Fuel element cladding external pressure test device and test method for determining external pressure of fuel element cladding

Abstract

The embodiment of the invention relates to the field of testing or analyzing materials by means of measuring the chemical or physical properties of the materials, in particular to a fuel element cladding external pressure testing device and a testing method for determining the external pressure of a fuel element cladding. The test device is used for testing the cladding of the fuel element and comprises a simulated fuel pellet sleeved on the cladding; the heating device is used for heating the cladding to the temperature required by the test; the superheated steam supply device is used for supplying superheated steam into the cladding, the pressurization connection sealing assembly is in sealed connection with the heating device and the superheated steam supply device, and a closed test space is formed by the pressurization connection sealing assembly and the heating device; the cladding sleeved with the simulated fuel pellet is heated and pressurized in the test space; and the detection assembly is used for detecting the temperature of the cladding and the pressure of the external air cavity. The test device provided by the embodiment of the invention can simulate the temperature and the external pressure of the cladding under the actual working condition, and is beneficial to improving the accuracy of the test result of the cladding.

Description

Technical Field

[0001] Embodiments of the present application relate to the field of testing or analyzing materials by measuring the chemical or physical properties of the materials, and specifically to a fuel element cladding external pressure test device and a test method for determining the external pressure of the fuel element cladding. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] During the operation of a nuclear reactor, the fuel elements will be subjected to external pressure from the primary coolant in the nuclear reactor. Their performance has a significant impact on the safety and economy of the nuclear reactor. Therefore, it is necessary to study the performance of the fuel elements before designing them.

[0004] The fuel element includes a cladding and fuel pellets arranged in the cladding. The performance of the fuel element is closely related to the performance of the fuel element cladding. Therefore, it is necessary to study the performance of the fuel element cladding. Summary of the invention

[0005] A brief overview of the present application is provided below in order to provide a basic understanding of certain aspects of the present application. It should be understood that this overview is not an exhaustive overview of the present application. It is not intended to identify the key or important parts of the present application, nor is it intended to limit the scope of the present application. Its purpose is merely to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0006] The embodiments of the present application provide a fuel element cladding external pressure test device and a test method for determining the external pressure of a fuel element cladding.

[0007] In the first aspect, the embodiment of the present application provides a fuel element cladding external pressure test device, which is suitable for testing the zirconium alloy cladding of the fuel element, and the test device includes a simulated fuel pellet, a heating device, a pressurized connection sealing assembly, a superheated steam supply device, and a detection assembly. The simulated fuel pellet is sleeved on the cladding; the heating device is configured to heat the cladding to the temperature required for the test; the pressurized connection sealing assembly is configured to be sealed and connected to the heating device and to form a closed test space with the heating device; the superheated steam supply device is configured to provide superheated steam into the cladding and is configured to be sealed and connected to the pressurized connection sealing assembly; the cladding sleeved with the simulated fuel pellet is heated and pressurized in the test space; the detection assembly is configured to detect the temperature of the cladding and the pressure of its external air cavity under different temperature and pressure conditions.

[0008] The test device provided in the embodiment of the present application can simulate the temperature and pressure of the cladding under the actual operating conditions of a nuclear reactor by heating and pressurizing the cladding covered with simulated fuel pellets in a test space, which is beneficial to improving the accuracy of the test results of the cladding.

[0009] In a second aspect, an embodiment of the present application further provides a test method for determining the external pressure of a fuel element cladding, which uses the test device provided in the embodiment of the first aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other objects and advantages of the present application will become apparent from the following description of the embodiments of the present application with reference to the accompanying drawings, and will help to provide a comprehensive understanding of the present application.

[0011] Figure 1 It is a structural schematic diagram of a fuel element cladding external pressure test device provided in an embodiment of the present application.

[0012] Figure 2 yes Figure 1 A cross-sectional view of the test apparatus is shown.

[0013] Figure 3 yes Figure 1 Another cross-sectional view of the test apparatus is shown.

[0014] Figure 4 It is a structural schematic diagram of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded.

[0015] Figure 5 It is a flow chart of the heating stage, the heat preservation stage and the cooling stage in the method for welding a zirconium alloy round tube and a stainless steel round tube provided in an embodiment of the present application.

