Passive cooling system and method for built-in cooling tower type containment of underground nuclear power plant

Abstract

The present invention discloses a passive cooling system in a built-in cooling tower type containment of an underground nuclear power plant. It includes a high-level emergency cooling water pool, a cooling water flow distribution loop, a cooling device, and a cooling water recirculation and heat dissipation system. The containment is a cylindrical sealed shell with upper and lower columnar through holes arranged inside; a cooling device is arranged inside the columnar through hole; the bottom elevation of the high-level emergency cooling water pool is greater than the elevation of the cooling water flow distribution loop; the high-level emergency cooling water pool, the cooling water flow distribution loop, the cooling device, and the cooling water recirculation and heat dissipation system are sequentially connected to form a closed loop. The present invention has the advantage of being able to realize the passive cooling function of the containment of an underground nuclear power plant. The present invention also discloses a cooling method for the passive cooling system in the built-in cooling tower type containment of the underground nuclear power plant.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power technology, more specifically, it is a passive cooling system in a built-in cooling tower type containment of an underground nuclear power plant. The present invention also relates to a passive cooling method in a built-in cooling tower type containment of an underground nuclear power plant, more specifically, it is a cooling method for the passive cooling system in a built-in cooling tower type containment of an underground nuclear power plant. Background Art

[0002] As the fourth barrier of a nuclear power plant, the integrity of the containment under accident conditions is crucial to the safety of the entire nuclear power plant. When a LOCA or steam pipe rupture accident occurs in the containment, high-temperature, high-pressure steam is sprayed into the containment, causing the pressure and temperature inside the containment to rise, which may cause overpressure damage to the containment and lead to the leakage of a large amount of radioactive materials. Therefore, ground nuclear power plants generally have a containment cooling system to cool and depressurize the containment under accident conditions such as LOCA. For example, the M310 reactor type is equipped with a spray system in the containment to reduce the pressure and temperature in the containment by spraying condensed steam; the AP1000 is equipped with a passive containment cooling system, which transfers the heat in the containment through the steel containment to the atmosphere outside the containment through natural forces such as gravity.

[0003] An underground nuclear power plant is a nuclear power plant that is placed in its entirety or in part in an underground engineering cavern. The rock mass and engineering measures are used to increase the safety barrier of the nuclear reactor and reduce the possibility of a large amount of radioactive substances being released into the environment. Some scholars have proposed that an underground nuclear power plant can cancel the outer concrete containment in the usual sense, and use the steel lining and cavern surrounding rock to form the underground nuclear power plant containment. It can effectively utilize the radioactive tolerance and resistance to external event interference of the cavern surrounding rock to provide the function of the conventional outer concrete containment, and has the function of improving the safety and economy of the nuclear power plant. Due to the cancellation of the outer concrete containment, the design of the containment cooling system of the underground nuclear power plant has different influencing factors from that of the ground power plant. The containment spray system realizes the spray cooling function in the containment through a spray water pump. Under accident conditions, a power supply is required to ensure the startup of the system. This puts forward higher reliability and redundancy requirements for the system, which is not conducive to simplifying the nuclear power plant system, especially for underground nuclear power plants. The size of the containment is limited by the size of the underground cavern space, and the containment spray system is difficult to implement. The containment of an underground nuclear power plant is located in an underground cavern, and it is impossible to use natural convection of the atmosphere to achieve passive containment cooling. Therefore, air cooling outside the containment is not feasible. It is necessary to develop and design a passive cooling system based on the characteristics of the containment of an underground nuclear power plant. Summary of the invention

[0004] The first purpose of the present invention is to provide a passive cooling system in a built-in cooling tower type containment of an underground nuclear power plant, so as to realize the passive cooling function of the containment of the underground nuclear power plant.

[0005] The second purpose of the present invention is to provide a cooling method for the passive cooling system in the built-in cooling tower type containment of the underground nuclear power plant.

[0006] In order to achieve the first object of the present invention, the technical solution of the present invention is: a passive cooling system in a built-in cooling tower type containment of an underground nuclear power plant, characterized in that it includes a high-level emergency cooling water pool, a cooling water flow distribution loop, a cooling device, and a cooling water recirculation heat dissipation system.

