Spent fuel storage and passive cooling system

Abstract

The embodiment of the present application discloses a kind of spent fuel storage and passive cooling system.Spent fuel storage and passive cooling system includes container subsystem, cooling subsystem, exhaust subsystem and water replenishing subsystem;Exhaust subsystem is connected with cooling subsystem, exhaust subsystem is used to ensure that container subsystem is always in full water state, ensure the natural circulation of cooling subsystem;Water replenishing subsystem is connected with container subsystem and cooling subsystem, and water replenishing subsystem is used to control container subsystem and timely water replenishing;All of container subsystem, all of cooling subsystem, lower part of exhaust subsystem and lower part of water replenishing subsystem are below sea level, and container subsystem and cooling subsystem are filled with boron-containing water or desalted water.The present application solves the problem that the existing cooling system cannot be used, resulting in the loss of spent fuel pool cooling function and the poor cooling effect caused by the exposure of spent fuel assembly, and can also meet the needs of storing spent fuel generated by nuclear power plant during design life.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power plant safety system equipment technology, and in particular to a spent fuel storage and passive cooling system. Background Technology

[0002] When nuclear fuel is used in a reactor, the consumption of fissile nuclides and the generation of fission products and heavy nuclides cause changes in the reactivity of the fuel, eventually making the reactor unable to maintain criticality. Therefore, nuclear fuel must be replaced after a certain period of use, and the unloaded fuel is also called spent fuel.

[0003] Although the chain fission reaction has ceased in spent fuel, it still releases a significant amount of heat due to the beta decay of its decay products. Spent nuclear fuel contains a large amount of radioactive elements and is therefore radioactive. Spent nuclear fuel removed from a nuclear reactor is typically stored in a water-filled spent fuel pool for several years to allow it to cool and shield its radioactivity. There are two methods of spent fuel storage: wet storage and dry storage. Currently, wet storage is the primary method, which involves storing fuel in a water pool. Each nuclear power unit has its own spent fuel pool. The spent fuel pool typically contains a certain concentration of boron-containing water to prevent chain fission reactions. The spent fuel pool is equipped with a cooling system to remove the decay heat from the spent fuel. In practice, spent nuclear fuel pools usually rely on passive cooling, requiring heat exchangers to circulate water and remove the heat generated by decay.

[0004] Currently, nuclear power plants typically use a cooling loop that relies on AC power and equipment cooling water for the storage and cooling of spent fuel pools. When a plant-wide power outage occurs and the equipment cooling water system becomes unavailable, this cooling loop becomes unusable, leading to the loss of cooling function in the spent fuel pool and potentially exposing spent fuel assemblies. Furthermore, the storage space in spent fuel pools is limited. For example, in passive nuclear power plants, spent fuel pools can typically only store spent fuel generated over 10 years of plant operation, far from meeting the needs for storing spent fuel generated during the plant's 60-year design life. Summary of the Invention

[0005] This invention provides a spent fuel storage and passive cooling system, which solves the problems of lost cooling function of spent fuel pools and poor cooling effect due to exposed spent fuel assemblies when existing cooling systems are unavailable. It can also meet the needs of storing spent fuel generated by nuclear power plants during their design life.

[0006] According to one aspect of the present invention, a spent fuel storage and passive cooling system is provided, the spent fuel storage and passive cooling system comprising: a container subsystem, a cooling subsystem, an exhaust subsystem, and a water replenishment subsystem;

[0007] The container subsystem is connected to the exhaust subsystem and the cooling subsystem. The container subsystem is used to store spent fuel, and the cooling subsystem is used to remove the decay heat generated by the spent fuel in the container subsystem by means of natural circulation.

[0008] The exhaust subsystem is connected to the cooling subsystem, and the exhaust subsystem is used to ensure that the container subsystem is always full of water and to ensure the natural circulation of the cooling subsystem.

[0009] The water replenishment subsystem is connected to the container subsystem and the cooling subsystem, and the water replenishment subsystem is used to control the container subsystem to replenish water in a timely manner;

[0010] The entire container subsystem, the entire cooling subsystem, the lower part of the exhaust subsystem, and the lower part of the water replenishment subsystem are located below sea level. The container subsystem and the cooling subsystem are filled with boron-containing water or demineralized water.

[0011] Optionally, the container subsystem includes a spent fuel container and a fuel rack, the fuel rack being disposed at the bottom of the spent fuel container, the spent fuel container being used to store spent fuel.

