A multi-stage suppression tank and method

Abstract

The present application relates to the technical field of nuclear reaction safety facilities, and provides a multi-stage pressure suppression water tank and method, which is arranged in a containment, and comprises a first-stage pressure suppression water tank to an Nth-stage pressure suppression water tank, wherein the water space of the first-stage pressure suppression water tank is communicated with the internal space of the containment through a first-stage pressure suppression pipe, and the water space of the Nth-stage pressure suppression water tank is communicated with the gas space of the (N-1)th-stage pressure suppression water tank through an intermediate pressure suppression pipe, wherein N is an integer greater than or equal to 2. The present application fully condenses the water vapor entering the pressure suppression water tank, improves the condensation efficiency, and improves the pressure suppression capacity of the pressure suppression water tank. Moreover, since the water vapor is fully condensed, the volume of the pressure suppression water tank can be greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of nuclear reaction safety facilities technology, and more specifically, to a multi-stage pressure suppression tank and method. Background Technology

[0002] The containment is the last barrier preventing fission products from the fuel and radioactive materials from the primary coolant loop from entering the environment. During normal operation, the containment is at normal pressure and temperature or slightly negative pressure. When a loss-of-coolant accident occurs in the reactor coolant system, the coolant from the primary coolant loop is discharged into the containment through the rupture. Because the temperature of the coolant from the primary coolant loop is much higher than the temperature inside the containment, some of the coolant discharged into the containment will vaporize, causing the temperature and pressure of the containment to rise. This is especially true in the event of a double-end shear fracture accident in the hot section of the main pipeline, where the coolant from the primary coolant is emptied in a very short time, causing the temperature and pressure of the containment to rise rapidly. Alternatively, when a rupture accident occurs in the main steam pipe of the secondary coolant loop, steam from the secondary coolant loop is ejected into the containment through the rupture. Because the temperature of the steam from the secondary coolant loop is much higher than the temperature inside the containment, this will cause the temperature and pressure of the containment to rise. This is especially true in the event of a double-end shear fracture accident in the main steam pipe of the generator, where the steam from the secondary coolant loop is instantly discharged into the containment, causing the temperature and pressure of the containment to rise rapidly.

[0003] Traditional pressurized water reactors have large dry containment structures with ample free volume, capable of containing short-term, large-scale mass-energy releases and keeping containment pressure within limits. In small reactors or offshore nuclear power plants, the containment structure is compact with a smaller free volume, resulting in less capacity to contain mass-energy releases. Therefore, short-term pressure suppression measures are necessary to reduce containment pressure and prevent it from exceeding limits. Pressure suppression measures typically include spray systems and pressure-suppressing tanks. Spray systems are generally used for long-term pressure suppression but are not very effective at suppressing short-term pressure peaks; in extreme cases, the containment pressure may have already exceeded limits before the spray system is activated. Therefore, pressure-suppressing tanks are generally used for short-term pressure suppression.

[0004] Existing pressure-suppressing water tanks, such as Figure 1 As shown, taking the primary loop consisting of reactor pressure vessel 8, main pump 9, steam generator 10, pressurizer 11, and coolant pipeline 12 as an example, when a loss-of-coolant accident occurs, coolant is discharged from rupture 13 to containment 14, and the temperature and pressure of containment 14 rise. Driven by the pressure difference, the mixture of water vapor and air in containment 14 is discharged into the water space 7 of pressure suppression tank 15 through the drain pipe. Since the water in pressure suppression tank 15 is at normal temperature and pressure, the water vapor entering the water space 7 through the drain pipe will be condensed, and the non-condensable air will rise into the air space 6 of pressure suppression tank 15 under the action of buoyancy, thereby achieving pressure suppression of containment 14.

[0005] However, due to the limited volume of the pressure-suppressing water tank, the existing pressure-suppressing water tank has insufficient steam condensation effect, resulting in the gas mixture entering the pressure-suppressing water tank's gas space still containing a lot of steam and having a high steam partial pressure. A larger gas space and water space are required to achieve the desired pressure suppression effect. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-stage pressure-suppressing water tank and method to overcome the above-mentioned defects in the prior art.

