upper tube holder

Abstract

An upper tube support for reducing the wear of a control rod. The upper tube support comprises a frame and a grid; the frame encloses a central passage and is provided with a boss which protrudes inwardly to shield part of the central passage; the grid is located in the central passage, axially opposite to the boss and axially spaced apart, and is provided with an array of water flow holes and an array of control rod insertion holes; wherein the boss is located outside the boundary of the array of control rod insertion holes, the array of water flow holes comprises a first array of water flow holes and a second array of water flow holes, the first array of water flow holes is located inside the boundary of the array of control rod insertion holes, the second array of water flow holes is located outside the boundary of the array of control rod insertion holes, and the flow area of the second array of water flow holes is smaller than that of the first array of water flow holes.

Description

Technical Field

[0001] This invention relates to nuclear engineering technology, and more specifically to an upper tube socket for a nuclear fuel assembly. Background Technology

[0002] The upper control rod holder, located at the very top of the nuclear fuel assembly, serves not only as the upper positioning and load-bearing component but also as a crucial part for the operation and hoisting of the fuel assembly. Based on operational experience from nuclear power plants, excessive wear of the control rods can occur after several cycles. The control rods regulate reactor power and enable shutdown; they function by being inserted into the guide tubes of the fuel assembly. The quality of the control rods is critical to the safety of the nuclear power plant; therefore, the wear of the control rods throughout their lifespan should be limited to acceptable levels. Summary of the Invention

[0003] The purpose of this invention is to provide an upper tube seat for reducing wear on the control rod.

[0004] According to an embodiment of the present invention, the upper tube seat includes a frame and a grid plate; the frame surrounds a central channel and is provided with a boss, the boss protruding inward and partially blocking the central channel; the grid plate is located in the central channel, axially opposite to and axially spaced from the boss, and is provided with a drainage hole array and a control rod insertion hole array; wherein, the boss is located outside the boundary of the control rod insertion hole array, the drainage hole array includes a first drainage hole array and a second drainage hole array, the first drainage hole array is located inside the boundary of the control rod insertion hole array, the second drainage hole array is located outside the boundary of the control rod insertion hole array, and the flow area of ​​the second drainage hole array is smaller than the flow area of ​​the first drainage hole array.

[0005] In one or more embodiments, the first water flow array includes a plurality of first water flow holes, the plurality of first water flow holes including irregularly shaped holes and covering the inner side of the boundary of the control rod socket array, and the second water flow array includes a plurality of second water flow holes, the second water flow holes being circular holes.

[0006] In one or more embodiments, the irregular hole includes a triangular hole and a quadrilateral hole.

[0007] In one or more embodiments, the plurality of second water outlets include a plurality of first circular holes arranged in a single row along the edge of the grid plate.

[0008] In one or more embodiments, the plurality of second drainage holes further includes a plurality of second circular holes located at the corners of the grid plate and inside the plurality of first circular holes.

[0009] In one or more embodiments, the frame is provided with a flow divider groove, which is located axially between the grid plate and the boss, and the flow divider groove extends through the frame.

[0010] In one or more embodiments, the diversion channel is inclined outward along the axial direction and from the grid plate toward the boss.

[0011] The embodiments of the present invention have at least the following beneficial effects:

[0012] The flow area of ​​the second water flow hole array is smaller than that of the first water flow hole array, which reduces the water flow rate of the grid outside the control rod arrangement area and the water flow rate towards the boss, thereby reducing the lateral flow and reducing the vibration wear caused by the impact of the lateral flow on the control rod. Attached Figure Description

[0013] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0014] Figure 1 A top view of a grating board in the prior art;

[0015] Figure 2 This is a perspective view of the upper tube seat and control rod according to an embodiment of the present invention;

[0016] Figure 3 This is a cross-sectional view of the upper tube seat according to an embodiment of the present invention;

[0017] Figure 4 This is a cross-sectional view of the upper tube seat according to an embodiment of the present invention;

[0018] Figure 5 This is a side view of the upper tube seat according to an embodiment of the present invention;

[0019] Figure label:

[0020] 1-Control rod;

[0021] 2-Upper tube seat;

[0022] 3-Grid Board;

[0023] 4-Border;

