Method for recovering operation of ship power reactor in LOCA accident

Abstract

The invention relates to a method for recovering operation of a ship power reactor in an LOCA accident. The operation recovery method comprises the following steps: shutting down the power reactor and shutting down a secondary side normal water supply system; the PRHR system is started; introducing seawater into the compartment containing the pressure vessel so that the seawater submerges the lower head; after the crevasse in the LOCA accident is isolated, inflating the compartment to discharge the introduced seawater; the PRHR system is closed, and the secondary side normal water supply system is opened again; and starting the power reactor. According to the invention, the condition that the temperature of the reactor core rapidly rises after an accident occurs can be effectively relieved, and partial or all power of the power reactor can be recovered step by step.

Description

Technical Field

[0001] The invention relates to the technical field of reactor engineering simulation, and in particular to a method for restoring operation of a ship power reactor in a LOCA accident. Background Art

[0002] LOCA accident (Loss Of Coolant Accident) is a serious situation that may occur during the operation of a nuclear reactor. LOCA accidents are mainly caused by ruptures in the pipes or equipment of the primary coolant system, resulting in a large amount of coolant leaking into the containment from the rupture. The loss of a large amount of coolant will cause the cooling capacity of the reactor core to drop sharply, leading to a sharp increase in the core temperature. If effective measures are not taken in time, the core temperature may exceed the design temperature limit of the fuel element, causing the fuel element cladding to break, and radioactive substances will be released into the coolant, causing a serious accident.

[0003] Especially after a LOCA accident occurs in a ship power reactor, it is usually difficult to obtain water that meets the reactor operation requirements in a timely manner. This means that after a LOCA accident occurs, even if the breach is isolated through damage control measures, the reactor cannot operate at power according to the original operating mode, which makes it difficult to restore the ship's power. Summary of the invention

[0004] In view of the above problems in the prior art, the present invention proposes a method for resuming operation of a ship power reactor in a LOCA accident, which can effectively alleviate the rapid rise in core temperature after the accident and gradually achieve partial or full power recovery of the power reactor.

[0005] Specifically, the present invention proposes a method for resuming operation of a ship power reactor in a LOCA accident, wherein the ship power reactor comprises a pressure vessel arranged in an independent compartment, the pressure vessel comprises a lower head and a cylinder, the bottom end of the cylinder is connected to the lower head; a hanging basket is arranged in the cylinder for suspending the core, a refrigerant descending channel is formed between the hanging basket and the inner wall of the cylinder, and a PRHR system is arranged in the descending channel; an ascending channel of the refrigerant passing through the active zone of the core is formed in the hanging basket; the method for resuming operation comprises the steps of: Shut down the power reactor and shut down the secondary side normal feed water system; Starting the PRHR system; Introducing seawater into the compartment containing the pressure vessel so that the seawater submerges the lower head; After the breach in the LOCA accident is isolated, the compartment is inflated to discharge the introduced seawater; Shut down the PRHR system and reopen the secondary side normal water supply system; The power reactor is started up.

[0006] According to one embodiment of the present invention, an air inlet is provided at the top of the compartment, and a drain outlet is provided at the bottom of the compartment, and the method comprises inflating the compartment through the air inlet to press the seawater out of the compartment through the drain outlet.

[0007] According to one embodiment of the present invention, after the normal secondary water feed system is reopened, the heat generated by the core is brought to the steam turbine through the primary and secondary side heat exchangers of the PRHR system to perform work.

[0008] According to one embodiment of the present invention, after the normal secondary side water supply system is reopened, a three-dimensional natural circulation is formed in the core and the upper chamber area of ​​the core, and under the cooling effect of the primary and secondary side heat exchangers, a three-dimensional natural circulation is formed in the descending channel.

[0009] According to one embodiment of the present invention, the two three-dimensional natural cycles perform heat exchange through hanging baskets.

[0010] According to one embodiment of the present invention, when a three-dimensional natural circulation is formed in the core and the upper chamber area above the core, mass transfer is realized inside the core and the lower head, and the refrigerant carrying heat flows downward from the core into the lower head, transferring the heat to the refrigerant in the lower head with which it contacts.

