JPH09243794A - X-ray or gamma-ray shielding equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray or γ-ray shielding equipment in which the space and material required for a shielding passage part can be significantly reduced. SOLUTION: In an X-ray or γ-ray shielding equipment in which an X-ray or γ-ray generating source 1 is enclosed by a shielding wall 2 having an opening part, a bent partitioning plate 4 is set in the opening part of the shielding wall 2 or a passage 3 leading to the opening part which uses the shielding wall as the outer wall (hereinafter referred to as shielding passage). The bent partitioning plate 4 is preferably set in such a manner that the outlet can not be directly seen from the shielding wall opening part or the inlet of the passage leading to it, and can be formed of a screen-like plate or spiral plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to X-ray or γ-ray shielding equipment, and more particularly to X-ray or γ-ray shielding equipment for shielding X-rays or γ-rays leaking from an opening to the outside.

[0002]

2. Description of the Related Art Conventionally, in the case of shielding X-rays or γ-rays, by surrounding the radiation source with a shielding wall made of concrete, lead, iron or the like, the X-rays or γ-rays are attenuated inside the wall to Prevents leakage. However, when the X-rays or γ-rays enter and exit the substance, the shielding wall cannot be completely sealed and there is an opening, for example, the source is part of the process of the production line, When taking out a product from the opening, or when taking out the processed product from the opening as a part of the continuous treatment process of exhaust gas or wastewater, or when the ventilation port in the shielding facility is leaked to the outside from the opening. X-rays or γ-rays
Must be shielded in another way. In general, X-rays or γ-rays, which are electromagnetic waves, are attenuated when they pass through a substance, and are attenuated as the distance from the radiation source increases, and are attenuated each time they are reflected by the substance surface. Therefore, in order to shield X-rays or γ-rays leaking from the opening to the outside, a passage surrounded by a shielding wall (hereinafter referred to as a shielding passage) between the radiation source portion and the opening so as not to leak X-rays or γ-rays. Is provided and the passage is lengthened and further bent to attenuate X-rays or γ-rays.

An example of shielding equipment using this method is shown in FIG. The distance in the shielded passage and the effect of attenuation due to reflection (hereinafter referred to as the attenuation rate. When the radiation intensity becomes 1/100 at the entrance and the exit of the shielded part, the attenuation rate of this shield is 10
0. ), The empirical formula shown in the following formula 1 is used, and the design of the shield passage portion as shown in FIG. I = I ₀ × L ⁻² × R ^{−N (} 1) where I ₀ is the intensity of the X-ray or γ-ray at the source, I is the intensity at the passage exit position, and L is the outlet from the source. To R, R is the attenuation rate per reflection of X-rays, and N is the number of reflections of X-rays or γ-rays from the radiation source to the opening. That is,
The attenuation rate η (= L ² × ^RN ) of X-rays in the shield passage portion is
It is proportional to the square of the distance from the radiation source and to the exponential power of the number of reflections.

Since the attenuation rate of X-rays or γ-rays depends on the distance and the number of reflections as shown by the equation 1, the shielding equipment having an opening portion requires more space and materials for shielding than the closed type equipment. However, this results in a large increase. As the amount of X-rays or γ-rays generated increases and the energy increases, the distance required for shielding and the number of reflections increase,
The rate of increase in space and materials required for shielding will also increase.
In addition, as the amount of substances entering and exiting the facility increases, the cross-sectional area of the shielding passage increases, and the rate of increase in space and materials also increases. An increase in space will be an obstacle to equipment layout, and an increase in materials will not only increase the cost of shielding equipment, but also increase the cost of foundation work due to the increase in weight.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of the prior art and provides an X-ray or γ-ray shield facility which can significantly reduce the space and materials required for the shield passage portion. This is an issue.

