A method for preparing a surface sprayed coating of a spent fuel transport container for nuclear power and application thereof

Abstract

The application discloses a kind of spent fuel transport container surface spraying coating preparation method and application for nuclear power, belong to metal material and component surface modification and processing, friction and wear protection technical field.The application is prepared by powder core nickel-based wire, electric arc spraying NiCrB primer layer and electric arc spraying Ni-based boron-containing composite coating surface layer, which greatly improves the bonding strength between Ni-based composite coating and A350LF3 steel and the density of coating.The obtained Ni-based boron-containing composite coating meets the bonding force and density requirements of the surface coating of A350LF3 steel for spent fuel transport container for nuclear power, and achieves the purpose of shielding gamma radiation and neutron radiation, can significantly improve the reliability and service life of spent fuel transport container for nuclear power, meets the high temperature, high radiation and severe service requirements of spent fuel transport container for nuclear power.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of spent fuel transport container coating preparation method and application for nuclear power, belong to metal material and component surface modification and processing, friction and wear protection technical field. BACKGROUND

[0002] With nuclear power operation, fissile nuclide uranium in fuel is gradually consumed, not enough to maintain fission reaction, the fuel removed from reactor is called spent fuel, or irradiated fuel. 3%~4% of the used uranium waste (spent fuel) is separated from fission products by chemical method, which is called spent fuel reslurry and reprocessing technology, which is also the most critical link in the later stage of nuclear fuel cycle. The research and development design of spent fuel transport container is more difficult than that of new fuel and uranium hexafluoride transport container. In addition to ensuring subcritical safety, it also needs to ensure safety under normal transportation conditions and accident conditions during transportation due to its radioactivity and decay heat. In order to achieve the purpose of safe transportation, neutron absorbing material is needed in the container to ensure subcritical safety; it needs to have enough shielding thickness and appropriate shielding material to shield γ radiation and neutron radiation; it needs to have a good heat dissipation structure to timely remove the decay heat and prevent the temperature of the component cladding from being too high; at the same time, it can effectively block external heat from entering, so that the container can ensure safety under the condition of 800℃ high temperature for half an hour.

[0003] In recent years, our country's nuclear power industry has developed rapidly, and the localization of spent fuel transport containers required by nuclear power plants has become a trend. A350 LF3 belongs to a new type of container steel material for storing and transporting high radioactive spent fuel. Due to the particularity of the use environment of A350 LF3, the performance requirements for high strength, high temperature corrosion resistance, radiation resistance, and low thermal expansion coefficient are more stringent, so it is necessary to develop materials for spent fuel transport containers that meet stringent requirements. Among them, Ni-based boron-containing composite material combines the toughness, ductility and formability of aluminum metal with the hardness, ablation resistance and low density of boron carbide ceramic, has low density, high thermal conductivity, good mechanical properties and high neutron absorption capacity, but the material is expensive and cannot be widely applied. The combination of A350 LF3 steel matrix + Ni-based boron-containing composite coating provides a more economical solution for spent fuel transport container materials, but to meet the structural strength requirements of large containers while achieving the purpose of radioactive shielding, the surface technology of setting composite coating on A350 LF3 steel matrix has higher requirements. Arc spraying process has the advantages of high production efficiency, high energy utilization rate, low spraying cost, good safety and high coating bonding strength, which is suitable for surface modification treatment of spent fuel transport large containers for nuclear power, but there is no relevant report on the method of spraying dense Ni-based boron-containing composite coating on A350 LF3 steel matrix by arc spraying at home and abroad. SUMMARY

[0004] The present application aims at solving the above problems and provides a coating preparation method and application of a spent fuel transport container for nuclear power, wherein the obtained Ni-based boron-containing composite coating meets the bonding force and density requirements of the surface coating of A350 LF3 steel material for the spent fuel transport container for nuclear power, achieves the purpose of shielding gamma radiation and neutron radiation, can significantly improve the reliability and service life of the spent fuel transport container for nuclear power, and meets the high-temperature and high-radiation severe service requirements of the spent fuel transport container for nuclear power.

