Spent fuel wet-process reshipment device and spent fuel wet-process reshipment method

Abstract

The invention discloses a spent fuel wet-process reshipment device and a spent fuel wet-process reshipment method. The spent fuel wet-process reshipment device comprises a reshipment container with an open top, a top cover matched and sealed at the top of the reshipment container, a protection cover matched at the top of the reshipment container and covering the outer side of the top cover, and a pressure relief protection device mounted on the top cover, the internal space of the transfer container is used for accommodating spent fuel and cooling water; the pressure relief protection device is located between the top cover and the protection cover, communicated with the inner space of the transferring container and used for conducting energy dissipation and pressure relief on cooling water in the transferring container in the boiling state. According to the wet-process reshipment device for the spent fuel, the pressure relief protection device, the top cover and the protection cover are arranged at the top of the reshipment container, so that the reshipment container can directly load a spent fuel assembly and cooling water for wet-process reshipment, and inflation drainage and vacuumizing drying operation are not needed.

Description

Technical Field

[0001] The present invention relates to the technical field of spent fuel transfer, and particularly relates to a wet transfer device for spent fuel and a wet transfer method for spent fuel. Background Art

[0002] After the fuel of a nuclear reactor has gone through a certain cycle period in the reactor core, it must be removed in time and stored in a spent fuel pool for cooling. Since the capacity of the spent fuel pool is limited, the spent fuel must be removed from the pool in time. There are two methods for transferring spent fuel: one is to use a transport container to transfer the spent fuel in the nearly full pool to the pool of other nuclear power plants with a larger storage margin for storage, and after storing for a certain number of years, it is transported to a reprocessing plant using a transport container. The other is to build a wet pool (temporary or permanent), use a transport container to transfer the spent fuel to the pool for storage, and after storing for a certain number of years, it is transported to a reprocessing plant using a transport container.

[0003] Regardless of which transfer method is used, during the transfer process, the above-mentioned solutions all need to first use a transport container to complete the underwater loading of spent fuel in the spent fuel pool, then hoist the transport container to a cleaning well to empty the water inside the container, perform vacuum drying on the spent fuel, then enter the pool for cooling again. When it is transported out after storing for a certain number of years, it is necessary to empty the water in the container again for secondary vacuum drying.

[0004] Although the existing transport container can solve the problem of fuel transfer through dry transfer, there are prominent problems such as affecting the nuclear safety of spent fuel and low operation efficiency, which are mainly manifested in:

[0005] 1. Repeated vacuum drying of high burnup spent fuel is likely to damage the cladding performance and cause breakage and leakage

[0006] The nuclear fuel cladding is mainly composed of zirconium alloy materials. During the operation of the nuclear reactor, in a high-temperature irradiation environment, zirconium alloy reacts with hydrogen in water to produce zirconium hydride, and this material is distributed inside the zirconium alloy material. Due to repeated cycle of vacuum drying inside the spent fuel transport container, the temperature and stress of the fuel cladding will fluctuate repeatedly within a large range, resulting in the redistribution of the originally distributed zirconium hydride in the zirconium alloy, thereby causing changes in the mechanical properties of the cladding material. Its typical characteristic is that due to hydrogen reorientation and localization in the circumferential and radial directions of the cladding, the yield strength of the cladding decreases, resulting in cladding breakage and leakage of fission gas nuclides. Especially for high burnup spent fuel, due to a longer cycle period and deeper reaction in the reactor, the safety risk of the cladding material being damaged and leaking after multiple vacuum dryings is higher. So far, it has been a difficult problem that cannot be solved in the safe operation of nuclear power plants at home and abroad.

[0007] 2. The operation cycle of repeated drying of spent fuel is long, the efficiency is low, and the radiation dose of personnel is high

[0008] According to the acceptance criteria for the vacuum drying operation of spent fuel containers, a vacuum degree of 3 torr for half an hour needs to be achieved to meet the spent fuel transportation standards. During this period, it takes about 30 to 40 hours for the vacuum drying time. After the vacuum drying operation, personnel are required for close-range pipeline operation, fixed installation of the container cover plate, and surface decontamination. The entire operation process takes nearly a week. Therefore, there are problems such as a long vacuum drying operation cycle, low transfer efficiency, and high personnel radiation dose.

