Heavy water reactor underwater deep hole channel coaxiality blind measurement method

Abstract

The invention provides a blind measurement method for the coaxiality of an underwater deep hole channel of a heavy water reactor. The blind measurement method comprises the following steps: step 1, establishing a measurement zero reference surface; 2, establishing an axis system vertical to the measurement zero reference surface by taking the measurement zero reference surface as a reference; 3, measuring the distance between the pre-measurement hole channel and the measurement zero reference surface; 4, measuring the diameter of the pre-measuring hole; and step 5, measuring the coaxiality of the pre-measuring hole and the upper port hole of the deep hole channel. According to the invention, high-irradiation, long-distance, underwater and blind measurement of the coaxiality of the inner hole of the vertical deep hole channel of the nuclear power heavy water stack is realized, accurate contact measurement is realized, the accuracy is high, a high-irradiation environment is furthest away, and the irradiation dose of an operator is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of coaxiality measurement of a heavy water reactor underwater deep channel, and in particular to a blind coaxiality measurement method for a heavy water reactor underwater deep channel. Background Art

[0002] In existing vertical deep channels, in some cases, it is necessary to measure the coaxiality between a certain depth of the inner hole and the inner opening of the channel. Currently, the commonly used deep hole coaxiality measurement methods are ultrasonic measurement method and mechanical measurement method.

[0003] The ultrasonic measurement method uses an ultrasonic thickness gauge to determine the thickness of the material being measured based on the principle of ultrasonic pulse reflection, and indirectly judges the coaxiality of the deep hole to the outer circle through the wall thickness of different parts. This method is greatly affected by the structure of the workpiece. Some shaft parts have irregular surfaces and are difficult to measure, and some parts cannot even be detected. Due to the influence of various factors, the data detected by the ultrasonic thickness gauge is unstable, and the accuracy of the coaxiality detection is not high.

[0004] Mechanical measurement is a contact measurement method that uses a measuring rod to drive the measuring head to contact the inner wall of the measured depth hole, and the coaxiality of the measured hole is obtained based on the coaxiality between the measuring rod and the outer circle. This measurement method requires the position of the measured hole to be known and the measuring head to accurately contact the inner wall of the measured hole, otherwise the data error will be large.

[0005] For heavy water reactors, there are a large number of narrow channels in the core of nuclear power heavy water reactors that are more than ten meters deep and vertically pass through the heavy water environment of the reactor core. The diameters of these channels vary, and the diameters of the steps at different depths are different. Since the unit has been in operation for more than ten years, these channels may be deformed under long-term irradiation, and the relevant structural dimensions may be inconsistent with the original design parameters. Before using these channels, it is necessary to measure the coaxiality of the corresponding inner hole and the inner opening of the channel.

[0006] The commonly used ultrasonic measurement method and mechanical measurement method cannot be used to measure the coaxiality of the inner hole of the heavy water reactor deep channel for the following reasons:

[0007] First, the ultrasonic measurement method uses the principle of ultrasonic pulse reflection. The flow of heavy water moderator in the reactor produces turbulence, which interferes with the conduction of ultrasonic waves and greatly reduces the precision and accuracy of the measurement. The hole is more than ten meters deep and the surrounding dose rate is as high as 106Gy / h, making it impossible for ultrasonic receiving instruments to enter.

[0008] Second, the measuring head of the mechanical measurement method enters the heavy water reactor. The situation inside the hole is complicated, and it is impossible to determine whether the measuring head is in precise contact with the measured hole, which greatly reduces the credibility of the measurement results.

[0009] It can be seen that conventional measurement methods can no longer meet the needs, and it is necessary to invent a new safe and accurate measurement method to support the high irradiation, long distance, underwater and blind measurement of the coaxiality of the inner hole of the vertical deep channel and the inner hole of the channel mouth of the nuclear power heavy water reactor. Summary of the invention

[0010] The purpose of the present invention is to provide a blind measurement method for the coaxiality of a heavy water reactor underwater deep channel, which solves the problem of safely and accurately measuring the coaxiality of a heavy water reactor highly irradiated underwater vertical deep hole and an inner hole of the channel mouth.

