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

Abstract

The 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 which are used as the inner wall and the outer wall of the nuclear fuel cladding tube, and at least one nano beta-SiC porous interface middle layer with the porosity of not less than 20% arranged between the refractory metal inner layer and the SiC-based composite material outer layer. The invention further provides an intelligent manufacturing method of the high-temperature-resistant nuclear fuel cladding tube based on the porous interface. According to the nanometer beta-SiC porous interface interlayer structure provided by the invention, the interface thermal stress caused by thermal mismatch and temperature gradient of the nuclear fuel cladding in a high-temperature environment is greatly reduced, the thermal stability and the high-temperature resistance of the nuclear fuel cladding are improved, the design and optimization of the nuclear fuel cladding interface structure are realized, and the nuclear fuel cladding interface structure is optimized. And based on a mechanical, digital and informationized preparation process, process parameters during preparation of the nuclear fuel cladding can be accurately controlled, high-quality production is ensured, and intelligent manufacturing of the nuclear fuel cladding is realized.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear reactor fuel elements, and in particular 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 key step in their successful application. Nuclear fuel cladding tubes are used to contain nuclear fuel pellets and prevent the released radioactive fission products from entering the external environment through the coolant. The emergence of micro reactors has brought new challenges to the performance of nuclear fuel cladding.

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

[0004] However, due to the large difference in material properties (thermal expansion coefficient, Young's modulus) between refractory metals and SiC-based composites, the interface between refractory metals and SiC ceramic matrix will be subject to thermal stress not only caused by temperature gradient but also by thermal stress caused by material thermal mismatch under high temperature environment conditions. This greatly increases the risk of heterogeneous material delamination, which in turn affects its application and development in reactor cores. Therefore, how to design the interface structure between refractory metals and SiC-based composites is a key issue to ensure that the interface has high bonding strength and 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 Mo gradient content between the refractory metal Mo and the SiC-based composite material to enhance the crack resistance of the heterogeneous interface and reduce the degree of mismatch in thermal expansion coefficients between the two materials. Although the problem of excessive interface stress has been improved to a certain extent, this gradient interface structure will still result in high interface thermal stress (up to 1100MPa) caused by temperature gradient and thermal mismatch, which will greatly reduce the high-temperature mechanical properties and thermal stability of the heterogeneous composite material. Summary of the invention

[0006] The purpose of the present invention is to avoid the shortcomings of the prior art and provide a high-temperature resistant nuclear fuel cladding tube based on a porous interface and an intelligent manufacturing method thereof, which can reduce the interfacial thermal stress caused by thermal mismatch of the composite cladding under high-temperature environmental conditions, while improving the thermal stability and high-temperature resistance of the composite cladding, and realize the optimization of the heterogeneous interface structure.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a high temperature resistant nuclear fuel cladding tube based on 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; 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.

[0008] Furthermore, the inner hole diameter of the high temperature resistant 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.

[0009] Furthermore, the volume fraction of SiC fibers in the inner layer of the SiC fiber preform is 20-40%.

[0010] Furthermore, the ambient temperature is 900°C to 1200°C.

[0011] Furthermore, the porosity of the nano-β-SiC porous interface intermediate layer is 20-50%.

[0012] The present invention also provides an intelligent manufacturing method for the high temperature resistant nuclear fuel cladding tube based on porous interface, comprising the following steps: 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; this step is performed in a woven machine, and the woven machine is a two-dimensional woven machine or a three-dimensional woven machine.

[0013] 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.

[0014] Furthermore, 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.

[0015] Furthermore, the specific process of judging the difficult-to-melt 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%.

[0016] Furthermore, 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.

[0017] Furthermore, 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.

[0018] The beneficial effects of the present invention are as follows: a porous SiC interface is set between a refractory metal and a SiC ceramic matrix, and a nuclear fuel cladding with a porous SiC interface is obtained by finite element calculation. Compared with a nuclear fuel cladding with a dense SiC interface with a porosity of less than 0.1% or a Mo transition layer interface, firstly, the present invention mainly aims at ensuring that the interface thermal stress of the nuclear fuel cladding is not higher than 700MPa when the ambient temperature is higher than 900°C. Secondly, the thermal stress of the present invention is reduced by 44% and 64% respectively compared with the thermal stress of the two interfaces, indicating that the porous SiC interface structure provided by the present invention greatly reduces the interface thermal stress of the fuel cladding caused by thermal mismatch and temperature gradient in a high temperature environment, improves the thermal stability and high temperature resistance of the nuclear fuel cladding, and realizes the design and optimization of the interface structure of the nuclear fuel cladding.

