Test device for simulating thermal hydraulic characteristics of fuel elements of gas cooled microreactor

Abstract

The application discloses a test device for simulating thermal hydraulic characteristics of a gas-cooled micro reactor fuel element, comprising a pressure vessel shell, a hanging basket unit arranged in the pressure vessel shell, and a cavity formed between the hanging basket unit and the pressure vessel shell. The pressure vessel shell comprises a pressure vessel shell body, a first inlet, a second inlet, and a first outlet. The first inlet is connected with a coolant channel, and test gas is introduced into the coolant channel through the first inlet. The second inlet is communicated with the cavity, and protective gas is introduced into the cavity through the second inlet. The hanging basket unit comprises a hanging basket shell, a graphite assembly, a coolant channel, a heating rod assembly, a heating rod channel, a heat preservation layer assembly, and a measurement unit. The device can carry out thermal hydraulic performance tests of prismatic gas-cooled micro reactor fuel elements, can focus on studying and verifying the heat exchange capacity of the reactor core under the design condition, and can provide pressure, flow, temperature and other thermal parameters for the iterative design of the reactor, so as to ensure that the safety requirements of the reactor under various conditions are met.

Description

Technical Field

[0001] This invention belongs to the field of core cooling technology for high-temperature gas-cooled reactor pressure vessels, specifically relating to a test device for simulating the thermal-hydraulic characteristics of fuel elements in gas-cooled microreactors. Background Technology

[0002] High-temperature gas-cooled reactors (HTGRs) are an advanced reactor type with inherent safety and broad application prospects. Miniature HTGRs are small in size and light in weight, making them more flexible to transport and applicable to a wider range of scenarios, meeting the energy needs of vehicle-mounted transport under long-distance and extreme weather conditions.

[0003] The novel prismatic gas-cooled microreactor employs TRISO-coated particulate fuel dispersed within a silicon carbide matrix to form dense fuel rods, which are then inserted into the fuel channels of graphite fuel blocks to create prismatic graphite fuel elements. As a novel gas-cooled microreactor technology, experimental research is needed to validate the core's thermal-hydraulic design to meet nuclear safety regulatory requirements. The overall objective of the experiments is to verify the core's heat transfer capacity under design conditions, providing thermal parameters such as pressure, flow rate, and temperature for iterative reactor design, ensuring that reactor safety requirements are met under various operating conditions.

[0004] To verify the thermal-hydraulic design scheme of the novel gas-cooled microreactor core, it is necessary to conduct experimental research on the thermal-hydraulic characteristics of the gas-cooled microreactor core under normal operating conditions and accident conditions. However, there is no existing large-scale comprehensive test facility suitable for conducting thermal characteristic research on prismatic reactor cores. Therefore, it is necessary to design a test facility with advanced concepts, reasonable structure, low cost, and the ability to achieve similar physical phenomena. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a test device for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements. This device is capable of conducting experimental research on the thermal-hydraulic characteristics of helium cooling performance of prismatic gas-cooled microreactor fuel elements.

[0006] The technical solution adopted to solve the technical problem of the present invention is to provide a test device for simulating the thermal-hydraulic characteristics of fuel elements of a gas-cooled microreactor, including a pressure vessel shell and a basket unit disposed within the pressure vessel shell, with a cavity formed between the basket unit and the pressure vessel shell. The basket unit includes a basket shell, a graphite assembly disposed within the basket shell, a coolant channel, a heating rod channel, a heating rod assembly, an insulation layer assembly, and a measuring unit. The coolant channel and the heating rod channel are respectively disposed on the graphite assembly, and the insulation layer assembly is disposed around the graphite assembly. The heating rod channel is used to hold the heating rod assembly, and the coolant channel is used to pass test gas. The measuring unit is used to measure thermal parameters such as pressure and temperature at the measuring points on the graphite assembly. The pressure vessel shell includes a pressure vessel shell body, a first inlet, a second inlet, and a first outlet disposed on the pressure vessel shell body. The first inlet is connected to the coolant channel, and test gas is introduced into the coolant channel through the first inlet. The second inlet is connected to the cavity, and protective gas is introduced into the cavity through the second inlet. The first outlet is used to discharge the mixed gas inside the pressure vessel shell.

[0007] Preferably, the cavity is an annular cavity.

[0008] Preferably, the graphite assembly is provided with at least one measuring point of a measuring unit, and a first wire groove is provided at a first radial position of the graphite assembly where the measuring point is located. The first wire groove is used to lead the lead wire of the measuring unit out of the graphite assembly from the measuring point. A second wire groove is provided at the second radial position of the insulation layer component, and the second wire groove is connected to the first wire groove. A third wire groove is provided on the axial outer surface of the insulation layer component, and the third wire groove is connected to the second wire groove. The lead wire of the measuring unit is led out of the basket unit through the first wire groove, the second wire groove, and the third wire groove.

[0009] Preferably, the graphite assembly includes at least one graphite block, and the measuring point of the measuring unit is a temperature measuring point. When the temperature measuring point is on the axial end face of the graphite block, the orthographic projection view of the first wire groove on the axial bottom surface of the graphite block is a broken line shape or a straight line shape; when the temperature measuring point is at other positions on the graphite block, the orthographic projection view of the first wire groove on the axial bottom surface of the graphite block is a straight line shape.

[0010] Preferably, temperature measuring points are set at both ends and in the middle of the graphite block along the axial direction of the graphite block.

[0011] Preferably, there are at least two temperature measurement points on the axial end face of the graphite block, distributed around the heating rod channel and the coolant channel.

[0012] Preferably, the graphite assembly includes at least one graphite block, the measuring point of the measuring unit is a pressure measuring point, the pressure measuring point is on the axial end face of the graphite block, and the first wire groove is a straight line in the orthographic projection view of the axial bottom surface of the graphite block.

[0013] Preferably, the second wire groove is a straight line in the orthographic projection view of the axial bottom surface of the insulation layer assembly.

