JP2000275347A - Dust-radiation monitoring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a measuring error due to the mixed existence of beams of light from an α-ray detecting layer and a β-ray detecting layer and to eliminate a measuring error due to the absorption of β-rays in the α-ray detecting layer. SOLUTION: In this dust-radiation monitoring apparatus, a radiation which is emitted from dust collected by a dust collection part is detected, and the existence of radioactive contamination is judged. An α-ray detecting part 5 and a β-ray detecting part 5 have a structure which detects α-rays and β-rays independently without being mixed. An α-ray detecting layer and a β-ray detecting layer are arranged on a substantially identical face. An α-ray measuring part 6 and a β-ray measuring part 7 find an α-ray measured value and a β-ray measured value individually on the basis of α-rays and β-rays which are detected independently. In a data processing part 8, the emission ratio, which is found in advance, of α-rays to β-rays, emitted by a natural nuclide is used as a correction factor so as to be multiplied by the α-ray measured value. The value of the β-rays in the natural nuclide is calculated, and the radioactive contamination is judged by using a value obtained by subtracting the calculated value of the β-rays from the β-rays measured value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust radiation monitor used in a facility for handling radiation sources, such as a nuclear power plant, for measuring the radioactivity concentration of dust in the air in the facility.

[0002]

2. Description of the Related Art Conventionally, dust radiation monitoring devices for measuring the radioactivity concentration of dust in the air in a radiation source facility such as a nuclear power plant have been widely used.

FIG. 23 is a schematic diagram showing an example of the configuration of a dust radiation monitoring device that is actually widely used in a radiation source handling facility such as a nuclear power plant.

In the conventional dust radiation monitor shown in FIG. 23, when air is sucked into the chamber C through the sampling pipe 1, radiation dust in the air is collected by a filter (filter paper or the like) of the dust collecting section 2, and the dust is collected. The air after collection is discharged via the sampling pump 3. On the other hand, β-rays are detected by the β-ray detector 5 from the radiation dust collected by the filter, and are converted into electric signals. When the β-ray measurement value is obtained by the β-ray measurement unit 7, the data processing unit 8 compares the measurement value with the alarm set value and determines contamination.

[0005] Natural radioactive materials exist in the natural world. Radon is a typical example of a naturally occurring nuclide (hereinafter referred to as "natural nuclide"). Radon is a rare gas and exists in the natural world, so it is also suspended in facilities. This nuclide collapses and turns into a daughter nuclide,
In addition, α-rays and β-rays are emitted in the process of decay into progeny.

Therefore, the radiation dust collected by the dust radiation monitor usually contains natural nuclides, and as shown in FIG.
Contains the contribution V2 of the natural nuclide in addition to the contribution V1 of the measured nuclide due to the leak. Due to the influence of natural nuclides, it is possible to determine as if there are many radionuclides to be measured (artificially contaminated nuclides). Therefore, the problem that the effects of natural nuclides must be separately evaluated There is.

As a technique for solving such a problem, Japanese Unexamined Patent Publication No. 9-111133 discloses a technique for accurately determining the presence or absence of radioactive contamination without separately evaluating the influence of natural nuclides. According to this technique, α-rays and β-rays emitted from natural nuclides are separately measured in advance by a measurement system, and the emission ratios of α-rays and β-rays by the measured natural nuclides are obtained in advance.
Next, in actual contamination determination, radiation emitted from the subject is detected by a radiation detector, and α-rays and β
The measurement is performed separately from the line. Then, the correction processing means obtains the β-ray value of the natural nuclide contained in the β-ray measurement value from the α-ray and β-ray emission ratios and the α-ray measurement value, and obtains the natural value from the β-ray measurement value. Subtract the value of β-ray by nuclide. As a result, a value of β-ray excluding the influence of natural nuclides can be obtained.

[0008]

However, in the above-mentioned dust radiation monitoring apparatus disclosed in Japanese Patent Application Laid-Open No. 9-111133, α-rays and β-rays are measured using a single radiation detector. Specifically, two radiation detectors
A detection unit composed of layers (α-ray detection layer and β-ray detection layer) is provided to perform detection measurement. For this reason, the following problems exist.

(1) Low energy β-rays are absorbed by the α-ray detection layer. That is, in the structure in which the α-ray detection layer and the β-ray detection layer are overlapped, the β-rays emitted from the dust collecting portion always pass through the α-ray detection layer before reaching the β-ray detection layer.
The detection efficiency of low-energy β-rays that are easily absorbed is reduced, resulting in measurement errors.

(2) Separation measurement of α-ray and β-ray is limited. That is, light from each detection layer of α rays and β rays is mixed. The mixed light is separated in the subsequent circuit due to its rise and the difference in the amount of emitted light, but it is not completely separated, and the energy of the α-ray and β-ray to be measured is not unitary. Are mixed in a certain energy region, which causes a measurement error. In particular, the low energy side of α rays and the high energy side of β rays are likely to be mixed.

Accordingly, an object of the present invention is to provide a dust radiation monitor device having a structure in which light from each detection layer of α-ray and β-ray is not mixed, and which can eliminate measurement errors due to mixing. is there.

Another object of the present invention is to eliminate the problem of absorption of β-rays by another detection layer when detecting β-rays and to improve the detection efficiency of low-energy β-rays, thereby enabling measurement by β-ray absorption. An object of the present invention is to provide a dust radiation monitoring device capable of eliminating an error.

[0013]

In order to achieve the above object, a dust radiation monitoring apparatus according to the present invention comprises:
In a dust radiation monitoring device that detects radiation emitted from dust collected by a dust collection unit to determine the presence or absence of radioactive contamination, an α-ray detection layer and a β-ray detection layer are substantially on the same plane. An α-ray detector and a β-ray detector that are arranged and independently detect without mixing α-rays and β-rays, and individually obtain α-rays from α-rays and β-rays detected independently The α-ray measurement unit and the β-ray measurement unit for obtaining the measurement value and the β-ray measurement value, and the α-ray measurement value as a correction coefficient using the emission ratio of the α-ray and the β-ray emitted by the natural nuclide determined in advance A data processing unit that calculates a value of β-ray of the natural nuclide by multiplying the value and subtracts the value of the calculated β-ray from the measured value of β-ray to determine contamination using a value obtained. And

According to the present invention, the light from the α-ray detecting layer and the light from the β-ray detecting layer are independently mixed without mixing the light from the α-ray detecting layer and the light from the β-ray detecting layer.
In addition to detecting and measuring radiation and performing correction processing to obtain the value of β-rays excluding the influence of natural nuclides, it is possible to further improve the accuracy of contamination determination as compared with the conventional technology. .

