JP4139093B2 - Dose reading magazine, dose reading method and dose reading apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a dose reading technique for reading the radiation exposure dose of a fluorescent glass element from the fluorescence intensity generated by ultraviolet excitation to the fluorescent glass element, and in particular, a dose reading magazine that enables high dose reading, The present invention relates to a dose reading method and a dose reading apparatus.
[0002]
[Prior art]
When installing and operating facilities such as nuclear reactors, accelerators, X-ray generators, radioisotopes, etc., it is necessary to make every effort to manage radiation in order to protect the living body from radiation. In particular, workers working in various facilities as described above and users of the facility must manage the radiation exposure dose to be within a predetermined allowable range. Dosimeters are used for such radiation management. This dosimeter should be installed at a specified location within the facility, or carried by a worker or user, and regularly read the exposure dose of each worker to manage the exposure dose of the worker or user. It is something that can be done.
[0003]
One of such widely used dosimeters is a fluorescent glass dosimeter. In general, as a fluorescent glass dosimeter, a glass element made of phosphate glass containing silver ions is used. This glass element generates a phenomenon (radioluminescence: RPL) that emits fluorescence when excited by ultraviolet rays having a wavelength of 300 to 400 nm after being irradiated with radiation and activated. Since the fluorescence intensity at this time is proportional to the radiation exposure dose received by the glass element, the radiation exposure dose can be measured by detecting the fluorescence intensity. In particular, such a fluorescent glass dosimeter is characterized in that the generated RPL center can be read repeatedly without disappearing even by a reading operation.
[0004]
In measurement of such a fluorescent glass dosimeter, light having a predetermined wavelength is selectively extracted by passing light projected from an ultraviolet excitation light source through an optical filter and then incident on one surface of the fluorescent glass element. At this time, the fluorescence emitted from the fluorescent glass dosimeter is passed through an optical filter to selectively pass light in a predetermined wavelength range, and then photoelectrically converted by a photomultiplier tube to an electric level at a level substantially proportional to the fluorescence intensity. A signal is obtained, and the fluorescence intensity and thus the radiation exposure dose is measured from the level of the electric signal.
[0005]
By the way, in recent years, small fluorescent glass dosimeters have been used for dose evaluation in radiotherapy and diagnosis, dose measurement in animal experiments, fine dose distribution measurement, various experiments, and the like. In the measurement of such a small fluorescent glass dosimeter, when a high dose of 2 Gy or more is applied, the fluorescent center of the fluorescent glass element is colored and absorbs ultraviolet rays. However, it attenuates inside the fluorescent glass element. For this reason, the fluorescence reading amount of 2 Gy or more is corrected by the linearity correction formula.
[0006]
[Problems to be solved by the invention]
However, in the dose reading method of the conventional fluorescent glass dosimeter as described above, when the exposure dose is 10 Gy or more, the attenuation of the excitation ultraviolet light becomes remarkable, and when the exposure dose is 100 Gy or more, the fluorescence dose is decreased. Resulting in. For this reason, the correction by the linearity correction formula cannot be performed, and it is difficult to accurately measure the radiation exposure dose.
[0007]
The present invention has been proposed in order to solve the above-described problems of the prior art, and the object of the present invention is to correct the linearity even with a high dose of radiation exposure, and thus the radiation exposure. It is an object of the present invention to provide a dose reading magazine, a dose reading method, and a dose reading apparatus capable of accurately reading a dose.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is directed to a dose reading magazine in which a fluorescent glass element that generates fluorescence by ultraviolet irradiation according to a radiation exposure dose is provided so as to be loadable. An opening through which only the fluorescence from the ultraviolet light incident side end can be emitted is provided.
According to the invention of claim 1 as described above, in the fluorescent glass element, only the fluorescence from the ultraviolet light incident side end portion where the attenuation of the excitation ultraviolet light is relatively small can be read, so that the exposure amount is 100 Gy or more. However, the amount of fluorescence is not reversed and decreased. That is, since the fluorescence amount simply increases without generating a local maximum value, it is possible to perform correction using a linearity correction equation, and measurement is possible even at a high dose of 100 Gy or more.
[0009]
The invention according to claim 2 irradiates the fluorescent glass element loaded in the dose reading magazine having an opening for emitting fluorescence with ultraviolet rays serving as an excitation light source, thereby increasing the fluorescence intensity emitted from the fluorescent glass element through the opening. In the dose reading method for reading the radiation exposure dose, the type of the magazine is determined based on the size of the opening provided in the dose reading magazine, and the fluorescence detection sensitivity is calibrated based on the determination result. In addition, the reading value is corrected.
