JPH071308B2 - Fluorescent glass dosimeter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent glass dosimeter used for measuring an individual exposure dose, and more particularly to a fluorescent glass dosimeter for directly measuring a plurality of types of dose equivalents affecting a living body.

[0002]

2. Description of the Related Art Generally, as a fluorescent glass dosimeter, a glass element for a fluorescent dosimeter made of phosphate glass containing silver ions is used. This glass element emits fluorescence when excited by ultraviolet rays having a wavelength of 300 to 400 nm after being activated by exposure to radiation, and the fluorescence intensity at this time is proportional to the radiation dose to be exposed. Therefore, it is necessary to detect this fluorescence intensity. Can measure the radiation dose.

By the way, conventional dosimeters for measuring individual exposure dose directly measure an individual exposure dose of 1 cm dose equivalent by combining various filters for transmitting radiation of various wavelengths and a fluorescent glass element. However, it has been required to measure the irradiation dose in free space without depending on energy.

[0004]

[Problems to be Solved by the Invention] By the way, since the act of radiation protection was amended since the beginning of the 1989 year, according to the act, the effective dose equivalent and the crystalline lens and the skin other than the eye should be used for the management of individual exposure dose. 1 cm as the tissue dose equivalent of
It is stipulated that the dose equivalent, the tissue dose equivalent of the crystalline lens of the eye be 3 mm dose equivalent, and the tissue dose equivalent of skin be 70 μm dose equivalent.

As a result, although it has been put into practical use to measure the irradiation dose of 1 cm dose equivalent by combining various types of filters, those for direct measurement of 3 mm dose equivalent and 70 μm dose equivalent have not been put into practical use. . Therefore, conventionally, a 1 cm dose equivalent measured by a dosimeter and an energy value measured by another measuring device such as a γ-ray spectrum meter are used to obtain a 3 mm dose equivalent and a 70 μm dose equivalent by conversion from the 1 cm dose equivalent. I am trying.

However, in the low energy region of 30 KeV or lower, the dose equivalent of 70 μm is more sensitive than the dose equivalent of 1 cm, and therefore, the dosimeter which can directly measure the dose equivalent of 70 μm in the offices handling low energy radiation. Was required.

The present invention has been made in view of the above situation, and it is possible to directly measure dose equivalents other than 1 cm dose equivalent, that is, 3 mm dose equivalent and 70 μm dose equivalent. The present invention aims to provide a fluorescent glass dosimeter.

[0008]

In order to solve the above problems, the present invention provides a filter group including a combination of at least two kinds of metal filters and plastic filters having different transmittances of photon energy to radiation, and these filters. A fluorescent detection amount obtained from the surface portion of the fluorescent glass device facing the filter by excitation light, and one or a plurality of fluorescent glass devices arranged at facing positions, and a dose equivalent to the detected fluorescence amount. It is a fluorescent glass dosimeter that obtains a plurality of types of dose equivalents using the conversion coefficient and.

[0009]

Therefore, according to the present invention, by taking the above-mentioned means, the respective fluorescence detection amounts obtained from the surface portion of the fluorescent glass element facing the two filters by the excitation light and the predetermined dose equivalent can be obtained. The 1 cm dose equivalent and 70 μm dose equivalent are calculated based on the predetermined calculation formulas (equation (1) and formula (2) described later) using the conversion factor of and the predetermined calculation is performed using these two dose equivalents. By determining the 3 mm dose equivalent based on the equation (equation (3) described later), a plurality of required dose equivalents are directly measured without using other measuring instruments.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 3 are views showing the relationship between the fluorescent glass element and the filter, and more specifically, FIG. 1 is an exploded perspective view showing the relationship between the fluorescent glass element and a support frame supporting the fluorescent glass element, FIG. 2 is a cross-sectional view of a filter case that accommodates a support frame that supports a fluorescent glass element, and FIG. 3 is a cross-sectional view showing an arrangement state of components inside the filter case.

As the fluorescent glass element for the fluorescent glass dosimeter of the present invention, for example, four fluorescent glass elements or one fluorescent glass element 11 having a length corresponding to four fluorescent glass elements 11 as shown in the figure. Is used, and the fluorescent glass element 11 is supported by a pair of support frames 12 and 13.

