A reaming device for a nuclear fuel assembly skeleton

Abstract

This invention relates to the field of nuclear fuel assembly manufacturing technology, specifically to a hole-expanding device for a nuclear fuel assembly skeleton, comprising a mandrel, an expansion roller, and an expansion roller holder. The expansion roller holder is cylindrical, and the mandrel passes through it. Multiple circumferentially distributed and penetrating insertion slots are formed on the circumferential sidewalls of the expansion roller holder, each slot housing an expansion roller. A sliding fit clearance exists between the expansion roller and the insertion slot. The mandrel has multi-tapered expansion sections, which can be driven to move axially within the expansion roller holder. The multi-tapered expansion sections, under the movement of the mandrel, can drive the expansion roller to expand out of the insertion slot for hole expansion. This invention can precisely control the expansion amount during repair expansion of dimensionally out-of-tolerance expansion joints, reducing the risk of damage to the sleeve and grid substrate, and is suitable for repair operations within the confined space of a nuclear fuel assembly skeleton.

Description

Technical Field

[0001] This invention relates to the field of nuclear fuel assembly manufacturing technology, and more specifically to a hole-expanding device for a nuclear fuel assembly skeleton. Background Technology

[0002] The nuclear fuel assembly skeleton is the core load-bearing structure of the reactor fuel assembly, formed by connecting components such as grids, guide tubes, and positioning tubes through an expansion joint process. The expansion joint between the guide tubes and the grid sleeves must ensure sufficient connection strength, positioning accuracy, and good dimensional consistency, making it a critical structure for ensuring the stable operation of the nuclear fuel assembly within the reactor. During the skeleton expansion joint production process, factors such as fluctuations in expansion parameters, tooling positioning deviations, and uneven performance of the tubing materials can lead to defects in some expansion joints, such as insufficient expansion, out-of-tolerance expansion dimensions, and poor local fit. These defects require rework and enlargement of the expansion joints, necessitating a complete re-expansion assembly.

[0003] In existing technologies, rework reaming methods mainly employ single-core rigid expansion heads or cutting reaming tools. Cutting reaming removes the base metal from the hole wall, altering the casing wall thickness and stress distribution. This easily creates machining marks and microcracks on the hole wall, reducing the fatigue and corrosion resistance of the expanded joint, which does not meet the stringent requirements for material integrity in nuclear fuel components. Traditional single-core expansion heads rely on a single conical surface to achieve reaming, resulting in concentrated reaming forces, uneven deformation of the material around the hole, poor roundness after reaming, and a high risk of localized over-expansion, bulging, or even damage to the grid matrix. Furthermore, the single-core expansion head has limited precision in controlling the reaming stroke and amount, making it difficult to accurately match the small-amplitude reaming requirements of rework.

[0004] Therefore, there is an urgent need for a hole enlargement device that can re-enlarge the expansion joints with out-of-tolerance dimensions while precisely controlling the expansion amount during the re-enlargement, reducing the risk of damage to the sleeve and grid substrate, and adapting to re-repair operations in the confined space of the nuclear fuel assembly skeleton. Summary of the Invention

[0005] The present invention aims to provide a hole enlargement device for nuclear fuel assembly skeleton, which can accurately control the enlargement amount of the hole during repair and expansion of expansion joints with out-of-tolerance dimensions, reduce the risk of damage to the sleeve and grid substrate, and is suitable for repair operations in the confined space of nuclear fuel assembly skeleton.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: it includes a mandrel, a forming roller, and a forming roller holder. The forming roller holder is cylindrical, and the mandrel passes through the forming roller holder. Multiple circumferentially distributed and penetrating insertion slots are provided on the circumferential sidewall of the forming roller holder. Each insertion slot is fitted with a forming roller, and there is a sliding fit gap between the forming roller and the insertion slot. The mandrel is provided with a multi-tapered forming section. The mandrel can be driven to move axially within the forming roller holder. The multi-tapered forming section can drive the forming roller to expand out of the insertion slot under the movement of the mandrel to expand the hole.

[0007] Furthermore, the multi-tapered bulging section is provided with a rapid bulging section, a slow bulging section, and a shaping section in sequence along the axial direction. The rapid bulging section, the slow bulging section, and the shaping section are all frustum-shaped. The taper angle of the rapid bulging section is 15° to 30°, the taper angle of the slow bulging section is 3° to 8°, and the taper angle of the shaping section is less than 1°.

