Integrated containment suppression, filtration and discharge system

Abstract

The invention provides an integrated containment pressure suppression, filtration and discharge system. The integrated containment pressure suppression, filtration and discharge system comprises a containment, a discharge valve, a discharge pipeline, a spray pipe, a first-stage pressure suppression water tank, a second-stage pressure suppression water tank, a baffle plate steam-water separator, an expansion tank, a rupture disk structure, a combined metal fiber filter layer, a radioactivity monitor, a first stop valve and a second stop valve. The two-stage pressure suppression water tank is arranged, the high removal efficiency of airborne radioactive substances is achieved through two-stage bubbling water washing, then the combined metal fiber filter is arranged by means of an existing cabin, and the requirements for rapid pressure reduction and radioactive substance removal of the containment under the LOCA accident working condition can be met; meanwhile, the problem that the containment filtering and discharging system of the existing nuclear power station occupies too many resources is solved, and the economical efficiency is high.

Description

Technical Field

[0001] The invention belongs to the technical field of special safety facilities for nuclear power plants, and in particular relates to an integrated containment pressure suppression filtering and exhaust system. Background Art

[0002] The containment is the compartment in the offshore nuclear power platform where reactors, primary circuit systems and other high-energy, high-radioactive equipment and pipelines are installed. It is the last safety barrier to prevent the release of radioactive materials into the external environment after a breach accident. Therefore, it is of great significance to ensure its integrity.

[0003] For marine nuclear power plants and floating power stations, the free volume of the containment is much smaller than that of the containment of nuclear power plants due to the constraints of overall resources. When a breach 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 in the containment will rise rapidly within tens of seconds and exceed its designed pressure. In view of the extremely high mass-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. At present, nuclear power plants are equipped with a containment filtration and discharge system, that is, through the method of active pressure relief, the pressure in the containment does not exceed its load limit, thereby ensuring the integrity of the containment. At the same time as the pressure relief, 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.

[0004] The containment filtration and discharge system mainly consists of two stages: wet Venturi water washing and dry metal fiber filtration. However, the volume and supporting facilities of this type of filter are large. If it is directly used on an offshore nuclear power platform, it will occupy more overall resources.

[0005] Therefore, how to provide an integrated containment pressure suppression filtration and discharge system that can meet the needs of rapid containment pressure reduction and radioactive material removal, while solving the problem of excessive resource occupation by the containment filtration and discharge system of existing nuclear power plants, has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] The embodiment of the present invention provides an integrated containment pressure suppression filtration and drainage system, which can meet the needs of rapid pressure reduction of the containment and removal of radioactive substances, while solving the problem of excessive resource occupation by the containment filtration and drainage system of existing nuclear power plants.

[0007] In an embodiment of the present invention, an integrated containment pressure suppression filtration and discharge system is provided, comprising: a containment, a discharge valve, a discharge pipe, a nozzle, a first-stage pressure suppression water tank, a second-stage pressure suppression water tank, a baffle steam-water separator, an expansion tank, a bursting membrane structure, a combined metal fiber filter layer, a radioactive monitor, a first stop valve and a second stop valve.

[0008] The containment shell is connected to the first-stage pressure suppression water tank through the discharge valve, the discharge pipe and the nozzle, and the first-stage pressure suppression water tank is connected to the second-stage pressure suppression water tank through the discharge pipe and the nozzle;

[0009] The first-stage pressure suppression water tank and the second-stage pressure suppression water tank are respectively loaded with a mixed solution for absorbing iodine in the exhaust gas; the first stop valve is arranged between the first-stage pressure suppression water tank and the expansion tank and the containment shell;

[0010] The bursting membrane structure is arranged upstream of the combined metal fiber filter layer, and the opening pressure of the bursting membrane structure should be less than the design bearing pressure of the containment shell and the first-stage pressure suppression water tank and the second-stage pressure suppression water tank; the downstream stop valve of the combined metal fiber filter layer is opened to filter the high-temperature and high-pressure gas in the containment shell and the first-stage pressure suppression water tank and the second-stage pressure suppression water tank;

[0011] The radioactivity monitor is connected to the combined metal fiber filter layer through the second stop valve, and is used to monitor the radioactive dose released into the environment and the filtering ability of the system for radioactive substances;

[0012] When the pressure in the first-level pressure suppression water tank, the second-level pressure suppression water tank and the expansion tank is higher than the pressure in the containment shell, the first stop valve is opened to relieve the pressure in the first-level pressure suppression water tank, the second-level pressure suppression water tank and the expansion tank; when the pressure in the containment shell is higher than the pressure in the first-level pressure suppression water tank and the second-level pressure suppression water tank, the first-level pressure suppression water tank and the second-level pressure suppression water tank realize the pressure suppression and water washing functions.

