected to a secondary nanofiltration membrane via a pipeline, and one end of the electro-desalination system away from the electro-desalination water inlet pump is connected to a boron-containing clear liquid pipeline.

[0027] The concentrated water produced by the electro-desalination is returned to the nanofiltration water tank through a pipeline.

[0028] Furthermore, the deep processing unit further comprises a clear liquid tank, which is arranged between the electric desalination and the boron-containing clear liquid pipeline, and the pipeline is provided with a clear liquid output pump.

[0029] Furthermore, a cesium adsorption module is provided between the pipe connecting the electro-deionization system and the clear liquid tank, wherein the cesium adsorption module is filled with a cesium removal adsorbent and is used to adsorb cesium in the deeply purified boron solution output by the secondary nanofiltration membrane system;

[0030] When entering the water 137 The activity of Cs is higher than 5×10 3 Bq / L, a cesium adsorption module is required.

[0031] Furthermore, the treatment system further comprises a concentrated water tank, which is connected to the nanofiltration water tank, the first-stage nanofiltration membrane, the second-stage nanofiltration membrane and the electric desalination through pipelines, and a concentrated water discharge proportional valve is provided on the pipeline.

[0032] Furthermore, the concentrated water tank is externally connected to a concentrated liquid pipe, and a waste liquid output pump is provided on the pipe.

[0033] Furthermore, the processing system also includes a control unit, which is composed of an input module, a control module, a communication module, an alarm module and a human-computer interaction module. The input module is responsible for collecting equipment signals, including liquid level switches, pressure sensors, flow meters, water pumps and valves, for monitoring parameters and equipment operating status. The control module receives and processes input signals, performs logical operations, and implements preset control logic. The communication module is responsible for data exchange. The alarm module is used to prompt abnormal conditions during operation, issue sound and light alarms, and prompt operators to deal with abnormalities in a timely manner. The human-computer interaction module is used to display a graphical operation interface, which is convenient for operators to monitor system status, adjust operating parameters and view alarm information in real time.

[0034] The control unit is used to realize automatic control of the treatment system, reduce manual operation, avoid close contact between personnel and radioactive materials, and effectively protect the health and safety of personnel.

[0035] The present invention also provides a method for treating boron-containing radioactive waste liquid from a nuclear power plant, which is carried out using the above-mentioned boron-containing radioactive waste liquid treatment system from a nuclear power plant, and the specific steps are as follows:

[0036] S1. Inputting the boron-containing radioactive waste liquid into an ultrafiltration system for separation, and pre-treating the boron-containing radioactive waste liquid to obtain an ultrafiltration clear liquid;

[0037] S2, inputting the ultrafiltration clear solution obtained in step S1 into the primary nanofiltration membrane system and the secondary nanofiltration membrane system in sequence for separation, and obtaining the secondary nanofiltration clear solution after removing the ionized nuclides;

[0038] S3. The secondary nanofiltration clear liquid obtained in step S2 is input into an electric desalination system for deep nuclide purification to obtain a final boron-containing clear liquid.

[0039] Furthermore, after step S3, step S4 is provided, when the boron-containing radioactive waste liquid 137 The activity of Cs is higher than 5×10 3 Bq / L, the deeply purified boron solution output from the secondary nanofiltration membrane system is input into the cesium adsorption module to obtain the final boron-containing clear solution after removing cesium.

[0040] The principles of the present invention are as follows:

[0041] After ultrafiltration separation, the particulate impurities and colloidal radionuclides in the boron-containing radioactive waste liquid of nuclear power plants enter the primary nanofiltration membrane system and the secondary nanofiltration membrane system in sequence. The two-stage nanofiltration can effectively remove the ionized radionuclides in the incoming water, greatly reducing the radioactive activity of the incoming water; the effluent of the secondary nanofiltration membrane system enters the electric desalination system, and is treated by the system to finally complete the deep purification of the radionuclides.

[0042] The ultrafiltration system, the primary nanofiltration system, the secondary nanofiltration system and the electric desalination system described in the present invention are mandatory processes, and the cesium adsorption module is an optional process.

