JPH11281746A - Personal alarm dosimeter and environmental dosimeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure radiation dose other than γ rays by calculating the amount of compensation for compensating for the detection amount of the γ rays of a detector other than the γ rays based on the count value of a γ-ray detector, and by integrating the difference between the count value and the amount of compensation. SOLUTION: The exposure dose of γ rays is calculated according to an integration count value up to the end of work. On the other hand, the exposure dose of β rays is calculated according to β- and γ-ray trend count values from the start to end of the work. Time from the start to end of the work is divided by the interval of five minutes. The amount of γ-ray compensation for each division time interval is calculated according to γ-ray count value for each division time interval, namely the γ-ray trend count value. On the other hand, the amount of γ-ray compensation is subtracted from β-ray count value for each division time interval, namely the β-ray trend count value, and the count value corresponding to the amount of the β rays for each division time interval is calculated. Only positive count values corresponding to the amount of the β rays for each division time interval are integrated over working time, and the integration value is set to the counter value corresponding to the amount of the βrays at the working time, thus the exposure dose of the β rays can be calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a personal alarm dosimeter for measuring the amount of radiation that a radiation worker is exposed to while working, and issuing an alarm when the measured dose exceeds a set value. Environmental dosimeters (both collectively referred to as dosimeters) for measuring radiation dose in the environment.

[0002]

2. Description of the Related Art A personal alarm dosimeter is a measuring instrument for measuring the dose of radiation exposed to radiation during work by a radiation worker, and is capable of measuring and displaying the radiation dose during work in real time. A warning is issued when the exposure dose exceeds a preset dose, and is used to prevent radiation workers from being excessively exposed to radiation. Therefore, when a radiation worker works in the radiation control area, he or she always carries this dosimeter and often uses it in a pocket of work clothes. Most of the conventional personal alarm dosimeters measure only gamma rays, but recently models that also measure beta rays have been announced, and also measure alpha rays and neutron rays. Are disclosed in the published patent gazette.

The environmental dosimeter measures the radiation dose in the environment inside and outside the radiation control area, and periodically collects the data. Like the personal alarm dosimeter, the main is dosimetry. However, other radiation is also measured. A conventional radiation detector used in such a dosimeter is disclosed in Japanese Patent Application Laid-Open No. 63-12179. As the radiation detector, a semiconductor detector that separates electron-hole pairs generated by radiation using a depletion layer formed by applying a voltage and detects the pair as a current pulse is used.

As detectors, a γ-ray detector that detects only γ-rays, a β-ray detector that detects β-rays and γ-rays, and an α-ray detector that detects α-rays, β-rays, and γ-rays Vessel, neutron beam and β
And a neutron detector for detecting gamma rays. To measure the dose of each radiation, the output of the beta detector is compensated by the output of the gamma detector, and the output of the alpha detector is compensated by the output of the beta detector and the output of the gamma detector. The output of the neutron detector is compensated by the output of the β-ray detector and the output of the γ-ray detector.

[0005] Gamma rays are detected by any detector due to their strong transmission. In addition, since the probability of interaction with the material of the detector greatly varies depending on the energy, the energy dependence of the γ-ray detection sensitivity varies depending on the configuration of the detector. Hereinafter, the energy dependence of sensitivity is referred to as energy characteristics. In a γ-ray detector, a filter of an appropriate material and an appropriate thickness is arranged in an entrance window thereof in order to improve the energy dependence of the detection sensitivity of the detector main body and to meet a characteristic specification. On the other hand, in the case of β-ray detectors or α-ray detectors, since β-rays or α-rays largely lose energy depending on the substance, a thin light-shielding film with low energy loss, for example, a metal-layer-deposited plastic thin film, is provided at the entrance window. Used. In the case of an α-ray detector, the energy loss is very large, so a special thin and durable film is used.

