Reactor Full-Condition Full-Range Passive Residual Heat Removal System and Method

Abstract

This invention discloses a passive residual heat removal system and method for reactors operating under all conditions and within a full range. The reactor is located within a containment vessel and includes a primary-side passive residual heat removal system, a secondary-side passive residual heat removal system, and a control system. The primary-side passive residual heat removal system is equipped with a first valve assembly, and the secondary-side passive residual heat removal system is equipped with a second valve assembly. The control system controls the opening and closing of the first and second valve assemblies to control the start and stop of the primary and secondary passive residual heat removal systems, respectively. This passive residual heat removal system and method for reactors operating under all conditions and within a full range reduces the heat transfer area of ​​the primary-side passive residual heat removal system, thus reducing the risk of heat exchanger tube damage, preventing leakage of radioactive primary coolant from its boundaries, and significantly increasing the volume of the primary-side passive residual heat removal system and reducing the volume of the containment water tank, thereby lowering construction costs.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant system equipment and safety, and in particular to a passive residual heat removal system and method for reactors operating under all conditions and in all ranges. Background Technology

[0002] Reactor exhaust heat refers to the removal of heat, primarily decay heat, from the reactor core after reactor shutdown. Both normal operation and accident operation reactor shutdowns require exhaust heat removal. For normal operation shutdowns, this primarily occurs during reactor startup and shutdown phases; for accident operation shutdowns, it mainly occurs after an emergency shutdown.

[0003] To remove residual heat from a reactor, the reactor temperature needs to go through a process of decreasing from high to low. In other words, by removing residual heat, the reactor temperature is reduced from a high temperature to a low temperature.

[0004] Among the current methods for removing residual heat after a nuclear power plant reactor shutdown, there are the following three existing technologies:

[0005] Existing technology 1: Waste heat removal under normal operating conditions: SG heat removal is used in the high-temperature stage, and normal waste heat removal system is used in the low-temperature stage;

[0006] Waste heat removal during accident operation: During the high-temperature stage, the primary side waste heat removal system is used for heat removal, and during the low-temperature stage, the normal waste heat removal system is used.

[0007] Existing technology 2: Waste heat removal under normal operating conditions: SG heat removal is used in the high-temperature stage, and normal waste heat removal system is used in the low-temperature stage;

[0008] Waste heat removal under accident operating conditions: During the high-temperature stage, SG heat removal or passive waste heat removal on the secondary side is used; during the low-temperature stage, a normal waste heat removal system is used.

[0009] Existing technology 3: Waste heat removal under normal operating conditions: SG heat removal is used in the high temperature stage, the secondary passive waste heat removal system is used in the intermediate temperature stage, and the pressure vessel and core are "immersed" in pool water in the low temperature stage (≤180℃) for heat removal.

[0010] Residual heat removal during accident operation: In the high-temperature stage, passive residual heat removal is carried out on the secondary side; in the low-temperature stage (≤180℃), heat removal is carried out by "immersing" the pressure vessel and core in pool water.

[0011] One drawback of existing passive secondary waste heat removal systems is that they rely on a steam generator as the primary-secondary heat transfer interface, and the system itself also requires a containment heat exchanger located inside the air-cooled tower (or cooling water tank) as the secondary-tertiary heat transfer interface. This results in a total of two layers of thermal resistance, leading to a significant overall thermal resistance and preventing the reactor primary side from being cooled to a sufficiently low temperature. Simulations of reducing the reactor primary side temperature in existing technology 3 show that as the primary side temperature decreases, the temperature difference between the primary and tertiary sides decreases, resulting in a decrease in heat transfer power and a slower rate of temperature reduction. Eventually, after the primary side temperature drops to around 180°C, the temperature can hardly be reduced further due to the small temperature difference. At this point, it is necessary to switch to another waste heat removal system to perform heat removal and cooling on the primary side, such as an active waste heat removal system (normal waste heat removal system) directly connected to the reactor primary side.

[0012] Existing passive residual heat removal devices on the primary side are directly connected to the primary side of the reactor, and these systems have numerous heat exchange tubes. Since these heat exchange tubes are directly connected to the primary side of the reactor, they effectively extend the primary loop boundary, and the thin walls of these tubes increase the risk of primary loop boundary damage.

[0013] In addition, the primary-side waste heat removal system contains a primary loop of radioactive fluid and, compared to the secondary-side passive waste heat removal system, lacks a safety barrier (containment structure), therefore it must be placed inside the containment structure. If the primary-side waste heat removal system is large in size (capacity), it will affect the volume and layout within the containment structure.

[0014] In summary, the existing technology has the following drawbacks:

[0015] 1. Passive waste heat removal cannot be achieved across the entire range of operating conditions. In current nuclear power plants, whether it is Existing Technology 2 or Existing Technology 1, a normal waste heat removal system is configured to achieve waste heat removal in low-temperature conditions (when the primary side temperature is low). This system is an active system.

