Testing device and method for measuring equivalent heat conductivity coefficient of pebble bed reactor core

Abstract

The invention discloses a pebble bed reactor core equivalent heat conductivity coefficient measurement test device, which comprises a pebble bed simulation body, a first graphite nodule and a second graphite nodule, and the pebble bed simulation body comprises a graphite nodule placing cavity; the first graphite nodule is placed in the graphite nodule placing cavity, a heating wire is arranged in the first graphite nodule, and the heating wire is connected with a heating wire; the second graphite nodules are isostatic pressing graphite nodules, are placed in the graphite nodule placing cavity and surround the first graphite nodules; and a plurality of first graphite nodules and a plurality of second graphite nodules are arranged. According to the test device for measuring the equivalent heat conductivity coefficient of the pebble-bed reactor core, the temperature distribution of the pebble-bed reactor core is closer to that of an actual high-temperature gas cooled reactor, the test reduction degree is higher, and the accuracy of test data of the equivalent heat conductivity coefficient of the pebble-bed reactor core is higher. The invention further provides a test method for measuring the equivalent heat conductivity coefficient of the pebble bed reactor core.

Description

Technical Field

[0001] The invention relates to the technical field of pebble bed cores of nuclear power high temperature gas-cooled reactors, and in particular to a test device and method for measuring equivalent thermal conductivity of a pebble bed core. Background Art

[0002] The accident of loss of forced cooling is one of the important design basis accidents of high temperature gas-cooled reactors. According to the safety design criteria of high temperature pebble bed reactors under accidents, the decay heat of the core must be able to be conducted out of the reactor by non-active means such as heat conduction and radiation. If the decay heat cannot be conducted out of the reactor in time, the maximum temperature of the fuel will exceed the safety limit of 1600℃, which will cause the damage of the coated fuel particles and release a large amount of fission products. The equivalent thermal conductivity of the core pebble bed is a macroscopic parameter that comprehensively reflects the heat transfer capacity of the pebble bed reactor. It is an equivalent parameter that considers the core of the high temperature gas-cooled reactor formed by the accumulation of spherical fuel elements as a single uniform porous medium and comprehensively considers the heat transfer in the pebble bed by heat conduction, convection and radiation. Therefore, the experimental study of the equivalent thermal conductivity of the pebble bed is of great significance for the improvement of the reactor analysis program, the possibility of improving the power of a single high temperature gas-cooled reactor, and the safety analysis of the project.

[0003] At present, when measuring the equivalent thermal conductivity of the pebble bed core, the heating method is mostly to surround the cylindrical pebble bed with an electromagnetic induction heating coil to transfer heat from the outside to the inside; or to use a central heating rod set in the cylindrical pebble bed to transfer heat from the inside to the outside to simulate the high temperature environment of the high-temperature pebble bed. The above two heating methods in the prior art are far from the actual heating and heat transfer of the heat source in the pebble bed of a high-temperature gas-cooled reactor, resulting in a large distortion in the test data of the equivalent thermal conductivity of the pebble bed core. Summary of the invention

[0004] In view of this, the present invention provides a test device for measuring the equivalent thermal conductivity of a pebble bed core, so that the temperature distribution of the pebble bed core is closer to the temperature distribution of an actual high-temperature gas-cooled reactor, the test reduction degree is higher, and the test data of the equivalent thermal conductivity of the pebble bed core is more accurate.

[0005] The invention also provides a test method for measuring the equivalent thermal conductivity of a pebble bed core.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A test device for measuring equivalent thermal conductivity of a pebble bed core, comprising:

[0008] A ball bed simulation body, including a graphite ball placement cavity;

[0009] A first graphite ball is placed in the graphite ball placement cavity, a heating wire is arranged in the first graphite ball, and the heating wire is connected to a heating wire;

[0010] The second graphite ball is an isostatically pressed graphite ball, which is placed in the graphite ball placement cavity and surrounds the first graphite ball;

[0011] A plurality of the first graphite balls and a plurality of the second graphite balls are provided.

