Combined internal regeneration nuclear power plant secondary loop radioactive stained sewage treatment method and device

Abstract

The invention provides a combined internal regeneration nuclear power plant secondary circuit radioactive contaminated water treatment method and device. The method comprises the steps that S1, secondary circuit contaminated water is conveyed into a raw water tank; s2, conveying the waste liquid in the raw water tank to a yin-yang mixed resin bed, and purifying radionuclides in the waste liquid; s3, conveying produced water generated after the anion and cation mixed resin bed treatment to a first-stage membrane unit, and purifying radionuclides; s4, concentrated water generated after treatment of the first-stage membrane unit is conveyed to a cesium removal medium bed for impurity removal, and then the concentrated water is conveyed to a concentrated water tank; and S5, conveying the concentrated solution in the concentrated water tank to a second-stage membrane unit for cyclic concentration until the concentration of non-radioactive impurities in the concentrated solution reaches a target value, and conveying produced water generated after treatment of the second-stage membrane unit back to the raw water tank. The liquid effluent discharge standard requirement can be met through single-time treatment, and meanwhile the liquid effluent treatment device has the advantages of being small in arrangement space requirement, small in solid waste generation amount, easy to operate and maintain and the like.

Description

Technical Field

[0001] This invention relates to the field of waste management technology, specifically to a method and apparatus for treating radioactive contaminated wastewater from the secondary loop of a nuclear power plant using a combined internal regeneration system. Background Technology

[0002] Secondary loop wastewater from nuclear power plants includes wastewater from both normal operating conditions and radioactive contamination conditions. Normal operating conditions typically result in non-radioactive wastewater, primarily originating from regeneration waste liquid from the condensate regeneration system, equipment maintenance waste liquid, and cooling tower effluent. Radioactive nuclides only leak from the primary loop to the secondary loop, causing radioactive contamination, when a leak or rupture occurs in the heat transfer tubes of the steam generator. Due to the diverse sources and complex composition of the secondary loop water, radioactive contaminated wastewater from nuclear power plants is characterized by large volume, relatively low radionuclide activity concentrations (1-2 orders of magnitude lower than the radioactive waste liquid from the nuclear island), and high levels of non-radioactive impurities. Typical water quality characteristics are as follows:

[0003] 1) pH: 6~11

[0004] 2) Suspended solids content: ≤50 mg / L

[0005] 3) Water temperature: ≤60℃

[0006] 4) Oil content: ≤5 mg / L

[0007] 5) Salt content: ≤10g / L

[0008] 6) COD Cr ≤15 mg / L

[0009] 7) Fe: ≤4 mg / L

[0010] 8) Ammonia nitrogen: ≤20 mg / L

[0011] 9) Radioactivity concentration approximately 10 4 ~10 5 Bq / L (excluding tritium and carbon-14), typical nuclides include Co-58, Fe-55, Mn-54, Cr-51, Sr-90, Cs-134 / 137, etc.

[0012] Currently, in traditional Generation II Plus nuclear power plants in China, contaminated secondary loop wastewater is returned to the nuclear island for treatment via a fixed radioactive waste treatment system. Due to the large volume of secondary loop wastewater, if contamination occurs, using the nuclear island's waste treatment system would require significant time commitment, potentially hindering the plant's normal operation and impacting its overall radioactive wastewater generation. The primary process used in Generation II nuclear power plant waste treatment systems is evaporation. However, evaporation for secondary loop contaminated wastewater treatment suffers from high energy consumption, long processing times, the generation of large amounts of concentrated radioactive liquid, large land area requirements, high construction and maintenance costs, and unsuitability for mobile treatment equipment. The CAP series nuclear power plant radioactive wastewater treatment system employs a chemical flocculation combined with ion exchange process. This process is unsuitable for treating wastewater with high background salt content, generates substantial secondary waste, and struggles to meet high decontamination factor requirements in a single treatment cycle. Furthermore, transporting secondary loop contaminated wastewater from the conventional island to the nuclear island would necessitate extensive laying of radioactive trenches within the plant area, resulting in resource waste and significant secondary waste generation during future decommissioning.

