JPS614911A - Method and device for dimensional measurement of nuclear fuel pellet - Google Patents

Abstract

PURPOSE:To enable an accurate measurement of an optional point by finding a vonvertion coefficient corresponding the size measured with rotating in peripheral direction a cylindrical pellet of the standard nuclear fuel with the known size and by correcting the similar measuring value to the pellet of the material to be measured. CONSTITUTION:A pellet P which is to be the standard or the material to be measured is placed on a base plate 14 and when phototubes 18, 19 detect it, a capstan roller 13 pushes the pellet P to free rollers 12a, 12b and the phototubes 18, 19 reconfirm the pellet P. The probe of digital dial gages 16, 17 is brought into contact with the outer peripheral face and the upper face and together with the rotation of the roller 13 at a fixed speed the pellet P is rotated as well. While the gage 16 is moved from the upper part to the lower part, then, the diameter and squareness of the outer peripheral face, the height and squareness of the upper face are measured, and the conversion coefficient is found by a microcomputer and also the measured value of the pellet P to be measured is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] ' The present invention relates to a method and apparatus for measuring dimensions such as the diameter and height of cylindrical nuclear fuel pellets.

[Prior art and its problems]

Nuclear fuel pellets (hereinafter abbreviated as pellets) are cylindrical, and their diameter, height, and other dimensions require precise measurement.In particular, the diameter requires highly accurate measurement on the order of 1 micron. be done. However, conventionally, the above dimensions are
Each sample pellet was measured using a direct-reading Magnescale. For this reason, defects in pellet positioning accuracy due to defects in the flatness or perpendicularity of the block gauge, etc., and defects in the measuring device itself due to unnecessary origin position of the probe or defective shape of the tip of the probe are unavoidable. In order to minimize the occurrence of these errors, it is necessary to spend a great deal of effort and time when performing automatic measurements, and it is also necessary to improve the finishing accuracy of mechanical parts such as measuring instruments as much as possible. Furthermore, the actual accuracy could only be expected to be from a few microns to several tens of microns. In addition, there was a problem in that it was difficult to measure dimensions over the entire circumference of the pellet in order to ensure accuracy.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and is a method and apparatus for measuring the dimensions of pellets, which can precisely measure the dimensions of pellets at any point, and in particular can measure the diameter with extremely high precision. The purpose is to provide

[Structure of the invention]

In order to achieve the above object, the method of the present invention measures the dimensions of a reference pellet whose dimensions are known while rotating it in the circumferential direction, determines a conversion coefficient that makes the measured value correspond to the known dimension, and then In this method, the dimensions of a nuclear fuel pellet as an object to be measured are measured while being rotated in the circumferential direction, and the measured value is corrected by the above-mentioned conversion coefficient.
equipment.

A pellet rotating means for rotating the pellet in the circumferential direction; a measuring device for measuring the dimensions of the pellet rotated by the pellet rotating means; and a measuring device for controlling the rotating means and the measuring device and measuring the dimensions obtained by the measuring device. This system consists of a computer that corrects the

[Embodiments of the invention]

Hereinafter, one embodiment of the apparatus of the present invention will be described based on the drawings.

5 to 7 show a dimensional density measuring device A for pellets P, which includes the dimensional measuring device 1 according to the present invention as one component, and is a device for measuring the size and density of pellets P, such as an automatic measuring balance for measuring the weight of pellets +-p. The weight measuring device 2 and the above-mentioned dimension measuring device 1 are installed between a sampling case 4 provided at the terminal end of the carrying-in conveyor 3 and a carrying-out case stand 6 provided at the starting end of the carrying-out conveyor 5, A microrobot 7 equipped with carbide fingers is disposed between the sampling case stand 4 and the weight measuring device 2, the weight measuring device 2 and the dimension measuring device 1, and the dimension measuring device 1 running and unloading case stand 6. Each of the above-mentioned devices is equipped with a microcomputer (not shown) that controls them overall and calculates the density of the pellet P from the measured dimensions and weight.

When the sampling case 10 containing a plurality of pellets P is carried onto the sampling case stand 4 by the carry-in conveyor 3, the microrobot 7 is activated.
The berets P in the sampling case 10 are lifted up one by one and transferred to the weight measuring device 2, and their weight is measured.When the weight measurement is completed, the micro robot 8 is activated. The pellet P is transferred to the dimension measuring device 1, and its dimensions are measured by a mechanism described later. The measured values are input to the microcomputer and the density of the pellet P is calculated. Also.

