JP3040326B2 - Radiation measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measuring apparatus for measuring radiation emitted from a sample using a scintillator.

[0002]

2. Description of the Related Art In the fields of medicine, biology, engineering and the like, measurement of radiation contained in various samples (for example, animals, vegetables, fruits, seafood, soil, etc.) is performed.

As a radiation measuring apparatus for performing such radiation measurement, for example, an apparatus using a well-type scintillator or a through-hole type scintillator is known. This apparatus is provided with a scintillator having a well (well) or a through hole (through hole). When performing radiation measurement, a test tube containing a sample is inserted into the well or through hole, and the sample is The scintillation light generated in the scintillator by the radiation from the detector is detected by, for example, a photomultiplier tube, and the radiation dose of the sample (radiation-related amount such as count rate (cps, cpm), radioactivity (Bq, dpm)).

A radiation measuring apparatus using such a scintillator can be used to measure any sample as long as it enters a test tube, and is therefore widely used in various fields.

[0005]

In radiation measurement, it is sometimes required to measure not only the radiation dose of the entire sample but also the radiation dose per unit mass of the sample.
In such a case, conventionally, the mass of the sample in the test tube has been measured in advance using an electronic balance or the like, and this mass data has been input to the radiation measuring apparatus as a measurement condition. Then, the radiation measuring device calculates the radiation dose per unit mass of the sample based on the radiation dose of the sample obtained by the measurement and the previously input mass data.

As described above, conventionally, in order to measure the radiation dose per unit mass of a sample, the mass of the sample is measured manually in advance, and the mass data of the sample obtained by this measurement is input to the radiation measuring apparatus. Therefore, the measurement procedure is troublesome, and there is a possibility that an error such as a wrong sample may occur.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a radiation measuring apparatus capable of automatically calculating a radiation dose per unit mass of a sample. I do.

[0008]

To achieve the above object, a radiation measuring apparatus according to the present invention comprises a scintillation detecting means for detecting radiation from a sample in a test tube;
A radiation dose measuring means for obtaining a radiation dose of the sample based on an output of the scintillation detecting means, a test tube guide table for holding the test tube in a detection area of the scintillation detecting means, and a test tube guide table for holding the test tube. Mass measuring means for measuring the mass of the sample in the test tube, and specific radiation for calculating the radiation dose per unit mass of the sample based on the measured value of the radiation dose measuring means and the measured value of the mass measuring means. And an amount calculating means.

The radiation measuring apparatus according to the present invention is characterized in that a radiation shielding means is provided on a base of the test tube guide table.

[0010] In addition to the above configuration, the radiation measuring apparatus according to the present invention further comprises: a sample height calculating means for obtaining a height of the sample in the test tube based on a mass of the sample measured by the mass measuring means; Height adjustment amount calculating means for obtaining the height adjustment amount of the test tube based on the obtained height of the sample, and height adjustment means for adjusting the height of the test tube based on the obtained height adjustment amount And adjusting the height of the test tube so that the sample in the test tube is located at the optimum detection position of the scintillation detection means.

Further, the radiation measuring apparatus according to the present invention comprises: a sample height calculating means for obtaining the height of the sample in the test tube based on the mass of the sample measured by the mass measuring means; And a correction means for correcting at least one of the measurement result of the radiation dose measurement means and the calculation result of the specific radiation dose calculation means.

[0012]

According to the present invention, the scintillation detecting means detects radiation from a sample inside a test tube held by a test tube guide table, and based on the detected output, detects a radiation dose. The measuring means determines the radiation dose of the sample. On the other hand, the mass measuring means measures the mass of the sample in the test tube held on the test tube guide table. And
Based on the obtained radiation dose of the sample and the mass of the sample, the specific radiation dose calculating means calculates the radiation dose per unit mass of the sample.

