A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies.

Abstract

A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies, relating to the field of nuclear engineering technology, includes a pre-loading box, an insertion platform, and a rod-pulling machine. The pre-loading box contains a pre-loading frame for loading nuclear fuel rods and a cooler capable of spraying cryogenic fluid onto the surface of the fuel rods. A grid cell is installed on the insertion platform between the pre-loading box and the rod-pulling machine. The rod-pulling machine pulls the nuclear fuel rods into the fixing units of the grid cell for fixation. A cooling ring with multiple cooling nozzles is fitted on the side of the rod-pulling rod closest to the fuel rod, and the cooling nozzles are connected to an external cooling assembly. This invention achieves ice lubrication during the rod-pulling process by spraying cryogenic water mist onto the surface of the fuel rods through the cooler to form ice crystals, greatly reducing frictional damage to the fuel rods during rod pulling. Furthermore, the cooling ring on the rod-pulling rod, capable of spraying cryogenic water mist, can generate ice crystals on the frame units of the grid cell during rod pulling, further improving the lubrication effect on the fuel rods.

Description

Technical Field

[0001] This invention relates to the field of nuclear engineering technology, and more specifically to a lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies. Background Technology

[0002] Nuclear fuel assemblies, as the core components for energy generation in nuclear power plants, consist of a framework, upper and lower tubes, and grid cells supporting the fuel rods. Ensuring the stability of the fuel rods is crucial during reactor operation. To prevent fuel rods from detaching or coming into contact with the framework and causing fretting wear, springs and rigid protrusions are installed in each grid cell where the framework contacts the fuel rods to support and secure them. However, while this design effectively reduces fuel rod movement, these springs and rigid protrusions can scratch the fuel rod surface during assembly, affecting its integrity. If the damage depth exceeds 10% of the fuel rod cladding thickness, these scratches can become the starting point for corrosion, leading to localized corrosion problems. Simultaneously, abrasive debris may be generated on the damaged surface. If this debris is not thoroughly cleaned, it will circulate with the coolant during fuel rod operation, causing secondary damage. To reduce fuel rod surface wear during fuel assembly, a water lubrication process is currently employed. Various water lubrication systems have been developed both domestically and internationally. For example, the system described in patent CN106935282B uses a brush to uniformly coat the fuel rod surface with a water-based medium, reducing the generation of zirconium shavings during the rod assembly process and lowering the risk of zirconium shavings abrading the fuel rods after the fuel assembly is installed in the reactor, which is crucial for the safe operation of the reactor. Patent CN211858169U further improves the water lubrication system by setting an overflow orifice to control the upper limit of the water level, effectively controlling costs, and simultaneously adjusting the upper limit of the level to adjust the water absorption effect of the brush layer. Besides water lubrication, a washable lubricant can also be applied to the fuel rod surface to reduce wear during assembly. While these measures have achieved some success in reducing fuel rod wear, some challenges remain. For example, although water lubrication can reduce zirconium shavings, the water film is not easily maintained on the rod surface and is often consumed after one layer, failing to significantly reduce the depth of wear marks on the fuel rod surface. While using washable lubricants can maintain the lubricating film for a longer period, residues may remain during the cleaning stage. These residues may affect the performance of the fuel rods and the safe operation of the reactor, bringing new challenges. Furthermore, existing water lubrication systems have some limitations in practical applications. For example, using rollers to brush water onto the fuel rod surface with absorbent textiles such as brushes or sponges, or directly spraying water onto the fuel rod surface with nozzles, can cause the water to easily clump together into large droplets. These droplets are prone to dripping and result in uneven water coverage on the fuel rod surface, reducing lubrication effectiveness. These problems not only affect lubrication performance but may also pose safety hazards to other electrical components. Therefore, a new lubrication technology is urgently needed to address the wear problem during the nuclear fuel rod pulling process. Summary of the Invention

[0003] Therefore, the present invention aims to provide a lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies, which can generate ice crystal particles on the surface of the nuclear fuel rods and grid cells during the rod pulling process, and lubricate the nuclear fuel rods through the ice crystal particles, thereby improving the wear problem during the nuclear fuel rod pulling process.

[0004] To solve at least one of the above-mentioned technical problems, the technical solution provided by the present invention is:

[0005] A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies includes a pre-loading box, an insertion platform, and a rod pulling machine. The pre-loading box is a container with an opening on one side and a hollow interior. It contains a pre-loading rack for loading nuclear fuel rods and a cooler that can spray cryogenic fluid onto the surface of the nuclear fuel rods.

