CN109994238B

CN109994238B - Method and system for concentrating and solidifying nuclides in radioactive waste liquid

Info

Publication number: CN109994238B
Application number: CN201810006458.6A
Authority: CN
Inventors: 赵璇; 李福志; 尉继英; 张猛
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2018-01-03
Filing date: 2018-01-03
Publication date: 2023-05-26
Anticipated expiration: 2038-01-03
Also published as: GB2583276A; GB202009626D0; WO2019134436A1; GB2583276B; CN109994238A

Abstract

The invention relates to a method and a system for concentrating and solidifying nuclides in radioactive waste liquid. The method for concentrating and solidifying nuclides in radioactive waste liquid comprises the following steps: step 1) pretreatment: extracting the radioactive waste liquid by using a first selective extractant; step 2) concentration: reverse osmosis concentrating the extracted radioactive waste liquid; step 3) extraction: extracting the radionuclide enriched in the concentrate to a solid phase by using an organic ion exchange resin and/or a second selective extractant; step 4) nuclide curing: and then forming a solidified body by the nuclide-rich organic ion exchange resin and/or the second selective extractant obtained in the step 3) and the first selective extractant obtained in the step 1). By the method and the system, the radionuclide in the concentrated radioactive waste liquid can be effectively extracted and safely stored, and meanwhile, the storage volume of the radioactive waste is minimized.

Description

Method and system for concentrating and solidifying nuclides in radioactive waste liquid

Technical Field

The invention relates to a method and a system for concentrating and solidifying nuclides in radioactive waste liquid.

Background

Nuclear power is becoming an important clean energy source and is becoming an important component of world energy structures. After the japanese foolish nuclear accident, nuclear security has become a major concern in the development of nuclear energy. In the daily operation and accident conditions of a nuclear power plant, a large amount of radioactive waste liquid is generally generated.

The radionuclides contained in the radioactive waste liquid mainly have two sources, one source is a fission product and the other source is an activation product and a corrosion product. The second source is mainly related to the activation, corrosion, precipitation and release behavior of the metallic material, and the part of the radionuclides include Ag, co, cr, mn, fe and the like. Long-life fission products with beta radioactivity appear in radioactive waste liquid when fuel breakage occurs ¹³⁴ Cs/ ¹³⁷ Cs and ⁹⁰ sr, etc. For radionuclides with long half-lives, it is necessary to separate from the waste liquid and store them for a long period of time after isolation from the environment until they decay to harmless levels.

Due to the high cost of long-term geological storage and disposal of radionuclides, the capacity of temporary storage or disposal sites is limited, and radioactive waste liquid is generally subjected to concentration and volume reduction, so that the volume is minimized as much as possible, and long-term storage can be performed. At present, in a nuclear power plant, the method for concentrating nuclides in radioactive waste liquid mainly comprises evaporation concentration and ion exchange. Whichever treatment is used, the radionuclide is essentially concentrated and enriched in a liquid medium or a solid medium, which is ultimately solidified for long-term geological storage. The evaporation concentration is to redistribute the radionuclides in the raffinate and the condensate to obtain the raffinate containing most radionuclides and the condensate with low radionuclides content. Ion exchange is the containment of radionuclides in their own material.

The evaporation concentration and the ion exchange have wide application in the radioactive waste liquid treatment, and have respective advantages and disadvantages. The evaporation process has the advantages of mature technology, strong decontamination capability and minimum radioactive waste production; the defects are high energy consumption, huge equipment, high investment, poor operating conditions, serious corrosion and scaling and the like. The ion exchange process is just opposite, and has the advantages of low energy consumption, simple equipment and convenient operation; the disadvantage is that a large amount of radioactive waste ion exchange resin is produced and the subsequent treatment is difficult.

In the design of the third generation nuclear power, the evaporation process is gradually withdrawn, and the ion exchange process becomes the main process. However, the existing ion exchange technology of the nuclear power plant is required to ensure that the discharged liquid meets the environmental emission requirements while concentrating and containing the radionuclides. This places high demands on the decontamination factor of the resin and therefore makes it impossible to fully utilize the adsorption capacity of the resin, resulting in a large amount of radioactive waste resin and a large pressure on the long-term storage in the later stages.

The radioactive waste liquid has larger treatment difficulty, and is mainly characterized in the following aspects:

1) The radioactive waste liquid of the nuclear power plant contains hundreds of nuclides such as Na-24, cr-51, mn-54, fe-55, fe-59, co-58, co-60, zn-65, sr-89, sr-91, zr-95, nb-95, mo-99, tc-99m, ru-103, ru-106m, ag-110m, te-129, te-131m, te-131, te-132, cs-134, cs-137, ba-140, la-140, ce-141, ce-143, ce-144, W-187, np-239 and the like. The properties of each nuclide (such as concentration and enrichment properties, presence morphology, concentration, valence, corrosiveness, etc.) are complex and can change under different operating conditions (such as pH value, ionic strength, temperature, etc.), which causes certain difficulty to concentration and enrichment of nuclides.

2) The mass concentration of the radionuclide is extremely low, typically 10 ^-3 Micrograms/liter or less; whereas the concentration of coexisting non-radioactive ions, such as K, na, ca, mg, is relatively high, typically mg/LOn the order of, and even up to, the g/l level, the presence of these non-radioactive ions severely affects the concentration and solidification of the nuclides in the radioactive waste.

3) It is desirable to reduce the amount (especially the volume) of radioactive waste as much as possible and concentrate the nuclides in the radioactive waste at a higher recovery rate.

4) Avoiding the generation of radioactive secondary waste liquid.

5) It is necessary to consider factors such as equipment operability and maintainability under radioactive conditions, fuel power consumption, the existence of each nuclide, and differences in concentration properties.

6) Under the condition of simplifying the process as much as possible, the treatment modes are difficult to coordinate and match with each other, and the nuclides in the radioactive waste liquid are difficult to concentrate efficiently.

Currently, methods or systems for concentrating and solidifying nuclides in radioactive waste solutions in the art have a certain distance from comprehensively solving the above problems.

Disclosure of Invention

In one aspect, the invention provides a method for concentrating and solidifying nuclides in radioactive waste liquid, comprising the steps of:

Step 1) pretreatment: extracting the radioactive waste liquid by using a first selective extractant;

step 2) concentration: reverse osmosis concentrating the extracted radioactive waste liquid;

step 3) extraction: extracting the radionuclide enriched in the concentrate to a solid phase using a first ion exchange resin and/or a second selective extractant;

step 4) nuclide curing: and then forming a solidified body by the nuclide-rich organic ion exchange resin and/or the second selective extractant obtained in the step 3) and the first selective extractant obtained in the step 1).

In another aspect, the invention provides a system for concentrating and solidifying a radionuclide in a radioactive waste solution, comprising:

a) A pretreatment unit comprising a first selective extractant;

b) The concentration unit comprises a concentrate tank provided with a reverse osmosis device, so that trapped liquid of the reverse osmosis device returns to the concentrate tank, and a water outlet of the pretreatment unit is connected with an inlet of the reverse osmosis device;

c) The extraction unit comprises an organic ion exchange bed and/or a second selective extractant, a water inlet of the extraction unit is connected with the concentrated solution tank so that liquid in the concentrated solution tank enters the extraction unit, and a water outlet of the extraction unit is connected with the concentrated solution tank so that liquid passing through the extraction unit returns to the concentrated solution tank;

d) And a nuclide curing unit in which a nuclide-rich selective extractant and/or a nuclide-rich organic ion exchange resin form a cured body.

