JPH0361883A - Dose-equivalent measuring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to measure both 1-cm dose equivalent and 3-mm dose equivalent efficiently with a single apparatus by providing a first incident window for transmitting a low energy region excellently and an adjusting window which can be freely attached to and removed from the first incident window. CONSTITUTION:A first incident window 29 and an adjusting window 30 are provided at a first detecting part 10. For example, a voltage of -500V is applied to an applying electrode 18 of the first detecting part 10. At this time, when, e.g. +20V is applied to a first capacitance correcting electrode 32, the effective volume of the ionization chamber of the first detecting part 10 can be reduced by about 4 - 5%. Thus, the total detecting sensitivity can be lowered by a specified level. Meanwhile, a voltage of +500V is applied to an applying electrode 20 of a second detecting part 12. At this time, when, e.g. -20V is applied to a second capacitance correcting electrode 34, the effective volume of the ionization chamber of the second detecting part 12 can be reduced by 4% or more. Thus the radiation of a characteristic curve 202 can be measured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a dose equivalent measuring device, which is used for controlling exposure to γ-rays and The present invention relates to the configuration of a dose equivalent measurement device that directly reads equivalents and 3mm dose equivalents.

[Conventional technology] In recent years, measurement of radiation has become important in fields related to nuclear power and fields that utilize radiation, but in the past, radiation doses such as γ-rays, X-rays, etc. were measured by personnel exposed to external radiation It was carried out by

However, due to the revision of the Act on Prevention of Radiation Hazards based on the recommendations of the International Commission on Physical Protection (ICRP), instead of measuring irradiated dose or absorbed dose, the dose equivalent, which is the radiation dose that takes into account the energy characteristics inside the living body, has been changed to the 1 cm dose equivalent. ,
External exposure doses are now specified by 3-open dose equivalent or 70 μm dose equivalent. However, with conventional measuring devices, it is not possible to directly read the dose equivalent, and the dose equivalent is calculated from the irradiation dose, etc., which poses a problem in that the measurement operation is complicated.

Therefore, the applicant of this application filed Japanese Patent Application No. 62-292295! We have proposed an apparatus capable of measuring IJ1 equivalent, and an example of this invention is schematically shown in FIG.

In FIG. 3, a first detection section 10 and a second detection section 12
has a cylindrical double structure, and the first detection part 10
For example, a first entrance window 14 with a thickness for measuring a 1 cm dose equivalent is provided, focusing on a low energy region (of course, medium and high energy regions are also detected), and a first entrance window 14 is provided in the second detection section 12. A second entrance window 16 is provided with a thickness to detect only a predetermined amount of radiation in medium and high energy regions other than low energy. The first entrance window 14 is made of copper (29), nickel (28), cobalt (27), iron (26), titanium (22), and aluminum (13) with an atomic number of 30 or less.
, is formed using a single metal such as beryllium (4), an alloy, or a plastic made conductive with carbon (5), etc., and the second entrance window 15 is made of iron (26), etc., and also serves as an electrode. do.

Therefore, as shown in FIG. 4, the radiation dose having the characteristic shown by the curve 101 is measured from the first detection unit 10,
In the 12 detection units 12, the radiation dose having the characteristics shown by the curve 102 is measured.

A predetermined negative voltage is applied to the application electrode 18 of the detection unit 10 of jfil, while a predetermined positive voltage is applied to the application electrode (center electrode) 20 of the second detection unit 12. The collector electrode (16), which also serves as the second entrance window of the detection section 12, collects the ionized charges generated within the detection section.

Note that the first detection section 10 and the second detection section 12 are connected to the insulator 2.
2, the second entrance window 16 and the application electrode 20 are insulators 24
electrically isolated by

The collected current captured by the second entrance window 15 in this way is collected by an electrometer 26 (an oscillating capacitance electrometer or the like may be used).
The radiation dose is measured here as a radiation dose.

In this case, since the polarities of the collected currents obtained by the first detecting section 10 and the second detecting section 12 are set to be opposite, the detected currents of both detecting sections 10.12 are canceled out, and the difference current is detected. That will happen. Therefore, as shown in FIG.
The radiation dose of the curve 102 detected by the second detection unit 12 is subtracted from the radiation dose of the curve 101 detected by the second detection unit 10, and as a result, the radiation dose characteristic of the curve 100 is measured. It turns out. This characteristic curve 100 is
As shown in Figure 5, it corresponds to the conversion curve from irradiation dose (C/kg) to dose equivalent jl (sievert Sv), and this allows measurement in the unit of dose equivalent (Sv). It becomes possible.