[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0044] (1) The method provided by the present invention can achieve efficient separation of nuclides and boron in boron-containing radioactive waste liquid. While deeply purifying the nuclides, boron can be fully permeated, with a boron permeability greater than 92%. The treated boron-containing clear liquid can be reused, thereby reducing the operating costs of nuclear power plants.

[0045] (2) After separating boron from radionuclides, the concentrated water containing radionuclides is efficiently concentrated and reduced through a membrane system, with a concentration ratio of 5 to 50 times, which greatly reduces the amount of waste generated and reduces the cost of waste disposal.

[0046] (3) The present invention can achieve efficient treatment of boron-containing radioactive waste liquid, and while separating nuclides from boron, it can also achieve deep purification of nuclides and recovery of boron, thereby reducing the output of radioactive waste and lowering the cost of waste disposal. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a system block diagram of the boron-containing radioactive waste liquid treatment system;

[0048] Figure 2 This is a process flow diagram of a boron-containing radioactive waste liquid treatment system;

[0049] Explanation of the accompanying figures: 1. Raw water tank, 2. Ultrafiltration water inlet pump, 3. Ultrafiltration membrane, 4. Ultrafiltration concentrate proportional valve, 5. Nanofiltration water tank, 6. First-stage nanofiltration booster pump, 7. First-stage nanofiltration high-pressure pump, 8. First-stage nanofiltration membrane, 9. First-stage nanofiltration concentrate proportional valve, 10. Second-stage nanofiltration high-pressure pump, 11. Second-stage nanofiltration membrane, 12. Second-stage nanofiltration concentrate proportional valve, 13. Concentrate discharge proportional valve, 14. Concentrate tank, 15. Desalted water tank, 16. Electrodialysis inlet pump, 17. Electrodialysis, 18. Cesium adsorption module, 19. Clear liquid tank, 20. Waste liquid output pump, 21. Clear liquid output pump, 22. Waste liquid input pipeline, 23. Concentrate discharge pipeline, 24. Boron-containing clear liquid pipeline. DETAILED DESCRIPTION

[0050] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0051] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not require further definition or explanation in subsequent drawings.

[0052] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," and "outside" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0054] The following describes some embodiments of the present invention in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0055] Example 1

[0056] See also Figures 1 to 2 This embodiment provides a boron-containing radioactive waste liquid treatment system for a nuclear power plant, including a pretreatment unit, a main treatment unit, and a deep treatment unit.

[0057] Boron-containing radioactive waste liquid first enters the pretreatment unit for preliminary radionuclide treatment. The pretreatment unit includes a raw water tank 1, an ultrafiltration system, piping, and a control circuit. The ultrafiltration system includes an ultrafiltration membrane 3, an ultrafiltration water pump 2, and an ultrafiltration concentrate proportional valve 4. The ultrafiltration membrane 3 is used to separate and remove particulate impurities and colloidal radionuclides from the boron-containing radioactive raw liquid. During this process, boron is not retained by the ultrafiltration membrane, and the transmittance is higher than 99%. After ultrafiltration separation, the concentrate is returned to the raw water tank 1, and the boron enters the nanofiltration water tank 5 along with the ultrafiltration product water, and then enters the main treatment unit.

[0058] The main treatment unit consists of a primary nanofiltration membrane system and a secondary nanofiltration membrane system, which are mainly used to remove ionized radionuclides in the wastewater; the ultrafiltration product water passes through the primary nanofiltration booster pump 6 and the primary nanofiltration high-pressure pump 7, enters the primary nanofiltration membrane 8, and the separated concentrated water is returned to the nanofiltration water tank 5 through the concentrated water pipeline, and the product water passes through the secondary nanofiltration high-pressure pump 10 and enters the secondary nanofiltration membrane 11 for further removal of ionized radionuclides. The concentrated water produced in this process is also connected to the concentrated water pipeline and returned to the nanofiltration water tank 5; the boron transmittance of the primary nanofiltration membrane 8 and the secondary nanofiltration membrane 11 is higher than 99%, and the boron enters the desalted water tank with the purified product water for deep treatment;

[0059] The deep treatment unit consists of an electro-desalination system and a cesium adsorption module 18. After being treated by the main treatment unit, the wastewater is pumped into the electro-desalination 17 through the electro-desalination water inlet pump 16. The concentrated water containing radioactive nuclides produced by the electro-desalination 17 enters the concentrated water pipeline, and the boron-containing clear liquid is output backward.

