GB2549641A

GB2549641A - Deflecting vane structure and mixing grid

Info

Publication number: GB2549641A
Application number: GB1710623.8A
Authority: GB
Inventors: Yu Wenchi; Hu Haixiang; Li Weicai; Yan Jingwen; Zhang Yuxiang; Xi Yanyan; Wang Renjun
Original assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd; CGN Power Co Ltd
Current assignee: China General Nuclear Power Corp; China Nuclear Power Technology Research Institute Co Ltd; CGN Power Co Ltd
Priority date: 2014-12-05
Filing date: 2015-11-30
Publication date: 2017-10-25
Anticipated expiration: 2035-11-30
Also published as: CN104485138B; GB2549641B; GB201710623D0; WO2016086810A1; CN104485138A

Abstract

A fairing-type guiding vane structure arranged on a stirring-mixing lattice outer band and a fuel component stirring-mixing lattice having the structure. Multiple grating units (13) are formed by multiple inner bands (11 and 12) in the stirring-mixing lattice (1). A first stirring-mixing vane (110) is provided within each of the grating units (13) adjacent to an outer band. The first stirring-mixing vanes (110) are each arranged on one inner band (11) and are bent and extended towards another inner band. The fairing-type guiding vane structure comprises multiple first guiding vanes (15). The multiple first guiding vanes (15) are arranged on the upper edge and/or lower edge of the outer band (10) and are inclined and extended towards the interior of the stirring-mixing lattice (1). The positions of the first guiding vanes (15) correspond to the first stirring-mixing vanes (110). A surface of each first guiding vane (15) facing the interior of the stirring-mixing lattice (1) is depressed to form a diversion groove (140) extending towards the interior of the stirring-mixing lattice (1). The guiding vane structure provides a fairing effect and is capable of preventing convective collision of a coolant in the stirring-mixing lattice, thus ensuring enhanced flow exchange among fuel components, and ensuring great thermal performance.

Description

DEFLECTING VANE STRUCTURE AND MIXING GRID

FIELD OF THE INVENTION

[0001] The invention relates to reactor components, and more particular to deflecting vane structure and a mixing grid with the same.

BACKGROUND OF THE INVENTION

[0002] Fuel rods with certain amount arranged in a predetermined spacing (such as 15x15, 17x17. etc.) and formed to a bunch are called as a nuclear reactor fuel assembly which mainly includes a top nozzle, a bottom nozzle, a mixing grid (also called as a spacer grid), guide thimbles and fuel rods. Therein, the mixing grid for loading the fuel rods includes multiple inner straps and outer straps surrounding the inner straps. The multiple inner straps are orthogonally interlaced with one another to form a latticed grid structure with multiple grid cells.

[0003] As well known, chain reaction in nuclear reactors will produce large quantity of radioactive substances such as 1-131, Cs-137. For preventing these radioactive substances from being leaked out from the nuclear reactors in explosion accidents, Zirconium alloy shell, reactor press vessel and concrete contentment are configured outside the nuclear reactors. However, these means just are emergency safety measures acted for nuclear reactor accidents, while the important factors for preventing explosion accidents are to control the speed and the temperature of the chain reaction in the nuclear reaction, thus the water flow control of the light water in the fuel assembly that is acted as moderators and coolant is critical, and the mixing grid of the fuel assembly is significant to the water flow control of the light water.

[0004] As illustrated in Fig. 1, in order to enhance the flow exchange and flowability of the mixed flow and light water among the fuel assemblies, mixing vanes la are commonly configured on the inner straps and extended into the grid cells. As a result, the coolant flow from bottom to up to reach the mixing vanes will be diverted, crossflow and eddies will be generated at downstream of the mixing grid to improve the flowability of the coolant thereby finally improving the thermal margin of the fuel assembly.

[0005] In addition, since the fuel assembly has high lateral flexibility, thus the loading and unloading of the fuel assemblies must be carried out in a vertical direction to prevent obvious lateral deformation. During the loading and unloading of the fuel assemblies, interferences will be generated among the fuel assemblies to be loaded or unloaded and that has been loaded or unloaded, since small spacing is existed among the fuel assemblies; and such interferences may be resulted due to irradiation deformation of fuel assemblies and fabrication tolerance between the fuel assembly and the hoisting equipment. Thus the mixing grid should have excellent guide function to avoid the interferences. Commonly, deflecting vanes lb are arranged to guide the fuel assemblies.