[0005] The present application is realized by the following technical solutions:

[0006] The present application is realized by the following technical solutions:

[0007] S1: B4C ceramic powder is added to an activation solution, and ultrasonic treatment is performed at room temperature for 60-90 min; after static settling, the activation solution is separated, and the powder is washed with deionized water for plating. Ni-Mo coated B4C powder is prepared by a normal-temperature ultrasonic-assisted chemical plating method, NaOH is used to adjust the pH value of the chemical plating solution to 9-11, the powder loading amount is 8-12 g / L, ultrasonic-assisted chemical plating is performed at normal temperature for 80-120 min, after the chemical plating is completed, the powder is washed with deionized water, dried, and Ni-Mo coated B4C powder is obtained.

[0008] S2: 30-50 parts by weight of Ni-Mo coated B4C powder, 20-30 parts by weight of FeB powder, and 20-50 parts by weight of FeCr67C6.0 powder are taken, stirred at high speed with a V-shaped powder mixer, and then filled into a U-shaped Ni-Cu (Monel 400) alloy strip with a purity of 99% and a certain shape, the filling rate is 30-50%, and the powder core nickel-based wire material with a diameter of 2.0-3.0 mm is made by rolling and drawing.

[0009] S3: An arc spraying method is used, the NiCrB powder core wire material is directly sprayed onto the surface of the A350 LF3 steel material for the spent fuel container for nuclear power through a spray gun, the spraying process parameters are as follows: voltage 28-35 V; current 180-220 A; spraying distance 150-200 mm; compressed air pressure 0.4-0.6 MPa, and a NiCrB primer layer with a thickness of 50-100 μm is prepared.

[0010] S4: using arc spraying method, the powder core nickel-based wire material in S1 is sprayed to the surface of the A350 LF3 steel material of the spent fuel container of nuclear power through a spray gun, and the spraying process parameters are as follows: voltage 30-35V; current 200-250A; spraying distance 150-200mm; compressed air pressure 0.4-0.6MPa, so that a nickel-based boron-containing composite coating with a thickness of 1000-2000μm is prepared.

[0011] The preparation method and application of the surface sprayed coating of the spent fuel transport container of nuclear power have the characteristics that the components and concentrations of the chemical plating solution in S1 are as follows: NiSO4·6H2O 15-20g / L, Na2MoO4·2H2O 10-15g / L, Na3C6H5O7·2H2O 20-30g / L, CN2H4S 0.02-0.10g / L and N2H4·H2O (80%) 80-100mL / L.

[0012] The preparation method and application of the surface sprayed coating of the spent fuel transport container of nuclear power have the characteristics that the particle size ranges of the Ni-Mo coated B4C powder, the FeB powder and the FeCr67C6.0 powder in S2 are all 20-60μm, and the high-speed stirring speed of the V-shaped powder mixer is 3000-5000r / min, and the stirring time is 60-120min.

[0013] The preparation method and application of the surface sprayed coating of the spent fuel transport container of nuclear power have the characteristics that the components of the NiCrB powder core wire material in S3 are as follows: Cr 18-20wt.%, B 5.0-7.0wt.%, O≤0.1wt.% and Ni the balance, the outer skin is a nickel strip, and the diameter of the finally formed powder core wire material is 2.0-3.0mm.

[0014] The preparation method and application of the surface sprayed coating of the spent fuel transport container of nuclear power have the characteristics that the porosity of the nickel-based composite coating obtained by spraying in S3 and S4 is not more than 3%, and the bonding strength with the A350 LF3 steel material is not less than 35MPa.

[0015] The preparation method and application of the surface sprayed coating of the spent fuel transport container of nuclear power have the characteristics that the thermal neutron absorption performance of the nickel-based boron-containing composite coating obtained by arc spraying in S3 and S4 together with the steel plate as a whole is not less than 90%.

[0016] The preparation method and application of the surface sprayed coating of the spent fuel transport container of nuclear power have the characteristics that the thermal neutron absorption performance of the nickel-based boron-containing composite coating obtained by arc spraying in S3 and S4 together with the steel plate as a whole is not less than 90%.