[0012] Optionally, a filling hemisphere is arranged between the second graphite ball and the cavity wall of the graphite ball placement cavity, and one side of the filling hemisphere contacts the adjacent second graphite ball, and the other side contacts the cavity wall of the graphite ball placement cavity.

[0013] Optionally, a thermocouple is installed on the first graphite ball and / or the second graphite ball;

[0014] There are a plurality of thermocouples, and at most one thermocouple is arranged on each graphite ball;

[0015] The thermocouple is threadedly connected to the sphere of the first graphite ball or the second graphite ball.

[0016] Optionally, the first graphite ball includes a first spherical shell and a second spherical shell connected together, and the heating wire is arranged in a containing chamber surrounded by the first spherical shell and the second spherical shell;

[0017] The first spherical shell or the second spherical shell is provided with a through hole, and the through hole is used for a heating wire connected to the heating wire to pass through.

[0018] Optionally, the first spherical shell and the second spherical shell are connected by threads.

[0019] Optionally, the accommodating chamber surrounded by the first spherical shell and the second spherical shell is filled with insulating thermally conductive powder.

[0020] Optionally, a pressure shell is provided outside the ball bed simulation body, the ball bed simulation body is placed inside the pressure shell, a high-pressure gas inlet and a vacuum port are provided on the pressure shell, and the inner cavity of the pressure shell is connected to the graphite ball placement cavity of the ball bed simulation body;

[0021] The high-pressure gas inlet is communicated with a high-pressure gas source, and the vacuum pumping port is communicated with a vacuum pumping device.

[0022] Optionally, the bottom of the ball bed simulation body is spaced apart from the inner bottom surface of the pressure shell by a first set distance, so that an air intake cavity is formed between the bottom of the ball bed simulation body and the inner bottom surface of the pressure shell, and the air intake cavity is communicated with the high-pressure gas inlet port;

[0023] The top of the ball bed simulation body is spaced apart from the inner top surface of the pressure shell by a second set distance, so that an air outlet cavity is formed between the top of the ball bed simulation body and the inner top surface of the pressure shell, and the air outlet cavity is communicated with the vacuum port;

[0024] The outer side surface of the ball bed simulation body contacts the inner surface of the pressure shell.

[0025] Optionally, the ball bed simulation body includes a graphite crucible, the first graphite ball and the second graphite ball are placed in the graphite crucible, and a fireproof brick layer is provided on the periphery of the graphite crucible.

[0026] It can be seen from the above technical scheme that the equivalent thermal conductivity measurement test device for the pebble bed core provided by the present invention can better simulate the situation that the heat source of the pebble bed comes from the inside of the ball and the middle of the ball pile by placing a first graphite ball with a heating wire inside the ball in the graphite ball placement cavity and placing a second graphite ball without a heating source around the first graphite ball. The heating condition is the same as that of an actual high-temperature gas-cooled reactor, so that the temperature distribution of the pebble bed core is closer to that of an actual high-temperature gas-cooled reactor, the test reduction degree is higher, and the test data of the equivalent thermal conductivity of the pebble bed core is more accurate, and the obtained test data is more reliable. The first graphite ball is electrically heated so that the heating power is controllable and the test device has a wider temperature range.

[0027] The present invention also provides a method for measuring the equivalent thermal conductivity of a pebble bed core, which is applied to the above-mentioned device for measuring the equivalent thermal conductivity of a pebble bed core, and comprises:

[0028] A heating wire for heating the sphere is arranged in the first graphite sphere, and the heating wire is connected to a power source through a heating wire;

[0029] A plurality of the first graphite balls are placed in a graphite ball placement cavity of a ball bed simulation body, and second graphite balls are placed at the bottom, top and surrounding of the first graphite balls, wherein the second graphite balls are isostatically pressed graphite balls.