[0007] This invention is achieved through the following technical solution:

[0008] A multi-stage pressure-suppressing water tank is disposed inside a containment vessel and includes a first-stage pressure-suppressing water tank to an Nth-stage pressure-suppressing water tank. The water space of the first-stage pressure-suppressing water tank is connected to the internal space of the containment vessel through a first-stage pressure-suppressing pipe. The water space of the Nth-stage pressure-suppressing water tank is connected to the air space of the (N-1)th-stage pressure-suppressing water tank through an intermediate pressure-suppressing pipe, wherein N≥2 and is an integer.

[0009] Optionally, the first-stage pressure suppression pipe includes a first vertical pipe and a first horizontal pipe closed at both ends. The first horizontal pipe is located in the water space of the first-stage pressure suppression water tank and its surface is provided with several vent holes. One end of the first vertical pipe is connected to the internal space of the containment vessel, and the other end of the first vertical pipe is connected to the middle of the first horizontal pipe.

[0010] Optionally, the primary pressure suppression pipe includes a first vertical pipe, a first horizontal pipe closed at both ends, and several second vertical pipes. The first horizontal pipe is located in the air space of the first-stage pressure suppression water tank. One end of the second vertical pipe is connected to the first horizontal pipe, and the other end of the second vertical pipe is connected to the water space of the first-stage pressure suppression water tank. One end of the first vertical pipe is connected to the internal space of the containment vessel, and the other end of the first vertical pipe is connected to the middle of the first horizontal pipe.

[0011] Optionally, the portion of the first vertical tube located inside the containment space is provided with a plurality of first air inlets along the height direction.

[0012] Optionally, the primary pressure suppression pipe includes several third vertical pipes arranged in parallel, one end of which is connected to the water space of the primary pressure suppression water tank, and the other end of which is connected to the internal space of the containment vessel.

[0013] Optionally, the height of the end of each of the third vertical tubes that connects to the interior space of the containment is different.

[0014] Optionally, each of the third vertical tubes has a plurality of second air inlets along its height in the portion located inside the containment space.

[0015] Optionally, the intermediate pressure-suppressing pipe includes a connecting pipe and a second horizontal pipe closed at both ends. The second horizontal pipe is located in the water space of the Nth-stage pressure-suppressing water tank and has several vent holes on its surface. One end of the connecting pipe is connected to the second horizontal pipe, and the other end of the connecting pipe is connected to the air space of the N-1th-stage pressure-suppressing water tank.

[0016] Optionally, the first-stage pressure-suppressing water tank to the Nth-stage pressure-suppressing water tank are all inherent water tanks within the containment.

[0017] The present invention also provides a pressure suppression method, which uses a multi-stage pressure suppression tank as described in any of the above-mentioned methods. When a containment mass release accident occurs, the containment temperature and pressure rise. Driven by the pressure difference, a mixture of water vapor and air enters the water space of the first-stage pressure suppression tank through a first-stage pressure suppression pipe. Some of the water vapor in the mixture will condense in the water space of the first-stage pressure suppression tank. The uncondensed water vapor and non-condensable air rise to the air space of the first-stage pressure suppression tank under the action of buoyancy, and then enter each stage of the pressure suppression tank for multiple condensations.

[0018] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0019] 1. In this invention, by setting up the first-stage to the Nth-stage pressure-suppressing water tanks working together, when a containment energy release accident occurs, the containment temperature and pressure rise. Driven by the pressure difference, the mixture of water vapor and air enters the water space of the first-stage pressure-suppressing water tank through the first-stage pressure-suppressing pipe. Some of the water vapor in the mixture will condense in the water space of the first-stage pressure-suppressing water tank. The uncondensed water vapor and non-condensable air rise to the air space of the first-stage pressure-suppressing water tank under the action of buoyancy, and then enter each stage of pressure-suppressing water tank for multiple condensations. The water vapor is gradually and completely condensed, that is, the water vapor entering the pressure-suppressing water tank is fully condensed, which improves the condensation efficiency and enhances the pressure-suppressing capacity of the pressure-suppressing water tank. Moreover, since the water vapor is fully condensed, the volume of the pressure-suppressing water tank can be significantly reduced.

