JPH11337679A - Reactor fuel assembly inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for inspecting the gap between a water rod and fuel rods in a fuel assembly from outside of the fuel assembly. SOLUTION: In a method for inspecting the gap between a water rod 510 provided in a fuel assembly 550 of a reactor and fuel rods 520, based on the result which an illumination from a transmission illumination device 200 is penetrated to a fuel assembly 550, and the fuel assembly 550 is photographed with an image input unit 100 at the opposite side of the transmission illumination device 200, apparent gap between the water rod 510 and the fuel rods 520 which cross perpendicular to the transmission direction is measured as an actual dimension. Then executed are a process for obtaining the actual dimension by the image process unit 300 of an image input unit 100, a process for deciding pass/fail by comparing the determined value and the actual dimension and a process for outputting and indicating the pass/fail decision results to an external output device 400.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for inspecting a distance between a water rod and a fuel rod, which are elements constituting a fuel assembly of a nuclear reactor, in the fuel assembly.

[0002]

2. Description of the Related Art A fuel assembly of a nuclear reactor has a structure in which a plurality of fuel rods are arranged in a grid arrangement of 8 rows and 8 rows or 9 columns and 9 rows, and a water rod is provided at the center thereof.

[0003] A conventional fuel rod is formed by putting uranium dioxide as a fuel into a tubular coating tube in the form of pellets.
It is referred to as an O ₂ (uranium dioxide) fuel assembly.

As inspection items for a fuel assembly of a nuclear reactor, there are inspection of a gap between fuel rods and inspection of a gap between a water rod and a fuel rod.

As for the UO ₂ (uranium dioxide) fuel assembly, since the fuel is not used in the inspection at the time of fresh fuel and no radiation is emitted from the fuel, the interval inspection between the water rod and the fuel rod is performed. The fuel inspector held the jig in his hand and inserted it between the water rod and the fuel rod. The jig was inspected by checking the jig insertion status and visual check to see if there was an interval longer than specified.

As another conventional example, the distance between fuel rods is limited. However, Japanese Patent Application Laid-Open No. 9-280828 discloses an image obtained by taking an image of the periphery of a fuel rod of a fuel assembly with a color camera and taking an image. A method of measuring the distance between fuel rods from information using an image processing device is described.

[0007]

In the conventional UO ₂ fuel assembly inspection at the time of new fuel, an inspector directly performs an inspection by using a test jig directly held by a hand, which requires a great deal of labor. Had become. The spent fuel emits radiation, and the fuel assembly is a mixture oxidized fuel (MOX fuel).
When the fuel is used as the fuel, the radiation from the fuel is emitted even when the fuel is fresh, so that the inspector cannot approach from the viewpoint of preventing exposure, and it is necessary to devise a remote inspection method. The remote inspection method and apparatus are disclosed in Japanese Patent Application Laid-Open No. 9-280828 as the above-mentioned prior art, but the water rod is located at the center of the fuel assembly and is surrounded by fuel rods. Due to their geometrical positional relationship, the fuel rod adjacent to the water rod is disturbed by the other fuel rods around it, and its color is measured from the direction in which the distance between the water rod and the adjacent fuel rod can be measured. It cannot be imaged or viewed directly by the camera.

Accordingly, an object of the present invention is to provide a method for remotely inspecting the distance between a water rod of a fuel assembly of a nuclear reactor and a fuel rod adjacent thereto.

