A time-indefinite passive residual heat removal system

Abstract

The present invention discloses a time-indefinite passive waste heat removal system, comprising a cooling circuit composed of a steam generator, a steam pipeline isolation valve, a passive waste heat removal cooler, and a condensate pipeline isolation valve connected in series in sequence, the cooling circuit is connected to the secondary side of the steam generator, an emergency cooling water tank is provided on the outside of the passive waste heat removal cooler; an exhaust chimney and an air intake channel are provided on the emergency cooling water tank, the exhaust chimney is arranged vertically, the top of the exhaust chimney passes through the bottom of the emergency cooling water tank to communicate with the outside, the bottom of the exhaust chimney is provided with an opening to communicate with the inside of the emergency cooling water tank, and the air intake channel is provided on the side wall of the water tank; the passive waste heat removal cooler is placed inside the exhaust chimney. Under limited resource conditions, time-indefinite passive waste heat removal is achieved; based on the load distribution and resource balancing design concepts, compared with the traditional solution that relies on boiling evaporation of water stored in the water tank or air convection cooling, it occupies less overall resources and is highly economical.

Description

Technical Field

[0001] The invention relates to the field of special safety facilities for nuclear power plants or floating nuclear power platforms, and in particular to a time-indefinite passive residual heat removal system. Background Art

[0002] When designing dedicated safety facilities, consideration should be given to the use of passive safety technologies that do not require external power to improve safety and reliability. At the same time, economic issues must also be considered to reduce overall resource requirements and construction costs while meeting functional and safety requirements.

[0003] Advanced technologies such as APR1400, KLT-40S, and Hualong One all use a non-passive residual heat removal scheme in which the cooler is placed in a high-level water tank and the water stored in the water tank is boiled and evaporated to remove the core decay heat. In this scheme, the effective operation time of the system depends on the amount of water stored in the water tank. The more water is stored, the longer the system will operate. On the one hand, the boiling evaporation scheme cannot achieve unlimited non-passive residual heat removal; at the same time, as the size of the water tank increases, the difficulty of the impact and seismic design of the water tank support structure also increases, and the required construction cost also gradually increases.

[0004] In addition, WWER has adopted a passive residual heat removal design based on air cooling, but due to the characteristics of decay heat release, the decay heat is high at the beginning of the accident and then drops rapidly. In order to meet the initial large-load decay heat removal requirements, a large-capacity air cooler and air flow channel are still required, which is not very economical. Summary of the invention

[0005] In view of the above-mentioned defects in the prior art, a time-limited passive waste heat removal system based on boiling evaporation-air convection coupled cooling is provided to achieve time-limited passive waste heat removal.

[0006] The technical solution adopted by the present invention to solve the above technical problems is:

[0007] A timeless passive waste heat removal system comprises a cooling circuit formed by a steam generator, a steam pipe isolation valve, a passive waste heat removal cooler, and a condensate pipe isolation valve connected in series in sequence, the cooling circuit is connected to the secondary side of the steam generator, and an emergency cooling water tank is arranged outside the passive waste heat removal cooler; it is characterized in that: an exhaust chimney and an air intake channel are arranged on the emergency cooling water tank, the exhaust chimney is arranged vertically, the top of the exhaust chimney passes through the bottom of the emergency cooling water tank to communicate with the outside, the bottom of the exhaust chimney is provided with an opening to communicate with the inside of the emergency cooling water tank, and the air intake channel is arranged on the side wall of the water tank; the passive waste heat removal cooler is placed inside the exhaust chimney.

[0008] According to the above technical solution, the heights of the passive waste heat removal cooler, the emergency cooling water tank, and the exhaust chimney are higher than the height of the steam output end of the steam generator.

[0009] According to the above technical solution, the exhaust chimney adopts a wind tube-like structure that is narrow at the top and wide at the bottom.

[0010] According to the above technical solution, the exhaust chimney is suspended in the emergency cooling water tank, and a shutter structure for connecting to the emergency cooling water tank is provided on the lower outer wall of the exhaust chimney.

