JP5847513B2 - Manufacturing method of radiation detector and manufacturing method of radioactive dust monitor - Google Patents

Description

The present invention relates to a method for producing a preparation and radioactive dust monitor of the radiation detector.

  The radioactive dust monitor for measuring the concentration of radioactive dust containing nuclides that emit beta rays in the air is a radiation detector that uses a plastic scintillator whose main component is low-sensitivity to γ rays as a radiation sensor. Is generally used. Such plastic scintillators mainly composed of polyvinyltoluene are usually weak at heat and begin to soften at about 60 ° C., and are used at temperatures lower than about 60 ° C.

  When the radiation detector is manufactured, a light shielding unit is provided that allows the radiation to be measured to pass through while blocking light incident from the outside from reaching the scintillator. As a method of providing this light shielding part, a method of thermally transferring a light shielding layer to a plastic scintillator as described in Japanese Patent Application Laid-Open No. 2007-248266 (Patent Document 1) or a method of depositing or sputtering a light shielding layer on the surface of the plastic scintillator There is.

On the other hand, in recent years generally widely used started with are polyethylene naphthalate (P oly e thylene n aphthalate: PEN) has been reported that emits light by radiation (for example, see Non-Patent Document 1). Further, the polyethylene naphthalate has a glass transition temperature of 155 ° C., are known to have excellent properties such as water vapor transmission rate 1.2g / m 2 / ^24h (e.g., see Non-Patent Document 2) .

JP 2007-248266 A

Hidemura Nakamura and three others (H. Nakamura et al.) “Evidence of deep-blue photon emission at high efficiency by common plastic” EPL (Europhysics Letters) (2011), 95 (2), [online], 2011 ( July 1, 2011, EDP Science, [Search September 22, 2011], Internet (URL: http://hdl.handle.net/2433/141973) Characteristics of PEN film, [online], Teijin DuPont Films Co., Ltd. website, [Searched on September 22, 2011], Internet (URL: http://www.teijindupontfilms.jp/product/name/pen/pen_teo.html )

  As described above, as a method for providing the light-shielding portion, a method of thermally transferring the light-shielding layer to the plastic scintillator (hereinafter referred to as “thermal transfer method”) or a method of depositing or sputtering the light-shielding layer on the surface of the plastic scintillator (hereinafter, referred to as “thermal transfer method”). These methods have advantages and disadvantages, respectively.

  Compared with the vapor deposition method, the thermal transfer method is disadvantageous in that the detection sensitivity is reduced by the amount of adhesion of the plastic scintillator and the light shielding layer. It is also disadvantageous when producing large areas or in large quantities.

  On the other hand, the vapor deposition method is more advantageous in terms of detection sensitivity and production efficiency than the thermal transfer method, but the light-shielding layer is used in a low temperature range where the plastic scintillator mainly composed of polyvinyltoluene is not softened. There is a problem that it is difficult to vapor-deposit etc. In addition, a protective layer may be deposited on the surface of the light shielding layer in order to protect the light shielding layer from being scratched. However, the protective layer is also deposited so that the plastic scintillator mainly composed of polyvinyltoluene is not softened. It is difficult to carry out in such a low temperature range.

  If the polyethylene naphthalate (PEN) described in Non-Patent Document 1 can be used as a scintillator, the conventional glass transition temperature (155 ° C.) of polyethylene naphthalate described in Non-Patent Document 2 is considered. Vapor deposition and the like can be performed at a temperature higher than that in the case of producing a plastic scintillator mainly composed of polyvinyl toluene or the like (about 60 ° C. or less). As a result, the difficulty of vapor deposition of the light shielding layer and the protective layer in the vapor deposition method is solved, and the vapor deposition method can be expected to be a more advantageous method than the current method compared to the thermal transfer method.

The present invention has been made in consideration of the above-described circumstances, and a radiation detector capable of obtaining a radioactive dust concentration in a gas at a temperature (60 ° C. or higher) that is softened by a general plastic scintillator, and An object of the present invention is to provide a radioactive dust monitor and a method for manufacturing the same.

