Method for restructuring and removing surface corrosion products of low-activation steel for water-cooled blanket of fusion reactor

Abstract

This invention relates to the field of surface treatment technology, and more particularly to a method for reconstructing and removing surface corrosion products of low-activation steel used in fusion reactor water-cooled blankets. The method includes placing the low-activation steel for fusion reactor water-cooled blankets in a high-temperature, high-pressure reactor containing a water medium for a first-stage high-temperature, high-pressure water corrosion treatment; performing a water medium renewal treatment; and then placing the steel, after the first-stage high-temperature, high-pressure water corrosion treatment, in a high-temperature, high-pressure reactor containing a renewed water medium for a second-stage high-temperature, high-pressure water corrosion treatment. This invention, through staged treatment in a high-temperature, high-pressure water environment, reduces or eliminates surface corrosion products, while simultaneously obtaining a more uniform and dense surface oxide layer, thus achieving the reconstruction and removal of surface corrosion products from low-activation steel.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and in particular to a method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of fusion reactors. Background Technology

[0002] The fusion reactor blanket system is a crucial component for energy conversion and tritium breeding in fusion reactors. The water-cooled blanket structural materials of fusion reactors are subjected to complex service conditions, including high temperature, high pressure water environment, and neutron irradiation. During contact with the coolant, the surface of the structural materials is prone to oxidation and corrosion, forming corrosion products primarily composed of iron oxides and chromium oxides. These corrosion products not only affect the uniformity, continuity, and stability of the oxide layer on the material surface but may also be released, migrate, and redeposited in the water-cooling loop, thus impacting the long-term operational safety of the fusion reactor water-cooling system. During fusion reactor operation, corrosion products on the surface of the structural materials can enter the reactor core or neutron irradiation area with the coolant and become activated under neutron influence. Existing technologies indicate that activated corrosion products, when deposited on the tube walls or present in the coolant, will continuously decay and release radiation, becoming a significant source of dose rate during normal operation and after shutdown of the fusion reactor. Therefore, reducing the risk of formation, release, and migration of corrosion products on the surface of the structural materials is of great significance for controlling the source terms of activated corrosion products in the water-cooling loop and improving the long-term operational safety of the fusion reactor water-cooling system.

[0003] Based on the above issues, for low-activation steel used in fusion reactor water-cooled blankets, it is necessary to propose a surface reconstruction and removal method suitable for high-temperature and high-pressure water environments to address existing or forming corrosion products on its surface. Existing research mainly focuses on the influence of corrosion rate, oxide film composition, film thickness, and service parameters on corrosion behavior in low-activation steel, with limited research on controllable reconstruction and removal methods for surface corrosion products. While traditional mechanical or chemical cleaning can remove some corrosion products, it easily causes surface damage, contamination, or chemical residues, which is detrimental to maintaining the true corrosion state of the material surface. Therefore, developing a method for reconstructing and removing surface corrosion products of low-activation steel based on high-temperature and high-pressure water-segmented treatment is of great significance for reducing corrosion product source terms, optimizing the surface oxide layer structure, and supporting the service safety evaluation of fusion reactor water-cooled blanket materials. Summary of the Invention

[0004] To address the problem that low-activation steel is prone to forming granular corrosion products and uneven oxide layer morphology after long-term continuous corrosion in a high-temperature and high-pressure water environment, this invention provides a method for reconstructing and removing corrosion products on the surface of low-activation steel used in fusion reactor water-cooled blankets.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor, comprising the following steps:

[0007] S1: The water-cooled blanket of the fusion reactor is placed in a high-temperature, high-pressure reactor containing water and sealed, using low-activation steel.

[0008] S2: Purging treatment is performed on the high-temperature and high-pressure reactor;

[0009] S3: The high-temperature and high-pressure reactor is heated and pressurized to carry out the first stage of high-temperature and high-pressure water corrosion treatment;

[0010] S4: After the first stage of high temperature and high pressure water corrosion treatment is completed, the low activation steel for the fusion reactor water-cooled blanket that has undergone the first stage of high temperature and high pressure water corrosion treatment is removed.

[0011] S5: Perform water medium replacement treatment;

[0012] S6: The fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, is placed again in a high-temperature and high-pressure reactor containing a new water medium and sealed.

[0013] S7: The high-temperature and high-pressure reactor is heated and pressurized again, so that the low-activation steel of the fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, undergoes the second stage of high-temperature and high-pressure water corrosion treatment in the renewed water medium.

