Porous guide plate for improving uniformity of outlet pressure of grid tray header and design method of porous guide plate

Abstract

The invention relates to a porous guide plate for improving the uniformity of the outlet pressure of a grid tray header and a design method thereof, and relates to the field of thermal hydraulic design. Comprising a cylindrical guide plate and an inlet pore plate arranged on the inlet side of the cylindrical guide plate; the cylindrical flow guide plates are mounted on the upper surface and the lower surface of the grid plate header through the connecting pieces, and a liquid sodium coolant from a main pipeline is pretreated through the inlet small hole plate before entering the cylindrical flow guide plates; a pre-pressure-equalizing cavity is formed between the inlet small hole plate and the cylindrical flow guide plate and used for diffusing and homogenizing inlet jet flow, and disturbance of inlet bias flow to a downstream hole area is reduced. Aiming at the strong disturbance characteristic of outlet jet flow and inlet bias flow of a main pipeline on a downstream pressure field, the inlet small hole plate is introduced into an inlet to perform pre-throttling and pre-pressure-equalizing on fluid, so that the influence of inlet high-momentum jet flow and bias flow on flow distribution in the header is weakened, the outlet pressure distribution uniformity of the grid tray header is improved, and the flow distribution efficiency is improved. And the accuracy and consistency of flow distribution of the fuel assembly are improved.

Description

Technical Field

[0001] This invention relates to the field of thermal hydraulic design, specifically to a porous guide plate for improving the uniformity of outlet pressure of a grid header and its design method. Background Technology

[0002] In fourth-generation liquid metal-cooled nuclear reactors, core fuel assemblies are typically connected to the primary loop main piping via grid headers. The three-dimensional flow pattern and outlet pressure distribution within the grid headers directly determine the inlet boundary conditions and coolant flow distribution for each fuel assembly, making it a crucial aspect of core thermal-hydraulic design and safety margin assessment. Engineering design often employs one-dimensional or simplified network models, approximating the grid header outlet pressure as a uniform average pressure, and adjusting flow rates by installing orifice plates at fuel assembly inlets. While these methods are convenient for engineering implementation, they fail to reflect the actual three-dimensional flow structure within the grid headers and the local pressure differences at different assembly locations, potentially introducing flow distribution errors.

[0003] Because grid headers often employ lateral inflow, complex flow structures such as high-momentum jets, backflow, and secondary flows easily form near the main pipe outlet, while low-momentum regions and insufficient flow areas tend to appear on the side farther from the main pipe. This results in a significant circumferential pressure non-uniformity at the grid header outlet. To mitigate this issue, existing technologies typically incorporate perforated guide plates or orifice plates within the grid header, using symmetrical or uniformly distributed orifice diameters and densities to weaken the velocity gradient and reduce local flow non-uniformity. However, this homogenization arrangement struggles to effectively suppress local high-momentum disturbances caused by the inlet jet and fails to provide directional compensation for low-momentum regions on the far side. Often, an increased overall throttling intensity is required to achieve uniformity, leading to increased total pressure drop in the header, higher pumping power, and potential engineering risks such as localized high-speed jets, scouring, and vibration.

[0004] Therefore, how to provide a porous guide plate for improving the uniformity of outlet pressure of the grid header and its design method has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] To address at least one technical problem in the background art, this invention provides a porous guide plate and its design method for improving the uniformity of outlet pressure in a grid header. Without significantly increasing the overall pressure drop of the grid header, and considering the strong disturbance characteristics of the main pipeline outlet jet and inlet deflection flow on the downstream pressure field, this invention introduces an inlet orifice plate at the inlet to pre-throttle and pre-equalize the fluid, weakening the influence of the high-momentum jet and deflection flow at the inlet on the flow distribution inside the header. This improves the uniformity of the outlet pressure distribution of the grid header, enhances the accuracy and consistency of fuel assembly flow distribution, and also simplifies component parameters and ensures the feasibility of engineering processing and assembly.

[0006] To achieve the above objectives, the present invention provides a porous guide plate for improving the uniformity of outlet pressure of a grid header, comprising: a cylindrical guide plate and an inlet orifice plate disposed on the inlet side of the cylindrical guide plate; the cylindrical guide plate is installed on the upper and lower surfaces of the grid header via connectors; the liquid sodium coolant from the main pipeline is pretreated by the inlet orifice plate before entering the cylindrical guide plate; a pre-equalizing cavity is formed between the inlet orifice plate and the cylindrical guide plate to diffuse and equalize the inlet jet, reducing the disturbance of inlet flow deviation to the downstream orifice region.

