An experimental device for studying the core bypass flow characteristics of a pebble bed high temperature gas cooled reactor

Abstract

The application discloses a kind of experimental devices for studying the characteristics of core bypass flow of pebble bed high temperature gas cooled reactor, comprising: inlet connection pipe, outlet connection pipe, temperature measuring conduit, temperature sensor, pressure lead, upper end cover, graphite pebble bed, lower chamber, gas collection disc, graphite brick, graphite square key and graphite brick interstitial temperature measuring channel.Graphite brick is stacked to form graphite cavity, graphite pebble bed is filled in the cavity, and two layers of graphite bricks are connected and fixed by graphite square key.Graphite brick interstitial temperature measuring channel is composed of temperature measuring channel in four adjacent graphite bricks from top to bottom and left to right, for inserting temperature sensor.The application arranges temperature sensor in the form of multi-angle, multi-point and multi-probe, is suitable for carrying out the modeling experiment of the characteristics of core bypass flow of pebble bed high temperature gas cooled reactor, obtains refined temperature field distribution, can reflect the coupling characteristics between pebble bed structure and graphite brick under bypass flow condition, and can also explore the influence of square key structure on brick interstitial gas flow.

Description

Technical Field

[0001] This invention relates to the field of reactor physics and thermal technology, specifically to an experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core. Background Technology

[0002] The bypass characteristics of gaseous coolant in the reactor core are one of the key issues that urgently need to be addressed in the design and development of pebble bed high-temperature gas-cooled reactors. In pebble bed high-temperature gas-cooled reactors, bypass flow typically refers to the portion of coolant that fails to flow through the pebble bed region of the core and carry away fuel heat. This includes functional bypass flow and structural bypass flow. Functional bypass flow is mainly used for cooling structures such as control rod channels and discharge pipes, while structural bypass flow mainly exists in the gap channels formed between graphite bricks due to manufacturing and assembly tolerances, thermal expansion, and irradiation deformation. The bypass flow characteristics in the reactor core have a significant impact on key thermal parameters such as the coolant flow distribution characteristics, the maximum core temperature, and the maximum thermal power level of the reactor. The bypass flow in the core has the following characteristics: numerous and widely distributed gap channels that are interconnected and influence each other; and the structural shapes of these channels are mostly irregular and may change with increasing core burnup or changes in operating conditions. Currently, experimental research on bypass characteristics both domestically and internationally mainly focuses on key local bypass channels, without conducting corresponding experimental studies on the bypass characteristics of the entire reactor core structure, thus lacking relevant experimental data support. Therefore, this invention provides an experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide an experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core, reflecting the coupling characteristics between the pebble bed structure and graphite bricks under bypass conditions, exploring the influence of the actual square bond structure on the gas flow between the bricks, and thereby verifying the effectiveness and accuracy of the CFD method in studying bypass problems.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core includes an inlet pipe 1, an inlet temperature measuring conduit 2, an inlet temperature sensor 4, an inlet pressure tap 5, an upper end cover 6, a graphite pebble bed 7, a lower chamber 10, a gas collecting plate 11, an outlet pressure tap 12, an outlet pipe 13, an outlet temperature measuring conduit 14, an outlet temperature sensor 15, lower layer graphite bricks 16, middle layer graphite bricks 17, upper layer graphite bricks 18, upper layer temperature measuring conduit 19, lower layer temperature measuring conduit 20, upper layer temperature sensor 21, lower layer temperature sensor 22, and temperature measuring channels between graphite bricks 23.

[0006] The inlet pipe 1 is used to connect the experimental device to an external gas source, allowing the introduction of a high-temperature, high-pressure working gas. An inlet temperature measuring conduit 2 and an inlet pressure tapping pipe 5 are sequentially arranged along the airflow direction on the inlet pipe 1. The inlet temperature measuring conduit 2 connects to the lower chamber 10 and is designed as a hollow pipe for installing an inlet temperature sensor 4. The inlet pressure tapping pipe 5 is also a hollow pipe, with a pressure transmitter and a differential pressure transmitter installed at its end, used to measure the gas pressure at the inlet of the experimental device and the pressure difference generated as the gas flows through the entire device, respectively. The lower end face of the upper cover 6 is in contact with the upper end face of the lower chamber 10.

