A nuclear power plant wet maintenance composition, its preparation method and use

Abstract

The application discloses a preparation method of a nuclear power plant wet maintenance composition, and comprises the following steps: adding carbazone and a catalyst into water, adding a pH regulator after dissolving, dissolving and standing to obtain the nuclear power plant wet maintenance composition; the molecular structural formula of the carbazone is CON4H5R, wherein R is -C x H y , x is a natural number greater than or equal to 0, and y is a natural number greater than or equal to 1. The preparation method of the nuclear power plant wet maintenance composition adopts the carbazone and a catalyst for accelerating the reduction rate of the carbazone, has lower ecological toxicity than hydrazine, and reaction products are mainly nitrogen, water and carbon dioxide, so that no harmful by-products are generated, and problems of the hydrazine used in the nuclear power plant steam generator wet maintenance stage, such as ecological toxicity and poor room temperature maintenance effect, can be solved.

Description

[0001] This application is a divisional application of the invention patent application filed on March 15, 2022, with application number 2022102543810 and invention title "A composition for wet maintenance of nuclear power plants and a method for wet maintenance of nuclear power plants". Technical Field

[0002] This invention relates to the field of nuclear power plant secondary loop maintenance technology, and more particularly to a method for preparing a composition for wet maintenance of nuclear power plant steam generators as a substitute for hydrazine, the composition for wet maintenance of nuclear power plants prepared by the method, and the application of the composition in wet maintenance of nuclear power plants. Background Technology

[0003] The steam generator in a nuclear power plant is a key piece of equipment for radioactive isolation and heat exchange in the primary and secondary loops. The heat transfer tubes of the steam generator are typically made of nickel-based alloys or nickel-chromium-iron alloys, which offer good corrosion resistance. However, structural components such as the steam generator shell are primarily made of carbon steel, which is highly susceptible to oxygen corrosion during long-term shutdowns of the nuclear power plant, producing porous corrosion products. Upon restarting, these corrosion products will be shed by the circulating pumps, affecting the long-term stable operation of the unit.

[0004] To inhibit oxygen absorption corrosion of carbon steel materials in steam generators during long-term shutdowns, wet maintenance is generally carried out by adding reducing preservative solutions.

[0005] For example, Chinese invention patent application with publication number CN111575718A discloses a wet maintenance method for the secondary loop of a nuclear power plant during shutdown, which maintains the reducing environment of the entire secondary loop system by adding 50-600 mg / kg hydrazine maintenance solution.

[0006] However, hydrazine maintenance solutions have the following drawbacks: at room temperature, hydrazine reacts slowly with oxygen, resulting in poor maintenance; hydrazine is ecotoxic, and direct discharge poses a long-term potential hazard to the environment. The new U.S. Occupational Safety and Health Act (OSHA), which came into effect in 1985, has officially listed hydrazine as a toxic substance, and the National Institute for Occupational Safety and Health (NIOSH) has classified it as a suspected carcinogen. The EU's REACH regulation lists hydrazine as a toxic and carcinogenic substance, limiting occupational exposure concentrations to 0.1 mg / kg in 2019 and further tightening the limit to 0.01 mg / kg in 2020.

[0007] With increasingly stringent environmental protection requirements in China in recent years, the "Water Ten Measures," the Marine Environmental Protection Law, and the Water Pollution Prevention and Control Law have been successively promulgated and implemented. According to the national occupational health standard GBZ2.1-2019, the domestic occupational exposure limit for hydrazine is approximately 0.046 mg / kg, close to the latest EU standard. Therefore, there is an urgent need to develop a hydrazine alternative for wet maintenance of nuclear power plant steam generators to reduce the ecotoxicity of the maintenance solution and improve the effectiveness of room temperature maintenance. Summary of the Invention

[0008] In view of this, in order to overcome the shortcomings of the prior art, the object of the present invention is to provide a method for preparing a composition for wet maintenance of nuclear power plants as an alternative to hydrazine, and the application of the composition for wet maintenance of nuclear power plants in the wet maintenance stage of nuclear power plants.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A composition for wet maintenance in nuclear power plants, comprising carbazone, a pH adjuster, a catalyst, and water, wherein the carbazone comprises 0.5%-2% by mass, the catalyst is used to accelerate the reduction reaction rate of carbazone, and the pH adjuster is used to adjust the composition to be alkaline. Preferably, the carbazone comprises 0.7%-1.8% by mass.