[0007] Furthermore, the inlet perforated plate covers the core area of ​​the inlet jet, and several inlet perforations are formed thereon.

[0008] Furthermore, the inlet holes are arranged in an array or staggered array along the longitudinal and transverse directions, with the hole spacing remaining consistent.

[0009] Furthermore, the orifice region of the cylindrical guide plate is not circumferentially segmented. Several guide holes are arranged in the orifice region. The guide holes adopt a uniform orifice diameter and are evenly distributed according to a predetermined orifice density, so as to provide the main flow capacity while ensuring a low additional pressure drop and to form a stable flow boundary condition for the downstream outlet pressure field.

[0010] Furthermore, the diameter of the inlet orifice is denoted as d0, which is smaller than the diameter D of the guide orifice on the cylindrical guide plate; and the opening ratio of the inlet orifice plate is lower than the opening ratio of the orifice area of ​​the cylindrical guide plate.

[0011] Furthermore, the perforated area extends circumferentially to form an annular flow zone, which is used to achieve uniform discharge and rectification of coolant within the circumferential range.

[0012] A design method for a porous guide plate for improving the uniformity of outlet pressure of a grid header includes the following steps: Step 1: Based on the geometric dimensions of the grid header, the operating parameters of the primary side liquid sodium, and the outlet flow rate of the core fuel assembly, propose uniformity indicators and drag characteristic constraints for the outlet pressure of the grid header; and based on the uniformity indicators and drag characteristic constraints, determine the position, installation height, and overall target opening ratio of the perforated guide plate within the grid header. An inlet perforated plate is installed at the inlet of the large grid header, and a pre-equalization cavity is formed between the inlet perforated plate and the cylindrical guide plate. At the same time, based on the corresponding direction of the main pipe inlet on the grid header, determine the circumferential arrangement reference of the perforated guide plate. Step 2: Based on the circumferential arrangement reference direction determined in Step 1, determine that the orifice area of ​​the cylindrical guide plate will not be circumferentially segmented; uniformly arrange several guide holes in the orifice area, and arrange the guide holes with a uniform hole diameter; and determine the number, hole density and arrangement of the guide holes according to the overall target opening ratio and resistance characteristics determined in Step 1, so that the cylindrical guide plate can provide the main flow capacity and provide stable boundary conditions for subsequent pressure equalization and rectification while meeting the pressure drop requirements; Step 3: Based on the main flow direction of liquid sodium in the grid header and the initial flow field distribution characteristics at the inlet, determine the coverage area of ​​the inlet jet core region, and arrange an inlet orifice plate at the inlet of the large grid header to form a pre-pressure equalization cavity between the inlet orifice plate and the cylindrical guide plate; at the same time, determine the orifice diameter, pore density and opening ratio of the inlet orifice plate so that the equivalent flow capacity of the inlet orifice plate is lower than that of the cylindrical guide plate in Step 2, thereby achieving pre-throttling and pre-pressure equalization of the inlet jet, and reducing the disturbance of inlet flow deviation and jet to the downstream orifice region under the premise of meeting the resistance characteristic constraints of Step 1; Step 4: Set the resistance and flow capacity difference in the axial direction of the perforated guide plate, determine the axial distance between the inlet orifice plate and the cylindrical guide plate to form the cavity depth of the pre-equalizing chamber, and optimize the parameters of the inlet orifice plate according to the cavity depth and the overall pressure drop constraint; in the case of including the baffle orifice plate, further determine the arrangement position of the baffle orifice plate relative to the cylindrical guide plate and its orifice parameters, so that the inlet orifice plate-pre-equalizing chamber-cylindrical guide plate-baffle orifice plate form a multi-stage rectification and pressure drop matching relationship in the axial direction, so as to achieve low pressure loss rectification and axial flow balance in the manifold while ensuring that the overall pressure drop of the grid manifold meets the design requirements; Step 5: Based on the uniform orifice layout scheme of the cylindrical guide vane determined in Step 2, and the inlet orifice plate parameters, pre-equalizing chamber depth, and baffle orifice plate parameters determined in Steps 3 and 4, the flow characteristics and outlet pressure distribution within the grid header are verified using computational fluid dynamics numerical simulation. When the pressure non-uniformity at the outlet of each fuel assembly does not exceed the predetermined limit and the overall resistance characteristic change of the grid header is within the allowable range, the final geometric structure and installation parameters of the perforated guide vane used in the grid header are determined, and it is uniformly arranged circumferentially along the sidewall of the header. If the criteria are not met, the inlet orifice plate parameters, pre-equalizing chamber depth, or baffle orifice plate parameters are adjusted and the verification is repeated until the requirements are met.