[0009] In summary, in view of the problems existing in the multiple-cycle drying and transfer of existing spent fuel transportation containers, it is necessary to develop a new spent fuel transfer method to solve the above problems. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide an improved wet transfer device for spent fuel and a wet transfer method for spent fuel.

[0011] The technical solution adopted by the present invention to solve its technical problems is: to provide a wet transfer device for spent fuel, including a transfer container with an open top, a top cover fitted and sealed on the top of the transfer container, a protective cover fitted on the top of the transfer container and covering the outside of the top cover, and a pressure relief protection device installed on the top cover;

[0012] The internal space of the transfer container is used to accommodate spent fuel and cooling water; the pressure relief protection device is located between the top cover and the protective cover and is connected to the internal space of the transfer container, and is used for energy dissipation and pressure relief of the cooling water in the transfer container in a boiling state.

[0013] In some embodiments, the pressure relief protection device includes a pressure relief safety valve, a buffer pipe, a condenser, and a sampling valve;

[0014] The pressure relief safety valve is inserted into the top cover and is connected to the internal space of the transfer container through a vent hole on the top cover; the buffer pipe is connected between the pressure relief safety valve and the condenser and sends the high-temperature steam from the transfer container into the condenser;

[0015] The sampling valve is connected to the condenser and is used for sampling to judge the pressure relief situation.

[0016] In some embodiments, the buffer pipe includes a plurality of S-shaped bent pipe segments.

[0017] In some embodiments, a plurality of fishbone plates are arranged in a staggered manner in the condenser.

[0018] In some embodiments, two groups of fishbone plate groups are provided in the condenser, and each fishbone plate group includes a plurality of fishbone plates;

[0019] The two groups of the fishbone plates are arranged vertically in the condenser, and the fishbone plates of the two groups of fishbone plate groups are arranged staggeredly respectively.

[0020] In some embodiments, the top cover is provided with an inflation hole and an exhaust hole respectively communicating with the internal space of the transfer container.

[0021] In some embodiments, the inflation hole extends in an S shape or a Z shape in the top cover; and / or, the exhaust hole extends in an S shape or a Z shape in the top cover.

[0022] In some embodiments, the transfer container includes a metal cylinder body, a hollow cylinder body surrounding the outer periphery of the metal cylinder body, and a neutron shielding material is filled in the hollow cylinder body;

[0023] A stepped flange surface is provided on the inner side of the top of the metal cylinder body, a stepped mating surface adapted to the stepped flange surface is provided on the outer periphery of the top cover, and the stepped mating surface is in sealing cooperation with the stepped flange surface; the protective cover is hermetically connected to the top end surface of the metal cylinder body.

[0024] In some embodiments, a drain port is provided at the bottom of the transfer container.

[0025] In some embodiments, the drain port extends in an L shape at the bottom of the transfer container.

[0026] In some embodiments, at least one upper trunnion is provided at the upper end of the outer surface of the transfer container, and at least one lower trunnion is provided at the lower end.

[0027] In some embodiments, the spent fuel wet transfer device further includes a support grid, and the support grid is arranged in the internal space of the transfer container for accommodating the spent fuel assembly.

[0028] The present invention also provides a spent fuel wet transfer method, adopting the spent fuel wet transfer device described in any one of the above, and the spent fuel wet transfer method includes the following steps:

[0029] S1. Inject cooling water into the transfer container until the water level reaches the elevation position;

[0030] S2. Hoist the spent fuel assembly in the first spent fuel pool into the transfer container;

[0031] S3. Hoist the top cover to the top of the transfer container and connect and fix it, and install the protective cover on the top of the transfer container after meeting the sealing requirements;

[0032] S4. Transfer the transfer container with the spent fuel assembly to the intermediate storage facility;

[0033] S5. Open the protective cover, take a sample for inspection of the pressure relief protection device on the top cover. If cooling water appears in the sample taken, perform auxiliary cooling treatment on the surface of the transfer container until no more cooling water appears in the sample;

[0034] S6. Lift and suspend the transfer container into the second spent fuel pool;

[0035] S7. Lift the top cover off the transfer container underwater, lift out the spent fuel assembly in the transfer container and place it in the pool grid of the second spent fuel pool.

