Passive Containment Cooling System of Nuclear Power Plant

Abstract

The present invention provides a passive containment cooling system for a nuclear power plant. The containment includes an inner steel containment and an outer concrete containment. A heat exchange annular cavity is formed between the inner steel containment and the outer concrete containment. An isolation cover is further provided between the inner steel containment and the outer concrete containment. The top end of the isolation cover penetrates through the top of the outer concrete containment, and the other end covers the outside of the inner steel containment and extends towards the bottom end of the inner steel containment. The isolation cover includes an absorption layer, a heat insulation layer, and heat pipes located between the absorption layer and the heat insulation layer. The absorption layer is arranged on the side close to the inner steel containment and cooperates with the heat insulation layer to wrap the heat pipes. In the above cooling system, by providing an isolation cover between the inner steel containment and the outer concrete containment, and the isolation cover is composed of an absorption layer, heat pipes, and a heat insulation layer, it can not only meet the heat removal of the inner steel containment, but also protect the outer concrete containment.

Description

Technical Field

[0001] The present invention relates to the technical field of containment cooling, and particularly to a passive containment cooling system for a nuclear power plant. Background Art

[0002] A passive containment cooling system discharges the heat of the air inside the containment after a loss-of-coolant accident (LOCA) or a main steam line break (MSLB) accident inside the containment by using the temperature difference, density difference, and gravity difference between cooling fluids as driving forces, reducing the temperature and pressure inside the containment to ensure the integrity of the containment structure.

[0003] Currently, most of the passive containment cooling systems in the design of nuclear power plants adopt a combination of water cooling and air cooling. This type of passive containment cooling system usually uses a steel containment as a heat conductor and sets up a concrete shield building outside the containment to form a flow channel for cooling air.

[0004] For water cooling, a large amount of water is required to wet the surface of the steel containment. Usually, a large water tank is set above the steel containment. Taking a nuclear power unit with a capacity of one million kilowatts as an example, the volume of the water tank can reach 3000m 3 , and it is an earthquake-resistant equipment with high structural construction difficulty and cost. Moreover, the maintenance of the water quality in the water tank and the operation and maintenance of anti-freezing are cumbersome, and there are many auxiliary systems supporting the water tank.

[0005] For air cooling, there are mainly two current design schemes for the air inlet, bottom air inlet and top air inlet. When the bottom air inlet is used, the air inlet will be affected by surrounding buildings and the air intake volume is low; when the top air inlet is used, there is a problem of inconvenient maintenance.

[0006] Based on this, the inventors of the present application propose a passive containment cooling system for a nuclear power plant in order to solve one or more of the above technical problems. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the defect of poor air cooling effect in the prior art and provide a passive containment cooling system for a nuclear power plant.

[0008] The present invention solves the above technical problems through the following technical solutions:

[0009] The present invention provides a passive containment cooling system for a nuclear power plant. The containment includes an inner steel containment and an outer concrete containment, and a heat exchange annular cavity is formed between the inner steel containment and the outer concrete containment;

[0010] A separation cover is also provided between the inner steel containment vessel and the outer concrete containment vessel. The top end of the separation cover penetrates through the top of the outer concrete containment vessel, and the other end covers the outside of the inner steel containment vessel and extends towards the bottom end of the inner steel containment vessel;

[0011] The separation cover includes an absorption layer, a heat insulation layer, and heat pipes located between the absorption layer and the heat insulation layer. The absorption layer is arranged on the side close to the inner steel containment vessel and cooperates with the heat insulation layer to wrap the heat pipes.

[0012] According to an embodiment of the present invention, the absorption layer is a fluorocarbon paint coating;

[0013] The heat insulation layer is a Guangna Nano GN-301 nano-ceramic high-temperature heat insulation coating.

[0014] According to an embodiment of the present invention, a high-emissivity coating is provided on the outer wall surface of the inner steel containment vessel facing the separation cover.

[0015] According to an embodiment of the present invention, the high-emissivity coating uses as a binder, SiC, as a high-emissivity filler, as a wear-resistant filler, as a stabilizer to be prepared.

