JPH0617793B2 - Bending inspection method for objects - Google Patents

Description

Detailed Description of the Invention TECHNICAL FIELD OF THE INVENTION

The present invention relates to a bending inspection method for a prismatic elongated object whose target is a fuel assembly for a fast breeder reactor, for example.

[Prior art and its problems]

As is well known, the fuel assembly described above is formed as a stainless steel hexagonal column body integrally formed by welding and joining an entrance nozzle portion and a trumpet tube containing a fuel element. Is normally inspected for deformation and the like before it is delivered to the reactor facility after being assembled and manufactured.
In this inspection, along with the inspection of the external dimensions of the fuel assembly, the presence / absence of scratches on the surface, the twist, etc., the bending inspection is an important inspection item. That is, as described above, the fuel assembly is formed as a welded joint between the entrance nozzle portion and the trumpet tube. Therefore, due to welding distortion and manufacturing error in the welding process, the fuel assembly is not along the longitudinal direction. Bends easily. On the other hand, the fuel assembly is strictly regulated so that its dimensional accuracy is within an allowable error of the order of μm in consideration of loadability to a nuclear reactor. In this regard, in the conventional inspection like this, various inspections are carried out by visually measuring or using a contact type sensor with the fuel assembly lying on the floor. In this method, the fuel is first placed in the horizontal posture. Therefore, the bending of the fuel assembly occurs due to the influence of gravity, and accurate bending measurement cannot be performed. Further, in the method using the contact type sensor, not only high inspection accuracy cannot be obtained due to wear of the contact portion of the sensor in the inspection process, but also the surface of the fuel assembly is scratched or soiled. There is a fear. In addition, if the inspection process for inspecting the fuel assembly as an inspection object is not a remote control method, there is a risk that the inspector is exposed to radiation.

[Object of the Invention]

The present invention has been made in view of the above points, and an object that solves the problems of the above-described conventional inspection method and is a non-bending type in which the object to be inspected is bent along the longitudinal direction and can be accurately inspected. It is intended to provide a bending inspection method for

[Points of the Invention]

In order to achieve the above-mentioned object, the present invention provides two sets of displacement sensors arranged in parallel with one set of two sensors along an object to be inspected, which is a regular polygonal prism long body having an even surface. From the output data of the displacement sensor measured for each facing surface at the reference position set on the axis of the object to be inspected in the upright holding state, with the object to be inspected sandwiched so as to be vertically movable. Obtain the cross-sectional center point of the reference measurement position, set a virtual center line in the axial direction passing through the cross-section center point, each of the object to be inspected at the target measurement position displaced from the virtual center line and the reference measurement position By comparing the cross-sectional center point of the target measurement position obtained from the output data of the displacement sensor for each surface, the relative deviation of the axis center between the reference measurement position and the target measurement position is obtained by calculation, and the comparison calculation thereof Result Wherein is obtained to detect the degree of bending along the longitudinal direction of the inspected object.