[0006] In the prior arts however, the deflecting vanes lb are defective. For ensuring the coolant to flow between two adjacent fuel assemblies, the deflecting vanes lb are alternately arranged on the outer straps, to make the coolant to flow to adjacent fuel assemblies along the gap between two deflecting vanes lb. But such a gap may bring interference problem during the hoisting process of the fuel assemblies, and the guiding effect is poor.

[0007] As shown in Fig. 2, if the deflecting vanes lb are arranged continuously, that is, no gap is formed between two adjacent deflecting vanes lb to allow coolant to flow, as a result, such an arrangement may not increase kinetic energy for the flow exchange among the fuel assemblies, and even may obstruct the cross flow among the fuel assemblies resulted by pressure drop of the mixing vanes la, thereby cutting off the flow and making the bent configuration for the deflecting vanes lb meaningless. Furthermore, it’s easy to generate coolant reflow in the flow channels to bring convection collision, which may weaken the cross flow. Meanwhile, because the surface of the deflecting vane lb is smooth, thus dispersion and turbulence will be generated once the coolant crashes on the deflecting vanes lb, which is bad for convection heat transfer. Finally, heat transfer deterioration may be caused due to the above-mentioned drawbacks.

[0008] By this token, shapes or patterns of the deflecting vanes will not only impact the guiding effectiveness of the mixing grid, but also impact the coolant flowability among the fuel assemblies. Therefore, it is necessary to provide improved deflecting vane structure to overcome the drawbacks mentioned above.

SUMMARY OF THE INVENTION

[0009] One objective of the invention is to provide deflecting vane structure with deflecting function.

[0010] Another objective of the invention is to provide a mixing grid with said deflecting vane structure.

[0011] To achieve the above-mentioned objectives, the present invention provides deflecting vane structure configured on outer straps of a mixing grid, wherein the mixing grid is provided with multiple inner straps to from multiple grid cells, a first mixing vane is provided within each of the grid cells abutted to the outer straps, the first mixing vane is configured on one of the inner straps that is connected with the outer straps and is bent and extended toward another of the inner straps that is connected with the outer straps; wherein the deflecting vane structure comprises multiple first deflecting vanes which are arranged on upper edges and/or lower edges of the outer straps and are slantwise extended into interior of the mixing grid, the first deflecting vanes have corresponding positions as the first mixing vanes, and a side, facing to the interior of the mixing grid, of the first deflecting vane is recessed to form a diversion groove which is extended toward the interior of the mixing grid along the outer straps.

[0012] In comparison of the prior art, since the diversion grooves are formed on the first deflecting vanes, by mean of which coolant from adjacent fuel assemblies can be guided to flow into the grid cells, thus flow exchange among the fuel assemblies is enhanced. Further, the coolant passing the diversion grooves is deflected by the mixing vanes to cause circumfluence around the fuel rods, thus the heat dissipation for the fuel rods is improved.

[0013] Preferably, a second mixing vane is provided within another grid cell that is adjacent to that grid cell with the first mixing vane provided and abutted to the outer straps, and the second mixing vane is arranged on the inner strap that is parallel to the outer straps and is bent and extended toward the outer straps; the deflecting vane structure further comprises multiple second deflecting vanes, the second deflecting vanes and the first deflecting vanes are alternately arranged on the upper edges and/or the lower edges of the outer straps and extended into the interior of the mixing grid, the second deflecting vanes have corresponding positions as the second mixing vanes, and a side, facing to the interior of the mixing grid, of the second deflecting vane is protruded to form a diversion ridge which is extended toward the interior of the mixing grid along the outer straps. Because the diversion grooves are formed on the first deflecting vanes and the diversion ridges are formed on the second deflecting vanes, thus integrated coolant flow path is formed by the first deflecting vanes, the second deflecting vanes, the first mixing vanes and the second mixing vanes, thereby heat dissipation for the fuel rods is improved. Further, the diversion ridges can deflect the backflow in the fuel assembly toward the sides of the second deflecting vane, thus the coolant flow towards the flow channels is reduced to reduce kinetic energy for convection collision in the flow channels. As a result, the coolant flow with sufficient kinetic energy can be flowed to the adjacent fuel assemblies to avoid flow cutoff and enhance flow exchange among the fuel assemblies. Further, due to the diversion grooves and the diversion ridges, smoothness of the first and second deflecting vanes and is reduced, and therefore direct crash on the vanes and is avoided to weaken coolant turbulence.

[0014] Specifically, the diversion grooves and the diversion ridges are extended toward the interior of the mixing grid along a direction perpendicular to an edge of the outer straps.

[0015] Specifically, an extending length, extending toward the interior of the mixing grid, of the first deflecting vane is larger than that of the second deflecting vane. Since the second deflecting vane is shorter, thus it’s easier for the coolant to flow to the adjacent fuel assembly via the second deflecting vane.

