In-pile natural circulation system applicable to wide working condition of pool type fast reactor

Abstract

The invention belongs to the field of waste heat removal of sodium-cooled fast reactors, and particularly relates to a pool-type fast reactor in-reactor natural circulation system applicable to wide working conditions, which comprises a cold pool independent heat exchanger, a cold pool independent heat exchanger, a heat exchanger and a heat exchanger, the in-pile supporting lower plate is arranged in the bottom area of the cold pool, the in-pile supporting lower plate and the bottom of the large grid plate header form an isolation surface, and the cold pool is divided into an upper cold pool and a lower cold pool; the in-reactor supporting lower plate throttling element is arranged at the bottom of the in-reactor supporting lower plate; the large grid tray header throttling element is arranged at the bottom of the large grid tray header; when a coolant in a fuel assembly box in a reactor core is heated and ascends to enter the hot pool, the coolant cooled by the cold pool independent heat exchanger sinks to the bottom of the upper cold pool and enters the reactor core fuel assembly box through the in-reactor supporting lower plate throttling element, the large grid tray header throttling element, the large grid tray header and the small grid tray header, and flowing in the fuel assembly box is formed. According to the invention, the nuclear fuel can be well cooled all the time under the wide working condition, and the safety and the operability of the reactor are effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of sodium-cooled fast reactor waste heat removal, and in particular relates to a natural circulation system in a pool-type fast reactor applicable to a wide range of working conditions. Background Art

[0002] In the design of pool-type fast reactors, natural circulation is significantly different from the loop system and is a semi-open natural circulation. In the heating area of ​​the fuel assembly, the flow of the coolant can be approximated as a one-dimensional flow, while in other areas it manifests as a large-space three-dimensional flow, which is a typical heat source-driven natural circulation. In this natural circulation mode, the coolant in the cold source cooling pool, such as the sodium flow, affects the temperature field and thermal stratification interface in the pool, thereby affecting the cold end driving force of the natural circulation. Therefore, how to arrange the cold source position and how to ensure that the natural circulation driving force in the reactor can bring out the heat of the core and maintain the low temperature state of the core are problems that need to be solved urgently in this field.

[0003] In a liquid metal cooled pool fast reactor, when the reactor is shut down due to an accident and the main heat transfer system is unavailable, a special accident residual heat removal system is required to replace the main heat transfer system to remove the residual heat from the core, and it is expected that the accident residual heat removal system will immediately perform heat removal when the core loses forced circulation. The requirement for high timeliness of the accident residual heat removal system makes it difficult for the reactor to achieve the high reliability goal of natural circulation residual heat removal. Pool-type reactors have good inherent safety due to their design characteristics, such as the core being immersed in a large amount of coolant. How to give full play to this advantage and ensure that after the reactor is shut down under abnormal operating conditions, design benchmark accident conditions, and severe accident conditions, the core can still be well cooled through a high-reliability natural circulation method under residual heating conditions is also a problem that needs to be solved urgently in this field. Summary of the invention

[0004] The object of the present invention is to provide a natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions. The system can ensure that the nuclear fuel of the reactor is always well cooled from normal operating conditions, abnormal conditions deviating from normal operation to design basis accident conditions and severe accident conditions (wide operating conditions include: normal operating conditions, abnormal conditions deviating from normal operation, design basis accident conditions and severe accident conditions) by arranging a reasonable cold source space layout, an economically acceptable core immersion depth, and a natural circulation flow channel throttling member (a throttling member on a lower plate of an in-core support), thereby effectively improving the safety and operability of the reactor.