[0017] 1.The Ni-based boron-containing composite coating obtained by the coating preparation method of the spent fuel transport container for nuclear power plants according to the present application, which greatly improves the bonding strength between the Ni-based composite coating and the A350 LF3 steel material and the density of the coating by preparing a powder core nickel-based wire, arc spraying a NiCrB primer layer and arc spraying a Ni-based boron-containing composite coating top layer. Due to the use of arc spraying and the creative labor of the inventor, the surface roughness is further increased by spraying the NiCrB primer layer and setting the arc spraying parameters, which ensures the bonding strength between the Ni-based coating and the A350 LF3 steel material. At the same time, the Ni-based coating has good high-temperature resistance and corrosion resistance, and the large amount of B element introduced can improve the shielding effect of gamma radiation and neutron radiation. Therefore, the combination of A350 LF3 steel + arc sprayed boron-containing Ni-based composite coating meets the structural strength requirements of the container and achieves the purpose of radioactive shielding, which helps to improve the service life of the spent fuel transport container for nuclear power plants.

[0018] 2.In the Ni-based boron-containing composite coating according to the present application, the Ni-Mo coated B4C powder has low B element loss during spraying, and AES detection shows that the B element content on the coating surface is ≥40at.%. Therefore, the arc sprayed Ni-based boron-containing composite coating obtained by the present application has strong thermal neutron absorption capacity, and the neutron absorption cross section is much higher than that of ordinary boron-containing steel, and the thermal neutron absorption performance is not less than 90%.

[0019] 3.The high-speed stirring of the V-type powder mixer ensures the uniform dispersion of the particles of each component in the powder core wire; and the arc spraying method ensures the uniform distribution of each component in the coating on the surface of the A350 LF3 steel.

[0020] 4.The nickel-based powder core wire is made of U-shaped Ni-Cu (Monel 400) alloy strip, and the Cu element contained therein helps to improve the electrical conductivity of the wire, obtain better melting and atomization effect, and help to reduce the porosity of the sprayed coating.

[0021] 5.The present application forms a Ni-based boron-containing composite coating on the surface of the spent fuel transport container for nuclear power plants by using arc spraying, which not only improves the corrosion resistance, high-temperature resistance and radioactive shielding performance, but also greatly reduces the energy consumption and cost of spraying, and improves the efficiency and safety of spraying. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 SEM morphology photograph of the surface of the Ni-based boron-containing composite coating prepared for the spent fuel transport container for nuclear power plants in Example 1 DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with Examples 1-3 and Comparative Example 1.

[0024] Example 1:

[0025] The following steps outline the preparation method and application of a spray coating for the surface of spent fuel transport containers for nuclear power plants:

[0026] S1: Add B4C ceramic powder to the activation solution and ultrasonically treat at room temperature for 90 min; after static sedimentation, separate the activation solution, then wash the powder with deionized water, ready for plating. Ni-Mo coated B4C powder was prepared using a room-temperature ultrasonic-assisted chemical plating method. The pH of the chemical plating solution was adjusted to 10 with NaOH, the powder loading was 10 g / L, and ultrasonic-assisted chemical plating was performed at room temperature for 120 min. After chemical plating, the powder was washed with deionized water and dried to obtain Ni-Mo coated B4C powder.

[0027] S2: Take 50 parts by weight of Ni-Mo coated B4C powder, 20 parts by weight of FeB powder and 30 parts by weight of FeCr67C6.0 powder, stir them at high speed with a V-type powder mixer, and fill them into a U-shaped Ni-Cu (Monel 400) alloy strip with a purity of 99% with a certain shape. The filling rate is 45%. After rolling and drawing, it is made into a Φ2.0mm powder core nickel-based wire.

[0028] S3: Using the arc spraying method, NiCrB powder core wire is directly sprayed onto the surface of A350 LF3 steel used in nuclear power spent fuel containers through a spray gun. The spraying process parameters are: voltage 30V; current 200A; spraying distance 150mm; compressed air pressure 0.5MPa, to prepare a NiCrB base layer with a thickness of 100μm.

[0029] S4: Using the arc spraying method, the nickel-based wire powder from S1 is sprayed onto the surface of A350 LF3 steel used in nuclear power spent fuel containers as a NiCrB base layer through a spray gun. The spraying process parameters are: voltage 35V; current 220A; spraying distance 150mm; compressed air pressure 0.5MPa, to prepare a nickel-based boron-containing composite coating with a thickness of 2000μm.

[0030] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power is characterized in that the components and concentrations of the chemical plating solution in S1 are as follows: NiSO4·6H2O 20g / L, Na2MoO4·2H2O 15g / L, Na3C6H5O7·2H2O 30g / L, CN2H4S 0.05g / L, and N2H4·H2O (80%) 100mL / L.