[0010]
According to a third aspect of the present invention, there is provided an irradiation means for irradiating ultraviolet light serving as an excitation light source to a fluorescent glass element loaded in a dose reading magazine having an opening for emitting fluorescence, and from the fluorescent glass element through the opening. In a dose reading apparatus having a fluorescence detection means for reading a radiation exposure dose based on the emitted fluorescence intensity, a determination means for determining the type of the magazine based on the size of the opening provided in the dose reading magazine; And dose reading processing means for calibrating the sensitivity of the fluorescence detecting means and correcting the reading value based on the determination result by the determining means.
[0011]
According to the invention of claim 2 or claim 3 as described above, the sensitivity of the fluorescence detection means can be calibrated and the read value can be corrected in accordance with the size of the opening from which the fluorescence is emitted. For example, if the normal dose reading magazine and the high dose reading magazine have different opening sizes, correct sensitivity calibration and reading correction can be automatically performed according to the dose, so accurate radiation The exposure dose can be measured.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be specifically described below with reference to the drawings. That is, in the embodiment described below, a dose reading magazine in which a large number of fluorescent glass elements X can be loaded, and a dose reading in which the radiation exposure dose is read in a state where the fluorescent glass elements X are loaded in the dose reading magazine. The present invention relates to an apparatus and a reading method.
[0013]
(1) Configuration of Dose Reading Magazine (1-1) First, the configuration of the dose reading magazine according to the present invention will be described. This dose reading magazine is used for measuring fluorescent glass elements exposed to a high dose of radiation.
That is, the high-dose reading magazine 10b of this embodiment has a black thin rectangular parallelepiped shape made of, for example, ABS (acrylonitrile butadiene styrene) resin, as shown in FIG. In parallel, 20 rows of loading portions 11 for loading fluorescent glass elements X are formed. As shown in FIG. 1B, the loading portion 11 is formed with a concave groove 11a that holds both ends of the fluorescent glass element X. In addition, on the extension line in the longitudinal direction of each loading portion 11, cutout portions 12a and 12b serving as optical paths are formed so that the ultraviolet laser beam can be incident and emitted. The loading unit 11 is assigned identification numbers from 1 to 20.
[0014]
Further, as shown in FIG. 1B, an opening hole 14 is formed in the vicinity of the ultraviolet incident side end of the fluorescent glass element X of each loading section 11 on the bottom surface of the high-dose reading magazine 10b. In the present embodiment, the sectional shape of the opening hole 14 is a tapered shape that expands in the fluorescence emission direction. As the opening hole 14, for example, a hole having a diameter of about 0.6 mm can be considered.
[0015]
Note that the notch 12a on the incident side is set to have a width wider than the incident ultraviolet laser beam. For example, when the ultraviolet laser beam is limited by a slit hole or the like, the width is set wider than the slit width. This is because if the slit function for restricting the incident laser beam by the magazine is to be realized, the slit portions of the respective notches cannot be made uniform due to a problem of processing accuracy, which causes variations in measurement accuracy.
[0016]
Further, as described in Japanese Patent No. 3057168, for the purpose of correcting the output fluctuation of the ultraviolet laser, the ultraviolet laser beam that has passed through the slit hole is branched and incident on the reference unit to monitor the ultraviolet intensity. However, if the magazine has a slit function, it is difficult to make the laser spot incident on the fluorescent glass element X the same as the laser spot incident on the reference unit.
[0017]
On the other hand, the cutout portion 12b on the emission side is provided to emit the laser light that has passed through the glass element as it is. This is because, if the optical path is blocked without providing a notch in this portion, the laser light that is not attenuated is reflected / scattered and incident on the adjacent glass element, causing a problem that the fluorescence from the adjacent element interferes.
[0018]
On the other hand, the basic structure of the dose reading magazine (hereinafter referred to as the normal reading magazine) used for exposure to normal radiation dose is as described above. This is the same as the high-dose magazine, except for the following points. That is, as shown in FIGS. 2A and 2B, a plurality of fluorescent glasses are placed on the bottom surface of the normal reading magazine 10a so as to cross the central portion of the fluorescent glass element X held by the loading unit 11. An opening window 13 is provided across the element X. Since the opening window 13 functions as a fluorescence detection hole, the influence of light reflection at the end face is eliminated, and the fluorescent glass element X is easily grasped so as to be integrated integrally in the longitudinal direction of the normal reading magazine 10a. Is formed. In the present embodiment, the opening window 13 is a slit having a width of about 6 mm.
