JP2001099938A - DETECTOR CAPABLE OF READING beta-RAY DOSAGE DIRECTLY - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the burden for measurement required for finding a dosage equivalent rate of β-rays when γ-rays and the β-rays are mixed. SOLUTION: Two kinds of detectors comprising a radiation detector for detecting only the γ-rays and a radiation detector for detecting the γ-rays or β-rays are provided on a radiation detecting face, and respective dosage equivalent rates are computed by a CPU to calculate the dosage equivalent rate of the β-rays alone, so as to be displayed. The dosage equivalent rate of the β-rays is thereby measured separately even when the γ-rays and the β-rays are mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a .beta.-ray direct-reading dosimeter for use in environmental surveys in nuclear power plants, radiation facilities and accelerator facilities.

[0002]

2. Description of the Related Art FIG. 5 is a sectional view showing a structure for explaining a conventional detecting device. The radiation detector 11 includes at least one detector having an independent radiation sensitive portion. When γ-rays and β-rays are simultaneously incident from the detector side of the detection device, the γ-rays and β-rays that have passed through the thin filter 17 that is always mounted are converted into the detector 11 and the subsequent detection circuit 13.
Are counted together.

[0003] As a filter 17, 10-20 mg /
A bonding material of aluminum and polyethylene having a thickness of about ² cm ² is often used for light shielding and electromagnetic shielding. The count value is converted into a dose equivalent rate (mSv / h) by the CPU circuit 14 and displayed on the display unit 16.
At this time, in a case where only the β-ray is separately measured, the dose equivalent rate (H1) is first determined. Next, by adding an aluminum filter to cut the β-ray in addition to the filter 17, only the γ-ray is measured so that the dose equivalent rate (H
Find 2).

[0004] The dose equivalent rate of β-ray is obtained by calculating the difference (H1-H2) between these indications.

[0005]

In the above conventional detection apparatus, when γ-rays and β-rays coexist, two measurements are required to determine the dose equivalent rate of β-rays, which increases the number of measurement steps. Is a heavy burden. Here, if the shape of the output pulse of γ-ray or β-ray from the detector is different, the output pulse of β-ray is stored, and it becomes possible to separate and measure β-ray by comparing with the output pulse. The ray generates a secondary electron beam in the detector, and since it is detected, there is no difference in the pulse shape from the β ray. In a nuclear power plant or the like, since the distributions of the energy (peak value) of the mixed γ-rays and β-rays are almost the same, they cannot be separated by the threshold.

[0006]

According to the detection apparatus of the present invention,
Equipped with two types of radiation detectors on the radiation detection surface: a radiation detector that detects only γ-rays and a radiation detector that detects γ-rays or β-rays. Since only the dose equivalent rate is calculated and displayed, even when γ rays and β rays are mixed, the dose equivalent rate of β rays can be separated and measured. Therefore, only one measurement is required to determine the dose equivalent rate of β-ray.

If the two types of radiation detectors are alternately arranged in a matrix, the angle dependence of the sensitivity depending on the incident direction of radiation is corrected, so that the dose equivalent rate can be measured more accurately and the characteristics can be further improved.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, there is provided a radiation detector for detecting only gamma rays on a radiation detection surface,
By providing two types of radiation detectors, that is, radiation detectors for detecting X-rays or β-rays, a β-ray direct reading detection device capable of measuring the β-ray dose equivalent rate in real time can be realized.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a detecting device according to an embodiment of the present invention.

The detector 1 is composed of at least one pair of two types of independent radiation sensitive parts. One is silicon γ · which is sensitive to γ-rays (or X-rays) and β-rays.
β-ray detector 1 and the other is γ-ray (or X-ray)
The silicon γ-ray detector 2 having sensitivity only to the silicon γ-ray detector 2.

FIG. 2 is a structural diagram of a detection unit including the γ / β-ray detector 1 and the γ-ray detector 2. γ / β ray detector 21 and γ
The line detectors 22 are arranged on the substrate 24, and the γ-ray detectors 2
2, a β-ray cut filter 23 for cutting the β-ray sensitivity is added.

The material and thickness of this filter are determined by the cut-off value of the β-ray energy, but about 1.5 mm of aluminum is suitable, and the β-ray having a maximum energy of 1 MeV is cut.