[0031] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power is characterized in that the particle size range of Ni-Mo coated B4C powder, FeB powder and FeCr67C6.0 powder in S2 is 40μm, the high-speed stirring rate of the V-type mixer is 4000 rpm and the stirring time is 120 min.

[0032] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power plants is characterized in that the composition of the NiCrB core wire in S3 is: Cr 20wt.%, B 5.0wt.%, O≤0.1wt.%, and Ni balance. The outer sheath is made of nickel strip, and the final formed core wire has a diameter of 2.0mm.

[0033] The steel grade for spent nuclear fuel containers is A350 LF3.

[0034] The porosity of the nickel-based boron-containing composite coatings obtained by spraying in S3 and S4, as tested according to GB / T 13298-2015 standard, is 2.8%, and the bonding strength with A350 LF3 steel, as tested according to GB / T 8642-2002 standard, is 36 MPa.

[0035] The nickel-based boron-containing composite coatings prepared by arc spraying in S3 and S4, together with the steel plate, exhibit a thermal neutron absorption capacity of approximately 95%. Within the reactor, a 4.0 × 10⁻⁶ ppm reaction was carried out. 13 ~2.5×10 14 cm -2 After neutron irradiation with a specific charge, the material did not show obvious irradiation damage; after a neutral salt spray test according to GB6458 standard for more than 2000 hours, no corrosion was observed on the coating surface.

[0036] Example 2:

[0037] The following steps outline the preparation method and application of a spray coating for the surface of spent fuel transport containers for nuclear power plants:

[0038] S1: Add B4C ceramic powder to the activation solution and ultrasonically treat at room temperature for 90 min; after static sedimentation, separate the activation solution, then wash the powder with deionized water, ready for plating. Ni-Mo coated B4C powder was prepared using a room-temperature ultrasonic-assisted chemical plating method. The pH of the chemical plating solution was adjusted to 10 with NaOH, the powder loading was 10 g / L, and ultrasonic-assisted chemical plating was performed at room temperature for 120 min. After chemical plating, the powder was washed with deionized water and dried to obtain Ni-Mo coated B4C powder.

[0039] S2: Take 40 parts by weight of Ni-Mo coated B4C powder, 30 parts by weight of FeB powder and 30 parts by weight of FeCr67C6.0 powder, stir them at high speed with a V-type powder mixer, and fill them into a U-shaped Ni-Cu (Monel 400) alloy strip with a purity of 99% with a certain shape. The filling rate is 40%. After rolling and drawing, it is made into a Φ2.0mm powder core nickel-based wire.

[0040] S3: Using the arc spraying method, NiCrB powder core wire is directly sprayed onto the surface of A350 LF3 steel used in nuclear power spent fuel containers through a spray gun. The spraying process parameters are: voltage 30V; current 200A; spraying distance 150mm; compressed air pressure 0.5MPa, to prepare a NiCrB base layer with a thickness of 100μm.

[0041] S4: Using the arc spraying method, the nickel-based wire powder from S1 is sprayed onto the surface of A350 LF3 steel used in nuclear power spent fuel containers as a NiCrB base layer through a spray gun. The spraying process parameters are: voltage 35V; current 220A; spraying distance 150mm; compressed air pressure 0.5MPa, to prepare a nickel-based boron-containing composite coating with a thickness of 2000μm.

[0042] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power is characterized in that the components and concentrations of the chemical plating solution in S1 are as follows: NiSO4·6H2O 20g / L, Na2MoO4·2H2O 15g / L, Na3C6H5O7·2H2O 30g / L, CN2H4S 0.05g / L, and N2H4·H2O (80%) 100mL / L.

[0043] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power is characterized in that the particle size range of Ni-Mo coated B4C powder, FeB powder and FeCr67C6.0 powder in S2 is 40μm, the high-speed stirring rate of the V-type mixer is 4000 rpm and the stirring time is 120 min.

[0044] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power plants is characterized in that the composition of the NiCrB core wire in S3 is: Cr 20wt.%, B 5.0wt.%, O≤0.1wt.%, and Ni balance. The outer sheath is made of nickel strip, and the final formed core wire has a diameter of 2.0mm.

