High-temperature resistant nuclear fuel cladding tube based on porous interface and its intelligent manufacturing method

Abstract

The present invention relates to a high-temperature resistant nuclear fuel cladding tube based on a porous interface, which comprises a refractory metal inner layer and a SiC-based composite material outer layer serving as the inner and outer walls of the nuclear fuel cladding tube, and at least one nano-β-SiC porous interface intermediate layer with a porosity of not less than 20% is provided between the refractory metal inner layer and the SiC-based composite material outer layer. A smart manufacturing method for the high-temperature resistant nuclear fuel cladding tube based on the porous interface is also provided. The nano-β-SiC porous interface intermediate layer structure provided by the present invention greatly reduces the interfacial thermal stress caused by thermal mismatch and temperature gradient of the nuclear fuel cladding in a high-temperature environment, improves the thermal stability and high-temperature resistance of the nuclear fuel cladding, realizes the design and optimization of the interface structure of the nuclear fuel cladding, and based on the mechanized, digital and information-based preparation process, the process parameters during the preparation of the nuclear fuel cladding can be precisely controlled to ensure high-quality production, thus realizing the smart manufacturing of the nuclear fuel cladding.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear reactor fuel elements, and particularly to a composite cladding structure and an intelligent manufacturing method thereof. Background Art

[0002] In the design and implementation of medium and small reactors, the selection of nuclear fuel cladding materials is a crucial step in their successful application. Nuclear fuel cladding tubes are used to contain nuclear fuel pellets and prevent the released radioactive fission products from finally entering the external environment through the coolant. The emergence of microreactors poses new challenges to the performance of nuclear fuel claddings.

[0003] Due to its excellent high-temperature mechanical properties, radiation resistance, corrosion resistance and other advantages, SiC-based composites are expected to be applied in the fourth-generation advanced reactors, such as high-temperature gas-cooled reactors, molten salt reactors and fast neutron reactors. However, at present, the airtight performance of SiC-based composites is poor, which limits their further application in advanced reactors. One of the key solutions to solve the poor airtightness of SiC / SiC materials is to compound refractory metals with SiC / SiC materials to form heterogeneous composites (such as Re-SiC / SiC, Ta-SiC / SiC).

[0004] However, due to the large difference in material properties (thermal expansion coefficient, Young's modulus) between refractory metals and SiC-based composites in heterogeneous composites, at high-temperature environmental conditions, the interface between refractory metals and SiC ceramic matrix will not only be subjected to thermal stress caused by temperature gradient, but also be subjected to thermal stress caused by material thermal mismatch. This greatly increases the risk of delamination of heterogeneous materials, and further affects their application and development in the reactor core. Therefore, how to design the interface structure between refractory metals and SiC-based composites is the key issue to ensure that the interface has high bonding strength and to improve its reliability and safety when serving in extreme environments.

[0005] In terms of the interface structure design of heterogeneous materials, CN113571209A proposes to design a transition layer interface with a gradient content of Mo between refractory metal Mo and SiC-based composites to improve the crack resistance of the heterogeneous interface and reduce the degree of mismatch in thermal expansion coefficient between the two materials. Although it improves the problem of excessive interface stress to a certain extent, this gradient interface structure will still have: high interface thermal stress (up to 1100 MPa) caused by temperature gradient and thermal mismatch, which will greatly reduce the high-temperature mechanical properties and thermal stability of heterogeneous composites. Summary of the Invention

[0006] The object of the present invention is to avoid the deficiencies of the prior art and provide a high-temperature resistant nuclear fuel cladding tube based on a porous interface and its intelligent manufacturing method, which can reduce the interfacial thermal stress caused by thermal mismatch of the composite cladding under high-temperature environmental conditions, improve the thermal stability and high-temperature resistance of the composite cladding, and optimize the heterogeneous interface structure.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a high-temperature resistant nuclear fuel cladding tube based on a porous interface, comprising a refractory metal inner layer and a SiC-based composite material outer layer as the inner and outer walls of the nuclear fuel cladding tube;

[0008] At least one nano-β-SiC porous interface intermediate layer with a porosity not less than 20% is provided between the refractory metal inner layer and the SiC-based composite material outer layer, and the thermal stress value of the nano-β-SiC porous interface intermediate layer is not higher than 700 MPa when the environmental temperature is higher than 900 °C;

[0009] The refractory metal inner layer is made of a refractory metal, and the refractory metal is a molybdenum-rhenium alloy or rhenium or tantalum or nickel with a porosity not exceeding 0.5%, which is used to improve the airtightness of the inner wall of the nuclear fuel cladding tube and cooperate with the SiC-based composite material outer layer to improve the overall load-bearing capacity of the nuclear fuel cladding tube;

[0010] The SiC-based composite material outer layer is composed of an inner layer of a SiC fiber preform and an outer layer of a SiC ceramic matrix with a porosity less than 10%, and the surface of the inner layer of the SiC fiber preform in contact with the outer layer of the SiC ceramic matrix is a pyrolytic carbon PyC interface;

[0011] Among them, the inner layer of the SiC fiber preform is used to improve the toughness of the nuclear fuel cladding tube, the outer layer of the SiC ceramic matrix is used to improve the strength of the nuclear fuel cladding tube and protect the inner layer of the SiC fiber preform, and cooperate with the pyrolytic carbon PyC interface to adjust the thermal stress between the inner layer of the SiC fiber preform and the outer layer of the SiC ceramic matrix.