[0013] Furthermore, the nozzles in the first-stage pressure suppression water tank and the second-stage pressure suppression water tank are installed vertically downward, so that the submersion depth of the nozzles is increased, which is convenient for condensation heat exchange of gas-liquid two phases in the first-stage pressure suppression water tank and the second-stage pressure suppression water tank and bubbling water washing of radioactive materials.

[0014] Furthermore, the first-stage pressure suppression water tank and the second-stage pressure suppression water tank are respectively loaded with a mixed solution for absorbing iodine in the exhaust gas, including:

[0015] The mixed solution is a mixed solution of sodium hydroxide iodide and sodium thiosulfate, and the mixed solution absorbs iodine in the exhaust gas through a chemical reaction.

[0016] Further, the system adopts two-stage bubbling water washing to remove radioactive source items including at least aerosol and iodine in the exhaust gas;

[0017] In the first stage of bubbling water washing, the outlet gas of the nozzle 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. As the energy of the exhaust gas dissipates, the gas flow pattern changes from a jet to a bubble group. The radioactive substances diffuse and migrate in the bubbles to the bubble surface and are then retained by the liquid phase. After the first stage of bubbling condensation, the exhaust gas mainly contains non-condensable gases. In the second stage of bubbling water washing, the nozzle outlet flow rate decreases, the bubble size decreases, the specific surface area increases, the residence time of the bubbles in the liquid phase increases, and the removal efficiency of radioactive substances increases.

[0018] Furthermore, the exhaust gas enters the second-stage pressure suppression water tank for bubbling and water washing, and after two-stage bubbling, condensation and water washing, the exhaust gas passes through the baffle steam-water separator to separate the entrained droplets and then enters the expansion tank.

[0019] Furthermore, when the pressure in the first-stage pressure suppression water tank, the second-stage pressure suppression water tank and the expansion tank reaches the opening pressure of the bursting membrane structure, the stop valve downstream of the combined metal fiber filter layer can be automatically opened to achieve the filtered discharge of high-temperature and high-pressure gases in the containment and the pressure suppression water tank.

[0020] The beneficial effects brought by the present invention are as follows:

[0021] It can be seen from the above scheme that the embodiment of the present invention provides an integrated containment pressure suppression filtration and discharge system, including: a containment, a discharge valve, a discharge pipe, a nozzle, a first-stage pressure suppression water tank, a second-stage pressure suppression water tank, a baffle steam-water separator, an expansion tank, a bursting membrane structure, a combined metal fiber filter layer, a radioactive monitor, a first stop valve and a second stop valve; when the pressure in the first-stage pressure suppression water tank, the second-stage pressure suppression water tank and the expansion tank is higher than the pressure in the containment, the stop valve is opened to release the pressure of the first-stage pressure suppression water tank, the second-stage pressure suppression water tank and the expansion tank, and when the pressure in the containment is higher than the pressure in the first-stage pressure suppression water tank and the second-stage pressure suppression water tank, the first-stage pressure suppression water tank and the second-stage pressure suppression water tank realize the pressure suppression and water washing functions. The technical scheme of the present invention can reduce the water volume of the pressure suppression water tank by means of expansion to achieve system weight reduction under the premise of ensuring the pressure suppression function of the pressure suppression water tank and the source term water washing efficiency. By installing a combined metal fiber filter in the existing cabin, the most penetrating particle size aerosols that are difficult to remove by bubbling water washing can be captured, the radioactive activity of the exhaust gas can be reduced, and the overall resource occupation can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1A schematic structural diagram showing an integrated containment pressure suppression filtration and drainage system according to an embodiment of the present invention;

[0023] In the figure, 1 is a containment shell, 2 is a discharge valve, 3 is a discharge pipe, 4 is a nozzle, 5 is a first-stage pressure suppression water tank, 6 is a second-stage pressure suppression water tank, 7 is a baffle steam-water separator, 8 is an expansion tank, 9 is a bursting membrane, 10 is a combined metal fiber filter layer, 11 is a second stop valve, 12 is a radioactive monitor, and 13 is a first stop valve. DETAILED DESCRIPTION

[0024] 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.