[0036] In some embodiments, step S3 further includes performing a seal check:

[0037] Fill the transfer container with a tracer gas through the gas charging hole on the top cover, so that the tracer gas fills the top space between the support grid in the transfer container and the top cover;

[0038] Close the gas charging hole and the exhaust hole on the top cover, perform vacuum sampling outside the top cover, and detect whether there is tracer gas in the sample taken, so as to judge the seal integrity of the top cover on the transfer container.

[0039] In some embodiments, in step S5, the operation of taking a sample for inspection of the pressure relief protection device is as follows: Open the sampling valve on the condenser and take a sample of the condenser through the sampling valve.

[0040] Advantages of the present invention: By arranging the pressure relief protection device, the top cover and the protective cover on the top of the transfer container, the transfer container can directly load the spent fuel assembly and cooling water for wet transfer, without the need for gas filling and drainage and vacuum drying operations.

[0041] First, it solves the problem that in the traditional spent fuel transport container, during multiple cycles of internal vacuum drying, the temperature and stress of the fuel cladding will fluctuate repeatedly within a large range, resulting in the redistribution of zirconium hydride originally distributed in the zirconium alloy, reducing the yield strength of the cladding and causing cladding breakage and leakage of fission gas nuclides;

[0042] Second, directly using cooling water for loading avoids the problems of long operation cycle, low efficiency and high personnel radiation dose in the multiple cycle drying operation of spent fuel;

[0043] Third, a special pressure relief protection device is configured on the top of the transfer container to gradually dissipate energy and relieve pressure on high-energy fluids, prevent external leakage of radioactive waste liquid, and ensure that the spent fuel assembly inside the transfer container is always in a safe and controllable state during the entire transfer process. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0045] Figure 1 is a schematic structural diagram (1 / 4 section) of the spent fuel wet transfer device according to an embodiment of the present invention;

[0046] Figure 2 is a schematic longitudinal sectional structural diagram of the spent fuel wet transfer device according to an embodiment of the present invention at an angle;

[0047] Figure 3 is a schematic longitudinal sectional structural diagram of the spent fuel wet transfer device according to an embodiment of the present invention at another angle;

[0048] Figure 4 is a schematic structural diagram (1 / 4 section) of the top cover in the spent fuel wet transfer device according to an embodiment of the present invention;

[0049] Figure 5 is a schematic structural diagram (1 / 4 section) of the protective cover in the spent fuel wet transfer device according to an embodiment of the present invention;

[0050] Figure 6 is a schematic structural diagram of the pressure relief protection device in the spent fuel wet transfer device according to an embodiment of the present invention;

[0051] Figure 7 is Figure 6 a schematic diagram of the fluid flow direction in the shown condenser;

[0052] Figure 8 is a schematic structural diagram of the support grid in the spent fuel wet transfer device according to an embodiment of the present invention. Detailed implementation manners

[0053] For a clearer understanding of the technical features, objectives, and effects of the present invention, the specific implementation manners of the present invention will now be described in detail with reference to the accompanying drawings.

[0054] The spent fuel wet transfer device of the present invention is used for wet transfer of spent fuel assemblies.

[0055] As Figures 1 - 2 shown, the spent fuel wet transfer device according to an embodiment of the present invention may include a transfer container 100, a top cover 30, a protective cover 40, and a pressure relief protection device 50.

[0056] The internal space of the transfer container 100 is used to load spent fuel assemblies and cooling water, so that the spent fuel assemblies are immersed in the cooling water inside the transfer container 100. The top of the transfer container 100 is open for easy loading and unloading of the spent fuel assemblies. The top cover 30 is fitted to the top of the transfer container 100 to seal the top. The pressure relief protection device 50 is installed on the top cover 30 and is connected to the internal space of the transfer container 100 for dissipating energy and relieving pressure of the cooling water in the transfer container 100 in the boiling state. The protective cover 40 is installed on the top of the transfer container 100 and covers the outside of the top cover 30, enclosing the top cover 30 inside the protective cover 40 and defining a space above the top cover 30, where the pressure relief protection device 50 is located.

