A miniaturized reactor core makeup tank natural circulation and gravity discharge experimental device and method

Abstract

This invention belongs to the field of natural circulation experimental technology, specifically relating to a miniaturized experimental device and method for natural circulation and gravity discharge of a core makeup tank. The invention uses a spherical tank to simulate the prototype CMT (Cyclic Motion Tank), allowing the free surface to oscillate with a uniform cross-section under ocean motion, facilitating mechanistic research and data analysis. The invention employs a modular design for the CMT experimental device and reserves an interface for connecting the steam system, greatly improving the flexibility of the steam-side system design and solving site layout issues. The invention adopts a miniaturized design, fixing the entire experimental device module within a steel frame, resulting in lightweight, compact structure, low center of gravity, and small size, facilitating overall hoisting. It can also be installed on ocean motion simulation platforms with limited space, improving the safety and convenience of ocean motion experiments, saving experimental time, and increasing experimental efficiency.

Description

Technical Field

[0001] This invention belongs to the field of natural circulation experimental technology, specifically relating to a miniaturized reactor core makeup water tank natural circulation and gravity discharge experimental device and method. Background Technology

[0002] Third-generation nuclear power units typically have two core makeup water tanks within the containment structure, capable of providing injection flow for extended periods. These tanks are exposed within the containment, without heating or insulation, and are filled with low-temperature concentrated borosilicate water at the same temperature as the containment environment. The injection of core makeup water into these tanks can be divided into two processes: if the primary coolant loop is full, injection is performed via water circulation, driven by the density difference between the high-temperature borosilicate water on the balancing line and the cold water in the tank; if the primary coolant loop water level decreases to the point where a steam cavity appears in the cold section, injection is performed via steam pressure injection, driven by the density difference between the steam in the cold section and the cold water in the tank. The core makeup water tank replaces the high-pressure safety injection system, providing a passive and reliable technical measure to ensure the nuclear power plant remains safe under accident conditions. Therefore, scholars both domestically and internationally have conducted extensive research on natural circulation and gravity discharge phenomena related to CMT (Continuous Metal-Injected Machining) safety injection.

[0003] With the expansion of nuclear energy applications into marine scenarios, the impact of various additional inertial accelerations brought about by the marine environment on the safety characteristics of CMT has become a key issue of concern in the research and design of nuclear energy systems. However, most current core makeup tank experimental devices are designed for land-based use, and the experimental devices are large in scale and heavy in weight, making it difficult to install them on different marine motion simulation platforms for experimental research. Therefore, it is necessary to design an experimental device that is compact in layout and lightweight in overall weight, and can be applied to marine motion simulation platforms to meet the experimental needs of CMT safety characteristics research in marine environments. Summary of the Invention

[0004] The purpose of this invention is to provide a miniaturized experimental apparatus and method for natural circulation and gravity discharge of a core makeup water tank, which can simulate the safety characteristics of natural circulation and gravity discharge operation of the core makeup water tank during a nuclear power plant accident. At the same time, it can meet the requirements of marine motion environment simulation experiments, can be used under severe motion conditions, and is ultimately used to obtain the safety characteristics of CMT under marine conditions.

[0005] A miniaturized reactor core makeup tank natural circulation and gravity discharge experimental device includes a spherical CMT tank, a pressurized water storage tank, a steam distributor, a natural circulation branch, a steam injection branch, a CMT discharge pipeline, and a steam supply and heating branch; the spherical CMT tank is located above the pressurized water storage tank; the steam distributor is installed at the upper inlet of the spherical CMT tank;

[0006] The natural circulation branch includes a first ball valve. One end of the first ball valve is connected to the inlet pipe of the steam distributor through a pipeline, and the other end is connected to the first thermocouple, the first electromagnetic flowmeter, the first pressure sensor and the second thermocouple in sequence through a pipeline. The ball valve then extends into the interior of the pressure-stabilizing water tank from the natural circulation inlet at the top of the pressure-stabilizing water tank.

[0007] The steam injection branch includes a steam warm-up circuit valve and a second ball valve. One end of the second ball valve is connected to the inlet pipe of the steam distributor through a pipeline, and the other end is connected in sequence to the third thermocouple, the vortex flow meter, the second pressure sensor, the fourth thermocouple, and the steam outlet at the top of the pressure-stabilizing water tank through a pipeline. One end of the steam warm-up circuit valve is connected to the pipeline between the second ball valve and the third thermocouple.

[0008] The CMT discharge pipeline includes a water inlet valve, a drain valve, and a third ball valve. One end of the third ball valve is connected sequentially to the fifth thermocouple and the lower outlet of the spherical CMT tank via a pipeline, and the other end is connected sequentially to the second electromagnetic flowmeter, a check valve, and the outlet at the lower end of the pressure-stabilizing water tank via a pipeline. One end of the water inlet valve is connected to the pipeline between the third ball valve and the fifth thermocouple. One end of the drain valve is connected to the pipeline between the check valve and the outlet at the lower end of the pressure-stabilizing water tank. The check valve restricts fluid flow only to the outlet at the lower end of the pressure-stabilizing water tank.

