A measuring tool for the position of a reactor protection tube assembly in a nuclear power plant

Abstract

The present invention belongs to the field of maintenance of nuclear power plant reactors, and particularly relates to a position measuring tool for a nuclear power plant reactor protection tube assembly, comprising: a measuring tool body, a measuring pawl, a digital display measuring instrument and a vernier caliper. The vernier caliper is fixed on the measuring tool body. A chute is provided at an intermediate position corresponding to the position of the vernier caliper on the measuring tool body. The digital display measuring instrument is installed in the chute of the measuring tool body. The measuring pawl is slidably installed on the measuring tool body, and the digital display measuring instrument is correspondingly connected to the measuring pawl. The present invention solves the problem of interference with on-site maintenance space objects existing in the use of existing tools, improves the measurement accuracy, shortens the measurement time, reduces the stay time of personnel in a high-temperature environment, and reduces the physical energy consumption of personnel.

Description

Technical Field

[0001] The present invention belongs to the field of nuclear power plant reactor maintenance, and particularly relates to a position measuring tool for a nuclear power plant reactor protection tube assembly. Background Art

[0002] The first phase of Tianwan Nuclear Power Plant has two VVER-1000 type units, and the reactor is a B-428 type reactor. The reactor includes reactor pressure vessel, core basket, core shroud, protection tube assembly, fuel assembly, control rod assembly, upper assembly, protection steel structure, control rod drive mechanism and other components. Among them, the protection tube assembly is a welded metal structure, and its main functions are: precise positioning and isolation of the fuel assembly head in height and in the core plane; installation of the protection tube of the control rod assembly and the neutron-temperature measurement tube to protect the control rod assembly and the neutron-temperature measurement sensor from the dynamic action of the coolant, while ensuring reliable dropping of the control rod; establishment of a certain pressure at the upper end of the fuel assembly to prevent the fuel assembly from "floating up"; formation of a uniformly mixed coolant flow at the core outlet and the inlet of the upper mixing chamber of the reactor; and installation of the steel "hot" supervision sample box for the reactor vessel.

[0003] To ensure the continuous stable operation of the unit, it is necessary to regularly monitor the position change of the protection tube assembly in the core. According to the requirements of the "Reactor Equipment Maintenance Outline of Tianwan Nuclear Power Plant" LYG-9-JA0.IS-M030, during each major overhaul of the Tianwan Nuclear Power Plant reactor, the position measurement of the protection tube assembly should be carried out during the reactor disassembly and assembly stages. The main measurement points are shown in Figure 1 , and the regularly measured data includes: the distance from the surface of the basket flange to the surface of the pressure vessel flange; the distance from the flange of the protection tube assembly to the surface of the pressure vessel flange; the thickness of the shoulder flange of the protection tube assembly, including the upper and lower gaskets.

[0004] The position measurement of the protection tube assembly requires high precision, and the precision requirement for the measured value is 0.01 mm. When on-site maintenance personnel measure the position of the protection tube assembly, precise measuring tools are needed. In the prior art, maintenance personnel have been using traditional measuring tools (vernier caliper + height vernier caliper) to measure the position of the protection tube assembly in the pressure vessel.

[0005] There are problems in the use of traditional general measuring tools:

[0006] The upper cantilever of the height vernier caliper is relatively short, and when it is used to cooperate with the pressure vessel flange surface for measurement, it cannot extend to the main seal flange surface;

[0007] The base size of the height vernier caliper is too large, which interferes with the shoulder of the protection tube assembly, resulting in interference between the base and the basket, and reducing the measurement accuracy of the height gauge;

[0008] When measuring with a length vernier caliper, the two lower pawls are too short to fully clamp and fit with the flange of the protective tube, which will also reduce the measurement accuracy of the vernier caliper.