In the methods and systems of the present invention, the first selective extractant used for pretreatment and the second selective extractant used for extraction may be the same or may be different. The selective extractant each independently comprises an inorganic oxide support and a nuclide extracting active component, or each independently comprises a molecular sieve or zeolite.

The inventors have surprisingly found that by the method and system of the present invention, radionuclides in concentrated radioactive waste solutions can be efficiently extracted for safe storage while minimizing radioactive waste. The method and the system of the invention not only fully utilize the adsorption capacity of the resin to minimize the generation amount of the radioactive waste resin, but also can ensure that the discharged liquid meets the environmental emission requirement. The method and the system of the invention have the advantages of low energy consumption, simple equipment, convenient operation, small quantity of nuclides after concentration and solidification, and the like.

Compared with the existing concentration method and system, the innovation of the novel method and system for concentrating and storing nuclides in radioactive waste liquid is at least represented by the following aspects:

1) And a reasonable and optimized combination mode of the process. In the art, radioactive waste is extremely specific. Some technical routes show quite different behaviors under the condition of non-radioactive feed liquid and the condition of radioactive feed liquid, and the determined process combination often has larger difference from the actual situation without passing the actual operation and test of the radioactive experiment. And there is a large difference between laboratory and real industrial scale, with no comparability. In the method and system of the present invention, the steps or units can be organically coordinated to form an integrated method and system, the results of which are evaluated as exemplary projects. The demonstration project is the only demonstration project in the nuclear island factory building of the nuclear power plant in China at present, and the real radioactive feed liquid is utilized to finish the project scale. The inventor repeatedly combines, tests, adjusts and verifies each unit under the radioactive condition by using an exemplary engineering prototype, and finally obtains the most effective organic whole, so that the mutual coordination among the units is optimal, and the function which cannot be realized by simply combining the units is realized.

2) The radioactive waste liquid of the nuclear power plant contains hundreds of nuclides. Through developing research on concentration and enrichment rules of each unit on single-component nuclides and multi-component nuclides, including laboratory simulation of nuclide concentration and solidification experiments in radioactive waste liquid and verification of radioactive real feed liquid in demonstration engineering of nuclear power plants, the inventor discovers for the first time that a plurality of nuclides, especially Cs, cannot be effectively concentrated by reverse osmosis in hundreds of nuclides, but can realize enrichment targets after adding a selective extractant; it was also found that 2 species (Ag and Co) could not be efficiently concentrated by ion exchange resins, but the enrichment objective could be achieved by oxidation followed by treatment with a selective extractant and ion exchange resin. Some species, such as Sr, when concentrated by ion exchange resins, will face competition for divalent cations present in the solution, thereby shortening the useful life of the resin, but may promote a small amount of total radioactive waste after the addition of the selective extractant. Aiming at the concentration property of various nuclides, the inventor designs a concentration and solidification method and a system to skillfully realize the concentration and solidification of various nuclides.

3) Because the method of the invention does not require evaporation to achieve concentration of radioactive waste, the system is highly simplified and the equipment employed has significant advantages over other methods in terms of size, operability, maintainability, fuel power consumption, etc.

4) Through reasonable arrangement of the process, the ion exchange resin has the function of concentrating and containing radionuclides, so that the decontamination coefficient of the resin is not particularly high, the adsorption capacity of the resin can be fully utilized, and the production amount of the radioactive resin can be greatly reduced.

5) The method and the system realize the recovery rate of nuclides in the radioactive waste liquid of more than 95 percent, and simultaneously ensure that the discharged liquid meets the environmental emission requirement.

6) The method and the system of the invention have no report at home and abroad, and the adopted specific combination mode provides an original design concept for the nuclide recovery of radioactive liquid.

Detailed Description

The method and system for concentrating and solidifying nuclides in radioactive waste liquid according to the present invention will be further described.

In one aspect, the invention provides a method for concentrating and solidifying nuclides in radioactive waste liquid, comprising the steps of: step 1) pretreatment: extracting the radioactive waste liquid by using a first selective extractant; step 2) concentration: reverse osmosis concentrating the extracted radioactive waste liquid; step 3) extraction: extracting the radionuclide enriched in the concentrate to a solid phase by using an organic ion exchange resin and/or a second selective extractant; step 4) nuclide curing: and then forming a solidified body by the nuclide-rich organic ion exchange resin and/or the first selective extractant obtained in the step 3) and the first selective extractant obtained in the step 1).

In the method of the invention, the selective extractant in the step 1) is mainly used for extracting partial nuclides which are not easy to be trapped by the membrane in the radioactive waste liquid, and especially for extracting partial nuclides Cs which are not easy to be trapped by the membrane. The inventors have for the first time found that of the hundreds of species, there are several species that cannot be efficiently concentrated by reverse osmosis, also referred to herein as "species that are not readily trapped by the membrane". According to the invention, the enrichment of nuclides, such as Cs, and the like, which are not easy to be trapped by the membrane can be effectively realized by adopting the selective extractant for treatment before the reverse osmosis treatment. The selective extractant in step 3) can extract "species not easily trapped by the membrane" as well as species easily competing for divalent cations, thereby promoting a small amount of total radioactive waste.

In some preferred embodiments, in step 3), the concentrate is treated to remove organics from the liquid prior to nuclide extraction. Preferably, activated carbon is used. The inventors have surprisingly found that by removing organics from the concentrate, avoiding enrichment of organics in the concentrate, the stability of the system can be further improved.

In a preferred embodiment, the pretreatment further comprises: before the extraction in step 1), the nuclides in the radioactive waste are oxidized to be converted into an ionic state, preferably by ultraviolet light, ozone, hydrogen peroxide and/or sodium hypochlorite.

In various stages of the process of the invention (e.g., prior to extraction or oxidation in step 1), the liquid may be filtered. Preferably, filtration is performed using flocculation, activated carbon, cartridge filters, paper core filters, self-cleaning filters, ultrafiltration devices, or any combination thereof, to remove fine suspended and colloidal materials.

In the oxidation, ultraviolet light is preferably used for catalytic oxidation. Can adopt H ₂ O ₂ Ozone and/or sodium hypochlorite are used as oxidizing agents, preferably H ₂ O ₂ . In some embodiments, the amount of oxidant added is controlled to be 2-30mg/L, preferably 3-25mg/L, more preferably 5-20mg/L, for example 10mg/L or 15mg/L.

As used herein, a "selective extractant" is a class of substances that are capable of selectively extracting, enriching, a nuclide.

In some embodiments of the invention, the selective extractant comprises an inorganic oxide support and a nuclide extraction active component. Preferably, the inorganic oxide support comprises silica, manganese dioxide, alumina, titania, zirconia, or any combination thereof. Preferably, the nuclide extraction active comprises ferrocyanide, antimonate, titanate, tin oxide, tungstate, or any combination thereof. Most preferably, the selective extractant comprises silica, alumina, ferrocyanide and antimonates.