[0013] In addition, after the GB6249-2025 standard was upgraded, there are clear requirements for the total nuclide concentration and the concentration of 17 major single nuclides in liquid effluents from nuclear power plants. In particular, for some coastal sites with long discharge distances, or for future inland nuclear power plants, the requirements for total nuclide concentration have been further reduced. Existing flocculation combined media bed technology cannot meet the treatment target requirements. However, the treatment of radioactive waste liquid and the discharge of liquid effluents under various operating conditions of nuclear power plants (such as accidents, contamination, etc.) are the key areas of focus for the reviewers.

[0014] Therefore, taking into account the water quality characteristics, treatment requirements, secondary waste generation, operation and maintenance convenience, and nuclear power development trends of the secondary loop contaminated wastewater, the inventors of this application have designed a combined internal regeneration method and apparatus for treating radioactive contaminated wastewater from the secondary loop of nuclear power plants, in order to overcome the above-mentioned technical problems. Summary of the Invention

[0015] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology for treating contaminated wastewater in the secondary loop of nuclear power plants, which has special characteristics and is not perfect. The present invention provides a method and apparatus for treating radioactive contaminated wastewater in the secondary loop of nuclear power plants with combined internal regeneration.

[0016] The present invention solves the above-mentioned technical problems through the following technical solution:

[0017] This invention provides a method for treating radioactive contaminated wastewater from the secondary loop of a nuclear power plant using a combined internal regeneration system. The method comprises the following steps: S1, transferring the contaminated wastewater from the secondary loop to a raw water tank; S2, transferring the wastewater from the raw water tank to a mixed anodic and cathodic resin bed for purification of radioactive nuclides; S3, transferring the permeate from the mixed anodic and cathodic resin bed to a primary membrane unit for purification of radioactive nuclides; S4, transferring the concentrate from the primary membrane unit to a cesium removal medium bed for impurity removal, and then to a concentrate tank; S5, transferring the concentrate from the concentrate tank to a secondary membrane unit for cyclic concentration until the concentration of non-radioactive impurities in the concentrate reaches a target value, and then transferring the permeate from the secondary membrane unit back to the raw water tank.

[0018] According to one or more embodiments of the present invention, the method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant further includes the following steps: S6, after the cation-anion mixed resin bed is shut down, the high-salt concentrate in the concentrate tank is transported to the cation-anion mixed resin bed for regeneration, the high concentration of salt ions in the concentrate is used as the regeneration driving force to desorb the radionuclides exchanged on the resin, the nuclides on the cation-anion mixed resin bed are eluted and regenerated, the performance of the cation-anion mixed resin bed is restored, and the eluent containing the concentrated nuclides is sent back to the concentrate tank.

[0019] According to one or more embodiments of the present invention, the concentrated liquid in the concentrated water tank is treated by using a nuclear power plant shielded transfer device to transport the concentrated liquid in the concentrated water tank to the plant site waste treatment center for subsequent evaporation, drying and crystallization treatment.

[0020] According to one or more embodiments of the present invention, in step S2, the cation-anion mixed resin bed uses RH / RNa and ROH / RCl / RSO4 to purify divalent or higher valent cations and anions of radionuclides in the waste liquid.

[0021] According to one or more embodiments of the present invention, in step S4, the cesium removal medium bed removes the radionuclide cesium, and the concentrated water produced by the primary membrane unit is passed into the cesium removal medium bed. The cesium removal efficiency of the cesium removal medium bed is improved by utilizing the increase in the concentration of the radionuclide in the concentrated water.

[0022] According to one or more embodiments of the present invention, in step S5, the target value of the concentration of non-radioactive impurities in the concentrate is set to 80 g / L.

[0023] This invention also provides a combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device, characterized in that the combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device adopts the combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment method described above. The radioactive contaminated wastewater treatment device includes a raw water tank, a cation-anion mixed resin bed, a primary membrane unit, a cesium removal media bed, a concentrate tank, and a secondary membrane unit; the outlet of the raw water tank is connected to the inlet of the cation-anion mixed resin bed; the outlet of the cation-anion mixed resin bed is connected to the inlet of the primary membrane unit; the concentrate outlet of the primary membrane unit is connected to the inlet of the cesium removal media bed; the outlet of the cesium removal media bed is connected to the inlet of the concentrate tank; the outlet of the concentrate tank is connected to the inlet of the secondary membrane unit; the concentrate outlet of the secondary membrane unit is connected to the inlet of the concentrate tank; and the permeate outlet of the secondary membrane unit is connected to the inlet of the raw water tank.