The pellets I-P whose weight and dimensions have been measured are then sequentially stored in the carry-out case 11 on top of the carry-out case table 6 by the micro robot 9, and when a predetermined number is reached, the pellets L-P are transferred to the next process along with the carry-out case 11 by the carry-out conveyor 5. configured to be delivered.

On the other hand, FIGS. 1 to 4 show an embodiment of the dimension measuring device 1 according to the present invention, in which a pair of free rollers 12a and 12b made of stainless steel measure a thin wire at a predetermined interval. In the vicinity of the pair of free rollers 12a and 12b, which are rotatably arranged parallel to each other, an outer circumferential surface is formed of a material such as polyurethane, which has a large contact resistance and does not undergo elastic deformation, and is rotated by a drive device. , a horizontal trajectory m passing through the midpoint of the pair of free rollers 12a, 12b.
The capstan roller 13, which is rotated at a constant speed (2 to 4 rpm) in a predetermined circumferential direction,
A disk-shaped base plate 14 made of cemented carbide is fixed below the space surrounded by the free rollers 12a, 12b and the capstan roller 13. It is placed horizontally. Then, the pellet P transferred from the IT measuring device 2 by the micro robot 8 is placed on the base plate 14 with its axis facing up and down, and is moved by the capstan roller 13j and the free roller 12a. , 12b and rotated at a constant speed in a predetermined direction, and the free rollers 12a, 12b, capstan roller 13, etc. constitute pellet rotating means 15.

Furthermore, a digital dial gauge (measuring instrument) for measuring the diameter of the pellet P rotated by the pellet rotating means 15 is provided near the pellet rotating means 15.
16 is provided to be located on the center line between one free roller 12a and the pellet P, and above it is provided a digital dial gauge (measuring device) 17 for measuring the height of the pellet P. . These digital dial gauges 16% and 17 are all equipped with a function to measure the perpendicularity of the end face of Pellet P, and are equipped with a movable measuring point made of cemented carbide, for example, 3 mm in diameter, and the moving speed of the measuring point is 4
0 am/min, the measurement accuracy may be about 1 micron to 5 microns, and one digital dial gauge 16 for diameter measurement has its support arm 16a moved in the vertical direction as shown in FIG. This allows the diameter of the pellet P at a predetermined height to be freely measured over the entire circumference. and,
The operations of the digital dial gauges 16 and 17 are controlled together with the pellet rotating means 15 by the microcomputer of the dimensional density measuring device A, and the measured values are corrected by the microcomputer in a manner described later. It is configured.

Further, in the vicinity of the pellet rotation means 15, a light emitting phototube 1 that emits light toward the placement position of the pellet P is provided.
8 and a light-receiving phototube 19 that receives light from the light-emitting phototube xsj) are provided on the same axis.
9 is connected to the microcomputer via a controller (not shown), and when Pellet P is positioned on the base plate 14, the free
, 12b, the pellet P is automatically detected and its position is confirmed.

Note that the free rollers 12a and 12b are constructed so that they can be replaced as needed.

Next, one method of the present invention will be explained.

In the method of the present invention, first, a plurality of reference pellets (P) whose dimensions at predetermined points are known and which have been measured with high precision are prepared in advance, and the dimensions of each one are measured using the dimension measuring device having the above-mentioned configuration. Measure with 1. Then, a calibration curve is drawn from the measurement results, and a conversion coefficient is determined that correlates the measured values with known dimensions. Next, the pellet P to be measured is
The dimensions of the object are sequentially measured by the dimension measuring device 1, and the measured values are corrected using the conversion coefficients described above to calculate highly accurate dimensions.

Here, the dimension measurement of the reference pellet P and the calculation of the conversion coefficient, the dimension measurement of the pellet P to be measured, and the correction thereof are carried out by controlling the dimension density measuring device A in an integrated manner and calculating the density from the measured dimensional weight. All of this is done automatically by the microcomputer that calculates the above. That is, when the reference pellet P or the pellet P to be measured is placed on the base plate 14 and detected by the phototube 18, 19, the capstan roller 13 presses it against the free rollers 12a, 12b. And photocell 1
When 8.19 reconfirms this pellet P, the probes of each digital dial gauge 16.17 gently touch the pellet P.
applied to the outer circumferential surface and top surface, respectively. Next, the capstan roller 13 rotates at a constant speed as shown by the arrow in FIG. 3, and the pellet P is rotated at the same speed.
The probe of the digital dial gauge 16 for measuring the diameter moves from point a to point d shown in FIG. Furthermore, the height of the pellet P and the squareness of the upper surface are measured using a digital dial gauge 17 for height measurement. Then, based on the measured value, the upper transformation U is determined, correction is made, and density calculation is also performed.