In other embodiments, the selective extractant comprises a molecular sieve. Cerium zirconium eutectic, natural or synthetic clinoptilolite, molecular sieve NaY, molecular sieve 13X, molecular sieve ZSM-5, molecular sieve SAPO-34, beta molecular sieve, chitosan adsorbent, montmorillonite, hydrous manganese oxide, titanium silicalite, metal antimonate, hydrous tin oxide or sodium titanate or any combination thereof may also be used as the selective extractant.

The inventors have also found that when the composition of the selective extractant comprises: the recovery rate of nuclides in radioactive waste liquid can be further improved when silicon dioxide, aluminum oxide, titanium oxide, ferrocyanide and antimonate are used.

In this context, reverse osmosis concentration is carried out in a concentrate tank. In a preferred embodiment, reverse osmosis concentration may also employ multiple stages of tanks such as concentrate and medium concentrate. In the concentrate tank, the liquid may be subjected to one or more stages of reverse osmosis concentration, for example, two or more stages of reverse osmosis concentration. When multi-stage reverse osmosis concentration is adopted, the permeate liquid of each stage of reverse osmosis sequentially enters the next stage of reverse osmosis, the trapped liquid of each stage of reverse osmosis returns to the concentrate tank, and the final permeate liquid leaves the concentrate tank. In some embodiments, the ratio of fresh water to concentrate produced by each stage of reverse osmosis is independently controlled, preferably from 1:1 to 8:1, such as 3:1 or 5:1. The electrical conductivity of the fresh water produced by the first stage reverse osmosis is less than or equal to 50. Mu.S/cm, for example 40. Mu.S/cm, 35. Mu.S/cm, 30. Mu.S/cm, 25. Mu.S/cm. The conductivity of the fresh water produced by the two or more stages of reverse osmosis is less than or equal to 25. Mu.S/cm, for example 20. Mu.S/cm, 15. Mu.S/cm, 11. Mu.S/cm, 10. Mu.S/cm. In the reverse osmosis concentration process, the total microbial index colony count of the final permeate is < 200CFU/mL, preferably < 100CFU/mL.

In some embodiments, the liquid produced during reverse osmosis concentration (i.e., the final permeate) is purified by desalination. The liquid purified concentrate may be returned to the concentration step. In some preferred embodiments, the method of the present invention further comprises step 5) liquid purification: desalting and purifying the reverse osmosis permeate produced in the step 2), and returning the concentrated liquid purified water rich in radionuclides to the step 2). Preferably, continuous electrodeionization purification is employed. In a preferred embodiment, in continuous electrodeionization, the anode is a pure titanium plate electrode and the cathode is a stainless steel plate. The ratio of fresh water to concentrate of the continuous electrodeionization unit is from 0.5:1 to 10:1, preferably from 1:1 to 5:1, for example 3:1. The purified fresh water after desalination meets the environmental emission.

In this context, the concentrated reverse osmosis liquid concentrate is extracted with an organic ion exchange resin and/or a selective extractant. Preferably, before extraction, the organic matters in the concentrated solution are removed by using activated carbon so as to avoid enrichment of the organic matters in the concentrated solution and further improve the stability of the system. The ion exchange resin bed and optional selective extractant are separated into one, two or more stages. When two or more stages of ion exchange resin beds and optionally a selective extractant are used, the liquid passes through each stage of ion exchange resin bed and each stage of selective extractant in sequence, and the ion exchange beds are filled with a cation-anion mixed ion exchange resin. Preferably, the cation exchange resin is in the hydrogen form and the anion exchange resin is in the hydroxide form. Based on the present description, a person skilled in the art is able to reasonably determine the particular ion exchange resin employed.

In some embodiments, the reverse osmosis concentrated concentrate is pumped into an organic ion exchange bed and a selective extractant bed. When the extraction step is performed using a selective extractant, the selective extractant described above may be used. The first selective extractant used for pretreatment and the second selective extractant used for extraction may be the same or may be different. The selective extractant at each stage used for extraction may be the same or may be different. After the extraction step, the pH value of the final effluent is controlled to be 6-8, and the final effluent returns to the concentrate tank.

The flow of liquid into the pretreatment is not critical, can be determined according to actual needs, and can be any value. In some exemplary embodiments of the invention, the liquid flow rate into the pretreatment is in the range of 0.05m3/h to 10m3/h, such as 0.1m3/h to 5m3/h, for example, 0.2m3/h and 1m3/h.

In some preferred embodiments, the nuclide-rich selective extractant and/or nuclide-rich ion exchange resin is stirred with cement, or dehydrated, dried to form a cured body.

In a particularly preferred embodiment, the present invention provides a method for concentrating nuclides in a solidified radioactive waste solution comprising the steps of:

Step 1) pretreatment: by H under ultraviolet light ₂ O ₂ Carrying out catalytic oxidation on the radioactive waste liquid, and then extracting by using a first selective extractant;

step 2) concentration: at least two-stage reverse osmosis concentration is carried out in the concentrate tank, the permeate liquid of each stage of reverse osmosis sequentially enters the next stage, and the trapped liquid of each stage of reverse osmosis returns to the concentrate tank;

step 3) extraction: extracting the liquid in the concentrate tank in the step 2) by using two or more stages of organic ion exchange resins and/or second selective extractants, sequentially passing the liquid through each stage of ion exchange resins and/or second selective extractants, and finally returning the effluent to the concentrate tank;

step 4) nuclide curing: curing the first selective extractant obtained in step 1) and/or the organic ion exchange resin obtained in step 3) and/or the second selective extractant to form a cured body;

the selective extractant comprises an inorganic oxide support comprising silica, alumina, titania, or any combination thereof, and a species extraction active component comprising ferrocyanide and/or antimonate.

In an even more preferred embodiment, the present invention provides a method for concentrating nuclides in a solidified radioactive waste comprising the steps of 3) extracting: firstly, extracting organic matters in the concentrated solution by using active carbon, then extracting the liquid in the concentrated solution tank in the step 2) by using two or more stages of organic ion exchange resins and/or second selective extractants, sequentially passing the liquid through each stage of ion exchange resins and/or second selective extractants, and finally returning the effluent to the concentrated solution tank.

In another aspect of the invention there is provided a method of concentrating and solidifying a radionuclide in a radioactive waste solution comprising the steps of:

step 1) pretreatment: enabling the waste liquid to enter an oxidation device, wherein the device is provided with a dosing device and an online pH control measurement and control device, and adding H ₂ O ₂ The effluent from the device is subjected to a selective extractant comprising the following components: i) Any combination of silica, alumina, titania, zirconia; and ii) any combination of ferrocyanide, antimonate, titanate, tin oxide, tungstate, and the effluent from the selective extractant enters the concentrate tank of step 2);

step 2) concentration: carrying out multistage reverse osmosis concentration in a concentrate tank, wherein the permeate liquid of each stage of reverse osmosis sequentially enters the next stage, and the trapped liquid of each stage of reverse osmosis returns to the concentrate tank;

step 3) extraction: firstly, treating the liquid in the concentrate tank in the step 2) by using active carbon to remove organic matters in the liquid, then pumping the treated liquid into an organic ion exchange bed, enabling the ion exchange resin bed to be divided into two or more stages, enabling the liquid to sequentially pass through the ion exchange resin beds at each stage, and finally enabling effluent to return to the concentrate tank;

step 4) nuclide curing: curing the selective extractant produced in step 1) and/or the ion exchange resin produced in step 3) to form a cured body.