[0016] According to an embodiment of the present invention, the separation cover divides the heat exchange annular cavity into a first annular cavity and a second annular cavity, and the bottoms of the first annular cavity and the second annular cavity are communicated;

[0017] A rectifying plate is further provided in the first annular cavity. The rectifying plate is annular and its two ends are respectively connected to the outer concrete containment vessel and the inner steel containment vessel;

[0018] At least one air inlet is further opened on the outer concrete containment vessel. The air inlet is communicated with the first annular cavity. The distance from the air inlet to the bottom surface of the outer concrete containment vessel is greater than the distance from the rectifying plate to the bottom surface of the outer concrete containment vessel. The cold air flowing in through the air inlet flows through the rectifying plate and circulates towards the bottom communication area of the first annular cavity and the second annular cavity;

[0019] An air outlet is further opened at the top of the outer concrete containment vessel. The air outlet is communicated with the second annular cavity.

[0020] According to an embodiment of the present invention, the number of the air inlets is at least two, and at least two of the air inlets are evenly distributed circumferentially around the outer concrete containment vessel.

[0021] According to an embodiment of the present invention, a shielding building is further provided on the outer peripheral side of the outer concrete containment vessel, and the bottom end of the shielding building is aligned with the bottom end of the outer concrete containment vessel;

[0022] The installation height of the air inlet in the outer concrete containment vessel is at least higher than the height of the shielding building.

[0023] According to an embodiment of the present invention, a deflector is provided at the air inlet of the outer concrete containment vessel, one end of the deflector is connected to the outer concrete containment vessel, and the other end extends towards the first annular cavity;

[0024] The deflector is arc-shaped so that the air entering through the air inlet flows towards the bottom end of the first annular cavity through the deflector.

[0025] According to an embodiment of the present invention, multiple rows of communication units are arranged along the circumferential circle of the rectifying plate, and each row of the communication units includes at least two communication holes along the radial direction of the rectifying plate; wherein,

[0026] The restricted pressure drop of the rectifying plate for the air flow entering through the air inlet is not higher than 50 kPa.

[0027] According to an embodiment of the present invention, the distance from the bottom end of the isolation cover to the bottom surface of the outer concrete containment vessel is one-fourth of the distance from the air inlet to the bottom surface of the outer concrete containment vessel.

[0028] The positive and progressive effects of the present invention are as follows:

[0029] In the passive containment cooling system of the nuclear power plant of the present invention, an isolation cover is provided between the inner steel containment vessel and the outer concrete containment vessel, thereby avoiding the direct thermal radiation of the inner steel containment vessel to the outer concrete containment vessel and playing a good protective role for the outer concrete containment vessel; moreover, the isolation cover is composed of heat pipes, an absorption layer and a heat insulation layer, and the absorption layer is on the side close to the inner steel containment vessel, thereby strengthening the radiative heat transfer between the inner steel containment vessel and the isolation cover. The inner steel containment vessel transfers the heat inside the containment vessel to the heat pipes through radiative heat transfer, and the heat pipes carry out the heat; at the same time, the side of the isolation cover close to the outer concrete containment vessel is the heat insulation layer, thereby weakening the heat transfer between the isolation cover and the outer concrete containment vessel. Therefore, the setting of the isolation cover not only meets the need of heat dissipation but also meets the protective effect on the outer concrete containment vessel.

