A method for overhauling a drive rod of a reactor upper assembly drive mechanism

Abstract

This invention relates to the field of nuclear power plant maintenance technology, and in particular to a method for maintaining the drive rod of a reactor upper assembly drive mechanism. The method comprises: after unlocking the drive rod, lifting it, installing a first clamp on the upper part of the drive rod, and a second clamp on the lower part of the drive rod; slowly lowering the drive rod to fix it to the head of the moving assembly; raising each drive rod to the head of the moving assembly; transferring the upper assembly to the inspection well, and installing a maintenance platform on the upper assembly column; laying a radiation shielding layer on the maintenance platform; hoisting the drive rod above the maintenance platform for a functional check, and lowering the drive rod back to its original position after the check; reinstalling the upper assembly into the reactor core, removing the second and first clamps from the drive rod, and lowering the drive rod to the bottom. This invention simplifies the drive rod maintenance process, reduces personnel workload and radiation exposure, shortens working time, and improves work efficiency.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant maintenance technology, and in particular to a method for maintaining the drive rod of a reactor superstructure drive mechanism. Background Technology

[0002] The control rod assembly drive rod (hereinafter referred to as the drive rod) is used to drive the nuclear reactor control rod assembly to move up and down in the reactor core, thereby controlling and regulating the nuclear reactor power.

[0003] The overhaul of the control rod assembly drive mechanism at a pressurized water reactor nuclear power plant mainly includes checking the drive rod interlocks, lifting the drive rods to the transport position, and inspecting the drive rods. Due to the special structure of the upper reactor assembly, before disassembling and moving the upper assembly, the 103 drive rods that drive the control rods vertically must be lifted to the transport position to prevent the drive rods from being exposed below the upper assembly during the lateral movement, which could cause unnecessary scratches and collisions, affecting the overall safety and reliability of the reactor. After the drive rods are lifted to the transport position, Russian-supplied clamps must be used, such as... Figure 1 It includes only a handle 1 and a chuck 2, with the chuck 2 used to secure the drive rod to the head of the moving component.

[0004] After transferring the upper components to the inspection well, the drive rods are inspected. The middle three rows of drive rods need to be moved to the storage rack to allow for a working path. Workers must then sequentially lift out the remaining drive rods (excluding the middle three rows) and perform a functional check on them in the inspection well. Once all are completed, the drive rods are sequentially lifted out of the storage rack and, after inspection, sequentially lifted back to their corresponding coordinates.

[0005] Based on years of maintenance experience, the following limitations have been identified in current drive rod maintenance work:

[0006] (1) The Russian-supplied clamp for the drive rod has no anti-detachment protection when in use. It is at risk of falling off when affected by external force. The falling off of the clamp will cause the drive rod to fall and damage the head of the control rod assembly, and the retrieval clamp will increase the operation time and other adverse consequences.

[0007] (2) When using the Russian-supplied clamps for the drive rod, the staff need to squat down and get close to the drive rod to install the clamps, which is labor-intensive and poses a risk of personnel contamination.

[0008] (3) When inspecting the drive rod, the staff need to stand in the middle of the drive rod, which greatly increases the radiation dose to the staff.

[0009] (4) The inspection of the drive rods requires repeated movement of the three middle rows of drive rods, which is a complicated process. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method for overhauling the drive rod of the reactor upper component drive mechanism, which simplifies the drive rod overhaul process, reduces the workload and radiation dose of personnel, shortens the working time, and improves the working efficiency.

[0011] This invention discloses a method for overhauling the drive rod of a reactor superstructure drive mechanism, comprising the following steps:

[0012] Step 1: After the drive rod is unlocked, lift the drive rod, install the first clamp on the upper part of the drive rod and the second clamp on the lower part of the drive rod, and slowly lower the drive rod to fix it to the head of the moving component; each drive rod is lifted to the head of the moving component.

