JP5679692B2 - Scintillator member, radiation detector and radiation monitor - Google Patents

Description

  The present invention relates to a scintillator member that converts radiation into light, a radiation detector having the scintillator member, and a radiation monitor.

  A radiation monitor for monitoring radioactive contamination in a nuclear facility or the like is provided with a radiation detector having a scintillator. As a solid scintillator which is a kind of scintillator, there is a plastic scintillator in which a phosphor such as anthracene or stilbenzene is dissolved in an organic solvent such as styrene or toluene, and polymerized such as polystyrene or polyvinyltoluene. Compared to crystalline organic scintillators, etc., it is easy to form a thin film with a large area and to be formed into a long shape, etc., and it is lightweight and flexible, so it has excellent impact resistance, and It is used for various radiation detectors because of its low cost and high availability. In addition, since the specific gravity of the material is small and the γ-ray sensitivity is low, it is applied to a highly sensitive radiation detector for measuring β-rays.

  In the above radiation detector, the fluorescence emitted from the plastic scintillator is weak, and a photomultiplier tube is required for detection. For this reason, the case of the radiation detector has a structure that blocks external light, and the plastic scintillator and the photomultiplier tube stored in the case can collect and detect the fluorescence emitted by the plastic scintillator. Has been placed.

  The case is provided with a radiation incident window, and the plastic scintillator is disposed so that the surface thereof approaches or closely contacts the surface of the radiation incident window. For the purpose of blocking external light while allowing β-rays to pass through, the radiation entrance window usually has one or several thin-film window materials in which a light shielding material such as aluminum is deposited on one or both sides of a resin film such as polyester. It is installed in a stacked state (Patent Documents 1 and 2).

  In such a radiation detector, the detection surface is installed at a position as close as possible to the measurement object at the time of measurement. However, the radiation entrance window material of the thin film on the detection surface is easily bent and extremely fragile to an external force. For this reason, when the measurement object is indefinite and the surface is not flat, or during maintenance, the radiation entrance window may be damaged by the measurement object or tool hitting.

  Therefore, a scintillator member has been proposed in which a light-shielding film sheet made of an aluminum layer and a protective layer is attached to the surface of a plastic scintillator through an adhesive layer by heat transfer or the like. As a result, the scintillator member has good light shielding properties and secures mechanical strength (Patent Document 3).

  Thus, in the scintillator member used for a radiation detector, it is calculated | required to improve the detection sensitivity of a beta ray and to prevent the mechanical strength fall.

JP-A-3-231187 Japanese Utility Model Publication No. 62-16486 JP 2007-147581 A

  In a plastic scintillator used in a conventional radiation detector, emitted fluorescence spreads uniformly at an isotropic angle in the plastic scintillator. For example, in the case of a plate-shaped plastic scintillator, the fluorescence is divided into a fluorescent component that is totally reflected and propagated inside the plastic scintillator at a critical angle caused by a difference in refractive index with the air layer, and a fluorescent component that is emitted outside the plastic scintillator. . The latter is reflected by the light shielding film, and many fluorescent components are transmitted through the plastic scintillator and emitted to the opposite side. Both of them largely depend on the surface state of the plastic scintillator. If an adhesive layer is present on the surface of the plastic scintillator, it causes fluorescence absorption, which causes a reduction in the amount of collected light. Further, it is considered that the adhesive layer needs to have a thickness of about several μm, and this is a thickness that cannot be ignored in terms of inhibiting β-ray transmission.

  An object of the present invention is to provide a scintillator member that can measure radiation with high sensitivity and has improved mechanical strength.

In order to solve the above-mentioned problems, a scintillator member of the present invention comprises a scintillator that generates fluorescence upon incidence of radiation, and aluminum or titanium dioxide that is directly formed on the surface of the radiation incident surface of the scintillator and prevents light transmission. A reflective layer, a light shielding layer made of a resin containing carbon black or titanium black laminated on the surface of the reflective layer, and a protective layer made of a glass-based or acrylic resin laminated on the surface of the light-shielding layer It is characterized by comprising.