[0011] In order to achieve the above object, the present invention provides the following technical solutions:

[0012] A blind measurement method for the coaxiality of a heavy water reactor underwater deep channel comprises the following steps:

[0013] Step 1: Establish the measurement zero reference plane;

[0014] Step 2: Taking the measurement zero reference plane as the reference, establish an axis system perpendicular to the measurement zero reference plane;

[0015] Step 3: Measure the distance between the pre-measured hole and the measurement zero reference plane;

[0016] Step 4: Measure the diameter of the pre-measured hole;

[0017] Step 5: Measure the coaxiality between the pre-measured hole and the port hole on the deep channel.

[0018] In step 1, an extension device is set up based on the upper surface of the predicted channel opening, the axis of the extension device coincides with the axis of the predicted channel opening, and the upper surface of the extension device is perpendicular to the axis, which is used as the zero reference plane for measurement.

[0019] In step 2, a working platform is set up on the artificial operation platform of the heavy water reactor where the deep channel is located. The first datum, the second datum and the third datum are respectively carried on the working platform. The cross-sections of the three datums are parallel to the measurement zero datum plane. Bushings are vertically installed on each datum plane. The axes of the three bushings are coaxial, and the three bushings can slide freely on their respective datum planes.

[0020] Furthermore, the distance h between three adjacent reference surfaces satisfies h=H / D, wherein H is the theoretical height of the predicted measuring hole from the zero base surface, and D is the theoretical diameter of the predicted measuring hole.

[0021] In step 3, the measuring ruler and the positioning gauge are connected together, and the measuring ruler and the positioning gauge are used to measure the precise height. The measuring ruler passes through the shaft sleeves of the first, second, and third datums of the working platform and descends along the pre-measured hole until the front positioning gauge stops at the upper step of the pre-measured hole. At this time, the measurement zero reference plane corresponds to a certain scale value on the measuring ruler, and the scale value is the depth value of the pre-measured hole from the measurement zero reference plane.

[0022] Furthermore, the measuring ruler is composed of several sections of rods with precise scales, which are assembled together with high axial and radial precision (with a straightness of 0.3 mm / 12 m) between the head and the tail according to the measurement requirements to form a standard measuring ruler with a single axis. The diameter of the measuring ruler is the same as the inner hole diameter of the sleeve. The positioning gauge is installed at the front end of the measuring ruler. The head of the positioning gauge is wide at the top and narrow at the bottom. The diameter of the wide end is larger than the predicted measuring hole, and the diameter of the narrow end is smaller than the predicted measuring hole.

[0023] In step 4, use a measuring ruler and a coaxial gauge to measure the diameter of the predicted hole. The coaxial gauge is a step-type structure. When a certain step of the coaxial gauge is the same as the diameter of the predicted hole, the measuring ruler stops descending. At this time, the measurement zero reference plane corresponds to a certain scale value on the measuring ruler. According to the scale value, it can be converted to which step of the coaxial gauge is the same as the diameter of the predicted hole, thereby obtaining the actual diameter of the predicted hole. Then, based on the comparison between the measured value and the theoretical value, it is judged whether the inner wall of the hole contacted by the coaxial gauge is the predicted hole.

[0024] Furthermore, the coaxial gauge consists of multiple steps with decreasing size from top to bottom: D n , D n-1 , D n- 2......D......D p-2 , D p-1 , D p , the height of each step is L n , L n-1 , L n-2 ......L......L p-2 , L p-1 , L p , where D is the theoretical diameter of the predicted hole.

[0025] Furthermore, the distance between the mounting surface of the coaxial gauge and the D step surface (a cylindrical step with a diameter of D) is the same as the distance between the mounting surface of the positioning gauge and the positioning step (a positioning regulating plane).