[0009] The steam supply and heating branch includes a steam input end, a steam supply valve, and a heating valve; one end of the steam supply valve is connected to the steam input end through a pipeline, and the other end is connected to the steam inlet at the top of the pressure-stabilizing water tank through a pipeline; one end of the heating valve is connected to the steam input end through a pipeline, and the other end extends into the pressure-stabilizing water tank from the heating port on the bottom side of the tank through a pipeline, with steam nozzles circumferentially provided in the extended portion of the pipeline.

[0010] Furthermore, the steam distributor is connected to the upper inlet of the spherical CMT tank via a flange. The outlet pipe of the steam distributor extends into the interior of the spherical CMT tank. The inlet pipe of the steam distributor merges with the natural circulation branch and the steam injection branch upstream. A fourth ball valve is provided near the merging point as an exhaust outlet.

[0011] Furthermore, the natural circulation branch includes a first horizontal section and a first vertical section. One end of the first horizontal section is connected to the inlet pipe of the steam distributor, and the other end is connected to the upper end of the first vertical section. The lower end of the first vertical section extends from the natural circulation inlet at the upper end of the pressure-stabilizing water tank into the interior of the pressure-stabilizing water tank. The first ball valve and the first thermocouple are installed on the first horizontal section, and the first electromagnetic flowmeter, the first pressure sensor, and the second thermocouple are installed on the first vertical section. A natural circulation warm-up pipe valve is provided on the first horizontal section. The natural circulation warm-up pipe valve is connected to the pipeline between the first ball valve and the first thermocouple and is used as an exhaust outlet.

[0012] Furthermore, the steam injection branch includes a second horizontal section and a second vertical section. One end of the second horizontal section is connected to the inlet pipe of the steam distributor, and the other end is connected to the upper end of the second vertical section. The lower end of the second vertical section is connected to the steam outlet at the upper end of the pressure-stabilizing water storage tank. The second ball valve, the steam warming loop valve, and the third thermocouple are installed on the second horizontal section, and the vortex flow meter, the second pressure sensor, and the fourth thermocouple are installed on the second vertical section.

[0013] Furthermore, the CMT discharge pipeline includes a third horizontal section and a third vertical section. One end of the third horizontal section is connected to the water outlet at the lower end of the pressure-stabilizing water storage tank, and the other end is connected to the lower end of the third vertical section. The upper end of the third vertical section is connected to the lower outlet of the spherical CMT tank. The water inlet valve, the third ball valve, the second electromagnetic flow meter, the check valve, and the drain valve are installed on the third horizontal section. The fifth thermocouple is installed on the third vertical section.

[0014] Furthermore, the CMT discharge pipeline also includes a backup bypass; a fifth ball valve is provided on the pipeline between the second electromagnetic flowmeter and the check valve; a sixth ball valve is provided on the backup bypass, one end of the sixth ball valve is connected to the second electromagnetic flowmeter and the fifth ball valve through a pipeline, and the other end of the sixth ball valve is connected to the water outlet at the lower end of the pressure-stabilizing water storage tank.

[0015] Furthermore, the steam supply and heating branch includes a fourth horizontal section, a fourth vertical section, and a steam heating pipe. One end of the fourth horizontal section is connected to the steam inlet at the upper end of the pressure-stabilizing water tank, and the other end is connected to the upper end of the fourth vertical section. The lower end of the fourth vertical section is connected to one end of the steam heating pipe, and the other end of the steam heating pipe extends into the interior of the pressure-stabilizing water tank from the heating port on the side of the bottom of the pressure-stabilizing water tank. The steam input end is installed at the upper end of the fourth vertical section, the steam supply valve is installed on the fourth horizontal section, and the heating valve is installed on the fourth vertical section.

[0016] An experimental method for natural circulation and gravity discharge of a miniaturized reactor core makeup tank includes the following steps:

[0017] Step 1: Open the water inlet valve, the first ball valve, the second ball valve, the third ball valve, and the steam warming pipe circuit valve, and close the other valves; fill the experimental device with water through the water inlet valve. When there is a continuous flow of fluid from the steam warming pipe circuit valve, it means that the experimental device is full. Then close all valves.

[0018] Step 2: Open the steam warming pipe loop valve and drain valve to partially drain the water in the pressure-stabilizing water tank, ensuring that the end of the pipe extending from the natural circulation branch into the pressure-stabilizing water tank is submerged in water with a certain water level reserved so that air will not enter the end of the pipe during marine motion condition tests; after draining, close the steam warming pipe loop valve and drain valve.

[0019] Step 3: Open the heating valve and input high-temperature steam into the water in the pressure-stabilizing water tank to heat the water in the tank. When the experimental working condition is reached, close the heating valve. At this time, the large amount of saturated water in the pressure-stabilizing water tank can act as a pressure regulator to provide a certain amount of steam and stable pressure for the entire system.

