Containment suppression, filtration and discharge system and method and application of containment suppression, filtration and discharge system and method

Abstract

The invention relates to a containment pressure suppression, filtration and discharge system and method and application thereof, and belongs to the field of special safety facilities and radiation protection of nuclear power devices. The containment pressure suppression, filtration and discharge system comprises a discharge valve (2), a discharge pipeline (3), a spray pipe (4), a pressure suppression pool, an expansion chamber (7), a steam-water separator (9), a metal fiber filter layer (10), a rupture disk (12), a heat exchanger and a valve. According to the containment pressure suppression filtering and discharging system, the seawater side heat exchanger and the pressure suppression pool heat exchanger are arranged, and a natural circulation loop is constructed by means of the potential difference between the seawater side heat exchanger and the pressure suppression pool heat exchanger and the temperature difference between seawater and a liquid phase in a pressure suppression pool under the accident condition; the heat of the suppression pool can be guided out without time limit under the condition of an LOCA accident or a main steam pipeline fracture accident in the containment; by adopting a pressure suppression washing method with multi-stage bubbling, rapid pressure suppression of the containment and efficient retention of airborne radioactive substances can be realized; occupation of total resources is reduced by arranging the combined metal fiber filter layer.

Description

Technical Field

[0001] The present invention belongs to the field of safety facilities and radiation protection for nuclear power plants, and in particular relates to a containment pressure suppression filtering and exhaust system and method and application thereof. Background Art

[0002] The containment is the last safety barrier to prevent the release of radioactive materials into the external environment after a breach accident in an offshore nuclear power platform. Therefore, it is of great significance to ensure its integrity. For marine nuclear power plants and floating power stations, the free volume of the containment is much smaller than that of the containment of a nuclear power plant due to the constraints of overall resources. When a breach accident occurs in the primary circuit of the containment, a large amount of high-temperature and high-pressure coolant flashes and sprays into the containment, causing the pressure in the containment to rise sharply. If the pressure cannot be reduced quickly, the pressure of the containment will rise rapidly within tens of seconds and exceed its design pressure. At present, the third-generation nuclear power Hualong One is equipped with a containment spray system and a passive containment heat removal system to meet the heat removal requirements of the containment under breach accident conditions. However, in view of the extremely high mass and energy release rate in the early stage of the containment breach accident, the spray system and the passive containment cooling system alone cannot meet the pressure reduction requirements of the containment. Japan's improved boiling water reactor (ABWR) nuclear power plant and Russia's marine nuclear power unit KLT-40S are both equipped with a suppression pool. Under accident conditions, the high-temperature and high-pressure gas in the dry well is quickly discharged into the wet well, and the steam directly contacts the liquid in the wet well to condense, thereby achieving rapid cooling and pressure reduction of the containment. Moreover, when the system is actually running, the radioactive substances carried in the exhaust gas will be retained in the liquid phase in large quantities under the action of various removal mechanisms, so the containment suppression system also plays a role in water washing and removal of radioactive substances.

[0003] The problem of containment overpressure in the later stage of a serious accident is also worthy of attention. At present, nuclear power plants are equipped with a containment filtration and emission system, which uses active pressure relief to ensure that the pressure inside the containment does not exceed its bearing limit, thereby ensuring the integrity of the containment. While relieving pressure, the radioactive substances in the exhaust gas are filtered through the filter device installed on the pressure relief pipeline to prevent the leakage of radioactive products. The current mainstream containment filtration and emission system mainly consists of two stages: wet Venturi water washing and dry metal fiber filtration. However, this type of filter has a large volume and supporting facilities, and occupies more overall resources.

[0004] When a LOCA accident (Loss of Coolant Accident) occurs in the primary circuit of the containment, after the suppression system is put into operation, if the containment spray system and the passive containment heat removal system fail, the temperature of the liquid phase in the suppression pool will gradually increase until it reaches the saturation temperature, at which time the suppression performance of the suppression system is basically ineffective. As the temperature of the liquid phase increases, the water washing efficiency of airborne radioactive substances will be significantly reduced. At the same time, along with the evaporation of the liquid phase, the aerosol particles originally retained in the liquid phase will be carried back into the gas phase by the gas phase, seriously affecting the water washing efficiency of the radioactive substances.

