JP2013061254A - Radioactive suspended particulate matter measuring instrument and radioactive suspended particulate matter measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radioactive suspended particulate matter measuring instrument and a radioactive suspended particulate matter measuring method capable of detecting radioactive rays respectively radiated from micro particulate matter and coarse particulate matter by separating suspended particulate matter into the micro particulate matter and the coarse particulate matter.SOLUTION: A radioactive suspended particulate matter measuring instrument 100 includes a storage wall part 1, a pump 2, a classifier 3 for classifying suspended particulate matter into coarse particulate matter and micro particulate matter, a tape supply part 4, and a radiation detection part 5 provided with a first detector 51 and a second detector 52.

Description

  The present invention relates to a radioactive suspended particulate matter measuring device and a radioactive suspended particulate matter measuring method, and in particular, for the purpose of automatically and continuously measuring radioactive materials suspended in the atmosphere with high time resolution. After classifying the suspended particulate matter floating in the filter, it is collected in a filter, and the radiation from the collected radioactive suspended particulate matter is detected by a radiation detector to detect coarse particles and The present invention relates to an apparatus and a method capable of measuring and monitoring the concentration of a radioactive material in a minute particle.

  The conventional radioactive suspended particulate matter measuring device is installed at the monitoring point of the radioactive material handling facility, detects the radiation from the suspended particulate matter in the atmosphere with a radiation detector, and determines the radioactive concentration present in the atmosphere. I was measuring and monitoring. Conventionally, airborne particulate matter has been brought back and analyzed by a sampler.

  Patent Documents 1 to 6 describe conventional radioactive suspended particulate matter measuring devices. Patent Documents 7 to 9 describe devices that detect radiation from a radioactive gas, not a radioactive suspended particulate matter.

JP 2003-098260 A JP 2002-250771 A JP 2003-315462 A JP 2010-019724 A JP 2010-054447 A JP 2006-126124 A JP 2010-145319 A JP 2010-237232 A JP 2011-128052 A

  Since the 1960s, it has been known that the pollution of air is localized by the wind direction around the source, based on the monitoring results and epidemiological data, and the monitoring is about once per hour. It is recognized that close observation is necessary. Atmospheric pollution by radioactive materials is currently monitored by monitoring the dose at the monitoring spot and take-out analysis by a sampler. However, take-out analysis by a sampler is measured at a time resolution of once a day at most. When considering weather conditions, there is a problem that this time resolution is too low.

  In addition, there is concern about contamination by radioactive substances localized in the area, possibly due to air masses that contain high concentrations of pollutants along with air currents, so spatially close monitoring is desired. However, take-away analysis by a sampler is labor-intensive and expensive, so there are currently very few observation points.

Humans are anxious to receive a great deal of damage by breathing 15 m ³ / day of air and inhaling very high concentrations of radioactive suspended particulate matter for several hours. In addition, the half-life of radioactive elements, where it is concentrated in the body, and how fast the human body can be discharged vary greatly depending on the substance, and there is no impact on the human body. Expected to be different.

  Furthermore, suspended particulate matter has been studied as having an adverse effect on human health. Among suspended particulate matter, microparticulate matter having a particle size of 2.5 μm or less is considered to have particularly great adverse effects. ing. The reason is that, among the suspended particulate matter, coarse particulate matter with a particle size larger than 2.5 μm is removed in the middle of the nose and respiratory tract, while the fine particulate matter is deepened into the lungs by breathing. It is because it is difficult to discharge once it settles and settles once. Therefore, even if the radiation dose from the suspended particulate matter in the atmosphere is the same as a whole, the radiation dose is reduced to a fine particulate matter compared to the case where the radiation dose is derived from coarse particulate matter. If it is derived, it is considered more dangerous for the human body.

  Although there has been little research on internal exposure to radioactive microparticulates, studies on carcinogenicity of microparticulates and epidemiological studies on cardiovascular diseases have been conducted, and radioactive microparticulates are once aspirated. If this happens, it is expected that internal exposure will occur over a long period of time, and future epidemiological studies will reveal the danger. However, with regard to radioactive suspended particulate matter, there is little epidemiological data and toxicity data, little observation data, and very little scientific knowledge. There is no automatic monitoring device.

  For example, the conventional measuring devices as described in Patent Documents 1 to 9 do not detect the radiation by dividing the suspended particulate matter into a fine particulate matter and a coarse particulate matter, and are detected. It cannot be determined whether the radiation is derived from radioactive fine particulate matter or from radioactive coarse particulate matter.

