High-temperature-resistant differential flow guide structure and installation method thereof

Abstract

The application provides a flow guide structure and a method for installing the same, and a nuclear reactor comprising the same. The flow guide structure is used for guiding a coolant of the nuclear reactor, and comprises a flow guide member and a mounting base of the flow guide member. The flow guide member comprises a flow guide part and a mounting part. The flow guide part is provided with a flow channel. The flow channel is provided with a stop wall at one end in an extending direction, and forms an open end at the opposite end. The coolant entering the flow channel can be blocked by the stop wall and flow out from the open end. The mounting part is used for mounting to the mounting base. The flow guide part is located between the mounting parts on both sides. A side wall of the flow guide part is connected with the mounting parts and forms a stress release groove. The stress release groove is open at both ends and open to one side of the mounting base in a thickness direction of the flow guide member.

Description

Technical Field

[0001] This application relates to the field of nuclear engineering technology, specifically to a flow guiding structure and its installation method, and a nuclear reactor containing the same. Background Technology

[0002] Nuclear reactors generate a large amount of heat through nuclear fission. This heat is carried away by the coolant in the primary loop to produce steam, which in turn drives a steam turbine generator to generate electricity. To ensure the safe operation of a nuclear reactor, the nuclear fuel must be continuously cooled to prevent the core from overheating or even melting down. Some advanced nuclear reactor designs employ Direct Vessel Injection (DVI) technology, which allows coolant to be injected directly into the reactor from nozzles on the reactor pressure vessel in case of an accident or insufficient coolant. To guide the injected coolant along a predetermined path to the core, a flow guiding structure is typically installed inside the nuclear reactor to guide the coolant downwards along the walls of the reactor internals and then upwards into the fuel zone.

[0003] However, the coolant injected into this water injection system is at a relatively low temperature, for example, about 20°C, while the normal operating temperature inside the reactor is as high as about 300°C. When the low-temperature coolant suddenly comes into contact with the high-temperature metal guide structure, the surface of the guide structure cools and contracts rapidly, while the mounting base, such as the in-reactor components connected to it, cools slowly due to its large heat capacity, resulting in a huge temperature difference and deformation difference between the two. Existing guide structures are usually rigidly fixed to the mounting base, and are subjected to cyclic thermal stress in repeated thermal expansion and contraction cycles. After long-term operation, fatigue cracks are likely to appear, and failure may even occur.

[0004] Based on this, this application provides a flow guiding structure and its installation method, as well as a nuclear reactor containing the same, in order to solve one or more of the above-mentioned technical problems. Summary of the Invention

[0005] The first aspect of this application provides a flow guiding structure.

[0006] A second aspect of this application provides a nuclear reactor.

[0007] A third aspect of this application provides a method for installing a flow guiding structure.

[0008] According to the first aspect of this application, a flow guiding structure for coolant flow in a nuclear reactor includes a flow guiding component and a mounting base for the flow guiding component. The flow guiding component includes a flow guiding portion and a mounting portion. The flow guiding portion has a flow channel. One end of the flow channel in the extending direction has a stop wall, and the other end forms an open end. Coolant entering the flow channel can be blocked by the stop wall and flow out from the open end. The mounting portion is used to install to the mounting base. The flow guiding portion is located between the mounting portions on both sides. The sidewall of the flow guiding portion is connected to the mounting portion and forms a stress relief groove. The stress relief groove is open at both ends and opens on one side of the flow guiding component towards the mounting base in the thickness direction.

[0009] The flow guiding structure provided in this application forms a stress relief groove with openings at both ends and facing the mounting base between the sidewall of the flow guiding part and the mounting parts on both sides. When the flow guiding part is subjected to the rapid cooling impact of the low temperature coolant, the differential thermal deformation generated relative to the mounting part can be absorbed by the local elastic deformation of the sidewall of the stress relief groove, blocking the rigid transmission path of thermal stress, thereby reducing the risk of fatigue cracks in the structure under cyclic thermal loads, improving the reliability of the flow guiding structure under high temperature difference conditions and extending its service life.

[0010] In some embodiments, the mounting portion is provided with a mounting hole and a positioning hole extending through the thickness direction of the flow guide. The flow guide structure further includes a bolt and a positioning pin. The bolt passes through the mounting hole to enable the flow guide to be detachably connected to the mounting base, and the positioning pin passes through the positioning hole to define the position of the flow guide relative to the mounting base.