[0005] Therefore, in order to solve the problem of rapid pressure relief of the containment and removal of radioactive materials when a breach accident occurs on a floating nuclear power platform, it is necessary to comprehensively consider various factors and optimize the design of the system. Summary of the invention

[0006] In order to meet the needs of rapid depressurization of the containment and efficient removal of radioactive materials after an accident on a floating nuclear power platform, and to solve the problem that the liquid phase temperature in the suppression water pool increases under long-term heat release conditions of a severe accident, resulting in reduced system suppression performance and water washing efficiency of airborne radioactive materials, the present invention proposes a containment suppression filtration and discharge system and method and applications thereof.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions.

[0008] In a first aspect, the present invention provides a containment pressure suppression filtration discharge system, including a discharge valve, a discharge pipeline, a nozzle, a pressure suppression water pool, an expansion chamber, a steam-water separator, a metal fiber filter layer, a bursting membrane, a heat exchanger and a valve; wherein

[0009] The containment shell is connected to the suppression water pool through the discharge pipe, the interface between the discharge pipe and the containment shell is located at the upper part of the containment shell, and the discharge valve is arranged at the top of the discharge pipe and is located outside the containment shell (for example, close to the outside of the containment shell);

[0010] The nozzle is arranged at the end of the discharge pipe and is located at the bottom of the pressure suppression pool;

[0011] The expansion chamber is arranged on one side of the pressure suppression water pool, and the expansion chamber is connected to the pressure suppression water pool through a pipeline;

[0012] The steam-water separator and the metal fiber filter layer are both arranged at the upper part of the interior of the expansion chamber, and the steam-water separator and the metal fiber filter layer are arranged adjacent to each other;

[0013] The bursting membrane is located on a filter discharge pipeline connected to the metal fiber filter layer;

[0014] The heat exchanger comprises a pressure suppression tank heat exchanger and a seawater side heat exchanger.

[0015] By adopting the containment pressure suppression filtration and discharge system of the present invention, after a LOCA accident occurs in the containment, when the pressure in the containment reaches the opening pressure of the discharge valve connected to the containment, the discharge valve automatically opens, and the steam-air mixture (i.e., the discharge gas) in the containment enters the pressure suppression water tank through bubbling of the nozzle, and directly contacts the solution in the pressure suppression water tank (due to the low temperature of the solution, it can also be called coolant) by bubbling for efficient heat exchange (wherein part of the discharge gas is condensed), thereby achieving rapid depressurization of the containment, thereby reducing the pressure peak of the containment at the initial stage of the accident.

[0016] As an optional implementation, the nozzle is installed vertically downward.

[0017] In the present invention, the nozzle in the suppression water pool is installed vertically downward so that the submerged depth of the nozzle is increased, which is beneficial to the heat exchange between gas and liquid phases and the bubbling water washing of radioactive substances.

[0018] As an optional implementation, the suppression water tank includes multiple stages of sub-suppression water tanks.

[0019] As an optional implementation, the pressure suppression water tank includes a first-stage pressure suppression water tank and a second-stage pressure suppression water tank; a connecting pipe is provided at the bottom of the first-stage pressure suppression water tank and the second-stage pressure suppression water tank.

[0020] As an optional embodiment, the interior of the pressure suppression water tank is loaded with a mixed solution of sodium hydroxide and sodium thiosulfate.

[0021] The present invention adopts multi-stage bubbling heat exchange and water washing, which can efficiently remove radioactive substances in the exhaust gas, including aerosols and iodine. Specifically, the mixed solution of sodium hydroxide and sodium thiosulfate loaded in the suppression water tank can absorb iodine in the exhaust gas through chemical reaction. Taking the secondary bubbling heat exchange and water washing as an example, in the first-stage bubbling water washing (occurring in the first-stage suppression water tank), the nozzle outlet gas is in a high-speed jet state, and the liquid phase is entrained into the gas plume to form a large number of entrained droplets. Aerosols are captured and removed by entrained droplets through capture mechanisms such as inertial collision and interception, and radioactive iodine is absorbed by entrained droplets. At the same time, the steam share of the exhaust gas is high, and steam condensation will also significantly improve the removal efficiency of aerosols. With the dissipation of the exhaust gas energy, the gas flow type is changed from a jet to a bubble group. The radioactive substance diffuses and migrates to the bubble surface in the bubble and is then retained by the liquid phase. After the first stage of bubbling condensation, the exhaust gas is mainly left with non-condensable gas. In the second stage bubbling water washing, the exhaust gas flow rate at the nozzle outlet is reduced, the bubble size is reduced, the specific surface area is increased, the residence time of the bubble in the liquid phase is increased, and the removal efficiency of the radioactive material is increased.

