Boric acid product for primary loop of nuclear power station as well as preparation method and application of boric acid product

Abstract

The invention discloses a boric acid product for a primary loop of a nuclear power station and a preparation method and application of the boric acid product. The preparation method at least comprises the following steps: providing boric acid mother liquor; filtering the boric acid mother liquor to obtain intermediate boric acid mother liquor; stirring and drying the intermediate boric acid mother liquor at low temperature in a vacuum state to obtain boric acid crystal particles; performing further pneumatic drying on the boric acid crystal particles in a vacuum state to obtain dried boric acid particles; and screening out the particles with the preset particle size to obtain a boric acid product. According to the boric acid product for the primary loop of the nuclear power station and the preparation method and application of the boric acid product, the high-quality boric acid product can be prepared, and therefore the fission reaction of nuclear fuel can be effectively controlled through boric acid.

Description

Technical Field

[0001] The invention relates to the technical field of boric acid for nuclear industry, and in particular to a boric acid product for a primary circuit of a nuclear power plant, and a preparation method and application thereof. Background Art

[0002] After the boric acid product is dissolved in water, it is contained in various pipes and containers of the nuclear device as a neutron absorption control material for controlling the fission reaction of nuclear fuel. However, when screening or producing boric acid products for nuclear devices, only the abundance, purity and metal impurity content of the boric acid product are considered, and the water solubility, color of the aqueous solution, particle uniformity and moisture absorption stability of the boric acid product are not considered, resulting in low quality of the boric acid product, which is not conducive to the control of nuclear fuel fission reaction by boric acid. Therefore, there is an urgent need for a preparation method of a boric acid product for the primary circuit of a nuclear power plant to prepare a high-quality boric acid product, so as to facilitate the effective control of nuclear fuel fission reaction by boric acid. Summary of the invention

[0003] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a boric acid product for the primary circuit of a nuclear power plant and a preparation method and application thereof, which can prepare high-quality boric acid products, thereby facilitating the boric acid to effectively control the fission reaction of nuclear fuel.

[0004] To solve the above technical problems, the present invention is implemented through the following technical solutions.

[0005] The present invention provides a method for preparing a boric acid product for a primary circuit of a nuclear power plant, comprising at least the following steps:

[0006] Providing a boric acid mother solution;

[0007] Filtering the boric acid mother liquor to obtain an intermediate boric acid mother liquor;

[0008] Under vacuum, the intermediate boric acid mother liquor is subjected to low-temperature stirring and drying to obtain boric acid crystals;

[0009] Under vacuum conditions, further drying the boric acid crystals with air flow to obtain boric acid particles; and

[0010] The boric acid particles with a preset particle size are screened out to obtain a boric acid product.

[0011] In one embodiment of the present invention, the pore size of the filter membrane used for filtering the boric acid mother liquor is less than or equal to 0.4 μm.

[0012] In one embodiment of the present invention, the low-temperature stirring drying process includes at least the following steps:

[0013] After placing the intermediate boric acid mother liquor in a crystallization device, the crystallization device is evacuated, and the gas in the crystallization device is discharged from the vacuum outlet of the crystallization device, and the absolute pressure in the crystallization device is maintained at a preset absolute pressure;

[0014] Stirring and heating the intermediate boric acid mother liquor in the crystallization device to a preset temperature; and

[0015] When the temperature of the gas discharged from the vacuum outlet is lower than the preset temperature by a preset temperature and the dew point of the gas discharged from the vacuum outlet reaches the preset dew point, the step of airflow drying is entered.

[0016] In one embodiment of the present invention, the preset temperature is less than 70°C, the stirring speed is 10r / min~100r / min, the preset absolute pressure is less than or equal to 30Kpa, the set temperature is greater than 10°C, and the preset dew point is less than or equal to 0°C.

