A reactor incore control rod guide tube inspection apparatus and method

Abstract

The present application belongs to the technical field of water immersion ultrasonic inspection, and particularly relates to a reactor in-core component control rod guide tube inspection device and method. The device comprises a water immersion focused ultrasonic probe, an acoustic reflector and a rotary motor, which are sequentially fixed on the same support. The method comprises the following steps: eliminating the central deviation influence by using a correlation contrast method; peak value interpolation algorithm; signal calibration; and actual profile measurement. The water immersion focused probe cooperated with the use of the acoustic reflector can change the sound velocity direction, increase the focal column length, and improve the inspection sensitivity. The processing of the B-scan signal obtained by the ultrasonic inspection can accurately measure the actual profile of the guide hole, improve the defect detection rate, and ensure the accuracy of the inspection results.

Description

Technical Field

[0001] This invention belongs to the field of water immersion ultrasonic testing technology, specifically relating to a device and method for inspecting control rod guide tubes of reactor internal components, which is particularly suitable for automatic ultrasonic testing of tubular inner surface contour measurement and slight wear measurement. Background Technology

[0002] The reactor internals control rod guide tube (CRGT) is a key component of a nuclear reactor. It is used to guide the reactor control rod bundle assembly (RCCA) for reactor startup, shutdown, and power adjustment, and to prevent interference between the RCCA frame and the guide plate. It is of great significance to the safe operation of nuclear power units.

[0003] The control rod guide tube (CRGT) mainly consists of an upper guide assembly and a lower guide assembly. The upper guide assembly is equipped with one type A upper guide plate, two type B upper guide plates, and one type C upper guide plate; the lower guide assembly has five lower guide plates. During nuclear reactor operation, the control rod guide tube is subjected to complex conditions of high temperature, high pressure water flow, and high radiation, which easily leads to wear on the guide plates. Since the in-core components containing the control rod guide tube are not pressure-bearing equipment, existing in-service inspection specifications do not include this part of the inspection.

[0004] According to international experience in nuclear power plant operation, the control rod guides of pressurized water reactors generally experience wear after a certain period of operation. This wear may cause the control rod assembly to jam during movement, seriously threatening the safe operation of the nuclear power unit.

[0005] Currently, the inspection of control rod guide cylinders mainly includes ultrasonic and video inspection. Ultrasonic inspection can quantify the wear size, but its detection accuracy is not high. Video inspection can only perform a rough detection of wear defects and cannot perform precise measurements. There is currently no non-destructive testing technology in China specifically for the guide cylinder guide clips of control rods.

[0006] Therefore, it is essential to develop a reactor control rod guide tube inspection device and method to enable regular inspection of the wear condition of the control rod guide tube guide clips, and to analyze the failure mechanism of the control rod clips, thereby ensuring the safe, efficient and economical operation of nuclear power units. Summary of the Invention

[0007] The purpose of this invention is to provide a device and method for inspecting control rod guide tubes of reactor internal components, which can accurately measure the profile, inner diameter, ligament opening width, and minor wear of the inner wall of the control rod guide tube.

[0008] The technical solution of the present invention is as follows: a test device for the control rod guide tube of a reactor internal component, comprising a water immersion focused ultrasonic probe, an acoustic reflector and a rotary motor, wherein the water immersion focused ultrasonic probe, the acoustic reflector and the rotary motor are sequentially fixed on the same bracket.

[0009] The aforementioned water immersion focused ultrasound probe has the following characteristics: focal length 10mm±2mm; frequency 10MHz±2MHz; bandwidth greater than 60%; focal spot diameter 0.25mm±0.1mm; and focal column length ≥4mm.

[0010] A method for inspecting the guide tube of a reactor internal component control rod, characterized by comprising the following steps:

[0011] Step 1: Apply the correlation comparison method to eliminate the influence of center offset;

[0012] Step 2: Peak interpolation algorithm;

[0013] Step 3: Signal calibration;

[0014] Step 4: Actual contour measurement.

[0015] Step 1 includes the following:

[0016] (A) The center offset δ is small enough.