[Problems to be Solved by the Invention] However, as mentioned above, it has become possible to measure the dose equivalent, but according to the Radiation Hazard Prevention Act, if the 3mtl dose equivalent is three times or more the Ics dose equivalent, There are 3
It is stipulated that the measurement and management should be performed using 0 dose equivalent.

Therefore, in this case, 3+aml from IC1I dose equivalent
! There was a problem in that conversion to ffi equivalent was necessary and complicated.

That is, in FIG. 5, i cII weight equivalent (100),
3 wg dose equivalent (200) or 70 μm dose equivalent (30
0) (conversion curve) is shown, and in the figure l
Comparing the ea dose equivalent conversion curve 100 and the 3-open dose equivalent conversion curve 200, the curves are near 30 keV and 500 keV.
Intersects near keV, from about 30 keV to about 500 k
In the peak region between eV, the ICl1l dose equivalent is high;
In other cases, the 5IIfil dose equivalent is high.

Therefore, it is understood that conversion to 3III dose equivalent is complicated.

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to make it possible to directly read the 3a+m dose equivalent, and to make it possible to read the 1CII dose equivalent and 3a+m dose equivalent directly.
An object of the present invention is to provide a dose equivalent measuring device that can efficiently measure both mm dose equivalent and mm dose equivalent with a single device.

[Means for Solving the Problems] In order to achieve the above object, a dose equivalent measuring device according to the present invention has an entrance window for passing radiation in a predetermined energy range and detects ionized charges generated by the radiation. In a dose equivalent measuring device that measures a dose equivalent by arranging a plurality of detecting sections that detect with electrodes in a stacked manner and adding and subtracting the outputs of the plurality of detecting sections, a method is provided in the first detecting section where radiation first enters. a first entrance window that transmits radiation in a low energy region that meets the characteristics of 3 mm dose equivalent measurement;
an adjustment window that is removably provided on the first entrance window and overlaps the first entrance window and transmits radiation in a low energy region that matches the characteristics of LCI dose equivalent measurement;
It is provided separately from the detection electrode in the detection part of 311III.
It is characterized in that it includes a capacitance correction electrode that performs level adjustment for measuring dose equivalent, and is capable of measuring both 1cm dose equivalent and 3III1 dose equivalent.

Further, the invention according to claim 2 provides a capacitance correction electrode in a detection unit other than the first detection unit, and the 3mm dose equivalent is 500.
It is characterized in that the level is adjusted so that it becomes higher than 1ca+dose equivalent in the energy region near keV or higher.

[Function] According to the above configuration, the measurement of the 31111 dose equivalent is performed with the adjustment window removed and a voltage applied to the capacitance correction electrode. The radiation in the region is transmitted to the first detection section without being annihilated, and the first detection section detects the radiation in the entire energy region including the low energy region. On the other hand, the second detection section detects a predetermined amount of medium/high energy radiation that has passed through the first detection section and through the second entrance window, with the low energy region removed.

In addition, since the first detection section is provided with a capacitance correction electrode, the output of the detection section will drop by about 4 to 5%, and this drop will be equal to the ICl1i amount equivalent in FIG. 5 and 3+n.
This roughly corresponds to the difference from the dose equivalent.

Then, at the collector electrode, the output of the second detector is canceled out by subtracting the output of the first detector, and when the capacitance correction electrode is turned on, the 3III dose equivalent is finally measured.

In addition, when measuring the 1clI dose equivalent, an adjustment window is installed.
And the voltage applied to the capacitance correction electrode is turned off.
In this case, the adjustment window reduces the radiation in the low energy region by 1
It is transmitted in such a way that the characteristics match those of cII dose equivalent measurements. Since the capacitance correction electrode also does not operate, the ionized charges generated in each of the first detection section and the second detection section are directly measured by the collector electrode, and the output of the rain detection section is eventually canceled out, resulting in a difference of 1 cm. Dose equivalents are measured.

In this way, in the present invention, the adjustment window can be attached and detached, and the capacitance correction electrode can be turned on and off by simple operations.
Direct reading of cIII dose equivalents and 3IImvA dose equivalents can be performed in a single device.