[0019] In addition, based on the mechanized, digital and information-based preparation process, the process parameters during the preparation of nuclear fuel cladding can be accurately controlled to ensure high-quality production and realize the intelligent manufacturing of nuclear fuel cladding. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flow chart of intelligent manufacturing of the present invention; Figure 2 The present invention provides a schematic diagram for comparing the thermal stress distribution curves of the nuclear fuel cladding tube in the thickness direction of the cladding tube under the condition of a temperature of 1000-1200°C by finite element calculation; Figure 3 A histogram comparing thermal stresses at the interface of the cladding tube when the interface temperature of the nuclear fuel cladding provided by the present invention is about 1100° C. by finite element calculation; Figure 4 The structural characterization diagram and component energy spectrum diagram of the nuclear fuel cladding prepared in Example 1 of the present invention; In the figure, (a) is a structural diagram of the nuclear fuel cladding; (b) is a microscopic structure diagram of the nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding; (c) is an energy spectrum diagram of the nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding; (d) is a structural diagram of the nano-β-SiC porous interface intermediate layer of the nuclear fuel cladding during finite element calculation; Figure 5 It is a structural characteristic diagram for judging the refractory metal pipe by the defect detection model of the present invention; In the figure, (a) is the unqualified refractory metal pipe; (b) is the qualified dense grade refractory metal pipe; Figure 6 The structural diagram reconstructed by the porous structure detection model of the present invention for judging the three-dimensional image data of the nano-β-SiC porous interface intermediate layer; In the figure, (a) is an unqualified porous interface; (b) is a qualified porous interface; Figure 7 The porous structure detection model of the present invention determines the structural diagram reconstructed from the three-dimensional image data of the SiC ceramic matrix; In the figure, (a) is the unqualified SiC ceramic matrix obtained by judgment; (b) is the qualified SiC ceramic matrix obtained by judgment; Figure 8 A physical picture of the nuclear fuel cladding prepared by the present invention; In the figure, (a) is a cross-sectional view of the Re-SiC / SiC nuclear fuel cladding; (b) is an appearance view of the Re-SiC / SiC nuclear fuel cladding with a porous interface. DETAILED DESCRIPTION

[0021] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0022] In order to achieve the above object, the present invention provides the following specific implementation methods: Example 1: Figure 8As 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 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 where the inner layer of the SiC fiber preform contacts the outer layer of the SiC ceramic matrix is ​​a pyrolytic carbon (PyC) interface; the volume fraction of SiC fiber in the inner layer of the SiC fiber preform is 20-40%; 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.

[0023] like Figure 8 As shown, the inner diameter of the high-temperature resistant nuclear fuel cladding tube based on the porous interface is 9.0~10.0mm; the thickness of the refractory metal inner layer in the thickness direction of the tube wall is 0.25~0.40mm, the thickness of the nano β-SiC porous interface middle layer is 5~20μm, and the thickness of the SiC-based composite material outer layer is 0.6~0.7mm.

[0024] Example 2 is the same as Example 1, except that the ambient temperature is 900° C. to 1200° C.; the porosity of the nano β-SiC porous interface intermediate layer is 20% to 50%.

[0025] Embodiment 3, as Figure 1 As shown, the present invention also provides an intelligent manufacturing method for the high temperature resistant nuclear fuel cladding tube based on porous interface as described above, comprising the following steps: Step 1: A refractory metal tube is made of refractory metal, and an industrial CT device is used to perform a 360° scan on the refractory metal tube to generate a three-dimensional image of the refractory metal tube with a pixel size of 512×512×N and including crack and pore defect features, wherein N is the length of the CT scan; and a defect detection model of the industrial CT device is used to count the number of crack and pore defect pixel points in the three-dimensional image data in the three-dimensional image.

[0026] Step 2: Set the defect volume fraction threshold to 0.5%. The defect detection model will screen out refractory metal pipes with a defect volume fraction not exceeding 0.5%, and the remaining refractory metal pipes will be scrapped.

[0027] Step 3: 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.

[0028] Step 4: Spray a nano-β-SiC suspension with a mass fraction of 40% to 45% onto the surface of the refractory metal pipe at an air spray pressure of 0.2 to 0.6 MPa.

[0029] Step 5: After spraying, freeze-dry for 20 to 24 hours at an initial freezing temperature of -80°C to -50°C to 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.

[0030] Step 6: Use industrial CT equipment to perform 360° scanning on the nano-β-SiC porous interface intermediate layer to generate a three-dimensional image of the nano-β-SiC porous interface intermediate layer with pore shape features and a pixel size of 512×512×N, wherein N is the length of the CT scan; 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.

[0031] Step 7: The pore volume fraction threshold of the nano-β-SiC porous interface intermediate layer is set to 20-50%, and the porous structure detection model screens out the nano-β-SiC porous interface intermediate layer with a porosity of 20-50%.

[0032] Step 8: Re-deposit 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, thereby repeating steps 6 and 7 again, and timely adjust the deposition process parameters of the nano β-SiC porous interface intermediate layer.