[0022] The present invention adopts two-stage or multi-stage bubbling water washing, which is equivalent to increasing the submerged depth of the suppression nozzle, so that the residence time of the gas in the liquid phase is significantly increased, and the removal efficiency of airborne radioactive substances can be effectively improved.

[0023] As an optional implementation, the suppression water tank heat exchanger is arranged inside the first-stage suppression water tank.

[0024] As an optional implementation, the seawater side heat exchanger is located in the seawater, and the position of the seawater side heat exchanger is higher than the height of the suppression water tank heat exchanger.

[0025] As an optional implementation, the top pipeline of the suppression tank heat exchanger is connected to the top pipeline of the seawater side heat exchanger, and the bottom pipeline of the suppression tank heat exchanger is connected to the bottom pipeline of the seawater side heat exchanger, thereby constructing a natural circulation loop.

[0026] As an optional implementation, the tube side of the heat exchanger is filled with demineralized water.

[0027] The present invention utilizes the height difference (or potential difference) between the seawater surface and the suppression water tank and the temperature difference between the seawater and the liquid phase in the suppression water tank under accident conditions, and constructs a natural circulation loop by arranging heat exchangers filled with desalted water on the tube side on the suppression water tank and the seawater side respectively. This can achieve unlimited time-limited heat extraction from the suppression water tank under accident conditions, thereby improving the suppression performance of the containment suppression filtration and discharge system and the removal efficiency of airborne radioactive substances.

[0028] In the present invention, under the premise of ensuring the pressure suppression function of the pressure suppression water tank and the source-term water washing efficiency, the water volume of the pressure suppression water tank is reduced by means of capacity expansion, thereby achieving system weight reduction.

[0029] As an optional implementation manner, the steam-water separator is arranged at a relative position of the pipeline connecting the expansion chamber and the metal fiber filter layer.

[0030] As an optional implementation, the steam-water separator is a folded plate type steam-water separator.

[0031] In the present invention, the steam-water separator is used to dehumidify the exhaust gas.

[0032] As an optional implementation, a discharge valve is provided upstream of the steam-water separator.

[0033] As an optional implementation, the opening pressure of the discharge valve is less than the designed pressure of the containment vessel and the suppression water pool.

[0034] As an optional implementation, a bursting membrane is arranged downstream of the metal fiber filter layer.

[0035] As an optional implementation, the opening pressure of the bursting disk is the same as the opening pressure of the discharge valve 8 .

[0036] The present invention arranges a discharge valve upstream of the metal fiber filter layer and a bursting membrane downstream, and the opening pressure of the discharge valve is appropriately less than the designed pressure of the containment shell and the pressure suppression water pool, and the opening pressure of the bursting membrane is the same as the opening pressure of the discharge valve. When the pressure of the pressure suppression water pool and the expansion chamber reaches the opening pressure of the discharge valve, the discharge valve and the bursting membrane are opened successively to realize the filtered discharge of the high-temperature and high-pressure gas in the containment shell and the pressure suppression water pool.

[0037] As an optional implementation, the metal fiber filter layer adopts a combined metal fiber filter layer.

[0038] In the present invention, a combined metal fiber filter is arranged with the help of the existing structural space to capture the most penetrating particle size aerosol that is difficult to remove by bubbling water washing, further reduce the radioactive activity of the exhaust gas, and reduce the occupation of overall resources.

[0039] As an optional implementation, the combined metal fiber filter layer is provided with multiple metal fiber layers with different mesh sizes and different wire diameters stacked together.

[0040] This combined metal fiber filter layer can achieve efficient capture of small particle aerosols.

[0041] As an optional implementation, a parallel pipeline is provided in the pipeline where the bursting membrane is located, and a valve is provided in the parallel pipeline, and the valve can be opened remotely electrically or manually (ie, opened manually on site).

[0042] In the present invention, a parallel pipeline is arranged in the pipeline where the bursting membrane is located. When the bursting membrane fails to open, the valve on the parallel pipeline can be opened remotely electrically or manually on site.

[0043] As an optional implementation, a valve is further provided inside the containment shell for connecting or isolating the containment shell with the suppression water pool and / or the expansion chamber, respectively.

[0044] In the present invention, when the pressure in the suppression water pool and the expansion chamber is significantly higher than the containment pressure, the valve connecting the suppression water pool and the containment and the valve connecting the expansion chamber and the containment are opened to relieve the pressure in the suppression water pool and the expansion chamber. When the containment pressure is higher than the suppression water pool pressure again, the suppression water pool continues to realize the heat sink and water washing functions.