As described above, the filter of the γ-ray detector and β
The difference between the sensitivity of gamma-ray detectors for gamma-ray energy and the sensitivity of gamma-ray detectors for gamma-ray energy differs greatly from that of gamma-ray detectors due to the difference between the gamma-ray detectors and the plastic thin films deposited with metal layers. I have. FIG. 3 is a diagram showing an example. The horizontal axis in FIG. 3 is the energy of γ-rays, and the vertical axis is the relative sensitivity with the sensitivity at ¹³⁷ Cs γ-ray energy (662 keV) [E ( ¹³⁷ Cs) in the figure] being 1.
The thin line in the figure is the energy characteristic of the γ-ray detector,
The bold line is the energy characteristic of the β-ray detector.

As shown in FIG. 3, the energy characteristic of the γ-ray detector is adjusted to be close to the relative sensitivity of 1, while the energy characteristic of the β-ray detector is smaller than 1 on both sides of E ( ¹³⁷ Cs). The rate of decrease greatly differs depending on the energy. Therefore, even if an attempt is made to compensate for the γ-ray detection component of another detector using the output of the γ-ray detector,
Accurate compensation is not possible unless the energy distribution of γ rays is known. Conversely, if compensation is performed based on E ( ¹³⁷ Cs), compensation will be excessive for γ-rays of other energies.
That is, the dose of other radiation is underestimated.

FIGS. 4 and 5 show such an overcompensated state.
It is the diagram which showed the state modelly. The thin line is the gamma ray detector
The count value, the broken line is the count value of the β-ray detector, and the dotted line is the γ-ray detector.
The gamma ray compensation component of the β-ray detector based on the
Is β-ray obtained by subtracting γ-ray compensation from the count value of β-ray detector
The corresponding count value is shown. Figure 4 shows the first time
Exposure to β-rays at a certain rate in one hour, and a certain percentage in the next 8 hours
Shows the time lapse of each count value when exposure to gamma rays
I have. Due to excessive γ-ray compensation, β-ray equivalent
The value is the count value C for one hour of working time._B1When (1) is the peak
9 hours after the end of the work
In C _B9It has decreased to (1).

FIG. 5 shows the time course of each count value when β-rays are exposed as in FIG. 4 and γ-rays are exposed from the beginning at the same constant rate as in FIG. The count value C _B1 (2) of β-rays after one hour is smaller than C _B1 (1) by the amount of excess γ-ray compensation, and after one hour, it decreases at the same slope as in FIG. . As described above, the γ-ray detector and the β-ray detector
If the energy characteristics with respect to the line energy are different, a difference occurs in the magnitude of the error included in the β-ray equivalent count value depending on which energy is used to calculate the gamma ray compensation component. When the γ-ray compensation component is calculated based on the energy other than E ( ¹³⁷ Cs), the tendency of the count value corresponding to the β-ray to fall to the right is alleviated as compared with the case of FIG. 4 or FIG.
In some cases, the γ-ray compensation component may be insufficient, resulting in an upward-sloping state.

Although the above description has been made on the assumption that the energy distribution of γ-rays does not change over the entire working time, the energy distribution of γ-rays actually changes over time. Therefore, the coefficient for calculating an appropriate γ-ray compensation component from the γ-ray detector count value must be determined according to the change in the γ-ray energy distribution.
However, in reality, it is not possible to grasp the energy distribution every moment, so the gamma ray compensation component is calculated using a coefficient that matches the expected average energy distribution of gamma rays. Such a situation will be described in more detail with reference to FIG.

In FIG. 6, the horizontal axis represents the working time, and the vertical axis represents the working time.
The axis is the integrated count value of the γ-ray detector in (a), and the β-ray in (b).
Detector integrated count value, (c) is β-ray count within a predetermined time interval
Value C _b(tr), and the bold line in (b) indicates the cumulative count of the β-ray detector.
The value and the thin line indicate the γ-ray compensation component. Depending on working time
The energy distribution of gamma rays has changed. From the start of work,
γ-ray detector integrated count and β-ray detector integrated count increase
At the end of work_GAnd ΣC_BReach
You. In the prior art, [ΣC_B−KΣC_G], A β-ray equivalent count value is calculated, and based on this, β
Calculate the radiation dose. That is, the final count value ΣC_GPassing
Bi-C_BΒ-ray exposure dose is calculated based on
You.

