JP2022059665A - Radiation analysis device and dust monitor device - Google Patents

Abstract

To provide a radiation analysis device capable of accurately evaluating strontium.SOLUTION: A radiation analysis device 100 comprises: a detector 1 that outputs an electric pulse signal P corresponding to energy of incident radiation when radiation is incident; a multiple wave height analyzer 3 that derives the wave height spectrum M indicating a count for each energy value of the electric pulse signal P; and a calculation section 50 that calculates radiation intensity on the basis of the wave height spectrum M. The calculation section 50 performs first calculation for calculating radiation of strontium on the basis of a shape of the wave height spectrum M of a β ray which is the radiation emitted from yttrium which is a daughter nuclide of the strontium.SELECTED DRAWING: Figure 1

Description

The present application relates to a radiation analyzer and a dust monitor device.

Due to the accident at the Fukushima Daiichi Nuclear Power Station, radioactive materials have poured into a vast area. Typical radionuclides that have poured down include cesium-137 and cesium-134, but a certain amount of radioactive strontium is also released and poured down. Among them, strontium-90 is a particularly important radionuclide in the evaluation of exposure, but the atmosphere. It is practically difficult to identify and measure strontium from the radioactive substances inside. That is, since strontium-90 is a nuclide that emits only β-rays and does not have an energy value peculiar to each nuclide, it is difficult to distinguish it from other β-ray emitting nuclides. Therefore, in general, strontium-90 is often observed as a total β-nuclide in which a plurality of radionuclides that emit β-rays are mixed. For this reason, strontium-90 will be treated as a β-ray emitting nuclide of unknown origin for which the nuclide cannot be identified, and the management standards for controlling radioactive substances will become stricter. In addition, considering that strontium in the atmosphere is expected to be internally exposed by respiration and has a long biological half-life, the management standards will become even stricter. Therefore, it is necessary to quickly identify strontium and evaluate its radioactivity.
As a technique for evaluating existing strontium, for example, a measuring device for a radioactive substance as a radiation analyzer, as shown below, is disclosed.

That is, the existing measuring device for radioactive substances absolutely measures the total β-ray emission rate from the β-ray counting rate, the γ-ray counting rate, and the simultaneous counting rate of β-rays and γ-rays. The measuring device absolutely measures the radioactivity of cesium-134 from the γ-ray spectrum information by the thumb peak method, estimates the sensitivity of cesium-137 to γ-rays from the obtained radioactivity of cesium-134 and the sensitivity curve of the γ-ray detector, and cesium. Radioactivity is measured from the photoelectric peak count rate of 137. The measuring device obtains the β-ray detection rate corresponding to the radioactivity of cesium-134 and the radioactivity of cesium-137 already obtained, and the β-ray emission rate of cesium-134 and the β-ray emission rate of cesium-137 are obtained from the total β-ray emission rate already obtained. The β-ray emission rate is subtracted to obtain the β-ray emission rate of strontium, and the radioactivity is measured (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-210317

The existing measuring device for radioactive substances as a radiation analyzer as described above utilizes the difference that cesium-137 does not synchronize the emission of β-rays and γ-rays, but the emission of β-rays and γ-rays of cesium-134 synchronizes. Then, in addition to the outputs of the β-ray detector and the γ-ray detector, the simultaneous measurement outputs of both detectors are measured. Then, while distinguishing between cesium-137 and cesium-134, the γ-ray count rate, which is the sensitivity to γ-rays, is obtained, and the respective radioactivity is estimated. Since it is known in advance that cesium-137 and cesium-134 also emit β-rays at a constant ratio, the β-ray radioactivity emitted by cesium-137 and cesium-134 is determined from the ratio, so that this is the total β. Subtract from the ray radioactivity and use the result as the radioactivity of strontium-90.

However, although such an existing measuring device for radioactive substances can identify strontium-90, it is necessary to have a special measurement environment in which γ-ray emitting nuclides are presumed to be cesium-137 and cesium-134. Therefore, there is a problem that the strontium 90 cannot be evaluated accurately when γ-ray emitting nuclides other than cesium-137 and cesium-134 are present in the measurement environment.
The present application discloses a technique for solving the above-mentioned problems, and an object of the present application is to provide a radiation analyzer and a dust monitor device capable of accurately evaluating strontium.

The radiation analyzer disclosed in the present application is
A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident.
An analysis unit for deriving a first energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A calculation unit for calculating the radioactivity intensity of the radioactive substance based on the first energy distribution is provided.
The arithmetic unit
Based on the shape of the first energy distribution of β rays, which is the radiation emitted from yttrium, which is the daughter nuclide of strontium as a radioactive substance, the first calculation for calculating the radiation of the strontium is performed.
It is a thing.
Further, the dust monitor device disclosed in the present application is:
With the radiation analyzer configured as described above,
The dust collecting filter paper is provided with a dust collecting mechanism for collecting the radioactive substances in the atmosphere.
The detection unit of the radiation analyzer detects the radiation emitted from the radioactive substance of the dust collecting filter paper.
It is a thing.

According to the radiation analyzer and the dust monitor device disclosed in the present application, a radiation analyzer and a dust monitor device capable of accurately evaluating strontium can be obtained.

It is a block diagram which shows the schematic structure of the radiation analyzer according to Embodiment 1. FIG. It is sectional drawing which shows the structure of the detector applied to the radiation analyzer according to Embodiment 1. FIG. It is a figure which shows the example of the wave height spectrum which is the output of the pulse height analyzer of the radiation analyzer according to Embodiment 1. FIG. It is a figure which shows the spectrum data recorded in advance in the database of the radiation analyzer by Embodiment 1. FIG. It is a block diagram which shows the schematic structure of the radiation analyzer according to Embodiment 2. It is a block diagram which shows the schematic structure of the radiation analyzer according to Embodiment 3. It is a figure which shows the example of the wave height spectrum which is the output of the pulse height analyzer of the radiation analyzer according to Embodiment 3. It is a figure which shows the example of the wave height spectrum which is the output of the pulse height analyzer of the radiation analyzer according to Embodiment 3. It is a figure which shows the example of the energy spectrum which was converted by applying the inverse problem operation using the response function to the wave height spectrum of the radiation analyzer according to Embodiment 3. It is a block diagram which shows the schematic structure of the radiation analyzer according to Embodiment 4. It is a figure which shows the example of the wave height spectrum which is the output of the pulse height analyzer of the radiation analyzer according to Embodiment 4. It is a figure which shows the schematic structure of the dust monitor apparatus provided with the radiation analyzer according to Embodiment 5. It is a figure which shows an example of the schematic structure of the hardware of the arithmetic unit of the radiation analyzer according to Embodiment 1 to Embodiment 5.

