A device for testing the bulging and bursting of the inner cladding of a pressurized annular fuel rod

Abstract

The present invention belongs to the technical field of nuclear fuel assembly test equipment, and specifically relates to a bulging and bursting test device for the inner cladding of a pressurized annular fuel rod. The bulging and bursting test device for the inner cladding of a pressurized annular fuel rod comprises a transition joint, an annular electric heating core assembly, an annular simulated core block, an inner cladding assembly, and an air intake pipe assembly. Through the arrangement of the above-mentioned structure and the connection of the various components therein, a large temperature difference can be formed in the circumferential direction of the inner cladding of the annular fuel rod to better simulate the temperature environment required for the test and completely simulate the heat transfer condition of the material from the outside to the inside. The bulging and bursting test device for the inner cladding of a pressurized annular fuel rod provided by the present invention can be applied to pressurized water reactors, boiling water reactors, heavy water reactors, fast reactors, power reactors, and marine power reactors.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear fuel assembly test devices, and in particular relates to a pressure-bearing annular fuel rod inner cladding bulging explosion test device. Background Art

[0002] During the operation of nuclear power plant reactors, the performance of nuclear fuel is an important factor affecting the safety and economy of the reactor. Therefore, the international community has always placed great emphasis on the research of fuel elements. By optimizing the design of fuel elements, using advanced structural materials, improving the manufacturing process of elements, and other methods, the various properties of nuclear fuel elements are continuously improved, which promotes the development of nuclear power in a safer and more economical direction.

[0003] Safety and economy are the foundation of nuclear power development. Almost all nuclear power technology development is aimed at increasing nuclear power safety and economy. Fuel elements are the core components of nuclear power plant reactors. Their performance is one of the most important factors affecting nuclear power safety and economy. Therefore, the international community has always placed the research of fuel elements in a very prominent position. By optimizing fuel element design, using advanced structural materials, improving element manufacturing processes and other methods, the various properties of nuclear fuel elements are continuously improved, which promotes the development of nuclear power in a safer and more economical direction.

[0004] At present, rod-shaped fuel is widely used in pressurized water reactor nuclear power plants. By deepening the fuel unloading burnup of the components and extending the refueling cycle, the operating cost of the power plant can be reduced and the economic efficiency of nuclear power can be improved. The average design fuel consumption of pressurized water reactor fuel assemblies has gradually increased from 10 to 15 GWd / tU in the early days to 60 to 70 GWd / tU so far, and the refueling cycle has also been correspondingly extended from 12 months to the current 18 or 24 months. The deepening of fuel assembly burnup also brings a series of problems such as increased fission gas release, increased cladding corrosion and hydrogen absorption, swelling of fuel pellets, and increased irradiation growth of fuel elements and assemblies. How to solve these problems has always been an important task in the international research on pressurized water reactor fuel elements. For example, the development of advanced cladding with good corrosion resistance and the use of pellets with low fission gas release rate. In addition, the overall safety of the reactor core has also been improved by improving the design of the positioning grid and increasing the critical heat flux density of the assembly. In general, the structure and parameters of rod-shaped fuel assemblies are the result of continuous optimization in the past 50 years. The potential of technical improvements based on rod-shaped fuel for improving the economy and safety of nuclear power is very limited. Therefore, in recent years, the use of fuel elements with other geometric structures has become a new development idea.

[0005] Fuel elements of new geometric structures must meet at least the following five basic requirements: 1) improve the "surface area / volume" ratio of the fuel; 2) reduce the thickness of the pellets; 3) have sufficient rigidity; 4) reduce the core pressure drop; 5) the components must have an open grid design. The concept of annular fuel elements for light water reactors, first proposed by the Massachusetts Institute of Technology, meets the above five requirements very well. The so-called annular fuel is to make the fuel pellets into annular shapes, and add cladding tubes on the inner and outer surfaces of the pellets, so that the coolant can cool the elements from both the inner and outer flow channels at the same time. Compared with traditional solid cylindrical fuels, the advantage of annular fuels is that at very high linear density, the temperature at the center of the fuel is still very low, the energy storage in the fuel is less, and the fission gas release is less. It can be expected that the fuel performance will be better under normal operation and transient conditions.

