JPH0519059A - Body surface radioactivity detector - Google Patents

Abstract

PURPOSE:To obtain a title device which can obtain exact measurement results of only radioactivity deposited on a body surface without previous measurement of radioactivity from inside a body. CONSTITUTION:A thin-type beta-ray detector 12 is fitted with a gamma-ray detector 16 on the back side to constitute the principal part. On the basis of a count value of the whole gamma rays of the gamma-ray detector 16, a gamma-ray count value (count of a part of gamma-rays) by the beta-ray detector 12 is calculated by a first arithmetic part 26. A calculated value of the first arithmetic part 26 is subtracted from a count value of the beta-ray detector 12 by a second arithmetic part 28 so as to obtain measurements only of beta rays due to radioactivity detected on the body surface of a subject 100.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a body surface radioactivity detecting apparatus for measuring radioactivity adhering to the surface of a human body which is a subject.

[0002]

2. Description of the Related Art For the safety of workers who work in a place where there is a risk of radioactive contamination, it has been conventionally performed to measure the presence or absence of radioactive adhesion to workers after the work.

As a measuring device therefor, for example, a radioactivity detecting device is known in which a β-ray detector is arranged so as to face a human body which is a subject, and β-rays from the surface of the human body are detected and counted.

[0004]

However, gamma rays are usually emitted from the human body, and the dose varies depending on the person.

Since γ-rays have a high penetrating power, they can easily penetrate through the human body and reach the β-ray detector installed facing the human body. As a result, the β ray detector detects a part of the γ ray and counts it. As a result, there is a problem in that some of the radioactivity from the inside of the body and the radioactivity attached to the surface of the human body during the work are counted without being distinguished. Further, the fact that the amount of radioactivity inside the human body varies from person to person as described above makes it more difficult to accurately determine the presence or absence of individual contamination and its amount.

[0006] In order to deal with this, it is necessary to grasp the γ-rays of the radioactivity in the body in a periodical checkup for each person in advance, which is extremely troublesome. was there.

OBJECTS OF THE INVENTION The present invention has been made to solve the above problems, and an object of the invention is to detect radioactivity attached to the surface of a human body without measuring the radioactivity in the body in advance. It is an object of the present invention to provide a body surface radioactivity detection device capable of accurately obtaining only the measurement result.

[0008]

In order to achieve the above object, a body surface radioactivity detecting apparatus according to the present invention comprises a thin β-ray detector for detecting β-rays, and radiation of the β-ray detector. A γ-ray detector attached to the back side opposite to the incident surface and measuring γ-rays transmitted through the β-ray detector, and the measured γ-rays based on the count value measured by this γ-ray detector Of the above, a first computing unit that computes a count that would have been counted by the β-ray detector, and a value calculated by the first computing unit is subtracted from the count value measured by the β-ray detector. A second calculation unit is included, and a measurement value of only β rays from the subject is obtained.

It is possible to easily form the body surface activity detecting chamber by arranging a pair of the body surface activity detecting devices in front, back, left, right and top of the human body.

[0010]

According to the body surface radioactivity detecting device having the above structure, the γ-rays emitted from the inside of the body pass through the thin β-ray detector and are detected by the γ-ray detector attached to the back surface of the detector.
All of them are counted. At this time, the β-ray detector is formed as a thin type, but when the γ-rays pass through the β-ray detector, the β-ray detector slightly counts it. First
The calculation unit calculates the count value counted by the β ray detector of the γ rays from the body. This is performed based on the count value detected by the γ-ray detector, that is, the total count value of γ-rays. That is, it is possible to easily calculate by previously measuring the ratio of counting the γ rays passing through the thin β-ray detector and multiplying the count value of the γ-ray detector by this ratio.

Then, in the second calculation unit, the first calculation unit calculates from the count value of the β-ray detector (including both the count value of β-rays and the count value of a part of γ-rays from the inside of the body). Subtract the value calculated in (the count value of a part of the γ ray from the body). This allows
It is possible to accurately and promptly measure the count value of only β rays, that is, the radioactivity attached to the human body surface during the work.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram showing the overall construction of an embodiment of the present invention. A β-ray detector 12 which is a component of the main body 10 is made of, for example, a plastic scintillator and is formed thin. ing. This is a structure for easily passing γ-rays, and the housing 14 in which the β-ray detector is set also absorbs γ-rays such as plastic or aluminum so that γ-rays easily pass through. It is made of few materials.

