Containment cooling and filtration system for nuclear power plants

Abstract

The application belongs to the technical field of nuclear equipment, and relates to a containment cooling and filtering system for a nuclear power plant. The containment cooling and filtering system comprises a containment inner shell (1), a containment outer shell (2), an annular space (5), an air cooling system, a surrounding water pool system and a filtering and discharging system. The annular space (5) is formed between the containment inner shell (1) and the containment outer shell (2). The air cooling system is used for introducing air into the annular space (5) from the outside of the containment outer shell to cool the containment. The surrounding water pool system is used for introducing cold water into the annular space (5) to contact the containment inner shell (1) and cool the containment. The filtering and discharging system is used for filtering the gas in the containment inner shell (1) and discharging the filtered gas into the annular space (5). The containment cooling and filtering system can improve the accident mitigation capability of the nuclear power plant, thereby improving the safety of the nuclear power plant.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of nuclear equipment, and relates to a containment cooling and filtering system for a nuclear power plant. BACKGROUND

[0002] After an accident occurs in a nuclear power plant, the temperature and pressure in the containment may rise and exceed the pressure limit of the containment, eventually leading to damage of the containment and release of radioactive substances to the environment. Therefore, as the last barrier of the nuclear power plant, effective cooling of the containment has always been the focus of the industry.

[0003] At present, most of the third-generation large-scale pressurized water reactor nuclear power plants at home and abroad adopt the design of double-layer containment, and many kinds of cooling schemes are designed for the double-layer containment. For example, the AP1000 nuclear power plant increases a high-position water tank on the top of the containment, and the water tank can inject water into the annular space between the steel containment and the concrete shell; the VVER nuclear power plant is provided with a containment passive heat export system which exports heat in the containment through gravity, convective heat transfer and other principles. This is a "blocking" way, which actively cools and depressurizes the containment to avoid overpressure damage of the containment and achieve the purpose of "avoiding" release of radioactive substances to the environment.

[0004] At the same time, most nuclear power plants also adopt a containment filtering and exhaust system, which filters, exhausts and depressurizes to prevent overpressure failure of the containment. For example, the Venturi water washer adopted by AREVA and the sand pile filter adopted by EDF. This is a "dilution" way, which directly filters and exhausts the gas in the containment to prevent potential overpressure failure of the containment and reduce the release of radioactive substances to the outside.

[0005] As can be seen, the above two systems are either "blocking" or "dilution", and vice versa. SUMMARY

[0006] The purpose of the present application is to provide a containment cooling and filtering system for a nuclear power plant, which can long-term and effectively cool and depressurize the containment, reduce the risk of damage to the containment and improve the ability of the nuclear power plant to relieve accidents, thereby improving the safety of the nuclear power plant.

[0007] To achieve this purpose, in the basic embodiment, the present application provides a containment cooling and filtering system for a nuclear power plant, which comprises an inner containment, an outer containment, an annular space, an air cooling system, a surrounding water pool system and a filtering and exhaust system,

[0008] The annular space is formed between the inner containment and the outer containment;

[0009] The air cooling system introduces air into the annular space from outside the containment vessel to cool the containment vessel.

[0010] The water cooling system introduces cold water into the annular space to contact the inner containment vessel to cool the containment vessel.

[0011] The filtered venting system filters the gas in the inner containment vessel and vents the filtered gas into the annular space.

[0012] In a preferred embodiment, the present application provides a nuclear power plant containment vessel cooling and filtering system, wherein the inner containment vessel is made of steel and the outer containment vessel is made of concrete.

[0013] In a preferred embodiment, the present application provides a nuclear power plant containment vessel cooling and filtering system, wherein the air cooling system includes a pipe and a vent, air is introduced into the annular space from the pipe and vented to the atmosphere from the vent above the top of the annular space after air cooling.

[0014] In a preferred embodiment, the present application provides a nuclear power plant containment vessel cooling and filtering system, wherein the pipe includes a vertically downward inlet pipe and a horizontally connected pipe.

[0015] In a preferred embodiment, the present application provides a nuclear power plant containment vessel cooling and filtering system, wherein the water cooling system includes a cold water tank, a water pump and a spray head, the cold water tank contacts the inner containment vessel, the water pump delivers cold water stored in the cold water tank to the spray head and the spray head sprays cold water onto the inner containment vessel.

[0016] In a preferred embodiment, the present application provides a nuclear power plant containment vessel cooling and filtering system, wherein the cold water tank is located at the bottom of the annular space and the spray head is located at the top of the annular space.

[0017] In a preferred embodiment, the present application provides a nuclear power plant containment vessel cooling and filtering system, wherein the filtered venting system includes a venting line, a filter and a vent, the gas in the inner containment vessel is filtered by the filter in the venting line and vented into the annular space through the vent in the annular space.

[0018] In a preferred embodiment, the present application provides a nuclear power plant containment vessel cooling and filtering system, wherein the filter and the vent are located at the bottom of the annular space.

