System for post-processing of hydrogen risk accidents in small space containment and method for controlling the same

Abstract

The present application relates to the technical field of nuclear power plant safety processing, and discloses a hydrogen risk accident post-processing system for a small-space containment vessel and a control method thereof, the system comprising an inert gas supply device, an oxygen supply device, a gas mixing device, a hydrogen reaction device, a tail gas treatment device and a processor, the inert gas supply device, the oxygen supply device and the containment vessel being connected to the gas mixing device, a first valve being arranged between the containment vessel and the gas mixing device, the hydrogen concentration detection device and the first valve being connected to the processor, the processor being capable of controlling the opening degree of the first valve according to the hydrogen concentration detected by the hydrogen concentration detection device, so that the hydrogen concentration in the gas mixing device is lower than a set value; the gas mixing device is connected to the hydrogen reaction device, and the hydrogen reaction device is connected to the tail gas treatment device. The present application can safely output and process high-concentration hydrogen in the small-space containment vessel in the late stage of a severe accident, and eliminate safety hazards.

Description

Technical Field

[0001] This invention relates to the field of nuclear power facility safety treatment technology, and more specifically, to a hydrogen risk accident post-treatment system and control method for a small containment space. Background Technology

[0002] During a severe accident in a small to medium-sized nuclear reactor, the zirconium alloy, stainless steel, and other metallic materials in the reactor core undergo oxidation. This chemical process produces a large amount of hydrogen gas. The hydrogen gas is released into the containment vessel through breaches in the primary coolant circuit, safety valves, or pressure relief valves. Within the containment vessel, it migrates and diffuses, mixing with water vapor released from the primary coolant circuit and air inside the containment vessel, forming a flammable gas cloud. When the hydrogen concentration within the containment vessel reaches a certain level, under certain conditions (such as temperature, pressure, and oxygen concentration), hydrogen combustion or an explosion may occur. The small containment vessel volume used in small to medium-power light water reactors means that an explosion of the flammable gas mixture could damage safety equipment and systems, compromise the integrity of the containment vessel, and result in the release of large amounts of radioactive material.

[0003] For hydrogen risk control in the event of a severe accident in a small or medium-sized nuclear reactor, in the early stages of a severe accident, a passive hydrogen recombiner or igniter is used to consume all the oxygen in the containment vessel. After this process, the oxidation reaction that removes hydrogen gradually stops. As the accident progresses, the hydrogen released from the primary circuit will accumulate further in the containment vessel. In the later stages of a severe accident, it is necessary to further treat the high concentration of hydrogen in the small containment space to completely eliminate the risk of hydrogen combustion and explosion in the small containment space.

[0004] Small and medium-sized nuclear reactors generally use small-space containment structures with lower construction and manufacturing costs. The compact arrangement of equipment and limited free space within the small-space containment structure makes it difficult to lay out conventional hydrogen removal equipment. At the same time, in the later stages of a severe accident, after the oxygen in the small-space containment structure is depleted, a high concentration of hydrogen accumulates inside. Without oxygen, it is difficult for the hydrogen removal equipment to carry out the hydrogen removal reaction. Summary of the Invention

[0005] This invention addresses the problem that in the later stages of a severe accident, after the oxygen in the small containment space is depleted, a high concentration of hydrogen accumulates within the containment space. The limited space within the containment makes it difficult for conventional hydrogen removal equipment to perform the hydrogen removal reaction. The invention provides a post-accident handling system and control method for hydrogen hazard incidents in small containment spaces. This system can safely remove and process the high concentration of hydrogen accumulated within the containment space, eliminating the possibility of leakage of the high concentration of hydrogen outside the containment and preventing further spread of the hydrogen hazard to more locations.

[0006] This invention is achieved through the following technical solution:

[0007] A post-accident handling system for hydrogen hazards in a small containment facility includes an inert gas supply device, an oxygen supply device, a gas mixing device, a hydrogen reaction device, a tail gas treatment device, and a processor. The inert gas supply device, the oxygen supply device, and the containment facility are respectively connected to the gas mixing device. A first valve is provided between the containment facility and the gas mixing device. A hydrogen concentration detection device is provided in the gas mixing device. The hydrogen concentration detection device and the first valve are both connected to the processor. The processor can control the opening of the first valve according to the hydrogen concentration detected by the hydrogen concentration detection device, so that the hydrogen concentration in the gas mixing device is lower than a set value. The gas mixing device is connected to the hydrogen reaction device, and the hydrogen reaction device is connected to the tail gas treatment device.