A dust radiation monitor according to a second aspect of the present invention is a dust radiation monitor which detects radiation emitted from dust collected by a dust collecting section to determine the presence or absence of radioactive contamination. An α-ray detector and a β-ray detector, wherein the α-ray detector and the β-ray detector have a structure in which the α-ray detection layer and the β-ray detection layer are arranged on substantially the same plane and independently detect α-rays and β-rays without being mixed
A ray detection unit, an α-ray measurement unit for individually obtaining an α-ray measurement value and a β-ray measurement value from an independently detected α-ray and β-ray, and β
A line measurement unit and a data processing unit capable of selectively setting a mode between a first mode for measuring natural nuclides and a second mode for measuring dust radioactivity concentration. The emission ratio of α-rays and β-rays emitted by the natural nuclides measured in the first mode is determined in advance as a correction coefficient, and the α-ray measurement value measured in the second mode is calculated. Calculate the β-ray value of the natural nuclide by multiplying by the correction coefficient, and use the value obtained by subtracting the calculated β-ray value from the β-ray measurement value measured in the second mode to perform contamination. A data processing unit for making a determination.

According to the present invention, in addition to the above effects, a mode is selectively set between the first mode for measuring natural nuclides and the second mode for measuring dust radioactivity concentration. Therefore, a correction coefficient based on the actual measurement value of the natural nuclide can be obtained, and the correction value can be made highly accurate.

According to a third aspect of the present invention, the data processing unit evaluates a change in a predetermined condition that is a cause of fluctuation of a natural nuclide, and corrects a change in a correction coefficient caused by the change in the condition. It may be. In this case, in addition to the above-described effects, there is an effect that further high-accuracy measurement can be realized.

According to a fourth aspect of the present invention, the dust radiation monitoring apparatus further includes a ventilation blower for ventilating gas containing dust to be measured, and the data processing unit operates / stops the ventilation blower. The relationship between the elapsed time from each start time and the concentration of the natural nuclide may be evaluated, and the change in the correction coefficient caused by the change in the concentration of the natural nuclide may be corrected. Also in this case, in addition to the above-described effects, there is an effect that more accurate measurement can be realized.

Further, the data processing section may store the condition at the time when the correction coefficient is larger than a predetermined value.
In this case, in addition to the above-described effects, there is an effect that the fluctuation factor and the soundness of the correction coefficient can be separately evaluated.

The data processing unit may store the condition at that time when the dust radioactivity concentration is higher than a predetermined value. In this case, in addition to the above-mentioned effects, there is an effect that the fluctuation factor and the soundness of the dust radioactivity concentration can be separately evaluated.

Further, as in the invention of claim 7, the α-ray detecting layer is constituted by a plurality of wavelength shift fibers coated with ZnS (Ag), and the β-ray detecting layer is constituted by a plurality of plastic scintillation fibers. The α-ray detector further includes an α-ray photomultiplier that converts a detection signal from the fiber that has detected the α-ray into an electrical signal, and the β-ray detector has a detection signal from the fiber that has detected the β-ray. May be further provided with a β-ray photomultiplier that converts the photons into an electric signal. In this case, since each fiber individually detects α-rays and β-rays and guides the detection signals to individual photomultipliers, the α-rays and β-rays can be detected independently without being mixed, and the measurement based on the mixed light can be performed. Errors can be eliminated. Further, since the fibers are arranged on the same surface, the problem of β-ray absorption is eliminated, and the detection efficiency can be improved. Further, since the configuration is simplified, the production cost can be reduced.

Further, as in the invention of claim 8, the α-ray detecting layer is constituted by a plurality of wavelength shift fibers coated with ZnS (Ag), and the β-ray detecting layer is constituted by a plurality of plastic scintillation fibers. An α-ray fiber for optically transmitting an α-ray detection signal from the α-ray detection layer, and an α-ray photomultiplier for converting the optically transmitted α-ray detection signal into an electric signal. The β-ray detector further includes a β-ray fiber for optically transmitting the β-ray detection signal from the β-ray detection layer, and an α-ray for converting the optically transmitted β-ray detection signal into an electric signal. A photomultiplier may be further provided. In this case, the same effect can be obtained.

Also, as in the ninth aspect of the present invention, the α-ray detecting layer is constituted by a plurality of wavelength shift fibers coated with ZnS (Ag), and the β-ray detecting layer is constituted by a plurality of plastic scintillation fibers. The α-ray detection unit includes an α-ray light guide that guides an α-ray detection signal detected on the entire surface of the α-ray detection layer to one point, and an α-ray that converts the guided α-ray detection signal into an electric signal. And a β-ray light guide for guiding the β-ray detection signal detected on the entire surface of the β-ray detection layer to a single point, and a β-ray detection signal to be guided. Β to convert to electrical signal
A line photomultiplier may be further provided. In this case, the same effect can be obtained.

Further, according to a tenth aspect of the present invention,
The area of the line detection layer may be larger than the area of the α-ray detection layer. In this case, in addition to the effects described above, there is an effect that the balance between the α-ray and β-ray detection sensitivities can be optimized.

Also, as in the invention of claim 11, the β
The line detecting unit may further include a filter provided between the β-ray detecting layer and the dust collecting unit to cut α-rays and transmit β-rays. In this case, in addition to the above effects, α ray and β
There is an effect that the line can be measured with higher accuracy.

According to a twelfth aspect of the present invention, a hole is provided in a part of the filter, and the filter selectively cuts off the radiation which is not cut off the α-ray and the radiation which cut off the α-ray. The position of the hole may be movable so that it can be detected by the β-ray detection layer. In this case, in addition to the above-described effects, there is an effect that the operation of inserting and removing the α-ray cut filter is facilitated, and highly accurate α-ray detection can be smoothly performed.

Further, according to the invention of claim 13, the α
The line detection layer is made of a wavelength-shifted fiber coated with ZnS (Ag), and is provided so as to surround the periphery of the β-ray detection layer. The α-ray detection unit is configured to transmit α-rays transmitted through the fiber. Α that converts the detection signal into an electric signal
A line photomultiplier may be further provided. In this case, α
Since the area of the line detection surface can be reduced and the area for β-ray detection can be increased, there is an effect that β-rays can be measured with higher sensitivity and accuracy.

[0028]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment) First, a first embodiment will be described. FIG. 1 is a schematic diagram illustrating a configuration example of the dust radiation monitoring device according to the first embodiment.

