Spent nuclear fuel cooling system, spent nuclear fuel storage and cooling system, method, and spent nuclear fuel transport and cooling system

Abstract

A spent nuclear fuel cooling system, a spent nuclear fuel storage and cooling system, a method, and a spent nuclear fuel transport and cooling system. The spent nuclear fuel cooling system comprises an external cooling apparatus (10) and an internal cooling apparatus (20); the external cooling apparatus (10) comprises a cooling capsule (11) covering the exterior of a spent nuclear fuel storage container, and a water filling annular line (12) and a water discharging annular line (13) that are separately sleeved on the outer side of the cooling capsule (11), and the water filling annular line (12) and the water discharging annular line (13) are separately communicated with the cooling capsule (11); the internal cooling apparatus (20) comprises a first water filling line (21) connected to a gas filling hole (101) on the spent nuclear fuel storage container, and a first water discharging line (22) connected to a water discharging hole (102) on the spent nuclear fuel storage container. The spent nuclear fuel cooling system cools the spent nuclear fuel storage container by means of the external cooling apparatus (10), the internal cooling apparatus (20) and the like, so as to take away heat released by a spent nuclear fuel assembly and control the temperature of water in the spent nuclear fuel storage container within a safe limit, so that emergency cooling can be performed in the event of a shutdown of an apparatus due to a failure, thereby ensuring the thermal-hydraulic safety and containment safety of the spent nuclear fuel storage container.

Description

Spent fuel cooling systems and methods for spent fuel storage and cooling, and spent fuel transportation cooling systems Technical Field

[0001] This invention relates to the field of nuclear fuel storage technology, and in particular to a spent fuel cooling system, a spent fuel storage cooling system and method, and a spent fuel transportation cooling system. Background Technology

[0002] After a certain number of cycles, nuclear reactor fuel releases a large amount of heat and has a high level of radioactivity, necessitating timely removal and storage in spent fuel pools for cooling. Due to the limited capacity of spent fuel pools and insufficient reprocessing capacity of reprocessing plants, both domestic and international efforts are focusing on dry storage methods to address the challenge of off-site spent fuel storage.

[0003] Current dry storage technology for spent fuel involves first hoisting an empty spent fuel tank into the internal cavity of a transfer container within the nuclear power plant's fuel building. Then, the assembly is hoisted underwater for loading. After loading, it is hoisted into a cleaning well, where a top cover is installed. Automatic welding machines are then used for sealing, vacuum drying, and helium filling. The spent fuel tank is then transported to the storage area via the transfer container, and finally removed from the transfer container and stored in concrete modules for long-term storage. While this technology allows for spent fuel loading within the fuel building, ensuring the thermal safety and sealing safety of the spent fuel under long-term failure conditions of the automatic welding machine and vacuum drying equipment remains a bottleneck restricting the safety of dry storage loading of spent fuel. This is particularly evident in the following aspects:

[0004] (1) Under long-term equipment failure mode, the fuel cladding temperature continues to rise beyond the thermal safety limit;

[0005] (2) High-temperature steam in the annular cavity affects the remote HMI (human-machine interface) automatic welding imaging operation;

[0006] (3) High-temperature steam in the storage tank affects the quality of the weld pool and the sealing safety of the container. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a spent fuel cooling system, a spent fuel storage cooling system and a cooling method having the spent fuel cooling system, and a spent fuel transportation cooling system having the spent fuel cooling system.

[0008] The technical solution adopted by the present invention to solve its technical problem is: to provide a spent fuel cooling system, including an external cooling device for cooling the outside of the spent fuel storage container and an internal cooling device for cooling the inner cavity of the spent fuel storage container;

[0009] The external cooling device includes a cooling bladder covering the outside of the spent fuel storage container, a water-filled ring and a drain ring respectively fitted on the outside of the cooling bladder, the water-filled ring and the drain ring respectively connected to the cooling bladder, the first cooling medium enters the cooling bladder through the water-filled ring and is discharged from the drain ring, taking away the heat emitted from the outside of the spent fuel storage container;

[0010] The internal cooling device includes a first water filling pipeline connected to an air filling hole on the spent fuel storage container and a first drain pipeline connected to a drain hole on the spent fuel storage container; a second cooling medium enters the inner cavity of the spent fuel storage container through the first water filling pipeline and is then discharged from the first drain pipeline, thereby displacing and cooling the boron-containing water in the inner cavity of the spent fuel storage container.

[0011] In some embodiments, the cooling bladder includes several relatively independent cooling bladder units, which are arranged along the outer periphery of the spent fuel storage container and attached to the outer surface of the spent fuel storage container.