[0057] The transfer container 100, together with the top cover 30 and the protective cover 40 installed on its top, forms a sealed container, which is a nuclear pressure-bearing container of nuclear safety class 1 and can directly load spent fuel assemblies and cooling water for wet transfer without the operations of inflating and draining water and vacuum drying. In terms of safety assurance measures, considering that the cooling water inside the transfer container 100 continuously absorbs the decay heat of the spent fuel assemblies during the transfer process, the pressure and temperature of the cooling water itself will continue to rise until the phenomenon of water vapor boiling occurs. To avoid the risks of high temperature and high pressure inside the container caused by water vapor boiling, a pressure relief protection device 50 is configured on the top of the transfer container 100, which can dissipate energy and relieve pressure of the high-energy fluid step by step and then collect and store it. At the same time, the entire transfer container 100 adopts double redundant sealing means (including the installation of the top cover 30 and the protective cover 40, etc.) to prevent the leakage of radioactive waste liquid, so as to ensure that the spent fuel assemblies inside the transfer container 100 are always in a safe and controllable state during the whole transfer process.

[0058] Specifically, the transfer container 100 may further include a metal cylinder 10 in its structure, and a hollow cylinder 20 surrounding the outer circumference of the metal cylinder 10, and the hollow cylinder 20 is filled with neutron shielding material.

[0059] The metal cylinder 10 serves as the inner cylinder of the transfer container 100, which is a thick-walled cylinder and undertakes the loading function. The internal space is used to accommodate spent fuel assemblies, cooling water, etc. The metal cylinder 10 can be made of materials such as stainless steel and lead and has a shielding effect.

[0060] The hollow cylinder 20 serves as the outer cylinder of the transfer container 100 and is hollow (with a sandwich) to fill neutron shielding material. Due to the hollow setting, the hollow cylinder 20 has an inner wall and an outer wall structure, and the inner wall and the outer wall are thin-walled settings relative to the metal cylinder 10. The neutron shielding material includes water, boron-containing polyethylene, etc.

[0061] In the height direction of the transfer container 100, the height of the hollow cylinder 20 is less than that of the metal cylinder 10. Therefore, the top of the metal cylinder 10 protrudes above the hollow cylinder 20, making the top of the metal cylinder 10 form the top of the transfer container 100, and both the top cover 30 and the protective cover 40 are installed on the top of the metal cylinder 10.

[0062] Combined with Figure 1 、 Figure 2 and Figure 4 , to achieve the sealing fit of the top cover 30 on the metal cylinder 10, a stepped flange surface 13 is provided on the inner side of the top of the metal cylinder 10, and a stepped mating surface 31 adapted to the stepped flange surface 13 is provided on the outer periphery of the top cover 30. The top cover 30 is hermetically fitted to the top of the metal cylinder 10 through the stepped mating surface 31 and the stepped flange surface 13, sealing the top of the metal cylinder 10 and closing the top of the metal cylinder 10. The top cover 30 is further locked to the stepped flange surface 13 by a number of flange bolts. A gasket can also be used to achieve pressing and sealing between the top cover 30 and the stepped flange surface 13.

[0063] Such as Figure 3 and Figure 4 shown, the top cover 30 may also be provided with an inflation hole 32 and an exhaust hole 33 respectively communicating with the internal space of the transfer container 100. The inflation hole 32 is used to fill the transfer container 100 with a tracer gas for leak detection. For easy connection of inflation, exhaust and closing, quick connectors can be respectively installed on the inflation hole 32 and the exhaust hole 33, and the end caps of the quick connectors can be covered when closing is required.

[0064] As an option, the inflation hole 32 can extend in an S-shape or a Z-shape in the top cover 30; the exhaust hole 33 can also extend in an S-shape or a Z-shape in the top cover 30. The quick connectors are respectively installed at the upper ends of the inflation hole 32 and the exhaust hole 33 facing away from the transfer container 100.

[0065] The usage of the inflation hole 32 and the exhaust hole 33 is as follows: when the transfer container 100 is filled with cooling water and the top cover 30 is installed, to verify the sealing integrity of the entire top cover 30, the inflation hole 32 and the exhaust hole 33 are respectively opened, a tracer gas is filled into the transfer container 100 through the inflation hole 32, then the inflation hole 32 and the exhaust hole 33 are respectively closed, and finally the entire top cover 30 is evacuated and sampled for inspection, and the sealing integrity of the top cover 30 is judged by checking whether there is a tracer gas in the sample.