Embodiment 1.
FIG. 1 is a block diagram showing a schematic configuration of the radiation analyzer 100 according to the first embodiment.
FIG. 2 is a cross-sectional view showing the structure of the detector 1 applied to the radiation analyzer 100 shown in FIG.
The radiation analyzer 100 is an apparatus for monitoring and evaluating radiation from a radioactive substance, particularly radiation from strontium-90 as a radioactive substance.
As shown in FIG. 1, the radiation analyzer 100 includes a detector 1 as a detection unit, an analog circuit 2, a multi-channel analyzer (MCA) 3, a calculation unit 50, and a display 4. To prepare for.

When the radiation emitted from the radioactive substance to be measured is incident, the detector 1 outputs an electric pulse signal P as a detection signal having a wave height corresponding to the energy value of the incident radiation.
The analog circuit 2 amplifies the signal level of the electric pulse signal P output by the detector 1, and shapes the electric pulse signal P into a pulse waveform suitable for the circuit in the subsequent stage.
The pulse height analyzer 3 AD (Analog to Digital) converts the electric pulse signal P from the analog circuit 2 into a digital value based on the wave height. Then, the pulse height analyzer 3 discriminates each electric pulse signal P into each channel (energy valve separate stage) having an energy range corresponding to the magnitude of the digital value, and determines the number of electric pulse signals P in each channel. Count. In this way, the pulse height analyzer 3 generates and outputs a wave height spectrum M as a first energy distribution showing a count for each energy value (peak value) of each electric pulse signal P.

The calculation unit 50 includes a spectrum comparator 51 and a database 59.
The spectrum comparator 51 determines the radioactivity of yttrium-90 based on the wave height spectrum M output by the pulse height analyzer 3 and the spectrum data D pre-recorded in the database 59, although the details of its control will be described later. Identify. If the radioactivity of yttrium-90 can be identified, since yttrium-90 is a 100% daughter nuclei of strontium-90 and is in radioactive equilibrium with strontium-90, the radioactivity of strontium-90 can also be identified.
In this way, the spectrum comparator 51 calculates the amount corresponding to yttrium-90 in the wave height spectrum M, calculates the amount corresponding to strontium-90 from the calculation result, and evaluates the radiation intensity thereof.
The display 4 displays the calculation result calculated by the spectrum comparator 51.

Hereinafter, the configuration of the detector 1 will be described.
In general, a radiation analyzer evaluates γ-rays, each of which has a unique energy value, and a radiation sensor called a talium-activated sodium iodide scintillator (NaI) is used as a detector to detect radiation. Well selected. However, strontium-90 and yttrium-90 are radionuclides that emit only β-rays, and β-rays have a short range, and are provided for protection from moisture in detectors that show strong deliquescent such as NaI radiation sensors. Beta rays cannot reach the inside of the crystal due to the crystal case. Therefore, it is difficult to identify the nuclides of strontium-90 and yttrium-90. Therefore, in the present embodiment, a detector 1 having a configuration capable of measuring β rays emitted from strontium-90 and yttrium-90 is introduced.

As shown in FIG. 2, the detector 1 includes a radiation sensor 1S, a photomultiplier tube 1A, and a detector case 1C as a case portion.
The radiation sensor 1S absorbs the incident energy by the incident radiation and generates light.
The photomultiplier tube 1A converts the generated light into an electric signal to generate and output an electric pulse signal P having a wave height corresponding to the energy value applied to the radiation sensor 1S by the radiation.
The detector case 1C has a side wall 1C1 as a wall portion and a bottom wall 1C2, and houses a radiation sensor 1S and a photomultiplier tube 1A.

Here, if a deliquescent sensor such as a NaI radiation sensor is selected for the radiation sensor, a crystal case is required around the radiation sensor, which has a double structure with the detector case. The thickness and material of the crystal case of the NaI radiation sensor are determined by the JIS standard (JISZ4321: Thallium-activated sodium scintillator for radiation measurement) and cannot be modified for the detection of strontium-90 and yttrium-90. .. Therefore, for the radiation sensor 1S, a crystal that does not require a crystal case is selected.
As an example of the radiation sensor 1S that does not require a crystal case, there are many examples such as a thallium-activated cesium iodide scintillator (CsI (Tl)) and a gadolinium aluminum gallium garnet (GAGG).

Further, by reducing the thickness of the detector case as much as possible in consideration of the selection of the material of the detector case, the β rays emitted by the strontium-90 and the yttrium-90 can be configured to pass through the detector case. In the detector case 1C of the present embodiment, the thickness X of the side wall 1C1 and the bottom wall 1C2 is adjusted so that the β rays emitted by the strontium 90 and the yttrium 90 can pass through. In this way, by selecting the type of sensor used for the radiation sensor 1S and adjusting the thickness X of the wall portion of the detector case 1C, the detector 1 emits β-rays emitted by strontium-90 and yttrium-90. Can be detected.

The thickness X of the detector case 1C is not limited to be as thin as possible. In order to accurately detect only the β-rays emitted by strontium-90 and yttrium-90, it is even better if the β-rays emitted by other than strontium-90 and yttrium-90 can be removed. Therefore, it is also possible to adjust the thickness X of the detector case 1C so that the relatively low-energy β-rays emitted by other than strontium-90 and yttrium-90 can be removed.

Next, the details of the radiation evaluation control performed by the calculation unit 50 will be described.
FIG. 3 is a diagram showing an example of a wave height spectrum M which is an output of the pulse height analyzer 3 shown in FIG.
FIG. 4 is a diagram showing spectrum data D pre-recorded in the database 59 shown in FIG.

When the detector 1 shown in FIG. 2 is applied, the pulse height analyzer 3 outputs a wave height spectrum M including the counts of γ-rays and β-rays as shown in FIG. Here, in the first energy band Ehi, which is an energy band higher than the first peak value Ed as the first value shown in FIG. 3, the distribution shown by the diagonal line appears. This is the distribution seen by detecting β rays from yttrium-90.
Although there are various radionuclides that emit β-rays, yttrium-90 has a characteristically higher maximum energy value of β-rays than other β-ray-emitting nuclides. Therefore, if yttrium-90 is present in the measurement environment, its presence is indicated as a count in the first energy band Ehi, which is higher than the first peak Ed.

Here, the first peak value Ed is set to be the maximum value of the energy distribution of γ-rays from the γ-ray emitting nuclide. In the present embodiment, the first peak value Ed is higher than the maximum energy value of γ-rays caused by nuclear power plants such as cesium-137 and cesium-134, and γ-rays having a relatively large energy value among nuclides prominently present in nature. The energy value of potassium-40, which is a γ-ray emitting nuclide that emits γ-rays, is 1.46 MeV. Actually, the distribution margin is secured for this 1.46 MeV, and the first peak value Ed is set to 1.7 to 1.8 MeV.