[0014] S8: After the second stage of high temperature and high pressure water corrosion treatment is completed, the low activation steel is removed to complete the reconstruction and removal of corrosion products on the surface of the low activation steel used for the water-cooled blanket of the fusion reactor.

[0015] The water medium used in the first and second stages of high-temperature and high-pressure water corrosion treatment has a resistivity of ≥18MΩ·cm and a dissolved oxygen content of ≤10ppb at 25℃.

[0016] The water medium used in the first stage of high-temperature and high-pressure water corrosion treatment and the second stage of high-temperature and high-pressure water corrosion treatment is deionized water, high-purity water or deoxygenated pure water.

[0017] The temperature of the first stage of high-temperature and high-pressure water corrosion treatment is 280~325℃, and the pressure is 10~15.5MPa; the temperature of the second stage of high-temperature and high-pressure water corrosion treatment is 280~325℃, and the pressure is 10~15.5MPa.

[0018] The water medium renewal process in step S5 is carried out after the high-temperature and high-pressure reactor has been cooled and depressurized.

[0019] Specifically, step S2 involves introducing high-purity nitrogen into the high-temperature and high-pressure reactor to purge the gas phase space and water medium inside the reactor.

[0020] The total corrosion time for the reconstruction and removal method of corrosion products on the surface of low-activation steel used in the water-cooled blanket of fusion reactors is 300~1000h.

[0021] The first stage of high-temperature and high-pressure water corrosion treatment lasts for 10 to 100 hours, and the second stage of high-temperature and high-pressure water corrosion treatment lasts for 50 to 1000 hours. Preferably, the second stage of high-temperature and high-pressure water corrosion treatment lasts for 100 to 1000 hours.

[0022] In step S5, the water medium renewal process can be a complete or partial renewal.

[0023] The low-activation steel used for the fusion reactor water-cooled blanket in S1 is a pre-treated low-activation steel for the fusion reactor water-cooled blanket. The pretreatment includes cutting, grinding, polishing, ultrasonic cleaning and drying of the low-activation steel sample.

[0024] The beneficial effects of this invention are as follows:

[0025] (1) This invention reduces or eliminates surface corrosion products through staged treatment in a high-temperature and high-pressure water environment, while obtaining a more uniform and dense surface oxide layer. It realizes the reconstruction and removal of surface corrosion products of low-activation steel without the need for additional removal methods such as mechanical grinding, strong acid cleaning or strong alkali cleaning. It can reduce the risk of secondary damage and contamination to the sample surface, thus providing a new technical approach for the pre-service treatment, corrosion product control and corrosion behavior optimization of low-activation steel.

[0026] (2) The surface corrosion product reconstruction and removal method of the present invention can effectively reduce or remove Fe3O4 particulate corrosion products on the surface of low-activation steel. Compared with the sample that was continuously corroded for 300 hours in a deionized water environment at 325℃ and 15.5MPa, the particulate corrosion products on the surface of low-activation steel treated by the method of the present invention were significantly reduced or basically disappeared, indicating that the method of the present invention can effectively control the evolution process of corrosion products on the surface of low-activation steel.

[0027] (3) The surface corrosion product reconstruction and removal method of the present invention can improve the morphology of the surface oxide layer after corrosion of low-activation steel. After treatment by the method of the present invention, the particulate corrosion products on the sample surface are reduced, the surface morphology is more uniform, and the cross-sectional oxide layer shows better continuity, which is conducive to obtaining a more uniform and dense surface oxide layer. This dense layer can further prevent the entry of O and H2O and the precipitation of Fe ions, thereby preventing further oxidation.

[0028] (4) The present invention achieves surface treatment of low-activation steel through a staged treatment method of “first stage high temperature and high pressure water corrosion - water medium renewal - second stage high temperature and high pressure water corrosion”.

[0029] (5) The surface corrosion product reconstruction and removal method of the present invention has a simple process and clear operating conditions. The reconstruction and removal of corrosion products can be achieved by only staged high temperature and high pressure water corrosion treatment and water medium renewal. It has good repeatability and operability. Attached Figure Description

[0030] Figure 1 This is a flowchart of the method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to the present invention.