[0007] The containment shell is a cylindrical sealed shell with a cylindrical through hole connected up and down inside. The cylindrical through hole and other walls of the containment shell together constitute a sealed shell to achieve the function of sealing and containing radioactive substances. The cylindrical through hole is a part of the steel containment shell and also serves as a vertical support member of the containment shell dome, providing vertical support force for the underground cavern dome.

[0008] A cooling device is arranged in the columnar through hole, and the heat inside the containment is transferred to the cooling medium inside the columnar through hole through heat exchange forms such as wall condensation heat exchange, heat conduction, and convection heat exchange, and then the heat is directly or indirectly discharged by the cooling medium;

[0009] The bottom elevation of the high-level emergency cooling water pool is greater than the elevation of the cooling water flow distribution loop;

[0010] The high-level emergency cooling water pool, cooling water flow distribution loop, cooling device, and cooling water recirculation and heat dissipation system are connected in sequence to form a closed loop.

[0011] In the above technical solution, the columnar through hole is arranged in the middle of the containment shell;

[0012] There are one or more columnar through holes.

[0013] In the above technical solution, the columnar through hole is a cylindrical structure with equal upper and lower cross-sections, or a truncated cone structure with a large upper cross-section and a small lower cross-section, so as to increase the heat exchange area of ​​the upper space of the containment.

[0014] In the above technical solution, the cooling device is selected from a cooling tower built into the containment vessel.

[0015] In the above technical solution, the cooling device includes a plurality of cooling pipes, and the plurality of cooling pipes are crisscrossed to form a cooling pipe network; the cooling pipe network is attached to the inner wall surface of the columnar through hole;

[0016] The inlet of the cooling pipe is connected to the cooling water flow distribution loop, and the outlet is connected to the cooling water recirculation heat dissipation system.

[0017] In the above technical solution, the cooling water flow distribution loop includes a flow regulating valve and a cooling water pipe; the cooling water enters the flow distribution loop after leaving the cooling water pool, and enters the cooling device built into the containment after flow distribution through the flow regulating valve and other devices; the cooling water flow is adjusted in real time according to the temperature and pressure distribution in the containment;

[0018] The water inlet of the cooling water pipe is connected to the water outlet of the high-level emergency cooling water pool, and the water outlet is connected to the water inlet of the cooling pipe;

[0019] The flow regulating valve is arranged on the cooling water pipe, and the flow regulating valve is arranged at the outlet end of the cooling water pipe for distributing the flow;

[0020] There are multiple cooling water pipes, and the flow distribution loop is connected to the built-in cooling tower of the containment by at least two independent cooling water pipes to increase system reliability.

[0021] In the above technical solution, the cooling water recycling and heat dissipation system collects the cooling water flowing through the cooling tower cooling pipe network in the containment, cools it in the radiator and returns it to the high-level emergency cooling water pool to realize the recycling of cooling water; the cooling water recycling and heat dissipation system includes a cooling water flow control valve group, a cooling water radioactivity detection device, a circulating water pump, a radiator and a temperature detection device, etc.;

[0022] The cooling water flow control valve group, the cooling water radioactivity detection device, the circulating water pump, the radiator and the temperature detection device are connected in sequence;

[0023] The cooling water flow control valve group is connected to the cooling pipe outlet; the cooling water is collected into the cooling water recirculation heat dissipation system through the cooling pipe network, and the cooling water flow control valve group at the cooling pipe network outlet adjusts the flow of cooling water in the cooling pipe network, thereby matching the cooling effect of the system with the demand;

[0024] The temperature detection device is connected to the inlet of the high-level emergency cooling water pool. The cooling water flowing out of the radiator can be injected into the high-level cooling water pool only after the temperature is detected by the temperature detection device and the temperature meets the requirements. If the cooling water temperature is too high, the radiator power is increased or the flow rate of cooling water entering the radiator is reduced to adjust the cooling water temperature to meet the requirements.