[0017] In one embodiment of the present invention, the pneumatic drying process includes at least the following steps:

[0018] Maintaining the preset absolute pressure, the preset temperature and the stirring speed, and introducing airflow into the crystallization device;

[0019] reducing the stirring speed so that the airflow further dries the boric acid crystals to obtain the boric acid particles; and

[0020] When the dew point of the gas discharged from the vacuum outlet is stable, the boric acid particles are manually sampled and analyzed for purity at regular intervals until the purity of the boric acid particles is qualified, and then the introduction of the gas flow, stirring and heating are stopped.

[0021] In one embodiment of the present invention, the stirring speed is reduced to 10 r / min to 60 r / min, the gas flow is clean nitrogen, inert gas or compressed air, and the dew point of the gas flow is lower than -30°C.

[0022] In one embodiment of the present invention, the preset particle size is 0.1 mm to 1.2 mm, and the boric acid product is spherical.

[0023] In one embodiment of the present invention, in the boric acid product, the content of the boric acid particles with the preset particle size is greater than 98 wt %.

[0024] The present invention also provides a boric acid product for a primary circuit of a nuclear power plant, which is obtained by adopting the above-mentioned preparation method.

[0025] The present invention also provides a nuclear device, which uses the boric acid product as a neutron absorption control material.

[0026] In summary, the present invention provides a boric acid product for a primary circuit of a nuclear power plant, a preparation method and an application thereof, which can obtain a boric acid product with excellent water solubility, high purity and high moisture absorption stability, thereby improving the quality of the boric acid product. Moreover, the boric acid product provided by the present invention, the preparation method and the application thereof, by using high-quality boric acid products in nuclear devices, facilitates the boric acid product to effectively control the fission reaction of nuclear fuel, thereby optimizing the operation of the nuclear device.

[0027] Of course, any method of implementing the present invention does not necessarily need to achieve all of the advantages mentioned above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0029] Figure 1 The present invention is a flowchart of a method for preparing a boric acid product according to an embodiment of the present invention.

[0030] Figure 2 This is a picture of the filter membrane after filtering a boric acid water sample that was not prepared in a clean environment.

[0031] Figure 3 Another filter membrane image after filtering a boric acid water sample that was not prepared in a clean environment.

[0032] Figure 4 This is a picture of the filter membrane after the filtration test of boric acid mother liquor.

[0033] Figure 5 This is a picture of the filter membrane after the filtration test of the intermediate boric acid mother liquor.

[0034] Figure 6 FIG. 4 is a schematic diagram of boric acid particles according to an embodiment of the present invention.

[0035] Figure 7 Schematic diagram of boric acid particles in a comparative example of the present invention.

[0036] Figure 8 Schematic diagram of boric acid particles in a comparative example of the present invention.

[0037] Fig. 9 Schematic diagram of a crystallization device in one embodiment of the present invention.

[0038] Description of labels:

[0039] 11. Outer shell; 12. Inner shell; 121. Vacuum outlet; 122. Air flow inlet; 13. Measuring device. DETAILED DESCRIPTION

[0040] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0041] It should be understood that the present invention can be implemented in different forms and should not be interpreted as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0042] The technical solution of the present invention is further described in detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0043] In nuclear devices, boric acid, as a neutron absorber, can control the nuclear reaction rate, make the nuclear reactor stable and safe, inhibit the generation of core corrosion products, ensure the safety of the core and the integrity of the pressure boundary, reduce the radiation dose of personnel, and improve the operational safety and flexibility of nuclear devices. Moreover, boron compounds with a high abundance of boron-10 can be made into control rods with elements such as lithium and chromium, which play an emergency and protective role in the reactor. Among them, nuclear devices have strict quality requirements for boric acid. If the quality indicators such as the purity and solubility of boric acid are poor, boric acid will have an adverse effect on the nuclear device. The present invention provides a boric acid product for the primary circuit of a nuclear power plant and a preparation method and application thereof. The preparation process of the boric acid product is improved from three aspects: the control process of the water-insoluble matter morphology, the product appearance control process and the product particle size control process, so that high-quality boric acid products can be obtained, thereby facilitating the boric acid product to effectively control the fission reaction of nuclear fuel and optimize the operation of the nuclear device.

[0044] See also Figure 1 As shown, the present invention provides a method for preparing a boric acid product for a primary circuit of a nuclear power plant, which at least includes the following steps S11 to S15.