[0012] Furthermore, the inner hole diameter of the high-temperature resistant nuclear fuel cladding tube is 9.0 - 10.0 mm;

[0013] In the thickness direction of the tube wall, the thickness of the refractory metal inner layer is 0.25 - 0.40 mm, the thickness of the nano-β-SiC porous interface intermediate layer is 5 - 20 μm, and the thickness of the SiC-based composite material outer layer is 0.6 - 0.7 mm.

[0014] Furthermore, the volume fraction of SiC fibers in the inner layer of the SiC fiber preform is 20 - 40%.

[0015] Furthermore, the environmental temperature is 900 °C - 1200 °C.

[0016] Furthermore, the porosity of the nano-β-SiC porous interface intermediate layer is 20% - 50%.

[0017] The present invention also provides an intelligent manufacturing method for the high-temperature resistant nuclear fuel cladding tube based on the porous interface described above, comprising the following steps:

[0018] First, use a defect detection model based on CT scanning to judge, and screen out refractory metal tubes with a defect volume fraction not exceeding 0.5%. The refractory metal tubes are made of the refractory metal;

[0019] Then, stabilize the temperature on the surface of the refractory metal tube at -50°C to -20°C to ensure that when spraying the SiC suspension next, the sprayed SiC suspension has no agglomeration phenomenon and can be evenly frozen on the surface of the refractory metal tube, thereby generating a nano-β-SiC porous interface intermediate layer with uniformly distributed pores;

[0020] Then, with an air spraying pressure of 0.2 - 0.6 MPa, spray a nano-β-SiC suspension with a mass fraction of 40% - 45% on the surface of the refractory metal tube. Immediately after spraying, carry out freeze-drying for 20 - 24 h under the condition that the initial freezing temperature is -80°C to -50°C, and then obtain the nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding tube. At this time, the refractory metal tube is the refractory metal inner layer of the nuclear fuel cladding tube;

[0021] Next, use a porous structure detection model based on CT scanning to judge, and screen out a nano-β-SiC porous interface intermediate layer with uniformly distributed pores and a porosity of 20% - 50%;

[0022] Then, in an isothermal CVI furnace under the conditions of a deposition temperature of 850 - 1000°C, a deposition pressure of 4 kPa - 6 kPa, and a deposition rate of 10 - 20 μm / h, deposit a 5 - 10 μm thick SiC protective layer on the surface of the nano-β-SiC porous interface intermediate layer to improve the chemical stability of the nano-β-SiC porous interface intermediate layer and enhance the interfacial bonding strength between the refractory metal inner layer and the SiC matrix composite outer layer;

[0023] Next, on the surface of the SiC protective layer, weave the SiC fibers in the SiC protective layer at a rotation speed of 0.3 - 0.4 rad / s and a winding speed of 1.5 - 4 mm / s to form an inner layer of a SiC fiber preform with a woven structure; this step is carried out in a weaving machine, and the weaving machine is a two-dimensional weaving machine or a three-dimensional weaving machine.

[0024] Then, deposit a pyrolytic carbon PyC protective layer and a SiC ceramic matrix for densifying the inner layer of the SiC fiber preform on the surface of the inner layer of the SiC fiber preform in stages;

[0025] Finally, a porous structure detection model based on CT scanning is used for judgment, and SiC ceramic matrices with a porosity less than 10% are screened out, thus obtaining high-temperature resistant nuclear fuel cladding tubes with a complete structure based on a porous interface;

[0026] At this time, a pyrolytic carbon PyC interface is formed in the pyrolytic carbon PyC protective layer between the SiC ceramic matrix and the inner layer of the SiC fiber preform; the SiC ceramic matrix is the outer layer of the SiC ceramic matrix.

[0027] Furthermore, the specific steps for stabilizing the temperature of the refractory metal tube are as follows:

[0028] The refractory metal tube is subjected to liquid nitrogen spray cooling treatment under the conditions of a spraying pressure of 0.1 - 0.2 MPa and a spraying distance of 20 - 25 cm. After the surface temperature of the refractory metal tube reaches -90°C to -80°C, the refractory metal tube is fixed at the central position of the high-frequency induction heating coil to uniformly heat the refractory metal tube, thereby ensuring that the temperature of the refractory metal tube is stabilized between -50°C and -20°C.

[0029] Furthermore, the specific process for the defect detection model based on CT scanning to judge the refractory metal tube is as follows:

[0030] First, the refractory metal tube is scanned 360° using an industrial CT device to generate a three-dimensional image of the refractory metal tube with a pixel of 512×512×N, which includes crack and pore defect features, where N is the length of the CT scan;

[0031] Then, the defect detection model of the industrial CT device counts the number of crack and pore defect pixel points in the three-dimensional image data in the three-dimensional image;

[0032] Finally, a defect volume fraction threshold of 0.5% is set, and the defect detection model screens out refractory metal tubes with a defect volume fraction not exceeding 0.5%.

[0033] Furthermore, the specific process for the porous structure detection model based on CT scanning to judge the nano-β-SiC porous interface intermediate layer and the SiC ceramic matrix is as follows:

[0034] First, the nano-β-SiC porous interface intermediate layer and the SiC ceramic matrix are scanned 360° respectively using an industrial CT device to generate three-dimensional images of the nano-β-SiC porous interface intermediate layer and the SiC ceramic matrix with a pixel of 512×512×N, which includes pore shape features, where N is the length of the CT scan;

[0035] Then, the porous structure detection model of the industrial CT device calculates the porosity, average pore diameter, and pore volume fraction based on the three-dimensional image;

[0036] Next, set the pore volume fraction threshold of the nano-β-SiC porous interface interlayer to 20-50%, and the pore volume fraction threshold of the SiC ceramic matrix to 10%. The porous structure detection model can then screen out the nano-β-SiC porous interface interlayer with a porosity of 20-50% and the SiC ceramic matrix with a porosity less than 10%.