[0005] The technical solution to achieve the purpose of the present invention is: A natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions, the system comprising: The cold pool independent heat exchanger is arranged in the cold pool; The lower plate of the pile support is arranged at the bottom area of ​​the cold pool. The lower plate of the pile support and the bottom of the large grid plate header form an isolation surface to separate the cold pool into an upper cold pool and a lower cold pool. The throttling member of the lower plate of the in-pile support is arranged at the bottom of the lower plate of the in-pile support; The throttling element of the large grid plate header is arranged at the bottom of the large grid plate header; When the coolant in the fuel assembly box in the core is heated and rises into the hot pool, a low-pressure area is formed in the lower cold pool connected to the throttling piece of the large grid plate header. The coolant cooled by the independent heat exchanger of the cold pool sinks to the bottom of the upper cold pool, passes through the throttling piece of the lower plate of the in-core support, the lower cold pool, the throttling piece of the large grid plate header, the large grid plate header, and the small grid plate header, and enters the core fuel assembly box, forming an in-box flow source of the flow channel of the throttling piece of the lower plate of the in-core support.

[0006] Furthermore, the system also includes: a heat pool independent heat exchanger, which is arranged in the heat pool; when the coolant between the fuel assembly boxes in the core is heated and rises into the heat pool, the coolant enters the heat pool independent heat exchanger, and the coolant flowing through the heat pool independent heat exchanger for cooling is sucked into the core box area from the top of the peripheral assembly connected to the fuel assembly, and the coolant reaches the lower position between the boxes from the peripheral assembly from top to bottom, passes through the core shroud opening at the lower part of the core shroud, and is laterally sucked into the fuel assembly box area, forming an inter-box flow from the reverse flow channel between the peripheral assembly boxes of the core.

[0007] Furthermore, the system also includes: an intermediate heat exchanger, which is arranged between the hot pool and the cold pool; when the coolant in the fuel assembly box in the core is heated and rises to enter the hot pool, the coolant enters the intermediate heat exchanger, and the coolant cooled by the intermediate heat exchanger enters the upper cold pool, enters the large grid plate header and the small grid plate header through the high-pressure pipe or the large grid plate header throttling piece of the lower cold pool, and enters the fuel assembly box of the core, forming an in-box flow source of the intermediate heat exchanger flow channel.

[0008] Furthermore, the system also includes a stack container cooling system, and the stack container cooling system includes: Shielding plates are arranged in the upper peripheral area of ​​the upper cold pool, and the shielding plates and the lower supporting plates in the reactor form an isolation surface; An isolation plate is arranged in the upper peripheral area of ​​the upper cold pool, and the isolation plate is located between the periphery of the cold pool independent heat exchanger and the shielding plate; The inlet throttling device of the container cooling system is arranged on the upper part of the shielding plate; The outlet throttling device of the container cooling system is arranged between the lower part of the isolation plate and the shielding plate; An ascending channel is formed between the shielding plate and the stack container, and a descending channel is formed between the isolation plate and the shielding plate; The stack container relies on the cold source formed by the heat dissipation on the outside of the stack container and the heat source formed by the high-temperature sodium pool on the inside for natural circulation; the coolant enters the core fuel assembly box through the outlet throttling device of the stack container cooling system, the descending channel of the stack container cooling system, the inlet throttling device of the stack container cooling system, the ascending channel of the stack container cooling system, the lower cold pool, the large grid plate header throttling device, the large grid plate header, and the small grid plate header, forming an in-box flow source of the reverse flow channel of the stack container cooling system.

[0009] Furthermore, the resistance coefficient of the throttling element of the lower plate of the in-stack support is as follows: the resistance in the natural circulation flow direction decreases, and the resistance in the forced flow direction increases.

[0010] Furthermore, there are a plurality of throttling members on the in-pile support lower plate, and the plurality of throttling members on the in-pile support lower plate are arranged at intervals at the bottom of the in-pile support lower plate.

[0011] Furthermore, the cold pool independent heat exchanger is arranged on the upper part of the cold and hot pool partitions.

[0012] Furthermore, the hot and cold pool baffles are arranged at a position higher than the upper edge of the heating section of the core.

[0013] Furthermore, the heat pool independent heat exchanger is arranged in the inner peripheral area of ​​the heat pool.

[0014] Furthermore, the number of cold pool independent heat exchangers arranged is 1 to 2, and the number of hot pool independent heat exchangers arranged is 1 to 2.