By setting the value of the first peak value Ed in this way, the count in the energy band higher than the first peak value Ed is counted from the count of γ-rays from the γ-ray emitting nuclides and from the β-ray emitting nuclides other than yttrium. The count of β-rays from yttrium-90 is shown, excluding the count of β-rays.
The spectral shape of the shaded area shown in FIG. 3 shows the characteristic shape of the spectrum on the high energy side of the β ray from yttrium-90.

In the database 59, the wave height spectral shapes of yttrium-90 and strontium-90 as shown in FIG. 4 obtained by simulation with known radioactivity set, experiments by irradiation with a standard radiation source, etc. are recorded in advance as spectral data D. ing. A plurality of shapes of the wave height spectra of yttrium-90 and strontium-90 shown in FIG. 4 are recorded according to, for example, the intensity of radioactivity and measurement conditions.
When the wave height spectrum M from the multiplex peak height analyzer 3 is input to the spectrum comparator 51, the shape of the input wave height spectrum M in the first energy band Ehi and the yttrium 90 recorded in the spectrum data D are recorded in the spectrum data D. A collation determination is performed to match the wave height spectrum with the shape in the first energy band Ehi.

The spectrum comparator 51 is detected by the detector 1 when the shape of the first energy band Ehi of the input peak height spectrum M matches one of the shapes of the plurality of peak height spectra recorded in the spectrum data D. The radioactive substance that emits radiation in the first energy band Ehi is identified as ittrium 90.
In this case, the spectrum comparator 51 performs the first calculation for calculating the detected radioactivity amount of yttrium-90 based on the wave height spectral shape in the spectral data D that matches in the collation determination.

In this first calculation, for example, the data of the shape of the wave height spectrum recorded in the spectrum data D may be standardized, and the radioactivity amount of yttrium-90 corresponding to the standardized spectrum may be recorded as known.
Alternatively, in the first calculation, the wave height spectral shape in the second energy band Elow, which is less than the first peak value Ed of the detected yttrium-90, is estimated based on the wave height spectral shape in the matched spectral data D, and this estimated shape. The amount of radioactivity of yttrium-90 derived based on may be calculated.

Alternatively, in the first calculation, if the input wave height spectrum M matches the recorded wave height spectrum shape by multiplying the input wave height spectrum M by a specific ratio, the spectrum comparator 51 may be used. The radioactivity of yttrium-90 may be specified by multiplying the known radioactivity of yttrium-90 by the ratio required for this shape matching.

As described above, in the first calculation, the spectrum comparator 51 corresponds to strontium-90 in the wave height spectrum M based on the shape of the wave height spectrum M of β rays emitted from yttrium-90, which is the daughter nucleus species of strontium-90. The first operation for calculating the amount to be performed is performed.

If it is determined that there is a disagreement in the collation determination, the spectrum comparator 51 may perform the process of not performing the first calculation. Not all the counts existing in the first energy band Ehi exceeding the first wave high value Ed are radiation caused by yttrium-90, and there are very few counts by natural nuclides, high-energy cosmic rays, etc. May be done. Such cosmic rays that are not yttrium-90 have a low radiation count. Therefore, in the counting of radiation from β-ray emitting nuclides other than yttrium-90, the distributed shape cannot be formed in the shaded portion having the first peak value Ed or more shown in FIG. In this case, the spectrum comparator 51 can determine that yttrium-90 and strontium-90 do not exist by the collation determination.

The first peak value Ed was set to the energy value of potassium-40, which is a γ-ray emitting nuclide having a relatively large energy value among the nuclides prominently present in the natural world, but the influence of radiation from cesium-134 and 137. In an environment or the like where it can be assumed that is mainly, the first peak value Ed may be set to a value exceeding the radiation energy of cesium-134.

The radiation analyzer of the present embodiment configured as described above is
A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident.
An analysis unit for deriving a first energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A calculation unit for calculating the radioactivity intensity of the radioactive substance based on the first energy distribution is provided.
The arithmetic unit
Based on the shape of the first energy distribution of β rays, which is the radiation emitted from yttrium, which is the daughter nuclide of strontium as a radioactive substance, the first calculation for calculating the radiation of the strontium is performed.
It is a thing.

The wave height spectrum derived by using the detector may change its wave height spectrum shape due to changes in the positional relationship between the detector and the radioactive substance, the installation environment of the detector, and the like. As described above, the calculation unit of the present embodiment performs the first calculation for calculating the radiation of the strontium-90 based on the shape of the wave height spectrum of the β-rays emitted from the yttrium-90.
As a result, the strontium-90 can be evaluated with high accuracy without being affected by the installation environment of the detector and the like. In addition, since the evaluation is based on yttrium-90, which has a characteristically high maximum energy value of radiation, strontium-90 can be evaluated accurately even when γ-ray emitting nuclides other than cesium-137 and cesium-134 are present in the measurement environment. You can.

Further, the radiation analyzer of the present embodiment configured as described above is
In the first calculation, the calculation unit is used.
The radiation intensity of the strontium is calculated based on the shape of the first energy distribution of β rays from the yttrium in the first energy band of the set first value or more.
It is a thing.

In this way, the calculation unit performs the first calculation based on the wave height spectral shape of the β ray from yttrium in the first energy band of the set first value or more. Therefore, for example, by appropriately adjusting the value of the set first value, it is possible to evaluate the radiation in a setting that is less affected by the radiation from other γ-ray emitting nuclides and β-ray emitting nuclides.

Further, the radiation analyzer of the present embodiment configured as described above is
The detector is
A sensor unit for detecting the incident radiation and a case unit having a wall portion adjusted to a thickness through which β rays, which are the radiation, are transmitted, and accommodating the sensor unit are provided.
It is a thing.
Further, the radiation analyzer of the present embodiment configured as described above is
The sensor unit of the detection unit has a single unit configuration.
It is a thing.

In this way, the detector can detect β rays emitted by strontium-90 and yttrium-90 by adjusting the thickness of the wall of the detector case. Further, the sensor unit for detecting radiation is composed of one unit. With such a configuration, both γ-ray and β-ray radiation can be measured at the same point and at the same time by the same radiation sensor.

As described above, the shape of the wave height spectrum may change depending on the positional relationship between the radioactive substance and the detector. Therefore, for example, if the γ-ray detector and the β-ray detector are independently provided and installed, the γ-ray and the β-ray cannot be detected at the same point. In this case, when the calculation using the β-ray counting and the γ-ray counting derived from each is performed, a deviation may occur and the radiation intensity may not be calculated accurately. In this embodiment, by detecting γ-rays and β-rays at the same point in this way, it is possible to secure an accurate correlation between the respective radiation counts and calculate the radiation intensity with high accuracy. Become.

Also, for example, when trying to realize radiation detection at the same point when using independent γ-ray detectors and β-ray detectors, after measuring with the γ-ray detector, remove the γ-ray detector and use it. A detection method newly installed in the β-ray detector at the point can be considered, but in this case as well, the influence of the deviation of the measured value due to the time difference may occur. Since the detector of the present embodiment simultaneously and continuously measures γ-rays and β-rays in real time, it is possible to prevent the influence of the time difference due to the time difference on each count value, and the radiation intensity is more accurate. Analysis becomes possible and measurement time can be shortened.