[0013] The first and second clamps have the same structure, including: a left clamp seat, a right clamp seat, a spring, and a limit lever;

[0014] A pin passes through the connecting hole between the left and right card holders, connecting the left and right card holders together; a spring is installed between the left and right card holders, and the left and right card holders achieve a clamping function under the action of the spring;

[0015] The two ends of the limit lever are connected to the limit holes of the left and right card seats, respectively;

[0016] Step 2: Transfer the upper component to the inspection well and install the maintenance platform on the upper component column; lay a radiation shielding layer on the maintenance platform;

[0017] Step 3: Hoist the drive rod to the top of the maintenance platform to check its function. After the check is completed, lower the drive rod back to its original position.

[0018] Step 4: Reinstall the upper component into the core, remove the second clamp and the first clamp from the drive rod, and lower the drive rod to the bottom.

[0019] In a specific embodiment of the present invention, step 1 specifically includes:

[0020] Step 1-1: After the drive rod is unlocked, raise the drive rod to the first height, install the first clamp on the drive rod, and slowly lower the drive rod to fix it to the head of the moving component; raise each drive rod to the head of the moving component.

[0021] Steps 1-2: Raise the drive rod and install the second clamp at the bottom of the drive rod; slowly lower the drive rod to fix it to the head of the moving component; raise each drive rod to the head of the moving component.

[0022] In one specific embodiment of the present invention, in steps 1-2,

[0023] Raise the drive rod, hook the head of the scale onto the head of the drive rod, and engage the tail of the scale with the joint of the drive rod. Use the scale to locate the position of the second clamp, and install the second clamp on the lower part of the drive rod, ensuring that the position of the second clamp on all drive rods is consistent.

[0024] In one specific embodiment of the present invention, the lower edge of the second clamp is infinitely close to the upper edge of the scale tail slot.

[0025] In one specific embodiment of the present invention, the scale includes: a rod body, a scale head, a scale handle, and a scale tail groove;

[0026] The head of the scale is hook-shaped and cooperates with the head of the drive rod;

[0027] The scale handle is located in the middle of the main body of the trunk.

[0028] The scale's tail end is connected to the end of the rod body, perpendicular to the rod body.

[0029] In one specific embodiment of the present invention, a connecting seat is welded to the limiting hole of the left card seat, one end of the limiting lever is engaged in the connecting seat, the limiting lever can rotate or be lifted in the connecting seat, and the other end of the limiting lever is inserted into the right card seat to realize the limiting of the left card seat and the right card seat.

[0030] In one specific embodiment of the present invention, step 4 specifically includes:

[0031] Step 4-1: After the upper component is reinstalled into the core, lift the drive rod, remove the second clamp, and slowly lower the drive rod so that it lands smoothly on the head of the moving component. The head of each drive rod is 400mm higher than the head of the moving component.

[0032] Step 4-2: Use the special tool for lowering the drive rod to connect the drive rod, lift the drive rod to remove the first clamp on the drive rod, and slowly lower the drive rod to the bottom; lower each drive rod to the bottom.

[0033] In one specific embodiment of the present invention, the maintenance platform is a modular design, divided into two parts. After being spliced ​​together, it is fixed at both ends of the splicing point using fixing clamps, so that it can be installed on the upper component column.

[0034] The maintenance platform is surrounded by a platform railing.

[0035] In one specific embodiment of the present invention, the radiation shielding layer is lead sheet.

[0036] In one specific embodiment of the present invention, in step 2, the maintenance platform is made entirely of aluminum.

[0037] Compared with the prior art, the reactor top assembly drive mechanism drive rod maintenance method of the present invention has the following beneficial effects:

[0038] (1) The present invention uses two sets of new clamps for drive rods, which are easy to operate, can be quickly positioned and installed, improve the reliability of drive rod fixing, and personnel do not need to squat down to install clamps, which greatly reduces the time of drive rod maintenance and the risk of personnel getting contaminated.

[0039] (2) The present invention uses an upper component maintenance platform, which is set up on the upper component during operation. Lead sheeting is laid on the platform to simplify the maintenance process and reduce the labor intensity and radiation exposure of the workers.