[0037] Finally, redeposit the nano-β-SiC porous interface interlayer with a pore volume fraction greater than 50% and less than 20% and the SiC ceramic matrix with a pore volume fraction greater than 10%, so as to use the porous structure detection model to calculate the pore volume fraction again and timely adjust the deposition process parameters of the nano-β-SiC porous interface interlayer and the SiC ceramic matrix.

[0038] Furthermore, deposit the pyrolytic carbon PyC protective layer and the SiC ceramic matrix on the inner layer surface of the SiC fiber preform in stages. The specific steps are as follows:

[0039] In an ultra-high temperature CVI furnace filled with propylene with a concentration of 1-5 vol%, at a deposition temperature of 900-1200 °C and a deposition pressure of 3 kPa-4 kPa, perform the first-stage deposition for a deposition time of 10-50 h, that is, deposit the pyrolytic carbon PyC protective layer on the inner layer surface of the SiC fiber preform.

[0040] Next, purge the furnace chamber with argon with a gas flow rate of 10-50 L / min for 0.5-1 h, and cool down the inner layer of the SiC fiber preform with the pyrolytic carbon PyC protective layer to 800-1000 °C to ensure the removal of residual reaction gases and by-products and prevent oxygen from entering to cause high-temperature oxidation and pollution.

[0041] Then, under the furnace environment conditions filled with trichloromethylsilane with a concentration of 2-4 vol%, at a deposition temperature of 960 °C-1180 °C and a deposition pressure of 2 kPa-4 kPa, perform the second-stage deposition for a deposition time of 100 h-200 h, that is, deposit the SiC ceramic matrix on the inner layer surface of the SiC fiber preform with the pyrolytic carbon PyC protective layer.

[0042] The beneficial effects of the present invention are as follows: By providing a porous SiC interface between the refractory metal and the SiC ceramic matrix, and through finite element calculation, it is found that compared with the nuclear fuel cladding with a dense SiC interface having a porosity less than 0.1% or a Mo transition layer interface, first, when the ambient temperature is higher than 900 °C, the nuclear fuel cladding of the present invention can still ensure that the interfacial thermal stress does not exceed 700 MPa. Second, compared with the thermal stresses of these two interfaces, the thermal stress of the present invention is reduced by 44% and 64% respectively, indicating that the porous SiC interface structure provided by the present invention greatly reduces the interfacial thermal stress caused by thermal mismatch and temperature gradient in the high-temperature environment of the fuel cladding, improves the thermal stability and high-temperature resistance of the nuclear fuel cladding, and realizes the design and optimization of the interfacial structure of the nuclear fuel cladding.

[0043] In addition, based on the mechanized, digital, and information-based preparation process, the process parameters during the preparation of the nuclear fuel cladding can be precisely controlled to ensure high-quality production, realizing the intelligent manufacturing of the nuclear fuel cladding. Brief Description of the Drawings

[0044] Figure 1 It is a flow chart of the intelligent manufacturing of the present invention;

[0045] Figure 2 It is a schematic comparison diagram of the thermal stress distribution curve in the thickness direction of the fuel cladding tube provided by the present invention under the condition of a temperature of 1000 - 1200 °C through finite element calculation;

[0046] Figure 3 It is a columnar diagram of the comparison of the interfacial thermal stress of the fuel cladding provided by the present invention when the interfacial temperature is about 1100 °C through finite element calculation;

[0047] Figure 4 It is a structural characterization diagram and a composition energy spectrum diagram of the nuclear fuel cladding prepared in Example 1 of the present invention;

[0048] In the figure, (a) is the structure diagram of the nuclear fuel cladding; (b) is the microscopic structure diagram of the nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding; (c) is the energy spectrum diagram of the nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding; (d) is the structure diagram of the nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding during finite element calculation;

[0049] Figure 5 It is a structural feature diagram of the refractory metal pipe judged by the defect detection model of the present invention;

[0050] In the figure, (a) is the judged unqualified refractory metal pipe; (b) is the judged qualified dense-grade refractory metal pipe;

[0051] Figure 6This is the three-dimensional image data reconstruction structure diagram for the judgment of the nano-β-SiC porous interface intermediate layer by the porous structure detection model of the present invention;

[0052] In the figure, (a) is the unqualified porous interface obtained by judgment; (b) is the qualified porous interface obtained by judgment;

[0053] Figure 7 This is the three-dimensional image data reconstruction structure diagram for the judgment of the SiC ceramic matrix by the porous structure detection model of the present invention;

[0054] In the figure, (a) is the unqualified SiC ceramic matrix obtained by judgment; (b) is the qualified SiC ceramic matrix obtained by judgment;

[0055] Figure 8 This is the physical diagram of the nuclear fuel cladding prepared by the present invention;

[0056] In the figure, (a) is the cross-sectional physical diagram of the Re-SiC / SiC nuclear fuel cladding; (b) is the external view of the Re-SiC / SiC nuclear fuel cladding with a porous interface. Detailed implementation manners

[0057] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0058] To achieve the above object, the present invention provides the following detailed implementation manners:

