Chemical cleaning agent and cleaning method for secondary side of high-temperature gas cooled reactor steam generator

Abstract

The invention discloses a chemical cleaning agent for a secondary side of a high-temperature gas cooled reactor steam generator and a cleaning method, and the chemical cleaning agent and the cleaning method have good solubility on corrosion products and sediments on the secondary side of the high-temperature gas cooled reactor steam generator. And meanwhile, corrosion of the metal matrix can be controlled within a design acceptable range and a safety range, local corrosion of the metal matrix, such as pitting corrosion, intergranular corrosion, stress corrosion and galvanic corrosion, is completely inhibited, and the corrosion inhibitor has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical cleaning of nuclear power units, and in particular relates to a chemical cleaning agent and a cleaning method for the secondary side of a high-temperature gas-cooled reactor steam generator. Background Art

[0002] The high temperature gas-cooled reactor is a fourth-generation nuclear power technology and an advanced reactor type with inherent safety. It has broad application prospects in power generation, heating, hydrogen production, seawater desalination and other fields. Compared with the pressurized water reactor nuclear power unit, the steam pressure and temperature of the secondary outlet of the high temperature gas-cooled reactor reach 14.3MPa and 570℃ respectively, which are much higher than the 6.71MPa and 283℃ of the pressurized water reactor, and the material grade is also higher; secondly, the steam generator of the high temperature gas-cooled reactor is a coil structure without a sewage discharge device. Based on the structural characteristics of the high temperature gas-cooled reactor steam generator, the corrosion products generated by the water supply system during operation will be brought into the steam generator and deposited in the secondary side of the steam generator heat transfer tube, causing the thermal conductivity of the steam generator heat transfer tube to decrease, and even the heat transfer tube blockage and rupture accident caused by the peeling of the deposits may occur. Chemical cleaning, as a cleaning method for boiler equipment in thermal power plants, has the advantages of mature technology, easy operation and good cleaning effect. It is an effective technology for cleaning high temperature gas-cooled reactor steam generators.

[0003] However, the high-temperature gas-cooled reactor steam generator adopts a complex coil structure, which has the risk of residual stress. Secondly, the steam generator adopts heterogeneous metal welding with very different grades of T22 and Incoloy-800H, and is equipped with a throttling component of nickel-based alloy. It is necessary to effectively control the stress corrosion, intergranular corrosion and galvanic corrosion of the steam generator heat transfer tube during the chemical cleaning process. If the cleaning agent and cleaning method are not selected properly, it will cause local corrosion or even damage to the heat exchange tube. Since the primary side is in a standby state during the cleaning period and is under normal pressure, the cleaning fluid will enter the primary side from the secondary side of the steam generator, severely corroding the primary side equipment and causing a major nuclear safety accident. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a chemical cleaning agent for the secondary side of a high temperature gas-cooled reactor steam generator, wherein: the components of the chemical cleaning agent include, by mass percentage, 3.0-10.0% of a descaling agent, 0.1-1.0% of a cosolvent, 0.3%-1.0% of a corrosion inhibitor, 0.05-0.5% of a reducing agent, and the rest is pure water;

[0007] Wherein, the descaling agent is composed of a mixture of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid;

[0008] The cosolvent comprises one or more of diisooctyl maleate sulfonate, sodium polyoxyethylene ether sulfonate, and diethanol monoisopropanolamine;

[0009] The corrosion inhibitor is composed of water-soluble sodium benzotriazole, 2-thiol benzothiazole, and oily hydroxyethyl imidazoline;

[0010] The reducing agent includes one of beta-mercaptoethanol, hydrazine and acetone oxime.

[0011] As a preferred solution of the secondary side chemical cleaning agent for the high temperature gas-cooled reactor steam generator described in the present invention, the mass percentage of ethylenediaminetetraacetic acid in the descaling agent is 50% to 70%, and the mass percentage of diethylenetriaminepentaacetic acid is 30% to 50%.