[0012] In some embodiments, the water filling ring includes a water filling ring sleeved on the lower end of the cooling bladder, a plurality of water filling branch pipes, and a water filling pipe connected to the water filling ring and used to access the first cooling medium; the plurality of water filling branch pipes are arranged at intervals along the circumference of the water filling ring and connected between the water filling ring and the corresponding cooling bladder unit.

[0013] In some embodiments, the drainage loop includes a drainage ring sleeved on the upper end of the cooling bladder, a plurality of drainage branch pipes, and a drainage pipe connected to the drainage ring and used to discharge a first cooling medium; the plurality of drainage branch pipes are arranged at intervals along the circumference of the drainage ring and connected between the drainage ring and the corresponding cooling bladder unit.

[0014] In some embodiments, the external cooling device further includes a support collar; the support collar is used to fit around the outer periphery of the spent fuel storage container, and the cooling bladder is connected to the support collar around it.

[0015] In some embodiments, the spent fuel cooling system further includes an annular cooling device for cooling the annular cavity of the spent fuel storage container;

[0016] The annular cavity cooling device includes a second water filling pipeline and a second drainage pipeline respectively connected to the annular cavity; a third cooling medium enters the annular cavity through the second water filling pipeline and is discharged from the second drainage pipeline to displace and cool the high-temperature water in the annular cavity.

[0017] The present invention also provides a spent fuel storage and cooling system, including a spent fuel storage tank for loading spent fuel assemblies, a transfer container, and a spent fuel cooling system;

[0018] The spent fuel storage tank is assembled inside the transfer container, and an annular cavity is formed between the outer periphery of the spent fuel storage tank and the inner periphery of the transfer container; the spent fuel cooling system includes an external cooling device, an internal cooling device, and an annular cavity cooling device.

[0019] The external cooling device includes a cooling bladder covering the outside of the transfer container, a water-filling ring and a draining ring respectively sleeved on the outside of the cooling bladder, the water-filling ring and the draining ring respectively connected to the cooling bladder, the first cooling medium enters the cooling bladder through the water-filling ring and is discharged from the draining ring, taking away the heat emitted from the outside of the transfer container;

[0020] The internal cooling device includes a first water filling pipeline connected to the air filling hole on the spent fuel tank and a first drain pipeline connected to the drain hole on the spent fuel tank; the second cooling medium enters the inner cavity of the spent fuel tank through the first water filling pipeline and is then discharged from the first drain pipeline, thereby displacing and cooling the boron-containing water in the inner cavity of the spent fuel tank.

[0021] The annular cavity cooling device includes a second water filling pipeline and a second drainage pipeline respectively connected to the annular cavity; a third cooling medium enters the annular cavity through the second water filling pipeline and is discharged from the second drainage pipeline to displace and cool the high-temperature water in the annular cavity.

[0022] In some embodiments, the upper and lower ends of the outer surface of the transfer container are respectively provided with an upper trunnion and a lower trunnion;

[0023] The external cooling device is located outside the transfer container, between the upper and lower trunnions.

[0024] The present invention also provides a cooling method for a spent fuel storage cooling system, comprising the following steps:

[0025] S1. When the automatic welding system and vacuum drying system of the spent fuel storage tank malfunction and stop operation, continuously monitor the temperature of the demineralized water in the annular cavity between the spent fuel storage tank and the transfer container.

[0026] S2. When the temperature of the demineralized water in the annular cavity exceeds the safe limit of water temperature, the annular cavity cooling device is turned on so that the amount of water entering the annular cavity through the second water filling pipeline is equal to the amount of water discharged from the annular cavity through the second drainage pipeline.

[0027] S3. Start the external cooling device, fill the cooling bladder with low-temperature demineralized water through the water filling loop, and discharge it from the drain loop;

[0028] S4. The annular cavity cooling device and the external cooling device continue to operate and continuously monitor the temperature of the demineralized water in the annular cavity. When the temperature of the demineralized water does not meet the water temperature safety limit, the internal cooling device is activated to replace and cool the boron-containing water in the inner cavity of the spent fuel storage tank until the temperature of the demineralized water meets the safety limit.

[0029] The present invention also provides a spent fuel transportation cooling system, including a transportation container for loading spent fuel assemblies and a spent fuel cooling system; the spent fuel cooling system includes an external cooling device and an internal cooling device;

[0030] The external cooling device includes a cooling bladder covering the outside of the transport container, a water-filled ring and a drain ring respectively sleeved on the outside of the cooling bladder, the water-filled ring and the drain ring respectively connected to the cooling bladder, the first cooling medium enters the cooling bladder through the water-filled ring and is discharged from the drain ring, taking away the heat dissipated from the outside of the transport container;

[0031] The internal cooling device includes a first water filling pipeline connected to an air filling hole on the transport container and a first drain pipeline connected to a drain hole on the transport container; a second cooling medium enters the inner cavity of the transport container through the first water filling pipeline and is then discharged from the first drain pipeline, thereby displacing and cooling the boron-containing water in the inner cavity of the transport container.