[0040] (3) Upper component maintenance platform, which facilitates on-site assembly and disassembly;

[0041] (4) When the drive rod is lifted to the transport position, the new drive rod clamp and the new scale are used. The operation time of each drive rod is reduced by about 40%, and the overall dose of the work is reduced by about 30% compared with the previous overhaul.

[0042] (5) The upper component maintenance platform was used in conjunction with the new drive rod clamp during the drive rod inspection, which simplified the maintenance tools and shortened the maintenance time by 1 hour. The overall dose of the entire operation was reduced by about 21% compared with the previous overhaul. Attached Figure Description

[0043] Figure 1 This diagram shows the Russian-supplied clamp for the drive lever.

[0044] Figure 2 This is a schematic diagram showing the structure of the first and second clamps in this invention;

[0045] Figure 3 This illustrates the disassembly of the first and second clamps in this invention.

[0046] Figure 4 This is a schematic diagram of the maintenance platform.

[0047] Figure 5 Indicates a schematic diagram of the scale;

[0048] Figure 6 This is a schematic diagram of the drive lever head;

[0049] In the diagram, 1-handle, 2-chuck, 3-pin, 4-right seat, 5-spring, 6-limit lever, 7-left seat, 8-maintenance platform, 9-fixing clamp, 10-platform railing, 11-ladder, 12-ruler head, 13-ruler handle, 14-ruler tail slot. Detailed Implementation

[0050] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0051] The overhaul of the drive lever mainly consists of three tasks:

[0052] The first task is to raise the drive rod to the transport height while the upper assembly is still in the reactor core during the reactor dismantling phase. This process involves using clamps to attach the drive rod to the upper assembly; otherwise, the drive rod cannot be hoisted to the inspection well with the upper assembly for functional inspection. The specific implementation steps are as follows:

[0053] 1. After the drive rod is unlocked, the maintenance personnel will raise the drive rod to the first height to install the first clamp, and then lower it to the head of the moving component (both the moving component and the drive rod are part of the drive mechanism; the drive rod is located inside the moving component, and the head of the moving component is below the personnel standing platform).

[0054] 2. After raising all the drive rods row by row to the first height, the maintenance personnel should then lift the drive rods one by one, attach a ruler to the head of the drive rod, and attach the second clamp above the slot at the tail of the ruler. Then, sit on the head of the moving component. This height is the transportation height, which is the length of the ruler. If it is too low, the drive rod will protrude from the bottom of the upper component and cannot be lowered to the bottom of the inspection well. If it is too high, the drive rod will hit the upper component lifting device and cannot be lifted.

[0055] The second task is to perform a functional test on the drive rod after the upper component is hoisted to the inspection well. After the maintenance platform is installed on the upper component, the drive rod can be lifted vertically up and down for inspection.

[0056] The third task is the reassembly phase. After the upper assembly has been reassembled into the reactor core, maintenance personnel first lift the drive rod, remove the second clamp from below, and then lower the drive rod from the transport height back to the first height, using the first clamp to seat it on the head of the moving assembly. After all rows are completed, the drive rods are lifted row by row, the first clamp is removed, and they are lowered from the first height to the bottom. Once all are completed, the drive rods are interlocked. An embodiment of this invention discloses a method for overhauling the drive rod of the reactor upper assembly drive mechanism, including the following steps:

[0057] Step 1: After the drive rod is unlocked, lift the drive rod, install the first clamp on the upper part of the drive rod and the second clamp on the lower part of the drive rod, and slowly lower the drive rod to fix it to the head of the moving component; each drive rod is lifted to the head of the moving component.

[0058] The first and second clamps have the same structure, such as Figure 2 and Figure 3 As shown, it includes: left card slot 7, right card slot 4, spring 5 and limit lever 6;

[0059] The pin 3 passes through the connecting hole between the left card seat 7 and the right card seat 4, connecting the left and right card seats 4 together; a spring 5 is set between the left card seat 7 and the right card seat 4, and the left card seat 7 and the right card seat 4 achieve the clamping function under the action of the spring 5.