[0024] 5-Central passage;

[0025] 6-Boss;

[0026] 7-Water flow hole;

[0027] 8-Control rod socket;

[0028] 9 - Lower end face of the boss;

[0029] 10-Boundary of the control stick jack array;

[0030] 11-First flow hole array;

[0031] 12-Second water flow hole array;

[0032] 13-First water outlet;

[0033] 14 - Second water outlet;

[0034] 15-Triangular hole;

[0035] 16- Quadrilateral hole;

[0036] 17 - First round hole;

[0037] 18 - Second round hole;

[0038] 19-Diversion channel;

[0039] 20 - Inner sidewall of the frame;

[0040] 21 - The outer wall of the frame. Detailed Implementation

[0041] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided to explain the invention and not to limit it. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the invention without departing from the scope or spirit thereof. For example, a feature shown or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. Therefore, the invention is intended to cover these modifications and variations that fall within the scope of the appended claims and their equivalents.

[0042] It should be noted that these and other accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the scope of protection of the present invention.

[0043] The terms “first”, “second”, etc., are used interchangeably to distinguish one feature from another and are not intended to indicate that each feature must be located in the position shown in the figure in each embodiment.

[0044] like Figure 2As shown, the nuclear fuel assembly includes control rods 1 and an upper tube seat 2. The upper tube seat 2 includes a frame 4. The frame 4 provides interfaces and mating functions for related components and in-core components. The frame 4 encloses a central channel 5. In a plane perpendicular to the axial direction, the frame 4 may have a rectangular profile, enclosing a central channel 5 with a rectangular profile. "Axial direction" is parallel to the extension direction of the control rods 1, the same applies below. The frame 4 is provided with a boss 6, which provides a mating plane for operating tools and a mounting plane for a compression spring. The boss 6 protrudes inward, partially obscuring the central channel 5. "Inward" refers to the direction from the frame 4 towards the central channel 5, and "outward" refers to the direction from the frame 4 away from the central channel 5, the same applies below. The boss 6 may be provided on all four sides of the frame 4 and located at one axial end of the frame 4. The boss 6 may have an elongated profile. The upper tube seat 2 also includes a grid plate 3. The grid plate 3 is located in the central channel 5. The grid plate 3 may be connected to the frame 4 at its four edges and has a rectangular profile. The grid plate 3 is axially opposite to and axially spaced from the boss 6. Further integration Figure 4 The grid 3 can be located at the other end of the axial direction of the frame 4. Further integration Figure 1 In the prior art, the grid plate 3 has an array of water flow holes 7 consisting of multiple water flow holes 7 and an array of control rod insertion holes 8 consisting of multiple control rod insertion holes 8. The water flow holes 7 penetrate the grid plate 3 to allow water flow through it. The distribution of multiple water flow holes 7 on the grid plate 3 maximizes the total flow area and ensures uniform flow distribution at all locations, thereby preventing excessive lateral flow and preventing fuel rods (not shown in the figure) from being ejected from the upper tube seat 2 through the water flow holes 7 in the event of an accident. "Large lateral flow" refers to water flow perpendicular to the axial direction. The control rod insertion holes 8 penetrate the grid plate 3 to allow control rods 1 to be inserted and pass through it.

[0045] Wear of control rod 1 during service is related to various factors, with lateral flow in the nuclear fuel assembly being a significant one. According to feedback from nuclear power plants, wear of control rod 1 primarily occurs at the upper tube seat 2 of the nuclear fuel assembly. This is because, axially, water flows through the flow holes 7, passes through the grid plate 3, and flows towards the boss 6. The boss 6 partially obstructs the central channel 5, causing the water flow towards the lower axial end face 9 of the boss 6. Figure 4 As shown in the figure, the flow direction changes due to the large flow resistance, forming a transverse flow that impacts the control rod 1, causing vibration and wear of the control rod 1.

