JPH07218641A - Radiation measuring apparatus - Google Patents

Abstract

PURPOSE:To provide a radiation measuring apparatus in which the radiation can be shielded perfectly through a simple structure and the radiation can be measured accurately with high efficiency while allowing reduction in size. CONSTITUTION:A measuring container 12 is moved to a first moving position in a measuring chamber 14 by means of a container moving mechanism 22 comprising a hollow outer shaft 20 and an inner shaft 18 sliding in the outer shaft 20 in the axial direction thereof and then the measuring chamber 14 is shielded by means of a first shielding shutter 24. The inner shaft 18 is then slid to move the container 12 to the measuring position in the measuring chamber 14. A second shielding shutter 26 is opened only when the first shutter 24 is closed thus releasing the shielding of a photomultiplier tube 16. Furthermore, when the container 12 is moved into the measuring chamber 14, an air damper section 28 imparts pneumatic urging force to the container 12 and removes vibration thereof caused by the operation of the container moving mechanism 22 thus measuring the radiation accurately with high efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a light-shielding structure of a measuring chamber of a radiation measuring apparatus for measuring the amount of radiation contained in a sample by using a liquid scintillator.

[0002]

2. Description of the Related Art In the field of analysis / inspection using radioisotopes, it is necessary to accurately classify and measure which nuclide and what amount are contained in a sample solution. Therefore,
As a method of measuring radiation, radiation measurement using a liquid scintillator has been conventionally performed. In this radiation measurement, a sample to be measured is mixed in a liquid scintillator, the radiation emitted from the sample is captured as light emission of the scintillator, and this is detected by, for example, a photomultiplier tube. Then, the amount of radioactivity of the sample is converted from the detection result, that is, the pulse count number.

Since the light emitted from the scintillator used for such radiation measurement is extremely weak, a photomultiplier tube having a very high sensitivity is used to detect this weak light with high accuracy. That is, when intense light such as external light directly hits the measurement surface during operation of the photomultiplier tube, the photomultiplier tube is saturated and the photomultiplier tube is damaged. Therefore, when the photomultiplier tube is used, it is necessary to perform it in a dark room in which external light is completely blocked (shielded).

FIG. 5 shows an example of a radiation measuring apparatus having a light shielding structure. In this radiation measuring apparatus 50, a measurement container 52 containing a liquid scintillator and a sample is stored in a dedicated rack 54 having a container take-out hole 54a on the bottom surface,
It moves from the left direction in FIG. 5 to the container take-out position (the position shown in the figure). When it is confirmed that the dedicated rack 54 has moved to this position, the rack-side lifting arm 56a of the container lifting mechanism 56 rotates about the fulcrum 56b to push up the rack-side lifting lift 58, and further the container ejection hole 54a. The measurement container 52 is taken out from the exclusive rack 54 through the passage and is held by the container holding mechanism 60 standing by above. The container holding mechanism 60 surely holds the measurement container 52 by a predetermined holding mechanism, for example, a vacuum chuck or a mechanical chuck mechanism, and stores the measurement container 52 inside the light shielding box 62.
The measurement container 52 is stored in a. The light shielding box 62 is arranged on the rotary table 64 and rotates around the rotation shaft 64a to move the light shielding box 62 to the measurement side where the photomultiplier tube 66 is arranged. A plurality of irregular shapes are formed on the lower surface of the turntable 64 to prevent external light from easily reaching the photomultiplier tube 66. Therefore, a high voltage is constantly applied to the photomultiplier tube 66, and radiation measurement is always possible. When the measurement container 52 moves to the measurement position side, the measurement-side elevating arm 56c of the container elevating mechanism 56 rotates about the fulcrum 56d, and the measurement-side elevating lift 68 is lowered to take out the measurement container 52 from the light shielding box 62 and increase the photoelectron increasing amount. The radiation is moved to the position of the double tube 66 and a predetermined radiation measurement is performed. After the measurement is completed, the reverse operation described above is performed and the measurement container 52 is returned to the dedicated rack 54. The above operation is repeated to sequentially measure the radiation of the samples in the plurality of measurement containers.

Another radiation measuring apparatus includes a device for protecting a photomultiplier tube by turning on and off a high voltage applied to the photomultiplier tube. In this radiation measuring apparatus, in order to simplify the light shielding structure, only the periphery of the photomultiplier tube is shielded during operation. That is, the light is shielded only when the measuring container moves to the position facing the photomultiplier tube, and after the light is completely shielded, a high voltage is applied to the photomultiplier tube to operate the photomultiplier tube. Protects.