[0011] Traditional flow guiding structures typically use welding to rigidly fix the flow guiding component to the mounting base. The weld seam is subject to cyclic thermal stress, which can easily lead to fatigue cracking. The flow guiding structure provided in this application uses a detachable connection method combining bolts and locating pins to replace the traditional welding fixation. The locating pin passes through the locating hole to perform the positioning function to ensure the positional accuracy of the flow guiding component relative to the mounting base, while the bolt passes through the mounting hole to perform the fastening function to provide sufficient connection force. This allows the flow guiding component to generate a small degree of freedom of thermal expansion when the temperature changes, further reducing the additional thermal stress introduced by the installation constraints, and facilitating the in-service maintenance and replacement of the flow guiding structure.

[0012] In some embodiments, the assembly of the flow guide and the mounting base is configured to withstand a temperature difference of not less than 300°C.

[0013] In some embodiments, at least a portion of the flow channel has an elliptical or a rectangular shape with rounded corners in the cross section perpendicular to the extension direction.

[0014] In some embodiments, at least a portion of the surface of the flow channel is configured as a hydrodynamic surface.

[0015] In some embodiments, the open end has a hydrodynamic surface.

[0016] In some embodiments, in the thickness direction, there is a height difference between the mounting surface of the mounting portion that contacts the mounting base and the surface of the guide portion on the side near the mounting base.

[0017] According to a second aspect of this application, a nuclear reactor includes a reactor pressure vessel and a flow guiding structure as described in the first aspect; the flow guiding structure is disposed in the coolant flow path of the nuclear reactor, and the flow direction of the coolant flow path is toward the flow channel of the flow guiding member.

[0018] In some embodiments, the mounting base is at least one of the following: the basket body, the distributor, and the coolant system piping.

[0019] According to the installation method of the flow guiding structure of the third aspect of this application, which is used to realize the installation of the flow guiding structure as described in the first aspect, the method includes: installing the flow guiding member on the mounting base by means of bolts passing through the mounting holes; and defining the position of the flow guiding member relative to the mounting base by means of positioning pins passing through the positioning holes. Attached Figure Description

[0020] The above and other features, properties, and advantages of this application will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, in which the same reference numerals always denote the same features. It should be noted that these drawings are merely illustrative and are not drawn to scale, and should not be construed as limiting the scope of protection actually claimed by this application, wherein: Figure 1 This is a schematic diagram of the flow guide component in one embodiment of the flow guide structure.

[0021] Figure 2 yes Figure 1 The diagram shows a top view of the flow guide.

[0022] Figure 3 This is a partial schematic diagram of a nuclear reactor according to one embodiment.

[0023] Figure 4 yes Figure 1 The diagram shows a cross-sectional view of the guide element (at the locating pin position).

[0024] Explanation of reference numerals in the attached figures: 1. Flow guiding structure; 10. Flow guide; 20. Mounting base; 30. Bolt; 40. Locating pin; 110. Flow guide; 111. Flow channel; 112. Baffle wall; 113. Open end; 120. Mounting part; 121. Mounting hole; 122. Positioning hole; 123. Mounting surface; 130. Stress relief groove. Detailed Implementation

[0025] Reference will now be made in detail to various embodiments of this application, examples of which are shown in the accompanying drawings and described below. Although this application will be described in conjunction with exemplary embodiments, it should be understood that this application is not intended to be limited to those exemplary embodiments. Rather, this application is intended to cover not only these exemplary embodiments, but also various alternatives, modifications, equivalents, and other embodiments that may be included within the spirit and scope of this application as defined by the appended claims.

[0026] This application uses specific terms to describe embodiments of the application. For example, "an embodiment" and / or "one embodiment" refers to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment" or "one embodiment" mentioned twice or more in different locations in this application does not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0027] In this application, the terms "first," "second," etc., are used only for distinguishing descriptions and should not be construed as indicating or implying positional relationships or order of importance.

[0028] In the following description, the orientation or positional relationship indicated by terms such as "upper," "lower," "inner," "outer," "front," "back," or other directional terms is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of describing this application and simplifying the description, and is not intended to indicate or imply that the device or component referred to must have a specific orientation, be constructed and / or be implemented in a specific orientation, and therefore should not be construed as a limitation of this application.