[0045] S11. Provide boric acid mother solution.

[0046] S12, filtering the boric acid mother liquor to obtain an intermediate boric acid mother liquor.

[0047] S13. Under vacuum conditions, the intermediate boric acid mother liquor is stirred and dried at low temperature to obtain boric acid crystals.

[0048] S14. Under vacuum conditions, the boric acid crystals are further dried by air flow to obtain boric acid particles.

[0049] S15, screening out boric acid particles of a preset particle size to obtain a boric acid product.

[0050] See also Figures 1 to 3 As shown, in one embodiment of the present invention, steps S11 to S15 are all performed in a clean environment, such as a clean room, to prevent external factors such as dust in the external environment and fibers from the operator's clothes from affecting the quality of the boric acid product. Figure 2 and Figure 3 It can be seen that if the preparation process of the boric acid product is not carried out in a clean environment, after the boric acid product is dissolved in water to obtain a boric acid water sample, the boric acid water sample is filtered, and impurities such as fibers and colored substances exist on the filter membrane, thereby affecting the purity of the boric acid product. Therefore, by controlling the preparation of the boric acid product in a clean environment, and filtering the boric acid mother liquor in step S12, the purity of the boric acid product can be improved.

[0051] See also Figure 1 As shown, in one embodiment of the present invention, in step S11, the present invention does not limit the method for preparing the boric acid mother solution, and can be selected according to actual needs. Wherein, the boric acid mother solution includes naturally abundant boric acid 10, and / or, a highly enriched boric acid 10 produced by an isotope separation process. In this embodiment, taking the highly enriched boric acid 10 produced by the isotope separation process as an example, the method for preparing the boric acid mother solution is described, and the method for preparing the boric acid mother solution, for example, includes steps S111-S112.

[0052] S111, provide a boron source, perform isotope separation on the boron source, and obtain enrichment 10 B.

[0053] S112, Enrichment 10 B is processed to obtain boric acid mother liquor.

[0054] See also Figure 1 As shown, in one embodiment of the present invention, in step S111, for example, the boron source is boron trifluoride, and the preparation process of the boric acid mother solution is described. The boron in the boron trifluoride includes, for example, boron-10 ( 10 B) and boron-11( 11 B) two isotopes, 11 B absorbs almost no neutrons, and 10B can be used as a neutron absorber, and has the advantages of wide absorption energy spectrum, stable absorption cross section, no strong secondary radiation and simple post-processing. It is widely used in the fields of nuclear industry and medicine. Therefore, it is necessary to separate the boron isotopes in boron trifluoride to obtain enriched 10 B's substance, that is 10 BF3. Specifically, the method of isotope separation is, for example, chemical exchange distillation, cascade membrane countercurrent circulation, cryogenic distillation, ion exchange chromatography or laser method. In this embodiment, for example, the isotope separation of the boron source is carried out by chemical exchange distillation. Specifically, in the chemical exchange distillation method, the difference in the binding ability between different isotopes and the complex is utilized, and the chemical exchange and distillation process is used to make 10 B and 11 B is used to separate the two. The complex is, for example, an ether or an acyl substance. Further, the ether includes, for example, at least one of methyl ether, ethyl ether and anisole.

[0055] See also Figure 1 As shown, in one embodiment of the present invention, obtaining 10 After BF3, in step S112, 10 BF3 is processed to obtain boric acid mother liquor. 10 BF3 processing methods include inorganic hydrolysis or organic esterification. Specifically, when the inorganic hydrolysis method is used, 10 BF3 is placed in water medium. 10 BF3 gradually hydrolyzes and defluorinates to generate boric acid mother liquor. 10 During the hydrolysis of BF3, a first defluorinating agent may be added to the aqueous medium, wherein the first defluorinating agent may include at least one of calcium oxide, lithium carbonate, and lithium hydroxide, to promote the hydrolysis process and accelerate the preparation of the boric acid mother liquor. In this embodiment, the boric acid in the boric acid mother liquor meets the requirements of the primary circuit of the nuclear power plant. In other embodiments, the boric acid that does not meet the requirements of the primary circuit of the nuclear power plant may also be used as a boron source, and the boric acid mother liquor may also be obtained by dissolving the boric acid in water having a resistance greater than 10 megohms.