In some preferred embodiments, the ion exchange resin (ion exchange resin enriched in nuclides) and/or the selective extractant in the first stage bed in the extraction step is subjected to step 4) nuclide solidification when the conductivity of the effluent from the extraction step is greater than or equal to the conductivity of the concentrate in the concentration step, or the conductivity of the final permeate from step 2) is greater than 50 μs/cm. Optionally, fresh ion exchange resin and/or fresh selective extractant is charged as the last stage ion exchange resin and/or selective extractant, with the other stages of ion exchange resins and/or selective extractants being advanced in sequence.

In some preferred embodiments, the ratio of the liquid exiting step 5) to the liquid entering step 3) is controlled, preferably 1-10:1, more preferably in the range of 3-10:1, such as 3:1, 5:1 or 8:1. By controlling the liquid ratio, higher nuclide recovery rate can be further realized, smaller volume of concentrated solidified nuclides can be obtained, concentration efficiency of the method and the system is further improved, and purified effluent can meet environmental emission requirements.

In a particularly preferred embodiment, the present invention provides a novel method for concentrating and solidifying nuclides in radioactive waste liquid, which comprises the following specific process steps:

Step 1) pretreatment: the radioactive waste liquid is first stored in a raw liquid tank, and after fine suspended matters in the liquid are removed by flocculation, active carbon, cartridge filter, paper core filter, self-cleaning filter, ultrafiltration and other methods, the liquid enters an oxidation device which is provided with a dosing device and an on-line pH control and measurement and control device for controlling the addition of a certain amount of H ₂ O ₂ . The effluent passes through the selective extractant at a certain flow rate and then enters the concentrate tank of step 2). The selective extractant comprises the following components: i) Any combination of silica, alumina, titania, zirconia; and ii) any combination of ferrocyanide, antimonate, titanate, tin oxide, tungstate.

Step 2) concentration: a high and a low working liquid level switch are arranged in the concentrated liquid tank. The concentrate tank is provided with a plurality of stages of reverse osmosis concentration, the permeate liquid of each stage of reverse osmosis sequentially enters the next stage and finally enters the step 5), and the trapped liquid of each stage of reverse osmosis returns to the concentrate tank.

Step 3) extraction: pumping the liquid in the concentrate tank in the step 2) into an organic ion exchange bed. The bed is filled with anion-cation mixed ion exchange resin. The cation exchange resin is in the hydrogen form, and the anion exchange resin is in the hydrogen-oxygen form. The ion exchange resin beds are divided into two or more stages, the liquid sequentially passes through the ion exchange resin beds at each stage, the pH value of the final effluent is controlled to be 6-8, and the final effluent returns to the concentrate tank. When the conductivity of the effluent of the ion exchange bed is not lower than that of the concentration tank, or the conductivity of the final permeate in the step 2) is higher than 50 mu S/cm, the ion exchange resin in the first-stage bed is conveyed into the step 4) through a feed pump, the ion exchange resin is filled with new resin and then is placed into the last stage, and other stages are sequentially moved forward.

Step 4) nuclide curing: the selective extractant produced in the step 1) and the ion exchange resin produced in the step 3) are conveyed into a standard barrel which is pre-provided with a certain amount of cement through a feed pump, and are stirred with the cement to form a solidified body, or are dehydrated and dried and then are conveyed into the standard barrel for storage.

Step 5) liquid purification: the reverse osmosis permeate liquid generated in the step 2) enters continuous electric desalting, residual radionuclides are enriched in the continuous electric desalting concentrated water, the reverse osmosis permeate liquid returns to the concentrated liquid tank in the step 2), and the residual liquid meets the environmental emission requirement. The ratio of the discharged liquid in the step 5) to the liquid in the concentrated liquid tank entering the step 3) is controlled to be 1-10:1.

In an even more preferred example, the present invention provides a novel method for concentrating nuclides in a solidified radioactive waste, comprising the steps of 3) extracting: pumping the liquid in the concentrate tank in the step 2) into an active carbon bed and then into an organic ion exchange bed.

In another aspect, the invention provides a system for concentrating and solidifying nuclides in radioactive waste, comprising:

a) A pretreatment unit comprising a first selective extractant;

d) And a nuclide curing unit in which a nuclide-enriched selective extractant and/or a nuclide-enriched ion exchange resin form a cured body.

In some preferred embodiments, in the pretreatment unit, the system further comprises an oxidation device located upstream of the first selective extractant. The oxidation device is preferably equipped with an ultraviolet light source or an ozone oxidation device. Preferably, the oxidation device is provided with a dosing device and an online pH control measurement and control device.

In some preferred embodiments, the system for concentrating and solidifying nuclides in radioactive waste according to the present invention comprises:

a) The pretreatment unit comprises a raw liquid tank and an oxidation device, and the pretreatment unit further comprises a selective extractant at the water outlet;

b) The concentration unit comprises a concentrated solution tank provided with at least two stages of reverse osmosis devices, the water outlet of the pretreatment unit is connected with the concentrated solution tank, and each stage of reverse osmosis device is connected with the concentrated solution tank so that the trapped liquid of each stage of reverse osmosis device returns to the concentrated solution tank;

c) The extraction unit comprises an organic ion exchange bed, wherein the organic ion exchange bed is filled with anion-cation mixed ion exchange resin, a water inlet of the extraction unit is connected with the concentrated solution tank so that liquid in the concentration unit enters the extraction unit, and a water outlet of the extraction unit is connected with the concentrated solution tank so that the liquid passing through the extraction unit returns to the concentrated solution tank;

d) And a nuclide curing unit in which a nuclide-rich selective extractant and/or a nuclide-rich ion exchange resin form a cured body.

In some preferred embodiments, a filtration device may be included in each unit. Preferably, the pretreatment unit further comprises a filtration device. More preferably, the filtration device is located at a position upstream of the oxidation device or the selective extractant. In some embodiments, the filtration device has a flocculation device, activated carbon, a cartridge filter, a paper core filter, a self-cleaning filter, an ultrafiltration device, or any combination thereof. The filtration is performed using flocculation, activated carbon, cartridge filters, paper core filters, self-cleaning filters, ultrafiltration devices, or any combination thereof, to remove fine suspended and colloidal materials.

In the system of the present invention, a high operating level switch, a low operating level switch, or a combination of both is provided in the concentrate tank.

In some preferred embodiments, in the system of the invention for concentrating a nuclide in a solidified radioactive waste, the extraction unit comprises a bed of activated carbon prior to the organic ion exchange bed and/or the second selective extractant. As discussed above, by removing organics in the concentrate, preferably using activated carbon in the extraction unit, avoiding enrichment of organics in the concentrate, the stability of the system can be further improved.

In a preferred embodiment, the system of the present invention further comprises e) a liquid purification unit. The liquid purification unit may comprise or consist of a desalination unit. The water inlet of the liquid purification unit is connected with the concentration unit, so that the permeate passing through the reverse osmosis device enters the liquid purification unit, and the concentrated water outlet of the liquid purification unit is connected with the concentration unit, so that the concentrated water obtained from the desalting unit returns to the concentrated liquid tank.

