A high-temperature in-pile irradiation test device for fuel rods and its manufacturing method

Abstract

The present application provides a high-temperature in-pile irradiation test device for fuel short rods and a manufacturing method thereof, belonging to the technical field of high-temperature irradiation tests. It includes: The high-temperature in-pile irradiation test device for fuel short rods provided by the embodiments of the present application includes a protection tube, a test piece assembly, and a first thermal resistance layer. By adding a first thermal resistance layer outside the fuel short rod, the temperature gradient between the fuel short rod and the internal cavity coolant is increased, so that the high temperature of the short rod cladding can be smoothly transferred to the internal cavity coolant through the first thermal resistance layer, realizing the high-temperature irradiation test of fuel short rods in low-temperature coolant, which is beneficial to increasing the upper limit of the irradiation test temperature of fuel short rods in the pile.

Description

Technical Field

[0001] This application belongs to the technical field of high-temperature irradiation test, and particularly relates to a high-temperature irradiation test device for fuel short rods in a reactor and a manufacturing method thereof. Background Art

[0002] In order to pursue higher thermal efficiency, more compact layout, smaller volume, and simpler disassembly and assembly solutions, the "new type of reactor" puts forward higher requirements for the technological performance of nuclear fuel, and there will be obvious differences from existing fuels in key materials, design technologies, manufacturing and testing processes. The main difficulty in the research and development of new type of reactor fuel is to carry out high-temperature irradiation tests in a research reactor. During the high-temperature irradiation test of the existing high-temperature irradiation test device, the temperature difference between the fuel core and the coolant is small. To prevent the leakage of high-temperature fission products, the upper limit of the test temperature should not be too high, and the irradiation test is limited. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related technologies.

[0004] To this end, the first aspect of the present invention provides a high-temperature irradiation test device for fuel short rods in a reactor.

[0005] The second aspect of the present invention provides a manufacturing method of a high-temperature irradiation test device for fuel short rods in a reactor.

[0006] In view of this, according to the first aspect of the embodiments of the present application, a high-temperature irradiation test device for fuel short rods in a reactor is proposed, including:

[0007] A protection tube, the protection tube includes a heat insulation cladding;

[0008] A test piece assembly, the test piece assembly is arranged in the accommodation cavity surrounded by the heat insulation cladding, the test piece assembly includes a plurality of fuel short rods, and the fuel short rods are arranged parallel to the axis of the heat insulation cladding;

[0009] A first thermal resistance layer, the first thermal resistance layer is arranged along the circumferential direction of the fuel short rod, and the first thermal resistance layer is located between the fuel short rod and the heat insulation cladding.

[0010] In a feasible implementation manner, the first thermal resistance layer includes:

[0011] A heat insulation layer, the heat insulation layer is arranged along the circumferential direction of the fuel short rod on the outside of the fuel short rod, the heat insulation layer is hermetically connected to the fuel short rod, and there is a first gap between the inner side wall of the heat insulation layer and the outer side wall of the fuel short rod;

[0012] A first filling layer, the first filling layer is arranged in the first gap, and the first filling layer is in contact with the heat insulation layer and the fuel short rod;

[0013] The outer cladding is arranged on the outer side of the heat insulation layer along the circumferential direction of the fuel pin. The outer cladding is hermetically connected to the heat insulation layer, and there is a second gap between the inner side wall of the outer cladding and the outer side wall of the heat insulation layer;

[0014] The second filling layer is arranged in the second gap, and the second filling layer is in contact with the outer cladding and the heat insulation layer.

[0015] In a feasible implementation manner, the in-pile high-temperature irradiation test device for fuel pins further includes:

[0016] The first installation groove is evenly arranged on the inner side wall of the heat insulation layer along the circumferential direction of the heat insulation layer, and the first installation groove is used for installing a temperature monitoring device;

[0017] The second installation groove is evenly arranged on the outer side wall of the heat insulation layer along the circumferential direction of the heat insulation layer, and the second installation groove is used for installing a temperature monitoring device. The second installation groove is arranged staggeredly with the first installation groove.

[0018] In a feasible implementation manner, the protection tube further includes an upper joint and a lower joint. The upper joint is arranged at the first end of the heat insulation cladding, and the lower joint is arranged at the second end of the heat insulation cladding;

[0019] At least two test piece assemblies are arranged in the accommodation cavity, and the test piece assemblies are arranged along the axial direction of the protection tube; the thickness of the first filling layer of the fuel pins in the upper test piece assembly is greater than the thickness of the first filling layer of the fuel pins in the middle test piece assembly; the thickness of the first filling layer of the fuel pins in the upper test piece assembly is greater than the thickness of the first filling layer of the fuel pins in the lower test piece assembly.