[0045] The steel grade for spent nuclear fuel containers is A350 LF3.

[0046] The porosity of the nickel-based boron-containing composite coatings obtained by spraying in S3 and S4, as tested according to GB / T 13298-2015 standard, is 2.3%, and the bonding strength with A350 LF3 steel, as tested according to GB / T 8642-2002 standard, is 41 MPa.

[0047] The nickel-based boron-containing composite coatings prepared by arc spraying in S3 and S4, together with the steel plate, exhibit a thermal neutron absorption capacity of approximately 93%. Within the reactor, a 4.0 × 10⁻⁶ ppm reaction was carried out. 13 ~2.5×10 14 cm -2 After neutron irradiation with a specific charge, the material did not show obvious irradiation damage; after a neutral salt spray test according to GB6458 standard for more than 2000 hours, no corrosion was observed on the coating surface.

[0048] Example 3:

[0049] The following steps outline the preparation method and application of a spray coating for the surface of spent fuel transport containers for nuclear power plants:

[0050] S1: Add B4C ceramic powder to the activation solution and ultrasonically treat at room temperature for 90 min; after static sedimentation, separate the activation solution, then wash the powder with deionized water, ready for plating. Ni-Mo coated B4C powder was prepared using a room-temperature ultrasonic-assisted chemical plating method. The pH of the chemical plating solution was adjusted to 10 with NaOH, the powder loading was 10 g / L, and ultrasonic-assisted chemical plating was performed at room temperature for 120 min. After chemical plating, the powder was washed with deionized water and dried to obtain Ni-Mo coated B4C powder.

[0051] S2: Take 30 parts by weight of Ni-Mo coated B4C powder, 30 parts by weight of FeB powder and 40 parts by weight of FeCr67C6.0 powder, stir them at high speed with a V-type powder mixer, and fill them into a U-shaped Ni-Cu (Monel 400) alloy strip with a purity of 99% with a certain shape. The filling rate is 40%. After rolling and drawing, it is made into a Φ2.0mm powder core nickel-based wire.

[0052] S3: Using the arc spraying method, NiCrB powder core wire is directly sprayed onto the surface of A350 LF3 steel used in nuclear power spent fuel containers through a spray gun. The spraying process parameters are: voltage 30V; current 200A; spraying distance 150mm; compressed air pressure 0.5MPa, to prepare a NiCrB base layer with a thickness of 100μm.

[0053] S4: Using the arc spraying method, the nickel-based wire powder from S1 is sprayed onto the surface of A350 LF3 steel used in nuclear power spent fuel containers as a NiCrB base layer through a spray gun. The spraying process parameters are: voltage 35V; current 220A; spraying distance 150mm; compressed air pressure 0.5MPa, to prepare a nickel-based boron-containing composite coating with a thickness of 2000μm.

[0054] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power is characterized in that the components and concentrations of the chemical plating solution in S1 are as follows: NiSO4·6H2O 20g / L, Na2MoO4·2H2O 15g / L, Na3C6H5O7·2H2O 30g / L, CN2H4S 0.05g / L, and N2H4·H2O (80%) 100mL / L.

[0055] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power is characterized in that the particle size range of Ni-Mo coated B4C powder, FeB powder and FeCr67C6.0 powder in S2 is 40μm, the high-speed stirring rate of the V-type mixer is 4000 rpm and the stirring time is 120 min.

[0056] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power plants is characterized in that the composition of the NiCrB core wire in S3 is: Cr 20wt.%, B 5.0wt.%, O≤0.1wt.%, and Ni balance. The outer sheath is made of nickel strip, and the final formed core wire has a diameter of 2.0mm.

[0057] The steel grade for spent nuclear fuel containers is A350 LF3.

[0058] The porosity of the nickel-based boron-containing composite coatings obtained by spraying in S3 and S4, as tested according to GB / T 13298-2015 standard, is 1.9%, and the bonding strength with A350 LF3 steel, as tested according to GB / T 8642-2002 standard, is 43 MPa.