In a preferred embodiment, the desalination unit is a continuous electrical desalination unit. Preferably, in the continuous electric desalting unit, the anode adopts a pure titanium plate electrode, and the cathode adopts a stainless steel plate.

The inventors of the present invention have surprisingly found that with the method and system of the present invention, an optimal concentration effect and a highly simplified process can be obtained, with recovery rates of nuclides in the radioactive waste of up to 95% or more, even up to 99.9%, and with each unit forming the most efficient organic whole. In the method and the system of the invention, the resin decontamination coefficient is not required, so that the adsorption capacity of the resin can be fully utilized, and the generation amount of the radioactive resin can be greatly reduced. The method and the system can recover nuclides in the radioactive waste liquid with very high recovery rate, and the discharged liquid meets the environmental emission requirement.

To further illustrate certain aspects of the invention, the invention also specifically provides some non-limiting embodiments as follows:

embodiment 1. A method for concentrating and solidifying nuclides in radioactive waste liquid, comprising the steps of:

step 3) extraction: extracting the radionuclide enriched in the concentrate to a solid phase by using an organic ion exchange resin and/or a second selective extractant;

Embodiment 2. The method for concentrating and solidifying nuclides in radioactive waste according to embodiment 1, wherein the pretreatment further comprises: prior to said extraction in step 1), the nuclides in the radioactive waste are oxidized to convert them to the ionic state, preferably with ultraviolet light, ozone, hydrogen peroxide and/or sodium hypochlorite.

Embodiment 3. The method for concentrating and solidifying nuclides in a radioactive waste according to embodiment 1, further comprising in step 3), removing organic matter from the liquid, preferably using activated carbon, before performing the nuclide extraction.

Embodiment 4. The method of concentrating and solidifying nuclides in a radioactive waste according to embodiment 1, further comprising step 5) liquid purification: the reverse osmosis permeate produced in step 2) is subjected to desalination purification, preferably continuous electrical desalination, and the liquid purified concentrate enriched in radionuclides is returned to step 2).

Embodiment 5. The method of concentrating and solidifying a nuclide in a radioactive waste according to any one of embodiments 1 to 4, wherein the selective extractant each independently comprises an inorganic oxide support and a nuclide extraction active component.

Embodiment 6. The method of concentrating and solidifying a radionuclide in a radioactive waste according to embodiment 5, wherein the inorganic oxide carrier comprises silica, manganese dioxide, alumina, titania, zirconia, or any combination thereof, and the nuclide extraction active component comprises ferrocyanide, antimonate, titanate, tin oxide, tungstate, or any combination thereof.

Embodiment 7. The method of concentrating and solidifying nuclides in a radioactive waste according to any one of the preceding embodiments, wherein the organic ion exchange resin comprises a hydrogen cation exchange resin and a hydroxide anion exchange resin.

Embodiment 8. The method of concentrating radionuclides in a solidified waste liquid according to any of embodiments 1-4, characterized in that the selective extractant each independently comprises a molecular sieve, preferably comprises molecular sieve NaY, molecular sieve 13X, molecular sieve ZSM-5, molecular sieve SAPO-34, beta molecular sieve or any combination thereof.

Embodiment 9. The method of concentrating a nuclide in a solidified radioactive waste according to any of the previous embodiments, comprising the steps of:

wherein the selective extractant each independently comprises an inorganic oxide support comprising silica, alumina, titania, or any combination thereof, and a species extraction active component comprising ferrocyanide and/or antimonate.

Embodiment 10. The method of concentrating the nuclides in a solidified radioactive waste according to any of the previous embodiments, characterized in that when the conductivity of the effluent in step 3) is greater than or equal to the conductivity of the concentrate in step 2), or the conductivity of the final permeate in step 2) is higher than 50 μs/cm, the first stage ion exchange resin and/or the selective extractant in step 3) is subjected to step 4) nuclide solidification, and optionally fresh ion exchange resin and/or fresh selective extractant is charged as the last stage ion exchange resin and/or selective extractant, and the other stages of ion exchange resin and/or selective extractant are advanced in sequence.

Embodiment 11. The method for concentrating and solidifying nuclides in a radioactive waste solution according to any one of the preceding embodiments, wherein the waste solution is treated with flocculation, activated carbon, cartridge filter, paper core filter, self-cleaning filter, ultrafiltration or any combination thereof before the pretreatment step of step 1).

Embodiment 12. The method for concentrating and solidifying nuclides in a radioactive waste according to any of embodiments 4-11, wherein the volume ratio of the fresh water discharged in step 5) to the liquid entering step 3) is controlled within the range of 1-10:1, preferably within the range of 3-10:1.

Embodiment 13. A system for concentrating nuclides in a solidified radioactive waste comprising:

a) A pretreatment unit comprising a first selective extractant;

Embodiment 14. The system for concentrating and solidifying nuclides in a radioactive waste according to embodiment 13, wherein in the pretreatment unit the system further comprises an oxidation device upstream of the first selective extractant, preferably equipped with an ultraviolet light source or an ozone device.

Embodiment 15. The system of concentrating and solidifying nuclides in a radioactive waste according to embodiment 13, wherein the extraction unit comprises an activated carbon bed before the organic ion exchange bed and/or second selective extractant.

Embodiment 16. The system for concentrating and solidifying a radionuclide in a radioactive waste according to embodiment 13, wherein the system further comprises e) a liquid purification unit in which a desalting unit is provided, a water inlet of the liquid purification unit is connected to the concentration unit such that permeate passing through the reverse osmosis device enters the liquid purification unit, and a concentrate outlet of the liquid purification unit is connected to the concentration unit such that concentrate obtained from the desalting unit is returned to the concentrate tank.

Embodiment 17. The system for concentrating and solidifying a nuclide in a radioactive waste according to any one of embodiments 13-16, wherein the selective extractant each independently comprises an inorganic oxide support and a nuclide extraction active component.

Embodiment 18. The system for concentrating and solidifying a radionuclide in a radioactive waste according to embodiment 17, wherein the inorganic oxide supports each independently comprise silica, manganese dioxide, alumina, titania, zirconia, or any combination thereof, and the nuclide extraction active component comprises ferrocyanide, antimonate, titanate, tin oxide, tungstate, or any combination thereof.

Embodiment 19. The system for concentrating and solidifying a radionuclide in a radioactive waste according to any of embodiments 13-16, wherein the organic ion exchange resin comprises a hydrogen cation exchange resin and a hydroxide anion exchange resin.

Embodiment 20. The system for concentrating and solidifying a radionuclide in a radioactive waste according to any of embodiments 13-16, characterized in that the selective extractant each independently comprises a molecular sieve, preferably comprises molecular sieve NaY, molecular sieve 13X, molecular sieve ZSM-5, molecular sieve SAPO-34, molecular sieve P or any combination thereof.

Embodiment 21. The system for concentrating and solidifying nuclides in a radioactive waste according to any one of embodiments 13-16, wherein the pretreatment unit further comprises a filtration device having a flocculation device, activated carbon, a cartridge filter, a paper core filter, a self-cleaning filter, an ultrafiltration device, or any combination thereof.