Here, K is a coefficient for calculating a gamma ray compensation value from the count value of the gamma ray detector. On the other hand, during counting, there are various situations between the γ-ray count value of the γ-ray detector and the corresponding γ-ray count value of the β-ray detector. For convenience of explanation, it is assumed that γ-ray compensation amount in the case of the energy E ₁ in FIG. 3 is a proper value. The work time B in FIG. 6 is a case where β-rays and γ-rays coexist, and C _b (tr) remains even if γ-rays are compensated. The working time C corresponds to a case where the compensation coefficient is appropriate and the compensation value exactly matches (when the energy distribution is equivalent to E ₁ ), and C _b (t
r) is zero. The working time D, when the count for the compensation is excessive (e.g., energy distribution when the E ₂ or equivalent) corresponds to a compensation value exceeds the count, C _b (tr) becomes negative as a result of ing. The work time E corresponds to the case where the count for compensation is too small (for example, when the energy near E ( ¹³⁷ Cs) is large), the compensation value does not reach the count value, and as a result, C _b (tr) Is positive.

The situations shown in FIGS. 4 and 5 correspond to the situation of the working time D in FIG. 6, and the exposure dose of β-ray is under-measured, so that the most dangerous situation must be avoided by all means. Corresponds to the case. In actual measurement sites,
It is considered that the various situations described above are mixed.
Therefore, normally, the coefficient for compensation must be determined on the safe side based on some degree of situation estimation.

Although the above description has been made for the case of β-ray measurement, the situation is exactly the same for other radiations. In the dosimeter, not only the final count values ΣC _G and ΣC _B but also a shorter time interval (for example, one minute interval or 10
Often, it has a function of storing the count value (called the trend count value) of (minute interval).

[0015]

As is apparent from the above description, it is difficult for a dosimeter according to the prior art to accurately compensate for a γ-ray detection component of a detector other than a γ-ray, and a slight error May cause large errors in the final measured values. In the case of the relative sensitivity as shown in FIG. 3, since the γ-ray sensitivity of the β-ray detector is smaller in most of the energy region, if the coefficient for calculating the compensation value is not reviewed, the working time D Is increased, and as a result, the β-ray count value is undercounted. Even if the γ-ray level is as low as the background in most of the time zones, if the situation such as the working time D continues, the β-ray equivalent count value will be significantly smaller than the actual exposure dose. The possibility comes out.

It is an object of the present invention to accurately measure a radiation dose other than γ-ray by avoiding an under-measurement of a measured dose due to an excessive compensation for γ-ray detection by a detector other than the γ-ray detector as described above. It is to provide a dosimeter that can measure.

[0017]

In the present invention, γ
Among the X-ray detector, β-ray detector, α-ray detector, and neutron detector, at least a γ-ray detector and a β-ray detector are provided, and the γ of the other detector is determined by the output of the γ-ray detector. In the personal alarm dosimeter in which the output by the line is compensated, the count value of each detector is measured at each predetermined time interval obtained by further dividing the working time, and is calculated based on the count value of the γ-ray detector. The difference obtained by subtracting the compensation amount corresponding to the γ-ray of each detector other than the γ-ray from the count value of each detector other than the γ-ray is calculated, and only the difference when the difference is positive is calculated. Accumulated for each detector over the entire working time, each integrated value is converted to the radiation exposure dose corresponding to each detector and output, and the count value of the γ-ray detector is integrated over the entire working time. converted to gamma-ray exposure and output (Invention of claim 1).