[0020] 2. In this invention, the first-stage pressure-suppressing pipe can be designed as a first vertical pipe plus a first horizontal pipe. The first horizontal pipe is located in the water space of the first-stage pressure-suppressing water tank and its surface is provided with several vent holes to form a bubbler structure. On the one hand, it divides water vapor into several small vent holes and sprays them out, forming several small bubbles that come into contact with the water in the first-stage pressure-suppressing water tank, increasing the contact area and improving the condensation efficiency. On the other hand, it can disperse water vapor to different areas in the water, improving the condensation effect.

[0021] 3. In this invention, the first-stage pressure suppression pipe can be designed as a first vertical pipe plus a first horizontal pipe. The portion of the first vertical pipe located inside the containment space is provided with several first air inlets along the height direction. Since the density of water vapor in the mixed gas is greater than that of air under the same conditions, the several first air inlets along the height direction, compared with air inlets set at a fixed height, allow water vapor to enter the first-stage pressure suppression pipe at the first time, thereby enabling the water vapor to be condensed by the first-stage pressure suppression water tank at the first time, which helps to improve the condensation efficiency.

[0022] 4. Those skilled in the art should understand that, for operational needs, some inherent water tanks are provided inside the containment, typically including but not limited to primary shielding water tanks, secondary shielding water tanks, reactor cavity injection water tanks, and safety injection water tanks. In this invention, the first-stage pressure suppression water tank to the Nth-stage pressure suppression water tank are all inherent water tanks inside the containment, achieving design simplification and functional integration, thereby reducing the design burden. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a pressure-suppressing water tank in the prior art;

[0024] Figure 2 This is a schematic diagram of the structure of a multi-stage pressure-suppressing water tank provided in Example 1;

[0025] Figure 3 This is a schematic diagram of the structure of a multi-stage pressure-suppressing water tank provided in Example 2;

[0026] Figure 4 This is a schematic diagram of the structure of a multi-stage pressure-suppressing water tank provided in Example 3;

[0027] Figure 5 This is a schematic diagram of the structure of a multi-stage pressure-suppressing water tank provided in Example 4;

[0028] Figure 6 This is a schematic diagram of the structure of a multi-stage pressure-suppressing water tank provided in Example 5;

[0029] Figure 7 This is a schematic diagram of the structure of a multi-stage pressure-suppressing water tank provided in Example 6;

[0030] Reference numerals: 1-First-stage pressure-suppressing water tank, 2-Second-stage pressure-suppressing water tank, 3-Third-stage pressure-suppressing water tank, 4-First-stage pressure-suppressing pipe, 401-First vertical pipe, 402-First horizontal pipe, 403-Second vertical pipe, 404-Third vertical pipe, 5-Intermediate pressure-suppressing pipe, 501-Connecting pipe, 502-Second horizontal pipe, 6-Gas space, 7-Water space, 8-Pressure vessel, 9-Main pump, 10-Steam generator, 11-Pressure stabilizer, 12-Coolant pipeline, 13-Break, 14-Containment vessel, 15-Pressure-suppressing water tank. Detailed Implementation

[0031] Example 1

[0032] refer to Figure 2A multi-stage pressure-suppressing water tank is disposed inside the containment vessel 14, comprising a first-stage pressure-suppressing water tank 1 to an Nth-stage pressure-suppressing water tank. The water space 7 of the first-stage pressure-suppressing water tank 1 is connected to the internal space of the containment vessel 14 via a first-stage pressure-suppressing pipe 4. The water space 7 of the Nth-stage pressure-suppressing water tank is connected to the air space 6 of the (N-1)th-stage pressure-suppressing water tank via an intermediate pressure-suppressing pipe 5, wherein N ≥ 2 and is an integer. As an example, in this embodiment, N = 3 (it should be understood that in other embodiments, N can of course be 2, or other integers greater than 3), that is, there are a total of three pressure-suppressing water tanks, namely the first-stage pressure-suppressing water tank 1, the second-stage pressure-suppressing water tank 2, and the third-stage pressure-suppressing water tank 3. The water space 7 of the second-stage pressure-suppressing water tank 2 is connected to the air space 6 of the first-stage pressure-suppressing water tank 1 via an intermediate pressure-suppressing pipe 5, and the water space 7 of the third-stage pressure-suppressing water tank 3 is connected to the air space 6 of the second-stage pressure-suppressing water tank 2 via an intermediate pressure-suppressing pipe 5.