[0020] Step 4: Arrange multiple thermocouples inside the spherical CMT tank to obtain the temperature distribution of the water inside the spherical CMT tank during the experiment;

[0021] Open the third ball valve and the first ball valve, close the second ball valve, and conduct a natural circulation experiment. During the experiment, monitor the water flow rate through the first electromagnetic flow meter, monitor the water temperature through the second thermocouple, monitor the pressure through the first pressure sensor, and monitor the CMT drainage flow rate through the second electromagnetic flow meter. When the driving force of the CMT system is insufficient to maintain the natural circulation flow rate, the experiment is considered to be over. At this time, close the third ball valve and stop collecting data.

[0022] Open the third and second ball valves, close the first ball valve, and conduct a gravity discharge experiment. During the experiment, monitor the steam flow rate through a vortex flow meter, monitor the steam temperature through a fourth thermocouple, monitor the steam pressure through a second pressure sensor, and monitor the CMT drainage flow rate through a second electromagnetic flow meter.

[0023] Step 5: After completing the experiment, drain the experimental apparatus through the drain valve.

[0024] Furthermore, in step 3, steam and pressure can be continuously supplied to the pressure-stabilizing water tank by opening the steam supply valve, so that it reaches the experimental working conditions.

[0025] The beneficial effects of this invention are as follows:

[0026] This invention uses a spherical tank to simulate the prototype CMT (Conductivity, Motion, and Tranquility), allowing the free surface to oscillate with a uniform cross-section under ocean motion, facilitating mechanistic research and data analysis. The invention employs a modular design for the CMT experimental device and includes an interface for connecting the steam system, significantly improving the flexibility of the steam-side system design and solving site layout issues. Furthermore, the invention utilizes a miniaturized design, fixing the entire experimental device module within a steel frame, resulting in lightweight, compact structure, low center of gravity, and small size. This facilitates overall hoisting and allows installation on space-constrained ocean motion simulation platforms, enhancing the safety and convenience of ocean motion experiments, saving experimental time, and increasing experimental efficiency. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a miniaturized reactor core makeup water tank natural circulation and gravity discharge experimental device according to the present invention.

[0028] Figure 2 This is a three-dimensional schematic diagram of a miniaturized reactor core makeup water tank natural circulation and gravity discharge experimental device according to the present invention.

[0029] Figure 3 This is a front view of a miniaturized reactor core makeup water tank natural circulation and gravity discharge experimental device according to the present invention.

[0030] Figure 4 This is a right-side schematic diagram of a miniaturized reactor core makeup water tank natural circulation and gravity discharge experimental device according to the present invention.

[0031] Figure 5 This is a schematic diagram of the bottom surface of a miniaturized reactor core makeup water tank natural circulation and gravity discharge experimental device according to the present invention.

[0032] Figure 6 A schematic diagram of the external steel frame of the experimental device for natural circulation and gravity discharge of a small reactor core makeup water tank.

[0033] Figure 7 for Figure 3 Schematic diagram of the connection point of the natural circulation branch pipeline at the top of the pressure-stabilizing water storage tank in the BB direction.

[0034] Figure 8 for Figure 4 Schematic diagram of the installation of the steam distributor on the upper part of the spherical CMT tank in the AA direction.

[0035] Figure 9 for Figure 4 A schematic diagram of the steam heating pipe structure inside the pressure-stabilizing water storage tank in the CC direction.

[0036] Figure 10 A schematic diagram showing the connection and assembly of the steam supply system for the experimental device of natural circulation and gravity discharge of small reactor core makeup water tank.

[0037] Figure 11 This is an example diagram showing the arrangement of temperature and pressure measuring points in a spherical CMT tank. Detailed Implementation

[0038] The present invention will now be further described with reference to the accompanying drawings.

[0039] The present invention provides a miniaturized reactor core makeup water tank natural circulation and gravity discharge experimental device, including a spherical CMT tank A, a pressure-stabilized water storage tank B, a steam distributor C, a natural circulation branch 1, a steam injection branch 2, a CMT discharge pipeline 3, and a steam supply and heating branch 4.

[0040] The spherical CMT tank A is located above the pressure-stabilizing water storage tank B; the steam distributor C is connected to the upper inlet of the spherical CMT tank A via a flange, the outlet pipe of the steam distributor C extends into the interior of the spherical CMT tank A, and the upstream of the inlet pipe of the steam distributor C merges with the natural circulation branch 1 and the steam injection branch 2. A fourth ball valve 007 is provided near the merging point as an exhaust outlet.

[0041] The natural circulation branch 1 includes a first horizontal section and a first vertical section. One end of the first horizontal section is connected to the inlet pipe of the steam distributor C, and the other end is connected to the upper end of the first vertical section. The lower end of the first vertical section extends from the natural circulation inlet at the upper end of the pressure-stabilizing water storage tank B into the interior of the pressure-stabilizing water storage tank B. A first ball valve 106 and a first thermocouple T104 are installed on the first horizontal section, and a first electromagnetic flowmeter 103, a first pressure sensor P102, and a second thermocouple T101 are installed on the first vertical section. One end of the first ball valve 106... The pipeline connects to the inlet pipe of the steam distributor C, and the other end is connected to the first thermocouple T104, the first electromagnetic flowmeter 103, the first pressure sensor P102 and the second thermocouple T101 in sequence through the pipeline. It extends into the interior of the pressure-stabilizing water storage tank B from the natural circulation inlet at the upper end of the tank. A natural circulation warm-up valve 105 is provided on the first horizontal section. The natural circulation warm-up valve 105 is connected to the pipeline between the first ball valve 106 and the first thermocouple T104 and is used as an exhaust outlet.