[0024] According to one or more embodiments of the present invention, the outlet of the anion-cation mixing resin bed is connected to the inlet of the concentrate tank, and the outlet of the concentrate tank is connected to the inlet of the anion-cation mixing resin bed.

[0025] According to one or more embodiments of the present invention, the radioactive contaminated wastewater treatment device for the secondary loop of the nuclear power plant further includes a raw water pump and a secondary membrane inlet pump, wherein the raw water pump is connected to the outlet of the raw water tank and the secondary membrane inlet pump is connected to the inlet of the secondary membrane unit.

[0026] According to one or more embodiments of the present invention, the inlet of the raw water tank is connected to the secondary loop non-radioactive wastewater treatment system, and the product water outlet of the primary membrane unit is connected to the secondary loop non-radioactive wastewater treatment system for monitoring and discharge.

[0027] The positive and progressive effects of this invention are as follows:

[0028] This invention employs a process combination that integrates ion exchange, regeneration, and radionuclide concentration, combining a resin bed, membrane retention and concentration, and selective cesium removal from the concentrate. It provides a method and apparatus for treating radioactive contaminated wastewater in the secondary loop of nuclear power plants with integrated regeneration. This method achieves single-stage treatment that meets the liquid effluent discharge standards, while also requiring less space, generating less solid waste, and being simple to operate and maintain. It provides an excellent solution and engineering application guarantee for the safe and stable operation and environmental friendliness improvement of the nuclear power industry. Attached Figure Description

[0029] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features, wherein:

[0030] Figure 1This is a schematic diagram of an embodiment of the combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device of the present invention. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0032] Reference will now be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used in all the drawings to denote the same or similar parts. Furthermore, although the terminology used herein is selected from commonly known and used terms, some terms mentioned in this specification may have been chosen by the applicant at his or her discretion, and their detailed meanings are explained in the relevant sections of the description herein. Moreover, the invention should be understood not only by the actual terminology used, but also by the meaning implied by each term. Also, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale.

[0033] This invention provides a method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant using a combined internal regeneration system. The method includes the following steps:

[0034] Step S1: Transfer the wastewater from the secondary loop to the raw water tank 11.

[0035] Preferably, in step S1, the secondary loop contaminated wastewater is transported from the storage tank of the nuclear power plant's non-radiative wastewater treatment system to the raw water tank 11 of the present invention.

[0036] Step S2: The waste liquid in the raw water tank 11 is transported to the cation-anion mixed resin bed 13 to purify the radioactive nuclides in the waste liquid.

[0037] Preferably, in step S2, the cation-anion mixed resin bed 13 uses RH / RNa and ROH / RCl / RSO4 to purify divalent or higher valent cations and anions of radionuclides in the waste liquid.

[0038] It should be noted that the waste liquid in the raw water tank 11 is pumped to the cation-anion mixed resin bed 13. The cation-anion mixed resin bed 13 is a double-layer resin bed containing cation resin and anion resin respectively. Taking advantage of the good decontamination ability of RH / RNa and ROH / RCl / RSO4 for divalent or higher valent cations and anions of radionuclides even in the background of salt concentration of 10 g / L, the radionuclides in the waste liquid are purified for the first time. The test verified that its decontamination factor can be greater than 10 (the test measured value is 80~1800, see Table 1 below for details).

[0039] Step S3: The permeate produced after treatment by the cation-anion mixed resin bed 13 is transported to the primary membrane unit 14 for purification of radionuclides.

[0040] It should be noted that the permeate after the exchange of the cation and anion mixed resin bed 13 directly enters the primary membrane unit 14, which has a high rejection rate for radionuclides and various impurities. The primary membrane unit 14 performs a second purification of radionuclides (the decontamination factor for radionuclides can be greater than 10 (the test value is greater than 100 (see Table 2 below for details), and the industry standard value is 10)). The permeate can meet the discharge standards, and the radionuclide concentration can be less than 100 Bq / L (except for tritium and carbon-14). At the same time, it meets the single radionuclide concentration limit requirements in Appendix D 17 of GB6249. The device can continuously produce water.