[0059] The nickel-based boron-containing composite coatings prepared by arc spraying in S3 and S4, together with the steel plate, exhibit a thermal neutron absorption capacity of approximately 91%. Within the reactor, a 4.0 × 10⁻⁶ ppm reaction was carried out. 13 ~2.5×10 14 cm -2 After neutron irradiation with a specific charge, the material did not show obvious irradiation damage; after a neutral salt spray test according to GB6458 standard for more than 2000 hours, no corrosion was observed on the coating surface.

[0060] Comparative Example 1

[0061] The following steps outline the preparation method and application of a spray coating for the surface of spent fuel transport containers for nuclear power plants:

[0062] S1: Add B4C ceramic powder to the activation solution and ultrasonically treat it at room temperature for 90 min; wash the powder with deionized water and dry it to obtain uncoated B4C powder.

[0063] S2: Take 50 parts by weight of uncoated B4C powder, 20 parts by weight of FeB powder and 30 parts by weight of FeCr67C6.0 powder, mix them at high speed with a V-type powder mixer, and fill them into a U-shaped pure Ni strip with a purity of 99% with a certain shape. The filling rate is 45%. The strip is then rolled and drawn to form a Φ2.0mm powder core nickel-based wire.

[0064] S3: Using the arc spraying method, the nickel-based wire powder from S1 is directly sprayed onto the surface of A350 LF3 steel for nuclear power spent fuel containers through a spray gun. The spraying process parameters are: voltage 35V; current 220A; spraying distance 150mm; compressed air pressure 0.5MPa, to prepare a nickel-based boron-containing composite coating with a thickness of 2000μm.

[0065] The above-mentioned method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power is characterized in that the particle size range of B4C powder, FeB powder and FeCr67C6.0 powder in S2 is 40μm, the high-speed stirring rate of the V-type mixer is 4000 rpm, and the stirring time is 120 min.

[0066] The steel grade for spent nuclear fuel containers is A350 LF3.

[0067] The porosity of the nickel-based boron-containing composite coating obtained by spraying in S3, as tested according to GB / T 13298-2015 standard, is 5.7%, and the bonding strength with A350 LF3 steel, as tested according to GB / T 8642-2002 standard, is 18 MPa, which is lower than that of Examples 1-3.

[0068] The nickel-based boron-containing composite coatings prepared by arc spraying in S3 and S4, along with the overall thermal neutron absorption performance of the steel plate, is approximately 77%, lower than that in Examples 1-3. The reaction was carried out in a reactor at 4.0 × 10⁻⁶ ppm. 13 ~2.5×10 14 cm -2 After neutron irradiation with a specific charge, the material did not show obvious irradiation damage; after a neutral salt spray test according to GB6458 standard for more than 2000 hours, no corrosion was observed on the coating surface.

[0069] As can be seen from Examples 1-3 and Comparative Example 1, the Ni-based boron-containing composite coating obtained by the coating preparation method of the nuclear power spent fuel transport container of the present invention has low boron element loss during the spraying process due to the Ni-Mo coating of B4C powder. AES detection shows that the boron element content on the coating surface is ≥40 at.%. Therefore, the arc-sprayed Ni-based boron-containing composite coating obtained by the present invention has strong thermal neutron absorption capacity, with a neutron absorption cross section far exceeding that of ordinary boron-containing steel, and a thermal neutron absorption performance of not less than 90%. The high-speed stirring of the V-type powder mixer ensures that the particles of each component in the core wire can be evenly dispersed. The core wire produced by rolling and drawing, as well as the arc spraying method, ensure the uniform distribution of each component in the coating on the surface of A350 LF3 steel. The nickel-based core wire is made by using U-shaped Ni-Cu (Monel 400) alloy strip. The Cu element contained in the core wire helps to improve the conductivity of the wire, obtain better melting and atomization effects, and help to reduce the porosity of the sprayed coating. Arc spraying of NiCrB as the base coat and arc spraying of Ni-based boron-containing composite coating as the top coat greatly improves the bonding strength between the Ni-based composite coating and A350 LF3 steel, as well as the density of the coating. Due to the use of arc spraying, the energy consumption and cost of spraying are also greatly reduced, while the efficiency and safety of spraying are improved. Furthermore, through the inventors' creative efforts, the surface roughness was further increased by spraying NiCrB as a base layer and setting the arc spraying parameters, ensuring the bonding strength between the Ni-based coating and the A350 LF3 steel. Simultaneously, the Ni-based coating exhibits excellent high-temperature resistance and corrosion resistance, while the large-scale introduction of boron enhances the shielding effect against gamma radiation and neutron radiation. The arc-sprayed Ni-based boron-containing composite coating obtained by this invention possesses strong thermal neutron absorption capacity, with a neutron absorption cross-section far exceeding that of ordinary boron-containing steel, achieving a thermal neutron absorption performance of no less than 90%. Therefore, the combination of A350 LF3 steel and arc-sprayed Ni-based boron-containing composite coating achieves the purpose of radioactive shielding while meeting the structural strength requirements of the container, contributing to the comprehensive improvement of the service life of spent fuel transport containers for nuclear power plants.