In this configuration, when a detector having, for example, a through-hole scintillator is used as the scintillation detecting means, a measuring plate of the mass measuring means is disposed vertically below the through-hole, and a base of the test tube guide table is provided. The guide tube is inserted through the through hole of the scintillator. Then, the test tube is held in the guide tube portion of the test tube guide table, radiation measurement and mass measurement are performed, and a radiation dose per unit mass is obtained based on these measurement results.

In this case, if a radiation shielding means is provided on the base portion of the test tube guide table, radiation from the sample can be efficiently shielded.

[0015] In the configuration of the present invention, the sample height measuring means obtains the height of the sample in the test tube based on the mass of the sample measured by the mass measuring means, and based on the height of the sample, The height adjustment amount of the test tube necessary for positioning the sample in the test tube at the optimum detection position of the scintillation detection means is obtained by the height adjustment amount calculation means. The height adjusting means adjusts the height of the test tube based on the height adjustment amount thus obtained.

Further, in the configuration of the present invention, the sample height measuring means obtains the height of the sample in the test tube based on the mass of the sample measured by the mass measuring means. The correction means corrects an error in the radiation dose measurement result caused by a difference in detection efficiency due to a difference in sample height in the test tube.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the radiation measuring apparatus according to the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 is a view showing the overall configuration of a radiation measuring apparatus according to a first embodiment. The first embodiment will be described below with reference to FIG.

In FIG. 1, a photomultiplier tube (PMT) 12 for capturing photons generated by scintillation is joined to an end face of a through-hole type scintillator 10. As shown in FIG. 2, a through hole (through hole) 11 is formed in the through hole scintillator 10 in a vertical direction. By inserting the test tube 100 containing the sample 110 into the through hole 11, the sample 110
Can be captured by the through-hole scintillator 10 with almost no leakage. The through-hole type scintillator 10 is one in which a solid scintillator is sealed in a case in which a reflective film is formed on the inner surface. Photons generated in the solid scintillator do not leak to the outside, and are efficiently guided to the photomultiplier tube 12. I will

The pulse output from the photomultiplier tube 12 is linearly amplified by an amplifier (AMP) 14 and then a pulse having a certain peak value or more is extracted by a pulse height discrimination circuit (PHA) 16. Then, the extracted pulses are counted by the counting circuit 18. The output (count data) of the counting circuit 18 is input to the microcomputer 20. The microcomputer 20 performs overall control of the radiation measuring device, calculates values such as a counting rate and radioactivity based on the output of the counting circuit 18, and further calculates a sample provided from a mass measuring device 22 described later. Calculate the count rate and radioactivity per unit mass of the sample using the mass data.

In this embodiment, a mass measuring device (for example, an electronic balance) 22 for measuring the mass of the sample 110 is disposed below the radiation detection system including the through-hole scintillator 10 and the photomultiplier tube 12. Has been established. The test tube guide table 3 is placed on the measuring plate of the mass measuring device 22.
0 is placed. The test tube guide table 30 holds the sample 11
Reference numeral 0 is a guide member for holding the test tube 100 at a height such that the test tube 100 fits inside the through hole of the through hole scintillator 10. The test tube guide table 30 is loosely inserted into the through hole of the through hole type scintillator 10. Therefore, when the test tube 100 is leaned against the test tube guide table 30 at the time of measurement, the mass of the test tube 100 can be measured by the mass measuring device 22.

FIG. 3 shows the structure of the test tube guide table 30 in detail. The test tube guide table 30 includes a base 32 mounted on the mass measuring device 22 and a base 32
And a guide cylinder 34 extending upward from the guide cylinder 34. The test tube guide table 30 is formed of resin or the like, and the inner diameter of the guide tube portion 34 is designed to be slightly larger than the outer diameter of the test tube 100. The guide tube portion 34 not only functions as a guide member for the test tube 100 but also serves to prevent contamination of the scintillator.

