Hybrid spacer grid

Abstract

A hybrid spacer grid according to one embodiment of the present invention comprises: a flow path for mixing a coolant having a bending angle formed in a region in contact with a nuclear fuel rod; and a mixing vane extending in the flow direction of the coolant at a height downstream of the outlet of the flow path.

Description

Hybrid support grid

[0001] The present invention relates to a hybrid support grid for enhancing turbulent mixing of coolant in a nuclear reactor.

[0002] The existing mixing vane support grid for nuclear fuel assemblies promotes cross-flow mixing between subchannels by attaching mixing vanes to the top of the unit grid supporting the nuclear fuel rods. However, due to the relatively large mixing vanes, the flow path blockage rate and pressure loss within the core are large, and there may be a risk of local overheating of the nuclear fuel rods due to the generation of insufficient turbulence intensity.

[0003] In addition, in the case of a mixed-flow channel type support grid that creates a coolant channel with a bending angle in the area in contact with the nuclear fuel rod, a flow field with a cross-flow is generated by the flow proceeding along the internal channel, but there is a problem that it may be difficult to provide sufficient mixing between the subchannels.

[0004] This patent was conducted with the support of the Korea Institute of Energy Technology Evaluation and Planning (RS-2024-00403194, IP-R&D Human Resources Development for Next-Generation Nuclear Power Source Technology Creation) through government funding (Ministry of Trade, Industry and Energy) in 2025.

[0005] The purpose of the present invention is to provide a hybrid support grid that can reduce the possibility of local overheating of nuclear fuel rods, thereby improving safety within a reactor core, and reducing the rate of fuel blockage that causes pressure loss within the reactor core.

[0006] According to one embodiment of the present invention for solving the above technical problem, a hybrid support grid may include a channel for mixing coolant having a bending angle formed in a region in contact with a nuclear fuel rod, and a mixing blade extending in the direction of the flow of the coolant at a height after the exit of the channel.

[0007] Additionally, the hybrid support grid may be provided in multiple numbers and arranged longitudinally and transversely to surround the nuclear fuel rod.

[0008] Additionally, a plurality of the above hybrid support grids surrounding one nuclear fuel rod can be set as a unit grid.

[0009] Additionally, the above-mentioned euro may have the bending angle such that the coolant rotates in one direction through the euro of the hybrid support grid included in the above-mentioned unit grid.

[0010] Additionally, the above hybrid wing may have a bending angle such that the hybrid support grids connected through different unit grid arrangements are in opposite directions.

[0011] Additionally, the mixing blade includes a first mixing blade and a second mixing blade, and the first mixing blade may have a larger volume than the second mixing blade.

[0012] Additionally, the first mixing wing may be formed at the end of the flow path in a direction opposite to the bending angle of the flow path, and may have a bending angle opposite to the flow path.

[0013] In addition, the second mixing wing is formed at the end of the flow path in the direction of the bending angle of the flow path, and may have a bending angle in the same direction as the flow path.

[0014] According to one embodiment of the present invention described above, a hybrid support grid can be provided that can reduce the possibility of local overheating of nuclear fuel rods, thereby improving safety within the core, and reducing the rate of fuel blockage that causes pressure loss within the core.

[0015] FIG. 1 is a drawing illustrating the configuration of a hybrid support grid according to one embodiment of the present invention.

[0016] FIG. 2 is a drawing showing an example of forming a unit grid of a hybrid support grid according to one embodiment of the present invention.

[0017] FIG. 3 is a drawing comparing a hybrid support grid according to one embodiment of the present invention with a conventional support grid.

[0018] FIG. 4 is a diagram illustrating the fluid analysis results of a hybrid support grid and a conventional support grid according to one embodiment of the present invention.

[0019] FIG. 5 is a diagram comparing the turbulence intensity of a hybrid support grid according to one embodiment of the present invention and a conventional support grid.

[0020] FIG. 6 is a drawing showing a contour of a nuclear fuel wall surface of a hybrid support grid according to one embodiment of the present invention.

[0021] FIG. 7 is a drawing showing a contour of the nuclear fuel surface temperature of a hybrid support grid according to one embodiment of the present invention.

[0022] FIG. 8 is a graph showing factors indicating the effect of a hybrid support grid according to one embodiment of the present invention.

[0023] The purposes and effects of the present invention, as well as the technical configurations for achieving them, will become clearer with reference to the embodiments described in detail below, along with the accompanying drawings. In describing the present invention, detailed descriptions of known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the invention.