[0045] As an optional embodiment, the containment pressure suppression filtration exhaust system also includes a filtration exhaust pipeline (or filtration exhaust pipe), and a flow limiting orifice plate is arranged downstream of the filtration exhaust pipeline to control the flow rate of the exhaust gas after filtration, so as to maximize the filtration efficiency of airborne radioactive substances while ensuring the pressure suppression effect.

[0046] In the present invention, the filter exhaust pipeline connects the steam-water separator and the metal fiber filter layer, and is used to discharge the exhaust gas after dehumidification and filtration.

[0047] As an optional implementation, a radioactivity monitor is provided downstream of the filter exhaust pipeline, which can be used to monitor the radioactive dose released into the environment and can also be used to monitor the system's filtering ability for airborne radioactive substances.

[0048] The containment pressure suppression filtration and discharge system provided by the present invention has a passive cooling function and is suitable for floating nuclear power platforms; it is used for rapid pressure reduction of the containment and efficient removal of radioactive substances after an accident on the floating nuclear power platform.

[0049] In a second aspect, the present invention provides a containment pressure suppression filtration and drainage method, using the above-mentioned containment pressure suppression filtration and drainage system, the containment pressure suppression filtration and drainage method comprises the following steps:

[0050] 1) When a LOCA accident occurs in the containment, the pressure in the containment reaches the opening pressure of the discharge valve, and the discharge valve automatically opens based on the pressure difference, and the discharge gas from the high-temperature and high-pressure steam-air mixture in the containment is bubbled into the suppression water pool through the nozzle for bubbling heat exchange (equivalent to the suppression water pool having a heat sink function) and water washing, so that the containment 1 is depressurized and the radioactive substances in the steam-air mixture are removed at the same time;

[0051] By taking advantage of the height difference between the seawater surface and the first-stage suppression water tank and the temperature difference between the seawater and the liquid phase in the first-stage suppression water tank under accident conditions, a natural circulation loop is constructed by arranging a heat exchanger filled with desalted water on the pipe side of the first-stage suppression water tank and the seawater side;

[0052] 2) When the pressure of the suppression water pool or the expansion chamber is higher than the pressure of the containment shell, the valve connecting the suppression water pool and the containment shell and / or the valve connecting the expansion chamber and the containment shell are opened to relieve the pressure of the suppression water pool and / or the expansion chamber; when the pressure of the containment shell is higher than the pressure of the suppression water pool again, the process of step 1) is performed again, so that the suppression water pool can continue to realize the functions of heat trap and water washing;

[0053] 3) The exhaust gas after multi-stage bubbling heat exchange and water washing enters the expansion chamber, and the containment pressure is further reduced by the method of pressure suppression + expansion;

[0054] 4) When the pressure of the containment or suppression pool reaches the design pressure of the filter discharge, the valve on the filter discharge pipeline is opened, and the gas first passes through the steam-water separator, then flows through the metal fiber filter layer for filtration (to remove aerosols in the exhaust gas), and the filtered exhaust gas passes through the bursting membrane or valve;

[0055] 5) The exhaust gas passing through the bursting membrane or valve is released into the environment through the limiting orifice plate, and the radioactive substances released into the environment are monitored at the same time.

[0056] As an optional implementation, the step 1) further includes the following steps:

[0057] By utilizing the height difference between seawater and the suppression water pool, as well as the temperature difference between seawater and the liquid phase in the suppression water pool under severe accident conditions, a natural circulation loop is constructed in the suppression water pool heat exchanger and the seawater side heat exchanger to achieve unlimited heat extraction from the containment and the suppression water pool, and improve the water washing retention efficiency of airborne radioactive materials.

[0058] As an optional implementation, in step 1), the suppression water tank further comprises a multi-stage sub-suppression water tank, and multi-stage bubbling water washing is used to remove radioactive substances in the exhaust gas.

[0059] Optionally, the suppression water pool includes a first-stage suppression water pool and a second-stage suppression water pool, and two-stage bubbling water washing is used to remove radioactive substances in the exhaust gas.

[0060] In a third aspect, the present invention provides an application of the above-mentioned containment pressure suppression filtration and discharge system in a floating nuclear power platform.

[0061] In the present invention, the containment pressure suppression filtering and exhaust system has a passive cooling function and is suitable for floating nuclear power platforms and is used for depressurizing the containment and removing radioactive substances after an accident of the floating nuclear power platform.

[0062] In the present invention, the above technical features can be freely combined to form a new technical solution without conflicting with each other.