[0009] In summary, during the actual measurement of the position of the protective tube assembly at the maintenance site, due to the installation position of the shoulder of the protective tube assembly being lower than the flange surface of the pressure vessel, and the fitting clearances among the pressure vessel body, the protective tube assembly, and the hanging basket, as well as the operation space available for measurement being narrow, although there are precise traditional precision measuring tools, the lengths of the upper pawls and cantilevers of the existing traditional tools interfere with the on-site space, resulting in large measurement errors and long measurement time. Coupled with the relatively high ambient temperature at this position, higher physical requirements are imposed on the maintenance and measurement personnel. Summary of the Invention

[0010] The purpose of the present invention is to provide a measuring tool for the position of a nuclear power plant reactor protection tube assembly, to solve the problem of interference with on-site maintenance space objects existing in the use of existing tools, improve the measurement accuracy, shorten the measurement time, reduce the residence time of personnel in a high-temperature environment, and reduce the physical energy consumption of personnel.

[0011] Technical solutions for achieving the purpose of the present invention:

[0012] A measuring tool for the position of a nuclear power plant reactor protection tube assembly, the measuring tool includes: a measuring tool body, measuring pawls, a digital display measuring instrument, and a vernier caliper. The vernier caliper is fixed on the measuring tool body. A chute is provided at the middle position corresponding to the position of the vernier caliper on the measuring tool body. The digital display measuring instrument is installed in the chute of the measuring tool body. The measuring pawls are slidably installed on the measuring tool body, and the digital display measuring instrument is correspondingly connected to the measuring pawls.

[0013] The measuring tool further includes a sliding sleeve. The digital display measuring instrument is fixed on the sliding sleeve. Two positioning pins are installed on the sliding sleeve. The sliding sleeve is installed in the chute of the measuring tool body through the positioning pins. The digital display measuring instrument is installed in the chute of the measuring tool body through the sliding sleeve.

[0014] A connecting sleeve is connected to the measuring pawls, and the positioning pins on the sliding sleeve are fixedly connected to the connecting sleeve on the measuring pawls.

[0015] The measuring pawls and the connecting sleeve are connected by welding.

[0016] A return spring is provided on the measuring pawls, and the return spring is positioned by a positioning screw installed on the measuring tool body.

[0017] The digital display measuring instrument includes a first digital display measuring instrument, a second digital display measuring instrument, and a third digital display measuring instrument. The first digital display measuring instrument is located at the 12 o'clock direction of the measuring tool body and is in the upper part of the measuring tool body; the third digital display measuring instrument is located at the 9 o'clock direction of the measuring tool body and is in the middle part of the measuring tool body; the second digital display measuring instrument is located at the 3 o'clock direction of the measuring tool body and is in the lower part of the measuring tool body.

[0018] The measuring pawl includes an upper measuring pawl, a middle measuring pawl, and a lower measuring pawl. The lower measuring pawl is located at the 3 o'clock direction of the measuring tool body and is in the lower part of the measuring tool body; the upper measuring pawl is located at the 9 o'clock direction of the measuring tool body and is in the middle part of the measuring tool body; the middle measuring pawl is located at the 3 o'clock direction of the measuring tool body and is in the middle and lower part of the measuring tool body.

[0019] The sliding sleeve of the third digital display measuring instrument is fixedly connected to the connecting sleeve on the upper measuring pawl through a positioning pin; the sliding sleeve of the second digital display measuring instrument is fixedly connected to the connecting sleeve on the middle measuring pawl through a positioning pin; the sliding sleeve of the first digital display measuring instrument is fixedly connected to the connecting sleeve on the lower measuring pawl through a positioning pin.

[0020] The lower measuring pawl is a rotatable structure, and the lower measuring pawl rotates circumferentially in the chute opened at the bottom of the measuring tool body.

[0021] The measuring tool further includes a measuring handle. The measuring handle is located at the top of the measuring tool body. The measuring handle rotates circumferentially in the chute opened at the top of the measuring tool body, and the measuring handle is connected to the lower measuring pawl.

[0022] The vernier caliper is detachably mounted on the measuring tool body.

[0023] The measuring tool further includes a calibration platform. The calibration platform includes a first measuring step, a second measuring step, and a third measuring step. The first measuring step is located at the topmost part of the calibration platform, the second measuring step is located in the middle of the calibration platform, and the third measuring step is located at the bottom of the calibration platform.

[0024] The height of the first measuring step is 115 mm, the height of the second measuring step is 40 mm, and the height of the third measuring step is 15 mm.

