JPH0749385A - Radioactivity measuring equipment - Google Patents

Abstract

PURPOSE:To measure the spatial distribution of radioactivity in the peripheral direction of glass solidified body. CONSTITUTION:The radioactivity measuring equipment for measuring spatial distribution of radioactivity of a specimen comprises an index 23 provided on the outer periphery of a specimen 22, means 26-31 for projecting a light beam to the specimen 22 and detecting the intensity of reflected light, means 32 for recognizing the initial position in the peripheral direction based on the intensity of reflected light, and means 32 for measuring the distribution of radioactivity in the peripheral direction of the specimen 22 based on the rotational amount of a rotary table 2 from the initial peripheral position recognized by the means 32 and an output from a radiation detector 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radioactivity measuring device which can be used to measure the spatial distribution of radioactivity of a vitrified body obtained by solidifying radioactive waste with glass.

[0002]

2. Description of the Related Art An example of the construction of such a radioactivity measuring device is shown in FIG.
Shown in. In this radioactivity measuring device, a rotary table 2 is provided on a lift table 12 supported by a lift mechanism 1. The vitrified body 3 is placed on the rotary table 2, and the radiation emitted from the vitrified body 3 is detected by the radiation detector 5 via the collimator 4. The detection signal from the radiation detector 5 is signal-processed by the computer 6 and then input to the sequencer 7, where the radioactivity distribution of the vitrified body 3 in the height direction is measured.

The sequencer 7 controls the rotary motor driver 8 and the lift motor driver 9 to drive the rotary motor 9 for rotating the rotary table 2 and the lift motor 11 for driving the lift mechanism 1 for lifting the rotary table 2.

FIG. 5 is a cross-sectional view of the lift table 12. The rotary shaft 13 of the rotary table 2 is held on the lift table 12 via a bearing 14. A guide portion 15 is formed on the outer circumference of the rotary table 2 to serve as a guide for placing the vitrified body 3 at the center of rotation.

In the above-described radioactivity measuring device, the vitrified body 3 is rotated at the same time as it is moved up and down, and the surface of the vitrified body 3 is helically scanned to measure the radioactivity distribution in the height direction of the vitrified body 3. ing. The specific measurement contents are
It is as shown below.

That is, the upper limit position (solid line position) and the lower limit position (broken line position) of the rotary table 3 (glass solidified body 3) are set, and the rotary table 3 loaded with the glass solidified body 3 is set to the upper limit position (initial stage). Position).

Simultaneously with the start of measurement, the lifting motor driver 9
From the sequencer 7, the sequencer 7 counts the pulses output in synchronization with the rotation of the lift motor 11, and the count value is input from the sequencer 7 to the computer 6. Then, the computer 6 identifies the current scanning position in the height direction of the vitrified body from the initial position and the number of pulses from the initial position, and associates the height position with the signal value of the radiation detection signal to determine the height. The radioactivity distribution in the direction was detected.

By the way, since a general vitrified body has a columnar shape, the upper end face or the lower end face of the vitrified body can be used as a reference position in the height direction as described above. However, since there is no reference position in the circumferential direction on the outer periphery of the vitrified body, the radioactivity distribution in the circumferential direction could only be measured relatively.

[0009]

As described above, in the conventional radioactivity measuring apparatus for measuring the spatial radioactivity distribution of the vitrified body, it is difficult to specify the initial position in the circumferential direction of the vitrified body. Therefore, the spatial radioactivity distribution of the vitrified body could not be measured even in the circumferential direction.

The present invention has been made in view of the above circumstances, and it is possible to specify the initial position in the circumferential direction of the vitrified body, and to determine the spatial radioactivity distribution in the circumferential direction of the vitrified body. It is an object of the present invention to provide a radioactivity measuring device capable of measuring.

[0011]

In order to achieve the above object, the radioactivity measuring apparatus of the present invention rotates a rotary table on which a subject formed by solidifying radioactive waste is placed and rotates in the vertical direction. By moving up and down to scan the entire circumference of the subject with a radiation detector arranged in the vicinity of the raising and lowering position of the subject, and measuring the radioactivity of the subject from the output of the radiation detector, Provided on the outer periphery of the subject, the reflectance is different from the other parts of the outer periphery of the subject, an index indicating the reference position in the circumferential direction on the outer periphery of the subject, and provided near the up-and-down position of the subject, Detecting means for irradiating the sample with light and detecting its reflected light intensity, position recognizing means for recognizing the initial position in the circumferential direction from the reflected light intensity detected by the detecting means, and position recognizing means Lap Wherein the amount of rotation of the rotary table and the output from the radiation detector from the initial position of the direction, and configured to and a distribution measuring means for measuring the circumferential direction of the radioactivity distribution of the subject.