Embodiment 22. The system for concentrating and solidifying a radionuclide in a radioactive waste according to any of embodiments 13-16, wherein the concentration unit comprises a concentrate tank provided with at least two stages of reverse osmosis devices, and the retentate outlet of each stage of reverse osmosis devices is connected to the concentrate tank such that the retentate of each stage of reverse osmosis devices is returned to the concentrate tank.

The technical scheme of the present invention is exemplified by the following examples.

Examples

Example 1:

the conductivity of radioactive waste liquid enters a raw liquid tank, and the flow is controlled at 1m3/h. The method comprises removing fine suspended substances from liquid by self-cleaning filter and ultrafiltration, and introducing into ultraviolet catalytic oxidation device, wherein the device comprises dosing device and on-line pH control and measurement and control device, and adding a certain amount of H under control ₂ O ₂ (the dosage is controlled at 5 mg/L), the effluent passes through the selective extractant at a certain flow rate, and the components of the selective extractant comprise: silica, titania, ferrocyanide and antimonates, the effluent enters a concentrate tank.

A high and a low working liquid level switch are arranged in the concentrated liquid tank. The concentrate tank is provided with two stages of reverse osmosis concentration, the permeate liquid of each stage of reverse osmosis sequentially enters the next stage and finally enters the continuous electric desalting unit, and the retentate liquid of each stage of reverse osmosis returns to the concentrate tank. When the system is started, the membrane component is automatically washed, and a normal working procedure is entered. When the system is out of operation, non-radioactive water or fresh water generated by the system is used for on-line flushing. The radioactive waste liquid firstly passes through a cartridge filter, and the effluent enters a first-stage reverse osmosis. The ratio of fresh water to concentrated water generated by the first-stage reverse osmosis is controlled at 5:1, the conductivity of the fresh water is 40 mu S/cm, the fresh water enters the second-stage reverse osmosis, and the concentrated water enters the ion exchange resin. The ratio of the second-stage reverse osmosis fresh water to the concentrated water is controlled at 5:1, the concentrated water returns to the concentration tank, the conductivity of the fresh water outlet is 11 mu S/cm, the total number of microbial index bacterial colonies is less than 100CFU/mL, and the fresh water enters the continuous electric desalting unit. The anode of the continuous electric desalting unit adopts a pure titanium plate electrode, and the cathode adopts a stainless steel plate. The ratio of fresh water to concentrated water of the continuous electric desalting unit is 5:1. The fresh water meets the environmental emission, and the concentrated water returns to the concentration tank through the booster pump.

Pumping the liquid in the medium concentration liquid tank into the active carbon bed, then pumping into the ion exchange resin bed, and controlling the flow rate at 100L/h. The ion exchange resin bed is divided into two stages, wherein 10L of each stage of resin is filled, the first stage of resin is filled with cation exchange resin, and the second stage of resin is filled with cation-anion mixed ion exchange resin. The cation exchange resin is in the hydrogen form, and the anion exchange resin is in the hydrogen-oxygen form. The liquid sequentially passes through the ion exchange resin beds of each stage, the pH value of the final effluent is controlled to be 6-8, and the final effluent returns to the concentrate tank. When the water conductivity of the ion exchange bed is not lower than the conductivity of the concentration tank, the ion exchange resin in the first stage bed is conveyed into a standard barrel which is pre-provided with a certain amount of cement through a feed pump, and is stirred with the cement to form a solidified body, or is dehydrated and dried and then is conveyed into the standard barrel for storage.

By using the process, the recovery rate of nuclides (except tritium) in the radioactive waste liquid reaches more than 99 percent, and the nuclides are stored in the selective extractant and the ion exchange material.

Example 2:

the conductivity of radioactive waste liquid enters a raw liquid tank, and the flow is controlled at 1m3/h. By self-cleaningFilter, ultrafiltration, removing fine suspended substances from liquid, and introducing into ultraviolet catalytic oxidation device, which is provided with dosing device and on-line pH control and measurement and control device, and adding a certain amount of H under control ₂ O ₂ (the dosage is controlled at 10 mg/L), the effluent passes through the selective extractant at a certain flow rate, and the components of the selective extractant comprise: alumina, titania, ferrocyanide and antimonate, and the effluent enters a concentrate tank.

A high and a low working liquid level switch are arranged in the concentrated liquid tank. The concentrate tank is provided with three-stage reverse osmosis concentration, the permeate liquid of each stage of reverse osmosis sequentially enters the next stage and finally enters the continuous electric desalting unit, and the retentate liquid of each stage of reverse osmosis returns to the concentrate tank. When the system is started, the membrane component is automatically washed, and a normal working procedure is entered. When the system is out of operation, non-radioactive water or fresh water generated by the system is used for on-line flushing. The radioactive waste liquid firstly passes through a cartridge filter, and the effluent enters a first-stage reverse osmosis. The ratio of fresh water to concentrated water generated by the first-stage reverse osmosis is controlled at 5:1, the conductivity of the fresh water is 40 mu S/cm, the fresh water enters the second-stage reverse osmosis and the third-stage reverse osmosis, and the concentrated water enters the ion exchange resin. The ratio of reverse osmosis fresh water to concentrated water is controlled at 5:1, the concentrated water returns to the concentration tank, the conductivity of fresh water outlet is 10 mu S/cm, the total number of microbial index bacterial colonies is less than 100CFU/mL, and the fresh water enters the continuous electric desalting unit. The anode of the continuous electric desalting unit adopts a pure titanium plate electrode, and the cathode adopts a stainless steel plate. The ratio of fresh water to concentrated water of the continuous electric desalting unit is 3:1. The fresh water meets the environmental emission, and the concentrated water returns to the concentration tank through the booster pump.

Pumping the liquid in the medium-concentration liquid tank into an activated carbon bed, pumping the effluent into an adsorption bed, controlling the flow rate of the adsorption bed to be 100L/h, and filling the adsorption bed with a selective extractant, wherein the selective extractant comprises the following components: alumina, titania, ferrocyanide and antimonates, totaling 10L. The effluent is pumped into an organic ion exchange bed, and the flow is controlled at 100L/h. The bed was packed with a total of 20L of anion-cation mixed ion exchange resin. The cation exchange resin is in the hydrogen form, and the anion exchange resin is in the hydrogen-oxygen form. The ion exchange resin beds are divided into two stages, the liquid sequentially passes through the ion exchange resin beds at each stage, the pH value of the final effluent is controlled to be 6-8, and the final effluent returns to the concentrate tank. When the water conductivity of the ion exchange bed is not lower than the conductivity of the concentration tank, the ion exchange resin in the first stage bed is conveyed into a standard barrel which is pre-provided with a certain amount of cement through a feed pump, and is stirred with the cement to form a solidified body, or is dehydrated and dried and then is conveyed into the standard barrel for storage. The resin bed is filled with new resin and then is arranged as the last stage, and other stages are sequentially moved forward.

By using the process, the recovery rate of nuclides (except tritium) in the radioactive waste liquid reaches over 99.9 percent, and the nuclides are stored in the selective extractant and the ion exchange material.

