Spent fuel transfer protection system and spent fuel transfer protection method

Abstract

The invention discloses a spent fuel reshipment protection system and a spent fuel reshipment protection method. The spent fuel reshipment protection system comprises a transportation device, a protection device and a spent fuel container, the protection device is installed on the transportation device, the spent fuel container is assembled in a containing cavity of the protection device in a vertical state, and an annular cavity surrounding the periphery of the spent fuel container is defined in the containing cavity. Through cooperative arrangement of the protection device and the transportation device, after the spent fuel container is hoisted into the protection device, the annular cavity located between the spent fuel container and the protection device is defined, and decay heat of the spent fuel container can be taken away through circulation of cooling water in the annular cavity; and decay heat of the spent fuel container can be taken away by air circulation in a passive cooling mode, and the device is suitable for batch transfer of high-fuel-consumption and high-enrichment-degree spent fuel.

Description

Technical Field

[0001] The present invention relates to the technical field of spent fuel transfer, and in particular to a spent fuel transfer protection system and a spent fuel transfer protection method. Background Art

[0002] After the nuclear reactor fuel has gone through a certain cycle period in the reactor core, due to its large heat release and high radioactivity level, it must be removed in time and stored in the spent fuel pool for cooling. Since the capacity of the spent fuel pool is limited, the spent fuel reprocessing capacity of the reprocessing plant is insufficient, and the geological disposal repository cannot be put into operation. Therefore, the current common means and measures are that after the spent fuel is stored in the pool for a certain number of years, the radiation source intensity and heat source intensity are reduced, and then the spent fuel is removed from the pool and transferred by using a spent fuel container for off-reactor storage.

[0003] For components with long-term cooling and low heat load, although the spent fuel container can be used to achieve the fuel transfer function, for the batch transfer of high burnup and high enrichment spent fuel, it has long been a bottleneck problem for batch transfer of high burnup spent fuel at home and abroad, which is prominently manifested in:

[0004] 1) Existing spent fuel containers are difficult to meet the requirements for transferring high-capacity and high-burnup spent fuel

[0005] To improve the operating economy of nuclear power plants, the current nuclear fuel cycle strategies of nuclear power plants are all developing towards high burnup and long-cycle fuel cycles. As a result, the heat release rate and radiation source intensity of spent fuel are significantly enhanced, which will inevitably impose extremely harsh requirements on the safety performance of spent fuel containers. However, due to material limitations, shielding safety, structural safety and economic requirements, existing spent fuel containers are difficult to meet the requirements for transferring high-capacity, high-burnup and high-heat load spent fuel, which greatly restricts the implementation of the economic fuel cycle strategy of nuclear power plants and affects the safe production operation of nuclear power plants.

[0006] 2) The transfer of high burnup spent fuel has great impacts and risks on the safety of operating personnel and the surrounding environment

[0007] Due to the high heat release rate and radiation source intensity of high burnup spent fuel, during the intermediate transfer process, once there is a failure of the transportation equipment during the transfer process, or natural events such as earthquakes, external tornadoes, and projectile impacts occur, it may lead to the abnormal transfer of the spent fuel container. During the long-term in-situ retention process, due to the too long transfer time, the temperature and pressure inside the container exceed the limits, and at the same time, the spent fuel shell exceeds the safety temperature limit requirement of 400°C. In addition, due to the relatively high surface dose rate level of the spent fuel container, it is also easy to cause radiation safety impacts on operating personnel and the environment.

[0008] Therefore, in view of the prominent problems such as thermal, shielding, and structural safety existing in the above-mentioned transportation of high-burnup spent fuel, it is necessary to develop a new spent fuel transportation protection system to comprehensively ensure the thermal, shielding, and structural safety of high-burnup spent fuel under normal and accident conditions while realizing the normal transportation of high-burnup spent fuel. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide an improved spent fuel transportation protection system and a spent fuel transportation protection method.