[0029] In the following description, unless otherwise expressly specified or limited, the terms "installation," "connection," "linking," "fixing," "contact," etc., should be interpreted broadly; for example, they can refer to fixed connections or movable connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in the embodiments of this application according to the specific circumstances.

[0030] It is understood that the flow guiding structure provided in this application is particularly suitable for the DVI water injection system of nuclear reactors, and can also be applied to other reactor-related equipment or systems that have high temperature difference, high flow velocity fluid guiding requirements, and require the flow guiding components to have good structural integrity and thermal stress release capabilities under rapid temperature change conditions, without being limited thereto.

[0031] like Figures 1 to 4 As shown, this application provides a flow guiding structure 1 for coolant flow guiding (e.g., DVI water injection guiding) in a nuclear reactor, including a flow guiding element 10 and its mounting base 20.

[0032] like Figure 1 As shown, the flow guide 10 includes a flow guide portion 110 and mounting portions 120 located on opposite sides of the flow guide portion 110. The flow guide portion 110 is provided with a flow channel 111. One end of the flow channel 111 in the extending direction is provided with a baffle wall 112, and an open end 113 is formed at the opposite end. After the coolant enters the flow channel 111 from the end near the baffle wall 112, it is blocked by the baffle wall 112 and flows out from the open end 113, thereby changing the flow direction of the coolant (e.g., ...). Figure 1 (As indicated by the arrow direction). The mounting part 120 is used to mount the guide member 10 to the mounting base 20.

[0033] The two side walls of the flow guide 110 are spaced apart from the adjacent mounting portion 120, forming stress relief grooves 130. The stress relief grooves 130 open on one side of the flow guide 10 toward the mounting base 20 in the thickness direction (e.g., ...). Figure 3 As shown), and an opening is made through both ends of the flow channel 111 in the extension direction (coolant flow direction) between the flow guide 110 and the mounting part 120, that is, the stress relief groove 130 is a through groove.

[0034] Figure 2 , Figure 4 The shape of the stress relief groove 130 is schematically shown. Generally, the stress relief groove 130 is configured as follows: a slot extending outward from the side of the guide member 10 that is against the mounting base 20, and retaining a solid end wall connecting the guide part 110 and the mounting part 120 on the side away from the mounting base 20, and the slot provides space to allow local elastic bending deformation.

[0035] When the low-temperature coolant (such as DVI injection water at approximately 20°C) rapidly cools the guide section 110, the temperature of the guide section 110 drops rapidly, resulting in significant shrinkage deformation. In contrast, the installation section 120 and its adjacent high-temperature installation base 20 (such as the in-core component basket at approximately 300°C) experience a slower temperature drop and smaller shrinkage, resulting in significant differential thermal deformation. The stress relief groove 130 absorbs this differential thermal deformation to a certain extent through localized elastic deformation, blocking the rigid transmission path of thermal stress. This prevents the difference in thermal deformation from being transmitted to locations such as the installation interface between the guide section 10 and the installation base 20, thus avoiding stress concentration and fatigue damage under repeated thermal expansion and contraction cycles. This improves the reliability of the guide structure 1 under high temperature differential conditions and extends its service life.

[0036] like Figure 2 , Figure 4As shown, in some embodiments, the mounting surface 123 of the mounting portion 120, i.e., the surface that adheres to the mounting base 20, forms a thickness difference with the surface of the guide portion 110 on the side near the mounting base 20. Thus, the surface of the guide portion 110 does not directly contact the mounting base 20, but rather forms a gap between them, which communicates with the stress relief grooves 130 on both sides. This design, on the one hand, reduces the direct solid heat transfer area of ​​the high-temperature mounting base 20 to the guide portion 110, reducing the temperature jump experienced by the guide portion 110 during low-temperature coolant injection; on the other hand, it provides additional deformation space for the guide portion 10 in the thickness direction, making the wall of the guide portion 110 more flexible and further enhancing its thermal stress relief capability.