[0016] Description of reference numerals:

[0017] 100. Test equipment;

[0018] 10. Simulated fuel pellets; 20. Heating device;

[0019] 30. Pressurized connection sealing assembly; 31. Pressurized part; 32. Connection sealing assembly; 321. Stainless steel sealing connector; 322. Dissimilar material connector; 3221. Nuclear grade zirconium alloy part; 3222. Stainless steel part; 301. Pressurized port;

[0020] 40. Superheated steam supply device; 41. Air inlet; 42. Air outlet; 51. Temperature detection component; 52. Pressure detection component;

[0021] 101. test space; 102. mounting piece; 1020. mounting slot;

[0022] 200. Cladding; 201. Superheated steam flow channel.

[0023] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding. DETAILED DESCRIPTION

[0024] Exemplary embodiments of the present application will be described below in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual implementation are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the process of developing any such actual implementation in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and these constraints may vary from implementation to implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is only a routine task for those skilled in the art who benefit from the content of this application.

[0025] It is also necessary to explain here that, in order to avoid obscuring the present application due to unnecessary details, only the device structure and / or processing steps closely related to the scheme according to the present application are shown in the accompanying drawings, while other details that are not very relevant to the present application are omitted.

[0026] The performance of the fuel element cladding in withstanding external pressure is usually studied by testing the cladding samples. In the related art, it is difficult to simulate the actual working conditions when testing the cladding samples, resulting in errors in the test results, which cannot fully reflect the performance of the cladding in withstanding pressure under actual working conditions.

[0027] In view of the above problems, an embodiment of the present application provides a fuel element cladding external pressure test device and a test method for determining the external pressure of a fuel element cladding.

[0028] See also Figure 1 , Figure 11 is a schematic diagram of the structure of the fuel element cladding external pressure test device provided by the embodiment of the present application. The test device 100 is suitable for testing the zirconium alloy cladding 200 of the fuel element, and includes a simulated fuel pellet 10, a heating device 20, a pressurized connection sealing assembly 30, a superheated steam supply device 40 and a detection assembly. The simulated fuel pellet 10 is sleeved on the cladding 200; the heating device 20 is configured to heat the cladding 200 to the temperature required for the test; the pressurized connection sealing assembly 30 is configured to be sealed and connected with the heating device 20 and to form a closed test space 101 with the heating device 20; the superheated steam supply device 40 is configured to provide superheated steam into the cladding 200 and is configured to be sealed and connected with the pressurized connection sealing assembly 30. The cladding 200 sleeved with the simulated fuel pellet 10 is heated and pressurized in the test space 101; the detection assembly is configured to detect the temperature of the cladding 200 and the pressure of its external air cavity under different temperature and pressure conditions.

[0029] The test device 100 provided in the embodiment of the present application can simulate the temperature and pressure of the cladding 200 under the actual operating conditions of a nuclear reactor by heating and pressurizing the cladding 200 on which the simulated fuel pellets 10 are mounted in the test space 101, which is beneficial to improving the accuracy of the test results of the cladding 200.

[0030] In some embodiments, a plurality of simulated fuel pellets 10 may be mounted on the cladding 200 .

[0031] In some embodiments, the radial dimension of the cladding 200 is set to be the same as that of the actual cladding 200, and the length of the cladding 200 is set to be adjusted according to the test requirements or the heating device 20. In such an embodiment, the radial dimension of the cladding 200 is set to be the same as that of the actual cladding 200, so that the test conducted on the cladding 200 is equivalent to the test conducted on the actual cladding 200, which is conducive to improving the accuracy and reliability of the obtained test results; at the same time, the length of the cladding 200 is set to be adjusted according to the test requirements or the heating device 20, so that the heating device 20 heats the cladding 200 to the temperature required for the test.

[0032] In some embodiments, the cladding 200 may be a cladding 200 having the same radial dimensions as the cladding of a rod-shaped fuel element, or a cladding 200 having the same radial dimensions as the cladding of an annular fuel element, that is, the performance of the cladding of a rod-shaped fuel element or the performance of the cladding of an annular fuel element may be tested by the test device 100 provided in the embodiments of the present application.

[0033] In some embodiments, the heating device 20 may be a ring-shaped electric heating element, a heating furnace or a high-temperature autoclave. In other embodiments, the heating device 20 may also be any device capable of heating the cladding 200 .

[0034] See also Figure 2 , Figure 2 yes Figure 1 A cross-sectional view of the test device 100 is shown. In some embodiments, the cladding 200 is formed with a superheated steam flow channel 201, and the superheated steam supply device 40 can supply superheated steam to the superheated steam flow channel 201.