[0060] The two ends of the limit lever 6 are connected to the limit holes of the left card seat 7 and the right card seat 4, respectively;

[0061] Preferably, a connecting seat is welded to the limiting hole of the left card seat 7, one end of the limiting lever 6 is engaged in the connecting seat, the limiting lever 6 can rotate or be lifted in the connecting seat, and the other end of the limiting lever 6 is inserted into the right card seat 4 to realize the limiting of the left card seat 7 and the right card seat 4;

[0062] The first and second clamps utilize a clamping principle. Once the operator clamps them onto the drive rod joint, the clamps are secured to the drive rod by springs. A limit lever can lock the clamps in place, preventing them from loosening or the drive rod from falling off even under strong external forces.

[0063] This invention employs two new sets of clamps, which, together with the drive rod ruler, ensure a consistent lifting height of the drive rod, without affecting the installation of the upper component's crossbeam during hoisting. The other two sets of clamps are used in conjunction with each other, offering simpler operation compared to Russian-supplied clamps, eliminating the need for personnel to squat down to install the clamps, and significantly reducing the risk of personnel contamination.

[0064] Step 1 specifically includes:

[0065] Step 1-1: After the drive rod is unlocked, raise the drive rod to the first height, install the first clamp on the drive rod, and slowly lower the drive rod to fix it to the head of the moving component; raise each drive rod to the head of the moving component.

[0066] The first height is the distance between the head of the drive rod and the head of the moving component, which is 400mm. It should not be too high, because the drive rods are densely distributed. If it is too high, it will be inconvenient for people to pass through, the radiation dose to people will be higher, and there will be a risk of contamination.

[0067] Steps 1-2: Raise the drive rod, hook the scale head 12 onto the head of the drive rod, and engage the scale tail slot 14 with the drive rod joint. Figure 6 As shown, the position of the second clamp is located using a ruler, and the second clamp is installed at the lower part of the drive rod to ensure that the position of the second clamp of all drive rods is consistent.

[0068] After the second clamp is installed, remove the ruler.

[0069] The lower edge of the second clamp is infinitely close to the upper edge of the scale tail slot 14.

[0070] like Figure 5 As shown, the scale includes: a rod body, a scale head 12, a scale handle 13, and a scale tail groove 14;

[0071] The head of the scale 12 is hook-shaped and cooperates with the head of the drive rod;

[0072] The scale handle 13 is located in the middle of the main body of the stem.

[0073] The scale tail slot 14 is connected to the end of the rod body and is perpendicular to the rod body.

[0074] Step 3: Transfer the upper component to the inspection well and install the maintenance platform 8 on the upper component column; lay a radiation shielding layer on the maintenance platform 8; the radiation shielding layer is preferably lead sheet;

[0075] like Figure 4 As shown, the maintenance platform 8 is a modular design, consisting of two parts, preferably two aluminum semi-circular bodies;

[0076] After the two semi-circular bodies are spliced ​​together, they are fixed at both ends of the splice using fixing clamps 9, so that they can be installed onto the upper component column.

[0077] The maintenance platform 8 is surrounded by a platform guardrail 10.

[0078] The maintenance platform 8 is erected on the upper component columns. Its height can be adjusted using the upper component column sleeves to accommodate maintenance work on different units. Because the reactor drive mechanism's drive rods receive a high radiation dose, personnel working above the maintenance platform can lay lead sheets on it to reduce radiation exposure. The platform simulates the upper component's upper plate, allowing workers to sequentially remove the drive rods according to coordinates for functional checks, preventing any omissions.

[0079] A ladder 11 was also installed at the entrance of maintenance platform 8 to facilitate maintenance personnel to enter maintenance platform 8.

[0080] Step 4: Hoist the drive rod to the top of the maintenance platform 8 to check its function. After the check is completed, lower the drive rod back to its original position.

[0081] Remove the maintenance platform 8 after the functional check of the drive lever is completed.

[0082] Step 5: Reinstall the upper component into the core, remove the second and first clamps from the drive rod, and lower the drive rod to the bottom.