[0059] Example 1: As Figure 8 shown, a high-temperature resistant nuclear fuel cladding tube based on a porous interface includes a refractory metal inner layer and a SiC-based composite material outer layer that serve as the inner and outer walls of the nuclear fuel cladding tube;

[0060] At least one nano-β-SiC porous interface intermediate layer with a porosity of not less than 20% is provided between the refractory metal inner layer and the SiC-based composite material outer layer, so that the thermal stress value of the nano-β-SiC porous interface intermediate layer does not exceed 700 MPa when the environmental temperature is higher than 900 °C;

[0061] The refractory metal inner layer is made of a refractory metal, and the refractory metal is a molybdenum-rhenium alloy or rhenium or tantalum or nickel with a porosity of not more than 0.5%, which is used to improve the airtightness of the inner wall of the nuclear fuel cladding tube and cooperate with the SiC-based composite material outer layer to improve the overall load-bearing capacity of the nuclear fuel cladding tube;

[0062] The SiC-based composite material outer layer is composed of an inner layer of a SiC fiber preform and an outer layer of a SiC ceramic matrix with a porosity of less than 10%, and the surface of the inner layer of the SiC fiber preform in contact with the outer layer of the SiC ceramic matrix is a pyrolytic carbon PyC interface; the volume fraction of SiC fibers in the inner layer of the SiC fiber preform is 20-40%;

[0063] Among them, the inner layer of the SiC fiber preform is used to improve the toughness of the nuclear fuel cladding tube, and the outer layer of the SiC ceramic matrix is used to improve the strength of the nuclear fuel cladding tube while protecting the inner layer of the SiC fiber preform, and cooperate with the pyrolytic carbon PyC interface to adjust the thermal stress between the inner layer of the SiC fiber preform and the outer layer of the SiC ceramic matrix.

[0064] As Figure 8 shown, the inner diameter of the high-temperature resistant nuclear fuel cladding tube based on the porous interface is 9.0 - 10.0 mm; the thickness of the refractory metal inner layer in the wall thickness direction is 0.25 - 0.40 mm, the thickness of the nano-β-SiC porous interface intermediate layer is 5 - 20 μm, and the thickness of the SiC matrix composite outer layer is 0.6 - 0.7 mm.

[0065] Example 2 is the same as Example 1, except that the environmental temperature is 900°C - 1200°C; the porosity of the nano-β-SiC porous interface intermediate layer is 20% - 50%.

[0066] Example 3, as Figure 1 shown, the present invention also provides an intelligent manufacturing method for the above-mentioned high-temperature resistant nuclear fuel cladding tube based on the porous interface, including the following steps:

[0067] Step 1: Make a refractory metal tube from refractory metal, use an industrial CT device to perform a 360° scan on the refractory metal tube to generate a three-dimensional image of the refractory metal tube with a pixel of 512×512×N and including crack and pore defect features, where N is the length of the CT scan; and use the defect detection model of the industrial CT device to count the number of crack and pore defect pixel points in the three-dimensional image data in the three-dimensional image.

[0068] Step 2: Set the defect volume fraction threshold to 0.5%, and the defect detection model will screen out the refractory metal tubes with a defect volume fraction not exceeding 0.5%, that is, screen out the refractory metal tubes with a defect volume fraction not exceeding 0.5%, and the remaining refractory metal tubes will be scrapped.

[0069] Step 3: Perform liquid nitrogen spray cooling treatment on the refractory metal tube under the conditions of a spraying pressure of 0.1 - 0.2 MPa and a spraying distance of 20 - 25 cm. After the surface temperature of the refractory metal tube reaches -90°C - -80°C, then fix the refractory metal tube at the center position of the high-frequency induction heating coil to make the refractory metal tube uniformly heated, so as to ensure that the temperature of the refractory metal tube is stable between -50°C - -20°C.

[0070] Step 4: Spray a nano-β-SiC suspension with a mass fraction of 40% - 45% on the surface of the refractory metal tube at an air spraying pressure of 0.2 - 0.6 MPa.

[0071] Step 5: Immediately after spraying, conduct freeze-drying for 20 - 24 h under the condition that the initial freezing temperature is -80°C to -50°C, and a nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding tube is obtained. At this time, the refractory metal tube is the refractory metal inner layer of the nuclear fuel cladding tube.

[0072] Step 6: Use an industrial CT device to perform a 360° scan on the nano-β-SiC porous interface intermediate layer respectively to generate a three-dimensional image of the nano-β-SiC porous interface intermediate layer with a pixel of 512×512×N and including pore shape characteristics, where N is the length of the CT scan; the porous structure detection model of the industrial CT device calculates the porosity, average pore diameter, and pore volume fraction based on the three-dimensional image.

[0073] Step 7: Set the pore volume fraction threshold of the nano-β-SiC porous interface intermediate layer to 20% - 50%, and the porous structure detection model will screen out the nano-β-SiC porous interface intermediate layer with a porosity of 20% - 50%.

[0074] Step 8: Redeposit the nano-β-SiC porous interface intermediate layer with a pore volume fraction greater than 50% and less than 20%, that is, return to Step 3 for reprocessing, and then repeat Step 6 and Step 7 again, and timely adjust the deposition process parameters of the nano-β-SiC porous interface intermediate layer.

[0075] Step 9: Deposit a 5 - 10 μm thick SiC protective layer on the surface of the nano-β-SiC porous interface intermediate layer in an isothermal CVI furnace under the conditions of a deposition temperature of 850 - 1000°C, a deposition pressure of 4 kPa - 6 kPa, and a deposition rate of 10 - 20 μm / h, which is used to improve the chemical stability of the nano-β-SiC porous interface intermediate layer and enhance the interfacial bonding strength between the refractory metal inner layer and the SiC matrix composite outer layer.