[0011] According to one embodiment of the present invention, when a three-dimensional natural circulation is formed in the core and the upper chamber area above the core, mass transfer is realized inside the descending channel and the lower head, and the refrigerant carrying heat flows downward from the descending channel into the lower head, transferring the heat to the refrigerant in the lower head with which it contacts.

[0012] According to one embodiment of the present invention, the step of starting the power reactor includes: gradually increasing the core power to enter a low-power operation recovery mode.

[0013] According to one embodiment of the present invention, the PRHR system includes a primary and secondary side heat exchanger, and surface modification technology is carried out on the surfaces of the primary and secondary side heat exchanger to enhance condensation efficiency.

[0014] According to one embodiment of the present invention, a two-dimensional or three-dimensional structure is etched on the surface of the primary and secondary side heat exchanger.

[0015] The present invention provides a method for restoring operation of a ship power reactor in a LOCA accident, which effectively alleviates the rapid rise in core temperature after the accident by starting the PRHR system and introducing seawater to submerge the bottom of the lower head; and after the breach is isolated, the introduced seawater is discharged, the PRHR system is closed, and the secondary side normal water supply system is reopened to gradually realize partial or full power recovery of the power reactor.

[0016] It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are included to provide further explanation of the present invention, and they are incorporated into and constitute a part of this application. The accompanying drawings illustrate embodiments of the present invention and together with this specification serve to explain the principles of the present invention. In the accompanying drawings: Figure 1 The schematic diagram of the structure and shutdown state of a pressure vessel according to an embodiment of the present invention is shown.

[0018] Figure 2 A flowchart of a method for restoring operation of a ship power reactor in a LOCA accident according to an embodiment of the present invention is shown.

[0019] Figure 3 A schematic diagram showing the structure of a pressure vessel according to an embodiment of the present invention and its state in a low-power operation recovery mode. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application may be combined with each other.

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0022] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the application. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0024] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0025] In addition, it should be noted that the use of words such as "first" and "second" to define components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above words have no special meaning and cannot be understood as limiting the scope of protection of this application. In addition, although the terms used in this application are selected from well-known and commonly used terms, some terms mentioned in the specification of this application may be selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant parts of the description of this article. In addition, it is required to understand this application not only by the actual terms used, but also by the meaning implied by each term.

[0026] Figure 1The structure of a pressure vessel of an embodiment of the present invention and a schematic diagram of a shutdown state are shown. As shown in the figure, a ship power reactor includes a pressure vessel 100 arranged in an independent compartment. The pressure vessel 100 includes a lower head 101 and a cylinder 102. The bottom end of the cylinder 102 is connected to the lower head 101. A hanging basket 103 is provided in the cylinder 102 for suspending the core 104. A refrigerant descending channel 105 is formed between the hanging basket 103 and the inner wall of the cylinder 102, and a PRHR (Passive Residual Heat Removal system, non-passive residual heat removal) system 106 is provided in the descending channel 105 for effectively cooling the refrigerant. An ascending channel 107 of the refrigerant passing through the active zone of the core 104 is formed in the hanging basket 103, and the refrigerant absorbs heat in the ascending channel 107. In the pressure vessel 100 of the ship power reactor, the refrigerant first flows from top to bottom in the descending channel 105 and enters the lower head 101. During this process, the refrigerant will release some heat and exchange heat with the surrounding environment. Then, the refrigerant enters the rising channel 107 from the lower head 101. In the rising channel 107, the refrigerant passes through the active area of ​​the core 104 and absorbs the heat generated by the core 104. In this way, the refrigerant completes a cycle process in the pressure vessel 100, realizing the alternation of heat release and heat absorption. Under normal circumstances, the refrigerant circulates continuously, and the refrigerant continuously takes away the heat of the core 104, maintaining the core 104 within a safe temperature range, ensuring the stable operation of the ship's power reactor, and providing a reliable power source for the ship. However, after a LOCA accident occurs, a breach occurs in the pipeline or equipment, causing a large amount of coolant to leak from the breach, resulting in a decrease in the refrigerant water level in the containment.

