Method and system for controlling sulfate radical of borate storage tank of nuclear power plant unit

Abstract

The application discloses a sulfate control method and system for a borate storage tank of a nuclear power plant unit, and the control method comprises the following steps: S1, conveying the outage primary circuit drainage to a TEP borate storage tank; S2, conveying borate water of the TEP borate storage tank to a REA borate storage tank after the borate water is treated by a TEP desalination bed purification unit and an evaporation unit; S3, conveying the borate water of the REA borate storage tank to a PTR desalination bed through a PTR loading well or a transfer well, then conveying the borate water to the TEP borate storage tank after the borate water is treated, and repeating the step S2; S4, conveying the borate water of the REA borate storage tank to the TEP borate storage tank through a RPE process waste liquid recovery tank; and S5, returning the borate water of the TEP borate storage tank to the REA borate storage tank after the borate water is treated by the TEP desalination bed purification unit and the evaporation unit. The application realizes sulfate removal purification treatment of the outage primary circuit drainage on line by using a nuclear power plant system, and solves the problem of high sulfate content of borate water of a nuclear power unit.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant water chemistry control technology, and in particular to a method and system for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit. Background Technology

[0002] In nuclear power plants, the REA boric acid storage tank plays a crucial role, storing all the boric acid required for reactivity control during normal unit operation. During normal operation, the REA boric acid storage tank is nearly full at the end of each fuel cycle. When the RCP reaches the refueling shutdown boron concentration and the pressurizer is full, the REA boric acid storage tank level reaches its minimum. At this point, the remaining boric acid capacity should be sufficient to bring the unit from startup to full power and immediately back to cold shutdown. Considering boric acid capacity, plant layout, and equipment maintenance requirements, the system uses two REA boric acid storage tanks to store the boric acid solution required for reactivity control, with each tank requiring a capacity of 50% of the total system capacity. The two REA boric acid storage tanks are connected or isolated via an intermediate connecting pipeline and its isolation valve. The boric acid feeder provides the initial 4% boric acid solution injection to the REA boric acid storage tanks. During subsequent unit operation, the REA boric acid storage tanks are replenished from boric acid recovered from the TEP evaporation unit.

[0003] However, water systems with high oxygen concentrations and irradiated environments can generate H2O2. The higher the dissolved oxygen concentration in the water and the stronger the irradiation, the higher the concentration of H2O2 produced. During major overhauls, hydrogen peroxide is sometimes artificially added to the primary circuit. Due to the presence of oxidants in the water, such as free chlorine and hydrogen peroxide, the cation exchange resin will oxidize and deteriorate during use. The specific mechanism of resin oxidation is not yet fully understood. The result of resin oxidation is the breaking of the carbon chains between benzene rings to form benzenesulfonic acid. The hydrolysis reaction of benzenesulfonic acid requires high temperature and time; the residual heat and surface temperature of the fuel assembly can promote the hydrolysis of benzenesulfonic acid to form sulfate. Theoretical calculations show that 1 liter of cation exchange resin, when completely oxidized, will produce 192 grams of sulfate. The process of hydrogen peroxide generation, resin oxidation, and hydrolysis to produce sulfate is as follows:

[0004]

[0005] In nuclear power plants, sulfate removal from borate water is primarily achieved through desalination bed treatment. However, when RCV and TEP desalination beds treat borate water containing hydrogen peroxide in the primary loop, oxidation releases sulfonic acid groups. These sulfonic acid groups then decompose into sulfate ions upon heating in the TEP evaporator, ultimately leading to high sulfate content in the REA borate storage tank. Furthermore, because the TEP desalination bed cannot handle large quantities of oxygenated radioactive borate water and releases sulfonic acid groups during the process, sulfate removal from the REA borate tank becomes difficult. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit and a control system for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit.

[0007] The technical solution adopted by this invention to solve its technical problem is: to provide a method for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit, comprising the following steps:

[0008] S1. Transport the drainage from the primary circuit of the nuclear power unit during overhaul to the TEP boric acid storage tank.