[0066] On the top cover 30, the inflation hole 32 and the exhaust hole 33 are preferably located on different sides. For example, for a circular top cover 30, the inflation hole 32 and the exhaust hole 33 can be respectively in the 90° and 180° directions.

[0067] The protective cover 40 is hermetically connected to the top end face of the metal cylinder 10. Taking the upright state of the transfer container 100 such as Figure 1 as an example, the top end face of the metal cylinder 10 is located above the stepped flange face 13.

[0068] As a nuclear pressure-bearing container, the protective cover 40 of the transfer container 100 undertakes the structural protection and redundant sealing function for the internal pressure relief protection device 50.

[0069] In some embodiments, such as Figure 1 and Figure 5 shown, the protective cover 40 is a spherical crown-shaped metal structure and is located on the top end face of the metal cylinder 10. A plurality of through bolt holes 41 are provided on the periphery of the protective cover 40, and a sealing gasket is provided on the outer edge of the bottom of the protective cover 40. When the protective cover 40 is installed on the top of the metal cylinder 10, the sealing gasket is located on the top end face, and the protective cover 40 is fastened and sealed on the metal cylinder 10 through bolts matching the bolt holes 41.

[0070] Furthermore, as Figure 3 shown, the bottom of the transfer container 100 is provided with a drain port 14 for undertaking the drainage function after the transfer container 100 completes the intermediate transfer. The drain port 14 is mainly provided at the bottom of the metal cylinder 10, and one or more can be provided. For example, drain ports 14 are respectively provided on both sides in the 90° direction at the bottom of the metal cylinder 10.

[0071] In Figure 3 the shown embodiment, the drain port 14 extends in an L shape at the bottom of the transfer container 100. For the L-shaped drain port 14, it has a vertical section and a horizontal section. The vertical section communicates with the internal space of the transfer container 100, and the horizontal section penetrates the outer surface of the transfer container 100. A drain valve is provided in the horizontal section of the drain port 14; when the transfer container 100 completes the transfer of spent fuel assemblies, the internal water body of the transfer container 100 can be completely emptied by opening the drain valve.

[0072] Furthermore, referring to Figure 1 and Figure 3 , to implement the lifting and flipping functions of the transfer container 100, at least one upper trunnion 11 is provided at the upper end of the outer surface of the transfer container 100, and at least one lower trunnion 12 is provided at the lower end. Preferably, the upper trunnion 11 protrudes from the upper end of the metal cylinder 10 and is outside the hollow cylinder 20; the lower trunnion 12 protrudes from the lower end of the metal cylinder 10 and is outside the hollow cylinder 20.

[0073] The pressure relief protection device 50 is used for the energy dissipation and pressure relief of the cooling water inside the transfer container 100 in the high-temperature boiling state to ensure the safety of the internal structure of the transfer container 100. Such as Figure 2 and Figure 6As shown in the figure, in terms of structure, the pressure relief protection device 50 may include a pressure relief safety valve 51, a buffer pipe 52, a condenser 53, and a sampling valve 54; the pressure relief safety valve 51 is inserted into the top cover 30 and is connected to the internal space of the transfer container 100 through the ventilation hole on the top cover 30; the buffer pipe 52 is connected between the pressure relief safety valve 51 and the condenser 53 to send the high-temperature steam from the transfer container 100 into the condenser 53; the sampling valve 54 is connected to the condenser 53 and is used for sampling to judge the pressure relief situation.

[0074] In some embodiments, a skirt may be provided in the middle of the pressure relief safety valve 51. The pressure relief safety valve 51 is inserted into the ventilation hole 34 of the top cover 30, and a groove 35 is provided around the ventilation hole 34. The skirt of the pressure relief safety valve 51 abuts against the groove 35. The pressure relief safety valve 51 may be further fixed to the top cover 30 by bolts.

[0075] The buffer pipe 52 is connected between the pressure relief safety valve 51 and the condenser 53 and functions to transport water vapor.

