Long distance liquid effluent discharge system and discharge control method for nuclear power plant

Abstract

The application provides a nuclear power plant liquid effluent long-distance discharge system and a discharge control method. The system comprises: each double-layer pipeline comprises an inner pipe, an outer pipe and a support member arranged between the inner pipe and the outer pipe to form an envelope chamber, and the outer pipe is closed by a sealing partition member at a well body to form a plurality of outer pipe cabin sections; each outer pipe cabin section is provided with a drainage member and is communicated with the envelope chamber; a liquid level detection member is arranged in a leakage monitoring container to detect the liquid level; a communication valve group comprises a communication pipeline, a switching valve and a partition valve; a leakage monitoring signal integration and processing system receives monitoring signals and liquid level signals of the double-layer pipeline, cross-verification is performed, leakage occurrence and a leakage position are confirmed, and the partition valve and the switching valve are controlled to switch the discharge pipeline. The application constructs a complete closed loop from physical containment of leakage, leakage drainage, multi-dimensional signal sensing to automatic switching of the pipeline, eliminates the environmental risk of uncontrolled diffusion of the leakage, and improves the reliability and safety of the discharge system.

Description

Technical Field

[0001] This invention relates to the field of liquid effluent discharge technology from nuclear power plants, and particularly to a long-distance discharge system and discharge control method for liquid effluent from nuclear power plants. Background Technology

[0002] The development of coastal nuclear power plant sites in my country is nearing completion, and the selection of subsequent coastal nuclear power plant sites shows a trend of extending from the coast to the inland. However, the receiving water for liquid effluents from nuclear power plants remains the ocean. Therefore, liquid effluents need to be transported to the seaside via discharge pipelines ranging from ten to tens of kilometers in length. Liquid effluents are both environmentally and publicly sensitive; leaks during long-distance transportation will directly threaten the environmental safety of soil and groundwater along the route and attract significant public attention. How to achieve reliable physical containment of liquid effluents, timely detection and location of leaks, and rapid response and handling after a leak in long-distance transportation scenarios has become the core challenge in the design of long-distance discharge of liquid effluents from nuclear power plants.

[0003] Currently, there are no mature engineering application examples for long-distance discharge of liquid effluents from nuclear power plants, and there is a lack of system design schemes that can be directly referenced.

[0004] Existing designs for long-distance liquid effluent discharge use single-walled pipes buried directly in the soil, with leak monitoring systems only installed at the beginning and end of the pipeline, and no dedicated liquid effluent protection structures. This approach has the following shortcomings: (1) It does not have the function of containment and retention. Single-walled pipes do not have an outer containment structure, and when the pipe wall ruptures, the liquid effluent directly diffuses into the surrounding environment.

[0005] (2) Lack of systematic design for leakage monitoring system. The systematic integrated design of leakage monitoring and protection design of discharge pipeline has not been realized, and the leakage monitoring equipment is difficult to achieve the monitoring accuracy required for use.

[0006] (3) Minor leaks cannot be detected. Single-walled pipes have no outer containment space or leak collection structure, so they cannot effectively monitor minor leaks below the detection limit of leak monitoring equipment.

[0007] (4) Lack of coordinated response capability. The linkage between leakage monitoring and power plant operation signals has not been realized. After leakage, the valves cannot be automatically controlled to switch pipelines, making it difficult to ensure the normal discharge of liquid effluent under leakage conditions.

[0008] (5) Insufficient long-distance monitoring accuracy. The acoustic / negative pressure wave monitoring equipment is placed only at the beginning and end of the pipeline with too large a spacing. The signal attenuation over long distances leads to a decrease in monitoring accuracy, which cannot meet the monitoring requirements of long-distance pipelines.

[0009] Existing technology also discloses a double-layer pipeline structure for discharging liquid effluent from nuclear power plants, employing a basic double-layer pipe layout with inner and outer pipes. While this structure can create a certain degree of envelope for the liquid effluent leaking from the inner pipe via the outer pipe, it is only a basic double-layer pipeline structure and does not form a systematic integrated design for leakage protection and monitoring. Specifically, it has the following shortcomings: (1) No internal pipe leakage monitoring module is set up, so the internal pipe operating status cannot be monitored, and the internal pipe leakage location cannot be located in a timely manner.

[0010] (2) No leakage monitoring module was installed, so the health status of the double-layer pipe could not be monitored in real time.

[0011] (3) When the inner and outer pipes rupture simultaneously, there is no matching leakage drainage structure, so the waste liquid cannot be diverted to the nearest leakage monitoring well.

[0012] (4) The linkage control between the leakage monitoring signal and the pipeline switching valve is not realized, and the discharge pipeline cannot be automatically switched under leakage conditions.

[0013] Therefore, the present invention provides a long-distance emission system and emission control method for liquid effluents from nuclear power plants, in order to overcome the above-mentioned technical problems. Summary of the Invention

[0014] The technical problem to be solved by the present invention is to overcome the defects of the existing technology in which the long-distance discharge of liquid effluent from nuclear power plants only uses single-wall pipes, lacks leakage containment and drainage structures, has insufficient leakage monitoring accuracy, and cannot realize automatic pipeline switching. The present invention provides a long-distance discharge system and discharge control method for liquid effluent from nuclear power plants.