[0025] The beneficial technical effects of the present invention are as follows:

[0026] 1. The position measuring tool for the nuclear power plant reactor protection tube assembly of the present invention can measure the Α, Β, and Γ values at one time at the measuring position point, instead of measuring 3 times at the same measuring point, reducing the number of measurements.

[0027] 2. The measurement tool for the position of the reactor protection tube assembly of the present invention has a difference in the measurement error between measuring all the required data at one time at the same measurement point and measuring three times at the same measurement point. In fact, when using traditional tools to measure three times, the cooperation between the measurement tool and each component may not be on the same radial axis. Therefore, the validity of the three measured values will decrease, affecting the subsequent position analysis of the protection tube assembly in the pressure vessel.

[0028] 3. The measurement tool for the position of the reactor protection tube assembly of the present invention lengthens the length of the pawl that cooperates with the pressure surface, enabling the pawl to fully cooperate with the main sealing surface of the pressure vessel. In addition, the mating surface of the pawl is also enlarged, making the cooperation between the pawl and the pressure vessel more stable.

[0029] 4. The measurement tool for the position of the reactor protection tube assembly of the present invention designs the pawl that cooperates with the protection tube into a rotatable structure. When using traditional tools for measurement, the pawl and the measurement tool body rotate together. In order to fully cooperate with the flange surface of the protection tube assembly, the measurement tool body does not need to rotate. Only the corresponding measurement pawl needs to rotate to achieve full cooperation with the flange surface of the protection tube assembly, avoiding the interference between the measurement pawl and the measured object and improving the measurement accuracy.

[0030] 5. The measurement tool for the position of the reactor protection tube assembly of the present invention also includes a calibration platform. During on-site work, according to the usage of the measurement tool, the measurement tool can be placed on the calibration platform at any time for re-zeroing and calibration, and it can be found at any time whether there is a measurement deviation in the measurement tool, improving the accuracy and reliability of the measurement data; solving the problem that traditional tools can only achieve zeroing operations and cannot be calibrated in real time, conveniently and quickly on the calibration platform.

[0031] 6. The measurement tool for the position of the reactor protection tube assembly of the present invention can directly measure the Γ value, subverting the idea of traditional tools that require multiple repeated measurements and calculations to obtain the Γ value, improving the measurement efficiency, reducing the measurement time, and saving manpower.

[0032] 7. The measurement tool for the position of the reactor protection tube assembly of the present invention uses a new vernier caliper structure, and the cooperation with the measurement tool body actually forms a detachable and reinstallable structure. Therefore, during the annual regular inspection of the new measurement tool, it is not necessary to send the entire set of tools for calibration. Only the three vernier calipers need to be removed and sent to the laboratory for calibration. The rest of the measurement tool body and the calibration platform are made of pure metal materials, which are stable and not easily deformed, so they do not need to be regularly calibrated. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram for measuring the position of the protection tube assembly;

[0034] Figure 2 Schematic diagram of the operating position of the protection tube assembly in the pressure vessel;

[0035] Figure 3 Schematic diagram of the installation position of the protection tube assembly in the pressure vessel;

[0036] Figure 4 Schematic diagram of the structure of a calibration platform for a position measurement tool of a nuclear power plant reactor protection tube assembly provided by the present invention;

[0037] Figure 5 Schematic diagram of the structure of a position measurement tool for a nuclear power plant reactor protection tube assembly provided by the present invention;

[0038] Figure 6 Schematic diagram of the structure of a sliding sleeve in a position measurement tool for a nuclear power plant reactor protection tube assembly provided by the present invention;

[0039] Figure 7 Schematic diagram of the structure of an upper measurement pawl in a position measurement tool for a nuclear power plant reactor protection tube assembly provided by the present invention;

[0040] Figure 8 Schematic diagram of the structure of an intermediate measurement pawl in a position measurement tool for a nuclear power plant reactor protection tube assembly provided by the present invention;

[0041] Figure 9 Schematic diagram of the structure of a lower measurement pawl in a position measurement tool for a nuclear power plant reactor protection tube assembly provided by the present invention;

[0042] Figure 10 Schematic diagram of the top chute of the measurement tool body (for accommodating the measurement handle) in a position measurement tool for a nuclear power plant reactor protection tube assembly provided by the present invention;

[0043] Figure 11 is Figure 10 A-A view of;

[0044] Figure 12 Schematic diagram of the bottom chute of the measurement tool body (for accommodating the lower measurement pawl) in a position measurement tool for a nuclear power plant reactor protection tube assembly provided by the present invention;

[0045] Figure 13 is Figure 12 B-B view of.

