Multi-effect water rectification method for treating nuclear waste water in primary loop of nuclear power plant

Abstract

The application discloses a multi-effect water rectification method for treating nuclear waste water of a primary loop of a nuclear power plant, and belongs to the technical field of nuclear waste water treatment. The method introduces tritium-containing nuclear waste water discharged from the primary loop of the nuclear power plant into a multi-effect water rectification unit, separates the tritium-containing nuclear waste water by water rectification based on the boiling point difference between water hydrogen isotopes and water oxygen isotopes, and forms tower top distillate and tower bottom concentration kettle liquid. Low-tritium and low-oxygen seventeen water is obtained from the tower top distillate and is reused as a primary loop coolant. Rich-tritium and rich-oxygen eighteen concentrated water is obtained from the tower bottom concentration kettle liquid, and tritium-containing hydrogen gas components and oxygen-containing eighteen oxygen gas components are obtained through electrolysis. The tritium-containing hydrogen gas components and the oxygen-containing eighteen oxygen gas components are respectively combined with oxygen and hydrogen to generate concentrated tritium-containing water and concentrated oxygen eighteen water. The method can simultaneously achieve the multiple effects of radioactive pollutant emission reduction and resource recovery, i.e., reducing the discharge of tritium-containing nuclear waste water of the primary loop, reducing the precursor oxygen seventeen in the reused coolant of radioactive carbon fourteen, and realizing the centralized storage of concentrated tritium-containing water after volume reduction and the recycling of concentrated oxygen eighteen water.

Description

Technical Field

[0001] This invention belongs to the field of nuclear wastewater treatment technology, specifically relating to a multi-effect water distillation method for treating nuclear wastewater from the primary loop of a nuclear power plant. Background Technology

[0002] During operation, the primary loop of a nuclear power plant generates tritium-containing liquid effluent. Tritium usually exists in the form of tritium-containing water, and its chemical properties are very similar to those of ordinary water. Conventional water treatment methods are insufficient to effectively remove it using only general chemical separation methods. Therefore, the reduction of tritium-containing liquid effluent and the reuse of primary loop coolant are of engineering significance.

[0003] Besides tritium, the oxygen isotope composition of the primary coolant also affects the subsequent generation of radionuclides. The activation of naturally abundant oxygen-17 neutrons in the coolant is the main source of primary radiocarbon generation, contributing 78%-98%. If oxygen-17-depleted water can be obtained simultaneously during the liquid effluent treatment process and reused in the primary loop, radiocarbon reduction at the source can be achieved at the coolant level.

[0004] Current treatment approaches typically focus on the discharge of liquid effluents or the centralized storage of tritium-containing water, making it difficult to simultaneously address the reuse of low-tritium water, the reuse of low-oxygen water-17, the concentration and storage of tritium, and the resource recovery of oxygen-18 water within the same process. Therefore, a method is needed that can utilize the differences in water isotope properties to achieve multi-target separation and diversion of tritium-containing liquid effluents from the primary loop. Summary of the Invention

[0005] Technical problem solved: To address the above-mentioned technical problems, this invention provides a multi-effect water distillation method for treating nuclear wastewater in the primary loop of nuclear power plants. This method can reduce the amount of liquid effluent discharged while treating tritium-containing nuclear wastewater, reduce the natural abundance of oxygen 17 in the recycled coolant, and convert the tritium and oxygen 18 enriched at the bottom of the distillation column into radioactive waste storage and oxygen 18 resource recovery, respectively.

[0006] Technical solution: A multi-effect water distillation method for treating nuclear wastewater from the primary loop of a nuclear power plant, comprising the following steps: S1, the nuclear wastewater discharged from the primary loop of the nuclear power plant is introduced into the multi-effect water distillation unit as water to be treated, and the primary loop nuclear wastewater contains tritium; S2, the water to be treated is distilled in the multi-effect water distillation unit, and the boiling point difference between water hydrogen isotopes and water oxygen isotopes is used to form the top distillate and the bottom concentrate. S3, obtain low-tritium and low-oxygen water (e.g., depleted of tritium and oxygen relative to the water to be treated) from the distillate at the top of the column, and reuse the low-tritium and low-oxygen water (e.g., the primary coolant of the nuclear power plant). S4, obtain tritium-rich and oxygen-rich concentrated water (eighteenths) from the concentrated liquid at the bottom of the tower, which is enriched with tritium and oxygen (eighteenths) relative to the water to be treated. S5, the tritium-rich and oxygen-rich octadecyl concentrated water is fed into an electrolysis device for electrolysis to obtain a tritium-containing hydrogen component and an oxygen-containing octadecyl oxygen component. S6, the tritium-containing hydrogen component is combined with oxygen to generate concentrated tritium-containing water, and the concentrated tritium-containing water is stored as radioactive waste; S7, the oxygen-containing octadecyl oxygen component is combined with hydrogen to generate concentrated octadecyl water, and the concentrated octadecyl water is recycled.