[0037] like Figure 1 As shown, in some embodiments, at least a portion of the surface of the flow channel 111 is configured as a hydrodynamic surface (such as a smoothly transitioning surface with continuous curvature). For example, the baffle wall 112 has an arched surface that smoothly transitions to the side walls of the flow channel 111, and / or the outlet edge of the opening end 113 is provided with a flared surface, and / or the inner wall of the flow channel 111 is configured as a smoothly transitioning hydrodynamic surface, etc. This helps to reduce the overall flow resistance of the coolant as it flows through the flow channel 111, making the velocity distribution of the coolant flowing downward from the opening end 113 more uniform, and facilitating the smooth and uniform entry of the coolant into the intended area.

[0038] In some embodiments, the guide member 10 is an integral component, with the guide portion 110 and the two side mounting portions 120 integrally machined from the same piece of corrosion-resistant alloy. The corrosion-resistant alloy material is, for example, austenitic stainless steel, nickel-based alloy, or other metallic materials that exhibit good corrosion resistance and high-temperature mechanical properties in the primary coolant environment of a nuclear reactor. The stress relief groove 130 can be formed by removing material from the bottom surface of the guide member 10 through machining methods such as milling. The integral molding structure avoids additional weld seams becoming weak points for stress concentration and corrosion under high-temperature differential conditions.

[0039] like Figure 3 As shown, in some embodiments, each mounting portion 120 has a mounting hole 121 and a positioning hole 122 extending along the thickness direction. For example... Figure 3As shown, each mounting portion 120 has a positioning hole 122 in the middle for fitting with the positioning hole of the mounting base 20. A positioning pin 40 passes through to define the circumferential and axial position of the guide member 10 relative to the mounting base 20. Mounting holes 121 are provided on both sides of the positioning hole 122 for bolts 30 to pass through to achieve a fast connection between the guide member 10 and the mounting base 20. Traditional flow guiding structures typically use welding to rigidly fix the flow guiding component to the mounting base. The weld seam is subject to cyclic thermal stress, which can easily lead to fatigue cracking. However, the flow guiding structure provided in this application uses a detachable connection method combining bolts 30 and positioning pins 40 to replace the traditional welding fixation. The positioning pins 40 pass through the positioning holes 122 to perform the positioning function to ensure the positional accuracy of the flow guiding component 10 relative to the mounting base 20. The bolts 30 pass through the mounting holes 121 to perform the fastening function to provide sufficient connection force. This allows the flow guiding component 10 to generate a small degree of freedom of thermal expansion when the temperature changes, thereby further reducing the additional thermal stress introduced by the installation constraints and facilitating the in-service maintenance and replacement of the flow guiding structure 1.

[0040] In some embodiments, the assembly of the flow guide 10 and the mounting base 20 is configured to withstand a temperature difference of not less than 300°C to ensure structural reliability under high temperature difference conditions within the reactor and to avoid fatigue cracking or connection failure. Specifically, one or more of the following technical means are used: absorbing thermal deformation through the stress relief groove 130; providing small degrees of freedom for thermal expansion through the connection method of bolts 30 and locating pins 40; reducing direct heat conduction through the gap between the bottom surface of the flow guide 110 and the mounting base 20; and selecting suitable corrosion-resistant alloy materials. Through finite element analysis and / or experimental verification, it is determined that the flow guide structure 1 can stably withstand temperature cycle loads of 300°C or even higher during normal service cycles, covering extreme temperature difference loads on the order of nearly 300°C under the emergency water injection conditions of the nuclear reactor DVI, thus better meeting the structural reliability requirements of nuclear facilities.

[0041] In some embodiments, at least a portion of the flow channel 111 has an elliptical or a rectangular shape with rounded corners in a cross-section perpendicular to the extending direction. For example... Figure 4 As shown, the bottom surface of flow channel 111 smoothly transitions to the side walls with rounded corners, forming a rectangular cross-section with rounded corners. Compared to a sharp-cornered rectangular cross-section, an elliptical or rounded-corner rectangular cross-section can reduce local eddies and pressure losses when the coolant flows back and forth within flow channel 111. It can be understood that the cross-section of flow channel 111 can also be selected in other shapes according to the actual flow field optimization requirements, such as a streamlined cross-section optimized by computational fluid dynamics (CFD).

[0042] This application also provides a nuclear reactor cooling system, which includes the flow guiding structure 1 described above. The flow guiding structure 1 is disposed in the coolant flow path of the nuclear reactor, and the flow direction of the coolant flow path is towards the flow channel 111 of the flow guiding member 10, so that it can be injected into the intended area, such as the reactor pressure vessel, after being guided by the flow guiding member 10.