[0016] More specifically, an extending length of the diversion groove is larger than that of the diversion ridge.

[0017] Specifically, both of the first deflector vane and the second deflector vane are located at junctions of two adjacent grid cells.

[0018] Accordingly, the present invention further provides a mixing grid comprising multiple outer straps and multiple inner straps. The multiple inner straps are interlaced with each other to form multiple grid cells, the multiple outer straps surround the grid units and are fixed to the inner straps, a first mixing vane and a second mixing vane are provided within two adjacent grid units abutted to the outer straps, the first mixing vane is configured on one of the inner straps that is connected with the outer straps and is bent and extended toward another of the inner straps that is connected with the outer straps, and the second mixing vane is configured on that inner strap that is parallel to the outer straps and is bent and extended toward the outer straps, wherein the mixing grid further comprises said deflecting vane structure.

[0019] In comparison of the prior art, since the first and second deflecting vanes are alternately and continuously arranged on the mixing grid, thus interferences may not be easily generated when the fuel assemblies are hoisted, to ensure the guiding effect. Furthermore, the diversion grooves and the diversion ridges are formed on the deflecting vanes, thereby improving the flow exchange among the fuel assemblies.

[0020] Preferably, the first mixing vane is fixed to an upper edge of the inner straps and closed to that inner strap parallel to the outer straps, and the second mixing vane is fixed to the upper edge of the inner straps and closed to that inner strap opposite to the first mixing vane.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Fig. 1 is a schematic view showing an arrangement of the conventional deflecting vanes; [0022] Fig. 2 is schematic view showing another arrangement of the conventional deflecting vanes; [0023] Fig. 3 shows flow field at positions of the outer straps of the adjacent mixing grids according to the present invention; [0024] Fig. 4 is an enlarged view of the first deflecting vane and the second deflecting vane according to the present invention; [0025] Fig. 5 is a cross section view of the first and second deflecting vanes along A-Aline in Fig. 4 a; [0026] Fig. 6 shows variations of the first and second deflecting vanes with diversion grooves and diversion ridges; [0027] Fig. 7 is a schematic view of a diversion groove according to another embodiment; [0028] Fig. 8 is a vertical cross sectional view of the first deflecting vane and the outer straps of Fig. 7.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

[0029] Preferred embodiments of the present invention will now be described with reference to the figures.

[0030] By combination of Figs.3~5, the present invention provides a mixing grid 1 adapted for fuel assembly, which includes an outer straps 10, multiple inner straps and deflecting vane structure.

[0031] The multiple inner straps include multiple first inner straps 11 that are vertically arranged and multiple second inner straps 13 that are transversely arranged, as shown in Fig. 3. Specifically, the first inner straps 11 are parallel to each other and arranged in predetermined space, the second inner straps 12 are parallel to each other and arranged in predetermined space as well, and the first and second inner straps 11 are interlaced with each other to form a grid structure which is provided with multiple hollow grid cells 110. Fuel rods are inserted into the gird cells 13. The outer straps 10 surround the grid cells 13 and fixed to the inner straps 11 and 12. Further, flow channels 130 are formed between two adjacent grid cells 13. More specifically, the grid cells abutted to the outer straps 10 are surrounded by three flow channels 130 and the outer straps 10, while the grid cells failed to abut to the outer straps 10 are surrounded by four flow channels 130.

[0032] First mixing vanes 110 are arranged on the first inner straps 11 and slantwise extended into the grid cells 13, and second mixing vanes 120 are arranged on the second inner straps 11 and slantwise extended into the grid cells 13. Effectiveness and functions of the first and second mixing vanes 110, 120 are to disturb the coolant flow from bottom to up to produce cross flow, thereby improving the mixing performance of the mixing grid 1 and thus improving thermal performance of the fuel assembly. The amount and positions of the first and second mixing vanes 110,120 can be set by person skilled in the art accordingly to the actual demands, which is not limited here. Now the arrangement of the first and second mixing vanes 110, 120 is described as follows, for better understanding their functions. Specifically, the first mixing vanes 110 are fixed to the upper edges of the first inner straps 11 and closed to the intersections of the first inner straps 11 and the second inner straps 12, and the second mixing vanes 120 are fixed to the upper edges of the second inner straps 12 and closed to the intersections of the first inner straps 11 and the second inner straps 12. Both of the first and second mixing vanes 120 are located within the flow channels 130. Further, two adjacent first mixing vanes 110 that are arranged on the same first inner straps 11 are symmetrical to two adjacent second mixing vanes 110 that are arranged on the same second inner straps 12 about the intersection of the first inner strap 11 and the second inner strap 12 (namely the axis perpendicular to plane of the mixing grid 1 shown in Fig. 3). As a result, when fuel rods 2 are inserted into the grid cells, a space will be formed among every four adjacent fuel rods 2, in which two adjacent first mixing vanes 110 located at the same first inner strap 11 and two adjacent second mixing vanes 120 located at the same second inner strap 12 are configured. Further, any two such spaces that are adjacent are provided with two first mixing vanes 110 and two second mixing vanes 120 respectively. Since the space and gap among the four adjacent fuel rods 2 are big, thus coolant turbulence will be easily generated; however such a phenomenon will be improved, because two adjacent mixing vanes are configured in this space and gap to deflect and guide the coolant.