[0010] The technical solution adopted by the present invention to solve its technical problems is: to provide a spent fuel transportation protection system, including a transportation device, a protection device, and a spent fuel container for loading spent fuel assemblies;

[0011] The protection device is installed on the transportation device. The protection device has an accommodation chamber. The spent fuel container is assembled in the accommodation chamber in a vertical state, and an annular chamber surrounding the outer periphery of the spent fuel container is defined in the accommodation chamber; the annular chamber is used for filling with cooling water, and the spent fuel container is cooled by circulating the cooling water.

[0012] In some embodiments, the protection device includes a shielding sleeve with an open top and a first sealing assembly;

[0013] The shielding sleeve is arranged on the transportation device with the top facing upwards, and the first sealing assembly is fitted at the top of the annular chamber to seal the top of the annular chamber;

[0014] The shielding sleeve is provided with a water filling interface and an exhaust interface. The water filling interface is located at the lower end of the shielding sleeve, and the exhaust interface is located at the upper end of the shielding sleeve.

[0015] In some embodiments, the protection device further includes an inlet pipe, an outlet pipe, a cooling fan, and a circulation pump;

[0016] The circulation pump is connected to the annular chamber through the inlet pipe and the outlet pipe to form a cooling water circulation loop; the cooling fan is arranged on the inlet pipe or the outlet pipe.

[0017] In some embodiments, the protection device further includes an exhaust overpressure water tank connected to the exhaust interface.

[0018] In some embodiments, the protection device further includes a second sealing assembly, and the second sealing assembly is used to cooperate at the bottom of the annular chamber to seal the bottom of the annular chamber.

[0019] In some embodiments, the transportation device includes a transportation platform and a support assembly. The support assembly is arranged in a ring shape on the transportation platform and is used to support and position the shielding sleeve on the transportation platform. The bottom of the spent fuel container passes through the bottom of the shielding sleeve and is supported on the transportation platform.

[0020] In some embodiments, the spent fuel container includes a metal cylinder body, a hollow cylinder body surrounding the outer periphery of the metal cylinder body, and a cover plate assembly sealingly fitted to the top of the metal cylinder body. The hollow cylinder body is filled with neutron shielding material.

[0021] In some embodiments, at least one upper trunnion is provided at the upper end of the outer surface of the metal cylinder body, and at least one lower trunnion is provided at the lower end.

[0022] In some embodiments, the spent fuel container further includes a support grid, which is arranged inside the metal cylinder body for the spent fuel assembly to be inserted therein.

[0023] In some embodiments, the spent fuel container further includes a pressure relief protection device installed in the cover plate assembly. The pressure relief protection device is connected to the inside of the metal cylinder body and is used for energy dissipation and pressure relief of the cooling water in the metal cylinder body in a boiling state.

[0024] In some embodiments, the spent fuel transfer protection system further includes a working platform, which is installed on the transportation device and surrounds the periphery of the protection device.

[0025] The present invention also provides a method for protecting the transfer of spent fuel. Using the spent fuel transfer protection system described in any one of the above, the method for protecting the transfer of spent fuel includes the following steps:

[0026] Lift the spent fuel container loaded with the spent fuel assembly into the protection device and support and fix it on the transportation device;

[0027] Fill and fill the annular cavity between the spent fuel container and the protection device with cooling water, and make the cooling water in the annular cavity circulate to cool the spent fuel container in a circulating manner;

[0028] Under accident conditions, open the annular cavity between the spent fuel container and the protection device. Air enters from the bottom of the annular cavity. The air entering the annular cavity rises after being heated by the decay heat of the spent fuel container and is discharged from the top of the annular cavity, continuously conducting the decay heat to the external environment.

[0029] Advantages of the present invention: Through the cooperative arrangement of the protection device and the transportation device, after the spent fuel container is hoisted into the protection device, an annular cavity is defined between the spent fuel container and the protection device. Cooling water can circulate in the annular cavity to carry away the decay heat of the spent fuel container, and air can also circulate to carry away the decay heat of the spent fuel container in a passive cooling manner. It is applicable to the batch transfer of high-burnup and high-enrichment spent fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0031] Figure 1 is a three-dimensional structural schematic diagram of a spent fuel transfer protection system according to an embodiment of the present invention;

[0032] Figure 2 is a side view of a spent fuel transfer protection system according to an embodiment of the present invention;

[0033] Figure 3 is a longitudinal sectional structural schematic diagram of a spent fuel transfer protection system according to an embodiment of the present invention;

[0034] Figure 4 is a schematic diagram of passive cooling of a spent fuel transfer protection system according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific embodiments of the present invention will now be described in detail with reference to the drawings.