[0042] Steam injection branch 2 includes a second horizontal section and a second vertical section. One end of the second horizontal section is connected to the inlet pipe of the steam distributor C, and the other end is connected to the upper end of the second vertical section. The lower end of the second vertical section is connected to the steam outlet at the upper end of the pressure-stabilizing water storage tank B. A second ball valve 206, a steam warm-up loop valve 205, and a third thermocouple T204 are installed on the second horizontal section. A vortex flow meter 203, a second pressure sensor P202, and a fourth thermocouple T201 are installed on the second vertical section. One end of the second ball valve 206 is connected to the inlet pipe of the steam distributor C through a pipeline, and the other end is connected sequentially to the third thermocouple T204, the vortex flow meter 203, the second pressure sensor P202, the fourth thermocouple T201, and the steam outlet at the upper end of the pressure-stabilizing water storage tank B through a pipeline. One end of the steam warm-up loop valve 205 is connected to the pipeline between the second ball valve 206 and the third thermocouple T204.

[0043] CMT discharge pipeline 3 includes a third horizontal section and a third vertical section. One end of the third horizontal section is connected to the water outlet at the lower end of the pressure-stabilizing water storage tank B, and the other end is connected to the lower end of the third vertical section. The upper end of the third vertical section is connected to the lower outlet of the spherical CMT tank A. Water inlet valve 302, third ball valve 303, second electromagnetic flowmeter 304, check valve 326 and drain valve 307 are installed on the third horizontal section. Fifth thermocouple T301 is installed on the third vertical section. One end of the third ball valve 303 is connected to the fifth thermocouple T301 and the lower outlet of the spherical CMT tank A via a pipeline, and the other end is connected to the second electromagnetic flowmeter 304, the check valve 326, and the water outlet at the lower end of the pressure-stabilizing water tank B via a pipeline; one end of the water inlet valve 302 is connected to the pipeline between the third ball valve 303 and the fifth thermocouple T301; one end of the drain valve 307 is connected to the pipeline between the check valve 326 and the water outlet at the lower end of the pressure-stabilizing water tank B; the check valve 326 restricts the fluid to flow only to the water outlet at the lower end of the pressure-stabilizing water tank B;

[0044] CMT discharge pipeline 3 also includes a backup bypass; a fifth ball valve 325 is provided on the pipeline between the second electromagnetic flow meter 304 and the check valve 326; a sixth ball valve 315 is provided on the backup bypass, one end of the sixth ball valve 315 is connected to the second electromagnetic flow meter 304 and the fifth ball valve 325 through a pipeline, and the other end of the sixth ball valve 315 is connected to the water outlet at the lower end of the pressure-stabilizing water storage tank B.

[0045] The steam supply and heating branch 4 includes a fourth horizontal section, a fourth vertical section, and a steam heating pipe. One end of the fourth horizontal section is connected to the steam inlet at the upper end of the pressure-stabilizing water storage tank B, and the other end is connected to the upper end of the fourth vertical section. The lower end of the fourth vertical section is connected to one end of the steam heating pipe, and the other end of the steam heating pipe extends into the interior of the pressure-stabilizing water storage tank B from the heating port on the bottom side of the tank. The steam input end is installed at the upper end of the fourth vertical section, the steam supply valve 001 is installed on the fourth horizontal section, and the heating valve 002 is installed on the fourth vertical section. One end of the steam supply valve 001 is connected to the steam input end through a pipeline, and the other end is connected to the steam inlet at the upper end of the pressure-stabilizing water storage tank B through a pipeline. One end of the heating valve 002 is connected to the steam input end through a pipeline, and the other end extends into the interior of the pressure-stabilizing water storage tank B from the heating port on the bottom side of the tank. Steam nozzles are circumferentially provided in the extended part of the pipeline.

[0046] An experimental method for natural circulation and gravity discharge of miniaturized reactor core makeup tanks includes the following steps:

[0047] Step 1: Open the water inlet valve 302, the first ball valve 106, the second ball valve 206, the third ball valve 303, and the steam heating pipe circuit valve 205, and close the other valves; fill the experimental device with water through the water inlet valve 302. When there is a continuous flow of fluid from the steam heating pipe circuit valve 205, it means that the experimental device is full. Close all valves.

[0048] Step 2: Open the steam heating pipe circuit valve 205 and the drain valve 307 to drain part of the water in the pressure-stabilizing water tank B, ensuring that the end of the pipe of the natural circulation branch 1 that extends into the pressure-stabilizing water tank B is submerged in water and a certain water level is reserved so that air will not enter the end of the pipe during the marine motion condition test; after draining, close the steam heating pipe circuit valve 205 and the drain valve 307.