[0014] Preferably, the pressure vessel shell further includes a second outlet disposed on the pressure vessel shell body. The second outlet is closer to the first end of the pressure vessel shell body relative to the second end of the pressure vessel shell body. The first radial end of the graphite assembly is close to the first end of the pressure vessel shell body, and the second radial end of the graphite assembly is close to the second end of the pressure vessel shell body. The first outlet is close to the second end of the pressure vessel shell body relative to the first end of the pressure vessel shell body.

[0015] The lead wire of the measuring unit corresponding to the measuring point on the graphite assembly near the first end of the pressure vessel shell body is guided to the radial direction of the first end of the graphite assembly through the third wire groove, and then enters the second outlet through the gap, which is the gap between the basket and the pressure vessel shell. The lead wire of the measuring unit corresponding to the measuring point on the graphite assembly near the second end of the pressure vessel shell body is guided to the radial direction of the second end of the graphite assembly through the third wire groove, and then enters the second outlet through the cavity.

[0016] Preferably, the test device for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements further includes a three-way sealing assembly disposed on the pressure vessel shell. The three-way sealing assembly includes a three-way cylinder, a three-way inlet disposed on the three-way cylinder, a three-way sealing cover, and a three-way outlet. The lead wire of the measuring unit enters the three-way cylinder through the three-way inlet and exits through the three-way outlet. The three-way sealing cover is used to open the three-way cylinder for wiring connection and inspection.

[0017] Preferably, the three-way outlet includes a first three-way outlet and a second three-way outlet, and the leads of the measuring unit include a first lead for measuring temperature and a second lead for measuring pressure. The first lead is led out from the first three-way outlet, and the second lead is led out from the second three-way outlet.

[0018] Preferably, the test apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements further includes: a heating rod flange cover, a sleeve, and a seal. The heating rod flange cover, sleeve, and seal are all located outside the pressure vessel shell. The heating rod assembly includes at least one heating rod, which includes a heating section and a non-heating section connected in sequence. The heating section is placed in a heating rod channel and penetrates the pressure vessel shell. The non-heating section passes through the pressure vessel shell and is located outside the pressure vessel shell for connection with a power regulating device. The heating rod flange cover has a countersunk hole, and the sleeve is disposed within the countersunk hole and fitted around the non-heating section of the heating rod. The countersunk hole has a first internal thread, and the sleeve has a first external thread. The sleeve has a second internal thread, and the non-heating section of the heating rod has a second external thread. The heating rod flange cover is connected to the sleeve via the countersunk hole by threads, and the sleeve is connected to the heating rod by threads. The seal is located within the countersunk hole and between the heating rod and the countersunk hole. One side of the seal contacts the countersunk hole surface, and the other side contacts the sleeve.

[0019] Preferably, the test device for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements further includes: a front-end electrical protection cover, a protection cover flange, and a support. The front-end electrical protection cover is connected to the pressure vessel shell through the protection cover flange. The front-end electrical protection cover covers the heating rod flange cover, sleeve, and seal. The front-end electrical protection cover has a semi-groove-shaped hole for the heating rod's wiring to be led out. The support is set on the front-end electrical protection cover and is used to support the sensor connected to the heating rod.

[0020] Preferably, the measuring unit includes a temperature measuring unit and a pressure measuring unit. The temperature measuring unit is used to measure the temperature of the graphite assembly, and the pressure measuring unit is used to measure the pressure and pressure loss of the test gas in the coolant channel.

[0021] Preferably, the test device for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements further includes: a guide plate disposed in the cavity, the guide plate being used to guide and increase the flow of protective gas in the cavity.

[0022] Preferably, the guide plate is spiral-shaped, which allows the protective gas to flow forward in a spiral shape, reducing the distance between the basket and the pressure vessel shell, thereby reducing the cross-sectional area in the spiral channel, and thus increasing the cross-sectional velocity of the protective gas compared to when it enters the cylinder.

[0023] Preferably, the coolant passing through the coolant channel is test gas, and the test device further includes: a flow equalization orifice plate assembly disposed in the pressure vessel shell, the flow equalization orifice plate assembly being disposed in the gap between the graphite assembly and the first outlet, the flow equalization orifice plate assembly being used to uniformly mix the test gas of the graphite assembly and the protective gas in the cavity before flowing out from the first outlet.

[0024] Preferably, the pressure vessel shell includes a cylindrical body, a front end cap, a rear end cap, and a saddle. The saddle is located at the bottom of the cylindrical body. The cylindrical body includes a front cylindrical body, a middle cylindrical body, and a rear cylindrical body connected in sequence. The front cylindrical body is connected to the front end cap, and the rear cylindrical body is connected to the rear end cap.