[0031] Figure 2 The image shows the microstructure of the low-activation steel used for the water-cooled blanket of the fusion reactor in Example 1 after treatment using the method of this invention. Figure 2 (a) in the figure is a surface morphology diagram of the sample from Example 1. Figure 2 (b) in the figure is a cross-sectional morphology diagram of the sample of Example 1.

[0032] Figure 3 The images show the microstructure of the low-activation steel used for the water-cooled blanket of the fusion reactor in Comparative Example 1 after continuous corrosion for 300 hours in a deionized water environment at 325℃ and 15.5MPa. Figure 3 Image (a) in the figure is a surface morphology diagram of the sample in Comparative Example 1. Figure 3 (b) in the figure is a cross-sectional morphology diagram of the sample of Comparative Example 1.

[0033] Figure 4 The image shows the surface morphology of the low-activation steel used for the fusion reactor water-cooled blanket in Example 2 after treatment using the method of this invention. Figure 4 Image (a) in the figure is a surface morphology image of the sample obtained in Example 2 at a scale of 1 μm. Figure 4 (b) is a surface morphology diagram of the sample obtained in Example 2 at a scale of 2 μm.

[0034] Figure 5 The images show the surface morphology of the low-activation steel used for the water-cooled blanket of the fusion reactor in Comparative Example 2 after continuous corrosion for 100 hours in a deionized water environment at 325℃ and 15.5MPa. (The images are at different magnifications.) Figure 5 (a) in the figure is a surface morphology diagram of the sample obtained in Comparative Example 2 at a scale of 1 μm. Figure 5 (b) in the figure is a surface morphology diagram of the sample obtained in Comparative Example 2 with a scale of 2 μm. Detailed Implementation

[0035] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Any adjustments or substitutions made by those skilled in the art to the processing time, processing temperature, processing pressure, sample size, type of low-activation steel, and water medium renewal method without departing from the concept of the present invention should fall within the scope of protection of the present invention.

[0037] See Figure 1 This invention provides a method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor. The method includes staged corrosion and intermediate water medium renewal; specifically, the method includes the following steps:

[0038] S1: Place the water-cooled blanket of the fusion reactor, made of low-activation steel, into a high-temperature and high-pressure reactor containing water and seal it. In this step, the high-temperature and high-pressure reactor needs to be sealed, and the sealing of the reactor body, lid, inlet, outlet and connecting pipelines needs to be checked to ensure that the system is in a closed state during the high-temperature and high-pressure water corrosion treatment.

[0039] S2: Purge the high-temperature, high-pressure reactor; after purging, the dissolved oxygen content in the water medium should be ≤10 ppb. After purging, close the vent to keep the reactor sealed.

[0040] S3: The high-temperature and high-pressure reactor undergoes a temperature and pressure increase process to perform the first stage of high-temperature and high-pressure water corrosion treatment. Specifically, after completing the above atmosphere replacement and sealing operations, the heating and pressure control system of the high-temperature and high-pressure reactor is activated to gradually raise the temperature of the water medium inside the reactor to the preset temperature and the pressure inside the reactor to the preset pressure for the first stage of high-temperature and high-pressure water corrosion treatment.

[0041] S4: After the first stage of high-temperature and high-pressure water corrosion treatment is completed, the low-activation steel used for the fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, is removed. During the sampling process, avoid wiping, rinsing, or mechanical contact with the sample surface to prevent damage to the formed Fe oxide corrosion product layer.

[0042] S5: Perform water medium replacement treatment.

[0043] S6: Place the low-activation steel of the fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, into a high-temperature and high-pressure reactor containing a new water medium and seal it; the sealing operation is the same as steps S1 and S2.

[0044] S7: The high-temperature and high-pressure reactor is subjected to a second heating and pressurization process, so that the low-activation steel of the fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, undergoes the second stage of high-temperature and high-pressure water corrosion treatment in the renewed water medium.

[0045] S8: After the second stage of high temperature and high pressure water corrosion treatment is completed, the low activation steel is removed to complete the reconstruction and removal of corrosion products on the surface of the low activation steel used for the water-cooled blanket of the fusion reactor.

[0046] The aforementioned low-activation steel for fusion reactor water-cooled blankets is not limited to CLF-1 low-activation steel; it can also be other low-activation ferritic / martensitic steels for fusion reactor water-cooled blankets, or low-activation structural steel materials with similar compositional systems and service environment requirements. The low-activation steel can be processed into sheet, block, disc, or other specimen forms suitable for high-temperature, high-pressure water corrosion testing.