[0035] In some embodiments, the superheated steam providing device 40 may include an air inlet 41 for allowing superheated steam to flow into the superheated steam flow channel 201 and an air outlet 42 for allowing superheated steam to flow out of the superheated steam flow channel 201. The air inlet 41 and the air outlet 42 are both sealedly connected to the pressurized connection sealing assembly 30, and the air inlet 41 and the air outlet 42 are both fluidically connected to the superheated steam flow channel 201.

[0036] In some embodiments, the simulated fuel pellet 10 can increase the heat exchange between the heating device 20 and the cladding 200, thereby increasing the temperature of the cladding 200 to ensure that the cladding 200 can be heated to the temperature required for the test. The simulated fuel pellet 10 is, for example, annular alumina ceramic. In other embodiments, the simulated fuel pellet 10 can also be other materials that can increase the heat exchange between the heating device 20 and the cladding 200.

[0037] See also Figure 1 In some embodiments, the pressurized connection sealing assembly 30 includes a pressurizing member 31 and a connection sealing assembly 32. A pressurizing port 301 is formed on the connection sealing assembly 32. The pressurizing member 31 is disposed at the pressurizing port 301. The pressurizing member 31 provides pressure to the test space 101 through the pressurizing port 301. The connection sealing assembly 32 is configured to be sealed and connected to the heating device 20 and to form a closed test space 101 with the heating device 20. The connection sealing assembly 32 is configured to be sealed and connected to the cladding 200 and to be sealed and connected to the superheated steam providing device 40. In such an embodiment, the test space 101 can be pressurized by the pressurizing member 31, and the connection sealing assembly 32 is sealed and connected to the heating device 20, the cladding 200 and the superheated steam providing device 40, so as to form a closed test space 101 outside the cladding 200, so as to test the performance of the cladding 200.

[0038] In some embodiments, both ends of the enclosure 200 and both ends of the heating device 20 are sealed with a connection sealing assembly 32 , and a pressurizing member 31 for providing pressure to the test space 101 is disposed on one of the two connection sealing assemblies 32 .

[0039] In some embodiments, compressed helium gas may be filled into the test space 101 through the pressurizing member 31 .

[0040] See also Figure 1In some embodiments, the connection sealing assembly 32 includes a stainless steel sealing connector 321 and a heterogeneous material connector 322. The stainless steel sealing connector 321 is configured to be sealed and connected to the heating device 20 at one end and sealed and connected to the heterogeneous material connector 322 at the other end. The pressurization port 301 is formed on the stainless steel sealing connector 321; the heterogeneous material connector 322 is configured to be sealed and connected to the cladding 200 at one end and sealed and connected to the superheated steam providing device 40 at the other end. In such an embodiment, the above configuration enables the superheated steam provided by the superheated steam providing device 40 to enter the superheated steam flow channel 201 formed by the cladding 200; and enables the heating device 20 and the connection sealing assembly 32 to form a closed test space 101. The stainless steel sealing connector 321 is, for example, an annular stainless steel part.

[0041] In some embodiments, both ends of the enclosure 200 are sealed with a heterogeneous material connector 322 , both ends of the heating device 20 are sealed with a stainless steel sealing connector 321 , and a pressurizing member 31 for providing pressure to the test space 101 is disposed on one of the two stainless steel sealing connectors 321 .

[0042] In some embodiments, the cladding 200 encasing the simulated fuel pellets 10 is disposed in the heating device 20, and both ends thereof extend outside the heating device 20. In such embodiments, the above arrangement facilitates the sealed connection between the cladding 200 and the heterogeneous material connector 322, and facilitates the formation of the test space 101.

[0043] See also Figure 1 and Figure 3 , Figure 3 yes Figure 1 Another cross-sectional view of the test device 100 is shown. In some embodiments, the detection assembly includes a temperature detection component 51 and a pressure detection component 52. The temperature detection component 51 is arranged on the inner wall of the cladding 200, and the pressure detection component 52 is arranged to be connected to the pressurizing device of the pressurizing port 301, and is used to measure the pressure of the pressurizing device. In such an embodiment, the temperature detection component 51 is arranged on the inner wall of the cladding 200, which is conducive to improving the accuracy of the temperature detection component 51 in measuring the temperature of the cladding 200; the pressure of the pressurizing device is measured by the pressure detection component 52, so as to measure the pressure in the test space 101, and then measure the pressure of the air cavity outside the cladding 200. The pressure detection component 52 is, for example, a pressure gauge. The temperature detection component 51 is, for example, a K-type thermocouple.