Examples of the invention

FIG. 1 is a configuration diagram of an inspection apparatus according to an embodiment of the present invention in which a fuel assembly of a nuclear reactor is an object to be inspected, FIG. 2 is an inspection system system diagram thereof, and FIG. 3 is a principle explanatory view of its measuring method,
FIG. 4 is an external side view and a cross-sectional view showing a bent state of the fuel assembly, FIG. 5 is a schematic diagram of FIG. 4, and FIG. 6 is an explanatory view of a vector synthesizing method for obtaining the bend amount. is there. In each figure, 1 is a fuel assembly and 11 is a fuel assembly 1.
Of the entrance nozzle portion, 12 is a trumpet tube portion containing a fuel element, and 13 is a top handling head 13. Reference numeral 14 indicates a welded portion between the entrance nozzle portion 11 and the trumpet tube portion 12. Second, the inspection device is second
As shown in the figure, an object holding mechanism 2 to be inspected for receiving the entrance nozzle portion 11 and standingly holding the fuel assembly 1 in a vertical posture, and a non-contact type which is spaced apart from the fuel assembly 1 and faces the side surface thereof. A displacement sensor 3, a remote-operated lift drive mechanism 4 for moving the displacement sensor 3 up and down along the longitudinal direction of the fuel assembly 1, an arithmetic control unit 5, an inspection monitor unit 6 and the like shown in FIG. It is composed of. The inspected object holding mechanism 2 described above receives the entrance nozzle portion 11 of the fuel assembly 1 from below and holds the holding cylinder 21 in an upright posture, and pivots the holding cylinder 21 around its axial center. Revolving drive unit 22 and holding cylinder 2
The encoder 23 detects one turning position. On the other hand, the displacement sensor 3 employs a highly accurate capacitance type sensor having a resolution of about 35 μm, and two sensors are provided on each side of the fuel assembly 1 with the sensor 1 interposed therebetween.
Two sets of sensors 31 to 34 are arranged in parallel and face each other. The lift drive mechanism 4 includes a lift table 41 having the displacement sensor 3 mounted thereon and a feed screw mechanism 4 for vertically moving the table 41 along the fuel assembly 1.
2, a drive unit 43 of the feed screw mechanism 42, and an elevation position detection encoder 44 of the sensor 3 mounted on the table. The holding mechanism 2 and the elevating / lowering mechanism 3 are both of a remote operation type that operates according to an operator's command from the outside. The arithmetic control unit 5 shown in FIG. 2 has an arithmetic function of taking in the output signals of the displacement sensors 31 to 34 and the encoders 23 and 44 and processing the data, and the inspection monitor unit 6 is further provided. It is equipped with a printer that outputs inspection results as numerical data and a display that outputs them as images. Reference numeral 51 is a signal converter of the sensor. With the above configuration, the fuel assembly 1 is held in the standing posture by the holding mechanism 2, and the displacement sensors 31 to 3 are provided on the side surface of the fuel assembly 1.
4 in a non-contact opposed position, and in this state, first, as shown in FIG. 3, the opposed distances d1 to d4 between the sensors 31 to 34 and the side surface of the fuel assembly 1 opposed thereto are measured from the sensor output. To do. The sensors 31 and 33, and 3 are obtained by taking in the known distances L ₁ and L ₂ from the origin X of the lifting drive system and the tip of each sensor described above, and performing arithmetic processing.
The central points m and n of the fuel assembly 1 measured on the line connecting the centers of 2 and 34 are obtained. Next, the center point O on the center line P connecting the center points m and n is calculated, and this center point O is set as the center point on the facing surface. This calculation will be described below with reference to FIG. 3, for example. I. Suppose that the surfaces to be measured are A and D surfaces. B. The facing distance from the A side reference surface of the sensor to the A surface is d
₁ , d ₂ , and the facing distances from the D-side reference surface of the sensor to the D surface are d ₃ and d ₄ . Coordinate from the origin X of the lifting drive system until the middle point m _{[L 2 -L 1 - (d 1} + d 3) ] _{/ 2 + L 1 + d 1} =
(L ₂ + L ₁ + d ₁ −d ₃ ) / 2 Coordinates from the origin X of the lifting drive system to the central point n [L ₂ −L ₁ − (d ₂ + d ₄ ) / 2 + L ₁ + d ₂ = (L ₂ + L ₁ + _d 2 _-d 4) / 2 c. The center point O of the A and D planes is obtained as the center between the coordinates of the center point m and the coordinates of the center point n, and the coordinates from the origin X of the lifting drive system to the point O = (coordinates of m point + coordinates of n point) / _{2 = (L 2 + L 1} ) / 2 + (d 1 + d 2 -d 3 -d 4) / 4 d. B, E side, C.I. The center coordinates between the F planes are calculated in the same manner. Further, the regular hexagonal fuel assembly 1 is rotated by 60 degrees around its axis by the holding mechanism 2 shown in FIG. 1, and the same measurement as above is carried out for each facing surface of the fuel assembly 1 each time. The center point obtained by the measurement of each facing surface is calculated by the least square method so that the error is minimized. Thereby, the center point O ₁ at the reference measurement position of the fuel assembly 1 can be set with high accuracy. Next, the procedure of the bending inspection in the longitudinal direction of the fuel assembly 1 as the object to be inspected by the above-described inspection device will be described. That is, the largest cause of the bending of the fuel assembly 1 is the manufacturing error caused by the welded joint between the entrance nozzle portion 11 and the trumpet tube portion 12 as described above, and the bending of the fuel assembly 1 occurs. Then, the situation is as shown in FIG. In this figure, a regular hexagon shown by a solid line shows a cross section of the entrance nozzle part 