[0047] In this invention, the water medium used in the first and second stages of high-temperature and high-pressure water corrosion treatment has a resistivity ≥18MΩ·cm and a dissolved oxygen content ≤10ppb at 25℃.

[0048] The water medium mentioned above is not limited to deionized water; it can also be deoxygenated pure water, high-purity water, or water medium that simulates the water-cooled blanket loop water chemical environment of a fusion reactor.

[0049] The temperature of the first stage of high-temperature and high-pressure water corrosion treatment is 280~325℃, and the pressure is 10~15.5MPa; the temperature of the second stage of high-temperature and high-pressure water corrosion treatment is 280~325℃, and the pressure is 10~15.5MPa.

[0050] The water medium renewal treatment is carried out after the high-temperature and high-pressure reactor has been cooled and depressurized.

[0051] Specifically, after the first stage of high-temperature and high-pressure water corrosion treatment is completed, heating is stopped and the reactor is cooled to an operable state, and the CLF-1 low-activation steel sample is removed. Subsequently, the original deionized water in the reactor is drained, and fresh deionized water is added to the reactor to achieve water medium renewal and obtain the water medium in the second high-temperature and high-pressure water medium environment.

[0052] Preferably, the water medium renewal process is a complete or partial renewal. The water medium renewal method can be either completely draining the original deionized water and then adding fresh deionized water, or partially draining the original water medium and then adding fresh deionized water. The water medium renewal ratio can be selected according to experimental conditions and treatment requirements, for example, it can be 25%, 50%, 75%, or 100%. Specifically, 100% water medium renewal means draining all the original water medium in the reactor and adding an equal volume of fresh water medium; 25%, 50%, and 75% water medium renewal means draining 25%, 50%, and 75% of the total volume of the original water medium in the reactor, respectively, and adding the corresponding volume of fresh water medium.

[0053] In other embodiments, water media renewal can be performed at different time points after the first stage of high-temperature and high-pressure water corrosion treatment. For example, water media renewal can be performed after 50h, 150h, 250h, or 500h of corrosion, followed by the second stage of high-temperature and high-pressure water corrosion treatment. Different water media renewal points correspond to different degrees of surface corrosion product layers, and can be selected according to the experimental purpose, the total corrosion time, and the corrosion product characterization results.

[0054] The water medium can be replaced once or multiple times. When multiple water medium replacements are used, they can be performed at preset time intervals during the corrosion treatment process. For example, one or more water medium replacements can be performed at nodes such as 50h, 150h, 250h, or 500h. Multiple water medium replacements can meet the treatment needs of different corrosion treatment cycles or different surface conditions. The specific treatment effect can be evaluated by indicators such as surface morphology, cross-sectional morphology, phase composition of corrosion products, and Fe content in the post-treatment water.

[0055] The total corrosion time can be 300-1000 hours. For example, when the total corrosion time is 300 hours, a staged corrosion scheme of 50 hours + 250 hours, 100 hours + 200 hours, or 150 hours + 150 hours can be used; when the total corrosion time is 1000 hours, a staged corrosion scheme of 50 hours + 950 hours, 150 hours + 850 hours, 250 hours + 750 hours, or 500 hours + 500 hours can be used. The above-mentioned staged corrosion schemes are used to illustrate that the first stage high-temperature and high-pressure water corrosion treatment time and the second stage high-temperature and high-pressure water corrosion treatment time in the method of the present invention can be adjusted according to actual needs.

[0056] In the preferred embodiment, a first-stage high-temperature and high-pressure water corrosion treatment of 50 hours, followed by 100% water medium replacement, and a second-stage high-temperature and high-pressure water corrosion treatment of 250 hours were employed. Experimental results show that, under the condition of a total corrosion time of 300 hours, compared with samples subjected to continuous corrosion for 300 hours, the use of this staged treatment scheme significantly reduced or partially removed the Fe3O4 particulate corrosion products on the surface of the low-activation steel, and the surface oxide layer morphology was more uniform.

[0057] The corrosion product reconstruction and removal described in this invention can be manifested as a reduction in the number of surface particulate corrosion products, a decrease in particle size, a change in particle morphology from regular to irregular, blurred corrosion product boundaries, an increase in local peeling area, redistribution of corrosion products, and smoothing or improvement of oxide layer surface continuity.