[0006] As an advanced fuel element with a completely innovative structure, annular fuel can greatly improve the heat transfer efficiency of fuel elements, reduce the temperature of fuel pellets, and significantly improve the safety and economy of reactors. It has become one of the important development trends of advanced fuel components for pressurized water reactors and has received much attention from the international industry. The United States, South Korea and other countries have successively carried out research and development of annular fuels, and studies have shown that annular fuels have good application prospects.

[0007] During the design of annular fuel assemblies, it is urgent to conduct research on the performance test of explosion tests. Is there any similar technology at present? The new structure also faces new problems. First, the large-diameter thin-walled cladding of the outer cladding has never been used in nuclear power plants, so the external pressure instability problem of the outer cladding needs to be recalculated; secondly, based on the previous operating experience of pressurized water reactors, even in the same assembly, different fuel rods will have different axial growth. Therefore, it can be inferred that double-clad annular fuel may also have different axial growth. Summary of the invention

[0008] The purpose of the present invention is to develop and design a bulging and bursting test device for the inner cladding of a pressurized annular fuel rod, so as to solve the problem of the test device used in the off-core safety test of the inner cladding of the annular fuel under different heating rate conditions, and to determine the corresponding relationship and specific values ​​of the bursting temperature, bursting pressure and bursting strain of the inner cladding of the annular fuel under LOCA conditions, so as to provide data support for the safety review of the annular fuel entering the reactor.

[0009] The technical solution of the present invention is as follows:

[0010] A pressure-bearing annular fuel rod inner cladding bulging and bursting test device comprises a transition joint, an annular electric heating core assembly, an annular simulated core block, an inner cladding assembly, and an air intake pipe assembly;

[0011] 1. The transition joint is a ring-shaped structure, which is respectively arranged at the upper end and the lower end of the entire device, including two joints arranged coaxially up and down, namely the upper transition joint and the lower transition joint;

[0012] 2. Ring electric heating core assembly

[0013] The double electric heating wire core is an annular structure as a whole; the effective heating section is located in the middle of the entire electric heating core;

[0014] Two electric heating wires are arranged inside the double electric heating wire core, and the electric heating power of each electric heating wire can be controlled separately;

[0015] 3. Inner Shell Assembly

[0016] The inner cladding assembly is a tubular structure;

[0017] An inner shell middle thermocouple is arranged on the inner wall at the center of the length of the inner shell assembly;

[0018] An inner cladding upper thermocouple is arranged on the inner wall at the upper third of the length of the inner cladding assembly;

[0019] 4. Ring-shaped simulation core block

[0020] The annular simulation core block is a tubular structural member;

[0021] 5. The air intake pipe assembly includes an air circuit connecting pipe, a test piece connecting pipe, a square air intake connecting block, and an air intake transition joint;

[0022] One end of the gas circuit connecting pipe is connected to the external gas supply system, and the other end is connected to the test piece connecting pipe;

[0023] The external supply system provides gas to the air intake pipe assembly, and the type of gas is one of helium and nitrogen;

[0024] The outer diameter of the test piece connecting pipe matches the inner diameter of the gas circuit connecting pipe and is welded and fixed. The pressure range of the weld is 10-15MPa.

[0025] The test piece connecting pipe is connected to the upper transition joint through a square air inlet connecting block;

[0026] The square air intake connection block is a rectangular parallelepiped structure with a circular channel in the middle and a circular hole on the side. The test piece connection pipe is inserted into the circular hole on the side and connected by welding to form an air intake pipe assembly.