[0056] See also Figure 1 As shown, in one embodiment of the present invention, in step S112, when the boric acid mother solution is prepared by organic esterification, 10 BF3 is placed in an organic medium, and methoxy substances are added to the organic medium. 10 BF3 reacts with methoxy substances to form a coordination reaction. 10BF3 is defluorinated to generate trimethyl borate, and after the reaction is completed, a mixed solution of trimethyl borate and methoxy substances is obtained, and then the mixed solution is distilled to separate trimethyl borate, and then the trimethyl borate is placed in an aqueous medium, and the trimethyl borate is hydrolyzed to obtain a boric acid mother liquor. The organic medium is, for example, methanol, and the methoxy substances include, for example, at least one of sodium methoxide and calcium methoxide.

[0057] See also Figure 1 As shown, in one embodiment of the present invention, after obtaining the boric acid mother liquor, in step S12, the boric acid mother liquor is filtered to obtain an intermediate boric acid mother liquor. The boric acid mother liquor is filtered, for example, by a mechanical filter such as a precision filter, and the pore size of the filter membrane for filtering the boric acid mother liquor is, for example, less than or equal to 0.4 μm. Figure 4 and Figure 5 As shown, the present invention also performs filtration tests on the boric acid mother liquor and the intermediate boric acid mother liquor respectively, and observes the state of the filter membrane after filtration to show the technical effect of step S12. Figure 4 and Figure 5 It can be seen that there are obviously visible colored substances on the filter membrane used for filtering the boric acid mother liquor, while there are no obviously visible impurities on the filter membrane used for filtering the intermediate boric acid mother liquor. Therefore, through the filtration in step S12, impurities such as insoluble matter, tiny foreign matter and colored matter in the boric acid mother liquor can be removed, ensuring that a clear, transparent and foreign-free intermediate boric acid mother liquor is obtained, thereby improving the purity of the intermediate boric acid mother liquor and the boric acid product.

[0058] See also Figure 1 , Figure 6 and Fig. 9As shown, in one embodiment of the present invention, after obtaining the intermediate boric acid solution, in step S13, the intermediate boric acid mother liquor is stirred and dried at low temperature under vacuum, and crystals are precipitated from the intermediate boric acid mother liquor to obtain boric acid crystals. Wherein, the crystallization is performed in a crystallization device, for example, the crystallization device includes an outer shell 11, an inner shell 12 and a measuring device 13, the inner shell 12 is arranged in the outer shell 11, and a vacuum outlet 121 and an air flow inlet 122 are arranged on the inner shell 12, and the vacuum outlet 121 and the air flow inlet 122 are respectively connected to the interior of the inner shell 12, and the measuring device 13 is arranged at the exhaust port of the vacuum outlet 121. Specifically, after the intermediate boric acid mother liquor is placed in the inner shell 12 of the crystallization device, the inner shell 12 is evacuated, and the gas in the inner shell 12 is discharged from the vacuum outlet 121. The absolute pressure in the inner shell 12 is maintained at a preset absolute pressure, and then the intermediate boric acid mother liquor is stirred and heated to a preset temperature. Then, when the measuring device 13 measures that the temperature of the gas discharged from the vacuum outlet 121 is lower than the preset temperature by a set temperature and the dew point of the gas discharged from the vacuum outlet 121 reaches the preset dew point, the next step S14 of airflow drying is entered. Among them, the preset temperature is less than 70°C to ensure that boric acid will not lose water molecules to generate metaboric acid due to excessively high crystallization temperature. The stirring speed is, for example, 10r / min to 100r / min to regulate the crystal form of boric acid crystals. The preset absolute pressure is less than or equal to 30Kpa, the set temperature is greater than 10°C, and the preset dew point is less than or equal to 0°C. By low-temperature stirring and drying, the water in the intermediate boric acid mother liquor is evaporated, and the intermediate boric acid mother liquor changes from an unsaturated state to a saturated state. If evaporation continues, the boric acid solute in the intermediate boric acid mother liquor will precipitate as crystals, thereby obtaining boric acid crystals. Figure 6 It can be seen that by controlling the temperature and rotation speed during the low-temperature stirring and drying process, spherical boric acid crystals can be obtained, and the particle size of the boric acid crystals is relatively uniform.