[0026] In step 5, the sleeves on the three reference surfaces of the working platform are moved to allow the measuring ruler to tilt freely along the axis of the predicted measuring hole, and a laser tracker is used to measure the coaxiality △L between the measuring ruler and the axis of the extension device, thereby measuring the coaxiality between the predicted measuring hole and the predicted measuring channel opening hole.

[0027] Compared with the prior art, the blind coaxiality detection method for underwater deep channels of heavy water reactors provided by the present invention has the following beneficial effects:

[0028] The invention solves the problem of measuring the coaxiality of the inner hole of a vertical deep channel in a nuclear power heavy water reactor under high irradiation, long distance, underwater and blind measurement. The invention has the advantages of precise contact measurement, high accuracy, and maximum distance from the high irradiation environment, thus greatly reducing the radiation dose of operators.

[0029] The present invention solves the problem of simultaneously measuring multiple parallel axis channels by establishing an axis system perpendicular to the measurement zero reference plane.

[0030] Furthermore, the present invention solves the problem of measuring related geometric tolerances in various shapes of channel openings by proposing the establishment of a measuring zero reference surface and an extension device.

[0031] The present invention establishes a measurement system for blind testing of the coaxiality of the inner hole and the port at any depth of a vertical deep channel, and comprehensively summarizes the measurement methods and related parameter selections of the inner diameter coaxiality of holes with different diameters, which is convenient for targeted and specific measurements and has guiding significance for blind testing of coaxiality of various deep holes in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for description.

[0033] Figure 1 It is a schematic diagram of a vertical deep channel of a heavy water reactor in the prior art;

[0034] Figure 2 for Figure 1 The enlarged view of point Ⅰ in the middle;

[0035] Figure 3 for Figure 1 The enlarged view of the middle II;

[0036] Figure 4 A schematic diagram of the relationship between the pre-measured channel and the zero reference plane provided by the present invention;

[0037] Figure 5 A schematic diagram of a working platform provided by the present invention;

[0038] Figure 6 A schematic diagram of the positional relationship between the pre-measurement hole and the positioning gauge provided by the present invention;

[0039] Figure 7 A schematic diagram of the connection between the measuring ruler and the positioning gauge provided by the present invention;

[0040] Figure 8 A schematic diagram of the connection between the measuring ruler and the coaxial gauge provided by the present invention;

[0041] Fig. 9 A schematic diagram of a blind measurement method for the coaxiality of the inner hole of a pre-measured hole and the hole opening provided by the present invention;

[0042] Fig.10 for Figure 1 The enlarged view of the middle part Ⅲ;

[0043] Fig.11 for Figure 1 Enlarged view of point IV in the middle.

[0044] Description of reference numerals:

[0045] 1. Pre-measured channel; 2. Pre-measured hole; 3. Extension device; 4. Zero reference plane; 5. Working platform; 6. First reference; 7. Second reference; 8. Third reference; 9. Measuring ruler; 10. Positioning gauge; 11. Coaxial gauge; 12. Bushing. DETAILED DESCRIPTION

[0046] The following is further explained in detail through specific implementation methods.

[0047] like Figures 1 to 11 As shown, the present invention provides a blind detection method for the coaxiality of a heavy water reactor underwater deep channel, and the specific steps are as follows:

[0048] Step 1: Establish a measurement zero reference plane 4 as the reference plane for subsequent measurements. The axis of the mouth of the predicted measurement channel 1 (the predicted heavy water reactor vertical deep channel) is used as a reference to extend upward, and a reference plane is established perpendicular to the extension axis as the measurement zero reference plane 4. The upper surface of the upper port of the deep channel where the predicted measurement channel 1 is located has different shapes, and the inclined or shaped surface cannot be used as a measurement reference plane. Therefore, it is necessary to establish an upward extension device 3 based on the upper surface of the predicted channel 1. The axis of the extension device 3 coincides with the axis of the mouth of the predicted measurement channel 1. The upper surface of the extension device 3 is perpendicular to the axis, which is used as the zero reference plane 4 for measurement.