[0058] The particulate corrosion products mentioned in this invention can be Fe3O4 particulate corrosion products or composite oxide corrosion products containing elements such as Fe and O. Preferably, the corrosion products are Fe3O4 particulate corrosion products formed on the surface of CLF-1 low-activation steel.

[0059] After the corrosion treatment is completed in this invention, the surface morphology of the sample can be observed by scanning electron microscopy, the thickness, continuity and compactness of the oxide layer can be analyzed by cross-sectional scanning electron microscopy, the elemental distribution of the corrosion products can be characterized by energy dispersive spectroscopy, the phase composition of the corrosion products can be confirmed by X-ray diffraction or Raman spectroscopy, and the dissolution, migration or release behavior of the corrosion products can be evaluated by Fe content analysis in the post-test water.

[0060] Preferably, the low-activation steel used for the fusion reactor water-cooled blanket in S1 is a pretreated low-activation steel for the fusion reactor water-cooled blanket. The pretreatment includes cutting, grinding, polishing, ultrasonic cleaning, and drying of the low-activation steel sample.

[0061] Example 1:

[0062] This embodiment provides a method for reconstructing and removing corrosion products on the surface of CLF-1 steel, a low-activation steel used in the water-cooled blanket of a fusion reactor. The specific operation is as follows:

[0063] S1: The low-activation steel used for the fusion reactor's water-cooled blanket is placed in a high-temperature, high-pressure reactor containing an aqueous medium and sealed. In this step, the low-activation steel sample is placed on a sample rack inside the high-temperature, high-pressure reactor, and deionized water with a resistivity ≥18 MΩ·cm is added to the reactor as the aqueous medium. After sample loading, the reactor is sealed, and the sealing of the reactor body, lid, inlet, outlet, and connecting pipelines is checked to ensure that the system remains in a closed state during the high-temperature, high-pressure water corrosion treatment. The samples used are pretreated samples that have undergone cutting, grinding, polishing, ultrasonic cleaning, and drying.

[0064] S2: Purging the high-temperature and high-pressure reactor. In this step, before heating and pressurizing, open the inlet and outlet of the high-temperature and high-pressure reactor and introduce high-purity nitrogen into the reactor to purge the gas phase space and water medium inside the reactor, thereby replacing residual air and reducing the dissolved oxygen content in the water medium. Preferably, the nitrogen purging time is 60-90 minutes; more preferably, the dissolved oxygen content in the water medium after purging is ≤10 ppb. After purging, close the outlet to keep the high-temperature and high-pressure reactor in a sealed state.

[0065] S3: The high-temperature and high-pressure reactor is heated and pressurized to perform the first stage of high-temperature and high-pressure water corrosion treatment. After completing the atmosphere replacement and sealing operations mentioned above, the heating and pressure control system of the high-temperature and high-pressure reactor is started to gradually raise the temperature of the water medium inside the reactor to 325°C and the pressure inside the reactor to 15.5 MPa. The first stage of high-temperature and high-pressure water corrosion treatment is carried out at 325°C and 15.5 MPa for 50 hours.

[0066] S4: After the first stage of high-temperature and high-pressure water corrosion treatment is completed, the low-activation steel used for the fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, is removed. In this step, after the first stage of high-temperature and high-pressure water corrosion treatment reaches the preset time (50h), the heating program of the high-temperature and high-pressure reactor is turned off, allowing the reactor to cool naturally or through a programmed cooling process to room temperature, and then slowly depressurizing to atmospheric pressure through the pressure relief valve or vent. After the temperature and pressure meet the safe operating conditions, the reactor lid is opened, and the low-activation steel sample after the first stage of corrosion is removed. Corrosion products are present on the surface of the low-activation steel sample after the first stage of corrosion. During the sampling process, avoid wiping, rinsing, or mechanically contacting the sample surface to prevent damage to the formed Fe oxide corrosion product layer.

[0067] S5: Perform water medium replacement treatment. The specific operation for water medium replacement treatment in this step is to drain all the original water medium in the reactor and add an equal volume of fresh deionized water or other media to achieve water medium replacement.

[0068] S6: The low-activation steel used for the fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, is placed again in a high-temperature and high-pressure reactor containing a fresh water medium and sealed. Specifically, the sample taken out in step S4 is placed back on the reactor sample rack, and the reactor is sealed again.