[0027] Figure 2 A flowchart of a method for restoring operation of a ship power reactor in a LOCA accident according to an embodiment of the present invention is shown. As shown in the figure, a method for restoring operation of a ship power reactor in a LOCA accident provided by the present invention comprises the following steps: S1, shut down the power reactor and the secondary side normal water supply system. When a LOCA accident occurs, the power reactor is shut down to stop the chain reaction and reduce the heat generation of the core 104. When the power reactor is operating normally, a large amount of heat will be generated through the fission reaction of the nuclear fuel. After the LOCA accident occurs, the loss of coolant has deteriorated the cooling environment of the core 104. Continuing to maintain the chain reaction will cause the temperature of the core 104 to continue to rise, further aggravating the severity of the accident. Shutting down the power reactor by inserting control rods and other methods can reduce the generation of heat from the source, which is the first step to mitigate the accident. It should be noted that the secondary side normal water supply system mainly transports water to the secondary side of the steam generator to take away the heat from the primary side and generate steam to drive the steam turbine to generate electricity. It is shut down during a LOCA accident because the normal operating conditions of the secondary circuit system are destroyed. If water is continued to be supplied to the secondary side of the steam generator, the heat exchange abnormality caused by the loss of primary side coolant may cause the steam generator and other equipment to suffer abnormal thermal stress and pressure changes.

[0028] S2, start the PRHR system 106. This can help remove the decay heat of the core 104 and prevent the core 104 from overheating. Decay heat is the heat that continues to be generated by the decay process of radioactive nuclides in nuclear fuel after the chain reaction stops. When the high-temperature refrigerant passes through the PRHR system 106, the heat will be transferred from the refrigerant to the heat exchange tubes of the PRHR system 106 by heat conduction. The operation of the PRHR system 106 can buy time for the repair of the LOCA accident. During the operation of the PRHR system 106, it can temporarily assume part of the cooling task of the secondary side normal water supply system to reduce the burden on the secondary side normal water supply system.

[0029] S3, introduce seawater into the compartment containing the pressure vessel 100 so that the seawater submerges the lower head 101. When the seawater submerges the lower head 101, the lower head 101 can be directly cooled. The lower head 101 is an important part of the refrigerant circulation path, and cooling the lower head 101 can indirectly cool the refrigerant inside it. Because there is heat transfer between the lower head 101 and the refrigerant, the lower temperature seawater absorbs the heat of the lower head 101, so that the temperature of the refrigerant can be effectively reduced during the process of entering and leaving the lower head 101. This helps to maintain the refrigerant in a suitable temperature range, better cool the core 104, and prevent the core 104 from overheating. Using seawater to submerge the pit where the lower head 101 is located is a relatively simple and effective cooling method. Compared with some complex active cooling equipment and systems, this method can reduce the dependence on complex mechanical devices to a certain extent.

[0030] Steps S2 and S3 are used to alleviate the rapid rise in temperature of the core 104 after an accident occurs, mainly by lowering the refrigerant temperature through the PRHR system 106 and the introduction of seawater, so that the refrigerant can continue to absorb the residual heat of the core 104 and effectively control the speed of water level drop in the pressure vessel 100.

[0031] S4, after the breach in the LOCA accident is isolated, the compartment is inflated to discharge the introduced seawater. When the power reactor needs to be restored to operation, the heat exchange effect of the lower head 101 is weakened and the equipment is restored to a relatively dry operating environment.

[0032] S5, turn off the PRHR system 106, and reopen the secondary side normal water supply system. Since the PRHR system 106 mainly plays the role of waste heat removal in emergency situations. When the power reactor needs to resume normal operation, shutting down the PRHR system 106 can avoid unnecessary interference to the system in normal operation, ensure that the operating parameters of the system are more stable, and facilitate precise control and adjustment. Starting the secondary side normal water supply system can provide a stable cooling water source for the system. The secondary side normal water supply system is specially designed to provide appropriate water volume and pressure according to the operating requirements of the system. During the operation resumption stage, the core 104 will still generate a lot of heat, and reliable cooling means are required to maintain the temperature within a safe range. The secondary side normal water supply system can effectively remove the heat generated by the core 104 through heat exchange and other means to ensure the safe operation of the reactor.