Since only the positive difference is integrated, even if the compensation by the count value of the gamma ray detector is excessive when only the gamma ray exists, the count value of the detectors other than the gamma ray is thereby reduced. Will not be deducted. In addition, γ-ray detector and β
Among the X-ray detector, α-ray detector and neutron detector, at least a γ-ray detector and a β-ray detector are provided, and the output of the other detector due to γ-ray is determined by the output of the γ-ray detector. In the compensated personal alarm dosimeter, the count value of each detector is measured at each predetermined time interval obtained by further dividing the working time, and the γ obtained based on the count value of the γ-ray detector is obtained.
Each difference is calculated by subtracting the compensation equivalent to the γ-ray of each detector other than the line from the count value of each detector other than the γ-ray, and the difference is positive and the count value of the γ-ray detector Only the difference when the difference is larger than the statistical error is integrated for each detector over the entire working time, and each integrated value is converted to the radiation exposure dose corresponding to each detector and output. The count value is integrated over the entire working time, converted into a γ-ray exposure dose, and output (the invention of claim 2).

When the difference is positive and larger than the statistical error of the count value of the γ-ray detector, the difference is accumulated. Therefore, when only γ-rays exist, the γ-ray detector and other detectors are used. Most of the positive differences generated due to the variation in the detection of γ-rays occurring between the two are removed. In the invention of claim 2, the predetermined time interval is set so that the count value of the γ-ray detector during that time is at least one count (the invention of claim 3).

Since the count value of the γ-ray detector is set to at least one count, the square root of the count number, which is a statistical error, does not become zero, and the accuracy of compensation is improved. The inventions of claims 4 to 6 are the same as the inventions of claims 1 to 3, except that the concept of the personal alarm dosimeter is completely replaced with an environmental dosimeter.
Description is omitted.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a dosimeter according to the present invention will be described with reference to examples. [First Embodiment] The dosimeter used in this embodiment is a personal alarm dosimeter provided with a γ-ray detector and a β-ray detector, and has a function of storing trend count values at 5-minute intervals. It has.

In this embodiment, the exposure dose of γ-rays is calculated from the integrated count value up to the end of the work as in the prior art. On the other hand, the exposure dose of β-ray is different from the conventional technology,
Β-ray trend count value and γ from the start of work to the end of work
It is calculated from the trend count value of the line. First, the time is divided at intervals of 5 minutes from the start of work to the end of work, and a γ-ray count value for each divided time interval, that is, a γ-ray compensation count for each divided time interval is calculated from a γ-ray trend count value, Β-ray count value for each divided time interval, that is, β-ray trend count value,
Is subtracted from each other, and a β-ray equivalent count value for each divided time interval is calculated. Only the positive values among the calculated β-ray equivalent count values for each of the divided time intervals are integrated over the working time, and the integrated value is used as the β-ray equivalent count value during the working time. The dose is calculated.

FIG. 1 is a diagram showing the result of performing the same measurement as in FIG. 4 described in the section of the prior art using the personal alarm dosimeter according to this embodiment, and FIG. 2 is the same as FIG. It is a diagram showing the result of having performed measurement. The β-ray equivalent count value after 1 hour in FIG. 1 is defined as C _B1 (3), and β value after 9 hours.
The line equivalent _count value C _B9 (3), the β-ray equivalent count value after one hour in FIG. 2 is C _B1 (4), and the β-ray equivalent _count value C _B9 ( ₉ ) after nine hours in FIG. .