[0076] Since the water body (such as cooling water) inside the transfer container 100 is radioactive and the water body is continuously heated by the decay heat of the spent fuel assembly during the transfer process, the water temperature will gradually rise. Once the water temperature and pressure continue to rise and boiling occurs, and the internal pressure of the transfer container 100 exceeds the design pressure set value, the pressure relief safety valve 51 will open to relieve the pressure in time. Since the high-temperature and high-pressure steam released by the pressure relief has a high flow rate, to avoid damage to the high-energy fluid ejection structure, it first enters the buffer pipe 52 and then enters the condenser 53.

[0077] To increase the pipe resistance of the buffer pipe 52 to reduce the steam pressure, the buffer pipe 52 includes a number of S-shaped bent pipe segments, so that the buffer pipe 52 has multiple bent segments in its conveying direction. After the high-temperature and high-pressure steam enters the buffer pipe 52, it flows along the buffer pipe 52, and the flow rate and pressure gradually decrease, and then it enters the condenser 53.

[0078] Furthermore, a number of fishbone plates 55 arranged in a staggered manner may be provided inside the condenser 53. The fishbone plates 55 are used for gradually dissipating energy and cooling the injected high-temperature steam, and finally converging and storing inside the cavity of the condenser 53.

[0079] As Figure 6 and Figure 7 In the embodiments shown, two groups of fishbone plate groups are provided inside the condenser 53, and each fishbone plate group includes a number of fishbone plates 55. The two groups of fishbone plate groups are arranged vertically inside the condenser 53, and the fishbone plates 55 of the two groups of fishbone plate groups are arranged in a staggered manner respectively.

[0080] In the cavity of the condenser 53, each fishbone plate 55 is inclined, with its length exceeding the center line position of the condenser 53. The fishbone plates 55 in the same group are arranged in parallel at intervals, and the inclination direction is towards the sampling valve 54. So that after the high-energy process jet enters the condenser 53, the function of gradually dissipating and attenuating the high-energy fluid can be exerted, and at the same time, the fluid intercepted and buffered is stored in the retention area between the lower fishbone plates 55. The flow direction of the fluid entering the condenser 53 is as Figure 5 indicated by the arrow in

[0081] The sampling valve 54 is used to sample the liquid stored in the condenser 53 after the transfer process of the spent fuel assembly is completed. By sampling and analyzing, it can be known whether pressure relief occurs during the entire transfer process, so as to judge whether the internal pressure of the transfer container 100 is in a safe, controllable and sealed containment state.

[0082] During sampling, the condenser 53 is placed vertically with the sampling valve 54 facing downwards. In the horizontal state, the residual water body between each fishbone plate 55 can flow slowly downward layer by layer along the inclined fishbone plate 55. Open the sampling valve 54, and then sampling and analysis can be carried out.

[0083] In some embodiments, as again Figures 1 - 3 shown, the wet transfer device for spent fuel further includes a support grid 60. The support grid 60 is arranged in the internal space of the transfer container 100 and is used to accommodate the spent fuel assembly.

[0084] In terms of structure, referring to Figure 1 、 Figure 2 and Figure 8 , the support grid 60 may include a grid unit 61 with several spaces for accommodating the spent fuel assembly and a support member 62 surrounding the outer periphery of the grid unit 61. The support member 62 undertakes the structural support and heat transfer functions on the outer periphery of the grid unit 61, and can also shape the outer periphery of the support grid 60, for example, form a cylindrical structure, which is adapted to the inner wall of the transfer container 100.

[0085] The grid unit 61 and the support member 62 can be fixedly connected by bolts or welded. Each grid unit 61 is a frame structure formed by welding and assembling or independent square tubes. One square tube forms a space for accommodating one spent fuel assembly. According to the need of fuel criticality control, neutron absorber materials can be attached to the inner wall of each space of the grid unit 61; or, neutron absorber plates can be clamped between each space.

[0086] The support member 62 can be a hollow special-shaped filling structure, made of a metal material with good thermal conductivity, such as aluminum. The configuration of the support member 62 can be adaptively adjusted according to the number of spent fuel loaded and the actual loading scheme. The special-shaped filling structure includes a fan-shaped structure, etc.

[0087] Referring toFigures 1 to 3 The spent fuel wet transfer method implemented by the spent fuel wet transfer device of the present invention includes the following steps in some embodiments:

[0088] S1. Inject cooling water into the transfer container 100 until the water level reaches the elevation position inside the transfer container 100.