[0012] As a preferred embodiment of the chemical cleaning agent for the secondary side of a high-temperature gas-cooled reactor steam generator described in the present invention, in which: in the corrosion inhibitor, the mass percentage of water-soluble sodium benzotriazole is 50% to 60%, the mass percentage of 2-thiolbenzothiazole is 30% to 40%, and the mass percentage of oily hydroxyethyl imidazoline is 10%.

[0013] Another object of the present invention is to overcome the deficiencies in the prior art and provide a method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator, which comprises: using the chemical cleaning agent, and also comprising:

[0014] The pH of the chemical cleaning agent is adjusted with liquid ammonia, and the secondary side components of the high temperature gas-cooled reactor steam generator are cleaned under closed conditions.

[0015] As a preferred solution of the method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator of the present invention, the pH value of the chemical cleaning agent is 8.5-9.5.

[0016] As a preferred embodiment of the method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator of the present invention, the cleaning temperature is 110-130°C.

[0017] As a preferred solution of the method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator according to the present invention, the cleaning time is 24 to 48 hours.

[0018] As a preferred solution of the method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator of the present invention, after cleaning with the chemical cleaning agent, the descaling rate of the secondary side components of the high temperature gas-cooled reactor steam generator is 98.2-99.7%.

[0019] As a preferred solution of the method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator of the present invention, the cleaning residue rate of the secondary side components of the high temperature gas-cooled reactor steam generator is 2.1-7.8% after cleaning with the chemical cleaning agent.

[0020] As a preferred solution of the cleaning method of the secondary side of the high temperature gas-cooled reactor steam generator of the present invention, wherein: the uniform corrosion rate of the secondary side components of the high temperature gas-cooled reactor steam generator is 0.01-0.33 g / (m 2 h), and there is no pitting corrosion, intergranular corrosion and stress corrosion.

[0021] Beneficial effects of the present invention:

[0022] (1) The chemical cleaning agent and cleaning method for the secondary side of a high temperature gas-cooled reactor steam generator of the present invention have little peeling property for the iron oxide layer generated during operation during the cleaning process; under the cleaning conditions, there is no pitting corrosion on T22 low alloy steel, Incoloy 800H nickel-based alloy and T22-Incoloy 800H welds, and there is no intergranular corrosion and stress corrosion on Incoloy 800H nickel-based alloy and T22-Incoloy 800H welds loaded with ultimate stress.

[0023] (2) Under cleaning conditions, the uniform corrosion rate of all metals is controlled within the design acceptable range and safety range, meeting the requirements of relevant power industry standards; under cleaning conditions, the galvanic corrosion rate of T22-Incoloy 800H dissimilar steel welding parts meets the requirements of relevant power industry standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0025] Figure 1 This is a corrosion diagram of the weld corrosion indicator sheet before and after chemical cleaning in Example 1 of the present invention.

[0026] Figure 2 This is a 500-fold magnified metallographic micrograph of the weld corrosion indicator sheet after cleaning in Example 1 of the present invention.

[0027] Figure 3 This is a diagram showing the corrosion condition of the corrosion indicator sheet before and after chemical cleaning in Comparative Example 1 of the present invention.

[0028] Figure 4 This is a 500-fold magnified metallographic micrograph of the weld curved beam after cleaning in Comparative Example 1 of the present invention.

[0029] Figure 5 This is a diagram showing the corrosion condition of the corrosion indicator sheet before and after chemical cleaning in Comparative Example 2 of the present invention.

[0030] Figure 6 This is a 500-fold magnified metallographic micrograph of the weld curved beam after cleaning in Comparative Example 2 of the present invention.