[0012] Optionally, the exhaust subsystem includes an exhaust line and a check valve, the check valve being disposed at the end of the exhaust line.

[0013] Optionally, the water replenishment subsystem includes: a water replenishment pipeline, a first isolation valve, a fluctuating water tank, a breather tube, a level gauge, a control unit, and a second isolation valve;

[0014] The wave tank, the first isolation valve, and the water supply line are connected in sequence. The water supply line is connected to the spent fuel container. The breather and the level gauge are located on the top of the wave tank. The wave tank is connected to the atmosphere through the breather. The second isolation valve is connected to the wave tank. The first isolation valve is used to isolate the water supply subsystem and the container subsystem. The second isolation valve is connected to the level gauge through the control unit.

[0015] Optionally, the cooling subsystem includes: cooling pipelines and a heat exchanger;

[0016] The first end of the cooling pipeline is connected to the exhaust pipeline and the top of the spent fuel container, the second end of the cooling pipeline is connected to the water supply pipeline and the bottom of the spent fuel container, and the heat exchanger is located in the middle of the cooling pipeline.

[0017] Optionally, the height of the exhaust port in the exhaust pipeline is higher than the height of the wave tank.

[0018] Optionally, the spent fuel container is filled with boron-containing water or demineralized water, and the lower part of the exhaust pipeline is located below sea level.

[0019] Optionally, the wave tank is filled with boron-containing water or demineralized water, and the lower part of the water supply pipeline is located below sea level.

[0020] Optionally, the spent fuel container includes: a cylindrical section, a first ellipsoidal section, and a second ellipsoidal section, wherein the second ellipsoidal section is connected to the cylindrical section by welding, and the first ellipsoidal section is connected to the cylindrical section by bolts.

[0021] Optionally, multiple ribs are provided in the cylindrical section, and the ribs are used for heat exchange.

[0022] The technical solution of this invention employs a passive cooling method for spent fuel. In the event of a loss of AC power or equipment cooling water, minimal intervention is required. The entire container subsystem and cooling subsystem, as well as the lower parts of the venting subsystem and makeup water subsystem, are located below sea level and completely submerged in seawater. This prevents the container and cooling subsystems from being exposed and thus losing cooling capacity, while also providing good cooling performance. The container subsystem's capacity is sufficient to store spent fuel generated during a single refueling cycle of a nuclear power plant, meeting the storage needs for spent fuel generated during the plant's 60-year design life. In summary, this invention solves the problem of existing nuclear power plants' storage and cooling of spent fuel pools, which rely on AC power and equipment cooling water cooling loops. When a plant-wide power outage occurs and the equipment cooling water system becomes unavailable, this cooling loop becomes unusable, leading to the loss of cooling function in the spent fuel pool and even exposure of spent fuel assemblies. This invention also addresses the problem of limited storage space in spent fuel pools, which is far from sufficient to store spent fuel generated during the 60-year design life of a nuclear power plant.

[0023] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a spent fuel storage and passive cooling system according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of another spent fuel storage and passive cooling system provided according to an embodiment of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] Figure 1 This is a schematic diagram of a spent fuel storage and passive cooling system according to an embodiment of the present invention. (Refer to...) Figure 1 This invention provides a spent fuel storage and passive cooling system, comprising: a container subsystem 100, a cooling subsystem 200, an exhaust subsystem 300, and a water replenishment subsystem 400; the container subsystem 100 is connected to the exhaust subsystem 300 and the cooling subsystem 200, the container subsystem 100 is used to store spent fuel, and the cooling subsystem 200 is used to remove the decay heat generated by the spent fuel in the container subsystem 100 by natural circulation; the exhaust subsystem 300 is connected to the cooling subsystem 200. The exhaust subsystem 300 is used to ensure that the container subsystem 100 is always full of water and to ensure the natural circulation of the cooling subsystem 200. The water replenishment subsystem 400 is connected to the container subsystem 100 and the cooling subsystem 200, and is used to control the timely replenishment of water to the container subsystem 100. The entire container subsystem 100, the entire cooling subsystem 200, the lower part of the exhaust subsystem 300 and the lower part of the water replenishment subsystem 400 are located below sea level. The container subsystem 100 and the cooling subsystem 200 are filled with boron-containing water or demineralized water.

[0030] Specifically, the container subsystem 100 holds spent fuel, with a capacity sufficient to store spent fuel generated during a single refueling cycle at the nuclear power plant. The venting subsystem 300 ensures that the container subsystem 100 is always full of water to avoid interfering with the natural circulation of the cooling subsystem 200. Additionally, in certain extreme situations, the venting subsystem 300 can also serve to relieve pressure.