[0025] This invention relates to an experimental apparatus for simulating the thermal-hydraulic characteristics of fuel elements in a gas-cooled microreactor. After being connected to a large helium loop system, it can conduct comprehensive thermal tests. By adjusting the electrical power of the heating rod assembly, it simulates the heating of fuel rods within the core of a high-temperature gas-cooled reactor. According to set operating parameters, test gas enters the apparatus through the first inlet, passes through the coolant channels of the graphite assembly, thereby carrying away the heat generated by the heating rod assembly. Simultaneously, the temperature of the test gas increases at the coolant channel outlet, accompanied by a flow resistance pressure drop. At the same time, protective gas enters the apparatus through the second inlet, flows along the outside of the basket, and effectively and uniformly mixes with the test gas at the flow equalization orifice plate assembly before flowing out of the apparatus through the first outlet. By measuring the temperature of the graphite assembly and the pressure of the coolant channels throughout the process, the flow heat transfer characteristics of helium in a prismatic gas-cooled microreactor and important thermal-hydraulic physical phenomena are mainly studied. This apparatus can focus on studying the heat transfer characteristics of fuel elements under various influencing factors and verify the heat transfer capacity of the reactor core under design conditions. It provides thermal parameters such as pressure, flow rate, and temperature for reactor iterative design, ensuring that reactor safety requirements are met under various operating conditions. Compared with the prior art, the present invention has the following advantages: 1. This invention enables thermal-hydraulic experimental research on the helium cooling performance of prism-type gas-cooled microreactor fuel elements. By arranging various types of wire grooves inside the graphite assembly, temperature and pressure measurements are achieved in different regions within the experimental device. The device features a dense distribution of measuring points along the axial and radial directions of the graphite assembly, facilitating the acquisition of temperature and pressure data during the experiment. This allows the device to focus on examining data differences and changes at various key measuring points within the reactor core, thereby enabling more targeted experimental research and design verification of various factors affecting heat transfer within the reactor core. 2. The experimental device of this invention has a simple overall structure, a small experimental scale, and features high similarity of physical phenomena, high flexibility, and convenient maintenance. Specifically, the heating rod achieves a quick seal between the heating rod and the pressure vessel shell through a sleeve or other device, allowing for rapid replacement in case of heating rod failure. This ensures continuous, safe, and reliable testing under high-temperature conditions, accelerates the testing process, and reduces overall testing costs. 3. From the perspective of equipment and system safety, this invention divides the circulating working medium into test gas entering the first inlet and protective gas entering the second inlet. Under the action of the flow equalization orifice plate assembly, the test gas and protective gas are fully and uniformly mixed before flowing out from the first outlet. This avoids the unevenly mixed high-temperature coolant directly eroding the pressure vessel shell and pipelines, ensuring the safety and reliability of experimental research under high-temperature conditions. Attached Figure Description

[0026] Figure 1 This is a front sectional view of the test apparatus used to simulate the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements in Embodiment 2 of the present invention.

[0027] Figure 2 This is a schematic diagram of the temperature measurement circuit of the test device used to simulate the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements in Embodiment 2 of the present invention.

[0028] Figure 3 This is a partial quarter-section isometric view of the tee sealing assembly.

[0029] Figure 4 This is a quarter-section isometric view of a graphite assembly.

[0030] Figure 5 Partial quarter section axonometric drawing of the insulation layer component

[0031] Figure 6 A quarter-section axonometric drawing of the graphite block and the insulation layer block.

[0032] Figure 7 This is a schematic diagram of the pressure measurement surfaces at the beginning and end of the suspended platform unit.

[0033] Figure 8 This is a schematic diagram of the temperature measurement surface on the end face of a graphite block.

[0034] Figure 9 This is a schematic diagram of the internal measurement surface of a graphite block.

[0035] Figure 10 This is a front view of the heating rod flange cover.

[0036] Figure 11 This is a cross-sectional view of the heating rod flange cover.

[0037] Figure 12 This is a partial sectional view of the assembly of the heating rod flange cover and the heating rod.

[0038] Figure 13 The left view of an experimental apparatus for simulating the helium cooling performance of fuel elements in a prism-shaped gas-cooled microreactor, according to the present invention.

[0039] In the diagram: 1-Front cylinder, 2-Middle cylinder, 3-Rear cylinder, 4-Front end cap, 5-Rear end cap, 6-Saddle, 7-Insulation layer assembly, 8-Graphite assembly, 9-Heating rod assembly, 10-Baffle plate, 11-Support, 12-Heating rod flange cover, 13-First inlet pipe, 14-Second inlet pipe, 15-Flow equalization orifice plate assembly, 16-Rear insulation layer, 17-Tee sealing assembly, 18-Sleeve, 19-Rubber gasket, 20-Front-end electrical protection cover, 2 1-Protective cover flange, 101-Front cylinder flange, 201-Middle cylinder flange, 301-Rear cylinder flange, 701-Insulation block, 702-Second wire guide groove, 703-Third wire guide groove, 801-Graphite block, 802-Coolant channel, 803-Heating rod channel, 804-Thermocouple sensor, 805-First wire guide groove, 171-T-way cylinder, 172-T-way sealing cover, 173-T-way line outlet interface, 174-Pressure outlet pipe. Detailed Implementation

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] The embodiments of this patent are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this patent, and should not be construed as limiting this patent.

[0042] In the description of this patent, it should be understood that the terms “center,” “upper,” “lower,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this patent and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this patent.

[0043] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.

[0044] Example 1

[0045] This embodiment provides a test device for simulating the thermal-hydraulic characteristics of fuel elements in a gas-cooled microreactor. It includes a pressure vessel shell and a basket unit disposed within the pressure vessel shell, forming a cavity between the basket unit and the pressure vessel shell. The basket unit includes a basket shell, a graphite assembly disposed within the basket shell, a coolant channel, a heating rod channel, a heating rod assembly, an insulation layer assembly, and a measuring unit. The coolant channel and heating rod channel are respectively disposed on the graphite assembly, and the insulation layer assembly is disposed around the graphite assembly. The heating rod channel is used to hold the heating rod assembly, and the coolant channel is used to pass test gas. The measuring unit is used to measure thermal parameters such as pressure and temperature at measurement points on the graphite assembly. The pressure vessel shell includes a pressure vessel shell body, a first inlet, a second inlet, and a first outlet disposed on the pressure vessel shell body. The first inlet is connected to the coolant channel, through which test gas is introduced. The second inlet is connected to the cavity, through which protective gas is introduced into the cavity. The first outlet is used to discharge the mixed gas inside the pressure vessel shell.

[0046] The experimental setup described in this embodiment, used to simulate the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements, allows for focused study of the heat transfer characteristics of fuel elements under various influencing factors and verification of the core's heat transfer capacity under design conditions. It provides thermal parameters such as pressure, flow rate, and temperature for iterative reactor design, ensuring compliance with reactor safety requirements under various operating conditions. This experimental setup features an advanced design concept, a rational overall structure, high similarity in physical phenomena, and a small experimental scale, offering advantages such as high flexibility, rapid testing progress, and low cost. Simultaneously, it provides crucial and reliable experimental data for safety evaluation and verification of safety analysis procedures for gas-cooled microreactor model design, thereby meeting nuclear safety regulatory requirements.