[0030] By means of the heat dissipation method of heat pipes, the heat dissipation efficiency is higher, and the temperature gradient in the heat exchange annular cavity can be reduced, avoiding local overheating and improving the overall heat dissipation uniformity. Moreover, by using heat pipes, the dependence on the external natural wind can be reduced, and stable operation can also be achieved in extreme weather. Description of the Drawings

[0031] The above and other features, properties, and advantages of the present invention will become more apparent from the following description in conjunction with the drawings and embodiments, where:

[0032] Figure 1 It is a schematic structural diagram of the passive containment cooling system of the nuclear power plant of the present invention;

[0033] Figure 2 is Figure 1 the top view of the rectifying plate in

[0034] Figure 3 is Figure 1 the axial cross-sectional view of the isolation cover in

[0035] 1. Inner steel containment; 11. High emissivity coating;

[0036] 2. Outer concrete containment; 21. Air inlet; 22. Air outlet; 23. Deflector; 24. Rectifying plate; 241. Connecting unit; 242. Connecting hole;

[0037] 3. Heat exchange annulus; 31. First annular cavity; 32. Second annular cavity;

[0038] 4. Shield building;

[0039] 5. Isolation cover; 51. Absorbing layer; 52. Insulating layer; 53. Heat pipe. Detailed implementation manners

[0040] The present invention will be further described below in conjunction with specific embodiments and the drawings. More details are elaborated in the following description to facilitate a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from this description. Those skilled in the art can make similar generalizations and deductions according to the actual application situation without departing from the connotation of the present invention. Therefore, the protection scope of the present invention should not be limited by the content of this specific embodiment.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above drawings are intended to cover non-exclusive inclusion.

[0042] Please refer to Figures 1 to 3 , the present invention provides a passive containment cooling system for a nuclear power plant. The containment includes an inner steel containment 1 and an outer concrete containment 2, and a heat exchange annulus 3 is formed between the inner steel containment 1 and the outer concrete containment 2.

[0043] Specifically, an isolation shield 5 is further provided between the inner steel containment 1 and the outer concrete containment 2. The top end of the isolation shield 5 is connected to the outer concrete containment 2, and the other end covers the outside of the inner steel containment 1 and extends towards the bottom end of the inner steel containment 1.

[0044] Referring to Figure 3 , the isolation shield 5 includes an absorption layer 51, a heat insulation layer 52, and heat pipes 53 located between the absorption layer 51 and the heat insulation layer 52; the absorption layer 51 is located inside the heat pipes 53 and cooperates with the heat insulation layer 52 to wrap the heat pipes 53.

[0045] An isolation shield 5 is provided between the inner steel containment 1 and the outer concrete containment 2. The isolation shield 5 is used to axially separate the outer concrete containment 2 and the inner steel containment 1 along the inner steel containment 1, thereby preventing the radiant heat of the inner steel containment 1 from directly acting on the outer concrete containment 2. Excessive heat radiation will cause the outer concrete containment 2 to be damaged and cracked, affecting the safety of the passive containment cooling system.

[0046] It should be noted that the isolation shield 5 proposed in this application is divided into three layers. The inner layer is the absorption layer 51 close to the inner steel containment 1, which is used to strengthen the radiant heat transfer between the isolation shield 5 and the inner steel containment 1, facilitating the transfer of heat from the inner steel containment 1 to the heat pipes 53, and then using the temperature difference, density difference, and gravity difference of the medium in the heat pipes 53 as the driving force to carry out the heat.

[0047] Specifically, the heat of the inner steel containment 1 can be absorbed by the absorption layer 51 in the form of infrared radiation. The working fluid in the heat pipes 53 is heated and evaporated, and the steam carries the heat to the cold end. The cold end is cooled by natural convection, and the working fluid condenses and flows back, completing the cycle relying on the gravity difference, realizing the passive transfer of heat from the inner steel containment 1 to the outside of the outer concrete containment 2.

[0048] The heat pipes 53 rely on the phase change (evaporation-condensation cycle) of the working fluid to transfer heat, and can quickly transfer the heat of the inner steel containment 1 to the external environment, with a higher heat dissipation efficiency than natural convection.

[0049] The heat pipes 53 are only driven by the temperature difference and can still operate stably in the absence of wind or extreme weather, meeting the principle of "passive safety" of nuclear power plants, with high reliability and low maintenance requirements.

[0050] Optionally, the absorption layer 51 is a fluorocarbon paint coating; the heat insulation layer 52 is a Guangna Nano GN-301 nano-ceramic high-temperature heat insulation coating.