[0025] In order to meet the needs of rapid depressurization of the containment and removal of radioactive materials, and to solve the problem of excessive resource occupation of the containment filtration and discharge system of existing nuclear power plants, an integrated containment pressure suppression filtration and discharge system solution based on multi-stage bubbling water washing-metal fiber filtration is proposed. This technical solution uses the water washing and filtration function of the existing pressure suppression water tank for airborne radioactive materials, and achieves a high removal efficiency of radioactive materials through two-stage bubbling water washing. Then, with the help of the existing cabin arrangement of combined metal fiber filters, the aerosols that are difficult to remove by bubbling water washing can be captured, which can reduce the occupation of overall resources and is highly economical.

[0026] In the embodiment of 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 expansion to achieve system weight reduction. By setting a combined metal fiber filter in the existing cabin, the most easily penetrating aerosols that are difficult to remove by bubbling water washing can be captured, further reducing the radioactive activity of the exhaust gas, and reducing the overall resource occupation. When the pressure in the pressure suppression water tank and the expansion cabin is significantly higher than the containment pressure, the valve connecting the pressure suppression water tank and the containment and the valve connecting the expansion cabin and the containment are opened to relieve the pressure of the pressure suppression water tank and the expansion cabin. When the containment pressure is higher than the pressure of the pressure suppression water tank again, the pressure suppression water tank continues to achieve the heat sink and water washing functions.

[0027] In the embodiment of the present invention, an integrated containment pressure suppression filtration and discharge system is based on multi-stage bubbling water washing and metal fiber filtration, and utilizes the water washing and filtration function of the existing pressure suppression water tank for airborne radioactive substances, and achieves a high removal efficiency of radioactive substances through two-stage bubbling water washing. Then, with the help of the existing cabin arrangement of the combined metal fiber filter, the aerosol that is difficult to remove by bubbling water washing can be captured, which can reduce the occupation of overall resources and has high economic efficiency.

[0028] In one embodiment of the present invention, the nozzles in the first-stage pressure suppression water tank and the second-stage pressure suppression water tank are installed vertically downward so that the submersion depth of the nozzles is increased, thereby facilitating the condensation heat exchange of gas-liquid phases in the first-stage pressure suppression water tank and the second-stage pressure suppression water tank and the bubbling water washing of radioactive materials.

[0029] In one embodiment of the present invention, the first-stage pressure suppression water tank and the second-stage pressure suppression water tank are respectively loaded with a mixed solution for absorbing iodine in the exhaust gas, including:

[0030] The mixed solution is a mixed solution of sodium hydroxide iodide and sodium thiosulfate, and the mixed solution absorbs iodine in the exhaust gas through a chemical reaction.

[0031] In one embodiment of the present invention, the system uses two-stage bubbling water washing to remove radioactive source items including at least aerosol and iodine in the exhaust gas;

[0032] In the first stage of bubbling water washing, the outlet gas of the nozzle 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; after the first stage of bubbling condensation, the nozzle outlet flow rate is reduced in the second stage of bubbling water washing, the bubble size is reduced, the specific surface area is increased, the residence time of the bubbles in the liquid phase is increased, and the removal efficiency of radioactive substances is increased.

[0033] In one embodiment of the present invention, the exhaust gas enters the second-stage pressure suppression water tank for bubbling and water washing. After two-stage bubbling, condensation and water washing, the exhaust gas passes through the baffle steam-water separator to separate the entrained droplets and then enters the expansion tank.