[0017] Step A1: Calibration. During the circumferential rotation of the mirror, the echo distance Ri (i corresponds to the phase angle) of the aperture wall is collected, and the average value of one revolution is Re.

[0018] Step A2: During the circumferential rotation of the reflector, the echo distance ri of the hole wall after sound velocity correction is collected;

[0019] Step A3: Add the echo distances of the relative phase angles, di = ri + rj;

[0020] Step A4: The diameter at phase angle i is D + di - Re * 2; where D is the nominal diameter.

[0021] Step 1 includes the following:

[0022] (B) The center offset δ may have a large value.

[0023] Step B1: Calibration. During the circumferential rotation of the mirror, the echo distance Ri from the hole wall is collected, and the normalized curve Rg is calculated and obtained.

[0024] Step B2: Use a fitting method to complete the curves into Ri and Rg;

[0025] Step B3: During the circumferential rotation of the reflector, the echo distance ri of the hole wall after sound velocity correction and the corresponding normalized curve rg are collected;

[0026] Step B4: Using a search algorithm and with the correlation coefficient as the metric, calculate the optimal phase offset pa of rg relative to Rg;

[0027] Step B5: Based on pa, correct the original curve ri to obtain the corrected curve rmi;

[0028] Step B6: Directly compare rmi and Ri, the phase deviation value at phase angle i.

[0029] Step 2 includes the following:

[0030] Step 21: Obtain the positive or negative peak position [X] n A n ], and the adjacent [X n-1 A n-1 ], [X n+1 A n+1 [Data coordinates]

[0031] Step 22: Obtain the true peak position PosX using symmetric interpolation.

[0032]

[0033] Step 23: Selecting the effective region

[0034] The effective area of ​​data is selected by using a measurement crosshair and a reference crosshair to select the area.

[0035] Step 24: Calculate the periodic region;

[0036] Step 25: Calculate the similarity curve;

[0037] Step 26: Locate and fix the target signal;

[0038] Search for all regions greater than Th on the similarity curve ABk, and denote the center position of each region as the fixed position.

[0039] Step 27: Locate the effective periodic signal region;

[0040] The effective periodic signal region is located in the middle area between two adjacent fixed target rectangles.

[0041] Step 24 includes the following:

[0042] The calculation of the periodic region is used to obtain effective hole wall contour signals; the calculation of the periodic region is achieved through image similarity level search, as detailed below:

[0043] Step 241: Regional Data Acquisition

[0044] Write the data within the rectangular area selected by the two crosshair cursors into an array Ai (i = 1, 2, 3...) in sequence, and set the horizontal dimension of the rectangle as w;

[0045] Step 242: Search threshold setting:

[0046] The threshold Th = (Ai, Ai)0.5 * coe is used as the inner product of the array Ai and a fixed coefficient, where the coefficient coe is determined by the system stability and is set to above 0.9.

[0047] Step 25 includes the following:

[0048] Step 251: Shift the area selected by the crosshair cursor to the right or left, and regenerate the data within the rectangular area after shifting by k horizontal resolutions into an array named Bk (k = 1, 2, 3...) in the same way as in Step 1;

[0049] Step 252: Calculate the inner product of Ai and Bk, denoted as ABk = (Ai, Bk)0.5;

[0050] Step 253: Calculate all ABk (k = 1, 2, 3...) with a horizontal resolution step to obtain the similarity curve.

[0051] Step 3 includes the following:

[0052] Step 31: Select points on the hole contour and mark the coordinates of the selected points in the array Cir, selecting a total of Nc contour points;

[0053] Step 32: Select any three points P1(x1,y1), P2(x2,y2), and P3(x3,y3) from Cir to calculate the center coordinates Cen(x,y). The calculation formula is as follows:

[0054] A=x1*(y2-y3)-y1*(x2-x3)+x2*y3-x3*y2

[0055] B = (x1) 2 +y1 2 )*(y3-y2)+

[0056] (x2 2 +y2 2 )*(y1-y3)+

[0057] (x3 2 +y3 2 )*(y2-y1)