[0069] S7: The high-temperature and high-pressure reactor is heated and pressurized again, so that the low-activation steel used for the fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, undergoes the second stage of high-temperature and high-pressure water corrosion treatment in the renewed water medium. In this step, the same heating and pressurization procedure as in the first stage is followed again, heating the water medium in the reactor to 325°C and pressurizing it to 15.5 MPa, and continuing the second stage of high-temperature and high-pressure water corrosion treatment under these conditions for 250 hours.

[0070] S8: After the second stage of high-temperature and high-pressure water corrosion treatment, the low-activation steel was removed, completing the reconstruction and removal of corrosion products on the surface of the low-activation steel used for the fusion reactor water-cooled blanket. In this step, after the second stage of corrosion was completed, the temperature was lowered, the pressure was released, and the sample was removed according to the same procedure. The surface morphology and cross-sectional morphology of the sample were observed. The results showed that the Fe oxide particulate corrosion products on the surface of the low-activation steel were significantly reduced or locally removed, and the morphology of the surface oxide layer tended to be uniform.

[0071] Comparative Example 1:

[0072] To verify the effectiveness of the method of the present invention, a continuous corrosion treatment was set as a comparative example, i.e., an untreated example.

[0073] The same CLF-1 low-activation steel sample as in Example 1 was selected and pretreated using the same cutting, grinding, polishing, ultrasonic cleaning, and drying methods. The sample was then placed in a high-temperature, high-pressure reactor and continuously corroded for 300 hours in a deionized water environment at 325°C and 15.5 MPa, without any water medium replacement.

[0074] After the corrosion was completed, the sample was removed and its surface and cross-sectional morphology were observed.

[0075] The surface morphology and cross-sectional morphology of the segmented corrosion samples in Example 1 and the untreated continuous corrosion samples in Comparative Example 1 were observed. Figure 2 The image shows the microstructure of the low-activation steel used for the water-cooled blanket of the fusion reactor in Example 1 after treatment using the method of this invention. Figure 2 (a) in the figure is a surface morphology diagram of the sample from Example 1. Figure 2 (b) in the figure is a cross-sectional morphology diagram of the sample of Example 1. Figure 3 The images show the microstructure of the low-activation steel used for the water-cooled blanket of the fusion reactor in Comparative Example 1 after continuous corrosion for 300 hours in a deionized water environment at 325℃ and 15.5MPa. Figure 3 Image (a) in the figure is a surface morphology diagram of the sample in Comparative Example 1. Figure 3 (b) in the figure is a cross-sectional morphology diagram of the sample of Comparative Example 1.

[0076] from Figure 3As can be seen, granular corrosion products exist on the surface of the continuously corroded CLF-1 low-activation steel sample in Comparative Example 1; further comparison with... Figure 2 The comparison shows that after the second stage of high-temperature and high-pressure water corrosion treatment for 250 hours, the coarse granular Fe3O4 corrosion products on the surface of the CLF-1 low-activation steel in Example 1 were significantly reduced or almost disappeared, and the surface oxide layer morphology was more uniform; the cross-sectional morphology after treatment also showed that... Figure 2 As can be seen in (b), a relatively continuous oxide layer structure was formed on the sample surface. This demonstrates that the method described in this embodiment can achieve the reconstruction and removal of corrosion products on the surface of low-activation steel under high-temperature and high-pressure water conditions.

[0077] The above results indicate that the present invention, through staged water medium renewal treatment, can alter the subsequent evolution process of corrosion products on the surface of low-activation steel, thereby reconstructing, reducing, or removing the already formed or forming surface particulate corrosion products, thus obtaining a more uniform surface oxide layer.

[0078] Example 2:

[0079] The operation steps of Example 2 are the same as those of Example 1, except that the time for the first stage of high temperature and high pressure water corrosion treatment is 50 hours, and the time for the second stage of high temperature and high pressure water corrosion treatment is 50 hours.

[0080] Comparative Example 2:

[0081] The same CLF-1 low-activation steel sample as in Example 2 was selected and pretreated using the same cutting, grinding, polishing, ultrasonic cleaning, and drying methods. The sample was then placed in a high-temperature, high-pressure reactor and continuously corroded for 100 hours in a deionized water environment at 325°C and 15.5 MPa, without any water medium replacement.

[0082] After the corrosion was completed, the sample was removed and its surface and cross-sectional morphology were observed.