[0030] The pebble bed core equivalent thermal conductivity measurement test method of the present invention is applied to the above-mentioned pebble bed core equivalent thermal conductivity measurement test device, and therefore has the advantages of the above-mentioned pebble bed core equivalent thermal conductivity measurement test device, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic diagram of the structure of a test device for measuring equivalent thermal conductivity of a pebble bed core provided by an embodiment of the present invention;

[0033] Figure 2 A schematic cross-sectional view of a ball bed simulation body provided by an embodiment of the present invention at one angle;

[0034] Figure 3 A schematic cross-sectional view of the pebble bed simulation body provided by an embodiment of the present invention from another angle;

[0035] Figure 4 A schematic structural diagram of a first graphite ball provided in one embodiment of the present invention;

[0036] Figure 5 for Figure 4 A schematic diagram of the cross-sectional structure of the first graphite ball;

[0037] Figure 6 for Figure 4 A schematic cross-sectional structural diagram of a first spherical shell of a first graphite sphere;

[0038] Figure 7 for Figure 4 A schematic cross-sectional structural diagram of a second spherical shell of a first graphite sphere;

[0039] Figure 8 A schematic cross-sectional structural diagram of a first graphite ball provided in another embodiment of the present invention.

[0040] in:

[0041] 1. Ball bed simulation body,

[0042] 101, first graphite ball, 1011, first spherical shell, 1012, second spherical shell, 1013, through hole, 1014, threaded hole, 1015, first thread, 1016, second thread, 102, second graphite ball, 103, graphite crucible, 104, fire brick layer, 105, filling hemisphere,

[0043] 2. Thermocouple,

[0044] 3. Pressure sensor,

[0045] 4. Heating wire,

[0046] 5. Pressure shell,

[0047] 6. Vacuum pump,

[0048] 7. Emptying device,

[0049] 8. High-pressure gas cylinders,

[0050] 9. The first valve,

[0051] 10. Safety valve,

[0052] 11. Second valve,

[0053] 12. The third valve,

[0054] 13. Empty the branch line. DETAILED DESCRIPTION

[0055] The present invention discloses a test device for measuring the equivalent thermal conductivity of a pebble bed core, which makes the temperature distribution of the pebble bed core closer to the temperature distribution of an actual high-temperature gas-cooled reactor, the test reduction degree is higher, and the test data of the equivalent thermal conductivity of the pebble bed core is more accurate.

[0056] The invention also discloses a test method for measuring the equivalent thermal conductivity of a pebble bed core.

[0057] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] See also Figures 1 to 8 The present invention provides a test device for measuring equivalent thermal conductivity of a pebble bed core, comprising a pebble bed simulation body 1, a first graphite ball 101 and a second graphite ball 102. The pebble bed simulation body 1 comprises a graphite ball placement cavity, and the first graphite ball 101 and the second graphite ball 102 are both placed in the graphite ball placement cavity. A heating wire is arranged in the first graphite ball 101, and the heating wire is connected to a power source through a heating wire 4, so as to realize electrical heating of the heating wire. The second graphite ball 102 is a solid isostatically pressed graphite ball, and the second graphite ball 102 surrounds the first graphite ball 101.

[0059] There are multiple first graphite balls 101 and multiple second graphite balls 102 .

[0060] The test device for measuring equivalent thermal conductivity of the pebble bed core of the present invention can better simulate the situation that the heat source of the pebble bed comes from the inside of the ball and the middle of the ball pile by placing a first graphite ball 101 with a heating wire in the ball in the graphite ball placement cavity and placing a second graphite ball 102 without a heating source around the first graphite ball 101. The heating condition is the same as that of an actual high-temperature gas-cooled reactor, so that the temperature distribution of the pebble bed core is closer to that of an actual high-temperature gas-cooled reactor, the test reduction degree is higher, the test data of the equivalent thermal conductivity of the pebble bed core is more accurate, and the obtained test data is more reliable. The first graphite ball 101 is electrically heated so that the heating power is controllable and the test device has a wider temperature range.

[0061] In order to avoid the gap between the cavity wall of the graphite ball placement cavity and the second graphite ball 102 being too large, a filling hemisphere 105 is arranged between the second graphite ball 102 and the cavity wall of the graphite ball placement cavity, and one side of the filling hemisphere 105 contacts the adjacent second graphite ball 102, and the other side contacts the cavity wall of the graphite ball placement cavity. In order to improve the fit, the surface of the filling hemisphere 105 in contact with the cavity wall of the graphite ball placement cavity is polished into an arc surface that follows the cavity wall, thereby increasing the contact area between the filling hemisphere 105 and the cavity wall of the graphite ball placement cavity, thereby avoiding the gas from flowing out too quickly when the flowing gas working medium is filled into the graphite ball placement cavity, and the gas that flows out too quickly cannot play a good heat transfer role.