[0015] The present invention solves the above-mentioned technical problems through the following technical solution: A long-distance discharge system for liquid effluent from a nuclear power plant, characterized in that it includes: Two double-layer pipelines, each of which includes an inner pipe, an outer pipe, and a support member disposed between the inner pipe and the outer pipe. An enveloping chamber is formed between the inner pipe and the outer pipe. The outer pipe is sealed and isolated at the well body by a sealing and partitioning member to form multiple outer pipe sections. A drainage component is provided in each of the outer tube sections. The drainage component is connected to the envelope chamber and configured to allow the liquid in the envelope chamber to flow into the leak monitoring container in the leak monitoring well. A liquid level detection component is disposed inside the leak monitoring container and configured to detect the liquid level inside the leak monitoring container; The connecting valve assembly includes a connecting pipeline connecting the two double-layer pipelines, a switching valve disposed on the connecting pipeline, and an isolation valve disposed on the double-layer pipeline. The leakage monitoring signal integration and processing system is configured to receive the monitoring signal of the double-layer pipeline and the liquid level signal of the liquid level detection component, perform cross-verification based on the received monitoring signal and the liquid level signal, confirm the occurrence of leakage and determine the leakage location, and control the isolation valve and the switching valve to switch the discharge pipeline based on the leakage confirmation result.

[0016] When an inner pipe leaks, the liquid effluent is trapped within the envelope chamber by the outer pipe, preventing it from spreading to the environment. The leaking liquid within the envelope chamber is guided through the drainage components of each outer pipe section to the leak monitoring container in the leak monitoring well, achieving containment, retention, and drainage of the leaked material. A liquid level detection component monitors the liquid level in the leak monitoring container, enabling even minute leaks below the detection limit of conventional monitoring equipment to be detected. The leak monitoring signal integration and processing system cross-validates the monitoring signal and the liquid level signal to reduce the false alarm rate. Upon confirmation of a leak, the system automatically controls the isolation valve and switching valve to switch the discharge pipeline, ensuring continuous and normal discharge of the liquid effluent even under leak conditions.

[0017] According to one embodiment of the present invention, the monitoring signal includes an optical fiber monitoring signal, which is obtained by monitoring an optical fiber laid along the entire outer wall of the inner tube. The optical fiber is configured to monitor the vibration or strain of the inner tube. The optical fiber laid along the entire outer wall of the inner tube can continuously monitor the vibration or strain of the inner tube in real time, promptly detect large leaks, and accurately locate the leak position.

[0018] According to one embodiment of the present invention, the sealing and isolation component is an annular sealing plate used to isolate fluid between adjacent outer pipe sections; the inner pipe remains continuously connected and is not interrupted by the segmentation of the outer pipe. Segmentation of the outer pipe forms multiple independently sealed outer pipe sections, limiting the leakage discharge range to a single section, reducing the scope of leak investigation, and facilitating segmented inspection and maintenance. The continuous connection of the inner pipe ensures the continuity of liquid outflow transportation.

[0019] According to one embodiment of the present invention, the leakage monitoring signal integration and processing system is configured to: determine a leakage flow rate less than 1% of the actual discharge flow rate of the pipeline as a leakage condition, and confirm the occurrence of leakage based on the change in the liquid level signal of the liquid level detection component. Confirming leakage based on the liquid level signal allows for the monitoring of minute leaks below the detection limit of conventional pipeline leakage monitoring equipment.

[0020] According to one embodiment of the present invention, for leaks with a leakage flow rate greater than or equal to 1% of the actual discharge flow rate of the pipeline, the location is determined by the monitoring signal; the leakage condition is located by the location of the leakage monitoring well corresponding to the outer pipe section. This classification and location strategy can simultaneously meet the needs of rapid location of large-break leaks and segmented location of minor leaks.

[0021] According to one embodiment of the present invention, the leak monitoring signal integration and processing system includes an interlock control module for generating a pipeline switching command after a leak is confirmed. The interlock control module can automatically generate a switching command after a leak is confirmed, ensuring the timeliness of the switching response.

[0022] According to one embodiment of the present invention, the support member includes a fixed bracket and a guide bracket arranged axially spaced along the inner tube; The inner side of the fixed bracket is fixedly connected to the outer wall of the inner tube, and the outer side of the fixed bracket is fixedly connected to the inner wall of the outer tube, so as to limit the relative displacement between the inner tube and the outer tube. The inner side of the guide bracket is fixedly connected to the outer wall of the inner tube, and the outer side of the guide bracket is provided with a support leg, which makes movable contact with the inner wall of the outer tube.

[0023] The fixed bracket and the guide bracket are used together to limit the relative displacement of the inner and outer tubes during operation, and to reduce frictional resistance and avoid damage to the inner wall of the outer tube during the assembly process, thereby improving the convenience of installation and construction.

[0024] According to one embodiment of the present invention, the leak monitoring container is used to collect and monitor minute leaks, and the discharge system further includes a waste liquid collection tank, which is connected to the leak monitoring container and is used to temporarily store waste liquid in the event of a large leak; The liquid level detection component is a liquid level gauge, which is installed inside the leakage monitoring container and outputs the liquid level signal through a wired transmission transmitter.

[0025] Leak monitoring containers and waste liquid collection tanks are used for tiered collection, which can handle minor leaks and large leaks respectively. A wired transmitter outputs a liquid level signal, ensuring stable and reliable signal transmission.

[0026] According to one embodiment of the present invention, the emission system further includes an acoustic or pressure wave sensor embedded inside the double-layer pipeline, the acoustic or pressure wave sensor being a two-end sensor, which is installed at both ends of each monitoring section.

[0027] Adding acoustic or pressure wave sensors in the middle of the pipeline can shorten the monitoring section length, reduce the impact of signal attenuation over long distances, and ensure monitoring accuracy over long distances.