11, and a dotted line shows a cross section of the trumpet tube part 12. Here, as shown in FIG. 4, with the welded joint portion 14 of the fuel assembly 1 as a boundary, the entrance nozzle portion 11 on the lower side thereof is set as a reference measurement range, and the upper trumpet tube portion 12 is set as a target measurement range. The reference measurement position A is set at 11, and the cross-section center point O ₁ is obtained from the output data of the displacement sensor 3 at the reference measurement position A by the method described in FIG. 3, and the fuel assembly is passed through this center point. An imaginary center line indicated by reference numeral C in FIG. The reference center line C is an axial center line on the assumption that the fuel assembly 1 is not bent. Next, the elevating and lowering drive mechanism 4 in FIG. 1 is operated to move the table 41 upward, and the displacement sensor 3 is moved to an arbitrary target measurement position B (fourth position) in the trumpet tube portion 12 of the fuel assembly 1.
(See figure). Next, similarly to the previous time, the cross-sectional center point O ₂ of the fuel assembly 1 at the target measurement position B is obtained from the output data of the displacement sensor 3. Here, the cross-sectional positions of the fuel assembly 1 at the reference measurement position A and the latter target measurement position B described above are the regular hexagons of the solid line and the dotted line shown in FIG. 6, and the centers of the solid line and the dotted line in this figure. The relative displacement of the points O ₁ and O _{2 in} the cross-sectional direction represents the bending amount S of the target measurement position B with respect to the reference measurement position A of the fuel assembly 1. On the other hand, the bending amount S can be obtained by vector synthesis. By the way, the method for determining the bending of the fuel assembly 1 which is a regular hexagonal prismatic long-length body No. 6
It will be described with reference to the drawings. 11 is an entrance nozzle portion of the fuel assembly 1, O ₁ is a cross-section center point at the reference measurement position, 12 is a trumpet tube portion of the fuel assembly 1, and O ₂ is a cross-section center point at the target measurement position. For each facing surface, the vectors S ₁ , S ₂ , and S ₃ of the relative displacement components with respect to the virtual center line in that direction are obtained, and first, the vector S
Combining ₁ and vector S ₂ , vector S ₂ and vector S
₃ and the combination of the vector S ₁ and the vector S ₃ . Furthermore, when the vector (S ₁ + S ₃ ), that is, O ₁ I is combined with the vector O ₁ G that is the combination of the vector (S ₁ + S ₂ ) and the vector (S ₂ + S ₃ ), the vector O ₁
H is obtained, which is 2 of the vector (S ₁ + S ₂ + S ₃ ).
Equivalent to double vector. Vector (S ₁ + S ₂ +
S ₃ ) is at the position 1/2 on the vector O ₁ H and is the vector O ₁ O ₂ . Cross-section center point O at target measurement position B
₂ is found in the center on the vector O ₁ H. In this way, the bending direction O ₁ O ₂ of O ₂ with respect to the center point O ₁ and the magnitude S of the bending amount can be obtained. Here, the degree of bending in the axial direction between the respective measurement positions A and B obtained in the above is represented by a line D in FIG. In addition, the target measurement position B described above is set to the trumpet pipe section 1
Setting several points along 2 to obtain the direction and magnitude of the bending amount at each position, display the measurement result on the inspection monitor unit 5 shown in FIG. 2 and output the numerical data as a target. This makes it possible to determine whether the fuel assembly bends or not. As is clear from the above description, bending inspection of a long inspected object such as a fuel assembly is performed in a holding state in which the inspected object is vertically erected and the displacement sensor is moved up and down along the inspected object. The measurement operation is performed in a non-contact type while moving. Therefore, as compared with the conventional inspection method, since the inspection object is in the vertical standing posture, the inspection object is not bent in the axial direction due to gravity, and the error in the inspection accuracy due to the influence of gravity can be eliminated. Further, since the displacement sensor measures the object to be inspected in a non-contact state, there is no risk of mechanical wear of the displacement sensor and damage or contamination of the surface of the object to be inspected. Since the sensors are arranged opposite to each other, even if there is an eccentricity error in the middle of the ascending / descending drive path of the sensor, the error can be offset and compensated, and correct measurement can always be performed. Furthermore, a series of inspection operations can be performed by remote control, and even when a fuel assembly is targeted, there is an advantage that the inspection can be safely performed without risk of radiation exposure. Although the illustrated embodiment has been described with respect to the bending inspection of the inspected object for the regular hexagonal fuel assembly, the inspected object is not limited to the fuel assembly, and the prismatic elongated body of various shapes is used. Needless to say, the same can be applied to the above. In this case, by arranging the displacement sensor in FIG. 1 so that it can move back and forth with respect to the lifting table and detecting the amount of movement by an encoder,
It is possible to easily deal with inspected objects of various sizes.
Even at the reference measurement position, the lower entrance nozzle portion of the fuel assembly was set as the reference measurement position in the illustrated embodiment,
The general inspected object is not limited to this, but the reference measurement position is set at an arbitrary position on the axis of the long body, and the relative bending between this position and the displaced target measurement position. The amount can be detected.