  The present invention is to solve the above-described problems, and divides floating particulate matter into fine particulate matter and coarse particulate matter and radiates radiation from each of the fine particulate matter and coarse particulate matter. It is an object of the present invention to provide a radioactive suspended particulate matter measuring apparatus and a radioactive suspended particulate matter measuring method capable of detecting water.

The present invention includes a storage unit having an internal space;
A suction part for sucking air containing suspended particulate matter from the outside of the storage part to the internal space;
The suspended particulate matter provided in the internal space and sucked by the suction portion is classified into coarse particulate matter having a particle size larger than 2.5 μm and fine particulate matter having a particle size of 2.5 μm or less. Classifying part to
A collecting unit that is provided in the internal space and collects the coarse particulate matter and the fine particulate matter classified by the classification unit, and
A radiation detection unit that is provided in the internal space and detects either radiation emitted from the coarse particulate matter collected by the collection unit or radiation emitted from the fine particulate matter. It is a characteristic radioactive suspended particulate matter measuring device.

The present invention also includes a storage unit having an internal space;
A suction part for sucking air containing suspended particulate matter from the outside of the storage part to the internal space;
The suspended particulate matter provided in the internal space and sucked by the suction portion is classified into coarse particulate matter having a particle size larger than 2.5 μm and fine particulate matter having a particle size of 2.5 μm or less. Classifying part to
A collecting unit that is provided in the internal space and collects the coarse particulate matter and the fine particulate matter classified by the classification unit, and
A radiation detector that is provided in the internal space and detects both radiation emitted from the coarse particulate matter collected by the collection portion and radiation emitted from the fine particulate matter; This is a radioactive suspended particulate matter measuring device.

Further, in the present invention, the classification unit performs classification in conjunction with the suction unit,
The collection unit performs collection in conjunction with the classification unit,
The radiation detecting unit detects radiation in conjunction with the collecting unit.

  In the invention, it is preferable that the radiation detection unit measures the energy of the detected radiation and the count for each energy with a scintillation detector.

  Further, in the present invention, the radiation detection unit simultaneously detects both the radiation emitted from the coarse particulate matter collected by the collection unit and the radiation emitted from the fine particulate matter, and performs anti-coincidence counting. The detection result of each radiation is corrected by the method.

  In the invention, it is preferable that the radiation detection unit detects at least one of α rays or β rays and γ rays as radiation.

The present invention also includes a step of sucking air containing suspended particulate matter;
Separating and collecting fine particulate matter having a particle size of 2.5 μm or less from the sucked suspended particulate matter;
And a step of detecting radiation emitted from the collected microparticulate matter. A method for measuring radioactive suspended particulate matter, comprising:

  According to the present invention, the suspended particulate matter can be divided into a fine particulate matter and a coarse particulate matter, and radiation emitted from either one can be detected. In addition, according to the present invention, the suspended particulate matter can be divided into a fine particulate matter and a coarse particulate matter, and radiation can be detected, respectively, from the radioactive particulate matter that is more dangerous to the human body. Since the radiation can be detected and the radiation from the radioactive coarse particulate matter is also detected, the radiation for the whole suspended particulate matter in the atmosphere can be detected.

  In addition, according to the present invention, since the suction unit, the classification unit, the collection unit, and the radiation dose measurement unit are interlocked with each other, the radiation suspended particulate matter in the atmosphere can be continuously and automatically monitored.

  Further, according to the present invention, the radiation detection unit measures the energy of the detected radiation and the count for each energy by the scintillation detector, so that the radionuclide can be identified.

  According to the present invention, since the radiation detection unit corrects the detection result by the anti-coincidence method, it is possible to reduce the influence of cosmic rays incident on the radioactive suspended particulate matter measuring device.

  According to the present invention, the radiation detection unit can detect γ rays as radiation, and can also detect at least one of α rays and β rays.

  Moreover, according to this invention, the radiation radiated | emitted from the microparticulate matter with high danger by the human body among the suspended particulate matter in air | atmosphere is detectable.

1 is a diagram illustrating a configuration of a measurement apparatus 100. FIG. It is a figure for demonstrating in detail about the classifier 3. FIG. It is a figure which shows a classification curve when the classifier 3 is drive | operated on predetermined conditions. It is a graph which shows the measurement result by the 1st detector 51 when using each standard radiation source. It is a graph when each peak is isolate | separated from the graph of FIG. 4 is a flowchart showing measurement processing by the measurement apparatus 100. It is a figure which shows an example of a measurement result. It is a figure which shows an example of a measurement result. It is a figure which shows an example of a measurement result. It is a figure which shows an example of a measurement result. It is a figure which shows an example of a measurement result. It is a figure which shows an example of a measurement result. 1 is an overall view of a measuring apparatus 100 that detects both γ rays and β rays. It is a schematic diagram of the 1st detector 51 in the measuring apparatus 100 which detects both a gamma ray and a beta ray.