[0033] A deflecting vane structure is configured on the outer straps 10 of the mixing grid 1, which includes multiple first deflecting vanes 14 and multiple second deflecting vanes 15. The first deflecting vanes 14 and the second deflecting vanes 15 are alternately arranged on the upper edges and the lower edges of the outer straps 10 and slantwise extended toward the interior of the mixing grid 1.

[0034] The deflecting vane structure will be explained in details, by taking an example of two grid cells 13 abutted to the outer traps 10.

[0035] In one grid cell 13 that is abutted to the outer straps 10, the first mixing vane 110 is arranged on one of the first inner strap 11 that is connected to the outer straps 10, and bent and extended toward another of the first inner straps 11, namely toward the second mixing vane 120. The second mixing vane 120 is arranged in another of grid cells 13 that is adj acent to that grid cell 13 with the first mixing vane 110, and connected with the second inner strap 12 that is parallel to the outer straps 10, and the second mixing vane 120 is bent and extended toward the outer straps 10. Further, the first mixing vane 110 is closed to the second inner straps 12 that is parallel to the outer straps 10, and the second mixing vane 120 is closed to the first inner strap 11 where is opposite to the first mixing vane 110 (that is the position with no first mixing vane 110 is arranged).

[0036] Both of the first deflecting vane 14 and the second deflecting vane 15 are located at junctions of two adjacent grid cells 13. The position of the first deflecting vane 14 is corresponding to the first mixing vane 110, and the position of the second deflecting vane 15 is corresponding to the second mixing vane 120. The extending length of the first deflecting vane 14 extending to the mixing grid 1 is larger than that of the second deflecting vane 15. By means of the first and second deflecting vanes 14, 15 arranged at the junctions of the grid cells 13, the strength of the mixing grid 1 is enhanced, and interferences between adjacent mixing grids happened during the loading and unloading of the fuel assemblies are prevented.

[0037] A diversion groove 140 is formed on a side, facing to the mixing grid 1, of the first deflecting vane 14; and a diversion ridge 150 is formed on a side, facing to the interior of the mixing grid 1, of the second deflecting vane 15. Both of the diversion groove 140 and the diversion ridge 150 are extended along a direction perpendicular to the edge of the outer straps 10 and extended to the interior of the mixing grid 1, and the extending length of the diversion groove 140 is larger than that of the diversion ridge 150. In such a way, the extending directions of the diversion groove 140 and the diversion ridge 150 are consistent to the arrangement directions of the first and the second inner straps 11, 12, which is beneficial to form an integrated coolant flow path.

[0038] The extending directions of the diversion grooves 140 and the diversion ridges 150 follow the flow channels 130, thus the coolant flow deflected by the diversion grooves 140 can maintain the consistent direction with the coolant flow in the flow channel 120; while the function of the diversion ridges 150 is to part the flow.

[0039] In the present embodiment, the shape of the diversion groove 140 is a recess that is formed on a side, facing to the interior of the mixing grid 1, of the first deflecting vane 14, and has a triangular cross section; the shape of the diversion ridge 150 is protruded from the second deflecting vane 15 toward the interior of the mixing grid 1, and has a triangular cross section. Of course, the diversion groove 140 and the diversion ridge 150 can have other shapes, such as arc cross section, trapezoid cross section, etc., as shown in Fig. 6. In addition, the diversion groove 140 and the diversion ridge 150 can be formed by bending the first and second deflecting vanes 14 and 15 toward different directions, causing the sides facing to the interior of the mixing grid 1 to be the grooves or ridges.

[0040] In another embodiment, as shown in Figs. 7 and 8, the diversion groove 140 can be formed by punching the first deflecting vane 14. More specifically, the first deflecting vane 14 is pressed from inside to outside, to form a boat-shaped structure 143 at the outer side of the first deflecting vane 14. The boat-shaped structure 143 is recessed to form the diversion groove 140. Similarly, another boat-shaped structure is formed by punching the second deflecting vane 15 from outside to inside to form the diversion ridge 150.