[0020] In a feasible implementation manner, several test piece assemblies are arranged at equal intervals along the axial direction of the protection tube in the accommodation cavity;

[0021] The fuel pins are evenly arranged in the accommodation cavity along the circumferential direction of the protection tube.

[0022] In a feasible implementation manner, the heat insulation cladding includes a cladding body;

[0023] The second thermal resistance layer is arranged on the outer side of the cladding body along the circumferential direction of the cladding body.

[0024] In a feasible implementation manner, the second thermal resistance layer includes:

[0025] The outer sleeve is arranged on the outer side of the cladding body along the circumferential direction of the cladding body. The outer sleeve is hermetically connected to the cladding body, and there is a third gap between the inner side wall of the outer sleeve and the outer side wall of the cladding body;

[0026] The third filling layer is arranged in the third gap, and the third filling layer is in contact with the outer sleeve and the cladding body.

[0027] In a feasible implementation, the high-temperature irradiation test device for fuel short rods in the reactor further includes:

[0028] An open ring plug, which includes a filling port and is arranged circumferentially along the cladding body at the first end of the outer casing. The closed ring plug is hermetically connected to the cladding body and the outer casing;

[0029] A closed ring plug, which is arranged circumferentially along the cladding body at the second end of the outer casing. The closed ring plug is hermetically connected to the cladding body and the outer casing.

[0030] According to the second aspect of the embodiments of the present application, a manufacturing method of a high-temperature irradiation test device for fuel short rods in the reactor is proposed, which is used to manufacture the high-temperature irradiation test device for fuel short rods in the reactor as described in any of the above technical solutions. The manufacturing method includes:

[0031] Based on the fuel phase volume and U 235 enrichment, perform core loading design to control the neutron flux level and linear power density of the fuel short rods;

[0032] According to the core loading design value, calculate the accurate fuel heat release rate and linear power, design the size of the fuel short rods, and design the size of the first thermal resistance layer;

[0033] Use electric heating tubes with the same linear power density to replace the fuel short rods for testing, and measure the temperature gradients inside and outside the first thermal resistance layer at the designed linear power;

[0034] Remove the electric heating tubes, install the fuel short rods, and encapsulate the irradiation device.

[0035] In a feasible implementation, design the inner diameter and outer diameter of the heat insulation layer according to the axial position of the fuel short rods in the inner coolant cavity.

[0036] A high-temperature irradiation test device for fuel short rods in the reactor and its manufacturing method according to the present application have the following beneficial effects compared with the prior art:

[0037] The high-temperature irradiation test device for fuel short rods provided by the embodiments of the present application includes a protection tube, a test piece assembly, and a first thermal resistance layer. By adding a first thermal resistance layer outside the fuel short rods, the temperature gradient between the fuel short rods and the inner cavity coolant is increased, so that the high temperature of the short rod cladding can be smoothly transferred to the inner cavity coolant through the first thermal resistance layer, realizing the high-temperature irradiation test of fuel short rods in low-temperature coolant, which is beneficial to increasing the upper limit of the irradiation test temperature of fuel short rods in the reactor. Description of the Drawings

[0038] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, throughout the drawings, the same reference numerals are used to denote the same components. In the drawings:

[0039] Figure 1 Schematic structural diagram of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application, from the first angle;

[0040] Figure 2 Schematic structural diagram of the first thermal resistance layer of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application;

[0041] Figure 3 Schematic structural diagram of a fuel short rod of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application;

[0042] Figure 4 Schematic structural diagram of a three-grip positioning structure of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application;

[0043] Figure 5 Schematic structural diagram of the first installation groove and the second installation groove of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application;

[0044] Figure 6 Schematic position diagram of the temperature monitoring points of a fuel short rod of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application;

[0045] Figure 7 Schematic structural diagram of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application, from the second angle;

[0046] Figure 8 Schematic structural diagram of the second thermal resistance layer of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application;

[0047] Figure 9 Schematic step flow chart of the manufacturing method of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application;

[0048] Figure 10 Schematic design structure diagram of a fuel short rod in-pile high-temperature irradiation test device according to an embodiment provided by the present application;

[0049] Wherein, Figures 1 to 10 The corresponding relationship between the reference numerals in

[0050] 1. Protection tube; 2. Test piece assembly; 3. First thermal resistance layer; 4. Three-jaw positioning structure; 5. First installation groove; 6. Second installation groove; 7. Second thermal resistance layer; 8. Open ring plug; 9. Closed ring plug;

[0051] 11. Heat insulation cladding; 12. Upper joint; 13. Lower joint; 14. Flow-blocking part; 15. Throttle plug;

[0052] 111. Cladding body; 112. Upper sleeve; 113. Lower sleeve;

[0053] 20. Fuel short rod; 21. Fuel core; 22. Short rod cladding; 23. Elastic part; 24. Mounting seat; 25. First sealing plug; 26. Second sealing plug; 27. Heat dissipation cavity;

[0054] 31. Heat insulation layer; 32. First filling layer; 33. Outer cladding; 34. Second filling layer;

[0055] 71. Outer sleeve; 72. Third filling layer. Detailed implementation manners

[0056] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present application.