[0008] Optionally, a gas heater is also connected between the inert gas supply device and the gas mixing device.

[0009] Optionally, the oxygen supply device includes a fan connected to an air delivery pipe, and the fan is connected to the gas mixing device.

[0010] Optionally, the hydrogen reaction device includes a hydrogen reaction chamber, in which a hydrogen recombination device is provided.

[0011] Optionally, the exhaust gas treatment device includes an exhaust gas cooling box, which contains cooling water and a cooler for cooling the cooling water, and the exhaust gas in the exhaust gas cooling box is introduced into the gas mixing device.

[0012] The control method for a hydrogen risk accident post-treatment system in a small containment space includes the following steps:

[0013] Step 1: Turn on the inert gas supply device and introduce inert gas into the gas mixing device in sequence through the gas heater and the second valve;

[0014] Step 2: Turn on the fan and open the third valve to draw air from the atmosphere through the air delivery pipe and deliver it to the gas mixing device;

[0015] Step 3: After the gas supplied in Step 1 and Step 2 has stabilized, open the first valve to connect the pipeline between the containment vessel and the gas mixing device;

[0016] Step 4: Monitor the hydrogen concentration of the gas mixing device measured by the hydrogen concentration detection device, and adjust the opening of the first valve according to the read hydrogen concentration to control the hydrogen concentration of the gas mixing device below 3%.

[0017] Step 5: After the mixed gas is mixed in the gas mixing device, it is introduced into the hydrogen reaction chamber. The hydrogen recombination device in the chamber combines hydrogen and oxygen at room temperature to generate water or water vapor. The water vapor condenses on the wall of the hydrogen reaction chamber. The condensed water flows to the bottom of the hydrogen reaction chamber and then flows to the gas mixing device located at the bottom of the hydrogen reaction chamber.

[0018] Step 6: The combined exhaust gas flows from the hydrogen reaction chamber to the cooling water in the exhaust gas cooling box. Water vapor condenses in the cooling water, while non-condensable gases in the exhaust gas flow to the gas mixing device. The cooler is used to cool the cooling water in the exhaust gas cooling box and keep the cooling water temperature below 50°C.

[0019] Step 7: After the exhaust gas flows back to the gas mixing device, it mixes with the inert gas from the inert gas supply device, the hydrogen from the containment vessel, and the air from the air supply pipe before continuing to enter the hydrogen reaction chamber.

[0020] Step 8: Periodically open the drain valve to discharge the wastewater in the gas mixing device into the waste liquid treatment plant;

[0021] Step 9: Repeat steps 5-8 until the hydrogen concentration inside the containment vessel is less than 0.5%.

[0022] This invention also provides another technical solution:

[0023] A post-accident handling system for hydrogen hazards in a small containment space includes an inert gas supply device, an oxygen supply device, a gas mixing device, a hydrogen reaction device, an exhaust gas treatment device, and a processor. The inert gas supply device, the oxygen supply device, and the containment are respectively connected to the gas mixing device. The gas mixing device is connected to the hydrogen reaction device. The hydrogen reaction device is connected to the exhaust gas treatment device, and the exhaust gas treatment device is then connected to the gas mixing device.

[0024] The gas mixing device includes a gas mixer, a gas storage chamber, and a gas storage chamber in sequence. The gas mixer is connected to the inert gas supply device, the oxygen supply device, and the exhaust gas treatment device, respectively, and is used to mix the inert gas, oxygen, and exhaust gas. A piston plate is provided in the gas storage chamber, and a first one-way valve is provided on the piston plate. The first one-way valve is located near the outer periphery of the piston plate. The piston plate is connected to a linear drive mechanism, which can drive the piston plate to fit against the end of the gas storage chamber near the gas mixer, thereby closing the gas mixer. A hydrogen concentration detection device is provided in the gas storage chamber. A gas compensation device is also provided between the gas storage chamber and the gas storage chamber. The gas compensation device is connected to the inert gas supply device and the containment vessel.