[0046] In the figure: 1 - Pressure vessel top cover; 2 - Protection tube assembly; 3 - Basket; 4 - Enclosure; 5 - Supervised sample; 6 - Fuel assembly; 7 - Pressure vessel body; 8 - Main sealing ring; 9 - Bourdon tube assembly; 10 - Upper backing plate on shoulder; 11 - Lower backing plate on shoulder; 12 - Flange shoulder; 13 - First measurement step; 14 - Second measurement step; 15 - Third measurement step; 16 - Measurement handle; 17 - First digital display measuring instrument; 18 - Second digital display measuring instrument; 19 - Third digital display measuring instrument; 20 - Upper measurement pawl; 21 - Intermediate measurement pawl; 22 - Lower measurement pawl; 23 - Measuring tool body; 24 - Slide sleeve; 25 - Positioning pin. Detailed implementation mode

[0047] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0048] As Figure 1 shown, for the position measurement work of the protection tube assembly, the main measurement points are as follows:

[0049] (1) Value Α, which is the distance from the surface of the basket flange to the surface of the pressure vessel flange;

[0050] (2) Value Β, which is the distance from the flange of the protection tube assembly to the surface of the pressure vessel flange;

[0051] (3) Value Б, which is the thickness of the flange of the shoulder of the protection tube assembly, including the upper and lower gaskets.

[0052] For the specific measurement positions of Α, Β, and Б, please refer to Figure 1 , and then calculate the value Γ (the distance from the lower surface of the shoulder of the protection tube assembly to the surface of the basket flange) through the formula Α - Β - Б = Γ. The acceptance standard for the value of Γ is that it meets the operation requirements of the reactor equipment when it is within the range of 16 - 21 mm.

[0053] Schematic diagram of the installation and operation position of the protection tube assembly in the pressure vessel, as Figures 2-3 shown.

[0054] As Figures 4-6 shown, a position measuring tool for a protection tube assembly of a nuclear power plant reactor provided by the present invention includes: a measuring tool body 23, a measuring pawl, a digital display measuring instrument, a measuring handle 16, a slide sleeve 24, a vernier caliper, and a calibration platform. The measuring pawl includes a lower measuring pawl 22, an intermediate measuring pawl 21, and an upper measuring pawl 20, and the digital display measuring instrument includes a first digital display measuring instrument 17, a second digital display measuring instrument 18, and a third digital display measuring instrument 19.

[0055] The overall appearance of the measuring tool body 23 is cylindrical. The vernier caliper is fixed on the measuring tool body 23. A sliding groove is provided on the measuring tool body 23 at the middle position corresponding to the position of the vernier caliper, for providing a digital measuring instrument and a measuring pawl to slide up and down. The digital measuring instrument is installed in the sliding groove of the measuring tool body 23 through a sliding sleeve 24, and slides up and down in the sliding groove of the measuring tool body 23. The measuring pawl is slidably installed on the measuring tool body 23, and the digital measuring instrument is correspondingly connected to the measuring pawl. The measuring handle 16 is installed on the measuring tool body 23, and the measuring handle 16 is connected to the measuring pawl.

[0056] The digital measuring instrument is fixed on the sleeve 24 by connecting fasteners. Two positioning pins 25 are installed on each measuring instrument sleeve 24. The two positioning pins 25 can slide up and down in the slide groove on the measuring tool body 23. Since the positioning pins 25, the sleeve 24 and the digital measuring instrument are connected as a whole, the positioning pins 25, the sleeve 24 and the digital measuring instrument as a whole will slide up and down along the slide groove on the measuring tool body 23.

[0057] The vernier caliper is fixed on the measuring tool body 23, and the head of the digital measuring instrument is installed above the vernier caliper. The digital measuring instrument slides up and down along the vernier caliper in the slideway, and the reading of the digital measuring instrument keeps changing while sliding.