[0070] The above embodiments are for illustrative purposes only and are not intended to limit the invention. Those skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions should also fall within the scope of the invention and should be defined by the claims.

Claims

1. A method for preparing and applying a coating for spraying onto the surface of a spent fuel transport container for nuclear power plants, characterized in that, The preparation method and application include the following steps: S1: Add B4C ceramic powder to the activation solution and ultrasonically treat at room temperature for 60-90 min; after static sedimentation, separate the activation solution and wash the powder with deionized water for plating; Ni-Mo coated B4C powder is prepared by room temperature ultrasonic-assisted chemical plating. The composition and concentration of the chemical plating solution are as follows: NiSO4·6H2O 15-20 g / L, Na2MoO4·2H2O 10-15 g / L, Na3C6H5O7·2H2O 20-30 g / L, CN2H4S 0.02-0.10 g / L and N2H4·H2O(80%) 80-100 mL / L. Adjust the pH of the chemical plating solution to 9-11 with NaOH. The powder loading is 8-12 g / L. Perform ultrasonic-assisted chemical plating at room temperature for 80-120 min. After chemical plating, wash the powder with deionized water and dry it to obtain Ni-Mo coated B4C powder. S2: Take 30-50 parts by weight of Ni-Mo coated B4C powder, 20-30 parts by weight of FeB powder, and 20-50 parts by weight of FeCr67C6.0 powder. After high-speed mixing with a V-type powder mixer, fill the mixture into a U-shaped Ni-Cu (Monel 400) alloy strip with a purity of 99% and a certain shape. The filling rate is 30-50%. Then, roll and draw the strip to form... Φ 2.0~3.0mm powder-cored nickel-based wire; S3: Using the arc spraying method, NiCrB powder-coated wire is directly sprayed onto the surface of A350LF3 steel used in nuclear power spent fuel containers through a spray gun. The spraying process parameters are: voltage 28~35V; current 180~220A; spraying distance 150~200mm; compressed air pressure 0.4~0.6MPa, to prepare a NiCrB underlayer with a thickness of 50~100μm. S4: Using the arc spraying method, the nickel-based wire powder from S1 is sprayed onto the surface of A350LF3 steel used in nuclear power spent fuel containers as a NiCrB base layer through a spray gun. The spraying process parameters are: voltage 30~35V; current 200~250A; spraying distance 150~200mm; compressed air pressure 0.4~0.6MPa, to prepare a nickel-based boron-containing composite coating with a thickness of 1000~2000μm.

2. The method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power plants as described in claim 1, characterized in that, The particle size range of Ni-Mo coated B4C powder, FeB powder and FeCr67C6.0 powder in S2 is 20~60μm. The high-speed stirring rate of the V-type mixer is 3000~5000 rpm and the stirring time is 60~120min.

3. The method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power plants as described in claim 1, characterized in that... The composition of the NiCrB core wire in S3 is: Cr 18~20wt.%, B 5.0~7.0wt.%, O≤0.1wt.%, Ni balance; the outer sheath is made of nickel strip, and the diameter of the final formed core wire is 2.0~3.0mm.

4. The method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power plants as described in claim 1, characterized in that, The porosity of the nickel-based composite coating obtained by spraying in S3 and S4 does not exceed 3%, and the bonding strength with A350 LF3 steel is not less than 35 MPa.

5. The method for preparing and applying a coating on the surface of a spent fuel transport container for nuclear power plants as described in claim 1, characterized in that, The nickel-based boron-containing composite coating prepared by arc spraying in S3 and S4, together with the steel plate, has a thermal neutron absorption performance of no less than 90%.

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