[0032] The beneficial effects of this invention are as follows: by using external and internal cooling devices, the spent fuel storage container is cooled to remove the heat released by the spent fuel components, and the water temperature inside the spent fuel storage container is controlled within a safe limit. This enables emergency cooling in the event of equipment failure and shutdown, ensuring the thermal safety and sealing safety of the spent fuel storage container. Attached Figure Description

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0034] Figure 1 is a schematic diagram of the structure of a spent fuel storage and cooling system in a cleaning well according to an embodiment of the present invention;

[0035] Figure 2 is a schematic diagram of the longitudinal cross-sectional structure of the system shown in Figure 1;

[0036] Figure 3 is a schematic diagram of the spent fuel storage container in Figure 1;

[0037] Figure 4 is a schematic diagram of the transfer container in Figure 3;

[0038] Figure 5 is a schematic diagram of the spent fuel cooling system in Figure 1;

[0039] Figure 6 is a schematic diagram of the cooling bladder in Figure 5;

[0040] Figure 7 is a schematic diagram of the water-filling loop and the drainage loop in Figure 5;

[0041] Figure 8 is a longitudinal cross-sectional structural diagram of a spent fuel transportation cooling system according to an embodiment of the present invention. Detailed Implementation

[0042] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0043] The spent fuel cooling system of the present invention is used in conjunction with a spent fuel storage container to cool the spent fuel storage container and generate heat from the spent fuel assemblies to maintain the temperature within safe limits. The spent fuel storage container can be a container for dry storage of spent fuel, or a transport container for transporting spent fuel assemblies, etc.

[0044] As shown in Figures 1-4, a spent fuel cooling system according to an embodiment of the present invention includes an external cooling device 10 for cooling the exterior of a spent fuel storage container, an internal cooling device 20 for cooling the interior of the spent fuel storage container, and an annular cooling device 30 for cooling the annular cavity of the spent fuel storage container.

[0045] In this embodiment, the spent fuel storage container may include a spent fuel tank 110 and a transfer container 120. The spent fuel tank 110 is assembled inside the transfer container 120, and an annular cavity 130 is formed between the outer periphery of the spent fuel tank 110 and the inner periphery of the transfer container 120. The spent fuel cooling system installed on the spent fuel storage container forms a spent fuel storage cooling system with the spent fuel storage container, which is applied to the dry storage technology of spent fuel. The spent fuel storage cooling system is installed in the cleaning well 100 of the fuel plant.

[0046] The spent fuel storage tank 110 is a thin-walled stainless steel cylindrical structure used to load spent fuel assemblies. The spent fuel storage tank 110 is equipped with an inflation port 101, a drainage port 102, and a drainage pipe. The transfer container 120 is a thick-walled metal container that provides structural and shielding protection. The bottom of the transfer container 120 has a drainage channel 105, an upper trunnion 103 is located at the upper end of its outer surface, and a lower trunnion 104 is located at the lower end of its outer surface.

[0047] An external cooling device 10 is mounted on the outside of the transfer container 120 to cool the exterior of the transfer container 120 and remove heat dissipated from the exterior. The external cooling device 10 is positioned outside the transfer container 120 between the upper trunnion 103 and the lower trunnion 104, effectively cooling the exterior of the transfer container 120 without covering the upper trunnion 103 and the lower trunnion 104, thus not affecting their use.

[0048] Specifically, referring to Figures 1, 2, and 5, the external cooling device 10 may include a cooling bladder 11, a water-filling ring 12, and a draining ring 13. The cooling bladder 11 covers the outside of the transfer container 120, specifically covering the outer surface of the transfer container 120; the water-filling ring 12 and the draining ring 13 are respectively sleeved on the outside of the cooling bladder 11 and connected to the cooling bladder 11. The first cooling medium enters the cooling bladder 11 through the water-filling ring 12 and is discharged from the draining ring 13. The first cooling medium may be demineralized water, which has the advantage of high water purity, avoiding corrosion and contamination of equipment components, pipelines, etc.

[0049] As shown in Figures 2 and 5-7, the cooling bladder 11 comprises several relatively independent cooling bladder units 111; these units are arranged along the outer periphery of the transfer container 120 and attached to its outer surface. Each cooling bladder unit 111 forms an independent cold source, independently cooling the attached outer surface. The cooling bladder units 111 are made of flexible non-metallic or metallic materials, forming a flexible cooling module.