[0009] The boric acid water from the S2 and TEP boric acid storage tanks is treated by the TEP desalination bed purification unit and the evaporation unit and then transported to the REA boric acid storage tank.

[0010] S3. The boric acid water in the REA boric acid storage tank is transported to the PTR desalination bed for treatment via the PTR loading well or transfer well, and then transported to the TEP boric acid storage tank. Step S2 is repeated.

[0011] S4. The boric acid water in the REA boric acid storage tank is transported to the TEP boric acid storage tank in an oxygen-free environment through the RPE process waste liquid recovery tank.

[0012] S5. The boric acid water in the TEP boric acid storage tank is returned to the REA boric acid storage tank after being treated by the TEP desalination bed purification unit and the evaporation unit.

[0013] Steps S4-S5 are repeated once or multiple times until the sulfate concentration in the boric acid water in the REA boric acid storage tank is ≤30ppb.

[0014] In some embodiments, steps S2-S3 are performed once or multiple times.

[0015] In some embodiments, in step S4, after the TEP boric acid storage tank receives boric acid water from the REA boric acid storage tank, the boric acid concentration of the boric acid water in the TEP boric acid storage tank is adjusted to ≤2000ppm.

[0016] In some embodiments, in step S3, the boric acid water in the REA boric acid storage tank is diluted before entering the PTR loading well or transfer well; or, the boric acid water in the REA boric acid storage tank is diluted in the PTR loading well or transfer well; the dilution factor corresponds to the volume ratio of the PTR loading well or transfer well to the REA boric acid storage tank.

[0017] In some embodiments, the boric acid solution is diluted with demineralized water.

[0018] In some embodiments, in step S3, the boric acid concentration of the boric acid water in the PTR loading well or transfer well is ≤1400ppm.

[0019] This invention provides another method for controlling sulfate ions in the boric acid storage tank of a nuclear power plant unit, comprising the following steps:

[0020] S1. Transport the drainage from the primary circuit of the nuclear power unit during overhaul to the TEP boric acid storage tank.

[0021] S2. The boric acid water in the TEP boric acid storage tank is treated by the TEP desalination bed purification unit and the evaporation unit and then transported to the REA boric acid storage tank.

[0022] S3. The boric acid water in the REA boric acid storage tank is transported to the TEP boric acid storage tank in an oxygen-free environment through the RPE process waste liquid recovery tank, and step S2 is repeated.

[0023] Steps S2-S3 are repeated once or multiple times until the sulfate concentration in the boric acid water in the REA boric acid storage tank is ≤30ppb.

[0024] In some embodiments, in step S3, after the TEP boric acid storage tank receives boric acid water from the REA boric acid storage tank, the boric acid concentration of the boric acid water in the TEP boric acid storage tank is adjusted to ≤2000ppm.

[0025] The present invention also provides a sulfate control system for a boric acid storage tank of a nuclear power plant unit, for use in the sulfate control method of the boric acid storage tank of a nuclear power plant unit as described in any of the above. The sulfate control system for the boric acid storage tank of the nuclear power plant unit includes an REA boric acid storage tank, a PTR loading well or transfer well, a PTR desalination bed, a TEP boric acid storage tank and an RPE process waste liquid recovery tank connected in sequence.

[0026] The TEP boric acid storage tank is also connected to the REA boric acid storage tank, forming a first loop with the REA boric acid storage tank, PTR loading or transfer well, PTR desalination bed, and TEP boric acid storage tank. The RPE process waste liquid recovery tank is connected between the REA boric acid storage tank and the TEP boric acid storage tank, providing an anaerobic environment for the flow of boric acid water between the REA boric acid storage tank and the TEP boric acid storage tank. The TEP boric acid storage tank, the REA boric acid storage tank, and the RPE process waste liquid recovery tank are connected to form a second loop.

[0027] The TEP boric acid storage tank receives the primary loop drainage from the nuclear power unit overhaul, allowing the boric acid water to enter the first loop and / or the second loop for circulation treatment, thereby reducing the sulfate content.