In order to solve the above-described problem, a method for manufacturing a radiation detector according to an embodiment of the present invention includes a scintillator and a light-shielding unit including a light-shielding layer that is opaque to visible light and shields extraneous light outside the scintillator. An optical sensor that receives light emitted from the scintillator and outputs an electric signal obtained by photoelectrically converting the received light to a signal processing unit; and the optical sensor and the scintillator from the scintillator side of the light shielding unit. A method of manufacturing a radiation detector, wherein the scintillator is constituted by one of polyethylene naphthalate and a mixture containing polyethylene naphthalate as a main component, and the light shielding. The layer is formed by either depositing metal at a surface of the scintillator at a temperature of 60 ° C. or higher and lower than 155 ° C. Wherein the at ways comprising forming on the surface of the scintillator.

The manufacturing method of the radioactive dust monitor which concerns on embodiment of this invention WHEREIN: In order to solve the subject mentioned above, the radiation detector installed in the flow path which introduce | transduces gas and discharges outside, The light-shielding part of the said radiation detector The radiation detector manufactured by the manufacturing method of the radiation detector is a manufacturing method of a radioactive dust monitor provided with a dust collection part that collects dust introduced into the flow path, A step of installing in the flow path; (1) a step of disposing the dust collecting part opposite to a light shielding part of the radiation detector; and (2) upstream of the flow path from the dust collecting part. Among the steps of further installing a heater on the side, at least the step (1) is provided.

  According to the present invention, it is also possible to determine the concentration of radioactive dust in a gas at a temperature that is softened by a general plastic scintillator.

The functional block diagram which shows the functional structure of the radiation detector which concerns on embodiment of this invention. It is the figure which showed roughly the main component of the radiation detector which concerns on embodiment of this invention, (A) is a structural example in case the detection surface of the radiation in a scintillator is larger than the incident surface of a photomultiplier tube FIG. 4B is a schematic diagram illustrating a configuration example when the radiation detection surface of the scintillator is smaller than the incident surface of the photomultiplier tube. Schematic which shows the structure of the experiment apparatus which each measures the beta ray detection sensitivity of the radiation detector which concerns on embodiment of this invention, and the conventional radiation detector. The graph which shows the sensitivity of the plastic scintillator and polyethylene naphthalate (PEN) with respect to beta ray energy. It is the figure which showed schematically the structural example of the light shielding part in the radiation detector which concerns on embodiment of this invention, (A) is the schematic of a 1st light shielding part, (B) is the outline of a 2nd light shielding part. FIG. 4C is a schematic diagram of a third light shielding portion. Schematic which shows the structure of the radioactive dust monitor which concerns on embodiment of this invention.

Hereinafter, a radiation detector, a radioactive dust monitor , and a manufacturing method thereof according to embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a functional block diagram showing a functional configuration of a radiation detector 10 which is an example of a radiation detector according to an embodiment of the present invention.

  The radiation detector 10 is a scintillator type radiation detector that detects radiation such as β-rays emitted from a radiation source such as the β-ray source 1. The radiation detector 10 includes, for example, a radiation detection unit 11 that detects radiation such as β rays, a signal processing unit 12 that performs signal processing on an electrical signal generated when the radiation detection unit 11 detects radiation, and a radiation detection unit 11. And a power supply unit 13 for supplying power to the signal processing unit 12.

  The radiation detection unit 11 has a radiation detection function of outputting an electrical signal when receiving radiation. For example, the radiation detection unit 11 detects radiation by photoelectrically converting light generated by receiving radiation to obtain an electrical signal.

  In the signal processing unit 12, the electric signal input from the radiation detection unit 11 is amplified by the amplifier 15, and an electric signal (pulse signal) having a level larger than a threshold (threshold) value set in advance by the counter 16, that is, Count the number of pulses.

  The amplifier 15 of the signal processing unit 12 has an electric signal amplification function, a threshold setting function for setting a desired threshold value with respect to the electric signal level, and a comparison function for comparing the set threshold value with the electric signal level. For example, an amplification circuit (amplifier) that amplifies an input signal and a comparison circuit (comparator) that compares the level of the input signal with a set threshold value are included.

  In the radiation detector 10, the amplifier 15 has a threshold setting function and a comparison function, but may be provided in another component such as the counter 16, and has a threshold setting function and a comparison function. Each component may be provided.