[0049] Step 2: Take the measurement zero reference plane 4 as the reference and establish an axis system perpendicular to the measurement zero reference plane 4. Establish a working platform 5 on the artificial operation platform of the heavy water reactor where the deep hole is located. The working platform 5 carries three references, namely the first reference 6, the second reference 7, and the third reference 8. The three reference cross-sections are parallel to the measurement zero reference plane 4. The axes of the sleeves 12 installed vertically on each reference plane are coaxial during installation and can slide freely on their respective reference planes. At this time, the axes of the sleeves 12 are parallel. The distance h between the three reference planes depends on the depth H and diameter D of the measured hole 2. The relationship between the three satisfies the following relationship:

[0050] h=H / D

[0051] Where h is the distance between the three benchmarks (meters);

[0052] H is the theoretical height (m) of the pre-measurement hole 2 from the zero base surface 4;

[0053] D is the theoretical diameter of the pre-measurement hole 2 (cm).

[0054] Step 3: Measure the distance between the predicted measuring channel 1 and the measuring zero reference plane 4. Taking the axis of the hole of the predicted measuring channel 1 as the reference, first measure the precise height of the predicted measuring hole 2 from the measuring zero reference plane 4. The measuring ruler 9 and the positioning gauge 10 are installed together, and the measuring ruler 9 (height measuring ruler) and the positioning gauge 10 are used to measure the precise height of the predicted measuring hole 2 from the measuring zero reference plane 4, wherein the height measuring ruler 9 is composed of several sections of rods with precise scales, which are assembled together with high precision in axial and radial directions between the head and the tail according to the measurement requirements to form a standard measuring ruler of sufficient length with a unique axis. The diameter of the measuring ruler 9 is the same as the inner hole diameter of the sleeve 12. The positioning gauge 10 is installed at the front end of the measuring ruler 9, and its head is wide at the top and narrow at the bottom. The diameter of the wide end is larger than the predicted measuring hole 2, and the diameter of the narrow end is smaller than the predicted measuring hole 2.

[0055] The measuring ruler 9 passes through the sleeves 12 of the first datum 6, the second datum 7, and the third datum 8 of the working platform, and descends along the pre-measurement channel 1 until the front positioning gauge 10 stops at the upper step of the pre-measurement hole 2. At this time, the measurement zero reference surface 4 corresponds to a certain scale value on the measuring ruler 9, and this value is the depth value of the pre-measurement hole 2 from the measurement zero reference surface 4.

[0056] Step 4: Measure the diameter of the pre-measured hole 2. The same shaft system datum, using the same measuring ruler 9 in step 3, with a coaxial gauge 11, first measure the inner diameter of the pre-measured hole 2, using the same working platform 5, first datum 6, second datum 7, third datum 8, sleeve 12 and measuring ruler 9, the front end positioning gauge 10 is replaced with a coaxial gauge 11. The coaxial gauge 11 consists of multiple steps with decreasing size from top to bottom: D n , D n-1 , D n-2 ......D......D p-2 , D p-1 , D p , the height of each step is L n , L n-1 , L n-2 ......L......L p-2 , L p-1 , L p . Wherein, D is the theoretical diameter size value of the predicted measuring hole 2. The value of the distance between the installation surface of the coaxial gauge 11 and the step surface D is the same as the value of the distance between the installation surface of the positioning gauge 10 and the positioning step. When a certain step of the coaxial gauge 11 is the same as the diameter of the predicted measuring hole 2, the measuring ruler 9 stops descending, and the measuring zero reference plane 4 corresponds to a certain scale value on the measuring ruler 9. According to this scale value, it can be calculated which step of the coaxial gauge 11 is the same as the diameter of the predicted measuring hole 2, thereby obtaining the actual diameter size of the predicted measuring hole 2. Based on the comparison between the measured value and the theoretical value, it can be judged whether the inner wall of the hole contacted by the coaxial gauge is the predicted measuring hole 2.