[0036] As Figure 1 , Figure 2 shown, a spent fuel transfer protection system according to an embodiment of the present invention may include a transportation device 100, a protection device 200, and a spent fuel container 300.

[0037] The protection device 200 and the spent fuel container 300 are both installed on the transportation device 100. The spent fuel container 300 is used to load spent fuel assemblies, and the spent fuel container is assembled vertically in the protection device 200. The protection device 200 cools the spent fuel container 300. The transportation device 100 is used to undertake the transportation function, carry the spent fuel container 300, and transfer the spent fuel container 300 from one place to another.

[0038] In some embodiments, the transportation device 100 may include a transportation platform 10 and a support assembly 11. The support assembly 11 is arranged in a ring on the transportation platform 10 and is used to support and position the protection device 200 on the transportation platform 10.

[0039] The transportation platform 10 can further be a transport vehicle, which includes a flat structure and a plurality of wheels installed below the flat structure. The flat structure is used to carry the weight load of the spent fuel container 300 and the protection device 200, and the wheels enable the movement of the transport vehicle.

[0040] The support assembly 11 can include a plurality of rib plates, which are distributed in a circular array on the transportation platform 10 and are used to support and lift the protection device 200. Through the lifting of the support assembly 11, a space distance is reserved between the bottom of the protection device 200 and the transportation platform 10, so as to serve as a bottom air inlet under accident conditions.

[0041] The transportation device 100 can further include a power supply mechanism 12 installed on the transportation platform 10, such as a diesel generator, to supply power to the electrical devices.

[0042] On the transportation platform 10, the protection device 200 surrounds the spent fuel container 300. In this regard, the protection device 200 has an accommodation chamber, and the spent fuel container 300 is assembled in the accommodation chamber in a vertical state, and an annular cavity 201 surrounding the outer periphery of the spent fuel container 300 is defined in the accommodation chamber. The annular cavity 201 is used to fill with cooling water, and the spent fuel container 300 is circulated and cooled by the cooling water. The annular cavity 201 can also be used for air circulation to cool the spent fuel container 300 in a passive cooling manner.

[0043] The protection device 200 can further include a shielding sleeve 20. The shielding sleeve 20 is a thick-walled metal cylinder structure, which is connected and fixed to the support assembly 11. The top of the shielding sleeve 20 is open to facilitate the hoisting in and out of the spent fuel container 300; the bottom of the shielding sleeve 20 is also open, so that it can communicate with the space between the bottom of the protection device 200 and the transportation platform 10, and the bottom of the spent fuel container 300 passes through the bottom of the shielding sleeve 20 and is supported on the transportation platform 10.

[0044] To prevent structural interference between the shielding sleeve 20 and the spent fuel container 300, it is required that in the vertical height, the length of the shielding sleeve 20 is not greater than the distance between the upper trunnion 301 and the lower trunnion 302 of the spent fuel container 300. This can not only very conveniently cover the outside of the spent fuel container 300, but also undertake the functions of strengthening shielding and structural safety protection for the spent fuel container 300.

[0045] The protection device 200 may further include a first sealing assembly 21, which is used to cooperate with the top of the annular cavity 201 to seal the top of the annular cavity 201. For the bottom of the shielding sleeve 20 being open, the protection device 200 may further include a second sealing assembly 22, which is used to cooperate with the bottom of the annular cavity 201 to seal the bottom of the annular cavity 201. The arrangement of the first sealing assembly 21 and the second sealing assembly 22 at the top and bottom of the annular cavity 201 forms a closed chamber in the annular cavity 201 for cooling water to fill and circulate therein to carry away the decay heat generated by the spent fuel assemblies in the spent fuel container 300.

