A fuel assembly with upper end limit

Abstract

The present invention relates to the technical field of nuclear fuel assemblies, and specifically discloses a fuel assembly with upper end limit, wherein a limit device is provided between the upper end of a fuel rod and the bottom of an upper tube seat, and is used to limit the upper end of the fuel rod in radial direction. The fuel assembly of the present invention can limit the fuel rod by using the radial positioning provided by the limit device provided between the upper end of the fuel rod and the bottom of the upper tube seat, and when the assembly is subjected to vibration or impact, the impact on the positioning grid is reduced, and damage caused by excessive bending of the fuel rod is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear fuel assemblies, and in particular relates to a fuel assembly with an upper end limit. Background Art

[0002] During the operation of nuclear power plant reactors, the performance of nuclear fuel is an important factor affecting the safety and economy of the reactor. Therefore, the international community has always placed great emphasis on the research of fuel elements. By optimizing the design of fuel elements, using advanced structural materials, improving the manufacturing process of elements, and other methods, the various properties of nuclear fuel elements are continuously improved, which promotes the development of nuclear power in a safer and more economical direction.

[0003] Safety and economy are the foundation of nuclear power development, and almost all nuclear power technology development is aimed at increasing nuclear power safety and economy. Fuel elements are the core components of nuclear power plant reactors, and their performance is one of the most important factors affecting nuclear power safety and economy. Therefore, the international community has always placed a very prominent position in the research of fuel elements. By optimizing fuel element design, using advanced structural materials, improving element manufacturing processes and other methods, the various properties of nuclear fuel elements are continuously improved, which promotes the development of nuclear power in a safer and more economical direction.

[0004] Most existing fuel assemblies are slender rod bundle structures. Generally, fuel assemblies are composed of upper and lower tube seats, fuel rods, positioning grids, guide tubes, instrument tubes and connecting screws. The upper and lower tube seats are connected by guide tubes, and multiple layers of positioning grids are welded on the outside of the guide tubes to fix the fuel rods. The fuel rods are generally suspended between the upper and lower tube seats. When the fuel assembly is installed in the reactor core, the upper and lower tube seats are generally fixed by the upper and lower grid plates of the core, and the fuel rods are restrained by guide tubes and positioning grids to prevent the fuel rods from moving in the core and then being damaged. In particular, in accidents such as earthquakes and LOCA, the fuel rods need to be restrained. However, the fuel rods are relatively slender and have a relatively low overall rigidity. In order to enable the fuel assembly to maintain its integrity in accidents such as earthquakes and LOCA, very high requirements are placed on the structural design of the fuel assembly.

[0005] Therefore, there is an urgent need to design a fuel assembly with higher vibration and impact resistance. Summary of the invention

[0006] The object of the present invention is to provide a fuel assembly with an upper end limit so as to enhance the anti-vibration and anti-impact capabilities of the assembly.

[0007] The technical solution of the present invention is as follows:

[0008] A fuel assembly with upper end limit, comprising an upper tube seat, a guide tube, a positioning grid, a fuel rod, a lower tube seat and an instrument tube;

[0009] The fuel rods, guide tubes and instrument tubes are inserted into the positioning grid;

[0010] There are multiple spacer grids, which are arranged in sequence along the axial direction of the fuel rod;

[0011] The upper ends of the guide tube and the instrument tube are fixedly connected to the upper tube seat, and the lower ends are fixedly connected to the lower tube seat;

[0012] A limiting device is provided between the upper end of the fuel rod and the bottom of the upper tube seat, for limiting the upper end of the fuel rod in radial direction;

[0013] The lower end of the fuel rod is inserted into the lower tube seat;

[0014] The upper tube seat is provided with an upper tube seat fuel rod hole, an upper tube seat water flow hole and an upper tube seat guide tube hole;

[0015] The lower tube seat is provided with a lower tube seat fuel rod hole, a lower tube seat water flow hole and a lower tube seat guide tube hole.

[0016] The fuel rod is a lower-end fixed fuel rod;

[0017] The limiting device is an upper extension section of the lower fixed fuel rod, and the upper extension section of the lower fixed fuel rod is arranged at the top end of the lower fixed fuel rod;

[0018] The upper end extension section of the lower end fixed fuel rod extends into the fuel rod hole of the upper tube seat, and the lower end of the lower end fixed fuel rod is fixed to the lower tube seat.