[0033] Through the combined action of the first-stage pressure-suppressing tank 1 to the third-stage pressure-suppressing tank 3, when a mass-energy release accident occurs in containment 14, the temperature and pressure of containment 14 rise. Driven by the pressure difference, the mixture of water vapor and air enters the water space 7 of the first-stage pressure-suppressing tank 1 through the first-stage pressure-suppressing pipe 4. Some of the water vapor in the mixture will condense in the water space 7 of the first-stage pressure-suppressing tank 1. The uncondensed water vapor and non-condensable air rise to the air space 6 of the first-stage pressure-suppressing tank 1 under the action of buoyancy, and then enter the second-stage pressure-suppressing tank 2 and the third-stage pressure-suppressing tank 3 in sequence for condensation. The water vapor is gradually and completely condensed, that is, the water vapor entering the pressure-suppressing tank is fully condensed, which improves the condensation efficiency and enhances the pressure-suppressing capacity of the pressure-suppressing tank. Moreover, since the water vapor is fully condensed, the volume of the pressure-suppressing tank can be significantly reduced.

[0034] In this embodiment, the first-stage pressure-suppressing pipe 4 includes a first vertical pipe 401 and a first horizontal pipe 402 closed at both ends. One end of the first vertical pipe 401 is connected to the internal space of the containment vessel 14, and the other end of the first vertical pipe 401 is connected to the middle of the first horizontal pipe 402. The first horizontal pipe 402 is located in the water space 7 of the first-stage pressure-suppressing water tank 1 and its surface is provided with several vent holes. The "surface" includes the side wall and the two end faces of the first horizontal pipe 402. In practical applications, vent holes can be provided only on the side wall of the first horizontal pipe 402, or vent holes can be provided on both the side wall and the two end faces. It is worth noting that the first horizontal pipe 402 vents air through several vent holes on its surface, forming a bubbler structure. On the one hand, it divides water vapor into several small vent holes and sprays them out, forming several small bubbles that come into contact with the water in the first-stage pressure-suppressing water tank 1, increasing the contact area and improving the condensation efficiency. On the other hand, it can disperse water vapor to different areas in the water, improving the condensation effect.

[0035] In this embodiment, the intermediate pressure-suppressing pipe 5 includes a connecting pipe 501 and a second horizontal pipe 502 closed at both ends. The second horizontal pipe 502 is located within the water space 7 of the Nth-stage pressure-suppressing water tank. The surface of the second horizontal pipe 502 is provided with several vent holes. One end of the connecting pipe 501 connects to the second horizontal pipe 502, and the other end of the connecting pipe 501 connects to the air space 6 of the (N-1)th-stage pressure-suppressing water tank. Taking the intermediate pressure-suppressing pipe 5 between the second-stage pressure-suppressing water tank 2 and the first-stage pressure-suppressing water tank 1 as an example, the second horizontal pipe 502 is located within the water space 7 of the second-stage pressure-suppressing water tank 2, and the other end of the connecting pipe 501 connects to the air space 6 of the first-stage pressure-suppressing water tank 1. It is easy to understand that the second horizontal pipe 502 vents air through its surface through several vent holes, thus forming a bubbler structure and achieving the aforementioned function.

[0036] Those skilled in the art should understand that, for operational needs, the containment 14 is provided with some inherent water tanks (not shown in the figure), which typically include, but are not limited to, primary shielding water tanks, secondary shielding water tanks, reactor cavity injection water tanks, and safety injection water tanks. In this invention, the first-stage pressure suppression water tank 1 to the Nth-stage pressure suppression water tank (specifically, in this embodiment, the first-stage pressure suppression water tank 1, the second-stage pressure suppression water tank 2, and the third-stage pressure suppression water tank 3) all adopt the inherent water tanks within the containment 14, thereby simplifying the design and integrating functions, thus reducing the design burden.