[0015] The beneficial technical effects of the present invention are: 1. The present invention can ensure that under transient conditions deviating from normal operation, in the residual heat extraction stage after shutdown, the core outlet temperature can be kept lower than the operating safety limit by natural circulation alone, without the need to maintain the circulating operation of the pump, thereby avoiding a large thermal shock to the reactor vessel and the components inside the reactor, by arranging the hot pool independent heat exchanger, the cold pool independent heat exchanger, the reactor support lower plate throttling device, and the main container cooling system throttling device (the reactor container cooling system inlet throttling device, the reactor container cooling system outlet throttling device).

[0016] 2. The present invention can ensure reliable cooling of the core and prevent serious damage to the core under design basis accidents and severe accident conditions by arranging a hot pool independent heat exchanger, a cold pool independent heat exchanger, a throttling device for the lower plate of the in-core support, and a throttling device for the main container cooling system (a throttling device for the inlet of the container cooling system and a throttling device for the outlet of the container cooling system).

[0017] 3. The present invention arranges the hot and cold pool partitions at a position higher than the upper edge of the heating section of the core, thereby ensuring that in the event of a serious accident where the core is seriously damaged, the damaged core or the molten material that falls to the lower part is kept cooled, thereby ensuring the integrity of the reactor vessel and preventing a large amount of radioactive material from being released to the outside; and by arranging the cold pool independent heat exchanger at the upper part of the hot and cold pool partitions, it ensures that when the molten fuel of the core migrates to the cold pool at the same height in the event of a serious accident, the cold pool independent heat exchanger at a high position will not be damaged. At this time, the cold pool independent heat exchanger can still cool the molten fuel by natural circulation, thereby reducing the consequences of a serious reactor accident.

[0018] 4. The present invention can ensure the cooling of the core under normal operating conditions by setting up the intermediate heat exchanger and the main pump.

[0019] 5. The present invention arranges cold sources such as the hot pool independent heat exchanger and the cold pool independent heat exchanger at a higher position, that is, arranges the hot pool independent heat exchanger and the cold pool independent heat exchanger on the upper part of the hot and cold pool partition, so as to cool down the high-temperature coolant flowing to a high position through natural circulation, and more effectively extract the sensible heat in the reactor; at the same time, the hot pool independent heat exchanger and the cold pool independent heat exchanger are arranged at a position far away from the core outlet, that is, arranged in the peripheral area of ​​the hot pool or the cold pool, so as to avoid the outflowing high-density low-temperature coolant from forming a "cold cover" in the core outlet area, thereby weakening the natural circulation capacity.

[0020] 6. The present invention arranges the hot and cold pool partitions at a position higher than the upper edge of the heating section of the core so that the core is completely immersed in the cold pool, thereby ensuring that the low temperature state of the core is maintained for a long time, and avoiding the fact that the natural circulation driving force in the reactor under the natural circulation flow state is insufficient to bring out enough core residual heat due to insufficient core immersion depth (from the time constant point of view, the core part has a smaller heat capacity and a faster temperature change; while the coolant and metal structural parts in the open space part have a larger mass and a slower temperature change), resulting in a rapid increase in the core inlet and outlet temperature and the core outlet temperature, and raising the overall core temperature.

[0021] 7. The present invention designs the resistance coefficient of the throttling member of the lower plate of the in-core support to ensure that the natural circulation flow in the core box can be increased during natural circulation flow under accident conditions (abnormal conditions deviating from normal operation to design basis accident conditions and severe accident conditions), while the normal operation of the reactor is not affected during forced circulation under normal operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of natural circulation in a pool-type fast reactor applicable to a wide range of operating conditions provided by the present invention. Figure 1 The direction of the middle arrow indicates the main flow channel of natural circulation; Figure 2This is a schematic diagram of forced circulation in a pool-type fast reactor applicable to a wide range of operating conditions provided by the present invention. Figure 2 The direction of the arrow in the middle indicates the forced circulation flow channel.