[0025] In order to achieve the second object of the present invention, the technical solution of the present invention is: the cooling method of the passive cooling system in the built-in cooling tower type containment of the underground nuclear power plant is characterized by comprising the following steps:

[0026] When a LOCA or steam pipe rupture accident occurs in the containment, high-temperature, high-pressure steam is sprayed into the containment, triggering the start-up of the passive cooling system in the built-in cooling tower containment;

[0027] Step 1: The low-temperature cooling water in the high-level emergency cooling water pool flows into the cooling water flow distribution loop under the action of gravity, and flows into each built-in cooling device after flow distribution through the cooling water flow distribution loop;

[0028] Step 2: When the cooling water flows in the cooling pipe network of the cooling device, the heat inside the containment is transferred to the cooling water through the heat transfer process of condensation heat exchange on the inner wall of the containment, heat conduction on the inner wall of the containment, and convection heat exchange on the outer wall of the containment. At this time, the heat inside the containment is reduced, the temperature and pressure are reduced, and the temperature of the cooling water in the cooling pipe network of the cooling device is increased;

[0029] Step 3: The heated cooling water flows out of the cooling pipe network of the cooling device and is collected into the cooling water recirculation and heat dissipation system. The collected cooling water is tested for radioactivity by a cooling water radioactivity detection device.

[0030] When the radioactivity of the collected cooling water is normal, the cooling water passes through the circulating water pump and enters the radiator for cooling. After cooling, it is injected into the high-level emergency cooling water pool for recirculation;

[0031] When the radioactivity of the collected cooling water exceeds the standard, the cooling water enters the wastewater treatment system for treatment.

[0032] The beneficial effects achieved by the present invention are:

[0033] 1) The present invention provides a passive cooling system for a built-in cooling tower-type containment vessel of an underground nuclear power plant. The system designs the containment vessel as a cylindrical sealed shell with upper and lower columnar through holes inside, and a cooling device is arranged in the columnar through holes to realize cooling of the containment vessel, thereby realizing external cooling of the containment vessel of the underground nuclear power plant after the outer concrete containment vessel is removed, thereby ensuring the integrity of the steel containment vessel.

[0034] 2) The upper and lower columnar through holes of the containment in the present invention can be used as a part of the containment cooling system, and can also be used as vertical support members to provide vertical support force for the dome of the underground cavern.

[0035] 3) The cooling water source of the passive cooling system in the built-in cooling tower containment of the underground nuclear power plant is the high-level emergency cooling water pool. In the event of a power outage in the entire plant, the passive cooling of the containment can still be achieved under the action of gravity, which can simplify the system redundancy and improve reliability.

[0036] 4) The passive cooling system in the built-in cooling tower containment of the underground nuclear power plant provides a set of cooling water recycling equipment, which can cool the heated cooling water and recycle it, thereby reducing the plant water consumption of the underground nuclear power plant in relatively water-scarce inland areas.

[0037] The present invention uses a built-in cooling tower type containment shell, and the containment shell adopts a columnar through-hole design that is connected up and down, which can not only ensure a closed containment shell and ensure the containment of radioactive materials, but also form an internal cavity as a space for cooling the containment shell. The heat inside the containment shell is transferred to the cooling medium inside the columnar through-hole through heat exchange forms such as wall condensation heat exchange-heat conduction-convection heat exchange, and then the heat is directly or indirectly extracted by the cooling medium, thereby safely and efficiently cooling the containment shell of the underground nuclear power plant; the columnar through-hole can also be used as a longitudinal supporting structure of the containment shell dome to enhance the structural strength of the thin-walled containment shell; the present invention realizes efficient cooling of the containment shell of the underground nuclear power plant without changing the size of the existing containment shell, and the cooling space is sufficient, the cooling process is safe, and the overall structure is stable; the problem that the outer side of the cavern-type containment shell of the existing underground nuclear power plant technology is overcome, that the outer side of the cavern-type containment shell is close to the cavern rock wall, and the spraying method outside the containment shell has difficulty in space to be deployed. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The present invention is a schematic structural diagram of a passive cooling system in a built-in cooling tower type containment of an underground nuclear power plant.

[0039] Figure 2 It is a top view of the containment and the position of the columnar through holes of the passive cooling system in the built-in cooling tower type containment of the underground nuclear power plant of the present invention.

[0040] Figure 3 This is a schematic diagram of the containment structure of the passive cooling system in the built-in cooling tower type containment of the single-column underground nuclear power plant in Example 1 of the present invention.