[0057] Step 5: Measure the coaxiality between the pre-measured hole 2 and the hole at the mouth of the channel (the upper hole of the deep channel). Move the sleeves 12 on the three reference surfaces of the working platform 5 to allow the measuring ruler 9 to tilt freely along the axis of the pre-measured hole 2. The axis of the measuring ruler 9 is the axis of the pre-measured hole 2. Use a laser tracker to measure the coaxiality △L between the measuring ruler 9 and the axis of the extension device 3. This value is the coaxiality between the pre-measured hole 2 and the hole at the mouth of the pre-measured channel 1.

[0058] The relationship between the diameter d of the measuring ruler 9, the depth H and diameter D of the measured hole 2, and the inner diameter D' of the hole of the predicted hole 1 is as follows:

[0059] d=ηD·H / 10·D'

[0060] Where, d is the diameter of the measuring ruler 9 (cm);

[0061] H is the theoretical height (m) of the pre-measurement hole 2 from the zero base surface 4;

[0062] D is the theoretical diameter of the pre-measurement hole 2 (cm);

[0063] D' is the inner diameter of the hole 1 of the predicted measurement channel (cm);

[0064] η is the correction coefficient, which is between 0.6 and 0.7.

[0065] For example, Figures 1 to 4 As shown, the coaxiality of the predicted hole 2 and the inner mouth of the predicted hole 1 (pre-measured vertical deep hole of heavy water reactor) at certain positions is measured. These holes are of different sizes, the depth is uncertain, and the position of the plane on the hole is uncertain, and they cannot be used as the measurement reference surface. Therefore, an upward extension device 3 is established on the upper surface of the predicted hole 1. The axis of the extension device 3 coincides with the axis of the hole at the mouth of the predicted hole 1, and the upper plane of the extension 3 is perpendicular to the axis of the hole at the mouth of the predicted hole 1. The upper plane of the extension device 3 is used as the zero reference surface 4 for measurement.

[0066] like Figure 5 As shown, a working platform 5 is established, and three reference platforms are mounted on the platform: the first reference 6, the second reference 7, and the third reference 8. The three reference planes are parallel to the measurement zero reference plane 4, and the three reference platforms are respectively provided with sleeves 12 that can be freely moved or fixed and whose axes are perpendicular to the reference platforms. First, the sleeve axes 12 on the three reference platforms are set to be coaxial, and parallel or coaxial with the axis of the extension device 3, and the axis system is established.

[0067] The distance h between the three reference surfaces depends on the depth H and diameter D of the measured hole 2. The relationship between the three satisfies the following relationship:

[0068] h=H / D

[0069] Where h is the distance between the three benchmarks (meters);

[0070] H is the theoretical height (m) of the pre-measurement hole 2 from the zero base surface 4;

[0071] D is the theoretical diameter of the pre-measurement hole 2 (cm).

[0072] The theoretical value of the diameter of the predicted measuring hole 2 is φ13.5 cm, the theoretical height of the predicted measuring hole 2 from the zero base surface 4 is 15 m, and the distance h between the three reference surfaces is 0.9 m.

[0073] like Figures 6 to 11 As shown, based on the axis system of the extension device 3, first measure the precise height of the predicted hole 2 from the zero reference plane 4: use a height measuring ruler 9 and a positioning gauge 10, where the height measuring ruler 9 is composed of several sections of rods with precise scales. According to the measurement requirements, the axial and radial directions between the head and tail are assembled together with high precision to form a standard measuring ruler of sufficient length with a single axis. The positioning gauge 10 is installed at the front end of the height measuring ruler, and its head is wide at the top and narrow at the bottom. The diameter of the wide end is larger than the measured hole, and the diameter of the narrow end is smaller than the predicted hole 2. The diameter of the predicted hole 1 is φ162mm, and the theoretical value of the diameter of the predicted hole 2 is φ135mm. The large diameter of the positioning gauge head is φ160mm, and the small diameter is φ125mm.