[0025] Optionally, the gas compensation device includes a connecting pipe with an air inlet in the radial direction for connecting the inert gas supply device and the containment. The connecting pipe also has a rotating body with an embedded part at one end. The embedded part has a docking hole and can be inserted into the air inlet, so that the docking hole aligns with the air inlet. The rotating body is connected to a rotating drive mechanism, which can drive the rotating body to rotate, so that the docking hole of the rotating body can be switched between the air inlet of the inert gas supply device, the air inlet of the containment, and a non-docking hole.

[0026] A valve plate is also installed in the middle of the connecting pipe, and a second check valve is installed on the valve plate. The air inlet of the inert gas supply device and the air inlet of the containment are both located on the side of the second check valve near the gas storage chamber.

[0027] Optionally, both the first check valve and the second check valve adopt a structure formed by multiple conical plates, with an elastic support component connected to the back of the conical plates.

[0028] Optionally, the gas mixer includes a mixing body, which adopts a tubular structure with a central cavity. The central cavity is connected to an inert gas supply device. Several annular cavities are arranged at intervals on the tube wall of the mixing body. The annular cavities are connected at intervals to an oxygen supply device, an exhaust gas treatment device, and a containment vessel. The annular cavities are also provided with several inclined holes to connect to the central cavity.

[0029] The technical solution of the present invention has at least the following beneficial effects:

[0030] The present invention relates to a hydrogen risk post-accident handling system and control method for small containment structures. By setting up an inert gas supply device, an oxygen supply device, and a gas mixing device outside the containment, hydrogen inside the containment is mixed with a high concentration of inert gas and air in the gas mixing device. Then, by setting up a hydrogen reaction device, the mixed gas is reacted in the hydrogen reaction device, thereby eliminating hydrogen. After continuous operation, it can eliminate the high concentration of hydrogen accumulated in the small containment structure and reduce the potential risk of high concentration of hydrogen accumulated in the small containment structure. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the post-accident handling system for hydrogen risk accidents in a small containment space according to Embodiment 1 of the present invention.

[0032] Figure 2 This is a half-sectional view of the gas mixing device according to Embodiment 2 of the present invention;

[0033] Figure 3 for Figure 2 Enlarged view of part A.

[0034] Figure label:

[0035] 1-Inert gas supply device, 2-Containment vessel, 3-First valve, 4-Fan, 5-Air delivery pipe, 6-Gas heater, 7-Second valve, 8-Third valve, 9-Hydrogen concentration detection device, 10-Hydrogen reaction chamber, 11-Hydrogen recombiner, 12-Gas mixing device, 13-Tail gas cooling box, 14-Cooler, 15-Drain valve;

[0036] 121-Gas mixer, 1211-Annular cavity, 122-Gas storage chamber, 1221-Linear drive mechanism, 1222-First check valve, 1223-Piston plate, 123-Gas storage chamber, 124-Gas compensation device, 1241-Rotating body, 1242-Rotating drive mechanism, 1243-Air inlet, 1244-Second check valve. Detailed Implementation

[0037] Example 1

[0038] Reference Figure 1 The present invention provides a hydrogen hazard accident post-processing system for a small containment 2, comprising an inert gas supply device 1, an oxygen supply device, a gas mixing device 12, a hydrogen reaction device, a tail gas treatment device, and a processor. The inert gas supply device 1, the oxygen supply device, and the containment 2 are respectively connected to the gas mixing device 12. The containment 2 and the gas mixing device 12 are provided with a first valve 3. By opening the first valve 3, the gas inside the containment 2 can be introduced into the gas mixing device 12.

[0039] In addition, a gas heater 6 and a second valve 7 are connected between the inert gas supply device 1 and the gas mixing device 12. The inert gas supply device 1 can use bottled nitrogen. When the second valve 7 is opened, the bottled nitrogen can be heated by the gas heater 6 and then introduced into the gas mixing device 12.

[0040] The oxygen supply device includes a fan 4 connected to an air delivery pipe 5. The fan 4 is connected to a gas mixing device 12 via a third valve 8. When the fan 4 and the third valve 8 are turned on, air from the atmospheric environment can be introduced into the gas mixing device 12.

[0041] The gas mixing device 12 is equipped with a hydrogen concentration detection device 9. Both the hydrogen concentration detection device 9 and the first valve 3 are connected to a processor. The processor can be a conventional PLC processor or a processor with similar control functions. The processor can control the opening of the first valve 3 according to the hydrogen concentration detected by the hydrogen concentration detection device 9, so that the hydrogen concentration in the gas mixing device 12 is lower than a set value, which is below 3% in this embodiment.

