JP2007114145A - Form variable radiation detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation detector which measures surface contamination of a sample having a complicated form with a simple structure. <P>SOLUTION: A scintillation fiber 1 which emits fluorescence when radiation enters is wired upon a form variable substrate 2, such as a flexible plastic sheet of which a agent or joining material is applied to the surface. One of its ends is bundled at a bundle part 4, and the whole fiber is covered by a thin shading film 3. The fiber is connected to a photomultiplier 5 as a photo detecting element. A signal is amplified with a preamplifier 6 by radiation incidence, and the signal is enabled to be taken out. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation detector used for a radioactive surface contamination monitor or the like in a nuclear reactor facility, a nuclear fuel facility, a nuclear fuel reprocessing facility, a radioactive isotope use facility, a radiation generator use facility or the like.

  Conventionally, although various shapes exist, radioactive surface contamination measurement has been provided with shape detection means for detecting the shape of the subject, and it has been necessary to drive the radiation detection element based on the shape. (For example, refer to Patent Document 1) Further, it was necessary to measure the radioactivity by scanning the radiation measuring instrument while recognizing the shape of the subject using a sensor that recognizes the local shape. (For example, see Patent Document 2)

JP-A-6-186342 JP-A-9-127247

  As described above, although there are various shapes, the measurement of the radioactive surface contamination requires some shape detection means in addition to the radiation detector, and there is a problem that the measuring apparatus itself becomes large.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radiation detector that measures the surface contamination of a subject having a complicated shape with a simple configuration.

  A variable shape radiation detector according to the present invention includes a variable shape substrate, a scintillation fiber that is arranged on the variable shape substrate and emits fluorescence when radiation is incident thereon, a light shielding film that covers the scintillation fiber, and the scintillation fiber. A light detection element that is optically connected to the end face of the light source and converts the fluorescence into an electric signal, and an amplifier that amplifies the electric signal from the light detection element.

  According to the variable shape radiation detector of the present invention, since the detector can be arranged along the surface shape of the subject having a complicated shape, the distance from the subject surface is shortened and the subject can be efficiently separated from the subject. Radiation can be measured.

Embodiment 1 FIG.
A first embodiment of the present invention will be described below with reference to FIG. FIG. 1 illustrates a variable shape radiation detector 100 in which one end is bundled, and is composed of a plastic scintillator that emits fluorescence when radiation enters.
The shape variable radiation detector 100 according to the first embodiment includes a scintillation fiber 1 as described above, for example, a shape of a flexible plastic sheet or the like in which an adhesive or an adhesive is applied to the surface for bonding a wiring material. Wiring is performed on the variable substrate 2, one end is bundled by a bundled wire portion 4, the whole is covered with a thin light-shielding film 3, connected to a photomultiplier tube 5 that is a light detection element, and a signal is preamplified by radiation incidence. 6 so that the signal can be extracted by amplification.
Note that the photomultiplier tube 5 and the preamplifier 6 can be reduced in size by being housed in the light detection unit case 7.

By configuring as described above, the variable shape radiation detector 100 can be realized, and light is emitted when the radiation enters the scintillation fiber 1 disposed on the variable shape substrate 2, and the light shielding film 3 emits light from the outside. In this state, the signal is incident on the optoelectronic amplifier 5 and amplified by the preamplifier 6, and a signal corresponding to the incident radiation can be extracted to the outside.
If such a variable shape radiation detector is used, the detector can be arranged along the surface shape of the subject having a complicated shape, so the distance from the subject surface to the variable shape radiation detector is shortened. The radiation from the subject can be measured efficiently, so that the measurement time can be shortened, and miniaturization can be achieved by incorporating an optoelectronic amplifier and a preamplifier.
Moreover, since it is a variable shape type, it can be folded and carried, so that it can be transported to a required location only when necessary and space saving can be achieved.
In addition, if the 0.5 mm-thick plastic sheet made of, for example, a tungsten-containing synthetic resin / super seal dein resin (trade name of Mitsubishi Electric Corporation) is used as the variable shape substrate 2, the β-ray detection efficiency can be further increased. Further, when a carbon-containing conductive PTFE (tetrafluoroethylene resin) having a thickness of 0.1 mm is used as the light-shielding film 3, for example, the variable shape radiation detector 100 with few false detections due to charged light emission can be obtained.