When γ-rays and β-rays are simultaneously incident from the detector side of the detection device, the γ-rays and β-rays that have passed through the thin filter 7 that is always mounted reach the γ / β-ray detector 1,
In the γ-ray detector 2, only γ-rays arrive. Thereafter, the count is performed by each detection circuit 3. As the filter 7, a bonding material of aluminum and polyethylene having a thickness of about 10 to ²⁰ mg / cm ² is used for light shielding and electromagnetic shielding.

The count value is calculated by the CPU 4 in a dose equivalent rate (m
Sv / h) and displayed on the display unit 6. At this time, the β-ray dose equivalent rate (Hβ) is obtained as follows.

FIG. 3 is a flowchart for calculating the β-ray dose equivalent rate (Hβ). Count rate from the γ / β-ray detector 1 (C
1) and the count rate (C2) from the γ-ray detector 2 are calculated by the CPU circuit 4 to obtain Hβ = k (C1−C2). Here, k is a count rate (count / h) -dose equivalent rate (mSv / h) conversion coefficient. Here, the counting rate (C
1, C2) is the number of radiation incident on the detector per unit time, and the unit is usually expressed in counts / hour (h).

If the two types of radiation detectors are alternately arranged in a matrix, the angle dependence of the sensitivity depending on the radiation incident direction is corrected, and the dose equivalent rate can be measured more accurately. The dose equivalent rate of β-rays (Hβ) is obtained as follows.

FIG. 4 is a flowchart for calculating the β-ray dose equivalent rate in a matrix arrangement. The CPU circuit 4 calculates the sum (計数 C1) of the count rates from the n γ-β detectors 1 and the sum (ΣC2) of the count rates from the n γ-ray detectors 2, and calculates Hβ = K / n * (ΣC1-ΣC2). Here, k is a count rate (count / h) -dose equivalent rate (mSv / h) conversion coefficient. The angle dependence of the sensitivity depending on the incident direction of the radiation is corrected, and the dose equivalent rate can be measured more accurately. The more the number of detectors in the same size detector is increased, the more the β-ray direct reading dose equivalent rate meter with less direction dependency can be realized.

Similar results can be obtained by using a gallium arsenide detector or a cadmium telluride detector or a combination of a CsI scintillator detector and a silicon photo detector instead of the silicon detector.

[0020]

As is apparent from the above description, according to the present invention, two types of radiation, a radiation detector for detecting only γ-rays on a radiation detection surface and a radiation detector for detecting γ-rays or β-rays, are provided. A detector is provided and the CPU calculates each dose equivalent rate and calculates and displays the dose equivalent rate of only β-rays. Therefore, even when γ-rays and β-rays are mixed, β It is capable of separately measuring the dose equivalent rate of radiation.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a β-ray direct reading detection device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a form detection unit of the β-ray direct reading detection device according to one embodiment of the present invention.

FIG. 3 is a flowchart for calculating a β-ray dose equivalent rate in one embodiment of the present invention.

FIG. 4 is a flowchart for calculating a β-ray dose equivalent rate in a matrix arrangement according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a configuration of a conventional detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 γ / β-ray detector 2 γ-ray detector 3 Detection circuit 4 CPU circuit 5 Power supply 6 Display section 7 Filter 11 Detector 13 Detection circuit 14 CPU circuit 15 Power supply 16 Display section 17 Filter 21 γ / β-ray detector 22 γ Ray detector 23 beta ray cut filter 24 substrate

Claims (6)

[Claims] 1. A radiation detector for detecting only γ-rays or X-rays on a radiation detection surface, and a radiation detector for detecting γ-rays, X-rays or β-rays,
A β-ray direct reading detection device that displays only the dose equivalent rate of β-rays from the difference between the signals from each detector. 2. The β-ray direct reading detection device according to claim 1, wherein the two types of radiation detectors are alternately arranged in a matrix. 3. The β-ray direct reading detection device according to claim 1, wherein the radiation detector is a silicon detector. 4. The β-ray direct detection device according to claim 1, wherein the radiation detector is a cadmium telluride detector. 5. The β-ray direct reading detection device according to claim 1, wherein the radiation detector is a gallium arsenide detector. 6. The β-ray direct reading detection device according to claim 1, wherein the radiation detector is a combination of a CsI scintillator detector and a silicon photodetector.