[0019] The diameter of the upper extension section of the lower fixed fuel rod is smaller than the diameter of the lower fixed fuel rod;

[0020] The height of the upper end extension section of the lower end fixed fuel rod extending into the fuel rod hole A of the upper tube seat is 3 to 10 mm.

[0021] The limiting device also includes an upper limiting plate installed below the upper tube seat;

[0022] The upper end limit plate is provided with a limit plate fuel rod hole, a limit plate water flow hole, a limit plate guide tube hole and a limit plate screw hole;

[0023] After the upper end extension section of the lower end fixed fuel rod passes through the fuel rod hole of the limiting plate, it is inserted into the fuel rod hole of the upper tube seat for positioning. The upper end extension section of the lower end fixed fuel rod can be telescopically slid in the fuel rod hole of the upper tube seat without affecting the function of the upper tube seat.

[0024] The upper end limit plate is connected to the upper tube seat by passing through the limit plate screw hole and the limit plate connecting sleeve in sequence and then being screwed into the limit plate connecting screw on the upper tube seat bottom plate.

[0025] The lower end of the lower end fixed fuel rod is fixed to the lower tube seat by a buckle;

[0026] The buckle is a raised hook structure processed on the outer side wall of the lower end of the lower fixed fuel rod, which can be firmly connected with the fuel rod hole of the lower tube seat.

[0027] The fuel rod is a non-fixed fuel rod, and the limiting device is a compression spring;

[0028] The lower end of the non-fixed fuel rod is inserted into the fuel rod hole of the lower tube seat, and the upper end of the non-fixed fuel rod passes through the compression spring and extends into the fuel rod hole of the upper tube seat. The compression spring cooperates with the upper tube seat to compress the non-fixed fuel rod so that the lower end of the non-fixed fuel rod will not pop out of the lower tube seat.

[0029] The limiting device also includes an upper limiting plate installed below the upper tube seat;

[0030] The upper end limit plate is provided with a limit plate fuel rod hole, a limit plate water flow hole, a limit plate guide tube hole and a limit plate screw hole;

[0031] The lower end of the non-fixed fuel rod is inserted into the fuel rod hole of the lower tube seat, and the upper end of the non-fixed fuel rod passes through the compression spring and the fuel rod hole of the limit plate in sequence, and is positioned in the fuel rod hole of the upper tube seat. The non-fixed fuel rod is compressed by the compression spring and the upper limit plate, so that the lower end of the non-fixed fuel rod will not pop out of the lower tube seat.

[0032] The upper end limit plate is connected to the upper tube seat by passing through the limit plate screw hole and the limit plate connecting sleeve in sequence and then being screwed into the limit plate connecting screw on the upper tube seat bottom plate.

[0033] The fuel assembly is suitable for pressurized water reactors, fast reactors, low-temperature heating reactors, space reactors, boiling water reactors, micro reactors, zero-power reactors, heavy water reactors, power reactors or marine power reactors.

[0034] The remarkable effects of the present invention are:

[0035] (1) The fuel assembly of the present invention is applicable to common rod-shaped fuel elements, and is also applicable to fuel elements with a larger outer diameter, such as annular fuel elements, and provides lateral positioning for the fuel rods to increase the strength of the fuel assembly without increasing the flow resistance of the fuel assembly.

[0036] (2) The fuel assembly of the present invention can limit the fuel rods by using the radial positioning provided by the limiting device arranged between the upper end of the fuel rod and the bottom of the upper tube seat. When the assembly is subjected to vibration or impact, the impact on the positioning grid is reduced to avoid damage caused by excessive bending of the fuel rods.

[0037] (3) The upper tube seat of the fuel assembly of the present invention can limit the fuel rods in the radial direction, but not in the axial direction. This can ensure that in the event of an earthquake or LOCA accident, the load on the fuel rods can ultimately act on the upper and lower tube seats, while reducing the load on the positioning grid and the guide tubes. Furthermore, if the safety margin allows, the design of the positioning grid and the guide tubes can be simplified, thereby reducing costs.