[0041] Figure 4 It is a schematic structural diagram of the passive cooling system in the built-in cooling tower-type containment of a four-column underground nuclear power plant in Example 2 of the present invention.

[0042] Figure 5 It is a top view of the containment and columnar through-hole positions of the passive cooling system in the built-in cooling tower-type containment of the four-column underground nuclear power plant in Example 2 of the present invention.

[0043] In the figure: 1-high-level emergency cooling water pool, 2-cooling water flow distribution loop, 3-containment built-in cooling tower, 4-cooling water recirculation heat dissipation system, 2.1-flow regulating valve, 2.2-cooling water pipe, 2.21-cooling water pipe I, 2.22-cooling water pipe II, 3-cooling device, 3.1-cooling pipe, 4.1-cooling water flow control valve group, 4.2-cooling water radioactivity detection device, 4.3-circulating water pump, 4.4-radiator, 4.5-temperature detection device, 5-containment, 5.1-columnar through hole, 5.2-containment inner wall, 5.3-containment outer wall. DETAILED DESCRIPTION

[0044] The following is a detailed description of the implementation of the present invention in conjunction with the accompanying drawings, but they do not constitute a limitation of the present invention and are only used as examples. At the same time, the advantages of the present invention are made clearer and easier to understand through the description.

[0045] The present invention is now described in detail by taking the application of the present invention to the cooling of the containment of a certain underground nuclear power plant as an example, which also has a guiding role in the application of the present invention to the cooling of the containment of other underground nuclear power plants.

[0046] Embodiment 1:

[0047] The containment of an underground nuclear power plant in this embodiment adopts a single-column underground nuclear power plant built-in cooling tower-type containment passive cooling system, that is, there is one columnar through hole 5.1.

[0048] like Figure 1 As shown, the passive cooling system in the built-in cooling tower type containment of the single-column underground nuclear power plant in this embodiment includes a high-level emergency cooling water pool 1, a cooling water flow distribution loop 2, a built-in cooling tower in the containment, and a cooling water recirculation and heat dissipation system 4.

[0049] The bottom elevation of the high-level emergency cooling water pool 1 is greater than the elevation of the cooling water flow distribution loop 2, and the water volume of the pool is at least greater than the water consumption for 72 hours when the cooling system is opened at 100% flow.

[0050] The inlet of the cooling water flow distribution loop 2 is connected to the outlet 1.1 of the high-level emergency cooling water pool. After the cooling water leaves the cooling water pool, it enters the flow distribution loop, and enters the built-in cooling tower of the containment after flow distribution through devices such as a flow regulating valve 2.1; the cooling water flow is adjusted in real time based on the temperature and pressure distribution in the containment; the cooling water flow distribution loop 2 is connected to the built-in cooling tower of the containment by at least two independent cooling water pipes 2.2 (in this embodiment, the two independent cooling water pipes 2.2 are cooling water pipe I 2.21 and cooling water pipe II 2.22, respectively) to increase system reliability.

[0051] The containment built-in cooling tower is a cooling device arranged inside the columnar through hole 3.1 in the middle of the containment, and the cooling device refers to a cooling pipe network attached to the inner wall of the columnar through hole, and the cooling pipe network is composed of crisscrossing cooling pipes 3.1, and the inlet of the cooling pipe 3.1 is connected to the outlet of the cooling water flow distribution loop 2. The columnar through hole 5.1 and other walls of the containment together form a sealed shell to achieve the function of sealing and containing radioactive substances; the columnar through hole 5.1 is a cylindrical shape with equal upper and lower cross-sections.

[0052] The cooling water recycling and heat dissipation system 4 collects the cooling water flowing through the cooling pipe network of the cooling tower in the containment, cools it through the radiator 4.4, and returns it to the high-level emergency cooling water pool to realize the recycling of cooling water. The cooling water recycling and heat dissipation system includes a cooling water flow control valve group 4.1, a cooling water radioactivity detection device 4.2, a circulating water pump 4.3, a radiator 4.4, and a temperature detection device 4.5.