[0051] It should be noted that fluorocarbon paint has a high infrared emissivity, can effectively absorb the thermal radiation on the surface of the inner steel containment 1, and convert it into the latent heat of vaporization of the working fluid in the heat pipe 53, which is conducive to improving the startup speed and heat transfer efficiency of the heat pipe 53; moreover, the coating coverage can reduce the thermal reflection on the surface of the inner steel containment 1, avoid local overheating, and improve the temperature distribution in the absorption section of the heat pipe 53.

[0052] The nano-ceramic structure can block the radial heat dissipation of the heat pipe 53 to the outer concrete containment 2 through the dual mechanisms of aerogel pores and infrared reflection, ensuring that the heat is conducted axially along the heat pipe 53 to the top condensation section and preventing the heat from accumulating in the heat exchange annulus 3.

[0053] Moreover, the nano-particles can reflect the infrared radiation emitted by the heat pipe 53, further reducing the heat loss. The nano-ceramic high-temperature heat-insulating coating can also block the transfer of high temperature to the outer concrete containment 2 and protect the strength of the outer concrete containment 2 from thermal damage.

[0054] Refer to Figure 1 On the outer wall surface of the inner steel containment 1 facing the isolation cover 5, a high-emissivity coating 11 is provided.

[0055] Specifically, the high-emissivity coating 11 uses as the binder, SiC, as the high-emissivity filler, as the wear-resistant filler, and is prepared with a stabilizer.

[0056] The binder is selected which has the advantages of high-temperature stability, strong adhesion and corrosion resistance. The binder can form a stable glass phase in the range of 300 - 800 °C, thus being able to withstand high temperatures. The reaction between the binder and the steel matrix (inner steel containment 1) can generate to achieve chemical bonding and prevent the coating from peeling off. Moreover, the aluminum phosphate film can block the penetration of , and other corrosive media, protecting the inner steel containment 1 from the erosion of the wet boron-containing environment inside the containment.

[0057] The high-emissivity filler is selected as SiC and . SiC has a high emissivity (ε≈0.85 - 0.95) in the 3 - 5 μm and 8 - 14 μm atmospheric window bands, and can effectively convert the heat of the inner steel containment 1 into radiant energy. Nano improves the mid- and far-infrared emissivity (ε≈0.9) through the surface phonon polarization effect and forms a multi-scale radiation enhancement network with SiC. Moreover, SiC can also improve the thermal conductivity of the coating and prevent heat from accumulating in the coating.

[0058] Selection of wear-resistant filler , micron level is beneficial to improving the wear resistance of the coating (wear rate < 0.1 mg / 1000 revolutions, ASTM D4060), and thus can resist the friction of the airflow in the containment or maintenance operations. Moreover, it can maintain its rigidity at high temperatures and prevent the coating from softening and deforming.

[0059] Selection of stabilizer , is converted into at high temperatures to form a dense passivation film, inhibit the high-temperature oxidation of the filler (such as SiC), and extend the coating life.

[0060] That is, when natural convection is limited, the high-emissivity coating 11 provided on the inner steel containment 1 can transfer heat to the heat pipe 53 efficiently through radiation, with a higher heat dissipation power. Moreover, setting the high-emissivity coating 11 on the inner steel containment 1 can radiate heat evenly, reduce thermal stress, and avoid local deformation of the inner steel containment 1.

[0061] The isolation cover 5 divides the heat exchange ring cavity 3 into a first annular cavity 31 and a second annular cavity 32, and the bottoms of the first annular cavity 31 and the second annular cavity 32 are connected.

[0062] A flow rectifying plate 24 is further provided in the first annular cavity 31. The flow rectifying plate 24 is annular and is respectively connected to the outer concrete containment 2 and the inner steel containment 1 at both ends; at least one air inlet 21 is further provided on the outer concrete containment 2. The air inlet 21 is communicated with the first annular cavity 31. The distance between the air inlet 21 and the bottom surface of the outer concrete containment 2 is greater than the distance between the flow rectifying plate 24 and the bottom surface of the outer concrete containment 2. The cold air flowing in through the air inlet 21 flows through the flow rectifying plate 24 and flows towards the bottom connection area of the first annular cavity 31 and the second annular cavity 32; an air outlet 22 is further provided at the top of the outer concrete containment 2, and the air outlet 22 is communicated with the second annular cavity 32.