[0050] The water-filling ring 12 includes a water-filling ring 121, several water-filling branch pipes 122, and a water-filling pipe 123. The water-filling ring 121 is sleeved on the outside of the cooling bladder 11; the several water-filling branch pipes 122 are arranged at intervals along the circumference of the water-filling ring 121, connecting the water-filling ring 121 and the corresponding cooling bladder unit 111, thus connecting the water-filling ring 121 and the cooling bladder unit 111. The water-filling pipe 123 is connected to the water-filling ring 121 and is used to introduce the first cooling medium. The first cooling medium enters the water-filling ring 121 through the water-filling pipe 123, and then is distributed along the water-filling ring 121 to each water-filling branch pipe 122, and enters the cooling bladder unit 111 along the water-filling branch pipes 122.

[0051] The drainage loop 13 includes a drainage ring 131, a plurality of drainage branch pipes 132, and a drainage pipe 133. The drainage ring 131 is sleeved on the outside of the cooling bladder 11; the plurality of drainage branch pipes 132 are arranged at intervals along the circumference of the drainage ring 131, connecting the drainage ring 131 and the corresponding cooling bladder unit 111, thus communicating between the drainage ring 131 and the cooling bladder unit 111. The drainage pipe 133 is connected to the drainage ring 131 and is used to discharge the first cooling medium. The first cooling medium in each cooling bladder unit 111 enters the drainage ring 131 through its respective connected drainage branch pipe 132, enters the drainage pipe 133 along the drainage ring 131, and is discharged from the drainage pipe 133.

[0052] To support and position the cooling bladder 11 outside the transfer container 120, the external cooling device 10 may further include at least one support collar 14. The support collar 14 is fitted around the outer periphery of the transfer container 120, with the cooling bladder 11 connected to it around the support collar 14. The support collar 14 serves as a frame fixation, positioning the cooling bladder 11 and even the entire external cooling device 10 on the transfer container 120. To achieve a close fit with the outer peripheral surface of the transfer container 120, the side of each cooling bladder unit 111 facing the transfer container 120 is curved, and all cooling bladder units 111 are concentrically fixed around the support collar 14.

[0053] Understandably, a water filling valve can be installed on the water filling pipe 123 to control the water filling flow rate. The end of the water filling pipe 123 away from the water filling ring 121 can be extended to connect to the demineralized water source of the nuclear power plant, and the demineralized water is pumped into the water filling ring 121 under the power provided by the water pump. A drain valve is installed on the drain pipe 133 to control the drain flow rate; the end of the drain pipe 133 away from the drain pipe 133 can face or be placed in the cleaning well 100 to discharge the demineralized water into the cleaning well 100.

[0054] Preferably, the water filling ring 121 is fitted on the outer periphery of the lower end of the cooling bladder 11, and the draining ring 131 is fitted on the outer periphery of the upper end of the cooling bladder 11, forming a direct current circulation cooling form with low-level water filling and high-level drainage. The first cooling medium discharges the decay heat generated by the spent fuel assembly into the cleaning well 100 through the flow mode of bottom filling and top discharge (as shown by the arrow in the external cooling device 10 in Figure 2). (The decay heat is dissipated as shown by the dashed arrow in Figure 2).

[0055] As shown in Figures 2, 3, and 5, the internal cooling device 20 is connected to the spent fuel storage tank 110 and communicates with the inner cavity of the spent fuel storage tank 110 to cool the inner cavity of the spent fuel storage tank 110. Specifically, the internal cooling device 20 may include a first water filling line 21 and a first drain line 22; the first water filling line 21 is connected to the air filling hole 101 on the spent fuel storage tank 110, and the first drain line 22 is connected to the drain hole 102 on the spent fuel storage tank 110. A second cooling medium enters the inner cavity of the spent fuel storage tank 110 through the first water filling line 21 and is then discharged from the first drain line 22, thereby displacing and cooling the boron-containing water inside the spent fuel storage tank 110.

[0056] The preferred cooling medium is boron-containing water used in nuclear power plants, characterized by the addition of boric acid to the water, which absorbs and moderates neutrons generated by the fission of spent fuel assemblies.

[0057] It is understandable that valves are installed on the first water filling pipeline 21 and the first drainage pipeline 22 to control the flow rate.

[0058] Typically, the air inlet 101 and drain outlet 102 on the spent fuel storage tank 110 are located on the upper part (such as on the cover), and the first drain line 22 can extend through the drain outlet 102 into the lower part or bottom of the spent fuel storage tank 110.