Further, according to the second claim, since the second detection section is provided with a capacitance correction electrode and is operated during 3 mm dose equivalent measurement,
It is possible to reduce the radiation detection level in the second detection section by more than 4%, and the final measured value can be reduced by 500 ke.
4% more than 1cm dose equivalent in the energy region near V or higher
It can be increased to a certain degree.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows the configuration of an embodiment in which the present invention is applied to an ionization chamber, and FIG. 2 shows the detection characteristics of each detection section, with the first detection section 10 and the second detection section 10 It is the same as the conventional one in that it has two detection parts, the detection part 12, and is provided with application electrodes 18 (negative electrode) and 20 (positive electrode) and a second entrance window 16 which also functions as a collector electrode.

Therefore, the second entrance window 16 of the second detection section 12
In order to obtain the characteristics of the curve 202 in the figure, it is made of iron with a thickness of 5 IIm, and also serves as a collecting electrode for collecting the ionized charges obtained in the first detecting section 10 and the second detecting section 12. The capacitance of the detecting section 12 is formed to be about 1/3 of the capacitance of the first detecting section 10.

A characteristic feature of the present invention is that the structure of the detection section
This makes it possible to measure both the cs dose equivalent and the 3mm dose equivalent.
An entrance window 28 and an adjustment window 30 are provided. That is, in the embodiment, the first entrance window 28 is formed of an iron plate or an aluminum plate with a thickness of 22 H/cm'', so as to enable the radiation measurement of the characteristic curve 201 regarding the 3-layer dose equivalent shown in FIG. do.

Further, the adjustment window 30 is formed to have a thickness of approximately g H/Cs", and together with the first entrance window 28 has a thickness of 30 H/cm", and is attached to and detached from the first entrance window 28 by a cap method. It is designed so that it can be attached freely (in the figure, it is slightly shifted to the front side), thereby making it possible to measure the radiation of the characteristic curve 101 regarding the lci dose equivalent shown in FIG. 2 (the curve 201 ).

Therefore, the first entrance window 28 and the adjustment window 30 make it possible to
1 of the first detection part of the device for cm dose equivalent (Fig. 3)
This will constitute an entrance window.

Then, these first detection section 10 and second detection section 1
2, in order to adjust the level difference shown in FIG. 5, which is necessary to measure and display 30 dose equivalents,
The first capacitance correction electrodes 32a, 32b are installed in the detection section 10 of
4b is provided.

That is, by applying a voltage of, for example, -500V to the application electrode 18 of the first detection section 10, and in this case, applying, for example, +20V to the first capacitance correction electrode 32, the ionization chamber of the first detection section 10 The effective volume can be reduced by about 4 to 5%, and the overall detection sensitivity can be reduced by a predetermined level.

On the other hand, the application electrode 20 of the second detection unit 12 has +500V.
In this case, by applying, for example, -20V to the second capacitance correction electrode 34, the effective capacity of the ionization chamber of the second detection section 12 can be reduced by 4% or more, as shown in FIG. It becomes possible to measure the radiation according to the characteristic curve 202 shown in FIG. In this case, the effective capacity is set to 4% or more so that the measured value in the energy region around 500 keV or higher becomes high, and therefore, as shown in the characteristic curve 200 in FIG.
At 3 mm dose equivalent, the characteristics exceed the IC1 dose equivalent curve 100 by about 4%.

Claims (2)

[Claims] (1) A plurality of detection units having an entrance window for passing radiation in a predetermined energy range and detecting ionized charges generated by the radiation using detection electrodes are arranged one on top of the other, and the outputs of the plurality of detection units are added and subtracted. In a dose equivalent measuring device that measures the dose equivalent by
a first entrance window that is provided in the detection section and transmits radiation in a low energy region that matches the characteristics of 3 mm dose equivalent measurement; An adjustment window that transmits radiation in a low energy region that matches the characteristics of dose equivalent measurement, and a capacitance correction electrode that is provided in at least the first detection section separately from the detection electrode and that performs level adjustment to measure the 3 mm dose equivalent. 1. A dose equivalent measuring device comprising: and capable of measuring both 1 cm dose equivalent and 3 mm dose equivalent. (2) In the apparatus according to claim (1), capacitance correction electrodes are provided in detection sections other than the first detection section, so that the 3 mm dose equivalent is higher than the 1 cm dose equivalent in an energy region of around 500 keV or higher. A dose equivalent measuring device characterized by performing level adjustment.