[0013] The beneficial effects of this invention are as follows: (1) Improved uniformity of outlet pressure: By setting an inlet orifice plate at the inlet of the grid header and forming a pre-equalizing cavity with the cylindrical guide plate, the inlet jet is pre-throttled and pre-equalized, which weakens the inlet deflection caused by the lateral inflow and the disturbance of the downstream pressure field by the local high momentum jet, thereby effectively improving the uniformity of outlet pressure distribution of the grid header and improving the consistency of inlet boundary conditions of each fuel assembly.

[0014] (2) The additional pressure drop is small and the impact on pumping power is controllable: The cylindrical guide plate adopts a uniform aperture arrangement in the orifice area to provide the main flow capacity. The main pressure equalization function is moved forward to the inlet pretreatment stage. While achieving the goal of pressure equalization and rectification, it avoids relying on the overall strong throttling. It can achieve outlet pressure uniformity under low additional pressure drop conditions and reduce the adverse impact on the pumping power of the primary loop.

[0015] (3) Enhanced flow stability and reduced risk of local scouring: The synergistic effect of inlet pre-equalization and secondary rectification by the baffle plate can suppress secondary flow and velocity pulsation, reduce local velocity peak and jet impact intensity, reduce the risk of scouring and vibration of the inner wall of the header and the grid structure, and improve flow stability under operating conditions.

[0016] (4) The structural parameters are simplified, and the processing, assembly and maintenance are convenient. The main hole area of ​​the cylindrical guide plate is not segmented and the hole diameter is uniform. The parameterization is high and it is convenient for engineering processing and quality control. The inlet small hole plate and the baffle small hole plate can be arranged in a modular manner, which is convenient for assembly, maintenance and replacement. It is suitable for grid headers with different geometric arrangements and has good engineering promotion and application value. Attached Figure Description

[0017] Figure 1 This is the front view of the present invention; Figure 2 This is a side view of the present invention; Figure 3 This is a top view of the present invention.

[0018] In the figure: 1-Cylindrical guide plate; 2-Inlet orifice plate; 3-Inlet orifice; 4-Guide hole; 11-Connector; 12-Pre-pressure equalization chamber; 13-Orifice area. Detailed Implementation

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0022] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0023] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0024] To achieve the above objectives, such as Figures 1 to 2 As shown, the present invention provides a porous guide plate for improving the uniformity of outlet pressure of a grid header, comprising: a cylindrical guide plate 1 and an inlet orifice plate 2 disposed on the inlet side of the cylindrical guide plate 1; the cylindrical guide plate 1 is installed on the upper and lower surfaces of the grid header through a connector 11; the liquid sodium coolant from the main pipeline (pressure pipeline) is pretreated by the inlet orifice plate 2 before entering the cylindrical guide plate 1; a pre-equalizing cavity 12 is formed between the inlet orifice plate 2 and the cylindrical guide plate 1, which is used to diffuse and equalize the inlet jet and reduce the disturbance of the inlet deflection to the downstream orifice region 13.

[0025] The inlet orifice plate 2 covers the inlet jet core region, and several inlet orifices 3 are formed on it. Pre-throttling and pre-pressure equalization are achieved through the small orifice diameter and low orifice ratio, reducing the disturbance of inlet flow deviation and jet to the downstream orifice region 13. This structure simplifies parameter settings, facilitates processing and assembly, and can effectively improve the uniformity of pressure distribution at the grid header outlet under asymmetric flow field conditions, enhance the consistency of fuel assembly inlet boundary conditions, and has good engineering application value.

[0026] This invention addresses the strong disturbance characteristics of the main pipeline outlet jet and inlet deflection flow on the downstream pressure field without significantly increasing the overall pressure drop of the grid header. It reduces the impact of the high momentum jet and deflection flow at the inlet on the internal flow distribution of the header by setting an inlet orifice plate 2 at the inlet to pre-throttle and pre-equalize the fluid, thereby improving the uniformity of the outlet pressure distribution of the grid header, enhancing the accuracy and consistency of fuel assembly flow distribution, and taking into account the simplification of component parameters and the feasibility of engineering processing and assembly.