[0024] However, this is not intended to limit the present invention to a specific embodiment, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0025] And the terms described below are terms defined in consideration of the functions in the present invention, and these may vary depending on the intention or custom of the user or operator.

[0026] However, the present invention is not limited to the embodiments disclosed below and can be implemented in various different forms. These embodiments are provided solely to ensure complete disclosure of the present invention and to fully inform those skilled in the art of the invention of the scope of the invention. The present invention is defined solely by the scope of the claims. Therefore, such definitions should be based on the contents of this specification.

[0027] The terminology used in this application is only used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, it should be understood that the terms "comprise" or "have" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0028] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0029] Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in more detail. In order to facilitate an overall understanding in describing the present invention, identical reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0030] FIG. 1 is a drawing showing the configuration of a hybrid support grid according to one embodiment of the present invention, and FIG. 2 is a drawing showing an example of forming a unit grid of a hybrid support grid according to one embodiment of the present invention.

[0031] Referring to FIG. 1, the hybrid support grid (100) may include a mixing blade (110) and a flow path (120).

[0032] The hybrid support grid (100) is one of the main components of the nuclear fuel assembly structure and refers to a support grid that supports nuclear fuel rods. Referring to FIGS. 1 and 2, a flow path (120) may be provided for coolant mixing, and a bending angle may be formed in the area in contact with the nuclear fuel rod (10).

[0033] The flow path (120) may include a bending angle formed from the support grid itself in the area in contact with the nuclear fuel rod (10). As illustrated in FIG. 1, the flow path (120) may have a bending angle formed at the end area (12 o'clock area) in the direction of travel of the coolant, thereby generating a crossflow due to the flow of the coolant traveling along the flow path (120). Here, the bending angle may have an angle of 5 to 20 degrees with respect to the direction of travel of the coolant. In addition, the position where the bending angle starts may start from a height that is 50% or more of the entire height of the support grid from the inlet of the flow path (120) of the support grid.

[0034] The mixing blade (110) can be extended in the direction of the coolant flow from a height after the outlet of the flow path (120). Fig. 1 shows a hybrid support grid (100) (a and b) using two types of mixing blades (110), and the types of mixing blades (110) will be described later.

[0035] As illustrated in Fig. 1, the mixing blade (110) may be formed by extending from the hybrid support grid (100) at the end of the flow path (120), i.e., the portion where the outlet is formed. The mixing blade (110) may promote cross-flow mixing of the coolant with respect to the subchannel.

[0036] Conventional fuel assembly support grids containing mixing vanes can promote cross-flow mixing between subchannels by attaching mixing vanes to the top of the unit grid supporting the fuel rods. However, the relatively large mixing vanes can lead to high blockage rates and pressure losses within the core, and the generation of insufficient turbulence can lead to localized overheating of the fuel rods.

[0037] In addition, in the case of a mixed-flow channel type support grid that creates a coolant channel having a bending angle in the area in contact with the nuclear fuel rods, a flow field having a cross-flow is generated by the flow proceeding along the internal channel, but it may be difficult to provide sufficient mixing between subchannels. Accordingly, the present invention provides a hybrid support grid (100) that is more economical by forming a flow mixing channel inside the support grid and additionally arranging mixing vanes on the top of the grid to provide a high turbulence intensity inside the nuclear fuel assembly subchannel, thereby reducing the possibility of local overheating of the nuclear fuel rods, thereby enhancing safety within the core, and achieving a reduction in the rate of channel blockage that causes pressure loss within the core.

[0038] Referring to FIG. 2, a plurality of hybrid support grids (100) may be arranged longitudinally and transversely to surround a nuclear fuel rod (10). At this time, a plurality of hybrid support grids (100) surrounding one nuclear fuel rod (10) may be set as a unit grid. That is, a unit grid means a plurality of hybrid support grids (100) arranged and connected in the east, west, south, and north directions with the nuclear fuel rod (10) as the center, as illustrated in FIG. 2.

[0039] Referring to FIG. 2, the flow paths (120) formed in each of the hybrid support grids (100) may have a bending angle so that the coolant rotates in one direction through the flow paths (120) of the hybrid support grids (100) included in the unit grid. Referring to FIGS. 1 and 2, as the flow paths (120) have a bending angle, the coolant may flow crosswise in the direction of the arrow in FIG. 2.