  Hereinafter, the radioactive suspended particulate matter measurement device 100 (hereinafter simply referred to as “measurement device 100”) according to the present invention will be described. FIG. 1 is a diagram illustrating a configuration of the measurement apparatus 100. In FIG. 1, the upper side of the paper is the upper side in the vertical direction, and the lower side of the paper is the lower side in the vertical direction.

  The measuring apparatus 100 includes a storage wall 1, and an internal space is formed by the storage wall 1, and a pump 2, a classifier 3, a tape supply unit 4, and a radiation detection unit 5 are accommodated in the internal space. . Moreover, the sample inlet 6 is provided so that the space enclosed by the storage wall part 1 and the exterior space may be connected. The material of the storage wall 1 may be any material, but is preferably concrete, iron, lead or the like that hardly transmits radiation.

  In general, the measuring device 100 sucks the sample atmosphere from the sample inlet 6 by the pump 2 that is a vacuum pump that sucks air to reduce the pressure and the blower 7 and floats in the sucked sample atmosphere. The particulate matter (Suspended Particulate Matter) is classified into a coarse particulate matter and a fine particulate matter by the classifier 3, and then the coarse particulate matter and the fine particles are fed by the tape filter 4a supplied by the tape supply unit 4. This is a device that separates and collects particulate matter and detects radiation radiated from the collected coarse particulate matter and fine particulate matter by the radiation detector 5. Here, the coarse particulate substance is a substance having an aerodynamic particle diameter (hereinafter simply referred to as “particle diameter”) larger than 2.5 μm among the suspended particulate substances. Is a substance having a particle size of 2.5 μm or less among the suspended particulate substances.

The sample inlet 6 may be a PM10 inlet configured integrally with an inertial collision type classifier (PM ₁₀ impactor) for permeating suspended particulate matter, or particles of 10 μm or more not including a classifier. May also be a TSP inlet. The sample inlet 6 feeds suspended particulate matter and gas in the sample atmosphere to the classifier 3. As the classifier 3, a cyclone classifier, an impactor, a virtual impactor, or the like is used. In the present embodiment, the classifier 3 is a virtual impactor, and classifies floating particulate matter into coarse particulate matter and fine particulate matter by generating an air flow with the pump 2 and the blower 7 that sucks air. The fine particulate matter is classified by the classifier 3, is discharged from the first outlet 3 a of the classifier 3 together with the gas in the sample atmosphere, and travels to the first flow path 8. Further, the classifier 3 discharges the suspended particulate matter mainly composed of coarse particulate matter from the second discharge port 3 b of the classifier 3 together with the gas in the sample atmosphere toward the second flow path 9.

  Between the first outlet 3a and the first channel 8 and between the second outlet 3b and the second channel 9, so as to face the first and second outlets 3a, 3b, One tape-like filter 4a is stretched by the tape supply unit 4, and coarse particulate matter and fine particulate matter are collected on the tape-like filter 4a. The tape-like filter 4a can pass air well and can collect particles efficiently. The air discharged from the first and second discharge ports 3a and 3b passes through the tape filter 4a and flows into the first and second flow paths 8 and 9, respectively. At this time, the flow rate of the fine particulate matter on the first flow path 8 side is 200 L / min, and the flow rate of the coarse particulate matter on the second flow path 9 side is 20 L / min. As described above, the blower 7 is used when suction is required at a large flow rate, and the pump 2 is used when suction is performed at a small flow rate.

  The tape-like filter 4a is close to the first and second discharge ports 3a and 3b at a distance of about 10 mm at different portions. In addition, inlets of the first and second flow paths 8 and 9 are provided on the opposite side of the tape-like filter 4a from the first and second discharge ports 3a and 3b, that is, on the back side of the tape-like filter 4a. Yes.

  In the 1st flow path 8, the 1st detector 51 is provided so that the tape-shaped filter 4a may be pinched and it may oppose the 1st discharge port 3a. As for the 1st detector 51, the detection surface 51a has faced the back side of the tape-shaped filter 4a, and the distance of the detection surface 51a and the tape-shaped filter 4a is 1 mm-50 mm. The first detector 51 detects radiation incident on the detection surface 51 a and inputs the detection result to the main control unit 54 via the multi-channel analyzer 53. Similarly, a second detector 52 is provided in the second flow path 9 so as to face the second discharge port 3b with the tape filter 4a interposed therebetween. As for the 2nd detector 52, the detection surface 52a has faced the back side of the tape-shaped filter 4a, and the distance of the detection surface 52a and the tape-shaped filter 4a is 1 mm-50 mm. The second detector 52 detects the radiation incident on the detection surface 52 a and inputs the detection result to the main control unit 54 via the multichannel analyzer 53. Based on the detection results input from the first and second detectors 51 and 52, the main control unit 54 calculates the radiation doses emitted from the collected fine particulate matter and coarse particulate matter, respectively. . As described above, the radiation detector 5 is configured by the first detector 51, the second detector 52, the multichannel analyzer 53, and the main controller 54.