[0042] A gas mixing device 12 is connected to a hydrogen reaction device, which includes a hydrogen reaction chamber 10. A hydrogen recombination device 11 is installed in the hydrogen reaction chamber 10, employing conventional technology in the art. The gas mixed by the gas mixing device 12 is introduced into the hydrogen reaction chamber 10. The hydrogen recombination device 11, under the action of a catalyst, enables hydrogen and oxygen to undergo a hydrogen-oxygen recombination reaction. The gas in the gas mixing device 12 enters from the bottom of the hydrogen reaction chamber 10 and exits through a top pipe after the reaction. The hydrogen reaction chamber 10 is chimney-shaped, facilitating the flow of heated gas from the bottom to the outlet, creating a chimney effect of natural gas flow.

[0043] Water vapor generated in hydrogen reaction chamber 10 may condense therein, and the condensed water may be left in gas mixing device 12. Gas mixing device 12 is connected to drain valve 15 for periodically draining the water accumulated in gas mixing device 12.

[0044] The hydrogen reactor is connected to a tail gas treatment device, which includes a tail gas cooling box 13. The tail gas cooling box 13 is equipped with cooling water and a cooler 14 for cooling the cooling water. When gas is generated in the hydrogen reaction chamber 10, it is introduced into the tail gas cooling box 13 and cooled by the cooling water. The tail gas in the tail gas cooling box 13 is introduced into a gas mixing device 12 for recycling.

[0045] The control method for the hydrogen risk accident post-treatment system in the small-space containment 2 according to this embodiment includes the following steps:

[0046] Step 1: Turn on the inert gas supply device 1, and sequentially introduce inert gas into the gas mixing device 12 through the gas heater 6 and the second valve 7.

[0047] Step 2: Turn on the fan 4 and the third valve 8 to draw air from the atmosphere through the air delivery pipe 5 and deliver it to the gas mixing device 12.

[0048] Step 3: After the gas supplied in Step 1 and Step 2 has stabilized, open the first valve 3 to connect the pipeline between the containment vessel 2 and the gas mixing device 12.

[0049] Step 4: Monitor the hydrogen concentration of the gas mixing device 12 measured by the hydrogen concentration detection device 9, and adjust the opening of the first valve 3 according to the read hydrogen concentration to control the hydrogen concentration of the gas mixing device 12 below 3%.

[0050] Step 5: After the mixed gas is mixed in the gas mixing device 12, it is introduced into the hydrogen reaction chamber 10. The hydrogen recombination device 11 in the chamber combines hydrogen and oxygen at room temperature to generate water or water vapor. The water vapor condenses on the wall of the hydrogen reaction chamber 10. The condensed water flows to the bottom of the hydrogen reaction chamber 10 and then flows to the gas mixing device 12 located at the bottom of the hydrogen reaction chamber 10.

[0051] Step 6: The combined exhaust gas flows from the hydrogen reaction chamber 10 to the cooling water in the exhaust gas cooling box 13. Water vapor condenses in the cooling water, and the non-condensable gases in the exhaust gas flow to the gas mixing device 12. The cooler 14 is used to cool the cooling water in the exhaust gas cooling box 13 and keep the cooling water temperature below 50°C.

[0052] Step 7: After the exhaust gas flows back to the gas mixing device 12, it mixes with the inert gas from the inert gas supply device 1, the hydrogen from the containment 2, and the air from the air supply pipe 5, and then continues to enter the hydrogen reaction chamber 10.

[0053] Step 8: Periodically open the drain valve 15 to discharge the wastewater in the gas mixing device 12 into the waste liquid treatment plant.

[0054] Step 9: Repeat steps 5-8 until the hydrogen concentration inside containment 2 is less than 0.5%.

[0055] Example 2:

[0056] This embodiment further defines the gas mixing device 12 based on embodiment 1.

[0057] The gas mixing device 12 includes a gas mixer 121, a gas storage chamber 122, and a gas storage chamber 123 in sequence. The gas mixer 121 is connected to an inert gas supply device 1, an oxygen supply device, and a tail gas treatment device, respectively, for mixing inert gas, oxygen, and tail gas. A piston plate 1223 is provided in the gas storage chamber 122, and a first one-way valve 1222 is provided on the piston plate 1223. The first one-way valve 1222 is located near the outer periphery of the piston plate 1223. The piston plate 1223 is connected to a linear drive mechanism 1221, which can drive the piston plate 1223 to fit against the end of the gas storage chamber 122 near the gas mixer 121, thereby closing the gas mixer 121. A hydrogen concentration detection device 9 is provided in the gas storage chamber 122. A gas compensation device 124 is also provided between the gas storage chamber 122 and the gas storage chamber 123. The gas compensation device 124 is connected to the inert gas supply device 1 and the containment vessel 2, respectively.