[0031] Figure 7 This is a 500-fold magnified metallographic micrograph of the weld curved beam after cleaning in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0033] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0034] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0035] The corrosion rate detection method of the present invention is as follows: 1) according to the requirements of DL / T 523-2017 chemical cleaning corrosion inhibitor application performance evaluation index and test method and GB / T 15970.2-2000 Corrosion of metals and alloys_Stress corrosion test_Part 2 Preparation and application of bent beam specimens, T22 low alloy steel, Incoloy800H nickel-based alloy, T22-Incoloy800H weld corrosion indicator sheets with a size of 50mm*8mm*2mm are prepared, and Incoloy 800H and T22-Incoloy 800H bent beam specimens with a bent beam size of 130mm*8mm*2mm are prepared; 2) stress is applied to the bent beam specimens by a four-point bent beam method according to a bending deflection of 1.76mm, and T22 low alloy steel, Incoloy 800H nickel-based alloy, T22-Incoloy 800H weld corrosion indicator sheet was weighed, and then hung in the cleaning agent together with the bent beam sample for heating and cleaning; 3) After cleaning, the T22 low alloy steel, Incoloy800H nickel-based alloy, and T22-Incoloy 800H weld corrosion indicator sheets were weighed, and the uniform corrosion rate was calculated based on the mass difference before and after and the surface area; 4) The surface of the T22 low alloy steel, Incoloy 800H nickel-based alloy, and T22-Incoloy 800H weld corrosion indicator sheet was observed using a metallographic microscope to check for pitting corrosion; the center area of ​​the Incoloy 800H and T22-Incoloy800H bent beams was observed to check for intergranular corrosion, stress corrosion, and galvanic corrosion.

[0036] Example 1

[0037] This embodiment provides a chemical cleaning agent and cleaning method for the secondary side of a high temperature gas-cooled reactor steam generator.

[0038] The components of the chemical cleaning agent include, by mass percentage, 5.0% of a descaling agent, 0.5% of a sodium diisooctyl maleate sulfonate cosolvent, 0.5% of a corrosion inhibitor, 0.3% of a β-mercaptoethanol reducing agent, and the remainder being pure water. Liquid ammonia is used to adjust the pH value of the cleaning agent to 8.5.

[0039] In the descaling agent, the mass proportion of ethylenediaminetetraacetic acid is 50%, and the mass proportion of diethylenetriaminepentaacetic acid is 50%; in the corrosion inhibitor, the mass proportion of water-soluble sodium benzotriazole is 50%, the mass proportion of 2-thiolbenzothiazole is 40%, and the mass proportion of oily hydroxyethylimidazoline is 10%.

[0040] Take 200 mL of the cleaning agent of this example, heat it to 120°C, and clean T22 and Incoloy800H spare tube samples (tube diameter is Length 5cm), clean for 24 hours.

[0041] After cleaning, the descaling rates of T22 and Incoloy 800H pipes were 99.1% and 99.3% respectively, and the cleaning residue rate was 5.1%.

[0042] Figure 1 The corrosion condition diagram of the weld corrosion indicator sheet before and after chemical cleaning, where (a) and (b) are the diagrams before and after Incoloy800H cleaning, (c) and (d) are the diagrams before and after T22 cleaning, and (e) and (f) are the diagrams before and after T22-Incoloy 800H cleaning. It can be seen that there is no pitting corrosion on the T22, Incoloy 800H, and T22-Incoloy 800H weld corrosion indicator sheets.

[0043] The corrosion rates of T22, Incoloy 800H, and T22-Incoloy 800H weld corrosion indicator sheets are 0.21 g / (m 2 ·h)、0.01g / (m 2 h) and 0.17g / (m 2 h); Figure 2 This is a 500x magnified metallographic micrograph of the weld corrosion indicator sheet after cleaning. It can be seen that no intergranular corrosion or stress corrosion is observed in the stress-loaded specimens of the Incoloy 800H and T22-Incoloy 800H welds under a 500x metallographic microscope.

[0044] Example 2

[0045] This embodiment provides a chemical cleaning agent and cleaning method for the secondary side of a high temperature gas-cooled reactor steam generator.