[0006] An insertion platform is set between the pre-loading box and the bar pulling machine, and grid cells are installed on it;

[0007] The rod pulling assembly in the rod pulling machine can be connected to the nuclear fuel rods through the rod pulling rods that pass through the grid cells. When the rod pulling assembly moves in the rod pulling machine, it can pull the nuclear fuel rods into the fixing unit of the grid cells to complete the fixing.

[0008] A cooling ring is fitted on the side of the rod close to the nuclear fuel rod. The cooling ring is equipped with multiple cooling nozzles that are parallel to the axis and point towards the nuclear fuel rod, as well as connecting conduits connected to the cooling nozzles. The connecting conduits are connected to a cooling assembly located outside the rod pulling machine.

[0009] One embodiment of the present invention is that the cooler is provided with multiple sets of fluid nozzles pointing towards the nuclear fuel rods, and cooling pipes capable of reducing the internal temperature of the pre-filled box are provided between the fluid nozzles.

[0010] Furthermore, the pre-packet is provided with an annular moving guide rail around its inner wall, and the cooler is provided with moving wheels that cooperate with the moving guide rail, enabling it to move along the moving guide rail around the nuclear fuel rods.

[0011] In one embodiment of the present invention, the pre-assembled box is disposed on the pre-assembled box base, the bar pulling machine is disposed on the bar pulling machine base, and the pre-assembled box base, the insertion platform, and the bar pulling machine base are all provided with casters for support.

[0012] One embodiment of the present invention is that at least one set of the cooling nozzles is capable of spraying water, and at least one set is capable of spraying dry ice.

[0013] In one embodiment of the present invention, the maximum diameter of the pull rod fitted with the cooling ring is smaller than the minimum width of the fixing unit in the grid cell used to accommodate the nuclear fuel rod.

[0014] One embodiment of the present invention is that the pre-loading box is provided with a temperature sensor and a fan whose air outlet direction is directed towards the nuclear fuel rods, and the fan is located between the cooler and the opening near the insertion platform.

[0015] In one embodiment of the present invention, the contact surface between the insertion platform and the grid cell is a temperature control plate, and a cooling component is also provided inside the insertion platform, which can reduce the temperature of the temperature control plate.

[0016] The technical effects achieved by this invention are:

[0017] 1. This invention sprays low-temperature water mist onto the surface of nuclear fuel rods through a cooler installed in the pre-assembled box to form ice crystals, thereby achieving ice lubrication during the rod pulling process. This can greatly reduce the damage caused by the contact friction between the nuclear fuel rods and the grid elements during rod pulling, and effectively reduce the risk of nuclear fuel rod breakage in the nuclear reactor.

[0018] 2. In this invention, a cooling ring capable of spraying low-temperature water mist is fitted on the rod used to pull the nuclear fuel rod. This ring can generate ice crystals on the frame unit of the grid cell that will house the nuclear fuel rod during the rod pulling process, thereby further improving the lubrication effect on the nuclear fuel rod. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0021] Figure 2 This is a schematic diagram of the cooling surface of the refrigerator in this invention;

[0022] Figure 3 This is the present invention. Figure 1 A magnified view of a section at point A in the middle;

[0023] Figure 4 This is an isometric view of the cooling ring in this invention;

[0024] 1-Pre-loading box, 2-Pre-loading box base, 3-Wheel casters, 4-Pre-loading rack, 5-Temperature sensor, 6-Refrigerator, 61-Moving wheels, 62-Fluid nozzle, 63-Refrigeration pipe, 7-Moving guide rail, 8-Fan, 9-Nuclear fuel rod, 10-Insertion platform, 11-Temperature control plate, 12-Cooling assembly, 13-Grid element, 14-Pull rod, 15-Pull rod machine base, 16-Pull rod machine, 17-Pull rod assembly, 18-Cooling assembly, 19-Cooling ring, 20-Cooling nozzle, 21-Connecting conduit. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0027] Example:

[0028] See Figure 1 A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies includes a pre-loading box 1, an insertion platform 10, and a rod pulling machine 16. The pre-loading box 1 is a container with an opening on one side and a hollow interior. Inside, there is a pre-loading rack 4 for loading nuclear fuel rods 9. Referring to the prior art, the nuclear fuel rods 9 are usually filled side by side in the pre-loading rack 4. The rod pulling machine 16 pulls the nuclear fuel rods 9 into the grid cells 13 set on the insertion platform 10. The pre-loading box 1 is also provided with a cooler 6 that can spray low-temperature fluid onto the surface of the nuclear fuel rods 9. This cooler sprays low-temperature water mist onto the surface of the nuclear fuel rods 9 during the rod pulling process to generate ice crystals. This allows the nuclear fuel rods 9 to be lubricated by the ice crystals between their contact surfaces when they enter the fixing unit in the grid cells 13, thereby minimizing frictional damage to the surface of the nuclear fuel rods 9.

