An integrated containment pressure-suppression filtration and exhaust system

Abstract

The application provides an integrated containment pressure-suppression filter discharge system, which comprises a containment, a discharge valve, a discharge pipeline, a nozzle, a first-stage pressure-suppression water tank, a second-stage pressure-suppression water tank, a baffle plate steam-water separator, an expansion tank, a bursting disc structure, a combined metal fiber filter layer, a radiation monitor, a first stop valve and a second stop valve. The application is provided with two-stage pressure-suppression water tanks, and the two-stage bubbling water washing realizes a high removal efficiency of gas-borne radioactive substances, and then the existing cabin arrangement combined metal fiber filter is used, so that the requirement of rapid pressure reduction and radioactive substance removal of the containment under LOCA accident conditions can be met, and the problem of too many resources occupied by the existing containment filter discharge system of a nuclear power plant is solved, and the economic efficiency is high.

Description

Technical Field

[0001] This invention belongs to the technical field of dedicated safety facilities for nuclear power plants, and specifically relates to an integrated containment pressure suppression and filtration emission system. Background Technology

[0002] As the compartment in an offshore nuclear power platform that houses high-energy, high-radioactivity equipment and pipelines such as reactors and primary loop systems, the containment vessel is the last line of defense against the release of radioactive materials into the external environment after a breach accident. Therefore, ensuring its integrity is of great importance.

[0003] For marine nuclear power plants and floating power plants, due to overall resource constraints, the free volume of the containment is much smaller than that of a nuclear power plant containment. When a rupture occurs in the primary loop of the containment, a large amount of high-temperature, high-pressure coolant flashes and is released into the containment, causing a rapid increase in pressure. If the pressure cannot be reduced quickly, the containment pressure will rise rapidly within tens of seconds and exceed its design pressure. Given the extremely high mass-energy release rate in the initial stage of a containment rupture accident, relying solely on spray systems and passive containment cooling systems is insufficient to meet the pressure reduction requirements. Current nuclear power plants are equipped with containment filtration and venting systems, which actively depressurize to ensure that the pressure inside the containment does not exceed its bearing limits, thus ensuring the integrity of the containment. Simultaneously, filtration devices installed on the depressurization lines filter radioactive materials in the vented gases to prevent leakage of radioactive products.

[0004] The containment filtration and venting system mainly consists of two stages: wet venturi scrubbing and dry metal fiber filtration. However, this type of filter is relatively large in size and requires significant supporting facilities. If used directly on an offshore nuclear power platform, it would consume a considerable amount of overall resources.

[0005] Therefore, how to provide an integrated containment pressure suppression filtration and discharge system that can meet the needs of rapid depressurization and removal of radioactive materials in the containment, while solving the problem of excessive resource consumption by existing containment filtration and discharge systems in nuclear power plants, has become an urgent technical problem to be solved. Summary of the Invention

[0006] This invention provides an integrated containment pressure suppression and filtration emission system that can meet the needs of rapid depressurization and removal of radioactive materials from the containment, while solving the problem of excessive resource consumption by existing containment filtration emission systems in nuclear power plants.

[0007] In this embodiment of the invention, an integrated containment pressure suppression and filtration discharge system is provided, comprising: a containment, a discharge valve, a discharge pipe, a nozzle, a first-stage pressure suppression water chamber, a second-stage pressure suppression water chamber, a baffle plate steam-water separator, an expansion chamber, a rupture membrane structure, a combined metal fiber filter layer, a radioactivity monitor, a first shut-off valve, and a second shut-off valve.

[0008] The containment vessel is connected to the first-stage pressure-suppressing water chamber via the discharge valve, discharge pipe and nozzle, and the first-stage pressure-suppressing water chamber and the second-stage pressure-suppressing water chamber are connected via the discharge pipe and nozzle.