[0044] In some embodiments, after the connection between the cladding 200, the heterogeneous material connector 322, the stainless steel sealing connector 321 and the heating device 20 is completed, the temperature detection component 51 can be set on the inner wall of the cladding 200 through a special installation device.

[0045] See also Figure 3 In some embodiments, a mounting member 102 for mounting the temperature detection member 51 is provided in the cladding 200. The mounting member 102 is fixedly connected to the inner wall of the cladding 200. A mounting groove 1020 is formed at the fixed connection between the mounting member 102 and the inner wall of the cladding 200. The temperature detection member 51 is configured to be able to enter the mounting groove 1020 so as to be set on the inner wall of the cladding 200.

[0046] In some embodiments, the mounting member 102 may be a hollow ring member to provide a passage for the superheated steam to flow, so that the superheated steam can flow through the mounting member 102 .

[0047] In some embodiments, the dissimilar material connector 322 includes a nuclear-grade zirconium alloy portion 3221 and a stainless steel portion 3222, which are formed by diffusion welding, wherein the nuclear-grade zirconium alloy portion 3221 is sealed and connected to the cladding 200, and the stainless steel portion 3222 is sealed and connected to the stainless steel sealing connector 321. Since the cladding 200 is made of zirconium alloy, and the linear expansion coefficients of zirconium alloy and stainless steel are quite different, directly welding the zirconium alloy to stainless steel will result in poor airtightness at the welding interface. Therefore, in the embodiments of the present application, by sealingly connecting the cladding 200 to the nuclear-grade zirconium alloy portion 3221 of the dissimilar material connector 322, and connecting the stainless steel sealing connector 321 to the stainless steel portion 3222 of the dissimilar material connector 322, it is possible to avoid the cladding 200 being directly connected to the stainless steel seal and causing failure to seal, so as to ensure the sealing of the test space 101.

[0048] The embodiment of the present application also provides a test method for determining the external pressure of a fuel element cladding 200, which uses the test device 100 provided in any embodiment of the present application.

[0049] In some embodiments, the test method includes the following steps: heating the test space 101; pressurizing the test space 101; and obtaining the temperature of the cladding 200 and the external pressure to which the cladding 200 is subjected. In such an embodiment, the test space 101 is heated and pressurized to simulate the temperature and external pressure to which the cladding 200 is subjected during actual use, so as to test the cladding 200.

[0050] In some embodiments, the heating power of the heating device 20 can be adjusted so that the cladding 200 is heated at different heating temperatures; and the temperature of the cladding 200 and the external pressure borne by the cladding 200 are obtained under different heating powers of the heating device 20. Since the actual cladding 200 will face various working conditions during use, the actual cladding 200 will have different temperatures and external pressures under various working conditions. Therefore, the embodiment of the present application tests the cladding 200 at different temperatures through the above settings to obtain the test results of the cladding 200 at different temperatures, and then study the performance of the actual cladding 200 under various temperature conditions.

[0051] In some embodiments, the test device 100 may also include a monitoring module for monitoring the temperature measured by the temperature detection component 51, the pressure measured by the pressure detection component 52, and the heating power of the heating device 20. The monitoring module includes a temperature monitoring module, a pressure monitoring module, and a heating monitoring module. The temperature monitoring module is communicatively connected to the temperature detection component 51 to monitor and record the temperature measured by the temperature detection component 51; the pressure monitoring module is communicatively connected to the pressure detection component 52 to monitor and record the pressure measured by the pressure detection component 52; the heating monitoring module is communicatively connected to the heating device 20 to control and record the heating power of the heating device 20. The heating detection module is, for example, an industrial computer, and the communication connection between the industrial computer and the heating device 20 is realized through configuration software.

[0052] In the related art, when preparing the dissimilar material connector 322, the zirconium alloy and the intermediate layer material are usually welded together, and the stainless steel and the intermediate layer material are welded together, so as to fix the zirconium alloy and the stainless steel with the intermediate layer material. However, due to the involvement of the intermediate layer material, the welding steps are more complicated, the welding efficiency is low, and in particular, the welding quality often fails to meet the requirements.

[0053] An embodiment of the present application also provides a method for welding a zirconium alloy round tube and a stainless steel round tube, which comprises the following steps: S10, processing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded; S20, fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded processed in step S10 on a graphite clamp; S30, placing the graphite clamp fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded into a welding device and welding under vacuum conditions; wherein, during the welding process, a staged heating and heat preservation method is adopted, and after the welding is completed, a staged cooling method is adopted; S40, after the welding is completed, the air tightness test of the welded structure is performed.