[0046] In an alternative embodiment, the first sealing assembly 21 may include a first sealing ring and a first support plate. The first support plate is circumferentially arranged inside the upper end of the shielding sleeve 20 and is also within the annular cavity 201; the first sealing ring is supported on the first support plate. The first sealing ring is a hollow flexible inflatable bag, and by filling compressed gas into the flexible inflatable bag, it expands to seal the top of the annular cavity 201 and undertakes the function of sealing the cooling water at the top of the annular cavity 201.

[0047] Similarly to the first sealing assembly 21, the second sealing assembly 22 may also include a second sealing ring and a second support plate. The second support plate is circumferentially arranged inside the lower end of the shielding sleeve 20 and is also within the annular cavity 201; the second sealing ring is supported on the second support plate. The second sealing ring is a hollow flexible inflatable bag, and by filling compressed gas into the flexible inflatable bag, it expands to seal the bottom of the annular cavity 201 and undertakes the function of sealing the cooling water at the bottom of the annular cavity 201.

[0048] To facilitate filling water into the annular cavity 201, the shielding sleeve 20 is provided with a water filling interface 23 and an exhaust interface 24. The water filling interface 23 is located at the lower end of the shielding sleeve 20 to fill cooling water into the annular cavity 201 in a low-level water filling manner. The exhaust interface 24 is located at the upper end of the shielding sleeve 20, which is at a high position relative to the water filling interface 23 and undertakes the exhaust function, so that after filling water from the low level, the entire space of the annular cavity 201 between the shielding sleeve 20 and the spent fuel container 300 can be filled with water all the time.

[0049] To cooperate with the exhaust interface 24, the protection device 200 further includes an exhaust overpressure water tank 25 connected to the exhaust interface 24. In order for the cooling water to overflow to the exhaust overpressure water tank 25 after filling the annular cavity 201, the exhaust overpressure water tank 25 also ensures that the annular cavity 201 is filled with water, that is: when filling water into the annular cavity 201 until the exhaust overpressure water tank 25 is also filled with water, it means that the annular cavity 201 is already filled with water. The exhaust overpressure water tank 25 is located at a high position of the shielding sleeve 20, and the installation position requires an area with a height exceeding 1 m above the vertical height of the entire shielding sleeve 20.

[0050] To realize the circulating cooling of cooling water, the protection device 200 also includes a water inlet pipe 26, a water outlet pipe 27, a cooling fan 28 and a circulating pump 29. The circulating pump 29 is connected to the annular cavity through the water inlet pipe 26 and the water outlet pipe 27 to form a cooling water circulation loop; the cooling fan 28 is arranged on the water inlet pipe 26 or the water outlet pipe 27 to air-cool the cooling water passing through. The cooling fan 28 has fan blades and a cooling coil. The power consumption of the cooling fan 28 and the circulating pump 29 is provided by the power supply mechanism on the transport platform.

[0051] exist Figure 3 In the illustrated embodiment, the water inlet pipe 26 is connected between the lower end of the shielding sleeve 20 and the outlet of the circulating pump 29, and the water outlet pipe 27 is connected between the upper end of the shielding sleeve 20 and the inlet of the circulating pump 29; the cooling fan 28 is arranged on the water outlet pipe 27. After the circulating pump 29 is started, the cooling water in the annular cavity 201 is pumped out, and the cooling water enters the circulating pump 29 through the water outlet pipe 27 and the cooling fan 28, and then enters the annular cavity 201 from the outlet of the circulating pump 29 and the water inlet pipe 26.

[0052] It can be understood that the cooling water circulation loop and the water filling interface 23 and the exhaust interface 24 are staggered on the shielding sleeve 20 , that is, they are located on different sides of the shielding sleeve 20 .

[0053] The first sealing assembly 21 and the second sealing assembly 22 can be combined to form a sealed state by inflation, and the annular cavity 201 can be opened when not inflated or deflated, so that air can flow in and out. During the intermediate transportation of the spent fuel container 300, if the annular cavity 201 loses water or power in an accidental working condition, passive air natural ventilation cooling can be achieved through the annular cavity 201, thereby ensuring that the spent fuel assembly inside the spent fuel container 300 is always in a low temperature, low pressure safety state during the entire vertical transportation process.