[0049] Step 3: Open heating valve 002, and high-temperature steam will be input into the submerged water in pressure-stabilizing water tank B to heat the water in the pressure-stabilizing water tank B. When the experimental working condition is reached, close heating valve 002. At this time, the large amount of saturated water in pressure-stabilizing water tank B can act as a pressure regulator to provide a certain amount of steam and stable pressure for the entire system. Alternatively, steam and pressure can be continuously supplied to pressure-stabilizing water tank B by opening steam supply valve 001 to achieve the experimental working condition.

[0050] Step 4: Arrange multiple thermocouples in spherical CMT tank A to obtain the temperature distribution of the water inside spherical CMT tank A during the experiment;

[0051] Open the third ball valve 303 and the first ball valve 106, close the second ball valve 206, and conduct a natural circulation experiment. During the experiment, the water flow rate is monitored by the first electromagnetic flow meter 103, the water temperature is monitored by the second thermocouple T101, the pressure is monitored by the first pressure sensor P102, and the CMT drainage flow rate is monitored by the second electromagnetic flow meter 304. When the driving force of the CMT system is insufficient to maintain the natural circulation flow rate, the experiment is considered to be over. At this time, the third ball valve 303 is closed and the data collection is stopped.

[0052] Open the third ball valve 303 and the second ball valve 206, close the first ball valve 106, and conduct a gravity discharge experiment. During the experiment, the steam flow rate is monitored by the vortex flow meter 203, the steam temperature is monitored by the fourth thermocouple T201, the steam pressure is monitored by the second pressure sensor P202, and the CMT drainage flow rate is monitored by the second electromagnetic flow meter 304.

[0053] Step 5: After completing the experiment, drain the experimental apparatus through the drain valve 307.

[0054] This invention does not include a steam supply system, but it does include an interface for a steam supply system access module. A steam distributor is installed at the top inlet of the spherical CMT tank, ensuring that the steam condensation process primarily occurs on the inner wall of the CMT tank. Multiple thermocouple measuring points and differential pressure sensors are arranged inside the tank to measure the temperature distribution and flow characteristics within the CMT tank under different operating conditions. The steam supply and heating pipelines are equipped with regulating valves, and the ends are fitted with bellows and single-sided flanges, allowing connection to different steam supply systems to achieve the required steam parameters for the experiment. A pressure-stabilizing water storage tank is equipped with thermocouples and differential pressure sensors to measure its internal temperature distribution and flow characteristics.

[0055] Example 1:

[0056] like Figures 1 to 8 As shown, the present invention provides a small reactor core makeup water tank natural circulation and gravity discharge experimental device, which consists of a spherical CMT tank A, a pressure-stabilized water storage tank B, a steam distributor C, a natural circulation branch 1, a steam injection branch 2, a CMT discharge pipeline 3, and a steam supply and heating branch 4.

[0057] The natural circulation branch 1 is equipped with, in sequence, thermocouple T101, pressure sensor P102, electromagnetic flowmeter 103, thermocouple T104, natural circulation warm-up valve 105, and electric ball valve 106. The steam injection branch 2 is equipped with, in sequence, thermocouple T201, pressure sensor P202, vortex flowmeter 203, thermocouple T204, steam warm-up valve 205, and electric ball valve 206. Ball valve 007 is installed at the junction of the two branches. The CMT discharge pipeline is equipped with, in sequence, thermocouple T301, water inlet valve 302, electric ball valve 303, electromagnetic flowmeter 304, ball valve 325, check valve 326, and drain valve 307. The branch equipped with ball valve 315 is a spare bypass. In the aforementioned branch circuits, the warm-up circuit valve 105, ball valve 007, and steam warm-up circuit valve 205 can all serve as exhaust outlets to remove gas from the pipeline. During drainage operations, the steam warm-up circuit valve 205 can also function as an inlet valve, opening simultaneously with the drain valve 307. Since electromagnetic flowmeters cannot detect steam flow, a vortex flowmeter 203 is used to detect the steam flow in the steam injection branch circuit 2. A steam distributor C is installed at the upper inlet of the spherical CMT tank A. Thermocouples can be installed by drilling holes and welding thermocouple mounts on A and B, and pressure sensors and differential pressure transmitters can be installed by drilling holes and welding pressure taps. For example, pressure sensor P006 is shown in this example, and thermocouples T003 and T004 and pressure sensor P005 are installed in the pressure-stabilizing water tank B. The steam supply and heating pipeline 4 is equipped with regulating valves 001 and 002, and its ends are fitted with bellows and single-sided flanges, allowing connection to various steam supply pipelines to achieve the required steam parameters for the experiment.