  The main controller 54 is connected not only to the multi-channel analyzer 53 but also to the first temperature sensor 10 and the first pressure sensor 11 provided in the first flow path 8. Pressure data is input. A blower 7 that generates an air flow for classification by the classifier 3 and a first flow rate sensor 12 that measures the flow rate of the air flow in the first flow path 8 generated by the blower 7 are also connected to the main control unit 54. The

  The main controller 54 is connected to the second temperature sensor 13 and the second pressure sensor 14 provided in the second flow path 9, and receives temperature data and pressure data in the second flow path 9. . In addition, the flow control unit 15 that controls the flow rate of the air flow in the second flow path 9 generated by the pump 2 and the second flow rate sensor 16 that measures the flow rate of the air flow in the second flow path 9 are also the main control unit 54. Connected to. The temperature data and pressure data are used for controlling the classifier 3 which is a virtual impactor. That is, the classifier 3 needs to control the passing air by the volume flow rate, but the first and second flow sensors 12 and 16 are mass flow sensors that measure the mass flow rate of the passing air, and thus converted to the volume flow rate. In order to do so, temperature data and pressure data are used.

  Next, the classifier 3 will be described. As described above, the classifier 3 in this embodiment is a virtual impactor, and is generated by the main flow generated by the blower 7 provided in the first flow path 8 and the pump 2 provided in the second flow path 9. The suspended particulate matter is classified into fine particulate matter and coarse particulate matter by the next flow. A main flow is generated in the classifier 3 by controlling the blower 7 by the main control unit 54 based on the measurement result by the first flow sensor 12. The pump 2 sucks the air in the second flow path 9 at a constant speed, for example, several hundred liters per minute, and the flow control unit 15 controls the main control unit 54 based on the measurement result by the second flow rate sensor 16. As a result, a secondary flow having a smaller flow rate than the main flow is generated in the classifier 3. The air that has passed through the blower 7 and the pump 2 is discharged out of the space surrounded by the storage wall 1 from the outlets of the first and second flow paths 8 and 9, respectively. The measuring apparatus 100 is provided with a silencer 17 for suppressing noise generated when air is discharged by the pump 2.

The classifier 3 will be described in more detail with reference to FIG. The classifier 3 includes a nozzle part 31, a gas collection part 32, and an outer pipe part 33. The nozzle portion 31 is connected to the contracted tube portion 31a to which the sample atmosphere is supplied from the sample inlet 6, the cylindrical portion 31b having an axial length of T [cm], and connected to the cylindrical portion 31b. And a spout 31c that spouts the sample atmosphere. The jet port 31c has a circular shape, and its inner diameter is D ₀ [cm]. The air ejected from the ejection port 31c is ejected at, for example, a linear velocity (20000 m / min to 25000 m / min) corresponding to a Reynolds number of about 10,000. The air collecting part 32 is a cylindrical member and communicates with the second outlet 3b shown in FIG. The axial line of the air collecting part 32 and the axial line of the cylindrical part 31b coincide, and the inner diameter D ₁ [cm] of the air collecting part 32 is larger than the inner diameter D ₀ . The distance between the air collecting part 32 and the ejection port 31c is S [cm]. The outer pipe portion 33 is a member having an inner diameter sufficiently larger than the outer diameter of the air collecting portion 32, accommodates the nozzle portion 31 and the air collecting portion 32, and communicates with the first discharge port 3a shown in FIG.

  The classifier 3 collects microparticulate matter in the outer pipe portion 33 and makes the air collection portion 32 coarse by using the airflow flowing into the outer pipe portion 33 as a main flow and the airflow flowing into the air collection portion 32 as a secondary flow. Collect particulate matter. More specifically, since the coarse particulate matter ejected from the ejection port 31c has a relatively large inertial force, the majority of the ejected coarse particulate matter is a gas collection that faces the ejection port 31c by the secondary flow. It flows into part 32. On the other hand, since the fine particulate matter ejected from the ejection port 31c has a relatively small inertial force, it is greatly influenced by the main flow having a large flow rate, and the majority of the ejected fine particulate matter It flows into 33.