[0028] According to one embodiment of the present invention, the isolation valve is an electric shut-off valve or an electric ball valve, and the valve position of the isolation valve is configured to be fully open or fully closed; The isolation valve is equipped with a valve position feedback device, which is connected to the leakage monitoring signal integration and processing system. This device provides feedback on the valve position status to the system, allowing it to confirm that the isolation valve has been properly activated. The valve position feedback device ensures the isolation valve is in operation, preventing pipeline switching failures due to valve jamming.

[0029] This invention also provides a method for controlling the long-distance emission of liquid effluent from nuclear power plants, characterized in that the emission control method employs the emission system described above, and the emission control method includes the following steps: S1. Obtain the fiber optic monitoring signal of the double-layer pipeline through fiber optic monitoring, obtain the acoustic or pressure wave monitoring signal through the acoustic or pressure wave sensor, and obtain the liquid level signal by detecting the liquid level in the leakage monitoring container through the liquid level detection component. S2. Cross-verify the fiber optic monitoring signal, the acoustic or pressure wave monitoring signal, and the liquid level signal to confirm that a leak has occurred and determine the location of the leak. S3. Based on the leakage confirmation result, control the isolation valve and switching valve of the communication valve group to switch the discharge pipeline.

[0030] Cross-verification of multi-source signals can reduce false alarm rates and avoid missed alarms. After confirming and locating the leak, the discharge pipeline is automatically switched to ensure uninterrupted operation of the discharge path under leak conditions.

[0031] According to one embodiment of the present invention, in step S2, a leakage flow rate less than 1% of the actual discharge flow rate of the pipeline is determined as a leakage condition, and the occurrence of leakage is confirmed based on the change in the liquid level signal of the liquid level detection component. By confirming leakage with the liquid level signal, reliable monitoring of minute leaks below the monitoring limit is achieved.

[0032] According to one embodiment of the present invention, in step S2, leaks with a leakage flow rate greater than or equal to 1% of the actual discharge flow rate of the pipeline are located using the fiber optic monitoring signal and the acoustic or pressure wave monitoring signal. Dynamic monitoring signals locate large-scale leaks, enabling rapid identification of the leak point.

[0033] According to one embodiment of the present invention, in step S3, after confirming that a leak has occurred, the following operations are performed sequentially: shutting down the plant discharge pump; closing the isolation valve located upstream of the leak point near the leak point; opening the switching valve on the connecting pipeline; opening the valve below the connecting pipeline of the other double-layer pipeline; and starting the plant discharge pump to switch the discharge pipeline to the other double-layer pipeline. This strictly timed interlocking switching operation avoids leak expansion or water hammer caused by pressurized operation, ensuring the safety of the switching process and the continuity of discharge.

[0034] According to one embodiment of the present invention, in step S2, the leak location is calculated based on the time difference between the acoustic or pressure wave monitoring signals received by the acoustic or pressure wave sensor at different locations in the pipeline. The time difference location algorithm can automatically calculate the leak location.

[0035] The positive and progressive effects of this invention are as follows: The long-distance emission system and emission control method for liquid effluents from nuclear power plants of the present invention have the following advantages: I. Construct a complete closed loop from the physical containment of leaked material, leakage drainage, multi-dimensional signal sensing to automatic pipeline switching, to eliminate the environmental risk of uncontrolled diffusion of leaked material under single-wall pipe schemes, and improve the operational reliability and environmental safety of long-distance emission systems.

[0036] Second, the outer pipe is divided into sections to form independent sealed compartments, which limits the leakage drainage range to a single compartment, reduces the physical scope of leakage investigation, and reduces the workload and downtime of pipeline investigation during maintenance and repair.

[0037] Third, the gravity-fed drainage structure does not require additional power extraction equipment, reducing the number of dynamic equipment configurations and failure points in the leakage drainage process, and lowering the operation and maintenance costs of the leakage collection process.

[0038] Fourth, the leakage detection logic based on multi-signal cross-verification can suppress false triggering caused by environmental interference of a single sensor, reduce the false alarm rate in the leakage monitoring process, and reduce unnecessary pipeline switching operations and unplanned shutdowns.

[0039] Fifth, the interlocking switching of redundant dual pipelines and connecting valve groups can maintain the continuous operation of the discharge system in the event of a leak in a single pipeline, ensuring the continuous availability of the liquid effluent discharge path of the nuclear power plant. Attached Figure Description

[0040] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features, wherein: Figure 1 This is a schematic diagram of the structure of the long-distance discharge system for liquid effluent from nuclear power plants according to the present invention.

[0041] Figure 2 This is a schematic diagram of the interconnection valve group in the long-distance discharge system for liquid effluent from nuclear power plants according to the present invention. Figure 1 .

[0042] Figure 3 This is a schematic diagram of the interconnection valve group in the long-distance discharge system for liquid effluent from nuclear power plants according to the present invention. Figure 2 .

[0043] Figure 4This is a schematic diagram of the exhaust structure in the long-distance emission system for liquid effluent from nuclear power plants according to the present invention. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0045] Embodiments of the invention will now be described in detail with reference to the accompanying drawings. It should be noted that these and subsequent drawings are merely illustrative and are not drawn to scale, and should not be construed as limiting the scope of the invention. Wherever possible, the same reference numerals will be used in all drawings to denote the same or similar parts.

[0046] Furthermore, although the terminology used in this invention is selected from commonly known and used terms, some terms mentioned in this specification may have been selected by the applicant in his or her judgment, and their detailed meanings are explained in the relevant sections of the description herein.

[0047] Furthermore, the invention should be understood not only through the actual terminology used, but also through the meaning implied by each term.