[0012]

In the radioactivity measuring apparatus of the present invention, the light is incident on the object placed on the rotary table from the detecting means. For example, if the positions of both the incident light incident from the detection means and the index provided on the subject in the height direction are set to match when the subject is at the reference position in the height direction, By rotating the subject at the reference position in the height direction, the state in which the incident light always enters the index occurs while the subject makes one rotation.

The amount of reflected light when the incident light is incident on the index is attenuated or increased as compared with the reflected light from other portions. Therefore, the position recognition means detects the change in the amount of light from the output of the detection means. Then, the reference position in the circumferential direction can be recognized.

As described above, since the position of the subject in the height direction can be easily known, the relative position in the height direction between the index and the detection means does not necessarily coincide with the initial position in the height direction. You don't have to.

The position recognizing means recognizes the circumferential scanning position of the subject from the recognized initial position in the circumferential direction and the rotation amount of the rotary table, and outputs it to the distribution measuring means. The distribution measuring means measures the circumferential radioactivity distribution of the subject from the circumferential scan position recognized by the position recognizing means and the output of the radiation detector.

[0016]

EXAMPLES Examples of the present invention will be described below. FIG. 1 shows functional blocks of a radioactivity measuring apparatus according to an embodiment of the present invention. The same parts as those of the device shown in FIG. 6 described above are designated by the same reference numerals.

In the radioactivity measuring apparatus of this embodiment, the elevating mechanism 1 supports the elevating table 21 shown in FIG. 2 so as to be movable in the vertical direction, and the rotary motor 10 rotates the upper end surface of the elevating table 21. A rotary table 2 for driving is provided.

An ID mark 23 is provided at a height position, which will be described later, on the vitrified body 22 which is the subject. The ID mark 23 is formed of a material or shape having a reflectance lower than the reflectance of the surface of the vitrified body 22, and the identification information of each vitrified body 22 is described.

The elevating table 21 is supported by the elevating mechanism 1 so as to be vertically movable over a distance longer than the entire length of the vitrified body 22. A radiation detector 5 is arranged adjacent to the elevating mechanism 1, and a collimator 24 is arranged between the elevating mechanism 1 and the radiation detector 5. The collimator 24 has a function of causing only radiation emitted from a predetermined height position (absolute height, not relative height on the subject) to enter the radiation detector 5.

The radioactivity measuring apparatus of this embodiment is equipped with a mark detection optical system for detecting the ID mark 23 of the vitrified body 22 placed on the rotary table 2 and arranged at the initial position in the height direction. There is. This optical system emits a laser beam generated from a laser light source 26 including a laser diode,
The light enters the mirror 28 through the half mirror 27 and then enters the collimator 29 at the mirror 28. Collimator 29
The central axis of is set to intersect perpendicularly with the central axis of the vitrified body 22 placed on the rotary table 2.

The mark detection optical system is composed of the vitrified body 2
The laser light reflected by 2 is passed through the collimator 29 again, is sequentially reflected by the mirror 28 and the half mirror 27, and is incident on the reflected light monitor 31.

The reflected light monitor 31 detects the reflected light intensity from the vitrified body 22 and outputs a reference position detection signal to the sequencer 32 when the detected reflected light intensity temporarily drops. Has been done.

The sequencer 32 is a lift motor driver 9
Recognizes the position of the vitrified body 22 in the height direction by counting the pulses output in synchronization with the rotation of the lifting motor 11, and makes the recognized height position correspond to the output of the radiation detector 5 to increase the height. Measure the radioactivity distribution in the vertical direction. Further, when the sequencer 32 receives the reference position detection signal from the reflected light monitor 31, the rotary motor driver 8 causes the rotary motor 1 to rotate.
Start counting pulses output in synchronization with 0 rotation,
The radioactivity distribution in the circumferential direction is measured by correlating the count value with the output of the radiation detector 5.