[0019]
In addition, although this opening window 13 can also be formed separately for every loading part 11, in order to prevent the dispersion | variation in a measurement precision in this case, each opening window 13 is made into a fixed area. It is desirable to form. As the fluorescent glass element X housed in the magazine 10 as described above, for example, a small one having a diameter of about 1.5 mm can be used.
[0020]
(1-2) Action / Effect According to the high-dose reading magazine 10b of the present embodiment, the following action / effect can be obtained.
That is, in the fluorescent glass element X irradiated with a high dose of radiation, the transmittance of the ultraviolet laser beam decreases as the dose increases, so that the excitation ultraviolet light gradually weakens toward the inside of the glass, and the generated fluorescence intensity Decreases. Therefore, for example, when the fluorescence glass element X irradiated with a high dose of radiation is read using the normal reading magazine 10a, the reading is performed at an exposure amount of 100 Gy or more as shown in FIG. The value goes down. For this reason, even with the same reading value, it cannot be distinguished whether the radiation dose is 100 Gy or more, and the reading value does not change even if the dose changes in the vicinity of 100 Gy. I can't.
[0021]
However, in the high-dose reading magazine 10b of the present embodiment, only the fluorescence from the end portion on the incident side of the ultraviolet laser beam is read, so that even an exposure amount of 100 Gy or more is detected as shown in FIG. The amount of fluorescence does not decrease but simply increases. Therefore, the correction by the linearity correction formula can be performed.
[0022]
(2) Dose Reading Device (2-1) Configuration of Dose Reading Device Next, the configuration of the dose reading device according to the present invention will be described. In addition, although the optical filter which selectively passes a specific wavelength is suitably arrange | positioned in the path | route of the ultraviolet laser beam and fluorescence described below, the description is abbreviate | omitted.
[0023]
That is, as shown in FIG. 5, the dose reading apparatus of the present embodiment includes a moving table 20, an ultraviolet irradiation unit (not shown), a condensing unit 30, a photomultiplier tube 40, and a reflective photoelectric sensor 50. ing. The moving table 20 is a table on which one of the two types of magazines, the normal reading magazine 10a and the high-dose reading magazine 10b, is placed, and can be installed at the fluorescence reading position by a magazine transport device (not shown). Is provided. In addition, the moving table 20 has a fluorescence passage window 20a through which fluorescence from the fluorescent glass element X passes at a position corresponding to the opening window 13 of the normal reading magazine 10a or the opening hole 14 of the high-dose reading magazine 10b. Is formed.
[0024]
Although not shown, the moving table 20 is provided with a calibration glass for calibrating the detection sensitivity of the photomultiplier tube 40. The fluorescence emission window from the calibration glass is set similarly to the opening window 13 of the normal reading magazine 10a. For example, when the opening window 13 is a slit having a width of 6 mm as described above, the opening window 13 has the same width.
[0025]
The light condensing unit 30 is a means for condensing the fluorescence from the fluorescent glass element X, which is provided below the moving table 20 at the fluorescence reading position. As this condensing part 30, a hemispherical lens can be used, for example. The photomultiplier tube 40 is means for detecting the fluorescence collected by the light collecting unit 30 by converting it into an electrical signal.
[0026]
Further, the reflection type photoelectric sensor 50 is fixed to the base of the lower part of the moving table 20, and as shown in FIG. 6, the reflection amount of the output light with respect to the bottom surfaces of both magazines 10a and 10b set at the fluorescence reading position. Based on this, it is a means for detecting whether the magazine is a normal reading magazine 10a or a high-dose reading magazine 10b. That is, since the magazine 10a for normal reading has the opening window 13 with a large opening area, the reflection amount of light from the reflective photoelectric sensor 50 is small as shown in FIG. On the other hand, since the magazine 10b for reading high dose has only the opening hole 14, as shown in FIG. 6B, the amount of reflection of light from the reflective photoelectric sensor 50 is large. Based on this phenomenon, it is detected whether the fluorescent glass element X to be measured is stored in the normal reading magazine 10a or the high-dose reading magazine 10b.
