JPH02183193A - Fluorescent glass dosimeter and reading apparatus thereof - Google Patents

Abstract

PURPOSE:To evaluate energy of each kind of incident radioactive rays and to presume the direction of incidence of said radioactive rays by irradiating a glass element with the rays using a plurality of filters each having different transmittance to low energy radioactive rays. CONSTITUTION:At the inner surface of a casing 1, a tin filter 4 is provided confronting to a glass element 3a, an aluminum filter 5 to a glass element 3b and a lead filter 6 to a glass element 3c, respectively. These elements 3a-3c are irradiated through filters 4-6 each having different transmittance to low energy radioactive rays, i.e., not higher than 200KeV radioactive rays. Since the exposing strength of the elements 3a-3c is different from each other, if the relation between the strength of fluorescence and the amount of exposure to the radioactive rays is preliminarily set, the exposing amount and energy can be detected through operation. If a small opening 7 is formed in the filter, an inclination of the locus of the radioactive rays when the rays pass through the filter becomes different in accordance with the incident angle of the rays whereby the peak position of fluorescence is shifted. Therefore, if the displacement of the peak position of fluorescence is measured in two directions orthogonal to each other, the incident angle of the rays can be presumed in a three-dimensional manner.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a fluorescent glass dosimeter and its reading device that are capable of not only measuring radiation dose and estimating its energy, but also estimating the direction of incidence. .

(Prior art) Fluorescent glass dosimeters generally use a glass element made of phosphate glass containing silver ions (hereinafter referred to as silver-activated phosphate glass), and this glass element is exposed to radiation. It emits fluorescence when activated by ultraviolet light with a wavelength of 300 to 400 nm, and the intensity of the fluorescence at this time is proportional to the amount of radiation exposure.By measuring the fluorescence intensity, the amount of radiation exposure is determined. It is something.

To measure such radiation dose, the light emitted from the excitation ultraviolet light source is transmitted through an optical filter to selectively extract ultraviolet rays in a predetermined wavelength range, and one side of a rectangular parallelepiped glass element that has been previously exposed to radiation is used. incident almost perpendicularly to. Then, the silver-activated phosphate glass of the glass element emits fluorescence due to the incident ultraviolet rays, so this fluorescence is extracted in a direction perpendicular to the incident ultraviolet rays, and light in a predetermined wavelength range is selectively extracted through an optical filter to generate photoelectrons. Fluorescence intensity is measured from an output signal obtained by photoelectric conversion using a photoelectric conversion element such as a multiplier tube.

(Problem to be Solved by the Invention) Such a glass dosimeter is carried by radiation workers and used for personal radiation dose management, and it is usually sufficient to measure only the dose. However, personal exposure dosimeters for the purpose of radiation protection are used to detect radiation exposure, especially when exposed to a significant amount of radiation.
Various types of radiation of 00KsV or less and having different energy values, such as γ-rays, X-rays, or their mixed radiation (
Hereinafter, it will be referred to as γ(X) ray. ), it is important to evaluate the energy and estimate the direction of incidence of the γ(X) rays. This is because there is an energy dependence in that the absorbed dose to specific organs such as red bone marrow, ovaries, male gonads, and lens of the eye is maximum at an energy of about 90 KeV.

Conventionally, exposure dose has been measured using an energy compensation filter such as a tin slit filter as previously proposed in Japanese Patent Application No. 61-133295, or Japanese Patent Application No. 62-317.
As previously proposed in No. 354, the calculation is based on the detection sensitivity difference between two glass elements using a tin plate and an aluminum plate as filters, which have significantly different transmittances for low-energy γ(X) rays below 200 eV. There is also a measurement method for determining the energy of low-energy γ(X) rays of 200 KeV or less, as described in the above-mentioned Japanese Patent Application No. 61-133.
As proposed in No. 295 and Japanese Patent Application No. 62-317354, the detection sensitivity ratio of two glass elements using two types of filters each having significantly different transmittance for low-energy γ(X) rays of 200 KeV or less There is a way to find out.

However, the method for estimating the direction of incidence of γ(X) rays was
Although there is a method as shown in Japanese Patent No. 5595, it is necessary to place the glass element in a special measurement cell during fluorescence reading, and this method lacks simplicity in automatic measurement systems that require rapid measurement.