[0034] In one embodiment of the present invention, when the pressure in the first-stage pressure suppression water tank, the second-stage pressure suppression water tank and the expansion tank reaches the opening pressure of the bursting membrane structure, the stop valve downstream of the combined metal fiber filter layer can be automatically opened to achieve the filtered discharge of the high-temperature and high-pressure gas in the containment and the pressure suppression water tank.

[0035] It can be seen that the technical solution of the present invention adopts a multi-stage bubbling pressure suppression water washing solution, which can make full use of the water resources in the pressure suppression water tank, and realize the rapid pressure suppression of the containment and the efficient retention of airborne radioactive substances under limited resource conditions. The use of combined metal fiber filter layers in existing cabins can reduce the occupation of overall resources. Compared with the mainstream containment filtration and discharge system of nuclear power, this solution can also ensure a higher efficiency of radioactive material removal, while reducing the Venturi water washing link and avoiding the trouble of regular refilling of the filtration and discharge device. The solution is simple and feasible, occupies less overall resources, and is economical.

[0036] Under normal operating conditions, all valves are in the closed state. The entire containment pressure suppression filtration and discharge system is filled with nitrogen to reduce the risk of hydrogen explosion in the system under accident conditions.

[0037] When a LOCA accident occurs in the primary circuit of the containment 1, the containment pressure rises to the opening pressure of the discharge valve 2, and the discharge valve 2 opens. The high-temperature and high-pressure steam-air mixture in the containment first enters the first-stage suppression water tank 5 through the discharge pipe 3 and the nozzle 4. With the efficient heat exchange of bubbling direct contact condensation, the containment is quickly depressurized, thereby reducing the pressure peak of the containment at the initial stage of the accident.

[0038] The mixed solution of sodium hydroxide and sodium thiosulfate is loaded in the pressure suppression water tank 5 / 6, which can absorb iodine in the exhaust gas through chemical reaction. During the bubbling water washing in the first-stage pressure suppression water tank 5, the gas at the nozzle outlet 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 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. As the energy of the exhaust gas dissipates, the gas flow pattern changes from a jet to a bubble group. The radioactive substances diffuse and migrate in the bubbles to the surface of the bubbles and are then retained by the liquid phase. After bubbling condensation in the first-stage pressure suppression water tank, the exhaust gas mainly remains non-condensable gas. The exhaust gas enters the second-stage pressure suppression water tank 6 for bubbling water washing. After two stages of bubbling condensation and water washing, the exhaust gas passes through the baffle steam-water separator 7 to separate the entrained droplets and enters the expansion tank 8.

[0039] When the pressure of the first-stage pressure suppression water tank 5, the first-stage pressure suppression water tank 6, and the expansion tank 8 reaches the opening pressure of the bursting membrane 9, the bursting membrane opens, and the first stop valve 11 downstream of the combined metal fiber filter layer 10 can be automatically opened to achieve the filtration and discharge of the high-temperature and high-pressure gas in the containment and the pressure suppression water tank. The radioactivity monitor 12 on the discharge pipeline is used to monitor the radioactive dose released into the environment, and can also be used to monitor the system's filtering ability for radioactive substances.

[0040] With the commissioning of other dedicated safety systems, when the pressure in the first-stage pressure suppression water tank 5, the first-stage pressure suppression water tank 6 or the expansion tank 8 is higher than the pressure in the containment shell 1, the second stop valve 13 is opened to relieve the pressure in the first-stage pressure suppression water tank 5, the first-stage pressure suppression water tank 6 and the expansion tank. When the pressure in the containment shell 1 is higher than the pressure in the first-stage pressure suppression water tank 5 and the first-stage pressure suppression water tank 6 again, the first-stage pressure suppression water tank 5 and the first-stage pressure suppression water tank 6 realize the pressure suppression and water washing functions again.

[0041] This technical solution makes use of the existing pressure suppression water tank's water washing and filtering function for airborne radioactive substances, and achieves a high removal efficiency of radioactive substances through two-stage bubbling water washing. Then, with the help of the existing cabin's arrangement of combined metal fiber filters, the aerosols that are difficult to remove by bubbling water washing can be captured, which can reduce the occupation of overall resources and is highly economical. The technical solution of 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, reduces the water volume of the pressure suppression water tank through capacity expansion to achieve system weight reduction. With the help of the existing cabin's arrangement of combined metal fiber filters, the most easily penetrating particle size aerosols that are difficult to remove by bubbling water washing can be captured, further reducing the radioactive activity of the exhaust gas and reducing the occupation of overall resources.