Returning to FIG. 1, the test tube 100, which has been leaned against a rack or the like before the measurement, is gripped by the manipulator 24 of the automatic sample exchange mechanism and pulled out of the rack at the time of measurement, and the through-hole type After being transported above the scintillator 10, the manipulator 2
It is transported downward while being gripped by 4. The bottom of the test tube 100 is the guide tube portion 34 of the test tube guide table 30.
Contacting the bottom surface 36 (see FIG. 3) of the test tube 100
Are released from the manipulator 24 and are supported only by the test tube guide table 30. In this state,
While the radiation measurement is performed, the mass of the test tube 100 including the sample 110 is measured by the mass measuring device 22. The mass data obtained by the mass measuring device 22 is input to the microcomputer 20.

The microcomputer 20 calculates the radiation amount Ns (counting rate, radioactivity, etc.) of the sample calculated based on the count data of the counting circuit 18 and the mass data from the mass measuring device 22 based on the mass data from the mass measuring device 22. Calculate the radiation dose per unit mass. In order to determine the radiation dose per unit mass, the mass W of only the sample 110 is required, but the mass meter 22 determines the mass Ws of the entire test tube 100 including the sample 110. Therefore, in the present embodiment, the mass Wt of the empty test tube 100 is measured in advance by the mass measuring device 22 and registered in the microcomputer 20. And the microcomputer 2
For 0, the mass W of the sample 110 is obtained using the equation W = Ws-Wt, and the radiation dose Ns / W per unit mass is obtained by dividing the radiation dose Ns of the sample by the mass W. The obtained radiation dose per unit mass is output to an output device such as a display device together with the radiation dose of the entire sample 110.

As described above, according to the present embodiment, since the radiation dose per unit mass of the sample can be automatically calculated, the labor of the measurer can be reduced and the problem such as the mistake of the sample can be solved. Is done.

The configuration of the present embodiment for obtaining the radiation dose per unit mass is not limited to a detector having a through-hole type scintillator, but also a device using a pair of opposed scintillation detectors as shown in FIG. It is also applicable to the case of a configuration. In the radiation measuring apparatus shown in FIG. 4, a test tube guide table 30 is installed in a gap between scintillators 10a and 10b of scintillation detectors facing each other. Output pulses of the respective photomultiplier tubes 12a and 12b are respectively supplied to amplifiers 14a and 1a.
4b and the pulse count discrimination circuits 16a and 16b are input to the coincidence circuit 28. The coincidence circuit 28 performs coincidence counting of these two input pulses, and inputs the counting result to the microcomputer 20. Except for these, the configuration in FIG. 4 is all the same as the configuration in FIG.
With the configuration described above, the radiation dose per unit mass of the sample can be obtained in exactly the same manner as in FIG.

In the above description, the test tube guide table 30 is made of resin or the like.
The hatched portion 38 of the base portion 32 of the test tube guide table 30, particularly below the test tube, may be formed of a radiation shielding material (for example, lead) as shown in FIG. According to this configuration, it is possible to efficiently prevent the radiation emitted from the sample in the test tube from leaking to the outside. That is, if the entire apparatus including the mass measuring device 22 is to be shielded from radiation, the shielding area becomes large, causing problems in terms of the apparatus scale and cost, but the base of the test tube guide table 30 close to the sample is caused. If shielding is performed by the unit 32, radiation can be efficiently shielded in a small area.

Second Embodiment FIG. 6 is a diagram showing the overall configuration of a radiation measuring apparatus according to a second embodiment of the present invention. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

The second embodiment has a mechanism for adjusting the height of the test tube according to the height L of the sample 110 in the test tube 100 in addition to the configuration of the first embodiment shown in FIG. I have.

In the through-hole scintillation detector, when the sample 110 is at a height near the center of the through-hole scintillator 10, radiation hardly leaks outside the scintillator 10, and the most efficient measurement can be performed. Therefore, in this embodiment, the height L of the sample 110 is obtained by the microcomputer 20 based on the mass of the sample 110 obtained from the mass measuring device 22. More specifically, the microcomputer 20 calculates the mass of the sample 110 and the test tube 100 input from the data input unit 44.
Test tube 100 based on the inner diameter of
The height L of the sample 110 in the inside is calculated. Then, the microcomputer 20 obtains a height adjustment amount of the test tube 100 based on the obtained height L of the sample 110, and issues a drive command including the height adjustment amount to the table driving unit 40.
The height adjustment amount is the amount of vertical movement of the test tube 100 required to bring the center of the sample 110 to the center of the through-hole scintillator 10.

