Novel safety injection box
By designing the nitrogen tank and water tank of the injection box separately and controlling them through isolation valves, the problems of inflexible injection timing, unadjustable flow, leakage and high operation and maintenance costs of traditional injection boxes are solved, achieving flexible control and reducing operation and maintenance costs. It is suitable for special-purpose nuclear power plants.
Patent Information
- Application Number
- CN202422627480.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-30
- Publication Date
- 2025-10-14
- Estimated Expiration
- 2034-10-30
AI Technical Summary
Traditional injection boxes have inflexible injection timing in large break loss of coolant accidents, unadjustable injection flow rates, leakage problems, high operation and maintenance costs, and inflexible layout, making it difficult to meet the needs of special-purpose nuclear power plants.
Design independent injection boxes, nitrogen tanks and water tanks, and control the connection between nitrogen and water through isolation valves to achieve flexible injection timing and flow adjustment, avoid leakage, reduce operation and maintenance costs, and allow flexible layout.
It realizes flexible control of injection timing and flow rate of the injection box, reduces operation and maintenance costs, and is suitable for nuclear power plants for special purposes.
Smart Images
Figure CN223436341U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of pressurized water reactor nuclear reactor devices, in particular to a novel injection box. Background Art
[0002] After a primary circuit LOCA occurs in a pressurized water reactor nuclear power plant, different rupture sizes will result in different injection flow requirements. After a large rupture LOCA (Loss of Coolant Accident), the development of the accident can generally be divided into four stages:
[0003] (1) Spraying stage
[0004] After the accident, the high-temperature and high-pressure coolant of the primary circuit system was sprayed into the containment through the rupture. The spraying process was accompanied by system pressure reduction and coolant pressure relief flash. When the spraying was completed, almost all the primary circuit coolant was sprayed into the containment, and after the spraying was completed, the primary circuit system pressure was balanced with the containment.
[0005] (2) Re-irrigation stage
[0006] During the refilling phase, the injection tank is already operational, and cooling water from the tank is injected into the pressure vessel at a high flow rate under nitrogen pressure. The cold water initially fills the lower head and lower chamber of the pressure vessel. As the flow rate continues, the refilling phase ends when the descending section is partially filled with water. During this phase, the core is in an adiabatic heating state.
[0007] (3) Reflooding stage
[0008] When the injection water reaches the lower edge of the core active section, reflooding begins. As the injection water is injected, the core water level gradually rises, and the quenching front continues to advance toward the core outlet, gradually cooling the core. The reflooding process ends when the core is completely quenched.
[0009] (4) Late stage of reflooding
[0010] The period from the end of flooding to the long-term cooling stage is collectively referred to as the late re-flooding stage. In this stage, it is necessary to remove the heat from the core and ensure the core water level, thereby ensuring that the core temperature does not rise any more and the core is in a safe state.
[0011] The ACCumulator is designed to handle large-break LOCAs. During a large-break LOCA, after the primary system is depressurized during the blowdown phase, the ACCumulator's check valve opens and injection begins. During the blowdown phase, core pressure remains relatively high, so most of the flow bypasses the rupture through the pressure vessel's downdraft and enters the containment. During the refill phase, the ACCumulator provides a high-flow injection rate, rapidly filling the pressure vessel's lower head, lower chamber, and downdraft. This shortens the core's adiabatic warming time and ensures that the core fuel rod cladding temperature remains within specified limits. During the reflooding phase, the ACCumulator's injection flow rate must meet both core flooding requirements and heat transfer requirements during the flooding process. In summary, in a large-break LOCA, the ACCumulator primarily provides injection flow during the post-accident refilling and reflooding phases. Utility Model Content
[0012] The utility model provides a new type of safety injection box, which includes a safety injection box nitrogen tank and a safety injection box water tank that are independently arranged; one end of the safety injection box water tank is connected to the safety injection box nitrogen tank via a gas-water tank connecting pipeline; the other end of the safety injection box water tank is connected to the safety injection box injection pipeline and is connected to the reactor coolant system;
[0013] The box bodies of the safety injection tank water tank and the safety injection tank nitrogen tank are different in size, and the box body of the safety injection tank water tank is larger than the box body of the safety injection tank nitrogen tank.