[0083] The surface morphology and cross-sectional morphology of the segmented corrosion samples in Example 2 and the untreated continuous corrosion samples in Comparative Example 2 were observed. Figure 4 The image shows the surface morphology of the low-activation steel used for the fusion reactor water-cooled blanket in Example 2 after treatment using the method of this invention. Figure 4 Image (a) in the figure is a surface morphology image of the sample obtained in Example 2 at a scale of 1 μm. Figure 4 (b) is a surface morphology diagram of the sample obtained in Example 2 at a scale of 2 μm. Figure 5 The images show the surface morphology of the low-activation steel used for the water-cooled blanket of the fusion reactor in Comparative Example 2 after continuous corrosion for 100 hours in a deionized water environment at 325℃ and 15.5MPa. (The images are displayed at different magnifications.) Figure 5(a) in the figure is a surface morphology diagram of the sample obtained in Comparative Example 2 at a scale of 1 μm. Figure 5 (b) in the figure is a surface morphology diagram of the sample obtained in Comparative Example 2 with a scale of 2 μm.

[0084] Observation of the final samples obtained in Example 2 and Comparative Example 2 revealed that, compared to Comparative Example 2, the surface of the low-activation steel sample obtained in Example 2 still showed granular corrosion products of Fe oxide, but the particle morphology changed from a more regular state to an irregular state, indicating that water medium renewal could cause morphological reconstruction of the outer corrosion product layer. This phenomenon suggests that after the initial corrosion product layer was formed in the first stage of corrosion, water medium renewal changed the material exchange state between the corrosion products on the sample surface and the water medium, causing the outer corrosion products to begin morphological reconstruction. However, due to the short processing time in the second stage, the reconstruction and removal process of the corrosion product layer was not sufficient, so a large number of granular corrosion products remained on the sample surface. In contrast, the granular corrosion products of Fe3O4 on the surface of the low-activation steel sample obtained in Example 1 were significantly reduced or almost disappeared, and traces of corrosion product peeling or removal could be observed in local areas, indicating that staged water medium renewal could promote the instability, reconstruction, and removal of the outer corrosion product layer.

[0085] Based on the experimental results of Examples 1 and 2, under the same temperature and pressure, when the time of the second-stage high-temperature and high-pressure water corrosion treatment was extended to 250 hours, the reconstruction and removal of the Fe oxide particulate corrosion products on the surface became more obvious.

[0086] In a specific embodiment of the present invention, a staged treatment scheme with a total corrosion time of 300 hours is preferably adopted. Specifically, the CLF-1 low-activation steel sample is subjected to a first-stage high-temperature and high-pressure water corrosion treatment at 325°C and 15.5MPa for 50 hours, so that Fe oxide granular corrosion products are formed on the sample surface; then the heating program is turned off, the reactor is cooled and depressurized to safe operating conditions, the sample is removed, the original water medium in the reactor is drained, and an equal volume of fresh deionized water, high-purity water, or deoxygenated pure water is added to achieve 100% water medium replacement; then the sample is placed back in the reactor, and the same sealing, atmosphere replacement, and heating and pressurization procedures are followed to continue the second-stage high-temperature and high-pressure water corrosion treatment at 325°C and 15.5MPa for 250 hours.

[0087] Observation of the surface and cross-sectional morphology of samples subjected to continuous corrosion for 300 hours revealed that obvious Fe oxide granular corrosion products still existed on the surface of the continuously corroded samples. However, samples treated with 50 hours of first-stage corrosion, 100% water media renewal, and 250 hours of second-stage high-temperature and high-pressure water corrosion showed a significant reduction or local removal of Fe oxide granular corrosion products on the surface, and the morphology of the surface oxide layer tended to be more uniform. This indicates that under the experimental conditions, staged water media renewal can alter the subsequent evolution process of the corrosion product layer on the surface of low-activation steel, causing the surface Fe oxide granular corrosion products to be reconstructed, reduced, or removed.

[0088] In other embodiments, the first-stage corrosion time, the second-stage corrosion time, and the water medium renewal ratio can be adjusted according to the experimental purpose and the formation state of corrosion products on the sample surface. For example, the first-stage corrosion time can be 50h, 100h, or 150h, the second-stage corrosion time can be 50h, 150h, or 250h, and the water medium renewal ratio can be partial or complete renewal. The above parameter adjustments are used to illustrate that the method of the present invention has a certain process adaptability, and its specific treatment effect should be evaluated by indicators such as surface morphology, cross-sectional morphology, phase composition of corrosion products, and Fe content in the post-test water.