[0031] The temperature of the boron-containing water or demineralized water in the container subsystem 100 increases and its density decreases under the heating effect of spent fuel, while the temperature of the boron-containing water or demineralized water in the cooling subsystem 200 is lower and its density is higher. The boron-containing water or demineralized water will flow under the action of density difference. When the heated boron-containing water or demineralized water flows through the cooling subsystem 200, it transfers heat to the seawater. After being cooled, it flows into the container subsystem 100 through the bottom and is heated when passing through the spent fuel, flowing out from the top of the container subsystem 100. This cycle is repeated to achieve cooling.

[0032] When the ambient temperature or the temperature of the boron-containing water or demineralized water in the container subsystem 100 changes, the volume of the boron-containing water or demineralized water will change. When the temperature rises and the volume expands, some water can be injected into the water replenishment subsystem 400. When the temperature drops and the volume shrinks, the water replenishment subsystem 400 automatically replenishes water to the container subsystem 100 under the action of gravity.

[0033] Currently, all completed and under-construction power plants in my country are located near the coast. Storing spent fuel in container subsystem 100 in seawater is convenient, as seawater acts as the final heat sink and provides ideal cooling under tidal conditions. The spent fuel does not directly contact seawater, avoiding corrosion. Consumption of boron-containing water or demineralized water is minimal; it only enters or exits the makeup water subsystem 400 when temperature changes cause volume changes. A small amount of evaporation loss occurs in the makeup water subsystem 400, while losses elsewhere are minimal, thus requiring less makeup water. The entire container subsystem 100 and cooling subsystem 200, the lower part of the venting subsystem 300, and the lower part of the makeup water subsystem 400 are located below sea level and completely submerged in seawater. The sea level is relatively fixed, preventing container subsystem 100 and cooling subsystem 200 from being exposed and losing cooling. Passive cooling of the spent fuel requires minimal intervention in the event of a loss of AC power or equipment cooling water. The container subsystem 100 is completely submerged in seawater, resulting in good cooling. The heat generated by spent fuel can be transferred to the seawater in two ways: through the cooling subsystem 200 and through the container subsystem 100.

[0034] The technical solution of this invention employs a passive cooling method for spent fuel. In the event of a loss of AC power or equipment cooling water, minimal intervention is required. The entire container subsystem and cooling subsystem, as well as the lower parts of the venting subsystem and makeup water subsystem, are located below sea level and completely submerged in seawater. This prevents the container and cooling subsystems from being exposed and thus losing cooling capacity, while also providing good cooling performance. The container subsystem's capacity is sufficient to store spent fuel generated during a single refueling cycle of a nuclear power plant, meeting the storage needs for spent fuel generated during the plant's 60-year design life. In summary, this invention solves the problem of existing nuclear power plants' storage and cooling of spent fuel pools, which rely on AC power and equipment cooling water cooling loops. When a plant-wide power outage occurs and the equipment cooling water system becomes unavailable, this cooling loop becomes unusable, leading to the loss of cooling function in the spent fuel pool and even exposure of spent fuel assemblies. This invention also addresses the problem of limited storage space in spent fuel pools, which is far from sufficient to store spent fuel generated during the 60-year design life of a nuclear power plant.

[0035] Figure 2 This is a schematic diagram of another spent fuel storage and passive cooling system provided according to an embodiment of the present invention, with reference to... Figure 2 Optionally, the container subsystem 100 includes a spent fuel container 5 and a fuel rack 6, the fuel rack 6 being disposed at the bottom of the spent fuel container 5, the spent fuel container 5 being used to store spent fuel.

[0036] Specifically, the container subsystem 100 consists of a spent fuel container 5 and a fuel rack 6, with the fuel rack 6 located at the bottom inside the spent fuel container 5. The fuel rack 6 has a capacity to store spent fuel produced during a single refueling of the nuclear power plant.

[0037] Continue to refer to Figure 2 Optionally, the exhaust subsystem 300 includes an exhaust line 2 and a check valve 1, wherein the check valve 1 is located at the end of the exhaust line 2.

[0038] Specifically, the exhaust subsystem 300 ensures that the spent fuel container 5 is always full of water to avoid interfering with the natural circulation of the cooling subsystem 200. The exhaust port of the exhaust line 2 is bent downwards to reduce the entry of external substances. A check valve 1 is installed at the end of the exhaust line 2 to minimize the entry of marine salt spray. In addition, the exhaust subsystem 300 can also serve as a pressure relief system in certain extreme situations.