[0009]

Means for attaining the object of the present invention is to provide a water rod and a fuel rod which are viewed from one side of a fuel assembly of a nuclear reactor including a water rod and a fuel rod. A fuel assembly inspection method for a nuclear reactor, characterized in that a pass / fail judgment is made by judging whether the interval satisfies a predetermined value to be a pass / fail judgment value when viewed from the one side, and a fuel assembly of the reactor. In the method for inspecting the interval between the equipped water rod and the fuel rod, the water rod and the fuel rod orthogonal to the direction of the transmission based on the result of imaging the fuel assembly that has passed through the illumination with an imaging device. Atomic distance is measured as an actual dimension, and a pass / fail judgment is made by determining whether the actual dimension satisfies a predetermined value to be a pass / fail judgment value of the apparent distance dimension. Furnace fuel Aggregate inspection method, and by an image processing unit that performs image processing based on the output signal from the imaging device, a process of obtaining the measured dimensions, and performing the pass / fail determination by comparing the default value and the measured dimensions. A method for inspecting a reactor fuel assembly, comprising: executing a process to be performed and a process of outputting a result of the pass / fail judgment to a display unit.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for inspecting a distance between a water rod and a fuel rod of a fuel assembly of a nuclear reactor according to the present invention will be described in detail with reference to the drawings.

As shown in FIG. 2, the fuel assembly inspection apparatus has an image input unit 100 (generally referred to as an image pickup device) and an image input unit 100 on the opposite side of the fuel assembly. , An image processing unit 300 connected to receive an output signal from the image input unit 100, and an external device serving as a display unit connected to receive an output signal from the image processing unit 300 It comprises an output device 400. The image input unit 100 and the transmitted illumination device 200 are located with the fuel assembly 550 to be inspected interposed therebetween.

First, the inspection dimensions 53 of the water rod 510 and the fuel rod 520 incorporated in the fuel assembly 550 for the fuel assembly 550 having the number of fuel rods of 8 × 8 type.
A method of inspecting whether or not one interval is properly secured will be described.

FIG. 3 shows the fuel assembly 55 of the 8 × 8 type.
0 shows a plan sectional view. 8 × 8 type fuel assembly 5
At 50, the fuel rods 520 are bundled and arranged in a grid arrangement of eight columns and eight rows, and the fuel rods at the center of the bundle are replaced with water rods 510. For this reason, the fuel assembly has four sides with a rectangular cross section.

Water rod 510 and water rod 5
Inspection dimension 53, which is the distance between fuel rods 520 adjacent to 10
1 needs to measure the location indicated by the arrow in FIG.
However, in order to measure this dimension with the image input unit 100, the image is taken from a direction perpendicular to a line connecting the center of the water rod 510 and the center of the fuel rod 520, that is, a direction perpendicular to the line of the thick arrow in FIG. However, other fuel rods are in the way, and it is difficult to take a picture at right angles.

Therefore, as shown in FIG. 4, the image input unit 100 is provided on one side of the fuel assembly 550 for the 8 × 8 type fuel assembly 550, and is opposed to the opposite side. The transmission illumination device 200 is located on the opposite side of the image input unit 100, and light from the transmission illumination device 200 is transmitted in the direction of the arrow in FIG. The dimensional inspection is performed by inputting and confirming that the image passes through the interval to the image input unit 100.

The dimensional inspection is performed by the method shown in FIG. The dimension of the space between the water rod 510 to be inspected and the adjacent fuel rod 520 is determined by an inspection dimension 531.
The width dimension of the light emitted from the transmitted illumination device 200 and passing between the water rod 510 and the adjacent fuel rod 520 and entering the image input unit 100 is determined by an apparent actually measured dimension 532 with respect to the inspection dimension 531. The center of the water rod 510 and the adjacent fuel rod 520
Of the center of the water rod 510 from the intersection of a perpendicular line extending from the center of the water rod 510 to a straight line connecting the centers of two adjacent fuel rods 520. The distance dimension to the center is B dimension 534, and from the intersection of a perpendicular line extending from the center of the water rod 510 to a straight line connecting the centers of two adjacent fuel rods 520 to the center of the water rod 510. Distance dimension of C dimension 535
Then, the diameter of the water rod 510 is changed to WR dimension 5
At 36, the diameter dimension of the adjacent fuel rods 520 is FR dimension 537 and two adjacent fuel rods 52 are adjacent to each other.
The distance dimension of a straight line connecting the center of 0 to the dimension 53 between FR centers
Shown at 8.