[0058] C=(x1 2 +y1 2 )*(x2-x3)+

[0059] (x2 2 +y2 2 )*(x3-x1)+

[0060] (x3 2 +y3 2 )*(x1-x2)

[0061] D=(x1 2 +y1 2 )*(x3*y2-x2*y3)+

[0062] (x2 2 +y2 2 )*(x1*y3-x3*y1)+

[0063] (x3 2 +y3 2 )*(x2*y1-x1*y2)

[0064] x = -B / 2A

[0065] y = -C / 2A

[0066] Step 33: Take the average value of the center coordinates of all three-point combinations as the accurate position of the center of the hole profile, Cenc.

[0067] Step 34: Calculate the distance from the center position Cenc to all points on Cir, and take the average value as the calibration radius Rc.

[0068] Step 35: During the calculation process, simultaneously record the sampling point position Tagc corresponding to the maximum value of the fixed target signal. This completes the measurement calibration.

[0069] Step 4 includes the following: using the same high-precision echo time calculation, effective area selection, periodic area calculation, and contour drawing method to calculate and image the hole under inspection. The obtained contour radius Rd and fixed target position Tagd are then used to draw a polar coordinate circle with the center position and Rd' = Rc + Tagd - Tagc as the radius. This circle is called the calibration circle and is marked with a dashed line in the figure. The distance from the abnormal position to the calibration circle is measured as D = R - Rd'.

[0070] The beneficial effects of this invention are as follows: The water immersion mirror inspection method used in the reactor internal component control rod guide tube inspection device and method of this invention reduces the overall space occupied, realizing the automatic inspection requirements of the small space occupied by the inspection area; the use of the water immersion focusing probe in conjunction with the acoustic reflector can change the direction of sound velocity and increase the focal length, thereby improving the inspection sensitivity; the processing of the B-scan signal obtained by ultrasonic inspection, and the fitting of the deviation between the ultrasonic probe axis and the center of the guide tube locator hole and the shape change of the control rod guide locator hole using a specific algorithm, can accurately measure the actual contour of the guide locator hole, improve the defect detection rate, and ensure the accuracy of the inspection results. Attached Figure Description

[0071] Figure 1 This is a schematic diagram of an ultrasonic testing system;

[0072] Figure 2 A schematic diagram of the test block structure for verifying the control rod guide cylinder;

[0073] Figure 3 for Figure 2 Enlarged cross-sectional view along the AA direction;

[0074] Figure 4 A schematic diagram of the control rod guide cylinder comparison test block structure;

[0075] Figure 5 for Figure 4 Enlarged cross-sectional view along the AA direction;

[0076] Figure 6 Actual measurement curves for different δ values;

[0077] Figure 7 Normalized measurement curves for different δ values;

[0078] Figure 8 A schematic diagram for calculating the peak echo location;

[0079] Figure 9 A schematic diagram showing the polar coordinate display of the echo time series;

[0080] Figure 10 This is a schematic diagram for calculating the center of the hole profile.

[0081] In the diagram: 1. Water immersion focused ultrasound probe, 2. Guide card, 3. Acoustic reflector, 4. Rotary motor. Detailed Implementation

[0082] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0083] In nuclear reactors, the guide tubes of the control rods are clustered together. Within a confined space, it is necessary to achieve full acoustic beam coverage of the inner surfaces of all guide tubes and to ensure a high detection rate and sensitivity for all defects.

[0084] This invention breaks away from the traditional method of directly hitting the surface of the object being inspected with a sound beam, and instead uses an acoustic reflection mirror detection system.