[0059] See also Figure 1 , Figure 6 and Fig. 9As shown, in one embodiment of the present invention, after obtaining boric acid crystals, in step S14, the preset absolute pressure, preset temperature and stirring speed are maintained, and airflow is introduced into the inner shell 12 of the crystallization device through the airflow inlet 122, and then the stirring speed is reduced, and the airflow further dries the boric acid crystals to obtain boric acid particles. Moreover, when the dew point of the gas discharged from the vacuum outlet 121 is stable, the boric acid particles are manually sampled and purity analyzed regularly until the purity of the boric acid particles is qualified, that is, when it meets the requirements of the primary circuit of the nuclear power plant, the airflow, stirring and heating are stopped, otherwise the airflow drying is continued. Among them, the stirring speed is reduced to 10r / min~60r / min, the airflow is nitrogen, inert gas or compressed air that has been cleaned, and the dew point of the airflow is, for example, lower than -30°C. When the change in the dew point of the gas discharged from the vacuum outlet 121 does not exceed 1°C and can be maintained for, for example, more than 30 minutes, it can be regarded as a stable dew point, and the regular period is, for example, every 4h. In the present embodiment, when the boric acid particles are subjected to purity analysis, for example, the boric acid particles are first dissolved in a solvent to obtain a boric acid test solution, and then an alkaline agent is added to the boric acid test solution and stirred continuously, and the addition of the alkaline agent is stopped when the pH of the boric acid test solution changes from acidic to neutral, and the purity of the boric acid particles is determined according to the amount of the alkaline agent, which is not elaborated here. Wherein, the solvent is, for example, deionized water, and the alkaline agent is, for example, sodium hydroxide. By airflow drying, it is possible to avoid that boric acid will not lose water molecules to generate metaboric acid due to excessively high drying temperature, thereby improving the purity of the boric acid particles, and it is also possible to obtain boric acid particles with rounded crystal edges and uniform particle size, thereby improving the water dissolution rate of the boric acid product.

[0060] See also Figure 1 As shown, in one embodiment of the present invention, after obtaining the boric acid particles, in step S15, the boric acid particles of a preset particle size are screened out and collected to obtain a boric acid product. Wherein, the preset particle size is, for example, 0.1 mm to 1.2 mm, the boric acid product is spherical, and the content of the boric acid particles of the preset particle size in the boric acid product is, for example, greater than 98 wt%. Specifically, for example, boric acid particles of a first particle size are screened out through a first metal woven mesh, and then boric acid particles of a second particle size are screened out from the boric acid particles of the first particle size through a second metal woven mesh, and the boric acid particles that pass through the first metal woven mesh but not through the second metal woven mesh are collected, which is the boric acid product. Wherein, the mesh number of the first metal woven mesh is, for example, 16 meshes, the first particle size is, for example, less than 1.2 mm, the mesh number of the second metal woven mesh is, for example, 150 meshes, and the second particle size is, for example, less than 0.1 mm. In this embodiment, the smaller the particle size of the boric acid product, the faster its dissolution rate. However, if the particle size of the boric acid product is too small, the boric acid product will float on the water surface or adhere to the inner wall of the container, thereby causing the dissolution rate of the boric acid product to slow down. Therefore, by screening out boric acid particles with a preset particle size, the dissolution rate of the boric acid product can be accelerated as much as possible.

[0061] See also Figure 1 and Figure 6 As shown, the present invention also provides a boric acid product obtained by the above-mentioned preparation method. Among them, the quality of the boric acid product is high. Specifically, in the preparation process, the purity of the boric acid product can be improved by filtering and removing impurities such as insoluble matter, tiny foreign matter and colored matter in the boric acid mother liquor. Through low-temperature stirring drying and airflow drying, the crystal form of the boric acid product can be controlled to be spherical, and its particle size is uniform. By screening and controlling the preset particle size of the boric acid product, the water dissolution rate of the boric acid product can be increased.