[0058] The experimental setup is connected as follows: A steam distributor C is connected to the upper part of the spherical CMT tank A. The steam distributor C extends into the CMT tank via a flange connection, and its assembly method is as follows: Figure 7 As shown, its upstream section merges with the natural circulation branch 1 and the steam injection branch 2, and is equipped with ball valve 007. The lower part of the CMT tank is connected to the discharge pipe 3. The upper part of the pressure-stabilizing water storage tank B is connected to three pipelines: the natural circulation branch 1, the steam injection branch 2, and the steam supply pipe (where 001 is located) of the steam supply and heating pipeline. The end of the injection branch pipe extends into the water storage tank. During the natural circulation experiment, the liquid level is higher than the end of the pipe. Its assembly method is as follows: Figure 8 As shown. The lower part of the pressure-stabilizing water tank is connected to two pipelines: the end of the CMT discharge pipeline and the steam heating pipe (located in section 002) of the steam supply and heating pipeline. The steam heating pipe is constructed as follows... Figure 9 As shown, the pipes extending into section B of the pressure-stabilizing water storage tank are perforated circumferentially to allow steam to be evenly injected into the tank, improving heat exchange efficiency. Both ends of the heating pipes are welded to the inner wall of the tank. The pipe connections are made using welded flanges, with single-sided flanges welded to the ends of the steam supply and heating pipes. All pipes and containers are made of 304 stainless steel. The CMT tank is divided into upper and lower hemispheres connected by flanges. Twelve M18 holes are drilled circumferentially around the flanges, sealed with asbestos gaskets and bolted together. The upper and lower end caps of the pressure-stabilizing water storage tank are welded to the cylinder. The steam supply and heating pipes, natural circulation branch, steam injection branch, CMT discharge pipe, and pressure-stabilizing water storage tank are wrapped with rock wool insulation to reduce heat loss. This experimental system is designed to be small in size and has low heat dissipation, so heat tracing facilities are not required. Based on the requirements for CMT prototype design verification in nuclear power plants, the spherical CMT tank can be insulated. The experimental device is ultimately assembled into a steel frame structure. Figure 6 The steel frame structure is simple, securing the two main mass-concentrated devices A and B of the experimental setup while utilizing the loop structure of the piping itself. The entire steel frame is connected by welding, ensuring good stability and high safety. The experimental setup can be installed by finally fixing the bottom of the steel frame, demonstrating good adaptability to different site conditions and marine simulation platforms, and offering high assembly flexibility.

[0059] like Figure 1 and Figure 2As shown, the operating procedure for using the small reactor core makeup tank natural circulation and gravity discharge experimental device is as follows: First, install and debug the experimental device with the ocean motion condition simulation platform. Then, open the water inlet valve 302, electric ball valves 106, 206, 303, and ball valve 205 to fill the entire experimental device with water. When there is a continuous flow of fluid out of ball valve 205, it indicates that the experimental device is full. Close all valves and open ball valve 205 and drain valve 307 to partially drain the water from the pressure-stabilized water storage tank B. This water volume is based on... Figure 8 The length of the pipe extension is determined by the amount of water, ensuring that the end of the pipe is submerged in water and does not protrude above the liquid surface during operation. This process is to keep branch 1 full of water, drain the water from branch 2, and ensure that the liquid level in the RPV also submerges the end of the pipe in branch 1, preventing gas from entering branch 1 during the experiment.

[0060] Figure 9 This diagram illustrates the connection between the steam supply system and the device. 401 is a steel bellows, and 402 is a single-piece flange. By adjusting the length of the bellows (401) and the position of the flange (402), the experimental device module can be connected to the steam supply system. Steam can then be supplied to the experimental device via the steam supply and heating pipeline 4. Heating valve 002 is opened independently for heating, and steam supply valve 001 is opened independently for steam supply. When the experimental operating conditions are met, heating valve 002 can be closed. At this time, the large amount of saturated water in B can act as a pressure regulator, providing a certain amount of steam and stable pressure to the entire system. Alternatively, steam supply valve 001 can be opened to continuously supply steam and pressure to the system. Temperature and pressure can be detected by thermocouple T003, pressure sensor P005, and other installed instruments. After experimental preparation, opening electric valves 106 and 303 initiates a natural circulation experiment, while opening electric valves 206 and 303 initiates a gravity discharge experiment. These two modes can be achieved by switching between branches 1 and 2. During the experiment, thermocouples 103 and 203 can monitor water flow and steam flow respectively. Thermocouples T101 and T102, and pressure sensors P102 and P202 can be used as pressure stabilization compensation signals to calculate mass flow rate. 304 can monitor the CMT drainage flow rate. Temperature measurement of the spherical CMT tank can be achieved by arranging multiple layers of thermocouples to measure temperature in all directions. An example measurement scheme is given below. Figure 11 T1-T19 are temperature measuring points, TA-TD are backup temperature measuring points, and DP1-DP2 are differential pressure transmitter water level measuring points. Pressure measurements can be completed using the DP1 measuring point. This measurement method can be applied to temperature measurements at various angles under marine conditions. The number of temperature measuring points can be appropriately increased to improve the resolution of temperature distribution within the CMT's internal waters. After the experiment is completed, the system can be drained via drain valve 307.