[0027] The top of the air intake pipe assembly is welded to the upper transition joint, and the bottom of the air intake pipe assembly is welded to the air intake transition joint;

[0028] The bottom end of the air inlet transition joint is connected to the top end of the annular electric heating core assembly;

[0029] The entire device is composed of a coaxially arranged upper transition joint, a square air intake connection block, an air intake transition joint, an annular electric heating core assembly, and a lower transition joint from top to bottom along the axial direction. A closed cavity is formed between the above components, and an annular fuel simulation core block is arranged in this cavity near the annular fuel inner cladding.

[0030] Furthermore, in the above-mentioned pressure-bearing annular fuel rod inner cladding bulging and bursting test device, the material of the upper transition joint is S30408, which is arranged at the upper end of the entire device, with an inner diameter of 11 mm and an outer diameter of 16 mm;

[0031] The material of the lower transition joint is Zr-4, which is set at the lower end of the entire device, with an inner diameter of 10.4mm and an outer diameter of 16mm.

[0032] Furthermore, in the above-mentioned pressurized annular fuel rod inner cladding bulging and bursting test device, the upper transition joint and the lower transition joint are respectively fixedly connected to the inner cladding assembly by welding, and the pressure range of the weld is 10-15MPa.

[0033] Furthermore, in the above-mentioned pressure-bearing annular fuel rod inner cladding bulging and bursting test device, the dual electric heating wire core body is an annular structure with a length of 800-1000mm, an inner diameter of 13mm, and an outer diameter of 25mm; wherein the effective heating section is 600mm long and is located in the middle of the entire electric heating core body; the outer surface of the dual electric heating wire core body is smooth, and the roughness is 1.6um;

[0034] The material of each electric heating wire is nickel-cadmium electric heating alloy, the material grade is Cr20Ni80, the diameter is 0.7mm, the maximum operating temperature is 1100℃-1200℃, the pitch is 1.45mm, the heating efficiency is >95%, and the adjustable electric heating maximum power is 10kW / m.

[0035] Furthermore, in the above-mentioned pressurized annular fuel rod inner cladding bulging and bursting test device, the inner cladding assembly is a tubular structure with a length of 690 mm, an outer diameter of 9.34 mm, and a thickness of 0.57 mm.

[0036] Furthermore, in the above-mentioned pressurized annular fuel rod inner cladding bulging and bursting test device, in the inner cladding assembly, the inner cladding middle thermocouple and the inner cladding upper thermocouple are fixed to the inner wall of the inner cladding assembly by spot welding, and the welding point diameter does not exceed twice the thermocouple diameter.

[0037] Furthermore, in the above-mentioned pressure-bearing annular fuel rod inner cladding bulging and bursting test device, the annular simulated pellet is a tubular structure of an alumina material with an inner diameter of 10.34 mm and an outer diameter of 12.34 mm.

[0038] Furthermore, in the above-mentioned pressure-bearing annular fuel rod inner cladding bulging and bursting test device, the gas circuit connecting pipe has an outer diameter of 10 mm, a thickness of 2 mm, and is made of S30408 ​​stainless steel;

[0039] The square air intake connection block is a rectangular structure with a length of 21.5mm, a width of 21.5mm, and a height of 12mm. There is a 15.48mm circular channel in the middle and a 6.2mm diameter circular hole on the side. The test piece connecting pipe with a diameter of 6mm is inserted 3mm into the circular hole on the side and welded to form an air intake pipe assembly.

[0040] Furthermore, a method for testing the bulging and bursting of the inner cladding of a pressurized annular fuel rod is provided, which uses a device for testing the bulging and bursting of the inner cladding of a pressurized annular fuel rod as described above; and is applied to one of pressurized water reactors, boiling water reactors, heavy water reactors, fast reactors, power reactors, and marine power reactors.