Further, for example, in the permeation ability difference measurement method in which the β-ray energy emitted from the strontium 90 and the yttrium-90 in a radiation equilibrium state is extremely high, the yttrium-90 is separated and measured by the difference in the permeation ability of the substance. Since radiation counting in the low energy region of Yttrium-90 is not used, simple detection is generally possible, but it is not suitable for quantitative measurement.
In addition, in the chemical separation method in which radioactive strontium is selectively extracted from radioactive cesium by chemical separation and liquid scintillation measurement or Cherenkov light measurement is performed, chemical treatment work is required to separate cesium and strontium in the sample, which is troublesome. It takes time and is not suitable for rapid measurement. On the other hand, the radiation analyzer of the present embodiment thus enables quantitative measurement and rapid measurement without performing any chemical separation.

According to the radiation analyzer disclosed in the present application, it is possible to identify and quantitatively measure the β-ray emitting nuclides such as strontium-90 and yttrium-90 and the γ-ray emitting nuclides such as cesium-137 or cesium-134 in real time. ..

Further, the radiation analyzer of the present embodiment configured as described above is
The arithmetic unit
Spectral data showing the shape of the first energy distribution in at least the first energy band of β rays from the yttrium is recorded in advance.
A collation determination is made to collate the recorded spectral data with the first energy distribution in the first energy band of the radiation from the incident radioactive material.
Further, the radiation analyzer of the present embodiment configured as described above is
The spectral data is
The shape of the first energy distribution of β rays from the yttrium.

As described above, since the spectral data indicating the wave height spectral shape of the yttrium-90 is recorded in advance, the existence of the yttrium-90 can be quickly and accurately determined in the collation determination. In addition, since the radiation evaluation of strontium-90 can be performed based on the wave height spectral shape of the recorded spectral data, it is possible to accurately evaluate the radiation intensity regardless of the positional relationship between the detector and the radioactive material and the installation environment of the detector. become.

Further, the radiation analyzer of the present embodiment configured as described above is
In the collation determination, the calculation unit
The shape of the first energy distribution in the first energy band indicated by the recorded spectral data and the shape of the first energy distribution in the first energy band of the incident radiation from the radioactive material. If they match,
The first operation is performed based on the first energy distribution of β rays from the yttrium indicated by the spectral data.
It is a thing.

In this way, the calculation unit performs a collation determination for collating the shape of the wave height spectrum indicated by the recorded spectral data with the shape of the wave height spectrum of the radiation from the incident radioactive substance, and the determination results match. In this case, the first operation is performed. As a result, the radiation intensity is calculated only when the presence of the strontium-90 is confirmed, so that the radiation intensity can be calculated with high accuracy. Further, for example, even if the presence of strontium-90 is present, if the radiation of other β-ray emitting nuclides other than strontium-90 has a large effect, the shape will not match. By doing so, it is possible to calculate the radiation intensity with high accuracy.

Embodiment 2.
Hereinafter, the radiation analyzer 200 of the second embodiment will be described with reference to the parts different from the first embodiment. The same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
FIG. 5 is a block diagram showing a schematic configuration of the radiation analyzer 200 according to the second embodiment.
The radiation analyzer 200 of the present embodiment has a different configuration of the calculation unit 250 from the radiation analyzer 100 shown in the first embodiment. The calculation unit 250 of the present embodiment includes a gloss counter 252, a β-ray counter 253, and a CPU 254.

Similar to the first embodiment, the pulse height analyzer 3 generates and outputs the wave height spectrum M shown in FIG. The output wave height spectrum M is input to the gloss counter 252 and the β-ray counter 253 of the calculation unit 250.

The β-ray counter 253 calculates the total number of β-ray counts in the shaded area in the first energy band Ehi having the first crest value Ed or higher shown in FIG. 3 based on the input crest spectrum M, and calculates the total number of β-ray counts for the CPU 254. And output.
The gloss counter 252 calculates the total number of counts of radiation including γ-rays and β-rays in the entire energy region of the wave height spectrum M, and outputs the total number to the CPU 254.

Here, in the spectrum data D recorded in the database 59, the total number Va of the radiation counts of the shaded portion β rays in the first energy band Ehi is recorded in advance.
This total number of Va is derived based on the wave height spectral shape of strontium-90 obtained by simulations with known radioactivity set, experiments by irradiation with a standard radioactive source, etc., depending on the intensity of radioactivity and measurement conditions. A plurality of total Vas are recorded.
Further, in the spectrum data D, the total number Vb of β rays in the second energy band Elow corresponding to the total number of β rays Va in the first energy band Ehi is recorded in association with the Va. This total number Vb can also be obtained by the above simulation or the like.

The CPU 254 has the total number of β-ray counts in the first energy band Ehi counted by the β-ray counter 253 based on the wave height spectrum M of the incident radiation, and the first wave height spectrum M recorded in advance in the spectrum data D. A collation determination is performed to collate the total number Va of β-ray counts in the energy band Ehi. Then, when the matching determinations match, the CPU 254 identifies that the radioactive substance that emits radiation in the first energy band Ehi detected by the detector 1 is yttrium-90.

In this case, in the first calculation, the CPU 254 is the total number of β-ray counts appearing in the second energy band Elow, that is, the β-rays of yttrium-90, based on the total number of β-rays Va in the spectral data D that matched in the collation determination. Of these, the total number Vb whose crest value is equal to or less than the first crest value Ed is derived based on the spectrum data D. Then, the CPU 254 derives the β-ray count of strontium-90 from the total number of β-ray counts of yttrium-90 above and below the first peak Ed.
In this way, if the β-ray counter 253 counts the radiation counts in the first energy band Ehi whose crest value is equal to or higher than the first crest value Ed, the total number of β-rays of strontium-90 and yttrium-90 can be found. ..

Further, the CPU 254 of the strontium-90 and yttrium-90 calculated above from the total number of radiation counts including γ-rays and β-rays in the entire energy region of the wave height spectrum M of the incident radiation counted by the gloss counter 252. By subtracting the total number of counts, it is also possible to calculate only the count of γ-rays from γ-ray radionuclides.

As described above, only the total number of β rays Va and Vb are recorded, and only numerical collation is performed in the collation determination. As a result, the load of the arithmetic processing in the arithmetic unit 250 can be reduced and the apparatus can be simplified as compared with the configuration in which the spectral data showing the wave height spectral shape shown in FIG. 4 of the first embodiment is recorded. Further, the capacity reduction effect of the database 59 can be obtained.

In the first calculation, for example, the count counted by the β-ray counter 253 by multiplying the total number of counts of the incident radiation counted by the β-ray counter 253 in the first energy band Ehi by a specific ratio. However, if it matches the total number recorded Vb, the CPU 254 may perform the first operation using, for example, the ratio r recorded in the database 59 as shown below.