[0033] S6, starting the power reactor, mainly by gradually increasing the power of the core 104 to enter a low-power operation recovery mode.

[0034] In some examples, reference Figure 1, the PRHR system 106 includes a primary and secondary heat exchanger 108, which brings heat to the external environment or other heat dissipation equipment through natural convection. The primary and secondary heat exchanger 108 brings the heat from the primary side to the secondary side. The primary and secondary heat exchanger 108 is generally a spiral tube heat exchanger, the inside of the tube is the secondary side, and the outside of the tube is the primary side. The refrigerant in the pressure vessel 100 runs outside the tube, and the refrigerant runs inside the tube to exchange heat with the external system. The primary side water vapor is condensed by the primary and secondary heat exchanger 108, and the condensed water generated by the water vapor is used to replenish the water level in the pressure vessel 100. This process helps to balance the pressure in the system. When the water level rises, part of the space in the pressure vessel 100 is occupied by liquid water, while the space of the gaseous part is relatively reduced, thereby reducing the internal pressure. This can effectively alleviate the excessive pressure that may occur in the pressure vessel 100 and ensure the safe and stable operation of the system. Furthermore, surface modification technology is carried out on the surface of the primary and secondary heat exchangers 108 to enhance the condensation efficiency. Effectively condensing the water vapor on the primary side is crucial to controlling the water level and pressure inside the pressure vessel 100. Surface modification technology mainly changes the physical or chemical properties of the heat exchanger surface so that more heat can be transferred from the primary side to the secondary side, thereby improving its ability to condense water vapor and thus improving the thermal efficiency of the entire system. Surface modification technology includes coating technology, surface roughening treatment, etc.

[0035] Preferably, a two-dimensional or three-dimensional structure is etched on the surface of the primary and secondary heat exchangers 108. The two-dimensional or three-dimensional etched structure can significantly increase the surface area of ​​the heat exchanger. A larger surface area means more space for water vapor to contact the surface and condense. The two-dimensional or three-dimensional etched structure can also guide the flow of fluid and improve fluid dynamics. For example, the microgroove structure can guide the flow direction of condensed water so that it can be discharged from the heat exchanger surface faster and reduce flow resistance.

[0036] In some examples, an air inlet is provided at the top of the compartment, and a drain is provided at the bottom of the compartment, and the compartment is inflated through the air inlet to press the seawater out of the compartment through the drain. When an emergency such as a LOCA accident occurs, seawater is introduced to cool the lower head 101. Once the breach is isolated, the seawater in the compartment needs to be discharged as soon as possible to restore the normal operation of the ship's power reactor. By inflating the compartment through the top air inlet, the pressure of the gas can be used to quickly press the seawater out of the bottom drain. This method can empty the seawater in the compartment in a shorter time and increase the recovery speed.

[0037] In some examples, the normal secondary water supply system is started, and the heat generated by the core 104 is brought to the steam turbine through the primary and secondary heat exchangers 108 to perform work. Specifically, the primary and secondary heat exchangers 108 of the PRHR system 106 are disconnected from the previous external system heat exchange and switched to the heat exchange of the steam turbine. When the normal secondary water supply system is started, a steady stream of feed water will be delivered to the primary and secondary heat exchangers 108. At this time, the power of the core 104 is gradually increased, and the heat of the core 104 can be efficiently transferred to the feed water on the secondary side, so that the temperature of the originally low-temperature water continues to rise, and then turns into high-temperature water or even high-temperature steam. After the refrigerant enters the steam turbine through heat exchange, it begins to expand, and with strong pressure, it drives the blades of the steam turbine to rotate at high speed. The rotational motion of the blades is transmitted to other related equipment, such as generators, through the transmission shaft, so as to realize the output of mechanical energy, and complete the key energy conversion process from the heat energy generated by the core 104 to the mechanical energy output of the steam turbine, and finally provide part of the power for the ship to save itself.