[0027] The inlet holes 3 are arranged in an array or staggered array along the longitudinal and transverse directions, with the hole spacing remaining consistent, in order to balance processability and reduce local separation.

[0028] The orifice region 13 of the cylindrical guide plate 1 is not circumferentially segmented. Several guide holes 4 are arranged within the orifice region 13. The guide holes 4 adopt a uniform orifice diameter arrangement (preferably D is a fixed value) and are evenly distributed according to a predetermined orifice density to provide main flow capacity while ensuring a low additional pressure drop, and to form stable flow boundary conditions for the downstream outlet pressure field. Further, the orifice diameter of the inlet orifice 3 is denoted as d0, which is smaller than the orifice diameter D of the guide holes 4 on the cylindrical guide plate 1; and the opening ratio of the inlet orifice plate 2 is lower than the opening ratio of the orifice region 13 of the cylindrical guide plate 1, thereby making the equivalent flow capacity of the inlet orifice plate 2 lower than the equivalent flow capacity of the cylindrical guide plate 1, achieving pre-throttling and pre-pressure equalization of the inlet jet.

[0029] like Figure 3 As shown, the dashed line represents the circumferential arrangement baseline of the cylindrical guide plate 1. The perforated area 13 extends circumferentially to form a ring-shaped flow area, used to achieve uniform discharge and rectification of the coolant within the circumferential range. It should be noted that... Figures 1-3 The arrangement of the holes is only for illustration. In actual engineering applications, the covering diameter, hole spacing and pre-equalization chamber depth of the inlet orifice plate 2 can be parametrically adjusted according to the main pipeline outlet size, allowable pressure drop range and target uniformity index. The hole density and number of guide holes 4 in the hole area 13 of the cylindrical guide plate 1 can also be optimized under the condition of meeting the overall target opening rate and resistance characteristics constraints. All the above changes do not depart from the protection scope of this invention.

[0030] The present invention also provides a design method for a porous guide plate for improving the uniformity of outlet pressure of a grid header, comprising the following steps: Step 1: Based on the geometric dimensions of the grid header, the operating parameters of the primary side liquid sodium, and the outlet flow rate of the core fuel assembly, propose uniformity indicators and drag characteristic constraints for the outlet pressure of the grid header; and based on the uniformity indicators and drag characteristic constraints, determine the position, installation height, and overall target opening ratio of the perforated guide plate within the grid header. An inlet perforated plate is installed at the inlet of the large grid header, and a pre-equalization cavity is formed between the inlet perforated plate and the cylindrical guide plate. At the same time, based on the corresponding direction of the main pipe inlet on the grid header, determine the circumferential arrangement reference of the perforated guide plate. Step 2: Based on the circumferential arrangement reference direction determined in Step 1, determine that the orifice area of ​​the cylindrical guide plate will not be circumferentially segmented; uniformly arrange several guide holes in the orifice area, and arrange the guide holes with a uniform hole diameter; and determine the number, hole density and arrangement of the guide holes according to the overall target opening ratio and resistance characteristics determined in Step 1, so that the cylindrical guide plate can provide the main flow capacity and provide stable boundary conditions for subsequent pressure equalization and rectification while meeting the pressure drop requirements; Step 3: Based on the main flow direction of liquid sodium in the grid header and the initial flow field distribution characteristics at the inlet, determine the coverage area of ​​the inlet jet core region, and arrange an inlet orifice plate at the inlet of the large grid header to form a pre-pressure equalization cavity between the inlet orifice plate and the cylindrical guide plate; at the same time, determine the orifice diameter, pore density and opening ratio of the inlet orifice plate so that the equivalent flow capacity of the inlet orifice plate is lower than that of the cylindrical guide plate in Step 2, thereby achieving pre-throttling and pre-pressure equalization of the inlet jet, and reducing the disturbance of inlet flow deviation and jet to the downstream orifice region under the premise of meeting the resistance characteristic constraints of Step 1; Step 4: Set the resistance and flow capacity difference in the axial direction of the perforated guide plate, determine the axial distance between the inlet orifice plate and the cylindrical guide plate to form the cavity depth of the pre-equalizing chamber, and optimize the parameters of the inlet orifice plate according to the cavity depth and the overall pressure drop constraint; in the case of including the baffle orifice plate, further determine the arrangement position of the baffle orifice plate relative to the cylindrical guide plate and its orifice parameters, so that the inlet orifice plate-pre-equalizing chamber-cylindrical guide plate-baffle orifice plate form a multi-stage rectification and pressure drop matching relationship in the axial direction, so as to achieve low pressure loss rectification and axial flow balance in the manifold while ensuring that the overall pressure drop of the grid manifold meets the design requirements; Step 5: Based on the uniform orifice layout scheme of the cylindrical guide vane determined in Step 2, and the inlet orifice plate parameters, pre-equalizing chamber depth, and baffle orifice plate parameters determined in Steps 3 and 4, the flow characteristics and outlet pressure distribution within the grid header are verified using computational fluid dynamics numerical simulation. When the pressure non-uniformity at the outlet of each fuel assembly does not exceed the predetermined limit and the overall resistance characteristic change of the grid header is within the allowable range, the final geometric structure and installation parameters of the perforated guide vane used in the grid header are determined, and it is uniformly arranged circumferentially along the sidewall of the header. If the criteria are not met, the inlet orifice plate parameters, pre-equalizing chamber depth, or baffle orifice plate parameters are adjusted and the verification is repeated until the requirements are met.