[0011] According to some embodiments of the present invention, the molecular structural formula of the carbazone is CON4H5R, wherein R is -C x H y In this equation, x is a natural number greater than or equal to 0, and y is a natural number greater than or equal to 1. When x is 0 and y is 1, carbazone has its simplest molecular structure, CON4H6; when x is not 0, it is a hydrocarbon carbazone. In some embodiments, CON4H6 is preferred as the carbazone. When the temperature is below 135°C, carbazone reacts with oxygen to produce nitrogen, water, and carbon dioxide, as shown in the following equation: CON4H6 + 2O2 = 2N2 + 3H2O + CO2.

[0012] According to some embodiments of the present invention, the carbazone is generated by a condensation reaction between hydrazine and a carbonyl group. The reaction equations are as follows: 2C2H5RCO + N2H4 = C2H6C2N2C2H5R + 2H2O; when R is -H, 2C2H6CO + N2H4 = C2H6C2N2C2H6 + 2H2O.

[0013] According to some embodiments of the invention, the mass percentage of the catalyst in the composition is 0.01%-0.2%.

[0014] According to some embodiments of the present invention, the catalyst is hydroxybenzene, which combines low toxicity and high catalytic efficiency.

[0015] According to some embodiments of the present invention, the catalyst is o-dihydroxybenzene and / or p-dihydroxybenzene, which combines low toxicity and high catalytic efficiency.

[0016] At room temperature, the reaction rate of carbazone with oxygen is slow, requiring the addition of hydroxybenzene as a catalyst. Its molecular formula is C6H6O. x When x is 2, the molecular structure of hydroxybenzene is C6H6O2, including o-dihydroxybenzene and p-dihydroxybenzene. The preferred catalyst is p-dihydroxybenzene, which has the highest catalytic efficiency. The concentration of p-dihydroxybenzene is 0.01%-0.2%, with a preferred concentration of 0.03%-0.18%. Concentration refers to the mass percentage in the system.

[0017] Carbazone and p-dihydroxybenzene react with oxygen at room temperature at a higher rate than hydrazine, which can improve the room temperature maintenance effect during the wet maintenance stage of nuclear power plant steam generators. Moreover, carbazone and p-dihydroxybenzene have lower ecotoxicity than hydrazine, about 1 / 5 of the ecotoxicity of hydrazine. Using this hydrazine substitute can reduce the inhalation risk to operators during the dosing process, and at the same time reduce the ecotoxicity of liquid effluents from nuclear power plants, which is significantly better than other hydroxybenzenes.

[0018] According to some embodiments of the invention, the pH adjuster in the composition is 0.05%-0.2% by mass.

[0019] According to some embodiments of the present invention, the pH adjuster is an ammonia-based substance, which can adjust the vapor-liquid distribution ratio as needed.

[0020] According to some embodiments of the present invention, the pH adjuster is one or more combinations selected from inorganic ammonia, ethanolamine, and morpholine, capable of adjusting the vapor-liquid distribution ratio as needed. In some embodiments of the present invention, inorganic ammonia is preferred as the pH adjuster, which can provide the maximum vapor-liquid distribution ratio and ensure the maintenance effect of the vapor-side space. Preferably, the concentration of inorganic ammonia in the composition (i.e., the mass percentage of inorganic ammonia in the system) is 0.07%-0.18%. The inorganic ammonia is ammonia water.