[0006]

However, in the conventional radiation measuring apparatus, in order to completely shield light and prevent external light from hitting the photomultiplier tube, a large scale is required to completely separate the injection position of the measurement container and the measurement position. There is a problem that the radiation measuring apparatus becomes large in size because the measurement container is moved in the light shielding structure using a simple light shielding structure or a complicated movement path to shield light.

Further, when the moving path of the measuring container becomes complicated, the measuring container often rubs the surroundings of the path to generate static electricity, and the discharge light due to the static electricity is measured by the photomultiplier tube together with the weak light of the scintillator for measurement. There was a problem of lowering the accuracy.

Furthermore, if the high voltage applied to the photomultiplier tube is turned on / off to simplify the light shielding structure, it is necessary to wait for the measurement until the high voltage stabilizes at each measurement, which significantly reduces the measurement efficiency. There was a problem.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to completely shield light with a simple structure and to achieve miniaturization capable of efficiently performing accurate radiation measurement. It is to provide a radiation measuring device.

[0010]

In order to achieve the above object, the present invention measures the radiation dose by detecting weak light emission of a liquid scintillator in a measuring container by a photomultiplier tube arranged in a measuring chamber. In the radiation measuring apparatus according to claim 1, the hollow outer shaft and the inner shaft that slides in the hollow inside of the outer shaft in the axial direction are moved, and the measurement container is moved to the first movement position in the measurement chamber by the movement of both the inner and outer shafts. ,
Further, the container moving mechanism for moving the measuring container to the measuring position of the measuring chamber by sliding the inner shaft, and the measuring container after moving the measuring container to the first moving position by the container moving mechanism, the measurement is performed by covering the inlet portion of the measuring chamber. A first light-blocking shutter that can be opened and closed to block light from the inside of the chamber, a second light-blocking shutter that can be opened and closed to release light blocking from the photomultiplier tube only when the first light-blocking shutter is closed, and a measurement container in the measurement chamber. And an air damper part for applying a biasing force to the measuring container by air pressure when moving, and for eliminating vibration of the measuring container due to the operation of the container moving mechanism.

[0011]

According to the above construction, the measuring container containing the sample and the liquid scintillator is moved stepwise to the first moving position and the measuring position in the measuring chamber by the container moving mechanism. When the measurement container moves to the first movement position, the entrance portion of the measurement chamber is covered by the first light-shielding shutter to prevent outside light from entering the measurement chamber. When the light is completely shielded at the entrance of the measurement chamber, the container moving mechanism moves the measurement container to the measurement position, and
The second light-blocking shutter, which was closed when the first light-blocking shutter was opened, is opened to start the measurement by the photomultiplier tube.

Further, when the measuring container is moved to the measuring chamber, an urging force due to the air pressure is applied to the measuring container by the air damper section to eliminate the vibration of the measuring container due to the operation of the container moving mechanism.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. 1 to 3 are schematic diagrams showing the configuration and operation of the radiation measuring apparatus.

The radiation measuring apparatus 10 includes an inner shaft 18 for moving a measuring container 12 containing a sample and a liquid scintillator to a position of a photomultiplier tube 16 arranged at a measuring position of a measuring chamber 14 and a circumference of the inner shaft 18. A container moving mechanism 22 having an outer shaft 20 provided therein, a first light-shielding shutter 24 provided at the entrance of the measurement chamber 14, and a first light-shielding member provided so as to face the photomultiplier tube 16 inside the measurement chamber 14. The second light-blocking shutter 26 that is opened only when the shutter 24 is closed, and the measurement container 12 that is provided with an urging force of the air pressure to the measurement container 12 when the measurement container 12 is moved to the measurement chamber 14 And an air damper portion 28 for eliminating the vibration of the.