[0062] See also Figure 7 As shown, the present invention also provides a comparative example 1 of a boric acid product. Compared with the preparation method of the boric acid product in the above embodiment, the preparation method of comparative example 1 adopts heating evaporation crystallization under normal pressure to obtain boric acid particles in steps S13 and S14 of comparative example 1, and comparative example 1 does not perform step S15. The remaining steps are the same as those in the embodiment and are not further elaborated here. The temperature of the intermediate boric acid mother liquor during heating evaporation crystallization is, for example, more than 90°C. Figure 7 It can be seen that the boric acid product obtained by heating evaporation crystallization in Comparative Example 1 is in the form of white powder crystals or flaky and shiny crystals with three oblique axis planes. Its crystal form has oblique axis planes and the crystal clusters are uneven in size.

[0063] See also Figure 8 As shown, the present invention also provides a comparative example 2 of a boric acid product. Compared with the preparation method of the boric acid product in the above embodiment, the preparation method of comparative example 2 adopts step S13, and does not perform steps S14 and S15. The remaining steps are the same as those in the embodiment, and are not further described here. Figure 8 It can be seen that the boric acid product obtained in Comparative Example 2 without low-speed stirring airflow drying and screening has uneven crystal sizes and a large number of fine particles.

[0064] See also Figure 6 and Figure 7 As shown, in one embodiment of the present invention, the boric acid product obtained in the embodiment and comparative example 1-2 is subjected to a long-term hygroscopic experiment. Specifically, 20g of the boric acid product of the embodiment and comparative example 1-2 is placed in a drum with a black polyethylene bag as the inner layer and kraft paper as the outer layer, and the drum is placed in a warehouse with indoor ventilation, and the temperature and humidity of the warehouse are not controlled. After 12 months, it is observed whether the boric acid product is hardened. Among them, the boric acid product of the embodiment did not absorb moisture and harden after 12 months, while the boric acid product of comparative example 1-2 had obvious hardening phenomenon. Boric acid products with a particle size lower than 0.1mm are more susceptible to moisture absorption and hardening, affecting use. Therefore, the boric acid crystals of the spherical crystal form obtained by the preparation method provided by the present invention have better moisture absorption stability, and their long-term storage is not easy to agglomerate due to moisture absorption.

[0065] Please refer to Table 1, the boric acid products produced by this process are screened according to different particle sizes, and the water dissolution rate is compared with the mixed distribution products without particle size control. Among them, in the product with uniform particle size distribution, the particle size distribution, for example, gradually increases from less than 0.125mm to more than 1.2mm. In the product with mixed particle size distribution, for example, 5 batches of products are tested. Because there is no particle size control, the particle size distribution of each batch of products is different, and the dissolution rate is also different. It can be seen from Table 1 that the smaller the particle size of the boric acid product, the faster its water dissolution rate. However, when the particle size of the boric acid product is less than 0.125mm, when a large amount of boric acid product is poured into the aqueous solution, the product will float on the water surface in large quantities, affecting the dissolution rate. In addition, a large amount of boric acid powder will also adhere to the inner wall and stirring rod of the dissolution tank, affecting the accuracy of the prepared concentration. Therefore, in the boric acid product provided in the embodiment of the present invention, its particle size and particle size distribution are uniform, and its water dissolution rate is fast, while in the boric acid product provided in the comparative example, its particle size is uneven, and its water dissolution rate is slow, which indicates that the boric acid product provided by the present invention has better water solubility.

[0066] Table 1. Dissolution rate of boric acid products with different particle size distributions

[0067]

[0068] See also Figure 1 and Figure 6 As shown, the present invention also provides a nuclear device, in which the above-mentioned boric acid product is dissolved in water to obtain a boric acid solution, and then the boric acid solution is placed in various pipes and containers of the nuclear device. The boric acid product is used as a neutron absorption control material to control the fission reaction of nuclear fuel. By using the high-quality boric acid product provided by the present invention in a nuclear device, it is possible to facilitate the boric acid to effectively control the fission reaction of nuclear fuel, thereby optimizing the operation of the nuclear device.