Of these one set of support frames 12 and 13,
The one support frame 12 has, for example, four openings 14a to 1
4d is formed, and element holding protrusions 15, ... Are provided in the vertical direction from the outer peripheral edge of the frame except for the portion which becomes the fluorescence output optical path of the fluorescent glass element 11, and these element holding protrusions 15, ... It is configured to support the fluorescent glass element 11 fitted from the direction.

The other supporting frame 13 is a fluorescent glass element 1
1 has a role of accommodating and holding the one support frame body 12 that supports 1, specifically, a plurality of openings 16a to 16d are formed similarly to the support frame body 12 and are orthogonal to the longitudinal direction. U-shaped portions 17 and 17 are provided by bending both ends of the U-shaped portions 17 and 17 so as to face each other in the same direction, and notches are formed in the surface portions of the U-shaped portions 17 and 17 in a positional relationship corresponding to the openings 16a to 16d. Portions 18a to 18d are formed. Further, a number hole 19 for optically reading the type of the fluorescent glass element 11 and the ID code of the operator is provided at one end of the support frame 13.

Then, the fluorescent glass element 11 as described above is used.
The pair of support frames 12 and 13 for supporting the filter are housed in the plastic filter case 20 having the shape shown in FIG.
The filter case 20 includes a tin filter 21a, an aluminum filter 21b, and
Plastic filters 21c and 21d are arranged. Therefore, when the filter case 20 accommodating the set of support frames 12 and 13 is cut across the filters, the cross section is as shown in FIG.

Further, when reading the exposure dose from a fluorescent glass dosimeter exposed by, for example, γ-ray or X-ray irradiation, one set of support frames 12 and 13 is taken out from the filter case 20, and then each filter is removed. 21a-21
Each face of the fluorescent glass element 11 facing d is installed at the fluorescence detecting position so as to face the reader side, that is, the photomultiplier tube 31 side. Thereafter, as shown in FIG. 4, excited ultraviolet rays are made incident on the fluorescent glass element 11 through the diaphragm 30a, and at this time, the fluorescence generated from the wide surface side of the fluorescent glass element 11 is detected by the photomultiplier tube 31 through the diaphragm 30b. It is composed.

Next, using the fluorescent glass dosimeter according to the present invention, 1 cm dose equivalent as individual exposure dose, 3 mm
An example of obtaining the dose equivalent and the 70 μm dose equivalent will be described. Now, regarding the fluorescent glass dosimeter according to the present invention,
In order to simulate the actual measurement condition and evaluate its performance, a fluorescent glass dosimeter is installed on the phantom, and then the fluorescent glass dosimeter is irradiated with the same irradiation dose of each photon energy of γ-ray and X-ray. Then, when excitation ultraviolet rays are incident and excited, each filter 21 of the fluorescent glass element 11 is
The relative fluorescence intensity of the fluorescence detection amount as shown in FIG. 5 can be measured from the surface portion facing the a to 21d.
In the figure, A is a tin filter 21a, B is an aluminum filter 21b, and C is a plastic filter 2
It is the fluorescence detection amount obtained from the surface portion of the fluorescent glass element 11 facing each of 1c and 21d. That is, FIG. 5 is a curve of the relative fluorescence intensity of the fluorescence detection amount for each photon energy.

Further, as is well known, the conversion coefficient when converting the conventional X-ray irradiation dose, which is a unit of measurement, into the present dose equivalent is as shown in FIG. Therefore, using this fluorescent glass dosimeter, 1 cm dose equivalent, 3 m
When obtaining m dose equivalent and 70 μm dose equivalent, the conversion factors for 1 cm dose equivalent, 3 mm dose equivalent and 70 μm dose equivalent as shown in FIG. I will keep it.

Then, in the above condition, 1 cm
When obtaining the dose equivalent H (1 cm), the tin filter 21
If the fluorescence detection amounts measured from the two surface portions of the fluorescent glass element 11 that face a and the aluminum filter 21b are R1 and R2, respectively, it can be calculated from the following arithmetic expression.

H (1 cm) = f {rR1 + (1-r) R2} (1) However, in the above equation, r is a fraction and 0 <r <1. f is a conversion coefficient from the fluorescence detection amount to the dose equivalent. Therefore, the 1 cm dose equivalent H (1 cm) is obtained by adding the fluorescence detection amounts R1 and R2 using the optimum fraction and then multiplying by the dose equivalent conversion coefficient.