[0089] The cooling water can be injected into the transfer container 100 through a hose from the top of the transfer container 100.

[0090] It can be understood that before water injection, the installation and sealing integrity of the pressure relief protection device 50 and the top cover 30, and the sealing integrity of the bottom drain port 14 of the transfer container 100 and the drain valve therein are checked in advance.

[0091] S2. Lift and install the spent fuel assembly in the first spent fuel pool into the transfer container 100.

[0092] Inside the transfer container 100, the spent fuel assembly is inserted into the support grid 60.

[0093] S3. Lift and install the top cover 30 to the top of the transfer container 100 and connect and fix it. After meeting the sealing requirements, install the protective cover 40 on the top of the transfer container 100.

[0094] To confirm whether the sealing requirements are met, this step S3 further includes performing a sealing inspection:

[0095] Fill the transfer container 100 with tracer gas through the gas injection hole 32 on the top cover 30, so that the tracer gas fills the top space between the support grid 60 and the top cover 30 inside the transfer container. After the tracer gas filling is completed, close the gas injection hole 32 and the exhaust hole 33 on the top cover 30.

[0096] Perform vacuum sampling outside the top cover 30 to detect whether there is tracer gas in the sampled sample, so as to judge the sealing integrity of the top cover 30 on the transfer container 100. If the sample does not contain tracer gas, the sealing requirements are met, and the protective cover 40 is installed. If it contains tracer gas, reinstall the top cover 30 until the sealing requirements are met.

[0097] S4. Transfer the transfer container 100 with the spent fuel assembly from the fuel building to other intermediate temporary storage facilities.

[0098] S5. Open the protective cover 40 and perform sampling and detection on the pressure relief protection device 50 on the top cover 30. If cooling water appears in the sampled sample, perform auxiliary cooling treatment on the surface of the transfer container 100 until cooling water no longer appears in the sample.

[0099] Among them, the operation of sampling and detecting the pressure relief protection device 50 is as follows: Open the sampling valve on the condenser 52, sample the condenser 53 through the sampling valve 54, and detect whether cooling water appears in the sample.

[0100] The auxiliary cooling treatment includes but is not limited to water cooling and / or air cooling.

[0101] S6. Lift the transfer container 100 and hoist it into the second spent fuel pool.

[0102] Among them, in order to facilitate lifting the top cover 30 underwater later, before entering the second spent fuel pool, remove the flange bolts on the top cover 30 and install the sling for the top cover 30.

[0103] S7. Lift the top cover 30 off the transfer container 100 underwater, lift out the spent fuel assemblies in the transfer container 100 and place them in the grid of the second spent fuel pool.

[0104] Lift the top cover 30 to the ground underwater through the sling for the top cover 30, thereby also opening the transfer container 100.

[0105] In summary, through the wet transfer of the spent fuel assemblies by the present invention, there is no need to perform inflation drainage and vacuum drying operations on the transfer container, avoiding the problem that the cladding temperature and stress of the spent fuel assemblies fluctuate repeatedly within a large range, thus avoiding the problems of cladding breakage and leakage of fission gas nuclides. Loading directly with cooling water avoids the problems of long operation cycle, low efficiency and high personnel radiation dose in multiple cycle drying operations of the spent fuel assemblies. The pressure relief protection device provided at the top of the transfer container can gradually dissipate energy and relieve pressure on high-energy fluids, prevent external leakage of radioactive waste liquid, and ensure that the spent fuel assemblies inside the transfer container are always in a safe and controllable state during the entire transfer process.

[0106] The above are only embodiments of the present invention, and thus do not limit the patent scope of the present invention. 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 equally included in the patent protection scope of the present invention.

Claims

1. A spent fuel wet transfer device, characterized in that: It comprises a top-opened inverting container, a top cover matched with and sealed on the top of the inverting container, a protective cover matched with the top of the inverting container and covered on the outside of the top cover, and a pressure relief protection device installed on the top cover; The internal space of the inversion container is used to accommodate spent fuel and cooling water; the pressure relief protection device is located between the top cover and the protection cover, and is connected to the internal space of the inversion container, and is used to dissipate energy and relieve pressure of the cooling water in the inversion container when it is in a boiling state.