[0076] Step 10: On the surface of the SiC protective layer, weave the SiC fibers in the SiC protective layer at a rotation speed of 0.3 - 0.4 rad / s and a take-up speed of 1.5 - 4 mm / s to form an inner layer of the SiC fiber preform with a woven structure; this step is carried out in a weaving machine, and the weaving machine is a two-dimensional weaving machine or a three-dimensional weaving machine.

[0077] Step 11: In an ultra-high temperature CVI furnace filled with propylene at a concentration of 1-5 vol%, at a deposition temperature of 900-1200 °C and a deposition pressure of 3 kPa-4 kPa, a first-stage deposition with a deposition time of 10-50 h is carried out on the inner layer surface of the SiC fiber preform, that is, a pyrolytic carbon PyC protective layer is deposited on the inner layer surface of the SiC fiber preform. At this time, that is, the inner layer of the SiC fiber preform with a pyrolytic carbon PyC protective layer is obtained.

[0078] Step 12: Use argon with a gas flow rate of 10-50 L / min to purge the furnace chamber for 0.5-1 h, and cool down the inner layer of the SiC fiber preform with a pyrolytic carbon PyC protective layer to 800-1000 °C to ensure the removal of residual reaction gases and by-products and prevent oxygen from entering to cause high-temperature oxidation and pollution.

[0079] Step 13: Under the furnace environment conditions filled with trichloromethylsilane at a concentration of 2-4 vol%, at a deposition temperature of 960 °C-1180 °C and a deposition pressure of 2 kPa-4 kPa, a second-stage deposition with a deposition time of 100 h-200 h is carried out, that is, a SiC ceramic matrix is deposited on the inner layer surface of the SiC fiber preform with a pyrolytic carbon PyC protective layer.

[0080] Step 14: Use an industrial CT device to scan the SiC ceramic matrix 360°, generate a three-dimensional image with a pixel of 512×512×N and including the SiC ceramic matrix, where N is the length of the CT scan; the porous structure detection model of the industrial CT device calculates the porosity, average pore diameter and pore volume fraction based on the three-dimensional image.

[0081] Step 15: Set the pore volume fraction threshold of the SiC ceramic matrix to 10%, and the porous structure detection model will screen out the SiC ceramic matrix with a porosity less than 10%.

[0082] Step 16: Redeposit the SiC ceramic matrix with a pore volume fraction greater than 10%, that is, return to Step 13 again, so as to calculate the pore volume fraction result using the porous structure detection model again and timely adjust the deposition process parameters of the SiC ceramic matrix.

[0083] Step 17: After screening out the SiC ceramic matrix with a porosity less than 10% based on the porous structure detection model of CT scan, a high-temperature resistant nuclear fuel cladding tube based on a porous interface with a complete structure is obtained;

[0084] At this time, the pyrolytic carbon PyC protective layer between the SiC ceramic matrix and the inner layer of the SiC fiber preform forms a pyrolytic carbon PyC interface; the SiC ceramic matrix is the outer layer of the SiC ceramic matrix.

[0085] AsFigures 2 - 7 As shown below, in order to further illustrate the technical solution and technical effect of the present invention, the following specific examples are provided:

[0086] Example 1: The high-temperature resistant nuclear fuel cladding tube based on a porous interface is composed of an inner layer of refractory metal Re and an outer layer of SiC-based composite material. The porosity of the nano-β-SiC porous interface intermediate layer between them is 20%. The inner diameter of the nuclear fuel cladding is 9.0 mm, the thickness of the refractory metal layer is 0.4 mm, the thickness of the nano-β-SiC porous interface intermediate layer is 15 μm, and the thickness of the SiC-based composite material layer is 0.7 mm.

[0087] Its preparation process is as follows:

[0088] (1) Non-destructive detection of internal defects of refractory metal: Use a full-automatic CT online detection system to scan the Re refractory metal pipe, construct a real-time three-dimensional model of it, and at the same time identify whether there are internal defects in the pipe, as Figure 5 shown in (a) below. Select dense-grade pipes with a porosity not exceeding 0.5% for the next step of processing, as Figure 5 shown in (b) below.

[0089] (2) Cooling the refractory metal with qualified quality: The robotic arm automatically grabs the dense-grade refractory metal pipe and performs liquid nitrogen spray cooling treatment. After the surface temperature of the refractory metal pipe reaches -80°C, then fix the refractory metal pipe at the center position of the high-frequency induction heating coil to make the refractory metal pipe evenly heated, so as to ensure that the target temperature of the refractory metal pipe is stably at -50°C.

[0090] (3) Spraying nano-β-SiC suspension and freeze-drying: After the target temperature in step (2) is stable, use an air spraying machine to spray a nano-β-SiC suspension with a mass fraction of 45% on the surface of the pipe, and then the robotic arm automatically grabs the pipe and puts it into the freeze-drying chamber and freeze-dries it for 20 h.

[0091] (4) Non-destructive detection of the porous interface and deposition of SiC protective layer: Use the CT online detection system to detect whether a nano-β-SiC porous interface intermediate layer with a thickness of 15 μm, as Figure 4 shown in (b) below, and a porosity of 20% is formed on the surface of the freeze-dried pipe, as Figure 6 shown in (b) below; the unqualified interface is re-cooled and sprayed, as Figure 6 shown in (a) below.