[0053] The operation process of the passive cooling system in the built-in cooling tower type containment of the single-column underground nuclear power plant in this embodiment is as follows:

[0054] When a LOCA or steam pipe rupture accident occurs in the containment, high-temperature, high-pressure steam is sprayed into the containment, triggering the start-up of the passive cooling system in the built-in cooling tower containment;

[0055] Step 1: The low-temperature cooling water in the high-level emergency cooling water pool 1 flows into the flow distribution loop 2 under the action of gravity, and flows into the built-in cooling tower after flow distribution;

[0056] Step 2: When the cooling water flows in the cooling pipe network, the heat inside the containment is transferred to the cooling water through the heat transfer process of condensation heat exchange on the inner wall of the containment, heat conduction on the wall of the containment, and convection heat exchange on the outer wall of the containment. At this time, the heat inside the containment is reduced, the temperature and pressure are reduced, and the temperature of the cooling water is increased;

[0057] Step 3: The heated cooling water flows out of the cooling pipe network and is collected into the cooling water recycling and heat dissipation system 4; the collected cooling water is tested for activity by the radioactivity detection device 4.2. If the activity is normal, the cooling water passes through the circulating water pump 4.3 and then enters the radiator 4.4 for cooling. After cooling, the cooling water is injected into the high-level cooling water pool 1 for recycling; if the radioactivity exceeds the standard, the cooling water enters the wastewater treatment system for treatment.

[0058] In this embodiment, the flow rate of cooling water in the cooling pipe network 3.3 can be adjusted by adjusting the flow regulating valve 3.4 at the outlet of the cooling pipe network 3.3, so as to match the cooling effect of the system with the demand.

[0059] In this embodiment, the cooling water flowing out of the radiator 4.4 can be injected into the high-level cooling water pool 1 only after the temperature is detected by the temperature measuring device 4.5 and meets the requirements; if the temperature is too high, it is necessary to increase the radiator power or reduce the flow rate of cooling water entering the radiator.

[0060] like Figure 2 As shown, the upper and lower through holes (i.e., columnar through holes 5.1) of the passive cooling system in the built-in cooling tower-type containment of the single-column underground nuclear power plant in this embodiment are located in the middle of the containment 5.

[0061] Figure 3The containment structure of the passive cooling system in the built-in cooling tower type containment of the single-column underground nuclear power plant of this embodiment is shown.

[0062] The above shows and describes the basic principles and main structural features of the present invention. The present invention is not limited to the above examples. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

[0063] Embodiment 2:

[0064] like Figure 4 As shown: the structure and operation process of this embodiment are basically the same as those of Embodiment 1, except that: the containment of an underground nuclear power plant in this embodiment adopts a multi-column underground nuclear power plant built-in cooling tower-type non-active cooling system in the containment, that is, there are multiple columnar through holes 5.1.

[0065] In this embodiment, the steel containment of the passive cooling system in the built-in cooling tower-type containment of the multi-column underground nuclear power plant is provided with a plurality of upper and lower through holes (i.e., columnar through holes 5.1), and each of the upper and lower through holes (i.e., columnar through holes 5.1) can be provided with a cooling device 3.

[0066] Figure 5 The positions of the upper and lower through holes of the passive cooling system containment in the built-in cooling tower-type containment of the multi-column underground nuclear power plant of this embodiment are shown.

[0067] Other parts not described belong to the prior art.

Claims

1. The passive cooling system in the built-in cooling tower containment of underground nuclear power plants, Features: It comprises a high-level emergency cooling water pool (1), a cooling water flow distribution loop (2), a cooling device (3), and a cooling water recirculation and heat dissipation system (4). The containment shell (5) is a cylindrical sealed shell having a columnar through hole (5.1) connected to each other from top to bottom. The columnar through hole (5.1) and the wall surface of the containment shell (5) together form a sealed shell to achieve the function of sealing and containing radioactive substances. The columnar through hole (5.1) is a part of the containment shell (5) and also serves as a vertical support member for the dome of the containment shell (5). A cooling device (3) is arranged in the columnar through hole (5.1); heat inside the containment vessel (5) is transferred to a cooling medium inside the columnar through hole (5.1) through wall condensation heat exchange-heat conduction-convection heat exchange, and the heat is then directly or indirectly removed by the cooling medium; The bottom elevation of the high-level emergency cooling water pool (1) is greater than the elevation of the cooling water flow distribution loop (2); The high-level emergency cooling water pool (1), the cooling water flow distribution loop (2), the cooling device (3), and the cooling water recirculation heat dissipation system (4) are connected in sequence to form a closed loop.