[0021] According to some embodiments of the present invention, when the composition is used in the wet maintenance of a nuclear power plant, the concentration of carbazone in the secondary loop system is controlled to be 90-120 mg / kg and the pH value of the secondary loop system is controlled to be 10.0-10.5; preferably, the concentration of carbazone in the secondary loop system is 105-120 mg / kg, that is, the concentration of carbazone in the system is controlled to be not less than 105 mg / kg.

[0022] In some embodiments of the present invention, the components in the composition for wet maintenance of nuclear power plants are in the following proportions by mass percentage: 0.5%-2% carbazone, 0.01%-0.2% catalyst, 0.05%-0.2% pH adjuster, and the balance (97.6%-99.44%) water, to ensure the homogeneity and stability of the composition.

[0023] When the temperature is below 135°C, carbazone reacts with oxygen to produce nitrogen, water, and carbon dioxide, as shown in the following equation: CON4H6 + 2O2 = 2N2 + 3H2O + CO2. When the temperature is above 135°C, carbazone hydrolyzes to produce hydrazine and carbon dioxide, as shown in the following equation: CON4H6 + H2O = 2N2H4 + CO2; hydrazine reacts with oxygen to produce nitrogen and water, as shown in the following equation: N2H4 + O2 = N2 + 2H2O; under high-temperature conditions (when the temperature is below 300°C), p-dihydroxybenzene reacts with oxygen to produce water and carbon dioxide, as shown in the following equation: 2C6H6O2 + 13O2 = 12CO2 + 6H2O. Therefore, the reaction products of the composition used to replace hydrazine in this invention are mainly nitrogen, water, and carbon dioxide, with no harmful byproducts, making it superior to other hydroxybenzenes. Another object of this invention is to provide an application of the composition described above in the wet maintenance of nuclear power plants.

[0024] Hydrazine is volatile and can easily cause inhalation during dosing, leading to toxic inhalation; while carbazone is not volatile, thus preventing toxic inhalation.

[0025] Another object of the present invention is to provide a method for preparing the composition for wet maintenance of nuclear power plants as described above, comprising the following steps:

[0026] Step 1: Add demineralized water to the preparation container and maintain the temperature at 25℃~30℃ using a constant temperature water bath;

[0027] Step 2: Add carbazone and catalyst to the demineralized water from Step 1, and stir thoroughly to dissolve for 10 minutes;

[0028] Step 3: Add pH adjuster to the solution obtained in Step 2 and stir thoroughly to dissolve. Stir for 10 minutes and then let stand for 1 hour to obtain the hydrazine substitute product composition for wet maintenance of nuclear power plant steam generators.

[0029] Another object of the present invention is to provide an application of carbazone in wet maintenance of nuclear power plants, comprising the step of adding carbazone to the secondary loop system of a nuclear power plant for wet maintenance, wherein the concentration of carbazone in the secondary loop system is 90-120 mg / kg, and the pH of the system is controlled at 10.0-10.5. In some embodiments, it is preferable to control the concentration of carbazone in the secondary loop system at 105-120 mg / kg.

[0030] Another object of the present invention is to provide an application of the composition described above in wet maintenance of nuclear power plants.

[0031] Another object of the present invention is to provide a wet maintenance method for a nuclear power plant, comprising the following steps:

[0032] Step 1) Purge the secondary side of the steam generator;

[0033] Step 2) Fill the secondary side of the steam generator with a wet maintenance solution, and adjust the carbazone concentration in the system to be not less than 105 mg / kg and the pH to be 10-10.5; the wet maintenance solution is formed by diluting the composition for wet maintenance of nuclear power plants as described above;

[0034] Step 3) Regularly monitor the carbazone concentration and pH value in the system, and ensure that the carbazone concentration in the system is not less than 105 mg / kg and the pH is between 10 and 10.5 by adding the above-mentioned wet maintenance composition for nuclear power plants in a timely manner.