[0027]
In addition, the dose reading apparatus of the present embodiment is provided with a dose reading processing unit as described later. The dose reading processing unit calibrates the sensitivity of the photomultiplier tube 40 in advance for the normal reading mode and the high dose reading mode based on the fluorescence amount detected by the calibration glass. It is configured as follows. In calculating the exposure dose, the linearity correction formula set separately separately for the normal reading mode (radiation dose of 2 Gy or more) and the high dose reading mode (radiation dose of 20 Gy or more). Thus, the fluorescence reading value is corrected. Furthermore, the calculated exposure dose is configured to be displayed with the unit changed to “μGy” or “mGy” in the normal reading mode and in the high-dose reading mode, respectively.
[0028]
(2-2) Configuration of Dose Reading Processing Unit A dose reading processing unit having the following configuration is provided in the dose reading apparatus of the present embodiment having the above configuration.
That is, as shown in FIG. 7, the dose reading processing unit is a magazine type determining unit 101 that determines whether the magazine installed at the measurement position is a normal reading magazine or a high-dose reading magazine (for example, , The reflection type photoelectric sensor 50), a measurement mode selection unit 102 for selecting a measurement mode based on the determination result by the magazine type determination unit 101, and a photoelectron based on the measurement mode selected by the measurement mode selection unit 102. An internal calibration setting unit 103 that calibrates the detection sensitivity of the multiplier 40, a correction formula determination unit 104 that determines a correction formula to be applied based on the measurement mode, and a fluorescence to be measured by a predetermined fluorescence detection element The fluorescence detection unit 105 that measures the fluorescence of the glass element and the amount of fluorescence detected by the fluorescence detection unit 105 are expressed in the above correction formula. A correction processing unit 106 for correcting Zui, a display unit determination unit 107 for determining the display unit, and a display unit 108 for displaying the detection result.
The dose reading processing unit as described above is realized by a computer program.
[0029]
(2-3) Operation The procedure of the dose reading process by the dose reading apparatus of the present embodiment as described above will be described with reference to the flowchart of FIG. First, in step 801, the reflection photoelectric sensor 50 determines whether the magazine containing the fluorescent glass element to be measured is a normal reading magazine or a high-dose reading magazine. If it is determined that the magazine is for normal reading, the internal calibration is set to “standard” (step 802), and the linearity correction formula for the detected value is set to “normal reading mode” (step 803). ) The exposure dose display mode is set to the “normal reading mode” (step 804).
[0030]
On the other hand, if it is determined in step 801 that the magazine containing the fluorescent glass element to be measured is a high-dose reading magazine, the internal calibration is set to “high dose” (step 805), Further, the linearity correction formula for the detected value is set to “high dose mode” (step 806), and the exposure dose display mode is set to “high dose mode” (step 807).
[0031]
In step 808, one of the plurality of fluorescent glass elements housed in the magazine is set at the measurement position, and the fluorescence generated from the fluorescent glass element X is shown in FIGS. As described above, the light passes through the opening window 13 or the opening hole 14 of the magazine and the fluorescent passage window 20a of the moving table 20, and is collected by the light collecting unit 30 and detected by the photomultiplier tube 40 (step 809). This detected value is corrected by the linearity correction formula set in step 803 or 806 (step 810). The calculated reading result is displayed on the display unit in units of the reading mode set in step 804 or 807 (step 811).
[0032]
Then, it is determined whether or not the measurement process has been completed for all the fluorescent glass elements stored in the magazine (step 812). If not completed, the process returns to step 808, and step 809 is performed for the next fluorescent glass element. Step 812 is repeated. On the other hand, when the measurement process is completed for all the fluorescent glass elements stored in the magazine, the dose reading process for the magazine is terminated.
[0033]
(2-4) Effects According to the dose reading apparatus of the present embodiment as described above, the normal reading magazine 10a and the high dose reading magazine 10b are discriminated and the detection sensitivity is corrected, the correction by the linearity correction formula, etc. Since the mode switching is automatically performed, the trouble of manual setting can be saved, reading errors due to incorrect settings can be prevented, and an accurate exposure dose can be calculated.
[0034]
(3) Other Embodiments The present invention is not limited to the embodiment as described above, and the size, shape, quantity, material, type, and the like of each member can be changed as appropriate. For example, the magazine only needs to be capable of loading a plurality of fluorescent glass elements and capable of ultraviolet irradiation and fluorescence detection in the loaded state, and the structure and the number of fluorescent glass elements accommodated are arbitrary.