[0040] Therefore, the bending angle of the flow path (120) can form an internal cross-flow field of coolant, and increase the intensity of turbulence. This can suppress the formation of bubbles on the surface of the cladding pipe, which can occur during normal and transient operation of a nuclear power plant. Furthermore, the formed bubbles can be smoothly removed from the surface of the cladding pipe.

[0041] Referring to FIG. 2, the hybrid support grids connected through different unit grid arrangements may have bending angles in opposite directions. Specifically, when the unit grids are arranged, for example, the hybrid support grid of the a unit grid and the hybrid support grid of the b unit grid may have bending angles in opposite directions.

[0042] In addition, the mixing blade (110) may include a first mixing blade (111) and a second mixing blade (112). Referring to FIG. 2, the first mixing blade (111) may have a larger volume than the second mixing blade. For example, the first mixing blade (111) may have a volume of 8.34 mm.2 The size of the second mixing wing (112) is 2.22 mm. 2 It may have a size of, but is not limited to, .

[0043] Referring to FIG. 2, in the case of the second mixing blade (112), it may have a bending angle that extends continuously from the exit of the flow path (120) and rotates in the same direction as the flow path (120) with respect to the center of one nuclear fuel rod (10).

[0044] At this time, if the size of the mixing blade is large enough to contact the nuclear fuel rod (10), that is, in the case of the first mixing blade (111), it can be extended from the hybrid support grid (100) in the opposite direction of the bending angle of the channel at the exit height of the channel of the unit grid as illustrated in (b) of FIG. 2. In this case, in a preferred embodiment, if the direction of the coolant flow by the channel (120) is a form in which the longitudinal and transverse support grids intersect in a orthogonal manner as illustrated in (b) of FIG. 2, the first mixing blade (111) can be positioned on the longitudinal support grid, and if the direction of the coolant flow is a form in which the coolant flow is gathered in the longitudinal direction, the first mixing blade (111) can be positioned on the transverse support grid.

[0045] FIG. 3 is a drawing comparing a hybrid support grid according to one embodiment of the present invention with a conventional support grid, and FIG. 4 is a drawing showing the results of fluid analysis of a hybrid support grid according to one embodiment of the present invention and a conventional support grid.

[0046] Fig. 3 (a) illustrates a support grid having a conventional mixing blade, and Fig. 3 (b) illustrates a hybrid support grid (100) having a second mixing blade (112). Referring to Fig. 3, the mixing blade of the conventional support grid is 10 mm. 2 17mm in diameter 2 It can have sizes in between.

[0047] The area of ​​the conventional support grid mixing wing is 10 mm 2 17mm in diameter 2It can have a size of 10mm, but in the case of the present invention, the size is 10mm. 2 By limiting it to within, the clogging rate (projected area of ​​mixing vane / area of ​​single subchannel) is greatly reduced, thereby solving the fundamental cause of the pressure drop, and the reduction in turbulence caused by the reduced size of the mixing vane can be solved by using a mixing channel. In addition, in order to compensate for the large pressure drop of the conventional mixing vane-type support grid, the self-flow mixing function of the support grid and the first and second mixing vanes are used to reduce the clogging rate, thereby reducing the pressure loss and thus reducing the required power required to drive the coolant pump, thereby improving economic efficiency.

[0048] In addition, while a conventional support grid with a mixed wing has a structure for supporting a nuclear fuel rod, the hybrid support grid of the present invention has the advantage of supporting a nuclear fuel rod while at the same time forming a shape of a flow path having a bending angle to improve the circulation of the coolant.

[0049] Figure 4 presents the results of a computational fluid dynamics analysis of the effects of designs with mixing channels (blue, red, and black) and a conventional grid design with mixing vanes (green) on the pressure drop that occurs as the coolant flows. The graph in Figure 4 plots the pressure drop versus (axial height / hydraulic diameter of the subchannel).

[0050] Referring to Fig. 4, in the pink area, which is the support grid area that does not include the hybrid wing, it can be seen that the support grid with the euro has a larger pressure drop due to the increase in the euro blockage rate due to the bending angle, but when the conventional support grid is used, the total pressure drop in the subchannel is 17% larger than when the hybrid support grid is used due to the influence of the large wing.

[0051] FIG. 5 is a diagram comparing the turbulence intensity of a hybrid support grid according to one embodiment of the present invention and a conventional support grid.