[0046] The components of the chemical cleaning agent include, by mass percentage, 8.0% of descaling agent, 0.8% of sodium polyoxyethylene ether sulfonate cosolvent, 0.8% of corrosion inhibitor, 0.1% of hydrazine reducing agent, and the rest is pure water. Liquid ammonia is used to adjust the pH value of the cleaning agent to 9.0.

[0047] In the descaling agent, the mass percentage of ethylenediaminetetraacetic acid is 60%, and the mass percentage of diethylenetriaminepentaacetic acid is 40%; in the corrosion inhibitor, the mass percentage of water-soluble sodium benzotriazole is 55%, the mass percentage of 2-thiolbenzothiazole is 35%, and the mass percentage of oily hydroxyethylimidazoline is 10%.

[0048] Take 200 mL of the cleaning agent of this example, raise the temperature to 130° C., and clean T22 and Incoloy 800H spare tube samples under closed conditions for 24 hours.

[0049] After cleaning, the descaling rates of T22 and Incoloy 800H pipes were 99.5% and 99.6% respectively, and the cleaning residue rate was 3.2%.

[0050] T22, Incoloy 800H, T22-Incoloy 800H weld corrosion indicator sheets have no pitting corrosion, and the corrosion rates are 0.29g / (m 2 ·h)、0.01g / (m 2 h) and 0.22g / (m 2 h), no intergranular corrosion and stress corrosion were observed in the stress-loaded specimens of Incoloy 800H and T22-Incoloy800H welds under a 500x metallographic microscope.

[0051] Example 3

[0052] This embodiment provides a chemical cleaning agent and cleaning method for the secondary side of a high temperature gas-cooled reactor steam generator.

[0053] The components of the chemical cleaning agent include, by mass percentage, 10.0% of a descaling agent, 0.5% of a diethanol monoisopropanolamine cosolvent, 1.0% of a corrosion inhibitor, 0.1% of an acetone oxime reducing agent, and the remainder being pure water. Liquid ammonia is used to adjust the pH value of the cleaning agent to 9.5.

[0054] In the descaling agent, the mass percentage of ethylenediaminetetraacetic acid is 70%, and the mass percentage of diethylenetriaminepentaacetic acid is 30%; in the corrosion inhibitor, the mass percentage of water-soluble sodium benzotriazole is 60%, the mass percentage of 2-thiolbenzothiazole is 30%, and the mass percentage of oily hydroxyethylimidazoline is 10%.

[0055] Take 200 mL of the cleaning agent of this example, raise the temperature to 130° C., and clean T22 and Incoloy 800H spare tube samples under closed conditions for 24 hours.

[0056] After cleaning, the descaling rates of T22 and Incoloy 800H pipes were 99.5% and 99.7% respectively, and the cleaning residue rate was 2.1%. There was no pitting corrosion on the T22, Incoloy 800H, and T22-Incoloy 800H weld corrosion indicator sheets, and the corrosion rates were 0.33 g / (m 2 ·h)、0.02g / (m 2 h) and 0.25g / (m 2 h), no intergranular corrosion or stress corrosion was observed in the stress-loaded specimens of Incoloy 800H and T22-Incoloy 800H welds under a 500x metallographic microscope.

[0057] Example 4

[0058] This embodiment provides a chemical cleaning agent and cleaning method for the secondary side of a high temperature gas-cooled reactor steam generator.

[0059] The components of the chemical cleaning agent include, by mass percentage, a descaling agent, 0.3% of a sodium polyoxyethylene ether sulfonate cosolvent, 0.5% of a diethanol monoisopropanolamine cosolvent, 0.3% of a corrosion inhibitor, 0.1% of a hydrazine reducing agent, and the rest being pure water. Liquid ammonia is used to adjust the pH value of the cleaning agent to 9.0.