[0048] like Figures 1 to 4 As shown, the long-distance discharge system for nuclear power plant liquid effluents in this embodiment includes two double-layer pipelines, a diversion component 60, a liquid level detection component, a connecting valve assembly, and a leakage monitoring signal integration and processing system. This system is designed for scenarios involving the safe transport of nuclear power plant liquid effluents to the ocean for discharge over distances of ten to tens of kilometers, forming a systematic integrated design encompassing containment, monitoring and location, and coordinated switching.

[0049] Under normal operating conditions, non-radicalized wastewater from both the conventional island and nuclear island sides, as well as liquid effluents from the nuclear island side, are transported to a double-layered pipeline. After mixing within the double-layered pipeline, the wastewater is discharged to the target water body. Two parallel double-layered pipelines are laid, and a single pipeline can meet all the drainage needs of the nuclear power plant. Under normal operating conditions, one pipeline is operational while the other is on standby, adaptable to discharge requirements during maintenance or in the event of a sudden leak.

[0050] The connection and switching methods between the two pipelines are not limited to the connecting valve group scheme given in this embodiment. As an alternative, the connecting bridge pipe 70 and valves may not be installed between the two pipelines; they can simply be laid in parallel, with the rest of the design remaining unchanged. This scheme only reduces the feasibility of connecting the two pipelines in series, while still achieving the purpose of the present invention. Furthermore, non-discharge wastewater and liquid effluent can be mixed in the double-layer pipe before discharge, or they can be mixed before entering the double-layer pipe, or they can be left unmixed and used only for long-distance discharge of liquid effluent.

[0051] The emission system in this embodiment meets the requirements of the "Technical Guidelines for Review of Long-Distance Intake and Drainage Pipelines of Nuclear Power Plants" for long-distance emission schemes of liquid effluents, and can monitor and respond to minor leaks (leakage flow rate less than 1% of the actual discharge flow rate of the pipeline) and ordinary leaks.

[0052] Each double-layer pipeline includes an inner pipe 10, an outer pipe 20, and a supporting member 50 disposed between the inner pipe 10 and the outer pipe 20. A through-walled chamber is formed between the inner pipe 10 and the outer pipe 20. The inner pipe 10 and the outer pipe 20 of the double-layer pipeline can be made of the same material or different materials. The inner pipe 10 can be made of HDPE pipe, which has chemical corrosion resistance and is suitable for transporting liquid effluents from nuclear power plants. The outer pipe 20 can be made of carbon steel pipe, which has high structural strength and provides reliable outer mechanical protection and containment capabilities.

[0053] The gap between the inner tube 10 and the outer tube 20 can be set to 1 / 3 of the diameter of the inner tube 10. This gap size ensures that the outer tube 20 has sufficient envelope retention volume. When the inner tube 10 leaks, the leaked liquid is temporarily stored in the envelope chamber and does not diffuse into the external environment. Moreover, the size of the gap has no impact on drainage efficiency and monitoring sensitivity. The diameter and wall thickness of the inner tube 10 and the outer tube 20 can be determined according to the actual drainage flow rate and the resistance along the pipeline. Both pipelines can withstand 80 years of radiation from liquid effluents from nuclear power plants.

[0054] The support component 50 includes fixed supports and guide supports spaced apart along the axial direction of the inner tube 10. It can be prefabricated in the factory and assembled with the inner and outer tubes, eliminating the need for on-site assembly. The inner side of the fixed support is fixedly connected to the outer wall of the inner tube 10, and the outer side is fixedly connected to the inner wall of the outer tube 20, limiting the relative displacement between the inner tube 10 and the outer tube 20 during operation and preventing misalignment due to thermal expansion and contraction or media impact. The inner side of the guide support is fixedly connected to the outer wall of the inner tube 10, and the outer side is equipped with a support leg. The bottom of the support leg can be equipped with pulleys or ball bearings, which roll in contact with the inner wall of the outer tube 20 during the insertion of the inner tube 10 into the outer tube 20, reducing frictional resistance during insertion and preventing the support from scratching and damaging the inner wall of the outer tube 20.

[0055] Taking a 10km prefabricated pipe section as an example, a set of fixed supports can be installed every 12m, and a set of guide supports can be installed every 6m. The ball bearings at the bottom of the guide support legs are made of stainless steel, which not only meets the sliding requirements during installation but also withstands the humid and corrosive environment within the enclosing cavity. As an alternative, the support components 50 can also be entirely sliding supports, entirely fixed supports, or a combination of both. During pipe installation, the inner pipe 10 and the outer pipe 20 can be connected simultaneously or separately, achieving the same positioning and support.

[0056] The outer pipe 20 is sealed and isolated at well sites such as the leak monitoring well, exhaust well 82, or connecting well by sealing isolation components 21, forming multiple independent outer pipe sections. The sealing isolation component 21 is an annular sealing plate, fully welded to the inner wall of the outer pipe 20 and the outer wall of the inner pipe 10, achieving fluid isolation between adjacent outer pipe sections. Each sealed section is not interconnected, and the sealing performance can be verified through a pressure test. The inner pipe 10 remains continuously connected and is not segmented with the outer pipe 20, ensuring the continuous transport of liquid effluent.

[0057] Each independently connected section of the outer pipe 20 is defined as a modular pipe compartment, which is equipped with drainage pipes and leakage monitoring wells, as well as other relevant components within the leakage monitoring module. This design enables segmented inspection and maintenance; when a problem occurs in a certain section, it is not necessary to shut down the entire pipeline, but only the corresponding section needs to be addressed.

[0058] An exhaust branch pipe and an exhaust valve 81 can also be installed on the inner pipe 10 of the double-layer pipeline. The exhaust branch pipe is located at a local high point in the entire drainage pipeline. The exhaust valve 81 is a pressure-driven self-exhausting valve used to discharge residual gas in the pipeline before the initial mixing. The residual gas is discharged into the exhaust well 82, which is connected to the atmosphere and is not collected or treated to avoid gas blockage in the pipeline affecting the conveying efficiency.