[0041] In other embodiments, the first and second deflecting vanes 14 and 15 can be only configured at the upper edge of the outer strap 10, or only configured at the lower edge of the outer strap 10, which is dependent on the actual demands.

[0042] In comparison of the prior arts, since the first and second deflecting vanes 14, 15 are alternately and continuously arranged on the mixing grid 1, thus interferences may not be easily generated when the fuel assemblies are hoisted, to ensure the guiding effect. Furthermore, the diversion grooves 140 are formed on the first deflecting vanes 14 and the diversion ridges 150 are formed on the second deflecting vanes 15, thus integrated coolant flow path is formed by the first deflecting vanes 14, the second deflecting vanes 15, the first mixing vanes 110 and the second mixing vanes 120, thereby heat dissipation for the fuel rods 2 is improved. Further, the diversion ridges 150 can deflect the backflow in the fuel assembly toward the sides of the second deflecting vane 15, thus the coolant flow towards the flow channels 130 is reduced to reduce kinetic energy for convection collision in the flow channels 130. As a result, the coolant flow with sufficient kinetic energy can be flowed to the adjacent fuel assemblies to avoid flow cutoff and enhance flow exchange among the fuel assemblies. Further, due to the diversion grooves 140 and the diversion ridges 150, smoothness of the first and second deflecting vanes 14 and 15 is reduced, and therefore direct crash on the vanes 14 and 15 is avoided to weaken coolant turbulence.

[0043] While the invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.

Claims

1. Deflecting vane structure, configured on outer straps of a mixing grid, the mixing grid being provided with multiple inner straps to from multiple grid cells, a first mixing vane being provided within each of the grid cells abutted to the outer straps, the first mixing vane being configured on one of the inner straps that is connected with the outer straps and being bent and extended toward another of the inner straps that is connected with the outer straps, wherein the deflecting vane structure comprises multiple first deflecting vanes which are arranged on upper edges and/or lower edges of the outer straps and are slantwise extended into interior of the mixing grid, the first deflecting vanes have corresponding positions as the first mixing vanes, and a side, facing to the interior of the mixing grid, of the first deflecting vane is recessed to form a diversion groove which is extended toward the interior of the mixing grid along the outer straps.

2. The deflecting vane structure according to claim 1, wherein a second mixing vane is provided within another grid cell that is adjacent to that grid cell with the first mixing vane provided and abutted to the outer straps, and the second mixing vane is arranged on the inner strap that is parallel to the outer straps and is bent and extended toward the outer straps; the deflecting vane structure further comprises multiple second deflecting vanes, the second deflecting vanes and the first deflecting vanes are alternately arranged on the upper edges and/or the lower edges of the outer straps and extended into the interior of the mixing grid, the second deflecting vanes have corresponding positions as the second mixing vanes, and a side, facing to the interior of the mixing grid, of the second deflecting vane is protruded to form a diversion ridge which is extended toward the interior of the mixing grid along the outer straps.

3. The deflecting vane structure according to claim 2, wherein the diversion grooves and the diversion ridges are extended toward the interior of the mixing grid along a direction perpendicular to an edge of the outer straps.

4. The deflecting vane structure according to claim 2, wherein an extending length, extending toward the interior of the mixing grid, of the first deflecting vane is larger than that of the second deflecting vane.

5. The deflecting vane structure according to claim 4, wherein an extending length of the diversion groove is larger than that of the diversion ridge.

6. The deflecting vane structure according to claim 2, wherein both of the first deflector vane and the second deflector vane are located at junctions of two adjacent grid cells.

7. A mixing grid, comprising multiple outer straps and multiple inner straps, the multiple inner straps interlaced with each other to form multiple grid cells, the multiple outer straps surrounding the grid units and fixed to the inner straps, a first mixing vane and a second mixing vane being provided within two adjacent grid units abutted to the outer straps, the first mixing vane being configured on one of the inner straps that is connected with the outer straps and being bent and extended toward another of the inner straps that is connected with the outer straps, and the second mixing vane being configured on that inner strap that is parallel to the outer straps and being bent and extended toward the outer straps, wherein the mixing grid further comprises a deflecting vane structure according to any one of claims 1~6.

8. The mixing grid according to claim 7, wherein the first mixing vane is fixed to an upper edge of the inner straps and closed to that inner strap parallel to the outer straps, and the second mixing vane is fixed to the upper edge of the inner straps and closed to that inner strap opposite to the first mixing vane.