[0085] like Figure 1 As shown, a reactor internals control rod guide tube inspection device includes: a water immersion focusing ultrasonic probe 1, an acoustic reflector 3, and a rotary motor 4, all fixed on the same bracket. The water immersion focusing ultrasonic probe 1 emits a sound beam, which is reflected by the acoustic reflector 3 onto a guide tube 2. The rotary motor 4 drives the acoustic reflector 3 to rotate at a constant speed. Simultaneously, the ultrasonic probe 1, acoustic reflector 3, and rotary motor 4 move upwards or downwards at a uniform speed, achieving full coverage of the sound beam on the inner wall of the guide tube. The distance between the water immersion focusing ultrasonic probe 1 and the acoustic reflector 3 must be greater than the probe's focal length and less than the sum of the focal length and the focal column length. The rotary motor 4 is a linear DC motor with a rotation speed of 0.1–100 r / s. The overall movement speed of the ultrasonic probe 1, acoustic reflector 3, and rotary motor 4 must be 0.1–20 mm / s, and coded position output is required.

[0086] The water immersion focused ultrasound probe 1 must meet the following requirements: focal length 10mm ± 2mm; frequency 10MHz ± 2MHz; bandwidth greater than 60%; focal spot diameter 0.25mm ± 0.1mm; focal column length ≥ 4mm.

[0087] Based on the actual operating conditions of the control rod guide plate and in accordance with specifications, the test block and the actual guide plate have the same material, structure, machining, and heat treatment processes. Three types of test blocks are designed for typical locations according to actual needs:

[0088] like Figure 2 and 3 As shown, the control rod guide tube verification test block has artificial reflectors designed on the inner surface of the guide card and the ligament area. The reflectors are designed to closely resemble actual wear and tear, and are used to verify the feasibility of the testing technology.

[0089] like Figure 4 and 5 As shown, the control rod guide tube comparison test block has artificial reflectors designed on the inner surface of the guide card and the ligament area. The guide card is divided into two parts in the thickness direction. One half is an artificial reflector with similar actual wear, and the other half is an intact guide card. In this way, the inspection signals can be clearly compared between the upper and lower parts on the same inspection interface and in the same inspection, which is convenient for comparative analysis.

[0090] The control rod guide tube capability verification test block has artificial reflectors designed on the inner surface of the guide card and in the ligament area. The size of the reflectors can be continuously varied from 0.00 to 2.00 mm in order to verify the testing capability of this testing technology.

[0091] Based on the possible forms and locations of defects during operation, five types of artificial reflectors were designed. These reflectors can cover all areas of the inner surface of the guide card and the ligament zone.

[0092] In the actual inspection process of the control rod guide cylinder, it is impossible to guarantee that the axis of the ultrasonic probe is coaxial with the center of the guide cylinder hole, nor can it guarantee that the center position remains unchanged. At the same time, the shape and size of the inspected guide hole may change due to wear. Therefore, directly using the ultrasonic reflected echo to calculate the outline of the guide cylinder has a large error.

[0093] Therefore, this invention employs a defect quantification method based on echo signal analysis and processing. For the B-scan signal obtained by ultrasonic testing, considering the deviation between the ultrasonic probe axis and the guide tube hole center and the change in the shape of the control rod guide hole, a specific algorithm is used for fitting, and finally the actual contour of the guide hole is measured to achieve accurate quantitative measurement of wear.

[0094] A method for inspecting the guide tubes of control rods for reactor internals includes the following steps:

[0095] Step 1: Apply the correlation comparison method to eliminate the influence of center offset.

[0096] The actual guide hole is not a complete circle, so the actual measured curve should have gaps, such as... Figure 6 As shown, after normalizing these curves, we obtain the normalized curves, as follows. Figure 7 As shown, the normalized measurement curves are almost identical. In cases with numerous uncertainties, the median measurement curve can be used as a calibration curve to calibrate the actual measurement curve.

[0097] Therefore, for the inspection of the guide cylinder, the following two algorithms are used to measure its external dimensions:

[0098] (A) The center offset δ is small enough.

[0099] Step A1: Calibration. During the circumferential rotation of the mirror, the echo distance Ri (i corresponds to the phase angle) of the aperture wall is collected, and the average value of one revolution is Re.

[0100] Step A2: During the circumferential rotation of the reflector, the echo distance ri of the aperture wall after sound velocity correction is collected;

[0101] Step A3: Add the echo distances of the relative phase angles together, di = ri + rj, where di is the sum of the echo distances of the two relative phase angles and rj is the echo distance at phase angle j;

[0102] Step A4: The diameter at phase angle i is D + di - Re * 2; where D is the nominal diameter.