[0062] In order to facilitate the detection of the temperature of the graphite ball, a thermocouple 2 can be installed on the first graphite ball 101 and the second graphite ball 102. Among them, there are several thermocouples 2, and the several here refers to the total number of thermocouples 2. At most one thermocouple 2 is set on each graphite ball, that is, one thermocouple 2 can be set on a graphite ball, or no thermocouple 2 can be set. Thermocouples 2 are set on the surface of graphite balls at different layers, and can also be set on the surfaces of different graphite balls in the same layer to detect the temperature of graphite balls at different positions. Specifically, each layer of graphite ball layer selects several graphite balls to set thermocouples 2 as needed, and the specific number is determined by those skilled in the art. Each thermocouple 2 is connected to a temperature measuring wire, so that the ball bed simulation body 1 will lead to multiple temperature measuring wires. By setting multiple thermocouples 2, the temperature distribution inside the ball bed simulation body 1 can be better measured, which is conducive to analyzing the heat transfer phenomenon in the entire test cavity. In one embodiment, the thermocouple 2 is threadedly connected to the sphere of the first graphite ball 101 or the second graphite ball 102. To identify thermocouple 2, Figure 1 In the figure, thermocouple 2 is connected to its temperature measuring wire for marking.

[0063] Wherein, the graphite balls are arranged in a prescribed distribution manner, preferably, as Figure 3 As shown, the line connecting the centers of the three graphite balls in contact with each other in the same layer forms an equilateral triangle, that is, the three graphite balls in contact are arranged in an equilateral triangle.

[0064] In one embodiment, the first graphite ball 101 includes a first ball shell 1011 and a second ball shell 1012 connected together, and the heating wire for heating is arranged in a receiving chamber surrounded by the first ball shell 1011 and the second ball shell 1012. In order to facilitate connection with a power source, a through hole 1013 is arranged on the first ball shell 1011 or the second ball shell 1012, and the through hole 1013 is used for the heating wire 4 connected to the heating wire to pass through. Specifically, as Figures 5 to 7As shown, the through hole 1013 is provided on the first spherical shell 1011, and the threaded hole 1014 for connecting the thermocouple 2 is also provided on the first spherical shell 1011. The first spherical shell 1011 is provided with a first thread 1015 near the second spherical shell 1012, and the second spherical shell 1012 is provided with a second thread 1016 near the first spherical shell 1011, and the first thread 1015 and the second thread 1016 are provided in coordination.

[0065] In another embodiment, if Figure 8 As shown, the through hole 1013 is provided on the second spherical shell 1012, and the threaded hole 1014 is provided on the first spherical shell 1011. It can be understood that the through hole 1013 and the threaded hole 1014 can also be provided on the second spherical shell 1012 at the same time.

[0066] In order to facilitate the transfer of heat generated by the heating wire to the surface of the sphere, the accommodating chamber surrounded by the first spherical shell 1011 and the second spherical shell 1012 is filled with insulating thermally conductive powder, which is a common material in the prior art and is not limited here.