Next, a γ-ray detector 16 is attached to the back side of the housing 14, and the γ-ray detector 16 is Na.
I (Tl). A collimator 18 is installed outside the γ-ray detector 16.
The collimator 18 is provided to remove γ-rays from outside the subject 100.

Then, the β-ray detector 12 and the γ-ray detector 1
Counters 20 and 22 are connected to 6 respectively, and the radiation is counted here for a fixed time. In addition,
The β ray detector 12 detects a portion of β rays from the body surface and γ rays from the body, and the counting circuit 20 counts the total of both. On the other hand, the γ-ray detector 16 detects all γ-rays from the inside of the body, and counts them.
Count at 2.

Here, each of these counting circuits 20 and 22
Is connected to the arithmetic unit 24, and the arithmetic unit 24 is provided with a first arithmetic unit 26 and a second arithmetic unit 28.
The first calculator 26 calculates a value X obtained by counting the γ rays from the inside of the subject 100 with the β ray detector. That is, γ
When the rays pass through the β-ray detector 12, the β-ray detector 12 counts a part of the rays. For example, the β-ray detector 12
Of the passing γ-rays is measured in advance, and when it is, for example, 1%, the first computing unit 26 adds 1/100 to the count value of the γ-ray detector 16 (count value of the entire γ-rays). The value X is calculated by multiplying.

Next, in the second operation section 28, the β ray detector 1
The value Y is calculated by subtracting the value X from the count value in 2.
That is, the count value based on the detection of both β-rays and part of γ-rays is subtracted from the count value of that part due to passage of γ-rays to obtain β
The count value Y is calculated only by lines. And
This value Y is displayed on the display 30 so that the user of the device can detect the radioactive deposition of each person.

As described above, the γ-rays from the inside of the subject 100 and the β-rays from the radioactivity adhering to the body surface can be discriminated and calculated, and the situation of the radioactive contamination during the work can be quickly grasped. It becomes possible.

By the way, when actually using the apparatus for detecting body surface radioactivity according to the present embodiment, in order to check the radioactive contamination of the site worker as closely as possible and perform sufficient health management, these A plurality of body surface radioactivity detection chambers, which are substantially life-size, are assembled and formed in a row inside the frame 40, and the subject 100 (site worker) is housed in the chamber to check for radioactive contamination. It will be. The structure of the body surface radioactivity detection chamber configured in this manner is shown in FIG. As shown in FIG. 2, if the body surface radioactivity detection chamber is configured, it is possible to eliminate the counting error due to the background during radiation formation. That is, when a pair of radiation detection devices are installed as shown in FIG. 2, it is possible to eliminate the counting error by simultaneously counting the outputs of the pair of body surface activity detection devices. By separately detecting the β-rays and the γ-rays, it is possible to shorten the measurement time and prevent the occurrence of counting errors.

[0020]

As described above, according to the body surface radioactivity detecting apparatus of the present invention, the count value of only β rays due to the radioactivity adhering to the body surface can be measured and calculated quickly and accurately. it can. As a result, it is possible to easily and surely grasp the state of radioactivity adhesion to the worker in the work at a place where there is a risk of radioactive contamination, and to obtain useful data for the safety measures of the worker.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an overall configuration of an embodiment.

FIG. 2 is an example of arrangement for measuring the amount of radioactivity deposited on the body surface throughout.

[Explanation of symbols]

10 Detection device body 12 β-ray detector 14 housing 16 γ-ray detector 18 Collimator 20,22 Counting circuit 24 arithmetic unit 26 First Operation Unit 28 Second operation unit 30 display 100 subject

Claims (2)

[Claims] 1. A thin β-ray detector for detecting β-rays, and a γ-ray transmitted through the β-ray detector, which is attached to the back side of the β-ray detector opposite to the radiation incident surface. Γ to measure
A ray detector, and a first calculation unit that calculates the count that would have been counted by the β ray detector among the measured γ rays based on the count value measured by the γ ray detector, A second calculation unit for subtracting the value calculated by the first calculation unit from the count value measured by the β-ray detector, and obtaining a measurement value of only β-rays from the subject. An apparatus for detecting radioactivity on the body surface. 2. A body surface activity detecting chamber, characterized in that the body surface activity detecting device according to claim 1 is formed by arranging a pair of front, rear, left and right, and upper and lower parts of a human body.