Example 3:

The conductivity of the radioactive waste liquid enters a raw liquid tank, and the flow is controlled at 0.2m3/h. The method comprises removing fine suspended substances from liquid by self-cleaning filter and ultrafiltration, and introducing into ultraviolet catalytic oxidation device, wherein the device comprises dosing device and on-line pH control and measurement and control device, and adding a certain amount of H under control ₂ O ₂ (the dosage is controlled at 10 mg/L), the effluent passes through the selective extractant at a certain flow rate, and the components of the selective extractant comprise: silica, alumina, titania, ferrocyanide, tin oxide and antimonate, and the effluent enters a concentrate tank.

A high and a low working liquid level switch are arranged in the concentrated liquid tank. The concentrate tank is provided with two stages of reverse osmosis concentration, the permeate liquid of each stage of reverse osmosis sequentially enters the next stage and finally enters the continuous electric desalting unit, and the retentate liquid of each stage of reverse osmosis returns to the concentrate tank. When the system is started, the membrane component is automatically washed, and a normal working procedure is entered. When the system is out of operation, non-radioactive water or fresh water generated by the system is used for on-line flushing. The radioactive waste liquid firstly passes through a cartridge filter, and the effluent enters a first-stage reverse osmosis. The ratio of fresh water to concentrated water generated by the first-stage reverse osmosis is controlled to be 1:1, the conductivity of the fresh water is 50 mu S/cm, the fresh water enters the second-stage reverse osmosis, and the concentrated water enters the ion exchange resin. The ratio of the second-stage reverse osmosis fresh water to the concentrated water is controlled at 1:1, the concentrated water returns to the concentration tank, the conductivity of the fresh water outlet is 20 mu S/cm, the total number of microbial index bacterial colonies is less than 100CFU/mL, and the fresh water enters the continuous electric desalting unit. The anode of the continuous electric desalting unit adopts a pure titanium plate electrode, and the cathode adopts a stainless steel plate. The ratio of fresh water to concentrated water of the continuous electric desalting unit is 1:1. The fresh water meets the environmental emission, and the concentrated water returns to the concentration tank through the booster pump.

Pumping the liquid in the medium-concentration liquid tank into an activated carbon bed and then into an adsorption bed, wherein the components of the selective extractant filled in the adsorption bed comprise: silica, alumina, titanium oxide, ferrocyanide, tin oxide and antimonate, and the effluent water is pumped into an organic ion exchange bed, and the flow is controlled at 50L/h. The bed was packed with a total of 10L of anion-cation mixed ion exchange resin. The cation exchange resin is in the hydrogen form, and the anion exchange resin is in the hydrogen-oxygen form. The ion exchange resin beds are divided into two stages, the liquid sequentially passes through the ion exchange resin beds at each stage, the pH value of the final effluent is controlled to be 6-8, and the final effluent returns to the concentrate tank. When the water conductivity of the ion exchange bed is not lower than the conductivity of the concentration tank, the ion exchange resin in the first stage bed is conveyed into a standard barrel which is pre-provided with a certain amount of cement through a feed pump, and is stirred with the cement to form a solidified body, or is dehydrated and dried and then is conveyed into the standard barrel for storage. The resin bed is filled with new resin and then is arranged as the last stage, and other stages are sequentially moved forward.

Example 4:

the conductivity of the radioactive waste liquid enters a raw liquid tank, and the flow is controlled at 0.2m3/h. After removing fine suspended matters in the liquid by using a self-cleaning filter and ultrafiltration, the liquid passes through a selective extractant at a certain flow rate, wherein the selective extractant comprises the following components: alumina, zirconia, ferrocyanide, tin oxide and tungstate, and the effluent enters a concentrate tank.

A high and a low working liquid level switch are arranged in the concentrated liquid tank. The concentrate tank is provided with two stages of reverse osmosis concentration, the permeate liquid of each stage of reverse osmosis sequentially enters the next stage and finally enters the continuous electric desalting unit, and the retentate liquid of each stage of reverse osmosis returns to the concentrate tank. When the system is started, the membrane component is automatically washed, and a normal working procedure is entered. When the system is out of operation, non-radioactive water or fresh water generated by the system is used for on-line flushing. The radioactive waste liquid firstly passes through a cartridge filter, and the effluent enters a first-stage reverse osmosis. The ratio of fresh water to concentrated water generated by the first-stage reverse osmosis is controlled at 3:1, the conductivity of the fresh water is 35 mu S/cm, the fresh water enters the second-stage reverse osmosis, and the concentrated water enters the ion exchange resin. The ratio of the second-stage reverse osmosis fresh water to the concentrated water is controlled at 5:1, the concentrated water returns to the concentration tank, the conductivity of the fresh water outlet is 10 mu S/cm, the total number of microbial index bacterial colonies is less than 100CFU/mL, and the fresh water enters the continuous electric desalting unit. The anode of the continuous electric desalting unit adopts a pure titanium plate electrode, and the cathode adopts a stainless steel plate. The ratio of fresh water to concentrated water of the continuous electric desalting unit is 5:1. The fresh water meets the environmental emission, and the concentrated water returns to the concentration tank through the booster pump.

Pumping the liquid in the medium-concentration liquid tank into an activated carbon bed and then into an adsorption bed, wherein the components of the selective extractant filled in the adsorption bed comprise: alumina, zirconia, ferrocyanide, tin oxide and tungstate, and the effluent water is pumped into an organic ion exchange bed, and the flow is controlled at 200L/h. The bed was packed with a total of 10L of anion-cation mixed ion exchange resin. The cation exchange resin is in the hydrogen form, and the anion exchange resin is in the hydrogen-oxygen form. The ion exchange resin beds are divided into two stages, the liquid sequentially passes through the ion exchange resin beds at each stage, the pH value of the final effluent is controlled to be 6-8, and the final effluent returns to the concentrate tank. When the water conductivity of the ion exchange bed is not lower than the conductivity of the concentration tank, the ion exchange resin in the first stage bed is conveyed into a standard barrel which is pre-provided with a certain amount of cement through a feed pump, and is stirred with the cement to form a solidified body, or is dehydrated and dried and then is conveyed into the standard barrel for storage. The resin bed is filled with new resin and then is arranged as the last stage, and other stages are sequentially moved forward.

By using the process, the recovery rate of nuclides (except tritium) in the radioactive waste liquid reaches more than 95%, and the nuclides are stored in the selective extractant and the ion exchange material.

Example 5:

the conductivity of radioactive waste liquid enters a raw liquid tank, and the flow is controlled at 1m3/h. The method comprises removing fine suspended substances from liquid by self-cleaning filter and ultrafiltration, and introducing into ultraviolet catalytic oxidation device, wherein the device comprises dosing device and on-line pH control and measurement and control device, and adding a certain amount of H under control ₂ O ₂ (the dosage is controlled at 5 mg/L), the effluent passes through the selective extractant at a certain flow rate,the selective extractant comprises the following components: silica, zirconia, ferrocyanide and tin oxide, and the effluent enters a concentrate tank.