[0023] In the figure: 1-main pump; 2-core shroud; 3-core; 4-throttling device of the lower plate of the inner support; 5-large grid plate header; 6-small grid plate header; 7-independent heat exchanger of the hot pool; 8-independent heat exchanger of the cold pool; 9-intermediate heat exchanger; 10-inner support lower plate; 11-upper cold pool; 12-lower cold pool; 13-cold and hot pool partition. 14-central measuring column; 15-hot pool; 16-high pressure pipe; 17-reservoir cooling system; 18-throttling device of the large grid plate header; 19-opening of the core shroud; 20-throttling device of the outlet of the reservoir cooling system; 21-throttling device of the inlet of the reservoir cooling system. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] like Figure 1-2 As shown, the present invention provides a natural circulation system for a pool-type fast reactor applicable to a wide range of working conditions, comprising: a main pump 1, a core shroud 2, a core 3, a throttling device 4 for the lower plate of the in-core support, a large grid plate header 5, a small grid plate header 6, an independent heat exchanger for the hot pool 7, an independent heat exchanger for the cold pool 8, an intermediate heat exchanger 9, a lower plate of the in-core support 10, an upper cold pool 11, a lower cold pool 12, a partition between the hot and cold pools 13, a central measuring column 14, a hot pool 15, a high-pressure pipe 16, a reactor container cooling system 17, a throttling device 18 for the large grid plate header, a core shroud opening 19, an outlet throttling device 20 for the reactor container cooling system, and an inlet throttling device 21 for the reactor container cooling system.

[0026] The heat pool independent heat exchanger 7 is arranged in the peripheral area of ​​the heat pool 15, and is used to cool the peripheral area of ​​the heat pool 15, reduce the inlet temperature of the coolant entering the fuel assembly box of the core 3, and increase the flow rate of the flow entering the fuel assembly box of the core 3.

[0027] The cold pool independent heat exchanger 8 is arranged in the cold pool to cool the upper area of ​​the cold pool, reduce the coolant inlet temperature entering the fuel assembly box of the core 3, and increase the flow rate of the coolant entering the fuel assembly box of the core 3.

[0028] The intermediate heat exchanger 9 is arranged between the hot pool 15 and the cold pool to cool the hot coolant in the hot pool, reduce the coolant inlet temperature entering the fuel assembly box of the core 3, and increase the flow rate entering the fuel assembly box of the core 3.

[0029] The lower support plate 10 in the pile is arranged at the bottom area of ​​the cold pool. The lower support plate 10 in the pile and the bottom of the large grid plate header 5 form an isolation surface to separate the cold pool into an upper cold pool 11 and a lower cold pool 12 .

[0030] An in-pile support lower plate throttling member 4 is provided at the bottom of the in-pile support lower plate 10 ; a large grid plate header throttling member 18 is provided at the bottom of the large grid plate header 5 .

[0031] When the coolant between the fuel assembly boxes in the core 3 is heated and rises into the heat pool 15, a low-pressure area is formed between the fuel assembly boxes in the core 3, and the coolant enters the heat pool independent heat exchanger 7. The coolant flowing through the heat pool independent heat exchanger 7 is cooled, and the cold coolant flowing out of the heat pool independent heat exchanger 7 is sucked into the area between the boxes of the core 3 from the top of the peripheral assembly connected to the fuel assembly. The coolant reaches the lower position between the boxes from the peripheral assembly from top to bottom, passes through the core shroud opening 19 at the lower part of the core shroud 2, and is then laterally sucked into the area between the fuel assembly boxes for coolant replenishment. Here, the reverse flow channel between the boxes of the peripheral assembly of the core 3 becomes the source of the flow between the boxes, forming the flow between the boxes.

[0032] At the same time, when the coolant in the fuel assembly box in the core 3 is heated and rises into the hot pool 15, the large grid header 5 and the small grid header 6 at the entrance of the core 3 form a low-pressure area, and the high-pressure pipe 16 and the large grid header throttle 18 connected to the large grid header 5 will replenish the coolant according to the pressure situation. Then, the upper cold pool 11 connected to the high-pressure pipe 16 forms a low-pressure area, and then the hot sodium inside the intermediate heat exchanger 9 is cooled by the cold sodium in the cold pool outside the lower part of the heat exchanger and enters the upper cold pool 11 for flow replenishment. Here, the flow channel of the intermediate heat exchanger becomes the flow source in the fuel assembly box of the core 3, forming the flow in the box. Its specific flow channel is: the hot sodium in the intermediate heat exchanger 9 is cooled and enters the upper cold pool 11, and then enters the large grid header 5 and the small grid header 6 through the high-pressure pipe 16 or the large grid header throttle 18 of the lower cold pool 12, and finally enters the fuel assembly box of the core 3.