[0041] Preferably, the primary membrane unit 14 can remove radionuclides and non-radioactive impurities (such as Na) from the permeate after the anolyte-coated resin bed 13 exchange. + Cl - SO4 2- (etc.) Concentrate about 10 times and discharge it from the concentrated water side.

[0042] Preferably, an ion exchange device can be added to the product water side of the primary membrane unit 14 to improve the decontamination factor without significantly increasing the amount of solid waste, thus meeting high standard discharge requirements.

[0043] Preferably, a continuous electro-deionization (EDI) device can be added to the product water side of the primary membrane unit 14 to improve the decontamination factor without significantly increasing the amount of solid waste, thus meeting high standard discharge requirements.

[0044] Step S4: The concentrate produced after treatment by the primary membrane unit 14 is transported to the cesium removal medium bed 15 for impurity removal, and then transported to the concentrate tank 16.

[0045] Preferably, in step S4, the cesium removal medium bed removes the radionuclide cesium. The concentrated water produced by the primary membrane unit is passed into the cesium removal medium bed, and the cesium removal efficiency of the cesium removal medium bed is improved by utilizing the increased concentration of the radionuclide in the concentrated water.

[0046] It should be noted that after passing through the high-rejection primary membrane unit 14, nuclides including Cs and non-radiative impurities (such as Na) are removed. + Cl - SO4 2- The radioactive nuclide Cs is concentrated by about 10 times by the primary membrane unit 14 (volume decreases, concentration increases). The concentrated water produced by the primary membrane unit 14 is then passed through the cesium removal medium bed 15 to remove the radioactive nuclide Cs before entering the concentrated water tank 16.

[0047] Step S5: The concentrate in the concentrate tank 16 is transported to the secondary membrane unit 18 for circulation concentration until the concentration of non-radioactive impurities in the concentrate reaches the target value. The permeate produced after treatment by the secondary membrane unit 18 is then transported back to the raw water tank 11.

[0048] Preferably, in step S5, the target value of the concentration of non-radioactive impurities in the concentrate is set to 80 g / L.

[0049] It should be noted that the concentrate in the concentrate tank 16 is pumped into the secondary membrane unit 18 with a high rejection rate for further circulation and concentration until the concentration of non-removable impurities in the concentrate reaches ~80g / L. The permeate from the secondary membrane unit 18 is then sent back to the raw water tank 11.

[0050] As a preferred embodiment of the combined internal regeneration method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant according to the present invention, the method further includes the following steps:

[0051] Step S6: After the cation-anion mixed resin bed 13 is shut down, the high-salt concentrate (salt content of about 80g / L) in the concentrate tank 16 is transported to the cation-anion mixed resin bed 13 for regeneration. The high concentration of salt ions in the concentrate is used as the regeneration driving force to desorb the radionuclides exchanged on the resin. The nuclides on the cation-anion mixed resin bed 13 are eluted and regenerated to restore the performance of the cation-anion mixed resin bed 13. The eluent containing the concentrated nuclides is then sent back to the concentrate tank 16.

[0052] It should be noted that the high concentration of salt ions in the concentrate is used as the regeneration driving force to desorb the radionuclides exchanged on the resin, thereby eluting and regenerating the radionuclides on the anion-cation mixed resin bed 13 and restoring its performance. It should also be noted that the concentrate can be used to regenerate the anion-cation mixed resin bed 13 after it has been shut down, allowing for efficient elution of the radionuclides exchanged on the resin bed to restore resin performance. The concentrated eluent is returned to the concentrate tank 16. The experimental results are shown in Table 3 below.

[0053] As a preferred embodiment of the combined internal regeneration method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant according to the present invention, the concentrated liquid in the concentrated water tank 16 is transported to the site waste treatment center by a nuclear power plant shielded transfer device for subsequent evaporation, drying and crystallization treatment.

[0054] It should be noted that the concentrate in concentrate tank 16 (with a nuclide concentration of approximately 10) 5 ~10 6 The concentration of concentrated water (Bq / L) and salt concentration (approximately 80 g / L) is approximately 80 g / L. The concentrated water is transported to the site waste treatment center using a shielded transfer device at the nuclear power plant for subsequent evaporation, drying, and crystallization treatment.