That is, if the wave height spectral shape of yttrium-90 is known, the count value (referred to as Va1) in the first energy band Ehi above the first wave height value Ed of yttrium-90 and the second energy less than the first wave height value Ed. The ratio (r = Vb1 / Va1) of the count value (referred to as Vb1) in the band Energy is constant. If all the count values Va1 having the first peak value Ed or more are considered to be caused by yttrium-90, the total count value of yttrium-90 (= Va1 + Vb1 = Va1 × (1 + r)) can be found from the ratio r.

The radiation analyzer of the present embodiment configured as described above is
In the first calculation, the calculation unit is used.
The first less than the first, based on the total number of β-ray radiation counts in the first energy band, derived based on the shape of the first energy distribution of β-rays from the yttrium in the first energy band. 2 The total number of β-ray radiation counts from yttrium in the energy band is derived to calculate the radiation intensity of the strontium.
It is a thing.
Further, the radiation analyzer of the present embodiment configured as described above is
The spectral data is
The total number of radiation counts derived based on the shape of the first energy distribution of β-rays from yttrium,
Is what it is.
Further, the radiation analyzer of the present embodiment configured as described above is
The total number of radiation counts in the first energy band derived from the shape of the first energy distribution in the first energy band indicated by the recorded spectral data and the radiation from the incident radioactive material. When the total number of radiation counts in the first energy band matches.
The first operation is performed based on the first energy distribution of β rays from the yttrium indicated by the spectral data.
It is a thing.

In this way, the total number of β-rays Va and Vb of strontium-90 obtained by simulations with known radioactivity set, experiments by irradiation with a standard radioactive source, etc. are recorded, and based on this total number, collation judgment or collation judgment or Perform the first operation. As a result, it is possible to obtain the effects of reducing the load of arithmetic processing in the CPU, simplifying the device, and reducing the capacity of the database.

Embodiment 3.
Hereinafter, the radiation analyzer 300 of the third embodiment will be described with reference to the parts different from the first embodiment. The same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
FIG. 6 is a block diagram showing a schematic configuration of the radiation analyzer 300 according to the third embodiment.
FIG. 7 is a diagram showing an example of a wave height spectrum M which is an output of the pulse height analyzer 3. In FIG. 7, the β-rays from yttrium-90 and strontium-90 are shown by broken lines.
FIG. 8 is a diagram showing a wave height spectrum obtained by subtracting the distributions of strontium-90 and yttrium-90 from the wave height spectrum M shown in FIG. 7.

The radiation analyzer 300 of the present embodiment has a different configuration of the calculation unit 350 from the radiation analyzer 300 shown in the first embodiment. The calculation unit 350 of the present embodiment includes a spectrum comparator 51 similar to that of the first embodiment, and a new inverse problem calculation unit 355. Further, in the database 59, the same spectrum data D as in the first embodiment and a new response function R are recorded.

Similar to the first embodiment, the spectrum comparator 51 collates the wave height spectrum shape of yttrium-90 with the wave height spectrum M of the output of the multiplex wave height analyzer 3 to calculate β-ray radioactivity corresponding to strontium-90 and yttrium-90. do. Further, the spectrum comparator 51 subtracts the calculated β-ray counts from the strontium-90 and yttrium-90 from the peak spectrum M of the output of the pulse height analyzer 3 shown in FIG. 7, and γ as shown in FIG. A wave height spectrum M showing a count for each energy value of a line only is generated.
As shown in FIG. 8, the count for each energy value of β rays from yttrium-90 is subtracted from the count for each energy value in the wave height spectrum M. The generated wave height spectrum M is output to the inverse problem calculation unit 355 in the subsequent stage.

The inverse problem calculation unit 355 reads the response function R related to the detector 1 from the database 59, and performs an inverse problem calculation on the wave height spectrum M using the response function R. That is, where the following (Equation 1) is established, where M is the first wave height spectrum, R is the response function, and S is the second wave height spectrum which is an energy spectrum excluding the influence of the interaction of radiation, the response function R In general, there is an inverse element because they form a commutative group. Therefore, the inverse problem calculation unit 355 extracts the energy spectrum S as the second energy distribution by calculating the following (Equation 2) which is the inverse conversion of this (Equation 1). Note that "R ^ -1" indicates the inverse element of the response function.
M = RS ... (Equation 1)
S = (R ^ -1) ・ M ・ ・ ・ (Equation 2)

Here, if the wave height spectra represented by M and the energy spectra represented by S are represented by vectors, that is, the count corresponding to the number of channels is represented as a vector component, the response function R and the inverse element R ^ -1 of the response function are matrices, respectively. , Can be referred to as an inverse matrix.

Then, a feedback operation is performed by a sequential approximation method (reference: Ministry of Education, Culture, Sports, Science and Technology, radioactivity measurement method series 20 "spatial γ-ray spectrum measurement method", (1990) Appendix 2), and the response function R calculated in advance by simulation. The energy spectrum S can be refined from the wave height spectrum M obtained by measuring the radiation, and the target energy spectrum S can be obtained.

When the successive approximation method is applied, the method of obtaining the energy spectrum S in (Equation 2) is as follows. Substituting the measured value M as it is as the initial value of the energy spectrum S,

Next, the following (Equation 4) and (Equation 5) are repeated in a feedback manner until S ^ (m + 1) / S ^ (m) converges.

The information contained in the energy spectrum S obtained as described above indicates the type of radionuclide.
By solving the above (Equation 2), the energy spectrum represented by S containing only the energy information of radiation can be extracted from the wave height spectrum represented by M. That is, in the derived energy spectrum S, the influence of the interaction between the detector 1 and the peripheral structures of the radioactive material and the influence of the statistical variation related to the detector 1 are excluded. Therefore, by solving the above (Equation 2), the energy information of the radiation can be accurately known, and the accuracy of the identification of the detected radioactive substance that emitted the radiation is improved.

As shown in FIG. 8, in the wave height spectrum M before the inverse problem calculation is applied, the shape of the total absorption peak of γ-rays appears at the positions indicated by E1 and E2, and two types having energies E1 and E2 appear. It shows that the γ-ray of No. 1 was incident on the detector 1.
However, with this peak spectrum M as it is, the total absorption peak spreads to the lateral peak value, and further, on the left side of each position of E1 and E2, there is a Compton scattering portion shown by continuous gentle undulations. Exists. This Compton scattering portion is a portion generated by the partial loss of the energy of the incident radiation due to the influence of Compton scattering. Normally, nuclide analysis and evaluation of radiation intensity are obtained only from the counts at E1 and E2 of the energy peak portion, and the counts at the Compton scattering region are not used because they cannot be used for nuclide identification of radiation. Therefore, when the radioactive substance is evaluated based on such a wave height spectrum M, there is a problem that the analysis accuracy is lowered and the radiation nuclide that emits γ-rays cannot be accurately identified. However, the inverse problem operation solves the problem.