[0092] The robotic arm automatically puts the pipe with a qualified nano-β-SiC porous interface intermediate layer into an isothermal CVI furnace. The deposition temperature of the isothermal CVI furnace is set at 1000°C, the deposition pressure is set at 6 kPa, and the deposition rate is 10 μm / h for depositing a 5-μm SiC protective layer, asFigure 4 As shown in (c), to improve the chemical stability of the porous SiC interface and enhance the interfacial bonding strength.

[0093] (5) Braided fiber preform: After depositing the SiC protective layer, the mechanical arm is used to automatically install the pipe into a two-dimensional braiding machine, and a SiC fiber preform is braided on the surface of the pipe to form a braided pipe, so as to improve the toughness and strength of the nuclear fuel cladding.

[0094] (6) Depositing pyrolytic carbon interface and matrix densification: The braided pipe in step (5) is placed into an ultra-high temperature CVI furnace, and the deposition program is set successively as follows:

[0095] Using propylene as the precursor gas source, deposition temperature of 900 °C, deposition pressure of 3 kPa, and deposition time of 10 h as the first stage, cooling down to 800 °C and purging the furnace with argon for 0.5 h as the second stage, and trichloromethylsilane as the precursor gas source, deposition temperature of 960 °C, deposition pressure of 2 kPa, and deposition time of 100 h as the third stage, respectively deposit the pyrolytic carbon protective layer and densify the SiC ceramic matrix.

[0096] (7) Nondestructive testing of the SiC ceramic matrix: Use a CT online detection system to detect the densified SiC ceramic matrix, and screen out the SiC ceramic matrix with a porosity of 9%, as shown in (b); the unqualified SiC ceramic matrix is redeposited, as shown in (a), to obtain a high-temperature resistant nuclear fuel cladding tube with a complete structure based on a porous interface, as shown in (a). Figure 7 as shown in (b); the unqualified SiC ceramic matrix is redeposited, as shown in (a), Figure 7 to obtain a high-temperature resistant nuclear fuel cladding tube with a complete structure based on a porous interface, as shown in (a). Figure 4 as shown in (a).

[0097] Example 2: The high-temperature resistant nuclear fuel cladding tube based on a porous interface consists of an inner layer of refractory metal Ta and an outer layer of SiC-based composite material. The porosity of the nano-β-SiC porous interface intermediate layer between them is 30%. The inner diameter of the nuclear fuel cladding is 10.0 mm, the thickness of the refractory metal layer is 0.2 mm, the thickness of the porous interface layer is 20 μm, and the thickness of the SiC-based composite material layer is 0.6 mm.

[0098] Its preparation process is as follows:

[0099] (1) Nondestructive testing of internal defects of refractory metal: Use a full-automatic CT online detection system to scan the Ta refractory metal pipe, construct a real-time three-dimensional model of it, and at the same time identify whether there are internal defects in the pipe, and screen out dense-grade pipes with a porosity not exceeding 0.5% for the next step of processing.

[0100] (2)Cool refractory metals with qualified cooling quality: The robotic arm automatically grabs dense refractory metal tubes and conducts liquid nitrogen spray cooling treatment. After the surface temperature of the refractory metal tubes reaches -80°C, the refractory metal tubes are fixed at the center position of the high-frequency induction heating coil to make the refractory metal tubes evenly heated, so as to ensure that the target temperature of the refractory metal tubes is stably at -20°C.

[0101] (3)Spray nano-β-SiC suspension and conduct freeze-drying: After the target temperature in step (2) is stable, use an air spraying machine to spray a nano-β-SiC suspension with a mass fraction of 40% on the surface of the tubes, and then the robotic arm automatically grabs the tubes and puts them into the freeze-drying chamber for 24 hours of freeze-drying.

[0102] (4)Nondestructively detect the porous interface and deposit a SiC protective layer: Use a CT online detection system to detect whether a porous SiC interface with a thickness of 20μm and a porosity of 30% is formed on the surface of the freeze-dried tubes. The robotic arm automatically puts the tubes with a nano-β-SiC porous interface intermediate layer that meets the requirements into an isothermal CVI furnace. The deposition temperature of the isothermal CVI furnace is set at 850°C, the deposition pressure is set at 4kPa, and the deposition rate is 20μm / h to deposit a 10μm SiC protective layer to improve the chemical stability of the porous SiC interface and enhance the interface bonding strength.

[0103] (5)Weave a fiber preform: After depositing the SiC protective layer, use the robotic arm to automatically install the tubes into a three-dimensional weaving machine and weave a SiC fiber preform on the surface of the tubes to form a woven tube to improve the toughness and strength of the nuclear fuel cladding.

[0104] (6)Deposit a pyrolytic carbon interface and densify the matrix: Put the woven tube in step (5) into an ultra-high temperature CVI furnace, and the deposition program is set as follows:

[0105] Using the precursor gas source propylene, deposition temperature 1200°C, deposition pressure 4kPa, deposition time 50h as the first stage, cooling down to 800°C and purging the furnace chamber with argon for 1h as the second stage, and the precursor gas source trichloromethylsilane, deposition temperature 1180°C, deposition pressure 4kPa, deposition time 200h as the third stage, deposit a pyrolytic carbon protective layer and a SiC ceramic matrix respectively for densification treatment.