[0014] Optionally, a normally closed isolation valve for the gas-water tank connecting pipe is provided on the gas-water tank connecting pipeline.
[0015] Optionally, a check valve for connecting a gas-water tank connection pipe is further provided on the gas-water tank connection pipeline, which is located between the nitrogen tank of the injection box and the normally closed isolation valve of the gas-water tank connection pipe.
[0016] Optionally, a normally closed isolation valve of the safety injection tank injection pipeline is provided on the safety injection tank injection pipeline.
[0017] Optionally, a safety injection tank injection pipeline check valve is further provided on the safety injection tank injection pipeline, and is located between the normally closed isolation valve of the safety injection tank injection pipeline and the reactor coolant system.
[0018] Optionally, the shape of the injection nitrogen box is spherical, or cylindrical with upper and lower hemispheres.
[0019] Optionally, the shape of the injection tank is spherical, or cylindrical with upper and lower hemispheres.
[0020] Optionally, the safety injection box nitrogen tank and the safety injection box water tank are centrally arranged or dispersedly arranged.
[0021] Optionally, a damper is provided in the water tank of the injection tank.
[0022] The novel safety injection tank separates nitrogen and water in the traditional safety injection tank, designs two different size tank bodies, and has the following advantages.
[0023] (1) The injection timing of the safety injection tank is more flexible. The injection pipeline of the traditional safety injection tank is isolated by a check valve, so the safety injection tank can only be injected when the system pressure is reduced below the safety injection tank pressure; the water tank and the gas tank in the safety injection tank in the utility model are separated and isolated by an isolation valve, and the isolation valve needs to be driven by a signal, so any set value can be set according to the needs, and the injection timing of the safety injection tank is more flexible.
[0024] (2) The safety injection tank is easy to operate, and the injection flow of the safety injection tank is adjustable. The traditional safety injection tank is affected by the downstream pressure when injecting, and when the safety injection tank pressure and the downstream pressure difference are large, the safety injection tank is injected at a high flow rate. The safety injection tank in the utility model can control the injection rate of nitrogen in the gas tank into the water tank by adjusting the opening of the isolation valve, thereby controlling the injection flow. Therefore, the injection flow can be adjusted by the valve, and the adjustability of the safety injection tank injection is realized. For example, in the event of a loss of water accident, according to the progress of the accident and the change of the reactor coolant system pressure, the adjusting valve is set at different openings, so that the injection flow can meet the needs of safety injection, and the waste of safety injection flow caused by excessive injection can be avoided, thereby providing a longer time window for low-pressure safety injection.
[0025] (3) Reducing operation and maintenance costs. The traditional safety injection tank is isolated from the reactor coolant system by two check valves, and since the check valve has an unavoidable leakage property, the coolant in the primary loop will continuously enter the safety injection tank, so the safety injection tank water needs to be discharged regularly to ensure that its pressure is within the required range. The safety injection tank in the utility model can be isolated by an isolation valve, so there is no leakage problem, and regular water replacement and inspection operations are not required, thereby reducing operation and maintenance costs. On the other hand, the water tank of the safety injection tank in the utility model can be completely isolated from the primary loop and isolated from the gas tank, so it can be in a normal pressure state during normal operation, which greatly facilitates daily maintenance.
[0026] (4) The safety injection tank in the utility model is more flexible in design and arrangement. In the traditional safety injection tank, nitrogen and water are in the same tank body, so the nitrogen and water pressures are basically the same. The safety injection tank in the utility model separates the gas and water, and the design pressure of the water tank can be smaller. Due to the compressibility of the gas, the nitrogen pressure can be higher, and the nitrogen tank volume can be smaller. On the other hand, the gas tank and the water tank are connected by a pipeline, so they can be arranged separately and more flexibly.
