JPH061188B2 - Twist inspection method for objects - Google Patents

Description

Detailed Description of the Invention TECHNICAL FIELD OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torsion inspection method for a prismatic elongated object in which a fuel assembly for a fast breeder reactor is an object to be inspected.

[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, the torsional inspection is an important inspection item, along with the inspection of the outer dimension of the fuel assembly, the presence or absence of scratches on the surface, and the bending. 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. Easily twisted. On the other hand, the dimensional accuracy of the fuel assembly is strictly regulated in consideration of the loadability to the nuclear reactor. In this regard, in the conventional inspection, various inspections are performed by using a visual measurement or a contact type sensor, but a high accuracy cannot be obtained by the visual measurement inspection method, and in the method using the contact type sensor, In the inspection process, not only high inspection accuracy cannot be obtained due to wear of the contact portion of the sensor, but also the surface of the fuel assembly may be scratched or soiled. 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 solves the above-mentioned problems of the conventional inspection method and enables a non-contact and accurate inspection of the twist along the longitudinal direction of the object to be inspected. An object is to provide a twist inspection method for an object.

[Points of the Invention]

In order to achieve the above object, the present invention provides two sets of displacement sensors arranged in parallel, each set of two sensors, along an object to be inspected, which is a regular polygonal prism long body having an even surface. The object to be inspected is sandwiched between the two sides of the object to be inspected so that the object can be moved up and down. The obtained virtual vertical center plane of the inspected object is compared with the twist center plane 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, and the reference Obtain the relative inclination of the center plane between the measurement position and the target measurement position, and the average value of the relative twist angle between the virtual center plane and the twist center plane for each opposing surface obtained as described above. The twist of the object to be inspected It is obtained to detect the.

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 a side view and a cross-sectional view showing the twisted state of the fuel assembly, and FIG. 5 is an explanatory diagram for obtaining the twist amount. In each drawing, 1 is a fuel assembly, 11 is an entrance nozzle portion of the fuel assembly 1, 12 is a trumpet tube portion that accommodates fuel elements, and 13 is a top handling head 13.
Reference numeral 14 represents a welded portion between the entrance nozzle portion 11 and the trumpet tube portion 12. On the other hand, the inspection device receives the entrance nozzle portion 11 as shown in FIG.
Object holding mechanism 2 that vertically holds the fuel assembly 1, a non-contact type displacement sensor 3 that is spaced apart from the fuel assembly 1 and faces the side surface of the fuel assembly 1, and the displacement sensor 3 in the longitudinal direction of the fuel assembly 1. It is composed of a remote-operated moving mechanism 4 for moving up and down along with, an arithmetic control unit 5, an inspection monitor unit 6 and the like shown in FIG. 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. It is composed of a turning drive unit 22 and an encoder 23 that detects the turning position of the holding cylinder 21. on the other hand,
As the displacement sensor 3, a highly accurate capacitance type sensor having a resolution of about 35 μm is adopted, and two sets of sensors, one set each including two sensors on both sides of the fuel assembly 1, are provided. ~ 34 are arranged in parallel and opposite to each other. In addition, the moving mechanism 4 is a lift table 41 on which the displacement sensor 3 is mounted.
And a feed screw mechanism 42 for vertically moving the table 41 up and down along the fuel assembly 1, a drive unit 43 of the feed screw mechanism 42, and an encoder for detecting the up-and-down position of the sensor 3 mounted on the table. It consists of 44 and. Both the inspected object holding mechanism 2 and the moving mechanism 4 are of a remote operation type which 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,
Further, the inspection monitor unit 6 is equipped with a printer for outputting the inspection result as a numerical data as a target and a display for outputting as an image. Reference numeral 51 is a signal converter of the sensor. With the above configuration, the fuel assembly 1 is held in the upright posture by the inspected object holding mechanism 2, and the displacement sensors 31 to 34 are opposed to each other on the side surface of the fuel assembly 1 in a non-contact manner. As shown in FIG. 3, the facing distances d1 to d4 between the sensors 31 to 34 and the side surfaces of the fuel assembly 1 facing the sensors 31 to 34 are measured from the sensor output. On the line connecting the centers of the sensors 31 and 33, and 32 and 34, the known distances L ₁ and L ₂ from the origin X of the sensor moving system and the tip of each sensor are read and calculated. The central points m and n of the fuel assembly 1 measured at
Then, a center line P connecting the central points m and n is obtained. Incidentally center point O at the measuring point from the intersection of the line connecting the centers of the sensor 31 based on the known distance L ₃ between 32 and 34 is obtained. The center line P in the cross-sectional direction passing through the center point O determined as described above at the fuel assembly position shown in the drawing coincides with the diagonal line of the fuel assembly 1 having a regular hexagonal cross section. 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. By
It is possible to set three center lines corresponding to each diagonal. Next, the procedure of the twist 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 factor of the twist of the fuel assembly 1 is, as mentioned above, the entrance nozzle portion 11 and the trumpet tube portion 12.
Assuming that the fuel assembly 1 is twisted due to a manufacturing error due to the welded joint between and, the state is as shown in FIG. In this figure, a regular hexagon shown by a solid line shows a cross section of the entrance nozzle portion 11, and a dotted line shows a cross sectional shape of the trumpet tube portion 12. First, as shown in FIG. 4, with the welded joint portion 14 of the fuel assembly 1 as a boundary, the lower entrance nozzle portion 11 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 in the section 11 and the first measurement is performed at this reference measurement position A.
The holding mechanism 2 shown in the figure is used to measure the fuel assembly 1 for each facing surface of the fuel assembly while rotating the fuel assembly 1 by 60 degrees.
By calculating the output data of the displacement sensor 3 by the method described in FIG. 3, the center line in the cross-sectional direction passing through the axial center of the fuel assembly 1 is obtained, and this center line is directly applied to the axial direction of the fuel assembly 1. Set the vertically divided virtual center plane P ₁ of the measurement standard obtained by extension. This imaginary center plane P ₁ is a longitudinally-divided center plane in a fixed direction along the axial direction when it is assumed that the fuel assembly 1 is not twisted, and in the regular hexagonal fuel assembly 1, there is a space between the diagonal ridges. Corresponds to a diagonally divided vertical connection. Next, the moving mechanism 4 shown in FIG. 1 is operated to move the table 41 upward to move the displacement sensor 3 to the trumpet pipe portion of the fuel assembly 1.
The position is set to face an arbitrary target measurement position B (FIG. 4) at 12. Then, similarly to the previous time, from the output data of the displacement sensor 3, the twist center plane P ₂ corresponding to the above-mentioned virtual center plane P ₁ is attached to each facing surface at the target measurement position B, that is, the vertical direction in each direction at the target measurement position B. Find the split diagonal. Here, the virtual center plane P ₁ and the twist center plane P ₂ of the vertical cracks measured on the respective facing surfaces of the fuel assembly 1 at the reference measurement position A and the target measurement position B are shown in FIG. Like In this figure, the relative inclination angles θ1 to θ3 formed by the center planes P ₁ and P ₂ shown by the solid and dotted lines are the reference measurement positions A on the respective facing surfaces of the fuel assembly 1.
Represents a twist angle between the target measurement position B and the target measurement position B. Here, the reference measurement position A and the target measurement position B in the fuel assembly 1 are obtained by obtaining the algebraic average value of the twist angles θ1 to θ3.
It is possible to detect the twist amount θ between and. In the actual inspection of the fuel assembly, the above-described target measurement position B is set at several points along the trumpet tube portion 12 to obtain the amount of twist at each position, and the measurement result is shown in FIG. By displaying the numerical data on the monitor unit 5 and outputting the numerical data as a target, it is possible to judge whether the fuel assembly is twisted or not. As is clear from the above description, for example, in the inspection of the twist of a prismatic elongated inspected object which is a fuel assembly, a displacement sensor is moved along the inspected object while performing a non-contact measurement operation. ing. Therefore, compared to the conventional inspection method, the displacement sensor measures the object to be inspected in a non-contact state, so there is no risk of mechanical wear of the displacement sensor, damage to the surface of the object to be inspected, or contamination, and displacement. Since the sensors are arranged facing each other across the fuel assembly,
Even if there is an eccentricity error in the sensor ascending / descending path, 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 twist 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 can be 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.
Further, even at the reference measurement position, the lower entrance nozzle portion of the fuel assembly is set as the reference measurement position in the illustrated embodiment, but it is not limited to a general inspected object, and a long body It is possible to set a reference measurement position at an arbitrary position on the axis of and to detect a relative twist amount between this position and the displaced target measurement position. Further, the object to be inspected can be inspected even in a state of lying on its side without being erected as in the illustrated embodiment.