The scintillator member of the present invention includes a scintillator that generates fluorescence upon incidence of radiation, a reflective layer made of aluminum or titanium dioxide that is directly formed on the surface of the radiation incident surface of the scintillator and blocks light transmission, and And a protective layer made of a glass-based or acrylic-based resin containing carbon black or titanium black laminated on the surface of the reflective layer.

  According to the present invention, the mechanical strength of the scintillator member is improved, the condensing property of fluorescence is improved, the material that disturbs the transmission of radiation is minimized, and the radiation is measured with high sensitivity using the radiation detector. Can do.

The figure which shows an example of the radiation monitor which concerns on Embodiment 1 of this invention. Sectional drawing of the radiation detector which has the scintillator member which concerns on Embodiment 1 of this invention. Sectional drawing of the scintillator member which concerns on Embodiment 1 of this invention. The figure which shows the scintillator member which concerns on Embodiment 2 of this invention. The figure which shows an example of a protection member. The figure which shows the other example of a protection member. The figure which shows the other example of a protection member. The figure which shows an example of the cleaning apparatus of the radiation monitor which concerns on Embodiment 3 of this invention.

  Hereinafter, embodiments of a scintillator member, a radiation detector, and a radiation monitor according to the present invention will be described with reference to the drawings. In the second and subsequent embodiments, the description of points common to the first embodiment is omitted.

(Embodiment 1)
An outline of the radiation monitor of this embodiment will be described.
FIG. 1 is a diagram illustrating an example of a radiation monitor according to the present embodiment.

  There are various types of radiation monitors depending on the object to be measured. A radiation detector having a scintillator member, a sample storage unit, a sampling collection device, a sampling status monitoring sensor, a data processing unit, a data output device, and a user It consists of an input device.

  As an example of the radiation monitor of the present embodiment, there is a dust monitor, and FIG. 1 shows an outline of the dust monitor.

  The dust monitor measures the concentration of the particulate radioactive material in the gas. In the dust monitor of FIG. 1, the sample accumulation unit is a dust collection filtering unit 3 that temporarily holds dust to be measured in order to measure a sample with the radiation detector 2 having the scintillator member 1. Is filter paper that collects dust. The radiation detector 2 is disposed to face the dust collection filtering unit 3.

  The sampling collection device is a device that collects a gas including a measurement target in the dust collection filtration unit 3 based on a signal output from the data processing unit 7. Based on a signal from the pipe for guiding the gas to the dust collecting filter paper, the filter paper winding mechanism 4, the pipe for exhausting the measured gas from the dust collecting filtering unit 3, the sampling pump 5 for transferring the gas, and the data processing unit 7 Consists of a control unit that controls gas collection.

  The sampling state monitoring sensor 6 is a sensor that monitors the sampling state and inputs it to the data processing unit 7, and is a sensor (flow meter, pressure gauge) that monitors the sampling flow rate, a sensor that monitors the measurement time, or the like.

  The data processing unit 7 uses the signals input from the radiation detector 2, the sampling status monitoring sensor 6, and the user input device 8 to transmit a control signal to the sampling collection device according to a pre-programmed logic, The result is output to the data output device 9.

  The data output device 9 is a device that displays, prints, or transmits the calculation result output from the data processing unit 7. For example, a liquid crystal display, a printer, a transmission module, and the like.

  The user input device 8 is a device for a user to input a signal to the data processing unit 7. For example, a mouse or a keyboard.

As another example of the radiation monitor, there is a smear type monitor that wipes off a measurement target.
In this case, the sample accumulation unit is a filter paper from which the measurement target is wiped. The sampling collection device is a wiping drive unit that drives the filter paper based on a signal from the data processing unit.

Another example of a radiation monitor is a gas monitor.
In this case, the sample storage unit is a container that stores the sampled gas to be measured. The sampling collection device is based on a pipe for introducing gas to a sample storage unit (gas sampler), a pipe for exhausting measured gas from the gas sampler, a pump for collecting gas, and a signal from a data processing unit. It consists of a controller that controls the flow rate of gas.