Since the airflow flowing into the outer pipe portion 33 is the mainstream, the flow rate of the sample atmosphere ejected from the ejection port 31c is Q ₀ [liter / min], and the flow rate of the sample atmosphere flowing into the air collection portion 32 is Q ₁ [liter / min]. min], the amount of the sample atmosphere flowing into the outer tube portion 33 is (Q ₀ -Q ₁ ), and (Q ₀ -Q ₁ )> Q ₁ . By setting Q ₁ / Q ₀ , inner diameter D ₁ / inner diameter D ₀ , distance S / inner diameter D ₀ , length T / inner diameter D ₀ as appropriate, most of the fine particulate matter is collected in the outer tube portion 33, Most coarse particulate matter can be collected in the air collecting section 32.

For example, Q ₀ = 27.7 liters / min, Q ₁ / Q ₀ = 0.1, inner diameter D ₀ = 3.912 mm, inner diameter D ₁ / inner diameter D ₀ = 1.28, distance S / inner diameter D ₀ = 1. When the classifier 3 is operated under the conditions of _0.0 , length T / inner diameter D ₀ = 2.0, a classification curve as shown in FIG. 3 is obtained. 3, the horizontal axis is the particle size (μm) and the vertical axis is the classification efficiency (%), and the graph X1 indicated by the solid line in FIG. 3 shows the classification curve of the suspended particulate matter collected in the outer tube portion 33. A graph X <b> 2 indicated by a broken line indicates a classification curve of the suspended particulate matter collected in the air collecting part 32. As shown in FIG. 3, the classifier 3 which is a virtual impactor cannot be completely classified with a particle size of 2.5 μm, but the two classification curves intersect at the position of the particle size of 2.5 μm. Most of the suspended particulate matter having a particle size of 2.5 μm or less is collected in the outer tube portion 33, and most of the suspended particulate matter having a particle size larger than 2.5 μm is collected in the air collecting portion 32. It can be said that the particulate matter and the coarse particulate matter can be classified.

  In the present embodiment, as described above, the sample atmosphere is sucked from the sample inlet 6 by the pump 2, the suspended particulate matter is fed into the classifier 3, and classification is performed by the pump 2 and the blower 7. It is configured. That is, in this embodiment, the suction of the sample atmosphere and the classification of the suspended particulate matter in the sample atmosphere are linked, and as a result, the aspirated suspended particulate matter is automatically and continuously classified without stagnation. Can do.

  Next, returning to FIG. 1, the tape supply unit 4 will be described. The tape supply unit 4 includes a feed roller 41, a take-up roller 42, a cover tape feed roller 43, and a plurality of guide rollers. The tape-like filter 4a is stretched around the feed roller 41, the take-up roller 42, and the guide roller. Examples of the tape-like filter 4a include a fluororesin membrane filter such as PTFE (polytetrafluoroethylene) filter paper. The width of the tape-like filter 4a is about 15 mm to 200 mm.

  The delivery roller 41 delivers the tape-like filter 4a at regular intervals, for example, at time intervals of 60 minutes to 240 minutes. Therefore, during the predetermined time, the fine particulate matter is continuously collected and accumulated in one place of the tape-like filter 4a. When the tape-like filter 4a is sent out, it is collected in another place. become. The same applies to coarse particulate matter.

  The take-up roller 42 winds the tape-like filter 4a fed from the feed roller 41 so as not to loosen, and also takes up the cover tape 4b fed by the cover tape feed roller 43, whereby the tape-like filter 4a. The surface of the classifier 3 is covered with the cover tape 4b. By covering with the cover tape 4b in this way, it is possible to prevent airborne particulate matter from adhering to the tape filter 4a when the tape filter 4a is recovered from the measuring device 100, and the recovered tape. Elemental analysis of the suspended particulate matter collected by the particulate filter 4a can be performed precisely. An element analyzer may be provided in the measuring apparatus 100 so that the elemental analysis is performed after the suspended particulate matter is collected on the tape-like filter 4a and before being covered with the cover tape 4b. Examples of the element analyzer include a fluorescent X-ray analyzer.

  In the present embodiment, as described above, since the tape-like filter 4a for collecting the fine particulate matter and coarse particulate matter discharged from the classifier 3 is sent out at regular intervals, the suspended particulate matter is There is no situation in which the gas in the sample atmosphere cannot pass through the tape-like filter 4a due to excessive accumulation in the tape-like filter 4a. Therefore, in this embodiment, the classification of the suspended particulate matter and the collection of the fine particulate matter and the coarse particulate matter after classification are linked, and as a result, the classified suspended particulate matter It can be collected automatically continuously.