[0054] The method provided in the embodiment of the present application adopts a staged heating and heat preservation method during the welding process, and a staged cooling method after the welding is completed, which is conducive to the mutual diffusion of atoms between the zirconium alloy round tube and the stainless steel round tube to achieve welding, so as to ensure that the zirconium alloy round tube and the stainless steel round tube can form a high-strength and high-density welding interface, thereby helping to improve the welding quality as well as the reliability and durability of the welding interface.

[0055] In some embodiments, the outer diameter of the zirconium alloy round tube and the stainless steel round tube may be 15-20 mm, and the inner diameter may be 2-4 mm.

[0056] In some embodiments, the welding equipment may be a vacuum diffusion welding equipment. In some embodiments, during the welding process, the vacuum degree does not exceed 10-5Pa to avoid oxidation affecting the welding quality.

[0057] In some embodiments, in step S30, a graphite fixture fixing the zirconium alloy round tube to be welded and the stainless steel round tube to be welded can be placed on the welding platform of the vacuum diffusion welding equipment, and the upper and lower welding machine pressure heads of the vacuum diffusion welding equipment can be aligned to apply pressure to the zirconium alloy round tube and the stainless steel round tube.

[0058] See also Figure 4 , Figure 4 It is a structural schematic diagram of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded. In some embodiments, in step S10, the following steps are also included: S11, forming a conical structure on the outer wall of one end of the zirconium alloy round tube 21 to be welded;

[0059] S12, an inverted cone structure relative to the cone structure is formed on the inner wall of one end of the stainless steel round tube 22 to be welded, and the inverted cone structure matches the cone structure. Due to the large difference in linear expansion coefficients between zirconium alloy and stainless steel, there is a problem of stress concentration at the welding interface during welding. In the embodiment of the present application, a cone structure is formed on the outer wall of one end of the zirconium alloy round tube 21 to be welded, and an inverted cone structure matching the cone interface is formed on the inner wall of one end of the stainless steel round tube 22 to be welded, so that the contact area between the zirconium alloy round tube 21 and the stainless steel round tube 22 can be increased to improve the stress concentration problem at the welding interface, thereby helping to improve the quality of welding; at the same time, it can also offset the difference in thermal expansion between zirconium alloy and stainless steel to ensure that the stress distribution of the welding interface during heating and cooling is uniform, thereby improving the strength and reliability of the welding interface. In particular, the mutual diffusion between metal atoms can be further improved so that the welding area can form a dense metallurgical bonding area.

[0060] In some embodiments, before step S11, it may also include determining to form a conical structure in the zirconium alloy round tube according to the difference in linear expansion coefficients between the zirconium alloy and the stainless steel, and determining to form an inverted conical structure matching the conical structure in the stainless steel round tube.

[0061] In some embodiments, the opening angle of the conical structure formed by the zirconium alloy round tube and the opening angle of the inverted conical structure formed by the stainless steel round tube can both be 10°-15°.

[0062] In some embodiments, in step S10, the following steps are also included: S13, roughening the surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded, and cleaning the treated zirconium alloy round tube to be welded and the stainless steel round tube to be welded; S14, drying the zirconium alloy round tube to be welded and the stainless steel round tube to be welded after the treatment in step S13 at a predetermined temperature for a predetermined time. In such an embodiment, by roughening the zirconium alloy round tube and the stainless steel round tube to be welded, the surface roughness of the zirconium alloy round tube and the stainless steel round tube is within a preset range, so as to ensure that the zirconium alloy round tube and the stainless steel round tube have a good diffusion bonding effect during the welding process and improve the welding quality.

[0063] In some embodiments, the surface roughness of the zirconium alloy round tube and the stainless steel round tube to be welded after roughening treatment is Ra 0.8-1.6 μm.

[0064] In some embodiments, in step S13, the treated zirconium alloy round tube to be welded and the stainless steel round tube to be welded can be cleaned with chemical reagents to remove oxide impurities and oil impurities on the surface of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded.

[0065] In some embodiments, in step S14, the predetermined drying temperature can be 120°C and the predetermined drying time can be 60 minutes to ensure that the surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded are completely dry and clean to avoid residual contaminants affecting the welding quality.