[0027] (5) The safety injection tank in the utility model can be used in special nuclear power devices due to its more flexible and compact arrangement, normal operation of the water tank in a normal pressure state, and safety injection tank injection flow.
[0028] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:
[0030] Figure 1 This is a schematic diagram of the injection box structure according to one embodiment;
[0031] Figure 2 A schematic structural diagram of an injection box according to another embodiment;
[0032] Figure 3a for Figure 1 The schematic diagram of the injection curve of the injection box is shown;
[0033] Figure 3b for Figure 2 The schematic diagram of the injection curve of the injection box is shown;
[0034] Figure 4 This is a schematic structural diagram of a new injection box according to an embodiment of the present utility model;
[0035] Figure 1 Middle: 1a-nitrogen in the injection tank; 2a-water in the injection tank; 3a-injection pipe in the injection tank; 4a-normally open isolation valve of the injection tank pipeline; 5a-check valve of the injection tank pipeline.
[0036] Figure 2 Middle: 1b-nitrogen for injection tank; 2b-water for injection tank; 3b-large pipe / riser; 4b-damper; 5b-small pipe; 6b-injection pipe for injection tank; 7b-normally open isolation valve for injection tank pipeline; 8b-check valve for injection tank pipeline;
[0037] Figure 4 Middle: 1- nitrogen tank in the injection box; 2- water tank in the injection box; 3- injection pipe in the injection box; 4- normally closed isolation valve of the injection pipeline in the injection box; 5- check valve of the injection pipeline in the injection box; 6- check valve of the gas-water tank connecting pipe; 7- normally closed isolation valve of the gas-water tank connecting pipe; 8- gas-water tank connecting pipeline. DETAILED DESCRIPTION
[0038] In the description of the utility model, it is understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and therefore cannot be understood as limiting the utility model. The device or element indicated or implied must have a particular orientation, a particular orientation and operation, and therefore cannot be understood as limiting the utility model.
[0039] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the utility model, the meaning of "multiple" is two or more, unless otherwise specifically limited.
[0040] In the utility model, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific situation.
[0041] The preferred embodiments of the utility model are described below in conjunction with the drawings, and it should be understood that the preferred embodiments described herein are only for describing and explaining the utility model, and are not intended to limit the utility model.
[0042] The structure of the conventional injection box is shown in Figure 1 The injection box body, the injection pipeline, the isolation valve and the check valve. The shape of the injection box body is generally a semispherical upper and lower body with a cylindrical middle part according to the arrangement inside the safety shell and the pressure bearing capacity, or a spherical body structure; the body is composed of water and nitrogen, and the ratio of nitrogen to water is about 1:3~1:4. The injection pipeline of the injection box connects the injection box and the injection point of the primary loop system, and two check valves and an always-open isolation valve are arranged on the injection pipeline of the injection box. In normal operation, the injection box is isolated from the primary loop system through the two check valves. After the accident, when the pressure of the primary loop system is lower than that of the injection box, the check valve of the injection box is opened, and the injection of the injection box begins. At present, the conventional injection box is widely used in nuclear power plants in China.
[0043] There is also an application of advanced accumulator in the design of dedicated safety system of nuclear power plant. The structure of advanced accumulator is shown in Figure 2 The structure of advanced accumulator is basically the same as that of traditional accumulator, and the only difference is that there is a flow resistance device in the water injection port of advanced accumulator. The main function of the damper is to automatically adjust the flow rate according to the water level of the accumulator, so as to match the flow rate requirement after a large break loss of coolant accident. The injection flow rate curves of traditional accumulator and advanced accumulator are shown in Fig. 3. Compared with the traditional accumulator, the advanced accumulator can provide injection flow rate matching the injection flow rate requirement according to the design of the reactor, so as to reduce the bypass waste of flow rate, and thus the volume of the accumulator can be reduced.