Therefore, the problem of the present invention is to measure the γ (X) dose and to
It is an object of the present invention to provide a fluorescent glass dosimeter and a reading device thereof, which are capable of not only evaluating the energy but also estimating the direction of incidence of low-energy γ(X) rays below KeV.

[Structure of the invention]

(Means for Solving the Problems) A first aspect of the present invention is a fluorescent glass dosimeter in which three or more rectangular parallelepiped glass elements are each covered with a filter, in which the filter covering at least one glass element is made of glass. The filter is a metal plate having a small opening compared to the surface, and the filters each covering at least two of the other glass elements have different transmittances for γ-rays or X-rays of 200 KeV or less. , which makes it possible to evaluate the energy of each type of incident radiation.

The second claim of the present invention is a device for reading the exposure dose of the fluorescent glass dosimeter according to the first claim, in which a portion of the glass element near the radiation irradiation surface is perpendicular to a perpendicular line erected to the irradiation surface. In this method, ultraviolet rays are incident from two directions perpendicular to each other to excite the glass element, and the intensity distribution of the emitted light is observed to detect the incident direction of the radiation.

(Function) If a glass element is irradiated using multiple filters with different transmittances for low-energy radiation of 200 KeV or less, the exposure intensity of each glass element will be different, so it is necessary to measure the relationship between the fluorescence intensity and the exposure amount in advance. By doing so, you can calculate the exposure dose and its energy value. Furthermore, if a small opening is provided in the filter, the slope of the locus of radiation transmitted will vary depending on the incident angle of the radiation, which will cause a deviation in the peak position of fluorescence. Therefore, by measuring the deviation of the fluorescence peak position in two orthogonal directions, the incident angle of the radiation can be estimated three-dimensionally.

(Example) The details of the present invention will be explained below with reference to the illustrated embodiments.

FIG. 1 shows a cross section of the fluorescent glass dosimeter of this example in an assembled state.
3b) and (3c) are three dosimeter glass elements arranged in parallel on this holder (2), and (2) and (3) are tin filters that cover both the front and back surfaces of the first glass element (3a).

■, ■ are aluminum filters that cover both the front and back surfaces of the second glass element (3b), 0, 0 are aluminum filters that cover both the front and back surfaces of the second glass element (3b);
), the lead filters (2) and (2) are the openings made in this lead filter e (6).

As shown in Figures 2 and 3, the above case (■) consists of a bottom body (11) and a lid body (12) integrally molded from synthetic resin.
It has a rectangular flat box shape formed by fitting the two.

The face pieces (11) and (12) are almost symmetrical, and each has three sets of filters on its inner surface.), (a), ■j■, ■, 0
are installed as described below.

As shown in Fig. 4, the holder (2) is made of synthetic resin or metal, has external dimensions to be accommodated in the case (ω), and has three glass elements (3a) along one long side.
, (3b) to (3c), respectively, are formed in such a way that their long sides are parallel to each other. It also has a display surface (23) along the other long side, and has a glass element (23) thereon.
3a).

(3b), (3c) An optical display (24) indicating the type number, etc. is provided.

The three glass elements (3a), (3b), (
3c) Haisuku also contains 60% by weight of aluminum phosphate, 20% by weight of sodium metaphosphate, and 20% by weight of sodium orthophosphate with 0.3% by weight of silver metaphosphate as seen in Japanese Patent Publication No. 50-10333. %, and as shown in Figure 5, it is cut into a rectangular parallelepiped of, for example, IOX 7 x 3 and polished, and is activated by exposure to γ (X) rays. This forms a fluorescent center that emits fluorescence when excited by ultraviolet light with a wavelength of 300 to 400 nm.
It has energy dependence such that it exhibits an excessive response to low-energy γ(X) rays below V. Then, each accommodation hole (21a) and (21b) of the holder (2).

(21c) are both this glass element (3a), (
3b) and (3c) are tightly fitted.

The above tin filter (A) is, for example, a tin plate with a thickness of 2 mm.
It has a property of having low transmittance for low energy γ(X) rays of 00 KsV or less.

The above aluminum filter (■) is, for example, an aluminum plate with a thickness of II, and has a low energy γ(X) of 200 KeV or less.
It has the property of transmitting wires well.

The lead filter (■) above is, for example, a lead plate with a thickness of 1 mm.