[0106] (7)Nondestructively detect the SiC ceramic matrix: Use a CT online detection system to detect the SiC ceramic matrix after densification treatment, screen out the SiC ceramic matrix with unqualified porosity for re-deposition, and the SiC ceramic matrix with qualified porosity is the high-temperature resistant nuclear fuel cladding tube with a complete structure based on the porous interface.

[0107] The structural diagram of the porous SiC interface for finite element calculation in the present invention is shown byFigure 4 The geometric diagram of the finite element calculation shown in (d) of the figure can be calculated as follows: Compared with the existing nuclear fuel cladding with a dense SiC interface with a porosity of less than 0.1% or a Mo transition layer interface, the thermal stress of the porous SiC interface provided by the present invention is not higher than 700 MP. Compared with the other two, the interface thermal stress is reduced by 44% and 64% respectively, as shown in Figure 3 the columnar diagram of the interface thermal stress shown in

[0108] As shown in Figure 2 the figure Figure 2 compares the upward thermal stress distribution of the nuclear fuel cladding structure with a porous SiC interface provided by the present invention and the existing nuclear fuel cladding with a dense SiC interface with a porosity of less than 0.1% or a Mo transition layer interface; it can be seen from the figure that the porous SiC interface structure greatly reduces the interface thermal stress caused by thermal mismatch of the nuclear fuel cladding in a high-temperature environment, improves the thermal stability and high-temperature resistance of the nuclear fuel cladding. At the same time, based on the mechanized, digital and information-based preparation process, the process parameters during the preparation of the nuclear fuel cladding can be precisely controlled to ensure high-quality production, realizing the intelligent manufacturing of the nuclear fuel cladding.

[0109] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high temperature resistant nuclear fuel cladding tube based on a porous interface, characterized in that: It includes a refractory metal inner layer and a SiC-based composite material outer layer as the inner and outer walls of the nuclear fuel cladding tube; At least one nano-β-SiC porous interface intermediate layer having a porosity of not less than 20% is provided between the refractory metal inner layer and the SiC-based composite material outer layer, and the thermal stress value of the nano-β-SiC porous interface intermediate layer is not higher than 700MPa when the ambient temperature is higher than 900°C; The refractory metal inner layer is made of refractory metal, and the refractory metal is a molybdenum-rhenium alloy or rhenium or tantalum or nickel with a porosity not exceeding 0.5%, and is used to improve the air tightness of the inner wall of the nuclear fuel cladding tube, and cooperates with the SiC-based composite material outer layer to improve the overall load-bearing capacity of the nuclear fuel cladding tube; The outer layer of the SiC-based composite material is composed of an inner layer of a SiC fiber preform and an outer layer of a SiC ceramic matrix having a porosity of less than 10%, and the surface in contact between the inner layer of the SiC fiber preform and the outer layer of the SiC ceramic matrix is ​​a pyrolytic carbon (PyC) interface; Among them, the inner layer of the SiC fiber preform is used to improve the toughness of the nuclear fuel cladding tube, and the outer layer of the SiC ceramic matrix is ​​used to improve the strength of the nuclear fuel cladding tube while protecting the inner layer of the SiC fiber preform, and cooperate with the pyrolytic carbon PyC interface to adjust the thermal stress between the inner layer of the SiC fiber preform and the outer layer of the SiC ceramic matrix.

2. The high temperature resistant nuclear fuel cladding tube based on porous interface according to claim 1, characterized in that: The inner diameter of the nuclear fuel cladding tube is 9.0-10.0 mm; The thickness of the refractory metal inner layer in the thickness direction of the tube wall is 0.25-0.40 mm, the thickness of the nano-β-SiC porous interface middle layer is 5-20 μm, and the thickness of the SiC-based composite material outer layer is 0.6-0.7 mm.

3. The high temperature resistant nuclear fuel cladding tube based on porous interface according to claim 1, characterized in that: The volume fraction of SiC fibers in the inner layer of the SiC fiber preform is 20-40%.

4. The high temperature resistant nuclear fuel cladding tube based on porous interface according to claim 1, characterized in that: The ambient temperature is 900°C to 1200°C.

5. The high temperature resistant nuclear fuel cladding tube based on porous interface according to claim 1, characterized in that: The porosity of the nano-β-SiC porous interface intermediate layer is 20-50%.

6. An intelligent manufacturing method for a high temperature resistant nuclear fuel cladding tube based on a porous interface as claimed in any one of claims 1 to 5, characterized in that: The following steps are involved: First, a defect detection model based on CT scanning is used to judge and select refractory metal pipes with a defect volume fraction not exceeding 0.5%, and the refractory metal pipes are made of the refractory metal; Then, the temperature of the surface of the refractory metal pipe is stabilized at -50°C to -20°C to ensure that when the SiC suspension is sprayed, the sprayed SiC suspension does not agglomerate and can be evenly frozen on the surface of the refractory metal pipe, thereby generating a nano-β-SiC porous interface intermediate layer with evenly distributed pores; Then, a nano-β-SiC suspension with a mass fraction of 40% to 45% is sprayed on the surface of the refractory metal tube at an air spray pressure of 0.2 to 0.6 MPa. After spraying, freeze-drying is performed for 20 to 24 hours at an initial freezing temperature of -80°C to -50°C to obtain a nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding tube. At this time, the refractory metal tube is the refractory metal inner layer of the nuclear fuel cladding tube. Then, the porous structure detection model based on CT scanning was used to screen out the nano-β-SiC porous interface intermediate layer with uniform pore distribution and a porosity of 20-50%. Then, in an isothermal CVI furnace under the conditions of a deposition temperature of 850-1000°C, a deposition pressure of 4kPa-6kPa, and a deposition rate of 10-20μm / h, a 5-10μm thick SiC protective layer is deposited on the surface of the nano-β-SiC porous interface intermediate layer to improve the chemical stability of the nano-β-SiC porous interface intermediate layer and enhance the bonding strength of the interface between the refractory metal inner layer and the SiC-based composite material outer layer; Next, on the surface of the SiC protective layer, the SiC fibers in the SiC protective layer are woven at a rotation speed of 0.3-0.4 rad / s and a winding speed of 1.5-4 mm / s to form an inner layer of a SiC fiber preform having a woven structure; Then, a pyrolytic carbon (PyC) protective layer and a SiC ceramic matrix for densifying the inner layer of the SiC fiber preform are deposited in stages on the surface of the inner layer of the SiC fiber preform; Finally, the porous structure detection model based on CT scanning was used to screen out the SiC ceramic matrix with a porosity of less than 10%, thus obtaining a high-temperature resistant nuclear fuel cladding tube with a complete structure based on a porous interface. At this time, the pyrolytic carbon PyC protective layer between the SiC ceramic matrix and the inner layer of the SiC fiber preform forms a pyrolytic carbon PyC interface; the SiC ceramic matrix is ​​the SiC ceramic matrix outer layer.