[0063] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0064] (1) The containment pressure suppression filtration and discharge system provided by the present invention adopts a multi-stage bubbling pressure suppression water washing method, which can fully utilize the water resources in the pressure suppression water pool, and realize the rapid pressure suppression of the containment and the efficient retention of airborne radioactive substances under limited resource conditions;

[0065] (2) The containment pressure suppression filtration and drainage system provided by the present invention utilizes the structural space of the containment pressure suppression filtration and drainage system in the prior art and can reduce the occupation of overall resources by arranging a combined metal fiber filter layer;

[0066] (3) Compared with the mainstream containment filtration and discharge system of nuclear power, the containment pressure suppression filtration and discharge system provided by the present invention can ensure a higher efficiency of radioactive material removal, while reducing the Venturi water washing link, avoiding the trouble of regular liquid replenishment of the filtration and discharge device. The solution is simple and feasible, occupies less overall resources, and has good economic efficiency;

[0067] (4) The containment pressure suppression filtration and discharge system provided by the present invention utilizes the height difference (or potential difference) between the seawater surface and the suppression water tank and the temperature difference between the seawater and the liquid phase in the suppression water tank under accident conditions. By arranging heat exchangers on the suppression water tank and the seawater side respectively, a natural circulation loop is constructed. This can achieve unlimited time-limited heat extraction from the suppression water tank under accident conditions, thereby improving the pressure suppression performance of the containment pressure suppression filtration and discharge system and the efficiency of removing airborne radioactive substances. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 A schematic structural diagram of a containment pressure suppression filtration and exhaust system according to the present invention is shown.

[0069] Among them, the accompanying drawings are marked as: 1-containment, 2-discharge valve, 3-discharge pipe; 4-nozzle, 5-first-stage suppression water tank, 6-second-stage suppression water tank, 7-expansion chamber, 8-discharge valve, 9-steam-water separator, 10-combined metal fiber filter layer, 11-valve, 12-bursting membrane, 13-valve, 14-flow limiting orifice plate, 15-radioactivity monitor, 16-suppression water tank heat exchanger, 17-seawater side heat exchanger, 18-seawater. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] Example 1

[0072] A containment pressure suppression filtration and drainage system based on a two-stage bubbling water washing-metal fiber filtration integrated type, such as Figure 1 As shown, it mainly includes discharge valves (2 and 8), discharge pipeline 3, nozzle 4, first-stage pressure suppression water tank 5, second-stage pressure suppression water tank 6, expansion chamber 7, steam-water separator 9, combined metal fiber filter layer 10, bursting membrane 12, flow limiting orifice plate 14, radioactivity monitor 15, pressure suppression water tank heat exchanger 16, seawater side heat exchanger 17 and valves (11 and 13). Specifically,

[0073] The containment shell 1 is connected to the first-stage pressure suppression water tank 5 through a discharge pipe 3, the interface between the discharge pipe 3 and the containment shell 1 is located at the upper part of the containment shell 1, the discharge valve 2 is arranged at the top of the discharge pipe 3, and is located outside the containment shell 1, close to the containment shell; the nozzle 4 is arranged at the end of the discharge pipe 3 in a vertical downward installation manner, and is located at the bottom of the first-stage pressure suppression water tank 5 and the second-stage pressure suppression water tank 6; the first-stage pressure suppression water tank 5 and the second-stage pressure suppression water tank 6 are connected at the bottom, and are both loaded with a mixed solution of sodium hydroxide and sodium thiosulfate.

[0074] The suppression water tank heat exchanger 16 is arranged inside the first-stage suppression water tank 5, and the seawater side heat exchanger 17 is located in the seawater, and the position of the seawater side heat exchanger 17 is higher than the height of the suppression water tank heat exchanger 16. The top pipeline of the suppression water tank heat exchanger 16 is connected to the top pipeline of the seawater side heat exchanger 17, and the bottom pipeline of the suppression water tank heat exchanger 16 is connected to the bottom pipeline of the seawater side heat exchanger 17, thereby constructing a natural circulation loop.