Embodiment 2. FIG.
In the first embodiment, one bundled wire portion 4 is provided and optically connected to one photomultiplier tube 5, but FIG. 2 shows a variable shape radiation using a strip scintillation fiber wired in a U shape. A detector 101 is shown, and bundled portions 4a and 4b are collectively provided at one end and the other end of two bundles of strip scintillation fibers 1 and 1 wired in a U-shape, and each bundled bundle portion 4a is provided. , 4b are optically connected to the photomultiplier tubes 5a and 5b, respectively, are connected to the preamplifiers 6a and 6b, and the photomultiplier tube 5a and the preamplifier 6a are housed in the photodetection unit case 7a to detect light. The photomultiplier tube 5b and the preamplifier 6b are housed in the unit case 7b so that they can be counted simultaneously on the measurement unit side (not shown) that receives the respective outputs.

In the case of light emission due to the incidence of radiation, the light enters the photomultiplier tube 5b within a predetermined time period (for example, about 1 nsec) before and after the time when it enters the photomultiplier tube 5a. Only in this case, it is possible to remove the noise pulse generated by the photomultiplier tube itself, by the simultaneous counting process for determining that radiation has been incident, to a level close to the noise level of the photomultiplier tube, or It becomes possible to enter the noise level region and measure low energy radiation.
In addition, the measurement range of the lower limit of detection depends on how much can be measured from the measured values in the background due to the normal surrounding environment. In other words, the fluctuation of the count in the background due to the surrounding environment can be identified if a count value that is three times or more the average standard deviation of the background is obtained, and that is the lower limit of detection. Therefore, the detection sensitivity can be increased as the background count due to the surrounding environment is smaller.
By adopting the coincidence counting method, noise generated by the photomultiplier tube itself can be removed, so that the count value in the background due to the surrounding environment can be reduced and the detection sensitivity can be increased.
In the second embodiment, since two bundles of U-shaped scintillation fibers 1 and 1 are used, it is possible to perform radiation measurement in a wider range than in the case of one bundle, and if necessary Two or more bundles can be used.

Embodiment 3 FIG.
FIG. 3 is a schematic configuration diagram showing a variable shape radiation detector combined with a time difference measuring device and a counting device. The preamplifier in the variable shape radiation detector 101 according to the second embodiment has time differences measured at 6a and 6B. In addition, by connecting a counting device 9, the position of radiation incident and the amount of incident radiation can be measured.
In the time difference measuring device, first, the incident signal from the photomultiplier tube 5b and the preamplifier 6b is delayed by a delay fiber for a certain time with respect to the signal incident through the photomultiplier tube 5a and the preamplifier 6a. From the signal incident via the photomultiplier tube 5a and the preamplifier 6a, and only when the signal is incident from the photomultiplier tube 5b and the preamplifier 6b within a predetermined time, a pulse signal is sent to the subsequent stage. Is generated. At that time, the time difference is also measured, and the pulses from the device are measured by a counting device.
Further, the delay time of the incidence on the photomultiplier tube 5b with respect to the incidence on the photomultiplier tube 5a is determined by the measured time difference. In addition, by making it enter into the photomultiplier tube 5a after being delayed for a certain time, the time difference of incidence can be increased and the accuracy of time measurement is improved. In this way, the position of the light generation source due to radiation incidence can be calculated.
As a result, it is possible to specify the position (the left-right direction in FIG. 3) where the radiation is incident on the radiation detector 101, and the object to be measured is measured with points for the purpose of specifying the position. It is possible to specify the radioactive site by measuring in a lump for the method of measuring by changing.

Embodiment 4 FIG.
FIG. 4 is a schematic configuration diagram showing a variable shape radiation detector combined with a counting device. The bundled wire portion 4 of the variable shape radiation detector 101 according to the second embodiment is integrated into the photomultiplier tube 5. By combining them and connecting the counting device 10 to the preamplifier 6, the incident radiation dose can be measured.
Thereby, the radiation dose incident on the variable shape radiation detector 101 can be measured with a simple configuration.
In this embodiment, the position cannot be specified, but it can be used due to the presence of radioactivity in any part of the range measured by the detector, or in a simple measurement scene where a large area is collectively measured. Can be applied.