[0016] 2. The primary side of the reactor cannot be lowered to a lower temperature. In current nuclear power plants, the passive residual heat removal system on the secondary side requires a steam generator as a heat transfer interface, and the system itself also needs to transfer heat to the cooling water tank on the tertiary side through a steam generator as a heat transfer interface. Therefore, there are two layers of heat transfer resistance, and the total thermal resistance is large. Therefore, the primary side of the reactor cannot be lowered to a lower temperature.

[0017] 3. The passive residual heat removal device on the primary side is directly connected to the primary side of the reactor. The total area of ​​the heat exchanger tubes in the passive residual heat removal device on the primary side is relatively large, thus posing a significant risk of primary loop boundary heat exchanger tube damage. These heat exchanger tubes are directly connected to the primary side of the reactor, which is equivalent to extending the primary loop boundary. The more tubes there are, the larger the boundary area becomes, and the greater the risk of primary loop boundary damage.

[0018] 4. The primary-side residual heat removal system contains primary loop radioactive fluid and, compared to the secondary-side passive residual heat removal system, lacks a safety barrier (containment structure). Therefore, it must be placed within the containment structure to enhance the radioactive barrier. Using a primary-side passive residual heat removal device requires a large-volume cooling water tank within the containment structure. If the volume (capacity) of the primary-side residual heat removal system and its cooling water tank increases, it will occupy more space within the containment structure, resulting in a larger containment structure and impacting the arrangement of other systems and equipment within the containment. A larger containment volume also increases construction costs. Summary of the Invention

[0019] The technical problem to be solved by the present invention is to provide a passive waste heat removal system and method for reactors under all operating conditions and in all ranges.

[0020] The technical solution adopted by the present invention to solve its technical problem is: to construct a passive waste heat removal system for reactors under all operating conditions and in all ranges, wherein the reactor is located inside the containment vessel and the reactor is connected to heat pipes and cold pipes, and includes: a primary passive waste heat removal system, a secondary passive waste heat removal system and a control system.

[0021] The primary-side passive waste heat removal system is located inside the containment and includes a primary-side heat exhaust circuit. The two ends of the primary-side heat exhaust circuit are respectively connected to the heat pipe and the cold pipe, and a first valve assembly is provided on the primary-side heat exhaust circuit.

[0022] The secondary passive residual heat removal system is located outside the containment, and includes a secondary heat removal circuit, and a second valve assembly is provided on the secondary heat removal circuit.

[0023] The control system controls the opening and closing of the first valve assembly and the second valve assembly to control the start and stop of the primary passive waste heat removal system and the secondary passive waste heat removal system, respectively, so as to realize the control method of the reactor full-condition full-range passive waste heat removal system under different reactor operating conditions.

[0024] In some embodiments, a steam generator is also included, one end of which is connected to the cold pipe, and the steam generator is connected to a steam outlet line and a water inlet line.

[0025] The two ends of the secondary side exhaust heat circuit are respectively connected to the steam outlet pipeline and the water inlet pipeline.

[0026] In some embodiments, the primary-side passive waste heat removal system includes a first heat exchanger disposed on the primary-side heat removal circuit, and a water exchange tank is provided around the first heat exchanger.

[0027] The height of the water exchange tank relative to the bottom of the containment vessel is higher than the height of the reactor relative to the bottom of the containment vessel.

[0028] In some embodiments, the cross-sectional shape of the water exchange tank matches the shape of the inner wall of the containment vessel to facilitate the transfer of heat from the water exchange tank to the containment vessel wall, and the water exchange tank is provided with vents.

[0029] In some embodiments, the primary side exhaust heat circuit includes a heat exchanger inlet pipeline and a heat exchanger outlet pipeline;

[0030] The heat exchanger inlet pipeline is connected to the first end of the first heat exchanger and the heat pipe.

[0031] The heat exchanger outlet pipeline is connected to the second end of the first heat exchanger and the cold pipe.

[0032] In some embodiments, the first valve assembly includes a first control valve, a second control valve, a third control valve, and a flow valve;

[0033] The first control valve is located on the inlet pipeline of the heat exchanger;

[0034] The second control valve, the third control valve, and the flow valve are respectively located on the heat exchanger outlet pipeline. The second control valve and the third control valve are connected in parallel and then connected in series with the flow valve to jointly regulate the flow rate on the heat exchanger outlet pipeline.

[0035] In some embodiments, the secondary passive waste heat removal system includes an air-cooled tower and a second heat exchanger disposed in the air-cooled tower;

[0036] The air-cooled tower is located outside the containment vessel, and the height of the air-cooled tower relative to the bottom of the containment vessel is higher than the height of the reactor relative to the bottom of the containment vessel.

[0037] In some embodiments, the secondary side exhaust heat circuit includes a steam pipeline and a return water pipeline;

[0038] The steam discharge pipeline is connected to the steam outlet pipeline and the first end of the second heat exchanger.