[0058] The positioning pin 25 on the sliding sleeve 24 is fixedly connected to the connecting sleeve on the measuring pawl. When the measuring pawl moves up and down, the connecting sleeve, the sliding sleeve 24 and the digital display measuring instrument are driven to move up and down together.

[0059] The measuring pawl and the connecting sleeve are connected by welding. In order to prevent the measuring pawl and the connecting sleeve from deformation during welding, vacuum electron beam welding is adopted, which effectively avoids the sliding and jamming of the mechanism caused by welding deformation and improves the manufacturing accuracy of the tool.

[0060] The measuring pawl is provided with a reset spring to ensure that the measuring pawl can fit closely with the surface of the corresponding workpiece during measurement, thereby improving the accuracy and effectiveness of the measurement. The reset spring is positioned by a positioning screw installed on the measuring tool body 23. When the spring is stressed, the spring is prevented from moving in the height axis direction, thereby improving the accuracy of the measurement and avoiding measurement deviation.

[0061] like Figure 5 As shown, the digital measuring instrument includes a first digital measuring instrument 17 , a second digital measuring instrument 18 and a third digital measuring instrument 19 .

[0062] The first digital display measuring instrument 17 is located at the 12 o'clock direction of the measuring tool body 23 and is in the upper part of the measuring tool body 23; the third digital display measuring instrument 19 is located at the 9 o'clock direction of the measuring tool body 23 and is in the middle part of the measuring tool body 23; the second digital display measuring instrument 18 is located at the 3 o'clock direction of the measuring tool body 23 and is in the lower part of the measuring tool body 23. Limited by the diameter and length of the rod of the measuring tool body 23, the three instruments, the sliding sleeve and the positioning pin must be arranged separately in space.

[0063] As Figure 5 shown, the measuring pawl includes an upper measuring pawl 20, a middle measuring pawl 21 and a lower measuring pawl 22. The structure of the measuring pawl including the upper measuring pawl 20, the middle measuring pawl 21 and the lower measuring pawl 22 is as Figures 7-9 shown. The length of the lower measuring pawl 22 is 50 mm and the width is 10 mm. The length of the middle measuring pawl 21 is 47.5 mm and the width is 10 mm. The length of the upper measuring pawl 20 is 150 mm and the width is 10 mm. The length and width of the mating surface of the measuring pawl match the dimensions of the corresponding mating surface to ensure the structural stability during mating and prevent tilting.

[0064] The lower measuring pawl 22 is located at the 3 o'clock direction of the measuring tool body 23 and is in the lower part of the measuring tool body 23; the upper measuring pawl 20 is located at the 9 o'clock direction of the measuring tool body 23 and is in the middle part of the measuring tool body 23; the middle measuring pawl 21 is located at the 3 o'clock direction of the measuring tool body 23 and is in the middle and lower part of the measuring tool body 23. Its spatial arrangement height matches the installation and operation position of the protective tube assembly in the pressure vessel as Figures 2-3 shown, and there is a space for the pawl to slide up and down to enable the connecting sleeve to drive the instrument to move up and down to achieve the display of measurement data.

[0065] The sliding sleeve 24 of the third digital display measuring instrument 19 is fixedly connected to the connecting sleeve on the upper measuring pawl 20 through the positioning pin 25. The sliding sleeve 24 of the second digital display measuring instrument 18 is fixedly connected to the connecting sleeve on the middle measuring pawl 21 through the positioning pin 25. The sliding sleeve 24 of the first digital display measuring instrument 17 is fixedly connected to the connecting sleeve on the lower measuring pawl 22 through the positioning pin 25. This makes the third digital display measuring instrument 19 move together with the upper measuring pawl 20, the second digital display measuring instrument 18 move together with the middle measuring pawl 21, and the first digital display measuring instrument 17 move together with the lower measuring pawl 22.

[0066] The measuring handle 16 is connected to the lower measuring pawl 22 through the core shaft of the central rod assembly of the measuring tool body 23. The measuring handle 16 is located at the top of the measuring tool body 23. There is a sliding groove opened at the top of the measuring tool body 23, and the measuring handle 16 rotates circumferentially in the sliding groove as Figures 10-11 shown.

