An optical centering device for lifting the top cover of the pressure vessel of a pressurized water reactor unit

Abstract

The present invention belongs to the field of nuclear power plant maintenance, and specifically relates to an optical centering device for lifting the top cover of the pressure vessel of a pressurized water reactor unit. The device includes a transmitting device, a receiving device and a calibration device. The receiving device includes a target and a guide column, and the target is installed on the guide column. The support seat is a hollow disk with a thread in the center; the transmitter is installed in a fixed sleeve, and the fixed sleeve and the support seat are fixedly connected by a central thread, and the fixed sleeve is fastened by a locking nut; 6 adjustment screws are passed through the fixed sleeve to adjust the coaxiality of the transmitter and the support seat. The device saves a lot of time spent on centering, reduces personnel dose, and increases the visibility and accuracy of the centering operation to ensure the safety of the equipment.

Description

Technical Field

[0001] The invention belongs to the field of nuclear power plant maintenance, and in particular relates to an optical centering device for hoisting a top cover of a pressure vessel of a pressurized water reactor unit. Background Art

[0002] During the refueling overhaul of a pressurized water reactor unit, the reactor cover needs to be lifted from the core to the cover storage room for nuclear fuel replacement. After the fuel replacement is completed, the cover is lifted and transported to the core for reinstallation.

[0003] At present, when the top cover of a pressurized water reactor unit is reinstalled, the guide column installed on the bottom hole of the pressure vessel is used as the centering reference, and the top cover flange through-hole is visually aligned. Due to the limitation of the observation angle, this alignment method requires personnel to be arranged at the bottom of the refueling pool for auxiliary alignment. At this time, the core is exposed and has extremely high radioactivity. At the same time, due to the limitations of the visual method, it is necessary to align directly below the top hoisting, and the operation is time-consuming, with extremely high radiation environmental dose acceptance and high industrial safety risks.

[0004] Taking the M310 reactor type as an example, the main lifting commander sent instructions to the ring crane driver through the intercom to lift the top cover from the top cover storage room to the top of the core. When aligning the top cover with the guide column, it is necessary to observe the gap between the guide column and the top cover through hole several times and adjust the ring crane position. Since the three guide columns need to be accurately aligned, the lifting commander needs to observe repeatedly to determine the ring crane position, and the alignment takes a long time. At the same time, because the top cover flange is thick, personnel standing above the pool cannot visually see the guide column enter the top cover through hole, and staff need to be arranged at the bottom of the pool for observation. At this time, personnel are exposed to the high-radioactivity environment of the core, which poses a great safety risk. At the same time, according to experience feedback, similar guide column scratching incidents have occurred in other power plants, which have had a certain impact on equipment safety and the main line of overhaul. Summary of the invention

[0005] 1. Purpose:

[0006] The development of an optical structure-assisted centering device for the lifting of the pressure vessel cover of a pressurized water reactor unit in a nuclear power plant can reduce the difficulty of the pressure vessel cover lifting operation, save a lot of time for centering, reduce personnel dose, and increase the visibility and accuracy of the centering operation to ensure the safety of the equipment. It is of great significance to the safety and economic benefits of nuclear power plants.

[0007] 2. Technical solution:

[0008] An optical centering device for lifting the top cover of a pressure vessel of a pressurized water reactor unit includes: a transmitting device, a receiving device and a calibration device; the transmitting device includes a lifting lug, a connecting head, a supporting seat, a bottom end cover, a transmitter and a flange; the lifting lug is installed on the upper end of the supporting head through a threaded connection, and the supporting head is connected to the supporting seat through bolts; the receiving device includes a target and a guide column, and the target is installed on the guide column. The supporting seat is a hollow disc with a thread in the center; the transmitter is installed in a fixed sleeve, and the fixed sleeve is fixedly connected to the supporting seat through a central thread, and the fixed sleeve is tightened by a locking nut; 6 adjustment screws are passed through the fixed sleeve to adjust the coaxiality of the transmitter and the supporting seat.

[0009] The calibration device comprises a calibration cylinder body, a guide plate, a cross mark and a bottom plate; the calibration cylinder body is an integrated structure and is a hollow cylinder as a whole; the guide plate is a disc with a center hole in the center.

[0010] The center of the bottom plate is a cross mark.

[0011] The cross mark line, the connecting line of the central hole of the guide plate and the central line of the calibration cylinder body are coaxial.

[0012] The bottom end cover is connected to the support seat through long bolts, and the end cover wall of the bottom end cover is in close contact with the inner wall of the flange center; a through hole is opened in the center of the bottom end cover, and the diameter of the through hole is the same as the diameter of the emitter.

[0013] The flange is evenly distributed with annular through holes, and the diameter of the support seat is larger than the inner diameter of the flange through holes.

[0014] The connector is a frame structure; the emitter is cylindrical, passes through the middle of the connector, passes through the fixing sleeve, and the bottom is located above the end cover.

[0015] The guide column is installed on the screw holes distributed in an annular manner in the pressure container at a certain angle.

[0016] 3. Effect:

[0017] This design invention has been successfully applied to the top cover reinstallation operation of the Fangjiashan 1# and 2# units of the Qinshan Nuclear Power Plant. According to the feedback from the on-site use experience, the device has a good effect, effectively shortening the top cover reinstallation alignment time, generating economic benefits and improving the safety of the unit. This device not only ensures the accuracy and safety of the top cover reinstallation operation, but also reduces the working time of personnel in a high-radioactive environment.

[0018] The present invention has the following advantages:

[0019] 1. Used for reinstallation of pressure vessel top cover of pressurized water reactor nuclear power plant.