[0059] Each outer tube section is equipped with a drainage component 60. The drainage component 60 communicates with the envelope chamber and is configured to allow the liquid in the envelope chamber to flow by gravity into the leak monitoring container 40 inside the leak monitoring well. The drainage component 60 can be made of stainless steel and welded to the outer tube section, requiring no additional power drive. Leakage trapped in the outer tube 20 flows by gravity through the drainage pipe into the leak monitoring container 40.

[0060] Even in the extreme case of simultaneous rupture of the inner and outer pipes, the leaked liquid can still flow by gravity through the drainage pipe of the corresponding outer pipe section into the nearest leak monitoring well. This not only prevents the leaked liquid from spreading to the environment and soil, but also facilitates the collection of leaked liquid samples at leak monitoring well 30 for leak cause analysis by operating personnel, and allows the leaked liquid to be drained through the supporting facilities of leak monitoring well 30.

[0061] A leak monitoring container 40 is installed inside the leak monitoring well, and a liquid level detection component is installed inside the leak monitoring container 40 to detect the liquid level. The leak monitoring container 40 is a cubic leak monitoring tank, preferably with a volume of 50L to 1m³, used to collect and monitor minute leaks. The system is also equipped with a waste liquid collection tank, connected to the leak monitoring container 40, with a volume of 0.5m³ to 2m³, used to temporarily store waste liquid in the event of a large leak, preventing the leaked liquid from overflowing and polluting the environment.

[0062] The liquid level detection component can be a level gauge, installed inside the leak monitoring tank. The measurement accuracy is no more than 2% of the range, and the range can be adjusted according to the size of the leak monitoring tank. The level gauge transmits the liquid level signal to the leak monitoring signal integration and processing system via a wired transmitter. Taking a 200L leak monitoring tank as an example, the liquid level gauge range can be set from 0 to 300mm, with a measurement accuracy of ±3mm, sensitively detecting slow rises in liquid level caused by minor leaks. In the event of a large rupture leak, the leaking liquid quickly fills the leak monitoring tank and is then diverted through an overflow port on the side of the tank to a 1m³ waste liquid collection tank for temporary storage until maintenance personnel arrive and handle the situation.

[0063] The optical fiber used to acquire fiber optic monitoring signals is laid along the entire outer wall of the inner tube 10, or it can be laid on the outer wall of the outer tube 20. The optical fiber is used to monitor the vibration or strain of the inner tube 10, rather than temperature, with a positioning accuracy of no more than 5m, enabling continuous real-time sensing of the operating status of the inner tube 10. In the event of a large leak, the optical fiber can quickly locate the leak point, compensating for the deficiency of the basic double-layer tube which can only contain the leak and cannot monitor the status of the inner tube 10 in real time.

[0064] The emission system is also equipped with acoustic or pressure wave sensors for acquiring acoustic or pressure wave monitoring signals. These sensors are embedded inside the double-layered pipeline and are two-end sensors, installed at both ends of each monitoring section. To avoid signal attenuation over long distances leading to decreased monitoring accuracy, each monitoring section is approximately 10 km long. When the total pipeline length exceeds 10 km, acoustic or pressure wave sensors are added in the middle of the pipeline along its extension direction to shorten the monitoring section length, reduce signal attenuation, and meet the monitoring needs of emission pipelines tens of kilometers long.

[0065] A support is installed between the inner pipe 10 and the outer pipe 20 of the double-layer pipeline. The inner pipe 10 and the outer pipe 20 are connected separately. The pipeline structure can meet the high-precision leakage monitoring operating pressure requirements of the leakage monitoring module, which helps to improve the accuracy of the two-stage acoustic / negative pressure wave leakage monitoring. The signal cables of the acoustic or pressure wave sensors, fiber optic signal cables, and level gauge signal cables are all directly buried and run along the entire pipeline. The signals are transmitted via wired means to ensure the stability of signal transmission.

[0066] The connecting valve assembly includes a connecting pipeline linking two double-layer pipelines, a switching valve installed on the connecting pipeline, and isolation valves installed on the double-layer pipelines. The connecting pipeline is a connecting bridge pipe 70, with the same diameter as the main pipes of the two double-layer pipelines, and is welded to the two main pipes. The isolation valves are electrically operated stop valves or electrically operated ball valves, configured to be fully open or fully closed, with a spacing of approximately 4 km between them.

[0067] Leakage monitoring wells and venting wells 82 are arranged at local low points and local high points of the pipeline according to the terrain. If there is no terrain undulation over a long distance (greater than 1 km), the spacing between leakage monitoring wells is about 1 km, and the length of pipeline covered by a single outer pipe section does not exceed 1 km.

[0068] The isolation valve is also equipped with a valve position feedback device, which is integrated with the leakage monitoring signal processing system and connected to provide feedback on the valve position status. Based on this feedback, the system confirms that the isolation valve has operated correctly, preventing pipeline switching failures due to valve jamming.

[0069] The leakage monitoring signal integration and processing system is configured to receive fiber optic monitoring signals from the double-layer pipeline, acoustic or pressure wave monitoring signals, and liquid level signals from the liquid level detection component. It performs cross-verification based on the three types of signals to confirm the occurrence of a leak and determine the location of the leak. Subsequently, it controls the isolation valve and switching valve to switch the discharge pipeline.