[0042] The above are preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. An integrated containment pressure suppression filtration and discharge system, characterized in that: The system comprises: a containment shell, a discharge valve, a discharge pipe, a nozzle, a first-stage pressure suppression water tank, a second-stage pressure suppression water tank, a baffle steam-water separator, an expansion tank, a bursting membrane structure, a combined metal fiber filter layer, a radioactive monitor, a first stop valve and a second stop valve; The containment shell is connected to the first-stage pressure suppression water tank through the discharge valve, the discharge pipe and the nozzle, and the first-stage pressure suppression water tank is connected to the second-stage pressure suppression water tank through the discharge pipe and the nozzle; The first-stage pressure suppression water tank and the second-stage pressure suppression water tank are respectively loaded with a mixed solution for absorbing iodine in the exhaust gas; the first stop valve is arranged between the first-stage pressure suppression water tank and the expansion tank and the containment shell; The bursting membrane structure is arranged upstream of the combined metal fiber filter layer, and the opening pressure of the bursting membrane structure should be less than the design pressure of the containment, the first-stage pressure suppression water tank, the second-stage pressure suppression water tank and the expansion tank; a second stop valve is arranged downstream of the combined metal fiber filter layer; The radioactivity monitor is connected to the combined metal fiber filter layer through the second stop valve, and is used to monitor the radioactive dose released into the environment and the filtering ability of the system for radioactive substances; When the pressure in the first-level pressure suppression water tank, the second-level pressure suppression water tank and the expansion tank is higher than the pressure in the containment shell, the first stop valve is opened to relieve the pressure in the first-level pressure suppression water tank, the second-level pressure suppression water tank and the expansion tank; when the pressure in the containment shell is higher than the pressure in the first-level pressure suppression water tank and the second-level pressure suppression water tank, the first-level pressure suppression water tank and the second-level pressure suppression water tank realize the pressure suppression and water washing functions.

2. The integrated containment pressure suppression filtration and drainage system according to claim 1, characterized in that: The nozzles in the first-stage pressure water tank and the second-stage pressure water tank are installed vertically downward, so that the submerged depth of the nozzles is increased, which is convenient for condensation heat exchange of gas-liquid two phases in the first-stage pressure water tank and the second-stage pressure water tank and bubbling water washing of radioactive materials.

3. The integrated containment pressure suppression filtration and drainage system according to claim 1, characterized in that: The first-stage pressure suppression water tank and the second-stage pressure suppression water tank are respectively loaded with a mixed solution for absorbing iodine in the exhaust gas, including: The mixed solution is a mixed solution of sodium hydroxide iodide and sodium thiosulfate, and the mixed solution absorbs iodine in the exhaust gas through a chemical reaction.

4. The integrated containment pressure suppression filtration and drainage system according to claim 1, characterized in that: The system uses two-stage bubbling water washing to remove radioactive aerosols and iodine from the exhaust gas; In the first stage of bubbling water washing, the outlet gas of the nozzle 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; after the first stage of bubbling condensation, the nozzle outlet flow rate is reduced in the second stage of bubbling water washing, the bubble size is reduced, the specific surface area is increased, the residence time of the bubbles in the liquid phase is increased, and the removal efficiency of radioactive substances is increased.

5. The integrated containment pressure suppression filtration and drainage system according to claim 1, characterized in that: The exhaust gas enters the second-stage pressure suppression water tank for bubbling and water washing. After two-stage bubbling, condensation and water washing, the exhaust gas passes through the baffle steam-water separator to separate the entrained droplets and then enters the expansion tank.

6. The integrated containment pressure suppression filtration and drainage system according to claim 1, characterized in that: When the pressure in the first-stage pressure suppression water tank, the second-stage pressure suppression water tank and the expansion tank reaches the opening pressure of the bursting membrane structure, the stop valve downstream of the combined metal fiber filter layer automatically opens to achieve the filtered discharge of high-temperature and high-pressure gases in the containment and the pressure suppression water tank.

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