Next, for the 70 μm dose equivalent, the tin filter 21a and the plastic filter 21c or 2 are used.
If the fluorescence detection amounts measured from the two surface portions of the fluorescent glass element 11 facing 1d are R1 and R4, R will be the same.
The calculation of H (70 μm) = f {rR1 + (1-r) R2} (2) is performed by adding 1 and R4 using the optimum fraction and multiplying by the dose equivalent conversion coefficient. It can be obtained by a formula.

Further, the 3 mm dose equivalent H (3 mm) is
As is clear from FIG. 6, since it is located between 1 cm dose equivalent and 70 μm dose equivalent and changes, it can be obtained as an approximate value if it is obtained based on the following equation.

H (3 mm) = H (1 cm) + {H (70 μm) −H (1 cm)} · 0.85 (3) Therefore, the above equations (1), (2) and (3) are By plotting each dose equivalent calculated using each photon energy, it is possible to obtain a curve that is approximately similar to the curve shown in FIG.

Therefore, according to the configuration of the above embodiment, after measuring the fluorescence detection amount in the facing direction of the two filters in the fluorescent glass element 11, these two fluorescence detection amounts and the dose equivalent conversion coefficient are measured. By performing a predetermined calculation using and, the 1 cm dose equivalent and 70 μm dose equivalent can be obtained, and further, 1 cm dose equivalent and 70 μm
If the m dose equivalent is used to perform a calculation using a predetermined calculation formula, the 3 mm dose equivalent can be obtained. Therefore, 1 cm dose equivalent can be obtained by using one fluorescent glass dosimeter without requiring energy information from other measuring devices.
It is possible to directly and easily measure the individual exposure dose related to the 3 mm dose equivalent and the 70 μm dose equivalent, and it is possible to directly measure the 70 μm dose equivalent even in an environment in a low energy region, and it is possible to appropriately manage the individual exposure dose.

In the above embodiment, the tin filter 21 is used.
Although a, the aluminum filter 21b, and the plastic filters 21c and 21d are used, they may be realized by using filters made of other materials. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

[0025]

As explained above, according to the present invention, it is possible to directly measure a plurality of types of dose equivalents, and moreover, it is possible to reliably measure dose equivalents in a low-energy radiation region, and it is possible to appropriately manage individual exposure doses. A fluorescent glass dosimeter can be provided.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a relationship between a fluorescent glass element and a support frame in a fluorescent glass dosimeter of the present invention.

FIG. 2 is a cross-sectional view of a filter case that houses a support frame that supports a fluorescent glass element.

FIG. 3 is a cross-sectional view showing a state inside the filter case.

FIG. 4 is a diagram showing a relative positional relationship among a fluorescent glass element, excited ultraviolet rays, and fluorescence detection directions.

FIG. 5 is a curve diagram of relative fluorescence intensity at a position facing each filter of the fluorescent glass element with respect to each photon energy.

FIG. 6: 1 from the irradiation dose for each photon energy
The curve figure of the conversion factor to cm, 3 mm, and 70 micrometer dose equivalent.

[Explanation of symbols]

11 ... Fluorescent glass element, 12, 13 ... Support frame, 14a
-14d, 16a-16d ... Opening part, 18a-18d ...
Notch, 20 ... Filter case, 21a ... Tin filter, 21b ... Aluminum filter, 21c, 21d ...
Plastic filter.

Claims (2)

[Claims] 1. A filter group composed of a combination of at least two kinds of metal filters and plastic filters having different transmittances of photon energy to radiation, and one or a plurality of fluorescent glasses arranged at a position facing these filters. And a plurality of types of dose equivalents using a fluorescence detection amount obtained from the surface of the fluorescent glass element facing the filter by excitation light and a conversion factor of the dose equivalent to the fluorescence detection amount. Fluorescent glass dosimeter characterized by. 2. The fluorescent glass dosimeter according to claim 1, wherein the plurality of types of dose equivalents are 1 cm dose equivalent of γ-ray and X-ray, 3 mm dose equivalent, and 70 μm dose equivalent.