[0074] The measuring ruler 9 passes through the sleeves 12 of the first datum 6, the second datum 7, and the third datum 8 of the working platform, and descends along the pre-measurement channel 1 until the front positioning gauge 10 stops at the upper step of the pre-measurement hole 2. At this time, the measured zero reference surface 4 corresponds to a certain scale value on the measuring ruler 9, and this value is the depth value of the pre-measurement hole 2 from the zero reference surface 4. The measured depth value is 9062mm.

[0075] The relationship between the diameter d of the measuring ruler 9, the depth H and diameter D of the measured hole 2, and the inner diameter D' of the hole of the predicted hole 1 is as follows:

[0076] d=ηD·H / 10·D'

[0077] Where, d is the diameter of the measuring ruler 9 (cm);

[0078] H is the theoretical height (m) of the pre-measurement hole 2 from the zero base surface 4;

[0079] D is the theoretical diameter of the pre-measurement hole 2 (cm);

[0080] D' is the inner diameter of the hole 1 of the predicted measurement channel (cm);

[0081] η is the correction coefficient, which is between 0.6 and 0.7.

[0082] The diameter of the measuring ruler 9 is selected to be 0.8 cm.

[0083] The same shaft system reference, using the same measuring ruler 9, with a coaxial gauge 11, measures the inner diameter of the pre-measured hole 2: Use the same working platform 5, reference (6, 7, 8), sleeve 12 and measuring ruler 9 mentioned above. The front positioning gauge 10 is replaced with a coaxial gauge 11. The coaxial gauge 11 consists of multiple steps with decreasing size from top to bottom: D n , D n-1 , D n-2 ......D......D p-2 , D p-1 , D p , the height of each step is L n , L n-1 , L n-2 ......L......L p-2 , L p-1 , L p D is the theoretical diameter value of the predicted hole 2. According to the size and depth of the predicted hole 2, the inner diameter gauge has six steps, with diameters of φ135.2mm, φ135.1mm, φ135mm, φ134.9mm, φ134.8mm, and φ134.7mm, and the corresponding step lengths are 1.5cm.

[0084] The distance between the mounting surface of the inner diameter gauge 11 and the step surface D is the same as the distance between the mounting surface of the positioning gauge 10 and the positioning step. When a certain step of the coaxial gauge 11 is the same as the actual diameter of the predicted hole 2, the measuring ruler 9 stops descending, and the zero reference surface 4 corresponds to a certain scale value on the measuring ruler 9. According to this scale value, it can be calculated which step of the coaxial gauge 11 is the same as the diameter of the predicted hole 2, thereby obtaining the diameter of the predicted hole 2. The actual measured height value is 9077mm. According to the length of the step of the coaxial gauge 11, which is 1.5cm, the actual diameter of the predicted hole 2 is φ134.9mm.

[0085] The sleeves 12 on the three reference surfaces of the mobile working platform 5 allow the measuring ruler 9 to tilt freely along the axis of the pre-measured hole 2. The axis of the measuring ruler 9 is the axis of the pre-measured hole 2. The coaxiality △L between the measuring ruler 9 and the axis of the extension 3 is measured using a laser tracker. This value is the coaxiality between the pre-measured hole 2 and the pre-measured channel 1. The actual coaxiality △L between the measuring ruler 9 and the axis of the extension 3 is 2.8 mm.