Here, the WR dimension 536 and the FR
The minimum value of the dimension 537 and the maximum value of the FR center-to-center dimension 538 are known in view of the manufacturing dimensional tolerance of the fuel assembly 500. From the geometric relationship in FIG.
3 is a half of the WR dimension 536 and the inspection dimension 531
And a half of the FR dimension 537.

(A dimension 533) = (WR dimension 536) / 2 +
(Inspection dimension 531) + (FR dimension 537) / 2 Also, from the geometric relationship in FIG. 1, the B dimension 534 is half of the FR center-to-center dimension 538.

(B dimension 534) = (FR center dimension 538) / 2 Also, from the geometric relationship in FIG. 1, the C dimension 535 is half of the WR dimension 536, the measured dimension 532, and the F dimension.
This is a dimension obtained by adding half of the R dimension 537.

(C dimension 535) = (WR dimension 536) / 2 +
(Measured size 532) + (FR size 537) / 2 Also, the A size 533, the B size 534, and the C size
Since the triangle having the dimension 535 is a right-angled triangle having the A dimension 533 on the hypotenuse from the geometric relationship in FIG.
According to the three-square theorem, the sum of the square of the dimension B 534 and the square of the dimension C 535 is the square of the dimension A 533.

From the relationship of (A dimension 533) ² = (B dimension 534) ² + (C dimension 535) ² or more, if the measured dimension 532 is measured, the inspection dimension 531 to be inspected can be obtained by calculation. .

Here, an example of a method of measuring dimensions by image processing will be described. The illumination light from the transmission illumination device 200 passes between the water rod 510 and the adjacent fuel rod 520 and is imaged by the image input unit 100. An analog video signal captured and input by the image input unit 100 is converted into a digital signal by the image processing unit 300, and becomes a signal having a luminance value as shown in FIG. At this time, as the illumination, the transmission illumination device 200 is used.
As shown in FIG. 8, the digitized image near the contour of the water rod 510 and the adjacent fuel rod 520, which is a measuring unit, has a feature that the brightness changes sharply.

In FIG. 8, a pixel 901 is arranged in the X-axis direction.
Indicates the luminance 902 in the Y-axis direction. Since the distance from when the pixel 901 in the X-axis direction changes from dark to bright and then becomes dark is the measured dimension 532 between the water rod 510 and the adjacent fuel rod 520, the number of pixels is calculated by using The calculation is performed by the processing unit 300. At this point, the unit of the calculated number of pixels is only "pixel",
It is necessary to multiply this by a conversion constant for converting this into the unit of dimension “mm”. The conversion constant is the same distance as the measurement site in advance, and a scale or the like whose dimensions are known in advance,
In the same manner as described above, it can be obtained by associating “pixels” calculated by photographing with the image input unit 100 and processing with the image processing unit 300 and “mm” which is the original dimension. The dimension measurement flow will be described with reference to FIG. First, in step 1, the analog video signal input from the image input unit 100 is digitized by the image processing unit 300 (A
/ D conversion). Next, in step 2, an end point (end point 1) on the measurement side of the water rod 510 is determined. next,
In step 3, the end point (end point 2) on the measurement side of the adjacent fuel rod 520 is determined. Next, in step 4, a distance (distance 1) between the end points 1 and 2 is obtained. Next, in step 5, in order to perform the actual distance conversion, the actual distance (the actual distance 1) is obtained by multiplying the distance 1 whose unit is “pixel” by a conversion constant to set the unit to “mm”. Next, in step 6, by comparing the actual distance 1 with a criterion as a default value,
The pass / fail of the inspection is determined. Finally, in step 7, an output representing the determination result from the image processing unit 300 is sent to the external output device 400, and the pass / fail determination result is displayed on the external output device 400. Further, a flow of obtaining the conversion constant will be described with reference to FIG. First, in step 1, the analog video signal input from the image input unit 100 is digitized by the image processing unit 300 (A
/ D conversion). Next, in step 2, one end point (end point 1) such as a scale is obtained. Next, in step 3, the other end point (end point 2) of the scale or the like is determined. next,
In step 4, the distance between end point 1 and end point 2 (distance 1)
Ask for. Finally, in step 5, the actual size of the scale or the like known in advance is divided by the distance 1 to obtain a conversion constant.