[0058] The gas mixer 121 includes a mixing body with a tubular structure having a central cavity. The central cavity is connected to an inert gas supply device 1. Several annular cavities 1211 are spaced apart on the tube wall of the mixer body. These annular cavities 1211 are spaced apart and connected to an oxygen supply device, an exhaust gas treatment device, and a containment vessel 2. Each annular cavity 1211 also has several inclined holes to connect to the central cavity. The central cavity structure is used to initially introduce inert gas because its high concentration provides the main supply. Various gases connected to the annular cavities 1211 are then introduced into the central cavity through the inclined holes at a near-tangential angle, allowing for better mixing with the inert gas. Furthermore, the spaced arrangement ensures more uniform gas mixing.

[0059] After mixing, the gases enter the gas storage chamber 122 and remain there briefly. Once a certain amount has accumulated, the piston plate 1223 is moved by a linear drive mechanism 1221. In this embodiment, the linear drive mechanism 1221 is a motor-driven reciprocating screw mechanism that moves the piston plate 1223. The piston plate 1223 is also equipped with several guide rods to ensure smooth movement in a straight line. The mixed gas passes through the first one-way valve 1222 on the piston plate 1223 to the other side. At this point, the hydrogen concentration is detected by the hydrogen concentration detection device 9. The mixed gas contains tail gas, and the hydrogen concentration in the tail gas is variable, causing the hydrogen concentration to be unstable after mixing. Controlling the valve opening of the containment vessel 2 has the problem of untimely response. Therefore, this embodiment uses the method of storing the mixed gas in the gas storage chamber 122 for accurate measurement of hydrogen concentration, which results in higher measurement accuracy. When the measured hydrogen concentration exceeds 3%, the gas compensation device 124 needs to add some inert gas to reduce the hydrogen concentration and ensure the safety of the reaction; when the measured hydrogen concentration is below 2%, the gas compensation device 124 needs to add some hydrogen to increase the hydrogen concentration and improve the efficiency of the reaction.

[0060] The gas compensation device 124 includes a connecting pipe with an inlet port 1243 radially connected to the inert gas supply device 1 and the containment vessel 2. A rotating body 1241 is also provided on the connecting pipe. One end of the rotating body 1241 has an insert portion with a mating hole. The insert portion can be inserted into the inlet port 1243, allowing the mating hole to align with the inlet port 1243. The rotating body 1241 is connected to a rotating drive mechanism 1242, which drives the rotating body 1241 to rotate. This allows the mating hole of the rotating body 1241 to switch between the inert gas supply device 1's inlet port 1243, the containment vessel 2's inlet port 1243, and a non-mating hole position. The rotating drive mechanism 1242 uses a motor, gears, and a gear ring arranged on the rotating body 1241. The motor output drives the gear to rotate, which in turn drives the gear ring and the rotating body 1241 to rotate.

[0061] A valve plate is also provided in the middle of the connecting pipe, and a second one-way valve 1244 is provided on the valve plate. The air inlet 1243 of the inert gas supply device 1 and the air inlet 1243 of the containment 2 are both located on the side of the second one-way valve 1244 near the gas storage chamber 122.

[0062] Both the first check valve 1222 and the second check valve 1244 adopt a structure formed by multiple conical plates, with an elastic support component, such as a spring, connected to the back of the conical plates.

[0063] When the compensation gas enters the connecting pipe, the piston plate 1223, driven by the linear drive mechanism 1221, returns to compression, forcing the mixed gas into the gas storage chamber 123. At this time, the gas passing through the second one-way valve 1244, due to its small pipe diameter, forms a brief high pressure, which can bring the compensation gas into the gas storage chamber together, and at the same time, they are mixed.