[0028] In some embodiments, the REA boric acid storage tank is connected to the PTR loading well or transfer well via REA system pipelines and PTR system pipelines, so that the boric acid water in the REA boric acid storage tank is mixed and diluted with demineralized water driven by the demineralized water pump under the drive of the REA boric acid transfer pump and then transported into the PTR loading well or transfer well.

[0029] The beneficial effects of this invention are as follows: The primary loop wastewater from a nuclear power plant undergoes online sulfate purification treatment. An RPE process waste liquid recovery tank connects the REA boric acid storage tank and the TEP boric acid storage tank, providing an oxygen-free transport pipeline for the boric acid water. This improves sulfate removal efficiency and reduces the sulfate content in the REA boric acid storage tank. The boric acid water transport process does not affect the normal function of the system along the transport pipeline. The sulfate-removed boric acid water can be returned to the original system (REA boric acid storage tank) without contamination, still meeting the original system's water quality requirements. This solves the problem of high sulfate content in boric acid water from nuclear power units. It also reduces waste liquid discharge, lowers costs, and increases efficiency, saving costs for the power plant. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0031] Figure 1 This is a schematic flowchart of a method for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit according to an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the connection of the sulfate control system of the boric acid storage tank of a nuclear power plant unit according to an embodiment of the present invention. Detailed Implementation

[0033] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0034] Combination Figure 1 and Figure 2 A method for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit according to an embodiment of the present invention may include the following steps:

[0035] S1. Monitor the sulfate content of the primary loop drainage (i.e., boric acid water) during the overhaul of the nuclear power unit, and transport the primary loop drainage during the overhaul of the nuclear power unit to the TEP (coolant storage and treatment system) boric acid storage tank 10.

[0036] S2. After being treated by the TEP desalination bed purification unit and evaporation unit, the sulfate content in the boric acid water is reduced, and then it is transported to the REA (Reactor Boron and Water Makeup System) boric acid storage tank 20.

[0037] In nuclear power plants, the REA boric acid storage tank stores all the boric acid required for reactivity control during normal unit operation. Typically, a nuclear power plant unit has two boric acid storage tanks to store the boric acid solution needed for reactivity control, with each tank having a capacity of 50% of the total system capacity. The two boric acid storage tanks are connected or isolated via an intermediate connecting pipeline and its isolation valve. In step S2, the boric acid solution, after being treated by the TEP desalination bed purification unit and the evaporation unit, is transported to the selected REA boric acid storage tank 20.

[0038] S3. The boric acid water in the REA boric acid storage tank 20 is transported to the PTR desalination bed for sulfate purification treatment via the PTR (Reactor Pool and Fuel Pool Cooling and Treatment System) loading well or transfer well 30, and then transported to the TEP boric acid storage tank 10. Step S2 is repeated, that is, the boric acid water in the TEP boric acid storage tank 10 is then treated by the TEP desalination bed purification unit and the evaporation unit and then transported to the REA boric acid storage tank 20.

[0039] The boric acid solution in the REA boric acid storage tank 20 is diluted before entering the PTR loading well or transfer well 30; or the boric acid solution in the REA boric acid storage tank 20 is diluted in the PTR loading well or transfer well 30.

[0040] Specifically, the REA boric acid storage tank 20 is connected to the PTR loading well or transfer well 30 via the REA system pipeline and the PTR system pipeline. Therefore, boric acid water can enter the PTR loading well or transfer well 30 through the REA system pipeline and the PTR system pipeline, driven by the REA boric acid transfer pump. During the transportation of boric acid water, the boric acid water is mixed and diluted with demineralized water driven by the demineralized water pump before being transported into the PTR loading well or transfer well 30. This ensures that the boric acid concentration of the boric acid water in the PTR loading well or transfer well 30 is ≤1400ppm, thus meeting the volume requirements of the PTR loading well or transfer well 30 and guaranteeing the purification efficiency of the subsequent PTR demineralization bed 40.