Next, the radiation detection unit 5 will be described. As described above, the radiation detection unit 5 includes the first detector 51 and the second detector 52, and the first and second detectors 51 and 52 are collected by the tape filter 4a. The radiation radiated from the suspended particulate matter containing the radioactive substance (hereinafter referred to as “radiated suspended particulate matter”) is always detected, and the detection result is always input to the main control unit 54. The first detector 51 and the second detector 52 are the same radiation detector, and for example, a scintillation detector or a germanium detector can be used as the radiation detector. In the present embodiment, both the first detector 51 and the second detector 52 are a combination of a scintillation detector and a multi-channel detector, and a spectrum analysis is performed from the emitted energy and the emitted count. I do. In the spectrum analysis, the energy level has a value specific to the radionuclide, so that the type of radionuclide can be identified. For example, ¹³¹ I mainly emits gamma rays with energies of 80.2 keV, 284 keV, 637 keV, and 723 keV. Next, the radioactivity Bq for each energy can be obtained by obtaining the counting efficiency of the detector from various standard radiation sources prepared in advance using the count per unit time (cps). Table 1 shows the energy levels of the standard radiation sources.

The γ-ray spectrum observed in normal time is the natural radionuclide ⁴⁰ K, ²³⁵ U, uranium series ( ²¹⁴ Pb, ²¹⁴ Bi, ²²⁶ Ra, ²³⁴ Pa, etc.), thorium series ( ²⁰⁸ Tl, ²¹² Pb, ²¹² Bi, ²²⁸ Ac, etc.) and a ⁷ Be peak created by cosmic rays. Next, artificial radionuclides are observed due to accidents at nuclear power plants, etc., which are ⁶⁵ Z, ⁹⁵ Nb, ⁹⁹ Mo, ^99m Tc, ¹¹³ Sn, ¹²⁹ Te, ^{129 m} Te, ¹³¹ I, ¹³² I, ¹³³ I, ¹³⁴ Cs, ¹³⁶ Cs, ¹³⁷ Cs, ¹⁴⁰ Ba, ¹⁴⁰ La, and ²⁰³ Pb. Further, at this time, it is known that the particles fly directly as fine particulate matter, and once absorbed into the soil and once again floating as sand dust, it is known to exist as coarse particulate matter.

  FIG. 4 (a) shows the influence of radionuclides generated by natural radionuclides and cosmic rays by detecting the radiation emitted from each standard radiation source by attaching each standard radiation source to the tape-like filter 4a with a predetermined mass. It is a graph which shows the measurement result by the 1st detector 51 after removing. FIG. 4B is an enlarged graph of a part of FIG. In FIG. 4, the horizontal axis is energy [keV], and the vertical axis is count [cps].

  In order to obtain the counting efficiency of the first detector 51, it is assumed that each peak in FIG. 4 has a Gaussian distribution and a plurality of peaks are overlapped, and the peak is separated from the graph in FIG. Do. FIG. 5A is a graph after peak separation, and FIG. 5B is a graph in which a part of FIG. 5A is enlarged. From the graph of FIG. 5, the count per unit mass [cps / g] can be calculated for each standard radiation source.

The first detector 51 is provided in the first flow path 8 so as to oppose the first discharge port 3a of the classifier 3, and as described above, one of the fine particulate matter and the gas in the sample atmosphere. Since the portion is collected in the outer tube portion 33 of the classifier 3 and discharged from the first discharge port 3a, the radiation detected by the first detector 51 is radioactive fine particles collected by the tape-like filter 4a. The radiation from the particulate material and the radiation from the radioactive gas flowing into the first flow path 8 through the tape filter 4a are combined. Similarly, the second detector 52 is provided in the first flow path 9 so as to face the second discharge port 3b of the classifier 3, and as described above, the coarse particulate matter and the sample atmosphere A part of the gas inside is collected in the air collecting part 32 of the classifier 3 and discharged from the second discharge port 3b, so that the radiation detected by the second detector 52 is collected by the tape filter 4a. The radiation from the radioactive coarse particulate matter and the radiation from the radioactive gas flowing through the tape-like filter 4a and flowing into the second flow path 9 are combined. Therefore, the main control unit 54 performs correction processing for removing the radiation dose from the gas passing through the tape-like filter 4a from the detection result by the first detector 51 and the detection result by the second detector 52, and the tape The radioactivity per unit area [μBq / cm ² ] of the radioactive fine particulate matter collected on the particulate filter 4a and the radioactivity per unit area of the radioactive coarse particulate matter are calculated. Then, by calculating the volume of air that has passed through the tape filter 4a, the radioactivity [μBq / m ³ ] per unit volume of the fine particulate matter (coarse particulate matter) contained in the sample atmosphere can be calculated.