2. The passive cooling system in the built-in cooling tower type containment of an underground nuclear power plant according to claim 1, Features: The columnar through hole (5.1) is arranged in the middle of the containment vessel (5); There are one or more columnar through holes (5.1).

3. The passive cooling system in the built-in cooling tower type containment of an underground nuclear power plant according to claim 1 or 2, Features: The columnar through hole (5.1) is in a cylindrical structure or a truncated cone structure.

4. The passive cooling system in the built-in cooling tower type containment of an underground nuclear power plant according to claim 3, Features: The cooling device (3) is selected from a cooling tower built into the containment vessel.

5. The passive cooling system in the built-in cooling tower type containment of an underground nuclear power plant according to claim 4, Features: The cooling device (3) comprises a plurality of cooling pipes (3.1), wherein the plurality of cooling pipes (3.1) are crisscrossed to form a cooling pipe network; the cooling pipe network is attached to the inner wall surface of the columnar through hole (5.1); The inlet of the cooling pipe (3.1) is connected to the cooling water flow distribution loop (2), and the outlet is connected to the cooling water recirculation heat dissipation system (4).

6. The passive cooling system in the built-in cooling tower type containment of an underground nuclear power plant according to claim 5, Features: The cooling water flow distribution loop (2) comprises a flow regulating valve (2.1) and a cooling water pipe (2.2); The water inlet of the cooling water pipe (2.2) is connected to the water outlet of the high-level emergency cooling water pool, and the water outlet is connected to the water inlet of the cooling pipe (3.1); The flow regulating valve (2.1) is arranged on the cooling water pipe (2.2); There are multiple cooling water pipes (2.2).

7. The passive cooling system in the built-in cooling tower type containment of an underground nuclear power plant according to claim 6, Features: The cooling water recirculation heat dissipation system (4) comprises a cooling water flow control valve group (4.1), a cooling water radioactivity detection device (4.2), a circulating water pump (4.3), a radiator (4.4) and a temperature detection device (4.5); The cooling water flow control valve group (4.1), the cooling water radioactivity detection device (4.2), the circulating water pump (4.3), the radiator (4.4) and the temperature detection device (4.5) are connected in sequence; The cooling water flow control valve group (4.1) is connected to the outlet of the cooling pipe (3.1); The temperature detection device (4.5) is connected to the inlet of the high-level emergency cooling water pool (1).

8. A cooling method for a passive cooling system in a built-in cooling tower type containment of an underground nuclear power plant according to any one of claims 1 to 7, Features: The following steps are included: When a LOCA or steam pipe rupture accident occurs in the containment, high-temperature, high-pressure steam is sprayed into the containment, triggering the start-up of the passive cooling system in the built-in cooling tower containment; Step 1: The low-temperature cooling water in the high-level emergency cooling water pool (1) flows into the cooling water flow distribution loop (2) under the action of gravity, and flows into the built-in cooling device (3) after flow distribution through the cooling water flow distribution loop (2); Step 2: When the cooling water flows in the cooling pipe network of the cooling device (3), the heat inside the containment (5) is transferred to the cooling water through the heat transfer process of condensation heat exchange on the inner wall surface (5.2) of the containment, heat conduction on the inner wall surface (5.2) of the containment, and convection heat exchange on the outer wall surface (5.3) of the containment. At this time, the heat inside the containment (5) is reduced, the temperature and pressure are reduced, and the temperature of the cooling water in the cooling pipe network is increased; Step 3: The heated cooling water flows out of the cooling pipe network and is collected into the cooling water recirculation and heat dissipation system (4). The collected cooling water is tested for radioactivity through a cooling water radioactivity detection device (4.2); When the radioactivity of the collected cooling water is normal, it passes through the circulating water pump (4.3) and then enters the radiator (4.4) for cooling. After cooling, it is injected into the high-level emergency cooling water pool (1) for recirculation; When the radioactivity of the collected cooling water exceeds the standard, it will enter the wastewater treatment system for treatment.

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