[0041] The dilution ratio of boric acid solution corresponds to the volume ratio of the PTR loading or transfer well 30 and the REA boric acid storage tank 20. For example, if the volume of the REA boric acid storage tank 20 is 60L and the volume of the PTR loading or transfer well 30 is 300L, and the volume ratio of the two is 1:5, then the boric acid solution from the REA boric acid storage tank 20 should be diluted 5 times, so that the volume ratio of the diluted solution to the original volume is 5:1.

[0042] The REA boric acid storage tank 20, PTR loading or transfer well 30, PTR desalination bed 40, and TEP boric acid storage tank 10 are connected to form a first loop 100. By repeatedly executing steps S2-S3, the boric acid solution can be circulated within this first loop 100 to gradually remove sulfate ions. The boric acid solution, after passing through the PTR desalination bed 40, can also undergo SRD purification treatment.

[0043] The sulfate content in the boric acid water in the REA boric acid storage tank 20 was monitored using the REA boric acid storage tank 20 as the monitoring point.

[0044] Based on the comparison between the monitored sulfate content and the required range (≤30ppb), when the sulfate content is higher than the required range, steps S2-S3 are executed and the cycle is repeated once or multiple times, so that the boric acid water is circulated in the first loop 100 formed by connecting the REA boric acid storage tank 20, the PTR loading well or transfer well 30, the PTR desalination bed 40 and the TEP boric acid storage tank 10, so as to reduce the sulfate content therein.

[0045] During major overhauls of nuclear power plants, hydrogen peroxide is sometimes artificially added to the primary circuit. Because the water contains oxidants, it causes the resin in the desalination bed to oxidize and deteriorate, leading to the breakage of carbon chains between benzene rings to form benzenesulfonic acid. The sulfonic acid groups decompose into sulfate ions upon heating in the TEP evaporator, resulting in a high sulfate content in the REA boric acid storage tank. Therefore, to completely remove sulfate ions from the boric acid water or reduce the sulfate content to meet the requirements of the "Chemical and Radiochemical Technical Specifications" (≤30 ppb), the presence or introduction of oxygen must be completely eliminated during sulfate removal.

[0046] In accordance with the requirements of an oxygen-free environment, the sulfate control method for the boric acid storage tank of a nuclear power plant unit of the present invention further includes the following steps:

[0047] S4. The boric acid solution in the REA boric acid storage tank 20 is transported to the TEP boric acid storage tank 10 in an oxygen-free environment via the RPE process waste liquid recovery tank 50.

[0048] The RPE process waste liquid recovery tank 50 is connected between the REA boric acid storage tank 20 and the TEP boric acid storage tank 10, providing an oxygen-free transport pipeline for the boric acid water. After receiving the boric acid water from the RPE process waste liquid recovery tank 50 and the REA boric acid storage tank 20, the TEP boric acid storage tank 10 adjusts the boric acid concentration of the boric acid water in the TEP boric acid storage tank 10 to ≤2000ppm to facilitate the control of the subsequent TEP desalination bed purification unit and evaporation unit. The adjustment method includes introducing primary loop replacement water (low-concentration boric acid water) into the TEP boric acid storage tank 10 to reduce the boric acid concentration of the boric acid water from the REA boric acid storage tank 20 to ≤2000ppm through dilution. If the boric acid concentration of the boric acid water received by the TEP boric acid storage tank 10 from the REA boric acid storage tank 20 is already ≤2000ppm, no adjustment is required.

[0049] S5. The boric acid water in TEP boric acid storage tank 10 is returned to REA boric acid storage tank 20 after being evaporated and recovered by the TEP desalination bed purification unit and evaporation unit. Since the boric acid water enters TEP boric acid storage tank 10 through RPE process waste liquid recovery tank 50, the introduction of oxygen during transportation is avoided, the release of sulfonic acid groups is prevented, and the purification efficiency of the TEP desalination bed purification unit for sulfate in boric acid water is improved.

[0050] Steps S4-S5 are repeated once or multiple times until the sulfate concentration in the boric acid water in the REA boric acid storage tank is ≤30ppb.