【The invention's effect】

As described above, according to the present invention, there are provided two sets of displacement sensors arranged in parallel with each other so as to face an object to be inspected, which is an elongated polygonal prism having an even surface. Of the displacement sensor at the reference measurement position set on the axis of the object to be inspected for each opposing surface of the object to be inspected so as to be movable along the object to be inspected. A fixed direction vertical center plane that serves as the measurement reference of the object to be inspected obtained from the output data, and the virtual 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. The relative center plane inclination between the reference measurement position and the target measurement position is obtained by comparing the twist center plane corresponding to the center plane, and the twist along the longitudinal direction of the inspected object is calculated from the comparison calculation result. To detect the degree By the, it is possible to provide a high torsional test system of practical value can be detected with even higher inspection accuracy only in a non-contact manner the degree of twisting of the inspected object.

[Brief description of drawings]

FIG. 1 is a structural 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 principle explanatory diagram of its measuring method, and FIG. FIG. 5 is a side view and a sectional view showing a twisted state of the object to be inspected, and FIG. 5 is an explanatory diagram for obtaining the twist amount. In each drawing, 1: fuel assembly as an inspected object, 2: inspected object holding mechanism, 3, 31 to 34: displacement sensor, 4: moving mechanism, A:
Reference measurement position, B: Target measurement position, P ₁ : Virtual center plane,
P ₂ : twist center plane, θ: twist amount, θ1 to θ3: twist angles in each direction.

Claims (2)

[Claims] 1. A method for inspecting the degree of twist along a 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,
For each facing surface of the object to be inspected, from the vertical virtual center plane 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, from the reference measurement position Determining the relative center plane inclination between the reference measurement position and the target position obtained from the output data of the displacement sensor at the displaced target measurement position, and a virtual center plane for each target surface obtained by the above A twist inspection method for an object, wherein the twist amount of the object to be inspected is detected by using an average value of a relative twist angle with respect to the twist center plane. 2. The inspection method according to claim 1, wherein the displacement sensor is a capacitance type displacement sensor.