[0057] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0058] In the present application, unless otherwise clearly specified and limited, the terms "install", "connect", "join", "fix", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0059] The preferred embodiments of the present application will be described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0060] As Figure 1 and Figure 2 shown, according to the first aspect of the embodiments of the present application, a high-temperature in-pile irradiation test device for fuel short rods is proposed, including: a protection tube 1, a test piece assembly 2, and a first thermal resistance layer 3; the protection tube 1 includes a heat insulation cladding 11; the test piece assembly 2 is arranged in the accommodation cavity surrounded by the heat insulation cladding 11, the test piece assembly 2 includes a plurality of fuel short rods 20, and the fuel short rods 20 are arranged parallel to the axis of the heat insulation cladding 11; the first thermal resistance layer 3 is arranged along the circumferential direction of the fuel short rods 20, the first thermal resistance layer 3 is located between the fuel short rods 20 and the heat insulation cladding 11, and the first thermal resistance layer 3 and the heat insulation cladding 11 surround an internal coolant cavity.

[0061] The high-temperature in-pile irradiation test device for fuel short rods provided by the embodiments of the present application includes a protection tube 1, a test piece assembly 2, and a first thermal resistance layer 3. By adding a first thermal resistance layer 3 outside the fuel short rods 20, the temperature gradient between the fuel short rods 20 and the internal cavity coolant is increased, so that the high temperature of the short rod cladding 22 can be smoothly transferred to the internal cavity coolant through the first thermal resistance layer 3, realizing the high-temperature irradiation test of the fuel short rods 20 in a low-temperature coolant, which is beneficial to increasing the upper limit of the in-pile irradiation test temperature of the fuel short rods 20.

[0062] Further, as Figure 1 shown, the protection tube 1 further includes an upper joint 12, a lower joint 13, a flow blocking member 14, and a throttle plug 15. The upper joint 12 is arranged at the first end of the heat insulation cladding 11, and the lower joint 13 is arranged at the second end of the heat insulation cladding 11; the flow blocking member 14 is arranged in the internal coolant cavity for simulating the situation of coolant flow channel blockage under extreme conditions, and researching and evaluating the possible blockage situations that the fuel short rods 20 may encounter during the actual reactor operation; the throttle plug 15 is arranged at one end of the heat insulation cladding 11 close to the lower joint 13, and an adjustment port is arranged on the throttle plug 15. By adjusting the opening size of the adjustment port of the throttle plug 15, the coolant flow rate flowing through the fuel rods is controlled to maintain the operation of the fuel short rods 20 at a specific power level.

[0063] Further, as Figure 3 shown, the fuel short rods 20 include a fuel core 21, a short rod cladding 22, an elastic member 23, a mounting seat 24, a first sealing plug 25, and a second sealing plug 26. A heat dissipation cavity 27 is arranged on the fuel core 21, the short rod cladding 22 is wound around the outside of the fuel core 21, the first sealing plug 25 and the second sealing plug 26 seal the fuel core 21 in the short rod cladding 22 at both ends of the short rod cladding 22, and the fuel core 21 is supported by the elastic member 23 to provide an expandable space for the fuel core 21.

[0064] As shown Figure 2 in FIG. 1, in a feasible embodiment, the first thermal resistance layer 3 includes: a heat insulation layer 31, a first filling layer 32, an outer shell 33, and a second filling layer 34; the heat insulation layer 31 is disposed on the outer side of the fuel rod 20 along the circumferential direction of the fuel rod 20, the heat insulation layer 31 is hermetically connected to the fuel rod 20, and there is a first gap between the inner side wall of the heat insulation layer 31 and the outer side wall of the fuel rod 20; the first filling layer 32 is disposed in the first gap, and the first filling layer 32 is in contact with the heat insulation layer 31 and the fuel rod 20; the outer shell 33 is disposed on the outer side of the heat insulation layer 31 along the circumferential direction of the fuel rod 20, the outer shell 33 is hermetically connected to the heat insulation layer 31, and there is a second gap between the inner side wall of the outer shell 33 and the outer side wall of the heat insulation layer 31; the second filling layer 34 is disposed in the second gap, and the second filling layer 34 is in contact with the outer shell 33 and the heat insulation layer 31.