[0089] Before obtaining corresponding experimental data, the total corrosion time of 1000 hours, the partial water replacement ratio of 25% to 75%, and the multiple water medium renewal scheme are not used as examples to prove the technical effect of the present invention, but only as directions for subsequent process optimization or optional parameter ranges. The currently verified preferred embodiment of the present invention is: first stage corrosion of 50 hours, 100% water medium renewal, second stage corrosion of 250 hours, and a total corrosion time of 300 hours.

[0090] In other embodiments, the method can be used not only for the removal of corrosion products on the surface of low-activation steel, but also for the control of oxide layer morphology on the surface of low-activation steel, the study of the evolution law of corrosion products, pre-service surface treatment, evaluation of high-temperature and high-pressure water corrosion behavior, and related experiments on the prediction of the life of fusion reactor water-cooled blanket structure materials.

[0091] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A method for restructuring and removing surface corrosion products of low-activation steel for water-cooled blanket of fusion reactors, characterized in that, The method includes the following steps: S1: The water-cooled blanket of the fusion reactor is placed in a high-temperature, high-pressure reactor containing water and sealed, using low-activation steel. S2: Purging treatment is performed on the high-temperature and high-pressure reactor; S3: The high-temperature and high-pressure reactor is heated and pressurized to carry out the first stage of high-temperature and high-pressure water corrosion treatment; S4: After the first stage of high temperature and high pressure water corrosion treatment is completed, the low activation steel for the fusion reactor water-cooled blanket that has undergone the first stage of high temperature and high pressure water corrosion treatment is removed. S5: Perform water medium replacement treatment; S6: The fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, is placed again in a high-temperature and high-pressure reactor containing a new water medium and sealed. S7: The high-temperature and high-pressure reactor is heated and pressurized again, so that the low-activation steel of the fusion reactor water-cooled blanket, which has undergone the first stage of high-temperature and high-pressure water corrosion treatment, undergoes the second stage of high-temperature and high-pressure water corrosion treatment in the renewed water medium. S8: After the second stage of high temperature and high pressure water corrosion treatment is completed, the low activation steel is removed to complete the reconstruction and removal of corrosion products on the surface of the low activation steel used for the water-cooled blanket of the fusion reactor.

2. The method of reconfiguration and removal of surface corrosion products of low-activation steel for water-cooled blanket of fusion reactor according to claim 1, characterized in that, The water medium used in the first and second stages of high-temperature and high-pressure water corrosion treatment has a resistivity ≥18MΩ·cm and a dissolved oxygen content ≤10ppb at 25℃.

3. The method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to claim 2, characterized in that, The water medium used in the first and second stages of high-temperature and high-pressure water corrosion treatment is deionized water, high-purity water, or deoxygenated pure water.

4. The method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to claim 1, characterized in that, The temperature of the first stage of high-temperature and high-pressure water corrosion treatment is 280~325℃, and the pressure is 10~15.5MPa; the temperature of the second stage of high-temperature and high-pressure water corrosion treatment is 280~325℃, and the pressure is 10~15.5MPa.

5. The method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to claim 1, characterized in that, The water medium renewal treatment in step S5 is carried out after the high-temperature and high-pressure reactor has been cooled and depressurized.

6. The method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to claim 1, characterized in that, The purging process in step S2 specifically involves introducing high-purity nitrogen gas into the high-temperature and high-pressure reactor to purge the gas phase space and water medium inside the reactor.

7. The method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to claim 1, characterized in that, The total corrosion time for the reconstruction and removal method of corrosion products on the surface of low-activation steel used in the water-cooled blanket of fusion reactors is 300~1000h.

8. The method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to claim 7, characterized in that, The first stage of high-temperature and high-pressure water corrosion treatment lasts for 10 to 100 hours, and the second stage of high-temperature and high-pressure water corrosion treatment lasts for 50 to 1000 hours.

9. The method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to claim 1, characterized in that, The water medium renewal process in step S5 can be a complete or partial renewal.

10. The method for reconstructing and removing corrosion products on the surface of low-activation steel used in the water-cooled blanket of a fusion reactor according to claim 1, characterized in that, The low-activation steel for the fusion reactor water-cooled blanket in S1 is a pretreated low-activation steel for the fusion reactor water-cooled blanket. The pretreatment includes cutting, grinding, polishing, ultrasonic cleaning and drying of the low-activation steel sample for the fusion reactor water-cooled blanket.

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