  In addition, there are radiation monitors that detect the object to be measured close to the radiation detector, for example, radiation monitors that directly measure the surface contamination of people and objects. In this case, there is no need to accumulate the sample, so there is a sample accumulation unit. do not do. The sampling and collecting apparatus takes the form of a radiation detector drive.

  FIG. 2 is a cross-sectional view of a radiation detector having a scintillator member according to the present embodiment, and FIG. 3 is a cross-sectional view of the scintillator member according to the present embodiment.

  The radiation detector 2 includes a light shielding case 11, a scintillator member 1 fixed to the opening of the light shielding case 11, and a photomultiplier tube 12 disposed at the bottom of the light shielding case 11. In FIG. 2, the scintillator member 1 is placed on the plate-like or frame-like transparent reinforcing member 13, but the transparent reinforcing member 13 may be omitted.

  The scintillator member 1 is composed of a flat plastic scintillator 14 and a laminated thin film 15 that transmits radiation, and forms an integrated radiation incident window. The laminated thin film 15 is configured in the order of a reflective layer 16, a light shielding layer 17, and a protective layer 18, and the reflective layer 16 is directly formed on the surface of the radiation incident surface of the scintillator 14.

When a typical plastic scintillator material is used for the scintillator 14, for example, the fluorescence emitted by the incidence of radiation has a wavelength of about 420 nm. The reflective layer 16 is a material that has the property of efficiently reflecting the fluorescence and blocking the transmission of light. For example, if a reflective material such as aluminum or titanium dioxide (TiO ₂ ) is used, a surface reflectance of 80% or more can be obtained. As a method for forming the reflecting material on the surface of the scintillator 14, for example, a film forming apparatus using a sputtering method or a vacuum evaporation method can be applied.

  In the case where the reflective layer 16 is a thin film on which aluminum or the like is vapor-deposited, pinholes due to film formation defects are present probabilistically, and the thin film such as titanium oxide transmits light as a whole, and sufficient light shielding cannot be obtained. . For this reason, a light shielding layer 17 that blocks light transmission is laminated on the entire surface of the reflective layer 16. As a material for the light shielding layer 17, for example, a resin material containing carbon black or titanium black is used.

  The protective layer 18 is laminated on the entire surface of the light shielding layer 17. Here, in addition to accidents during manufacturing and operation, damage to window materials is due to the fact that a person accidentally struck or scratched the tip of a toe, pencil, or mechanical pencil. It is said.

  For example, when expressed in accordance with the scratch hardness (pencil method) of JIS K5600-5-4 (ISO / DIN 15184), it is generally said that the toe hardness of a person is around 2H, and the lead of a pencil is usually between B and H. Is often used. As described above, since the laminated thin film 15 is formed directly on the surface of the scintillator 14 and the scintillator 14 is placed on the transparent reinforcing member 13, the local stress applied to the surface of the laminated thin film 15 is entirely The laminated thin film 15 is not easily broken. Therefore, by making the surface hardness of the protective layer 18 2H or more, the damage due to the above factors can be further reduced. As a material for the protective layer 18, for example, glass or acrylic resin can be applied.

In addition, there is a possibility that the laminated thin film 15 is subjected to electrostatic discharge (ESD) destruction, and dust is adsorbed on the surface of the window material due to electrification, and the background of radiation may increase due to the influence of radioactive materials of radon progeny nuclides contained in the dust. Therefore, the surface of the protective layer 18 is conductive and grounded. In general, since the surface resistance value effective for antistatic is 10 ¹⁰ Ω / cm ² or less, the surface resistance value of the surface of the protective layer 18 is set to 10 ¹⁰ Ω / cm ² or less.

  In this way, the laminated thin film 15 can efficiently reflect the fluorescence of the scintillator 14 by directly forming the reflective layer 16 on the surface of the scintillator 14. Further, by stacking the light shielding layer 17 on the entire surface of the reflective layer 16, it is possible to shield a pinhole that occurs stochastically. Furthermore, the light shielding layer 17 can be protected from external force by laminating the protective layer 18 on the entire surface of the light shielding layer 17.