[0059] The internal cooling device 20 employs a top-filling and top-draining method, draining the high-temperature boron-containing water inside the spent fuel storage tank 110 from the top of the tank at the same flow rate (as indicated by the arrow in the internal cooling device 20 shown in Figure 2). This equal-volume replacement and rapid cooling of the high-temperature boron-containing water ensures that the water inside the tank still has a high boiling margin, preventing it from being in an evaporating boiling state during subsequent welding operations. It also keeps the water level inside the spent fuel storage tank 110 at a stable level, ensuring that the spent fuel assemblies are always submerged, preventing a drop in water level that would increase the intensity of exposed radiation sources and raise the collective dose to operating personnel. Furthermore, it prevents excessively high water levels from overflowing from the top of the tank and causing large-scale radioactive waste contamination.

[0060] As shown in Figures 2 and 5, the annular cavity cooling device 30 connects the annular cavity 130 between the spent fuel storage tank 110 and the transfer container 120, and is used to cool the annular cavity 130. The annular cavity cooling device 30 may further include a second water filling pipeline 31 and a second drain pipeline 32 respectively connected to the annular cavity 130; a third cooling medium enters the annular cavity 130 through the second water filling pipeline 31 and is discharged from the second drain pipeline 32, thereby displacing and cooling the high-temperature water in the annular cavity 130.

[0061] The third cooling medium is preferably demineralized water, the same as the first cooling medium.

[0062] One end of the second water filling pipeline 31 is connected to the upper part of the annular cavity 130, and the end away from the annular cavity 130 can extend to connect to the demineralized water source of the nuclear power plant. A valve may be installed on the second water filling pipeline 31 to control the water filling flow rate. The second drainage pipeline 32 is connected to the drainage channel 105 at the bottom of the transfer container 120, or the second drainage pipeline 32 is formed by the drainage channel 105 at the bottom of the transfer container 120. A valve may be installed on the second drainage pipeline 32 to control the drainage flow rate; this second drainage pipeline 32 discharges the third cooling medium into the cleaning well 100.

[0063] The annular cavity cooling device 30 injects low-temperature demineralized water into the upper part of the annular cavity 130 via an upward filling and downward discharge method (as shown by the arrow in the annular cavity cooling device 30 in Figure 2). Simultaneously, a drainage pipeline is connected to the drainage channel 105 at the bottom of the transfer container 120. The discharge flow rate is controlled by a valve to discharge the high-temperature water accumulated in the annular cavity 130 to the cleaning well 100. This achieves the removal of the decay heat of spent fuel, ensures that the water in the annular cavity 130 is in a low-temperature state, and avoids rapid evaporation and boiling to form high-temperature steam that diffuses and affects the imaging of the automatic welding machine camera, thus affecting the remote welding process operation and adjustment.

[0064] In the dry storage of spent fuel, the spent fuel storage and cooling system first suspends the spent fuel tank 110 within the inner cavity of the matching transfer container 120, forming an annular cavity 130 between them. A sealing ring is used to inflate and seal the top of the annular cavity 130. Then, the transfer container 120 is suspended in the spent fuel water pool, and each spent fuel assembly is individually hoisted into the spent fuel tank 110 for storage underwater. Next, the top cover of the spent fuel tank 110 is hoisted and installed. Finally, the transfer container 120 is suspended in the cleaning well 100, and the annular cavity sealing ring is removed. At this point, the spent fuel tank 110 is filled with boron-containing water from the spent fuel water pool, completely submerging the spent fuel assemblies.

[0065] Referring to Figures 1, 2, and 5, in some embodiments, after the spent fuel assembly is loaded, the cooling method of the spent fuel storage cooling system includes the following steps:

[0066] S1. During the failure of the charging and operation equipment, continuously monitor the temperature of the demineralized water in the annular cavity 130 between the spent fuel storage tank 110 and the transfer container 120.

[0067] The fuel loading and operation equipment includes the spent fuel tank automatic welding system and the vacuum drying system; these systems are existing systems in the nuclear power plant and will not be described in detail here. During periods of equipment failure, specifically during periods when the spent fuel tank automatic welding system and the vacuum drying system malfunction and cease operation, the fuel loading and operation equipment will be affected.

[0068] For the annular water, under long-term equipment downtime operation, continuous heating from the spent fuel assemblies can easily lead to boiling and the formation of large amounts of steam. This steam can interfere with the clear imaging of the automatic welding machine's camera, making it difficult for operators to adjust welding process parameters in a timely manner based on the weld pool. This necessitates frequent interruptions and close-range adjustments to the welding position, increasing welding time and personnel radiation exposure. Therefore, to address this highly likely situation, continuous real-time monitoring of the temperature within the annular cavity 130, specifically the temperature of the demineralized water within 130, is necessary for timely cooling measures.