[0039] The return water pipeline is connected to the inlet water pipeline and the second end of the second heat exchanger.

[0040] In some embodiments, the second valve assembly includes a fourth control valve disposed on the steam outlet line and a fifth control valve disposed on the return water line;

[0041] When the control system starts the secondary passive waste heat removal system, the fourth control valve and the fifth control valve open.

[0042] In some embodiments, a water supply line is connected between the steam discharge line and the water return line;

[0043] A water supply tank is provided on the water supply pipeline, and the water supply tank is used to supply water to the secondary passive waste heat discharge system;

[0044] A sixth control valve is provided between the water supply tank and the return water pipeline;

[0045] A seventh control valve is provided between the water supply tank and the steam removal pipeline.

[0046] In some embodiments, the steam generator is further provided with a main pump and a drive motor connected to the main pump, and the heat pipe is provided with a voltage regulator.

[0047] In this embodiment, a passive waste heat removal method for reactors operating under all conditions and within the entire range is also constructed and applied to the aforementioned passive waste heat removal system for reactors operating under all conditions and within the entire range. The method includes the following steps:

[0048] Step S1: Establish a passive waste heat removal system for the reactor under all operating conditions and within the entire range;

[0049] Step S2: Based on the different operating conditions and states of the reactor, the primary side passive residual heat removal system and the secondary side passive residual heat removal system are started and stopped by the control system to complete the removal of reactor residual heat.

[0050] In some embodiments, in step S2, when the reactor is in normal operation and the reactor condition is a hot shutdown condition, the control system controls the secondary passive residual heat removal system to start.

[0051] When the reactor is in a safe shutdown condition, the control system controls the activation of the secondary passive residual heat removal system.

[0052] When the reactor is in a transitional operating condition, the control system controls the primary-side passive residual heat removal system to start.

[0053] When the reactor is in refueling mode, the water from the refueling tank is directly injected into the reactor.

[0054] In some embodiments, in step S2, based on the reactor being in an accident operation, when the reactor operating condition is a hot shutdown condition, the control system controls the secondary side passive residual heat removal system to start.

[0055] When the reactor is in a safe shutdown condition, the control system controls the activation of the secondary passive residual heat removal system.

[0056] When the reactor is in a transitional operating condition, the control system controls the primary-side passive residual heat removal system to start.

[0057] In some embodiments, the hot shutdown condition is when the reactor reactivity is less than 0.99 and the primary side temperature of the reactor is 300°C;

[0058] The safe shutdown condition is when the reactor reactivity is less than 0.99 and the primary side temperature of the reactor is greater than 180°C and less than 300°C.

[0059] The transition condition is when the reactor reactivity is less than 0.95 and the primary side temperature of the reactor is greater than 80°C and less than or equal to 180°C.

[0060] The refueling condition is when the reactor reactivity is less than 0.95 and the primary side temperature of the reactor is greater than or equal to 20°C and less than or equal to 80°C.

[0061] Implementing this invention offers the following advantages: The reactor's full-condition, full-range passive residual heat removal system and method utilize a passive residual heat removal system for all operating conditions. This invention proposes dividing residual heat removal into three stages, employing different passive systems for each stage. This reduces the heat transfer area of ​​the primary-side passive residual heat removal system, thus lowering the risk of heat exchanger tube damage and preventing leakage of radioactive primary coolant from its boundaries. Furthermore, it significantly increases the volume of the primary-side passive residual heat removal system and reduces the volume of the containment water tank, lowering construction costs. Attached Figure Description

[0062] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort. In the drawings:

[0063] Figure 1 These are schematic diagrams illustrating different heat dissipation methods under different operating conditions and stages in the prior art and this embodiment;

[0064] Figure 2This is a schematic diagram of the passive waste heat removal system for reactors under all operating conditions and in all ranges, as shown in some embodiments of the present invention.

[0065] Figure 3 This is a schematic diagram of the primary-side passive waste heat removal system in some embodiments of the present invention;

[0066] Figure 4 This is a schematic diagram of the secondary-side passive waste heat removal system in some embodiments of the present invention;

[0067] Figure 5 These are schematic diagrams illustrating the use of the reactor full-condition, full-range passive waste heat removal system under different operating conditions in some embodiments of the present invention. Detailed Implementation

[0068] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on this invention.