[0038] (4) The fuel assembly of the present invention uses a plurality of axially arranged positioning grids to clamp the fuel elements, fix the fuel elements, and maintain the spacing between the fuel elements, so that the fuel elements are located in a fixed position in the core of a pressurized water reactor nuclear power plant, and the fuel rods can be laterally supported and positioned at both ends, thereby increasing the overall strength.

[0039] (5) The fuel assembly of the present invention adopts a structure in which the lower end of the fuel rod is fixed or the upper end is fixed by a compression spring, thereby avoiding the defect that the clamping force of the positioning grid is reduced when the suspended fuel element is irradiated for a long time, resulting in the fall of the fuel element. At the same time, the compression spring does not affect the elongation of the fuel rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the upper tube seat;

[0041] Figure 2 It is a schematic diagram of the lower pipe seat;

[0042] Figure 3 It is a schematic diagram of the upper end limit fuel assembly;

[0043] Figure 4 This is a schematic diagram of the upper end limit fuel rod;

[0044] Figure 5 This is a schematic diagram of the upper limit installation of the fuel rod;

[0045] Figure 6 This is a schematic diagram of the fuel rod being fixed in the lower tube seat;

[0046] Figure 7 It is a schematic diagram of an upper end limited fuel assembly with a fuel rod compression spring;

[0047] Figure 8 It is a schematic diagram of a fuel rod with the upper end limited and the lower end not fixed to the lower tube seat;

[0048] Fig. 9 A is a schematic diagram of the upper end limit installation of the fuel rod with the fuel rod compression spring;

[0049] Fig.10 This is a schematic diagram of the fuel rod compression spring;

[0050] Fig.11 is a schematic diagram of an upper end limiting fuel assembly with an upper end limiting plate;

[0051] Fig.12 Schematic diagram of an upper tube seat with an upper end limit plate;

[0052] Fig.13 Schematic diagram of the upper limit plate;

[0053] Fig.14 This is a schematic diagram of the upper limit installation of the fuel rod;

[0054] Fig.15 A schematic diagram of an upper end limiting fuel assembly with an upper end limiting plate and a fuel rod holding spring;

[0055] Fig.16 Schematic diagram B of the upper limit installation of the fuel rod with the fuel rod compression spring.

[0056] In the figure: 1. Upper tube seat; 2. Guide tube; 3. Positioning grid; 4. Lower end fixed fuel rod; 5. Lower tube seat; 6. Upper end extension of lower end fixed fuel rod; 7. Fuel rod hole A in upper tube seat; 8. Buckle; 9. Compression spring; 10. Upper end of non-fixed fuel rod; 11. Fuel rod hole B in upper tube seat; 12. Instrument tube; 13. Upper end limit plate; 14. Limit plate connecting sleeve; 15. Limit plate connecting screw; 16. Fuel rod hole in limit plate; 17 . Limit plate water flow hole; 18. Limit plate guide tube hole; 19. Limit plate screw hole; 20. Upper tube seat fuel rod hole C; 21. Upper tube seat fuel rod hole D; 22. Upper tube seat fuel rod hole; 23. Upper tube seat water flow hole; 24. Upper tube seat guide tube hole; 25. Lower end of lower fixed fuel rod; 26. Lower tube seat fuel rod hole; 27. Lower tube seat water flow hole; 28. Lower tube seat guide tube hole; 29. ​​Lower end of non-fixed fuel rod; 30. Non-fixed fuel rod. DETAILED DESCRIPTION

[0057] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] A fuel assembly with an upper end limit comprises an upper tube seat 1, a guide tube 2, a positioning grid 3, a fuel rod, a lower tube seat 5 and an instrument tube 12.

[0059] The fuel rods, guide tubes 2 and instrument tubes 12 are inserted into the spacer grids 3. There are multiple spacer grids 3, which are arranged in sequence along the axial direction of the fuel rods.

[0060] The upper ends of the guide tube 2 and the instrument tube 12 are fixedly connected to the upper tube seat 1 , and the lower ends are fixedly connected to the lower tube seat 5 .

[0061] A limiting device is provided between the upper end of the fuel rod and the bottom plate of the upper tube seat 1, for limiting the upper end of the fuel rod in radial direction.