[0007] The lower chamber 10 is used to install a gas collecting plate 11, lower layer graphite bricks 16, middle layer graphite bricks 17, upper layer graphite bricks 18, and a graphite ball bed 7. The graphite ball bed 7 is located within the cavity formed by the lower layer graphite bricks 16, middle layer graphite bricks 17, and upper layer graphite bricks 18, simulating the graphite ball bed structure in a high-temperature gas-cooled reactor core. The gas collecting plate 11 is installed in a groove formed by the lower layer graphite bricks 16 surrounding the bottom of the lower chamber 10, supporting the graphite ball bed 7 and collecting and converging the high-temperature gas working fluid. The gas collecting plate 11 has gas collecting grooves 111 in all directions from the center point to the apex, arranged radially to guide the gas at the bottom of the device to converge to the outlet pipe 13. An outlet channel is opened at the bottom of the lower chamber 10 and connected to the outlet pipe 13 for discharging the gas working fluid. The outlet pipe 13 is equipped with an outlet pressure tap 12 and an outlet temperature measuring conduit 14 for installing an outlet temperature sensor 15.

[0008] The upper temperature measuring conduit 19 is located outside the temperature measuring channel 23 between graphite bricks, which is composed of upper graphite brick 18 and middle graphite brick 17, and is used to install the upper temperature sensor 21; the lower temperature measuring conduit 20 is located outside the temperature measuring channel 23 between graphite bricks, which is composed of middle graphite brick 17 and lower graphite brick 16, and is used to install the lower temperature sensor 22; the upper temperature sensor 21 and the lower temperature sensor 22 are used to measure the gas temperature distribution between graphite bricks under the bypass effect.

[0009] The end of the inlet temperature measuring conduit 2 is provided with a temperature sensor sealing sleeve 3, which is used to achieve a seal between the inlet temperature sensor 4 and the inlet temperature measuring conduit 2, and to ensure the airtightness at this location.

[0010] The temperature sensor 4 is inserted along the inlet temperature measuring conduit 2 to the central axis of the inlet pipe 1.

[0011] The vertical projections of the inlet temperature measuring conduit 2 and the inlet pressure tapping tube 5 are arranged at 180 degrees on the projection plane; both the inlet temperature measuring conduit 2 and the inlet pressure tapping tube 5 are fixed to the inlet connecting pipe 1 by welding.

[0012] The outer edge of the upper end cover 6 is provided with eight threaded through holes arranged in a centrally symmetrical manner. The central axis of the through holes coincides with the axis of eight threaded blind holes on the upper end face of the lower chamber 10. Bolts are used to fasten the connection to the threaded holes. The surface finish of the contact surfaces between the lower end face of the upper end cover 6 and the upper end face of the lower chamber 10 is required to reach level six or above.

[0013] The lower chamber 10 has a cylindrical exterior and an octagonal prism interior for installing the gas collecting plate 11, the lower layer graphite bricks 16, the middle layer graphite bricks 17, the upper layer graphite bricks 18, and the graphite ball bed 7; the lower chamber 10 is covered with thermal insulation material on the outside.

[0014] The gas collecting plate 11 has a regular octagonal cross-section and a plate thickness of 10-20mm. It is installed in the regular octagonal groove at the bottom of the lower chamber 10, which is surrounded by eight lower-layer graphite bricks 16.

[0015] The middle layer graphite brick 17 has an isosceles trapezoidal cross-section, with the upper base side length equal to the side length of the regular octagon of the gas collecting plate 11 cross-section, and the lower base side length equal to the side length of the regular octagon of the lower chamber 10 cross-section. The upper and lower end faces of the middle layer graphite brick 17 are parallel to each other and perpendicular to the four edges in the height direction. A quarter-graphite keyway 171 and a quarter-temperature measuring channel 172 are provided at the two sides of the isosceles trapezoid, which are used to install the upper graphite square key 8, the lower graphite square key 9, the upper temperature sensor 21, and the lower temperature sensor 22, respectively. The temperature measuring channel 23 between graphite bricks is composed of the quarter-temperature measuring channels of four adjacent graphite bricks, which are used to insert the temperature measuring probe of the temperature sensor to measure the temperature of the bypass gas.

[0016] The difference between the shape and structure of the lower graphite brick 16 and the upper graphite brick 18 and the middle graphite brick 17 is that the lower graphite brick 16 is provided with a graphite keyway and a temperature measuring channel on the upper end face, while the upper graphite brick 18 is provided with a graphite keyway and a temperature measuring channel on the lower end face.