In addition, the dimension measuring device 1 includes: (1) Each free roller 12! , the parallelism of the outer cylinder of 12b, the precision finish of the surface, (2) the perpendicularity of each free roller 12a, 12b to the base plate 14, (3) the perpendicularity of the contact point of the digital dial gauge 17 for height measurement to the base plate 14. (4) the parallelism of the gauge head of the digital dial gauge 16 for diameter measurement with respect to the base plate 14, and the perpendicularity of the vertical movement line of its support arm 16a with respect to the base plate 14 so that no errors occur. It is virtually impossible to manufacture, and errors also occur due to thermal expansion due to temperature rise and wear due to use. However, the above conversion coefficient is a parameter that specifically quantifies the factors that influence these accuracy, and if this conversion coefficient is used to correct it, the accuracy of Pellet's dimension measurement value will be significantly increased. . Therefore, measurement results with sufficient accuracy can be obtained without forcibly increasing the accuracy of the measuring instrument as in the conventional case. This eliminates the need to manufacture highly accurate measuring instruments, significantly reducing costs.

In addition, in the above calculation of the conversion coefficient using the reference pellet l-P, it is only necessary to calculate the conversion coefficient once before measuring the dimensions of the pellet P to be measured. It is preferable to do this again when there is a change in the external temperature to a certain degree, and it is even better if you do this periodically to prevent accuracy from decreasing due to wear of each part of the device. preferable.

Furthermore, in the past, not only the dimensions of pellets (P) but also their weight and density were measured manually, which resulted in poor work efficiency, but with the dimension and density measuring device A mentioned above, everything can be done automatically. Therefore, it is extremely efficient, making it possible to shorten measurement time and greatly reduce labor costs.

Further, in the above description, the digital dial gauges 16 and 17 are used as the measuring instruments, but other types of measuring instruments such as optical measuring instruments using a laser or the like may be used.

〔Effect of the invention〕

As explained above, the present invention measures the dimensions of a standard pellet with a measuring device while rotating it in the circumferential direction using a rotating means, and calculates a conversion coefficient that makes the measured value correspond to the known dimensions. Next, the dimensions of the pellet to be measured are measured using a measuring device while being rotated in the circumferential direction by the same rotating means, and the measured values are corrected using the above conversion coefficient, so the device itself It is possible to measure the dimensions of pellets with high precision without being affected by errors that are unavoidable during production, errors due to thermal expansion, abrasion, etc., and it is also extremely easy to measure dimensions at any point on pellets. be able to.

[Brief explanation of drawings]

1 to 4 show an embodiment of the apparatus of the present invention, in which FIG. 1 is a plan view, FIG. 2 is a side view, FIG. 3 is a schematic perspective view of the main parts, and FIG. FIG. 3 is a view taken along the IVVlv arrow in FIG. 3; In addition, Figures 5 to 7 show the dimensional density measuring device, with Figure 5 being a plan view and Figure 6 being Vl-V of Figure 5.
The l arrow view and FIG. 7 are the same V+t-■ arrow view. 1...Dimension measuring device for nuclear fuel pellets, P...
...Nuclear fuel pellets, 12a, 12b...
Free roller, 13...capstan roller,
15... Pellet rotation means, 16...
Digital dial gauge (measuring instrument), 17...
Digital dial gauge (measuring instrument).

Claims (2)

[Claims] (1) Measure the dimensions of a cylindrical reference nuclear fuel pellet with known dimensions while rotating it in the circumferential direction, find a conversion coefficient that correlates the measured value with the known dimensions, and then A method for measuring the dimensions of a nuclear fuel pellet, comprising measuring the dimensions of the nuclear fuel pellet while rotating it in the circumferential direction, and correcting the measured value using the conversion coefficient. (2) a pellet rotation means for rotating a cylindrical nuclear fuel pellet in the circumferential direction; a measuring device for measuring the dimensions of the nuclear fuel pellet rotated by the pellet rotation means;
A nuclear fuel pellet size measuring device comprising the rotating means and a computer that controls the measuring device and corrects the dimension measurements obtained by the measuring device.