[0037] Example 2

[0038] refer to Figure 3 The difference between this embodiment and Embodiment 1 lies in the structure of the primary pressure-suppressing pipe 4. Specifically, in this embodiment, the primary pressure-suppressing pipe 4 includes a first vertical pipe 401, a first horizontal pipe 402 closed at both ends, and several second vertical pipes 403. The first horizontal pipe 402 is located in the air space 6 of the first-stage pressure-suppressing water tank 1. One end of the second vertical pipe 403 is connected to the first horizontal pipe 402, and the other end of the second vertical pipe 403 is connected to the water space 7 of the first-stage pressure-suppressing water tank 1. One end of the first vertical pipe 401 is connected to the internal space of the containment vessel 14, and the other end of the first vertical pipe 401 is connected to the middle of the first horizontal pipe 402. It is worth noting that in this embodiment, the primary pressure-suppressing pipe 4 vents air into the water of the first-stage pressure-suppressing water tank 1 through several second vertical pipes 403, which can also constitute the bubbler structure mentioned in Embodiment 1 and achieve the same effect.

[0039] Example 3

[0040] refer to Figure 4This embodiment further optimizes upon embodiment 1. Specifically, in this embodiment, the portion of the first vertical pipe 401 located within the containment vessel 14 has several first air inlets along its height. It is easy to understand that the top of the first vertical pipe 401 can be closed or open (or have a hole) to serve as a first air inlet. It is worth noting that, under the same conditions, the density of water vapor in the gas mixture is greater than that of air. Compared to a first air inlet set at a fixed height, having several first air inlets along its height allows water vapor to enter the first-stage pressure-reducing pipe 4 more quickly, thus enabling the water vapor to be condensed by the first-stage pressure-reducing water tank 1 more quickly, which helps improve condensation efficiency.

[0041] It is easy to understand that in other embodiments, based on embodiment 2, a plurality of first air inlets can be provided along the height direction in the portion of the first vertical tube 401 located in the internal space of the containment 14.

[0042] Example 4

[0043] refer to Figure 5 The difference between this embodiment and Embodiment 1 lies in the structure of the primary pressure-suppressing pipe 4. Furthermore, the structure of the primary pressure-suppressing pipe 4 in this embodiment differs from that provided in Embodiment 2. Specifically, in this embodiment, the primary pressure-suppressing pipe 4 includes several parallelly arranged third vertical pipes 404. One end of each third vertical pipe 404 connects to the water space 7 of the first-stage pressure-suppressing water tank 1, and the other end connects to the internal space of the containment vessel 14. This embodiment uses several third vertical pipes 404 to disperse water vapor to different areas of the first-stage pressure-suppressing water tank 1, thereby improving the condensation effect.

[0044] Example 5

[0045] refer to Figure 6 This embodiment is a further optimization based on embodiment 4. Specifically, in this embodiment, the height of the end of each third vertical pipe 404 that connects to the internal space of the containment shell 14 is different. In this way, water vapor has an inlet point at different heights, just like in embodiment 2. This makes full use of the fact that the density of water vapor in the mixed gas is greater than that of air under the same conditions. Compared with setting the inlet point at a fixed height, water vapor can enter the first-stage pressure suppression pipe 4 at the first time, so that the water vapor can be condensed by the first-stage pressure suppression water tank 1 at the first time, which helps to improve the condensation efficiency.

[0046] Example 6

[0047] refer to Figure 7This embodiment is also a further optimization based on embodiment 4. Specifically, in this embodiment, each third vertical pipe 404 located within the internal space of the containment vessel 14 has several second air inlets along its height. Similarly, with the same effect as embodiment 5, by fully utilizing the characteristic that the density of water vapor in the mixed gas is greater than that of air under the same conditions, compared with setting the air inlet at a fixed height, water vapor can enter the first-stage pressure-reducing pipe 4 immediately, thereby allowing the water vapor to be condensed by the first-stage pressure-reducing water tank 1 immediately, which helps to improve condensation efficiency. In addition, this embodiment allows water vapor to have more air inlets, making it easier for all water vapor to enter the first-stage pressure-reducing water tank 1 in a shorter time, thus improving efficiency.