[0039] Continue to refer to Figure 2 Optionally, the water replenishment subsystem 400 includes: a water replenishment pipeline 7, a first isolation valve 8, a fluctuating water tank 9, a breather tube 10, a level gauge 11, a control unit 12, and a second isolation valve 13;

[0040] The wave tank 9, the first isolation valve 8, and the water supply line 7 are connected in sequence. The water supply line 7 is connected to the spent fuel container 5. The breather pipe 10 and the level gauge 11 are installed on the top of the wave tank 9. The wave tank 9 is connected to the atmosphere through the breather pipe 10. The second isolation valve 13 is connected to the wave tank 9. The first isolation valve 8 is used to isolate the water supply subsystem 400 and the container subsystem 100. The second isolation valve 13 is connected to the level gauge 11 through the control unit 12.

[0041] Specifically, the water replenishment subsystem 400 consists of a water replenishment pipeline 7, a first isolation valve 8, a wave-shaped water tank 9, a breather pipe 10, a level gauge 11, a control unit 12, and a second isolation valve 13. When the ambient temperature or the temperature of the boron-containing water or demineralized water in the spent fuel container 5 changes, the volume of the boron-containing water or demineralized water will change. When the temperature rises and the volume expands, some water can be waved into the wave-shaped water tank 9. When the temperature decreases and the volume shrinks, the wave-shaped water tank 9 automatically replenishes water to the spent fuel container 5 under the action of gravity.

[0042] A single wave tank 9 can be connected to several spent fuel containers 5. The wave tank 9 is open to the atmosphere via a breather pipe 10. The wave tank 9 is equipped with a level gauge 11. When the level gauge 11 detects a level below a certain set value (L1), the control unit 12 automatically opens the second isolation valve 13 to replenish water to the wave tank 9. When the level gauge 11 detects a level above a certain set value (H1), the control unit 12 automatically closes the second isolation valve 13 to cut off water replenishment to the wave tank 9. When the level gauge 11 detects a level below a certain set value (L2), the control unit 12 issues an alarm. When the wave tank 9 requires maintenance, the first isolation valve 8 can be closed to isolate the water replenishment subsystem 400 from the container subsystem 100.

[0043] Continue to refer to Figure 2 Optionally, the height of the exhaust port in the exhaust pipe 2 is higher than the height of the wave tank 9.

[0044] Continue to refer to Figure 2 Optionally, the spent fuel container 5 is filled with boron-containing water or demineralized water, and the lower part of the exhaust pipeline 2 is located below sea level.

[0045] Continue to refer to Figure 2 Optionally, the wave tank 9 is filled with boron-containing water or demineralized water, and the lower part of the water supply pipeline 7 is located below sea level.

[0046] Specifically, the vent of exhaust pipe 2 is positioned at a certain height above the wave tank 9 to prevent boron-containing water or demineralized water from being discharged through exhaust pipe 2 under normal circumstances. When the boron-containing water or demineralized water in spent fuel container 5 expands, it should be pumped into the wave tank 9 instead of being discharged through exhaust pipe 2.

[0047] Continue to refer to Figure 2Optionally, the cooling subsystem 200 includes: cooling pipelines 3 and heat exchanger 4;

[0048] The first end of the cooling pipeline 3 is connected to the exhaust pipeline 2 and the top of the spent fuel container 5, the second end of the cooling pipeline 3 is connected to the water supply pipeline 7 and the bottom of the spent fuel container 5, and the heat exchanger 4 is located in the middle of the cooling pipeline 3.

[0049] Specifically, the cooling subsystem 200 consists of cooling pipes 3 and a heat exchanger 4. The upper part of the cooling pipes 3 is connected to the exhaust pipe 2 and to the top of the spent fuel container 5; the lower part of the cooling pipes 3 is connected to the makeup water pipe 7 and to the bottom of the spent fuel container 5. The boron-containing water or demineralized water in the spent fuel container 5 experiences a temperature increase and a density decrease due to the heating effect of the spent fuel, while the boron-containing water or demineralized water in the cooling pipes 3 and the heat exchanger 4 has a lower temperature and a higher density. The boron-containing water or demineralized water flows due to this density difference. As the heated boron-containing water or demineralized water flows through the heat exchanger 4, it transfers heat to the seawater, is cooled, and then flows into the spent fuel container 5 through the bottom. It is then heated again as it passes through the spent fuel and flows out from the top of the spent fuel container 5, thus achieving cooling through a continuous cycle.