[0035] Due to the adoption of the above technical solutions, the advantages of the present invention compared with the prior art are as follows: The composition for wet maintenance of nuclear power plants of the present invention uses carbazone and a catalyst to accelerate its reduction rate. Its ecotoxicity is lower than that of hydrazine, and the reaction products are mainly nitrogen, water and carbon dioxide, without producing harmful by-products. It can solve the problems of ecotoxicity and poor room temperature maintenance effect of hydrazine in the wet maintenance stage of nuclear power plant steam generators. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used 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 those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of a wet maintenance method for a nuclear power plant in a preferred embodiment of the present invention. Detailed Implementation

[0038] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] The main objective of this invention is to provide a hydrazine substitute product for the wet maintenance stage of a nuclear power plant steam generator. The hydrazine substitute composition product includes carbazone, a pH adjuster, a catalyst, and water, wherein the concentration of the hydrocarbon carbazone is 0.5%-2%, the concentration of the catalyst is 0.01%-0.2%, the concentration of the pH adjuster is 0.05%-0.2%, and the concentration of water is 97.6%-99.44%.

[0040] The main component of the hydrazine substitute involved is carbazone. Carbazone is formed by the condensation reaction between hydrazine and a carbonyl group, and its molecular formula is CON4H5R. Here, R is an alkyl group (-C). x H y When x is 0 and y is 1, the alkyl carbazone has the simplest molecular structure, CON4H6. At temperatures below 135°C, carbazone reacts with oxygen to produce nitrogen, water, and carbon dioxide, as shown in the following equation: CON4H6 + 2O2 = 2N2 + 3H2O + CO2. The carbazone concentration involved in this invention is 0.5%-2%, with a preferred concentration of 0.7%-1.8%.

[0041] The preferred catalyst in this invention is hydroxybenzene. At room temperature, the reaction rate of carbazone with oxygen is slow, necessitating the addition of hydroxybenzene as a catalyst; its molecular formula is C6H6O. x When x is 2, the molecular structure of hydroxybenzene is C6H6O2, including o-dihydroxybenzene and p-dihydroxybenzene. The preferred catalyst is p-dihydroxybenzene, with a concentration of 0.01%-0.2%, and more preferably 0.03%-0.18%.

[0042] The preferred pH adjuster of this invention is an ammonia-based substance, including ammonia water, ethanolamine, morpholine, etc. The preferred ammonia-based substance is ammonia water, and the concentration of ammonia water in the composition is 0.05%-0.2%, preferably 0.07%-0.18%.

[0043] The carbazone and p-dihydroxybenzene used in this invention have a higher reaction rate with oxygen at room temperature than hydrazine, which can improve the room temperature maintenance effect during the wet maintenance stage of nuclear power plant steam generators. Carbazone and p-dihydroxybenzene have lower ecotoxicity than hydrazine, approximately one-fifth of the ecotoxicity of hydrazine. Using this hydrazine substitute can reduce the inhalation risk to operators during chemical dosing and also reduce the ecotoxicity of liquid effluents from nuclear power plants. Furthermore, carbazone and p-dihydroxybenzene do not produce harmful byproducts during maintenance. At temperatures below 135°C, carbazone reacts with oxygen to produce nitrogen, water, and carbon dioxide; at temperatures above 135°C, carbazone hydrolyzes to produce hydrazine and carbon dioxide, as shown in the following equation: CON4H6 + H2O = 2N2H4 + CO2; under high-temperature conditions, p-dihydroxybenzene reacts with oxygen to produce water and carbon dioxide, as shown in the following equation: 2C6H6O2 + 13O2 = 12CO2 + 6H2O. The reaction products of the hydrazine substitute product involved in this invention are mainly nitrogen, water and carbon dioxide, with no harmful byproducts.