FIG. 9 is a diagram showing an example of an energy spectrum S converted by applying an inverse problem operation using the above response function R to a wave height spectrum M.
As shown in FIG. 9, the inverse problem operation eliminates the Compton scattering and the spread of the total absorption peak seen in the wave height spectrum M, and improves the analysis accuracy.
Note that FIG. 9 shows a case where only radiation from two types of radioactive substances having energies E1 and E2 is incident, but the count is also shown when one type or three or more types of energy are incident. ..

The amount of radioactivity to be obtained can be obtained by multiplying the count number obtained for each energy by a coefficient such as the emission rate determined for each nuclide, such as the count number 101a of E1 and the count number 101b of E2 shown in the figure.

The radiation analyzer of the present embodiment configured as described above is
The arithmetic unit
Based on the shape of the first energy distribution from the yttrium, at least the count for each energy value of β rays from the yttrium is subtracted from the count for each energy value of the first energy distribution.
For the subtracted first energy distribution, the distribution of γ-rays, which are the radiation emitted from the radioactive substance, for each energy value is obtained by performing a signal restoration operation using the response function of the detection unit. The second energy distribution shown is derived to discriminate the nuclei of the radioactive material, and the radiation intensity of the discriminated radioactive material is calculated.
It is a thing.

In this way, the spectrum comparator subtracts at least the count for each energy value of β rays from yttrium-90 from the count for each energy value of the wave height spectrum. Then, by performing a signal restoration calculation on the wave height spectrum of γ-rays excluding the count of β-rays from yttrium-90, the accuracy of identification of radionuclides and the evaluation of radiation intensity can be further improved.

Embodiment 4.
Hereinafter, the radiation analyzer 400 of the fourth embodiment will be described with reference to the parts different from those of the first, second, and third embodiments. The same parts as those of the first, second, and third embodiments are designated by the same reference numerals, and the description thereof will be omitted.
FIG. 10 is a block diagram showing a schematic configuration of the radiation analyzer 400 according to the fourth embodiment.
FIG. 11 is a diagram showing an example of a wave height spectrum M which is an output of the pulse height analyzer 3 according to the fourth embodiment.

The radiation analyzer 400 of the present embodiment has a different configuration of the calculation unit 450 from the radiation analyzer 100 shown in the first embodiment. The calculation unit 450 of the present embodiment is configured to include the β-ray counter 253 shown in the second embodiment, the CPU 254, and the inverse problem calculation unit 355 shown in the third embodiment.

In the present embodiment, the calculation unit 450 performs a removal calculation for subtracting the set subtraction value D from the radiation count in the wave height distribution M. In this removal calculation, in the first radioactive substance which is a radioactive substance other than the γ-ray emitting nuclide and is a β-ray emitting nuclide other than yttrium-90, the count of β rays from the first radioactive substance is counted from the wave height spectrum M. It is to be removed.
Hereinafter, the details of this removal operation will be described.

Similar to the first embodiment, the pulse height analyzer 3 generates and outputs the wave height spectrum M shown in FIG. The output wave height spectrum M is input to the β-ray counter 253 of the calculation unit 450. In FIG. 11, the first peak value Eda as the first value set to the same value as the first peak value Ed of the first embodiment and the second value higher than the first peak value Eda are used. The second wave high value Edb of is shown. In the present embodiment, the second peak value Edb is set to the maximum energy value of yttrium-90.

Here, as shown in FIG. 11, radiation is counted in the third energy band Ehi2, which is higher than the second peak value Edb. The first wave high value Eda is set to the energy value of the radionuclide that emits γ-rays having a relatively large energy value among the nuclides that are prominently present in the natural world as in the first embodiment, and further, the second wave. The high value Edb is set to the maximum energy value of yttrium-90 as described above. Therefore, the count in the third energy band Ehi2 having the second wave high value Edb or more is a radioactive substance other than the γ-ray emitting nuclide, and there is a first radioactive substance which is a β-ray emitting nuclide other than yttrium-90. Show that.

The β-ray counter 253 calculates the total number of β-ray counts in the shaded area in the first energy band Ehi having the first peak value Eda or more shown in FIG. 11 based on the input peak height spectrum M, and calculates the total number of β-ray counts with respect to the CPU 254. Output. Using the counting result, the first calculation for calculating the total number of countings of strontium-90 and yttrium-90 is performed by the CPU 254 in the subsequent stage in the same manner as in the second embodiment. At the same time, the CPU 254 sets the count N1 in the first crest value Eda of the crest spectrum M in FIG. 11 as the subtraction value D. Then, the CPU 254 performs a removal operation of subtracting the count N1, which is the subtraction value D, over the entire energy region of the wave height spectrum M. By this removal operation, the wave height spectrum M showing the count for each energy value of γ-rays, which is shown in FIG. 8, is obtained.

The wave height spectrum M thus obtained is obtained by excluding the counting of β rays from yttrium-90 and the counting of β rays from the first radioactive substance other than yttrium-90. After that, the inverse problem calculation unit 355 applies the inverse problem solution method to the peak height spectrum M in the same manner as in the third embodiment to discriminate the γ-ray emitting nuclide and obtain the radioactivity amount thereof.

The calculation unit 450 may perform a collation determination before performing the removal calculation. That is, before performing the removal operation, the total number of β-ray counts in the first energy band Ehi counted by the β-ray counter 253 and the first energy band Ehi of yttrium-90 recorded in advance in the spectrum data D. A collation determination is performed to collate with the total number of β-ray counts Va.
In this case, since radiation from β-ray emitting nuclides other than yttrium-90 is counted, the collation determination is inconsistent. If the calculation unit 450 controls to perform the above removal calculation only when the collation determination does not match, the β-ray emitting nuclide of this β-ray emitting nuclide only when it is confirmed that a β-ray emitting nuclide other than yttrium-90 exists. The removal operation to remove the influence will be performed. Therefore, it is possible to accurately discriminate γ-ray emitting nuclides and calculate the amount of radioactivity.

Further, the calculation unit 450 may be configured to include the spectrum comparator 51 as shown in the first embodiment. In this case, the calculation unit 450 may perform the collation determination by comparing the shapes of the wave height spectra in the shaded areas having the first peak value Eda or more.

In the above, as the subtraction value D in the removal operation, the count N1 in the first crest value Eda of the crest spectrum M is set as the subtraction value D. That is, the count of β rays from yttrium-90 and the count of β rays from the first radioactive substance other than yttrium-90 were excluded from the wave height spectrum M. However, the subtraction value D is not limited to this, and for example, the count N2 at the second peak value Edb may be set as the subtraction value D. Then, this count N2 may be subtracted from the count for each energy value of radiation in the energy band below the second peak value Edb. In this case, the wave height spectrum M excluding only the count of β rays from the first radioactive substance is obtained.