[0060] In the descaling agent, the mass percentage of ethylenediaminetetraacetic acid is 60%, and the mass percentage of diethylenetriaminepentaacetic acid is 40%; in the corrosion inhibitor, the mass percentage of water-soluble sodium benzotriazole is 55%, the mass percentage of 2-thiolbenzothiazole is 35%, and the mass percentage of oily hydroxyethylimidazoline is 10%.

[0061] Take 200 mL of the cleaning agent of this example, raise the temperature to 110° C., and clean T22 and Incoloy 800H spare tube samples under closed conditions for 24 hours.

[0062] After cleaning, the descaling rates of T22 and Incoloy 800H pipes were 98.2% and 98.9% respectively, and the cleaning residue rate was 6.1%.

[0063] T22, Incoloy 800H, T22-Incoloy 800H weld corrosion indicator sheets have no pitting corrosion, and the corrosion rates are 0.21g / (m 2 ·h)、0.01g / (m 2 h) and 0.16g / (m 2 h), no intergranular corrosion and stress corrosion were observed in the stress-loaded specimens of Incoloy 800H and T22-Incoloy800H welds under a 500x metallographic microscope.

[0064] Example 5

[0065] This embodiment provides a chemical cleaning agent and cleaning method for the secondary side of a high temperature gas-cooled reactor steam generator.

[0066] The components of the chemical cleaning agent include, by mass percentage, 3.0% of a descaling agent, 0.5% of sodium diisooctyl maleate sulfonate cosolvent, 0.5% of sodium polyoxyethylene ether sulfonate cosolvent, 0.5% of a corrosion inhibitor, 0.1% of a β-mercaptoethanol reducing agent and deionized water, and liquid ammonia is used to adjust the pH value of the cleaning agent to 9.0.

[0067] In the descaling agent, the mass percentage of ethylenediaminetetraacetic acid is 65%, and the mass percentage of diethylenetriaminepentaacetic acid is 35%; in the corrosion inhibitor, the mass percentage of water-soluble sodium benzotriazole is 55%, the mass percentage of 2-thiolbenzothiazole is 35%, and the mass percentage of oily hydroxyethylimidazoline is 10%.

[0068] Take 200 mL of the cleaning agent of this example, raise the temperature to 120° C., and clean T22 and Incoloy 800H spare tube samples under closed conditions for 24 hours.

[0069] After cleaning, the descaling rates of T22 and Incoloy 800H pipes were 98.5% and 99.1% respectively, and the cleaning residue rate was 7.8%.

[0070] T22, Incoloy 800H, T22-Incoloy 800H weld corrosion indicator sheets have no pitting corrosion, and the corrosion rates are 0.22g / (m 2 ·h)、0.01g / (m 2 h) and 0.15g / (m 2 h), no intergranular corrosion and stress corrosion were observed in the stress-loaded specimens of Incoloy 800H and T22-Incoloy800H welds under a 500x metallographic microscope.

[0071] After cleaning with the chemical cleaning agent of Examples 1-5, the descaling rate of the weld corrosion indicator sheet is 98.2-99.7%, the cleaning residue rate is 2.1-7.8%, and the corrosion rate is 0.01-0.33 g / (m 2 ·h), refer to T / CEC 144-2017 "Guidelines for Chemical Cleaning of Superheaters and Reheaters", the uniform corrosion rate and galvanic corrosion rate of the weld corrosion indicator are both lower than the uniform 2g / (m 2 h), in line with relevant requirements. Under cleaning conditions, the uniform corrosion rate of all metals is controlled within the design acceptable range and safety range, meeting the requirements of relevant power industry standards; under cleaning conditions, the galvanic corrosion rate of T22-Incoloy 800H dissimilar steel welding parts meets the requirements of relevant power industry standards.

[0072] Comparative Example 1

[0073] The difference between this comparative example and Example 1 is that the descaling agent component is adjusted, the mass percentage of ethylenediaminetetraacetic acid is 100%, and the other steps are the same as those in Example 1 to prepare the chemical cleaning agent.