Claims

1. A post-accident handling system for hydrogen hazards in small containment spaces, characterized in that, It includes an inert gas supply device, an oxygen supply device, a gas mixing device, a hydrogen reaction device, an exhaust gas treatment device, and a processor. The inert gas supply device, the oxygen supply device, and the containment are respectively connected to the gas mixing device. The gas mixing device is connected to the hydrogen reaction device. The hydrogen reaction device is connected to the exhaust gas treatment device, and the exhaust gas treatment device is then connected to the gas mixing device. The gas mixing device includes a gas mixer, a gas storage chamber, and a gas storage chamber. The gas mixer is connected to the inert gas supply device, the oxygen supply device, and the exhaust gas treatment device, and is used to mix the inert gas, oxygen, and exhaust gas. The gas storage chamber is equipped with a piston plate, and a first one-way valve is provided on the piston plate. The first one-way valve is located near the outer periphery of the piston plate. The piston plate is connected to a linear drive mechanism, which can drive the piston plate to fit against the end of the gas storage chamber near the gas mixer, thereby closing the gas mixer. The gas storage chamber is equipped with a hydrogen concentration detection device. A gas compensation device is also provided between the gas storage chamber and the gas storage chamber. The gas compensation device is connected to the inert gas supply device and the containment vessel. The gas compensation device includes a connecting pipe with an air inlet in the radial direction for connecting the inert gas supply device and the containment. The connecting pipe also has a rotating body with an embedded part at one end. The embedded part has a docking hole and can be inserted into the air inlet, so that the docking hole aligns with the air inlet. The rotating body is connected to a rotating drive mechanism, which can drive the rotating body to rotate, so that the docking hole of the rotating body can be switched between the air inlet of the inert gas supply device, the air inlet of the containment, and a non-docking hole. A valve plate is also installed in the middle of the connecting pipe, and a second check valve is installed on the valve plate. The air inlet of the inert gas supply device and the air inlet of the containment are both located on the side of the second check valve near the gas storage chamber.

2. The post-accident handling system for hydrogen hazard accidents in small containment spaces according to claim 1, characterized in that, Both the first and second check valves adopt a structure formed by multiple conical plates, with an elastic support component connected to the back of the conical plates.

3. The post-accident handling system for hydrogen hazard accidents in small containment spaces according to claim 1, characterized in that, The gas mixer includes a mixing body, which adopts a tubular structure with a central cavity. The central cavity is connected to an inert gas supply device. Several annular cavities are arranged at intervals on the tube wall of the mixing body. The annular cavities are connected at intervals to an oxygen supply device, an exhaust gas treatment device, and a containment vessel. The annular cavities are also provided with several inclined holes to connect to the central cavity.

4. The control method for a hydrogen risk accident post-treatment system in a small-space containment facility according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Turn on the inert gas supply device and introduce inert gas into the gas mixing device in sequence through the gas heater and the second valve; Step 2: Turn on the fan and open the third valve to draw air from the atmosphere through the air delivery pipe and deliver it to the gas mixing device; Step 3: After the gas supplied in Step 1 and Step 2 has stabilized, open the first valve to connect the pipeline between the containment vessel and the gas mixing device; Step 4: Monitor the hydrogen concentration of the gas mixing device measured by the hydrogen concentration detection device, and adjust the opening of the first valve according to the read hydrogen concentration to control the hydrogen concentration of the gas mixing device below 3%. Step 5: After the mixed gas is mixed in the gas mixing device, it is introduced into the hydrogen reaction chamber. The hydrogen recombination device in the chamber combines hydrogen and oxygen at room temperature to generate water or water vapor. The water vapor condenses on the wall of the hydrogen reaction chamber. The condensed water flows to the bottom of the hydrogen reaction chamber and then flows to the gas mixing device located at the bottom of the hydrogen reaction chamber. Step 6: The combined exhaust gas flows from the hydrogen reaction chamber to the cooling water in the exhaust gas cooling box. Water vapor condenses in the cooling water, while non-condensable gases in the exhaust gas flow to the gas mixing device. The cooler is used to cool the cooling water in the exhaust gas cooling box and keep the cooling water temperature below 50°C. Step 7: After the exhaust gas flows back to the gas mixing device, it mixes with the inert gas from the inert gas supply device, the hydrogen from the containment vessel, and the air from the air supply pipe before continuing to enter the hydrogen reaction chamber. Step 8: Periodically open the drain valve to discharge the wastewater in the gas mixing device into the waste liquid treatment plant; Step 9: Repeat steps 5-8 until the hydrogen concentration inside the containment vessel is less than 0.5%.

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