Nuclear fuel assembly and its upper nozzle

Abstract

A nuclear fuel assembly and its upper nozzle for reducing the wear of control rods. The upper nozzle 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 has an axial spacing, and is provided with a flow hole and a control rod insertion hole; wherein an inner side wall of the boss is provided with a flow guide groove which is recessed from the inner side wall of the boss to the outside and penetrates the boss along the axial direction, the flow guide groove is located outside the control rod insertion hole, the flow guide groove is configured to be opposite to the side wall of the control rod with a spacing, the flow guide groove comprises a connected inlet section and an outlet section, along the axial direction, the inlet section is configured to be closer to the side wall of the control rod, and the outlet section is configured to be farther away from the side wall of the control rod.

Description

Technical Field

[0001] This invention relates to nuclear engineering technology, specifically to a nuclear fuel assembly and its upper tube socket. 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 a nuclear fuel assembly and its upper tube seat for reducing the wear of control rods.

[0004] In a first aspect, the present invention provides an upper tube seat. 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 water flow hole and a control rod insertion hole; wherein, a guide groove is provided on the inner sidewall of the boss, the guide groove is recessed from the inner sidewall of the boss outward and extends through the boss axially, the guide groove is located outside the control rod insertion hole, the guide groove is configured to be opposite to and spaced from the sidewall of the control rod, the guide groove includes a communicating inlet section and an outlet section, along the axial direction, the inlet section is configured to decrease in distance from the sidewall of the control rod, and the outlet section is configured to increase in distance from the sidewall of the control rod.

[0005] In one or more embodiments, the inlet segment is connected to the axial end face of the boss by a first chamfer.

[0006] In one or more embodiments, the entrance segment has the same inclination angle as the first chamfer and is integrally connected to the wall surface.

[0007] In one or more embodiments, the outlet section is connected to the axial end face of the boss by a second chamfer.

[0008] In one or more embodiments, the guide groove is configured to have a uniformly consistent width with the sidewall of the control rod in a plane perpendicular to the axial direction.

[0009] In one or more embodiments, the guide groove has an arcuate profile in a plane perpendicular to the axial direction.

[0010] In one or more embodiments, the boss is provided with a flow divider groove, which is located inside the boss and extends through the boss axially.

[0011] Secondly, the present invention provides a nuclear fuel assembly. According to an embodiment of the present invention, the nuclear fuel assembly includes a control rod and the aforementioned upper tube seat; wherein the control rod is inserted into the control rod insertion hole, the flow guide groove is opposite to and spaced from the sidewall of the control rod, and along the axial direction, the distance between the inlet section and the sidewall of the control rod decreases, and the distance between the outlet section and the sidewall of the control rod increases.

[0012] In one or more embodiments, the guide groove and the sidewall of the control rod have a uniformly consistent width in a plane perpendicular to the axial direction.

[0013] In one or more embodiments, the control rod has a circular profile in a plane perpendicular to the axial direction, and the guide groove has an arcuate profile.

[0014] The embodiments of the present invention have at least the following beneficial effects:

[0015] The inlet and outlet sections enhance the axial guiding effect of the flow channel on the water flow, guiding more water to flow axially from the gap between the flow channel and the control rod, reducing the flow resistance of the boss on the water flow, reducing the lateral flow, and reducing the vibration wear caused by the impact of the lateral flow on the control rod. Attached Figure Description

[0016] 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:

[0017] Figure 1 An oblique view of the upper tube seat and control rod;

[0018] Figure 2 Top view of the upper tube seat and control rod;

[0019] Figure 3 This is a sectional view of the upper tube seat and control rod;

[0020] Figure 4 This is a perspective view of the border;

[0021] Figure 5 This is a sectional view of the upper tube seat;

[0022] Figure label:

[0023] 1-Control rod;

[0024] 2-Upper tube seat;

[0025] 3-Grid Board;

[0026] 4-Border;

[0027] 5-Central passage;

[0028] 6-Boss;

[0029] 7-Water flow hole;

[0030] 8-Control rod socket;

[0031] 9 - Lower end face of the boss;

[0032] 10 - The inner wall of the boss;

[0033] 11-Guide channel;

[0034] 12 - Upper shaft end face of the boss;

[0035] 13-entrance section;

[0036] 14-Exit section;

[0037] 15 - First chamfer;

[0038] 16 - Second chamfer;

[0039] 17-Diversion channel. Detailed Implementation

[0040] 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.