The control of setting the count N2 at the second crest Edb as the subtraction value D can be applied, for example, when the nuclide of the first radioactive material is unknown. That is, since the wave height spectrum of the first radioactive material in the energy band below the second peak value Edb is unknown, it is assumed that the count of the first radioactive material in the energy band below the second peak value Edb is the same as the count N2. , This count N2 is subtracted.

Further, if the wave height spectrum of the first radioactive substance is known in advance in simulations, experiments, or the like, the subtraction value D may be set as follows.
That is, the CPU 254 is based on at least one of the wave height spectral shape in the third energy band Ehi2 having a second value of Edb or more, or the total number of radiation counts in the third energy band Ehi2 derived in advance from this wave height spectral shape. Derivation of β-ray counts from the first radioactive material in the energy band below the second value Edb. Then, this derived count may be set as the subtraction value D.

Further, in the above, an example is shown in which the removal operation is performed after the first operation for calculating the radioactive intensity of the strontium-90 and before the inverse problem calculation. However, the present invention is not limited to this, and the removal operation may be performed before the first operation for calculating the radioactive intensity of strontium-90. This makes it possible to accurately calculate the radioactive intensities of yttrium-90 and strontium-90 by excluding the β-ray count from the first radioactive substance from the wave height spectrum M.

The radiation analyzer of the present embodiment configured as described above is
The arithmetic unit
If the determinations in the collation determination do not match, a removal operation is performed in which the set subtraction value is subtracted from the radiation count in the energy band of the first energy distribution.
It is a thing.

If the determinations in the collation determination do not match, the arithmetic unit subtracts the subtraction value set from the wave height spectrum, assuming that there is a count due to radiation other than yttrium-90. As a result, it is possible to perform accurate radiation evaluation by removing the count due to radiation other than yttrium-90.

Further, the radiation analyzer of the present embodiment configured as described above is
The arithmetic unit
A second value, which is the maximum energy value of the yttrium, is recorded, and the first value is set to a value less than the second value.
The first is based on at least one of the shape of the first energy distribution in the third energy band above the second value, or the total number of radiation counts in the third energy band derived from the first energy distribution. 3 A count of β-rays from the first radioactive substance as the radioactive substance emitting radiation in the energy band in the energy band lower than the second value is derived, and the derived count is set as the subtraction value. ,
It is a thing.

In this way, based on the wave height spectrum of the first radioactive substance in the third energy band above the second value, the count of the first radioactive substance in the energy band below the second value is derived, and this count is less than the second value. By subtracting from the count of the wave height spectrum in the energy band, the count of β rays from the first radioactive substance is subtracted from the energy band below the maximum energy value of Ittrium 90, and the first calculation and the inverse problem calculation with high accuracy can be performed. It will be possible.

Further, the radiation analyzer of the present embodiment configured as described above is
The arithmetic unit
The count value of radiation in the first value or the second value is set as the subtraction value, and the set subtraction value is subtracted from the count of each energy value of radiation in the energy band less than the second value. do,
It is a thing.
In this way, by subtracting the count N1 at the first value from the wave height spectrum, the count of the first radioactive substance and the count of yttrium-90 can be removed, and accurate γ-ray radiation evaluation can be performed.
Further, by subtracting the count N2 in the second value from the wave height spectrum, the count of the first radioactive substance can be removed, and accurate radiation evaluation of yttrium-90 and strontium-90 and subsequent radiation evaluation of γ-rays can be performed.

Further, when the β-ray energy from the first radioactive substance serving as an interfering nuclide is sufficiently higher than that of the yttrium-90 to be measured as in the present embodiment, the second wave high value Edb is emitted by the beta-rays emitted by the yttrium-90. By setting the maximum energy value of 2.28 MeV, most of the influence of the first radioactive substance can be eliminated, and the measurement accuracy with a high S / N ratio can be ensured. In reality, the wave height spectrum may shift due to an error caused by the measuring device. Therefore, the value of the second crest value Edb may be adjusted with a margin set based on the shape of the obtained crest spectrum.

On the other hand, when the β-ray energy from the first radioactive substance is slightly higher than that of yttrium-90 to be measured, the S / N ratio may be worse than in the above case. Therefore, the S / N ratio can be improved by correcting the second wave high value Edb to the low energy side in advance, such as the maximum energy of the beta ray that can be reached, in consideration of the energy attenuation up to the detector 1.

Further, the values of the first peak value Ed and the first peak value Eda of the present embodiment shown in the third embodiment are the maximum energy imparted by γ-rays due to the detector structure and the first radioactive nuclide. Considering the influence of the substance, the first crest value Eda from which the measurement accuracy is most obtained is determined. For example, the first peak value Eda is the maximum energy value of the spectrum of γ-rays only, or the peak end on the high energy side of the maximum energy peak that appears. As a result, it is possible to improve the accuracy of extracting the spectrum of only γ-rays in the wave height spectrum after subtracting the β-ray component.

Embodiment 5.
Hereinafter, the dust monitor device 1000 of the fifth embodiment will be described.
FIG. 10 shows a schematic configuration of a dust monitor device 1000 applied to a dust sampler 60 as a dust collecting mechanism unit with respect to the radiation analyzers 100, 200, 300, and 400 shown in the first to fourth embodiments. It is a block diagram.

The dust sampler 60 includes a sample introduction pipe 61, a dust collecting unit 62, and a filter paper 63.
The sample introduction pipe 61 takes in the atmosphere containing the radioactive substance to be measured, and collects the measurement target in the dust collecting unit 62. The object to be measured containing radioactive substances is collected on the filter paper 63 installed in the dust collecting unit 62. The flow of the atmosphere during dust collection is drawn by a vacuum pump (not shown) provided downstream of the dust collection unit 62.

The flow of the atmosphere is controlled by a flow meter (not shown) installed between the dust collector 62 and a vacuum pump (not shown), and the volume of the atmosphere that has passed through the dust collector 62 is obtained by temporally integrating the flow rate of the flow meter. The radioactivity for each radionuclide calculated by the radioactivity analyzers of the first to fourth embodiments is included in the unit volume by dividing by the volume obtained from the integrated flow rate of the flow meter (not shown). It can be calculated as the radioactivity concentration.

As shown in FIG. 12, the detector 1 of the radioactivity analyzer of the first to fourth embodiments is installed close to the measurement object containing the radioactive substance collected by the filter paper 63. Therefore, it is possible to detect radioactive substances contained in the object to be measured with high efficiency, and it is possible to obtain a dust monitor equipped with a highly accurate radioactivity analyzer.

The filter paper 63 shown in FIG. 12 may be either a fixed filter paper or a long filter paper. In the case of a long filter paper, an automatic filter paper feeding mechanism including a filter paper winding member and a motor is introduced to automatically replace the filter paper. May be.