[0066] In some embodiments, in step S30, during the welding process, a pressure within a preset pressure range is applied to the surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded. In such an embodiment, by applying pressure to the surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded, atoms of the zirconium alloy round tube and the stainless steel round tube can diffuse through the surface, thereby achieving diffusion welding of the zirconium alloy round tube and the stainless steel round tube; at the same time, applying a pressure within a preset pressure range is conducive to improving the welding quality, so as to ensure that the zirconium alloy round tube and the stainless steel round tube can form a high-strength, high-density welding interface, thereby helping to improve the welding quality and improve the reliability and durability of the welding interface.

[0067] In some embodiments, the preset pressure range of the pressure applied to the welding surfaces of the zirconium alloy round tube to be welded and the stainless steel round tube to be welded is 12-14 MPa, for example, 13 MPa.

[0068] In some embodiments, in step S30, after welding is completed, the pressure is gradually released until the welding temperature drops to a predetermined value. In such an embodiment, the above arrangement is conducive to improving the welding quality and avoiding affecting the compactness of the welding interface between the zirconium alloy round tube and the stainless steel round tube.

[0069] In some embodiments, the predetermined value may be 500° C., that is, the pressure is gradually released after the welding temperature is lower than 500° C.

[0070] See also Figure 5 , Figure 5 It is a flow chart of the heating stage, the insulation stage and the cooling stage in the method for welding a zirconium alloy round tube and a stainless steel round tube provided in an embodiment of the present application. In some embodiments, in step S30, the staged heating and insulation method adopted may specifically include a first heating and insulation stage 31, a second heating and insulation stage 32 and a third heating and insulation stage 33. The first heating and insulation stage 31: heating to a first predetermined temperature 301 at a first heating rate and maintaining the first predetermined time; the second heating and insulation stage 32: heating to a second predetermined temperature 302 at a second heating rate and maintaining the second predetermined time; the third heating and insulation stage 33: heating to a third predetermined temperature 303 at a third heating rate and maintaining the third predetermined time. In such an embodiment, by raising the temperature in stages to the first predetermined temperature 301, the second predetermined temperature 302 and the third predetermined temperature 303, and maintaining the first predetermined time, the second predetermined time and the third predetermined time respectively, the zirconium alloy round tube and the stainless steel round tube can be diffusion welded under appropriate temperature conditions, which is conducive to forming a high-strength and high-density welding interface.

[0071] In some embodiments, the first heating rate is equal to the second heating rate, and the second heating rate is greater than the third heating rate; the first predetermined temperature 301 is less than the second predetermined temperature 302, and the second predetermined temperature 302 is less than the third predetermined temperature 303; the first predetermined time is less than the second predetermined time, and the second predetermined time is less than the third predetermined time. In such an embodiment, the above settings are conducive to more precise control of the welding temperature, which can effectively avoid stress concentration and deformation in the zirconium alloy round tube and the stainless steel round tube, and further improve the quality of welding and the reliability and durability of the obtained welding interface.

[0072] In some embodiments, the first heating rate is 10-15°C / min, the second heating rate is 10-15°C / min, and the third heating rate is 5-10°C / min; the first predetermined temperature 301 is 500°C, the second predetermined temperature 302 is 800°C, and the third predetermined temperature 303 is 1030°C; the first predetermined time is 20-30min, the second predetermined time is 20-30min, and the third predetermined time is 1-1.5h.

[0073] In some embodiments, in step S30, the staged cooling method specifically includes a first cooling stage 34, a second cooling stage 35, and a third cooling stage. The first cooling stage 34: cooling to a fourth predetermined temperature 304 at a first cooling rate; the second cooling stage 35: cooling to a fifth predetermined temperature 305 at a second cooling rate; the third cooling stage: cooling from the fifth predetermined temperature 305 to room temperature. In such an embodiment, the above arrangement also enables the zirconium alloy round tube and the stainless steel round tube to be diffusion welded under appropriate temperature conditions, which is conducive to forming a high-strength, high-density welding interface.

[0074] In some embodiments, the first cooling rate is less than the second cooling rate, and the fourth predetermined temperature 304 is greater than the fifth predetermined temperature 305. In such an embodiment, the above configuration is conducive to more accurate control of the temperature during the cooling process, and can effectively avoid stress concentration and deformation in the zirconium alloy round tube and the stainless steel round tube, further improving the quality of welding and the reliability and durability of the obtained welding interface.