  In addition, since the deposition cost of the laminated thin film 15 increases according to the number of layers, the deposition cost can be suppressed if the number of layers can be reduced by giving many functions to one layer. For this reason, the laminated thin film 15 can be formed by two layers of the reflective layer 16 and the protective layer 18 by using a material having light shielding properties, electrical conductivity, and surface hardness for the protective layer 18.

  The scintillator member of this embodiment can improve the mechanical strength of the scintillator member, improve the light condensing property, minimize the material that interferes with the transmission of radiation, and measure β rays with high sensitivity. it can.

(Embodiment 2)
The size of the radiation incident surface of the radiation detector depends on the scintillator size. For this reason, when the area and capacity of the measurement target are large, the radiation detector used for the monitor requiring a large area detection surface is required to have a large area scintillator.

  The scintillator member of the present embodiment is a radiation incident window of a radiation detector in which a plurality of scintillator members shown in the first embodiment are juxtaposed and joined together by a protective member.

FIG. 4 is a view showing a scintillator member according to this embodiment.
The scintillator member 1 according to the first embodiment is defined as a unit, which is referred to as a unit scintillator member 22. A lattice-shaped protection member 23 is installed between the plurality of unit scintillator members 22 so as to serve both as a joint and a light shield, and the entire scintillator member 21 is used.

FIG. 5 is a diagram illustrating an example of the protection member, and FIGS. 6 and 7 are diagrams illustrating another example of the protection member.
The protection member 23 holds and fixes the unit scintillator members 22 and may have a shape whose cross section becomes narrower in the radiation transmitting direction, for example, a wedge shape, a semicircular shape, a trapezoidal shape, or the like. The protective member 23 protrudes from the surface of the unit scintillator member 22 (the surface of the protective layer 18), and has a function of protecting from an external force. The protective member 23 may be entirely made of a light-shielding material, or at least a portion protruding from the surface of the protective layer 18 may be another material having a light-shielding property. The entire scintillator member 21 may be placed on a large-area transparent reinforcing member.

  In FIG. 5, the contact portion 24 that contacts the unit scintillator member 22 of the protection member 23 may be a member having a high reflectance, or may be processed to have a high reflectance. Further, the contact portion 24 has a portion having the same or similar optical characteristics as the scintillator 14 with respect to the emission wavelength of the scintillator 14 of the unit scintillator member 22, for example, a refractive index and a transmittance, and is in contact with the unit. The scintillator member 22 may be a member that is optically bonded, or may be processed so as to be optically bonded. In either case, the fluorescence emitted from the scintillator 14 can be efficiently guided to the photomultiplier tube.

  Further, as shown in FIG. 6, a light shielding sheet 25 that fills the gap between the unit scintillator member 22 and the protective member 23 may be installed, or as shown in FIG. 7, the protective member 23 is covered. A light shielding sheet 25 having an adhesive surface may be provided.

  In the scintillator member 21 of the present embodiment, the protective member 23 has optical functions similar to those of the light reflection or scintillator 14 at the inner scintillator joint, in addition to the function of a protective device protecting from external force and the function of joining the unit scintillator member 22. It also has an optical joining function and a light shielding function.

  The scintillator member 21 of the present embodiment can not only suppress the decrease in β-ray sensitivity but also suppress the self-weight deflection of the scintillator member 21 by the protective member 23 and increase the size of the detection surface. Thereby, sufficient strength is ensured, and even when the measurement object is not flat, it can be protected from external force. Moreover, since it is planarized, the contact of the contact member in the cleaning device as shown in the third embodiment, spraying, sucking, and the like are facilitated.

(Embodiment 3)
In the radiation monitor, when the measurement object is brought into close contact with the detection surface like a gas sampler, the radiation incident window may be contaminated. In that case, a person checks the BG count value, and if BG is high, maintenance such as removing the radiation entrance window or radiation detector and wiping the surface of the radiation entrance window is necessary. Sometimes it was provided.

  The radiation monitor of this embodiment includes a cleaning device that removes contamination on the surface of the scintillator member that is a radiation entrance window of the radiation detector. The scintillator member is the scintillator member 1 of the first embodiment or the scintillator member 21 of the second embodiment.