[0055] See Figure 1The present invention also provides a combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device, which adopts the combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment method as described above. The radioactive contaminated wastewater treatment device includes a raw water tank 11, an anion-cation mixed resin bed 13, a primary membrane unit 14, a cesium removal medium bed 15, a concentrate tank 16, and a secondary membrane unit 18.

[0056] The outlet of the raw water tank 11 is connected to the inlet of the anion-cation mixed resin bed 13; the outlet of the anion-cation mixed resin bed 13 is connected to the inlet of the primary membrane unit 14; the concentrate outlet of the primary membrane unit 14 is connected to the inlet of the cesium removal media bed 15; the outlet of the cesium removal media bed 15 is connected to the inlet of the concentrate tank 16; the outlet of the concentrate tank 16 is connected to the inlet of the secondary membrane unit 18; the concentrate outlet of the secondary membrane unit 18 is connected to the inlet of the concentrate tank 16; and the permeate outlet of the secondary membrane unit 18 is connected to the inlet of the raw water tank 11.

[0057] Preferably, an ion exchange device can be added to the product water side of the primary membrane unit 14 to increase the decontamination factor without significantly increasing the amount of solid waste, thus meeting high-standard discharge requirements. Adding an ion exchange device requires further addition of a water tank and pump.

[0058] Preferably, a continuous electro-deionization (EDI) device can be added to the product water side of the primary membrane unit 14 to improve the decontamination factor without significantly increasing the amount of solid waste, thus meeting high-standard discharge requirements. Adding an EDI device requires further addition of a water tank and pump.

[0059] See Figure 1 In a preferred embodiment of the nuclear power plant secondary loop radioactive contaminated wastewater treatment device with combined internal regeneration according to the present invention, the outlet of the anion-cation mixed resin bed 13 is connected to the inlet of the concentrate tank 16, and the outlet of the concentrate tank 16 is connected to the inlet of the anion-cation mixed resin bed 13.

[0060] It should be noted that the reason for leading the concentrate tank 16 to the anion-cation mixing resin bed 13 is to guide the concentrate to the resin bed for use as a regenerant. See also Figure 1 As a preferred embodiment of the nuclear power plant secondary loop radioactive contaminated wastewater treatment device with combined internal regeneration according to the present invention, the nuclear power plant secondary loop radioactive contaminated wastewater treatment device further includes a raw water pump 12 and a secondary membrane inlet pump 17. The raw water pump 12 is connected to the outlet of the raw water tank 11, and the secondary membrane inlet pump 17 is connected to the inlet of the secondary membrane unit 18.

[0061] See Figure 1 In a preferred embodiment of the nuclear power plant secondary loop radioactive contaminated wastewater treatment device with combined internal regeneration according to the present invention, the inlet of the raw water tank 11 is connected to the secondary loop non-radioactive wastewater treatment system, and the product water outlet of the primary membrane unit 14 is connected to the secondary loop non-radioactive wastewater treatment system for monitoring and discharge.

[0062] This invention addresses the water quality characteristics and volume of secondary loop contaminated wastewater by employing a combined process of ion exchange, regeneration, and radionuclide concentration using a resin bed, membrane retention and concentration, and selective cesium removal from the concentrate. This results in a combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device suitable for nuclear power plant secondary loop contaminated wastewater treatment. The entire device can be integrated and arranged within a 20-foot container, forming a mobile treatment equipment that can be flexibly moved.

[0063] The present invention provides a combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device, which can be equipped with main equipment such as water tank, filter, pump, resin bed, membrane unit, and cesium removal bed, and can also be further equipped with conductivity meter, thermometer, flow meter, differential pressure gauge, supporting pipelines, valves and shielding layer.

[0064] The following are the performance data of an embodiment of the combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device of the present invention after conducting contaminated wastewater treatment tests:

[0065] 1. Adsorption effect test data of cation-anion mixed resin bed 13

[0066] The NaCl content of the mixed cation-anion resin bed 13 is 10 g / L. Under simulated solution conditions where the concentrations of nuclides Co, Cr, Fe, Mn, and Sr are all 1 mg / L, the decontamination factors for each nuclide are shown in Table 1 below.