[0063] That is, the cold air flowing in through the air inlet 21 flows through the flow rectifying plate 24, is rectified by the flow rectifying plate 24 and then flows to the bottom connection area of the first annular cavity 31 and the second annular cavity 32, and then flows upward through the second annular cavity 32, and finally is dissipated through the air outlet 22, thereby taking out the heat of the inner steel containment 1.

[0064] Optionally, the number of the air inlets 21 is at least two, and at least two air inlets 21 are circumferentially distributed evenly around the outer concrete containment 2.

[0065] Specifically, the number of air inlets 21 can be adjusted according to the situation of the containment layout area. If the containment is arranged in an area with a relatively high amount of cold air input from the external environment, the number of air inlets 21 can be relatively small; and if the containment is arranged in an area with a relatively low amount of cold air input from the external environment, the number of air inlets 21 can be set to be relatively large. The specific number is not limited here.

[0066] The evenly distributed air inlets 21 are conducive to a more uniform flow rate of air entering the heat exchange ring cavity 3. Compared with the traditional method of opening the air inlet 21 on the ground outside the outer concrete containment 2, the air inlet 21 of the present invention has a higher air flow rate.

[0067] Please continue to refer to Figure 1 A shielding building 4 is also provided on the outer peripheral side of the outer concrete containment shell 2, and the bottom end of the shielding building 4 is aligned with the bottom end of the outer concrete containment shell 2; the setting height of the air inlet 21 in the outer concrete containment shell 2 is at least higher than the height of the shielding building 4.

[0068] That is, the present invention provides an air inlet 21 on the outer concrete containment shell 2, and an air outlet 22 on the top of the outer concrete containment shell 2. The air inlet 21 is connected to the first annular cavity 31 and is located at least above the shielding plant 4. The air outlet 22 is connected to the second annular cavity 32. The wind entering through the air inlet 21 flows through the first annular cavity 31 and the second annular cavity 32 in sequence and is discharged from the air outlet 22.

[0069] The present invention arranges the air inlet 21 in the middle of the outer concrete containment 2 and above the shielding building 4. Compared with the traditional air inlet 21 arranged at the bottom, the middle air inlet can avoid the obstruction of ground obstacles (such as surrounding buildings) to the air intake, and the air intake into the heat exchange ring cavity 3 is smoother. Moreover, placing the air inlet 21 above the shielding building 4 is conducive to maintenance and increases the convenience of operation and maintenance.

[0070] It should be noted that the traditional air inlet 21 is generally opened from the outside of the outer concrete containment shell 2, and is arranged through the ground at the bottom of the outer concrete containment shell 2, extending from the ground to the chamber between the inner steel containment shell 1 and the outer concrete containment shell 2.

[0071] On the one hand, the air inlet flow channel of this method is U-shaped, flowing downward first and then upward. The heat of the inner steel containment 1 is in the relatively middle part, so the hot air flow in the middle will flow toward both sides, and then form convection with the incoming cold air. When the external cold air flow is relatively low, the heat in the inner steel containment 1 will flow back to the outside of the outer concrete containment 2 through the air inlet flow channel, which is not conducive to the removal of the heat of the inner steel containment 1.

[0072] On the other hand, this runner arrangement requires laying pipelines below the ground surface. The heat radiation inside the inner steel containment 1 will conduct to the pipelines and then be transferred to the ground by the pipelines. This heat will change the stress distribution of the formation, which is not conducive to the support of the outer concrete containment. There is a risk that the outer concrete containment may tilt or settle due to the thermal expansion and cracking of the formation, posing a safety risk.