[0052] Referring to Fig. 5, it can be seen that a higher turbulence intensity (T) can be generated when using a euro compared to when using a conventional mixing vane design, and in particular, the highest turbulence intensity can be generated in the second mixing vane. This indicates that the hybrid support grid of the present invention can reduce crud that can be deposited on the nuclear fuel surface and impose additional thermal resistance on the nuclear fuel, as the momentum of crud erosion is the turbulence intensity.

[0053] FIG. 6 is a drawing showing a contour of a nuclear fuel wall surface of a hybrid support grid according to one embodiment of the present invention, and FIG. 7 is a drawing showing a contour of a nuclear fuel surface temperature of a hybrid support grid according to one embodiment of the present invention.

[0054] Referring to FIGS. 6 and 7, when comparing the nuclear fuel surface temperatures for securing core integrity and safety margin, the maximum nuclear fuel surface temperature was highest at approximately 603 K in the case of the conventional mixing vane, and the maximum nuclear fuel surface temperature was approximately 594 K when only the flow path was used, 596 K when the first mixing vane was used, and 591 K when the second mixing vane was used, proving that the use of the second mixing vane is most advantageous in securing safety in terms of maximum nuclear fuel surface temperature.

[0055] FIG. 8 is a graph showing factors indicating the effect of a hybrid support grid according to one embodiment of the present invention.

[0056] Referring to Fig. 8, several thermo-hydraulic factors related to the support grid were compared, and it can be confirmed that the hybrid support grid proposed in the present invention has excellent performance in terms of pressure drop, which is an indicator related to economic feasibility, turbulence intensity related to crud deposition, and nuclear fuel surface temperature, which is related to core integrity and safety.

[0057] As a result, the heat transfer performance between the coolant and the nuclear fuel rods can be improved by the bending angle of the flow path (120), and even if the mixing blade is located at the top of the flow path and has a small volume, the insufficient degree of cross-flow mixing can be compensated for. In addition, the pressure loss can be reduced by reducing the blockage rate of the auxiliary channel by the hybrid support grid (100), thereby securing corresponding economic efficiency.

[0058] The features, structures, effects, etc. described in the above-described embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified and implemented in other embodiments by a person having ordinary skill in the art to which the embodiments belong.

[0059] Accordingly, the contents related to such combinations and modifications should be interpreted as being included within the scope of the present invention. In addition, although the above description focuses on the embodiments, these are merely examples and do not limit the present invention. Those skilled in the art to which the present invention pertains will appreciate that various modifications and applications not illustrated above are possible without departing from the essential characteristics of the present embodiments. For example, each component specifically shown in the embodiments can be modified and implemented. In addition, the differences related to such modifications and applications should be interpreted as being included within the scope of the present invention defined in the appended claims.

Claims

1. A path for mixing coolant with a bending angle formed in the area in contact with the nuclear fuel rod; and A hybrid support grid comprising mixing vanes extending in the direction of the flow of the coolant from a height beyond the exit of the above-mentioned euro.

2. In paragraph 1, The hybrid support grid is provided in multiple units, arranged longitudinally and transversely to surround the nuclear fuel rod.

3. In paragraph 2, A hybrid support grid, wherein a plurality of the hybrid support grids surrounding a single nuclear fuel rod are set as a unit grid.

4. In paragraph 3, The above euro is, A hybrid support grid having the bending angle such that the coolant rotates in one direction through the path of the hybrid support grid included in the unit grid.

5. In paragraph 3, The above mixed wing, A hybrid support grid having a bending angle so that the hybrid support grids connected through different unit grid arrangements are in opposite directions.

6. In paragraph 1, The above mixed wing, Including a first mixing wing and a second mixing wing, A hybrid support grid, wherein the first mixing wing has a larger volume than the second mixing wing.

7. In paragraph 6, The above first mixing wing, Formed at the end of the above-mentioned euro in the direction opposite to the bending angle of the above-mentioned euro, A hybrid support grid having a bending angle opposite to that of the above-mentioned euro.

8. In paragraph 6, The above second mixing wing, Formed at the end of the above-mentioned euro in the direction of the bending angle of the above-mentioned euro, A hybrid support grid having a bending angle in the same direction as the above euro.

9. In paragraph 6, A hybrid support grid that supplements the degree of cross-flow mixing of nuclear fuel by the second mixing vane located at the upper end of the above-mentioned euro.

10. In paragraph 6, A hybrid support grid that increases the turbulence intensity and cross-flow characteristics inside the auxiliary channel through combined use of the above-mentioned mixing channel, the first mixing blade, and the second mixing blade.

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