[0069] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0070] Please see Figures 2 to 4This is a passive waste heat removal system for reactors operating under all conditions and in all ranges, as described in some embodiments of the present invention. It is used to remove waste heat from reactor 4 during normal operation and accident operation. Reactor 4 is located within containment 5 and is connected to heat pipe 41 and cold pipe 42. The system includes a primary-side passive waste heat removal system 1, a secondary-side passive waste heat removal system 2, a steam generator 3, and a control system. The primary-side passive waste heat removal system 1 is located within containment 5 and includes a primary-side heat exhaust circuit, with both ends connected to the heat pipe. 41 is connected to cold pipe 42, and a first valve assembly 15 is provided on the primary side heat exhaust circuit. The secondary side passive residual heat exhaust system 2 is located outside the containment 5, and includes a secondary side heat exhaust circuit, on which a second valve assembly 26 is provided. The control system controls the opening and closing of the first valve assembly 15 and the second valve assembly 26 to control the start and stop of the primary side passive residual heat exhaust system 1 and the secondary side passive residual heat exhaust system 2 respectively, so as to realize the control method of the passive residual heat exhaust system under different operating conditions of the reactor 4. Figure 1 The diagram shows different heat dissipation methods under different operating conditions and stages in the prior art and this embodiment.

[0071] Understandably, the primary-side passive waste heat removal system 1 is used to remove reactor waste heat in the first temperature range, and the secondary-side passive waste heat removal system 2 is connected to the steam generator 3 and is used to remove reactor waste heat in the second temperature range. The first temperature range is 80°C to 180°C, and the second temperature range is 180°C to 300°C.

[0072] Specifically, "full operating condition" refers to both normal operating conditions and accident operating conditions. "Full range" means applicable to the entire range of primary side temperatures from high to low. This reactor full operating condition full range passive residual heat removal system is applicable to both normal residual heat removal systems and accident residual heat removal systems. Specifically, when reactor 4 is operating normally, such as during reactor 4 startup or shutdown, if reactor 4 does not yet have the conditions to transfer heat to the secondary side, such as if the primary loop water level of reactor 4 is too low, or if the secondary side steam power conversion equipment or steam consumption equipment has not yet reached the operating conditions, then the residual heat of reactor 4 will be removed through the reactor 4 normal residual heat removal system. When reactor 4 experiences an unexpected emergency, its normal heat removal pathways, such as heat removal through steam generator 3 and the normal residual heat removal system, are damaged, preventing the normal removal of heat from the primary circuit and core. This results in a high-temperature and high-pressure state on the primary circuit, potentially causing further heating of the core and fuel damage. In this situation, the emergency residual heat removal system is needed to remove heat from the primary circuit and core of reactor 4. Therefore, reactor 4 is equipped with an emergency residual heat removal system for heat removal in such emergency situations. This passive residual heat removal system, which operates under all conditions and within all ranges, can play a crucial role in emergency residual heat removal.

[0073] Among them, the passive residual heat removal system for the reactor under all operating conditions and in all ranges also belongs to the category of passive residual heat removal systems. This passive residual heat removal system refers to a system that does not rely on power sources or active components similar to main pumps, but only on natural driving forces such as natural circulation, gravity, and capillary force to naturally remove heat, ensuring that the reactor core of reactor 4 remains in a cooled state, and has high system reliability.

[0074] In some embodiments, one end of the steam generator 3 is connected to a cooling pipe 42, which is used to convert water into steam using the waste heat transmitted through the cooling pipe 42. The steam generator 3 is connected to a steam outlet pipe 31 and a water inlet pipe 32, and both ends of the secondary side exhaust heat circuit are connected to the steam outlet pipe 31 and the water inlet pipe 32, respectively. Further, the steam generator 3 is also equipped with a main pump 33 and a drive motor connected to the main pump 33. The main pump 33 is used to drive the waste heat transmitted through the cooling pipe 42 into the steam generator 3, and the drive motor is used to drive the main pump 33 to operate.

[0075] Furthermore, such as Figure 3As shown, the primary-side passive waste heat removal system 1 includes a first heat exchanger 12 disposed on the primary-side waste heat loop 13, and a water exchange tank 11 is disposed around the first heat exchanger 12. The primary-side passive waste heat removal system 1 and the steam generator 3 are both disposed in the containment 5. It can be understood that the first heat exchanger 12 can preferably be a passive waste heat removal heat exchanger. The primary-side passive waste heat removal system 1 relies on the natural circulation generated between the cold source of the first heat exchanger 12 and the heat source of the reactor core 4 to drive the reactor primary-side coolant from the heat pipe 41 into the first heat exchanger 12, and then back to the cold pipe 42. The first heat exchanger 12 discharges the waste heat of the reactor 4 into the water exchange tank 11.

[0076] The heat pipe 41 is also equipped with a voltage regulator 411. This voltage regulator 411 stabilizes the power supply voltage, which fluctuates significantly or fails to meet the requirements of electrical equipment, within its set range, ensuring that various circuits or electrical equipment can operate normally under their rated operating voltage. The voltage regulator 411 consists of a voltage regulating circuit, a control circuit, and a servo motor. When the input voltage or load changes, the control circuit samples, compares, and amplifies the signal, then drives the servo motor to rotate, changing the position of the voltage regulator's carbon brushes to ensure the normal operation of the reactor's passive waste heat removal system under all operating conditions and within its entire range.