[0083] Step 5 specifically includes:

[0084] Step 5-1: After the upper component is reinstalled into the core, lift the drive rod, remove the second clamp, and slowly lower the drive rod so that it lands smoothly on the head of the moving component. The head of each drive rod is 400mm higher than the head of the moving component to facilitate personnel operation.

[0085] Step 5-2: Use the special tool for lowering the drive rod to connect the drive rod, lift the drive rod to remove the first clamp on the drive rod, and slowly lower the drive rod to the bottom; lower each drive rod to the bottom.

[0086] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0087] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for overhauling the drive rod of a reactor superstructure drive mechanism, characterized in that, Includes the following steps: Step 1: After the drive rod is unlocked, lift the drive rod, install the first clamp on the upper part of the drive rod and the second clamp on the lower part of the drive rod, and slowly lower the drive rod to fix it to the head of the moving component. Each drive lever is raised to the head of the moving component; The first and second clamps have the same structure, including: a left clamp seat, a right clamp seat, a spring, and a limit lever; A pin passes through the connecting hole between the left and right card holders, connecting the left and right card holders together; a spring is installed between the left and right card holders, and the left and right card holders achieve a clamping function under the action of the spring; The two ends of the limit lever are connected to the limit holes of the left and right card seats, respectively; Step 2: Transfer the upper component to the inspection well and install the maintenance platform on the upper component column; lay a radiation shielding layer on the maintenance platform; Step 3: Hoist the drive rod to the top of the maintenance platform to check its function. After the check is completed, lower the drive rod back to its original position. Step 4: Reinstall the upper component into the core, remove the second clamp and the first clamp from the drive rod, and lower the drive rod to the bottom.

2. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 1, characterized in that, Step 1 specifically includes: Step 1-1: After the drive rod is unlocked, raise the drive rod to the first height, install the first clamp on the drive rod, and slowly lower the drive rod to fix it to the head of the moving component; raise each drive rod to the head of the moving component. Steps 1-2: Raise the drive rod and install the second clamp at the bottom of the drive rod; slowly lower the drive rod to fix it to the head of the moving component; raise each drive rod to the head of the moving component.

3. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 2, characterized in that, In steps 1-2, Raise the drive rod, hook the head of the scale onto the head of the drive rod, and engage the tail of the scale with the joint of the drive rod. Use the scale to locate the position of the second clamp, and install the second clamp on the lower part of the drive rod, ensuring that the position of the second clamp on all drive rods is consistent.

4. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 3, characterized in that, The lower edge of the second clamp is infinitely close to the upper edge of the scale tail slot.

5. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 1, characterized in that, The scale includes: a rod body, a scale head, a scale handle, and a scale tail groove; The head of the scale is hook-shaped and cooperates with the head of the drive rod; The scale handle is located in the middle of the main body of the trunk. The scale's tail end is connected to the end of the rod body, perpendicular to the rod body.

6. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 1, characterized in that, A connecting seat is welded to the limiting hole of the left card slot. One end of the limiting lever is engaged in the connecting seat. The limiting lever can rotate or be lifted in the connecting seat. The other end of the limiting lever is inserted into the right card slot to achieve the limiting of the left and right card slots.

7. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 1, characterized in that, Step 4 specifically includes: Step 4-1: After the upper component is reinstalled into the core, lift the drive rod, remove the second clamp, and slowly lower the drive rod so that it lands smoothly on the head of the moving component. The head of each drive rod is 400mm higher than the head of the moving component. Step 4-2: Use the special tool for lowering the drive rod to connect the drive rod, lift the drive rod to remove the first clamp on the drive rod, and slowly lower the drive rod to the bottom; lower each drive rod to the bottom.

8. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 1, characterized in that, The maintenance platform is a modular design, consisting of two parts. After being spliced ​​together, it is fixed at both ends of the splicing point using fixing clamps, so that it can be installed on the upper component column. The maintenance platform is surrounded by a platform railing.

9. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 1, characterized in that, The radiation shielding layer is made of lead.

10. The method for overhauling the drive rod of the reactor superstructure drive mechanism according to claim 1, characterized in that, In step 2, the maintenance platform is made entirely of aluminum.

Images