Pumping the liquid in the medium-concentration liquid tank into an adsorption bed, wherein the composition components of the selective extractant filled in the bed comprise: silica, zirconia, ferrocyanide and tin oxide, and then pumped into an organic ion exchange bed with a flow rate of 100L/h. The organic ion exchange bed is filled with cation-anion mixed ion exchange resin, and the total amount is 5L. The cation exchange resin is in the hydrogen form, and the anion exchange resin is in the hydrogen-oxygen form. The ion exchange resin beds are divided into two stages, the liquid sequentially passes through the ion exchange resin beds at each stage, the pH value of the final effluent is controlled to be 6-8, and the final effluent returns to the concentrate tank. When the water conductivity of the ion exchange bed is not lower than the conductivity of the concentration tank, the ion exchange resin in the first stage bed is conveyed into a standard barrel which is pre-provided with a certain amount of cement through a feed pump, and is stirred with the cement to form a solidified body, or is dehydrated and dried and then is conveyed into the standard barrel for storage. The resin bed is filled with new resin and then is arranged as the last stage, and other stages are sequentially moved forward.

By using the process, the recovery rate of nuclides (except tritium) in the radioactive waste liquid reaches more than 95%, and the nuclides are stored in the selective extractant ion exchange material.

The various aspects of the present invention have been explained above by way of specific examples, but it will be understood by those skilled in the art that: the invention is not limited to the specific embodiments described above, and equivalents of the various means, materials, devices, process steps, etc., disclosed herein, as well as combinations of the various means, materials, devices, process steps, etc., will be within the scope of the invention.

Claims

1. A method for concentrating nuclides in a solidified radioactive waste liquid, comprising the steps of:

step 1) pretreatment: catalytic oxidation is carried out on the radioactive waste liquid, and then the radioactive waste liquid is extracted by using a first selective extractant;

step 2) concentration: at least two-stage reverse osmosis concentration is carried out on the extracted radioactive waste liquid in a concentrated liquid tank, the permeate liquid of each stage of reverse osmosis sequentially enters the next stage, and the trapped liquid of each stage of reverse osmosis returns to the concentrated liquid tank;

2. The method of concentrating nuclides in a solidified radioactive waste as defined in claim 1, wherein said pretreatment further comprises: before the extraction in step 1), the nuclides in the radioactive waste are oxidized to be converted into ionic state, and ultraviolet light, ozone, hydrogen peroxide and/or sodium hypochlorite are used for oxidation.

3. The method of concentrating nuclides in a solidified radioactive waste as defined in claim 1, further comprising the step of 3) removing organics from the liquid prior to extracting the nuclides.

4. A method of concentrating and solidifying nuclides in a radioactive waste as claimed in claim 3, wherein activated carbon is used to remove organics from the liquid.

5. The method of concentrating nuclides in a solidified radioactive waste as defined in claim 1, further comprising the step of 5) liquid purification of: desalting and purifying the reverse osmosis permeate produced in the step 2), and returning the concentrated liquid purified water rich in radionuclides to the step 2).

6. The method of concentrating nuclides in a solidified radioactive waste as defined in claim 5, wherein the reverse osmosis permeate produced in step 2) is continuously electrically desalted.

7. The method of concentrating nuclides in a radioactive waste according to any one of claims 1-6, wherein the organic ion exchange resin comprises a hydrogen cation exchange resin and a hydroxide anion exchange resin.

8. The method of concentrating nuclides in a radioactive waste according to any one of claims 1-6, wherein the selective extractant each independently comprises a molecular sieve.

9. The method of concentrating nuclides in a solidified radioactive waste according to claim 8, wherein the selective extractants each independently comprise molecular sieve NaY, molecular sieve 13X, molecular sieve ZSM-5, molecular sieve SAPO-34, beta molecular sieve, or any combination thereof.

10. The method of concentrating nuclides in a solidified radioactive waste as claimed in any one of claims 1-6, wherein when the conductivity of the effluent in step 3) is greater than or equal to the conductivity of the concentrate in step 2), or the conductivity of the final permeate in step 2) is greater than 50 μs/cm, the first stage ion exchange resin and/or selective extractant in step 3) is subjected to step 4) nuclide solidification, and optionally fresh ion exchange resin and/or fresh selective extractant is charged as the last stage ion exchange resin and/or selective extractant, and the other stages of ion exchange resin and/or selective extractant are advanced sequentially.

11. The method of concentrating nuclides in a solidified radioactive waste liquid according to any of claims 1-6, wherein the waste liquid is treated with flocculation, activated carbon, cartridge filter, paper core filter, self-cleaning filter, ultrafiltration or any combination thereof prior to the step of 1) pretreatment.

12. The method of concentrating nuclides in a radioactive waste according to any one of claims 5-6, wherein the volume ratio of the fresh water discharged in step 5) to the liquid entering step 3) is controlled within the range of 1-10:1.

13. The method of concentrating nuclides in a radioactive waste of claim 12 wherein the volume ratio of fresh water discharged in step 5) to liquid entering step 3) is controlled to be in the range of 3-10:1.

14. A system for concentrating a nuclear species in a solidified radioactive waste for performing the method of concentrating a nuclear species in a solidified radioactive waste as set forth in claim 1, the system comprising:

a) A pretreatment unit comprising a first selective extractant;

d) A nuclide curing unit in which a nuclide-rich selective extractant and/or a nuclide-rich organic ion exchange resin form a cured body,

in the pretreatment unit, the system further comprises an oxidation device upstream of the first selective extractant;

15. A system for concentrating and solidifying nuclides in a radioactive waste as in claim 14 wherein an ultraviolet light source or an ozone device is provided at said oxidation device.

16. The system for concentrating nuclides in a solidified radioactive waste liquid of claim 14, wherein the extraction unit comprises a bed of activated carbon prior to the organic ion exchange bed and/or a second selective extractant.

17. The system for concentrating nuclides in a solidified radioactive waste liquid as in claim 14, wherein said system further comprises e) a liquid purification unit having a desalination unit disposed therein, a water inlet of said liquid purification unit being connected to said concentration unit such that permeate passing through said reverse osmosis device enters said liquid purification unit, and a concentrate outlet of said liquid purification unit being connected to said concentration unit such that concentrate obtained from said desalination unit is returned to said concentrate tank.

18. The system for concentrating nuclides in a radioactive waste according to any one of claims 14-17, wherein the organic ion exchange resin comprises a hydrogen cation exchange resin and a hydroxide anion exchange resin.

19. The system for concentrating nuclides in a radioactive waste solution of any one of claims 14-17, wherein the selective extractants each independently comprise a molecular sieve.

20. The system for concentrating nuclides in a solidified radioactive waste of claim 19, wherein the selective extractants each independently comprise molecular sieve NaY, molecular sieve 13X, molecular sieve ZSM-5, molecular sieve SAPO-34, P molecular sieve, or any combination thereof.

21. The system for concentrating nuclides in a solidified radioactive waste according to any of claims 14-17, wherein the pretreatment unit further comprises a filtration device having a flocculation device, activated carbon, a cartridge filter, a paper core filter, a self-cleaning filter, an ultrafiltration device, or any combination thereof.

22. The system for concentrating nuclides in a solidified radioactive waste according to any of claims 14-17, wherein the concentrating unit comprises a concentrate tank provided with at least two stages of reverse osmosis devices and the retentate outlet of each stage of reverse osmosis devices is connected to the concentrate tank such that the retentate of each stage of reverse osmosis devices is returned to the concentrate tank.