In this embodiment, the mass measuring device 22 is installed on a table 42 which can be moved up and down.
2 is driven in the vertical direction by a table driving unit 40. Therefore, the table driving unit 40 adjusts the height of the test tube 100 to a height at which the radiation measurement can be performed most efficiently by moving the table 42 up and down by a required height adjustment amount based on a driving command from the microcomputer 20. I do.

As described above, according to this embodiment, the height of the test tube can be automatically adjusted to the height at which the most efficient radiation measurement can be performed.

In this embodiment, the height L of the sample 110 is
In order to determine the inner diameter of the test tube 100 and the sample 110,
Was manually input from the data input unit 44,
For example, the inner diameter of the test tube 100 can be automatically measured by providing a sensor on the manipulator 24.

In this embodiment, the height of the test tube 100 is adjusted by moving the mass measuring device 22 up and down.
The configuration is not limited to this, and the height of the test tube 100 may be adjusted by incorporating an elevating mechanism into the base portion 32 of the test tube guide table 30.

FIG. 4 shows a configuration of height adjustment according to this embodiment.
The present invention can also be applied to a configuration in which simultaneous counting is performed by a plurality of detectors as shown in FIG.

Third Embodiment FIG. 7 is a diagram showing the overall configuration of a radiation measuring apparatus according to a third embodiment of the present invention. The same components as those in the first embodiment or the second embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In the third embodiment, the height L of the sample 110 is determined in the same manner as in the second embodiment based on the mass data obtained from the mass measuring device 22, and the radiation dose is corrected based on the height L. Is what you do.

Since the geometric efficiency of the through-hole scintillator 10 with respect to the sample 110 changes according to the height L of the sample 110 in the test tube 100, the detection efficiency of the entire radiation measuring apparatus also increases. It changes according to L. For example, when the height of the sample is high, the detection efficiency decreases. Therefore, in the present embodiment, the accuracy of radiation measurement is improved by correcting the influence of the difference in detection efficiency due to the variation in the height L of the sample.

That is, in the present embodiment, the microcomputer 20 determines the second data based on the mass data from the mass measuring device 22 and the data of the inner diameter of the test tube 100 and the density of the sample 110 input from the data input unit 44. The height L of the sample 110 is calculated in the same manner as in the second embodiment. Then, the microcomputer 20 obtains the detection efficiency corresponding to the obtained height L from the efficiency table 46, and corrects the measurement value regarding the radiation dose obtained based on the count data by the detection efficiency.

More specifically, the efficiency table 4
In FIG. 6, the relationship between the sample height L and the detection efficiency is tabulated, and the microcomputer 20 obtains the detection efficiency corresponding to the sample height L obtained by calculation from the efficiency table 46. And the microcomputer 20
Calculates the corrected radiation dose by multiplying the radiation dose of the sample obtained based on the count data from the counting circuit 18 by the reciprocal of the detection efficiency.

Such correction of the detection efficiency is effective not only for the radiation dose of the entire sample but also for the radiation dose per unit mass of the sample.

The configuration for correcting a change in detection efficiency according to the present embodiment is also applicable to a configuration in which multiple detectors perform simultaneous counting as shown in FIG.

[0043]

As described above, according to the radiation measuring apparatus of the present invention, the radiation dose per unit mass of the sample can be automatically calculated, the labor of the measurer can be reduced, and Problems such as mistakes are also eliminated.

Further, according to the present invention, the height of the test tube is automatically adjusted to the height at which the most efficient radiation measurement can be performed by obtaining the height of the sample in the test tube using the result of the mass measurement of the sample. Can be adjusted.