[0073] In the present invention, the air inlet 21 is provided in the middle of the outer concrete containment 2, and structures such as pipeline arrangements are cancelled. On the one hand, the air inlet 21 at a higher position from the ground can obtain airflows with higher velocities, which is conducive to improving the heat extraction efficiency of the inner steel containment 1. On the other hand, the cold air flowing into the heat exchange annular cavity 3 basically flows in the direction from bottom to top, thus avoiding the formation of convection between the cold air and the heat of the inner steel containment 1 and affecting the heat extraction.

[0074] Please continue to refer to Figure 1 , a flow guide plate 23 is provided at the air inlet 21 of the outer concrete containment 2. One end of the flow guide plate 23 is connected to the outer concrete containment 2, and the other end extends towards the inside of the first annular cavity 31.

[0075] Specifically, the flow guide plate 23 is arc-shaped so that the air entering through the air inlet 21 flows towards the bottom end of the first annular cavity 31 along the flow guide plate 23.

[0076] That is, the air entering through the air inlet 21 flows towards the bottom of the first annular cavity 31 under the guiding action of the flow guide plate 23, and then flows to the communication area between the first annular cavity 31 and the second annular cavity 32. Then, the entering gas flows towards the second annular cavity 32 under the isolation of the isolation cover 5, taking away the heat at the bottom of the inner steel containment 1.

[0077] Because the flow guide plate 23 is arc-shaped, the entering air blows onto the wall of the isolation cover 5 close to the outer concrete containment 2 and then flows obliquely downwards until it flows to the communication area between the first annular cavity 31 and the second annular cavity 32 and enters the second annular cavity 32 and flows upwards to the air outlet 22.

[0078] It should be noted that the air inlet 21 is provided in the middle of the outer concrete containment 2. If it flows directly upwards, the heat at the bottom of the inner steel containment 1 cannot be taken out. Therefore, the flow guide plate 23 is used to make the cold air flow to the communication area at the bottom of the first annular cavity 31 and the second annular cavity 32, and then take away the heat at the bottom of the inner steel containment 1.

[0079] In one embodiment, the restricted pressure drop of the flow rectifying plate 24 for the air flow entering through the air inlet 21 is not higher than 50 kPa.

[0080] Specifically, a plurality of rows of communication units 241 are provided on the rectifying plate 24 along its circumference, and each row of communication units 241 includes at least two communication holes 242 along the radial direction of the rectifying plate 24 .

[0081] Therefore, when the limiting pressure drop of the rectifying plate 24 on the incoming airflow is less than 50 kPa, the rectifying plate 24 has little effect on the inlet airflow, and under the rectifying effect of the rectifying plate 24, the wind speed reaching the surface of the inner steel containment 1 through the rectifying plate 24 is more uniform. For a steel containment with a height of 70 m and a diameter of 50 m, the heat exchange efficiency can be increased by at least 10%.

[0082] Because the number of air inlets 21 is limited, the cooling effect of the inner steel containment 1 area close to the air inlet 21 is good, while the cooling effect of the inner steel containment 1 located between the two air inlets 21 is poor. As a whole, the inner steel containment 1 has poor heat exchange uniformity and low efficiency.

[0083] Therefore, the present invention can make the airflow distribution on the surface of the inner steel containment 1 more uniform by setting the rectifying plate 24, thereby avoiding local overheating or insufficient heat exchange. This can avoid the formation of a low-speed zone in the inner steel containment 1 due to inertia in the traditional design. The rectifying plate 24 can enhance the turbulence, and moderate turbulence can destroy the boundary layer and improve the heat transfer coefficient.

[0084] Regarding the design of the rectifying plate 24, the present invention balances uniformity and resistance through the opening ratio and the shape of the flow channel, thereby selecting a rectifying structure with the least effect on the flow velocity. Thus, the use of the rectifying plate 24 can improve the heat exchange efficiency.