In FIG. 1, a chamber C blocks external radiation, inhales gas such as air, and discharges gas after dust collection.

The sampling pipe 1 guides gas at a predetermined location in the radiation control area to the inside of the chamber C.

The dust collecting section 2 is for collecting dust in the gas sucked into the chamber C through the sampling pipe 1 by using a sheet-like filter (filter paper or the like). It has a mechanism to move it. The sampling pump 3 urges gas to be sucked into the chamber C and discharged to the outside.

The α-ray detector 4 independently detects α-rays from the dust collected by the filter. The α-rays detected by the α-ray detector 4 are converted into electric signals and sent out as detection signals. On the other hand, the β-ray detector 5
Is to independently detect β-rays from dust collected by a filter. The β-rays detected by the β-ray detector 5 are converted into electric signals and sent out as detection signals.

The α-ray detector 4 and the β-ray detector 5
Are provided in parallel, and are arranged such that the detection layers of the respective detection units exist on the same plane. For this reason, the structure is such that light from the detection layer of the α-ray detection unit 4 and light from the detection layer of the β-ray detection unit 5 can be independently detected without mixing the light from the detection layer. .

The α-ray measuring section 6 measures an α-ray based on the detection signal from the α-ray detecting section 4 and outputs a measured value of the α-ray. On the other hand, the β-ray measuring unit 7 measures the β-ray based on the detection signal from the β-ray detecting unit 5 and outputs the measured value of the β-ray.

The data processing section 8 has two modes, a natural various measurement mode and a dust radioactivity concentration measurement mode, and can set one of the desired modes. The data processing unit 8 performs a predetermined calculation, which will be described later, based on the measured value of the α-ray and the measured value of the β-ray measured at the time of setting each of the natural various measurement modes and the dust radioactivity concentration measurement mode. Then, the value of β rays excluding the influence of natural nuclides is obtained. Further, the data processing unit 8 compares the measured value obtained by the above calculation with the alarm set value and makes a contamination determination.

By the way, natural nuclides have the property of emitting α-rays in the process of decay, whereas measurement nuclides generated by leakage do not emit α-rays. This fact will be specifically described with reference to FIGS.

FIG. 2 is a diagram showing the decay process of natural nuclides. As shown in this figure, the natural nuclide ²²⁶ Ra
Is contained in concrete and underground, and has a half-life of 16
It will be ²²² Rn in 2002 (stable). At this time, α rays are emitted. ^{Since 222} Rn is a noble gas, some of it exudes from concrete or the ground and floats in the air, and becomes a daughter nuclide ²²² Rn with a half-life of 3.8 days (metastable). Also at this time, α rays are emitted. Since the daughter nuclide ²²² Rn is suspended in the air, it is collected together with the sampling gas. The daughter nuclide ²²² Rn emits α rays, β rays and γ rays. The daughter nuclide ^{2 22} Rn has a half-life of ²¹⁰ Pb on the order of seconds to minutes (unstable). Further, β-rays and γ-rays are emitted in the process of ²¹⁰ Pb decay with a half-life of 20.4 years (stable).

FIGS. 3 and 4 are diagrams showing the decay process of the measured nuclide generated by the leak. As shown in FIG. 3, the measurement nuclide I, Br (radioisotope of iodine and bromine; solid) becomes Xe, Kr (noble gas) in the decay process. At this time, β rays and γ rays are emitted. Xe, Kr
Becomes Cs, Rb (solid) in the next decay process. Also at this time, β rays and γ rays are emitted. Further, β-rays and γ-rays are emitted in the process of Cs and Rb decay. In addition, as shown in FIG. 4, the measured nuclide ⁶⁰ Co, ⁵⁴
Β- and γ-rays are also emitted when Mn decays.

In the present embodiment, the following facts are taken advantage of the fact that the measurement nuclide generated by the leak does not emit α-rays, whereas the natural nuclide emits α-rays during the decay process. Β excluding the effects of natural nuclides by calculation
Find the value of the line.

That is, the emission ratio of α-rays and β-rays emitted by natural nuclides based on the measured values of α-rays and β-rays measured in various natural measurement modes (measurement contribution used later as a correction coefficient) Ratio) is determined in advance, and then the value of β-rays due to natural nuclides is calculated by multiplying the measured value of α-rays measured in the dust radioactivity concentration measurement mode by the above measurement contribution ratio. Then, the value of the calculated β-ray is subtracted from the measured value of the β-ray measured in the dust radioactivity concentration measurement mode, thereby obtaining the value of the β-ray excluding the influence of the natural nuclide.

FIG. 5 is a flowchart showing the processing in the data processing unit 8 according to the first embodiment.

First, in the various natural measurement modes, the measured value Nb (α) of the α-ray and the measured value Nb of the β-ray by natural nuclides
(Β) is measured (step A1), and K = Nb (β) / N
b (α) is calculated and stored in a memory or the like in advance as a correction coefficient (step A2). This correction coefficient K is
Since the value is based on the actually measured value, the reliability is high.

Next, in the dust radioactivity concentration measurement mode, the measured value Ng (α) of the object to be measured and the measured value Ng (β) of the β-ray are measured, and based on these values, the natural nuclide Β-ray value Ns (β) = Ng (β) excluding the influence
-K · Ng (α) is obtained (step A3). Thus, the correction processing of the measured value of the β-ray is performed.

That is, the value of β-rays due to natural nuclides is calculated by multiplying the measured value Ng (α) of α-rays measured in the dust radioactivity concentration measurement mode by the correction coefficient K, and then calculated in the dust radioactivity concentration measurement mode. The measured value N of the measured beta ray
By subtracting the value of the β ray calculated above from g (β),
The value Ns (β) of β rays excluding the influence of natural nuclides is obtained.

Thereafter, the Ns (β) obtained by the above processing is obtained.
Then, contamination determination is performed by comparing with the alarm reference value set in advance (step A4). Here, when it is determined that there is no contamination, the process returns to step A3, and the calculation of Ns (β) is performed again. On the other hand, if it is determined that there is contamination, an alarm is issued (step A5). After that, step A3
And the calculation of Ns (β) is performed again.

According to the first embodiment, the light from the detection layer of the α-ray detector 4 and the light from the detection layer of the β-ray detector 5 are independently mixed without mixing the α-ray and the β-ray. And the value of β-ray excluding the effects of natural nuclides (Fig. 24)
Since the correction process for obtaining the contribution V1) of the measurement nuclide due to the leak is performed, the accuracy of the contamination determination can be further improved as compared with the related art.