[0047] Example 2

[0048] like Figures 1-13As shown, this embodiment provides a test apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements. It includes a pressure vessel shell and a basket unit disposed within the pressure vessel shell, forming a cavity between the basket unit and the pressure vessel shell. The basket unit includes a basket shell, a graphite assembly 8 disposed within the basket shell, a coolant channel 802, a heating rod channel 803, a heating rod assembly 9, an insulation layer assembly 7, and a measuring unit. The coolant channel 802 and the heating rod channel 803 are respectively disposed on the graphite assembly 8, and the insulation layer assembly 7 is disposed around the graphite assembly 8. The rod channel 803 is used to hold the heating rod assembly 9, the coolant channel 802 is used to pass test gas, the measuring unit is used to measure the pressure, temperature and other thermal parameters on the graphite assembly 8, and the pressure vessel shell includes the pressure vessel shell body, a first inlet, a second inlet and a first outlet provided on the pressure vessel shell body. The first inlet is connected to the coolant channel 802 and test gas is introduced into the coolant channel 802 through the first inlet. The second inlet is connected to the cavity and protective gas is introduced into the cavity through the second inlet. The first outlet is used to discharge the mixed gas in the pressure vessel shell.

[0049] Specifically, in this embodiment, the heating rod assembly 9 is used to simulate a fuel element.

[0050] Preferably, the cavity is an annular cavity.

[0051] Preferably, the graphite assembly 8 is provided with at least one measuring point of the measuring unit, and a first wire groove 805 is provided at the first radial position of the graphite assembly 8 where the measuring point is located. The first wire groove 805 is used to lead the lead wire of the measuring unit out of the graphite assembly 8 from the measuring point. A second wire groove 702 is provided at the second radial position of the insulation layer component 7. The second wire groove 702 is connected to the first wire groove 805. A third wire groove 703 is provided on the axial outer surface of the insulation layer component 7. The third wire groove 703 is connected to the second wire groove 702. The lead wire of the measuring unit is led out of the basket unit through the first wire groove 805, the second wire groove 702, and the third wire groove 703.

[0052] Preferably, the graphite assembly 8 includes at least one graphite block 801, and the measuring point of the measuring unit is a temperature measuring point. When the temperature measuring point is on the axial end face of the graphite block 801, the orthographic projection view of the first wire groove 805 on the axial bottom surface of the graphite block 801 is a broken line shape or a straight line shape; when the temperature measuring point is at other positions of the graphite block 801, the orthographic projection view of the first wire groove 805 on the axial bottom surface of the graphite block 801 is a straight line shape.

[0053] Preferably, temperature measuring points are provided at both ends and in the middle of the graphite block 801 along the axial direction of the graphite block 801.

[0054] Preferably, there are at least two temperature measurement points on the axial end face of the graphite block 801, with the temperature measurement points distributed around the heating rod channel 803 and the coolant channel 802.

[0055] Preferably, the graphite assembly 8 includes at least one graphite block 801, the measuring point of the measuring unit is a pressure measuring point, the pressure measuring point is on the axial end face of the graphite block 801, and the first wire groove 805 is a straight line shape in the orthographic projection view of the axial bottom surface of the graphite block 801.

[0056] Preferably, the second wire groove 702 is a straight line shape in the orthographic projection view of the axial bottom surface of the insulation layer assembly 7.

[0057] Preferably, the pressure vessel shell further includes a second outlet disposed on the pressure vessel shell body. The second outlet is closer to the first end of the pressure vessel shell body relative to the second end of the pressure vessel shell body. The first radial end of the graphite assembly 8 is close to the first end of the pressure vessel shell body, and the second radial end of the graphite assembly 8 is close to the second end of the pressure vessel shell body. The first outlet is close to the second end of the pressure vessel shell body relative to the first end of the pressure vessel shell body.

[0058] The lead wire of the measuring unit corresponding to the measuring point on the graphite assembly 8 near the first end of the pressure vessel shell is guided to the graphite assembly 8 radially towards the first end through the third guide wire groove 703, and then enters the second outlet through the gap, which is the gap between the basket and the pressure vessel shell; specifically, the lead wire of the measuring unit here does not pass through the cavity, but is directly led out from the flange connected to the basket, enters the gap between the basket and the pressure vessel shell, and then enters the second outlet.

[0059] The lead wire of the measuring unit corresponding to the measuring point on the graphite assembly 8 near the second end of the pressure vessel shell body is guided to the radial direction of the second end of the graphite assembly 8 through the third wire groove 703, and then enters the second outlet through the cavity.

[0060] like Figure 1 , Figure 4 and Figure 5As shown, specifically, in this embodiment, the basket unit consists of, from the outside to the inside, a basket shell, an insulation layer assembly 7, a graphite assembly 8, and a heating rod assembly 9. The insulation layer assembly 7 is a thermally conductive insulating material, primarily used to provide an insulating boundary and prevent heat from the graphite assembly and test gas from being transferred to the protective gas via thermal conductivity, thus affecting the heat balance between the test gas and the graphite assembly 8 inside the basket. The graphite assembly 8 is used to simulate the fuel assemblies of an actual reactor. The heating rod channels are used to simulate the channels of actual fuel rods. The test device is equipped with a row of four layers of individual simulated fuel assemblies, each containing 18 electric heating rods as simulated heat sources. After connecting this test device to a large helium loop system, by setting the test operating parameters, comprehensive thermal-hydraulic tests can be conducted on localized areas at the core fuel assembly level under different temperatures, flow rates, and power conditions.

[0061] Preferably, the test device for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements further includes a three-way sealing assembly 17 disposed on the pressure vessel shell. The three-way sealing assembly 17 includes a three-way cylinder 171, a three-way inlet disposed on the three-way cylinder 171, a three-way sealing cover 172, and a three-way outlet. The lead wire of the measuring unit enters the three-way cylinder 171 through the three-way inlet and is then exited through the three-way outlet. The three-way sealing cover 172 is used to open the three-way cylinder 171 for wiring connection and inspection.