[0054] The second sealing component 22 is movably arranged in the bottom of the annular cavity 201 . The second sealing component 22 can be not only lifted to a predetermined position in the annular cavity 201 for fixation, but also moved away from the annular cavity 201 to open the bottom of the annular cavity 201 .

[0055] The transport device 100 may further include a lifting mechanism 13 , which is located in the space between the shielding sleeve 20 and the transport platform 10 and is disposed below the second sealing assembly 22 , and is used to drive the second sealing assembly 22 to move up and down in the annular cavity 201 .

[0056] The lifting mechanism 13 supports the lifting platform below the second sealing assembly 22. The lifting drive of the lifting mechanism 13 can be a screw lifting device or a hydraulic lifting device, and has the following functions: 1) Under normal conditions, lift the second sealing assembly 22 to facilitate the positioning and installation of the second sealing assembly 22 into the annular cavity 201 area. 2) Under normal conditions, when the annular cavity 201 between the shielding sleeve 20 and the spent fuel container 300 is filled with water, the lifting mechanism 13 vertically supports the second sealing assembly 22, bears the vertical water pressure of the entire annular cavity 201, and prevents the second sealing assembly 22 from falling off due to high pressure in the annular cavity 201 area. 3) Under accident earthquake conditions, such as the unfavorable situation of the second sealing ring of the second sealing assembly 22 failing to seal and the cooling water being lost, lower the second sealing assembly 22 so that the entire annular cavity 201 is converted from active cooling by cooling water to passive cooling by air.

[0057] When the protection device 200 is working, the heat transfer path of its cooling water circulation loop refers to Figure 3 , and the specific heat transfer process is as follows:

[0058] The heat generated inside the spent fuel container 300 is continuously transferred to the annular cavity fluid between the spent fuel container 300 and the shielding sleeve 20 through heat conduction, causing the low-temperature fluid sent into the annular cavity 201 from the water inlet pipe 26 to turn into a high-temperature fluid; under the driving action of the circulation pump 29, the high-temperature fluid in the annular cavity fluid flows upward and flows out from the water outlet pipe 27; the high-temperature fluid flowing out from the water outlet pipe 27 then enters the coil inside the cooling fan 28; the fluid in the coil of the cooling fan 28 is cooled by the fan, and the heat is conducted to the external atmospheric environment and turns into a low-temperature fluid; the low-temperature fluid enters from the water inlet pipe 26 under the action of the circulation pump 29 and circulates in this way to achieve circulating cooling. The flow direction of the cooling water is as shown by the solid line arrow in Figure 3 , and the heat conduction direction is as shown by the dashed line arrow in Figure 3 .

[0059] Combined with Figure 3 、 Figure 4 , in accident conditions such as earthquakes and impacts by external flying objects, once there is a situation of cooling water loss in the annular cavity 201 or power failure resulting in the loss of circulating power, the lifting platform of the lifting mechanism 13 can be lowered to drive the second sealing assembly 22 to descend and disengage from the annular cavity 201, opening the bottom of the annular cavity 201; remove the first sealing ring of the first sealing assembly 21, so that the entire annular cavity 201 between the spent fuel container 300 and the shielding sleeve 20 is in a state of being connected and exposed to the atmospheric environment. In this situation, affected by the heat flux density difference of the decay heat of the spent fuel assembly on the annular cavity air at the entire vertical height, cold air at the bottom enters the annular cavity 201 and then turns into hot air and is discharged from the top, forming a stable and continuous passive cooling method. Combined with Figure 4 , the specific heat transfer process is as follows:

[0060] External natural air enters through the air inlet between the support assembly 11 and the bottom of the shielding sleeve 20; the natural air in the annular cavity 201 is heated by the decay heat of the spent fuel container 300 and turns into hot air. Due to the decrease in density, it gradually rises; the continuously rising hot air is then exhausted from the top of the annular cavity 201 and enters the surrounding atmospheric environment. Through a stable and continuous passive natural ventilation cycle, the decay heat in the spent fuel container 300 is continuously conducted to the atmospheric environment.