[0075] In some embodiments, the first cooling rate is equal to the third heating rate, and the fourth predetermined temperature 304 is equal to the second predetermined temperature 302 ; the second cooling rate is equal to the first heating rate, and the fifth predetermined temperature 305 is less than the first predetermined temperature 301 .

[0076] In some embodiments, the first cooling rate is 5-10°C / min, the second cooling rate is 10-15°C / min; the fourth predetermined temperature 304 is 800°C, and the fifth predetermined temperature 305 is 400°C.

[0077] In some embodiments, in step S30, the temperature of the zirconium alloy round tube and the stainless steel round tube can be reduced from the fifth predetermined temperature 305 to room temperature by natural cooling, so as to avoid large thermal stress at the welding interface and ensure the integrity of the welding interface.

[0078] In some embodiments, in step S20, a solder resist is further provided on the surface of the graphite fixture in contact with the zirconium alloy round tube to be welded and the stainless steel round tube to be welded. In such an embodiment, the above-mentioned setting can prevent the zirconium alloy round tube and the stainless steel round tube from adhering to the graphite fixture during the welding process, so as to avoid affecting the welding of the zirconium alloy round tube and the stainless steel round tube.

[0079] In some embodiments, in step S40, the air tightness test of the structure obtained by welding includes: sealing one end of the structure obtained by welding; introducing gas of a predetermined pressure into the structure obtained by welding through the unsealed end of the structure obtained by welding, and maintaining the air pressure in the structure obtained by welding at the predetermined pressure; if no leakage occurs within a predetermined time, the air tightness of the structure obtained by welding is good and can meet the use requirements; if leakage occurs before the predetermined time, the air tightness of the structure obtained by welding is poor and cannot meet the use requirements.

[0080] In some embodiments, in step S40, when performing an air tightness test on the structure obtained by welding, the preset pressure of the gas introduced into the structure obtained by welding may be 13-15 MPa, and the preset time may be 60 seconds.

[0081] The dissimilar material connector 322 provided in the embodiment of the present application is obtained by welding a zirconium alloy round tube and a stainless steel round tube provided in any embodiment of the present application.

[0082] The following is a description of the process of welding a zirconium alloy round tube and a stainless steel round tube using the method for welding a zirconium alloy round tube and a stainless steel round tube provided in an embodiment of the present application; wherein the zirconium alloy round tube is a Zr-3 zirconium alloy round tube with an outer diameter of 17 mm and an inner diameter of 6 mm, and the stainless steel round tube is a 304 stainless steel round tube with an outer diameter of 17 mm and an inner diameter of 2.8 mm.

[0083] First, one end of the Zr-3 zirconium alloy round tube and one end of the 304 stainless steel round tube to be welded are processed respectively to form a conical structure with an opening angle of 10° at one end of the Zr-3 zirconium alloy round tube to be welded, and an inverted conical structure with an opening angle of 10° is formed at one end of the 304 stainless steel round tube to be welded.

[0084] Afterwards, the processed Zr-3 zirconium alloy round tube and 304 stainless steel round tube are roughened to ensure that the surface roughness of the Zr-3 zirconium alloy round tube and 304 stainless steel round tube after the roughening treatment reaches Ra 0.8μm; and the surfaces of the Zr-3 zirconium alloy round tube and 304 stainless steel round tube after the roughening treatment are cleaned with chemical reagents, and after the cleaning is completed, the cleaned Zr-3 zirconium alloy round tube and 304 stainless steel round tube are placed in a drying oven and dried at 120°C for 60 minutes.

[0085] Afterwards, the cleaned and dried Zr-3 zirconium alloy round tube and 304 stainless steel round tube are taken out of the drying oven, the conical structure of the Zr-3 zirconium alloy round tube is inserted into the inverted conical structure of the 304 stainless steel round tube, and the Zr-3 zirconium alloy round tube and the 304 stainless steel round tube are fixed in a graphite fixture; and solder resist is sprayed on the contact surface of the graphite fixture with the Zr-3 zirconium alloy round tube and the contact surface of the graphite fixture with the 304 stainless steel round tube.

[0086] Afterwards, the graphite fixture and the Zr-3 zirconium alloy round tube and 304 stainless steel round tube fixed thereon are placed on the welding platform of the vacuum diffusion welding equipment, the upper and lower welding machine pressure heads are aligned, and the equipment is started to evacuate until the vacuum degree reaches 10-5Pa, and the welding process begins; during the welding process, the temperature is first increased to 500°C at a heating rate of 12°C / min and maintained for 20 minutes, then increased to 800°C at a heating rate of 12°C / min and maintained for 25 minutes, then increased to 1030°C at a heating rate of 8°C / min and maintained for 1.5 hours; during the entire welding process, a pressure of 13MPa is always applied to the surface of the Zr-3 zirconium alloy round tube and the 304 stainless steel round tube to be welded until the temperature drops to 500°C and the pressure is gradually released.