[0011] According to the above technical solution, the minimum height of the passive waste heat removal cooler is not higher than the height of the shutter structure.

[0012] According to the above technical solution, the air intake passage is arranged on the top of the side wall of the emergency cooling water tank.

[0013] The present invention has the following beneficial effects:

[0014] This device uses cooling water in the early stage and air convection in the later stage for heat conduction. The high-efficiency and compact heat exchange unit can take into account both water cooling and air cooling modes, which is adapted to the amount of decay heat generated during the accident. When a large amount of decay heat is generated in the early stage, water cooling is used for rapid heat conduction. When less decay heat is generated in the later stage, air cooling is used for continuous heat conduction to achieve unlimited waste heat export. Under limited resource conditions, unlimited non-active waste heat discharge is achieved; based on the load distribution and resource balancing design concept, compared with the traditional solution that relies on boiling evaporation of water stored in the water tank or air convection cooling, it occupies less overall resources and is more economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of an embodiment provided by the present invention;

[0016] In the figure, 1. steam generator; 2. steam pipe isolation valve; 3. passive waste heat discharge cooler; 4. condensate pipe isolation valve; 5. emergency cooling water tank; 6. air intake channel; 7. exhaust chimney; 8. steam pipe; 9. shutter structure. DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0018] Reference Figure 1As shown, the present invention provides a non-time-limited passive waste heat removal system, including a cooling circuit composed of a steam generator 1, a steam pipe isolation valve 2, a passive waste heat removal cooler 3, and a condensate pipe isolation valve 4 connected in series in sequence (each component is connected through a steam pipe 8), the cooling circuit is connected to the secondary side of the steam generator, and an emergency cooling water tank 5 is provided outside the passive waste heat removal cooler. An exhaust chimney 7 and an air intake channel 6 are provided on the emergency cooling water tank. The exhaust chimney is arranged vertically, and the top of the exhaust chimney passes through the bottom of the emergency cooling water tank to communicate with the outside world. The bottom of the exhaust chimney is provided with an opening to communicate with the inside of the emergency cooling water tank, and the air intake channel is provided on the side wall of the water tank; the passive waste heat removal cooler is placed inside the exhaust chimney, and the steam and external air generated by the boiling of the passive waste heat removal cooler can be discharged through the chimney with heat.

[0019] The coupling cooling technology of boiling evaporation of water stored in the water tank and natural convection of air is adopted. In the initial state, cooling water is injected into the emergency cooling water tank. A large amount of decay heat is generated in the early stage of the accident, which is transferred to the cooling water inside the exhaust chimney through the passive residual heat discharge cooler. The large amount of decay heat generated in the early stage of the accident is quickly discharged by the boiling evaporation of cooling water (i.e. natural convection and pool boiling of cooling water). Less decay heat is generated in the middle stage of the accident, and most of the passive residual heat discharge cooler is exposed to the air. At this time, the boiling evaporation of cooling water and the air convection formed by the exhaust chimney and the air intake channel are used to conduct the decay heat. A small amount of decay heat is generated in the late stage of the accident. At this time, the cooling water is exhausted. After the cooling water in the emergency cooling water tank is evaporated, the low decay heat generated in the late stage of the accident is conducted by air convection through the air convection formed by the exhaust chimney and the air intake channel (i.e., the exhaust chimney is used to form a "chimney effect"), so as to achieve unlimited residual heat discharge. This device uses cooling water for heat conduction in the early stage and air convection for heat conduction in the later stage. The high-efficiency and compact heat exchange unit adopted can take into account both water cooling and air cooling modes, which is adapted to the amount of decay heat generated during the accident. When a large amount of decay heat is generated in the early stage, water cooling is used for rapid heat conduction. When less decay heat is generated in the later stage, air cooling is used for continuous heat conduction, thereby realizing unlimited waste heat conduction.

[0020] Furthermore, the heights of the passive waste heat removal cooler, the emergency cooling water tank, and the exhaust chimney are higher than the height of the steam output end of the steam generator, so as to facilitate the establishment of natural circulation.