[0065] In this technical solution, the first filling layer 32, the heat insulation layer 31, the second filling layer 34, and the outer shell 33 are sequentially disposed on the outer side of the short rod cladding 22 from the inside out. By providing the heat insulation layer 31, a large temperature gradient is established between the fuel rod 20 and the internal cavity coolant. The outer shell 33 serves as the second boundary of the fuel rod 20, further reducing the risk of leakage of radioactive substances inside the short rod cladding 22 and improving the safety during the test of the fuel rod 20; the first filling layer 32 isolates the physical contact between the heat insulation layer 31 and the short rod cladding 22, and the second filling layer 34 isolates the physical contact between the heat insulation layer 31 and the outer shell 33, reducing the uncertainty brought by the contact thermal resistance between the short rod cladding 22, the heat insulation layer 31, and the outer shell 33 to the establishment of the test temperature field. At the same time, the first filling layer 32 and the second filling layer 34 also have a certain heat insulation and heat preservation effect, which is beneficial to maintaining the temperature gradient between the fuel rod 20 and the internal cavity coolant.

[0066] Furthermore, the heat insulation layer 31 is made of a ceramic material for heat insulation, the outer shell 33 is made of a stainless steel material to protect the internal structure, the first filling layer 32 between the heat insulation layer 31 and the short rod cladding 22 is formed by filling helium, the second filling layer 34 between the heat insulation layer 31 and the outer shell 33 is formed by filling helium, and the first filling layer 32 and the second filling layer 34 further insulate and preserve heat, avoiding the influence of contact thermal resistance on the accuracy of temperature field establishment. Specifically, when the wall thickness of the heat insulation layer 31 is 4 mm, a temperature difference of about 550 °C can be established between the fuel rod 20 and the internal coolant.

[0067] In some examples, as Figure 4, the first filling layer 32 is formed by using a three-jaw positioning structure 4 to support and position the heat insulation layer 31 at both ends of the fuel rod 20 to form a cavity, and then helium flushing and welding are carried out inside the heat insulation layer 31; the second filling layer 34 is formed by using a three-jaw positioning structure 4 to support and position the outer cladding 33 at both ends of the heat insulation layer 31 to form a cavity, and then helium flushing and welding are carried out inside the outer cladding 33.

[0068] In some examples, the three-jaw positioning structure 4 has a total of 3 positioning surfaces. The inner wall of the jaw stuffing block contacts the short rod cladding 22, and the outer wall of the jaw stuffing block contacts and supports the inner wall of the heat insulation layer 31, forming a stable and reliable first gap on the side of the heat insulation layer 31 close to the short rod cladding 22; the outer wall of the jaw positioning rib contacts and supports the inner wall of the outer cladding 33, forming a stable and reliable second gap on the side of the heat insulation layer 31 far from the short rod cladding 22.

[0069] As a preferred solution, the thicknesses of the first gap and the second gap are set according to the heat release rate. For example, a larger gap is required in the upper test piece to reduce the heat dissipation of the fuel rod 20, and smaller gaps are required in the middle and lower test pieces to increase the heat dissipation of the fuel rod 20. As a preferred solution, the first gap ≤ 0.2 mm; the temperature gradient on the outer side of the first thermal resistance layer 3 is small, and changing the thickness of the second filling layer 34 has little effect on the temperature. As a preferred solution, the second gap = 0.015 - 0.025 mm.

[0070] As Figure 5 As shown in the figure, in a feasible implementation manner, the in-pile high-temperature irradiation test device for fuel rods further includes: a first installation groove 5 and a second installation groove 6; the first installation groove 5 is uniformly arranged on the inner side wall of the heat insulation layer 31 along the circumferential direction of the heat insulation layer 31, and the first installation groove 5 is used to install a temperature monitoring device; the second installation groove 6 is uniformly arranged on the outer side wall of the heat insulation layer 31 along the circumferential direction of the heat insulation layer 31, and the second installation groove 6 is used to install a temperature monitoring device, and the second installation groove 6 is arranged staggeredly with the first installation groove 5.

[0071] In this technical solution, the first installation groove 5 is arranged on the side wall of the heat insulation layer 31 close to the fuel rod 20, and the temperature of the inner side surface of the heat insulation layer 31 is detected by installing a temperature monitoring device in the first installation groove 5; the second installation groove 6 is arranged on the side wall of the fuel rod 20 close to the outer cladding 33, and the temperature of the outer side surface of the heat insulation layer 31 is detected by installing a temperature monitoring device in the second installation groove 6. The first installation groove 5 and the second installation groove 6 are arranged staggeredly to monitor the temperature of the fuel rod 20 from different angles, so as to obtain more comprehensive thermal performance data, ensure that the fuel rod 20 is within a safe operating temperature range, prevent the fuel rod 20 from being damaged due to overheating, and subsequent data analysis and research can be carried out on the first thermal resistance layer 3 according to the monitored data, verify and improve the thermodynamic model of the fuel rod, optimize the design of the fuel rod 20, and improve the performance and reliability of the fuel rod 20 in practical applications.