[0067] In order to adjust the pressure environment of the ball bed simulation body 1, a pressure shell 5 is provided outside the ball bed simulation body 1, and the ball bed simulation body 1 is placed in the pressure shell 5. The pressure shell 5 is provided with a high-pressure gas inlet and a vacuum port, and the inner cavity of the pressure shell 5 is connected with the graphite ball placement cavity of the ball bed simulation body 1. The high-pressure gas inlet is connected with the high-pressure gas source, and the vacuum port is connected with the vacuum device. Specifically, the high-pressure gas source is a high-pressure gas cylinder 8, and the high-pressure gas cylinder 8 contains high-pressure gas. The connecting pipeline between the high-pressure gas cylinder 8 and the pressure shell 5 is provided with a first valve 9 and a safety valve 10. In order to facilitate the heat exchange of the graphite balls in the ball bed simulation body 1, the high-pressure gas can flow into the ball bed simulation body 1. The vacuum device is a vacuum pump 6, and a second valve 11 is provided at the front end of the vacuum pump 6. The front end of the vacuum pump 6 refers to the end of the vacuum pump 6 close to the pressure shell 5. An emptying device 7 is provided at the rear end of the vacuum pump 6. Specifically, the emptying device 7 can be an emptying valve. The vacuum pump 6 is used to evacuate the ball bed simulation body 1, and the high-pressure gas cylinder 8 is used to fill the ball bed simulation body 1 with a specific gas. In order to facilitate direct emptying, an emptying branch 13 is also provided, and a third valve 12 is provided on the emptying branch 13. The pressure housing 5 is provided with a pressure sensor 3 for monitoring the pressure inside the pressure housing 5.

[0068] In order to facilitate the gas circulation and heat exchange in the pressure shell 5, the bottom of the ball bed simulation body 1 is spaced apart from the inner bottom surface of the pressure shell 5 by a first set distance, thereby forming an air inlet cavity between the bottom of the ball bed simulation body 1 and the inner bottom surface of the pressure shell 5, and the air inlet cavity is connected to the high-pressure gas inlet port. The top of the ball bed simulation body 1 is spaced apart from the inner top surface of the pressure shell 5 by a second set distance, thereby forming an air outlet cavity between the top of the ball bed simulation body 1 and the inner top surface of the pressure shell 5, and the air outlet cavity is connected to the vacuum port, and the outer side surface of the ball bed simulation body 1 is in contact with the inner surface of the pressure shell 5, so as to avoid the air inlet cavity and the air outlet cavity being directly connected through the gap between the side walls of the two. Among them, the first set distance and the second set distance are set by those skilled in the art according to actual needs. The pressure shell 5 is made of 304 stainless steel.

[0069] Specifically, the ball bed simulation body 1 includes a graphite crucible 103, in which the first graphite ball 101 and the second graphite ball 102 are placed, and a fireproof brick layer 104 is arranged on the periphery of the graphite crucible 103. The material of the fireproof brick layer 104 is alumina.

[0070] In a specific embodiment, a ball bed simulation body 1 formed by stacking 209 graphite balls is arranged in the graphite crucible 103. The ball bed simulation body 1 is provided with an inlet and outlet of the temperature measuring wire of the thermocouple 2 and the heating wire 4 of the heating wire. The inlet and outlet positions are sealed with high-temperature sealant. A vacuum port and a high-pressure gas inlet are arranged on the side of the pressure shell 5 for vacuuming and filling the ball bed simulation body 1 with a specific gas. Among them, the inner diameter of the graphite crucible 103 of the ball bed simulation body 1 is 300 mm, and the graphite balls with an outer diameter of 60 mm are filled in the graphite crucible 103. The graphite balls include a first graphite ball 101 and a second graphite ball 102. The first graphite ball 101 is a graphite ball with an internal heat source, and the second graphite ball 102 is a graphite ball without an internal heat source. The graphite balls in the same layer are arranged in a regular triangle. Specifically, the outer diameter of the first graphite ball 101 is 60 mm, the inner diameter is 40 mm, and the ball body is composed of two hollow hemispheres, the first ball shell 1011 and the second ball shell 1012. The threaded hole 1014 is provided in the first ball shell 1011, and is used for the installation and fixation of the thermocouple 2. The through hole 1013 is provided in the first ball shell 1011, and the aperture of the through hole 1013 is 8 mm, which is used for the lead-out of the heating wire 4, and the lead-out position is installed with a porcelain bead for insulation. The heating wire in the first graphite ball 101 is a molybdenum wire, which is used to simulate the nuclear heat release of the prototype TRISO fuel ball. The heating wire is heated by an AC power supply, and the heating power is feedback-regulated by a voltage regulator. The first graphite ball 101 is evenly filled with insulating heat-conducting powder. The second graphite ball 102 is an isostatically pressed graphite ball with a diameter of 60 mm, a density of about 1.73 g / cm3, and a thermal conductivity (1000°C) of about 30 W / (m•K).