[0074] After cleaning, the descaling rates of T22 and Incoloy 800H pipes were 98.2% and 98.9% respectively, and the cleaning residue rate was 6.3%.

[0075] Figure 3 The following are the corrosion conditions of the weld corrosion indicator sheet before and after chemical cleaning. (a) and (b) are the pictures before and after Incoloy800H cleaning, and (c) and (d) are the pictures before and after T22 cleaning. It can be seen that there is no pitting corrosion on the T22 and Incoloy 800H corrosion indicator sheets.

[0076] The corrosion rates of T22 and Incoloy 800H corrosion indicator sheets are 0.26 g / (m 2 ·h)、0.01g / (m 2 h); Figure 4 The 500-fold magnified metallographic micrograph of the weld curved beam after cleaning shows that intergranular corrosion and galvanic corrosion were observed in the stress-loaded specimens of the Incoloy 800H and T22-Incoloy800H welds under a 500-fold metallographic microscope.

[0077] Therefore, diethylenetriaminepentaacetic acid in the descaling agent is the key component affecting the intergranular corrosion of Incoloy 800H and the galvanic corrosion of T22-Incoloy800H welds.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that the corrosion inhibitor components and mass percentages are adjusted, the mass percentage of water-soluble sodium benzotriazole is 65%, the mass percentage of 2-thiolbenzothiazole is 35%, and the other steps are the same as Example 1 to prepare the cleaning agent.

[0080] After cleaning, the descaling rates of T22 and Incoloy 800H pipes were 98.6% and 99.3% respectively, and the cleaning residue rate was 4.2%.

[0081] Figure 5 The following are the corrosion conditions of the weld corrosion indicator sheet before and after chemical cleaning. (a) and (b) are the pictures before and after Incoloy800H cleaning, and (c) and (d) are the pictures before and after T22 cleaning. It can be seen that there is no pitting corrosion on the T22 and Incoloy 800H corrosion indicator sheets.

[0082] The corrosion rates of T22 and Incoloy 800H corrosion indicator sheets are 1.04 g / (m 2 ·h)、0.06g / (m 2 h), Figure 6 The 500-fold magnified metallographic micrograph of the weld bent beam after cleaning shows that no intergranular corrosion and stress corrosion were observed in the stress-loaded specimens of the Incoloy800H and T22-Incoloy800H welds under a 500-fold metallographic microscope.

[0083] Therefore, the components and mass percentage of the corrosion inhibitor are the key factors for uniform corrosion.

[0084] Comparative Example 3

[0085] Conventional industrial cleaning agents include hydrochloric acid, formic acid, and acetic acid. This comparative example uses formic acid cleaning agent for comparison. The cleaning agent concentration is 4%, the corrosion inhibitor concentration is 0.5%, the corrosion inhibitor components are the same as in Example 1, and the remaining components are pure water. The cleaning temperature is 85°C.

[0086] After cleaning, the descaling rates of T22 and Incoloy 800H pipes were 98.3% and 98.4% respectively, and the cleaning residue rate was 34.5%.

[0087] The corrosion rates of T22 and Incoloy 800H corrosion indicator sheets are 1.86 g / (m 2 ·h)、0.13g / (m 2 h), Figure 7 The following is a 500-fold magnified metallographic micrograph of the welded curved beam after cleaning. It can be seen that severe intergranular corrosion was observed in the stress-loaded specimen of the T22-Incoloy 800H weld under a metallographic microscope.

[0088] The corrosion rate and cleaning residue rate of the corrosion indicator sheet in Examples 1-5 are much lower than those in Comparative Example 1, and the descaling effect of the chemical cleaning agent in Examples 1-5 is better than that of the conventional cleaning agent.

[0089] Although conventional cleaning agents have good descaling effects, they mainly peel off the oxide layer, leaving a large amount of residue that leads to the risk of pipe blockage; secondly, conventional cleaning agents such as hydrochloric acid, formic acid, and acetic acid intensify the uniform corrosion of T22 material and are extremely sensitive to intergranular corrosion of nickel-based alloys, leading to intergranular corrosion perforation, which cannot be suppressed by optimizing corrosion inhibitors.