The upper limit position (solid line position) and the lower limit position (broken line position) of the lift table 21 are predetermined, and the upper limit position is the initial position in the height direction. When the lift table 21 is stopped at the upper limit position, the lift table 21 is at a lower position than the lower end portion of the vitrified body 22 placed on the rotary table 2, and the lift table 21 is set at the lower limit position. When stopped, one end of the collimator 24 is located above the upper end of the vitrified body 22.

When the lift table 21 is stopped at the upper limit position, the vitrified body 22 placed on the rotary table 2 is also included.
The angle of the mirror 28 and the collimator 2 so that the laser light from the laser light source 26 is incident at the same height as the index forming position of
9 is set.

2 and 3 are a perspective view and a cross-sectional view of the lift table 21, respectively. A guide member 33 is provided on the upper surface of the lift table 21 so as to surround the outer periphery of the rotary table 2. The guide member 33 is a collimator 29.
A vertically long slit 34 is formed at a position opposed to. The lower side of the slit 34 is cut out to the upper surface of the lift table 21 so that the guide member 33 does not block the laser beam. The inner surface of the guide member 33 has a vitrified body 2
In order to facilitate the installation of No. 2, the taper surface 35 is cut obliquely. Further, the lift table 21 rotatably supports the rotary table 2 via a bearing 36.

Next, the operation of this embodiment configured as described above will be described. First, the vitrified body 22 is placed on the rotary table 2, and the lifting motor 11 is driven to move the rotary table 2 to the initial position in the height direction (step 1). By matching the initial position in the height direction with the predetermined upper limit position, the movement to the initial position in the height direction can be easily realized.

When the vitrified body 22 is arranged at the initial position in the height direction, the height direction position of the ID mark 23 of the vitrified body 22 and the optical axis position of the mark detection optical system are set by the above-mentioned setting. The position in the vertical direction matches.

Next, when the rotary table 2 is placed at the initial position in the height direction, the sequencer 32 controls the rotary motor driver 8 to output a drive pulse from the rotary motor driver 8 to the rotary motor 10. (Step 2).

The rotary motor 10 supplied with the drive pulse from the rotary motor driver 8 drives the rotary table 2 to rotate by the number of drive pulses. During the drive control period of the turntable 2, the sequencer 32 operates the reflected light monitor 31.
It waits for the input of the reference position detection signal from (step 3).

When the rotary table 2 rotates at the initial position in the height direction, the vitrified body 22 placed on the rotary table 2 also rotates together with the rotary table 2. Laser light from the mark detection optical system enters the rotating vitrified body 22, and the reflected light reflected by the peripheral surface of the vitrified body 22 enters the reflected light monitor 31 through the mark detection optical system.

When the ID mark 23 of the vitrified body 22 is irradiated with the laser light, the intensity of the reflected light at that time is attenuated because the ID mark 23 is a material or a shape having a low reflectance. In the reflected light monitor 31, the laser light is emitted from the ID mark 23.
When the reflected light intensity changes abruptly due to the incidence on the formation position of, the reference position detection signal is output to the sequencer 32.

Upon receiving the reference position detection signal from the reflected light monitor 31, the sequencer 32 stops the rotation of the rotary table 2 at the position where the reference position detection signal is received (step 4). As a result, the vitrified body 22 is stopped at the position where the ID mark 23 is formed facing the collimator 29. In this embodiment, the vitrified body 22 is ID
The distribution in the circumferential direction is measured with the formation position of the mark 23 (position in the circumferential direction) as the initial position in the circumferential direction.

Next, the sequencer 32 simultaneously controls the lifting motor driver 9 and the rotation motor driver 8 to lower the lifting platform 21 to a lower limit position at a predetermined speed and rotate the rotary table 2 at a constant speed ( Step 5).

The sequencer 32 counts the number of drive pulses output from the rotary motor driver 8 and the lifting motor driver 9 during the period in which the vitrified body 22 is moved from the upper limit position to the lower limit position.
The amount of movement in the height direction and the amount of rotation are measured (step 6).

Then, the height of the vitrified body 22 is made to correspond by correlating the amount of movement of the vitrified body 22 in the height direction from the initial position in the height direction with the amount of radioactivity detected by the radiation detector 5 in real time. Measure the radioactivity distribution in the direction. Further, the amount of rotation of the vitrified body 22 from the initial position in the circumferential direction is made to correspond to the amount of radioactivity, and the activity distribution in the circumferential direction of the vitrified body 22 is measured (step 7).