  FIG. 2 is a diagram schematically showing the main configuration of the radiation detector 10, and FIG. 2A shows a case where the radiation detection surface of the scintillator 22 is larger than the incident surface of the photomultiplier tube (PMT) 24. FIG. 2B is a schematic diagram illustrating a configuration example when the radiation detection surface of the scintillator 22 is smaller than the incident surface of the photomultiplier tube (PMT) 24.

  In the radiation detector 10 shown in FIG. 2A, a light shielding unit 21, a scintillator 22, a light guide unit 23, and a photomultiplier tube 24 as a radiation detection unit are accommodated in a case 25. Connected to the photomultiplier tube 24 accommodated in the case 25 are a signal line 26 for transmitting an electric signal to the signal processor and a high voltage line 27 for supplying a high voltage to the photomultiplier tube 24.

  The light-shielding unit 21 prevents the extraneous light from reaching the scintillator 22 on the incident side (input side) of the scintillator 22 while allowing the radiation to be measured to pass therethrough. The light-shielding part 21 is selected from, for example, a light-shielding film made of polyethylene having excellent extensibility on both surfaces of a polyethylene terephthalate (PET) resin film, which is opaque to visible light, and a metal material such as aluminum.

  The scintillator 22 is polyethylene naphthalate (PEN). In configuring the scintillator 22, a small amount of a fluorescent substance or the like may be mixed into the polyethylene naphthalate as in a conventional plastic scintillator. That is, the scintillator 22 can be made of polyethylene naphthalate alone or a mixture containing polyethylene naphthalate as a main component.

  The light guide unit 23 is a component that is made of, for example, a transparent material having excellent light transmittance such as an acrylic plate and efficiently guides light emitted from the scintillator 22 to the photomultiplier tube 24. The light guide 23 may be omitted as in the radiation detector 10 shown in FIG. 2B depending on the thickness of the scintillator 22 and the size of the incident surface of the photomultiplier tube 24. is there.

  A photomultiplier tube (PMT) 24 as an optical sensor has a function of converting light energy into electric energy using a photoelectric effect, and an electron multiplication function (current amplification function). The photomultiplier tube 24 outputs an electric signal obtained by photoelectrically converting and amplifying light incident from the scintillator 22 side.

  The case 25 accommodates the light shielding part 21, the scintillator 22, the light guide part 23, and the photomultiplier tube 24, and also serves as a light shielding structure that blocks external light on the light emission side (output side) of the scintillator 22.

In configuring the radiation detector 10, the thickness of the light shielding layer of the light shielding unit 21 is set to 0. 0 in order to reduce the attenuation of β rays of cobalt 60 ( ⁶⁰ Co) having a maximum β ray energy of 318 keV as much as possible. The thickness is desirably about 015 g / cm ² (100 μm for a substance having a density of 1.5 g / cm ³ ) or less. However, a thicker material may be used when measuring mainly a substance having a higher β-ray energy.

As shown in Non-Patent Documents 1 and 2 described above, polyethylene naphthalate is a material that emits light having a peak at 425 nm when radiation is incident. Further, the polyethylene naphthalate has a glass transition temperature of 155 ° C., with than plastic scintillator composed mainly of polyvinyl toluene which is a material that can withstand under high temperature environment, the water vapor transmission rate 1.2g ^/ m 2 / 24h It has a high gas barrier property (thickness 125 micrometers).

  Therefore, in order to verify the sensitivity of the radiation detector 10 using polyethylene naphthalate or a material mainly composed of polyethylene naphthalate as a scintillator to β rays, polyethylene naphthalate is used by using an experimental apparatus 30 shown in FIG. 3 described later. The sensitivity of (PEN) and plastic scintillator was evaluated. The evaluation results are shown in FIG.

  In addition, the evaluation criteria of whether or not a radiation detector that employs a scintillator mainly composed of polyethylene naphthalate (PEN) can be applied is based on the detection performance of a conventional radiation detector that employs a plastic scintillator. As a result, in view of the point that it can be used as a radiation detector if a sensitivity of 10% or more is obtained with respect to a conventional radiation detector, radiation employing a scintillator mainly composed of polyethylene naphthalate (PEN). If the sensitivity of the detector exceeds 10% of the sensitivity of the conventional radiation detector, it is evaluated that a radiation detector employing a scintillator mainly composed of polyethylene naphthalate (PEN) can be applied. .