[0070] The three types of signals do not require strict time synchronization. Fiber optic monitoring signals, acoustic or pressure wave monitoring signals are real-time dynamic signals, while liquid level signals are hysteresis signals resulting from leakage accumulation. Liquid level changes can only be monitored after the leaking liquid is diverted through the outer pipe 20mm envelope to the leakage monitoring tank inside the leakage monitoring well.

[0071] The leakage detection logic is as follows: When the leakage flow rate is not less than 1% of the actual discharge flow rate of the pipeline, fiber optic, acoustic, or pressure wave sensors will detect abnormal dynamic signals. Multiple signal coupling and verification confirm the occurrence of a leak. Simultaneously, the leaked liquid flows into the leak monitoring tank, triggering a level signal for further verification. This multi-signal cross-verification significantly reduces the false alarm rate. When the leakage flow rate is less than 1% of the actual discharge flow rate of the pipeline, it is determined to be a seepage condition. At this time, fiber optic, acoustic, or pressure wave sensors are unable to capture instantaneous signal changes. The seepage is confirmed when the leaked liquid flows by gravity through the outer pipe 20 to the leak monitoring tank and triggers a change in the level gauge signal.

[0072] The 1% criterion is the actual discharge flow rate of the pipeline. From a theoretical perspective, regardless of the amount of minute leakage, as long as the leaked fluid continuously collects in the outer pipe 20 and flows by gravity to the leakage monitoring tank in the leakage monitoring well, leakage monitoring can be completed. The monitoring sensitivity of the liquid level in the leakage monitoring tank does not exceed 2% of the measurement range.

[0073] The leak location logic is as follows: For large rupture leaks with a leakage flow rate not less than 1% of the actual pipeline discharge flow rate, the leak can be located using fiber optic monitoring signals, acoustic or pressure wave monitoring signals. Acoustic or pressure wave sensors calculate the leak location based on the time difference of signals received at different locations in the pipeline. Combined with the location accuracy of fiber optics (no more than 5m), the leak point of a large rupture can be quickly located. For minor leaks, the location is determined by the location of the leak monitoring well corresponding to the outer pipe section. Since the maximum spacing between leak monitoring wells does not exceed 1km, the location range for minor leaks is no more than 1km, which meets the location requirements for small leaks. The response time of the liquid level signal is determined by the distance between the leak location and the nearest leak monitoring well in the direction of drainage, as well as the pipeline slope. The closer the distance and the greater the slope, the faster the response, with a maximum response time of 2 minutes.

[0074] The leak monitoring signal integration and processing system includes an interlock control module. This module is configured to generate a pipeline switching command upon confirmation of a leak, and execute a strictly timed interlock switching operation.

[0075] The present invention also discloses a method for controlling the long-distance discharge of liquid effluent from nuclear power plants, which is applied to the long-distance discharge system of liquid effluent from nuclear power plants as described above. The method includes steps S1 to S3.

[0076] Step S1 (Multi-source signal acquisition): Obtain fiber optic monitoring signals for the double-layer pipeline through fiber optic monitoring, obtain acoustic or pressure wave monitoring signals through acoustic or pressure wave sensors, and obtain liquid level signals by detecting the liquid level in the leakage monitoring container 40 through the liquid level detection component.

[0077] An optical fiber, laid along the entire outer wall of the inner pipe 10, monitors the vibration or strain of the inner pipe 10 in real time, outputting a continuous optical fiber monitoring signal with a positioning accuracy of no more than 5m. Segmented acoustic or pressure wave sensors embedded inside the pipe collect dynamic signals of sound waves or negative pressure waves in real time. Each monitoring segment is approximately 10km long, with additional sensors installed in the middle of long pipelines to reduce signal attenuation. A level gauge installed in the leakage monitoring tank collects the liquid level data in real time and outputs the liquid level signal via a wired transmitter, with a measurement accuracy of no more than 2% of the range.

[0078] All three types of signals are transmitted to the leak monitoring signal integration and processing system via wired cables accompanying the directly buried pipeline. The fiber optic and acoustic / pressure wave signals are real-time dynamic signals, while the liquid level signal is a delayed signal resulting from accumulated leakage. Strict time synchronization is not required for these three types of signals. The fiber optic cable can be a distributed strain sensing fiber with a sampling frequency of 1kHz, capable of capturing micro-vibration signals on the pipe wall when a leak occurs. The acoustic / negative pressure wave sensor has a sampling frequency of 10kHz, capable of capturing pressure transient signals caused by leakage. The liquid level gauge samples once per minute, continuously monitoring the cumulative changes in the liquid level within the tank.

[0079] Step S2 (Leak Verification and Location): Cross-verify the fiber optic monitoring signal, acoustic or pressure wave monitoring signal, and liquid level signal to confirm the occurrence of the leak and determine the location of the leak.

[0080] The system couples and verifies the abnormal characteristics of different signals to avoid false alarms caused by a single signal triggering the system. When the leakage flow is greater than or equal to 1% of the actual discharge flow of the pipeline, both fiber optic and acoustic or pressure wave sensors will capture clear abnormal dynamic signals, and the system confirms the occurrence of the leak through multi-signal coupling and verification.

[0081] When the leakage flow rate is less than 1% of the actual discharge flow rate of the pipeline, it is determined to be a leakage condition. At this time, fiber optic, acoustic, or pressure wave sensors are difficult to capture instantaneous signal changes. The system confirms the occurrence of leakage when the leaking liquid flows through the envelope chamber to the leakage monitoring tank and triggers a continuous cumulative change in the level gauge signal.

[0082] During the location process, large leaks with a leakage flow rate of 1% or more are located using a combination of fiber optic monitoring signals and acoustic or pressure wave monitoring signals. Acoustic or pressure wave sensors calculate the leak location based on the time difference of the monitoring signals received at different locations in the pipeline, and the leak point is pinpointed by combining the high-precision strain positioning results from fiber optics.