[0090] In summary, the chemical cleaning agent and cleaning method for the secondary side of a high-temperature gas-cooled reactor steam generator of the present invention have little peeling property for the iron oxide layer generated during operation during the cleaning process; under cleaning conditions, there is no pitting corrosion on T22 low alloy steel, Incoloy 800H nickel-based alloy and T22-Incoloy 800H welds, and there is no intergranular corrosion and stress corrosion on Incoloy 800H nickel-based alloy and T22-Incoloy 800H welds loaded with ultimate stress; under cleaning conditions, the uniform corrosion rate of all metals is controlled within the design acceptable range and safety range, meeting the requirements of relevant power industry standards; under cleaning conditions, the galvanic corrosion rate of T22-Incoloy 800H dissimilar steel welding parts meets the requirements of relevant power industry standards.

[0091] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A chemical cleaning agent for the secondary side of a high temperature gas-cooled reactor steam generator, characterized in that: The components of the chemical cleaning agent include, by mass percentage, 3.0-10.0% of a descaling agent, 0.1-1.0% of a cosolvent, 0.3-1.0% of a corrosion inhibitor, 0.05-0.5% of a reducing agent, and the remainder being pure water; Wherein, the descaling agent is composed of a mixture of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid; The cosolvent comprises one or more of diisooctyl maleate sulfonate, sodium polyoxyethylene ether sulfonate, and diethanol monoisopropanolamine; The corrosion inhibitor is composed of water-soluble sodium benzotriazole, 2-thiol benzothiazole, and oily hydroxyethyl imidazoline; The reducing agent includes one of beta-mercaptoethanol, hydrazine and acetone oxime.

2. The secondary side chemical cleaning agent for a high temperature gas-cooled reactor steam generator according to claim 1, characterized in that: In the descaling agent, the mass percentage of ethylenediaminetetraacetic acid is 50% to 70%, and the mass percentage of diethylenetriaminepentaacetic acid is 30% to 50%.

3. The secondary side chemical cleaning agent for a high temperature gas-cooled reactor steam generator according to claim 1, characterized in that: In the corrosion inhibitor, the mass percentage of water-soluble sodium benzotriazole is 50% to 60%, the mass percentage of 2-thiol benzothiazole is 30% to 40%, and the mass percentage of oily hydroxyethyl imidazoline is 10%.

4. A method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator, characterized in that: include, Using the chemical cleaning agent as described in any one of claims 1 to 3, further comprising: The pH of the chemical cleaning agent is adjusted with liquid ammonia, and the secondary side components of the high temperature gas-cooled reactor steam generator are cleaned under closed conditions.

5. The method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator according to claim 4, characterized in that: The pH of the chemical cleaning agent is 8.5-9.

5.

6. The method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator according to claim 4, characterized in that: The cleaning temperature is 110-130°C.

7. The method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator according to claim 6, characterized in that: The cleaning time is 24 to 48 hours.

8. The method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator according to any one of claims 4 to 7, characterized in that: After being cleaned by the chemical cleaning agent, the descaling rate of the secondary side components of the high temperature gas-cooled reactor steam generator is 98.2-99.7%.

9. The method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator according to claim 8, characterized in that: After being cleaned by the chemical cleaning agent, the cleaning residue rate of the secondary side components of the high temperature gas-cooled reactor steam generator is 2.1-7.8%.

10. The method for cleaning the secondary side of a high temperature gas-cooled reactor steam generator according to claim 8, characterized in that: The uniform corrosion rate of the secondary side components of the high temperature gas-cooled reactor steam generator is 0.01 to 0.33 g / (m 2 h), and there is no pitting corrosion, intergranular corrosion and stress corrosion.

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