2. The spent fuel wet transfer device according to claim 1, characterized in that: The pressure relief protection device includes a pressure relief safety valve, a buffer tube, a condenser and a sampling valve; The pressure relief safety valve is plugged into the top cover and communicates with the internal space of the transfer container through the vent hole on the top cover; the buffer pipe is connected between the pressure relief safety valve and the condenser to deliver the high-temperature steam from the transfer container into the condenser; The sampling valve is connected to the condenser and is used for taking samples to determine the pressure relief condition.

3. The spent fuel wet transfer device according to claim 2, characterized in that: The buffer tube includes a plurality of S-shaped bent tube sections.

4. The spent fuel wet transfer device according to claim 2, characterized in that: A plurality of staggered herringbone plates are arranged in the condenser.

5. The spent fuel wet transfer device according to claim 2, characterized in that: Two groups of fishbone plates are arranged in the condenser, and each of the fishbone plates includes a plurality of fishbone plates; The two groups of fishbone plates are arranged up and down in the condenser, and the fishbone plates of the two groups of fishbone plates are arranged alternately.

6. The spent fuel wet transfer device according to claim 1, characterized in that: The top cover is provided with an air filling hole and an air exhaust hole which are respectively connected to the inner space of the inversion container.

7. The spent fuel wet transfer device according to claim 6, characterized in that: The inflation hole extends in the top cover in an S shape or a Z shape; and / or the exhaust hole extends in the top cover in an S shape or a Z shape.

8. The spent fuel wet transfer device according to claim 1, characterized in that: The transfer container comprises a metal cylinder and a hollow cylinder arranged around the outer periphery of the metal cylinder, wherein the hollow cylinder is filled with neutron shielding material; The inner side of the top of the metal cylinder is provided with a stepped flange surface, and the outer periphery of the top cover is provided with a stepped mating surface adapted to the stepped flange surface, and the stepped mating surface is sealingly matched with the stepped flange surface; the protective cover is sealingly connected to the top end surface of the metal cylinder.

9. The spent fuel wet transfer device according to claim 1, characterized in that: A drain port is provided at the bottom of the inverted container.

10. The spent fuel wet transfer device according to claim 9, characterized in that: The drain port extends in an L-shape in the bottom of the dump container.

11. The spent fuel wet transfer device according to claim 1, characterized in that: The outer surface of the inverted container is provided with at least one upper trunnion at the upper end and at least one lower trunnion at the lower end.

12. The spent fuel wet transfer device according to any one of claims 1 to 11, characterized in that: The spent fuel wet transfer device further comprises a support grid, which is arranged in the inner space of the transfer container and is used to accommodate the spent fuel assembly.

13. A spent fuel wet transport method, characterized in that: The spent fuel wet transfer device according to any one of claims 1 to 12 is used, and the spent fuel wet transfer method comprises the following steps: S1. Pour cooling water into the transport container until the water level reaches the elevation position; S2, hoisting the spent fuel assembly in the first spent fuel pool into the transfer container; S3, hoisting the top cover to the top of the inverted container and connecting and fixing it, and installing a protective cover on the top of the inverted container after the sealing requirements are met; S4. Transfer the transfer container with the spent fuel assembly to the intermediate storage facility; S5, opening the protective cover, sampling and testing the pressure relief protection device on the top cover, if cooling water appears in the sample, performing auxiliary cooling treatment on the surface of the inverted container until cooling water no longer appears in the sample; S6, hoisting the transfer container into the second spent fuel pool; S7. Lift the top cover off the transfer container underwater, lift the spent fuel assembly in the transfer container out and place it in a water pool grid of a second spent fuel pool.

14. The spent fuel wet transport method according to claim 13, characterized in that: Step S3 also includes performing a sealing check: Filling the transfer container with tracer gas through the gas filling hole on the top cover, so that the tracer gas fills the top space between the support grid and the top cover in the transfer container; The inflation holes and exhaust holes on the top cover are closed, vacuum sampling is performed on the outside of the top cover, and the presence of tracer gas in the sample is detected to determine the sealing integrity of the top cover on the transfer container.

15. The spent fuel wet transport method according to claim 13, characterized in that: In step S5, the operation of sampling and testing the pressure relief protection device is as follows: opening a sampling valve on the condenser, and sampling the condenser through the sampling valve.

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