[0071] Furthermore, in order to simulate the heat transition zone above and below the core active section, 11 layers of graphite balls are filled in the graphite crucible 103 along the working medium flow direction, with a total height of about 660 mm, of which the height of the heating section is about 300 mm, i.e., five layers of the first graphite balls 101, such as Figure 2 As shown. The graphite balls in the graphite crucible 103 can be divided into three areas from bottom to top, namely the inlet section, the heating section and the outlet section. The inlet section and the outlet section here are defined according to the flow direction of the gas. The high-pressure working fluid gas enters from the bottom of the ball bed simulation body 1 and flows out from the top. The inlet section area is from the 1st layer to the 3rd layer from bottom to top, with a total of 93 graphite balls, including 57 second graphite balls 102 and 36 filling hemispheres 105. All graphite balls in this area do not generate heat. The heating section area is from the 4th layer to the 8th layer from bottom to top, with a total of 155 graphite balls (including hemispheres), including 35 first graphite balls 101 that generate heat. 120 non-heating graphite balls are arranged around the first graphite balls 101, including 60 second graphite balls 102 and 60 filling hemispheres 105. The exit section area is the 9th layer to the 11th layer from bottom to top, with a total of 93 graphite balls, of which 57 are second graphite balls 102 and 36 are filling hemispheres 105. All graphite balls in this area do not generate heat.

[0072] Before the test begins, the test circuit is adjusted through the high-pressure gas cylinder 8 and the vacuum pump 6 so that the inner cavity of the pressure shell 5 reaches a predetermined pressure. The heating wire in the first graphite ball 101 is energized and adjusted to a predetermined power, and the vacuum pump 6 is turned off. During the test, the temperature change of the test section is monitored. When the temperature of the test section remains stable, the temperature, pressure and other data of the test section are recorded. After the test is completed, the heating wire in the first graphite ball 101 is stopped from being energized; the external fan is started, and the fan is stopped when the temperature of the first graphite ball 101 drops below 300°C; the test is completed.

[0073] The present invention discloses a test device for measuring equivalent thermal conductivity of a pebble bed core, wherein the pebble bed simulation body 1 includes a first graphite ball 101 with an internal heat source and a second graphite ball 102 without an internal heat source, wherein the first graphite ball 101 has a heating wire inside, and the graphite ball with the heating wire inside is used to simulate a self-heating nuclear fuel ball, and the first graphite ball 101 is electrically heated under specific atmosphere conditions, and the temperature change of the fuel simulation balls at various locations in the pebble bed and the temperature distribution characteristics of the pebble bed in the axial and radial directions are measured, and then the thermal conductivity under three conditions of radiation heat transfer, radiation and contact heat conduction, and radiation, contact heat conduction and convection heat transfer is calculated, and the correctness of the theoretical model is evaluated and verified, and the missing test data at 1600°C-1800°C is filled, so as to support research work such as subsequent reactor power increase of high-temperature reactors and evaluation of TRISO fuel damage share.

[0074] The pebble bed core equivalent thermal conductivity measurement test device of the present invention has a pebble bed heat source from the inside of the simulated sphere, which is the same as an actual high-temperature gas-cooled reactor. The pebble bed core temperature distribution is similar to that of an actual high-temperature gas-cooled reactor, and the test reduction degree is higher. The heating power of the electrically heated graphite sphere is controllable, and a wider temperature range can be studied with a higher upper limit. The size and porosity of the simulated sphere are consistent with those of the actual pebble bed, and the test results are more accurate.

[0075] The present invention also provides a test method for measuring the equivalent thermal conductivity of a pebble bed core, which is applied to the above-mentioned test device for measuring the equivalent thermal conductivity of a pebble bed core, comprising: a heating wire for heating the sphere is arranged in the first graphite ball 101, and the heating wire is connected to a power supply through a heating wire 4; a plurality of first graphite balls 101 are placed in a graphite ball placement cavity of a pebble bed simulation body 1, and second graphite balls 102 are placed at the bottom, top and around the first graphite balls 101, and the second graphite balls 102 are isostatically pressed graphite balls.