Each of the steps shown in FIGS. 9 and 10 is processed by the image processing unit 300. For this purpose, the image processing unit 300 is provided with processing means such as a program for processing these steps.

The dimensions between the water rod and the fuel rod are measured by these methods. In practice, in the case of the 8 × 8 type fuel assembly 550, the WR dimension 536 is 34.0.
0 mm, the FR dimension 537 is 12.27 mm, the FR center dimension 538 is 16.256 mm, and assuming that the measured dimension 532 is 0.000 mm, the inspection dimension 531 is assumed.
Is 1.39 mm.

On the other hand, since the inspection dimension 531 is 1.3 mm or more from the requirement of the fuel inspection, if the measured dimension 532 exceeds 0.00 mm, the 8 × 8
The inspection of the distance between the water rod 510 and the adjacent fuel rod 520 for the type of fuel assembly 550 is determined to be acceptable.

That is, in the case of the 8 × 8 type fuel assembly 550, there is no need to actually measure the dimensions.
If the light from the transmission illumination device 200 is captured by the image input unit 100 and can be confirmed by the external output device 400, the inspection is determined to be a pass. This allows the image processing unit 300 to judge the presence or absence of the light so that the inspection determination can be performed by an unattended person without a person checking the image of the external output device 400. this is,
In FIG. 8, the image processing unit 300 only needs to determine that the luminance value has changed. The water rod 510 and the adjacent fuel rod 5
Although the transmission illumination device 200 and the image input unit 100 are used for the inspection during the period 20, the same can be applied by using other sensors such as a light emitting unit and a light receiving unit of infrared rays or laser.

Next, a method of inspecting the distance between the water rod and the fuel rod for the fuel assembly 570 having 9 × 9 fuel rods will be described.

FIG. 5 shows the 9 × 9 type fuel assembly 57.
0 shows a sectional view. Fuel rods are bundled and arranged in nine columns and nine rows, and the center part of the bundle is composed of two water rods 510.
In the 9 × 9 type fuel assembly 570 replaced with the above, the distance between the water rod 510 and the adjacent fuel rod 520 needs to be measured at the location indicated by the arrow in FIG.

However, the size of the image input unit 10
To measure at zero, it is necessary to take a picture from a direction perpendicular to these arrows, but it is difficult to take a picture from the perpendicular direction because other fuel rods are in the way.

Therefore, as shown in FIG. 6, the image input unit 1 is attached to the 9 × 9 type fuel assembly 570.
00, the light from the transmitted illumination device 200 located on the opposite side to the water rod 510 and the adjacent fuel rod 5
It is said that the image input unit 1
A dimensional inspection is performed by checking at 00. The dimensional inspection is performed by the method shown in FIG.

The water rod 5 to be inspected for dimensions
The distance between the fuel rod 10 and the adjacent fuel rod 520 is the inspection dimension 531, emitted from the transmitted illumination device 200, passed between the water rod 510 and the adjacent fuel rod 520, and transmitted to the image input unit 100. The width dimension of the incoming light is the measured dimension 532, and the distance between the center of the water rod 510 and the center of the adjacent fuel rod 520 is A
With respect to a straight line connecting the center of the adjacent fuel rod 520 and the adjacent fuel rod 525 located on the center line of the 9 × 9 type fuel assembly 570 with the dimension 533, the center of the water rod 510 The distance dimension from the intersection with the lowered perpendicular line to the center of the adjacent fuel rod 520 is B dimension 534, and the distance dimension between the adjacent fuel rod 520 and the center line of the 9 × 9 type fuel assembly 570 adjacent to the adjacent fuel rod 520. With respect to the straight line connecting the center with the fuel rod 525 located at
The distance dimension from the intersection with the perpendicular line lowered from the center of the water rod 510 to the center of the water rod 510 is C dimension 535, the diameter dimension of the water rod 510 is WR dimension 536, and the distance dimension of the adjacent fuel rod 520 is The diameter dimension is FR dimension 537, and the adjacent fuel rod 520
The distance dimension of a straight line extending from the center of the water rod 510 to the center of the fuel rod 525 positioned adjacent to the center of the 9 × 9 type fuel assembly 570 is defined as an FR center distance dimension 538. × 9 type fuel assembly 5
The length of the perpendicular line lowered on the center line of 70 is indicated by WR perpendicular line size 539.