[0041] The beneficial effects of the technical solution of the present invention are:

[0042] 1. The annular electric heating core assembly, in which the electric heating power of each electric heating wire can be controlled separately, can controllably heat the inner cladding; and the linear power density is large, which can meet the test requirements and achieve a higher heating rate.

[0043] 2. Through the arrangement of the above structure and the connection of the various components therein, a large temperature difference can be formed in the circumferential direction of the inner cladding of the annular fuel rod to better simulate the temperature environment required for the test and completely simulate the heat transfer condition of the material from the outside to the inside.

[0044] 3. Through the arrangement of the above structure and the connection of the various components therein, the requirements for internal pressure of the annular fuel rod inner cladding during various tests can be met; and the volume of the air cavity therein is adjustable, which can better simulate various test environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the overall structure of the annular fuel rod inner cladding bulging explosion test device of the present invention;

[0046] Figure 2 It is the appearance drawing of the transition joint assembly parts (the upper transition joint and the lower transition joint have exactly the same structure);

[0047] Figure 3 It is a schematic diagram of the structure of an annular electric heating core;

[0048] Figure 4 It is a schematic diagram of the structure of the annular simulation core block;

[0049] Figure 5 This is a schematic diagram of the structure of the annular fuel inner cladding test sample;

[0050] Figure 6 It is a schematic diagram of the structure of the air intake transition joint;

[0051] Figure 7 It is a schematic diagram of the structure of a square air intake connection block;

[0052] Figure 8 It is a schematic diagram of the structure of the air intake connecting pipe of the test piece.

[0053] In the figure: 1: transition joint; 2: annular electric heating core; 3: annular simulated core block; 4: upper thermocouple; 5: middle thermocouple; 6: annular fuel inner cladding test sample; 7: air intake transition joint; 8: square air intake connection block; 9; air circuit connection pipe. DETAILED DESCRIPTION

[0054] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0055] like Figure 1 As shown, a device for testing the bulging and bursting of inner cladding of a pressurized annular fuel rod according to the present invention comprises a transition joint, an annular electric heating core assembly, an annular simulated pellet, an inner cladding assembly, and an air intake pipe assembly;

[0056] 1. If Figure 2 As shown, the transition joint is an annular structure, which is respectively arranged at the upper end and the lower end of the entire device, and includes two joints arranged coaxially up and down, namely an upper transition joint and a lower transition joint;

[0057] The material of the upper transition joint is S30408, which is set at the upper end of the whole device, with an inner diameter of 11mm and an outer diameter of 16mm;

[0058] The material of the lower transition joint is Zr-4, which is set at the lower end of the entire device, with an inner diameter of 10.4mm and an outer diameter of 16mm.

[0059] The upper transition joint and the lower transition joint are fixedly connected to the inner shell assembly by welding, and the pressure bearing range of the weld is 10-15MPa.

[0060] 2. Ring electric heating core assembly

[0061] like Figure 3 As shown, the dual electric heating wire core is a ring structure with a length of 800-1000mm, an inner diameter of 13mm and an outer diameter of 25mm; the effective heating section is 600mm long and is located in the middle of the entire electric heating core; the outer surface of the dual electric heating wire core is smooth with a roughness of 1.6um;

[0062] The material of each electric heating wire is nickel-cadmium electric heating alloy, the material grade is Cr20Ni80, the diameter is 0.7mm, the maximum operating temperature is 1100℃-1200℃, the pitch is 1.45mm, the heating efficiency is >95%, and the adjustable electric heating maximum power is 10kW / m.

[0063] 3. Inner Shell Assembly

[0064] like Figure 5 As shown, the inner shell assembly is a tubular structure with a length of 690 mm, an outer diameter of 9.34 mm, and a thickness of 0.57 mm.