FIG. 8 is a diagram illustrating an example of a cleaning device for a radiation monitor according to the present embodiment.
In the radiation monitor of FIG. 1, the cleaning device 31 cleans the surface of the scintillator member based on the cleaning control signal output from the data processing unit 7, but the contact member 32 that contacts the surface of the scintillator member, and the contact member It is comprised with the contact surface moving mechanism 33 which moves 32. FIG. Contaminants adhering to the scintillator member are removed by moving to the contact member 32. In addition, a fluid spraying mechanism that sprays fluid onto the surface of the scintillator member or a suction mechanism that sucks the surface of the scintillator member may be provided to remove contaminants attached to the surface of the scintillator member.

  Further, the data processing unit 7 may output a cleaning control signal according to a preprogrammed logic based on an input signal from the user input device 8, or may output a cleaning control signal according to a preliminarily incorporated determination logic. May be.

  Since the radiation monitor of this embodiment does not use a contamination prevention sheet, it does not hinder the transmission of β-rays and can eliminate contamination on the surface of the scintillator member without requiring maintenance.

  DESCRIPTION OF SYMBOLS 1,21 ... Scintillator member, 2 ... Radiation detector, 11 ... Light shielding case, 12 ... Photomultiplier tube, 13 ... Transparent reinforcement member, 14 ... Scintillator, 15 ... Laminated thin film, 16 ... Reflective layer, 17 ... Light shielding layer, 18 ... Protective layer, 22 ... Unit scintillator member, 23 ... Protective member, 31 ... Cleaning device.

Claims (12)

A scintillator that produces fluorescence upon incidence of radiation, a reflective layer made of aluminum or titanium dioxide that is directly formed on the surface of the radiation incident surface of the scintillator and blocks light transmission, and carbon laminated on the surface of the reflective layer A scintillator member comprising: a light shielding layer made of a resin containing black or titanium black; and a protective layer made of a glass or acrylic resin laminated on the surface of the light shielding layer. A scintillator that produces fluorescence upon incidence of radiation, a reflective layer made of aluminum or titanium dioxide that is directly formed on the surface of the radiation incident surface of the scintillator and blocks light transmission, and carbon laminated on the surface of the reflective layer A scintillator member comprising a protective layer made of a glass or acrylic resin containing black or titanium black .   The scintillator member according to claim 1, wherein the protective layer has a predetermined hardness and conductivity.   A scintillator member comprising a plurality of scintillator members according to any one of claims 1 to 3 arranged side by side, and a protective member installed between the plurality of scintillator members.   The scintillator member according to claim 4, wherein the protective member has a shape whose cross section becomes narrower in a radiation transmitting direction.   6. The scintillator member according to claim 4, wherein a portion of the protective member that is in contact with the plurality of scintillator members has a light reflecting function.   6. The scintillator member according to claim 4, wherein portions of the protective member that are in contact with the plurality of scintillator members have the same or similar optical characteristics as the scintillator.   The scintillator member according to claim 4 or 5, wherein a light shielding sheet is provided between the protective member and the plurality of scintillator members.   The scintillator member according to claim 4 or 5, wherein the protective member is covered with a light shielding sheet.   10. A radiation detection comprising: a light shielding case; a scintillator member according to claim 1 fixed as a radiation incident window to the light shielding case; and a photomultiplier tube installed in the light shielding case. vessel. 11. The radiation detector according to claim 10, a sample storage unit that is disposed opposite to the radiation detector and holds a measurement target, a sampling collection device that collects the measurement target in the sample storage unit, and a sampling status monitoring sensor And a data processing unit, a data output device, and a user input device,
The data processing unit transmits a control signal to the sampling collection device according to signals input from the radiation detector, the sampling state monitoring sensor, and the user input device, and outputs a measurement result to the data output device. A radiation monitor characterized by that.   The radiation monitor according to claim 11, wherein the radiation detector includes a cleaning device that removes contamination on a surface of the scintillator member.

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