[0067] The lower measuring pawl 22 is a rotatable structure. A chute is provided at the bottom of the measuring tool body 23. The side surface of the lower measuring pawl 22 is matched with the slot on the measuring tool body 23. The lower measuring pawl 22 rotates circumferentially in the chute to achieve rotation at a certain angle, such as Figures 12-13 shown. The measuring handle 16 is integrally connected to the lower measuring pawl 22 for rotation.

[0068] The vernier caliper body is in a long strip shape, with openings at both ends. Screws are installed at the opening positions, and the vernier caliper is detachably installed on the measuring tool body 23 through the screws. The digital display measuring instrument head slides up and down along the long strip track of the vernier caliper, and at the same time, the readings on the digital display measuring instrument change continuously.

[0069] The calibration platform provides a zeroing and calibration function for the measuring tool of the protection tube assembly. As Figure 4 shown, the calibration platform includes a first measuring step 13, a second measuring step 14 and a third measuring step 15. The first measuring step 13 is located at the top of the calibration platform, 115 mm away from the third measuring step 15. The second measuring step 14 is located in the middle, 75 mm away from the third measuring step 15. The third measuring step 15 is located at the bottom, 15 mm away from the bottom plane of the calibration platform.

[0070] The structural height of the calibration platform is carefully calculated. The height of the first measuring step 13 is 115 mm, the height of the second measuring step 14 is 40 mm, and the height of the third measuring step 15 is 15 mm. During calibration, the three measuring pawls of the measuring tool of the protection tube assembly are respectively matched with the above three measuring steps. During calibration, the upper measuring pawl 20 is closely attached to the surface of the first measuring step 13, the middle measuring pawl 21 is closely matched with the surface of the second measuring step 14, and the lower measuring pawl 22 is closely matched with the surface of the third measuring step 15. Therefore, when the digital display measuring instrument is zeroed, it is not zeroed in the traditional sense, but the digital display measuring instrument is set on the calibration platform as follows: the first digital display measuring instrument 17 is set to "+15.00 mm", the second digital display measuring instrument 18 is set to "+115.00 mm", and the third digital display measuring instrument 19 is set to "+40.00 mm". The "+" and "-" signs are related to the up and down installation directions of the instrument and can be adjusted on the instrument for convenient reading.

[0071] Adopting the measuring method of a measuring tool for the position of a nuclear power plant reactor protection tube assembly provided by the present invention, the method includes the following steps:

[0072] Step 1. Calibration and debugging of the measuring tool of the protection tube assembly

[0073] Check whether the button battery in the position measuring tool of the protection tube assembly has sufficient power. If it does not meet the usage requirements, replace it with a new button battery.

[0074] Prepare several metal sheets or thin sheets that are not easily deformed with standard thicknesses. It is required that the thickness of each metal sheet or thin sheet of other materials is uniform, so as to simulate the height changes of the surfaces of the three measurement steps, namely the first measurement step 13, the second measurement step 14, and the third measurement step 15, on the calibration platform.

[0075] Measurement instrument parameter setting: Turn on the first digital display measurement instrument 17, the second digital display measurement instrument 18, and the third digital display measurement instrument 19 (press the ON / OFF button). Adjust the unit of the measurement instrument to the mm state through the mm / in button on each digital display measurement instrument. At this time, the mm information will be displayed on the electronic screen of the measurement instrument. When the HOLD mark appears on the electronic screen, the HOLD display information can be cancelled by pressing the HOLD button on the measurement instrument.

[0076] Place the protection tube assembly measuring tool on the calibration platform. Before placing it on the calibration platform, lift the handle 16, and then rotate the handle 16 clockwise (viewed from above the tool) to rotate the lower measurement pawl 22 assembly to the position of entering the platform. After the measuring tool body 23 enters the measurement platform and is lowered to the 115 mm step 13, rotate the handle 16 counterclockwise to screw the lower measurement pawl 22 into the platform installation position. Press the SET button on the measurement instrument multiple times to zero the measurement instrument and set other values. The "+" and "-" in front of the numbers represent the increase and decrease directions of the measurement values. In order to cooperate with the calibration platform and ensure quick reading at the maintenance site, the following settings are made for the rounded values of the measurement instruments: the first digital display measurement instrument 17 is set to "15.00 mm", the second digital display measurement instrument 18 is set to "115.00 mm", and the third digital display measurement instrument 19 is set to "+40.00 mm".