[0085] That is, the present invention sets a rectifying plate 24 below the air inlet 21, and the air can obtain a uniform flow rate through the surface of the inner steel containment 1 by flowing through the rectifying plate 24 with a porous flow channel structure. This method can improve the flow heat transfer capacity of the air, and the air in the uniform flow channel transfers the heat in the inner steel containment 1 through convection heat transfer, and the heat is discharged to the atmospheric environment from the air outlet 22 at the top of the outer concrete containment 2 along with the air.

[0086] Optionally, the distance between the bottom end of the isolation cover 5 and the bottom surface of the outer concrete containment shell 2 is one quarter of the distance between the air inlet 21 and the bottom surface of the outer concrete containment shell 2 .

[0087] Therefore, under the setting of the guide plate 23, the airflow entering through the air inlet 21 can form sufficient circulation space at the bottom of the inner steel containment shell 1, avoiding the airflow rising directly along the second annular cavity 32 and ignoring the bottom area of the inner steel containment shell 1.

[0088] It can be seen that the bottom of the isolation cover 5 needs to be as close as possible to the bottom of the cavity of the outer concrete containment 2, so as to avoid the influence of thermal radiation on the bottom of the outer concrete containment 2. However, if the isolation cover 5 is too close to the bottom of the outer concrete containment 2, there will be too small a volume at the connection between the first annular cavity 31 and the second annular cavity 32, which is not conducive to air flow.

[0089] Based on this, in the present invention, the distance between the bottom end of the isolation cover 5 and the bottom surface of the outer concrete containment 2 is set to be one-fourth of the distance from the air inlet 21 to the bottom surface of the outer concrete containment 2, thereby ensuring that the bottom of the outer concrete containment 2 is less affected by thermal radiation and ensuring that there is sufficient space at the bottom of the isolation cover 5 for air flow.

[0090] Thus, the cold air flow at the bottom of the isolation cover 5 can also isolate the thermal radiation of the inner steel containment 1 from affecting the bottom area of the outer concrete containment 2.

[0091] In summary, in the passive containment cooling system of the nuclear power plant of the present invention, an isolation cover 5 is provided between the inner steel containment 1 and the outer concrete containment 2, thereby avoiding the direct thermal radiation of the inner steel containment 1 to the outer concrete containment 2 and playing a good protective role for the outer concrete containment 2; moreover, the isolation cover 5 is composed of heat pipes 53, an absorption layer 51 and a heat insulation layer 52, and the absorption layer 51 is on the side close to the inner steel containment 1, thereby strengthening the radiative heat transfer between the inner steel containment 1 and the isolation cover 5. The inner steel containment 1 transfers the heat inside the containment to the heat pipes 53 through radiative heat exchange, and the heat pipes 53 carry out the heat; at the same time, the side of the isolation cover 5 close to the outer concrete containment is the heat insulation layer 52, thereby weakening the heat transfer between the isolation cover 5 and the outer concrete containment 2. Thus, the setting of the isolation cover 5 not only meets the need of heat dissipation but also meets the protective effect on the outer concrete containment 2.

[0092] By means of heat dissipation through the heat pipes 53, the heat dissipation efficiency is higher, and the temperature gradient in the heat exchange annular cavity 3 can be reduced, avoiding local overheating and improving the overall heat dissipation uniformity. Moreover, by using the heat pipes 53, the dependence on the external natural wind can be reduced, and stable operation can also be achieved in extreme weather.

[0093] At the same time, the present invention also adjusts the position of the air inlet 21 to avoid the influence of surrounding buildings on the inlet wind speed while increasing the convenience of operation and maintenance.

[0094] Moreover, by setting the flow rectifying plate 24 to strengthen the convective heat transfer of air and increasing the heat transfer area through the heat pipes 53 of the isolation cover 5, the enhancement of the pure air cooling capacity is realized.

[0095] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "attachment", and "fixation" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral one; it can also be a mechanical connection. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0096] The present application uses specific terms to describe the embodiments of the present application. Such as "one embodiment", "an embodiment", and / or "some embodiments" mean a certain feature, structure, or characteristic related to at least one embodiment of the present application. Therefore, it should be emphasized and noted that the "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more at different positions in this specification is not necessarily the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the present application can be appropriately combined.