[0075] The expansion chamber 7 is arranged on one side of the second-stage pressure suppression water pool 6 and is connected to the second-stage pressure suppression water pool 6 through a pipeline;

[0076] The steam-water separator 9 and the combined metal fiber filter layer 10 are both arranged at the upper part of the expansion chamber 7, and the two are adjacently arranged and connected; in addition, the steam-water separator 9 is arranged at the relative position of the pipeline connecting the expansion chamber 7 and the combined metal fiber filter layer 10; the discharge valve 8 is arranged upstream of the steam-water separator 9; the bursting membrane 12 is arranged downstream of the combined metal fiber filter layer 10, and is located on the filter discharge pipeline connected to the combined metal fiber filter layer 10. The opening pressure of the discharge valve 8 is less than the design pressure of the containment 1 and the first-stage pressure suppression water pool 5 and the second-stage pressure suppression water pool 6; the opening pressure of the bursting membrane 12 is the same as the opening pressure of the discharge valve 8; the combined metal fiber filter layer 10 is provided with multiple layers of metal fiber layers with different mesh sizes and different wire diameters stacked together.

[0077] A parallel pipeline is provided in the pipeline where the bursting membrane 12 is located, and a manually openable valve 13 is provided in the parallel pipeline. In addition, a valve 11 is also provided inside the containment 1 for connecting or isolating the containment with the suppression water pool or / and the expansion chamber. A limited flow orifice plate (14) and a radioactivity monitor (15) are provided downstream of the filter discharge pipeline.

[0078] The containment pressure suppression, filtration and drainage system provided in this embodiment is applicable to a floating nuclear power platform and is used for depressurizing the containment and removing radioactive substances after an accident of the floating nuclear power platform.

[0079] First, under normal working conditions, all valves in the containment pressure suppression filtration and exhaust system of this embodiment are in a closed state. The entire containment pressure suppression filtration and exhaust system is filled with nitrogen to reduce the risk of hydrogen explosion in the system under accident conditions.

[0080] When a LOCA accident occurs in a primary circuit of the containment 1, the containment pressure suppression, filtration and discharge method includes the following steps.

[0081] Step S1: When the containment pressure rises to the opening pressure of the discharge valve 2, the discharge valve 2 automatically opens, and the high-temperature and high-pressure steam-air mixture in the containment (i.e., the discharge gas, including radioactive substances, such as aerosols and iodine) is bubbled into the first-stage suppression water tank 5 and the second-stage suppression water tank 6 through the discharge pipe 3 and the nozzle 4; by bubbling, the discharge gas directly contacts the solution in the suppression water tank (i.e., the mixed solution of sodium hydroxide and sodium thiosulfate) to condense, thereby performing efficient heat exchange, achieving rapid depressurization of the containment 1, and thereby reducing the peak pressure of the containment 1 at the initial stage of the accident. In addition, the mixed solution of sodium hydroxide and sodium thiosulfate loaded in the suppression water tank can absorb iodine in the discharge gas through chemical reaction.

[0082] Specifically, in the first-stage bubbling condensation and water washing in the first-stage suppression water tank 5, the gas at the outlet of the nozzle 4 is in a high-speed jet state, and the liquid phase is entrained into the gas plume to form a large number of entrained droplets. Aerosols are captured and removed by entrained droplets through capture mechanisms such as inertial collision, interception, and Brownian diffusion, and radioactive iodine is absorbed by the entrained droplets. At the same time, the steam share of the exhaust gas is relatively high, and steam condensation will also significantly improve the removal efficiency of aerosols. As the energy of the exhaust gas dissipates, the gas flow pattern changes from a jet to a bubble group. The radioactive substance diffuses and migrates in the bubble to the bubble surface and is then retained by the liquid phase. After the bubbling heat exchange in the first-stage suppression water tank, the exhaust gas is mainly left with non-condensable gases.

[0083] The exhaust gas after passing through the first-stage suppression water tank 5 enters the second-stage suppression water tank 6 for second-stage bubbling heat exchange and water washing.

[0084] In addition, in step S1, with the help of the height difference between the liquid surface of seawater 18 and the first-stage suppression water tank 5 and the temperature difference between the seawater and the liquid phase in the first-stage suppression water tank 5 under accident conditions, a natural circulation loop is constructed by arranging heat exchangers 16 / 17 filled with desalted water on the tube side of the first-stage suppression water tank 5 and the seawater 18 side, so as to realize the unlimited extraction of heat from the suppression water tank under accident conditions, thereby improving the suppression performance of the containment suppression filtration and discharge system and the removal efficiency of airborne radioactive substances.

[0085] Step S2: When the pressure in the suppression water pool (5 and 6) or the expansion chamber 7 is higher than the pressure in the containment vessel 1, the valve 11 is opened to release the pressure in the suppression water pool and the expansion chamber. When the pressure in the containment vessel 1 is higher than the pressure in the suppression water pool 5 / 6 again, the process in step S1 is performed again, so that the suppression water pool (5 and 6) can realize the suppression and water washing functions again.