[0009] The first-stage pressure-suppressing water tank and the second-stage pressure-suppressing water tank are respectively loaded with a mixed solution for absorbing iodine in the exhaust gas; the first shut-off valve is provided between the first-stage pressure-suppressing water tank and the expansion tank and the containment vessel;

[0010] The burst membrane structure is located upstream of the combined metal fiber filter layer. The opening pressure of the burst membrane structure should be less than the design pressure of the containment and the first-stage and second-stage pressure-suppressing water chambers. The downstream shut-off valve of the combined metal fiber filter layer is opened to filter the high-temperature and high-pressure gas in the containment and the first-stage and second-stage pressure-suppressing water chambers.

[0011] The radioactivity monitor is connected to a combined metal fiber filter layer via the second shut-off valve, and is used to monitor the radioactive dose released into the environment, as well as the system's ability to filter radioactive materials.

[0012] When the pressure inside the first-stage pressure-suppressing water tank, the second-stage pressure-suppressing water tank, and the expansion tank is higher than the pressure inside the containment, the first shut-off valve is opened to depressurize the first-stage pressure-suppressing water tank, the second-stage pressure-suppressing water tank, and the expansion tank. When the pressure inside the containment is higher than the pressure inside the first-stage pressure-suppressing water tank and the second-stage pressure-suppressing water tank, the first-stage pressure-suppressing water tank and the second-stage pressure-suppressing water tank perform pressure suppression and water washing functions.

[0013] Furthermore, the nozzles in the first-stage and second-stage pressure-suppressing water chambers are installed vertically downwards, which increases the submersion depth of the nozzles, facilitating the condensation and heat exchange of the gas-liquid two-phase system and the bubbling washing of radioactive materials in the first-stage and second-stage pressure-suppressing water chambers.

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

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

[0016] Furthermore, the system employs a two-stage bubbling water wash to remove radioactive source items from the emitted gas, including at least aerosols and iodine.

[0017] In the first-stage 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, forming 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 the entrained droplets. At the same time, the vapor fraction of the exhaust gas is relatively high, and vapor condensation also significantly improves the aerosol removal efficiency. As the energy of the exhaust gas dissipates, the gas flow pattern changes from a jet to a bubble swarm. Radioactive materials diffuse and migrate within the bubbles to the bubble surface and are then retained by the liquid phase. After the first-stage bubbling condensation, the exhaust gas mainly consists of non-condensable gases. In the second-stage bubbling water washing, the nozzle outlet velocity 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 materials increases.

[0018] Furthermore, the exhaust gas enters the second-stage pressure-suppressing water chamber for bubbling and washing. After two stages of bubbling condensation and washing, the exhaust gas passes through the baffle plate steam-water separator to separate the entrained droplets before entering the expansion chamber.

[0019] Furthermore, when the pressure inside the first-stage pressure-suppressing water chamber, the second-stage pressure-suppressing water chamber, and the expansion chamber reaches the opening pressure of the burst membrane structure, the shut-off valve downstream of the combined metal fiber filter layer can be automatically opened to achieve the filtration and discharge of high-temperature and high-pressure gases in the containment and pressure-suppressing water chamber.

[0020] The beneficial effects of this invention are as follows:

[0021] As can be seen from the above scheme, the embodiments of the present invention provide an integrated containment pressure suppression and filtration discharge system, including: a containment, a discharge valve, a discharge pipe, a nozzle, a first-stage pressure suppression water chamber, a second-stage pressure suppression water chamber, a baffle plate steam-water separator, an expansion chamber, a rupture membrane structure, a combined metal fiber filter layer, a radioactivity monitor, a first shut-off valve, and a second shut-off valve. When the pressure inside the first-stage pressure suppression water chamber, the second-stage pressure suppression water chamber, and the expansion chamber is higher than the pressure inside the containment, the shut-off valves are opened to depressurize the first-stage pressure suppression water chamber, the second-stage pressure suppression water chamber, and the expansion chamber. When the pressure inside the containment is higher than the pressure inside the first-stage pressure suppression water chamber and the second-stage pressure suppression water chamber, the first-stage pressure suppression water chamber and the second-stage pressure suppression water chamber achieve pressure suppression and water washing functions. The technical solution of the present invention can reduce the water volume of the pressure suppression water chamber by expanding the capacity, thereby reducing the system weight, while ensuring the pressure suppression function of the pressure suppression water chamber and the source water washing efficiency. By using existing compartments to install combined metal fiber filters, the most penetrating aerosol particles that are difficult to remove by bubbling and washing can be captured, reducing the radioactivity of emitted gases and thus reducing the overall resource consumption. Attached Figure Description

[0022] Figure 1This is a schematic diagram illustrating the structure of an integrated containment pressure suppression and filtration emission system according to an embodiment of the present invention.