[0097] Although the present invention is disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, all modifications, equivalent changes, and decorations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention fall within the protection scope defined by the claims of the present invention.

Claims

1. An passive containment cooling system for nuclear power plants, characterized in that The containment vessel includes an inner steel containment vessel and an outer concrete containment vessel, and a heat exchange annular cavity is formed between the inner steel containment vessel and the outer concrete containment vessel; A separator is further provided between the inner steel containment vessel and the outer concrete containment vessel. The top end of the separator penetrates through the top of the outer concrete containment vessel, and the other end covers the outside of the inner steel containment vessel and extends towards the bottom end of the inner steel containment vessel; The separator includes an absorption layer, a heat insulation layer, and heat pipes located between the absorption layer and the heat insulation layer. The absorption layer is arranged on the side close to the inner steel containment vessel and cooperates with the heat insulation layer to wrap the heat pipes; The separator divides the heat exchange annular cavity into a first annular cavity and a second annular cavity, and the bottoms of the first annular cavity and the second annular cavity are communicated; A flow rectifying plate is further provided in the first annular cavity. The flow rectifying plate is annular and its two ends are respectively connected to the outer concrete containment vessel and the inner steel containment vessel; At least one air inlet is further opened on the outer concrete containment vessel. The air inlet is communicated with the first annular cavity. The distance from the air inlet to the bottom surface of the outer concrete containment vessel is greater than the distance from the flow rectifying plate to the bottom surface of the outer concrete containment vessel. The cold air flowing in through the air inlet flows through the flow rectifying plate and circulates towards the bottom communication area of the first annular cavity and the second annular cavity; An air outlet is further opened at the top of the outer concrete containment vessel. The air outlet is communicated with the second annular cavity.

2. The passive containment cooling system for a nuclear power plant according to claim 1, wherein The absorption layer is a fluorocarbon paint coating; The heat insulation layer is a Guangna Nano GN-301 nano-ceramic high-temperature heat insulation coating.

3. The passive containment cooling system of a nuclear power plant according to claim 1, wherein A high emissivity coating is provided on the outer wall surface of the inner steel containment vessel on the side facing the separator.

4. The passive containment cooling system of a nuclear power plant according to claim 3, characterized in that, The high emissivity coating uses as the binder, SiC, as the high emissivity filler, as the wear-resistant filler, and is prepared with a stabilizer.

5. The passive containment cooling system of a nuclear power plant according to claim 1, wherein The number of the air inlets is at least two, and at least two of the air inlets are evenly distributed circumferentially around the outer concrete containment vessel.

6. The passive containment cooling system of a nuclear power plant according to claim 1, characterized in that, A shielding building is further provided on the outer peripheral side of the outer concrete containment vessel. The bottom end of the shielding building is aligned with the bottom end of the outer concrete containment vessel; The installation height of the air inlet on the outer concrete containment vessel is at least higher than the height of the shielding building.

7. The passive containment cooling system of a nuclear power plant according to claim 1, characterized in that, A flow guiding plate is provided at the air inlet of the outer concrete containment vessel. One end of the flow guiding plate is connected to the outer concrete containment vessel, and the other end extends towards the inside of the first annular cavity; The flow guiding plate is arc-shaped so that the air flowing in through the air inlet flows towards the bottom end of the first annular cavity through the flow guiding plate.

8. The passive containment cooling system of a nuclear power plant according to claim 1, characterized in that, A plurality of rows of communication units are arranged circumferentially along the circumference of the flow rectifying plate. Each row of the communication units includes at least two communication holes along the radial direction of the flow rectifying plate; wherein, The restricted pressure drop of the flow rectifying plate for the air flow flowing in through the air inlet is not higher than 50 kPa.

9. The passive containment cooling system of a nuclear power plant according to claim 1, characterized in that, The distance from the bottom end of the separator to the bottom surface of the outer concrete containment vessel is one-fourth of the distance from the air inlet to the bottom surface of the outer concrete containment vessel.

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