[0077] Preferably, the height of the water exchange tank 11 relative to the bottom of the containment 5 is higher than the height of the reactor 4 relative to the bottom of the containment 5. Understandably, the water exchange tank 11 is placed inside the containment 5 at a certain height difference relative to the reactor core, which facilitates the formation of a height difference between the first heat exchanger 12 and the core that is conducive to natural circulation, thus ensuring the stability and convenience of the operation of the primary side passive residual heat removal system 1.

[0078] Furthermore, the cross-sectional shape of the water tank 11 matches the shape of the inner wall of the containment 5 to facilitate the transfer of heat from the water tank 11 to the wall of the containment 5, and the water tank 11 is provided with a vent 111 for ventilation and heat dissipation. In this embodiment, the inner wall of the containment 5 is circular, and the top view cross-sectional shape of the water tank 11 is annular, with its outer wall tightly attached to the inner wall of the containment 5 to facilitate the transfer of heat from the water tank 11 to the steel wall of the containment 5, and then further to the air on the outer wall of the containment 5, finally being cooled by the flowing air. In other embodiments, the top view cross-sectional shape of the water tank 11 can be rectangular, elliptical, or other shapes, as long as it matches the shape of the wall of the containment 5; no specific limitation is made here. The side view cross-sectional shape of the water tank 11 is rectangular, and a steel cover can be provided at its top, with the vent 111 provided in the steel cover.

[0079] In some embodiments, the first valve assembly 15 includes a first control valve 131, a second control valve 141, a third control valve 142, and a flow valve 143. The first control valve 131 is located on the heat exchanger inlet pipeline 13, and the second control valve 141, the third control valve 142, and the flow valve 143 are located on the heat exchanger outlet pipeline 14. The second control valve 141 and the third control valve 142 are connected in parallel and then connected in series with the flow valve 143 to jointly regulate the flow rate on the heat exchanger outlet pipeline 14.

[0080] Understandably, the first control valve 131 can be an isolation valve, which remains normally open on the inlet pipeline to maintain the reactor 4 coolant system pressure, ensuring that the first heat exchanger 12 is filled with cryogenic coolant and enhancing the working efficiency of the first heat exchanger 12. Both the second control valve 141 and the third control valve 142 can be pneumatic valves. Furthermore, when the control system activates the primary-side passive residual heat removal system 1, the second control valve 141 and the third control valve 142 open. Understandably, once the primary-side passive residual heat removal system 1 receives a start-up trigger signal, the second control valve 141 and the third control valve 142 automatically open simultaneously. Due to the positional and temperature differences between the first heat exchanger 12 and the reactor 4, a natural circulation head of the reactor 4 coolant can be generated. The heat exchanger inlet pipe 13 and heat exchanger outlet pipe 14 may also be equipped with filters to intercept various contaminants such as abrasive particles generated by the hydraulic components of the primary passive waste heat discharge system 1 during operation. Pressure gauges may also be provided to measure the flow rate and pressure on the heat exchanger inlet pipe 13 and heat exchanger outlet pipe 14.

[0081] Among them, such as Figure 4 As shown, the secondary-side passive residual heat removal system 2 includes an air-cooled tower 21 and a second heat exchanger 22 disposed within the air-cooled tower 21. The air-cooled tower 21 is located outside the containment 5, and the height of the air-cooled tower 21 relative to the bottom of the containment 5 is higher than the height of the reactor 4 relative to the bottom of the containment 5. Understandably, the air-cooled tower 21 being located outside the containment 5 and its installation position higher than the reactor 4 creates a certain height difference between the air-cooled tower 21 and the reactor core, facilitating the formation of a height difference between the second heat exchanger 22 and the reactor core that promotes natural circulation.

[0082] Furthermore, the secondary side exhaust heat loop includes a steam outlet pipeline 23 and a return water pipeline 24. The steam outlet pipeline 23 is connected to the steam outlet pipeline 31 and the first end of the second heat exchanger 22, and the return water pipeline 24 is connected to the water inlet pipeline 32 and the second end of the second heat exchanger 22. Understandably, the secondary side passive waste heat removal system 2 is connected and cooperates with the steam generator 3 to form a natural circulation loop. The steam generator 3 is the heat sink of this loop, and the second heat exchanger 22 is the cold sink of this loop, capable of removing core waste heat from the primary loop of the reactor 4. The core waste heat is conducted to the external cooling water pool of the containment 5 or to the air in the air-cooled tower 21 through the second heat exchanger 22. The cooling water in the pool absorbs heat, heats up, and evaporates.

[0083] In some embodiments, the second valve assembly 26 includes a fourth control valve 231 and a fifth control valve 241. The fourth control valve 231 is provided on the steam outlet line 23, and the fifth control valve 241 is provided on the return water line 24. The fourth control valve 231 and the fifth control valve 241 are preferably electrically controlled valves, which can be used to regulate the flow and pressure on the secondary passive waste heat discharge system 2. When the control system starts the secondary passive waste heat discharge system 2, the fourth control valve 231 and the fifth control valve 241 open, and then the secondary passive waste heat discharge system 2 automatically establishes a natural circulation before starting.