[0067] Table 1. Decontamination factors of mixed anodic and anionic resins for various nuclides

[0068]

[0069] 2. Test data on membrane process treatment effect

[0070] The membrane process involves a primary membrane unit 14 and a secondary membrane unit 18. The membrane unit is used to process a simulated solution with an initial concentration of 1 mg / L for nuclides and an initial concentration of 1 mg / L for NaCl. Typical decontamination factors for the treatment are shown in Table 2 below.

[0071] Table 2. Radionuclide decontamination factors of membrane units

[0072]

[0073] 3. Elution test data of the mixed cation and anion resin bed 13

[0074] The elution data of the cation resin in the mixed cation and anion resin after partial saturation with nuclides using 80 g / L NaCl solution are shown in Table 3 below.

[0075] Table 3. Elution data of cation and anion exchange resins with 80 g / L NaCl solution.

[0076]

[0077] Existing secondary loop contaminated wastewater treatment processes mainly include evaporation, selective adsorption + ion exchange processes. The proposed method and apparatus for treating radioactive contaminated wastewater from the secondary loop of nuclear power plants, which combines internal regeneration, are compared in terms of treatment effect, land area, solid waste generation, and investment cost. See Table 4 below for details.

[0078] Table 4 Comparison data between the present invention and the prior art

[0079]

[0080] Note: The above data is based on a device processing flow rate of 5m³ / h. 3 / h, total water treatment capacity is 3000m³ 3 Compare them.

[0081] This invention addresses the characteristics of contaminated wastewater from the secondary loop of nuclear power plants, namely low radioactivity, high salt content, large waste volume, and very low probability of occurrence. It designs a combined internal regeneration method and apparatus for treating radioactive contaminated wastewater from the secondary loop of nuclear power plants, incorporating ion exchange, regeneration, and radionuclide concentration using a resin bed, membrane retention and concentration, and selective cesium removal from the concentrate. This invention can reduce the radionuclide concentration in the secondary loop contaminated wastewater from 10... 4 ~10 5 After a single pass, the concentration of Bq / L (excluding tritium and carbon-14) is reduced to below 100 Bq / L (excluding tritium and carbon-14), while meeting the activity concentration limits for 17 single nuclides in Appendix D of GB6249-2025.

[0082] Evaporation processes offer high single-pass decontamination factors, meeting emission requirements in a single treatment. However, this process requires significant land area and investment, and is complex to maintain. This invention utilizes a resin and membrane combination in series to achieve high decontamination factors, and significantly reduces land area and investment compared to evaporation processes. The device can be centrally located within a 20-foot shipping container. The media bed and membrane units used in this invention are low-cost, reducing total costs by approximately 90%. Maintenance is also simple; highly radioactive media can be replaced via hydraulic conveying, and membranes can be directly replaced after rinsing. There are no high-radiation operations such as scaling, chemical cleaning, or equipment maintenance, making it more environmentally friendly in reducing personnel radiation exposure.

[0083] The selective adsorption combined resin bed process, already in engineering application, is used to treat radioactive contaminated wastewater from the secondary loop. This process is designed for coastal nuclear power projects prior to the upgrade of GB6249-2025. Based on the upgraded GB6249 and the increased environmental friendliness requirements for nuclear power plants in China, the treated contaminated wastewater from the secondary loop must also have a permeate concentration of less than 100 Bq / L and meet the activity concentration limits for 17 single nuclides in Appendix D. Due to the high background salt content of the influent, the selective adsorption combined resin bed process cannot achieve a decontamination factor greater than 10 in a single pass. 3 The lifespan of resin beds is relatively short, therefore the effluent can only meet the target of less than 1000 Bq / L. This invention utilizes a combination of ion exchange resin, selective media, and membrane technology. Relying on the primary decontamination of the media bed, and combined with the excellent decontamination capability of the membrane technology for radionuclides, the combined process can achieve a single-pass decontamination factor greater than 10. 3 This achieves the goal of effluent concentration of less than 100 Bq / L after treatment. Simultaneously, utilizing the membrane's concentration effect on non-radioactive substances, the design employs a secondary membrane to further concentrate the primary membrane's concentrate, ultimately obtaining a concentrated solution with a salt content of ~80 g / L. This concentrated brine is used to rinse and regenerate the mixed resin, transferring the radionuclides adsorbed on the resin into the concentrate. This allows the resin to continue operating without replacement, while minimizing the volume of the concentrate. The concentrate can be transferred via an interface to an existing waste treatment center at the nuclear power plant site for further processing. The increased concentrate volume does not affect the original process design, achieving a low-cost closed-loop process. The solid waste generation is almost identical to that of an evaporation process that meets emission requirements, but the land area and investment are reduced by over 90%, representing an innovative breakthrough in this operating condition.