[0061] This invention uses a spherical tank to simulate the prototype CMT (Conductivity, Motion, and Tranquility), allowing the free surface to oscillate with a uniform cross-section under ocean motion, facilitating mechanistic research and data analysis. The invention employs a modular design for the CMT experimental device and includes an interface for connecting the steam system, significantly improving the flexibility of the steam-side system design and solving site layout issues. Furthermore, the steam connection utilizes a corrugated pipe connection, greatly enhancing the freedom of movement of the experimental device. This invention adopts a miniaturized design, fixing the entire experimental device module within a steel frame. It features lightweight, compact structure, low center of gravity, and small size, facilitating overall hoisting. It can also be installed on ocean motion simulation platforms with limited space, improving the safety and convenience of ocean motion experiments, saving experimental time, and increasing experimental efficiency.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A miniaturized reactor core makeup tank natural circulation and gravity discharge experimental device, characterized in that: It includes a spherical CMT tank (A), a pressure-stabilizing water storage tank (B), a steam distributor (C), a natural circulation branch (1), a steam injection branch (2), a CMT discharge pipeline (3), and a steam supply and heating branch (4); the spherical CMT tank (A) is located above the pressure-stabilizing water storage tank (B); the steam distributor (C) is installed at the upper inlet of the spherical CMT tank (A); The natural circulation branch (1) includes a first ball valve (106). One end of the first ball valve (106) is connected to the inlet pipe of the steam distributor (C) through a pipeline, and the other end is connected to the first thermocouple (T104), the first electromagnetic flowmeter (103), the first pressure sensor (P102) and the second thermocouple (T101) in sequence through a pipeline. It extends into the interior of the pressure-stabilizing water storage tank (B) from the natural circulation inlet at the top of the pressure-stabilizing water storage tank (B). The steam injection branch (2) includes a steam warm-up circuit valve (205) and a second ball valve (206). One end of the second ball valve (206) is connected to the inlet pipe of the steam distributor (C) through a pipeline, and the other end is connected in sequence to the steam outlet at the upper end of the third thermocouple (T204), the vortex flow meter (203), the second pressure sensor (P202), the fourth thermocouple (T201), and the pressure stabilizing water tank (B) through a pipeline. One end of the steam warm-up circuit valve (205) is connected to the pipeline between the second ball valve (206) and the third thermocouple (T204). The CMT discharge pipeline (3) includes a water inlet valve (302), a drain valve (307), and a third ball valve (303). One end of the third ball valve (303) is connected to the fifth thermocouple (T301) and the lower outlet of the spherical CMT tank (A) via a pipeline, and the other end is connected to the second electromagnetic flowmeter (304), the check valve (326), and the outlet at the lower end of the pressure-stabilizing water tank (B) via a pipeline. One end of the water inlet valve (302) is connected to the pipeline between the third ball valve (303) and the fifth thermocouple (T301). One end of the drain valve (307) is connected to the pipeline between the check valve (326) and the outlet at the lower end of the pressure-stabilizing water tank (B). The check valve (326) restricts the fluid to flow only to the outlet at the lower end of the pressure-stabilizing water tank (B). The steam supply and heating branch (4) includes a steam input end, a steam supply valve (001) and a heating valve (002); one end of the steam supply valve (001) is connected to the steam input end through a pipeline, and the other end is connected to the steam inlet at the top of the pressure-stabilizing water tank (B) through a pipeline; one end of the heating valve (002) is connected to the steam input end through a pipeline, and the other end extends into the pressure-stabilizing water tank (B) from the heating port on the bottom side of the pressure-stabilizing water tank (B) through a pipeline, and the pipeline extending into the pressure-stabilizing water tank (B) is provided with steam nozzles in the circumferential direction.

2. The miniaturized reactor core makeup tank natural circulation and gravity discharge experimental device according to claim 1, characterized in that: The steam distributor (C) is connected to the upper inlet of the spherical CMT tank (A) via a flange. The outlet pipe of the steam distributor (C) extends into the interior of the spherical CMT tank (A). The inlet pipe of the steam distributor (C) merges with the natural circulation branch (1) and the steam injection branch (2) upstream. A fourth ball valve (007) is provided near the merging point as an exhaust outlet.

3. The miniaturized reactor core makeup tank natural circulation and gravity discharge experimental device according to claim 1, characterized in that: The natural circulation branch (1) includes a first horizontal section and a first vertical section. One end of the first horizontal section is connected to the inlet pipe of the steam distributor (C), and the other end is connected to the upper end of the first vertical section. The lower end of the first vertical section extends from the natural circulation inlet at the upper end of the pressure-stabilizing water tank (B) into the interior of the pressure-stabilizing water tank (B). The first ball valve (106) and the first thermocouple (T104) are installed on the first horizontal section. The first electromagnetic flowmeter (103), the first pressure sensor (P102), and the second thermocouple (T101) are installed on the first vertical section. A natural circulation warm-up pipe valve (105) is provided on the first horizontal section. The natural circulation warm-up pipe valve (105) is connected to the pipe between the first ball valve (106) and the first thermocouple (T104) and is used as an exhaust outlet.

4. The miniaturized reactor core makeup tank natural circulation and gravity discharge experimental device according to claim 1, characterized in that: The steam injection branch (2) includes a second horizontal section and a second vertical section. One end of the second horizontal section is connected to the inlet pipe of the steam distributor (C), and the other end is connected to the upper end of the second vertical section. The lower end of the second vertical section is connected to the steam outlet at the upper end of the pressure-stabilizing water tank (B). The second ball valve (206), the steam warming loop valve (205), and the third thermocouple (T204) are installed on the second horizontal section. The vortex flow meter (203), the second pressure sensor (P202), and the fourth thermocouple (T201) are installed on the second vertical section.