[0086] Step S3: The exhaust gas after two-stage bubbling heat exchange and water washing enters the expansion chamber 7. The exhaust gas first passes through the steam-water separator 9 to remove the carried droplets, and then flows through the combined metal fiber filter layer 10 to filter the high-temperature and high-pressure gas in the containment 1, the pressure suppression pool (5 and 6) and the expansion chamber 7. The filtered gas is discharged through the bursting membrane 12 or the valve 13. Among them, the combined metal fiber filter layer is provided with multiple layers of metal fiber layers with different mesh sizes and different wire diameters, which can realize the efficient capture of small-particle aerosols.

[0087] Specifically, since the opening pressure of the bursting membrane 12 arranged downstream of the metal fiber filter layer 10 is the same as the opening pressure of the discharge valve 8, when the pressure in the suppression water pool (5 and 6) and the expansion chamber 7 reaches the opening pressure of the discharge valve 8, the discharge valve 8 and the bursting membrane 12 are opened successively to realize the filtered discharge of the high-temperature and high-pressure gas in the containment 1, the suppression water pool (5 and 6) and the expansion chamber 7.

[0088] When the bursting membrane fails to open due to failure, the valve 13 arranged on the parallel pipeline on the pipeline where the bursting membrane 12 is located is opened electrically remotely or manually on site to realize the filtered discharge of high-temperature and high-pressure gas in the containment 1, the suppression water pool (5 and 6) and the expansion chamber 7.

[0089] Step S4: The filtered gas is restrictedly discharged through the flow limiting orifice 14 provided on the filter discharge pipeline to ensure that the discharge flow rate is substantially consistent with the design flow rate of the filter discharge system over a period of time, thereby ensuring the filtering efficiency of the system; at the same time, a radioactivity monitor 15 is used to monitor the radioactive dose released into the environment, which can also be used to monitor the filtering capacity of the system for radioactive substances.

[0090] The above embodiments are only preferred implementations of the present invention, but the present invention is not limited to the contents disclosed in the embodiments and the accompanying drawings. It should be pointed out that for ordinary technicians in this technical field, improvements and equivalent modifications can be made without departing from the principle of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A containment pressure suppression filtration and exhaust system, characterized in that: The containment pressure suppression filtration discharge system comprises a discharge valve (2), a discharge pipeline (3), a nozzle (4), a pressure suppression water pool, an expansion chamber (7), a steam-water separator (9), a metal fiber filter layer (10), a bursting membrane (12), a heat exchanger and a valve; wherein: The containment shell (1) is connected to the suppression water pool via the discharge pipe (3), and the interface between the discharge pipe (3) and the containment shell (1) is located at the upper part of the containment shell (1); The discharge valve (2) is arranged at the top of the discharge pipe (3) and is located outside the containment vessel (1); The nozzle (4) is arranged at the end of the discharge pipe (3) and is located at the bottom of the pressure suppression pool; the expansion chamber (7) is arranged on one side of the pressure suppression pool, and the expansion chamber (7) is connected to the pressure suppression pool through a pipeline; The steam-water separator (9) and the metal fiber filter layer (10) are both arranged at the upper part of the expansion chamber (7), and the steam-water separator (9) and the metal fiber filter layer (10) are adjacently arranged and connected; The bursting membrane (12) is located on a filter discharge pipeline connected to the metal fiber filter layer (10); The heat exchanger comprises a pressure suppression tank heat exchanger (16) and a seawater side heat exchanger (17).

2. The containment pressure suppression filtration and exhaust system according to claim 1, characterized in that: The nozzle (4) is installed vertically downward; or / and The suppression water pool comprises a multi-stage sub-suppression water pool; or / and The interior of the pressure suppression water tank is loaded with a mixed solution of sodium hydroxide and sodium thiosulfate; or / and The tube side of the heat exchanger is filled with demineralized water.

3. The containment pressure suppression filtration and exhaust system according to claim 2, characterized in that: The pressure suppression water pool comprises a first-stage pressure suppression water pool (5) and a second-stage pressure suppression water pool (6); connecting pipes are arranged at the bottom of the first-stage pressure suppression water pool (5) and the second-stage pressure suppression water pool (6).