[0019] In a preferred embodiment, the present application provides a nuclear power plant containment cooling and filtering system, wherein the containment cooling and filtering system further comprises a pool water replenishing system for replenishing the water source of the surrounding pool system.

[0020] In a preferred embodiment, the present application provides a nuclear power plant containment cooling and filtering system, wherein the pool water replenishing system comprises an external refueling water tank and an electric isolation valve, and the water stored in the external refueling water tank is replenished into the water source of the surrounding pool system through the electric isolation valve.

[0021] The nuclear power plant containment cooling and filtering system of the present application can effectively cool and depressurize the containment in a long term when a containment energy release accident occurs in a nuclear power plant, thereby reducing the risk of containment damage and improving the accident mitigation capability of the nuclear power plant, and thus improving the safety of the nuclear power plant.

[0022] The nuclear power plant containment cooling and filtering system of the present application can realize the functions of blocking and unblocking, and overcome the defect of complicated system of the nuclear power plant, thereby having high value for improving the safety and economy of the nuclear power plant.

[0023] The beneficial effects of the present application are embodied in the following aspects:

[0024] (1) The whole passive cooling system adopts a combination of passive surrounding pool and air cooling, and the pool cold water evaporation, air convection heat transfer and radiation heat transfer are combined to more effectively remove the heat of the containment.

[0025] (2) The surrounding pool system is composed of passive pool and active spray, wherein the active spray sprays cold water on the outer wall of the steel containment to form a liquid film to remove the heat of the containment, and the combination of active and passive systems makes the whole system more efficient and reliable.

[0026] (3) The filtering and discharging system is arranged in the surrounding pool, which reduces the complexity of the system, and can more quickly and conveniently filter and discharge the gas in the containment, thereby enhancing the safety of the nuclear power plant.

[0027] (4) The water source of the pool water replenishing system is from the external refueling water tank, which increases the function of the refueling water tank.

[0028] (5) The present application can more effectively and reliably remove the heat of the containment, which is beneficial to reduce the frequency of large amount of radioactive release in the probabilistic safety analysis of the nuclear power plant, and the passive system is beneficial to reduce the probability of human error. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1The figure shows the structure of the exemplary containment cooling and filtering system of the present application. DETAILED DESCRIPTION

[0030] The figure shows the structure of the exemplary containment cooling and filtering system of the present application. Figure 1 The figure shows the structure of the exemplary containment cooling and filtering system of the present application.

[0031] The annular space 5 is formed between the steel containment inner shell 1 and the concrete containment outer shell 2.

[0032] The air cooling system is arranged outside the containment, and air is introduced into the annular space 5 through the vertical downward inlet pipe 6 and the horizontal pipe 7 (which penetrates the containment outer shell 2) to cool the containment. The cooled air is discharged into the atmosphere through the exhaust outlet 3 above the top of the annular space 5. Multiple air cooling systems can be arranged in multiple directions of the containment, but attention should be paid to the strength of the containment outer shell 2. The air cooling system is passive, and mainly removes the heat of the containment through convective heat transfer and radiative heat transfer. After an accident occurs in the containment, the temperature of the containment inner shell 1 rises, and the temperature of the cold air in the annular space 5 also rises through convective heat transfer and radiative heat transfer. The air is discharged into the atmosphere through the exhaust outlet 3 after rising along the annular space 5. The inlet pipe 6 can be circular or square, and multiple inlet pipes 6 can be arranged outside the containment. The shape can be determined according to the heat transfer requirements and flow characteristics, and the number should mainly focus on the strength of the containment outer shell 2.

[0033] The surrounding pool system comprises a cold water tank 8, a water pump 9 and a spray head 4. The cold water tank 8 is in contact with the inner containment shell 1. The water pump 9 transports the cold water stored in the cold water tank 8 to the spray head 4 and sprays the cold water on the outer wall of the inner containment shell 1 to cool the containment shell. The cold water tank 8 is located at the bottom of the annular space 5 (the liquid level of the tank is higher than the reactor primary loop in the inner containment shell 1), and the spray head 4 is located at the top of the annular space 5. The surrounding pool system is a combination of active and passive systems. The passive part is in contact with the inner containment shell 1 through the cold water tank 8 to transfer heat, and the steam evaporates to take away heat. The active part sprays cold water on the outer layer of the inner containment shell 1 through the water pump 9 and the spray head 4 to form a liquid film to take away heat. Specifically, the cold water in the passive part of the cold water tank 8 is in direct contact with the lower part of the inner containment shell 1. Heat is transferred from the inner containment shell 1 to the cold water in the cold water tank 8, which naturally evaporates to take away heat. The evaporated water vapor is discharged from the bottom to the top of the annular space 5 and is discharged into the atmosphere through the discharge port 3. The highest level of the liquid surface of the cold water tank 8 should be lower than the bottom level of the horizontal pipeline 7. The active part can be opened by the operator according to the need. The water pump 9 sprays water from the cold water tank 8 on the outer layer of the inner containment shell 1 to form a liquid film. The liquid film evaporates to form steam to take away heat, and then is discharged into the atmosphere through the discharge port 3. At the same time, the condensed water flows back to the cold water tank 8 along the outer side of the inner containment shell 1.