Further, according to the present invention, the accuracy of radiation measurement can be improved by correcting the effect of the difference in detection efficiency due to the variation in sample height.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an overall configuration of a first embodiment of a radiation measuring apparatus according to the present invention.

FIG. 2 is a perspective view showing a structure of a through-hole scintillator.

FIG. 3 is a perspective view showing a structure of a test tube guide table.

FIG. 4 is a diagram showing a modification of the first embodiment.

FIG. 5 is a cross-sectional view showing a case where a part of a base portion of a test tube guide table is formed of a radiation shielding member.

FIG. 6 is a view for explaining the overall configuration of a second embodiment of the radiation measuring apparatus according to the present invention.

FIG. 7 is a diagram for explaining the overall configuration of a third embodiment of the radiation measuring apparatus according to the present invention.

[Explanation of symbols]

Reference Signs List 10 through-hole scintillator, 12 photomultiplier tube, 14 amplifier, 16 wave height discrimination circuit, 18 counting circuit, 20 microcomputer, 22 mass measuring instrument,
24 manipulator, 30 test tube guide table, 40
Table drive unit, 42 tables, 44 data input unit, 46 efficiency table.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-5-302981 (JP, A) JP-A-6-11574 (JP, A) JP-A-7-43472 (JP, A) JP-A-62-1987 273479 (JP, A) JP-A-7-159541 (JP, A) JP-A-61-196186 (JP, A) JP-A-49-81192 (JP, U) JP-A-62-44289 (JP, U) Japanese Utility Model Showa 49-146983 (JP, U) JP-B 43-6600 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01T 1/20 G01T 1/167

Claims (6)

(57) [Claims] A scintillation detecting means for detecting radiation from a sample in a test tube; a radiation dose measuring means for obtaining a radiation dose of the sample based on an output of the scintillation detecting means; A test tube guide table held in the detection region, a mass measuring unit for measuring the mass of the sample in the test tube held by the test tube guide table, and a measurement value of the radiation dose measuring unit and the mass measuring unit. A specific radiation dose calculating means for calculating a radiation dose per unit mass of the sample based on the measured value. 2. The radiation measuring apparatus according to claim 1, wherein the scintillation detecting means has a scintillator having a through hole formed in a vertical direction, and the mass measuring means is provided vertically below the through hole. The test tube guide table is provided on a measurement plate of the mass measuring means, and extends vertically upward from the base section and is inserted into a through hole of the scintillator. A radiation measuring device, comprising: a guide tube portion, wherein the measurement is performed while holding the test tube in a guide tube portion of the test tube guide table. 3. The radiation measuring apparatus according to claim 1, wherein the scintillation detecting means has at least one scintillation detector having a detection surface facing the detection area, and the mass measuring means has a function of the detection. A measuring plate provided vertically below the region, wherein the test tube guide table is provided with a base portion installed on the measuring plate of the mass measuring means, and the detection is performed from above the base portion vertically upward. A radiation measuring device having a guide cylinder extending through a region, wherein the measurement is performed by holding the test tube in a guide cylinder of the test tube guide table. 4. The radiation measuring apparatus according to claim 2, wherein a radiation shielding means is provided on a base portion of the test tube guide table. 5. The radiation measuring apparatus according to claim 1, wherein a height of the sample in the test tube is calculated based on a mass of the sample measured by the mass measuring unit. Means, height adjustment amount calculating means for obtaining the height adjustment amount of the test tube based on the obtained height of the sample, and height for adjusting the height of the test tube based on the obtained height adjustment amount. And a height adjusting means for adjusting the height of the test tube so that the sample in the test tube is located at the optimum detection position of the scintillation detecting means. 6. The radiation measuring apparatus according to claim 1, wherein a height of the sample in the test tube is calculated based on a mass of the sample measured by the mass measuring unit. Means, and correction means for correcting at least one of the measurement result of the radiation dose measurement means and the calculation result of the specific radiation dose calculation means in accordance with the determined height of the sample. Radiation measurement device.