[0044] The technical solution of the present invention is described below with reference to specific embodiments:

[0045] Example 1: Composition for wet maintenance of nuclear power plants and its preparation method

[0046] The composition for wet maintenance of nuclear power plants in this embodiment comprises the following raw material components in weight percentage: 0.7% carbazone, 0.03% catalyst, 0.07% pH adjuster, and 99.2% water.

[0047] The molecular formula of carbazone is CON4H6, the catalyst is p-dihydroxybenzene, and the pH adjuster is ammonia.

[0048] The above-mentioned composition for wet maintenance of nuclear power plants is prepared by the following method:

[0049] Step 1: Add 99.2 parts of demineralized water to the preparation container and maintain it at 25°C using a constant temperature water bath;

[0050] Step 2: Add 0.7 parts of carbazone and 0.03 parts of p-dihydroxybenzene to the deionized water from Step 1, and stir thoroughly to dissolve for 10 minutes;

[0051] Step 3: Add 0.07 parts of ammonia water to the mixed solution obtained in Step 2, and stir thoroughly to dissolve. Stir for 10 minutes, and then let stand for 1 hour to obtain the hydrazine substitute product composition for wet maintenance of nuclear power plant steam generators.

[0052] Example 2: Composition for wet maintenance of nuclear power plants and its preparation method

[0053] The composition for wet maintenance of nuclear power plants in this embodiment comprises the following raw material components in weight percentage: 1.8% carbazone, 0.18% catalyst, 0.18% pH adjuster, and 97.84% water.

[0054] The molecular formula of carbazone is CON4H6, the catalyst is p-dihydroxybenzene, and the pH adjuster is ammonia.

[0055] The above-mentioned composition for wet maintenance of nuclear power plants is prepared by the following method:

[0056] Step 1: Add 97.84 parts of demineralized water to the preparation container and maintain it at 25°C using a constant temperature water bath;

[0057] Step 2: Add 1.8 parts of carbazone and 0.18 parts of p-dihydroxybenzene to the deionized water from Step 1, and stir thoroughly to dissolve for 10 minutes;

[0058] Step 3: Add 0.18 parts of ammonia water to the mixed solution obtained in Step 2, and stir thoroughly to dissolve. Stir for 10 minutes, and then let stand for 1 hour to obtain the hydrazine substitute product composition for wet maintenance of nuclear power plant steam generators.

[0059] Example 3: Composition for wet maintenance of nuclear power plants and its preparation method

[0060] The composition for wet maintenance of nuclear power plants in this embodiment comprises the following raw material components in weight percentage: 0.5% carbazone, 0.01% catalyst, 0.05% pH adjuster, and 99.44% water.

[0061] Among them, carbazone is a hydrocarbon carbazone with the molecular formula CON4H5CH3, the catalyst is o-dihydroxybenzene, and the pH adjuster is ethanolamine.

[0062] The above-mentioned composition for wet maintenance of nuclear power plants is prepared by the following method:

[0063] Step 1: Add 99.44 parts of demineralized water to the preparation container and maintain it at 25°C using a constant temperature water bath;

[0064] Step 2: Add 0.5 parts of alkyl carbazone and 0.01 parts of o-dihydroxybenzene to the deionized water from Step 1, and stir thoroughly to dissolve for 10 minutes.

[0065] Step 3: Add 0.05 parts of ethanolamine to the mixed solution obtained in Step 2, and stir thoroughly to dissolve for 10 minutes. Then let it stand for 1 hour to obtain the hydrazine substitute product composition for wet maintenance of nuclear power plant steam generators.

[0066] Example 4: Composition for wet maintenance of nuclear power plants and its preparation method

[0067] The composition for wet maintenance of nuclear power plants in this embodiment comprises the following raw material components in weight percentage: 2% carbazone, 0.2% catalyst, 0.2% pH adjuster, and 97.6% water.