[0046] Further reference Figure 3 In an embodiment of the invention, the boss 6 is located outside the boundary 10 of the control rod socket 8 array, and the control rod 1 protrudes from the inner side of the boss 6 into the central channel 5. The boundary 10 of the control rod socket 8 array is defined by the outermost plurality of control rod sockets 8, and the boundary 10 of the control rod socket 8 array encompasses all of the plurality of control rod sockets 8. Figure 3In the diagram, the boundary 10 of the control stick socket 8 array is shown as a circular boundary with dashed lines for simplification, so that the outermost control stick socket 8 portion protrudes outside the boundary 10. It should be understood that this is due to the simplification of the boundary 10 as a circle in the diagram. The boundary 10 of the control stick socket 8 array actually encloses all the multiple control stick sockets 8 and has a roughly circular outline.

[0047] like Figure 3 As shown, the orifice array 7 includes a first orifice array 11 and a second orifice array 12. The first orifice array 11 is located inside the boundary 10 of the control rod socket 8 array, and the first orifice array 11 includes a plurality of first orifices 13, all of which are enveloped by the boundary 10 of the control rod socket 8 array. Figure 3 In the diagram, the boundary 10 of the control rod socket 8 array is shown as a circular boundary with dashed lines for simplification, making the outermost first water flow hole 13 protrude beyond the boundary 10. It should be understood that this is due to the simplification of the boundary 10 as a circle in the diagram; the boundary 10 of the control rod socket 8 array actually encloses all of the multiple first water flow holes 13 and has a roughly circular outline. The second water flow hole array 12 is located outside the boundary 10 of the control rod socket 8 array. The second water flow hole array 12 includes multiple second water flow holes 14, all of which are located outside the boundary 10 of the control rod socket 8 array. The flow area of ​​the second water flow hole array 12 is smaller than the flow area of ​​the first water flow hole array 11, and the total flow area of ​​all the multiple second water flow holes 14 is smaller than the total flow area of ​​all the multiple first water flow holes 13. This reduces the water flow rate of the grid plate 3 outside the control rod 1 arrangement area and reduces the flow to the lower shaft end face 9 of the boss 6. Figure 4 (As shown in the figure) water flow rate, thereby reducing lateral flow and reducing vibration wear caused by the impact of lateral flow on control rod 1.

[0048] like Figure 3 As shown, the plurality of first drainage holes 13 may include irregularly shaped holes. The cross-section of the irregularly shaped holes is not circular. The shape of the irregularly shaped holes can be set according to the shape and size of the boundary 10 of the control rod insertion hole 8 array, as well as the distribution, shape, and size of the control rod insertion holes 8. This facilitates the plurality of first drainage holes 13 filling the inner side of the boundary 10 of the control rod insertion hole 8 array, reducing the plate area between the first drainage holes 13, the control rod insertion holes 8, and the boundary 10 of the control rod insertion hole 8 array, increasing the flow area of ​​the first drainage hole array 11, and making the flow area of ​​the first drainage hole array 11 larger than that of the second drainage hole array 12. The irregularly shaped holes may include triangular holes 15 and quadrilateral holes 16. The triangular hole 15 has three sides and the corners where the sides meet are rounded. The quadrilateral hole 16 has four sides and the corners where the sides meet are rounded. The plurality of first drainage holes 13 may also include circular holes. In the illustrated embodiment, the first drainage hole array 11 has a plurality of circular holes on its outer edge.

[0049] like Figure 3 As shown, the second drainage hole 14 can be a circular hole. A circular hole increases the spacing between adjacent second drainage holes 14, thereby increasing the plate area between multiple second drainage holes 14, reducing the flow area of ​​the second drainage hole array 12, and making the flow area of ​​the second drainage hole array 12 smaller than that of the first drainage hole array 11. In another embodiment, the second drainage hole 14 can include an irregularly shaped hole. By setting the hole area of ​​the irregularly shaped hole, the flow area of ​​the second drainage hole 14 is reduced, thereby reducing the flow area of ​​the second drainage hole array 12.

[0050] like Figure 3 As shown, the second water flow array 12 may include a plurality of first circular holes 17, which are arranged in a single row along the edge of the grid plate 3. The grid plate 3 has a ring of first circular holes 17 on its outermost side to ensure water flow outside the area where the control rod 1 is arranged. This ring of first circular holes 17 may be located on the four sides of the rectangular grid plate 3, extending in a rectangular shape along the four sides of the grid plate 3. Figure 3 As shown, the second water flow hole array 12 may also include a plurality of second circular holes 18, which are located at the corners of the grid plate 3 and inside the plurality of first circular holes 17, to ensure the water flow rate of the grid plate 3 at the corners. The rectangular grid plate 3 may have second circular holes 18 provided at all four corners, and the plurality of second circular holes 18 are arranged in a right-angled zigzag shape at each corner.