[0041] 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.

[0042] 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.

[0043] like Figures 1 to 3As 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 5 The grid plate 3 can be located at the other end of the axial direction of the frame 4. The grid plate 3 has multiple water flow holes 7 and 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, thus preventing excessive lateral flow and preventing the fuel rod (not shown) 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 the control rod 1 to be inserted and pass through it. The water flow holes 7 and control rod insertion holes 8 of the grid plate 3 are located at... Figure 2 The text is omitted.

[0044] Wear of control rod 1 during service is related to a variety of factors, with the lateral flow of nuclear fuel assemblies being one of the most significant. According to feedback from nuclear power plants, wear of control rod 1 mostly 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 blocks the central channel 5, and the water flows towards the lower axial end face 9 of the boss 6. Due to the greater flow resistance, the flow direction changes, forming a lateral flow that impacts the control rod 1, causing vibration wear of the control rod 1.

[0045] like Figures 1 to 4As shown, a flow guide groove 11 is provided on the inner sidewall 10 of the boss 6. The flow guide groove 11 is recessed outward from the inner sidewall 10 of the boss 6. The flow guide groove 11 extends axially and penetrates the boss 6. The inlet of the flow guide groove 11 is located at the lower axial end face 9 of the boss 6, and the outlet of the flow guide groove 11 is located at the upper axial end face 12 of the boss 6. The flow guide groove 11 is located outside the outermost control rod socket 8 in the array of control rod sockets 8, so that the flow guide groove 11 is opposite to and spaced from the sidewall of the outermost control rod 1 in the array of control rods 1. The flow guide groove 11 guides the water flow axially from the gap between the flow guide groove 11 and the control rod 1, reducing the flow resistance of the boss 6 to the water flow, reducing the lateral flow, and thus reducing the vibration wear caused by the impact of the lateral flow on the control rod 1. Figure 3 As shown, the guide channel 11 includes an inlet section 13 and an outlet section 14. The inlet section 13 provides the inlet of the guide channel 11 and is located in the lower axial part of the guide channel 11. The outlet section 14 provides the outlet of the guide channel 11 and is located in the upper axial part of the guide channel 11. The inlet section 13 and the outlet section 14 are axially connected, and the boundary between the inlet section 13 and the outlet section 14 is at... Figure 3 The diagram is shown in dashed lines. Along the axial direction and in the flow direction, the distance between the inlet section 13 and the sidewall of the control rod 1 decreases, and the interval between them decreases, forming a converging tube. The inlet section 13 can be considered as the wall of the converging tube. Along the axial direction and in the flow direction, the distance between the outlet section 14 and the sidewall of the control rod 1 increases, and the interval between them increases, forming a diverging tube. The outlet section 14 can be considered as the wall of the diverging tube. The inlet section 13 and outlet section 14 cause the guide channel 11 and the sidewall of the control rod 1 to form a Venturi tube, enhancing the axial guiding effect of the guide channel 11 on the water flow. This guides more water to flow axially through the gap between the guide channel 11 and the control rod 1, further reducing the flow resistance of the boss 6, further reducing lateral flow, and further reducing vibration wear caused by the impact of lateral flow on the control rod 1.

[0046] like Figure 3 As shown, the axial height of the inlet section 13 can be much smaller than the axial height of the outlet section 14, and the axial height of the outlet section 14 is more than five times the axial height of the inlet section 13.

[0047] like Figure 3 As shown, the inlet section 13 and the lower shaft end face 9 of the boss 6 can be connected by a first chamfer 15. The first chamfer 15 is located at the edge where the lower shaft end face 9 of the boss 6 connects with the inlet section 13, so that the guide channel 11 transitions smoothly at the inlet, guiding the water flow to flow more smoothly into the guide channel 11, reducing turbulence, thereby reducing the vibration and wear caused by the impact of turbulence on the control rod 1.

[0048] like Figure 3As shown, the inlet section 13 can be an inclined wall and can have the same inclination angle as the first chamfer 15. The inlet section 13 and the first chamfer 15 are connected as an integral wall to avoid the edge at the connection between the inlet section 13 and the first chamfer 15, guide the water flow to enter the guide channel 11 more smoothly, reduce turbulence, and thus reduce the vibration wear caused by the impact of turbulence on the control rod 1.