[0029] An insertion platform 10 is positioned between the pre-loading box 1 and the rod pulling machine 16, and a grid cell 13 is mounted on it. The rod pulling rod 14 of the rod pulling machine 16 needs to pass through the grid cell 13 to pull the nuclear fuel rod 9 into the fixing unit of the grid cell 13 for fixing. In this embodiment, the contact surface between the insertion platform 10 and the grid cell 13 is a temperature control plate 11, and a cooling component 12 is also provided inside the insertion platform 10. The cooling component 12 can reduce the temperature of the temperature control plate 11. That is, during the rod pulling process, the temperature control plate 11 can be cooled by the cooling component 12 in the insertion platform 10, further reducing the overall temperature of the grid cell 13. This allows the ice crystals on the surface of the nuclear fuel rod 9 to be kept in a low-temperature environment as much as possible when it is pulled into the grid cell 13, prolonging the time that the ice crystals stay on the surface of the nuclear fuel rod 9 and ensuring the lubrication effect. The structure of the temperature control plate 11 controlled by the cooling component 12 can adopt the medium heat conduction method commonly used in the art, such as embedding a medium circulation pipe in the temperature control plate 11, and circulating the low temperature medium in the circulation pipe by the cooling component 12 to achieve the cooling effect, or adopting a cooling conduction method to reduce the temperature of the temperature control plate 11.

[0030] The rod pulling assembly 17 in the rod pulling machine 16 can be connected to the nuclear fuel rod 9 through the rod pulling rod 14 that passes through the grid cell 13. When the rod pulling assembly 17 moves in the rod pulling machine 16, it can pull the nuclear fuel rod 9 into the fixing unit of the grid cell 13 for fixing. The rod pulling assembly 17 can refer to the common design in the prior art, that is, a track is built into the rod pulling machine 16 to control the movement of the rod pulling assembly 17 on the track of the rod pulling machine 16 to realize the rod pulling function.

[0031] See Figure 3 , 4A cooling ring 19 is fitted on the side of the rod 14 closest to the nuclear fuel rod 9. The cooling ring 19 is equipped with multiple sets of cooling nozzles 20 parallel to the axis and pointing towards the nuclear fuel rod 9, and connecting conduits 21 connected to the cooling nozzles 20. The connecting conduits 21 are connected to a cooling assembly 18 located outside the rod pulling machine 16. At least one set of the cooling nozzles 20 can spray water, and at least one set can spray dry ice. During operation, both water and dry ice are sprayed simultaneously. When the water and dry ice come into close contact, the heat in the water is rapidly absorbed and sublimated by the dry ice, thus freezing the water into ice crystals. Since the rod 14 needs to be... Since the fuel rod 9 passes through the fixed unit of the grid cell 13, a cooling ring 19 is fitted onto the pull rod 14. This allows ice crystals to be sprayed onto the surface of the fixed unit of the grid cell 13 where the fuel rod 9 will enter during the pull-in process. During the pull-in process, after the fuel rod 9 is pulled out of the pre-loading box 1, the ice crystals on the surface of the fuel rod 9 may melt due to the ambient temperature, leading to a reduction in lubrication. Therefore, by setting the cooling ring 19, ice crystals can also be sprayed onto the fixed unit during the pull-in process to offset the loss of lubrication performance caused by the melting of ice crystals on the surface of the fuel rod 9, while further reducing the lubrication effect of the grid cell 14. The overall temperature also allows the ice crystals on the surface of the nuclear fuel rod 9 to be retained as much as possible when it is stretched into the grid cell 13, ultimately ensuring and improving the lubrication effect during the rod pulling process. Obviously, in order to achieve the above effect, the cooling ring 19 should be positioned as close as possible to the connection between the rod pulling rod 14 and the nuclear fuel rod 9, and pointing towards the nuclear fuel rod 9. At the same time, the cooling ring 19 can be detachably mounted on the rod pulling rod 14, and its structure can be in the form of a buckle, a ring-shaped Velcro, etc., or the structure of the cooling ring 19 can be set as a fixed ring and set by directly sleeved on the rod pulling rod 14; the rod pulling rod 14 is equipped with the cooling ring 19. After the cooling ring 19, its maximum diameter should be smaller than the minimum width of the fixed unit in the grid cell 13 used to accommodate the nuclear fuel rods 9, so that it can move normally through the grid cell 13. In addition, the cooling ring 19 needs to be connected to the external cooling assembly 18. The cooling assembly 18 can integrate the dry ice manufacturing equipment and the chilled water equipment in the conventional way. It is connected to the cooling nozzles for spraying dry ice and the cooling nozzles for spraying water mist 20 respectively through the connecting conduits 21 of sufficient length. The cooling nozzles for spraying water mist need to be atomizing nozzles, while the cooling nozzles for spraying dry ice 20 can be conventional dry ice nozzles.