  FIG. 3 shows a conventional radiation detector employing polyethylene naphthalate (PEN) as a scintillator (hereinafter referred to as “radiation detector according to an embodiment of the present invention”) and a plastic scintillator mainly composed of polyvinyltoluene. 1 is a schematic diagram showing the configuration of an experimental apparatus 30 for measuring the β-ray detection sensitivity of each radiation detector (hereinafter simply referred to as “conventional radiation detector”).

  The experimental device 30 is a device for verifying (evaluating) the sensitivity of the radiation detector according to the embodiment of the present invention to β rays, and the surface of the light shielding unit 21 of the radiation detector 10 shown in FIG. In this configuration, the β-ray source 1 is installed. In this experimental apparatus 30, a radiation detector employing polyethylene naphthalate (PEN) as a scintillator and a conventional radiation detector are different in the material constituting the scintillator 22, but the other portions have the same conditions.

  More specifically, in the radiation detector according to the embodiment of the present invention, the scintillator 22 is a polyethylene naphthalate (PEN) film (QF65FA, manufactured by Teijin DuPont Films) having a thickness of 200 micrometers. In the conventional radiation detector, The scintillator 22 is a plastic scintillator (EJ-212, Ergen Co.) whose main component is polyvinyl toluene having a thickness of 200 micrometers. The size of the scintillator 22 is 80 mm × 30 mm × 0.2 mm.

  In the experimental apparatus (radiation detector) 30, the light shielding portion 21 is a layer having a thickness of 12 micrometers (μm) obtained by superposing two aluminum vapor deposition mylar sheets. The aluminum vapor deposited mylar sheet has a thickness of 6 micrometers (μm) and is made opaque to visible light by vapor-depositing aluminum having excellent extensibility on both surfaces of a polyethylene terephthalate (PET) resin film. The light shielding film (light shielding layer). The dimension of the light shielding part 21 is 80 mm × 30 mm × 0.012 mm.

  The light guide unit 23 is formed of a transparent acrylic plate that is bonded to the surface opposite to the side where the scintillator 22 contacts the light shielding unit 21 by using an adhesive having excellent light transmittance such as an optical adhesive. . The dimensions are 80 mm × 30 mm × 3 mm.

  FIG. 4 is a graph showing the sensitivity of plastic scintillator and polyethylene naphthalate (PEN) to β-ray energy. In the graph shown in FIG. 4, the horizontal axis is β-ray energy (keV), and the vertical axis is the sensitivity of PEN to plastic scintillator. Ratio (%). Note that the threshold voltage value was measured at 300 mV.

The sensitivity of a radiation detector employing a scintillator composed mainly of polyethylene naphthalate (PEN), as shown in FIG. 4, Cobalt ⁶⁰ (60 Co), chlorine ^{36 (36} Cl) and uranium oxide _(U 3 O ₈ ) In a wide range where the β-ray energies are different from each other, a sensitivity ratio of about 55 to 70% was shown with respect to the sensitivity of the radiation detector using the plastic scintillator. From this result, it has been confirmed that a radiation detector employing a scintillator mainly composed of polyethylene naphthalate (PEN) can be applied.

  As described above, according to the radiation detector 10 employing the polyethylene naphthalate alone or the scintillator 22 containing polyethylene naphthalate as a main component, the polyethylene naphthalate is a polyethylene naphthalate even at a temperature of about 60 ° C. at which the general plastic scintillator starts to soften. Since phthalate (glass transition temperature of 155 ° C.) is not softened, it can be used even in a higher temperature environment than before.

  In addition, since the scintillator 22 can withstand a higher temperature than a general plastic scintillator, the temperature when forming the light shielding portion 21 is also higher than the conventional temperature, that is, 60 ° C., which is softened by a general plastic scintillator. Even if the temperature is higher than about, it can be carried out within a temperature range that does not affect the properties of polyethylene naphthalate (PEN). This means that vapor deposition and sputtering are easier than before, and a processing method that can easily cope with a large area or a large amount of processing can be selected.