[0038] Figure 3 The following is a schematic diagram showing the state of a pressure vessel and a low power operation recovery mode according to an embodiment of the present invention. Figure 1 and Figure 3The specific process of step S5 is described as shown in the figure. In some examples, when the secondary side normal water supply system is started, a three-dimensional natural circulation is formed in the core 104 and the upper chamber 109 area above the core 104. The upper chamber 109 is an important space area in the reactor pressure vessel 100, which is directly connected to the core 104. It is a chamber structure located at the upper part of the core 104 and surrounded by the hanging basket 103 and the upper wave plate 110. The rising channel 107 is located in the upper chamber 109, and the rising channel 107 is composed of a fuel assembly, a supporting structure, etc. The channel system. Under normal conditions without a LOCA accident, the refrigerant passing through the active area of ​​the core 104 enters the rising channel 107 in the upper chamber 109 upward, and the refrigerant absorbs heat in the rising channel 107. In the method of restoring operation in a LOCA accident, when the secondary side normal water supply system starts to work, water is transported to the primary and secondary side heat exchangers 108 for heat exchange. In the core 104 area, the nuclear reaction continues to generate heat. Due to the temperature difference, the water around the core 104 is heated, and the water density decreases after the temperature rises. Under the action of buoyancy, the hot water moves upward and enters the upper chamber 109 area. Refer to the upward arrow in the middle of the core 104 and the upper chamber 109 area, which indicates that the hot water moves upward. The upper chamber 109 is similar to a "transfer station" for heat convergence and distribution. The hot water gathers here, making the upper area of ​​the upper chamber 109 have a higher temperature. Under the action of gravity, the relatively cold water is replenished from the surrounding or other parts of the system to the bottom of the core 104. This exchange of hot and cold fluids unfolds in three-dimensional space, forming a complex natural cycle. Refer to the downward arrow on the inner side of the basket 103 near the edge of the core 104 and the upper chamber 109, which indicates that the cold water moves downward. In this three-dimensional natural circulation process formed by hot water upward and cold water downward, there is not only vertical flow in the up and down directions, but also horizontal flow. The horizontal flow is mainly due to the temperature difference and fluid pressure difference at different positions. For example, at the edge and center of the core 104, due to uneven heat distribution, the temperature and density of water are also different, which triggers horizontal fluid exchange. This three-dimensional natural circulation can ensure that the heat generated by the core 104 is taken away in time and the temperature of the core 104 is maintained within a safe range.

[0039] At the same time, under the cooling effect of the primary and secondary heat exchangers 108, a natural circulation is formed in the descending channel 105. When the primary and secondary heat exchangers 108 begin to play a cooling role, the temperature of the refrigerant near them will be affected first and decrease. In the descending channel 105, there is a temperature difference between the refrigerants. The temperature of the refrigerant close to the primary and secondary heat exchangers 108 is relatively lower, while the temperature of the part far away from it is higher. Due to the principle of thermal expansion and contraction, the density of the refrigerant with a higher temperature is smaller, and the density of the refrigerant with a lower temperature is larger. Under the action of gravity, the refrigerant with a higher density will naturally flow downward. Figure 3 The downward arrow at the position of the primary and secondary side heat exchanger 108 indicates that the refrigerant flows downward. The refrigerant with higher temperature and lower density near the side of the hanging basket 103 will move upward under the action of buoyancy, referring to the upward arrow on the outside of the hanging basket 103, to fill the space vacated by the downward flow. In this way, a three-dimensional natural circulation is formed in the descending channel 105. This three-dimensional natural circulation is like an automatically adjusted heat transfer chain, which enables the refrigerant to flow continuously in the descending channel 105, and transfers the heat to the primary and secondary side heat exchangers 108 in an orderly manner for exchange cooling, thereby ensuring the heat balance of the entire system. Moreover, the formation of the three-dimensional natural circulation does not require additional power drive, and can operate stably relying on its own physical properties, which not only reduces energy consumption, but also improves the reliability of system operation and ensures partial power recovery of the ship's power reactor.