[0083] Leakage is located by identifying the location of the corresponding leak monitoring well in the outer pipe section. Since the maximum spacing between leak monitoring wells does not exceed 1 km, the leakage location range is no greater than 1 km. The response time of the liquid level signal is determined by the distance between the leakage location and the nearest leak monitoring well, as well as the pipe slope, with a fastest response time of 2 minutes.

[0084] Taking the scenario where the leakage flow rate is 0.5% of the actual discharge flow rate of the pipeline as an example: the fiber optic and acoustic sensors did not detect any abnormal signals exceeding the threshold. After 2 minutes of leakage accumulation, the liquid level in the leakage monitoring tank rose by 12 mm, triggering the level gauge threshold. The system confirmed the leakage and, based on the location of the leakage monitoring well that triggered the level signal, locked the leakage point within a 1 km pipe section corresponding to that well.

[0085] Step S3 (Pipeline Switching Control): Based on the leakage confirmation results, control the isolation valve and switching valve of the interconnection valve group to switch the discharge pipeline.

[0086] Upon confirmation of a leak, the system executes interlocking operations in a strict sequence to prevent leak expansion or water hammer caused by pressurized operation. First, the plant's discharge pump is shut down, stopping media transport within the pipeline. Once the pipeline pressure stabilizes, the isolation valve located upstream of the leak point is closed, completely isolating the faulty section. Next, the switching valve on the connecting pipeline is opened to establish a connection between the operating and standby pipelines. Then, the downstream isolation valve on the connecting pipeline of the other double-layer pipeline is opened, opening the complete transport path of the standby pipeline. Finally, the plant's discharge pump is restarted, completely switching the discharge pipeline to the standby double-layer pipeline, restoring normal discharge of the liquid effluent.

[0087] The entire switching process takes no more than 30 minutes. The interlocking process includes a manual intervention interface and protection against misoperation, and key valves are equipped with valve position feedback. The system confirms that each action is in place based on valve position feedback before executing the next step, preventing valve jamming and switching failure.

[0088] Taking a leak at 3km along the operating pipeline as an example: The system first triggers a pump stop command. After receiving feedback of the pump stop signal, it closes the nearest upstream isolation valve at the 3km location. Upon receiving feedback that the valves are fully closed, it sequentially opens the 70 switching valve on the connecting bridge and the valves on the standby pipeline side. After receiving feedback that all valves are fully open, it starts the discharge pump. The entire process takes 18 minutes, with no leakage or overflow, and the discharge is uninterrupted.

[0089] It should be noted that while the signal acquisition process is continuous and parallel, the leak detection, location, and pipeline switching steps have strict time dependencies. Leak confirmation and location must be completed before pipeline switching can proceed. Valve operations within the pipeline switching process must be performed in the following sequence: pump stop, isolation valve close, connecting valve open, standby valve open, pump start. Valve position feedback from the preceding actions is a prerequisite for the subsequent actions; the order cannot be reversed to avoid media leakage or pipeline water hammer accidents.

[0090] This invention relates to a long-distance discharge system and control method for liquid effluent from nuclear power plants. It utilizes a double-layered pipeline enveloping chamber to contain and retain leaked liquid effluent, preventing direct diffusion into the environment. Cross-validation of three types of signals—fiber optic, acoustic / pressure wave, and level gauge—achieves comprehensive monitoring and precise location of both large and small leaks, significantly reducing false alarm rates. Interlocking valve groups and interlocking control modules enable rapid pipeline switching after a leak, ensuring continuous and stable discharge of liquid effluent in long-distance transport scenarios and meeting the safety requirements for liquid effluent discharge from nuclear power plants.

[0091] Taking a large leak in a pipeline located 5km from the power plant as an example: fiber optic and acoustic sensors detect the abnormal signal and locate the leak point within 10 seconds. After confirming the leak, the system immediately triggers the interlock process, sequentially executing the pump stop, valve closure, interconnection valve opening, and pump start-up operations. The entire process takes about 22 minutes to switch the discharge path to the backup pipeline. There is no liquid effluent leakage into the environment throughout the process, and the discharge is uninterrupted.

[0092] This invention achieves physical containment and retention of leaked materials through a double-layered pipeline system, orderly collection of leaked liquid through segmented compartment drainage, leak monitoring through multi-source signal cross-verification, and coordinated pipeline control through interlocking switching. This forms a complete closed loop from leak containment, leakage drainage, signal sensing to automatic pipeline switching. This solution meets the safety management requirements for long-distance liquid effluent discharge as outlined in the "Technical Guidelines for the Review of Long-Distance Intake and Drainage Pipelines for Nuclear Power Plants," and provides a safe and reliable systemic solution for the discharge of liquid effluents into the ocean over distances of ten to tens of kilometers as coastal nuclear power plant sites extend inland.

[0093] For those skilled in the art, the above disclosure is merely illustrative and does not constitute a limitation of this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and corrections to this application. Such modifications, improvements, and corrections are suggested in this application and therefore remain within the spirit and scope of the exemplary embodiments of this application.