[0031] This invention improves outlet pressure uniformity by setting an inlet orifice plate at the grid header inlet, forming a pre-equalization chamber with the cylindrical guide plate. This achieves pre-throttling and pre-equalization of the inlet jet, weakening the inlet flow deviation caused by lateral inflow and the disturbance of the downstream pressure field by local high-momentum jets. This effectively improves the uniformity of the outlet pressure distribution of the grid header and enhances the consistency of inlet boundary conditions for each fuel assembly. The additional pressure drop is small, and the impact on pumping power is controllable: the cylindrical guide plate uses a uniform orifice arrangement to provide main flow capacity, moving the main equalization function forward to the inlet pretreatment stage. While achieving the goal of equalization and rectification, it avoids reliance on overall strong throttling, enabling outlet pressure uniformity under relatively low additional pressure drop conditions. It reduces the adverse impact on the primary loop pumping power; enhances flow stability and reduces the risk of local scouring. The synergistic effect of inlet pre-equalization and secondary rectification by the baffle orifice plate can suppress secondary flow and velocity pulsation, reduce local velocity peaks and jet impact intensity, reduce the risk of scouring and vibration on the inner wall of the header and the grid structure, and improve flow stability under operating conditions. The structural parameters are simplified, and the processing, assembly and maintenance are convenient. The main orifice area of ​​the cylindrical guide plate is not segmented and the orifice diameter is uniform. The parameterization degree is high, which facilitates engineering processing and quality control. The inlet orifice plate and the baffle orifice plate can be arranged in a modular manner, which facilitates assembly, maintenance and replacement. It is suitable for grid headers with different geometric arrangements and has good engineering application value.

[0032] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A porous guide plate for improving the uniformity of outlet pressure of a grid header, characterized in that, include: A cylindrical guide plate and an inlet orifice plate disposed on the inlet side of the cylindrical guide plate; the cylindrical guide plate is installed on the upper and lower surfaces of the grid header via connectors; the liquid sodium coolant from the main pipeline is pretreated by the inlet orifice plate before entering the cylindrical guide plate; a pre-equalizing cavity is formed between the inlet orifice plate and the cylindrical guide plate to diffuse and equalize the inlet jet and reduce the disturbance of the inlet deflection to the downstream orifice region.

2. The porous guide plate for improving the uniformity of outlet pressure of the grid header as described in claim 1, characterized in that, The inlet perforated plate covers the core area of ​​the inlet jet, and several inlet holes are formed on it.

3. A porous guide plate for improving the uniformity of outlet pressure of a grid header as described in claim 2, characterized in that, The inlet holes are arranged in an array or staggered array along the longitudinal and transverse directions, with the hole spacing remaining consistent.

4. A porous guide plate for improving the uniformity of outlet pressure of a grid header as described in claim 3, characterized in that, The cylindrical guide plate does not have circumferential segmentation in the orifice area. Instead, several guide holes are arranged within the orifice area. The guide holes are arranged with a uniform aperture and are uniformly distributed according to a predetermined orifice density. This provides the main flow capacity while ensuring a low additional pressure drop and forms a stable flow boundary condition for the downstream outlet pressure field.