[0040] In some examples, two natural cycles exchange heat through the basket 103. From the three-dimensional natural cycle of the core 104 and the upper chamber 109 area, the high-temperature fluid carries the heat generated by the core 104 and moves upward into the upper chamber 109, and these high-temperature fluids are in close contact with the basket 103. The basket 103 has good thermal conductivity, and it can quickly transfer the absorbed heat to the refrigerant in the descending channel 105 in contact with it, so that the heat can be effectively transferred from the circulation system inside the basket 103 with a higher temperature to the circulation system outside the basket 103 with a lower temperature. This heat exchange makes the two originally relatively independent natural circulation systems interconnected to form a complete heat exchange network. Through the heat conduction of the basket 103, the system can more efficiently utilize and distribute heat, avoiding local accumulation of heat. This natural heat exchange method utilizes the temperature difference and fluid movement characteristics of the two circulation systems themselves, does not require additional complex power devices to drive heat exchange, and improves the reliability and economy of the system. Furthermore, this heat exchange mechanism can ensure that the heat of the core 104 can be removed in time, maintaining the temperature of the core 104 within a safe range, and ensuring partial power recovery of the ship's power reactor.

[0041] In some examples, mass transfer is achieved inside the core 104 and the lower head 101. The core 104 is the core area where the nuclear reaction occurs. When the nuclear reaction continues, a large amount of heat will be generated, accompanied by changes in the state of various substances and the migration of substances. Inside the core 104, the coolant absorbs heat, the temperature rises, the state changes, and some of its internal components will also undergo corresponding physical and chemical changes. The core 104 and the lower head 101 are connected through a specific structure, so that mass transfer can be achieved between the two. For example, high-temperature coolant will flow downward from the core 104 area to the lower head 101. In this process, the heat carried by the coolant is transferred downward as the coolant flows. The lower head 101 receives the coolant from the core 104, and its heat will continue to be transferred to the surrounding environment or other media in contact with it. This mass transfer inside the core 104 and the lower head 101 helps to maintain the stability of the thermal-hydraulic state of the core 104, and promptly transfers the heat generated by the core 104 through the lower head 101, avoiding excessive heat accumulation that affects the safety of the core 104, while also ensuring the reasonable flow and distribution of materials in this area.

[0042] In some examples, mass transfer is achieved inside the descending channel 105 and the lower head 101. The coolant in the descending channel 105 has its own flow characteristics and thermal state, and it circulates continuously in the channel to achieve heat transfer. When the coolant flows downward along the descending channel 105, it will eventually flow into the lower head 101. In the lower head 101, the coolant from the descending channel 105 interacts with the original substances in the lower head 101 to achieve mass transfer. For example, the coolant flowing in from the descending channel 105 brings a certain amount of heat, possible impurities, and different chemical components, which will mix and exchange with the existing substances in the lower head 101. At the same time, the substances in the lower head 101 will also affect the inflowing coolant, such as changing its temperature, composition ratio, etc. Moreover, the flow state and temperature change of the coolant in the lower head 101 will in turn affect the mass transfer process between it and the descending channel 105. This mass transfer inside the descending channel 105 and the lower head 101 can further optimize the heat transfer path of the entire system, ensure that the coolant continuously adjusts its own thermal and material states during the circulation process, work better together, and efficiently take away the heat generated by the core 104, maintaining the stable operation of various parts of the system under appropriate temperature, pressure and material composition conditions, which plays an indispensable role in the partial power recovery of the ship power reactor.

[0043] In some examples, the pipes passing through the pressure vessel 100 are arranged upward as much as possible, and the aperture of the pipes is controlled. In this way, the size of the pipe rupture can be controlled to be smaller after the LOCA accident, and the position of the rupture can be relatively higher, so that the refrigerant loss speed is relatively slow, which is conducive to realizing the method for restoring the operation of the ship power reactor in the LOCA accident provided by the present invention.