[0077] Check the mating condition of the tips of the upper measurement pawl 20, the middle measurement pawl 21, and the lower measurement pawl 22 with the surfaces of the respective measurement steps on the calibration platform. It is required that the fit is tight. At the same time, observe whether there are any abnormalities in the readings. If necessary, re-set the parameters of the digital display measurement instrument. Remove the protection tube assembly measuring tool from the calibration platform.

[0078] On the calibration platform, place the prepared metal sheets or non-deformable thin sheets of standard thickness on the surfaces of each measurement step. The operator can place metal sheets or thin sheets of different thicknesses on each measurement step according to needs. Then place the measuring tool on the calibration platform. At this time, there is no need to perform the zeroing operation again. Just closely fit each measuring pawl with the surface of each measurement step. If necessary, use the handle 16 to closely fit the surface of the lower measuring pawl 22 with the lower surface of the second measurement step 14. Note: At this time, gently press the heads of the 3 measuring instruments, and at the same time gently press each measuring pawl until it is in place. Excessive pressing is likely to cause errors in data measurement.

[0079] Record the readings of the first digital display measuring instrument 17, the second digital display measuring instrument 18, and the third digital display measuring instrument 19. Combine the values of the newly added metal sheets or thin sheets of other non-deformable materials with known thicknesses on the calibration platform to check the accuracy of the measuring tool. Then remove the measuring tool again, place metal sheets or thin sheets of different thicknesses on the surfaces of each measurement step, and repeatedly verify and debug the tool. Repeat 3 - 5 times. Through this calibration and debugging, the accuracy and reliability of the tool measurement can be verified, and the training of the operator can be realized synchronously.

[0080] Step 2: On-site operation and use of the measuring tool for the protection tube assembly

[0081] Before the formal measurement work starts, calibrate the measuring tool according to Step 1. At the same time, check whether there are any parts of the measuring tool for the protection tube assembly that are likely to fall off, and take measures to prevent foreign objects.

[0082] Transport the measuring tool and the calibration platform to the vicinity of the main mating surface of the reactor pressure vessel using a self-made small object transport container. During the process, pay attention to keeping the measuring handle of the measuring tool and each measuring pawl from colliding, being damaged, and deformed.

[0083] Place the calibration platform on the main sealing surface of the reactor pressure vessel, and pay attention to handling it gently to prevent the calibration platform from damaging the main sealing surface.

[0084] Before use, place the measuring tool on the calibration platform for calibration. After the calibration work is completed, perform the measurement operation.

[0085] Place the measuring tool at the corresponding measurement position of the protection tube assembly, read and record the readings of each measuring instrument.

[0086] To ensure the accuracy of the measurement result data, it is recommended that for each change of the measurement axis along the axis of the protection tube assembly, use the calibration platform to calibrate the measuring tool once. After calibration, continue with the measurement of the next position.

[0087] After the measurement work is completed, the tools should be carefully transported to the storage room. After turning off the power supplies of the three digital display measuring instruments on the measuring tools, they should be packed in special storage boxes. During transportation and storage, it is strictly prohibited to put the measuring handle and the three measuring pawls under pressure to avoid deformation.

[0088] A measuring tool for the position of a nuclear power plant reactor protection tube assembly provided by the present invention effectively solves the problems of interference between the lengths of the pawls and the cantilever of traditional tools and the on-site space, large measurement errors, and long measurement time.

[0089] When using the measuring tool for the position of a nuclear power plant reactor protection tube assembly of the present invention for measurement, the required Γ value can be directly read out, effectively shortening the measurement time, reducing the time for maintenance personnel to stay in the high-temperature environment for a long time, reducing the physical energy consumption of maintenance personnel, improving work efficiency, making the measurement values more accurate, improving the effectiveness of measurement data, and providing a reliable basis for subsequent analysis of the position change of the protection tube assembly in the pressure vessel.