  The main control unit 54 further removes the influence of cosmic rays on the detection result of the first detector 51 and the detection result of the second detector 52 by a correction process using the anti-coincidence method. Cosmic rays have very high energy, and when the cosmic rays are incident on the measuring apparatus 100, sharp peaks appear in the detection results of the first detector 51 and the second detector 52 at substantially the same time. Therefore, the main control unit 54 corrects the detection results of the first and second detectors 51 and 52 so as to remove this sharp peak by the anti-coincidence method.

  In the present embodiment, radioactive suspended particulate matter can be collected continuously and automatically on the tape-like filter 4a delivered every fixed time, and the radiation from the collected radioactive suspended particulate matter is the first. , Always detected by the second detectors 51 and 52. Therefore, in this embodiment, the collection of radioactive suspended particulate matter is linked with the detection of radiation from the collected radioactive suspended particulate matter, and as a result, radioactive suspended particulate matter in the atmosphere is Can be continuously monitored automatically.

  FIG. 6 is a flowchart showing measurement processing by the measurement apparatus 100. 7A to 7F are diagrams illustrating examples of measurement results. 7A to 7F are graphs in which the horizontal axis represents energy [keV] and the vertical axis represents count [cps].

  Immediately after sending out the tape-like filter 4a (step S1), no suspended particulate matter is collected in the tape-like filter 4a. At this time, blank measurement is performed (step S2). FIG. 7A (a) shows the output from the first detector 51 in step S2, and FIG. 7A (b) shows the output from the second detector 52 in step S2. As shown in FIGS. 7A (a) and 7A (b), the output results are almost the same before the collection of the suspended particulate matter.

  After the measurement of the blank, the classifier 3 classifies the fine particulate matter and the coarse particulate matter (step S3) and collects them on the tape filter 4a (step S4). And it measures by the 1st, 2nd detectors 51 and 52, performing collection (step S5). FIG. 7B (c) shows the output from the first detector 51 in step S5, and FIG. 7B (d) shows the output from the second detector 52 in step S5.

  Next, the influence of the natural radionuclide is removed by subtracting the measurement result in step S2 from the measurement result in step S5 (step S6). FIG. 7C (e) shows the extraction result of the first detector 51 in step S6, and FIG. 7C (f) shows the extraction result of the second detector 52 in step S6.

  Next, noise removal processing is performed on the extraction result of step S6 (step S7). FIG. 7D (g) shows the noise removal processing result of the first detector 51 in step S7, and FIG. 7D (h) shows the noise removal processing result of the second detector 52 in step S7.

  Next, a common peak is extracted from the two noise removal processing results in step S7 (step S8). FIG. 7E (i) shows the extraction result of the common peak in step S8.

  Next, the influence of gaseous radionuclides produced by cosmic rays is removed by the anti-coincidence method of subtracting the peak extraction result in step S8 from the noise removal processing result in step S7 (step S9). As a result, the radioactivity of the fine particulate matter in the atmosphere, which is more dangerous to the human body, can be extracted, and the radioactivity of the coarse particulate matter that is a radionuclide re-scattered from the soil can be extracted. FIG. 7F (j) shows the anti-coincidence processing result for the first detector 51 in step S9, and FIG. 7F (k) shows the anti-coincidence processing result for the second detector 52 in step S9. Yes.

  Thereafter, the radionuclide is identified based on the counting efficiency obtained from the standard substance and the result of step S9 (step S10), and the radioactivity concentration in the atmosphere is determined for each radionuclide from the flow rate of the measuring device 100 and the like. Is calculated (step S11).

  In this way, the present invention classifies fine particulate matter and coarse particulate matter, and further separates radionuclides existing in nature and gaseous radionuclides by anti-coincidence, and then in the atmosphere. It is possible to calculate the radioactive concentration of the fine particulate matter and coarse particulate matter. In the present invention, the radioactivity concentration of only the fine particulate matter may be calculated, or the radioactivity concentration of only the coarse particulate matter may be calculated.

  In the present invention, only γ rays may be detected as radiation, or both γ rays and β rays may be detected. FIG. 8 is an overall view of the measuring apparatus 100 that detects both γ rays and β rays, and FIG. 9 is a schematic diagram of the first detector 51 in the measuring apparatus 100.