[0048] Example 7

[0049] This embodiment provides a pressure suppression method using the multi-stage pressure suppression tank provided in Embodiment 1 (of course, any other multi-stage pressure suppression tank provided in any embodiment can also be used). The method is as follows: When a mass energy release accident occurs in containment 14, the temperature and pressure of containment 14 rise. Driven by the pressure difference, the mixture of water vapor and air enters the water space 7 of the first-stage pressure suppression tank 1 through the first-stage pressure suppression pipe 4. Some of the water vapor in the mixture will condense in the water space 7 of the first-stage pressure suppression tank. The uncondensed water vapor and non-condensable air rise to the air space 6 of the first-stage pressure suppression tank 1 under the action of buoyancy, and then enter each stage of pressure suppression tank for multiple condensations.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-stage pressure-suppressing water tank, disposed inside the containment vessel, characterized in that, It includes a first-stage pressure-suppressing water tank to an Nth-stage pressure-suppressing water tank. The water space of the first-stage pressure-suppressing water tank is connected to the internal space of the containment through a first-stage pressure-suppressing pipe. The water space of the Nth-stage pressure-suppressing water tank is connected to the air space of the (N-1)th-stage pressure-suppressing water tank through an intermediate pressure-suppressing pipe. N ≥ 2 and is an integer. The structure of the primary pressure suppressor tube adopts Scheme 1, Scheme 2, or Scheme 3; Option 1: The first-stage pressure suppression pipe includes a first vertical pipe and a first horizontal pipe closed at both ends. The first horizontal pipe is located in the water space of the first-stage pressure suppression water tank and its surface is provided with several vent holes. One end of the first vertical pipe is connected to the internal space of the containment vessel, and the other end of the first vertical pipe is connected to the middle of the first horizontal pipe. The portion of the first vertical pipe located in the internal space of the containment vessel is provided with several first air inlets along the height direction. Option 2: The primary pressure suppression pipe includes a first vertical pipe, a first horizontal pipe closed at both ends, and several second vertical pipes. The first horizontal pipe is located in the air space of the first-stage pressure suppression water tank. One end of the second vertical pipe is connected to the first horizontal pipe, and the other end of the second vertical pipe is connected to the water space of the first-stage pressure suppression water tank. One end of the first vertical pipe is connected to the internal space of the containment vessel, and the other end of the first vertical pipe is connected to the middle of the first horizontal pipe. The portion of the first vertical pipe located in the internal space of the containment vessel is provided with several first air inlets along the height direction. Option 3: The primary pressure suppression pipe includes several third vertical pipes arranged in parallel. One end of the third vertical pipe is connected to the water space of the primary pressure suppression water tank, and the other end of the third vertical pipe is connected to the internal space of the containment vessel. The height of the end of each third vertical pipe connected to the internal space of the containment vessel is different, or the portion of each third vertical pipe located in the internal space of the containment vessel is provided with several second air inlets along the height direction.

2. The multi-stage pressure-suppressing water tank according to claim 1, characterized in that, The intermediate pressure-suppressing pipe includes a connecting pipe and a second horizontal pipe closed at both ends. The second horizontal pipe is located in the water space of the Nth-stage pressure-suppressing water tank and has several vent holes on its surface. One end of the connecting pipe is connected to the second horizontal pipe, and the other end of the connecting pipe is connected to the air space of the N-1th-stage pressure-suppressing water tank.

3. The multi-stage pressure-suppressing water tank according to claim 1, characterized in that, All of the first-stage pressure-suppressing water tanks to the Nth-stage pressure-suppressing water tanks are inherent water tanks within the containment vessel.

4. A pressure suppression method, employing the multi-stage pressure suppression water tank as described in any one of claims 1-3, characterized in that, When a containment energy release accident occurs, the containment temperature and pressure rise. Driven by the pressure difference, a mixture of water vapor and air enters the water space of the first-stage pressure relief tank through the first-stage pressure relief pipe. Some of the water vapor in the mixture will condense in the water space of the first-stage pressure relief tank. The uncondensed water vapor and non-condensable air rise to the air space of the first-stage pressure relief tank under the action of buoyancy, and then enter each stage of pressure relief tank for multiple condensations.

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