[0065] An inner shell middle thermocouple is arranged on the inner wall at the center of the length of the inner shell assembly;

[0066] An inner cladding upper thermocouple is arranged on the inner wall at the upper third of the length of the inner cladding assembly;

[0067] The thermocouple in the middle of the inner shell and the thermocouple in the upper part of the inner shell are fixed on the inner wall of the inner shell assembly by spot welding, and the diameter of the welding spot does not exceed twice the diameter of the thermocouple.

[0068] 4. Ring-shaped simulation core block

[0069] like Figure 4 As shown, the annular simulated core block is a tubular structure of an aluminum oxide material with an inner diameter of 10.34 mm and an outer diameter of 12.34 mm.

[0070] 5. The air intake pipe assembly includes an air circuit connecting pipe, a test piece connecting pipe, a square air intake connecting block, and an air intake transition joint;

[0071] The outer diameter of the gas circuit connecting pipe is 10mm, the thickness is 2mm, and the material is S30408 ​​stainless steel;

[0072] One end of the gas circuit connecting pipe is connected to the external gas supply system, and the other end is connected to the test piece connecting pipe;

[0073] The external supply system provides gas to the air intake pipe assembly, and the type of gas is one of helium and nitrogen;

[0074] The outer diameter of the test piece connecting pipe matches the inner diameter of the gas circuit connecting pipe and is welded and fixed. The pressure range of the weld is 10-15MPa.

[0075] The test piece connecting pipe is connected to the upper transition joint through a square air inlet connecting block;

[0076] like Figure 7As shown, the square air inlet connection block is a rectangular parallelepiped structure with a length of 21.5 mm, a width of 21.5 mm, and a height of 12 mm. A 15.48 mm circular channel is opened in the middle, and a 6.2 mm diameter circular hole is opened on the side. The 6 mm diameter test piece connection pipe is inserted into the side circular hole for 3 mm and connected by welding, forming a structure as shown in FIG. Figure 8 Intake manifold assembly shown.

[0077] The top of the air intake pipe assembly is welded to the upper transition joint, and the bottom of the air intake pipe assembly is welded to the air intake transition joint; Figure 6 As shown, the bottom end of the air inlet transition joint is connected to the top end of the annular electric heating core assembly;

[0078] The entire device is composed of a coaxially arranged upper transition joint, a square air intake connection block, an air intake transition joint, an annular electric heating core assembly, and a lower transition joint from top to bottom along the axial direction. A closed cavity is formed between the above components, and an annular fuel simulation core block is arranged in this cavity near the annular fuel inner cladding.

[0079] A method for testing the bulging and bursting of the inner cladding of a pressurized annular fuel rod is disclosed. The method uses the device for testing the bulging and bursting of the inner cladding of a pressurized annular fuel rod as described above. The method is applicable to pressurized water reactors, boiling water reactors, heavy water reactors, fast reactors, power reactors, and marine power reactors.

[0080] The pressurized annular fuel rod inner cladding bulging and bursting test device as described above can also be used in the fields of tubular heat transfer test, dynamic water corrosion test, etc.

[0081] The above is a detailed description of the implementation method of the present invention in conjunction with the embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. The contents not described in detail in the specification of the present invention can adopt the existing technology.