In FIG. 1, the measuring container 12 is housed in a dedicated rack 30 having a container take-out hole 30a on the bottom surface and capable of accommodating a plurality of measuring containers 12, and is movable at a predetermined pitch in the direction of arrow A in the figure. It is conveyed to the measurement start position by the transfer conveyor 32. When the measurement container 12 reaches the measurement start position, the transfer conveyor 32 stops, and at the same time, the drive motor 34 (for example, a precisely controllable motor such as a pulse motor) of the container moving mechanism 22 starts rotating in the direction of arrow L in the figure. . A pulley 34a is fixed to the drive motor 34, and a drive belt 36 is wound around the pulley 34a. Therefore, when the drive motor 34 rotates in the direction of arrow L in the figure, the drive belt 36 follows the direction of arrow B in the figure. A part of the drive belt 36 is fixed to the lower end of the inner shaft 18 having a container push-up pad 18a at the tip through a connecting member 38. The inner shaft 18 is slidably inserted into the hollow portion of the hollow outer shaft 20 having an engaging groove 20a that engages with the first light shielding shutter 24 at the upper end. Also,
A stopper 20b is provided around the lower end of the outer shaft 20, and a spring 40 that constantly biases the outer shaft 20 upward is fixed. Therefore, the drive motor 3
When the inner shaft 18 moves upward by 4, the outer shaft 20 also moves upward by the spring 40. At this time, since the upper end of the outer shaft 20 is in contact with the lower end of the container lifting pad 18a of the inner shaft 18, the inner shaft 18
And the outer shaft 20 move simultaneously.

FIG. 2 shows an inner shaft 18 and an outer shaft 20.
Shows the state in which the measurement container 12 has been pushed up to the first movement position after passing through the container extraction hole 30a of the dedicated rack 30. When the stopper 20b comes into contact with the upper wall of the container moving mechanism 22 and the measuring container 12 reaches the first moving position, the drive motor 34 is temporarily stopped, and at the same time, it can be moved horizontally by a predetermined drive mechanism, for example, the air cylinder 42. The first light-blocking shutter 24 protrudes from the left and right of the outer shaft 20 and engages with the engagement groove 20a to accommodate the measurement container 12 in the measurement chamber 14
The measurement chamber 14 is shielded from the outside by blocking the light from the outside. In the present embodiment, the first light-shielding shutter 24 having a two-stage structure is used to perform complete light-shielding so that outside light does not enter the inside of the measurement chamber.

On the other hand, the photomultiplier tubes 16 are provided on the left and right sides of the measuring chamber 14 so as to face each other, and the photomultiplier tubes 16 are shielded from light when the first light-shielding shutter 24 is opened.
A light shielding shutter 26 is arranged in front of each photomultiplier tube 16. An expandable and retractable multi-stage container guide 44 is engaged with the second light-shielding shutter 26, a container retainer 44a (see FIG. 1) is provided on the lower surface of the container guide 44, and the container moving mechanism 22 raises the measurement. Reliably receives the container 12.

The measurement container 12 starts to rise and the measurement container 12 starts.
When pushes up the container retainer 44a, the measurement container 12 moves the container guide 44, which is formed in a stepped shape by the upper surface of the container retainer 44a, one step at a time and moves to the first movement position. At this time, the measuring container 12 is pressed down by the downward biasing force generated by the air damper portion 28 formed by the container guide 44, and is vibrated by the driving of the container moving mechanism 22, for example, the vertical movement caused by the stepwise rotation of the pulse motor. Eliminate vibration, etc. That is, the measurement container 12
As the container rises, the container guide 44 contracts and the air damper 2
When the volume of 8 is reduced, an air flow is generated inside the air damper portion 28, the air opening / closing valve 28a provided at the upper end of the air damper portion 28 is lifted, the air release port 28b is closed, and the air pressure inside the air damper portion 28 is increased. Let And
This increase in air pressure generates a downward urging force to suppress the contraction operation of the container guide 44, presses the measurement container 12 downward, and prevents the measurement container 12 from vibrating up and down.

By eliminating the vibration during the movement of the measuring container 12 in this way, it is possible to eliminate the static electricity due to the friction caused by the contact of the measuring container 12 with the peripheral members. That is, the sparks generated by the discharge of static electricity are eliminated, and only the weak light of the scintillator is accurately measured, and it is possible to eliminate the decrease in measurement accuracy.

When the light is completely shielded by the first light-shielding shutter 24, the drive motor 34 restarts to rotate only the inner shaft 18 upward as shown in FIG. When the measurement container 12 is pushed up by the inner shaft 18,
The contracted container guide 44 further rises inside the measurement chamber 14. At the same time, the upper surface of the container presser 44a of the container guide 44 pushes up the push-up claw 26a of the second light-shielding shutter 26 arranged in front of the photomultiplier tube 16 as shown in FIG. 4 to open the second light-shielding shutter 26. I do. Also, FIG.
As described above, the air damper portion 28 described above generates a biasing force even when the second light-shielding shutter 26 is opened, and the measurement container 1
Eliminate vibration when moving 2.