[0017] The lower layer graphite bricks 16 are installed in a circular manner at the bottom of the regular octagonal prism cavity in the lower chamber 10; the middle layer graphite bricks 17 are stacked on top of the lower layer graphite bricks 16, and the two layers of graphite bricks are connected and fixed by the lower layer graphite square key 9; the upper layer graphite bricks 18 are stacked on top of the middle layer graphite bricks 17, and the two layers of graphite bricks are connected and fixed by the upper layer graphite square key 8; the graphite bricks are stacked to form a graphite cavity.

[0018] The gas collecting plate 11 has gas collecting grooves 111 in each direction from the center point of the plate to the eight vertices, arranged radially from the center; the cross-sectional shape of the gas collecting grooves 111 is rectangular with rounded ends.

[0019] The upper graphite square key 8 adopts the form of a B-type key, that is, the two ends are square and the cross-sectional shape is rectangular; the twelve edges of the upper graphite square key 8 are rounded to reduce the stress at the edges; the lower graphite square key 9 has the same shape, structure and material as the upper graphite square key 8, the only difference is the installation position of the two.

[0020] The graphite ball bed 7 is composed of several graphite balls with a diameter of 5 to 8 mm. Under the action of gravity, the graphite balls are randomly stacked and distributed inside the cavity composed of graphite bricks. The graphite balls are solid and have no heat source inside.

[0021] There are eight upper temperature measuring conduits 19, which are arranged radially and are all fixed to the side wall of the lower chamber 10 by welding. The end of each upper temperature measuring conduit 19 is provided with a temperature sensor sealing sleeve 3 to achieve a seal between the upper temperature sensor 21 and the upper temperature measuring conduit 19. The lower temperature measuring conduit 20 has the same shape and structure as the upper temperature measuring conduit 19.

[0022] The outlet pressure tap 12 is welded to the outlet pipe 13 and cooperates with the inlet pressure tap 5 to measure the pressure difference generated by the high temperature and high pressure gas working medium flowing through the entire device.

[0023] The outlet temperature measuring conduit 14 is arranged below the outlet pressure tapping pipe 12 to prevent the outlet temperature sensor 15 from interfering with the accurate measurement of pressure and pressure difference due to the flow around the airflow.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This invention enables experimental research on the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core. The experimental section is constructed by stacking graphite bricks and filling the pebble bed with graphite. Temperature sensors are arranged in a multi-angle, multi-point, and multi-probe manner to obtain a refined temperature field distribution. This can reflect the coupling characteristics between the pebble bed structure and the graphite bricks under bypass conditions, and can also explore the influence of the actual square bond structure on the gas flow between the bricks.

[0026] 2. This invention uses a scaled-down graphite ball bed and graphite bricks to form the experimental section. On the one hand, it fully restores the key features of the reactor core structure, thereby better revealing the bypass characteristics of the gas coolant in the reactor core. On the other hand, it effectively reduces the geometric size of the experimental device, reduces the construction and operation costs of the experimental device, and is more economical and feasible.

[0027] 3. In the experimental apparatus of the present invention, the lower chamber and the upper end cover are connected by bolts and threaded holes, which has the advantages of convenient installation and disassembly. The experimental section inside the chamber can be replaced in a timely manner according to different experimental conditions. It is suitable for sensitivity analysis: to explore the influence of factors such as different structural dimensions of the square key, different stacking states of the graphite ball bed, and different vertical and horizontal gap sizes between graphite bricks on the core bypass characteristics.

[0028] 4. The experimental apparatus of this invention, under the condition of meeting the experimental requirements, has good airtightness and can operate safely under high temperature and high pressure conditions of the working gas. A sealing sleeve is provided at the connection between the temperature measuring tube and the temperature sensor; the surface finish of the connection end face between the lower chamber and the upper end cover is required to reach level six or above, so as to achieve a tight fit and ensure airtightness.

[0029] 5. The experimental apparatus of the present invention can provide experimental data support for the thermal design and safety analysis of the pebble bed high-temperature gas-cooled reactor core by conducting sideflow characteristic experiments between the pebble bed structure and the graphite brick structure. Attached Figure Description

[0030] Figure 1 This is a cross-sectional view of the overall structure of an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram of the overall structure of an embodiment of the present invention.

[0032] Figures 3(a), 3(b), and 3(c) are schematic diagrams of the lower, middle, and upper graphite brick structures of an embodiment of the present invention.

[0033] Figure 4 This is a schematic diagram of a three-layer graphite brick block and a temperature measuring channel according to an embodiment of the present invention.

[0034] Figure 5 This is a schematic diagram of the assembly positions of the bricks, ball bed, and square key in an embodiment of the present invention.

[0035] Figure 6 This is a schematic diagram of the gas collecting plate structure according to an embodiment of the present invention.