[0062] The lower end of the fuel rod is inserted into the lower tube seat 5.

[0063] like Figure 1 As shown, the upper tube seat 1 is provided with an upper tube seat fuel rod hole 22 , an upper tube seat water flow hole 23 and an upper tube seat guide tube hole 24 .

[0064] like Figure 2 As shown, the lower tube seat 5 is provided with a lower tube seat fuel rod hole 26 , a lower tube seat water flow hole 27 and a lower tube seat guide tube hole 28 .

[0065] The arrangement of the upper tube seat fuel rod hole 22, the upper tube seat guide tube hole 24, the lower tube seat fuel rod hole 26 and the lower tube seat guide tube hole 28 is the same as the arrangement of the fuel rods and guide tubes in the fuel assembly.

[0066] Example 1

[0067] like Figure 3 The fuel assembly with upper end limit shown in the figure, wherein the fuel rod is a lower end fixed fuel rod 4, and the limiting device is an upper end extension section 6 of the lower end fixed fuel rod, as shown in the figure. Figure 4 The upper extension section 6 of the lower fixed fuel rod is arranged at the top of the lower fixed fuel rod 4 , and its diameter is smaller than that of the lower fixed fuel rod 4 .

[0068] like Figures 5-6 As shown, the upper extension section 6 of the lower fixed fuel rod extends into the upper tube seat fuel rod hole A7 by 3 to 10 mm, and the lower end 25 of the lower fixed fuel rod is fixed to the lower tube seat 5 by a buckle 8. The buckle 8 is a raised barb structure processed on the outer side wall of the lower end 25 of the lower fixed fuel rod, which can be firmly connected to the lower tube seat fuel rod hole 26.

[0069] Example 2

[0070] like Figures 7-8 The upper end limiting fuel assembly shown in the figure has a fuel rod which is a non-fixed fuel rod 30 and a limiting device which is a compression spring 9 .

[0071] like Figures 9-10 As shown, the lower end 29 of the non-fixed fuel rod is inserted into the fuel rod hole 26 of the lower tube seat, and the upper end 10 of the non-fixed fuel rod passes through the clamping spring 9 and extends into the fuel rod hole B11 of the upper tube seat. The non-fixed fuel rod 30 is clamped by the clamping spring 9 and the upper tube seat 1, so that the lower end 29 of the non-fixed fuel rod will not pop out of the lower tube seat 5.

[0072] Example 3

[0073] like Figures 11 to 14The upper end limiting fuel assembly shown in the figure has a fuel rod which is a lower end fixed fuel rod 4. The limiting device is an upper end limiting plate 13 installed below the upper tube seat 1, and an upper end extension section 6 of the lower end fixed fuel rod is provided.

[0074] The upper end limiting plate 13 is provided with a limiting plate fuel rod hole 16 , a limiting plate water flow hole 17 , a limiting plate guide tube hole 18 and a limiting plate screw hole 19 .

[0075] The upper stop plate 13 is connected to the upper tube seat 1 by passing through the stop plate screw hole 19 and the stop plate connecting sleeve 14 in sequence and then screwed into the stop plate connecting screw 15 on the bottom plate of the upper tube seat 1. The upper stop plate 13 can also be integrally formed with the upper tube seat 1.

[0076] After the upper extension section 6 of the lower fixed fuel rod passes through the fuel rod hole 16 of the stop plate, it is inserted into the fuel rod hole C20 of the upper tube seat for positioning. The upper extension section 6 of the lower fixed fuel rod can be telescopically slid in the fuel rod hole C20 of the upper tube seat without affecting the function of the upper tube seat 1. The lower end 25 of the lower fixed fuel rod is fixed to the lower tube seat 5 by the buckle 8. The buckle 8 is a raised barb structure processed on the outer side wall of the lower end 25 of the lower fixed fuel rod, which can be firmly connected to the fuel rod hole 26 of the lower tube seat.

[0077] Example 4

[0078] like Fig.15 The upper end limiting fuel assembly shown in the figure has a non-fixed fuel rod 30, and the limiting device is an upper end limiting plate 13 installed below the upper tube seat 1, and a compression spring 9 is provided at the same time.