[0035]
It is also possible to detect the normal reading magazine and the high-dose reading magazine by providing structural differences other than the openings as described above or differences for identification. Further, the types of magazines are not limited to the above two types, but may be three or more types. Further, the material of the magazine is preferably one that generates little or no fluorescence.
[0036]
Moreover, the shape and size of the fluorescent glass element to be used are also free. For example, since only the incident side end of the ultraviolet laser beam is used at the time of high dose reading, even a smaller fluorescent glass element X as shown in FIG. 11 can be measured. Furthermore, the fluorescence reading apparatus to which the present invention is applied is not limited to the one exemplified in the above embodiment, as long as it can perform ultraviolet irradiation for fluorescence glass excitation and detection of fluorescence.
[0037]
【The invention's effect】
As described above, according to the present invention, a dose reading magazine and a dose reading method that can correct linearity even with a high dose of exposure and can accurately read out the radiation exposure. In addition, a dose reader can be provided.
[Brief description of the drawings]
1A and 1B are diagrams showing a configuration of an embodiment of a high-dose reading magazine according to the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a partially enlarged perspective view.
2A and 2B are diagrams illustrating a configuration of a normal reading magazine, in which FIG. 2A is a perspective view, and FIG. 2B is a partially enlarged perspective view.
FIG. 3 is a graph showing a calibration curve when high dose reading is performed using a normal reading magazine.
FIG. 4 is a graph showing a calibration curve when high-dose reading is performed using a high-dose reading magazine.
FIG. 5 is a longitudinal sectional view showing a configuration of one embodiment of a dose reading apparatus according to the present invention.
6A and 6B are diagrams showing the principle of detection of the type of magazine in the dose reading apparatus of FIG. 5, wherein FIG. 6A is a normal reading magazine, and FIG. 6B is a high-dose reading magazine.
FIG. 7 is a functional block diagram showing a configuration of a dose reading processing unit of the dose reading apparatus according to the present invention.
FIG. 8 is a flowchart showing a reading procedure in a dose reading processing unit.
9 is a longitudinal sectional view showing fluorescence emission from a fluorescent glass element in the normal reading magazine shown in FIG. 2. FIG.
10 is a longitudinal sectional view showing fluorescence emission from a fluorescent glass element in the high-dose reading magazine shown in FIG. 1. FIG.
FIG. 11 is a longitudinal sectional view showing a fluorescent glass element according to another embodiment of the present invention.
[Explanation of symbols]
10a ... Normal reading magazine 10b ... High dose reading magazine 11 ... Loading section 12 ... Notch 13 ... Opening window 14 ... Opening hole 20 ... Moving table 20a ... Fluorescence passing window 30 ... Condensing section 40 ... Photomultiplier tube 50 Reflection type photoelectric sensor 101 Magazine type determination unit 102 Measurement mode selection unit 103 Internal calibration setting unit 104 Correction formula determination unit 105 Fluorescence detection unit 106 Correction processing unit 107 Display unit determination unit 108 Display unit

Claims (3)

In a dose reading magazine provided with a fluorescent glass element that generates fluorescence by ultraviolet irradiation according to the radiation exposure dose,
The dose reading magazine, wherein the fluorescent glass element is provided with an opening through which only fluorescence from an ultraviolet incident side end can be emitted. A fluorescent glass element loaded in a dose reading magazine having an opening for emitting fluorescence is irradiated with ultraviolet rays serving as an excitation light source, and a radiation exposure dose is read based on the fluorescence intensity emitted from the fluorescent glass element through the opening. In the dose reading method,
Based on the size of the opening provided in the dose reading magazine, determine the type of the magazine,
A dose reading method characterized in that the fluorescence detection sensitivity is calibrated and the reading value is corrected based on the determination result. Radiation based on the irradiation means for irradiating the fluorescent glass element loaded in the dose reading magazine having an opening for fluorescent emission with ultraviolet rays serving as an excitation light source and the fluorescence intensity emitted from the fluorescent glass element through the opening. In a dose reader having a fluorescence detection means for reading an exposure dose,
A determination means for determining the type of the magazine based on the size of the opening provided in the dose reading magazine;
Dose reading processing means for calibrating the sensitivity of the fluorescence detection means and correcting the reading value based on the determination result by the determination means;
A dose reading apparatus comprising:

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