[0008] Furthermore, the mandrel has a working end near the rapid expansion section and a driving end at the other end. The driving end is equipped with an adjustment assembly, which includes an adjustment knob, a handle, and a hollow reducer. The adjustment knob has a clearance hole through which the mandrel can pass. The handle is fixed on the expansion roller holder and has an annular groove on the side near the driving end. The inner hole of the multi-stage hollow reducer is inserted into the mandrel and can be rotatably installed in the annular groove. The input end of the hollow reducer faces the working end of the mandrel. The adjustment knob is located on the input end of the hollow reducer. The output end of the hollow reducer is located at the contact point between the inner hole and the mandrel, and the output end is equipped with a feed thread.

[0009] Furthermore, the mandrel is provided with a threaded section that mates with the feed thread. Rotating the adjustment knob drives the hollow reducer to rotate in the annular groove, and under the deceleration of the hollow reducer, the mandrel is driven to move axially through the feed thread.

[0010] Furthermore, it also includes a limiting sleeve, which is set on the drive end of the mandrel. The limiting sleeve can be driven by the mandrel to pass through the relief hole of the adjusting knob and abut against the hollow reducer.

[0011] Furthermore, when the limiting sleeve is in its initial position on the mandrel, the axial distance between the limiting sleeve and the hollow reducer along the mandrel is the same as the distance the mandrel needs to move when the hole is expanded to the required position.

[0012] Furthermore, the adjustment knob is equipped with a scale that can read the outer diameter of the expansion roller.

[0013] The beneficial effects of this scheme are as follows: This device uses multiple circumferentially arranged expanding rollers to compress and expand the hole, without cutting to remove the base material, thus avoiding defects such as knife marks and microcracks; the expanding rollers expand synchronously under the constraint of the embedded groove, the sleeve is subjected to uniform circumferential force, the hole has high roundness, reduces local bulging damage, and meets the material integrity requirements of nuclear fuel components. The mandrel is equipped with multi-tapered expansion sections. The fast expansion section enables the expansion roller to quickly approach the tube wall, shortening the idle stroke; the slow expansion section enables small-amplitude precision expansion; and the shaping section provides pressure holding to counteract the elastic rebound of the zirconium alloy tube during hole expansion, ensuring the stability of the repair hole diameter. Equipped with a hollow reducer, the number of knob rotations is amplified through speed reduction transmission, reducing the axial movement speed of the mandrel, realizing micro-feeding of the mandrel, improving the control accuracy of the hole diameter, and adapting to the small hole enlargement conditions of nuclear fuel skeleton rework. A mechanical limiting structure with a limiting sleeve is set up. Hard limiting is achieved by the contact between the limiting sleeve and the hollow reducer. When the spindle moves to the preset expansion position, it is locked. Even if the knob is accidentally rotated, the spindle cannot continue to feed. This mechanical structure prevents over-expansion and protects the sleeve and grid base. The adjustment knob integrates a dial, which can directly read the outer diameter of the expansion roller, making it easy for operators to intuitively control the hole expansion size and improving the convenience of rework operations. Attached Figure Description

[0014] Figure 1 This is a side view of the present invention; Figure 2 This is a schematic diagram of the working end of the mandrel in this invention; Figure 3 This is a schematic diagram of the multi-tapered bulging section in this invention; Figure 4 This is a cross-sectional view of the working end of the mandrel in this invention; Figure 5 This is a cross-sectional view of the mandrel drive end in this invention; Figure 6 This is a schematic diagram of the adjustment knob in this invention.

[0015] The following detailed description illustrates the specific implementation method: The reference numerals in the accompanying drawings include: 1. Mandrel, 101. Working end, 102. Drive end, 103. Multi-tapered forming section, 1031. Rapid forming section, 1032. Slow forming section, 1033. Forming section, 2. Forming roller, 3. Forming roller retainer, 301. Insertion groove, 4. Adjustment knob, 5. Clearance hole, 6. Dial, 7. Handle, 8. Annular groove, 9. Hollow reducer, 10. Input end, 11. Output end, 12. Feed thread, 13. Limit sleeve. Detailed Implementation

[0016] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0017] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0018] The basic implementation examples are as follows: Figure 1-6 As shown in the attached document Figure 1 and attached Figure 2 The device shown is for expanding holes in a nuclear fuel assembly frame. It includes a mandrel 1, an expanding roller 2, and an expanding roller holder 3. The expanding roller holder 3 is cylindrical. The mandrel 1 passes through the expanding roller holder 3. Multiple circumferentially distributed and penetrating insertion slots 301 are formed on the circumferential sidewall of the expanding roller holder 3. Each insertion slot 301 is fitted with an expanding roller 2. There is a sliding fit gap between the expanding roller 2 and the insertion slot 301. The mandrel 1 is provided with a multi-tapered expanding section 103. The mandrel 1 can be driven to move axially within the expanding roller holder 3. The multi-tapered expanding section 103 can drive the expanding roller 2 to expand out of the insertion slot 301 to expand the hole under the movement of the mandrel 1. The cylindrical expanding roller holder 3 provides a foundation for the installation and movement constraint of the expanding roller 2. The circumferentially distributed insertion slots 301 limit the expansion roller 2, and the sliding gap ensures that the expanding roller 2 can slide smoothly within the slot. When the mandrel 1 moves axially, the tapered surface of the multi-tapered expansion section 103 pushes each expansion roller 2, and the expansion roller 2 expands outward along the embedded groove 301 radially. Multiple points simultaneously squeeze the inner wall of the sleeve to achieve plastic expansion. When the mandrel 1 moves in the opposite direction, the expansion roller 2 can retract inward. The whole process does not require cutting the base material, and the circumferential force of the expansion is uniform, avoiding local deformation and damage to the sleeve caused by single-point extrusion.