[0084] Furthermore, a water supply line 25 is connected between the steam outlet line 23 and the return water line 24. A water supply tank 251 is installed on the water supply line 25. A sixth control valve 252 is installed between the water supply tank 251 and the return water line 24, and a seventh control valve 253 is installed between the water supply tank 251 and the steam outlet line 23. Understandably, the water supply tank 251 is a tank-type container filled with low-temperature cooling water. Connecting lines are connected to its upper and lower parts; the upper connecting line is connected to the steam outlet line 23, and the lower connecting line is connected to the return water line 24. The water supply tank 251 can be used to replenish water to the passive waste heat discharge system 2 on the secondary side after an accident, so as to avoid water shortage in the device. Both the sixth control valve 252 and the seventh control valve 253 can be electrically controlled valves. The sixth control valve 252 is used to control the opening and closing of the water supply tank 251 to replenish water to the passive waste heat discharge system 2 on the secondary side, and the seventh control valve 253 is used to control the opening and closing of water from the steam pipeline 23 entering the water supply tank 251.

[0085] In this embodiment, a passive residual heat removal method for reactors under all operating conditions and within the full range is also constructed, specifically addressing residual heat removal after reactor shutdown under normal operating conditions and residual heat removal after reactor shutdown under accident conditions (e.g. Figure 5 As shown):

[0086] (1) Residual heat removal after shutdown under normal operating conditions

[0087] Operating mode ① (e.g.) Figure 5 As shown): When the core reactivity is greater than or equal to 0.99 and the primary side temperature of the reactor is about 300°C, the reactor is operating at power and has not been shut down. It only uses the steam generator 3 for heat dissipation, which is not the situation targeted by this patent.

[0088] Operating mode ② (e.g.) Figure 5 (As shown): When the reactor status parameters are within the range of the hot shutdown condition, the control system controls the secondary passive residual heat removal system 2 to start; Operation mode ③: When the reactor condition is the safe shutdown condition, the control system controls the secondary passive residual heat removal system 2 to start; Operation mode ④: When the reactor condition is the transition condition, the control system controls the primary passive residual heat removal system 1 to start; Operation mode ⑤: When the reactor condition is the refueling condition, the water in the refueling tank 11 or the refueling pool is directly injected into the reactor 4.

[0089] (2) Residual heat removal after reactor shutdown under accident conditions

[0090] Operating mode ② (e.g.) Figure 5 (As shown): When the reactor is in a hot shutdown condition, the control system activates the secondary-side passive residual heat removal system 2; Operation mode ③: When the reactor is in a safe shutdown condition, the control system activates the secondary-side passive residual heat removal system 2; Operation mode ④: When the reactor is in a transition condition, the control system activates the primary-side passive residual heat removal system 1. Understandably, in an accident operation, after an emergency shutdown of reactor 4, protection signals such as "high hot section temperature" are triggered. These signals will open the fourth control valve 231 and the fifth control valve 241 of the secondary-side passive residual heat removal system 2, thereby activating the secondary-side passive residual heat removal system 2. The secondary-side passive residual heat removal system 2 removes heat from the primary side of the reactor until the primary side temperature reaches approximately 180°C. Then the operator shuts down the secondary passive residual heat removal system 2 and starts the primary passive residual heat removal system 1. The primary passive residual heat removal system 1 removes heat from the primary side of the reactor until the temperature of the primary side of the reactor reaches about 80°C.

[0091] In the above operating conditions, the hot shutdown condition is when the reactivity of reactor 4 is less than 0.99 and the primary side temperature of the reactor is 300°C; the safe shutdown condition is when the reactivity of reactor 4 is less than 0.99 and the primary side temperature of the reactor is greater than 180°C and less than 300°C; the transition condition is when the reactivity of reactor 4 is less than 0.95 and the primary side temperature of the reactor is greater than 80°C and less than or equal to 180°C; and the refueling condition is when the reactivity of reactor 4 is less than 0.95 and the primary side temperature of the reactor is greater than or equal to 20°C and less than or equal to 80°C.

[0092] To further improve the space utilization rate of the passive waste heat removal system under all operating conditions and range of the reactor, reduce the size of the passive waste heat removal system under all operating conditions and range of the reactor, and improve economic efficiency, it is necessary to determine the power of the first heat exchanger 12, the power of the second heat exchanger 22, the size of the air-cooled tower 21, and the volume of the water exchange tank 11.

[0093] Specifically, the determination of the power of the second heat exchanger 22 needs to consider the maximum heat removal power under the operating conditions of the secondary passive residual heat removal system 2. After an emergency shutdown of reactor 4, the secondary passive residual heat removal system 2 will be started as soon as possible. After the emergency shutdown, reactor 4 can rely on its own cooling heat capacity to accommodate a portion of the reactor 4 residual heat. Therefore, the heat exchange power of the second heat exchanger 22 is preferably 3%FP to 5%FP, where FP is the full power of reactor 4.