[0043] In some embodiments, coolant flows from the DVI water injection line to the guide member 10, enters the flow channel 111, is blocked by the arched stop wall 112 and changes direction, and flows downward from the opening end 113, flowing towards the core along a predetermined path.

[0044] In some embodiments, the mounting base 20 is configured as the outer side of the in-core component basket, at least one of a distributor and a coolant system conduit, but is not limited thereto.

[0045] This application also provides a method for installing a flow guiding structure, which is used to install the flow guiding structure 1 described above, including: Insert the positioning pin 40 into the positioning hole 122 on the guide 10 and the corresponding pin hole on the mounting base 20 to define the position of the guide 10 relative to the mounting base 20; pass the bolt 30 through the mounting hole 121 and tighten it with the corresponding threaded hole or nut on the mounting base 20 to install the guide 10 on the mounting base 20.

[0046] In summary, the beneficial technical effects of this application include, but are not limited to, at least one of the following: The flow guide structure forms a stress relief groove with openings at both ends and facing the mounting base between the sidewall of the flow guide and the mounting parts on both sides. When the flow guide is subjected to the rapid cooling impact of the low temperature coolant, the differential thermal deformation generated relative to the mounting part can be absorbed by the local elastic deformation of the sidewall of the stress relief groove, blocking the rigid transmission path of thermal stress. This reduces the risk of fatigue cracks in the structure under cyclic thermal loads, improves the reliability of the flow guide structure under high temperature difference conditions, and extends its service life.

[0047] While this application discloses preferred embodiments as described above, it is not intended to limit the scope of this application. Any changes and modifications can be made by those skilled in the art without departing from the spirit and scope of this application. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application, without departing from the content of the technical solution of this application, fall within the protection scope defined by the claims of this application.

Claims

1. A flow guiding structure, characterized in that, Coolant guiding for nuclear reactors, including a guiding element and a mounting base for the guiding element; The flow guide includes a flow guide portion and a mounting portion; the flow guide portion is provided with a flow channel; one end of the flow channel in the extending direction is provided with a stop wall, and the opposite end forms an open end, so that coolant entering the flow channel can be blocked by the stop wall and flow out from the open end; the mounting portion is used to install to the mounting base; The flow guide is located between the mounting portions on both sides. The sidewall of the flow guide is connected to the mounting portion and forms a stress relief groove. The stress relief groove is open at both ends and opens towards the mounting base in the thickness direction of the flow guide.

2. The flow guiding structure as described in claim 1, characterized in that, The mounting portion is provided with a mounting hole and a positioning hole that extend through the thickness direction of the flow guide. The flow guide structure also includes a bolt and a positioning pin. The bolt passes through the mounting hole to enable the flow guide to be detachably connected to the mounting base. The positioning pin passes through the positioning hole to define the position of the flow guide relative to the mounting base.

3. The flow guiding structure as described in claim 1, characterized in that, The assembly of the flow guide and the mounting base is configured to withstand a temperature difference of not less than 300°C.

4. The flow guiding structure as described in claim 1, characterized in that, At least a portion of the flow channel has an elliptical or rectangular cross-section perpendicular to the extension direction.

5. The flow guiding structure as described in claim 1, characterized in that, At least a portion of the surface of the flow channel is configured as a hydrodynamic surface.

6. The flow guiding structure as described in claim 5, characterized in that, The open end has a hydrodynamic surface.

7. The flow guiding structure as described in claim 1, characterized in that, In the thickness direction, there is a height difference between the mounting surface of the mounting part that contacts the mounting base and the surface of the guide part that is close to the mounting base.

8. A nuclear reactor, characterized in that, Includes the flow guiding structure as described in any one of claims 1 to 7; The flow guiding structure is disposed in the coolant flow path of the nuclear reactor, and the flow direction of the coolant flow path is towards the flow channel of the flow guiding component.

9. The nuclear reactor as described in claim 8, characterized in that, The mounting base is at least one of the following: the basket body, the distributor, and the coolant system piping.

10. A method for installing a flow guiding structure, characterized in that, The method for installing the flow guide structure as described in any one of claims 2 to 7 includes: installing the flow guide into the mounting base by means of bolts passing through the mounting holes; and defining the position of the flow guide relative to the mounting base by means of positioning pins passing through the positioning holes.

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