[0076] In the description of this solution, it should be understood that the terms "upper", "lower", "vertical", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this solution.

[0077] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this solution, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0078] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0079] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A test device for measuring equivalent thermal conductivity of a pebble bed core, characterized in that: include: A ball bed simulation body, including a graphite ball placement cavity; A first graphite ball is placed in the graphite ball placement cavity, a heating wire is arranged in the first graphite ball, and the heating wire is connected to a heating wire; The second graphite ball is an isostatically pressed graphite ball, which is placed in the graphite ball placement cavity and surrounds the first graphite ball; A plurality of the first graphite balls and a plurality of the second graphite balls are provided.

2. The pebble bed core equivalent thermal conductivity measurement test device according to claim 1, characterized in that: A filling hemisphere is arranged between the second graphite ball and the cavity wall of the graphite ball placement cavity, one side of the filling hemisphere contacts the adjacent second graphite ball, and the other side contacts the cavity wall of the graphite ball placement cavity.

3. The pebble bed core equivalent thermal conductivity test device according to claim 1 or 2, characterized in that: A thermocouple is installed on the first graphite ball and / or the second graphite ball; There are a plurality of thermocouples, and at most one thermocouple is arranged on each graphite ball; The thermocouple is threadedly connected to the sphere of the first graphite ball or the second graphite ball.

4. The pebble bed core equivalent thermal conductivity test device according to claim 1, characterized in that: The first graphite ball comprises a first spherical shell and a second spherical shell connected together, and the heating wire is arranged in a containing chamber surrounded by the first spherical shell and the second spherical shell; The first spherical shell or the second spherical shell is provided with a through hole, and the through hole is used for a heating wire connected to the heating wire to pass through.

5. The pebble bed core equivalent thermal conductivity test device according to claim 4, characterized in that: The first spherical shell and the second spherical shell are connected by threads.

6. The pebble bed core equivalent thermal conductivity test device according to claim 4, characterized in that: The accommodating chamber surrounded by the first spherical shell and the second spherical shell is filled with insulating heat-conductive powder.

7. The pebble bed core equivalent thermal conductivity test device according to claim 1 or 2, characterized in that: A pressure shell is arranged outside the ball bed simulation body, the ball bed simulation body is placed inside the pressure shell, a high-pressure gas inlet and a vacuum port are arranged on the pressure shell, and the inner cavity of the pressure shell is connected with the graphite ball placement cavity of the ball bed simulation body; The high-pressure gas inlet is communicated with a high-pressure gas source, and the vacuum pumping port is communicated with a vacuum pumping device.

8. The pebble bed core equivalent thermal conductivity test device according to claim 7, characterized in that: The bottom of the ball bed simulation body is spaced apart from the inner bottom surface of the pressure shell by a first set distance, so that an air inlet cavity is formed between the bottom of the ball bed simulation body and the inner bottom surface of the pressure shell, and the air inlet cavity is communicated with the high-pressure gas inlet port; The top of the ball bed simulation body is spaced apart from the inner top surface of the pressure shell by a second set distance, so that an air outlet cavity is formed between the top of the ball bed simulation body and the inner top surface of the pressure shell, and the air outlet cavity is communicated with the vacuum port; The outer side surface of the ball bed simulation body contacts the inner surface of the pressure shell.

9. The pebble bed core equivalent thermal conductivity test device according to claim 1, characterized in that: The ball bed simulation body comprises a graphite crucible, the first graphite ball and the second graphite ball are placed in the graphite crucible, and a fireproof brick layer is arranged on the periphery of the graphite crucible.

10. A test method for measuring equivalent thermal conductivity of a pebble bed core, characterized in that: The test device for measuring equivalent thermal conductivity of a pebble bed core as claimed in any one of claims 1 to 9 comprises: A heating wire for heating the sphere is arranged in the first graphite sphere, and the heating wire is connected to a power source through a heating wire; A plurality of the first graphite balls are placed in a graphite ball placement cavity of a ball bed simulation body, and second graphite balls are placed at the bottom, top and surrounding of the first graphite balls, wherein the second graphite balls are isostatically pressed graphite balls.

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