This measurement was performed under the following two conditions. First condition: a γ-ray sensitivity of the γ-ray sensitivity and β-ray detector γ-ray detector, determining the coefficients for calculating the γ ray compensation amount to be the same in E of FIG. 3 ^{(1 37} Cs) And ⁶⁰ Co as gamma-ray source
(Gamma ray energy E ⁽⁶⁰ Co) equivalent to FIG. 3) is used. The measurement result under this condition is: C _B1 (3) = C _B9 (3) C _B1 (4) = C _B9 (4) C _B1 (3)> C _B1 (4) In the case of coexistence with the radiation, the count value corresponding to the β-ray is estimated to be somewhat smaller, but no effect due to the exposure to the γ-ray after 1 hour is seen at all, and the results are compared with the results of FIGS. 4 and 5. Significantly superior results have been obtained.

In the coexistence field, the reason why the count value for the β-ray equivalent is estimated somewhat smaller is that the coefficient for calculating the γ-ray compensation component is too large for the γ-ray to be irradiated (γ-ray of ⁶⁰ Co). It is estimated that Second condition: a γ-ray sensitivity of the γ-ray sensitivity and β-ray detector γ-ray detector, to determine the coefficients for calculating the γ ray compensation amount as the same in E of FIG. 3 ^{(1 37} Cs) ¹³⁷ C as gamma-ray source
Use s).

According to the measurement results under these conditions, C _B9 (3) is somewhat larger than C _B1 (3), and C _B9 (3) is larger than C _B1 (4).
_B9 (4) is somewhat larger, C _B1 (3) ≒ C _B1 (4), and the accuracy of the β-ray equivalent count value in the coexistence field is improved, but the γ-ray after 2 hours There is a slight effect of exposure. However, significantly superior results are obtained compared to the results of FIGS.

It is presumed that the slight increase tendency after one hour has occurred because the coefficient for compensation has become an appropriate value. That is, due to the statistical error of the count values of the γ-ray detector and the β-ray detector, the γ-ray count value of the β-ray detector may be larger than the γ-ray compensation component. It is presumed that the difference obtained by subtracting the γ-ray compensation component from the count value becomes positive, and that the positive difference is integrated to show an increasing tendency.

[Second Embodiment] This embodiment also uses the same personal alarm dosimeter as the first embodiment. The difference between this embodiment and the first embodiment is that the calculated β
Of the positive line equivalent count values, only those larger than the statistical error of the γ-ray detector count value among the positive ones are integrated over the working time, and the integrated value is used as the β-ray equivalent count value in the working time. That is to calculate the β-ray exposure dose.

The purpose of this embodiment is to improve a slight increasing tendency which is estimated according to the statistical error that has appeared under the second condition of the first embodiment. The results obtained by using the personal alarm dosimeter according to this embodiment under the same two measurement conditions as in the first embodiment are as follows. In the case of the first condition, C _B1 (3) = C _B9 (3) C _B1 (4) = C _B9 (4) C _B1 (3)> C _B1 (4) I got the same result.

Under the second condition, C _B9 (3) is slightly larger than C _B1 (3), and C _B9 (3) is larger than C _B1 (4).
_B9 (4) was slightly larger, and C _B1 (3) ≒ C _B1 (4), and the slight increase tendency after 2 hours was improved.

It is shown that the counting error due to γ-rays can be reduced by excluding the positive difference from the statistical error. Furthermore, in order not to increase the measurement error, it is effective to avoid that the γ-ray trend count value becomes zero. Because, in a situation where the count value becomes zero, either the count value of the γ-ray detector due to γ-rays or the count value of the β-ray detector due to γ-rays is often zero, and γ This is because, when the count value of the ray detector due to γ-rays is zero, the statistical error is zero, and when the count value of the β-ray detector is 1, the accumulation is performed.

Therefore, in the above-described embodiment, an example has been described in which the trend count value is used as it is. However, when the trend count value of the γ-ray detector is 1 or less, several divided time intervals are used. It is also effective to use as a unit.
In the above, the case of a personal alarm dosimeter that measures γ-rays and β-rays has been described. However, the present invention is similarly effective for a personal alarm dosimeter that includes other radiation detectors. Is similarly effective.