It has a characteristic that the transmittance of low-energy γ(X) rays of 200 eV or less is even smaller than that of a tin filter, and a 2×
It has a 2m square opening (■).

Then, on the inner surfaces of the bottom body (11) and the lid body (12) of the case ■, the tin filters) and (to) are attached to the first glass element (3a), and the aluminum filter 0°■ is attached to the second glass element (3a). A lead filter (6) in the glass element (3b),
(E9 each faces the third glass element (3c),
The size and position are determined and fixed so as to sufficiently cover each of the front and back surfaces.

Next, we will explain the functions of the fluorescent glass dosimeter and its reading device according to the present embodiment.Since the dosimeter according to the present embodiment was constructed as described above, when exposed to γ(X) rays, the γ(
X) The rays enter the glass elements (3a) - (3b), (3c) through the respective filters (to), Glass element (3a) at this time showing fluorescence intensity
Figure 6 shows the energy dependence of the fluorescence intensity for the γ(X) ray in (3b). In Figure 1, the horizontal axis represents the γ(X) ray energy in units of Kev, and the vertical axis represents the relative fluorescence intensity. Curve (A) is the relative intensity curve of the first glass element (3a) covered with a tin filter (2), and curve (B) is the relative intensity curve of the second glass element (3b) covered with an aluminum filter.
Curve (A) of this figure 6 showing the relative intensity curve of ( ), (
From B), a curve (C) showing the most uniform response to each γ(X) ray energy was obtained using the following equation and is shown in FIG.

C= (A+bB)/a... ωHere,
a and b are coefficients.

Next, the fluorescence reading method of the glass elements (3a), (3b) is shown in FIG.
Exciting ultraviolet rays are incident from the direction (a) perpendicular to the perpendicular line (b) erected on the irradiation surface (3a,)=(3bz) in b), and fluorescence generated from the perpendicular line (b) direction is detected, for example. At this time, the excited ultraviolet rays are transmitted through the glass elements (3a) and (3b).
incident on the entire area within.

Light is emitted from all luminescent centers. Therefore, γ(X
) Dose value R = (Ra + b Rb) / a -・
Find by ■.

Next, we will explain the energy evaluation method that is required when significant radiation exposure is recognized. The ratio between curve (B) and curve (A) in FIG. 6 was calculated, and this value is shown in FIG. 8 as a curve (B/A). Therefore, the reading R,b of the second glass element (3b) and the first glass element (
If the ratio Rh/Ra with the reading value Ra of 3a) is calculated, the 8th
From the curve (B/A) in the figure, the energy of low energy Ge (X) rays of 200 KaV or less can be evaluated.

Next, a method for estimating the incident direction necessary when exposure to low-energy (X) rays of 200 aV or less is confirmed will be explained. As mentioned above, the third glass element (3c)
is γ(X
) is irradiated to the line. However.

If the γ (X) ray has a low energy of 200 KeV or less,
In this case, the shielding effect of the lead filter ■ is strong.

The concentration of fluorescence center generation differs greatly between the surface of the lead filter 0 that is shielded by the plate and the surface that is not shielded because it faces the opening (2). Therefore, in the fluorescence reading section of the reading device, the third glass element (
3C), the perpendicular direction (
Excite ultraviolet light from the direction (c) perpendicular to (b) with a diameter of 0.
．． This irradiation surface (3c
, ) is scanned in parallel to the irradiation surface (3c, ), and the intensity distribution of the fluorescence generated at this time is measured. Next, the irradiation surface (
3c1) in a plane parallel to the irradiation surface (3c1), and rotate the part of the third glass element (3c) near the irradiation surface (3c1) to the irradiation surface (3c1).
3c) and measure the intensity distribution of the fluorescence generated at this time.

When the intensity distribution of fluorescence of the third glass element (3C) is read in this way, for example, when the incident direction of the γ(x) ray is perpendicular, as shown in FIG. A peak of fluorescence intensity is observed at the center of the width 7 widths of 3C), that is, at a position corresponding to the center line of the opening (2). On the other hand, for example, when the incident direction of the γ(X) ray makes an angle of 60° with respect to the perpendicular direction, the peak position of the fluorescence intensity is at the center of the width of the glass element (3c), as shown in FIG. Furthermore, when the direction of incidence of the γ(X) rays forms an angle of 80° with respect to the perpendicular direction, as shown in Figure 11, the shift in the peak position of the fluorescence intensity becomes even more pronounced. growing. Therefore, by measuring the shift in the peak position of the fluorescence intensity, the angle of incidence of the γ(X) rays can be estimated. In this way, by rotating the holder ■ by 901 rotations and measuring twice, the
The shift in the peak position of fluorescence intensity can be measured in two directions that intersect at 0°, and the angle of incidence of γ(X) rays can be estimated three-dimensionally.