[0062] Preferably, the three-way outlet includes a first three-way outlet and a second three-way outlet, and the leads of the measuring unit include a first lead for measuring temperature and a second lead for measuring pressure. The first lead is led out from the first three-way outlet, and the second lead is led out from the second three-way outlet.

[0063] Preferably, the test apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements further includes: a heating rod flange cover 12, a sleeve 18, and a seal. The heating rod flange cover 12, sleeve 18, and seal are all located outside the pressure vessel shell. The heating rod assembly 9 includes at least one heating rod, which includes a heating section and a non-heating section connected in sequence. The heating section is placed within a heating rod channel, and the heating rod penetrates the pressure vessel shell. The non-heating section passes through the pressure vessel shell and is located outside the pressure vessel shell for connection to a power control device. The flange cover 12 of the heating rod is provided with a countersunk hole, and the sleeve 18 is provided in the countersunk hole. The sleeve 18 is sleeved on the outside of the non-heating section of the heating rod. The countersunk hole is provided with a first internal thread, the sleeve 18 is provided with a first external thread, the sleeve 18 is provided with a second internal thread, and the heating rod is provided with a second external thread. The flange cover 12 of the heating rod is connected to the sleeve 18 through the countersunk hole by threads, and the sleeve 18 is connected to the heating rod by threads. The sealing element is located in the countersunk hole, between the heating rod and the countersunk hole. One side of the sealing element is in contact with the surface of the countersunk hole, and the other side of the sealing element is in contact with the sleeve 18.

[0064] Preferably, the experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements further includes: The front-end electrical protective cover 20, the protective cover flange 21, and the support 11 are provided. The front-end electrical protective cover 20 is connected to the pressure vessel shell through the protective cover flange 21. The front-end electrical protective cover 20 covers the heating rod flange cover 12, the sleeve 18, and the seal. The front-end electrical protective cover 20 has a semi-groove hole for the heating rod's wiring to be led out. The support 11 is provided on the front-end electrical protective cover 20 and is used to support the sensor connected to the heating rod.

[0065] Preferably, the measuring unit includes a temperature measuring unit and a pressure measuring unit. The temperature measuring unit is used to measure the temperature of the graphite assembly 8, and the pressure measuring unit is used to measure the pressure and pressure loss of the test gas in the coolant channel 802.

[0066] Preferably, the test apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements further includes: a guide plate 10 disposed within the cavity, the guide plate 10 being used to guide and increase the flow of protective gas within the cavity. The guide plate 10 is fixedly connected to the outside of the basket shell.

[0067] Preferably, the guide plate 10 is spiral-shaped, which can make the protective gas flow forward in a spiral shape, reduce the distance between the basket and the pressure vessel shell, thereby reducing the cross-sectional area in the spiral channel, and thus increasing the cross-sectional velocity of the protective gas compared to when it enters the cylinder.

[0068] Preferably, the coolant passing through the coolant channel 802 is test gas, and the test device further includes: a flow equalization orifice plate assembly 15 disposed in the pressure vessel shell, the flow equalization orifice plate assembly 15 being disposed in the gap between the graphite assembly 8 and the first outlet, the flow equalization orifice plate assembly 15 being used to uniformly mix the test gas of the graphite assembly 8 and the protective gas in the cavity before flowing out through the first outlet.

[0069] Preferably, the pressure vessel shell includes a cylinder, a front end cap 4, a rear end cap 5, and a saddle 6. The saddle 6 is located at the bottom of the cylinder. The cylinder includes a front cylinder 1, a middle cylinder 2, and a rear cylinder 3 connected in sequence. The front cylinder 1 is connected to the front end cap 4, and the rear cylinder 3 is connected to the rear end cap 5.

[0070] Specifically, in this embodiment, the front cylinder 1 is connected to the middle cylinder flange 201 welded to the left side of the middle cylinder 2 via the front cylinder flange 101, and the rear cylinder 3 is connected to the middle cylinder flange 201 welded to the right side of the middle cylinder 2 via the rear cylinder flange 301.

[0071] The left side of the cylinder is connected to the front end cap 4, and the right side of the cylinder is connected to the rear end cap 5; two saddles 6 are symmetrically welded to the bottom of the cylinder.

[0072] Specifically, in this embodiment, the inner side of the basket shell is connected to the insulation layer assembly 7, the inner side of the insulation layer assembly 7 is connected to the graphite assembly 8, the heating rod assembly 9 simulating the fuel element passes through the graphite assembly 8, the guide plate 10 has a spiral structure, the outer side of the guide plate 10 is connected to the cylinder, and the inner side of the guide plate 10 is connected to the basket shell. The guide plate 10 is distributed throughout the inner side of the cylinder.

[0073] Specifically, in this embodiment, the insulation layer component 7 is composed of several insulation blocks 701 stacked together. The insulation layer component 7 has a hollowed-out hexagonal center and is assembled with the hexagonal prism graphite component 8. Furthermore, the radial and axial surfaces of the insulation layer component 7 are engraved with wire grooves through which leads can pass, for the arrangement of lead wires for the temperature measurement points and differential pressure measurement points of the graphite component 8.

[0074] Specifically, in this embodiment, the graphite assembly 8 is composed of several layers of prism graphite blocks 801 stacked together. The graphite block 801 has a regular hexagonal cross-section and contains several evenly distributed coolant channels 802 and heating rod channels 803. The heating rod channels 803 are arranged in two hexagonal rings, totaling 18. The coolant channels 802 are arranged in a regular hexagonal shape with the heating rod channels 803 as the axis. Adjacent heating rod channels 803 will share the coolant channels 802. There are a total of 48 coolant channels 802.

[0075] Specifically, in this embodiment, the heating section of the heating rod assembly 9 is in contact with the heating rod channel 803 inside the graphite assembly 8, and the non-heating section of the heating rod assembly 9 passes through the front insulation layer and the heating rod flange cover 12 and is connected to the power supply wire.