[0049] like Figure 3 As shown, the outlet section 14 and the upper shaft end face 12 of the boss 6 can be connected by a second chamfer 16. The second chamfer 16 is located at the edge where the upper shaft end face 12 of the boss 6 connects with the outlet section 14, so that the guide channel 11 smoothly transitions at the outlet, guiding the water flow to flow out of the guide channel 11 more smoothly, reducing turbulence, thereby reducing the vibration and wear caused by the impact of turbulence on the control rod 1.

[0050] like Figure 2 As shown, in a plane perpendicular to the axial direction, the guide groove 11 and the sidewall of the control rod 1 can have a uniformly spaced interval, which has the same width at all positions in the plane perpendicular to the axial direction. In the plane perpendicular to the axial direction, the outline of the guide groove 11 is the same as the outline shape of the control rod 1, thereby ensuring that the interval between the guide groove 11 and the sidewall of the control rod 1 has a uniformly spaced width. In the plane perpendicular to the axial direction, the control rod 1 can have a circular outline, a cylindrical body, and cylindrical sidewalls. In the plane perpendicular to the axial direction, the guide groove 11 has an arc-shaped outline, and in the plane perpendicular to the axial direction, the guide groove 11 and the sidewall of the control rod 1 have an annular gap, which has the same width at all positions along the arc length direction.

[0051] like Figure 1 and Figure 4 As shown, the aforementioned guide grooves 11 can be distributed on the four protrusions 6 on the four sides of the frame 4, respectively corresponding to the control rods 1 on the four sides of the control rod 1 array.

[0052] like Figure 4 and Figure 5 As shown, a diversion channel 17 can be provided on the boss 6. The diversion channel 17 is located inside the boss 6, extends axially and penetrates the boss 6, with the inlet of the diversion channel 17 located at the lower axial end face 9 of the boss 6 and the outlet of the diversion channel 17 located at the upper axial end face 12 of the boss 6. The diversion channel 17 guides the water flow axially through the boss 6, reducing the flow resistance of the boss 6 to the water flow and reducing lateral flow, thereby reducing vibration wear caused by the impact of lateral flow on the control rod 1. In the plane perpendicular to the axial direction, the diversion channel 17 can have an integral elongated profile. In the plane perpendicular to the axial direction, the diversion channel 17 can also include multiple independent, non-communicating circular profile holes. The diversion channels 17 can be distributed on the four bosses 6 on the four sides of the frame 4.

[0053] 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 protrudes 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 water flow holes and control rod insertion holes; in, The inner sidewall of the boss is provided with a flow guide groove. The flow guide groove is recessed from the inner sidewall of the boss outward and passes through the boss axially. The flow guide groove is located outside the control rod insertion hole. The flow guide groove is configured to be opposite to the sidewall of the control rod and have a gap. The flow guide groove includes a connected inlet section and an outlet section. Along the axial direction, the inlet section is configured to decrease in distance from the sidewall of the control rod, and the outlet section is configured to increase in distance from the sidewall of the control rod.

2. The upper tube seat according to claim 1, characterized in that: The inlet section is connected to the shaft end face of the boss by a first chamfer.

3. The upper tube seat according to claim 2, characterized in that: The entrance section has the same inclination angle as the first chamfer and is connected to form a single wall surface.

4. The upper tube seat according to claim 2, characterized in that: The outlet section is connected to the shaft end face of the boss by a second chamfer.

5. The upper tube seat according to claim 1, characterized in that: In a plane perpendicular to the axial direction, the guide groove is configured to have a uniformly consistent width of spacing with the sidewall of the control rod.

6. The upper tube seat according to claim 5, characterized in that: In a plane perpendicular to the axial direction, the guide channel has an arc-shaped profile.

7. The upper tube seat according to claim 1, characterized in that: The boss is provided with a flow divider groove, which is located inside the boss and extends through the boss axially.

8. A nuclear fuel assembly, characterized in that... include: Control stick; as well as The upper tube seat as described in any one of claims 1 to 7; in, The control rod is inserted into the control rod socket. The guide groove is opposite to and spaced from the side wall of the control rod. Along the axial direction, the distance between the inlet section and the side wall of the control rod decreases, and the distance between the outlet section and the side wall of the control rod increases.

9. The nuclear fuel assembly according to claim 8, characterized in that: In a plane perpendicular to the axial direction, the guide groove and the sidewall of the control rod have a uniformly consistent spacing.

10. The nuclear fuel assembly according to claim 9, characterized in that: In a plane perpendicular to the axial direction, the control rod has a circular profile, and the guide groove has an arc-shaped profile.

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