[0032] See Figure 1 , Figure 2The cooler 6 is equipped with multiple sets of fluid nozzles 62 pointing towards the nuclear fuel rods 9, and cooling pipes 63 are spaced apart between the fluid nozzles 62 to reduce the internal temperature of the pre-loading box 1. The fluid nozzles 62 are used to connect to the liquid injection equipment, and their nozzle type is atomizing nozzles. The liquid sprayed is usually atomized water. The cooling pipes 63 between the nozzles can cool the inside of the pre-loading box 1. Since they are close to the fluid nozzles 62, they can preferentially cool the mist sprayed from the fluid nozzles 62, causing it to condense into ice crystals and adhere to the surface of the nuclear fuel rods 9. The equipment for supplying water to the fluid nozzles 62 and the equipment for controlling the cooling of the cooling pipes 63 can be integrated into the cooler 6 according to existing technology, or they can be set in the pre-loading box 1 and connected by corresponding pipelines. The pre-loading box 1 is provided with an annular moving guide rail 7 around its inner wall. The cooler 6 is provided with moving wheels 61 that cooperate with the moving guide rail 7, so that it can move around the nuclear fuel rods 9 along the moving guide rail 7. The moving guide rail 7 is attached to the inner wall of the pre-loading box 1 and is arranged around the internal space of the pre-loading box 1, so that the cooler 6 can move along the moving guide rail 7. The structure of the device for the cooler 6 to move in a ring on the moving guide rail 7 can refer to the design method of the automatic pipe welding machine in the prior art, and replace its welding machine components with cooler components accordingly. If the cooler 6 moves along the inner ring of the moving guide rail 7, it can be directly used for cooling. If the cooler 6 moves along the outer ring of the moving guide rail 7, corresponding movement space needs to be reserved in the pre-loading box 1. At the same time, the aforementioned equipment for supplying water to the fluid nozzle 62 and the equipment for controlling the cooling of the cooling pipe 63 can also be set up by integrating with the cooler 6 or connecting it to the pipeline. The number of coolers 6 can be determined according to actual needs, so that during the rod pulling process, the cooler 6 can move around the nuclear fuel rod 9, thereby better uniformly coating the surface of the nuclear fuel rod 9 with the ice crystals it generates in the full range of angles.

[0033] The pre-loading box 1 is equipped with a temperature sensor 5 and a fan 8 that directs the airflow towards the nuclear fuel rods 9. The temperature sensor 5 is used to monitor the temperature changes inside the pre-loading box 1, and the fan 8 is located between the cooler 6 and the opening near the insertion platform 10. When in operation, the fan 8 will continuously blow air towards the nuclear fuel rods 9. On the one hand, the airflow from the fan 8 can make the water mist more evenly distributed, further improving the ice crystal dispersion effect on the surface of the nuclear fuel rods 9. On the other hand, the fan 8 can form an air curtain at the opening, reducing the loss of cooling capacity.

[0034] In some embodiments, the pre-assembly box 1 is mounted on the pre-assembly box base 2, and the rod pulling machine 16 is mounted on the rod pulling machine base 15. The pre-assembly box base 2, the insertion platform 10, and the rod pulling machine base 15 are all equipped with casters 3 for support. Referring to the arrangement in the prior art, it is convenient to adjust the relative positions of the pre-assembly box 1, the insertion platform 10, and the rod pulling machine 16.