[0007] Preferably, the multi-effect water distillation unit includes at least two cascaded water distillation sections, in which the water to be treated is distilled step by step along the material flow direction in the water distillation sections.

[0008] Preferably, the multi-effect water distillation unit enriches tritium-containing water and oxygenated octadeca water relative to light water in the bottom concentrate of the column, and depletes oxygenated heptadeca water relative to light water in the top distillate of the column.

[0009] Preferably, the distillate from the top of the column is condensed to form the low-tritium, low-oxygen heptadecane, which is then reused as makeup water for the primary coolant circuit of the nuclear power plant.

[0010] Preferably, the concentrated liquid at the bottom of the tower is used as the input of the tritium-rich and oxygen-rich 18-eighths concentrated water into the electrolysis device.

[0011] Preferably, the electrolysis device includes an electrolytic cell, a hydrogen output channel, and an oxygen output channel. The tritium-containing hydrogen component is output through the hydrogen output channel, and the oxygen-containing oxygen component is output through the oxygen output channel.

[0012] Preferably, the tritium-containing hydrogen component is combined with the supplied oxygen and then condensed and collected to form the concentrated tritium-containing water.

[0013] Preferably, the oxygen-containing octadecyl oxygen component is combined with the supplied hydrogen and then collected by condensation to form the concentrated octadecyl water.

[0014] Preferably, the concentrated oxygen-containing water and the concentrated tritium-containing water are collected separately.

[0015] Preferably, the coolant reuse path of the low-tritium, low-oxygen water-17, the radioactive waste storage path of the concentrated tritium-containing water, and the resource recovery path of the concentrated oxygen-18 water are arranged separately from each other.

[0016] Beneficial effects: Compared with the prior art, the present invention has at least the following beneficial effects: First, by using multi-effect water distillation to deplete tritium in the distillate from the top of the column relative to the water to be treated, and by reusing the low-tritium, low-oxygen 17-water as a primary coolant, the amount of tritium-containing wastewater discharged from the primary loop can be reduced.

[0017] Second, oxygen-depleted water obtained from the same top distillate stream is reused in the primary loop, reducing the amount of oxygen-depleted water in the reused coolant and thus reducing the source of radioactive carbon-14 generation in the primary loop from the outset.

[0018] Third, tritium-rich and oxygen-rich 18 concentrated water is obtained from the bottom liquid of the tower. Tritium and oxygen 18 are concentrated into a smaller stream, and then through electrolysis and separate recombination, the tritium-containing hydrogen component is converted into concentrated tritium-containing water for radioactive waste storage, and the oxygen-containing 18 oxygen component is converted into concentrated oxygen 18 water for resource recovery, thus realizing the separation of tritium-containing waste and oxygen 18 resources. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of a multi-effect water distillation method for treating nuclear wastewater from the primary loop of a nuclear power plant, provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of the multi-effect water distillation method for treating nuclear wastewater from the primary loop of a nuclear power plant provided in an embodiment of the present invention; In the diagram, solid arrows indicate the flow of materials or products, dashed arrows indicate externally supplied gas, and dotted lines indicate unit boundaries. In the diagram: 100, Nuclear wastewater from the primary loop of a nuclear power plant to be treated; 200, Multi-effect water distillation unit; 210, First-stage water distillation column; 220, Second-stage water distillation column; 230, Third-stage water distillation column; 240, Fourth-stage water distillation column; 300, Top distillate (low-tritium, low-oxygen heptadeca); 310, Primary loop coolant reuse path; 400, Bottom concentrate (tritium-rich, oxygen-rich octadeca); 500, Electrolysis unit; 510, Electrolyzer; 520, Hydrogen output channel; 530, Oxygen output channel; 600, First recombination unit; 610, First condenser; 620, Concentrated tritium-containing water; 630, Radioactive waste storage path; 700, Second recombination unit; 710, Second condenser; 720, Concentrated oxygen octadeca; 730, Oxy octadeca resource recovery path. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example 1

[0021] like Figure 1 and 2As shown, this embodiment provides a multi-effect water distillation method for treating nuclear wastewater from the primary loop of a nuclear power plant. This method uses the nuclear wastewater 100 from the primary loop of the nuclear power plant to be treated as raw water. Through a combination of a multi-effect water distillation unit 200, an electrolysis device 500, a combiner, and a condenser, it achieves the reuse of low-tritium, low-oxygen hexadecimal water, the storage of concentrated tritium-containing radioactive waste, and the resource recovery of concentrated oxygenated hexadecimal water.