Further, since the mode can be selectively set between the natural various measurement modes and the dust radioactivity concentration measurement mode, a correction coefficient based on the actual measurement value of the natural nuclide can be obtained. The value can be made highly accurate.

The above-described first embodiment can be selectively combined with various embodiments described below.

(Second Embodiment) Next, a second embodiment will be described. In the second embodiment, the data processing unit 8 in the first embodiment evaluates in detail changes in various conditions that cause natural nuclide fluctuations, and changes in correction constants caused by changes in various conditions. A case will be described in which a function for correcting the error is further provided. In addition,
The detailed description of the same parts as those in the first embodiment is omitted. Hereinafter, a description will be given focusing on portions different from the first embodiment.

FIG. 6 is a schematic diagram showing a configuration example of a dust radiation monitor device according to the second embodiment.

In FIG. 6, a suction port of the sampling pipe 1 is attached to a room 40 to be measured by the dust radiation monitor. The gas in the room 40 is sent to the chamber C through the sampling pipe 1. Further, the room 40 is provided with a suction port for the ventilation duct 41. The gas in the room 40 is discharged to the outside by the ventilation blower 42 through the ventilation duct 41.

The room 40 is provided with a temperature sensor 43, a humidity sensor 44, and an atmospheric pressure sensor 45, and a detection signal from each sensor is sent to the data processing unit 8. An operation presence / absence signal indicating the operation / stop state of the ventilation blower 42 is sent from the ventilation blower 42 to the data processing unit 8.

The data processing unit 8 has a function of evaluating in detail changes in various conditions that cause natural nuclide fluctuations and correcting changes in correction constants caused by changes in various conditions. The data processing unit 8 obtains the measured value of α-ray and the measured value of β from the α-ray measuring unit 6 and the β-ray measuring unit 7, and also detects whether or not the ventilation blower 42 is operating. Room 4 from sensor 44 and barometric pressure sensor 45
Know the temperature, humidity, and pressure within 0. The data processing unit 8 can obtain the current date and time from inside or outside. The data processing unit 8 determines these conditions (whether or not the ventilation blower 42 is operating, the temperature, humidity,
The correction coefficient K is corrected to an appropriate value according to the atmospheric pressure and the date / time.

FIG. 7 is a flowchart showing processing in the data processing unit 8 according to the second embodiment.

First, in the various natural measurement modes, the measured value Nb (α) of the α-rays and the measured value Nb of the β-rays by natural nuclides
(Β) is measured (step B1).

Next, all or a part of various conditions (whether or not the ventilation blower 42 is operating, the temperature, humidity, and pressure in the room 40, and the date and time) are selectively read (step B).
2) The values of each condition are classified (step B3).

In the present embodiment, a correction coefficient K (x1, x2,...) Is provided which corrects the above-mentioned K = Nb (β) / Nb (α) in consideration of various conditions. Coefficient K
(X1, x2,...) Is represented by a predetermined mathematical expression as a function of the conditions x1, x2,. After classifying the values of the respective conditions, the value of the correction coefficient K (x1, x2,...) Is calculated by using this equation, and the calculated value is stored in a memory or the like in advance (step B).
4). At the same time, the values of the conditions x1, x2,... Are also stored in a memory or the like.

Then, in the dust radioactivity concentration measurement mode, the measured value Ng (α) of the α-ray and the measured value Ng (β) of the β-ray to be measured are measured, and the values of the conditions x1, x2,. After that (step B5), in the correction process, based on these values, the value Ns of the β-ray excluding the influence of the natural nuclide is excluded.
(Β) = Ng (β) −K (x1, x2,...) · Ng (α) is obtained (step B6).

Thereafter, the Ns (β) obtained by the above processing is obtained.
Then, contamination is determined by comparing with the preset alarm reference value (step B7). If it is determined that there is no contamination, the process returns to step B5. On the other hand, if it is determined that there is contamination, an alarm is issued (step B5). Thereafter, the process returns to step B5.

According to the second embodiment, changes in various conditions that cause natural nuclide fluctuation are evaluated in detail, and changes in correction coefficients caused by changes in various conditions are corrected. In addition to the effects of the embodiment, there is an effect that even higher precision measurement can be realized.

(Third Embodiment) Next, a third embodiment will be described. In the third embodiment, the data processing unit 8 in the second embodiment corrects a change in the correction coefficient that occurs in accordance with the elapsed time from each start time of the operation / stop of the ventilation blower 42. A description will be given of a case further including: Note that a detailed description of portions common to the above-described embodiment will be omitted. Hereinafter, a description will be given mainly of a portion different from the above-described embodiment.

In the air in the room 40 in FIG.
It was seeping out of concrete such as walls ²²²Natural nuclei such as Rn
Contains seeds. Air containing these natural nuclides
Ventilation blower 42 discharging to the outside operates or stops
Then, the concentration of natural nuclides in the air changes, and as a result,
The correction coefficient changes.

FIG. 8 is a time chart showing how the concentration of the natural nuclide changes according to the elapsed time from the start time of the operation / stop of the ventilation blower 42.

In FIG. 8, when the ventilating blower 42 in operation stops, the concentration of the natural nuclide increases according to the elapsed time t from the stop time, and becomes stable after a while. When the ventilation blower 42 is stopped, the concentration of the natural nuclide decreases in accordance with the elapsed time t 'from the operation start time, and the concentration is stabilized after a while.

As described above, since the concentration of the natural nuclide changes in accordance with the elapsed time from the start time of the operation / stop of the ventilation blower 42, the correction coefficient also changes. For this reason, in the present embodiment, the relationship between the elapsed times t, t ′ from the respective start times of the operation / stop of the ventilation blower 42 and the concentration of the natural nuclide is evaluated, and based on the result, the correction to be corrected is made. The coefficient is defined as a function of the elapsed times t and t '.

The data processing section 8 performs the operation of the ventilation blower 42 based on the signal sent from the ventilation blower 42 (the operation presence / absence signal indicating the operation / stop state of the ventilation blower 42).
The start time of the operation / stop of the operation can be acquired. Thereby, the data processing unit 8 sets the ventilation blower 42
A correction coefficient which is a function of the elapsed times t and t 'is calculated in accordance with a lapse of time from each start time of the operation / stop of the calculation, and based on this, a β-ray value excluding the influence of natural nuclides is calculated. Perform contamination judgment, etc.