Embodiment 5. FIG.
FIG. 5 is a schematic configuration diagram showing a configuration for realizing the variable shape radiation monitor in a lattice shape.
The scintillation fibers 1 are arranged in a grid pattern on the variable shape substrate 2 and covered with a thin light-shielding film, and a plurality of vertical scintillation fiber end faces and lateral scintillation fiber end faces are bundled to form photoelectrons. The photomultiplier tube 5 is optically connected, and a radiation incident location is specified on the basis of signals from a plurality of photomultiplier tubes 6 in the vertical and horizontal directions, and the incident radiation dose is measured by the number of measurement.
In the third embodiment, a time difference measuring device is required on the measuring instrument side. However, by configuring as shown in FIG. 5, it is possible to detect at which position of the lattice the radiation is incident. A simple variable shape radiation detector 102 that does not require time difference measurement can be realized.

Embodiment 6 FIG.
FIGS. 6A and 6B are diagrams schematically showing an example of use when a variable shape radiation monitor is placed on a subject whose shape is unspecified, wherein FIG. 6A is a top view and FIG. 6B is a side view.
As shown in FIG. 6, the variable shape radiation detector 100 shown in FIG. 1, the variable shape radiation detector 101 shown in FIGS. 2 to 4, and the shape shown in FIG. The variable radiation detector 102 is covered so as to be entirely covered, and the radiation from the subject 11 is incident on the scintillation fiber 1 so as to be in close contact with the subject 11, and the light is incident on the light detection unit case 7. By guiding and counting the signals, the location of surface contamination and the degree of surface contamination can be measured by a simple method.

Embodiment 7 FIG.
FIG. 7 is a diagram schematically showing an example of use in which a variable shape radiation monitor is placed on a lying human body.
As shown in FIG. 7, the deformable radiation detector 100 shown in FIG. 1, the variable shape radiation detector 101 shown in FIGS. 2 to 4, and the shape shown in FIG. The radiation from the human body is incident on the scintillation fiber 1 in such a manner that the entire surface is covered with one of the variable radiation detectors 102 so as to be in close contact with the human body 12, and the light is guided to the light detection unit case 7. By counting the signals, the location of surface contamination and the degree of surface contamination can be measured by a simple method.
As a result, it is possible to carry out a survey by holding the small detector by hand and measuring the surface contamination that has been measured over the whole body in a short time.

Embodiment 8 FIG.
FIG. 8 is a schematic configuration diagram showing a variable shape radiation monitor built in a stretcher. FIG. 8A is a side view and FIG. 8B is a plan view.
When the lying human body is a victim, etc., it must be transported on a stretcher. However, if the victim is transported from the radiation control area, the surface contamination of the human body must be measured. Rather than moving the patient with a survey meter or the like, the lateral surface of the patient 12 is measured by the apparatus 200 in which the variable shape radiation detectors 100, 101, 102 that can be wound up as shown in FIG. By measuring the anti-recumbent surface, it is possible to provide a measuring device that does not put a burden on the patient and the measurer.
As described above, according to this embodiment, since the surface contamination can be measured by covering the victim in a state of jealousy, the patient is moved and the measurement that causes pain to the victim such as measuring the surface contamination with a survey meter or the like is performed. The surface contamination site can be identified and decontamination can be shortened.

Embodiment 9 FIG.
10A and 10B are diagrams schematically showing a variable shape radiation monitor applied to a hand foot cross monitor, where FIG. 10A is a schematic perspective view showing the whole, and FIG. 10B is an enlarged explanatory view showing the main part thereof.
In the hand foot cross monitor 202 used for the inspection of the surface contamination of the human body, the cross portion (clothing portion) is usually a detector in the form of a hand held by the examiner himself, and there is a complexity of performing his own contamination inspection and unevenness of the inspection. It was. As shown in FIG. 10 (a), the shape variable radiation detectors 100, 101, 102 constitute a hand foot cross monitor that can be automatically measured by the shape variable detector 103 arranged along the body shape. be able to. Further, by providing the body shape selection mechanism 18 that can select the shape by itself according to the body shape, it is possible to obtain the hand foot cross monitor 202 capable of performing a highly sensitive surface contamination inspection in a more closely contacted form.
Further, as shown in FIG. 10B, the opening angle of the cross-shaped variable radiation detector 103 is designated by the body shape selection mechanism 18 and along the body line of the person 12 to be measured. Therefore, it can be moved to a close contact position, and the surface contamination of the body surface clothes can be inspected efficiently.