[0006]

In order to solve the above problems, the present invention provides an X-ray or γ-ray shielding facility in which an X-ray or γ-ray source is surrounded by a shielding wall having an opening. A bent partition plate is installed in the opening of the shield wall or a passage (hereinafter referred to as a shield passage) leading to the opening having the shield wall as an outer wall. In the X-ray or γ-ray shielding equipment, it is preferable that the bent partition plate is installed so as not to directly see the entrance to the exit of the shield wall opening or the passage leading to it. , A folding plate or a spiral plate. In addition, X of the present invention
The X-ray or γ-ray shielding facility can shield X-rays or γ-rays generated during electron beam irradiation in an exhaust gas treatment method using an electron beam.

[0007]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a horizontal sectional view showing an example of X-ray or γ-ray shielding equipment of the present invention, and FIG. 2 shows an enlarged perspective view of a partition plate used in FIG. In FIG. 1, 1 is an X-ray generation source (electron accelerator), 2 is a shield wall, 3 is an opening or an opening passage, 4 is a partition plate, and here two plates of 4 _-1 , 4 _-2 are installed. ing. Let X be the incident side of X-rays and B be the exit side. An enlarged view of the partition plate 4 is shown in FIG. 2. In FIG. 2, 5 is a top plate for fixing the plate 7, 6 is the same floor plate, and here, the plates 7 are bent at 90 ° to form 5 and 6 It is fixed as and is used as the partition plate 4. FIG. 3 is a horizontal cross-sectional view showing another example of the X-ray or γ-ray shielding equipment of the present invention. In this example, the partition plate 4 has a spiral shape 8 and is otherwise the same as FIG. .

[0008]

The present invention will be described below in more detail with reference to examples. Example 1 The partition plate used in the test is shown in FIG. 2, and the partition plate of FIG. 2 was arranged in two stages as shown in FIG. 1 to perform an X-ray shielding test by electron beam irradiation. Maximum energy of incident X-ray is 0.5
Measurement was performed at MeV and 0.8 MeV, and the material and thickness of the partition plate were changed as shown in Table 1 for each energy. The ratio to the half-value layer in Table 1 is the thickness ratio of the partition plate to the half-value layer (thickness required to reduce the X-ray intensity to half) shown in Table 2.

[0009]

[Table 1]

[0010]

[Table 2] Note: In calculating the half-value layer, the total absorption coefficient of the substance was quoted from "Radiation" (Kyoritsu Publishing), and the density was quoted from "Science Chronology" (Maruzen).

In FIG. 1, the X-ray entrance side of the shielding equipment is designated as point A, and the exit side is designated as point B. X-ray intensity at point _A is I _A , X at point B
If the line intensity is I _B , the X-ray attenuation rate η in this test apparatus is
Becomes η = I _A / I _B. FIG. 4 is a graph showing the attenuation rate with respect to the half-value layer ratio in a series of experiments in which the material and thickness of the partition plate and the incident X-ray energy were changed. The thickness of the partition plate is 2.5 times that of the half-value layer (22.5 = 5.
It was confirmed that the transmitted X-rays could be suppressed if 7). Further, it was confirmed that even when the partition plate is thinner than 2.5 times the half-value layer, a large damping effect can still be obtained against the attenuation of only the distance when there is no partition plate. For example, even when the half-value layer ratio is 0.1, the effect is large with an attenuation rate of 50 to 100. On the contrary, even if the partition plate is made thicker, the damping effect does not change, but only the demerit in construction or economically increases, so in reality, it is considered that the upper limit is about several tens of times the half-value layer.