Here, the WR dimension 536, the FR dimension 537, the FR center-to-center dimension 538, and the WR perpendicular dimension 539 are known in consideration of manufacturing dimension tolerance of the fuel assembly 500.

From the geometric relationship shown in FIG.
3 is a half of the WR dimension 536 and the inspection dimension 531
And a half of the FR dimension 537. (A dimension 533) = (WR dimension 536) / 2 + (Inspection dimension 5
31) + (FR dimension 537) / 2 Further, from the geometric relationship in FIG. 7, the B dimension 534 is a dimension obtained by subtracting the WR perpendicular dimension 539 from the FR center dimension 538.

(Dimension B 534) = (Dimension 538 between FR centers)
− (WR perpendicular dimension 539) Also, from the geometric relationship in FIG. 7, the C dimension 535 is half of the WR dimension 536, the measured dimension 532, and the F dimension.
This is a dimension obtained by adding half of the R dimension 537.

(C dimension 535) = (WR dimension 536) / 2 +
(Measured size 532) + (FR size 537) / 2 Also, the A size 533, the B size 534, and the C size
Since the triangle having the dimension 535 is a right-angled triangle having the A dimension 533 on the hypotenuse from the geometric relationship in FIG.
According to the theorem of three squares, the sum of the square of the dimension B 534 and the square of the dimension C 535 is the square of the dimension A 533.

From the relationship of (A dimension 533) ² = (B dimension 534) ² + (C dimension 535) ² or more, if the actually measured dimension 532 is measured, the inspection dimension 531 to be inspected can be obtained by calculation. .

The method of measuring the dimensions by image processing is the same as the method of measuring the dimensions of the 8 × 8 type fuel assembly described above. The dimensions between the water rod and the fuel rod are measured by these methods. Actually, in the case of the 9 × 9 type fuel assembly 570, the WR dimension 536 is 24.89 mm, and the FR dimension 537 is 11.2 mm. 18 mm, the FR center dimension 538 is 14.376 mm, and the WR perpendicular dimension 539 is 9.
Since it is 35 mm, assuming that the inspection dimension 531 is 1.41 mm, which is a requirement for fuel inspection, the measured dimension 532 is calculated to be 0.75 mm, so that the measured dimension 532 is 0.75 mm or more. If there is, the interval dimension inspection between the water rod 510 and the adjacent fuel rod 520 with respect to the 9 × 9 type fuel assembly 570 is determined to be calculationally acceptable.

In consideration of the dimensional tolerance and the like, the actually measured size 532 is 0.7 to satisfy the fuel inspection requirement.
6 mm or more is required. In addition, the water rod 51
Although the transmission illumination device 200 and the image input unit 100 are used for the inspection between the fuel rod 520 and the adjacent fuel rod 520, other sensors such as a light-emitting part and a light-receiving part of an infrared ray or a laser may be used. It is equally possible.

According to each embodiment of the present invention, the dimensional inspection of the interval between the water rod and the fuel rod of the fuel assembly, which was conventionally difficult, can be performed from the outside of the fuel assembly. Eliminating the work inside the fuel assembly, which is in between, reduces the exposure of inspectors,
It also has the advantage of reducing the labor required for inspectors and contributing to nuclear safety management. For this reason, even if the fuel assembly uses MOX fuel, it is possible to contribute to the safety management of nuclear power by executing the pass / fail inspection of the interval between the water rod and the fuel rod while reducing the exposure of the inspector.