[0103] (B) The center offset δ may have a large value.

[0104] Step B1: Calibration. During the circumferential rotation of the mirror, the echo distance Ri (i corresponds to the phase angle) of the hole wall is collected, and the normalized curve Rg is calculated and obtained.

[0105] Step B2: Use a fitting method to complete the curves into Ri and Rg;

[0106] Step B3: During the circumferential rotation of the reflector, the echo distance ri of the hole wall after sound velocity correction (sound velocity correction) and the corresponding normalized curve rg are collected;

[0107] Step B4: Using a search algorithm and with the correlation coefficient as the metric, calculate the optimal phase offset pa of rg relative to Rg (δ may not be in a fixed phase angle);

[0108] Step B5: Based on pa, correct the original curve ri to obtain the corrected curve rmi;

[0109] Step B6: Directly compare rmi and Ri, the phase deviation value at phase angle i.

[0110] Step 2: Peak Interpolation Algorithm

[0111] To improve the accuracy of shape measurement, it is necessary to obtain the relatively accurate echo positions of each phase angle in the B-scan image, such as... Figure 8 As shown.

[0112] The specific algorithm is as follows:

[0113] Step 21: Obtain the positive or negative peak position [X] n A n ], and the adjacent [X n-1 A n-1 ], [X n+1 A n+1 The data coordinates, where X n A represents the distance from the starting position to a certain positive or negative wave crest. n For X n The amplitude at X n-1 To reduce the distance from the starting position by one unit length, A n-1 For X n-1 The amplitude at X n+1 To increase the distance from the starting position by one unit length, A n+1 For X n+1 The amplitude at that point;

[0114] Step 22: Obtain the true peak position PosX using symmetric interpolation.

[0115]

[0116] Step 23: Selecting the effective region

[0117] In the current system state, the ultrasonic signal is unstable, with numerous interference and noise signals that are easily confused with the effective area, making it difficult to accurately calculate the effective area using a unified algorithm. Therefore, area calculation is performed manually, using a measurement crosshair and a reference crosshair to select the effective area of ​​the data. The two vertical crosshairs are used to select a fixed target signal, while the horizontal crosshair is used to select the effective range in the depth direction.

[0118] Step 24: Calculation of Periodic Region

[0119] The calculation of periodic regions is used to obtain effective hole wall contour signals. Periodic region calculation is achieved through image similarity level search.

[0120] The specific implementation is as follows:

[0121] Step 241: Regional Data Acquisition

[0122] Write the data within the rectangular area selected by the two crosshair cursors into an array Ai (i = 1, 2, 3...) in sequence, and set the horizontal dimension of the rectangle as w (horizontal resolution);

[0123] Step 242: Search threshold setting:

[0124] The threshold Th = (Ai, Ai)0.5*coe is used as the inner product of the array Ai and a fixed coefficient, where the coefficient coe is determined by the system stability and is set to above 0.9.

[0125] Step 25: Similarity Curve Calculation:

[0126] Step 251: Shift the area selected by the crosshair cursor to the right (left), and regenerate the data within the rectangular area after shifting by k horizontal resolutions into an array named Bk (k = 1, 2, 3...) in the same way as in Step 1;

[0127] Step 252: Calculate the inner product of Ai and Bk, denoted as ABk = (Ai, Bk)0.5;

[0128] Step 253: Calculate all ABk (k = 1, 2, 3...) with a horizontal resolution step to obtain the similarity curve;

[0129] Step 26: Locate and fix the target signal:

[0130] Search for all regions greater than Th on the similarity curve ABk, and denote the center position of each region as the fixed position.

[0131] Step 27: Locate the effective periodic signal region;

[0132] The effective periodic signal region is located in the middle area between two adjacent fixed target rectangles.