[0044] The embodiment of the utility model provides a novel accumulator, which separates the water volume and the gas volume of the accumulator, and connects them through a pipeline and a valve. The design scheme of the novel accumulator provided by the embodiment of the utility model can be applied to the design of a nuclear power plant or other nuclear power devices.
[0045] As shown in Figure 4 The novel accumulator of the embodiment of the utility model comprises an accumulator nitrogen tank 1 and an accumulator water tank 2 which are independently arranged; one end of the accumulator water tank 2 is connected with the accumulator nitrogen tank 1 through a gas-water tank connecting pipeline 8; the other end of the accumulator water tank 2 is connected with an accumulator injection pipeline 3 and a reactor coolant system; the size of the accumulator nitrogen tank 1 of the accumulator water tank 2 is different, and the size of the accumulator water tank 2 is greater than that of the accumulator nitrogen tank 1. The shapes of the accumulator nitrogen tank 1 and the accumulator water tank 2 are spherical or cylindrical, and the shapes of the accumulator nitrogen tank 1 and the accumulator water tank 2 can be the same or different. The accumulator nitrogen tank 1 and the accumulator water tank 2 are arranged in a centralized manner or a decentralized manner. The decentralized arrangement means that the accumulator nitrogen tank 1 and the accumulator water tank 2 can be arranged at different positions, and the actual situation needs to be determined.
[0046] The gas-water tank connecting pipeline 8 is provided with a gas-water tank connecting pipeline normally closed isolation valve 7, which is controlled by the reactor coolant system. The isolation valve 7 is in a normally closed state in normal operation, and is opened only after receiving a signal from the protection system after an accident occurs. The gas-water tank connecting pipeline 8 is also provided with a gas-water tank connecting pipeline check valve 6, which is located between the accumulator nitrogen tank 1 and the gas-water tank connecting pipeline normally closed isolation valve 7. The function of the check valve 6 is to prevent reverse flow, that is, to prevent the water in the water tank 2 from flowing into the gas tank 1 in the reverse direction after the isolation valve 7 is opened after an accident occurs.
[0047] Continuing to refer to Figure 4The injection line 3 is equipped with a normally closed isolation valve 4. A check valve 5 is also installed on the injection line 3, located between the normally closed isolation valve 4 and the reactor coolant system. The check valve 5 prevents the primary coolant from flowing back into the water tank 2. The isolation valve 4 isolates the injection line from the reactor's primary system during normal operation.
[0048] like Figure 4 As shown, during normal reactor operation, the normally closed isolation valve 4 and check valve 5 on the injection line 3 are closed. The check valve 6 and normally closed isolation valve 7 on the gas-water tank connecting pipe between the injection nitrogen tank 1 and the injection water tank 2 are also closed. After a LOCA accident, the reactor coolant system pressure decreases. When the system pressure drops to the set injection pressure, the normally closed isolation valve 4 and check valve 5 on the injection line 3, as well as the check valve 6 and normally closed isolation valve 7 on the gas-water tank connecting pipe 8, open in sequence. Driven by the pressure of the gaseous nitrogen, the water in the water tanks is injected into the core.
[0049] Alternatively, the injection tank in this embodiment can be a traditional injection tank without a damper, or an advanced injection tank with a damper. Figure 4 The form shown is not provided with a damper, and a damper may also be provided in the injection tank water tank, which is not limited in this embodiment.
[0050] The new safety injection tank in this embodiment requires a trigger signal, which is automatically triggered by the reactor protection system. No operator intervention is required; the only signal required is the reactor coolant system pressure signal. The specific operational process is as follows: After a LOCA accident, as coolant leaks through the breach, the reactor coolant system pressure decreases. When the system pressure drops to the safety injection tank injection pressure setting, the protection system receives the system pressure signal and issues a start command to the safety injection tank. The valves on the safety injection tank injection line and the gas and liquid tank connecting lines open in response to the signal. Driven by the nitrogen pressure in the gas tank, water from the safety injection tank is injected into the core, ensuring the core is flooded and its safety is guaranteed.