5. A porous guide plate for improving the uniformity of outlet pressure of a grid header as described in claim 4, characterized in that, The diameter of the inlet orifice is denoted as d0, which is smaller than the diameter D of the guide orifice on the cylindrical guide plate; and the opening ratio of the inlet orifice plate is lower than the opening ratio of the orifice area of ​​the cylindrical guide plate.

6. A porous guide plate for improving the uniformity of outlet pressure of a grid header as described in claim 5, characterized in that, The perforated area extends circumferentially to form a ring-shaped flow region, which is used to achieve uniform discharge and rectification of coolant within the circumferential range.

7. A design method for a porous guide plate used to improve the uniformity of outlet pressure of a grid header, characterized in that, Includes the following steps: Step 1: Based on the geometric dimensions of the grid header, the operating parameters of the primary side liquid sodium, and the outlet flow rate of the core fuel assembly, propose uniformity indicators and drag characteristic constraints for the outlet pressure of the grid header; and based on the uniformity indicators and drag characteristic constraints, determine the position, installation height, and overall target opening ratio of the perforated guide plate within the grid header. An inlet perforated plate is installed at the inlet of the large grid header, and a pre-equalization cavity is formed between the inlet perforated plate and the cylindrical guide plate. At the same time, based on the corresponding direction of the main pipe inlet on the grid header, determine the circumferential arrangement reference of the perforated guide plate. Step 2: Based on the circumferential arrangement reference direction determined in Step 1, determine that the hole area of ​​the cylindrical guide plate will not be circumferentially segmented; arrange several guide holes evenly in the hole area, and arrange the guide holes with a uniform hole diameter. Based on the overall target opening ratio and resistance characteristics constraints determined in step one, the number, density and arrangement of the guide holes are determined so that the cylindrical guide plate can provide the main flow capacity and provide stable boundary conditions for subsequent equalization and rectification while meeting the pressure drop requirements. Step 3: Based on the main flow direction of liquid sodium in the grid header and the initial flow field distribution characteristics at the inlet, determine the coverage area of ​​the inlet jet core region, and arrange an inlet orifice plate at the inlet of the large grid header to form a pre-pressure equalization cavity between the inlet orifice plate and the cylindrical guide plate; at the same time, determine the orifice diameter, pore density and opening ratio of the inlet orifice plate so that the equivalent flow capacity of the inlet orifice plate is lower than that of the cylindrical guide plate in Step 2, thereby achieving pre-throttling and pre-pressure equalization of the inlet jet, and reducing the disturbance of inlet flow deviation and jet to the downstream orifice region under the premise of meeting the resistance characteristic constraints of Step 1; Step 4: Set the resistance and flow capacity difference in the axial direction of the perforated guide plate, determine the axial distance between the inlet orifice plate and the cylindrical guide plate to form the cavity depth of the pre-equalizing chamber, and optimize the parameters of the inlet orifice plate according to the cavity depth and the overall pressure drop constraint; in the case of including the baffle orifice plate, further determine the arrangement position of the baffle orifice plate relative to the cylindrical guide plate and its orifice parameters, so that the inlet orifice plate-pre-equalizing chamber-cylindrical guide plate-baffle orifice plate form a multi-stage rectification and pressure drop matching relationship in the axial direction, so as to achieve low pressure loss rectification and axial flow balance in the manifold while ensuring that the overall pressure drop of the grid manifold meets the design requirements; Step 5: Based on the uniform orifice layout scheme of the cylindrical guide vane determined in Step 2, and the inlet orifice plate parameters, pre-equalizing chamber depth, and baffle orifice plate parameters determined in Steps 3 and 4, the flow characteristics and outlet pressure distribution within the grid header are verified using computational fluid dynamics numerical simulation. When the pressure non-uniformity at the outlet of each fuel assembly does not exceed the predetermined limit and the overall resistance characteristic change of the grid header is within the allowable range, the final geometric structure and installation parameters of the perforated guide vane used in the grid header are determined, and it is uniformly arranged circumferentially along the sidewall of the header. If the criteria are not met, the inlet orifice plate parameters, pre-equalizing chamber depth, or baffle orifice plate parameters are adjusted and the verification is repeated until the requirements are met.

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