[0051] The RPE process waste liquid recovery tank 50 is connected between the REA boric acid storage tank 20 and the TEP boric acid storage tank 10, and is also connected to the REA boric acid storage tank 20 and the TEP boric acid storage tank 10 to form a second loop 200. When steps S5-S6 are repeated, the boric acid water is driven to circulate in the second loop 200 for sulfate purification treatment until the sulfate content is reduced to 30 ppb or below.

[0052] Preferably, after each boric acid solution enters the TEP boric acid storage tank 10 from the RPE process waste liquid recovery tank 50, it is mixed and diluted with the primary loop water to make the boric acid concentration ≤2000ppm. After being treated by the TEP desalination bed purification unit and the evaporation unit, it is returned to the REA boric acid storage tank 20.

[0053] In some embodiments, when the sulfate concentration of the boric acid solution in the REA boric acid storage tank 20 is higher than 30 ppb, steps S4 and S5 are performed.

[0054] Another embodiment of the present invention provides a method for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit, comprising the following steps:

[0055] S1. Monitor the sulfate content of the primary circuit drainage (i.e., boric acid water) during the overhaul of the nuclear power unit, and transport the primary circuit drainage during the overhaul of the nuclear power unit to the TEP boric acid storage tank.

[0056] S2. After being treated by the TEP desalination bed purification unit and the evaporation unit, the boric acid water is transported to the REA boric acid storage tank.

[0057] S3. The boric acid solution from the REA boric acid storage tank is transferred to the TEP boric acid storage tank in an oxygen-free environment via the RPE process waste liquid recovery tank. Step S2 is repeated, i.e., the boric acid solution from the TEP boric acid storage tank is then treated by the TEP desalination bed purification unit and the evaporation unit before being transferred to the REA boric acid storage tank. Because the boric acid solution enters the TEP boric acid storage tank via the RPE process waste liquid recovery tank, oxygen is avoided during the transportation process, the release of sulfonic acid groups is prevented, and the purification efficiency of the TEP desalination bed purification unit for sulfate in the boric acid solution is improved.

[0058] Steps S2-S3 involve one or more cycles of treatment until the sulfate concentration in the boric acid water in the REA boric acid storage tank is ≤30 ppb. The RPE process waste liquid recovery tank is connected between the REA boric acid storage tank and the TEP boric acid storage tank, providing an oxygen-free transport pipeline for the boric acid water, and also forming a loop with the REA boric acid storage tank and the TEP boric acid storage tank (e.g., Figure 2 The second circuit 200 shown in the diagram. When steps S2-S3 are repeated, the boric acid water is driven to circulate in the circuit for sulfate purification treatment until the sulfate content is reduced to 30 ppb or below.

[0059] In step S3, after the TEP boric acid storage tank receives boric acid water from the RPE process waste liquid recovery tank and the REA boric acid storage tank, the boric acid concentration of the boric acid water in the TEP boric acid storage tank is adjusted to ≤2000ppm. The adjustment method includes introducing primary loop replacement water (low-concentration boric acid water) into the TEP boric acid storage tank to reduce the boric acid concentration of the boric acid water from the REA boric acid storage tank through dilution, ensuring that the boric acid concentration is ≤2000ppm. If the boric acid concentration is ≤2000ppm after the TEP boric acid storage tank receives boric acid water from the REA boric acid storage tank, no adjustment is required. In this invention, based on the REA boric acid storage tank storing all the boric acid required for reactivity control during normal unit operation, the sulfate content of the boric acid water stored in the REA boric acid storage tank is purified to meet the relevant technical specifications, thereby reducing the sulfate content of the boric acid required for unit operation.

[0060] Combination Figure 1 and Figure 2 A sulfate control system for a borate storage tank in a nuclear power plant unit, used to implement the sulfate control method for the borate storage tank in the above-mentioned nuclear power plant unit, may include an REA borate storage tank 20, a PTR loading well or transfer well 30, a PTR desalination bed 40, and a TEP borate storage tank 10 connected in sequence. The TEP borate storage tank 10 is also connected to the REA borate storage tank 20, so that the REA borate storage tank 20, the PTR loading well or transfer well 30, the PTR desalination bed 40, and the TEP borate storage tank 10 form a first loop 100.