[0041]

According to the first aspect of the present invention, it is possible to determine whether the distance between the water rod and the fuel rod inside the fuel assembly, which cannot be directly measured, is acceptable or not based on the measurement result that can be measured from outside the fuel assembly. In addition, the pass / fail inspection of the distance between the water rod and the fuel rod can be performed, and the exposure of the worker during the inspection can be reduced.

According to the second aspect of the present invention, data required for inspection can be easily captured from a remote place by using a change in luminance by using an image device, thereby facilitating inspection work and further reducing exposure of workers. it can.

According to the third aspect of the present invention, in addition to the effect of the second aspect of the present invention, it is possible to automatically judge whether or not the distance between the water rod and the fuel rod is acceptable by using the data acquired by the video equipment. Inspection work is further facilitated.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an inspection method of an 8 × 8 type fuel assembly according to an embodiment of the present invention.

FIG. 2 is an overall view of an inspection apparatus according to an embodiment of the present invention.

FIG. 3 is a plan cross-sectional view of a fuel assembly in which a dimension inspection point of an 8 × 8 type fuel assembly according to an embodiment of the present invention is indicated by a thick arrow.

FIG. 4 is a conceptual diagram showing an inspection status of an 8 × 8 type fuel assembly according to an embodiment of the present invention.

FIG. 5 is a plan cross-sectional view of the fuel assembly of the 9 × 9 type fuel assembly according to the embodiment of the present invention, in which dimension inspection points are indicated by thick arrows.

FIG. 6 is a conceptual diagram showing an inspection state of a 9 × 9 type fuel assembly according to an embodiment of the present invention.

FIG. 7 is an explanatory diagram of a method for inspecting a 9 × 9 type fuel assembly according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a change in luminance between a water rod and a fuel rod and a relationship between the water rod and the fuel rod according to the embodiment of the present invention.

FIG. 9 is a diagram showing a flow of dimension measurement according to the embodiment of the present invention.

FIG. 10 is a diagram showing a flow of a method of obtaining a conversion constant according to the embodiment of the present invention.

[Explanation of symbols]

100 image input unit, 200 transmission illumination device, 3
00: image processing unit, 400: external output device, 50
0: Fuel assembly, 510: Water rod, 520: Fuel rod, 525: Fuel rod located on the center line of the fuel assembly, 531: Inspection dimensions, 532: Actual measurement dimensions, 550: 8
× 8 type fuel assemblies, 570... 9 × 9 type fuel assemblies.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Mikihiko Yamauchi 3-2-2, Sachimachi, Hitachi-shi, Ibaraki Prefecture Within Hitachi New Clear Engineering Co., Ltd. (72) Kiyoshi Izumi 3-chome, Sachimachi, Hitachi-shi, Ibaraki No. 1-1 Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Hideteru Ishizaki 3-1-1 Sakaicho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant

Claims (3)

[Claims] 1. A predetermined value which is determined as a pass / fail judgment value when the distance between the water rod and the fuel rod as viewed from one side of the fuel assembly of the nuclear reactor including the water rod and the fuel rod is viewed from the one side. A method for inspecting a reactor fuel assembly, comprising determining whether or not the above conditions are satisfied and making a pass / fail determination. 2. A method of inspecting a distance between a water rod and a fuel rod mounted on a fuel assembly of a nuclear reactor, the method comprising the steps of: The apparent distance between the water rod and the fuel rod, which is orthogonal to the direction, is measured as an actual measurement, and it is determined whether the actual measurement satisfies a predetermined value to be a pass / fail judgment value of the apparent distance. And a pass / fail decision is made. 3. An image processing unit for performing image processing based on an output signal from the image pickup device, wherein a process for obtaining the measured dimensions and a comparison between the predetermined value and the measured dimensions are performed. A method for inspecting a reactor fuel assembly, comprising: executing a process of performing the pass / fail determination and outputting a result of the pass / fail determination to a display unit.