[0072] In some examples, the first mounting groove 5 and the second mounting groove 6 are wire grooves. The included angle between two adjacent first mounting grooves 5 in the circumferential direction on the inner wall surface of the heat insulation layer 31 is 120°; the included angle between two adjacent second mounting grooves 6 in the circumferential direction on the outer wall surface of the heat insulation layer 31 is 120°; the first mounting groove 5 and the second mounting groove 6 are cross-distributed on the heat insulation layer 31 at an angle of 60°, such as Figure 6 , which can meet the representativeness of the measurement points and facilitate the installation and sealing of the leads of the measurement points.

[0073] In a feasible implementation manner, the protection tube 1 further includes an upper joint 12 and a lower joint 13. The upper joint 12 is arranged at the first end of the heat insulation shell 11, and the lower joint 13 is arranged at the second end of the heat insulation shell 11; at least two test piece assemblies 2 are arranged in the accommodation cavity, and the test piece assemblies 2 are arranged along the axial direction of the protection tube 1; the thickness of the first filling layer 32 of the fuel short rod 20 in the upper test piece assembly 2 is greater than the thickness of the first filling layer 32 of the fuel short rod 20 in the middle test piece assembly 2; the thickness of the first filling layer 32 of the fuel short rod 20 in the upper test piece assembly 2 is greater than the thickness of the first filling layer 32 of the fuel short rod 20 in the lower test piece assembly 2.

[0074] In this technical solution, the thickness of the first thermal resistance layer 3 outside the fuel short rod 20 is set according to the axial position of the test piece assembly 2 where the fuel short rod 20 is located. The upper test piece assembly 2 is located at a position in the accommodation cavity close to the upper joint 12. The upper test piece assembly 2 is located at the upper part of the reactor, and the heat release rate is relatively low; the middle test piece assembly 2 is located in the middle of the accommodation cavity. The middle test piece assembly 2 is located in the middle of the reactor, at the hottest position in the core, and the heat release rate is relatively high; the lower test piece assembly 2 is located at a position in the accommodation cavity close to the lower joint 13. The lower test piece assembly 2 is located at the lower part of the reactor, relatively close to the core, and the heat release rate is relatively high. By making the thickness of the first filling layer 32 of the fuel short rod 20 in the upper test piece assembly 2 larger and the thickness of the first filling layer 32 of the fuel short rod 20 in the middle test piece assembly 2 and the lower test piece assembly 2 smaller, the overall heat transfer characteristics of the test device are controlled to ensure that the fuel short rods 20 at each position reach similar working temperatures under different heat release rates, which is beneficial to the accurate temperature control of the test device, and further helps to accurately evaluate the behavior of materials in different thermal environments and optimize the design and operation of the nuclear reactor.

[0075] Such as Figure 1 and Figure 7 shown, in a feasible implementation manner, a plurality of test piece assemblies 2 are arranged at equal intervals along the axial direction of the protection tube 1 in the accommodation cavity; the fuel short rods 20 are arranged uniformly along the circumferential direction of the protection tube 1 in the accommodation cavity.

[0076] In this technical solution, a plurality of test piece assemblies 2 are arranged axially in the protection tube 1, and the distance between two adjacent test piece assemblies 2 is equal, so as to detect the temperature at different axial positions when the test device is working, which can ensure the uniformity of the power distribution in the reactor core, avoid local overheating or power peaks, and thus improve the thermal performance and fuel utilization rate of the fuel pellet 21; a plurality of fuel short rods 20 are arranged in each test piece assembly 2, and the fuel short rods 20 are used to detect the temperature at different circumferential positions when the test device is working, which helps to accurately control the neutron flux, achieve fine control of the reaction, helps to evaluate the performance of the reactor core, and optimize the reactor core design.

[0077] As Figure 8 shown, in a feasible implementation, the heat insulation cladding 11 includes a cladding body 111; the second thermal resistance layer 7 is arranged on the outer side of the cladding body 111 along the circumferential direction of the cladding body 111.

[0078] In this technical solution, a second thermal resistance layer 7 is added outside the cladding body 111 to establish an approximate adiabatic layer between the coolant in the inner cavity of the protection tube 1 and the external coolant, so that a large temperature gradient is maintained between the temperature of the inner cavity coolant and the external coolant.