[0094] The size of the air-cooled tower 21 needs to be matched with the heat exchange power of the second heat exchanger 22, taking into account the maximum heat dissipation power under its required operating conditions. The heat exchange power requirement of the heat exchanger must be met, i.e., 3% FP to 5% FP.

[0095] Determining the power output of the first heat exchanger 12 requires considering the maximum heat removal power under the operating conditions of the passive residual heat removal system 1 on the primary side. Regardless of whether it's normal or accident operation, the passive residual heat removal system 1 will only be activated after 24 hours, and this system needs to operate for 72 hours before other non-safety-level cooling measures can be implemented. Therefore, the decay heat power 24 hours after reactor shutdown is used as the maximum value across all markets as the design benchmark for the heat exchange power, at which point the core decay heat power is approximately 0.7%FP.

[0096] Determining the volume of the water exchange tank 11 requires considering the duration of the passive residual heat removal system's operation across the entire reactor operating condition and the power required to remove heat. The volume of the water exchange tank 11 is calculated by calculating the decay heat integral over 24 to 72 hours after reactor 4 shutdown, and then further considering the latent and sensible heat of the coolant to obtain the required water volume. Since the primary-side passive residual heat removal system 1 is only used for heat removal during long-term low-temperature operations, its power can be significantly reduced, meaning the first heat exchanger 12 and the water exchange tank 11 can also be significantly smaller.

[0097] Understandably, the beneficial effects of this passive waste heat removal system across all operating conditions and ranges of the reactor are:

[0098] 1. Passive waste heat removal is achieved across all operating conditions and ranges. A passive waste heat removal system is employed for all operating conditions. In this embodiment, waste heat removal is divided into three stages, each using a different passive system.

[0099] 2. In this embodiment, the primary side passive residual heat removal system 1 is only used to perform residual heat removal under lower conditions. At this time, the core residual heat is relatively small, so the volume capacity of the primary side passive residual heat removal system 1 and the volume of the cooling water tank in the containment can be greatly reduced, the total area of ​​the heat exchanger heat transfer tubes can be greatly reduced, and the risk of primary loop boundary damage can be greatly reduced.

[0100] 3. In this embodiment, the volume of the passive waste heat removal system 1 on the primary side is greatly reduced, which can greatly reduce the volume of the water tank inside the containment 5, thereby helping to reduce the volume of the containment 5 and reduce construction costs.

[0101] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A reactor full-power full-range passive residual heat removal method applied to a reactor full-power full-range passive residual heat removal system, characterized in that, The reactor full-condition, full-range passive waste heat removal system includes a primary-side passive waste heat removal system (1), a secondary-side passive waste heat removal system (2), and a control system. The reactor full-condition, full-range passive waste heat removal method includes the following steps: Step S1: Establish a passive waste heat removal system for the reactor under all operating conditions and within the entire range; Step S2: Based on the different operating conditions and running status of the reactor (4), the primary side passive residual heat removal system (1) and the secondary side passive residual heat removal system (2) are controlled by the control system to complete the removal of residual heat from the reactor (4); In step S2, when the reactor (4) is in normal operation, the control system controls the secondary passive residual heat removal system (2) to start when the reactor (4) is in hot shutdown condition. When the reactor (4) is in a safe shutdown condition, the control system controls the secondary passive residual heat removal system (2) to start. When the reactor (4) is in a transitional operating condition, the control system controls the primary side passive residual heat removal system (1) to start. When the reactor (4) is in refueling mode, the water in the water tank (11) is directly injected into the reactor (4); In step S2, based on the reactor (4) being in an accident operation, when the reactor (4) is in a hot shutdown condition, the control system controls the secondary passive residual heat removal system (2) to start. When the reactor (4) is in a safe shutdown condition, the control system controls the secondary passive residual heat removal system (2) to start. When the reactor (4) is in a transitional operating condition, the control system controls the primary side passive residual heat removal system (1) to start.

2. The method for passively removing residual heat from a reactor under all operating conditions and within the entire range according to claim 1, characterized in that, The hot shutdown condition is when the reactivity of the reactor (4) is less than 0.99 and the primary side temperature of the reactor (4) is 300°C; The safe shutdown condition is that the reactivity of the reactor (4) is less than 0.99 and the primary side temperature of the reactor (4) is greater than 180°C and less than 300°C; The transition condition is that the reactivity of the reactor (4) is less than 0.95 and the primary side temperature of the reactor (4) is greater than 80°C and less than or equal to 180°C; The refueling condition is that the reactivity of the reactor (4) is less than 0.95 and the primary side temperature of the reactor (4) is greater than or equal to 20°C and less than or equal to 80°C.