[0060] In this embodiment, the boron-containing radioactive waste liquid is mainly composed of radioactive nuclides and boron, and contains one or more nuclides, the types of which include: 110m Ag, 58 Co、 60 Co、 54 Mn, 125 Sb and 137 Cs et al.

[0061] In this embodiment, the cesium adsorption module 18 is connected in series to the outlet pipe of the electro-desalination clear liquid. A valve is set on the pipe, and the control module is switched to the operation process by switching the valve. 137 The activity of Cs is higher than 5×10 3 Bq / L, the cesium adsorption module 18 is activated, and the electro-desalination clear liquid flows through the cesium adsorption module 18 to remove 137 After Cs, it is input into the clear liquid tank 19; this unit is mainly used for deep purification of radionuclides. The activity of the purified radionuclides is lower than 10 Bq / L. At the same time, it ensures that boron fully penetrates, and the boron transmittance is greater than 92%, forming concentrated waste liquid containing radionuclides and clear liquid containing boron.

[0062] The concentrate pipeline is connected to the nanofiltration water tank 5, and a branch pipeline is separated to connect to the concentrate tank 14. A concentrate discharge proportional valve 13 is set on the branch pipeline. When the concentration ratio reaches the set value (5 to 50 times), the opening of the concentrate discharge proportional valve 13 is changed according to the flow rate of the boron-containing clear liquid, and the concentrate is input into the concentrate tank 14 at the designed flow rate.

[0063] In this embodiment, the raw water tank 1 and the nanofiltration water tank 5 are made of stainless steel.

[0064] In addition, this embodiment also provides a method for treating boron-containing radioactive waste liquid from a nuclear power plant, which is performed using the above-mentioned boron-containing radioactive waste liquid treatment system from a nuclear power plant. The specific steps are as follows:

[0065] Step 1: After the boron-containing radioactive waste liquid is input into the raw water tank 1, it is pumped into the ultrafiltration membrane 3 through the ultrafiltration water inlet pump 2. The operating pressure is controlled within 3 Bar. The ultrafiltration membrane 3 is backwashed for 30 minutes per time, and the flushing time is 1 minute. The ultrafiltration concentrate proportional valve 4 is used to adjust the pressure and the return flow of the ultrafiltration concentrate. After separation by the ultrafiltration membrane 3, the ultrafiltration concentrate is returned to the raw water tank 1, and the ultrafiltration clear liquid is input into the nanofiltration water tank 5 to achieve pretreatment of the waste liquid;

[0066] Step 2: After the ultrafiltration clear liquid is temporarily stored in the nanofiltration water tank 5, the ultrafiltration clear liquid is sequentially pumped into the first-level nanofiltration membrane 8 through the first-level nanofiltration booster pump 6 and the first-level nanofiltration high-pressure pump 7 for treatment. After separation by the first-level nanofiltration membrane 8, the first-level nanofiltration membrane concentrated water is returned to the nanofiltration water tank 5. The first-level nanofiltration membrane clear liquid is pumped into the second-level nanofiltration membrane 11 through the second-level nanofiltration high-pressure pump 10 for further treatment. After separation by the second-level nanofiltration membrane 11, the second-level nanofiltration concentrated water is returned to the nanofiltration water tank 5. The second-level nanofiltration clear liquid is input into the desalted water tank 15. The ionized nuclides in the stock solution are removed by the first-level nanofiltration membrane system and the second-level nanofiltration membrane system to obtain a preliminary boron-containing clear liquid;

[0067] Step 3: The above-mentioned boron-containing clear liquid is pumped into the electric desalination 17 through the electric desalination water inlet pump 16 for deep nuclide purification to obtain the final boron-containing clear liquid, and the concentrated water of the electric desalination 17 is connected to the concentrated water pipeline and returned to the nanofiltration water tank 5.

[0068] In this embodiment, in step 1, a backwash module is provided in the ultrafiltration membrane system, and the ultrafiltration system performs backwashing according to a set period to prevent the accumulation of particulate impurities and colloidal nuclides on the membrane surface.

[0069] In this embodiment, in step 2, the primary nanofiltration brine proportional valve 9 and the secondary nanofiltration brine proportional valve 12 are used to adjust the operating pressure and brine reflux volume of the primary and secondary nanofiltration systems, respectively.