[0061] In some embodiments, as Figure 3 shown, the spent fuel container 300 may include a metal cylinder body 30, a hollow cylinder body 31 surrounding the outer periphery of the metal cylinder body 30, a cover plate assembly 32 sealingly fitted to the top of the metal cylinder body 30, and a support grid 33 provided inside the metal cylinder body 30; neutron shielding material is filled in the hollow cylinder body 31. The support grid 33 is used for the spent fuel assembly to be inserted therein; the spent fuel assembly is loaded in the metal cylinder body 30 and is positioned by being inserted into the support grid 33. The annular cavity 201 is formed between the outer periphery of the hollow cylinder body 31 and the shielding sleeve 20.

[0062] The upper trunnion 301 is provided at the upper end of the outer surface of the metal cylinder body 30, and the lower trunnion 302 is provided at the lower end of the outer surface of the metal cylinder body 30. The upper end of the metal cylinder body 30 having the upper trunnion 301 extends out of the top of the hollow cylinder body 31, and the lower end having the lower trunnion 302 extends out of the bottom of the hollow cylinder body 31. The upper trunnion 301 and the lower trunnion 302 are respectively used for hoisting to realize the hoisting and flipping functions of the spent fuel container 300.

[0063] Corresponding to the lower trunnion 302 of the spent fuel container 300, the transportation device 100 may further include a trunnion limiter 14 provided on the transportation platform 10. The trunnion limiters 14 are respectively located at both ends of the lower trunnion 302 at the lower end of the spent fuel container 300 and are symmetrically distributed around the vertical axis of the spent fuel container 300. They can be configured in a matching manner according to the number of the lower trunnions 302 of the spent fuel container 300, and 2 or 4 can be selected. After the spent fuel container 300 is seated on the transportation platform 10, the diameter position of the trunnion limiter 14 on the same horizontal plane is adjusted through a screw drive device or a hydraulic device, so as to gradually approach, tightly fit and fasten the lower trunnion 302 of the spent fuel container 300.

[0064] The spent fuel container 300 further includes a pressure relief protection device 34 installed in the cover plate assembly 32. The pressure relief protection device 34 is connected to the inside of the metal cylinder body 30 and is used for energy dissipation and pressure relief of the cooling water in the metal cylinder body 30 in a boiling state.

[0065] The cover plate assembly 32 may further include a top cover 321 and a protective cover 322. The top cover 321 is fitted inside the upper end of the metal cylinder 30 to close the top of the metal cylinder 30. The protective cover 322 is connected to the top end face of the metal cylinder 30 and covers the top cover 321 at the same time, defining a top space between the top cover 321 and the protective cover 322. The pressure relief protection device 34 is installed on the top cover 321 and is in the top space.

[0066] The pressure relief protection device 34 may further include a pressure relief safety valve, a buffer pipe, a condenser and a sampling valve; the pressure relief safety valve is plugged into the top cover 321 and is connected to the internal space of the metal cylinder 30 through a vent hole on the top cover 321; the buffer pipe is connected between the pressure relief safety valve and the condenser to send the high-temperature steam from the metal cylinder 30 into the condenser; the sampling valve is connected to the condenser for sampling to judge the pressure relief situation.

[0067] The buffer pipe is a bent pipe, for example, including several S-shaped bent pipe segments, so that the buffer pipe has multiple bent segments in its conveying direction.

[0068] Since the water body (such as cooling water) inside the metal cylinder 30 is radioactive and the water body is continuously heated by the decay heat of the spent fuel assembly during transportation, the water temperature will gradually rise. Once the water temperature and pressure continue to rise and boiling occurs, and the internal pressure of the metal cylinder 30 exceeds the design pressure set value, the pressure relief safety valve will open to relieve pressure in time. Since the high-temperature and high-pressure steam released by pressure relief has a high flow rate, in order to avoid damage to the high-energy fluid ejection structure, it first enters the buffer pipe to reduce the steam pressure by increasing the pipe resistance, and then the high-temperature steam enters the condenser.

[0069] Further, for another example Figure 1 and Figure 2 As shown, in some embodiments, the spent fuel transfer protection system further includes a working platform 400. The working platform 400 is supported by a bracket and installed on the transportation platform 10 and surrounds the periphery of the protection device 200. The working platform 400 is used to complete the installation and inflation sealing operations of the annular cavity 201 seal between the spent fuel container 300 and the protection device 200.