According to the third embodiment, the relationship between the elapsed time from each start time of the operation / stop of the ventilation blower 42 and the concentration of the natural nuclide is evaluated, and the correction caused by the change in the concentration of the natural nuclide is evaluated. Since the change in the coefficient is corrected, there is an effect that more highly accurate measurement can be realized in addition to the effects of the first and second embodiments.

(Fourth Embodiment) Next, a fourth embodiment will be described. In the fourth embodiment, the data processing unit 8 in the second embodiment has a function of saving various conditions at that time before performing the correction processing when the correction coefficient is larger than a predetermined value. The case of further provision will be described. Note that a detailed description of portions common to the above-described embodiment will be omitted. Hereinafter, a description will be given mainly of a portion different from the above-described embodiment.

FIG. 9 is a flowchart showing processing in the data processing unit 8 according to the fourth embodiment.

The processing in the natural various measurement modes (natural nuclide measurement, condition reading, condition classification, correction parameter storage) is performed in step B of FIG. 7 described in the second embodiment.
Since it is the same as 1 to B4, the description is omitted here.

In the dust radioactivity concentration measurement mode, the measured value of the α-ray and the measured value of the β-ray of the object to be measured are measured, and the conditions x1,
After reading the values of x2,... (step C1), the following processing is performed immediately before the correction processing without executing the correction processing.

That is, a correction coefficient K (x1, x2,...) Is calculated based on the values of the conditions x1, x2,.
It is determined whether or not the correction coefficient is larger than a predetermined value (Step C3). If it is larger, the values of the conditions x1, x2,... Relating to the correction coefficient are stored (step C4). On the other hand, if it is small, no particular storage is performed.

Thereafter, as in the case of the above-described second embodiment, a β-ray value excluding the influence of natural nuclides is obtained in the correction processing (step C5), and the β-ray value obtained in the above processing is obtained. The contamination is determined by comparing the value of the line with the preset alarm reference value (step C6), and an alarm is issued when it is determined that there is contamination (step C7).

According to the fourth embodiment, when the correction coefficient is larger than the predetermined value, the various conditions at that time are stored before the correction processing is performed. In addition to the effects of the embodiment, there is an effect that the fluctuation factor of the correction coefficient and the soundness can be separately evaluated.

(Fifth Embodiment) Next, a fifth embodiment will be described. In the fifth embodiment, when the dust activity concentration is higher than a predetermined value, the data processing unit 8 in the second embodiment stores various conditions at that time before performing the correction process. A case in which a function is further provided will be described. Note that a detailed description of portions common to the above-described embodiment will be omitted. Hereinafter, a description will be given mainly of a portion different from the above-described embodiment.

FIG. 10 is a flowchart showing processing in the data processing unit 8 according to the fifth embodiment.

The processing in the natural various measurement modes (natural nuclide measurement, condition reading, condition classification, correction parameter storage) is performed in step B of FIG. 7 described in the second embodiment.
Since it is the same as 1 to B4, the description is omitted here.

In the dust radioactivity concentration measurement mode, the measured value of the α ray and the measured value of the β ray of the object to be measured are measured, and the conditions x1,
After reading the value of x2,... (step D1), the following processing is performed immediately before the correction processing without performing the correction processing.

That is, based on the values of the conditions x1, x2,..., The correction coefficient K (x1, x2,...) Is calculated, and the dust activity concentration (before correction) is calculated (step D2). It is determined whether the active density is greater than a preset alarm reference value (step D3). If it is larger, the values of the conditions x1, x2,... Relating to the correction coefficient are stored (step D4). On the other hand, if it is small, no particular storage is performed.

Thereafter, as in the case of the above-described second embodiment, a value of β-ray excluding the influence of natural nuclides is obtained in the correction processing (step D5), and β obtained by the above processing is obtained. The contamination is determined by comparing the value of the line with a preset alarm reference value (step D6), and an alarm is issued when it is determined that there is contamination (step D7).

According to the fifth embodiment, when the dust radioactivity concentration is higher than the predetermined value, the various conditions at that time are stored before the correction processing is performed. In addition to the effects of the embodiment, there is an effect that the fluctuation factor of the dust radioactivity concentration and the soundness can be separately evaluated.

(Sixth Embodiment) Next, a sixth embodiment will be described. In the sixth embodiment, a modification of the α-ray detector 4 and the β-ray detector 5 in the first embodiment will be described. Note that a detailed description of portions common to the first embodiment is omitted. Hereinafter, a description will be given focusing on portions different from the first embodiment.

FIG. 11 is a schematic diagram showing an example of the configuration of the α-ray detector and the β-ray detector used in the dust radiation monitor according to the sixth embodiment.

In FIG. 11, ZnS (Ag) wavelength shift fibers 81a to 81n are formed by using ZnS (Ag)
g) is applied, an α-ray is detected, and an α-ray detection signal as an optical signal is sent out. On the other hand, the plastic scintillation fibers 82a to 82n are obtained by converting plastic scintillation into optical fibers.
A line is detected, and a β-ray detection signal is sent out as an optical signal.

A detection surface is formed by alternately arranging these ZnS (Ag) wavelength shift fibers 81a to 81n and plastic scintillation fibers 82a to 82n on the same plane. Each optical fiber constituting the detection surface is connected to the dust collecting section 2 of the dust radiation monitor.
Are arranged at the same distance from each other.

The photomultiplier 83a is connected to the ends of the ZnS (Ag) wavelength shift fibers 81a to 81n, converts the α-ray optical signal detected by these into an electric signal, and sends it to the measuring section. The photomultiplier 83b is connected to the ends of the plastic scintillation fibers 82a to 82n, converts the β-ray optical signal detected by these into an electric signal, and sends it to the measuring unit.

According to the sixth embodiment, since each optical fiber individually detects α-rays and β-rays and guides the detection signals to individual photomultipliers, α-rays and β-rays are mixed. The detection can be performed independently without performing the measurement, and the measurement error due to the mixture can be eliminated. Further, since the optical fibers are arranged on the same plane, there is no problem of β-ray absorption, and the detection efficiency can be improved. Further, since the configuration is simplified, the production cost can be reduced.

(Seventh Embodiment) Next, a seventh embodiment will be described. Also in the seventh embodiment, modified examples of the α-ray detector and the β-ray detector will be described.

FIG. 12 is a schematic diagram showing a configuration example of the α-ray detector and the β-ray detector used in the dust radiation monitor according to the seventh embodiment.

In FIG. 12, ZnS (Ag) layer 84
Is an α-ray detection layer for detecting α-rays. The plastic scintillator layer 85 is a β-ray detection layer for detecting β-rays.