The dust monitor device of the present embodiment configured as described above is
The radiation analyzers of the first to fourth embodiments,
The dust collecting filter paper is provided with a dust collecting mechanism for collecting the radioactive substances in the atmosphere.
The detection unit of the radiation analyzer detects the radiation emitted from the radioactive substance of the dust collecting filter paper.
It is a thing.

As a result, the radiation evaluation of the collected radioactive material can be performed with high accuracy. Furthermore, even in a dust monitor where it is difficult to install multiple detectors when such radioactive substances are collected in one place and there is a dust collection mechanism and dust collection filter paper, one radiation sensor for the detector is configured. By detecting γ-rays and β-rays at the same point at the same time, the radiation intensity can be calculated more accurately.

The arithmetic unit shown in the first to fourth embodiments is composed of a processor and a storage device as shown in FIG. 13 as an example of hardware. In the first embodiment, the processor corresponds to the spectrum comparator 51 of the arithmetic unit 50, and the storage device corresponds to the database 59.
Although the storage device is not shown, it includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory.
Further, an auxiliary storage device of a hard disk may be provided instead of the flash memory. The processor 51 executes the program input from the storage device 59. In this case, a program is input from the auxiliary storage device to the processor 51 via the volatile storage device. Further, the processor 51 may output data such as a calculation result to the volatile storage device of the storage device 59, or may store the data in the auxiliary storage device via the volatile storage device.

Although the present application describes various exemplary embodiments and examples, the various features, embodiments, and functions described in one or more embodiments are applications of a particular embodiment. It is not limited to, but can be applied to embodiments alone or in various combinations.
Therefore, innumerable variations not exemplified are envisioned within the scope of the techniques disclosed in the present application. For example, it is assumed that at least one component is modified, added or omitted, and further, at least one component is extracted and combined with the components of other embodiments.

1 detector (detection part), 1C1 side wall (wall part), 1C2 bottom wall (wall part),
M wave height spectrum (first energy distribution), S energy distribution (second energy distribution),
50, 250, 350, 450 detector,
100,200,300,400 radiation analyzer, 1000 dust monitor device.

Claims (15)

A detector that outputs a detection signal corresponding to the energy of the incident radiation when the radiation emitted from the radioactive material is incident.
An analysis unit for deriving a first energy distribution showing a count for each energy value of the detection signal, and an analysis unit.
A calculation unit for calculating the radioactivity intensity of the radioactive substance based on the first energy distribution is provided.
The arithmetic unit
Based on the shape of the first energy distribution of β rays, which is the radiation emitted from yttrium, which is the daughter nuclide of strontium as a radioactive substance, the first calculation for calculating the radiation of the strontium is performed.
Radiation analyzer. In the first calculation, the calculation unit is used.
The radiation intensity of the strontium is calculated based on the shape of the first energy distribution of β rays from the yttrium in the first energy band of the set first value or more.
The radiation analyzer according to claim 1. The detector is
A sensor unit for detecting the incident radiation and a case unit having a wall portion adjusted to a thickness through which β rays, which are the radiation, are transmitted, and accommodating the sensor unit are provided.
The radiation analyzer according to claim 2. In the first calculation, the calculation unit is used.
The first less than the first, based on the total number of β-ray radiation counts in the first energy band, derived based on the shape of the first energy distribution of β-rays from the yttrium in the first energy band. 2 The total number of β-ray radiation counts from yttrium in the energy band is derived to calculate the radiation intensity of the strontium.
The radiation analyzer according to claim 2 or 3. The arithmetic unit
Spectral data showing the shape of the first energy distribution in at least the first energy band of β rays from the yttrium is recorded in advance.
Any one of claims 2 to 4, wherein the collation determination is performed to collate the recorded spectral data with the first energy distribution in the first energy band of the radiation from the incident radioactive substance. The radiation analyzer described in. The spectral data is
At least one of the shape of the first energy distribution of β-rays from yttrium or the total number of radiation counts derived based on the shape of the first energy distribution of β-rays from yttrium.
The radiation analyzer according to claim 5. In the collation determination, the calculation unit
The shape of the first energy distribution in the first energy band indicated by the recorded spectral data and the shape of the first energy distribution in the first energy band of the incident radiation from the radioactive material. If they match, or
The total number of radiation counts in the first energy band derived from the shape of the first energy distribution in the first energy band indicated by the recorded spectral data and the radiation from the incident radioactive material. When the total number of radiation counts in the first energy band matches.
The first operation is performed based on the first energy distribution of β rays from the yttrium indicated by the spectral data.
The radiation analyzer according to claim 6. The arithmetic unit
If the determinations in the collation determination do not match, a removal operation is performed in which the set subtraction value is subtracted from the radiation count in the energy band of the first energy distribution less than the first value.
The radiation analyzer according to any one of claims 5 to 7. The arithmetic unit
A second value, which is the maximum energy value of the yttrium, is recorded, and the first value is set to a value less than the second value.
The first is based on at least one of the shape of the first energy distribution in the third energy band above the second value, or the total number of radiation counts in the third energy band derived from the first energy distribution. 3 A count of β-rays from the first radioactive substance as the radioactive substance emitting radiation in the energy band in the energy band lower than the second value is derived, and the derived count is set as the subtraction value. ,
The radiation analyzer according to claim 8. The arithmetic unit
The count value of radiation at the first value or the second value which is the maximum energy value of the yttrium is set as the subtraction value, and the set subtraction value is set as each of the radiations in the energy band less than the second value. Subtract from the count for each energy value,
The radiation analyzer according to claim 8. The arithmetic unit
Based on the shape of the first energy distribution from the yttrium, at least the count for each energy value of β rays from the yttrium is subtracted from the count for each energy value of the first energy distribution.
For the subtracted first energy distribution, the distribution of γ-rays, which are the radiation emitted from the radioactive substance, for each energy value is obtained by performing a signal restoration operation using the response function of the detection unit. The second energy distribution shown is derived to discriminate the nuclei of the radioactive material, and the radiation intensity of the discriminated radioactive material is calculated.
The radiation analyzer according to any one of claims 2 to 10. The first value is set to a value that exceeds the radiation energy of cesium-134.
The radiation analyzer according to any one of claims 2 to 11. The first value is set to a value exceeding the radiation energy of potassium 40, or an energy value at the energy peak having the highest energy value among the plurality of energy peaks in the first energy distribution.
The radiation analyzer according to any one of claims 2 to 11. The sensor unit of the detection unit has a single unit configuration.
The radiation analyzer according to claim 3. The radiation analyzer according to any one of claims 1 to 14,
The dust collecting filter paper is provided with a dust collecting mechanism for collecting the radioactive substances in the atmosphere.
The detection unit of the radiation analyzer detects the radiation emitted from the radioactive substance of the dust collecting filter paper.
Dust monitor device.

Images