[0033] At the same time, when the coolant in the fuel assembly box in the core 3 is heated and rises into the hot pool 15, the lower cold pool 12 connected to the large grid plate header throttling piece 18 forms a low-pressure area, and the coolant cooled by the cold pool independent heat exchanger 8 sinks to the bottom of the upper cold pool 11, enters the lower cold pool 12 through the throttling piece 4 of the lower plate in the stack, and is sucked into the large grid plate header 5 and the small grid plate header 6 at the entrance of the core 3 through the large grid plate header throttling piece 18 at the bottom of the large grid plate header 5, and finally enters the fuel assembly box of the core 3. Here, the throttling piece flow channel of the lower plate in the stack becomes the source of the flow in the fuel assembly box of the core 3, forming the flow in the box. The setting of the throttling piece flow channel of the lower plate in the stack further increases the flow in the box and reduces the inlet temperature of the flow in the box.

[0034] like Figure 1-2As shown, the stack container cooling system 17 is provided with an isolation plate and a shielding plate, which are arranged in the upper peripheral area of ​​the upper cold pool 11, and the shielding plate and the lower support plate 10 in the stack form an isolation surface. The isolation plate is located between the periphery of the cold pool independent heat exchanger 8 and the shielding plate (similarly, the isolation plate is located between the periphery of the main pump 1 and the shielding plate); an ascending channel is formed between the shielding plate and the stack container, and a descending channel is formed between the isolation plate and the shielding plate; an inlet throttling device 21 of the stack container cooling system is provided on the upper part of the shielding plate, and an outlet throttling device 20 of the stack container cooling system is provided radially between the lower part of the isolation plate and the shielding plate.

[0035] Regardless of natural circulation or forced circulation, the reactor vessel cooling system 17 can ensure that the flow channel of the reactor vessel cooling system always maintains the coolant flow rate, ensuring that the reactor main vessel is in a cooling state.

[0036] like Figure 2 As shown, under the forced circulation condition, the flow of the reactor vessel cooling system is maintained by the pressure head of the primary pump 1, the large grid plate header throttling piece 18, the reactor vessel cooling system inlet throttling piece, and the reactor vessel cooling system outlet throttling piece. The coolant in the lower area of ​​the upper cold pool 11 enters the lower cold pool 12 through the large grid plate header throttling piece 18, and then enters the ascending channel of the reactor vessel cooling system 17, enters the descending channel of the reactor vessel cooling system 17 through the reactor vessel cooling system inlet throttling piece, and then returns to the upper area of ​​the upper cold pool 11 through the reactor vessel cooling system outlet throttling piece. Here, the forward flow channel of the reactor vessel cooling system constitutes a coolant circulation loop of the reactor vessel cooling system under forced circulation, ensuring that the flow channel of the reactor vessel cooling system always maintains the coolant flow and ensures that the reactor main vessel is in a cooling state.

[0037] like Figure 1As shown, under the natural circulation condition, the primary pump 1 of the primary circuit stops operating, and the reactor container cooling system loses forced circulation. At this time, the reactor container relies on the cold source formed by the heat dissipation outside the reactor container and the heat source formed by the high-temperature sodium pool inside to maintain cooling through natural circulation flow. After losing the forced circulation flow, the coolant in the rising channel of the reactor container cooling system 17 cools down due to the heat dissipation of the reactor container, and the density increases and begins to sink; at the same time, the coolant in the descending channel of the reactor container cooling system 17 is heated by the high-temperature coolant in the heat pool, and the density decreases and begins to rise. Subsequently, the flow direction of the coolant in the reactor container cooling system 17 is reversed, and the cold coolant in the upper area of ​​the upper cold pool 11 enters the descending channel of the reactor container cooling system 17 through the reactor container cooling system outlet throttling device, and then enters the rising channel of the reactor container cooling system 17 through the reactor container cooling system inlet throttling device, and then enters the lower cold pool 12, and then is sucked into the grid header 5 and the small grid header 6 through the large grid header throttling device 18, and finally enters the fuel assembly box of the core 3. Here, the reverse flow channel of the reactor vessel cooling system becomes the flow source of the fuel assembly box of the core 3, forming an in-box flow, ensuring that the flow channel of the reactor vessel cooling system always maintains the coolant flow rate and ensures that the reactor main container is in a cooling state.