[0079] Furthermore, as Figure 8 shown, the heat insulation cladding 11 further includes an upper sleeve 112 and a lower sleeve 113. The upper sleeve 112 and the lower sleeve 113 are located at both ends of the cladding body 111. The upper sleeve 112 connects the upper joint 12 at one end of the cladding body 111, and the lower sleeve 113 connects the other end of the cladding body 111 with the lower joint 13.

[0080] As Figure 8 shown, in a feasible implementation, the second thermal resistance layer 7 includes: an outer sleeve 71 and a third filling layer 72; the outer sleeve 71 is arranged on the outer side of the cladding body 111 along the circumferential direction of the cladding body 111. The outer sleeve 71 is hermetically connected to the cladding body 111, and there is a third gap between the inner side wall of the outer sleeve 71 and the outer side wall of the cladding body 111; the third filling layer 72 is arranged in the third gap, and the third filling layer 72 is in contact with the outer sleeve 71 and the cladding body 111.

[0081] In this technical solution, the third filling layer 72 and the outer sleeve 71 are sequentially arranged outside the cladding body 111 from the inside to the outside. By arranging the third filling layer 72, a large temperature gradient is established between the inner cavity coolant and the external coolant. At the same time, the third filling layer 72 isolates the physical contact between the outer sleeve 71 and the cladding body 111, so that a temperature gradient is maintained between the water temperature of the inner cavity coolant and the water temperature of the external coolant.

[0082] Furthermore, the cladding body 111 is made of stainless steel to protect the internal structure. The outer cladding 33 is made of stainless steel as the second boundary to seal the third filling layer 72 and serve as the second layer boundary for protecting the internal structure of the protection tube 1. The third filling layer 72 between the outer sleeve 71 and the cladding body 111 is formed by filling graphite. The third filling layer 72 further insulates and keeps warm, avoiding the influence of contact thermal resistance on the accuracy of establishing the overall temperature field of the test device.

[0083] As Figure 8 shown, in a feasible implementation, the high-temperature irradiation test device for fuel short rods in the reactor further includes: an open ring plug 8 and a closed ring plug 9; the open ring plug 8 includes a filling port, the open ring plug 8 is arranged along the circumferential direction of the cladding body 111 at the first end of the outer sleeve 71, and the closed ring plug 9 is hermetically connected to the cladding body 111 and the outer sleeve 71; the closed ring plug 9 is arranged along the circumferential direction of the cladding body 111 at the second end of the outer sleeve 71, and the closed ring plug 9 is hermetically connected to the cladding body 111 and the outer sleeve 71.

[0084] In this technical solution, the closed ring plug 9, the open ring plug 8, the cladding body 111 and the outer sleeve 71 enclose a cavity with an annular cross-section. Fill materials are injected into the cavity through the opening on the open ring plug 8, and then the opening of the open ring plug 8 is sealed to form the third filling layer 72 between the cladding body 111 and the outer sleeve 71, which blocks the cladding body 111 and the outer sleeve 71, and is beneficial to increasing the temperature gradient difference between the internal cavity coolant and the external coolant.

[0085] As a preferred solution, the graphite is selected as flexible graphite. After the flexible graphite is injected into the annular cavity as the material of the third filling layer 72, the gaps between it and the cladding body 111 and the outer sleeve 71 are eliminated by mechanical extrusion, and close contact is maintained.

[0086] As Figure 9 shown, according to the second aspect of the present application, a manufacturing method of a high-temperature irradiation test device for fuel short rods in the reactor is proposed, which is used to manufacture the high-temperature irradiation test device for fuel short rods in the reactor according to any one of the above technical solutions. The manufacturing method includes:

[0087] According to the fuel phase volume and U 235 enrichment, the core loading design is carried out to control the neutron flux level and linear power density of the fuel short rod 20;

[0088] According to the core loading design value, the accurate fuel heat release rate and linear power are calculated, the size of the fuel short rod 20 is designed, and the size of the first thermal resistance layer 3 is designed;

[0089] Use an electric heating tube with the same linear power density to replace the fuel short rod 20 for testing, and measure the temperature gradients inside and outside the first thermal resistance layer 3 at the designed linear power;

[0090] Remove the electric heating tube, install the fuel short rod 20, and encapsulate the irradiation device.