[0070] The working platform 400 provides a working operation space for operators and has a fence, which is convenient for operations such as taking and placing the first sealing ring of the first sealing assembly 21, plugging the inflation pipe or the water filling pipe on the working platform 400.

[0071] The spent fuel transfer protection method implemented by the spent fuel transfer protection system of the present invention includes the following steps:

[0072] Under normal operating conditions, cooling water is filled and completely fills the annular cavity 201 between the loaded and sealed spent fuel container 300 and the protection device 200, and the cooling water in the annular cavity 201 circulates to cool the spent fuel container 300 cyclically and carry away the decay heat of the spent fuel assembly.

[0073] Under accident conditions (such as in accident conditions like earthquakes, impacts by external projectiles, etc., where the cooling water in the annular cavity 201 is lost or the circulating power is lost due to power failure), the annular cavity 201 between the spent fuel container 300 and the protection device 200 is opened, air enters from the bottom of the annular cavity 201, the air entering the annular cavity 201 rises after being heated by the decay heat of the spent fuel container 300, and is discharged from the top of the annular cavity 201, continuously conducting the decay heat to the external environment (i.e., the atmospheric environment).

[0074] The specific operations of the above steps are as follows:

[0075] 1), Lift and place the loaded and sealed spent fuel container 300 on the transportation platform 10 for preliminary installation and positioning; adjust the positions of the electric screw and the hydraulic rod so that the trunnion limiter 14 slowly contacts and fixes with the lower trunnion 302 of the spent fuel container 300, making the spent fuel container 300 in a fixed state.

[0076] 2), The operator installs the first sealing ring on the first support plates distributed circumferentially on the working platform 400 to form the first sealing assembly 21; fills compressed gas into the first sealing ring through the inflation valve, making the top of the annular cavity 201 in a sealed state.

[0077] 3), Lift the lifting platform of the lifting mechanism 13 to lift the second sealing assembly into the bottom area of the annular cavity 201. Inflate the second sealing ring of the second sealing assembly 22 through the special inflation valve, making the bottom of the annular cavity 201 in a sealed state.

[0078] 4), Introduce external water source through the water filling interface 23 to inject water into the annular cavity 201 area between the spent fuel container 300 and the shielding sleeve 20; continuously fill the water body inside the annular cavity 201 until the liquid level inside the exhaust overpressure water tank 25 reaches the area more than 1 m above the vertical height of the entire shielding sleeve 20;

[0079] 5), Close the valves of the water filling interface 23 and the exhaust overpressure water tank 25.

[0080] 6), Turn on the cooling fan 28 to make the water in the water inlet pipe 26, the annular cavity between the spent fuel container 300 and the shielding sleeve 20, and the water outlet pipe 27 in continuous circulation.

[0081] 7), Once an accident condition occurs, directly lower the lifting platform to lower the second sealing assembly 22 to the area below the shielding sleeve 20.

[0082] 8), The operator removes the first sealing ring on the working platform 400.

[0083] 9), The spent fuel container 300 is converted to the passive cooling mode of the annular cavity, and continuously removes the decay heat of the spent fuel to the surrounding atmosphere.

[0084] In summary, as a means to enhance the heat transfer capacity, shielding effect and structural protection of the spent fuel container, the present invention has the following effects:

[0085] First, it can effectively solve the problems of material limit, shielding safety, structural safety and economic transportation of the spent fuel container, meet the transportation requirements of high-capacity, high-burnup and high-heat-load spent fuel, effectively match the implementation of the long-cycle and economic fuel cycle strategy of nuclear power plants, and effectively ensure the safe production operation of nuclear power plants.

[0086] Second, aiming at the problems of high heat release rate and high radiation source intensity of high-burnup spent fuel assemblies, it can play a role in thermal safety, shielding safety and structural protection of the spent fuel container during the transportation process under normal and accident conditions, ensure that the cladding of the spent fuel in the container does not exceed the safety limit during the too-long in-situ retention and transportation process, and guarantee the radiation safety of the surrounding operating personnel and the environment.