Many of the fission products decay into stable nuclides while repeating β ^- decay. At this time, most nuclides emit β ^- rays and γ-rays at the same time, but some nuclides emit only β ^- rays. Since the energy of γ-rays has values specific to radionuclides, the type of radionuclide can be identified by measuring γ-ray energy. The four nuclides of ⁸⁹ Sr, ⁹⁰ Sr, ⁹⁰ Y, and ¹⁴³ Pr are beta ^- since lines only is the nuclide not released, it is necessary to perform also detection of beta rays.

  When detecting both γ-rays and β-rays, the first detector 51 and the second detector 52 are both a NaI scintillation detector 511, a plastic scintillation detector 512, and a γ-ray multichannel detector 513. , And a β-ray multi-channel detector 514 in combination. As shown in FIG. 9, γ rays A1 emitted from the suspended particulate matter collected by the tape-like filter 4a are incident on the first detector 51 below the tape-like filter 4a. At this time, the γ-ray A1 passes through the plastic scintillation detector 512 and enters the NaI scintillation detector 511. When the γ-ray A1 enters the NaI scintillation detector 511, fluorescence A2 is generated, and the fluorescence A2 enters the γ-ray multichannel detector 513. In the multi-channel detector 513 for γ-rays, the current output of the photomultiplier tube is converted into a voltage pulse by an integrating preamplifier, and the pulse height is analyzed by a PHA (Pulse Height Analyzer). And are measured. The β rays A3 emitted from the suspended particulate matter collected by the tape filter 4a enter the plastic scintillation detector 512. When β-rays are incident on the plastic scintillation detector 512, fluorescence A4 is generated. The fluorescence A4 is incident on the β-channel multichannel detector 514, and in the same manner as the γ-ray multichannel detector 513, The count number is measured. By configuring in this way, it is possible to detect both γ rays and β rays.

  In addition, the radiation detection unit 5 is not limited thereto, and may be configured to detect at least one of α rays or β rays and γ rays. For example, it may be configured to detect α rays and γ rays, or may be configured to detect all of α rays, β rays, and γ rays.

DESCRIPTION OF SYMBOLS 1 Storage wall part 2 Pump 3 Classifier 4 Tape supply part 5 Radiation detection part 6 Sample inlet 7 Blower 51 1st detector 52 2nd detector 54 Main control part 100 Radioactive suspended particulate matter measuring device (measuring device)

Claims (7)

A storage unit having an internal space;
A suction part for sucking air containing suspended particulate matter from the outside of the storage part to the internal space;
The suspended particulate matter provided in the internal space and sucked by the suction portion is classified into coarse particulate matter having a particle size larger than 2.5 μm and fine particulate matter having a particle size of 2.5 μm or less. Classifying part to
A collecting unit that is provided in the internal space and collects the coarse particulate matter and the fine particulate matter classified by the classification unit, and
A radiation detection unit that is provided in the internal space and detects either radiation emitted from the coarse particulate matter collected by the collection unit or radiation emitted from the fine particulate matter. Radioactive particulate matter measuring device featuring A storage unit having an internal space;
A suction part for sucking air containing suspended particulate matter from the outside of the storage part to the internal space;
The suspended particulate matter provided in the internal space and sucked by the suction portion is classified into coarse particulate matter having a particle size larger than 2.5 μm and fine particulate matter having a particle size of 2.5 μm or less. Classifying part to
A collecting unit that is provided in the internal space and collects the coarse particulate matter and the fine particulate matter classified by the classification unit, and
A radiation detector that is provided in the internal space and detects both radiation emitted from the coarse particulate matter collected by the collection portion and radiation emitted from the fine particulate matter; Radioactive suspended particulate matter measuring device. The classification unit performs classification in conjunction with the suction unit,
The collection unit performs collection in conjunction with the classification unit,
The radioactive suspended particulate matter measuring device according to claim 1, wherein the radiation detection unit detects radiation in conjunction with the collection unit.   The radioactive suspended particulate matter measuring device according to any one of claims 1 to 3, wherein the radiation detecting unit measures the energy of the detected radiation and the count for each energy with a scintillation detector.   The radiation detection unit simultaneously detects both radiation emitted from the coarse particulate matter collected by the collection unit and radiation emitted from the microparticulate matter, and each of them is detected by an anti-coincidence method. The radioactive suspended particulate matter measuring device according to claim 3 or 4, wherein the radiation detection result is corrected.   The radioactive suspended particulate matter measuring device according to any one of claims 1 to 5, wherein the radiation detection unit detects at least one of α rays or β rays and γ rays as radiation. . Aspirating air containing suspended particulate matter;
Separating and collecting fine particulate matter having a particle size of 2.5 μm or less from the sucked suspended particulate matter;
And a step of detecting radiation radiated from the collected microparticulate matter.