[0036] Figures 7(a) and 7(b) are schematic diagrams of the square key and graphite sphere structures in an embodiment of the present invention.

[0037] Figure 8 This is a schematic diagram of the lower chamber structure according to an embodiment of the present invention.

[0038] Explanation of reference numerals in the attached diagram: 1. Inlet connector; 2. Inlet temperature measuring conduit; 3. Temperature sensor sealing sleeve; 4. Inlet temperature sensor; 5. Inlet pressure tap; 6. Upper end cap; 7. Graphite ball bed; 8. Upper graphite square key; 9. Lower graphite square key; 10. Lower chamber; 11. Gas collecting plate; 111. Gas collecting groove; 12. Outlet pressure tap; 13. Outlet connector; 14. Outlet temperature measuring conduit; 15. Outlet temperature sensor; 16. Lower graphite brick; 17. Middle graphite brick; 171. Quarter graphite keyway; 172. Quarter temperature measuring channel; 18. Upper graphite brick; 19. Upper temperature measuring conduit; 20. Lower temperature measuring conduit; 21. Upper temperature sensor; 22. Lower temperature sensor; 23. Temperature measuring channel between graphite bricks. Detailed Implementation

[0039] To better illustrate the present invention, the accompanying drawings are now provided. Figure 1-8 The present invention will be further described in detail below:

[0040] like Figure 1 and Figure 2 As shown, this invention is an experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core, comprising the following main parts: inlet pipe 1, inlet temperature measuring conduit 2, temperature sensor sealing sleeve 3, inlet temperature sensor 4, inlet pressure tapping pipe 5, upper end cover 6, graphite pebble bed 7, upper layer graphite square key 8, lower layer graphite square key 9, lower chamber 10, gas collecting plate 11, outlet pressure tapping pipe 12, outlet pipe 13, outlet temperature measuring conduit 14, outlet temperature sensor 15, lower layer graphite brick 16, middle layer graphite brick 17, upper layer graphite brick 18, upper layer temperature measuring conduit 19, lower layer temperature measuring conduit 20, upper layer temperature sensor 21, lower layer temperature sensor 22, and temperature measuring channel 23 between graphite bricks.

[0041] The inlet pipe 1 is used to connect the experimental apparatus to an external gas source, allowing the introduction of a high-temperature, high-pressure working gas. An inlet temperature sensing conduit 2 and an inlet pressure tap 5 are sequentially arranged on the inlet pipe 1 along the airflow direction. The inlet temperature sensing conduit 2 is a hollow pipe design used to install the inlet temperature sensor 4. A temperature sensor sealing sleeve 3 is provided at the end of the inlet temperature sensing conduit 2 to ensure a seal between the inlet temperature sensor 4 and the inlet temperature sensing conduit 2, guaranteeing airtightness at this location. The temperature probe of the inlet temperature sensor 4 is inserted along the inlet temperature sensing conduit 2 to the central axis of the inlet pipe 1 to accurately measure the inlet temperature.

[0042] The inlet pressure tap 5 is a hollow pipe design, with a pressure transmitter and a differential pressure transmitter installed at its end. These are used to measure the gas pressure at the inlet of the experimental apparatus and the pressure difference generated by the gas flowing through the entire apparatus, respectively. The vertical projections of the inlet temperature measuring conduit 2 and the inlet pressure tap 5 are arranged at 180 degrees on the projection plane to minimize airflow disturbance and mutual interference between pressure and temperature measurements. The hollow pipes of the inlet temperature measuring conduit 2 and the inlet pressure tap 5 have an inner diameter of 2–3 mm and a length of 100–200 mm, and are both fixed to the inlet connecting pipe 1 by welding.

[0043] The outer edge of the upper end cover 6 is provided with eight centrally symmetrically arranged threaded through holes. The central axis of the through holes coincides with the axis of eight threaded blind holes on the upper end face of the lower chamber 10. Bolts are used to fasten the connection to the threaded holes. The lower end face of the upper end cover 6 is in contact with the upper end face of the lower chamber 10. The surface finish of the contact surfaces is required to reach level six or above to achieve a tight fit and ensure sealing.

[0044] The lower chamber 10 has an external cylindrical design and an internal octagonal prism cavity for installing the gas collecting plate 11, lower layer graphite bricks 16, middle layer graphite bricks 17, upper layer graphite bricks 18, and graphite ball bed 7. The octagonal cross-section of the lower chamber 10 provides strict geometric constraints and precise assembly positioning for the graphite bricks, ensuring minimal angular deviation in the circumferential direction of the upper, middle, and lower layers. An outlet channel at the bottom of the lower chamber 10 connects to the outlet pipe 13 for discharging the working gas. The lower chamber 10 is covered with insulation material.