[0069] In summary, the present invention provides a boric acid product for a nuclear power plant primary circuit, a preparation method and an application thereof, by adopting low-temperature stirring drying and airflow drying to precipitate boric acid crystals in a boric acid solution, and screening out a boric acid product with a preset particle size, a boric acid product with a fast dissolution rate, high purity and high moisture absorption stability can be obtained, thereby improving the quality of the boric acid product. Moreover, the boric acid product for a nuclear power plant primary circuit provided by the present invention, a preparation method and an application thereof, by using a high-quality boric acid product in a nuclear device, facilitates the boric acid product to effectively control the fission reaction of nuclear fuel, thereby optimizing the operation of the nuclear device.

[0070] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a boric acid product for a primary circuit of a nuclear power plant, characterized in that: At least the following steps are included: Providing a boric acid mother solution; Filtering the boric acid mother liquor to obtain an intermediate boric acid mother liquor; Under vacuum, the intermediate boric acid mother liquor is subjected to low-temperature stirring and drying to obtain boric acid crystals; Under vacuum conditions, further airflow drying the boric acid crystals to obtain boric acid particles; as well as The boric acid particles with a preset particle size are screened out to obtain a boric acid product.

2. The method for preparing the boric acid product according to claim 1, characterized in that: The pore size of the filter membrane when filtering the boric acid mother liquor is less than or equal to 0.4 μm.

3. The method for preparing the boric acid product according to claim 1, characterized in that: When low-temperature stirring drying is carried out, at least the following steps are included: After placing the intermediate boric acid mother liquor in a crystallization device, the crystallization device is evacuated, and the gas in the crystallization device is discharged from the vacuum outlet of the crystallization device, and the absolute pressure in the crystallization device is maintained at a preset absolute pressure; Stirring and heating the intermediate boric acid mother liquor in the crystallization device to a preset temperature; and When the temperature of the gas discharged from the vacuum outlet is lower than the preset temperature by a preset temperature and the dew point of the gas discharged from the vacuum outlet reaches the preset dew point, the step of airflow drying is entered.

4. The method for preparing the boric acid product according to claim 3, characterized in that: The preset temperature is less than 70°C, the stirring speed is 10r / min to 100r / min, the preset absolute pressure is less than or equal to 30Kpa, the set temperature is greater than 10°C, and the preset dew point is less than or equal to 0°C.

5. The method for preparing the boric acid product according to claim 3, characterized in that: When performing the airflow drying, at least the following steps are included: Maintaining the preset absolute pressure, the preset temperature and the stirring speed, and introducing airflow into the crystallization device; The stirring speed is reduced, and the airflow further dries the boric acid crystals to obtain the boric acid particles; as well as When the dew point of the gas discharged from the vacuum outlet is stable, the boric acid particles are manually sampled and analyzed for purity at regular intervals until the purity of the boric acid particles is qualified, and then the introduction of the gas flow, stirring and heating are stopped.

6. The method for preparing the boric acid product according to claim 5, characterized in that: The stirring speed is reduced to 10 r / min to 60 r / min, the gas flow is clean nitrogen, inert gas or compressed air, and the dew point of the gas flow is lower than -30°C.

7. The method for preparing the boric acid product according to claim 1, characterized in that: The preset particle size is 0.1 mm to 1.2 mm, and the boric acid product is spherical.

8. The method for preparing a boric acid product according to claim 1, characterized in that: In the boric acid product, the content of the boric acid particles with the preset particle size is greater than 98 wt %.

9. A boric acid product for a nuclear power plant primary circuit, characterized in that: A boric acid product obtained by the preparation method according to any one of claims 1 to 8.

10. A nuclear device, characterized in that: The boric acid product for the primary circuit of a nuclear power plant as claimed in claim 9 is used as a neutron absorption control material.

Images