5. The miniaturized core makeup tank natural circulation and gravity discharge experimental device according to claim 1, characterized in that: The CMT discharge pipeline (3) includes a third horizontal section and a third vertical section. One end of the third horizontal section is connected to the outlet at the lower end of the pressure-stabilizing water storage tank (B), and the other end is connected to the lower end of the third vertical section. The upper end of the third vertical section is connected to the lower outlet of the spherical CMT tank (A). The water inlet valve (302), the third ball valve (303), the second electromagnetic flowmeter (304), the check valve (326), and the drain valve (307) are installed on the third horizontal section. The fifth thermocouple (T301) is installed on the third vertical section.

6. The miniaturized core makeup tank natural circulation and gravity discharge experimental device according to claim 5, characterized in that: The CMT discharge pipeline (3) also includes a backup bypass; a fifth ball valve (325) is provided on the pipeline between the second electromagnetic flowmeter (304) and the check valve (326); a sixth ball valve (315) is provided on the backup bypass, one end of the sixth ball valve (315) is connected to the second electromagnetic flowmeter (304) and the fifth ball valve (325) through a pipeline, and the other end of the sixth ball valve (315) is connected to the water outlet at the lower end of the pressure-stabilizing water storage tank (B).

7. The miniaturized reactor core makeup tank natural circulation and gravity discharge experimental device according to claim 1, characterized in that: The steam supply and heating branch (4) includes a fourth horizontal section, a fourth vertical section, and a steam heating pipe. One end of the fourth horizontal section is connected to the steam inlet at the upper end of the pressure-stabilizing water tank (B), and the other end is connected to the upper end of the fourth vertical section. The lower end of the fourth vertical section is connected to one end of the steam heating pipe, and the other end of the steam heating pipe extends from the heating port on the bottom side of the pressure-stabilizing water tank (B) into the interior of the pressure-stabilizing water tank (B). The steam input end is installed at the upper end of the fourth vertical section, the steam supply valve (001) is installed on the fourth horizontal section, and the heating valve (002) is installed on the fourth vertical section.

8. An experimental method for a miniaturized reactor core makeup tank natural circulation and gravity discharge experimental device according to claim 1, characterized in that, Includes the following steps: Step 1: Open the water inlet valve (302), the first ball valve (106), the second ball valve (206), the third ball valve (303), and the steam warming pipe circuit valve (205), and close the other valves; fill the experimental device with water through the water inlet valve (302). When there is a continuous flow of fluid from the steam warming pipe circuit valve (205), it means that the experimental device is full. Close all valves. Step 2: Open the steam heating pipe loop valve (205) and drain valve (307) to partially drain the water in the pressure-stabilizing water tank (B), ensuring that the end of the pipe extending from the natural circulation branch (1) into the pressure-stabilizing water tank (B) is submerged in water and a certain water level is reserved so that air will not enter the end of the pipe during the marine motion condition test; after draining, close the steam heating pipe loop valve (205) and drain valve (307); Step 3: Open the heating valve (002) and input high-temperature steam into the water in the pressure-stabilizing water tank (B) to heat the water in the pressure-stabilizing water tank (B). When the experimental working condition is set, close the heating valve (002). At this time, the large amount of saturated water in the pressure-stabilizing water tank (B) can act as a pressure regulator to provide a certain amount of steam and stable pressure for the entire system. Step 4: Arrange multiple thermocouples in the spherical CMT tank (A) to obtain the temperature distribution of the water inside the spherical CMT tank (A) during the experiment; Open the third ball valve (303) and the first ball valve (106), close the second ball valve (206), and conduct a natural circulation experiment. During the experiment, the water flow rate is monitored by the first electromagnetic flowmeter (103), the water temperature is monitored by the second thermocouple (T101), the pressure is monitored by the first pressure sensor (P102), and the CMT drainage flow rate is monitored by the second electromagnetic flowmeter (304). When the driving force of the CMT system is insufficient to maintain the natural circulation flow rate, the experiment is considered to be over. At this time, the third ball valve (303) is closed and the data collection is stopped. Open the third ball valve (303) and the second ball valve (206), close the first ball valve (106), and conduct a gravity discharge experiment. During the experiment, the steam flow rate is monitored by the vortex flow meter (203), the steam temperature is monitored by the fourth thermocouple (T201), the steam pressure is monitored by the second pressure sensor (P202), and the CMT drainage flow rate is monitored by the second electromagnetic flow meter (304). Step 5: After completing the experiment, drain the experimental apparatus through the drain valve (307).

9. The experimental method based on a miniaturized core makeup tank natural circulation and gravity discharge experimental device according to claim 8, characterized in that: In step 3, steam and pressure can be continuously supplied to the pressure-stabilizing water tank (B) by opening the steam supply valve (001) to achieve the experimental working conditions.

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