3. The reactor full duty full range passive residual heat removal method according to claim 1, characterized in that, The reactor (4) is connected to a heat pipe (41) and a cold pipe (42). The primary-side passive residual heat removal system (1) is located inside the containment (5) and includes a primary-side heat removal circuit. The two ends of the primary-side heat removal circuit are respectively connected to the heat pipe (41) and the cold pipe (42), and a first valve assembly (15) is provided on the primary-side heat removal circuit. The secondary passive residual heat removal system (2) is located outside the containment (5), and includes a secondary heat removal circuit, and a second valve assembly (26) is provided on the secondary heat removal circuit. The control system controls the opening and closing of the first valve assembly (15) and the second valve assembly (26) to control the start and stop of the primary passive waste heat removal system (1) and the secondary passive waste heat removal system (2) respectively, so as to realize the control method of the passive waste heat removal system of the reactor under different operating conditions of the reactor (4) in the full range of the reactor.

4. The reactor full duty full range passive residual heat removal method according to claim 3, characterized in that, It also includes a steam generator (3), one end of which is connected to the cold pipe (42), and the steam generator (3) is connected to a steam outlet pipe (31) and a water inlet pipe (32). The two ends of the secondary side exhaust heat circuit are connected to the steam outlet pipeline (31) and the water inlet pipeline (32), respectively.

5. The reactor full duty full range passive residual heat removal method according to claim 4, characterized in that, The primary side passive waste heat discharge system (1) includes a first heat exchanger (12) provided on the primary side heat discharge circuit, and a water exchange tank (11) is provided around the first heat exchanger (12). The height of the water exchange tank (11) relative to the bottom of the containment vessel (5) is higher than the height of the reactor (4) relative to the bottom of the containment vessel (5).

6. The reactor full duty full range passive residual heat removal method according to claim 5, characterized in that, The cross-sectional shape of the water exchange tank (11) matches the shape of the inner wall of the containment vessel (5) so as to transfer the heat of the water exchange tank (11) to the containment vessel wall, and the water exchange tank (11) is provided with a vent (111).

7. The full-power, full-range, passive residual heat removal method of claim 5, wherein, The primary side exhaust heat circuit includes a heat exchanger inlet pipeline (13) and a heat exchanger outlet pipeline (14). The heat exchanger inlet line (13) is connected to the first end of the first heat exchanger (12) and the heat pipe (41). The heat exchanger outlet pipeline (14) is connected to the second end of the first heat exchanger (12) and the cold pipe (42).

8. The reactor full duty full range passive residual heat removal method according to claim 7, characterized in that, The first valve assembly (15) includes a first control valve (131), a second control valve (141), a third control valve (142), and a flow valve (143). The first control valve (131) is located on the inlet pipeline (13) of the heat exchanger; The second control valve (141), the third control valve (142), and the flow valve (143) are respectively located on the heat exchanger outlet pipeline (14). The second control valve (141) and the third control valve (142) are connected in parallel and then connected in series with the flow valve (143) to jointly regulate the flow rate on the heat exchanger outlet pipeline (14).

9. The reactor full duty full range passive residual heat removal method according to claim 8, characterized in that, The secondary passive waste heat removal system (2) includes an air-cooled tower (21) and a second heat exchanger (22) disposed in the air-cooled tower (21). The air-cooled tower (21) is located outside the containment vessel (5), and the height of the air-cooled tower (21) relative to the bottom of the containment vessel (5) is higher than the height of the reactor (4) relative to the bottom of the containment vessel (5).

10. The method for passively removing residual heat from a reactor under all operating conditions and within the entire range according to claim 9, characterized in that, The secondary side exhaust heat circuit includes a steam pipeline (23) and a return water pipeline (24). The steam discharge line (23) is connected to the steam outlet line (31) and the first end of the second heat exchanger (22); The return water line (24) is connected to the inlet water line (32) and the second end of the second heat exchanger (22).

11. The method for passively removing residual heat from a reactor under all operating conditions and within the entire range according to claim 10, characterized in that, The second valve assembly (26) includes a fourth control valve (231) disposed on the steam outlet line (23) and a fifth control valve (241) disposed on the return water line (24). When the control system starts the secondary passive waste heat discharge system (2), the fourth control valve (231) and the fifth control valve (241) open.

12. The reactor full duty full range passive residual heat removal method according to claim 11, characterized in that, A water supply line (25) is connected between the steam outlet line (23) and the return water line (24); The water supply pipeline (25) is equipped with a water supply tank (251), which is used to supply water to the secondary passive waste heat discharge system (2). A sixth control valve (252) is provided between the water supply tank (251) and the return water pipeline (24); A seventh control valve (253) is provided between the water supply tank (251) and the steam discharge pipeline (23).

13. The method for passively removing residual heat from a reactor under all operating conditions and within the entire range according to claim 4, characterized in that, The steam generator (3) is also equipped with a main pump (33) and a drive motor connected to the main pump (33), and the heat pipe (41) is equipped with a voltage regulator (411).

Images