[0033] Step 9: In an isothermal CVI furnace at 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.

[0034] Step 10: On the surface of the SiC protective layer, the SiC fibers in the SiC protective layer are braided 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 braided structure; this step is performed in a braiding machine, and the braiding machine is a two-dimensional braiding machine or a three-dimensional braiding machine.

[0035] 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 of deposition is performed on the surface of the inner layer of the SiC fiber preform for 10-50 hours, i.e., a pyrolytic carbon PyC protective layer is deposited on the surface of the inner layer of the SiC fiber preform. At this point, the inner layer of the SiC fiber preform having the pyrolytic carbon PyC protective layer is obtained.

[0036] Step 12: Use argon gas with a gas flow rate of 10-50 L / min to purge the furnace for 0.5-1 h, and cool the inner layer of the SiC fiber preform with the pyrolytic carbon PyC protective layer to 800-1000°C to ensure that residual reaction gases and by-products are removed and prevent oxygen from entering to cause high-temperature oxidation and pollution.

[0037] Step 13: Under the condition of a furnace filled with trichloromethylsilane with a concentration of 2-4 vol%, the second stage deposition is carried out with a deposition temperature of 960°C-1180°C, a deposition pressure of 2 kPa-4 kPa, and a deposition time of 100 h-200 h, that is, a SiC ceramic matrix is ​​deposited on the surface of the inner layer of the SiC fiber preform with a pyrolytic carbon PyC protective layer.

[0038] Step 14: Use an industrial CT device to perform a 360° scan on the SiC ceramic matrix to generate a three-dimensional image with a pixel size 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 size and pore volume fraction based on the three-dimensional image.

[0039] Step 15: The pore volume fraction threshold of the SiC ceramic matrix is ​​set to 10%, and the porous structure detection model screens out SiC ceramic matrices with a porosity of less than 10%.

[0040] Step 16: Re-deposit the SiC ceramic matrix with a pore volume fraction greater than 10%, that is, return to step 13, so as to use the porous structure detection model to calculate the pore volume fraction results again, and adjust the deposition process parameters of the SiC ceramic matrix in time.

[0041] Step 17: After judging based on the porous structure detection model of CT scanning and selecting the SiC ceramic matrix with a porosity of less than 10%, a high-temperature resistant nuclear fuel cladding tube with a complete structure based on a porous interface is obtained; 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.

[0042] like Figure 2-Figure 7 To further illustrate the technical solution and technical effects of the present invention, the following specific examples are provided: Example 1: The high-temperature resistant nuclear fuel cladding tube based on porous interface consists 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 middle 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 middle layer is 15 μm, and the thickness of the SiC-based composite material layer is 0.7 mm.

[0043] The preparation process is as follows: (1) Nondestructive testing of internal defects of refractory metals: Use a fully automatic CT online detection system to scan the Re refractory metal pipe, build a three-dimensional model in real time, and identify whether the pipe has internal defects, such as Figure 5 As shown in (a), the dense grade pipes with a porosity of no more than 0.5% are selected for the next step of processing, such as Figure 5 As shown in (b).

[0044] (2) Cooling of refractory metals 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, the refractory metal pipe is fixed at the center position of the high-frequency induction heating coil to ensure that the refractory metal pipe is evenly heated, thereby ensuring that the target temperature of the refractory metal pipe is stable at -50°C.

[0045] (3) Spraying nano-β-SiC suspension and freeze-drying: After the target temperature in step (2) is stabilized, a nano-β-SiC suspension with a mass fraction of 45% is sprayed on the surface of the pipe using an air sprayer. The robot arm automatically grabs the pipe and puts it into a freeze-drying chamber for freeze-drying for 20 hours.

[0046] (4) Nondestructive testing of porous interfaces and deposition of SiC protective layer: Use the CT online detection system to detect whether a 15 μm thick SiC protective layer is formed on the surface of the freeze-dried pipe. Figure 4 As shown in (b), the nano-β-SiC porous interface intermediate layer with a porosity of 20% is Figure 6 As shown in (b); the unqualified interface is re-cooled and sprayed, such as Figure 6 As shown in (a).

[0047] The robot automatically puts the tube of nano-β-SiC porous interface intermediate layer that meets the requirements into the isothermal CVI furnace. The deposition temperature of the isothermal CVI furnace is set to 1000℃, the deposition pressure is set to 6kPa, and the deposition rate is 10μm / h to deposit a 5μm SiC protective layer. Figure 4 As shown in (c), the chemical stability of the porous SiC interface is improved and the interface bonding strength is enhanced.

[0048] (5) Braided fiber preform: After depositing the SiC protective layer, a robotic arm is used to automatically install the tube into a two-dimensional braiding machine, and the SiC fiber preform is braided on the surface of the tube to form a braided tube to improve the toughness and strength of the nuclear fuel cladding.