  Further, when forming the light-shielding portion 21, aluminum that becomes a light-shielding layer is left in a state where a process of removing minute protrusions on the scintillator surface and smoothing the surface (hereinafter simply referred to as “surface treatment”) is not performed. There is a problem that pinholes are likely to occur when vapor deposition or sputtering is performed, but this surface treatment method is also conventional (plastic scintillator) if the radiation detector 10 uses a polyethylene naphthalate (PEN) simple substance as a scintillator 22. Then, an organic solvent such as cyclohexanone that cannot be selected can be used.

  Conventionally, the surface treatment of the plastic scintillator has been performed by polishing because the plastic scintillator contains a fluorescent substance uniformly mixed therein, and there is a problem that the sensitivity is lowered when an organic solvent is used. Because. That is, in order to avoid the sensitivity reduction of the plastic scintillator, the surface treatment has to be performed by polishing.

  On the other hand, in the radiation detector 10 using the polyethylene naphthalate (PEN) simple substance as the scintillator 22, since the fluorescent substance is not mixed uniformly like the plastic scintillator, even if an organic solvent such as cyclohexanone is used, It is considered that the sensitivity of the scintillator 22 does not decrease. A method using an organic solvent such as cyclohexanone is advantageous in that the area that can be treated per unit time is large compared to polishing.

  In the radiation detector 10 described above, several examples of the configuration of the light shielding unit 21 are conceivable, such as a configuration including only a light shielding layer and a configuration having a light shielding layer and a protective layer for protecting the light shielding layer. Therefore, next, a configuration example of the light shielding unit 21 in the radiation detector 10 will be described.

  FIG. 5 is a diagram schematically illustrating a configuration example of the light shielding unit 21 in the radiation detector 10, and FIG. 5A is a first configuration including a metal film that is opaque to visible light such as aluminum. FIG. 5B is a schematic diagram of a second light shielding part 21B configured by laminating a protective film (protective layer) 32 on the first light shielding part 21A as a light shielding layer. In FIG. 5C, first light-shielding portions 21A and protective films (protective layers) 32 as light-shielding layers are alternately stacked, and at least one of the first light-shielding portions 21A and the protective films (protective layers) 32 is a plurality of layers. It is the schematic of the 3rd light-shielding part 21C used as follows.

  For example, as shown in FIG. 5A, the first light-shielding portion 21A is formed by directly depositing or sputtering a metal that is opaque to visible light, such as aluminum, and has a thickness of 0.5 micrometers. Consists of a film of the degree. Polyethylene naphthalate has a glass transition temperature of 155 ° C, and it does not soften even at a temperature of about 60 ° C where general plastic scintillators begin to soften, so it can be deposited or sputtered in a higher temperature environment than before. Become. Therefore, vapor deposition of the light shielding layer in the vapor deposition method can be facilitated.

  According to the radiation detector (hereinafter, referred to as “first radiation detector”) 10 </ b> A including the first light shielding part 21 </ b> A, the thickness is larger than that of the light shielding part having the light shielding layer formed by overlapping the light shielding films. Therefore, it is possible to reduce attenuation of radiation due to a light shielding layer that is not sensitive to radiation. That is, a more sensitive radiation detector can be provided.

  In addition, polyethylene naphthalate (PEN) does not soften even at a temperature of about 60 ° C. where it begins to soften in a general plastic scintillator, so in a higher temperature environment (however, the glass transition temperature is less than 155 ° C.). The first radiation detector 10A can be used.

  For example, as shown in FIG. 5B, the second light shielding part 21B is configured by laminating a protective film (protective layer) 32 on the surface of the first light shielding part 21A as a metal film (light shielding layer). Is done. The generation of the protective film 32 can be arbitrarily selected from known materials and techniques as long as the properties of polyethylene naphthalate are not affected.