[0020] 2. Optical structure design, visualized centering, reduces the difficulty of centering.

[0021] 3. Lightweight structure design, simple and easy to operate.

[0022] 4. Target design, optical centering, and hoisting centering with high accuracy.

[0023] 5. The centering precision calibration device is designed to ensure the accuracy of the optical transmitter.

[0024] 6. Eliminate visual blind spots, remove the need for observers in the pool, and improve the safety of lifting operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of optical centering device

[0026] Figure 2 Schematic diagram of optical centering calibration cylinder

[0027] Figure 3 Top view of the installation position of the optical centering device

[0028] In the figure: 1, lifting ear, 2, connector, 3, bolt, 4, support seat, 5, bottom end cover, 6, launcher, 7, fixing sleeve, 8, adjusting screw, 9, locking nut, 10, top cover flange, 11, target, 12, guide column, 13, calibration cylinder body, 14, guide plate, 15, cross mark, 16, bottom plate DETAILED DESCRIPTION

[0029] The device mainly consists of three parts: a transmitting device, a receiving device and a calibration device.

[0030] like Figure 1 As shown, the lifting lug 1 is installed on the connector 2 by threaded connection, and the connector 2 is connected to the support base 4 by bolts. The fixing sleeve 7 is connected to the support base 4 by threads and fastened by a locking nut 9. The transmitter 6 is installed in the fixing sleeve 7, and the coaxiality between the transmitter and the support base 4 can be adjusted by adjusting the 6 adjustment screws 8 on the fixing sleeve 7. The bottom end cover 5 is connected to the support base 4 by threads.

[0031] like Figure 2 As shown, the target 11 is mounted on a guide column 12 .

[0032] like Figure 3 As shown, the calibration cylinder body 13 is an integrated process, and the upper cylindrical surface of the cylinder body cooperates with the cylindrical surface of the support seat 4 to play a positioning role. The center cross mark 15 of the bottom plate 16 and the center hole connecting line of the guide plate 14 are coaxial with the center line of the calibration cylinder body 13 to ensure the centering accuracy.

[0033] The device cooperates with the through hole of the top cover flange through the cylindrical surface of the support seat 4 to ensure the centering accuracy of the through hole center and the emitter 6.

[0034] The specific steps are as follows:

[0035] Calibration of optical centering device: Install the optical centering device on the optical centering calibration tube, adjust the laser emitted by the transmitter 6 through the guide plate 14 by adjusting the screw 8, and make fine adjustments according to the position of the laser on the cross mark 15 to ensure the accuracy of the optical centering device.

[0036] Installation of the optical centering device: Connect one end of the long rope to the optical centering device lifting lug 1. The maintenance personnel climb onto the top cover, insert the optical centering device into the corresponding guide column through hole of the top cover flange 10, and fix the other end of the long rope to the top cover lifting fixture. Install the target 11 in the upper screw hole of the guide column 12.

[0037] Auxiliary centering of pressure vessel top cover hoisting: The top cover is hoisted above the core. The main commander of the hoisting can directly observe the relative position of the laser point emitted by the emitter 6 and the target 11, and find the centering position by adjustment. Slowly lower the top cover until the guide column 12 contacts the lower end cover 5 and pushes the laser launch device out of the through hole. Continue to lower the top cover until the core is in place.

[0038] Optical centering device removal: Maintenance personnel use a long rope to remove the laser transmitting device from the top cover.

Claims

1. An optical centering device for hoisting a pressure vessel top cover of a pressurized water reactor unit, the optical centering device comprising: A launching device, a receiving device and a calibration device; the launching device comprises a lifting lug (1), a connecting head (2), a supporting seat (4), a bottom end cover (5), a launcher (6) and a flange (10); the lifting lug (1) is installed on the upper end of the supporting head (2) by means of a threaded connection, and the supporting head (2) is connected to the supporting seat (4) by means of a bolt (3); the receiving device comprises a target (11) and a guide column (12), and the target (11) is installed on the guide column (12); The invention is characterized in that: the support seat (4) is a hollow disc with a thread at the center; the emitter (6) is installed in the fixing sleeve (7), the fixing sleeve (7) and the support seat (4) are fixedly connected by the center thread, and the fixing sleeve (7) is fastened by a locking nut (9); six adjusting screws (8) are passed through the fixing sleeve (7) to adjust the coaxiality between the emitter (6) and the support seat (4); The calibration device comprises a calibration cylinder body (13), a guide plate (14), a cross mark (15), and a bottom plate (16); the calibration cylinder body (13) is an integrated structure and is a hollow cylinder; the guide plate (14) is a disc and has a center hole at the center of the disc; The center of the bottom plate (16) is a cross mark (15); The cross mark (15), the connecting line of the center hole of the guide plate (14) and the center line of the calibration cylinder body (13) are coaxial; The bottom end cover (5) is connected to the support seat (4) by means of long bolts, and the end cover wall of the bottom end cover (5) is in close contact with the inner wall of the center of the through hole of the flange (10); a through hole is opened in the center of the end cover of the bottom end cover (5), and the diameter of the through hole is the same as the diameter of the emitter (6); The guide column (12) is installed on the screw holes distributed in an annular manner on the pressure vessel.

2. The device according to claim 1, characterized in that: The flange (10) is evenly distributed with annular through holes, and the diameter of the support seat (4) is larger than the inner diameter of the through holes of the flange (10).

3. The device according to claim 1, characterized in that: The connector (2) is a frame structure; the emitter (6) is cylindrical, passes through the middle of the connector (2), passes through the fixing sleeve (7), and has its bottom located above the end cover (5).

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