[0021] Furthermore, the exhaust chimney adopts a wind tube-like structure that is narrow at the top and wide at the bottom. When the liquid level in the water tank drops to a predetermined height (i.e. the interior of the exhaust chimney is connected to the interior of the emergency cooling water tank), a "chimney effect" can be automatically formed to enhance the system's natural air circulation and heat removal capacity.

[0022] Furthermore, the exhaust chimney is suspended in the emergency cooling water tank, and a shutter structure 9 for connecting to the emergency cooling water tank is provided on the lower outer wall of the exhaust chimney. When the cooling water level in the exhaust chimney drops to the shutter structure, the inside of the exhaust chimney is connected to the inside of the emergency cooling water tank through the shutter structure, thereby forming a "chimney effect" and improving the natural air circulation heat removal capacity of the system.

[0023] Further, the lowest height of the passive waste heat removal cooler is not higher than the height of the shutter structure.

[0024] Furthermore, the air intake passage is arranged on the top of the side wall of the emergency cooling water tank.

[0025] Working principle of the present invention:

[0026] After the passive waste heat removal system is started, the steam on the secondary side of the steam generator that needs to be cooled enters the passive waste heat removal cooler through the steam pipe. In the early stage of the accident, due to the large amount of decay heat released, the cooling water is heated to boiling and evaporated by relying on the heat exchange between the passive waste heat removal cooler and the cooling water in the exhaust chimney. The steam generated by the boiling of the cooling water is discharged to the atmosphere through the exhaust chimney, thereby achieving the effect of heat conduction.

[0027] As the liquid level in the emergency cooling water tank decreases and the louver structure on the lower side wall of the exhaust chimney emerges from the waterline, external air begins to enter the exhaust chimney through the air intake passage, and natural convection begins to form under the action of the "chimney effect".

[0028] As the decay heat is released and heated continuously until the cooling water in the emergency cooling water tank is evaporated, the shutter structure and the bottom opening on the lower side wall of the exhaust chimney are completely connected to the air in the emergency cooling water tank. At this time, a large amount of external air begins to enter the chimney through the air intake channel on the side wall of the emergency cooling water tank, and the decay heat is discharged to the atmosphere through the heat exchange between the convective air and the passive waste heat exhaust cooler, realizing unlimited passive waste heat discharge.

[0029] The above are only preferred embodiments of the present invention, and certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the scope of the patent application of the present invention still fall within the protection scope of the present invention.

Claims

1. A time-indefinite passive waste heat removal system, comprising a cooling circuit consisting of a steam generator, a steam pipeline isolation valve, a passive waste heat removal cooler, and a condensate pipeline isolation valve connected in series, the cooling circuit is connected to the secondary side of the steam generator, and an emergency cooling water tank is provided outside the passive waste heat removal cooler; characterized in that: An exhaust chimney and an air intake passage are provided on the emergency cooling water tank. The exhaust chimney is arranged vertically. The top of the exhaust chimney passes through the bottom of the emergency cooling water tank and is connected to the outside. An opening is provided at the bottom of the exhaust chimney and is connected to the inside of the emergency cooling water tank. The air intake passage is provided on the side wall of the water tank. The passive waste heat discharge cooler is placed inside the exhaust chimney. The exhaust chimney is suspended in the emergency cooling water tank, and a shutter structure for connecting to the emergency cooling water tank is provided on the lower outer wall of the exhaust chimney; The minimum height of the passive waste heat removal cooler shall not be higher than the height of the louver structure.

2. The time-indefinite passive residual heat removal system according to claim 1 is characterized in that: The heights of the passive waste heat removal cooler, the emergency cooling water tank, and the exhaust chimney are higher than the height of the steam output end of the steam generator.

3. The unlimited passive residual heat removal system according to claim 1, characterized in that: The exhaust chimney adopts a wind tube-like structure that is narrow at the top and wide at the bottom.

4. The unlimited time passive residual heat removal system according to claim 1, characterized in that: The air intake passage is arranged on the top of the side wall of the emergency cooling water tank.

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