[0049] (6) Deposition of pyrolytic carbon interface and matrix densification: The braided tube in step (5) is placed in an ultra-high temperature CVI furnace, and the deposition program is set as follows: The precursor gas source is propylene, the deposition temperature is 900°C, the deposition pressure is 3kPa, and the deposition time is 10h as the first stage, the temperature is cooled to 800°C, and the furnace is purged with argon for 0.5h as the second stage, and the precursor gas source is trichloromethylsilane, the deposition temperature is 960°C, the deposition pressure is 2kPa, and the deposition time is 100h as the third stage, and a pyrolytic carbon protective layer and a SiC ceramic matrix are deposited for densification treatment.

[0050] (7) Nondestructive testing of SiC ceramic matrix: Use the CT online testing system to test the SiC ceramic matrix after densification treatment and screen out SiC ceramic matrix with a porosity of 9%, such as Figure 7 As shown in (b); the unqualified SiC ceramic matrix is ​​re-deposited, such as Figure 7 As shown in (a), a high temperature resistant nuclear fuel cladding tube based on a porous interface with a complete structure is obtained. Figure 4 As shown in (a).

[0051] Example 2: The high-temperature resistant nuclear fuel cladding tube based on 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.

[0052] The preparation process is as follows: (1) Nondestructive testing of internal defects of refractory metals: Use a fully automatic CT online detection system to scan Ta refractory metal pipes, build a three-dimensional model in real time, and identify whether there are internal defects in the pipes. Select dense-grade pipes with a porosity of no more than 0.5% for the next step of processing.

[0053] (2) Cooling of refractory metals 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, the refractory metal pipe is fixed at the center position of the high-frequency induction heating coil to ensure that the refractory metal pipe is evenly heated, thereby ensuring that the target temperature of the refractory metal pipe is stable at -20°C.

[0054] (3) Spraying nano-β-SiC suspension and freeze-drying: After the target temperature in step (2) is stabilized, a nano-β-SiC suspension with a mass fraction of 40% is sprayed on the surface of the pipe using an air sprayer. The robot arm automatically grabs the pipe and puts it into a freeze-drying chamber for freeze-drying for 24 hours.

[0055] (4) Nondestructive testing of porous interfaces and deposition of SiC protective layers: A CT online detection system is used to detect whether a porous SiC interface with a thickness of 20 μm and a porosity of 30% is formed on the surface of the freeze-dried tube. The robotic arm automatically places the tube 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 to 850 °C, the deposition pressure is set to 4 kPa, and the deposition rate is 20 μm / h to deposit a 10 μm SiC protective layer to improve the chemical stability of the porous SiC interface and enhance the interface bonding strength.

[0056] (5) Braided fiber preform: After the SiC protective layer is deposited, a robotic arm is used to automatically install the tube into a three-dimensional braiding machine, and the SiC fiber preform is braided on the surface of the tube to form a braided tube to improve the toughness and strength of the nuclear fuel cladding.

[0057] (6) Deposition of pyrolytic carbon interface and matrix densification: The braided tube in step (5) is placed in an ultra-high temperature CVI furnace, and the deposition program is set as follows: The precursor gas source is propylene, the deposition temperature is 1200°C, the deposition pressure is 4 kPa, and the deposition time is 50 h as the first stage, the temperature is cooled to 800°C, and the furnace is purged with argon for 1 h as the second stage, and the precursor gas source is trichloromethylsilane, the deposition temperature is 1180°C, the deposition pressure is 4 kPa, and the deposition time is 200 h as the third stage, and a pyrolytic carbon protective layer and a SiC ceramic matrix are deposited for densification treatment. (7) Nondestructive testing of SiC ceramic matrix: Use the CT online detection system to detect the SiC ceramic matrix after densification treatment, screen out the SiC ceramic matrix with unqualified porosity for redeposition, and the SiC ceramic matrix with qualified porosity is the high-temperature resistant nuclear fuel cladding tube with a complete structure based on a porous interface.

[0058] The porous SiC interface structure diagram calculated by finite element method in the present invention is as follows: Figure 4 The finite element calculation geometry shown in (d) shows that: compared with the existing nuclear fuel claddings with dense SiC interfaces or Mo transition layer interfaces with a porosity of less than 0.1%, the porous SiC interface thermal stress provided by the present invention is not higher than 700MP, and compared with the other two, the interface thermal stress is reduced by 44% and 64%, respectively. Figure 3 The interfacial thermal stress histogram is shown; like Figure 2 As shown, Figure 2 The thermal stress distribution of the nuclear fuel cladding structure with porous SiC interface provided by the present invention is compared with that of the existing dense SiC interface with porosity less than 0.1% or 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 under high temperature environment, and 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 accurately controlled to ensure high-quality production and realize the intelligent manufacturing of the nuclear fuel cladding.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in 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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