4. The containment pressure suppression filtration and exhaust system according to claim 3, characterized in that: The suppression water tank heat exchanger (16) is arranged inside the first-stage suppression water tank (5); or / and The seawater side heat exchanger (17) is located in the seawater, and the position of the seawater side heat exchanger (17) is higher than the height of the suppression tank heat exchanger (16); or / and The top pipeline of the suppression water tank heat exchanger (16) is connected to the top pipeline of the seawater side heat exchanger (17), and the bottom pipeline of the suppression water tank heat exchanger (16) is connected to the bottom pipeline of the seawater side heat exchanger (17), thereby constructing a natural circulation loop.

5. The containment pressure suppression filtration and exhaust system according to claim 1, characterized in that: The steam-water separator (9) is arranged at a relative position of the pipeline connecting the expansion chamber (7) and the metal fiber filter layer; or / and A discharge valve (8) is arranged upstream of the steam-water separator (9); a bursting membrane (12) is arranged downstream of the metal fiber filter layer (10); or / and The steam-water separator is a folded plate type steam-water separator; or / and The metal fiber filter layer adopts a combined metal fiber filter layer; optionally, the combined metal fiber filter layer is provided with multiple metal fiber layers with different mesh sizes and different wire diameters stacked together.

6. The containment pressure suppression filtration and exhaust system according to claim 5, characterized in that: The opening pressure of the discharge valve (8) is less than the design pressure of the containment vessel and the suppression water pool; or / and The opening pressure of the bursting disk (12) is the same as the opening pressure of the discharge valve (8).

7. The containment pressure suppression filtration and exhaust system according to claim 1, characterized in that: A parallel pipeline is arranged on the pipeline where the bursting membrane is located, and a valve 13 is arranged on the parallel pipeline; the valve 13 can be opened remotely electrically or manually; or / and A valve 11 is also provided inside the containment shell for connecting or isolating the containment shell with the suppression water pool or / and the expansion chamber; or / and The containment pressure suppression filtration and drainage system further comprises a filtration and drainage pipeline, a flow limiting orifice plate (14) is arranged downstream of the filtration and drainage pipeline; or / and A radioactivity monitor (15) is arranged downstream of the filter discharge pipeline.

8. A containment pressure suppression filtration and discharge method, characterized in that: Using the containment pressure suppression filtration and drainage system according to any one of claims 1 to 7, the containment pressure suppression filtration and drainage method comprises the following steps: 1) When a LOCA accident occurs in the containment, the pressure inside the containment reaches the opening pressure of the discharge valve, and the discharge valve can be automatically opened based on the pressure difference. The high-temperature and high-pressure steam-air mixture in the containment is bubbled through the discharge pipe and the nozzle into the suppression water pool for bubbling heat exchange and water washing; By taking advantage of the height difference between the seawater surface and the first-stage suppression water tank and the temperature difference between the seawater and the liquid phase in the first-stage suppression water tank under accident conditions, a natural circulation loop is constructed by arranging a heat exchanger filled with desalted water on the pipe side of the first-stage suppression water tank and the seawater side; 2) When the pressure of the suppression water pool or the expansion chamber is higher than the pressure of the containment shell, the valve connecting the suppression water pool and the containment shell and / or the valve connecting the expansion chamber and the containment shell are opened to relieve the pressure of the suppression water pool and / or the expansion chamber; when the pressure of the containment shell is higher than the pressure of the suppression water pool again, the process of step 1) is performed again; 3) The exhaust gas after multi-stage bubbling heat exchange and water washing enters the expansion chamber, and the containment pressure is further reduced by pressure suppression and expansion; 4) When the pressure of the containment or suppression pool reaches the filter discharge design pressure, the valve on the filter discharge pipeline opens, the exhaust gas first passes through the steam-water separator, then flows through the metal fiber filter layer for filtration, and the filtered exhaust gas passes through the bursting membrane or valve; 5) The exhaust gas passing through the bursting membrane or valve is released into the environment through the limiting orifice plate, and the radioactive substances released into the environment are monitored at the same time.

9. The containment pressure suppression filtration and discharge method according to claim 8, characterized in that: Step 1) also includes the following steps: By utilizing the height difference between the seawater surface and the suppression water pool, as well as the temperature difference between the seawater and the liquid phase in the suppression water pool under accident conditions, a suppression water pool heat exchanger and a seawater side heat exchanger are installed to construct a natural circulation loop, thereby achieving unlimited heat extraction from the containment and the suppression water pool, and improving the water washing retention efficiency of airborne radioactive materials.

10. Use of the containment pressure suppression filtration and drainage system according to any one of claims 1 to 7 in a floating nuclear power platform.

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