[0069] S2. When the temperature of the demineralized water in the annular cavity 130 exceeds the safe water temperature limit (such as the safe temperature limit of 400℃ for fuel cladding), the annular cavity cooling device 30 is turned on so that the amount of water entering the annular cavity 130 through the second water filling pipeline 31 is equal to the amount of water discharged from the annular cavity 130 through the second drain pipeline 32 (or drain hole 105).

[0070] S3. Start the external cooling device 10, fill the cooling bladder 11 with low-temperature demineralized water through the water filling ring 12, and discharge it from the drain ring 13.

[0071] When starting the external cooling device 10, the specific operation is as follows: First, open the valve on the drainage loop 13 to connect the drainage loop 13 with the surrounding atmosphere; open the valve on the water filling loop 12 to fill the water pump inlet; start the water pump to fill the cooling bladder 11 with low-temperature demineralized water through the water filling loop 12, and continuously discharge it from the drainage loop 13 to the drain in the cleaning well 100.

[0072] S4. The annular cavity cooling device 30 and the external cooling device 10 continue to operate and continuously monitor the temperature of the demineralized water in the annular cavity 130. When the demineralized water temperature margin is insufficient or does not meet the water temperature safety limit, the internal cooling device 20 is activated to replace and cool the boron-containing water in the inner cavity of the spent fuel storage tank 110 until the demineralized water temperature meets the water temperature safety limit.

[0073] Referring to FIG8, another embodiment of the spent fuel cooling system of the present invention includes an external cooling device 10 for cooling the exterior of the spent fuel storage container and an internal cooling device 20 for cooling the interior of the spent fuel storage container.

[0074] The spent fuel storage container includes a transport container 140, which is used to load spent fuel assemblies.

[0075] In the embodiment shown in Figure 8, the transport container 140 is a thick-walled metal container. The external cooling device 10 is disposed outside the transport container 140 to cool the outer wall of the transport container 140. The internal cooling device 20 is connected to the inner cavity of the transport container 140 to cool the inner cavity of the transport container 140. This can solve the problem of rising shell temperature and water boiling affecting the operation of operators during long-term interruption of operation of the transport container 140 during the loading process.

[0076] The spent fuel cooling system is installed on the transport container 140, forming a spent fuel transport cooling system together with the transport container 140.

[0077] Specifically, referring to Figures 5-7, the external cooling device 10 may include a cooling bladder 11, a water-filling ring 12, and a draining ring 13. The cooling bladder 11 covers the outside of the transport container 140, specifically covering the outer surface of the transport container 140; the water-filling ring 12 and the draining ring 13 are respectively sleeved on the outside of the cooling bladder 11 and connected to the cooling bladder 11. The first cooling medium enters the cooling bladder 11 through the water-filling ring 12 and is discharged from the draining ring 13. The first cooling medium may be demineralized water, which has the advantage of high water purity, avoiding corrosion and contamination of equipment components, pipelines, etc.

[0078] The cooling bladder 11 comprises several relatively independent cooling bladder units 111; these cooling bladder units 111 are arranged along the outer periphery of the transport container 140 and attached to the outer surface of the transport container 140. Each cooling bladder unit 111 forms an independent cold source, independently cooling the attached outer surface. The cooling bladder units 111 are made of flexible non-metallic or metallic materials, forming a flexible cooling module.

[0079] The water-filling ring 12 includes a water-filling ring 121, several water-filling branch pipes 122, and a water-filling pipe 123. The water-filling ring 121 is sleeved on the outside of the cooling bladder 11; the several water-filling branch pipes 122 are arranged at intervals along the circumference of the water-filling ring 121, connecting the water-filling ring 121 and the corresponding cooling bladder unit 111, thus connecting the water-filling ring 121 and the cooling bladder unit 111. The water-filling pipe 123 is connected to the water-filling ring 121 and is used to introduce the first cooling medium. The first cooling medium enters the water-filling ring 121 through the water-filling pipe 123, and then is distributed along the water-filling ring 121 to each water-filling branch pipe 122, and enters the cooling bladder unit 111 along the water-filling branch pipes 122.

[0080] The drainage loop 13 includes a drainage ring 131, a plurality of drainage branch pipes 132, and a drainage pipe 133. The drainage ring 131 is sleeved on the outside of the cooling bladder 11; the plurality of drainage branch pipes 132 are arranged at intervals along the circumference of the drainage ring 131, connecting the drainage ring 131 and the corresponding cooling bladder unit 111, thus communicating between the drainage ring 131 and the cooling bladder unit 111. The drainage pipe 133 is connected to the drainage ring 131 and is used to discharge the first cooling medium. The first cooling medium in each cooling bladder unit 111 enters the drainage ring 131 through its respective connected drainage branch pipe 132, enters the drainage pipe 133 along the drainage ring 131, and is discharged from the drainage pipe 133.