[0038] In summary, the in-box flow in the reactor includes three flow sources, namely the intermediate heat exchanger flow, the throttling device flow under the support plate in the reactor, and the reverse flow of the reactor vessel cooling system; the inter-box flow includes one flow source, which is the reverse flow between the core peripheral components. Under the natural circulation state, the sodium flows in the in-box flow channel and the inter-box flow channel are coordinated with each other to work together to remove the heat from the core.

[0039] The cold pool independent heat exchanger 8 cooperates with the throttling member 4 of the lower plate of the support inside the reactor to form an additional dedicated natural circulation flow channel for the source path of the flow inside the core 3 box.

[0040] Under forced circulation conditions, the coolant circulates through the intermediate heat exchanger flow channel to ensure that the core can be cooled.

[0041] Under natural circulation conditions, coolant circulates through the intermediate heat exchanger flow channel (the cold source is the cold sodium in the outer cold pool at the bottom of the intermediate heat exchanger), the reverse flow channel of the reactor vessel cooling system, the reverse flow channel between the core peripheral component boxes, and the throttling device flow channel under the support plate inside the reactor (i.e., the dedicated natural circulation flow channel) to ensure that the core can be cooled.

[0042] The cold pool independent heat exchanger 8 is arranged on the upper part of the cold and hot pool partition 13 to control the height of the thermal stratification interface in the upper cold pool 11 and prevent the cold pool independent heat exchanger 8 from being damaged by the migration of molten fuel in the event of a serious accident.

[0043] The higher temperature fluid at the upper part of the upper cold pool 11 and near the cold and hot pool partition 13 is sucked into the sleeve of the cold pool independent heat exchanger 8, enters the cold pool independent heat exchanger 8 for cooling, and sinks to the bottom of the upper cold pool 11 after cooling. This process effectively reduces the thermal stratification effect of the upper cold pool 11, and at the same time, by raising the cold source height of the upper cold pool 11, the natural circulation driving force of the flow in the core 3 box is enhanced, thereby increasing the coolant flow from the high-pressure pipe 16 to the large grid header 5, the small grid header 6 and finally entering the core 3 box, while reducing the coolant inlet temperature of the flow in the box; because the cold pool independent heat exchanger 8 is arranged higher than the cold and hot pool partition 13, and the lateral cold and hot pool partition 13 is higher than the core 3, when a serious accident occurs and the core molten fuel migrates to the cold pool at the same height, it will not damage the cold pool independent heat exchanger 8 at a high position. At this time, the cold pool independent heat exchanger 8 can still cool the molten fuel through natural circulation, reducing the consequences of a serious reactor accident.

[0044] The hot and cold pool baffle 13 is arranged at a position higher than the upper edge of the heating section of the core 3. The setting of the position of the hot and cold pool baffle 13 significantly improves the safety and cooling performance of the reactor. First, the high hot and cold pool baffle 13 increases the sodium capacity of the upper cold pool 11, thereby enhancing the inherent safety of the reactor. Under the natural circulation condition of emergency shutdown, this design can maintain a lower core 3 inlet temperature for a longer time, effectively improving the safety of the reactor; secondly, the high hot and cold pool baffle 13 raises the height of the cold pool cold source (cold pool independent heat exchanger 8), increases the natural circulation driving force of the box flow of the core 3, is conducive to forming a stable natural circulation, and enhances the natural circulation cooling capacity of the reactor; thirdly, the heating section of the core 3 is surrounded by the upper cold pool 11. This layout plays a key role in the event of serious accidents such as core fuel melting. If the molten core 3 melts through the longitudinal hot and cold pool baffle 13, it will be surrounded by the cold coolant of the upper cold pool 11, which can effectively reduce the consequences of the accident.