[0051] The distribution of the water flow holes 7 on the grid plate 3 ensures that, in the event of an accident, fuel rods (not shown) cannot be ejected from the upper tube seat 2 through the water flow holes 7, and does not affect the conclusions of the existing thermal-hydraulic analysis, namely, that the non-uniformity of water flow will not cause the coolant flow of any fuel rod to fall below the minimum thermal-hydraulic requirement. Based on this, the flow area of ​​the second water flow hole array 12 should be as small as possible to minimize the flow to the lower shaft end face 9 of the boss 6. Figure 4 The water flow rate (shown in the figure) is reduced to minimize lateral flow and thus minimize vibration and wear caused by the impact of lateral flow on control rod 1.

[0052] like Figure 4 and Figure 5 As shown, a diversion channel 19 can be provided on the frame 4. The diversion channel 19 is located axially between the grid plate 3 and the boss 6. The diversion channel 19 penetrates the frame 4, with its inlet located on the inner sidewall 20 of the frame 4 and its outlet located on the outer sidewall 21 of the frame 4. During the process of water flowing from the grid plate 3 to the lower shaft end face 9 of the boss 6, the diversion channel 19 guides the water flow through the frame 4 and out of the upper pipe seat 2, reducing the water flow to the lower shaft end face 9 of the boss 6, thereby reducing the lateral flow and reducing the vibration and wear caused by the lateral flow impacting the control rod 1.

[0053] like Figure 4As shown, along the axial direction and from the grid plate 3 to the boss 6, the diversion channel 19 is inclined outward. This makes the outlet of the diversion channel 19 located on the axial upper side of the inlet of the diversion channel 19, in line with the flow direction of water from the grid plate 3 to the lower shaft end face 9 of the boss 6. This enhances the guiding effect of the diversion channel 19 on the water flow, guides more water flow from the diversion channel 19 out of the upper pipe seat 2, further reduces the lateral flow, and further reduces the vibration wear caused by the impact of the lateral flow on the control rod 1.

[0054] like Figure 4 and Figure 5 As shown, the flow divider 19 may have an integral elongated profile. The flow divider 19 may be distributed on the four sides of the frame 4.

[0055] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention.

Claims

1. An upper tube seat, characterized in that... include: A frame surrounds the central channel and provides a protrusion that extends inward to partially obscure the central channel; as well as A grid plate, located in the central channel, is axially opposite to and spaced from the boss, and is provided with an array of water flow holes and an array of control rod insertion holes; in, The boss is located outside the boundary of the control rod socket array. The drainage hole array includes a first drainage hole array and a second drainage hole array. The first drainage hole array is located inside the boundary of the control rod socket array, and the second drainage hole array is located outside the boundary of the control rod socket array. The flow area of ​​the second drainage hole array is smaller than the flow area of ​​the first drainage hole array.

2. The upper tube seat according to claim 1, characterized in that: The first water flow hole array includes multiple first water flow holes, the multiple first water flow holes including irregularly shaped holes, and are distributed on the inner side of the boundary of the control rod insertion hole array. The second water flow hole array includes multiple second water flow holes, the second water flow holes being round holes.

3. The upper tube seat according to claim 2, characterized in that: The irregular holes include triangular holes and quadrilateral holes.

4. The upper tube seat according to claim 2, characterized in that: The plurality of second water flow holes include a plurality of first circular holes, which are arranged in a single row along the edge of the grid plate.

5. The upper tube seat according to claim 4, characterized in that: The plurality of second water flow holes also include a plurality of second circular holes, which are located at the corners of the grid plate and inside the plurality of first circular holes.

6. The upper tube seat according to claim 1, characterized in that: The frame is provided with a flow divider groove, which is located axially between the grid plate and the boss, and the flow divider groove passes through the frame.

7. The upper tube seat according to claim 6, characterized in that: Along the axial direction and from the grid plate toward the boss, the diversion channel is inclined outward.

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