[0045] like Figure 6 As shown, the gas collecting plate 11 has a regular octagonal cross-section, allowing for a tight fit with the regular octagonal groove formed by the lower layer of graphite bricks 16. The gas collecting plate 11 has a thickness of 10-20 mm and is installed in the regular octagonal groove formed by eight lower layer graphite bricks 16 at the bottom of the lower chamber 10. It supports the graphite spherical bed and collects and gathers the high-temperature gaseous working fluid. The gas collecting plate 11 has gas collecting grooves 111 arranged radially from its center point to each of the eight vertices. The gas collecting grooves 111 have a rectangular cross-section with rounded ends, extending through the gas collecting plate 11, and guiding the gas at the bottom of the device to the outlet pipe 13.

[0046] As shown in Figures (a), 3(b), and 3(c), the cross-sectional shape of the middle layer graphite brick 17 is an isosceles trapezoid. The side length of the upper base is equal to the side length of the regular octagon of the cross-section of the gas collecting plate 11, and the side length of the lower base is equal to the side length of the regular octagon of the cross-section of the lower chamber 10. The upper and lower end faces of the middle layer graphite brick 17 are parallel to each other and perpendicular to the four edges in the height direction. A quarter-graphite keyway 171 and a quarter-temperature measuring channel 172 are provided at the two sides of the isosceles trapezoid, which are used to install the upper layer graphite square key 8, the lower layer graphite square key 9, the upper layer temperature sensor 21, and the lower layer temperature sensor 22, respectively.

[0047] like Figure 4 and Figure 5 As shown, the lower graphite brick 16 and upper graphite brick 18 have basically the same shape and structure as the middle graphite brick 17, except that the lower graphite brick 16 has graphite keyways and temperature measuring channels on its upper end face, while the upper graphite brick 18 has them on its lower end face. The lower graphite brick 16 is installed in a ring around the bottom of the regular octagonal prism cavity in the lower chamber 10. The middle graphite brick 17 is stacked on top of the lower graphite brick 16, and the two layers of graphite bricks are connected and fixed by the lower graphite square key 9. The upper graphite brick 18 is stacked on top of the middle graphite brick 17, and the two layers of graphite bricks are connected and fixed by the upper graphite square key 8. The stacked graphite bricks form a graphite cavity. Using graphite square keys as the connection and fixing method between graphite bricks can not only fully reproduce the arrangement of graphite components in the core of a high-temperature gas-cooled reactor, but also explore the influence of the square key structure on the gas flow between the bricks. Figure 4 As shown, the temperature measuring channel 23 between graphite bricks is composed of one-quarter temperature measuring channels of four adjacent graphite bricks (top, bottom, left, and right), used to insert the temperature measuring probe of the temperature sensor to measure the temperature of the bypass gas.

[0048] As shown in Figure 7(a), the upper graphite square key 8 adopts the form of a type B key, that is, square ends and rectangular cross-section. The twelve edges of the upper graphite square key 8 are rounded to reduce stress at the edges. The lower graphite square key 9 has the same shape, structure and material as the upper graphite square key 8, the only difference being their installation position.

[0049] As shown in Figure 7(b), the graphite sphere bed 7 consists of several graphite spheres with a diameter of 5–8 mm. Under the influence of gravity, the graphite spheres are randomly distributed inside the cavity composed of graphite bricks to simulate the graphite sphere bed structure in the core of a high-temperature gas-cooled reactor. The graphite spheres are solid and have no internal heat source.

[0050] like Figure 8As shown, the upper temperature measuring conduit 19 is located outside the temperature measuring channel 23 between the graphite bricks, which is composed of upper graphite bricks 18 and middle graphite bricks 17, and is used to install the upper temperature sensor 21. There are eight upper temperature measuring conduits 19 in total, arranged radially, for arranging temperature sensors at multiple angles, points, and probes to obtain a refined temperature field distribution. The upper temperature measuring conduits 19 are fixed to the side wall of the lower chamber 10 by welding. The inner diameter of the conduit is 2-3 mm, and the length is 100-200 mm. A temperature sensor sealing sleeve 3 is provided at the end of the upper temperature measuring conduit 19 to achieve a seal between the upper temperature sensor 21 and the upper temperature measuring conduit 19.