[0022] Specifically, the nuclear power plant primary loop wastewater 100 to be treated is introduced into a multi-effect water distillation unit 200. The nuclear power plant primary loop wastewater 100 contains tritium and water-oxygen isotope components. The multi-effect water distillation unit 200 includes a first-stage water distillation column 210, a second-stage water distillation column 220, a third-stage water distillation column 230, and a fourth-stage water distillation column 240 arranged in cascades. This embodiment uses a four-stage water distillation column as an example and does not limit the number of stages in the multi-effect water distillation unit 200. The water to be treated is distilled stage by stage along the material flow direction in each stage of the water distillation column, causing a difference in the distribution of different isotope water components between the top and bottom of the column.

[0023] In the multi-effect water distillation unit 200, the boiling point difference between water hydrogen isotopes and water oxygen isotopes is utilized to enrich tritium-containing water and oxygen-containing octadecyl water relative to light water in the bottom concentrate, while simultaneously depleting tritium and oxygen hexadecimals in the overhead distillate relative to the water to be treated. The overhead distillate obtained from the top of the multi-effect water distillation unit 200 is low-tritium, low-oxygen hexadecimal water 300. This low-tritium, low-oxygen hexadecimal water 300 is returned to the nuclear power plant's primary loop as coolant makeup water via the primary loop coolant reuse path 310. Since naturally abundant oxygen hexadecimals in the coolant, activated by neutrons, are the main source of radioactive carbon-14 production in the primary loop, reusing low-oxygen hexadecimal water can reduce the production and emission of carbon-14 at its source.

[0024] The concentrated liquid discharged from the bottom of the multi-effect water distillation unit 200 is tritium-rich and oxygen-rich octadecyl water 400. The tritium-rich and oxygen-rich octadecyl water 400 enters the electrolysis unit 500. The electrolysis unit 500 is equipped with an electrolytic cell 510, in which the tritium-rich and oxygen-rich octadecyl water 400 undergoes electrolysis to generate a tritium-containing hydrogen component and an oxygen-containing octadecyl oxygen component. The tritium-containing hydrogen component is output through the hydrogen output channel 520, and the oxygen-containing octadecyl oxygen component is output through the oxygen output channel 530.

[0025] Tritium-containing hydrogen components enter the first recombination unit 600 via hydrogen output channel 520, while oxygen is simultaneously supplied to the outside of the first recombination unit 600. The tritium-containing hydrogen components recombine with the externally supplied oxygen in the first recombination unit 600 to generate tritium-containing water vapor or a tritium-containing aqueous phase component, which then enters the first condenser 610 for condensation and collection, yielding concentrated tritium-containing water 620. The tritium in the concentrated tritium-containing water 620 is further enriched relative to the nuclear power plant primary loop wastewater 100 to be treated, and is then transported to the radioactive waste storage unit for storage via radioactive waste storage path 630, thereby achieving volume reduction treatment of the tritium-containing nuclear wastewater.

[0026] Oxygen-containing octadecyl oxygen components enter the second recombination unit 700 via the oxygen output channel 530, while hydrogen is simultaneously supplied to the outside of the second recombination unit 700. The oxygen-containing octadecyl oxygen components and the externally supplied hydrogen recombine in the second recombination unit 700 to generate oxygen-containing octadecyl water vapor or an oxygen-containing octadecyl aqueous phase component, which then enters the second condenser 710 for condensation and collection, yielding concentrated oxygen-containing octadecyl water 720. The octadecyl oxygen in the concentrated oxygen-containing octadecyl water 720 is further enriched relative to the nuclear power plant primary loop wastewater 100 to be treated, and is collected and utilized as a resource through the octadecyl resource recovery path 730.

[0027] In this embodiment, the primary coolant reuse path 310, the radioactive waste storage path 630, and the oxygen 18 resource recovery path 730 are set up independently. Therefore, low-tritium, low-oxygen 17-water 300, concentrated tritium-containing water 620, and concentrated oxygen 18-water 720 can be output separately, avoiding cross-contamination between the reused water, the radioactive waste concentrate, and the oxygen 18 resource recovery products.