[0084] This invention adds a cesium removal process to the concentrate stage of the primary membrane treatment process. It cleverly utilizes the excellent tolerance of the cesium removal media bed 15 to high salt background. After increasing the cesium concentration in the feed water, the total adsorption capacity of the cesium removal media per unit volume of the feed water can be significantly increased. Moreover, the volume of the concentrate in the membrane is only ~10% of that of the raw water. Therefore, the amount of cesium removal media that needs to be packed can be significantly reduced. Ultimately, it achieves excellent removal effect in a limited space while generating as little solid waste as possible.

[0085] This invention relates to a combined internal regeneration system for treating radioactive contaminated wastewater in the secondary loop of nuclear power plants. The system can be integrated into a 20-foot container and, in the event of secondary loop contamination, can be transported by vehicle to the vicinity of the secondary loop contaminated wastewater collection tank for treatment. Because the probability of secondary loop contamination is very low, the mobile equipment design simplifies the design of the conventional island building and the extensive laying of radioactive trenches between the primary and secondary loops compared to a system that directly pipes radioactive waste into the nuclear island. This reduces the amount of secondary waste generated and also addresses the lack of storage capacity for radioactive treatment equipment and the ability to replace and treat radioactive solid waste in the conventional island of a nuclear power plant.

[0086] As described above, the combined internal regeneration method and apparatus for treating radioactive contaminated wastewater in the secondary loop of nuclear power plants of the present invention has high removal efficiency, low cost, good safety and economy, and can cope with low probability radioactive contamination of secondary loop water.

[0087] In summary, the present invention provides a combined internal regeneration method and apparatus for treating radioactive contaminated wastewater from the secondary loop of a nuclear power plant, which has the following advantages:

[0088] I. To reduce the concentration of radionuclides in high-salinity (0.5~10 g / L) loop contaminated wastewater from 10 4 ~10 5 The entire process route involves processing nuclei (excluding tritium and carbon-14) to below 100 Bq / L (excluding tritium and carbon-14) in a single pass, while simultaneously meeting the single nuclide activity concentration limits in Appendix D of GB6249-2025.

[0089] Second, the selected process route allows the equipment to be integrated and assembled in a container within 20 feet, making it mobile.

[0090] Third, taking advantage of the resin's ability to efficiently exchange radionuclides at a salt concentration of 10 g / L and to elute almost 100% of radionuclides at a salt concentration of ~80 g / L, this process is designed for raw water with an influent salt content of less than 10 g / L. It utilizes a highly concentrated solution (~80 g / L salt concentration) from the membrane treatment process as the regenerator for the ion exchange bed, enabling repeated in-process regeneration of the ion exchange bed. This enhances the decontamination capacity of a single treatment cycle without requiring frequent resin replacement, ensuring treatment effectiveness while significantly reducing the amount of secondary waste generated.

[0091] IV. Utilizing the excellent tolerance of cesium removal media beds to high salinity backgrounds, a cesium removal process is added to the concentrate stage of the primary membrane treatment process. The cesium concentration in the concentrate produced by the primary membrane treatment process is higher than that in the raw water, which can significantly increase the total adsorption capacity of the cesium removal media per unit volume for cesium. In addition, the volume of the concentrate produced by the primary membrane treatment process is only ~10% of the volume of the raw water. Therefore, compared with directly treating the source water using cesium removal media, the amount of cesium removal media can be reduced by 90%, thus significantly reducing the amount of solid waste generated during operation.