By arranging the ZnS (Ag) layer 84 and the plastic scintillator layer 85 on the same plane, a detection surface is formed. Each detection layer constituting the detection surface is arranged such that the optical fiber is at the same distance from the dust collecting unit 2 of the dust radiation monitoring device.

One end of the wavelength shift fiber 86a is connected to the ZnS (Ag) layer 84, and the ZnS (Ag)
The α-ray detection signal detected by the layer 84 is transmitted as an optical signal. The photomultiplier 83a is a wavelength shift fiber 86
The optical signal of α-rays which is connected to the other end of “a” and transmitted is converted into an electric signal and transmitted to the measuring unit.

On the other hand, one end of the wavelength shift fiber 86b is connected to the plastic scintillator layer 85, and β detected by the plastic scintillator layer 85
The line detection signal is transmitted as an optical signal. Photomaru 83b
Is connected to the other end of the wavelength shift fiber 86b, converts the transmitted β-ray optical signal into an electric signal, and sends it to the measuring unit.

In the seventh embodiment, the same effects as in the sixth embodiment can be obtained.

(Eighth Embodiment) Next, an eighth embodiment will be described. Also in the eighth embodiment, a modification of the α-ray detector / β-ray detector will be described.

FIG. 13 is a schematic diagram showing an example of the configuration of the α-ray detector and the β-ray detector used in the dust radiation monitor according to the eighth embodiment.

Referring to FIG. 13, a ZnS (Ag) layer 84 is formed.
Is an α-ray detection layer for detecting α-rays. The plastic scintillator layer 85 is a β-ray detection layer for detecting β-rays.

By arranging the ZnS (Ag) layer 84 and the plastic scintillator layer 85 on the same plane, a detection surface is formed. Each detection layer constituting the detection surface is arranged such that the optical fiber is at the same distance from the dust collecting unit 2 of the dust radiation monitoring device.

The light guide 89a is attached so as to cover the ZnS (Ag) layer 84, and guides the α-ray detection signal detected on the entire surface of the ZnS (Ag) layer 84 to one point. The photomultiplier 83a converts the α-ray detection signal guided by the light guide 89a into an electric signal and sends out the electric signal to the measuring unit.

On the other hand, the light guide 89b is attached so as to cover the plastic scintillator layer 85, and β detected on the entire surface of the plastic scintillator layer 85.
The line detection signal is led to one point. The photomultiplier 83b converts the β-ray detection signal guided by the light guide 89b into an electric signal and sends it out to the measuring unit.

In the eighth embodiment, the same effects as in the sixth embodiment can be obtained.

(Ninth Embodiment) Next, a ninth embodiment will be described. Also in the ninth embodiment, a modified example of the α-ray detector / β-ray detector will be described.

FIG. 14 is a schematic diagram showing a configuration example of the α-ray detector and the β-ray detector used in the dust radiation monitor according to the ninth embodiment. Further, FIG.
FIG. 4 is a sectional view of a portion A of a detection surface in FIG.

In FIGS. 14 and 15, ZnS (A
g) The wavelength-shifting fibers 92a to 92n are made of optical fibers coated with ZnS (Ag), detect α-rays, and send out α-ray detection signals as optical signals. On the other hand, the plastic scintillation layer 85 detects β rays,
A β-ray detection signal is sent out as an optical signal. Wavelength shift fibers 91a and 92b for plastic scintillation
Transmits the β-ray detected by the plastic scintillation layer 85 as an optical signal.

The ZnS (Ag) wavelength shift fiber 9
2a to 92n and plastic scintillation layer 85
Are arranged on the same surface to form a detection surface.

The photomultiplier 83a is connected to the ends of the ZnS (Ag) wavelength shift fibers 81a to 81n, converts the α-ray optical signal detected by these into an electric signal, and sends it to the measuring section. The photomultipliers 86a and 86b are connected to the ends of the wavelength shift fibers 91a and 92b, respectively, convert the β-ray optical signals detected by these into electric signals, and send out the electric signals to the measuring unit.

In the ninth embodiment, the same effects as in the sixth embodiment can be obtained.

(Tenth Embodiment) Next, a tenth embodiment will be described. In the tenth embodiment, a modification of the detection surface in the ninth embodiment will be described. Note that a detailed description of portions common to the ninth embodiment is omitted. Less than,
The following description focuses on the differences from the ninth embodiment.

FIG. 16 is a sectional view of a detection surface according to the tenth embodiment. As shown in this figure, ZnS
(Ag) Plastic scintillator layer 8 rather than layer 84
5 has a larger detection surface area. this is,
This is because β-rays need to be detected with particularly high sensitivity compared to α-rays. That is, this embodiment utilizes the property that the detection sensitivity increases as the detection surface increases.

According to the tenth embodiment, in addition to the effects of the ninth embodiment, there is an effect that the balance between the α-ray and β-ray detection sensitivities can be optimized.

(Eleventh Embodiment) Next, an eleventh embodiment will be described. In the eleventh embodiment, the α-ray detector 4 and β
A modified example of the line detection unit 5 will be described. In addition, the first
The detailed description of the same parts as those of the first embodiment is omitted. Hereinafter, a description will be given focusing on portions different from the first embodiment.

FIG. 17 is a schematic diagram showing a configuration example of a dust radiation monitor device according to the eleventh embodiment. FIG.
8 is α used in the dust radiation monitor of FIG.
It is a figure for explaining a line cut filter.

In FIGS. 17 and 18, the α-ray detector 4
Is formed by a ZnS (Ag) layer 84, and β
The surface of the line detector 5 is a plastic scintillator layer 85.
It is formed with. The ZnS (Ag) layer 84 and the plastic scintillator layer 85 are arranged on the same plane. On the radiation incident side of the plastic scintillator layer 85, a removable α-ray cut filter 111 is provided.

In such a configuration, by detecting the β-rays with the plastic scintillator layer 85 in a state where the α-ray cut filter 111 is inserted, it is possible to accurately measure the value of the correct β-rays from which the α-rays have been cut. Can be. Further, the value of the α-ray can be measured with high accuracy from the difference between the β-ray detection value when the α-ray cut filter 111 is inserted and the β-ray detection value when the α-ray cut filter 111 is not inserted. The arithmetic processing at this time is performed by the data processing unit 8.

According to the eleventh embodiment, the first
In addition to the effects of the embodiment, there is an effect that α-rays and β-rays can be measured with higher accuracy.