[0081] To support and position the cooling bladder 11 outside the transport container 140, the external cooling device 10 may further include at least one support collar 14. The support collar 14 is used to fit around the outer periphery of the transport container 140, and the cooling bladder 11 is connected to the support collar 14 around it. The support collar 14 serves as a frame fixation, positioning the cooling bladder 11 and even the entire external cooling device 10 on the transport container 140. To achieve a close fit with the outer peripheral surface of the transport container 140, the side of each cooling bladder unit 111 facing the transport container 140 is an arc-shaped surface, and all cooling bladder units 111 are concentrically fixed around the support collar 14.

[0082] Understandably, a water filling valve can be installed on the water filling pipe 123 to control the water filling flow rate. The end of the water filling pipe 123 away from the water filling ring 121 can be extended to connect to the demineralized water source of the nuclear power plant, and the demineralized water is pumped into the water filling ring 121 under the power provided by the water pump. A drain valve is installed on the drain pipe 133 to control the drain flow rate.

[0083] Preferably, the water filling ring 121 is fitted on the outer periphery of the lower end of the cooling bladder 11, and the drain ring 131 is fitted on the outer periphery of the upper end of the cooling bladder 11, forming a direct current circulation cooling form with low-level water filling and high-level drainage. The first cooling medium carries away the decay heat generated by the spent fuel assembly through the flow mode of bottom filling and top drainage.

[0084] As shown in Figure 8, the internal cooling device 20 is connected to the inner cavity of the transport container 140 and is used to cool the inner cavity of the transport container 140. Specifically, the internal cooling device 20 may include a first water filling line 21 and a first drain line 22; the first water filling line 21 is connected to the air filling hole on the transport container 140, and the first drain line 22 is connected to the drain hole on the transport container 140. A second cooling medium enters the inner cavity of the transport container 140 through the first water filling line 21 and then exits through the first drain line 22, displacing and cooling the boron-containing water in the inner cavity of the transport container 140. The first drain line 22 can extend through the drain hole into the lower part or bottom of the transport container 140.

[0085] The preferred cooling medium is boron-containing water used in nuclear power plants, characterized by the addition of boric acid to the water, which absorbs and moderates neutrons generated by the fission of spent fuel assemblies.

[0086] It is understandable that valves are installed on the first water filling pipeline 21 and the first drainage pipeline 22 to control the flow rate.

[0087] The internal cooling device 20 adopts an upward filling and upward discharge method, and discharges the high-temperature boron-containing water inside the transport container 140 from the top of the transport container 140 at the same water filling flow rate.

[0088] Referring to Figure 8, after the spent fuel cooling system of this embodiment is filled with spent fuel assemblies, the cooling method includes the following steps: activating the internal cooling device 20 to displace and cool the boron-containing water inside the spent fuel storage tank 110; activating the external cooling device 10 to fill the cooling bladder 11 with low-temperature demineralized water through the water filling loop 12 and discharge it from the drainage loop 13. The above cooling method can solve the problems of increased cladding temperature and water boiling affecting operator operations during long-term interruptions in the loading process of transport containers.

[0089] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A spent fuel cooling system, characterized in that, This includes an external cooling device for cooling the exterior of the spent fuel storage container and an internal cooling device for cooling the interior of the spent fuel storage container. The external cooling device includes a cooling bladder covering the outside of the spent fuel storage container, a water-filled ring and a drain ring respectively fitted on the outside of the cooling bladder, the water-filled ring and the drain ring respectively connected to the cooling bladder, the first cooling medium enters the cooling bladder through the water-filled ring and is discharged from the drain ring, taking away the heat emitted from the outside of the spent fuel storage container; The internal cooling device includes a first water filling pipeline connected to an air filling hole on the spent fuel storage container and a first drain pipeline connected to a drain hole on the spent fuel storage container; a second cooling medium enters the inner cavity of the spent fuel storage container through the first water filling pipeline and is then discharged from the first drain pipeline, thereby displacing and cooling the boron-containing water in the inner cavity of the spent fuel storage container.

2. The spent fuel cooling system according to claim 1, characterized in that, The cooling bladder comprises several relatively independent cooling bladder units, which are arranged along the outer periphery of the spent fuel storage container and attached to the outer surface of the spent fuel storage container.

3. The spent fuel cooling system according to claim 2, characterized in that, The water filling ring includes a water filling ring sleeved on the lower end of the cooling bladder, a plurality of water filling branch pipes, and a water filling pipe connected to the water filling ring and used to access the first cooling medium; the plurality of water filling branch pipes are arranged at intervals along the circumference of the water filling ring and connected between the water filling ring and the corresponding cooling bladder unit.