Therefore, after the measurement chamber 14 is completely shielded from light by the first light shielding shutter 24, the photomultiplier tube 1 is
Since the light shielding for 6 is released and the weak light of the scintillator is measured, it is possible to perform accurate measurement that is not affected by external light. Furthermore, since the measurement container 12 does not vibrate due to the action of the air damper portion 28, weak light of the scintillator can be accurately measured without being affected by sparks due to static electricity or the like.

When the measurement of the measurement container 12 moved to the measurement position is completed, the above-described operation is performed in reverse, and the radiation measuring apparatus 1
0 is the closing of the second light shielding shutter 26, and the first light shielding shutter 2
4 is performed in the order of opening, and the measurement container 12 is stored in a predetermined position of the dedicated rack 30. When the measuring container 12 descends,
Since the air opening / closing valve 28a of the air damper part 28 is opened, and air flows in from the outside, the container guide 44 constituting the air damper part 28 is easily lowered by gravity and can return to the measurement container standby state (state of FIG. 1). .

When the measurement container 12 whose measurement has been completed is stored in the dedicated rack 30, the transfer conveyor 32 is driven in the direction of arrow A in the figure at a predetermined pitch to start the measurement of the next measurement container 12.

In this embodiment, the air damper portion 28 is formed by using the container guide 44, but an air damper may be separately used. Further, both the inner and outer shafts are driven by the drive motor 34 and the spring 40, but a drive mechanism such as a double stroke cylinder may be used.
Furthermore, in the embodiment, the multi-stage container guide 44 is used to reduce the size of the apparatus, but the shape of the container guide is not limited to this, and any container that can guide the measurement container can be used. Well, the second light-shielding shutter 26
Also, the state of the first light-shielding shutter 24 may be detected and driven by another mechanism without interlocking with the container guide 44.

[0025]

As described above, according to the present invention,
The measuring container containing the sample and the liquid scintillator can be moved stepwise to the first moving position and the measuring position in the measuring chamber by the container moving mechanism, and the first light shielding shutter and the second light shielding shutter are alternately opened and closed. This makes it possible to completely shield the photomultiplier tube. Therefore, the radiation measuring device can be completely shielded from light with a simple structure, and the radiation measuring device can be downsized because the movement of the measuring container is simplified.

Further, when the measuring container is moved to the measuring chamber, an urging force due to the air pressure is applied to the measuring container by the air damper part to eliminate the vibration of the measuring container due to the operation of the container moving mechanism, and the static electricity or the like due to the movement of the measuring container. The accurate radiation measurement can be efficiently performed by eliminating the measurement error factor due to.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a standby state of a measurement container in a radiation measuring apparatus according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a moving state of a measurement container in a first movement position in the radiation measuring apparatus according to the present invention.

FIG. 3 is a schematic cross-sectional view showing a measurement position moving state of a measurement container in the radiation measuring apparatus according to the present invention.

FIG. 4 is a schematic enlarged view of a container guide and a second light-shielding shutter portion in the radiation measuring apparatus according to the present invention.

FIG. 5 is a schematic cross-sectional view showing the configuration of a conventional radiation measuring apparatus.

[Explanation of symbols]

 10 Radiation Measuring Device 16 Photomultiplier Tube 18 Inner Shaft 20 Outer Shaft 22 Container Moving Mechanism 24 First Shading Shutter 26 Second Shading Shutter 28 Air Damper Section

Claims (1)

[Claims] 1. A radiation measuring apparatus for measuring a radiation dose by detecting weak light emission of a liquid scintillator in a measuring container by a photomultiplier tube arranged in a measuring chamber, wherein a hollow outer shaft and a hollow outer shaft It consists of an inner shaft that slides in the hollow interior in the axial direction. The inner and outer shafts move to move the measuring container to the first moving position in the measuring chamber, and the sliding of the inner shaft moves the measuring container to the measuring position in the measuring chamber. And a container movement mechanism for moving the measurement container to a first movement position by the container movement mechanism, and a first light-blocking shutter that can be opened and closed to cover the entrance portion of the measurement chamber and shield the inside of the measurement chamber from light. A second light-blocking shutter that can be opened and closed to release the light blocking from the photomultiplier tube only when the first light-blocking shutter is closed; Radiation measuring apparatus comprising: the air damper unit to eliminate the vibration of the measuring container in connection with an operation of said container moving mechanism gives a biasing force by the gas pressure, the.