[0051] like Figure 8 As shown, the shape, structure and arrangement of the lower temperature measuring conduit 20 are basically the same as those of the upper temperature measuring conduit 19. The difference is that the lower temperature measuring conduit 20 is located outside the temperature measuring channel 23 between the graphite bricks, which is composed of the middle graphite brick block 17 and the lower graphite brick block 16.

[0052] The outlet pressure tap 12 is welded to the outlet connector 13 and works in conjunction with the inlet pressure tap 5 to measure the pressure difference generated by the high-temperature, high-pressure working gas flowing through the entire device. The outlet temperature measuring conduit 14 is positioned below the outlet pressure tap 12 to prevent the flow around the gas caused by the outlet temperature sensor 15 from interfering with the accurate measurement of pressure and pressure difference. The upper temperature sensor 21 and the lower temperature sensor 22 are used to measure the gas temperature distribution between the graphite bricks under the bypass effect.

[0053] In a preferred embodiment of the present invention, the height of the graphite brick is preferably 200 mm; the outer diameter of the lower chamber is preferably 600 mm; the inner diameter of the inlet / outlet pipe is preferably 80 mm, and the wall thickness is preferably 10 mm. Using the above-mentioned geometric dimensions can fully reproduce the core characteristics and reveal the bypass characteristics of the pebble bed high-temperature gas-cooled reactor core; it can also effectively control the overall size of the experimental device, saving manufacturing and operating costs and maintaining the economic advantages of model experiments.

[0054] In a preferred embodiment of the present invention, the working gas circulating in the experimental apparatus is preferably an inert gas such as helium, argon, nitrogen, or a helium-xenon mixture. On the one hand, these inert gases are commonly used as coolants in high-temperature gas-cooled reactors, and experimental results obtained using them as working gases are more representative; on the other hand, using an inert gas working gas can effectively suppress the oxidation and corrosion reaction of graphite bricks and graphite spheres under high-temperature conditions, thus extending their service life.

[0055] In a preferred embodiment of the present invention, the gaseous working medium needs to be fully preheated before being introduced into the inlet pipe of the experimental device, with the inlet temperature preferably ranging from 300 to 450°C. The pressure range of the gaseous working medium inside the experimental device is preferably 1.0 to 1.5 MPa. The above-mentioned helium temperature and pressure parameter ranges are close to the actual operating parameters of the gas-cooled reactor, making the experimental results more convincing and representative. In a preferred embodiment of the present invention, the materials of the lower chamber and the upper end cover are preferably 304 stainless steel, which has good processing performance and corrosion resistance. The material of the temperature sensor sealing sleeve is preferably a high-temperature resistant metal or alloy, used to prevent significant thermal deformation of the sealing sleeve under high-temperature conditions and ensure the airtightness of the temperature measuring conduit. In a preferred embodiment of the present invention, the temperature sensor is preferably a K-type armored thermocouple, with an armor diameter preferably of 2 to 3 mm and an armor length preferably of 400 to 500 mm, which has advantages such as good chemical stability, high sensitivity, and good linearity.

[0056] In a preferred embodiment of the present invention, the insulation material covering the outer side of the lower cavity is preferably glass fiber cotton, which is uniformly wrapped around the outer wall of the lower cavity to form an insulation layer, and the surface is covered with aluminum foil, which can effectively reduce the heat dissipation of the experimental section.

[0057] The working principle and experimental procedure of the experimental device described in this invention are as follows:

[0058] Three layers of graphite bricks (upper, middle, and lower) are stacked in a specific pattern within the lower chamber to form a graphite cavity. Multiple graphite spheres are randomly distributed within the cavity to form a graphite sphere bed structure. Both are located within a pressure vessel consisting of the lower chamber and the upper end cover. Adjacent graphite bricks are fixedly connected by square keys, and the gaps between the bricks form a bypass channel. Sixteen temperature sensors are inserted into the temperature measurement channels between the graphite bricks via temperature-measuring conduits along the sidewall of the lower chamber, enabling multi-angle, multi-point, and multi-probe temperature measurements to obtain a refined temperature field distribution. The working gas flows into the experimental device through the inlet pipe, with the main stream flowing through the graphite sphere bed structure and the bypass stream flowing through the gap channel. After reaching the bottom of the experimental device, the working gas is collected and converged by a gas collecting plate, flowing out of the device through the outlet pipe. Temperature and pressure measuring points are set at appropriate locations on the inlet and outlet pipes to measure thermal parameters such as inlet and outlet temperatures and pressure differences. This invention mainly uses the measured refined temperature field distribution to characterize the gas flow distribution at various locations, thereby obtaining the bypass characteristics.