[0087] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied to other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A spent fuel transshipment protection system, characterized in that: Includes transport devices, protection devices and spent fuel containers for containing spent fuel assemblies; The protection device is installed on the transport device, and the protection device has a accommodating chamber, the spent fuel container is installed in a vertical state in the accommodating chamber, and an annular cavity surrounding the outer periphery of the spent fuel container is defined in the accommodating chamber; The annular cavity is used to fill cooling water, and the spent fuel container is circulated and cooled by the cooling water; or the annular cavity is used for air circulation, and the spent fuel container is cooled in a passive cooling manner.

2. The spent fuel transshipment protection system according to claim 1, characterized in that: The protection device comprises a shielding sleeve with an open top and a first sealing assembly; The shielding sleeve is arranged on the transport device with the top facing upward, and the first sealing assembly is fitted on the top of the annular cavity to seal the top of the annular cavity; The shielding sleeve is provided with a water filling interface and an exhaust interface, the water filling interface is located at the lower end of the shielding sleeve, and the exhaust interface is located at the upper end of the shielding sleeve.

3. The spent fuel transshipment protection system according to claim 2, characterized in that: The protection device also includes a water inlet pipe, a water outlet pipe, a cooling fan and a circulation pump; The circulating pump is connected with the annular cavity through the water inlet pipe and the water outlet pipe to form a cooling water circulation loop; the cooling fan is arranged on the water inlet pipe or the water outlet pipe.

4. The spent fuel transshipment protection system according to claim 2, characterized in that: The protection device also includes an exhaust overpressure water tank connected to the exhaust interface.

5. The spent fuel transshipment protection system according to claim 2, characterized in that: The protection device also includes a second sealing component, which is used to cooperate with the bottom of the annular cavity to seal the bottom of the annular cavity.

6. The spent fuel transshipment protection system according to any one of claims 2 to 5, characterized in that: The transport device comprises a transport platform and a support assembly, wherein the support assembly is arranged in a ring shape on the transport platform and is used to support and position the shielding sleeve on the transport platform; the bottom of the spent fuel container passes through the bottom of the shielding sleeve and is supported on the transport platform.

7. The spent fuel transshipment protection system according to any one of claims 2 to 5, characterized in that: The spent fuel container comprises a metal cylinder, a hollow cylinder surrounding the outer periphery of the metal cylinder, and a cover assembly sealed and matched on the top of the metal cylinder; the hollow cylinder is filled with neutron shielding material.

8. The spent fuel transshipment protection system according to claim 7, characterized in that: The outer surface of the metal cylinder is provided with at least one upper trunnion at the upper end and at least one lower trunnion at the lower end.

9. The spent fuel transshipment protection system according to claim 7, characterized in that: The spent fuel container further comprises a supporting grid, which is arranged in the metal cylinder and is used for the spent fuel assembly to be inserted therein.

10. The spent fuel transshipment protection system according to claim 7, characterized in that: The spent fuel container also includes a pressure relief protection device installed in the cover plate assembly, and the pressure relief protection device is connected to the inside of the metal cylinder and is used for dissipating energy and relieving pressure of cooling water in the metal cylinder in a boiling state.

11. The spent fuel transshipment protection system according to claim 1, characterized in that: The spent fuel transshipment protection system further comprises a working platform, which is installed on the transport device and surrounds the periphery of the protection device.

12. A spent fuel transshipment protection method, characterized in that: The spent fuel transshipment protection system according to any one of claims 1 to 11 is adopted, wherein the spent fuel transshipment protection method comprises the following steps: Lift the spent fuel container containing the spent fuel assembly into the protective device and support and fix it on the transport device; Filling cooling water into and filling up the annular cavity between the spent fuel container and the protection device, and circulating the cooling water in the annular cavity to circulate cooling for the spent fuel container; Under accident conditions, the annular cavity between the spent fuel container and the protection device is opened, and air enters the annular cavity from the bottom thereof. The air entering the annular cavity rises after being heated by the decay heat of the spent fuel container, and is discharged from the top of the annular cavity, continuously conducting the decay heat to the external environment.

Images