[0051] The design of this new safety injection tank utilizes the concept of separating nitrogen and water, employing two tanks of different sizes. The larger tank is filled with water, known as the water tank; the smaller tank is filled with nitrogen, known as the gas tank. The two tanks are connected by pipelines and valves. During normal operation, the valves on the connecting pipelines are closed, and the gas tank is subject to nitrogen pressure, while the water tank is not. After an accident, the valves on the gas-water tank pipeline are opened, and the nitrogen in the gas tank is used to inject water from the water tank into the core. During this process, the water tank is subjected to the same pressure as the gas tank. Since the new safety injection tank in this utility model is not subject to pressure during normal operation, it greatly facilitates operation and maintenance. Furthermore, since the gas and water tanks are separated by valves, the injection flow rate can be adjusted using regulating valves. This advantage can be applied to the nuclear power design of specialized devices.
[0052] This utility model proposes a novel safety injection tank design. Unlike traditional systems, this design separates the compressed nitrogen used for driving the system from the safety injection water used as a water source, storing them in a gas phase and a water tank, respectively. The two tanks are then connected by a pipeline, with a valve on the pipeline controlling the connection / isolation between the two tanks. During normal operation of the nuclear power plant, the isolation valve is closed, isolating the gas phase from the water tank. If the safety injection tank needs to be put into operation, such as in the event of a LOCA accident, the valve is signaled to open, connecting the water tank to the gas tank, thus ensuring effective injection of the safety injection tank.
[0053] Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if such modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention is intended to include such modifications and variations.
Claims
1. A new type of injection box, characterized in that: The injection tank comprises an injection tank nitrogen tank (1) and an injection tank water tank (2) which are independently arranged; one end of the injection tank water tank (2) is connected to the injection tank nitrogen tank (1) via a gas-water tank connecting pipeline (8); the other end of the injection tank water tank (2) is connected to the injection tank injection pipeline (3) and is connected to the reactor coolant system; The box bodies of the safety injection box water tank (2) and the safety injection box nitrogen tank (1) are different in size, and the box body of the safety injection box water tank (2) is larger than the box body of the safety injection box nitrogen tank (1).
2. The new injection box according to claim 1 is characterized in that: The gas-water tank connecting pipeline (8) is provided with a gas-water tank connecting pipe normally closed isolation valve (7).
3. The new injection box according to claim 2 is characterized in that: The gas-water tank connecting pipeline (8) is also provided with a gas-water tank connecting pipe check valve (6), which is located between the injection box nitrogen tank (1) and the gas-water tank connecting pipe normally closed isolation valve (7).
4. The new injection box according to claim 1 is characterized in that: The injection line (3) of the safety injection tank is provided with a normally closed isolation valve (4) for the injection line of the safety injection tank.
5. The new injection box according to claim 4 is characterized in that: The injection line (3) of the safety injection tank is also provided with a check valve (5) of the safety injection tank injection line, which is located between the normally closed isolation valve (4) of the safety injection tank injection line and the reactor coolant system.
6. The new injection box according to any one of claims 1 to 5, characterized in that: The shape of the injection nitrogen box (1) is spherical, or cylindrical with upper and lower hemispheres.
7. The new injection box according to any one of claims 1 to 5, characterized in that: The shape of the injection tank water tank (2) is spherical, or cylindrical with upper and lower hemispheres.
8. The new injection box according to any one of claims 1 to 5, characterized in that: The safety injection box nitrogen box (1) and the safety injection box water tank (2) are arranged in a centralized or decentralized manner.
9. The new injection box according to any one of claims 1 to 5, characterized in that: A damper is provided in the injection tank water tank (2).