[0023] In the diagram, 1 is the containment vessel, 2 is the discharge valve, 3 is the discharge pipe, 4 is the nozzle, 5 is the first-stage pressure-suppressing water chamber, 6 is the second-stage pressure-suppressing water chamber, 7 is the baffle plate steam-water separator, 8 is the expansion chamber, 9 is the rupture membrane, 10 is the combined metal fiber filter layer, 11 is the second shut-off valve, 12 is the radioactivity monitor, and 13 is the first shut-off valve. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0025] To meet the requirements of rapid depressurization and radioactive material removal within the containment system, and to address the issue of excessive resource consumption in existing containment filtration and emission systems at nuclear power plants, an integrated containment pressure suppression and filtration emission system based on multi-stage bubbling water washing and metal fiber filtration is proposed. This technical solution leverages the existing pressure suppression water chamber's water washing and filtration function for airborne radioactive materials, achieving high removal efficiency through two stages of bubbling water washing. Then, by incorporating combined metal fiber filters within existing compartments, aerosols that are difficult to remove through bubbling water washing are captured, reducing overall resource consumption and demonstrating high economic efficiency.

[0026] In this embodiment of the invention, while ensuring the pressure suppression function of the pressure-suppressing water tank and the efficiency of source-phase water washing, the water volume of the pressure-suppressing water tank is reduced by expanding its capacity, thereby achieving system weight reduction. By utilizing existing compartments with combined metal fiber filters, the most penetrating aerosol particles that are difficult to remove by bubbling water washing are captured, further reducing the radioactivity of the emitted gases and minimizing overall resource consumption. When the pressure in the pressure-suppressing water tank and the expansion tank is significantly higher than the containment pressure, the valves connecting the pressure-suppressing water tank and the containment, as well as the valves connecting the expansion tank and the containment, are opened to depressurize the pressure-suppressing water tank and the expansion tank. Once the containment pressure is again higher than the pressure in the pressure-suppressing water tank, the pressure-suppressing water tank continues to perform its heat trap and water washing functions.

[0027] In this embodiment of the invention, an integrated containment pressure suppression filtration and emission system is provided. Based on multi-stage bubbling water washing and metal fiber filtration, it utilizes the existing pressure suppression water chamber's water washing and filtration function for airborne radioactive materials, achieving high removal efficiency of radioactive materials through two-stage bubbling water washing. Then, by employing a combined metal fiber filter arranged in existing compartments, it captures aerosols that are difficult to remove through bubbling water washing, reducing overall resource consumption and achieving high economic efficiency.

[0028] In one embodiment of the present invention, the nozzles in the first-stage and second-stage pressure-suppressing water chambers are installed vertically downwards, which increases the submersion depth of the nozzles and facilitates the condensation and heat exchange of the gas-liquid two-phase system and the bubbling washing of radioactive materials in the first-stage and second-stage pressure-suppressing water chambers.

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

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

[0031] In one embodiment of the present invention, the system employs a two-stage bubbling water wash to remove radioactive source terms in the emitted gas, including at least aerosols and iodine.

[0032] In the first-stage 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 bubbling condensation, in the second-stage bubbling water washing, the outlet flow velocity of the nozzle 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 materials increases.

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

[0034] In one embodiment of the present invention, when the pressure inside the first-stage pressure-suppressing water chamber, the second-stage pressure-suppressing water chamber, and the expansion chamber reaches the opening pressure of the burst membrane structure, the shut-off valve downstream of the combined metal fiber filter layer can be automatically opened to achieve the filtration and discharge of high-temperature and high-pressure gas in the containment and pressure-suppressing water chamber.