[0045] The installation of the large grid plate header throttling piece 18 and the in-core support lower plate throttling piece 4 is also to cope with the problem of core melt cooling in severe accidents.

[0046] In a specific embodiment, 1 to 2 hot pool independent heat exchangers 7 are arranged at intervals in the hot pool, and 1 to 2 cold pool independent heat exchangers 8 are arranged at intervals in the cold pool.

[0047] In a specific embodiment, the coolant in the stack container is sodium coolant.

[0048] Since the passage from the upper cold pool 11 to the large grid header 5 at the inlet of the core 3, that is, the position of the high-pressure pipe 16 and the pump 1 inlet is relatively high, it is not conducive for the low-temperature coolant in a low position due to the thermal stratification effect of the upper cold pool 11 to enter the large grid header 5. The present invention forms a flow channel of the throttling member of the lower plate of the in-pile support by arranging the throttling member of the lower plate of the in-pile support 4 on the lower plate of the in-pile support 10, as a dedicated natural circulation flow channel. By arranging the cold pool independent heat exchanger 8 at a high position of the upper cold pool 11, and arranging the throttling member of the lower plate of the in-pile support 4 at the bottom of the upper cold pool 11, a high-low position arrangement is formed, so that the cold sodium from the cold pool independent heat exchanger 8 can enter the lower cold pool 12 through the throttling member of the lower plate of the in-pile support 4 after sinking, and then enter the large grid header 5 through the throttling member of the large grid header 18, forming the cooperation of the throttling member flow channel of the lower plate of the in-pile support and the cold pool independent heat exchanger 8, which plays an important role under the natural circulation working condition. In other words, after the cold coolant cooled in the cold pool independent heat exchanger 8 arranged at the top of the upper cold pool 11 sinks down to the bottom of the upper cold pool 11, it is sucked into the large grid header 5 through the throttling piece 4 of the lower plate of the in-pile support at the bottom of the upper cold pool 11 through the lower cold pool 12 and the throttling piece 18 of the large grid header, forming an important source channel of the low-temperature coolant in the box. The resistance design of the throttling piece 4 of the lower plate of the in-pile support should meet the following requirements: in the natural circulation flow direction (from the upper cold pool 11 to the lower cold pool 12), the resistance should be as small as possible to increase the natural circulation flow; in the forced flow direction, from the lower cold pool 12 to the upper cold pool 11, the resistance should be as large as possible to minimize the impact on the forced circulation condition. Through the resistance design of the throttling piece 4 of the lower plate of the in-pile support, the natural circulation of the coolant under the accident condition can be realized, and it is ensured that the reactor can maintain the coolability of the core when only considering this natural circulation flow channel in the box.

[0049] In a specific embodiment, a plurality of in-piles supporting lower plate throttling members 4 are provided at intervals at the bottom of the in-piles supporting lower plate 10 .

[0050] The present invention is described in detail above with reference to the accompanying drawings and embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the field without departing from the purpose of the present invention. The contents not described in detail in the present invention can adopt the existing technology.

Claims

1. A natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions, characterized in that: The system comprises: A cold pool independent heat exchanger (8) is arranged in the cold pool; The lower plate (10) for supporting the pile is arranged at the bottom area of ​​the cold pool. The lower plate (10) for supporting the pile and the bottom of the large grid plate header (5) form an isolation surface, isolating the cold pool into an upper cold pool (11) and a lower cold pool (12); The in-pillar support lower plate throttling member (4) is arranged at the bottom of the in-pillar support lower plate (10); A large grid plate header throttling member (18) is arranged at the bottom of the large grid plate header (5); When the coolant in the fuel assembly box in the core (3) is heated and rises into the hot pool (15), a low-pressure area is formed in the lower cold pool (12) connected to the large grid plate header throttling piece (18). The coolant cooled by the cold pool independent heat exchanger (8) sinks to the bottom of the upper cold pool (11), passes through the throttling piece (4) of the lower plate of the in-core support, the lower cold pool (12), the throttling piece (18) of the large grid plate header, the large grid plate header (5), and the small grid plate header (6), and enters the fuel assembly box of the core (3), forming an in-box flow source of the flow channel of the throttling piece of the lower plate of the in-core support.

2. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 1, characterized in that: The system further comprises: a heat pool independent heat exchanger (7) arranged in the heat pool (15); when the coolant between the fuel assembly boxes in the core (3) is heated and rises to enter the heat pool (15), the coolant enters the heat pool independent heat exchanger (7), and the coolant flowing through the heat pool independent heat exchanger (7) is cooled and sucked into the core (3) box area from the top of the peripheral assembly connected to the fuel assembly, and the coolant reaches the lower position of the box from the peripheral assembly from top to bottom, passes through the core shroud opening (19) at the lower part of the core shroud (2), and is then sucked into the fuel assembly box area laterally, forming the box flow from the reverse flow channel between the peripheral assembly boxes of the core (3).

3. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 1, characterized in that: The system further comprises: an intermediate heat exchanger (9) which is arranged between the hot pool (15) and the cold pool; when the coolant in the fuel assembly box in the core (3) is heated and rises to enter the hot pool (15), the coolant enters the intermediate heat exchanger (9), the coolant flows through the intermediate heat exchanger (9) and enters the upper cold pool (11), enters the large grid header (5) and the small grid header (6) through the high-pressure pipe (16) or the large grid header throttling piece (18) of the lower cold pool (12), and enters the fuel assembly box of the core (3), thereby forming an in-box flow source of the intermediate heat exchanger flow channel.

4. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 1, characterized in that: The system further comprises a stack container cooling system (17), wherein the stack container cooling system (17) comprises: A shielding plate is arranged in the upper peripheral area of ​​the upper cold pool (11), and the shielding plate and the lower supporting plate (10) in the pile form an isolation surface; An isolation plate is arranged in the upper peripheral area of ​​the upper cold pool (11), and the isolation plate is located between the periphery of the cold pool independent heat exchanger (8) and the shielding plate; A stack container cooling system inlet throttling element (21) is arranged on the upper part of the shielding plate; A stack container cooling system outlet throttling member (20) is arranged between the lower part of the isolation plate and the shielding plate; An ascending channel is formed between the shielding plate and the stack container, and a descending channel is formed between the isolation plate and the shielding plate; The stack container relies on the cold source formed by the heat dissipation on the outside of the stack container and the heat source formed by the high-temperature sodium pool on the inside to perform natural circulation; the coolant passes through the stack container cooling system outlet throttling device, the stack container cooling system (17) descending channel, the stack container cooling system inlet throttling device, the stack container cooling system (17) ascending channel, the lower cold pool (12), the large grid plate header throttling device (18), the large grid plate header (5), and the small grid plate header (6), and enters the core (3) fuel assembly box, forming the in-box flow of the stack container cooling system reverse flow channel source.

5. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 1, characterized in that: The resistance coefficient of the lower plate throttling element (4) of the in-pillar support is as follows: the resistance in the natural circulation flow direction decreases, and the resistance in the forced flow direction increases.

6. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 1, characterized in that: There are a plurality of in-pile support lower plate throttling members (4), and the plurality of in-pile support lower plate throttling members (4) are arranged at intervals at the bottom of the in-pile support lower plate (10).

7. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 1, characterized in that: The cold pool independent heat exchanger (8) is arranged on the upper part of the cold and hot pool partition (13).

8. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 7, characterized in that: The cold and hot pool baffles (13) are arranged at a position higher than the upper edge of the heating section of the core (3).

9. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 2, characterized in that: The heat pool independent heat exchanger (7) is arranged in the inner peripheral area of ​​the heat pool.

10. The natural circulation system in a pool-type fast reactor applicable to a wide range of operating conditions according to claim 2, characterized in that: The number of cold pool independent heat exchangers (8) arranged is 1 to 2, and the number of hot pool independent heat exchangers (7) arranged is 1 to 2.

Images