(Twelfth Embodiment) Next, a twelfth embodiment will be described. In the twelfth embodiment, a modification of the application of the α-ray cut filter 111 in the eleventh embodiment will be described. Note that a detailed description of portions common to the eleventh embodiment is omitted. Hereinafter, a description will be given mainly of portions different from the eleventh embodiment.

FIG. 19 is a schematic diagram showing a configuration example of a dust radiation monitor device according to the twelfth embodiment. FIG.
FIG. 0 is a diagram for explaining a movable α-ray cut filter used in the dust radiation monitor device of FIG.

In FIGS. 19 and 20, ZnS (A
g) An α-ray cut filter 121 having a hole H is provided between the dust collecting section 2 and the detection surface composed of the layer 84 and the plastic scintillator layer 85. The α-ray cut filter 121 can be moved by a driving unit, and thereby the position of the hole H with respect to the dust collection pattern P can be moved to a desired position.

According to the twelfth embodiment, the first
In addition to the effects of the first embodiment, the α-ray cut filter 12
1 can be easily inserted and removed, and there is an effect that highly accurate α-ray detection can be performed smoothly.

(Thirteenth Embodiment) Next, a thirteenth embodiment will be described. In the thirteenth embodiment, the α-ray detector 4 and β
A modified example of the line detection unit 5 will be described. In addition, the first
The detailed description of the same parts as those of the first embodiment is omitted. Hereinafter, a description will be given focusing on portions different from the first embodiment.

FIG. 21 is a schematic diagram showing a configuration example of a dust radiation monitoring apparatus according to the thirteenth embodiment. FIG.
FIG. 2 is a diagram for explaining the configuration of a wavelength shift fiber used in the dust radiation monitoring device of FIG.

At the part A in FIG. 21, as shown in FIG. 22, the α-ray detecting layer surrounds the periphery of the detecting layer of the β-ray detecting section 5 so that the wavelength of the α-ray detecting layer is coated with ZnS (Ag). The shift fiber 131 is formed. The wavelength shift fiber 131 is connected to the photomultiplier 132 through the inner wall of the sampling pipe 1. The photomultiplier 132 converts the α-ray detection signal from the wavelength shift fiber 131 into an electric signal and sends it to the measuring unit 6.

According to the thirteenth embodiment, the first
In addition to the effects of the first embodiment, the area of the detection surface for α-rays can be reduced and the area for β-ray detection can be increased, so that β-rays can be measured with even higher sensitivity and accuracy. is there.

The present invention is not limited to the above-described embodiments, but can be implemented in various modifications within the scope of the invention. For example, the present invention can be implemented by selectively combining the contents described in the embodiments.

[0125]

As described above in detail, according to the dust radiation monitoring apparatus of the present invention, the α-rays and the β-rays are independently emitted without mixing the lights from the respective detection layers of the α-rays and the β-rays. Since detection and measurement are performed, it is possible to eliminate a measurement error due to mixing.

Further, by providing each detection layer on the same surface, the problem of β-ray absorption by other detection layers when detecting β-rays is eliminated, so that the efficiency of detecting low-energy β-rays is improved, and the β-ray absorption is improved. It is possible to eliminate the measurement error due to.

Further, by introducing a method of accurately obtaining a value of β-ray excluding the influence of natural nuclides, it becomes possible to further improve the accuracy of contamination determination.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration example of a dust radiation monitoring device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining the decay process of natural nuclides.

FIG. 3 is a diagram for explaining a decay process of a measurement nuclide generated by a leak.

FIG. 4 is a diagram for explaining a decay process of a measurement nuclide generated by a leak.

FIG. 5 is a flowchart showing processing in a data processing unit according to the first embodiment of the present invention.

FIG. 6 is a schematic diagram showing a configuration example of a dust radiation monitoring device according to a second embodiment of the present invention.

FIG. 7 is a flowchart illustrating processing in a data processing unit according to a second embodiment of the present invention.

FIG. 8 is a time chart showing a state in which the concentration of a natural nuclide changes according to an elapsed time from each start time of operation / stop of the ventilation blower in the third embodiment of the present invention.

FIG. 9 is a flowchart showing processing in a data processing unit according to a fourth embodiment of the present invention.

FIG. 10 is a flowchart showing processing in a data processing unit according to a fifth embodiment of the present invention.

FIG. 11 is a schematic diagram illustrating a configuration example of an α-ray detection unit and a β-ray detection unit used in a dust radiation monitoring device according to a sixth embodiment of the present invention.

FIG. 12 is a schematic diagram showing a configuration example of an α-ray detector and a β-ray detector used in the dust radiation monitor according to the seventh embodiment of the present invention.

FIG. 13 is a schematic diagram showing a configuration example of an α-ray detector and a β-ray detector used in the dust radiation monitor according to the eighth embodiment of the present invention.

FIG. 14 is a schematic diagram showing a configuration example of an α-ray detector and a β-ray detector used in the dust radiation monitor according to the ninth embodiment of the present invention.

FIG. 15 is a sectional view of a portion A of the detection surface in FIG. 14;

FIG. 16 is a sectional view of a detection surface according to a tenth embodiment.

FIG. 17 is a schematic diagram showing a configuration example of a dust radiation monitoring device according to an eleventh embodiment of the present invention.

FIG. 18 is a diagram for explaining an α-ray cut filter used in the dust radiation monitoring device of FIG.

FIG. 19 is a schematic diagram showing a configuration example of a dust radiation monitoring device according to a twelfth embodiment of the present invention.

FIG. 20 is a view for explaining a movable α-ray cut filter used in the dust radiation monitor device of FIG. 19;

FIG. 21 is a schematic diagram showing a configuration example of a dust radiation monitoring device according to a thirteenth embodiment of the present invention.

FIG. 22 is a diagram illustrating a configuration of a wavelength shift fiber used in the dust radiation monitoring device of FIG. 21.

FIG. 23 is a schematic diagram showing a configuration example of a dust radiation monitoring device that is actually widely used in a radiation source handling facility such as a nuclear power plant.