[0076] Specifically, in this embodiment, the first inlet is provided with a first inlet pipe 13, which extends through the front cylinder 1, passes through the basket connecting pipe, connects to the annular cavity, and flows into the coolant channel 802 of the graphite component 8 inside the insulation layer component 7, and then sprays out from the center of the rear insulation layer 16; the second inlet is provided with a second inlet pipe 14, which extends through the front cylinder 1, passes through the annular cavity inside the cylinder, and accelerates by bypassing the guide plate 10, and then mixes with the test gas flowing out from the coolant channel 802 sprayed from the rear insulation layer 16 through the flow equalization orifice plate component 15, and the mixed gas is sprayed out from the pipe connected to the first outlet on the rear end cap 5.

[0077] Specifically, in this embodiment, the temperature measurement unit is a thermocouple sensor 804. The thermocouple sensor 804 has a measuring surface at the center and both ends of each graphite block 801 in the graphite assembly 8, and there are a total of several measuring surfaces. Several measuring points are evenly distributed around the heating rod channel 803 and the coolant channel 802 on each measuring surface of the graphite assembly 8 and inside the graphite. The wires of the thermocouple sensor 804 start from the measuring points and pass radially through the graphite assembly 8 and the insulation layer assembly 7. The wire grooves on the front and rear end faces of the graphite block 801 have zigzag grooves with a semi-circular cross-section. The wire grooves on the measuring surface in the middle of the graphite block 801 only have straight grooves with a circular cross-section. The insulation block 701 has radial wire grooves and axial wire grooves.

[0078] Figure 2 Specifically, in this embodiment, the pressure vessel shell is connected to the three-way sealing assembly 17 via a sealing assembly interface. The leads (measuring wires) of the measuring unit inside the pressure vessel shell are all led out through the three-way sealing assembly 17 connected to the sealing assembly interface. The sealing assembly interface is connected to the front cylinder 1, and the three-way sealing assembly 17 is horizontally connected to the sealing assembly interface. The three-way sealing assembly 17 includes a three-way cylinder 171, a three-way sealing cover 172, and a three-way line outlet interface 173. The three-way line outlet interface 173 is connected to the first three-way outlet. The lead of the thermocouple sensor 804 is the first lead. The three-way cylinder 171 is connected to the three-way sealing cover 172 and the three-way line outlet interface 173 on both the front and rear sides. The lead of the thermocouple sensor 804 within the measuring surface of the front half of the graphite assembly 8 is insulated. The lead wires of the thermocouple sensor 804 in the measuring surface of the rear half of the graphite component 8 are led out from the rear end through the insulation layer component 7, and then introduced into the front end through the conduit in the cavity. All thermocouple lines converge into the three-way sealing component 17 and then exit through the three-way line outlet interface 173, and finally exit through the aviation plug-in. One end of the aviation plug-in is connected to the flange of the three-way sealing component 17, and the other end of the aviation plug-in is connected to the end of the thermocouple line. In case of line failure, the front and rear three-way sealing covers 172 can be opened for line inspection.

[0079] Figure 3 Specifically, in this embodiment, the pressure measuring unit is a pressure tapping tube, and the lead wire of the pressure tapping tube is the second lead wire. The front pressure tapping tube is led out radially from the front end of the graphite assembly 8, and the rear pressure tapping tube is led out radially from the rear end of the graphite assembly 8 and enters the front end through the pipe. The pressure tapping tube enters the three-way sealing assembly 17 through the front cylinder 1 and then exits from the pressure outlet pipe 174 to connect to the pressure measuring instrument. The pressure outlet pipe 174 is connected to the second three-way outlet.

[0080] like Figure 9 and Figure 10As shown, specifically, in this embodiment, the heating rod flange cover 12 has countersunk holes with a first internal thread inside; the sleeve 18 has a first external thread and several grooves at one end; the sleeve 18 is externally connected to the heating rod flange cover 12 via threads; the heating rod is internally connected to the sleeve 18 via threads, and the sealing element is a rubber gasket 19. One side of the rubber gasket 19 contacts the countersunk hole surface of the heating rod flange cover 12; the other side of the rubber gasket 19 contacts the sleeve 18. The sealing between the heating rod and the heating rod flange cover 12 can be achieved through the threaded connection and the rubber gasket 19; the sleeve 18 has a groove at one end to accommodate a corresponding installation tool for threaded assembly of the sleeve 18.

[0081] Specifically, in this embodiment, the front electrical protective cover 20 is connected to the protective cover flange 21, and the protective cover flange 21 is welded to the front end cap; a semi-groove hole is opened on one side of the front electrical protective cover 20 to facilitate the lead-out of the heating rod circuit; several thermocouple sensor supports 11 are connected around the front electrical protective cover 20.

[0082] like Figure 1 and Figure 2 As shown, the front end of the cylinder is provided with a first inlet. After the test device is connected to a large helium circuit system, the test gas flows in from the first inlet of the test device and enters the first inlet pipe 13. After being installed at the determined positions at the head of the cylinder and the basket unit, it is fixed to the front end of the cylinder and the basket respectively by welding. The bottom of the first inlet pipe 13 is connected to an axially arranged cavity by welding. Its function is to prevent the test gas from contacting the heat insulation layer in the basket unit and contaminating the test gas. The test gas is a high-purity gas coolant, and the gas coolant is helium. The top of the pressure vessel shell has a through hole for the non-working section of the heating rod to pass through. A second inlet pipe 14 is provided on the left side of the first inlet pipe 13 of the fuel element. Cold helium gas flowing from the large helium circuit system flows into the second inlet pipe 14 of this test device and then enters the cavity formed between the pressure vessel and the basket shell. This cavity is an annular cavity. The high-pressure cold helium gas entering the cavity is the protective gas. After passing through the spiral guide plate 10 set on the outer side of the middle of the basket shell, the flow rate is increased. Under the premise of achieving the same cooling effect, the flow distance of the helium coolant along the radial direction between the basket shell and the cylinder can be reduced, effectively reducing the volume of the entire test device and enhancing heat exchange and adjusting the pressure drop of the protective gas. Finally, the protective gas flowing along the cavity chamber and the test gas heated by the fuel assembly converge and mix evenly at the flow equalization plate assembly 15 welded on the inner side of the rear cylinder 3. The flow equalization plate assembly 15 is provided with flow equalization holes to ensure that the test gas and the protective gas are fully mixed, which can enhance the heat transfer of the two gases to achieve the temperature required for the test. Finally, the mixed gas flows out from the outlet pipe section connected to the first outlet of the rear head 5 into the downstream main circuit.