As the vitrified body 22 descends,
When the laser light comes into a position lower than the upper end of the guide portion 33, the laser light will enter the slit 3 of the guide portion 33.
4 enters the side surface of the vitrified body 22, and the reflected light thereof again enters the reflected light monitor 31 through the slit 34 of the guide portion 33. Therefore, the entire length from the upper end to the lower end can be scanned without being blocked by the guide portion 33 up to the lower end of the vitrified body 22.

As described above, according to this embodiment, the ID mark 23 is formed on the outer periphery of the vitrified body 22, the laser beam is incident on the height position of the ID mark 23 at the initial position in the height direction, and the reflection thereof is performed. Since the ID mark detection optical system for measuring the light intensity is provided and the initial position in the circumferential direction is detected from the reflected light intensity, the activity distribution in the circumferential direction of the vitrified body 22 and the activity distribution in the height direction can be calculated. Both can be measured.

Further, since the slit 34 is provided at the laser beam passing position of the guide portion 33, it is possible to measure up to the lower end portion of the vitrified body 22. FIG. 4 shows a modification of the rotary table.

In this modification, the lifting table 21 is the turntable 4.
One rotary shaft 42 is rotatably supported via a bearing 36, and a truncated cone-shaped convex portion 43 is formed on the upper surface of the rotary table 41. The convex portion 43 is inserted into a conical concave portion 44 formed on the lower surface of the vitrified body 22 and functions to position the vitrified body 22. Since the vitrified body 22 is positioned by the convex portion 43 of the rotary table 41, the guide portion described above is removed from the outer periphery of the rotary table 41.

According to the present modification as described above, it is possible to measure up to the lower end portion of the vitrified body 22 as in the case where the slit is formed in the guide portion. Although the initial position in the circumferential direction and the formation position of the ID mark 23 are made coincident with each other in the above embodiment, the formation position of the ID mark 23 may be used as a reference position when viewing the distribution in the circumferential direction. Therefore, the present invention is not limited to use as an initial position for starting measurement. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0042]

As described above in detail, according to the present invention, the initial position in the circumferential direction of the vitrified body can be specified.
It is possible to provide a radioactivity measuring device capable of measuring the spatial radioactivity distribution in the vitrified body in the circumferential direction.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a radioactivity measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view of a lift table portion included in the radioactivity measuring apparatus shown in FIG.

FIG. 3 is a cross-sectional view of the lift table portion shown in FIG.

FIG. 4 is a view showing a modified example of a lift table portion.

FIG. 5 is a cross-sectional view of a lift table portion provided in a conventional radioactivity measuring apparatus.

FIG. 6 is a configuration diagram of a conventional radioactivity measuring device.

[Explanation of symbols]

1 ... Elevating mechanism, 2 ... Rotating table, 5 ... Radiation detector,
8 ... Rotating motor driver, 9 ... Lifting motor driver, 1
0 ... Rotating motor, 11 ... Lifting motor, 21 ... Lifting table, 2
2 ... Vitrified body, 23 ... ID mark, 24, 29 ... Collimator, 31 ... Reflected light monitor, 32 ... Sequencer.

Claims (1)

[Claims] 1. A radiation detector disposed near the ascending / descending position of the subject by rotating and vertically moving a rotary table on which the subject formed by solidifying radioactive waste is placed. Scanning the entire circumference of the subject, in the radioactivity measuring device for measuring the radioactivity of the subject from the output of the radiation detector, provided on the outer periphery of the subject, the reflectance with other parts of the outer periphery of the subject Differently, an index indicating a reference position in the circumferential direction on the outer circumference of the subject, and detection means provided in the vicinity of the elevation position of the subject, which makes light incident on the subject and detects the reflected light intensity thereof Position recognition means for recognizing an initial position in the circumferential direction from the intensity of reflected light detected by the detection means, the rotation amount of the rotary table from the initial position in the circumferential direction recognized by the position recognition means, and the radiation detection And an output from the vessel, the radioactivity measuring apparatus characterized by comprising a distribution measuring means for measuring the circumferential direction of the radioactivity distribution of the subject, the.