[0133] The effective hole wall profile signal is the signal within an effective periodic region and within an adjacent fixed target signal range. By progressively performing high-precision echo time calculations on each longitudinal data point in the transverse direction, an echo signal sequence ET over one period can be obtained, with a sequence length (period) of N. Due to the use of equal intervals, the echo time sequence ET can be depicted using polar coordinates.

[0134] The echo time series data comes from a calibration aperture. The notched area in the figure represents the fixed target signal region, while other areas are approximately circular, but some areas are not smooth enough due to signal instability.

[0135] Step 3: Signal Calibration

[0136] Due to the effects of eccentricity, gaps, and signal jitter, the polar coordinate image (aperture profile) of the echo time series is approximately circular. To calibrate the probe system, the measured radius Rc of the calibration aperture needs to be accurately obtained. First, a circle fitting is required for the aperture profile; the center position is first determined, and then the radius is calculated. The specific steps are as follows:

[0137] Step 31: Select points on the hole contour and mark the coordinates of the selected points in the array Cir, selecting a total of Nc contour points;

[0138] Step 32: Select any three points P1(x1,y1), P2(x2,y2), and P3(x3,y3) from Cir to calculate the center coordinates Cen(x,y). The calculation formula is as follows:

[0139] A=x1*(y2-y3)-y1*(x2-x3)+x2*y3-x3*y2

[0140] B = (x1) 2 +y1 2 )*(y3-y2)+

[0141] (x2 2 +y2 2 )*(y1-y3)+

[0142] (x3 2 +y3 2)*(y2-y1)

[0143] C=(x1 2 +y1 2 )*(x2-x3)+

[0144] (x2 2 +y2 2 )*(x3-x1)+

[0145] (x3 2 +y3 2 )*(x1-x2)

[0146] D=(x1 2 +y1 2 )*(x3*y2-x2*y3)+

[0147] (x2 2 +y2 2 )*(x1*y3-x3*y1)+

[0148] (x3 2 +y3 2 )*(x2*y1-x1*y2)

[0149] x = -B / 2A

[0150] y = -C / 2A

[0151] Step 33: Take the average value of the center coordinates of all three-point combinations as the accurate position of the center of the hole profile, Cenc.

[0152] Step 34: Calculate the distance from the center position Cenc to all points on Cir, and take the average value as the calibration radius Rc.

[0153] Step 35: During the calculation process, simultaneously record the sampling point position Tagc corresponding to the maximum value of the fixed target signal. This completes the measurement calibration.

[0154] Step 4: Actual contour measurement

[0155] Using the same high-precision echo time calculation, effective area selection, periodic area calculation, and contour drawing methods, the inspected hole is calculated and imaged, yielding the contour radius Rd and the fixed target position Tagd. Subsequently, a polar coordinate circle, called the calibration circle, is drawn using the center position and Rd' = Rc + Tagd - Tagc as the radius, and is marked with a dashed line on the diagram. The distance from the measurement anomaly location to the calibration circle is D = R - Rd'.