Claims

1. A device for testing the bulging and bursting of the inner cladding of a pressurized annular fuel rod, characterized in that: It includes a transition joint, an annular electric heating core assembly, an annular simulation core block, an inner shell assembly, and an air intake pipe assembly; 1. The transition joint is a ring-shaped structure, which is respectively arranged at the upper end and the lower end of the entire device, including two joints arranged coaxially up and down, namely the upper transition joint and the lower transition joint; 2. Ring electric heating core assembly The double electric heating wire core is an annular structure as a whole; the effective heating section is located in the middle of the entire electric heating core; Two electric heating wires are arranged inside the double electric heating wire core, and the electric heating power of each electric heating wire can be controlled separately; 3. Inner Shell Assembly The inner cladding assembly is a tubular structure; An inner shell middle thermocouple is arranged on the inner wall at the center of the length of the inner shell assembly; An inner cladding upper thermocouple is arranged on the inner wall at the upper third of the length of the inner cladding assembly; 4. Ring-shaped simulation core block The annular simulation core block is a tubular structural member; 5. The air intake pipe assembly includes an air circuit connecting pipe, a test piece connecting pipe, a square air intake connecting block, and an air intake transition joint; One end of the gas circuit connecting pipe is connected to the external gas supply system, and the other end is connected to the test piece connecting pipe; The external supply system provides gas to the air intake pipe assembly, and the type of gas is one of helium and nitrogen; The outer diameter of the test piece connecting pipe matches the inner diameter of the gas circuit connecting pipe and is welded and fixed. The pressure range of the weld is 10-15MPa. The test piece connecting pipe is connected to the upper transition joint through a square air inlet connecting block; The square air intake connection block is a rectangular parallelepiped structure with a circular channel in the middle and a circular hole on the side. The test piece connection pipe is inserted into the circular hole on the side and connected by welding to form an air intake pipe assembly. The top of the air intake pipe assembly is welded to the upper transition joint, and the bottom of the air intake pipe assembly is welded to the air intake transition joint; The bottom end of the air inlet transition joint is connected to the top end of the annular electric heating core assembly; The entire device is composed of a coaxially arranged upper transition joint, a square air intake connection block, an air intake transition joint, an annular electric heating core assembly, and a lower transition joint from top to bottom in the axial direction. A closed cavity is formed between the above components, and an annular fuel simulation pellet is arranged in the cavity near the annular fuel inner cladding. The material of the upper transition joint is S30408, which is set at the upper end of the whole device, with an inner diameter of 11mm and an outer diameter of 16mm; The material of the lower transition joint is Zr-4, which is set at the lower end of the whole device, with an inner diameter of 10.4mm and an outer diameter of 16mm; The upper transition joint and the lower transition joint are fixedly connected to the inner shell assembly by welding, and the pressure bearing range of the weld is 10-15MPa; The double electric heating wire core is a ring structure with a length of 800-1000mm, an inner diameter of 13mm and an outer diameter of 25mm. The effective heating section is 600mm long and is located in the middle of the entire electric heating core. The outer surface of the double electric heating wire core is smooth with a roughness of 1.6um. The material of each electric heating wire is nickel-cadmium electric heating alloy, the material grade is Cr20Ni80, the diameter is 0.7mm, the maximum operating temperature is 1100℃-1200℃, the pitch is 1.45mm, the heating efficiency is >95%, and the adjustable electric heating maximum power is 10kW / m; The inner shell assembly is a tubular structure with a length of 690 mm, an outer diameter of 9.34 mm, and a thickness of 0.57 mm; In the inner shell assembly, the thermocouple in the middle of the inner shell and the thermocouple in the upper part of the inner shell are fixed to the inner wall of the inner shell assembly by spot welding, and the diameter of the welding spot shall not exceed 2 times the diameter of the thermocouple; The annular simulation core block is a tubular structure of an alumina material with an inner diameter of 10.34 mm and an outer diameter of 12.34 mm; The outer diameter of the gas circuit connecting pipe is 10mm, the thickness is 2mm, and the material is S30408 ​​stainless steel; The square air intake connection block is a rectangular structure with a length of 21.5mm, a width of 21.5mm, and a height of 12mm. There is a 15.48mm circular channel in the middle and a 6.2mm diameter circular hole on the side. The test piece connecting pipe with a diameter of 6mm is inserted 3mm into the circular hole on the side and welded to form an air intake pipe assembly.

2. A method for testing the bulging and bursting of the inner cladding of a pressurized annular fuel rod, characterized in that: The method uses a pressurized annular fuel rod inner cladding bulging and bursting test device as claimed in claim 1; it is applied to one of pressurized water reactors, boiling water reactors, heavy water reactors, fast reactors, power reactors, and marine power reactors.

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