[0070] In this embodiment, in step 2, the brine produced by the primary nanofiltration membrane system, the secondary nanofiltration membrane system, and the electro-deionization system is returned to the nanofiltration water tank 5 through the brine pipeline. The concentration multiple (5 to 50 times) is set. The opening of the brine discharge proportional valve 13 is controlled according to the final boron-containing clear liquid flow rate, and the brine is input into the brine tank 14 at the designed flow rate.

[0071] The concentration multiple and the designed output of concentrated water are determined by the following formula I:

[0072] (I),

[0073] Among them, CT is the concentration multiple; Qi is the flow rate of the boron-containing clear liquid (m 3 / h), Qe is the concentrated water flow rate (m 3 / h).

[0074] In this embodiment, in step 3, the water produced by electro-desalination is 137 The activity of Cs determines whether to directly enter the clear liquid tank 19; when the boron-containing radioactive waste liquid 137 The activity of Cs is higher than 5×10 3 Bq / L, the cesium adsorption module 18 needs to be connected to the system. After the cesium in the electro-deionized clear liquid is removed by the cesium adsorption module 18, it is input into the clear liquid tank 19 to obtain the final boron-containing clear liquid.

[0075] Example 2

[0076] This embodiment provides a specific application experiment of a boron-containing radioactive waste liquid treatment system in a nuclear power plant. The specific steps are as follows:

[0077] The design processing capacity of the treatment system is 100L / h. The boron concentration in the boron-containing radioactive waste liquid is 1255 ppm. The main nuclides are 110m Ag, 58 Co、 60 Co、 54 Mn, 125 Sb and 137 The Cs activities were 326 Bq / L, 118 Bq / L, 857 Bq / L, 2145 Bq / L, 3873 Bq / L, and 1466 Bq / L, respectively, with a total gamma activity of 9364 Bq / L. The process flow employed was ultrafiltration → primary nanofiltration → secondary nanofiltration → electrodialysis. After treatment with ultrafiltration membrane 3, the total gamma activity was reduced to 7023 Bq / L, with a boron concentration of 1248 ppm. After treatment with primary nanofiltration membrane 8 and secondary nanofiltration membrane 11, the total gamma activity was reduced to 395 Bq / L, with a boron concentration of 1242 ppm. After treatment with electrodialysis membrane 17, the total gamma activity was reduced to 1.58 Bq / L, with a boron concentration of 1183 ppm. The treated volume of the original solution was 500 L, yielding 460 L of boron-containing clear solution, a concentration factor of 12.5.

[0078] Example 3

[0079] This embodiment provides a specific application experiment of a boron-containing radioactive waste liquid treatment system in a nuclear power plant. The specific steps are as follows:

[0080] The design processing capacity of the treatment system is 100 L / h. The boron concentration in the boron-containing radioactive waste liquid is 1075 ppm. The main nuclides are 110m Ag, 58 Co、 60 Co、 54 Mn, 125 Sb, 124 Sb and 137 The Cs activities were 216 Bq / L, 141 Bq / L, 1533 Bq / L, 1782 Bq / L, 2754 Bq / L, 1682 Bq / L, and 6437 Bq / L, respectively, with a total gamma activity of 15783 Bq / L. The process flow employed was ultrafiltration → primary nanofiltration → secondary nanofiltration → electrodialysis → cesium adsorption module.

[0081] The filling material inside the cesium adsorption module 18 used in this embodiment is a composite material of graphene oxide (GO) and potassium copper ferrocyanide (KCuHCF).

[0082] In this embodiment, the preparation method of the GO and potassium copper ferrocyanide composite material is as follows:

[0083] First, 70 mL of concentrated sulfuric acid was added to a flask, followed by 3 g of graphite powder and 1.5 g of sodium nitrate. The mixture was stirred continuously in an ice bath for 30 minutes, followed by the addition of 9 g of potassium permanganate and continued stirring for 1 hour. The mixture was heated to 35°C and stirred for 2 hours. 140 mL of deionized water was added and the mixture was heated in a 95°C water bath for 15 minutes. 500 mL of deionized water and hydrogen peroxide were added, and the solution turned from brown to yellow. 5% hydrochloric acid solution was added, and the mixture was repeatedly washed with deionized water. Purified GO was obtained after multiple centrifugation. One gram of the prepared GO was weighed and placed in 100 mL of 100 mmol / L copper nitrate solution, stirred for 24 hours, centrifuged and dried, and then placed in 100 mL of 100 mmol / L potassium ferrocyanide solution, stirred for 24 hours. After centrifugation and washing, the mixture was dried to prepare a GO-potassium ferrocyanide copper composite.