  The protective film 32 is at least one selected from, for example, a resin that does not soften under the intended temperature environment, an oxide such as silicon oxide, titanium oxide, aluminum oxide (alumina) or zirconium dioxide (zirconia), diamond-like carbon (DLC), or the like. Is a single layer or multilayer film. Diamond like carbon (DLC) is difficult to produce a good film such as a film forming temperature is low at a temperature of about 60 ° C. where softening is started in a general plastic scintillator, and the film thickness is not uneven. With a radiation detector using polyethylene naphthalate as a scintillator, it is possible to form a film at a higher temperature than before, so that a film better than before can be generated.

  A radiation detector (hereinafter referred to as a “second radiation detector”) including a second light-shielding portion 21B configured by laminating a protective film 32 selected from the above materials on the surface of the first light-shielding portion 21A. ) 10B can prevent damage due to physical contact with the first light shielding portion 21A as the light shielding layer and deterioration of the light shielding layer due to dusting.

  When a resin is selected as the protective film 32, a black resin may be selected. If black resin is selected as the protective film 32, the protective film 32 can have a light shielding function in addition to the function of protecting the first light shielding part 21A serving as the light shielding layer in the second light shielding part 21B.

  The third light-shielding part 21C has a multilayer structure in which the first light-shielding part 21A as a metal film and the protective film 32 as a non-metal film are alternately stacked, and at least the first light-shielding part 21A and the protective film 32 There are multiple ones. The surface where the third light shielding portion 21C contacts the scintillator may be the first light shielding portion 21A as a metal film (light shielding layer) or the protective film 32.

  FIG. 6 is a schematic view showing a configuration of a radioactive dust monitor 50 which is an example of the radioactive dust monitor according to the embodiment of the present invention.

  Reference numeral 51 denotes a flow path that introduces (intakes) gas into the sampling region 52 and leads (exhaust) it to the outside. Reference numeral 54 introduces the gas into the flow path 51 and moves the gas in the flow path 51 to the outside. It is a pump that exhausts.

  The radioactive dust monitor 50 is opposed to the radiation detector 10 which is an example of the radiation detector according to the embodiment of the present invention installed in the sampling region 52 in the flow path 51 and the light shielding portion 21 of the radiation detector 10. And a dust collecting unit 53 such as a filter paper that collects dust floating in the sampling area 52. The radioactive dust monitor 50 collects dust floating in the gas introduced from the upstream side of the flow channel 51 with respect to the sampling region 52 by the dust collecting unit 53 and measures the concentration of the dust collected in the dust collecting unit 53. .

  In addition, since the radioactive dust monitor 50 may introduce a gas having a temperature higher than a temperature (about 60 ° C. or higher) that is softened in a general plastic scintillator, the gas, the radiation detector 10, the flow path 51, Condensation may occur due to the temperature difference. In order to prevent the occurrence of such dew condensation, the radioactive dust monitor 50 may be appropriately provided with a heater 56 for heating at a position upstream of the dust collecting portion 53 in the flow path 51.

  Further, the signal processing unit (not shown in FIG. 6) of the radiation detector 10 does not necessarily have to be installed in the sampling region 52 that can be at a high temperature (about 60 ° C. or higher). It may be installed in. For example, you may install in the space other than the sampling area | region 52 in normal temperature.

  According to the radioactive dust monitor 50, a conventional radioactive dust monitor having a radioactive detector employing a general plastic scintillator is a high-temperature gas at a temperature (about 60 ° C. or higher) at which the scintillator softens when introduced as it is. Even if it exists, if the polyethylene naphthalate (PEN) is at a stable temperature, the concentration of the dust that is introduced as it is and collected in the dust collecting portion 53 can be measured.

  When using a conventional radioactive dust monitor to measure radioactive dust in a high-temperature gas, a preliminary process such as cooling the sampled gas is required before collecting dust. An extra process occurs. Moreover, when gas is high temperature and high humidity, water condenses in the location to cool, and there exists a possibility that a water-soluble radioactive substance may melt | dissolve in the condensed water. In this case, there is a disadvantage that the radioactive dust concentration at the measurement location is lower than the radioactive dust concentration at the gas introduction location (actual radioactive dust concentration).

  In this way, the radioactive dust monitor 50 that does not require the cooling process required when using the conventional radioactive dust monitor is a place where the cooling equipment and the cooling process are not required compared to the case where the conventional radioactive dust monitor is used. You can save in terms of cost and time. In addition, there is an advantage that there is no inconvenience that the measurement result is lower than the actual radioactive dust concentration.