[0061] TEP boric acid storage tank 10 receives drainage from the primary loop of the nuclear power unit during overhaul, allowing the boric acid water to enter the primary loop for circulation treatment and reducing the sulfate content.

[0062] During the process of transporting boric acid water from TEP boric acid storage tank 10 to REA boric acid storage tank 20, it is treated by TEP desalination bed purification unit and evaporation unit before entering REA boric acid storage tank 20.

[0063] Specifically, the REA boric acid storage tank 20 is connected to the PTR loading well or transfer well 30 through the REA system pipeline and the PTR system pipeline, so that the boric acid water in the REA boric acid storage tank 20 is mixed and diluted with the demineralized water driven by the demineralized water pump under the drive of the REA boric acid transfer pump and then transferred into the PTR loading well or transfer well 30.

[0064] In the PTR loading or transfer well, the boric acid concentration of the boric acid solution is ≤1400ppm to meet the volume requirements of the PTR loading or transfer well and to ensure the purification efficiency of the subsequent PTR desalination bed.

[0065] In some embodiments, the sulfate control system of the boric acid storage tank of a nuclear power plant unit further includes an RPE process waste recovery tank 50, which is connected between the REA boric acid storage tank 20 and the TEP boric acid storage tank 10, providing an oxygen-free environment for the flow of boric acid water between the REA boric acid storage tank 20 and the TEP boric acid storage tank 10. The TEP boric acid storage tank 10, the REA boric acid storage tank 20, and the RPE process waste recovery tank 50 are connected to form a second loop 200.

[0066] After receiving boric acid water from RPE process waste liquid recovery tank 50 and REA boric acid storage tank 20, TEP boric acid storage tank 10 can introduce primary loop replacement water (low-concentration boric acid water) into TEP boric acid storage tank 10 to make the boric acid concentration of the boric acid water in TEP boric acid storage tank 10 ≤2000ppm. The diluted boric acid water with a boric acid concentration ≤2000ppm is then treated by TEP desalination bed purification unit and evaporation unit, and then returned to REA boric acid storage tank 20.

[0067] Depending on the selected sulfate control method for the borate storage tank of the different nuclear power plant unit, the startup process... Figure 2 The diagram shows different loops in the sulfate control system of the boric acid storage tank of a nuclear power plant unit. For example, when selecting... Figure 1 When the sulfate control method is executed in the process of the illustrated embodiment, Figure 2 Both the first and second loops of the control system shown are in operation. When the anaerobic path is selected to implement the sulfate control method... Figure 2 The second loop of the control system shown is put into use.

[0068] In summary, the sulfate control system for the boric acid storage tank of the nuclear power plant unit of the present invention is an existing system of the nuclear power plant unit. It realizes online removal and purification of sulfate in boric acid water, which is simple to operate, efficient, reduces waste liquid discharge, reduces costs and increases efficiency, and saves costs for the power plant.

[0069] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit, characterized in that, Includes the following steps: S1. Transport the drainage from the primary circuit of the nuclear power unit during overhaul to the TEP boric acid storage tank. The boric acid water from the S2 and TEP boric acid storage tanks is treated by the TEP desalination bed purification unit and the evaporation unit and then transported to the REA boric acid storage tank. S3. The boric acid water in the REA boric acid storage tank is transported to the PTR desalination bed for treatment via the PTR loading well or transfer well, and then transported to the TEP boric acid storage tank. Step S2 is repeated. S4. The boric acid water in the REA boric acid storage tank is transported to the TEP boric acid storage tank in an oxygen-free environment through the RPE process waste liquid recovery tank. S5. The boric acid water in the TEP boric acid storage tank is returned to the REA boric acid storage tank after being treated by the TEP desalination bed purification unit and the evaporation unit. Steps S4-S5 are repeated once or multiple times until the sulfate concentration in the boric acid water in the REA boric acid storage tank is ≤30ppb.

2. The method for controlling sulfate ions in the boric acid storage tank of a nuclear power plant unit according to claim 1, characterized in that, Steps S2-S3 are processed once or multiple times.