[0035] The method of using the above-mentioned device for inserting nuclear fuel rods into the grid cell is as follows:

[0036] (1) The pre-loading rack 4 containing nuclear fuel rods 9 is placed in the pre-loading box 1, and the relative positions of the pre-loading box 1, the insertion platform 10, and the rod pulling machine 16 are adjusted to control the number of rod pulling rods 14 with cooling rings 19 to pass through the grid cell 13 and connect to the nuclear fuel rods 9.

[0037] (2) Start the cooler 6 to coat the surface of the nuclear fuel rod 9 with ice crystals. At the same time, control the rod pulling assembly 17 to move and pull the nuclear fuel rod 9 into the grid cell 13. When the nuclear fuel rod 9 is about to enter the grid cell 13, control the cooling nozzle 20 on the cooling ring 19 to spray dry ice and water mist respectively, so as to generate ice crystals on the grid cell 13 fixing unit that the nuclear fuel rod 9 is about to contact. Then, under the combined action of the ice crystals on the surface of the nuclear fuel rod 9 and the ice crystals on the contact surface of the grid cell 13 fixing unit, the nuclear fuel rod 9 smoothly enters the fixing unit of the grid cell 13 and completes the insertion and fixing.

[0038] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limitations on this invention.

[0039] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies, characterized in that, It includes a pre-loading box (1), an insertion platform (10), and a rod pulling machine (16). The pre-loading box (1) is a container with an opening on one side and a hollow interior. Inside it is a pre-loading rack (4) for loading nuclear fuel rods (9). The pre-loading box (1) is also equipped with a cooler (6) that can spray cryogenic fluid onto the surface of the nuclear fuel rods (9). An insertion platform (10) is set between the pre-loading box (1) and the bar pulling machine (16), and a grid cell (13) is provided on it; The rod assembly (17) in the rod pulling machine (16) can be connected to the nuclear fuel rod (9) through the rod rod (14) that passes through the grid cell (13). When the rod assembly (17) moves in the rod pulling machine (16), it can pull the nuclear fuel rod (9) into the fixing unit of the grid cell (13) to complete the fixing. A cooling ring (19) is fitted on the side of the rod (14) near the nuclear fuel rod (9). The cooling ring (19) is provided with multiple sets of cooling nozzles (20) that are parallel to the axis and point towards the nuclear fuel rod (9), and a connecting conduit (21) connected to the cooling nozzles (20). The connecting conduit (21) is connected to a cooling assembly (18) located outside the rod pulling machine (16).

2. A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies according to claim 1, characterized in that: The cooler (6) is provided with multiple sets of fluid nozzles (62) pointing to the nuclear fuel rods (9), and cooling pipes (63) that can reduce the internal temperature of the pre-packet (1) are provided between the fluid nozzles (62).

3. A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies according to claim 2, characterized in that: The pre-loading box (1) is provided with an annular moving guide rail (7) around its inner wall, and the cooler (6) is provided with a moving wheel (61) that cooperates with the moving guide rail (7), so that it can move around the nuclear fuel rod (9) along the moving guide rail (7).

4. A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies according to claim 1, characterized in that: The pre-assembled box (1) is set on the pre-assembled box base (2), the bar pulling machine (16) is set on the bar pulling machine base (15), and the pre-assembled box base (2), the insertion platform (10), and the bar pulling machine base (15) are all equipped with casters (3) for support.

5. A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies according to claim 1, characterized in that: At least one set of the cooling nozzles (20) is capable of spraying water, and at least one set is capable of spraying dry ice.

6. A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies according to claim 1, characterized in that: The maximum diameter of the pull rod (14) fitted with the cooling ring (19) is less than the minimum width of the fixing unit in the grid cell (13) used to accommodate the nuclear fuel rod (9).

7. A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies according to claim 1, characterized in that: The pre-loading box (1) is equipped with a temperature sensor (5) and a fan (8) whose air outlet direction is directed towards the nuclear fuel rods (9), and the fan (8) is located between the cooler (6) and the opening near the insertion platform (10).

8. A lubrication device for inserting nuclear fuel rods into nuclear fuel assemblies according to claim 1, characterized in that: The contact surface between the insertion platform (10) and the grid cell (13) is a temperature control plate (11), and a cooling component (12) is also provided inside the insertion platform (10). The cooling component (12) can reduce the temperature of the temperature control plate (11).

Images