Claims

1. A method for inspecting control rod guide tubes for reactor internals, the method employing a reactor internals control rod guide tube inspection device, the device comprising a water immersion focused ultrasonic probe, an acoustic reflector, and a rotary motor, wherein the water immersion focused ultrasonic probe, the acoustic reflector, and the rotary motor are sequentially fixed on the same support, characterized in that... Includes the following steps: Step 1: Apply the correlation comparison method to eliminate the influence of center offset; Step 1 includes the following: (A) The center offset δ is small enough. Step A1: Calibration. During the circumferential rotation of the mirror, the echo distance Ri from the aperture wall is collected, i corresponds to the phase angle, and the average value for one revolution is Re. Step A2: During the circumferential rotation of the reflector, the echo distance ri of the hole wall after sound velocity correction is collected; Step A3: Add the echo distances of the relative phase angles together, di = ri + rj, where rj is the echo distance at phase angle j; Step A4: The diameter at phase angle i is D + di - Re * 2; where D is the nominal diameter; (B) The center offset δ may have a large value. Step B1: Calibration. During the circumferential rotation of the mirror, the echo distance Ri from the hole wall is collected, and the normalized curve Rg is calculated and obtained. Step B2: Use a fitting method to complete the hole wall echo distance Ri and the normalized curve Rg; Step B3: During the circumferential rotation of the reflector, the echo distance Ri from the hole wall after sound velocity correction and the corresponding normalized curve Rg are collected; Step B4: Using a search algorithm and with the correlation coefficient as the metric, calculate the optimal phase offset pa of rg relative to Rg; Step B5: Based on pa, correct the original curve ri to obtain the corrected curve rmi; Step B6: Directly compare rmi and Ri, the phase deviation value at phase angle i; Step 2: Peak interpolation algorithm; Step 2 includes the following: Step 21: Obtain the positive or negative peak position [Xn, An], and the data coordinates of the adjacent [Xn-1, An-1] and [Xn+1, An+1]; Step 22: Obtain the true peak position PosX using symmetric interpolation. ， Step 23: Selecting the effective region The effective area of ​​data is selected by using a measurement crosshair and a reference crosshair to select the area. Step 24: Calculation of the periodic region; Step 25: Calculate the similarity curve; Step 26: Locate and fix the target signal; Search for all regions greater than Th on the similarity curve ABk, and denote the center position of each region as the fixed target position, where Th is the threshold. Step 27: Locate the effective periodic signal region; The effective periodic signal region is located in the middle area between two adjacent fixed target rectangles. Step 3: Signal calibration; Step 4: Actual contour measurement.

2. The method for inspecting control rod guide tubes for reactor internals as described in claim 1, characterized in that, Step 24 includes the following: The calculation of the periodic region is used to obtain effective hole wall contour signals; the calculation of the periodic region is achieved through image similarity level search, as detailed below: Step 241: Regional Data Acquisition Write the data within the rectangular area selected by the two crosshair cursors into an array Ai in sequence, i=1,2,3..., and set the horizontal dimension of the rectangle as w; Step 242: Search threshold setting: The threshold Th = (Ai, Ai)0.5*coe is used as the inner product of the array Ai and a fixed coefficient, where the coefficient coe is determined by the system stability and is set to above 0.

9.

3. The method for inspecting control rod guide tubes for reactor internals as described in claim 1, characterized in that, Step 25 includes the following: Step 251: Shift the area selected by the crosshair cursor to the right or left, and regenerate the data within the rectangular area after shifting by k horizontal resolutions into an array called Bk, where k = 1, 2, 3...; Step 252: Calculate the inner product of Ai and Bk, denoted as ABk = (Ai, Bk)0.5; Step 253: Calculate all ABk with a horizontal resolution step of 1, where k=1,2,3..., to obtain the similarity curve.

4. The method for inspecting control rod guide tubes of reactor internals as described in claim 1, characterized in that, Step 3 includes the following: Step 31: Select points on the hole contour and mark the coordinates of the selected points in the array Cir, selecting a total of Nc contour points; Step 32: Select any three points P1(x1,y1), P2(x2,y2), and P3(x3,y3) from Cir to calculate the center coordinates Cen(x,y). The calculation formula is as follows: ， Step 33: Take the average value of the center coordinates of all three-point combinations as the accurate position of the center of the hole profile, Cenc. Step 34: Calculate the distance from the center position Cenc to all points on Cir, and take the average value as the calibration radius Rc; Step 35: During the calculation process, simultaneously record the sampling point position Tagc corresponding to the maximum value of the fixed target signal. This completes the measurement calibration.

5. The method for inspecting control rod guide tubes for reactor internals as described in claim 1, characterized in that, Step 4 includes the following: using the same high-precision echo time calculation, effective area selection, periodic area calculation, and contour drawing method to calculate and image the hole under inspection, obtain the contour radius Rd and the fixed target position Tagd, and then use the center position and Rd'=Rc+Tagd-Tagc as the radius to draw a polar coordinate circle, called the calibration circle, which is marked with a dashed line in the figure. The distance from the abnormal position to the calibration circle is D = R-Rd', where Rc is the calibration radius and Tagc is the sampling point position corresponding to the maximum value of the fixed target signal.

Images