However, the above measurement can be applied to all types of radiation by combining filters with transmittances corresponding to the energy of the radiation, but from a practical point of view, in the present invention, it is possible to apply the measurement to 200 KeV or less. limited to gamma rays, X-rays, and their mixed radiation.

Furthermore, the present invention can be applied even when various types of radiation are mixed,
In this case, it is desirable to increase the number of filters to more than three to improve measurement accuracy. Further, there may be a plurality of filters having openings, and the radiation transmittance of these openings may be less than 100%.Furthermore, if there are multiple filters having openings, each filter may have a radiation transmittance of less than 100%. The radiation transmittance of the apertures may be different.

〔Effect of the invention〕

Thus, the first claim of the present invention is a fluorescent glass dosimeter in which each of three or more rectangular glass elements is covered with a filter, in which the filter covering at least one glass element has a glass surface. The filters that cover at least two of the other glass elements were made to have smaller openings compared to the other glass elements, and had different transmittance for γ-rays or X-rays of 200 KeV or less, so each glass element It has the advantage that the exposure dose and its energy value can be calculated by comparing the fluorescence intensity after exposure, and the direction of incidence of the radiation can also be estimated.

Further, the second claim of the present invention is the radiation dose reading device for the fluorescent glass dosimeter described in the first claim, in which a portion of the glass element near the radiation irradiation surface is perpendicular to a perpendicular line to the irradiation surface. Since ultraviolet rays are incident from two directions perpendicular to each other and the intensity distribution of the emitted fluorescence is observed, the direction of incidence of the radiation can be estimated three-dimensionally from the shift in the peak position of the fluorescence intensity.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an embodiment of the fluorescent glass dosimeter of the present invention, Fig. 2 is a perspective view of the case, Fig. 3 is a perspective view of the bottom of the case, and Fig. 4 is a perspective view of the holder. Figure 5 is a perspective view of the glass element, Figure 6 is a graph showing the sensitivity characteristics of the first glass element and the second glass element to γCX) ray energy, Figure 7 is the excitation ultraviolet rays of each glass element. A perspective view showing the incident direction and the fluorescence detection direction, FIG. 8 is a graph showing the sensitivity ratio between curve A and curve B in FIG. 6, and FIG.
In Figures 1 to 11, the incident direction of the γ(X) ray is o.
It is an explanatory view showing the peak position of fluorescence intensity in the third glass element at @, so' and 80°. ■...Case (11)...Bottom body (1
2) Lid ■ Holder (21a
), (21b), (21c) - accommodation hole (3a)
, (3b), (3c)-Glass element (3a, )
, (3b, ), (3c, ) - on the irradiated surface), ■
, (to)...Filter ■...Aperture agent Patent attorney Ogo Nenfu l-Case No. 13 7: FJ opening Fig. 3 Fig. 5 Fig. Fig. ? tx) Vase Literary Enerui <Kev) Diagram I Stand” L Funeral Diagram

Claims (2)

[Claims] (1) three or more rectangular parallelepiped fluorescent dosimeter glass elements;
In the fluorescent glass dosimeter, the fluorescent glass dosimeter includes a housing that houses the glass elements in parallel, and three or more sets of filters that cover one or both sides of each of the glass elements, in which the filter that covers at least one glass element is A metal plate filter having small openings compared to the coated glass surface, and at least two of the other glass elements.
There are 200 filters covering each of the glass elements.
A fluorescent glass dosimeter characterized by having different transmittances for gamma rays or X-rays below KeV. (2) In the reading device for reading the exposure dose of a fluorescent glass dosimeter according to claim 1, a portion of the glass element housed in the dosimeter near the radiation irradiation surface is erected on the radiation irradiation surface. A reading device for a fluorescent glass dosimeter, characterized in that ultraviolet rays are incident from two directions perpendicular to a perpendicular line and at right angles to each other to excite the glass element and observe the intensity distribution of the emitted light.