[0035] As can be seen, the technical solution of this invention, employing a multi-stage bubbling depressurization water washing scheme, can fully utilize the water resources within the depressurization tank, achieving rapid depressurization of the containment vessel and efficient retention of airborne radioactive materials under limited resource conditions. Utilizing existing compartments to arrange combined metal fiber filter layers reduces the overall resource consumption. Compared to mainstream containment filtration and emission systems in nuclear power plants, this solution also ensures high radioactive material removal efficiency while reducing the Venturi scrubbing stage, avoiding the inconvenience of periodic liquid replenishment for the filtration and emission device. The solution is simple, feasible, consumes few overall resources, and is economically viable.

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

[0037] When a LOCA (Local Occurrence-Oriented Collapse) accident occurs in the primary circuit of containment 1, the containment pressure rises to the opening pressure of discharge valve 2, and discharge valve 2 opens. The high-temperature, high-pressure steam-air mixture inside the containment first enters the first-stage pressure-reducing water chamber 5 through discharge pipe 3 and nozzle 4. Utilizing the efficient heat exchange of direct contact condensation via bubbling, the containment pressure is rapidly reduced, thereby lowering the initial pressure peak of the containment during the accident.

[0038] The pressure chambers 5 and 6 contain a mixed solution of sodium hydroxide and sodium thiosulfate, which can absorb iodine in the exhaust gas through a chemical reaction. During the bubbling wash in the first-stage pressure chamber 5, the gas exiting the nozzle is in a high-speed jet state, and the liquid phase is entrained into the gas plume, forming a large number of entrained droplets. Aerosols are captured and removed by the entrained droplets through inertial collision, interception, Brownian diffusion, and other capture mechanisms, and radioactive iodine is absorbed by the entrained droplets. Simultaneously, the exhaust gas has a high vapor content, and vapor condensation significantly improves the aerosol removal efficiency. As the energy of the exhaust gas dissipates, the gas flow pattern changes from a jet to a bubble swarm. Radioactive materials diffuse and migrate within the bubbles to the bubble surface and are then retained by the liquid phase. After bubbling condensation in the first-stage pressure chamber, the exhaust gas mainly consists of non-condensable gases. The exhaust gas then enters the second-stage pressure chamber 6 for bubbling wash. After two stages of bubbling condensation and washing, the exhaust gas passes through a baffle plate vapor-water separator 7 to separate the entrained droplets before entering the expansion chamber 8.

[0039] When the pressure in the first-stage pressure-suppressing water tank 5, the first-stage pressure-suppressing water tank 6, and the expansion tank 8 reaches the opening pressure of the rupture membrane 9, the rupture membrane opens. At this time, the first shut-off valve 11 downstream of the combined metal fiber filter layer 10 can automatically open, realizing the filtration and discharge of high-temperature and high-pressure gases in the containment and pressure-suppressing water tanks. 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 filtration capacity for radioactive materials.

[0040] With the commissioning of other dedicated safety systems, when the pressure inside the first-stage pressure-suppressing tank 5, the first-stage pressure-suppressing tank 6, or the expansion tank 8 is higher than the pressure inside the containment 1, the second shut-off valve 13 is opened to depressurize the first-stage pressure-suppressing tank 5, the first-stage pressure-suppressing tank 6, and the expansion tank. When the pressure inside the containment 1 is again higher than the pressure inside the first-stage pressure-suppressing tank 5 and the first-stage pressure-suppressing tank 6, the first-stage pressure-suppressing tank 5 and the first-stage pressure-suppressing tank 6 will once again perform pressure suppression and water washing functions.