3. The method for controlling sulfate ions in the boric acid storage tank of a nuclear power plant unit according to claim 1, characterized in that, In step S4, after the TEP boric acid storage tank receives boric acid water from the REA boric acid storage tank, the boric acid concentration of the boric acid water in the TEP boric acid storage tank is adjusted to ≤2000ppm.

4. The method for controlling sulfate ions in the boric acid storage tank of a nuclear power plant unit according to any one of claims 1-3, characterized in that, In step S3, the boric acid water in the REA boric acid storage tank is diluted and then enters the PTR loading well or transfer well; or, the boric acid water in the REA boric acid storage tank is diluted in the PTR loading well or transfer well; the dilution ratio corresponds to the volume ratio of the PTR loading well or transfer well and the REA boric acid storage tank.

5. The method for controlling sulfate ions in the boric acid storage tank of a nuclear power plant unit according to claim 4, characterized in that, The boric acid solution was diluted with demineralized water.

6. The method for controlling sulfate ions in the boric acid storage tank of a nuclear power plant unit according to any one of claims 1-3, characterized in that, In step S3, the boric acid concentration of the boric acid water in the PTR loading well or transfer well is ≤1400ppm.

7. A method for controlling sulfate ions in a boric acid storage tank of a nuclear power plant unit, characterized in that, Includes the following steps: S1. Transport the drainage from the primary circuit of the nuclear power unit during overhaul to the TEP boric acid storage tank. S2. The boric acid water in the TEP boric acid storage tank is treated by the TEP desalination bed purification unit and the evaporation unit and then transported to the REA boric acid storage tank. S3. The boric acid water in the REA boric acid storage tank is transported to the TEP boric acid storage tank in an oxygen-free environment through the RPE process waste liquid recovery tank, and step S2 is repeated. Steps S2-S3 are repeated once or multiple times until the sulfate concentration in the boric acid water in the REA boric acid storage tank is ≤30ppb.

8. The method for controlling sulfate ions in the boric acid storage tank of a nuclear power plant unit according to claim 7, characterized in that, In step S3, after the TEP boric acid storage tank receives boric acid water from the REA boric acid storage tank, the boric acid concentration of the boric acid water in the TEP boric acid storage tank is adjusted to ≤2000ppm.

9. A sulfate control system for a boric acid storage tank in a nuclear power plant unit, characterized in that, The sulfate control system for the boric acid storage tank of a nuclear power plant unit as described in any one of claims 1-7 or the boric acid storage tank of a nuclear power plant unit as described in claim 8, wherein the sulfate control system for the boric acid storage tank of the nuclear power plant unit comprises, in sequence, an REA boric acid storage tank, a PTR loading well or transfer well, a PTR desalination bed, a TEP boric acid storage tank, and an RPE process waste liquid recovery tank. The TEP boric acid storage tank is also connected to the REA boric acid storage tank, forming a first loop with the REA boric acid storage tank, PTR loading or transfer well, PTR desalination bed, and TEP boric acid storage tank. The RPE process waste liquid recovery tank is connected between the REA boric acid storage tank and the TEP boric acid storage tank, providing an anaerobic environment for the flow of boric acid water between the REA boric acid storage tank and the TEP boric acid storage tank. The TEP boric acid storage tank, the REA boric acid storage tank, and the RPE process waste liquid recovery tank are connected to form a second loop. The TEP boric acid storage tank receives the primary loop drainage from the nuclear power unit overhaul, allowing the boric acid water to enter the first loop and / or the second loop for circulation treatment, thereby reducing the sulfate content.

10. The sulfate control system for the boric acid storage tank of a nuclear power plant unit according to claim 9, characterized in that, The REA boric acid storage tank is connected to the PTR loading well or transfer well via the REA system pipeline and the PTR system pipeline, so that the boric acid water in the REA boric acid storage tank is mixed and diluted with the demineralized water driven by the demineralized water pump under the drive of the REA boric acid transfer pump and then transported into the PTR loading well or transfer well.

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