FIG. 24 is a view for explaining that a measured value of β-ray includes a contribution of a natural nuclide.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... sampling pipe, 2 ... dust collection part, 3 ... sampling pump, 4 ... alpha ray detection part, 5 ... beta ray detection part, 6 ... alpha ray measurement part, 7 ... beta ray measurement part, 8 ... data processing part, 41: Ventilation duct, 42: Ventilation blower, 43: Temperature sensor, 44: Humidity sensor, 45: Barometric pressure sensor, 81a to 81n: ZnS (Ag) wavelength shift fiber, 82a to 82n: Plastic scintillation fiber, 83a, 83b ... 84: ZnS (Ag) layer, 85: Plastic scintillator layer, 86a, 86b: Wavelength shift fiber, 89a, 89b: Light guide, 91a, 91b: Wavelength shift fiber for plastic scintillation, 92a to 92n: ZnS (Ag) ) Wavelength shift fiber, 111: α-ray cut filter, 121: movable α-ray filter Filter, 131 ... ZnS (Ag) wavelength shifting fiber, 132 ... photomultiplier, C ... chamber.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Junsei Endo 1 Toshiba-cho, Fuchu-shi, Tokyo F-term in the Fuchu Plant of Toshiba Corporation 2G088 AA03 EE12 EE21 FF05 FF06 GG10 GG11 GG14 GG15 HH03 JJ08 KK07 KK11 KK24 KK28 KK29 LL06 LL21 LL22

Claims (13)

[Claims] 1. A dust radiation monitoring apparatus for detecting radiation emitted from dust collected in a dust collecting section to determine the presence or absence of radioactive contamination, wherein the α-ray detection layer and the β-ray detection layer substantially have An α-ray detector and a β-ray detector, which are arranged on the same surface and independently detect α-rays and β-rays without being mixed, and independently detect α-rays and β-rays. An α-ray measurement unit and a β-ray measurement unit that individually obtain an α-ray measurement value and a β-ray measurement value from the above, and the emission ratio of α-rays and β-rays emitted by natural nuclides obtained in advance as a correction coefficient is used as a correction coefficient. A data processing unit that calculates the value of β-ray of the natural nuclide by multiplying the α-ray measurement value, and performs a contamination determination using a value obtained by subtracting the calculated β-ray value from the β-ray measurement value. A dust radiation monitor device comprising: 2. A dust radiation monitoring apparatus for detecting radiation emitted from dust collected by a dust collecting section to determine the presence or absence of radioactive contamination, wherein the α-ray detection layer and the β-ray detection layer substantially have An α-ray detector and a β-ray detector, which are arranged on the same surface and independently detect α-rays and β-rays without being mixed, and independently detect α-rays and β-rays. An α-ray measuring section and a β-ray measuring section for individually obtaining an α-ray measurement value and a β-ray measurement value from a first mode for measuring natural nuclides and a second mode for measuring dust radioactivity concentration A data processing unit capable of selectively setting a mode between the first mode and the second mode;
The emission ratio is determined in advance from the X-ray and β-ray as a correction coefficient, and the α-ray measurement value measured in the second mode is multiplied by the correction coefficient to obtain β
A data processing unit that calculates a line value and performs a contamination determination using a value obtained by subtracting the calculated β-ray value from the β-ray measurement value measured in the second mode. Dust radiation monitor device characterized by the above-mentioned. 3. The data processing unit according to claim 1, wherein the data processing unit evaluates a change in a predetermined condition that is a cause of fluctuation of the natural nuclide, and corrects a change in a correction coefficient caused by the change in the condition. A dust radiation monitoring device according to claim 1. 4. The dust radiation monitoring apparatus further includes a ventilation blower for ventilating gas containing dust to be measured, and the data processing unit determines a time elapsed from each start time of operation / stop of the ventilation blower and a natural time. 4. The dust radiation monitoring apparatus according to claim 3, wherein a relationship with the concentration of the nuclide is evaluated, and a change in a correction coefficient caused by a change in the concentration of the natural nuclide is corrected. 5. The dust radiation monitoring apparatus according to claim 3, wherein the data processing unit stores the condition at that time when the correction coefficient is larger than a predetermined value. 6. The dust radiation monitoring apparatus according to claim 3, wherein the data processing section stores the condition at that time when the dust radioactivity concentration is higher than a predetermined value. 7. The α-ray detection layer is composed of a plurality of wavelength-shifted fibers coated with ZnS (Ag), the β-ray detection layer is composed of a plurality of plastic scintillation fibers, The apparatus further includes an α-ray photomultiplier that converts a detection signal from the fiber that has detected the line into an electric signal, and the β-ray detection unit is configured to convert the detection signal from the fiber that has detected the β-ray into an electric signal. 7. The dust radiation monitor according to claim 1, further comprising a photomultiplier. 8. The α-ray detecting layer is composed of a plurality of wavelength-shifted fibers coated with ZnS (Ag), the β-ray detecting layer is composed of a plurality of plastic scintillation fibers, and the α-ray detecting unit is an α-ray fiber for optically transmitting the α-ray detection signal from the α-ray detection layer, and an α-ray photomultiplier for converting the optically transmitted α-ray detection signal into an electric signal, wherein the β-ray detection unit Further comprises a β-ray fiber for optically transmitting the β-ray detection signal from the β-ray detection layer, and an α-ray photomultiplier for converting the optically transmitted β-ray detection signal into an electric signal. 7. The method according to claim 1, wherein
The dust radiation monitoring device according to any one of the above. 9. The α-ray detection layer is composed of a plurality of wavelength-shifted fibers coated with ZnS (Ag), the β-ray detection layer is composed of a plurality of plastic scintillation fibers, and the α-ray detection unit is an α-ray light guide that guides an α-ray detection signal detected on the entire surface of the α-ray detection layer to a single point, and an α-ray photomultiplier that converts the guided α-ray detection signal into an electric signal, further comprising: The β-ray detection unit includes a β-ray light guide for guiding the β-ray detection signal detected on the entire surface of the β-ray detection layer to a single point, and a β-ray photo for converting the guided β-ray detection signal to an electric signal. The dust radiation monitor according to any one of claims 1 to 6, further comprising a circle. 10. The dust radiation monitor according to claim 1, wherein an area of the β-ray detection layer is larger than an area of the α-ray detection layer. 11. The apparatus according to claim 11, wherein the β-ray detecting section further includes a filter provided between the β-ray detecting layer and the dust collecting section to cut α rays and transmit β rays. Item 11. The dust radiation monitoring device according to any one of Items 1 to 10. 12. A hole is provided in a part of the filter so that radiation not cut off α-rays and radiation cut off α-rays can be selectively detected by the β-ray detection layer. The dust radiation monitoring device according to claim 11, wherein the position of the hole is movable. 13. The α-ray detection layer is made of a wavelength-shifted fiber coated with ZnS (Ag), and is provided so as to surround a periphery of the β-ray detection layer. The dust radiation monitor device according to any one of claims 1 to 12, further comprising an α-ray photomultiplier for converting an α-ray detection signal transmitted through the optical signal into an electric signal.