Next, without changing the thickness of the partition plate, the number of installation stages of the apparatus of FIG. 1 was increased and the measurement was carried out (a partition plate was also installed in the broken line portion in FIG. did). Maximum energy of X-ray is 0.5 MeV, partition plate thickness is lead 20 mm
Fig. 5 shows the results of measuring the attenuation rate at 1st stage, 2nd stage and 3rd stage.
It is. 5 shows that the lead partition plate has a thickness of 20 mm,
Only the attenuation effect of reflected X-rays without the influence of transmitted X-rays is shown. As a result, it was confirmed that the relation between the number of installation steps of the partition plate and the damping rate obtained does not satisfy the relational expression of Equation 1 but the following relational equation (Equation 2) that we independently found. I _n = I _n-1 × (α × L _n ² / S + β) ^-1 Equation 2

Equation 2 will now be described. For example, in a shielded passage as shown in FIG. 6, curved portions P ₁ , P ₂ ,
..., X-ray intensities at P _n are I ₁ , I ₂ , ...
.., I _n , cross-sectional area of passage S, passage bent portion P
If the distance from the _n-1 to P _n and L _n, X-ray intensity I _n at P _n, the intensity I _n-1 at the previous bend P _n-1
Based on, it can be calculated as in Equation 2. α and β are constants depending on the cross-sectional shape of the passage, and (α × L _n ² / S + β) is the damping rate per turn. That is, according to Equation 2, it can be seen that the attenuation at the curved portion of the shielded passage is proportional to the square of the distance from the reflection point and inversely proportional to the cross-sectional area of the passage. Focusing on this action, in addition to increasing the number of reflections and the distance, the damping effect can be enhanced by reducing the passage cross-sectional area by narrowing the partition plate pitch.

Example 2 Next, an X-ray shielding test by electron beam irradiation was conducted using a spiral partition plate. The whole experimental apparatus is as shown in FIG. A 10 mm thick iron plate was used as the partition plate, and the maximum energy of the incident X-ray was measured at 0.5 MeV and 0.8 MeV. As a result of this test, the X-ray attenuation rate η
_{(Η = I A / I B} ) as in 0.5 MeV eta = 200
Η = 1500 was obtained at 0 and 0.8 MeV, and the same shielding effect as in Example 1 was confirmed.

[0015]

According to the present invention, the partition plate is installed in the opening portion or the shield passage portion of the X-ray shielding equipment having the opening portion as described above, whereby the X-ray shielding efficiency is improved and the shielding equipment Installation space and construction cost can be saved.

[Brief description of drawings]

FIG. 1 is a horizontal sectional view showing an example of X-ray or γ-ray shielding equipment of the present invention.

FIG. 2 is an enlarged perspective view of the partition plate of FIG.

FIG. 3 is a horizontal sectional view showing another example of X-ray or γ-ray shielding equipment of the present invention.

FIG. 4 is a graph showing an X-ray attenuation rate with respect to a half-value layer ratio.

FIG. 5 is a graph showing the number of partitions installed and the X-ray attenuation rate.

FIG. 6 is a shielding path diagram for explaining Expression 2.

FIG. 7 is a horizontal sectional view of a conventional shielding facility having an opening.

[Explanation of symbols]

1: X-ray generation source, 2: Shielding wall, 3: Opening or opening passage, 4: Partition plate, 5: Fixed top plate, 6: Fixed floor plate, 7:
Board, 8: spiral partition board,

Claims (6)

[Claims] 1. An X-ray or γ-ray shielding facility in which a source of X-rays or γ-rays is surrounded by a shielding wall having an opening, in an opening of the shielding wall or an opening having the shielding wall as an outer wall. A shielding facility for X-rays or γ-rays, characterized in that a curved partition plate is installed in a passage (hereinafter referred to as a shielding passage) to reach. 2. The X-ray or γ according to claim 1, wherein the bent partition plate is installed so that an opening and an exit of a shielding wall opening or a passage leading to the opening cannot be directly seen through.
Line shielding equipment. 3. The X-ray or γ-ray shielding facility according to claim 1, wherein the bent partition plate is a folding screen plate. 4. The X-ray or γ-ray shielding facility according to claim 1, wherein the bent partition plate is a spiral plate. 5. The shielding of X-rays or γ-rays according to claim 1, wherein the X-rays or γ-rays are X-rays or γ-rays generated during electron beam irradiation. Facility. 6. The X-ray or γ-ray shielding facility according to claim 5, wherein the electron beam irradiation is performed in an exhaust gas treatment method using an electron beam.