[0041] This technical solution utilizes the existing pressure-suppressing water chamber's water washing and filtration function for airborne radioactive materials, achieving high removal efficiency through two-stage bubbling water washing. Then, by incorporating a combined metal fiber filter within the existing chamber, it captures aerosols that are difficult to remove through bubbling water washing, reducing overall resource consumption and offering high economic efficiency. This invention, while maintaining the pressure-suppressing function of the pressure-suppressing water chamber and the source-head water washing efficiency, reduces the water volume of the pressure-suppressing water chamber through capacity expansion, achieving system weight reduction. By incorporating a combined metal fiber filter within the existing chamber, it captures the most penetrating aerosol particles that are difficult to remove through bubbling water washing, further reducing the radioactivity of the emitted gas and minimizing overall resource consumption.

[0042] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An integrated containment pressure suppression and filtration discharge system, characterized in that, The system includes: containment vessel, discharge valve, discharge pipe, nozzle, first-stage pressure-suppressing water chamber, second-stage pressure-suppressing water chamber, baffle plate steam-water separator, expansion chamber, rupture membrane structure, combined metal fiber filter layer, radioactivity monitor, first shut-off valve and second shut-off valve. The containment vessel is connected to the first-stage pressure-suppressing water chamber via the discharge valve, discharge pipe and nozzle, and the first-stage pressure-suppressing water chamber and the second-stage pressure-suppressing water chamber are connected via the discharge pipe and nozzle. The first-stage pressure-suppressing water tank and the second-stage pressure-suppressing water tank are respectively loaded with a mixed solution for absorbing iodine in the exhaust gas; the first shut-off valve is provided between the first-stage pressure-suppressing water tank and the expansion tank and the containment vessel; The burst membrane structure is located upstream of the combined metal fiber filter layer. The opening pressure of the burst membrane structure should be less than the design pressure of the containment vessel, the first-stage pressure-suppressing water chamber, the second-stage pressure-suppressing water chamber, and the expansion chamber. A second shut-off valve is located downstream of the combined metal fiber filter layer. The radioactivity monitor is connected to a combined metal fiber filter layer via the second shut-off valve, and is used to monitor the radioactive dose released into the environment, as well as the system's ability to filter radioactive materials. When the pressure inside the first-stage pressure-suppressing water tank, the second-stage pressure-suppressing water tank, and the expansion tank is higher than the pressure inside the containment, the first shut-off valve is opened to depressurize the first-stage pressure-suppressing water tank, the second-stage pressure-suppressing water tank, and the expansion tank. When the pressure inside the containment is higher than the pressure inside the first-stage pressure-suppressing water tank and the second-stage pressure-suppressing water tank, the first-stage pressure-suppressing water tank and the second-stage pressure-suppressing water tank perform pressure suppression and water washing functions.

2. The integrated containment pressure suppression and filtration system according to claim 1, characterized in that, The nozzles in the first-stage and second-stage pressure-suppressing water chambers are installed vertically downwards, which increases the submersion depth of the nozzles and facilitates the condensation and heat exchange of the gas and liquid phases in the first-stage and second-stage pressure-suppressing water chambers as well as the bubbling and washing of radioactive materials.

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

4. The integrated containment pressure suppression and filtration system according to claim 1, characterized in that, The system employs a two-stage bubbling water wash to remove radioactive aerosols and iodine from the emitted gas; In the first-stage 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 bubbling condensation, in the second-stage bubbling water washing, the outlet flow velocity of the nozzle 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 materials increases.

5. An integrated containment pressure suppression and filtration system according to claim 1, characterized in that, The exhaust gas enters the second-stage pressure-suppressing water chamber for bubbling and washing. After two stages of bubbling, condensation, and washing, the exhaust gas passes through the baffle plate steam-water separator to separate the entrained droplets before entering the expansion chamber.

6. An integrated containment pressure suppression and filtration system according to claim 1, characterized in that, When the pressure inside the first-stage pressure-suppressing water chamber, the second-stage pressure-suppressing water chamber, and the expansion chamber reaches the opening pressure of the burst membrane structure, the shut-off valve downstream of the combined metal fiber filter layer will automatically open, thereby achieving the filtration and discharge of high-temperature and high-pressure gases from the containment vessel and the pressure-suppressing water chamber.

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