[0028] Through the above methods, this embodiment can achieve the concentration and reduction of tritium in the primary loop nuclear wastewater of nuclear power plants, the reuse of low-tritium and low-oxygen water-17 as coolant, and the resource recovery of oxygen-18 water in the same processing flow, thereby improving the comprehensive utilization value of primary loop nuclear wastewater treatment.

Claims

1. A multi-effect water distillation method for treating nuclear wastewater from the primary loop of a nuclear power plant, characterized in that, Includes the following steps: S1, the nuclear wastewater discharged from the primary loop of the nuclear power plant is introduced into the multi-effect water distillation unit as water to be treated, and the primary loop nuclear wastewater contains tritium; S2, the water to be treated is distilled in the multi-effect water distillation unit, and the boiling point difference between water hydrogen isotopes and water oxygen isotopes is used to form the top distillate and the bottom concentrate. S3, obtain low-tritium and low-oxygen water (e.g., depleted of tritium and oxygen relative to the water to be treated) from the distillate at the top of the column, and reuse the low-tritium and low-oxygen water (e.g., the primary coolant of the nuclear power plant). S4, obtain tritium-rich and oxygen-rich concentrated water (eighteenths) from the concentrated liquid at the bottom of the tower, which is enriched with tritium and oxygen (eighteenths) relative to the water to be treated. S5, the tritium-rich and oxygen-rich octadecyl concentrated water is fed into an electrolysis device for electrolysis to obtain a tritium-containing hydrogen component and an oxygen-containing octadecyl oxygen component. S6, the tritium-containing hydrogen component is combined with oxygen to generate concentrated tritium-containing water, and the concentrated tritium-containing water is stored as radioactive waste; S7, the oxygen-containing octadecyl oxygen component is combined with hydrogen to generate concentrated octadecyl water, and the concentrated octadecyl water is recycled.

2. The multi-effect water distillation method for treating primary loop nuclear wastewater in a nuclear power plant according to claim 1, characterized in that, The multi-effect water distillation unit includes at least two cascaded water distillation sections, in which the water to be treated is distilled step by step along the material flow direction.

3. The multi-effect water distillation method for treating primary loop nuclear wastewater from a nuclear power plant according to claim 1, characterized in that, The multi-effect water distillation unit enriches tritium-containing water and oxygenated octadecane relative to light water in the bottom concentrate of the column, and depletes oxygenated heptadecane relative to light water in the top distillate.

4. The multi-effect water distillation method for treating primary loop nuclear wastewater from a nuclear power plant according to claim 1, characterized in that, The distillate from the top of the column is condensed to form the low-tritium, low-oxygen heptadecane, which is reused as makeup water for the primary coolant circuit of the nuclear power plant.

5. The multi-effect water distillation method for treating primary loop nuclear wastewater from a nuclear power plant according to claim 1, characterized in that, The concentrated liquid at the bottom of the tower is used as the input of the tritium-rich and oxygen-rich 18-eighths concentrated water into the electrolysis device.

6. The multi-effect water distillation method for treating primary loop nuclear wastewater in a nuclear power plant according to claim 1, characterized in that, The electrolysis device includes an electrolytic cell, a hydrogen output channel, and an oxygen output channel. The tritium-containing hydrogen component is output through the hydrogen output channel, and the oxygen-containing oxygen component is output through the oxygen output channel.

7. The multi-effect water distillation method for treating primary loop nuclear wastewater from a nuclear power plant according to claim 1, characterized in that, The tritium-containing hydrogen component combines with the supplied oxygen and is then condensed and collected to form the concentrated tritium-containing water.

8. The multi-effect water distillation method for treating nuclear wastewater from the primary loop of a nuclear power plant according to claim 1, characterized in that, The oxygen-containing octadecyl oxygen component is combined with the supplied hydrogen gas and then collected by condensation to form the concentrated oxygen-octadecyl water.

9. A multi-effect water distillation method for treating primary loop nuclear wastewater from a nuclear power plant according to claim 1, characterized in that, The concentrated oxygen-containing water and the concentrated tritium-containing water are collected separately.

10. A multi-effect water distillation method for treating nuclear wastewater from the primary loop of a nuclear power plant according to claim 1, characterized in that, The coolant reuse path for the low-tritium, low-oxygen water-17, the radioactive waste storage path for the concentrated tritium-containing water, and the resource recovery path for the concentrated oxygen-18 water are all separated from each other.

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