[0059] The above embodiments are merely illustrative examples of the present invention. The present invention may also be implemented in other specific ways or forms without departing from its spirit or essential characteristics. Therefore, the described embodiments should be considered illustrative rather than limiting in any respect. The scope of the present invention should be defined by the appended claims, and any variations equivalent to the intent and scope of the claims should also be included within the scope of the present invention. Contents not described in detail in this invention are conventional technical content.

Claims

1. An experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core, characterized in that: Includes inlet pipe (1), inlet temperature measuring conduit (2), inlet temperature sensor (4), inlet pressure tap (5), upper end cap (6), graphite ball bed (7), lower chamber (10), gas collecting plate (11), outlet pressure tap (12), outlet pipe (13), outlet temperature measuring conduit (14), outlet temperature sensor (15), lower layer graphite brick (16), middle layer graphite brick (17), upper layer graphite brick (18), upper layer temperature measuring conduit (19), lower layer temperature measuring conduit (20), upper layer temperature sensor (21), lower layer temperature sensor (22), and temperature measuring channel between graphite bricks (23). The inlet pipe (1) is used to connect the experimental device to an external gas source and to introduce a high-temperature, high-pressure working gas. An inlet temperature measuring pipe (2) and an inlet pressure tapping pipe (5) are arranged sequentially along the airflow direction on the inlet pipe (1). The inlet temperature measuring pipe (2) is connected to the lower chamber (10) and is designed as a hollow pipe for installing an inlet temperature sensor (4). The inlet pressure tapping pipe (5) is designed as a hollow pipe and has a pressure transmitter and a differential pressure transmitter installed at its end, which are used to measure the pressure of the gas at the inlet of the experimental device and to measure the pressure difference generated by the gas flowing through the entire device, respectively. The lower end face of the upper end cover (6) is in contact with the upper end face of the lower chamber (10). The lower chamber (10) is used to install a gas collecting plate (11), lower layer graphite bricks (16), middle layer graphite bricks (17), upper layer graphite bricks (18), and a graphite ball bed (7); wherein, the graphite ball bed (7) is located in the cavity formed by the lower layer graphite bricks (16), middle layer graphite bricks (17), and upper layer graphite bricks (18), and is used to simulate the graphite ball bed structure in the core of a high-temperature gas-cooled reactor; the gas collecting plate (11) is installed in a groove formed by the lower layer graphite bricks (16) surrounding the bottom of the lower chamber (10), and is used for The graphite ball bed (7) is supported and the high-temperature gas working medium is collected and gathered. The gas collecting plate (11) has gas collecting grooves (111) in each direction from the center point to the top of the plate, arranged in a central radial pattern, to guide the gas at the bottom of the device to converge to the outlet pipe (13). The bottom of the lower chamber (10) is opened with an outlet channel connected to the outlet pipe (13) for exporting the gas working medium. The outlet pipe (13) is provided with an outlet pressure tap (12) and an outlet temperature measuring conduit (14) for installing an outlet temperature sensor (15). The upper temperature measuring conduit (19) is located outside the temperature measuring channel (23) between graphite bricks composed of upper graphite bricks (18) and middle graphite bricks (17), and is used to install the upper temperature sensor (21); the lower temperature measuring conduit (20) is located outside the temperature measuring channel (23) between graphite bricks composed of middle graphite bricks (17) and lower graphite bricks (16), and is used to install the lower temperature sensor (22); the upper temperature sensor (21) and the lower temperature sensor (22) are used to measure the gas temperature distribution between graphite bricks under the bypass effect.

2. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 1, characterized in that, The end of the inlet temperature measuring conduit (2) is provided with a temperature sensor sealing sleeve (3) to achieve a seal between the inlet temperature sensor (4) and the inlet temperature measuring conduit (2) and ensure the airtightness at this location; The temperature sensor probe of the inlet temperature sensor (4) is inserted along the inlet temperature measuring conduit (2) to the central axis position of the inlet pipe (1).

3. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 1, characterized in that, The vertical projections of the inlet temperature measuring conduit (2) and the inlet pressure tap (5) are arranged at 180 degrees on the projection plane; the inlet temperature measuring conduit (2) and the inlet pressure tap (5) are both fixed to the inlet pipe (1) by welding.

4. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 1, characterized in that, The outer edge of the upper end cover (6) is provided with eight threaded through holes arranged in a centrally symmetrical manner. The central axis of the through holes coincides with the axis of the eight threaded blind holes on the upper end face of the lower chamber (10). Bolts are used to achieve a fastening connection with the threaded holes. The surface finish of the contact surface between the lower end face of the upper end cover (6) and the upper end face of the lower chamber (10) is required to reach level 6 or above.

5. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 1, characterized in that, The lower chamber (10) is externally cylindrical and internally an octagonal prism cavity for installing the gas collecting plate (11), lower layer graphite bricks (16), middle layer graphite bricks (17), upper layer graphite bricks (18) and graphite ball bed (7); the lower chamber (10) is externally covered with thermal insulation material. The cross-sectional shape of the gas collecting plate (11) is a regular octagonal structure with a plate thickness of 10~20mm. It is installed in the regular octagonal groove formed by eight lower layer graphite bricks (16) at the bottom of the lower chamber (10). The cross-sectional shape of the middle layer graphite brick (17) is an isosceles trapezoid. The side length of the upper base is equal to the side length of the regular octagon of the cross-section of the gas collecting plate (11), and the side length of the lower base is equal to the side length of the regular octagon of the cross-section of the lower chamber (10). The upper and lower end faces of the middle layer graphite brick (17) are parallel to each other and perpendicular to the four edges in the height direction. A quarter graphite keyway (171) and a quarter temperature measuring channel (172) are provided at the two waists of the isosceles trapezoid, which are used to install the upper graphite square key (8), the lower graphite square key (9), the upper temperature sensor (21), and the lower temperature sensor (22), respectively. The temperature measuring channel (23) between the graphite bricks is composed of the quarter temperature measuring channels of four adjacent graphite bricks, which are used to insert the temperature measuring probe of the temperature sensor to measure the temperature of the bypass gas. The difference between the shape and structure of the lower graphite brick (16) and the upper graphite brick (18) and the middle graphite brick (17) is that the lower graphite brick (16) is provided with a graphite keyway and a temperature measuring channel on the upper end face, while the upper graphite brick (18) is provided with a graphite keyway and a temperature measuring channel on the lower end face. The lower layer graphite bricks (16) are installed in a ring around the bottom of the regular octagonal prism cavity in the lower chamber (10); the middle layer graphite bricks (17) are stacked on top of the lower layer graphite bricks (16), and the two layers of graphite bricks are connected and fixed by the lower layer graphite square key (9); the upper layer graphite bricks (18) are stacked on top of the middle layer graphite bricks (17), and the two layers of graphite bricks are connected and fixed by the upper layer graphite square key (8); the graphite bricks are stacked to form a graphite cavity.

6. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 5, characterized in that, The gas collecting plate (11) has gas collecting grooves (111) in each direction from the center point of the plate to the eight vertices, arranged radially from the center; the cross-sectional shape of the gas collecting grooves (111) is rectangular with rounded ends.

7. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 5, characterized in that, The upper graphite square key (8) adopts the form of a B-type key, that is, the two ends are square and the cross-sectional shape is rectangular; the twelve edges of the upper graphite square key (8) are rounded to reduce the stress at the edges; the lower graphite square key (9) and the upper graphite square key (8) have the same shape, structure and material, the only difference is the installation position of the two.

8. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 1, characterized in that, The graphite ball bed (7) is composed of several graphite balls with a diameter of 5~8mm; under the action of gravity, the graphite balls are randomly stacked and distributed inside the cavity composed of graphite bricks. The graphite balls are solid and have no heat source inside.

9. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 1, characterized in that, There are eight upper temperature measuring conduits (19) in total, arranged radially, and all are fixed to the side wall of the lower chamber (10) by welding. The end of the upper temperature measuring conduit (19) is provided with a temperature sensor sealing sleeve (3) to achieve a seal between the upper temperature sensor (21) and the upper temperature measuring conduit (19). The shape and structure of the lower temperature measuring conduit (20) are the same as those of the upper temperature measuring conduit (19).

10. The experimental apparatus for studying the bypass characteristics of a pebble bed type high-temperature gas-cooled reactor core according to claim 1, characterized in that, The outlet pressure tap (12) is arranged at the outlet pipe (13) by welding and cooperates with the inlet pressure tap (5) to measure the pressure difference generated by the high temperature and high pressure gas working medium flowing through the entire device; The outlet temperature measuring conduit (14) is arranged below the outlet pressure tap (12) to prevent the outlet temperature sensor (15) from interfering with the accurate measurement of pressure and pressure difference due to the flow around the airflow.

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