[0091] Through the manufacturing method of the in-pile high-temperature irradiation test device for fuel short rods provided by the embodiments of the present application, first, carry out core loading design according to the fuel phase volume and U 235 enrichment, control the neutron flux level of the fuel short rod 20, so that the linear power density of the fuel short rod 20 is not less than 15 kW / m; then calculate the accurate fuel heat release rate and linear power according to the core loading result, and carry out the design of an in-pile high-temperature irradiation test device for fuel short rods, and design the inner diameter and outer diameter of the first thermal resistance layer 3; for the design scheme, select an electric heating tube with the same power density as the substitute for the fuel short rod 20, implant a temperature sensor, and measure whether the temperature gradient on the inner and outer sides of the ceramic layer under the designed linear power is consistent with the design value; remove the temperature sensor and the electric heating tube, install the fuel short rod 20 to encapsulate the test piece, and then the in-pile high-temperature irradiation test of the fuel short rod 20 can be carried out.

[0092] In a feasible implementation manner, design the inner diameter and outer diameter of the heat insulation layer 31 according to the axial position of the fuel short rod 20 in the inner coolant cavity.

[0093] In this technical solution, design the inner diameter and outer diameter of the heat insulation layer 31 in sections according to the upper test piece assembly 2, the middle test piece assembly 2, and the lower test position, so as to reduce the temperature difference caused by the axial power unevenness.

[0094] It can be understood that the manufacturing method of the in-pile high-temperature irradiation test device for fuel short rods provided by the embodiments of the present application is applied to the in-pile high-temperature irradiation test device of the fuel short rod in any of the above technical solutions, so the manufacturing method of the in-pile high-temperature irradiation test device for fuel short rods has all the beneficial effects of the in-pile high-temperature irradiation test device of the fuel short rod in the above technical solutions.

[0095] Example:

[0096] Design the test device according to the manufacturing method, such as Figure 10As shown in the figure, there are 4 test piece assemblies arranged in the accommodation cavity of the protection tube, and each test piece assembly includes 3 fuel short rods. The total length L2 of the fuel short rod is 160 mm, the radius r1 of the fuel pellet is 2.425 mm, helium is filled between the fuel pellet and the short rod cladding, and the inner diameter r2 of the short rod cladding is 3 mm; a ceramic thermal insulation layer is arranged outside the short rod cladding, the inner diameter r3 of the ceramic thermal insulation layer is 3.015 mm, the outer diameter r4 is 4.515 mm, and helium is filled between the ceramic thermal insulation layer and the short rod cladding; a stainless steel outer cladding is arranged outside the ceramic thermal insulation layer, the inner diameter r5 of the stainless steel outer cladding is 4.53 mm, and the outer diameter r6 is 5.53 mm. 5 detection points are arranged at the same axial position every L1 = 35 mm on the fuel short rod to respectively detect the inner wall temperature of the short rod cladding, the inner and outer wall temperatures of the ceramic thermal insulation layer, and the inner and outer wall temperatures of the stainless steel outer cladding. It is measured that the inner wall temperature of the short rod cladding provided with the first thermal resistance layer is about 73% higher than the average inner wall temperature of the short rod cladding provided with the first thermal resistance layer, and the average temperature of the outer coolant is reduced by about 60%. The upper limit of the in-pile irradiation test temperature of the fuel short rod is increased, and the high-temperature irradiation test of the fuel short rod can be successfully carried out in a low-temperature coolant.

[0097] It is easy for those skilled in the art to understand that, on the premise of no conflict, the above-mentioned advantageous ways can be freely combined and superimposed.

[0098] The above are only the preferred embodiments of the present application, and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above is only the preferred implementation manner of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present application, several improvements and modifications can still be made, and these improvements and modifications should also be regarded as the protection scope of the present application.

Claims

1. A high-temperature irradiation test device for fuel short rods in a reactor, characterized in that, The in-pile high-temperature irradiation test device for fuel short rods includes: A protection tube, and the protection tube includes a heat-insulating cladding; A test piece assembly, and the test piece assembly is arranged in the accommodation cavity surrounded by the heat-insulating cladding. The test piece assembly includes a plurality of fuel short rods, and the fuel short rods are arranged parallel to the axis of the heat-insulating cladding; A first thermal resistance layer, and the first thermal resistance layer is arranged along the circumferential direction of the fuel short rod, and the first thermal resistance layer is located between the fuel short rod and the heat-insulating cladding; The first thermal resistance layer includes: A heat-insulating layer, and the heat-insulating layer is arranged along the circumferential direction of the fuel short rod on the outer side of the fuel short rod. The heat-insulating layer is hermetically connected to the fuel short rod, and there is a first gap between the inner side wall of the heat-insulating layer and the outer side wall of the fuel short rod; A first filling layer, and the first filling layer is arranged in the first gap, and the first filling layer is in contact with the heat-insulating layer and the fuel short rod; An outer cladding, and the outer cladding is arranged along the circumferential direction of the fuel short rod on the outer side of the heat-insulating layer. The outer cladding is hermetically connected to the heat-insulating layer, and there is a second gap between the inner side wall of the outer cladding and the outer side wall of the heat-insulating layer; A second filling layer, and the second filling layer is arranged in the second gap, and the second filling layer is in contact with the outer cladding and the heat-insulating layer; The fuel short rod includes a fuel core body, a short rod cladding, an elastic member, a mounting seat, a first sealing plug and a second sealing plug. A heat dissipation cavity is provided on the fuel core body. The short rod cladding is wound around the outer side of the fuel core body. The first sealing plug and the second sealing plug seal the fuel core body in the short rod cladding at both ends of the short rod cladding. The fuel core body is supported by the elastic member to provide an expandable space for the fuel core body.