[0068] Among them, carbazone is a hydrocarbon carbazone with the molecular formula CON4H5CH3, the catalyst is a mixture of o-dihydroxybenzene and p-dihydroxybenzene, each accounting for half; the pH adjuster is morpholine.

[0069] The above-mentioned composition for wet maintenance of nuclear power plants is prepared by the following method:

[0070] Step 1: Add 97.6 parts of demineralized water to the preparation container and maintain it at 25°C using a constant temperature water bath;

[0071] Step 2: Add 2 parts of alkyl carbazone, 0.1 parts of o-dihydroxybenzene, and 0.1 parts of p-dihydroxybenzene to the deionized water from Step 1 in sequence, and stir thoroughly to dissolve for 10 minutes;

[0072] Step 3: Add 0.2 parts of morpholine to the mixed solution obtained in Step 2, and stir thoroughly to dissolve. Stir for 10 minutes, and then let stand for 1 hour to obtain the hydrazine substitute product composition for wet maintenance of nuclear power plant steam generators.

[0073] Example 5: Composition for wet maintenance of nuclear power plants and its preparation method

[0074] The composition for wet maintenance of nuclear power plants in this embodiment differs from that in Example 2 in that the carbazone in this embodiment is a hydrocarbon carbazone with the molecular structural formula CON4H5CH3. The preparation methods of other components and the composition are basically the same as those in Example 2.

[0075] Example 6: Wet Maintenance Method for Nuclear Power Plants

[0076] like Figure 1 As shown, this embodiment provides a method for wet maintenance of a nuclear power plant based on the composition for wet maintenance of nuclear power plants in Examples 1-5, specifically including the following steps:

[0077] Step 1: Purge the secondary side of the steam generator;

[0078] Step 2: Fill the secondary side of the steam generator with wet maintenance solution, which is formed by diluting the composition for wet maintenance of nuclear power plants in Examples 1-5 and the preferred Example 2; the specific dilution ratio is determined according to the monitoring indicators: the target concentration of carbazone in the system is adjusted to 105-120 mg / kg and not lower than 105 mg / kg, and the target pH value is 10-10.5;

[0079] Step 3: Regularly monitor the carbazone concentration and pH in the wet maintenance solution, and ensure that the carbazone concentration in the system is not less than 105 mg / kg and the pH is between 10 and 10.5 by adding the wet maintenance composition for nuclear power plants in Examples 1-5 in a timely manner.

[0080] Comparative Example 1

[0081] The maintenance solution composition in this comparative example comprises 0.075 parts hydrazine, 0.018 parts ammonia water, and 99.907 parts demineralized water, which are mixed evenly to obtain the final product.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 2 is that the carbazone in Example 2 is replaced with a substance with the following molecular structure: C4H 11 NO, the other components and preparation methods are basically the same as in Example 2.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 2 is that the catalyst in Example 2 is replaced with CoO. The other components and preparation methods are basically the same as in Example 2.

[0086] Comparative Example 4

[0087] The difference between this comparative example and Example 2 is that the pH adjuster in Example 2 is replaced with sodium hydroxide. The other components and preparation methods are basically the same as in Example 2.

[0088] Comparative Example 5

[0089] The difference between this comparative example and Example 2 is that the composition in this comparative example does not contain a catalyst. The other components and preparation methods are basically the same as in Example 2.

[0090] Comparative Example 6

[0091] The composition in this comparative example is the same as that in Example 2. The difference is that in the subsequent testing process, the pH value of the system was controlled to be around 8 and the carbazone concentration was 80 mg / kg.

[0092] Tests and Discussions

[0093] Using the compositions from the above examples and comparative examples, the dissolved oxygen concentration (in mg / kg) in three solutions was measured online over time in a closed self-circulating container. The results illustrate the deoxygenation effect of the hydrazine substitute composition for wet maintenance of nuclear power plant steam generators prepared in the examples. The experimental results are shown in Table 1.