[0083] Specifically, the experimental setup in this embodiment is mainly used to study the flow heat transfer characteristics between the surface of the fuel assembly and the coolant. In order to obtain the temperature field distribution inside the graphite assembly 8 and the heating rod, several measurement points need to be arranged at different locations inside the graphite block 801 and the heating rod. For example... Figure 1 , Figure 2 , Figure 4 , Figure 5 , Figure 7 and Figure 8 As shown, the temperature of the simulated fuel assembly gradually increases from the inlet to the outlet in the test device. In order to measure the temperature distribution and changes of each layer of graphite blocks 801 in the axial direction, several temperature measuring points are arranged at the beginning and end of each layer of graphite assembly 8 and in the middle of each layer of graphite blocks 801 to monitor the temperature distribution at different positions of the heating rod, graphite assembly 8 and cooling channel. In this device, several semi-circular first wire grooves 805 can be opened on the end face of each layer of graphite block 801. The first wire grooves 805 are either zigzag or straight grooves. The first wire grooves 805 with circular cross-sections are opened at the middle part of each layer of graphite block 801 where the measuring points are arranged. In this case, the first wire grooves 805 can only be straight circular holes. Finally, all thermocouple lines are led out through grooves on the surface and axial direction of the insulation layer assembly 7. The insulation layer assembly 7 is composed of several insulation blocks 701, the number of which is twice that of graphite blocks 801. Both ends of the insulation block 701 are opened with several semi-circular second wire grooves 702 along the radial direction and third wire grooves 703 along the axial direction, corresponding to the graphite assembly 8, for the lead-out of thermocouple lines. The second wire grooves 702 are... Several circular tubes are evenly distributed outside the basket unit and pass through the guide plate 10 along the axial direction, which can better protect the measurement signal lines of the internal measurement unit. The thermocouple wires of the front half of the graphite assembly 8 are led forward through the axial slot outside the insulation layer assembly 7, and the thermocouple wires of the rear half of the graphite assembly 8 are led backward through the axial slot outside the insulation layer assembly 7 and enter several evenly distributed circular tubes inside the guide plate 10; finally, all thermocouple wires converge inside the front cylinder 1 and enter the three-way sealing assembly 17 connected to the side of the front cylinder 1.

[0084] To measure the inlet and outlet pressures and differential pressure of the coolant passage 802 inside the fuel assembly, such as Figure 1 , Figure 2 and Figure 6 As shown, pressure measurement points are distributed at both ends of the graphite assembly 8. The front pressure tapping pipe is led out radially from the front end of the graphite assembly 8, and the rear pressure tapping pipe is led out radially from the rear end of the graphite assembly 8. It passes through the cavity and enters the front end of the cylinder through the pipe. The two pressure tapping pipes enter the three-way sealing assembly 17 through the front cylinder 1.

[0085] like Figure 2 and Figure 3As shown, after the thermocouple temperature measuring wire enters the three-way sealing assembly 17, it is connected to the pressure-bearing aviation sealing plug through eight three-way line outlet interfaces 173, where the three-way line outlet interfaces 173 are connected to the aviation sealing plug; after the pressure guide tube enters the three-way sealing assembly 17, it is connected to the pressure measuring instrument through the pressure outlet pipe 174; when installing and debugging the internal circuit of the three-way sealing assembly 17, simply open the front and rear three-way sealing covers 172.

[0086] The experimental setup described in this embodiment, used to simulate the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements, allows for focused study of the heat transfer characteristics of fuel elements under various influencing factors and verification of the core's heat transfer capacity under design conditions. It provides thermal parameters such as pressure, flow rate, and temperature for iterative reactor design, ensuring compliance with reactor safety requirements under various operating conditions. This experimental setup features an advanced design concept, a rational overall structure, high similarity in physical phenomena, and a small experimental scale, offering advantages such as high flexibility, rapid testing progress, and low cost. Simultaneously, it provides crucial and reliable experimental data for safety evaluation and verification of safety analysis procedures for gas-cooled microreactor model design, thereby meeting nuclear safety regulatory requirements.

[0087] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A test apparatus for simulating the thermal-hydraulic characteristics of fuel elements in a gas-cooled microreactor, characterized in that, The system includes a pressure vessel shell and a basket unit disposed within the pressure vessel shell, forming a cavity between the basket unit and the pressure vessel shell. The basket unit includes a basket shell, a graphite assembly disposed within the basket shell, a coolant channel, a heating rod channel, a heating rod assembly, an insulation layer assembly, and a measuring unit. The coolant channel and the heating rod channel are respectively disposed within the graphite assembly, and the insulation layer assembly is disposed around the graphite assembly. The heating rod channel is used to hold the heating rod assembly, and the coolant channel is used to pass test gas. The measuring unit is used to measure the pressure and temperature thermal parameters at measuring points on the graphite assembly. The pressure vessel shell includes a pressure vessel shell body, a first inlet, a second inlet, and a first outlet disposed on the pressure vessel shell body. The first inlet is connected to the coolant channel, through which test gas is introduced into the coolant channel. The second inlet is connected to the cavity, through which protective gas is introduced into the cavity. The first outlet is used to discharge the mixed gas inside the pressure vessel shell, the mixed gas including test gas and protective gas.

2. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 1, characterized in that, The graphite assembly has at least one measurement point of a measurement unit. A first wire groove is provided at the first radial position of the graphite assembly where the measurement point is located. The first wire groove is used to lead the lead wire of the measurement unit out of the graphite assembly from the measurement point. A second wire groove is provided at the second radial position of the insulation layer component. The second wire groove is connected to the first wire groove. A third wire groove is provided on the axial outer surface of the insulation layer component. The third wire groove is connected to the second wire groove. The lead wire of the measuring unit is led out of the basket unit from the measuring point through the first wire groove, the second wire groove, and the third wire groove.

3. The experimental apparatus for simulating the thermo-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 2, characterized in that, The graphite assembly includes at least one graphite block. The measuring point of the measuring unit is a temperature measuring point. When the temperature measuring point is on the axial end face of the graphite block, the orthographic projection view of the first wire groove on the axial bottom surface of the graphite block is a broken line shape or a straight line shape. When the temperature measuring point is at other positions on the graphite block, the orthographic projection view of the first wire groove on the axial bottom surface of the graphite block is a straight line shape.

4. The experimental apparatus for simulating the thermo-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 3, characterized in that, Temperature measurement points are set at both ends and in the middle of the graphite block along its axial direction.

5. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 3, characterized in that, There are at least two temperature measurement points, located on the axial end face of the graphite block, with the temperature measurement points distributed around the heating rod channel and the coolant channel.

6. The experimental apparatus for simulating the thermo-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 2, characterized in that, The graphite assembly includes at least one graphite block, the measuring point of the measuring unit is a pressure measuring point, the pressure measuring point is on the axial end face of the graphite block, and the first wire groove is a straight line in the orthographic projection view of the axial bottom surface of the graphite block.

7. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 2, characterized in that, The second guide groove is a straight line in the orthographic projection view of the axial bottom surface of the insulation layer assembly.

8. The experimental apparatus for simulating the thermo-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 2, characterized in that, The pressure vessel shell also includes a second outlet disposed on the pressure vessel shell body. The second outlet is closer to the first end of the pressure vessel shell body than to the second end of the pressure vessel shell body. The first axial end of the graphite assembly is close to the first end of the pressure vessel shell body, and the second axial end of the graphite assembly is close to the second end of the pressure vessel shell body. The first outlet is closer to the second end of the pressure vessel shell body than to the first end of the pressure vessel shell body. The lead wire of the measuring unit corresponding to the measuring point on the graphite assembly near the first end of the pressure vessel shell body passes through the first wire groove, the second wire groove, and then through the third wire groove to guide the graphite assembly axially towards the first end, and then enters the second outlet through the cavity; The lead wire of the measuring unit corresponding to the measuring point on the graphite assembly near the second end of the pressure vessel shell body passes through the first wire groove, the second wire groove, and then through the third wire groove to guide the graphite assembly axially towards the second end, and then enters the second outlet through the cavity.

9. The experimental apparatus for simulating the thermo-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 1, characterized in that, It also includes a three-way sealing assembly installed on the pressure vessel shell. The three-way sealing assembly includes a three-way cylinder, a three-way inlet, a three-way sealing cover, and a three-way outlet. The lead wire of the measuring unit enters the three-way cylinder through the three-way inlet and is then exited through the three-way outlet. The three-way sealing cover is used to open the three-way cylinder for wiring connection and inspection.

10. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 9, characterized in that, The three-way outlet includes a first three-way outlet and a second three-way outlet. The leads of the measuring unit include a first lead for measuring temperature and a second lead for measuring pressure. The first lead is led out from the first three-way outlet, and the second lead is led out from the second three-way outlet.

11. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 1, characterized in that, Also includes: The heating rod assembly includes a flange cover, sleeve, and seal, all located outside the pressure vessel shell. The heating rod assembly comprises at least one heating rod, which includes a heating section and a non-heating section connected sequentially. The heating section is placed within a heating rod channel and penetrates the pressure vessel shell. The non-heating section passes through the pressure vessel shell and is located outside the shell for connection to a power regulating device. A countersunk hole is provided on the heating rod flange cover, and a sleeve is positioned within this hole, fitting around the non-heating section of the heating rod. The flange cover and sleeve are connected by threads via the countersunk hole and the sleeve is also connected by threads to the heating rod. The seal is located within the countersunk hole, between the heating rod and the countersunk hole, with one side of the seal contacting the countersunk hole surface and the other side contacting the sleeve.

12. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to claim 11, characterized in that, Also includes: The front-end electrical protective cover, protective cover flange, and support are provided. The front-end electrical protective cover is connected to the pressure vessel shell through the protective cover flange. The front-end electrical protective cover covers the heating rod flange cover, sleeve, and seals. The front-end electrical protective cover has a semi-groove hole for the heating rod's wiring to be led out. The support is set on the front-end electrical protective cover and is used to support the sensor connected to the heating rod.

13. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to any one of claims 1 to 12, characterized in that, The measurement unit includes a temperature measurement unit and a pressure measurement unit. The temperature measurement unit is used to measure the temperature of the graphite assembly, and the pressure measurement unit is used to measure the pressure and pressure loss of the test gas in the coolant channel.

14. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to any one of claims 1 to 12, characterized in that, Also includes: The guide plate installed inside the cavity is used to guide and increase the flow of protective gas inside the cavity.

15. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to any one of claims 1 to 12, characterized in that, The test apparatus also includes: a flow equalization orifice plate assembly disposed inside the pressure vessel shell, the flow equalization orifice plate assembly being disposed in the gap between the graphite assembly and the first outlet, the flow equalization orifice plate assembly being used to uniformly mix the test gas of the graphite assembly and the protective gas in the cavity before flowing out through the first outlet.

16. The experimental apparatus for simulating the thermal-hydraulic characteristics of gas-cooled microreactor fuel elements according to any one of claims 1 to 12, characterized in that, The pressure vessel shell includes a cylinder, a front end cap, a rear end cap, and a saddle. The saddle is located at the bottom of the cylinder. The cylinder includes a front cylinder, a middle cylinder, and a rear cylinder connected in sequence. The front cylinder is connected to the front end cap, and the rear cylinder is connected to the rear end cap.

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