4. The spent fuel cooling system according to claim 2, characterized in that, The drainage loop includes a drainage ring sleeved on the upper end of the cooling bladder, a plurality of drainage branch pipes, and a drainage pipe connected to the drainage ring and used to discharge the first cooling medium; the plurality of drainage branch pipes are arranged at intervals along the circumference of the drainage ring and connected between the drainage ring and the corresponding cooling bladder unit.

5. The spent fuel cooling system according to claim 1, characterized in that, The external cooling device also includes a support collar; the support collar is used to be fitted around the outer periphery of the spent fuel storage container, and the cooling bladder is connected to the support collar around it.

6. The spent fuel cooling system according to any one of claims 1-5, characterized in that, The spent fuel cooling system also includes an annular cooling device for cooling the annular cavity of the spent fuel storage container. The annular cavity cooling device includes a second water filling pipeline and a second drainage pipeline respectively connected to the annular cavity; The third cooling medium enters the annular cavity through the second water filling pipeline and is then discharged from the second drain pipeline, thereby displacing and cooling the high-temperature water in the annular cavity.

7. A spent fuel storage and cooling system, characterized in that, This includes spent fuel storage tanks, transfer containers, and spent fuel cooling systems for loading spent fuel assemblies; The spent fuel storage tank is assembled inside the transfer container, and an annular cavity is formed between the outer periphery of the spent fuel storage tank and the inner periphery of the transfer container; the spent fuel cooling system includes an external cooling device, an internal cooling device, and an annular cavity cooling device. The external cooling device includes a cooling bladder covering the outside of the transfer container, a water-filling ring and a draining ring respectively sleeved on the outside of the cooling bladder, the water-filling ring and the draining ring respectively connected to the cooling bladder, the first cooling medium enters the cooling bladder through the water-filling ring and is discharged from the draining ring, taking away the heat emitted from the outside of the transfer container; The internal cooling device includes a first water filling pipeline connected to the air filling hole on the spent fuel tank and a first drain pipeline connected to the drain hole on the spent fuel tank; the second cooling medium enters the inner cavity of the spent fuel tank through the first water filling pipeline and is then discharged from the first drain pipeline, thereby displacing and cooling the boron-containing water in the inner cavity of the spent fuel tank. The annular cavity cooling device includes a second water filling pipeline and a second drainage pipeline respectively connected to the annular cavity; The third cooling medium enters the annular cavity through the second water filling pipeline and is then discharged from the second drain pipeline, thereby displacing and cooling the high-temperature water in the annular cavity.

8. The spent fuel storage and cooling system according to claim 7, characterized in that, The upper and lower ends of the outer surface of the transfer container are respectively provided with an upper trunnion and a lower trunnion; The external cooling device is located outside the transfer container, between the upper and lower trunnions.

9. A cooling method for a spent fuel storage cooling system as described in claim 7 or 8, characterized in that, Includes the following steps: S1. When the automatic welding system and vacuum drying system of the spent fuel storage tank malfunction and stop operation, continuously monitor the temperature of the demineralized water in the annular cavity between the spent fuel storage tank and the transfer container. S2. When the temperature of the demineralized water in the annular cavity exceeds the safe limit of water temperature, the annular cavity cooling device is turned on so that the amount of water entering the annular cavity through the second water filling pipeline is equal to the amount of water discharged from the annular cavity through the second drainage pipeline. S3. Start the external cooling device, fill the cooling bladder with low-temperature demineralized water through the water filling loop, and discharge it from the drain loop; S4. The annular cavity cooling device and the external cooling device continue to operate and continuously monitor the temperature of the demineralized water in the annular cavity. When the temperature of the demineralized water does not meet the water temperature safety limit, the internal cooling device is activated to replace and cool the boron-containing water in the inner cavity of the spent fuel storage tank until the temperature of the demineralized water meets the safety limit.

10. A spent fuel transportation cooling system, characterized in that, It includes a transport container for loading spent fuel assemblies and a spent fuel cooling system; the spent fuel cooling system includes an external cooling device and an internal cooling device; The external cooling device includes a cooling bladder covering the outside of the transport container, a water-filled ring and a drain ring respectively sleeved on the outside of the cooling bladder, the water-filled ring and the drain ring respectively connected to the cooling bladder, the first cooling medium enters the cooling bladder through the water-filled ring and is discharged from the drain ring, taking away the heat dissipated from the outside of the transport container; The internal cooling device includes a first water filling pipeline connected to an air filling hole on the transport container and a first drain pipeline connected to a drain hole on the transport container; a second cooling medium enters the inner cavity of the transport container through the first water filling pipeline and is then discharged from the first drain pipeline, thereby displacing and cooling the boron-containing water in the inner cavity of the transport container.

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