2. The high-temperature in-pile irradiation test device for fuel short rods according to claim 1, wherein The in-pile high-temperature irradiation test device for fuel short rods further includes: A first installation groove, and the first installation groove is uniformly arranged along the circumferential direction of the heat-insulating layer on the inner side wall of the heat-insulating layer, and the first installation groove is used for installing a temperature monitoring device; A second installation groove, and the second installation groove is uniformly arranged along the circumferential direction of the heat-insulating layer on the outer side wall of the heat-insulating layer, and the second installation groove is used for installing a temperature monitoring device. The second installation groove is arranged staggeredly with the first installation groove.

3. The in-pile high-temperature irradiation test device for fuel short rods according to claim 1, wherein The protection tube further includes an upper joint and a lower joint. The upper joint is arranged at the first end of the heat-insulating cladding, and the lower joint is arranged at the second end of the heat-insulating cladding; At least two test piece assemblies are arranged in the accommodation cavity, and the test piece assemblies are arranged along the axial direction of the protection tube; the thickness of the first filling layer of the fuel short rods in the upper test piece assembly is greater than the thickness of the first filling layer of the fuel short rods in the middle test piece assembly; the thickness of the first filling layer of the fuel short rods in the upper test piece assembly is greater than the thickness of the first filling layer of the fuel short rods in the lower test piece assembly.

4. The in-pile high-temperature irradiation test device for fuel short rods according to claim 1, wherein A plurality of the test piece assemblies are arranged at equal intervals along the axial direction of the protection tube in the accommodation cavity; The fuel pins are uniformly arranged in the circumferential direction of the protection tube within the accommodation cavity.

5. The high-temperature in-pile irradiation test device for fuel pins according to claim 1, wherein the heat-insulating cladding includes a cladding body; a second thermal resistance layer, which is arranged on the outer side of the cladding body along the circumferential direction of the cladding body.

6. The high-temperature in-pile irradiation test device for fuel pins according to claim 5, wherein the second thermal resistance layer includes: an outer sleeve tube, which is arranged on the outer side of the cladding body along the circumferential direction of the cladding body, the outer sleeve tube is hermetically connected to the cladding body, and there is a third gap between the inner side wall of the outer sleeve tube and the outer side wall of the cladding body; a third filling layer, which is arranged in the third gap, and the third filling layer is in contact with the outer sleeve tube and the cladding body.

7. The high-temperature in-pile irradiation test device for fuel pins according to claim 6, wherein the high-temperature in-pile irradiation test device for fuel pins further includes: an open ring plug, the open ring plug includes a filling port, the open ring plug is arranged on the first end of the outer sleeve tube along the circumferential direction of the cladding body, and the open ring plug is hermetically connected to the cladding body and the outer sleeve tube; a closed ring plug, the closed ring plug is arranged on the second end of the outer sleeve tube along the circumferential direction of the cladding body, and the closed ring plug is hermetically connected to the cladding body and the outer sleeve tube.

8. A manufacturing method of a high-temperature in-pile irradiation test device for fuel rods, characterized in that, For manufacturing the high-temperature in-pile irradiation test device for fuel pins according to any one of claims 1 to 7, the manufacturing method includes: Based on the fuel phase volume and U 235 enrichment, the core loading design is carried out to control the neutron flux level and linear power density of the fuel short rods; According to the core loading design value, calculate the accurate fuel heat release rate and linear power, design the size of the fuel pins, and design the size of the first thermal resistance layer; Use an electric heating tube with the same linear power density to replace the fuel pins for testing, and measure the temperature gradients inside and outside the first thermal resistance layer under the designed linear power; Remove the electric heating tube, install the fuel pins, and encapsulate the irradiation device.

9. The manufacturing method of the high-temperature in-pile irradiation test device for fuel pins according to claim 8, wherein Design the inner diameter and outer diameter of the heat-insulating layer according to the axial position of the fuel pins in the inner coolant cavity.

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