It is a schematic block diagram which shows the shape-variable type radiation detector concerning Embodiment 1 of this invention. It is a schematic block diagram which shows the shape variable type | mold radiation detector concerning Embodiment 2 of this invention. It is a schematic block diagram which shows the shape-variable type radiation detector concerning Embodiment 3 of this invention. It is a schematic block diagram which shows the shape-variable type radiation detector concerning Embodiment 4 of this invention. It is a schematic block diagram which shows the shape-variable type radiation detector concerning Embodiment 5 of this invention. It is explanatory drawing which shows typically the usage example of the shape-variable type radiation monitor concerning Embodiment 6 of this invention. It is explanatory drawing which shows typically the usage example of the shape-variable type radiation monitor concerning Embodiment 7 of this invention. It is a schematic block diagram which shows the shape-variable type radiation monitor concerning Embodiment 8 of this invention. It is a schematic block diagram which shows the hand foot cross monitor concerning Embodiment 9 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Scintillation fiber 2 Shape variable board | substrate 3 Light-shielding film 4 Bundling part 5 Photomultiplier tube 6 Preamplifier 7 Photodetection part case 9 Time difference measurement and counting apparatus 10 Counting apparatus 11 Subject 12 Human body 13 Stretcher 18 Body shape selection mechanism 100, 101, 102 Shape variable radiation detector 103 Shape variable radiation detector 201 Shape variable radiation monitor 202 Shape variable radiation monitor 203 Hand foot cross monitor

Claims (11)

  A shape variable substrate, a scintillation fiber that is disposed on the shape variable substrate and emits fluorescence when radiation is incident thereon, a light shielding film that covers the scintillation fiber, and an optically connected end face of the scintillation fiber, and the fluorescence A variable-shape radiation detector comprising: a photodetecting element that converts an electric signal into an electric signal; and an amplifier that amplifies the electric signal from the photodetecting element.   2. The variable shape radiation detector according to claim 1, wherein a plastic sheet containing tungsten is used as the variable shape substrate, and carbon-containing conductive PTFE (tetrafluoroethylene resin) is used as the light shielding film.   A scintillation fiber is arranged in a U-shape, bundled portions are collectively provided at one end and the other end of the U-shaped scintillation fiber, and the light detection element and the amplifier are connected to each bundled bundle portion. The variable shape radiation detector according to claim 1, wherein the variable shape radiation detector is provided.   4. The variable shape radiation detector according to claim 3, wherein two or more bundles of the U-shaped scintillation fibers are arranged.   A time difference measuring device and a counting device are connected to the amplifier, and the time difference of measurement at one end and the other end of the U-shaped scintillation fiber is measured to specify the radiation incident location and the incident radiation dose. The variable shape radiation detector according to claim 3 or 4, characterized in that:   5. The variable shape radiation detector according to claim 3, wherein a counting device is connected to the preamplifier to measure the amount of radiation incident.   The scintillation fibers are arranged in a lattice pattern, and the end faces of the vertical scintillation fibers and the end faces of the horizontal scintillation fibers are bundled and optically connected to the light detection elements. 3. The variable shape radiation detector according to claim 1, wherein a radiation incident point is specified based on the electrical signal.   The variable shape radiation detector according to any one of claims 1 to 7, wherein the shape can be freely changed along the shape of the subject.   The variable shape radiation detector according to any one of claims 1 to 7, wherein the radiation from the subject can be measured by covering the subject along the shape of the subject.   The radioactivity from the victim is measured by covering the floor of the stretcher carrying the victim and the shape of the victim placed on the floor. The variable shape radiation detector according to one.   The variable shape radiation detector according to any one of claims 1 to 7, wherein the variable shape radiation detector is used for automatic measurement of a cross portion of a handfoot cross monitor used in surface contamination measurement of a human body.