[0034] The filtering and discharging system comprises a discharge pipeline 10, a discharge valve 11, a filter 12 and a discharge port 13. The gas in the inner containment shell 1 is filtered through the discharge valve 11 and the filter 12 of the discharge pipeline 10 and is discharged into the annular space 5 through the discharge port 13 located in the annular space 5. The filter 12 and the discharge port 13 are located at the bottom of the annular space 5. When the filtering and discharging operation of the containment shell is performed, the discharge valve 11 of the discharge pipeline 10 is opened, the gas in the containment shell enters the filter 12, and the cold water in the cold water tank 8 can enter the filter 12 (the cold water tank 8 can continuously supplement the water required in the filter 12). After the gas is filtered, the clean gas enters the annular space 5 through the discharge port 13 and is then discharged into the atmosphere through the discharge port 3.

[0035] The passive pool water supplementing system comprises an external replacement water tank 15 and an electric isolation valve 14. The water stored in the external replacement water tank 15 is supplemented into the cold water tank 8 of the surrounding pool system through the control of the electric isolation valve 14. The bottom level of the external replacement water tank 15 should be higher than the top level of the cold water tank 8, and the electric isolation valve 14 is normally open. When the water level in the cold water tank 8 is lower than a certain level, the cold water in the external replacement water tank 15 is automatically injected into the cold water tank 8 to supplement water.

[0036] It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application cover modifications and variations of this application provided they come within the scope of the appended claims and their equivalents. The above embodiments or examples are merely illustrative of the present application, and not restrictive of the present application. The present application can be practiced in other specific forms or modes without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only illustrative and not restrictive, and the scope of the application to be indicated by the appended claims rather than the foregoing description. It is intended to claim all modifications and variations equivalent to those specifically described herein.

Claims

1. A nuclear power plant containment cooling filtration system, characterized by: The safety shell cooling and filtering system comprises a safety shell inner shell (1), a safety shell outer shell (2), an annular space (5), an air cooling system, a surrounding water pool system, a filtering and discharging system, The annular space (5) is formed between the safety shell inner shell (1) and the safety shell outer shell (2). The air cooling system introduces air into the annular space (5) from the safety shell outer shell to cool the safety shell. The surrounding water pool system introduces cold water into the annular space (5) to contact the safety shell inner shell (1) and cool the safety shell. The filtering and discharging system filters the gas in the safety shell inner shell (1) and discharges the filtered gas into the annular space (5). The surrounding water pool system comprises a cold water tank (8), a water pump (9) and a spraying head (4). The cold water tank (8) contacts the safety shell inner shell (1) and is located at the bottom of the annular space (5). The liquid level of the cold water tank (8) is higher than the liquid level of the reactor primary loop in the safety shell inner shell (1), and the highest liquid level of the cold water tank (8) is lower than the bottom elevation of the air cooling system. The filtering and discharging system comprises a discharging pipeline (10), a filter (12) and a discharging port (13). The gas in the safety shell inner shell (1) is filtered by the filter (12) in the discharging pipeline (10) and then discharged into the annular space (5) through the discharging port (13) in the annular space (5). The filter (12) and the discharging port (13) are located at the bottom of the annular space (5). The filter (12) is accommodated in the cold water tank (8). The cold water in the cold water tank (8) continuously replenishes the filter (12). The water pump (9) delivers the cold water stored in the cold water tank (8) to the spraying head (4) and sprays the cold water onto the safety shell inner shell (1) through the spraying head (4). The spraying head (4) is located at the top of the annular space (5). The cold water sprayed by the spraying head (4) forms a liquid film on the outer layer of the safety shell inner shell (1). The liquid film evaporates under heat and takes away heat. The condensed liquid flows back to the cold water tank (8) along the outer side of the safety shell inner shell.

2. The containment cooling filtration system of claim 1, wherein: The safety shell inner shell (1) is made of steel, and the safety shell outer shell (2) is made of concrete.

3. The containment cooling filtration system of claim 1, wherein: The air cooling system comprises a pipeline and a discharging port (3). Air enters the annular space (5) from the pipeline and is discharged into the atmosphere through the discharging port (3) above the top of the annular space (5) after completing air cooling.

4. The containment cooling and filtration system of claim 3, wherein: The pipeline comprises a vertically downward inlet pipeline (6) and a horizontally connected pipeline (7).

5. The containment cooling filtration system of claim 1, wherein: The safety shell cooling and filtering system further comprises a water pool water replenishing system for replenishing the water source of the surrounding water pool system.

6. The containment cooling and filtration system of claim 5, wherein: The water tank replenishing system comprises an external replacement water tank (15) and an electric isolation valve (14), water stored in the external replacement water tank (15) is replenished into the water source of the surrounding water tank system through the control of the electric isolation valve (14).

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