[0079] The upper end limiting plate 13 is provided with a limiting plate fuel rod hole 16 , a limiting plate water flow hole 17 , a limiting plate guide tube hole 18 and a limiting plate screw hole 19 .

[0080] The upper stop plate 13 is connected to the upper tube seat 1 by passing through the stop plate screw hole 19 and the stop plate connecting sleeve 14 in sequence and then screwed into the stop plate connecting screw 15 on the bottom plate of the upper tube seat 1. The upper stop plate 13 can also be integrally formed with the upper tube seat 1.

[0081] like Fig.16 As shown, the lower end 29 of the non-fixed fuel rod is inserted into the lower tube seat fuel rod hole 26, and the upper end 10 of the non-fixed fuel rod passes through the clamping spring 9 and the limiting plate fuel rod hole 16 in sequence, and is positioned in the upper tube seat fuel rod hole D21. The non-fixed fuel rod 30 is clamped by the clamping spring 9 and the upper limiting plate 13, so that the lower end 29 of the non-fixed fuel rod will not pop out of the lower tube seat 5.

Claims

1. A fuel assembly with upper end limit, characterized in that: It comprises an upper tube seat (1), a guide tube (2), a positioning grid (3), a fuel rod, a lower tube seat (5) and an instrument tube (12); The fuel rods, guide tubes (2) and instrument tubes (12) are inserted into the positioning grid (3); There are a plurality of the spacer grids (3), which are arranged in sequence along the axial direction of the fuel rods; The upper ends of the guide tube (2) and the instrument tube (12) are fixedly connected to the upper tube seat (1), and the lower ends are fixedly connected to the lower tube seat (5); A limiting device is provided between the upper end of the fuel rod and the bottom of the upper tube seat (1), for limiting the upper end of the fuel rod in radial direction; The lower end of the fuel rod is inserted into the lower tube seat (5); The upper tube seat (1) is provided with an upper tube seat fuel rod hole, an upper tube seat water flow hole and an upper tube seat guide tube hole; The lower tube seat (5) is provided with a lower tube seat fuel rod hole, a lower tube seat water flow hole and a lower tube seat guide tube hole; The fuel rod is a lower-end fixed fuel rod (4); the limiting device is an upper extension section (6) of the lower-end fixed fuel rod, and the upper extension section (6) of the lower-end fixed fuel rod is arranged at the top of the lower-end fixed fuel rod (4); the upper extension section (6) of the lower-end fixed fuel rod extends into the fuel rod hole of the upper tube seat, and the lower end (25) of the lower-end fixed fuel rod is fixed to the lower tube seat (5); The limiting device also includes an upper limiting plate (13) installed below the upper tube seat (1); The upper end limiting plate (13) is provided with a limiting plate fuel rod hole (16), a limiting plate water flow hole (17), a limiting plate guide tube hole (18) and a limiting plate screw hole (19); After the upper extension section (6) of the lower fixed fuel rod passes through the fuel rod hole (16) of the limiting plate, it is inserted into the fuel rod hole of the upper tube seat for positioning; the upper extension section (6) of the lower fixed fuel rod can be telescopically slidable in the fuel rod hole of the upper tube seat without affecting the function of the upper tube seat (1); The upper end limit plate (13) is connected to the upper tube seat (1) by passing through the limit plate screw hole (19) and the limit plate connecting sleeve (14) in sequence and then screwed into the limit plate connecting screw (15) on the bottom plate of the upper tube seat (1).

2. A fuel assembly with an upper end limit as claimed in claim 1, characterized in that: The lower end (25) of the lower end fixed fuel rod is fixed to the lower tube seat (5) via a buckle (8); The buckle (8) is a raised hook structure processed on the outer side wall of the lower end (25) of the lower fixed fuel rod, and can be firmly connected with the fuel rod hole of the lower tube seat.

3. A fuel assembly with an upper end limit as claimed in claim 1 or 2, characterized in that: The fuel assembly is suitable for pressurized water reactors, fast reactors, low-temperature heating reactors, space reactors, boiling water reactors, micro reactors, zero-power reactors, heavy water reactors, power reactors or marine power reactors.

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