[0019] In this embodiment, as shown in the appendix Figure 3 and attached Figure 4As shown, the multi-tapered bulging section 103 is provided axially with a rapid bulging section 1031, a slow bulging section 1032, and a shaping section 1033. All three sections are frustum-shaped. The taper angle of the rapid bulging section 1031 is 15°–30°, the taper angle of the slow bulging section 1032 is 3°–8°, and the taper angle of the shaping section 1033 is less than 1°. The rapid bulging section 1031 has a large taper, allowing the bulging roller 2 to move quickly outwards and rapidly approach the inner wall of the sleeve when the mandrel 1 moves, reducing ineffective idle strokes and improving rework efficiency. The slow bulging section 1032 has a small taper, resulting in a small radial expansion of the bulging roller 2 for the same axial displacement of the mandrel 1, achieving fine micro-bulging and meeting the precision requirements of small-amplification in rework conditions. The taper of the shaping section 1033 is very small. When the forming roller 2 runs to the position of the shaping section 1033, it can continuously output a stable radial forming force to maintain pressure on the sleeve expansion hole, counteract the elastic rebound after the zirconium alloy is expanded, and ensure the stability of the hole diameter after repair.

[0020] In this embodiment, as shown in the appendix Figure 5 As shown, the mandrel 1 has a working end 101 near the rapid forming section 1031 and a driving end 102 at the other end. The driving end 102 is equipped with an adjustment assembly, which includes an adjustment knob 4, a handle 7, and a hollow reducer 9. The adjustment knob 4 has a clearance hole 5 through which the mandrel 1 can pass. The handle 7 is fixed to the forming roller holder 3 and has an annular groove 8 on the side near the driving end 102. The inner hole of the multi-stage hollow reducer 9 is inserted into the mandrel 1 and rotatably mounted in the annular groove 8. The input end 10 of the hollow reducer 9 faces the working end 101 of the mandrel 1. The adjustment knob 4 is located on the input end 10 of the hollow reducer 9, and the output end 11 of the hollow reducer 9 is located between the inner hole and the mandrel. At the contact point of 1, the output end 11 is provided with a feed thread 12; the handle 7 is fixed to the expansion roller retainer 3, and during operation, the operator holds the handle 7 or uses a fixed bracket to support the handle 7 to achieve overall positional fixation of the device; the annular groove 8 provides a rotation mounting position for the hollow reducer 9, and the hollow reducer 9 can rotate inside the annular groove 8 without axial movement; the adjustment knob 4 is installed at the input end 10, and the operator can input rotational motion to the hollow reducer 9 by rotating the adjustment knob 4; the speed is reduced inside the hollow reducer 9, and the feed thread 12 at the output end 11 converts the rotational motion into the axial linear motion of the spindle 1; the clearance hole 5 allows the end of the spindle 1 to pass through, avoiding interference with the movement of the spindle 1.

[0021] In this embodiment, the mandrel 1 is provided with a threaded section that mates with the feed thread 12. Rotating the adjustment knob 4 drives the hollow reducer 9 to rotate in the annular groove 8. Under the deceleration of the hollow reducer 9, the mandrel is driven to move axially through the feed thread 12. When the operator rotates the adjustment knob 4, the rotational power is transmitted to the hollow reducer 9. After the speed is reduced by the reducer, the feed thread 12 at the output end 11 rotates at a low speed. The feed thread 12 meshes with the threaded section of the mandrel 1, converting the rotational motion of the hollow reducer 9 into the axial feed motion of the mandrel 1. After deceleration, the larger rotation angle of the adjustment knob 4 corresponds to only a very small axial movement of the mandrel 1, further improving the precision of the hole enlargement adjustment.