[0094] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A long-distance discharge system for liquid effluent from a nuclear power plant, characterized in that, include: Two double-layer pipelines, each of which includes an inner pipe, an outer pipe, and a support member disposed between the inner pipe and the outer pipe. An enveloping chamber is formed between the inner pipe and the outer pipe. The outer pipe is sealed and isolated at the well body by a sealing and partitioning member to form multiple outer pipe sections. A drainage component is provided in each of the outer tube sections. The drainage component is connected to the envelope chamber and configured to allow the liquid in the envelope chamber to flow into the leak monitoring container in the leak monitoring well. A liquid level detection component is disposed inside the leak monitoring container and configured to detect the liquid level inside the leak monitoring container; The connecting valve assembly includes a connecting pipeline connecting the two double-layer pipelines, a switching valve disposed on the connecting pipeline, and an isolation valve disposed on the double-layer pipeline. The leakage monitoring signal integration and processing system is configured to receive the monitoring signal of the double-layer pipeline and the liquid level signal of the liquid level detection component, perform cross-verification based on the received monitoring signal and the liquid level signal, confirm the occurrence of leakage and determine the leakage location, and control the isolation valve and the switching valve to switch the discharge pipeline based on the leakage confirmation result.

2. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 1, characterized in that, The monitoring signal includes an optical fiber monitoring signal, which is obtained by monitoring an optical fiber that is laid along the entire outer wall of the inner tube. The optical fiber is configured to monitor the vibration or strain of the inner tube.

3. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 1, characterized in that, The sealing and partitioning component is an annular sealing plate used to isolate fluid between adjacent outer pipe sections; the inner pipe remains continuous throughout and is not separated by the outer pipe sections.

4. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 1, characterized in that, The leakage monitoring signal integration and processing system is configured to: determine leakage flow less than 1% of the actual discharge flow of the pipeline as a leakage condition, and confirm the occurrence of leakage based on the liquid level signal change of the liquid level detection component.

5. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 4, characterized in that, For leaks with a leakage flow rate greater than or equal to 1% of the actual discharge flow rate of the pipeline, the location is determined by the monitoring signal; the leakage condition is located by the location of the leakage monitoring well to which the corresponding outer pipe section belongs.

6. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 1, characterized in that, The leakage monitoring signal integration and processing system includes an interlocking control module, which generates a pipeline switching command after a leak is confirmed.

7. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 1, characterized in that, The supporting components include fixed brackets and guide brackets spaced apart along the axial direction of the inner tube. The inner side of the fixed bracket is fixedly connected to the outer wall of the inner tube, and the outer side of the fixed bracket is fixedly connected to the inner wall of the outer tube, so as to limit the relative displacement between the inner tube and the outer tube. The inner side of the guide bracket is fixedly connected to the outer wall of the inner tube, and the outer side of the guide bracket is provided with a support leg, which makes movable contact with the inner wall of the outer tube.

8. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 1, characterized in that, The leak monitoring container is used to collect and monitor minute leaks, and the discharge system also includes a waste liquid collection tank, which is connected to the leak monitoring container and is used to temporarily store waste liquid in the event of a large leak. The liquid level detection component is a liquid level gauge, which is installed inside the leakage monitoring container and outputs the liquid level signal through a wired transmission transmitter.

9. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 1, characterized in that, The emission system also includes acoustic or pressure wave sensors embedded inside the double-layer pipeline. The acoustic or pressure wave sensors are two-ended sensors, which are installed at both ends of each monitoring section.

10. The long-distance discharge system for liquid effluent from nuclear power plants according to claim 1, characterized in that, The isolation valve is an electric shut-off valve or an electric ball valve, and the valve position of the isolation valve is configured to be fully open or fully closed. The isolation valve is equipped with a valve position feedback device, which is connected to the leakage monitoring signal integration and processing system. The valve position feedback device is used to provide feedback on the valve position status of the isolation valve to the leakage monitoring signal integration and processing system. The leakage monitoring signal integration and processing system confirms that the isolation valve has been activated based on the valve position status.

11. A method for controlling long-distance emissions of liquid effluent from nuclear power plants, characterized in that, The emission control method employs the emission system as described in any one of claims 1-10, and the emission control method includes the following steps: S1. Obtain the fiber optic monitoring signal of the double-layer pipeline through fiber optic monitoring, obtain the acoustic or pressure wave monitoring signal through the acoustic or pressure wave sensor, and obtain the liquid level signal by detecting the liquid level in the leakage monitoring container through the liquid level detection component. S2. Cross-verify the fiber optic monitoring signal, the acoustic or pressure wave monitoring signal, and the liquid level signal to confirm that a leak has occurred and determine the location of the leak. S3. Based on the leakage confirmation result, control the isolation valve and switching valve of the communication valve group to switch the discharge pipeline.

12. The method for controlling long-distance discharge of liquid effluent from nuclear power plants according to claim 11, characterized in that, In step S2, a leakage flow rate less than 1% of the actual discharge flow rate of the pipeline is identified as a leakage condition, and the leakage is confirmed based on the change in the liquid level signal of the liquid level detection component.

13. The method for controlling long-distance discharge of liquid effluent from nuclear power plants according to claim 11, characterized in that, In step S2, leaks with a leakage flow rate greater than or equal to 1% of the actual discharge flow rate of the pipeline are located by the optical fiber monitoring signal and the acoustic or pressure wave monitoring signal.

14. The method for controlling long-distance discharge of liquid effluent from nuclear power plants according to claim 11, characterized in that, In step S3, after confirming that a leak has occurred, the following operations are performed in sequence: shut down the plant discharge pump; shut down the isolation valve located upstream of the leak point near the leak point; open the switching valve on the connecting pipeline; open the isolation valve on the downstream side of the connecting pipeline of the other double-layer pipeline; and start the plant discharge pump to switch the discharge pipeline to the other double-layer pipeline.

15. The method for controlling long-distance discharge of liquid effluent from nuclear power plants according to claim 11, characterized in that, In step S2, the leak location is calculated based on the time difference between the acoustic or pressure wave monitoring signals received by the acoustic or pressure wave sensor at different locations in the pipeline.

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