[0092] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant using a combined internal regeneration system, characterized in that, The method for treating radioactive contaminated wastewater from the secondary loop of a nuclear power plant includes the following steps: S1. Transfer the wastewater from the secondary circuit to the raw water tank; S2. The waste liquid in the raw water tank is transported to the cation-anion mixed resin bed to purify the radioactive nuclides in the waste liquid; S3. The permeate produced after treatment by the cation-anion mixed resin bed is transported to the primary membrane unit for purification of radionuclides; S4. The concentrate produced after treatment by the primary membrane unit is transported to the cesium removal medium bed for impurity removal, and then transported to the concentrate tank. S5. The concentrate in the concentrate tank is transported to the secondary membrane unit for circulation and concentration until the concentration of non-radioactive impurities in the concentrate reaches the target value. The permeate produced by the secondary membrane unit is then transported back to the raw water tank.

2. The method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant using combined internal regeneration as described in claim 1, characterized in that, The method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant also includes the following steps: S6. After the cation-anion mixed resin bed is shut down, the high-salt concentrate in the concentrate tank is transported to the cation-anion mixed resin bed for regeneration. The high concentration of salt ions in the concentrate is used as the regeneration driving force to desorb the radionuclides exchanged on the resin. The radionuclides on the cation-anion mixed resin bed are eluted and regenerated to restore the performance of the cation-anion mixed resin bed. The eluent containing the radionuclides is then sent back to the concentrate tank.

3. The method for treating radioactive contaminated wastewater from the secondary loop of a nuclear power plant using combined internal regeneration as described in claim 1 or 2, characterized in that, The concentrated liquid in the concentrate tank is transported to the on-site waste treatment center by a nuclear power plant shielded transfer device for subsequent evaporation, drying, and crystallization.

4. The method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant using combined internal regeneration as described in claim 1, characterized in that, In step S2, the cation-anion mixed resin bed uses RH / RNa and ROH / RCl / RSO4 to purify divalent or higher valence cations and anions of radionuclides in the waste liquid.

5. The method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant using combined internal regeneration as described in claim 1, characterized in that, In step S4, the cesium removal medium bed removes the radioactive nuclide cesium. The concentrated water produced by the primary membrane unit is passed into the cesium removal medium bed. The increased concentration of the nuclide in the concentrated water improves the cesium removal efficiency of the cesium removal medium bed.

6. The method for treating radioactive contaminated wastewater in the secondary loop of a nuclear power plant using combined internal regeneration as described in claim 1, characterized in that, In step S5, the target value for the concentration of non-radioactive impurities in the concentrate is set to 80 g / L.

7. A combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device, characterized in that, The combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device adopts the combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment method as described in any one of claims 1-6. The radioactive contaminated wastewater treatment device includes a raw water tank, an anion-cation mixed resin bed, a primary membrane unit, a cesium removal media bed, a concentrate tank, and a secondary membrane unit. The outlet of the raw water tank is connected to the inlet of the anion-cation mixed resin bed; the outlet of the anion-cation mixed resin bed is connected to the inlet of the primary membrane unit; the concentrate outlet of the primary membrane unit is connected to the inlet of the cesium removal medium bed; the outlet of the cesium removal medium bed is connected to the inlet of the concentrate tank; the outlet of the concentrate tank is connected to the inlet of the secondary membrane unit; the concentrate outlet of the secondary membrane unit is connected to the inlet of the concentrate tank; and the permeate outlet of the secondary membrane unit is connected to the inlet of the raw water tank.

8. The combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device as described in claim 7, characterized in that, The outlet of the anion-cation mixing resin bed is connected to the inlet of the concentrate tank, and the outlet of the concentrate tank is connected to the inlet of the anion-cation mixing resin bed.

9. The combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device as described in claim 7, characterized in that, The radioactive contaminated wastewater treatment device for the secondary loop of the nuclear power plant also includes a raw water pump and a secondary membrane inlet pump. The raw water pump is connected to the outlet of the raw water tank, and the secondary membrane inlet pump is connected to the inlet of the secondary membrane unit.

10. The combined internal regeneration nuclear power plant secondary loop radioactive contaminated wastewater treatment device as described in claim 7, characterized in that, The inlet of the raw water tank is connected to the secondary loop non-radioactive wastewater treatment system, and the product water outlet of the primary membrane unit is connected to the secondary loop non-radioactive wastewater treatment system for monitoring and discharge.

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