As described above, according to the radiation detector and the radioactive dust monitor and the manufacturing method thereof according to the embodiment of the present invention, the scintillator portion is not softened even at a temperature (about 60 ° C. or higher) at which the scintillator is softened by a general plastic scintillator. Further, the concentration of radioactive dust in a gas at a temperature (about 60 ° C. or higher) that is softened by a general plastic scintillator can be obtained.

Further, according to the radiation detector and the radioactive dust monitor according to the embodiment of the present invention, and the manufacturing method thereof , the temperature at which the light shielding layer and the protective layer of the radiation detector are formed is higher than the conventional temperature, that is, In general, plastic scintillators can be softened even if the temperature is about 60 ° C. or higher, so long as they are within the temperature range that does not affect the properties of polyethylene naphthalate (PEN). It becomes easy and it is easy to cope with a large area or a large amount of processing. Furthermore, since the film forming environment is improved as compared with the conventional case, it is possible to realize a good film with less thickness unevenness and the like than the conventional case.

  Furthermore, when forming the light-shielding portion, as a surface treatment method for removing the fine protrusions on the scintillator surface and smoothing the surface, if the radiation detector 10 uses a polyethylene naphthalate (PEN) simple substance as the scintillator 22, An organic solvent such as cyclohexanone, which cannot be selected with a plastic scintillator, can be used.

  Therefore, when manufacturing a radiation detector employing a scintillator composed of polyethylene naphthalate or a mixture mainly composed of polyethylene naphthalate, the step of removing fine irregularities on the surface of the scintillator with an organic solvent, Forming a light-shielding portion that is opaque to visible light by any one of vapor deposition and sputtering of a metal material on the surface of the scintillator from which fine irregularities on the surface have been removed by the removing step. Can be adopted.

  Furthermore, since the radioactive dust monitor according to the embodiment of the present invention does not require the cooling equipment and the cooling process required when using the conventional radioactive dust monitor, compared with the case where the conventional radioactive dust monitor is used, Space, cost and time can be saved, and the measurement results will not be lower than the actual radioactive dust concentration.

  In the present specification, the described embodiments are presented as examples, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 10 Radiation detector 11 Radiation detection part 12 Signal processing part 15 Amplifier 16 Counter 21 (21A, 21B, 21C) Light-shielding part 22 Scintillator 23 Light guide part 24 Photomultiplier tube 25 Case 26 Signal line 27 High voltage line 30 Experimental apparatus 32 Protective film 50 Radioactive dust monitor 51 Flow path 52 Sampling area 53 Dust collector 54 Pump 56 Heater

Claims (3)

A scintillator, a light-shielding portion having a light-shielding layer opaque to visible light outside the scintillator, and an electric signal obtained by receiving the light emitted by the scintillator and photoelectrically converting the received light A light sensor for outputting to a signal processing unit, and a case for shielding the light sensor and the scintillator from light incident from the scintillator side with respect to the light shielding unit, and a radiation detector manufacturing method,
Configuring the scintillator with one of polyethylene naphthalate and a mixture based on polyethylene naphthalate;
The radiation detector comprising the step of forming the light shielding layer on the surface of the scintillator by any one of vapor deposition and sputtering at a temperature of the scintillator of 60 ° C. or higher and lower than 155 ° C. Manufacturing method. The front light-shielding layer forming on the surface of the scintillator, the manufacturing method of the radiation detector according to claim 1, further comprising the step of smoothing the surface of the scintillator by using the organic solvent. A radiation detector installed in a flow path for introducing gas and discharging it to the outside; and a dust collection section that is disposed opposite to a light shielding portion of the radiation detector and collects dust introduced into the flow path. A method of manufacturing a radioactive dust monitor comprising:
Installing the radiation detector manufactured by the method of manufacturing a radiation detector according to claim 1 or 2 in the flow path;
(1) Among the steps of disposing the dust collection unit opposite to the light shielding unit of the radiation detector, and (2) further installing a heater on the upstream side of the flow path from the dust collection unit, A method for manufacturing a radioactive dust monitor, comprising at least the step (1).

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