[0044] It should be noted that, usually after a LOCA accident occurs, the system water volume loss in the pressure vessel 100 is large, and the primary side water flow hole has been exposed. After the PRHR system 106 is turned off in step S5 and the normal water supply system on the secondary side is started, the core 104 cannot be started according to the normal process in step S6, so a low-power recovery operation mode is adopted, and the ship can recover the power to move forward at a low speed through the aforementioned different flow heat exchange methods. In rare cases, if the system water volume loss is small, the primary side water flow hole is still flooded, and after the PRHR system 106 is turned off in step S5 and the normal water supply system on the secondary side is started, the core 104 can be started normally, and the primary side forms a single-phase natural circulation in the flow channel of the core 104-upper chamber 109-primary and secondary side heat exchangers 108-down channel 105, so that the secondary side can absorb the heat of the core 104 and generate steam to drive the steam turbine to do work.

[0045] It will be apparent to those skilled in the art that various modifications and variations may be made to the above exemplary embodiments of the present invention without departing from the spirit and scope of the present invention. Therefore, it is intended that the present invention covers modifications and variations of the present invention that fall within the scope of the appended claims and their equivalent technical solutions.

Claims

1. A method for restoring operation of a ship power reactor in a LOCA accident, the ship power reactor comprising a pressure vessel arranged in an independent compartment, the pressure vessel comprising a lower head and a cylinder, the bottom end of the cylinder being connected to the lower head; a hanging basket is arranged in the cylinder for suspending a core, a refrigerant descending channel is formed between the hanging basket and the inner wall of the cylinder, a PRHR system is arranged in the descending channel; an ascending channel of the refrigerant passing through the active zone of the core is formed in the hanging basket; the method for restoring operation comprises the steps of: Shut down the power reactor and shut down the secondary side normal feed water system; Starting the PRHR system; Introducing seawater into the compartment containing the pressure vessel so that the seawater submerges the lower head; After the breach in the LOCA accident is isolated, the compartment is inflated to discharge the introduced seawater; Shut down the PRHR system and reopen the secondary side normal water supply system; The power reactor is started up.

2. The method for resuming operation according to claim 1, characterized in that: An air inlet is provided at the top of the compartment, and a drain outlet is provided at the bottom of the compartment. The method comprises inflating the compartment through the air inlet to press the seawater out of the compartment through the drain outlet.

3. The method for resuming operation according to claim 1, characterized in that: After the normal secondary water feed system is reopened, the heat generated by the core is brought to the steam turbine through the primary and secondary heat exchangers of the PRHR system to perform work.

4. The method for resuming operation according to claim 3, characterized in that: After the normal water supply system on the secondary side is reopened, a three-dimensional natural circulation is formed in the core and the upper chamber area above the core, and a three-dimensional natural circulation is formed in the descending channel under the cooling effect of the primary and secondary side heat exchangers.

5. The method for resuming operation according to claim 4, characterized in that: The two three-dimensional natural cycles exchange heat through the hanging basket.

6. The method for resuming operation according to claim 4, characterized in that: When a three-dimensional natural circulation is formed in the core and the upper chamber area above the core, mass transfer is achieved inside the core and the lower head, and the refrigerant carrying heat flows downward from the core into the lower head, transferring the heat to the refrigerant in the lower head with which it contacts.

7. The method for resuming operation according to claim 4, characterized in that: When a three-dimensional natural circulation is formed in the core and the upper chamber area above the core, mass transfer is achieved inside the descending channel and the lower head. The refrigerant carrying heat flows downward from the descending channel into the lower head, transferring the heat to the refrigerant in the lower head with which it contacts.

8. The method for resuming operation according to claim 1, characterized in that: The steps of starting the power reactor include: gradually increasing the core power to enter a low-power operation recovery mode.

9. The method for resuming operation according to claim 1, characterized in that: The PRHR system includes a primary and secondary side heat exchanger, and surface modification technology is carried out on the surfaces of the primary and secondary side heat exchangers to enhance condensation efficiency.

10. The method for resuming operation according to claim 9, characterized in that: A two-dimensional or three-dimensional structure is etched on the surface of the primary and secondary side heat exchanger.

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