[0033]

According to the present invention, at least a γ-ray detector and a β-ray detector among the γ-ray detector, the β-ray detector, the α-ray detector, and the neutron detector are provided. In a personal alarm dosimeter in which the output of another detector is compensated by the output of the gamma ray by the output of the line detector, the count value of each detector is measured at predetermined time intervals obtained by further dividing the working time. Each difference is calculated by subtracting the compensation amount corresponding to γ-rays of each detector other than γ-rays obtained based on the count value of γ-ray detectors from the count value of each detector other than γ-rays. Only the difference when the difference is positive is integrated for each detector over the entire working time, and each integrated value is converted into the radiation exposure dose corresponding to each detector and output, and γ-ray detection is performed. The instrument count is integrated over the entire working time. It is converted to γ-ray exposure and output, so if only γ-rays are present, even if the compensation by the count value of the γ-ray detector is excessive, the count values of detectors other than γ-rays are thereby reduced. It will not be deducted.
Therefore, a personal alarm dosimeter that can accurately measure radiation doses other than γ-rays by preventing the counts of other detectors from being excessively deducted and becoming abnormally lower than the actual exposure dose is provided. (The invention of claim 1).

Further, among the γ-ray detector, β-ray detector, α-ray detector and neutron detector, at least the γ-ray detector and β
A line detector and a personal alarm dosimeter in which the output of the other detector due to γ-rays is compensated for by the output of the γ-ray detector. The count value of each detector other than γ-ray is calculated based on the count value of the detector of γ-ray detector, and the compensation value equivalent to γ-ray of each detector other than γ-ray is calculated based on the count value of each detector other than γ-ray. Each difference subtracted from is calculated,
Only the difference in the case where the difference is positive and larger than the statistical error of the count value of the γ-ray detector is integrated for each detector over the entire working time, and each integrated value is calculated for the radiation equivalent to each detector. It is output after being converted to the exposure dose, and the count value of the γ-ray detector is integrated over the entire working time and output after being converted to the γ-ray exposure dose. Most of the positive differences caused by the variation in gamma ray detection occurring between the other detectors are removed. Accordingly, the present invention provides a personal alarm dosimeter capable of reducing an error generated due to a variation in γ-ray detection between detectors, increasing detection accuracy, and more accurately measuring a radiation dose other than γ-ray. (Invention of claim 2).

According to the second aspect of the present invention, since the predetermined time interval is set so that the count value of the γ-ray detecting unit during the predetermined time interval is at least one count, the square root of the count number, which is a statistical error, is zero. And the accuracy is further improved. Therefore, it is possible to provide a personal alarm dosimeter capable of measuring radiation doses other than γ-rays more accurately (the invention of claim 3).

The invention of claims 4 to 6 provides the invention of claim 1
Since the concept of the personal alarm dosimeter according to the invention of claim 3 is completely replaced with an environmental dosimeter as it is, according to the invention of claim 4 to claim 6, the radiation dose other than γ-ray is accurately measured. Environmental dosimeter that can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing the elapsed time of a count value in a first embodiment of a personal alarm dosimeter according to the present invention;

FIG. 2 is another diagram showing the elapsed time of the count value in the first embodiment.

FIG. 3 is a diagram showing the relative sensitivity of a γ-ray detector and a β-ray detector to γ-ray energy.

FIG. 4 is a diagram showing a time course of a count value of a conventional personal alarm dosimeter when β-rays are irradiated for the first hour and γ-rays are irradiated for the next 8 hours.