[0022] In this embodiment, as shown in the appendix Figure 5 and attached Figure 6 As shown, it also includes a limiting sleeve 13, which is set on the drive end 102 of the spindle 1. The limiting sleeve 13, which can be driven by the spindle 1, passes through the relief hole 5 of the adjusting knob 4 and abuts against the hollow reducer 9. The limiting sleeve 13 moves axially synchronously with the spindle 1. When the spindle 1 feeds towards the working end 101 to expand the hole, the limiting sleeve 13 moves together with the spindle 1. When the end face of the limiting sleeve 13 contacts the end face of the hollow reducer 9, a hard mechanical stop is formed, and the spindle 1 cannot continue to feed forward, thereby limiting the maximum feed stroke of the spindle 1.

[0023] In this embodiment, when the limiting sleeve 13 is in its initial position on the mandrel 1, the axial distance between the limiting sleeve 13 and the hollow reducer 9 along the mandrel 1 is the same as the distance the mandrel 1 needs to move when the hole is enlarged to the required position. When the device is assembled but the hole enlargement has not started, the axial distance reserved between the limiting sleeve 13 and the hollow reducer 9 is exactly equal to the feed amount of the mandrel 1 required to reach the target hole diameter. When the mandrel 1 has traveled this distance, the limiting sleeve 13 just abuts against the hollow reducer 9, and the mandrel 1 is locked. Without the need for additional repeated adjustments, the preset hole enlargement stroke is directly limited, preventing over-expansion and avoiding damage to nuclear fuel components due to misoperation.

[0024] In this embodiment, as shown in the appendix Figure 6 As shown, the adjustment knob 4 is equipped with a scale 6 that can read the outer diameter of the expansion roller 2; the scale 6 and the adjustment knob 4 are linked, and the operator can directly read the current outer diameter of the expansion roller 2, intuitively grasp the real-time size of the expanded hole, facilitate the control of the rework hole diameter, and improve the convenience of operation.

[0025] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A perforation device for a nuclear fuel assembly skeleton, characterized in that: It includes a mandrel, a forming roller, and a forming roller holder. The forming roller holder is cylindrical, and the mandrel passes through the forming roller holder. The circumferential sidewall of the forming roller holder has multiple circumferentially distributed and penetrating insertion slots. Each insertion slot is fitted with a forming roller, and there is a sliding fit clearance between the forming roller and the insertion slot. The mandrel has a multi-tapered forming section. The mandrel can be driven to move axially within the forming roller holder. The multi-tapered forming section can drive the forming roller to expand out of the insertion slot under the movement of the mandrel to expand the hole.

2. The reaming device for a nuclear fuel assembly skeleton according to claim 1, characterized in that: The multi-tapered bulging section is provided with a rapid bulging section, a slow bulging section and a shaping section in sequence along the axial direction. The rapid bulging section, the slow bulging section and the shaping section are all frustum-shaped. The taper angle of the rapid bulging section is 15° to 30°, the taper angle of the slow bulging section is 3° to 8°, and the taper angle of the shaping section is less than 1°.

3. The reaming device for a nuclear fuel assembly skeleton according to claim 2, characterized in that: The mandrel has a working end near the rapid expansion section and a driving end at the other end. The driving end is equipped with an adjustment assembly, which includes an adjustment knob, a handle, and a hollow reducer. The adjustment knob has a clearance hole through which the mandrel can pass. The handle is fixed on the expansion roller holder and has an annular groove on the side near the driving end. The inner hole of the multi-stage hollow reducer is inserted into the mandrel and can be rotatably installed in the annular groove. The input end of the hollow reducer faces the working end of the mandrel. The adjustment knob is located on the input end of the hollow reducer. The output end of the hollow reducer is located at the contact point between the inner hole and the mandrel, and the output end is equipped with a feed thread.

4. The reaming device for a nuclear fuel assembly skeleton according to claim 3, characterized in that: The mandrel is provided with a threaded section that mates with the feed thread. Rotating the adjustment knob drives the hollow reducer to rotate in the annular groove, and under the deceleration of the hollow reducer, the mandrel is driven to move axially through the feed thread.

5. A perforation device for a nuclear fuel assembly skeleton according to claim 4, characterized in that: It also includes a limiting sleeve, which is set on the drive end of the spindle. The limiting sleeve can be driven by the spindle to pass through the relief hole of the adjusting knob and abut against the hollow reducer.

6. The reaming device for a nuclear fuel assembly skeleton according to claim 5, characterized in that: When the limiting sleeve is in its initial position on the mandrel, the axial distance between the limiting sleeve and the hollow reducer along the mandrel is the same as the distance the mandrel needs to move when the hole is expanded to the required position.

7. A perforation device for a nuclear fuel assembly skeleton according to claim 6, characterized in that: The adjustment knob is equipped with a scale that can read the outer diameter of the expansion roller.

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