[0050] Continue to refer to Figure 2 Optionally, the spent fuel container 5 includes: a cylindrical section 51, a first ellipsoidal section 52 and a second ellipsoidal section 53, wherein the second ellipsoidal section 53 is connected to the cylindrical section 51 by welding, and the first ellipsoidal section 52 is connected to the cylindrical section 51 by bolts.

[0051] Continue to refer to Figure 2 Optionally, multiple ribs are provided in the cylinder section 51 for heat exchange.

[0052] Specifically, the spent fuel container 5 consists of one cylindrical section and two ellipsoidal sections, upper and lower. The first ellipsoidal section 52 can be the upper ellipsoidal section, and the second ellipsoidal section 53 can be the lower ellipsoidal section. The lower ellipsoidal section is welded to the cylindrical section 51. After spent fuel is loaded into the spent fuel container 5, the upper ellipsoidal section is bolted to the cylindrical section 51 and sealed with a sealing weld. Several lifting lugs are provided at the top of the upper ellipsoidal section for easy lifting. Several ribs can be provided on the cylindrical section 51 to increase heat exchange efficiency. The spent fuel container 5 has only two through-holes, one at the top and one at the bottom.

[0053] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A spent fuel storage and passive cooling system, characterized in that, include: The system comprises a container subsystem, a cooling subsystem, an exhaust subsystem, and a water makeup subsystem. The container subsystem is connected to the exhaust subsystem and the cooling subsystem. The container subsystem is used to store spent fuel, and the cooling subsystem is used to remove the decay heat generated by the spent fuel in the container subsystem by means of natural circulation. The exhaust subsystem is connected to the cooling subsystem, and the exhaust subsystem is used to ensure that the container subsystem is always full of water and to ensure the natural circulation of the cooling subsystem. The water replenishment subsystem is connected to the container subsystem and the cooling subsystem, and the water replenishment subsystem is used to control the container subsystem to replenish water in a timely manner; The entire container subsystem, the entire cooling subsystem, the lower part of the exhaust subsystem, and the lower part of the water replenishment subsystem are located below sea level. The container subsystem and the cooling subsystem are filled with boron-containing water or demineralized water.

2. The system according to claim 1, characterized in that, The container subsystem includes a spent fuel container and a fuel rack, the fuel rack being disposed at the bottom of the spent fuel container, the spent fuel container being used to store spent fuel.

3. The system according to claim 2, characterized in that, The exhaust subsystem includes an exhaust pipeline and a check valve, wherein the check valve is located at the end of the exhaust pipeline.

4. The system according to claim 3, characterized in that, The water replenishment subsystem includes: a water replenishment pipeline, a first isolation valve, a fluctuating water tank, a breather tube, a level gauge, a control unit, and a second isolation valve; The wave tank, the first isolation valve, and the water supply line are connected in sequence. The water supply line is connected to the spent fuel container. The breather and the level gauge are located on the top of the wave tank. The wave tank is connected to the atmosphere through the breather. The second isolation valve is connected to the wave tank. The first isolation valve is used to isolate the water supply subsystem and the container subsystem. The second isolation valve is connected to the level gauge through the control unit.

5. The system according to claim 4, characterized in that, The cooling subsystem includes: cooling pipelines and heat exchangers; The first end of the cooling pipeline is connected to the exhaust pipeline and the top of the spent fuel container, the second end of the cooling pipeline is connected to the water supply pipeline and the bottom of the spent fuel container, and the heat exchanger is located in the middle of the cooling pipeline.

6. The system according to claim 4, characterized in that, The height of the exhaust port in the exhaust pipeline is higher than the height of the wave tank.

7. The system according to claim 5, characterized in that, The spent fuel container is filled with boron-containing water or demineralized water, and the lower part of the exhaust pipeline is located below sea level.

8. The system according to claim 4, characterized in that, The wave tank is filled with boron-containing water or demineralized water, and the lower part of the water supply pipeline is located below sea level.

9. The system according to claim 5, characterized in that, The spent fuel container includes a cylindrical section, a first ellipsoidal section, and a second ellipsoidal section. The second ellipsoidal section is connected to the cylindrical section by welding, and the first ellipsoidal section is connected to the cylindrical section by bolts.

10. The system according to claim 9, characterized in that, Multiple ribs are provided in the cylindrical section, and the ribs are used for heat exchange.

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