[0090] The measuring tool of the present invention can be popularized and applied in relevant measurement work of the same type of units, and can also be used to measure other similar equipment in the power station with the measuring tool of the present invention. And the measuring tool of the present invention also has good reference significance for the measurement work of other similar equipment in the same industry.

[0091] The present invention has been described in detail above in conjunction with the accompanying drawings and embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the purpose of the present invention. The content not described in detail in the present invention can all adopt the prior art.

Claims

1. A position measuring tool for a reactor protection tube assembly in a nuclear power plant, characterized in that, the measuring tool includes: a measuring tool body (23), measuring pawls, a digital display measuring instrument and a vernier caliper. The vernier caliper is fixed on the measuring tool body (23). A chute is provided at an intermediate position corresponding to the position of the vernier caliper on the measuring tool body (23). The digital display measuring instrument is installed in the chute of the measuring tool body (23). The measuring pawls are slidably installed on the measuring tool body (23), and the digital display measuring instrument is correspondingly connected to the measuring pawls; the digital display measuring instrument includes a first digital display measuring instrument (17), a second digital display measuring instrument (18) and a third digital display measuring instrument (19); the measuring pawls include an upper measuring pawl (20), an intermediate measuring pawl (21) and a lower measuring pawl (22). The lower measuring pawl (22) is located at the 3 o'clock direction of the measuring tool body (23) and is at the lower part of the measuring tool body (23). The upper measuring pawl (20) is located at the 9 o'clock direction of the measuring tool body (23) and is at the middle part of the measuring tool body (23). The intermediate measuring pawl (21) is located at the 3 o'clock direction of the measuring tool body (23) and is at the middle and lower part of the measuring tool body (23); the sliding sleeve (24) of the third digital display measuring instrument (19) is fixedly connected to the connecting sleeve on the upper measuring pawl (20) through a positioning pin (25). The sliding sleeve (24) of the second digital display measuring instrument (18) is fixedly connected to the connecting sleeve on the intermediate measuring pawl (21) through a positioning pin (25). The sliding sleeve (24) of the first digital display measuring instrument (17) is fixedly connected to the connecting sleeve on the lower measuring pawl (22) through a positioning pin (25).

2. The position measuring tool for a reactor protection tube assembly in a nuclear power plant according to claim 1, characterized in that, the measuring pawl and the connecting sleeve are connected by welding.

3. The position measuring tool for a reactor protection tube assembly in a nuclear power plant according to claim 2, characterized in that, a return spring is provided on the measuring pawl, and the return spring is positioned by a positioning screw installed on the measuring tool body (23).

4. The position measuring tool for a reactor protection tube assembly in a nuclear power plant according to claim 3, characterized in that, the lower measuring pawl (22) is a rotatable structure, and the lower measuring pawl (22) rotates circumferentially in a chute provided at the bottom of the measuring tool body (23).

5. The position measuring tool for a reactor protection tube assembly in a nuclear power plant according to claim 4, characterized in that, the measuring tool further includes a measuring handle (16). The measuring handle (16) is located at the top of the measuring tool body (23). The measuring handle (16) rotates circumferentially in a chute provided at the top of the measuring tool body (23), and the measuring handle (16) is connected to the lower measuring pawl (22).

6. The position measuring tool for a reactor protection tube assembly in a nuclear power plant according to claim 5, characterized in that, the vernier caliper is detachably installed on the measuring tool body (23).

7. A position measuring tool for a nuclear power plant reactor protection tube assembly according to claim 6, characterized in that, the measuring tool further includes a calibration platform, the calibration platform includes a first measuring step (13), a second measuring step (14) and a third measuring step (15), the first measuring step (13) is located at the top of the calibration platform, the second measuring step (14) is located in the middle of the calibration platform, and the third measuring step (15) is located at the bottom of the calibration platform.

8. A position measuring tool for a nuclear power plant reactor protection tube assembly according to claim 7, characterized in that, the height of the first measuring step (13) is 115 mm, the height of the second measuring step (14) is 40 mm, and the height of the third measuring step (15) is 15 mm.

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