[0084] After treatment with ultrafiltration membrane 3, the total gamma activity dropped to 11,678 Bq / L, and the boron concentration was 1,072 ppm. After treatment with primary nanofiltration membrane 8 and secondary nanofiltration membrane 11, the total gamma activity dropped to 2,754 Bq / L, and the boron concentration was 1,065 ppm. After treatment with electrodialysis 17, the total gamma activity dropped to 45 Bq / L, and the boron concentration was 1,014 ppm. After treatment with cesium adsorption module 18, the total gamma activity dropped to 0.31 Bq / L, and the boron concentration was 1,008 ppm. The volume of the treated raw liquid was 300 L, and 292 L of boron-containing clear liquid was produced, with a concentration factor of 37.5.

[0085] It can be seen from the above examples that the present invention can achieve efficient treatment of boron-containing radioactive waste liquid from nuclear power plants, while separating nuclides from boron, achieving deep purification of nuclides and recovery of boron, and significantly reducing the discharge of concentrated liquid, effectively reducing waste disposal costs.

[0086] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A boron-containing radioactive waste liquid treatment system for a nuclear power plant, characterized in that: Including pre-processing unit, main processing unit and deep processing unit, The pretreatment unit includes an ultrafiltration system, which is used to separate particulate impurities and colloidal nuclides in the boron-containing radioactive waste liquid; The main treatment unit includes a primary nanofiltration membrane system and a secondary nanofiltration membrane system, one end of the primary nanofiltration membrane system is connected to the pretreatment unit through a pipeline, and the other end of the primary nanofiltration membrane system is connected to the secondary nanofiltration membrane system through a pipeline, and the primary nanofiltration membrane system and the secondary nanofiltration membrane system are used to separate ionized nuclides in the clear liquid output from the pretreatment unit; The deep processing unit includes an electric desalination system, one end of which is connected to a secondary nanofiltration membrane system through a pipeline. The electric desalination system is used to deeply purify the boron solution containing a small amount of radioactive nuclides output by the main processing unit.

2. A boron-containing radioactive waste liquid treatment system for a nuclear power plant according to claim 1, characterized in that: The ultrafiltration system has a boron transmittance greater than 99%; The boron transmittance of the first-stage nanofiltration membrane system and the second-stage nanofiltration membrane system is greater than 99%; The electro-desalination system has a boron recovery rate greater than 95%.

3. A boron-containing radioactive waste liquid treatment system for a nuclear power plant according to claim 1, characterized in that: The pretreatment unit further comprises a raw water tank (1), and the ultrafiltration system comprises an ultrafiltration membrane (3), an ultrafiltration water inlet pump (2), and an ultrafiltration concentrated water proportional valve (4). One end of the raw water tank (1) is connected to the waste liquid input pipe (22), and the other end of the raw water tank (1) is connected to the ultrafiltration membrane (3) through a pipe, and the pipe is provided with an ultrafiltration water inlet pump (2). The concentrated water produced by the ultrafiltration membrane (3) flows back to the raw water tank (1) through a pipeline, and the pipeline is provided with an ultrafiltration concentrated water proportional valve (4); The ultrafiltration membrane (3) is used to remove particulate impurities and colloidal nuclides in the boron-containing radioactive waste liquid, and plays a protective role for subsequent units.