7. The intelligent manufacturing method of the high temperature resistant nuclear fuel cladding structure based on porous interface according to claim 6 is characterized in that: The specific steps for stabilizing the temperature of the refractory metal pipe are: The refractory metal pipe is subjected to liquid nitrogen spray cooling treatment under the conditions of a spray pressure of 0.1-0.2 MPa and a spray distance of 20-25 cm. After the surface temperature of the refractory metal pipe reaches -90°C to -80°C, the refractory metal pipe is fixed at the center position of the high-frequency induction heating coil to heat the refractory metal pipe evenly, thereby ensuring that the temperature of the refractory metal pipe is stable between -50°C and -20°C.

8. The intelligent manufacturing method of the high temperature resistant nuclear fuel cladding structure based on porous interface according to claim 6, characterized in that: The specific process of judging the refractory metal pipe based on the defect detection model of CT scanning is as follows: First, the refractory metal pipe is scanned 360° using an industrial CT device to generate a 3D image of the refractory metal pipe with a pixel size of 512×512×N and including crack and porosity defect features, where N is the length of the CT scan. Then, the defect detection model of the industrial CT equipment counts the number of crack and pore defect pixels in the three-dimensional image data; Finally, the defect volume fraction threshold is set to 0.5%, and the defect detection model screens out refractory metal pipes with a defect volume fraction not exceeding 0.5%.

9. The intelligent manufacturing method of the high temperature resistant nuclear fuel cladding structure based on porous interface according to claim 6, characterized in that: The specific process of judging the nano-β-SiC porous interface intermediate layer and the SiC ceramic matrix based on the porous structure detection model of CT scanning is as follows: Firstly, the nano-β-SiC porous interface intermediate layer and SiC ceramic matrix were scanned 360° using industrial CT equipment to generate a three-dimensional image of the nano-β-SiC porous interface intermediate layer and SiC ceramic matrix with pore features and a pixel size of 512×512×N, where N is the length of the CT scan. Then, the porous structure detection model of the industrial CT equipment calculates the porosity, average pore size and pore volume fraction based on the three-dimensional image; Next, the pore volume fraction threshold of the nano-β-SiC porous interface intermediate layer is set to 20-50%, and the pore volume fraction threshold of the SiC ceramic matrix is ​​set to 10%. The porous structure detection model screens out the nano-β-SiC porous interface intermediate layer with a porosity of 20-50% and the SiC ceramic matrix with a porosity of less than 10%. Finally, the nano-β-SiC porous interface intermediate layer with a pore volume fraction greater than 50% and less than 20% and the SiC ceramic matrix with a pore volume fraction greater than 10% are re-deposited, so that the porous structure detection model can be used again to calculate the pore volume fraction results and adjust the deposition process parameters of the nano-β-SiC porous interface intermediate layer and the SiC ceramic matrix in time.

10. The intelligent manufacturing method of the high temperature resistant nuclear fuel cladding structure based on porous interface according to claim 6, characterized in that: The pyrolytic carbon PyC protective layer and the SiC ceramic matrix are deposited in stages on the inner surface of the SiC fiber preform, and the specific steps are as follows: In an ultra-high temperature CVI furnace filled with propylene at a concentration of 1-5 vol%, the first stage of deposition is carried out at a deposition temperature of 900-1200°C and a deposition pressure of 3kPa-4kPa for a deposition time of 10-50 hours, that is, a pyrolytic carbon PyC protective layer is deposited on the surface of the inner layer of the SiC fiber preform; Next, use argon gas with a gas flow rate of 10-50 L / min to purge the furnace for 0.5-1 hour, and cool the inner layer of the SiC fiber preform with the pyrolytic carbon PyC protective layer to 800-1000°C to ensure the removal of residual reaction gas and by-products, and prevent oxygen from entering to cause high-temperature oxidation and pollution; Then, in a furnace environment filled with 2-4 vol% trichloromethylsilane, the second stage of deposition was carried out at a deposition temperature of 960°C-1180°C, a deposition pressure of 2kPa-4kPa, and a deposition time of 100h-200h, that is, a SiC ceramic matrix was deposited on the inner surface of the SiC fiber preform with a pyrolytic carbon PyC protective layer.

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