FIG. 5 shows the irradiation of γ-rays and β-rays during the first hour,
Diagram showing the elapsed time of the count value of a conventional personal alarm dosimeter when only gamma rays are irradiated at the time

FIG. 6 is a diagram for explaining a problem of a conventional dosimeter;
(A) is a diagram showing a time change of the integrated count value of the γ-ray detector,
(B) is a diagram showing a time change of the β-ray detector integrated count value,
(C) is a β-ray count value C _b within a predetermined time interval for each work time.
Diagram showing (tr)

Claims (6)

[Claims] An γ-ray detector, a β-ray detector, an α-ray detector, and a neutron detector are provided with at least a γ-ray detector and a β-ray detector. In a personal alarm dosimeter in which the output of other detectors due to γ-rays is compensated, the count value of each detector is measured at predetermined time intervals obtained by further dividing the working time, and the γ-ray detector Γ of each detector other than γ-rays obtained based on the count value
Each difference obtained by subtracting the compensation equivalent to the line from the count value of each detector other than γ-ray is calculated, and only the difference when the difference is positive is integrated for each detector over the entire working time. , Each integrated value is converted and output to the radiation exposure dose corresponding to each detector, and the count value of the γ-ray detector is integrated over the entire working time and converted to γ-ray exposure dose and output. A personal alarm dosimeter characterized by the following. 2. A γ-ray detector, a β-ray detector, an α-ray detector, and a neutron detector, wherein at least a γ-ray detector and a β-ray detector are provided, and an output of the γ-ray detector is provided. In a personal alarm dosimeter in which the output of other detectors due to γ-rays is compensated, the count value of each detector is measured at predetermined time intervals obtained by further dividing the working time, and the γ-ray detector Γ of each detector other than γ-rays obtained based on the count value
Each difference is calculated by subtracting the compensation equivalent to the line from the count value of each detector other than γ-ray, and only the difference when the difference is positive and larger than the statistical error of the count value of the γ-ray detector is calculated. Is integrated for each detector over the entire working time, each integrated value is converted to the radiation exposure dose corresponding to each detector and output, and the count value of the γ-ray detector is integrated over the entire working time. A personal alarm dosimeter, which is converted into a gamma-ray exposure dose and output. 3. The personal alarm dosimeter according to claim 2, wherein the predetermined time interval is set so that a count value of the γ-ray detector during the predetermined time interval is at least one count. 4. A γ-ray detector, a β-ray detector, an α-ray detector and a neutron detector, wherein at least a γ-ray detector and a β-ray detector are provided, and according to an output of the γ-ray detector. In an environmental dosimeter in which the output of the other detectors due to γ-rays is compensated, the count value of each detector is calculated at predetermined time intervals obtained by dividing the period of one period for periodically collecting measurement data into shorter periods. Each difference obtained by subtracting the compensation equivalent to γ-rays of each detector other than γ-rays, which was measured based on the count value of γ-ray detectors, was subtracted from the count value of each detector other than γ-rays. Calculated, only the difference when the difference is positive is integrated for each detector over one cycle period, and each integrated value is converted into the radiation exposure dose of radiation corresponding to each detector and output. The line detector count is multiplied over one period. An environmental dosimeter characterized in that it is calculated and converted into a γ-ray exposure dose and output. 5. A γ-ray detector, a β-ray detector, an α-ray detector, and a neutron detector, wherein at least a γ-ray detector and a β-ray detector are provided, and according to an output of the γ-ray detector. In an environmental dosimeter in which the output of the other detectors due to γ-rays is compensated, the count value of each detector is calculated at predetermined time intervals obtained by dividing the period of one period for periodically collecting measurement data into shorter periods. Each difference obtained by subtracting the compensation equivalent to γ-rays of each detector other than γ-rays, which was measured based on the count value of γ-ray detectors, was subtracted from the count value of each detector other than γ-rays. Only the difference when the difference is positive and larger than the statistical error of the count value of the γ-ray detector is integrated for each detector over one period, and each integrated value is equivalent to each detector. Is output after being converted to the radiation exposure dose of An environmental dosimeter characterized in that the count value of the γ-ray detector is integrated over one cycle period, converted into γ-ray exposure dose, and output. 6. The environmental dosimeter according to claim 5, wherein the predetermined time interval is set such that a count value of the γ-ray detector during the predetermined time interval is at least one count.