[0094] Table 1 Test Results

[0095]

[0096]

[0097] As shown in Table 1, the hydrazine substitute product prepared in Example 2 exhibits excellent deoxygenation effects in a shorter time, and is superior to traditional hydrazine maintenance solutions. The carbazone used in this invention has strong reducing properties; under the catalysis of hydroxybenzene, the reduction effect is enhanced. Simultaneously, the addition of a pH adjuster ensures the anti-corrosion effect of the maintenance solution. Applying the above-mentioned hydrazine substitute product to the wet maintenance of nuclear power plant steam generators offers advantages such as low toxicity, high efficiency, and no harmful byproducts.

[0098] The wet maintenance composition for nuclear power plants in this invention exhibits good maintenance effects at room temperature: the reaction rate of carbazone and p-dihydroxybenzene with oxygen at room temperature is higher than that of hydrazine, achieving better room temperature maintenance results; low ecotoxicity: the ecotoxicity of carbazone and p-dihydroxybenzene is far lower than that of hydrazine, approximately 1 / 5 of the ecotoxicity of hydrazine. Using this hydrazine substitute reduces the inhalation risk to operators during chemical dosing and also reduces the ecotoxicity of liquid effluents from nuclear power plants; no harmful byproducts are produced: the reaction products of carbazone and p-dihydroxybenzene are mainly nitrogen, water, and carbon dioxide, without producing harmful byproducts.

[0099] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a composition for wet maintenance of nuclear power plants, characterized in that, Includes the following steps: Carbazone and catalyst were added to water, dissolved, and then a pH adjuster was added. The mixture was dissolved and allowed to stand to obtain the composition for wet maintenance of nuclear power plants. The molecular structural formula of the carbazone is CON4H5R, where R is -C. x H y x is a natural number greater than or equal to 0, and y is a natural number greater than or equal to 1; The catalyst is o-dihydroxybenzene and / or p-dihydroxybenzene, and the pH adjuster is an ammonia-based substance; The composition contains 0.7%-1.8% carbazone by mass; the composition contains 0.01%-0.2% catalyst by mass; and the composition contains 0.05%-0.2% pH adjuster by mass.

2. The preparation method according to claim 1, characterized in that, The water is demineralized water at a temperature of 25℃~30℃; the dissolution process involves stirring for 5~15 minutes.

3. The preparation method according to claim 1, characterized in that, The carbazone is generated by the condensation reaction between hydrazine and carbonyl group.

4. The preparation method according to claim 1, characterized in that, The composition comprises, by weight percentage: 0.7%-1.8% carbazone, 0.01%-0.2% catalyst, 0.05%-0.2% pH adjuster, and the balance being water.

5. The preparation method according to claim 1, characterized in that, The catalyst is used to accelerate the reduction rate of carbazone.

6. The preparation method according to claim 1 or 5, characterized in that, The catalyst is p-dihydroxybenzene, and the concentration of p-dihydroxybenzene in the composition is 0.03%-0.18%.

7. The preparation method according to claim 1, characterized in that, The pH adjuster is used to adjust the composition to be alkaline.

8. The preparation method according to claim 7, characterized in that, The pH adjuster is selected from one or more combinations of inorganic ammonia, ethanolamine, and morpholine.

9. The preparation method according to claim 1 or 7, characterized in that, The pH adjuster is inorganic ammonia, and the concentration of inorganic ammonia in the composition is 0.07%-0.18%.

10. The preparation method according to claim 9, characterized in that, The inorganic ammonia is ammonia water.

11. A composition for wet maintenance of nuclear power plants prepared by the preparation method according to any one of claims 1-10.

12. The application of the composition for wet maintenance of nuclear power plants as described in claim 11 in the wet maintenance of nuclear power plants, characterized in that, The concentration of carbazone in the secondary loop system is 90-120 mg / kg; the pH value of the secondary loop system is maintained at 10-10.5.

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