4. A boron-containing radioactive waste liquid treatment system for a nuclear power plant according to claim 3, characterized in that: The main treatment unit further comprises a nanofiltration water tank (5), the first-level nanofiltration membrane system comprises a first-level nanofiltration membrane (8), and the second-level nanofiltration membrane system comprises a second-level nanofiltration membrane (11). One end of the nanofiltration water tank (5) is connected to the ultrafiltration membrane (3) via a pipeline, and the other end of the nanofiltration water tank (5) is connected to the first-stage nanofiltration membrane (8) via a pipeline. The first-stage nanofiltration booster pump (6) and the first-stage nanofiltration high-pressure pump (7) are sequentially provided on the pipeline. The end of the first-stage nanofiltration membrane (8) away from the nanofiltration water tank (5) is connected to the second-stage nanofiltration membrane (11) via a pipeline, and the pipeline is provided with a second-stage nanofiltration high-pressure pump (10).

5. A boron-containing radioactive waste liquid treatment system for a nuclear power plant according to claim 4, characterized in that: The concentrated water produced by the primary nanofiltration membrane (8) and the secondary nanofiltration membrane (11) is returned to the nanofiltration water tank (5) through a pipeline. A first-stage nanofiltration concentrated water proportional valve (9) is provided on the pipeline connecting the nanofiltration water tank (5) and the first-stage nanofiltration membrane (8). A secondary nanofiltration concentrated water proportional valve (12) is provided on the pipeline connecting the nanofiltration water tank (5) and the secondary nanofiltration membrane (11).

6. A boron-containing radioactive waste liquid treatment system for a nuclear power plant according to claim 4, characterized in that: The electro-deionization system comprises a deionized water tank (15), an electro-deionization water inlet pump (16) and an electro-deionizer (17) which are sequentially connected via a pipeline, wherein one end of the deionized water tank (15) away from the electro-deionization water inlet pump (16) is connected to a secondary nanofiltration membrane (11) via a pipeline, and one end of the electro-deionizer (17) away from the electro-deionization water inlet pump (16) is connected to a boron-containing clear liquid pipeline (24). The concentrated water generated by the electro-desalination (17) flows back to the nanofiltration water tank (5) through a pipeline.

7. A boron-containing radioactive waste liquid treatment system for a nuclear power plant according to claim 6, characterized in that: The deep treatment unit further comprises a clear liquid tank (19), wherein the clear liquid tank (19) is arranged between the electro-desalting (17) and the boron-containing clear liquid pipeline (24), and the pipeline is provided with a clear liquid output pump (21); A cesium adsorption module (18) is further provided between the pipe connecting the electro-desalination (17) and the clear liquid tank (19). The interior of the cesium adsorption module (18) is filled with a cesium removal adsorbent. The cesium adsorption module (18) is used to adsorb cesium in the deeply purified boron solution output by the secondary nanofiltration membrane system.

8. A boron-containing radioactive waste liquid treatment system for a nuclear power plant according to claim 1, characterized in that: The treatment system further includes a concentrated water tank (14), which is connected to the nanofiltration water tank (5), the first-stage nanofiltration membrane (8), the second-stage nanofiltration membrane (11), and the electric desalination (17) through pipelines, and a concentrated water discharge proportional valve (13) is provided on the pipeline; The concentrated water tank (14) is externally connected to a concentrated liquid discharge pipeline (23), on which a waste liquid output pump (20) is provided.

9. A method for treating boron-containing radioactive waste liquid from a nuclear power plant, characterized in that: The method is carried out using the boron-containing radioactive waste liquid treatment system of a nuclear power plant as described in any one of claims 1 to 8, wherein the specific steps are as follows: S1. Inputting the boron-containing radioactive waste liquid into an ultrafiltration system for separation, and pre-treating the boron-containing radioactive waste liquid to obtain an ultrafiltration clear liquid; S2, inputting the ultrafiltration clear solution obtained in step S1 into the primary nanofiltration membrane system and the secondary nanofiltration membrane system in sequence for separation, and obtaining the secondary nanofiltration clear solution after removing the ionized nuclides; S3. The secondary nanofiltration clear liquid obtained in step S2 is input into an electric desalination system for deep nuclide purification to obtain a final boron-containing clear liquid.

10. The method for treating boron-containing radioactive waste liquid from a nuclear power plant according to claim 9, characterized in that: After step S3, step S4 is provided, when the boron-containing radioactive waste liquid is 137 The activity of Cs is higher than 5×10 3 Bq / L, the deeply purified boron solution output from the secondary nanofiltration membrane system is input into the cesium adsorption module (18), and the final boron-containing clear solution is obtained after cesium removal.

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