【The invention's effect】

As described above, according to the present invention, an object to be inspected, which is a polygonal prismatic elongated body, is held in an upright posture, and a non-contact displacement sensor is attached to the object to be inspected on the side of the object to be inspected. It is arranged so that it can move up and down along the surface of the object to be inspected, and it becomes the measurement reference of the object to be inspected obtained from the output data of the displacement sensor at the reference measurement position set on the axis of the object to be inspected while standing up and holding for each opposing surface. Of the reference measurement position and the target measurement position by comparing the virtual center line in the axial direction and the cross-sectional center point at the target measurement position obtained from the output data of the displacement sensor at the target measurement position displaced from the reference measurement position By calculating the relative deviation of the axis center between them, and detecting the degree of bending along the longitudinal direction of the inspected object from the comparison calculation result, the degree of bending of the inspected object is non-contact In the formula It is possible to provide a high bending test method of practical value which can be detected with high inspection accuracy.

[Brief description of drawings]

FIG. 1 is a configuration layout diagram of an inspection device according to an embodiment of the present invention, FIG. 2 is a system diagram of an inspection system of the inspection device of FIG. 1, FIG. 3 is a diagram explaining the principle of the measuring method, and FIG. FIG. 5 is a side view and a cross-sectional view showing the bending state of the object to be inspected, FIG. 5 is a schematic diagram schematically showing the bending state of FIG. 4, and FIG. 6 is an explanatory diagram of a vector combining method for obtaining the bending amount. In each figure, 1: fuel assembly as an inspected object, 2: inspected object holding mechanism, 3, 31 to 34: displacement sensor, 4: lifting drive mechanism, A: reference measurement position, B: target measurement position, C: virtual center line set at the reference measurement position, O ₁ : cross-section center point of the reference measurement position, O ₂ : cross-section center point of the target measurement position, S: bending amount, S _{1 to} S ₃ : each of the inspected objects Bending component in the opposite direction.

Claims (2)

[Claims] 1. A method for inspecting the degree of bending along the longitudinal direction of an object to be inspected, which is an elongated polygonal prism having an even numbered surface, and is a parallel arrangement having two sensors as one set. The two sets of displacement sensors are arranged opposite to each other on both sides of the object to be inspected so as to be movable up and down along the object to be inspected,
Obtain the cross-sectional center point of the reference measurement position from the output data of the displacement sensor measured for each facing surface at the reference position set on the axis of the object to be inspected in the upright holding state, and the axial direction passing through this cross-sectional center point. The virtual center line is set, and the cross-sectional center point of the target measurement position obtained from the output data of the displacement sensor for each facing surface of the inspected object at the target measurement position displaced from the virtual center line and the reference measurement position. In order to detect the degree of bending along the longitudinal direction of the inspected object from the comparison calculation result, the relative deviation of the axial center between the reference measurement position and the target measurement position is calculated. Bending inspection method for objects characterized by 2. A bending inspection method for an object according to claim 1, wherein the displacement sensor is a capacitance type displacement sensor.