[0086] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A blind measurement method for the coaxiality of a heavy water reactor underwater deep channel, characterized in that: The following steps are involved: Step 1: Establish the measurement zero reference plane; Step 2: Taking the measurement zero reference plane as the reference, establish an axis system perpendicular to the measurement zero reference plane; Step 3: Measure the distance between the pre-measured hole and the measurement zero reference plane; Step 4: Measure the diameter of the pre-measured hole; Step 5: Measure the coaxiality between the pre-measured hole and the port hole on the deep channel.

2. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 1 is characterized in that: In step 1, an extension device is set up based on the upper surface of the predicted channel opening, the axis of the extension device coincides with the axis of the predicted channel opening, and the upper surface of the extension device is perpendicular to the axis, which is used as the zero reference plane for measurement.

3. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 1 is characterized in that: In step 2, a working platform is set up on the artificial operation platform of the heavy water reactor where the deep channel is located. The first datum, the second datum and the third datum are respectively carried on the working platform. The cross-sections of the three datums are parallel to the measurement zero datum plane. Bushings are vertically installed on each datum plane. The axes of the three bushings are coaxial, and the three bushings can slide freely on their respective datum planes.

4. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 3 is characterized in that: The distance h between three adjacent reference surfaces satisfies h=H / D, wherein H is the theoretical height of the predicted measuring hole from the zero base surface, and D is the theoretical diameter of the predicted measuring hole.

5. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 3 is characterized in that: In step 3, the measuring ruler and the positioning gauge are connected together, and the measuring ruler and the positioning gauge are used to measure the precise height. The measuring ruler passes through the shaft sleeves of the first, second, and third datums of the working platform and descends along the pre-measured hole until the front positioning gauge stops at the upper step of the pre-measured hole. At this time, the measurement zero reference plane corresponds to a certain scale value on the measuring ruler, and the scale value is the depth value of the pre-measured hole from the measurement zero reference plane.

6. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 5 is characterized in that: The measuring ruler is composed of several sections of rods with precise scales, which are assembled together with a straightness of 0.3 mm / 12 m in the axial and radial directions between the head and tail according to the measurement requirements to form a standard measuring ruler with a unique axis. The diameter of the measuring ruler is the same as the inner diameter of the sleeve. The locating gauge is installed at the front end of the measuring ruler. The head of the locating gauge is wide at the top and narrow at the bottom. The diameter of the wide end is larger than the predicted measuring hole, and the diameter of the narrow end is smaller than the predicted measuring hole.

7. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 1 is characterized in that: In step 4, use a measuring ruler and a coaxial gauge to measure the diameter of the predicted hole. The coaxial gauge is a step-type structure. When a certain step of the coaxial gauge is the same as the diameter of the predicted hole, the measuring ruler stops descending. At this time, the measurement zero reference plane corresponds to a certain scale value on the measuring ruler. According to the scale value, it can be converted to which step of the coaxial gauge is the same as the diameter of the predicted hole, thereby obtaining the actual diameter of the predicted hole. Then, based on the comparison between the measured value and the theoretical value, it is judged whether the inner wall of the hole contacted by the coaxial gauge is the predicted hole.

8. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 7 is characterized in that: The coaxial gauge consists of multiple steps with decreasing size from top to bottom: D n , D n-1 , D n-2 ......D......D p-2 , D p-1 , D p , the height of each step is L n , L n-1 , L n-2 ......L......L p-2 , L p-1 , L p , where D is the theoretical diameter of the predicted hole.

9. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 8, characterized in that: The distance between the mounting surface of the coaxial gauge and the step surface D is the same as the distance between the mounting surface of the positioning gauge and the positioning step.

10. The method for blindly measuring the coaxiality of underwater deep channels of heavy water reactors according to claim 1, characterized in that: In step 5, the sleeves on the three reference surfaces of the working platform are moved to allow the measuring ruler to tilt freely along the axis of the predicted measuring hole, and a laser tracker is used to measure the coaxiality △L between the measuring ruler and the axis of the extension device, thereby measuring the coaxiality between the predicted measuring hole and the predicted measuring channel opening hole.

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