[0087] After welding is completed, the cooling process begins; during the cooling process, the temperature is first cooled to 800°C at a cooling rate of 8°C / min, then cooled to 400°C at a cooling rate of 12°C / min, and then naturally cooled to room temperature.

[0088] After the cooling is completed, the welded structure is taken out of the vacuum diffusion welding equipment, and the welding interface is tested for air tightness: one end of the welded structure is sealed, and 15MPa of gas is introduced into the welded structure from the unsealed end and the pressure is maintained for 60s to ensure that there is no gas leakage, so as to determine that the welding interface has good air tightness and obtain the dissimilar material connector 322.

[0089] Regarding the embodiments of the present application, it should also be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other to obtain new embodiments.

[0090] The above are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto. The protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A fuel element cladding external pressure test device, which is suitable for testing the zirconium alloy cladding of fuel elements, characterized in that: It includes: A simulated fuel pellet, wherein the simulated fuel pellet is sleeved on the cladding; A heating device, the heating device being configured to heat the cladding to a temperature required for the test; a pressurized connection sealing assembly, the pressurized connection sealing assembly being configured to be sealedly connected to the heating device and to form a closed test space with the heating device, a superheated steam supply device, configured to supply superheated steam into the cladding and configured to be sealedly connected to the pressurized connection sealing assembly; The cladding encasing the simulated fuel pellets is heated and pressurized in the test space; A detection component is configured to detect the temperature of the cladding and the pressure of the air cavity outside the cladding under different temperature and pressure conditions.

2. The test device according to claim 1, characterized in that: The pressurized connection sealing assembly includes a pressurizing member and a connection sealing assembly. A pressurizing port is formed on the connection sealing assembly. The pressurizing member is arranged at the pressurizing port. The pressurizing member provides pressure to the test space through the pressurizing port. The connection sealing assembly is configured to be sealed and connected to the heating device and to form a closed test space with the heating device, and The connection sealing assembly is configured to be sealed and connected to the enclosure, and is configured to be sealed and connected to the superheated steam providing device.

3. The test device according to claim 2, characterized in that: The connection sealing assembly includes a stainless steel sealing connector and a heterogeneous material connector. The stainless steel sealing connector is configured such that one end thereof is sealedly connected to the heating device, and the other end thereof is sealedly connected to the heterogeneous material connector. The pressurizing port is formed on the stainless steel sealing connector. The heterogeneous material connecting piece is arranged so that one end thereof is sealedly connected to the cladding, and the other end thereof is sealedly connected to the superheated steam providing device.

4. The test device according to any one of claims 1 to 3, characterized in that: The cladding with the simulated fuel pellets is arranged in the heating device, and both ends of the cladding extend outside the heating device.

5. The test device according to claim 3, characterized in that: The detection assembly includes a temperature detection component and a pressure detection component. The temperature detection component is arranged on the inner wall of the cladding, and the pressure detection component is arranged to be connected to the pressurizing device of the pressurizing port, so as to measure the pressure of the pressurizing device.

6. The test device according to claim 3, characterized in that: The dissimilar material connector includes a nuclear-grade zirconium alloy part and a stainless steel part, which are formed by diffusion welding, wherein the nuclear-grade zirconium alloy part is sealedly connected to the cladding, and the stainless steel part is sealedly connected to the stainless steel sealed connector.

7. A test method for determining the external pressure of a fuel element cladding, characterized in that: The method adopts the test device according to any one of claims 1-6.

8. The test method according to claim 7, characterized in that: It includes the following steps: heating the test space; Pressurizing the test space; The temperature of the cladding and the external pressure on the cladding are obtained.

9. The method according to claim 8, characterized in that adjusting the heating power of the heating device so that the cladding is heated at different heating temperatures; And under different heating powers of the heating device, the temperature of the cladding and the external pressure borne by the cladding are obtained.

10. The method according to any one of claims 7 to 9, characterized in that: The radial dimension of the cladding is set to be the same as that of the actual cladding, and the length of the cladding is set to be adjusted according to test requirements or the heating device.

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