JPH09243793A - 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 is enclosed by a shielding wall 3 having an opening part through a passage, and the passage enclosed by the shielding wall 3 is bent, the section of at least a part of the passage enclosed by the shielding wall 3 is divided into a plurality of pieces by partitioning plate and/or inner bulkheads 4. The X-ray or γ-ray shielding equipment shields the X-ray or γ-ray leaked to the outside from the opening part through the shielding passage which is generated in electron beam emission.

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 shielding X-rays or γ-rays leaking from an opening through a shielding passage generated during electron beam irradiation or the like. Shielding equipment for

[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 in the wall so as to Prevents leakage. However, when X-rays or γ-rays are generated, substances can come and go, so that it is not possible to completely seal and there is an opening. For example, the source is a part of the process of the production line, For example, when the product is taken out from the opening, or when the source is part of the continuous treatment process of exhaust gas and effluent and the processed product is taken out from the opening, X-ray or γ leaking into
The wire must be shielded in another way. In general, X-rays and γ-rays, which are electromagnetic waves, are attenuated when they pass through a substance, and become weaker as the distance from the radiation source increases, and attenuated each time they are reflected on the substance surface. Therefore, in order to shield the X-rays or γ-rays leaking from the opening, the outer wall of the passage leading to the opening is made a shielding wall that does not leak X-rays or γ-rays, and the distance of the passage is increased. A method of attenuating X-rays or γ-rays by bending the passage is used.

FIG. 7 shows an example of a shielding passage (a curved passage surrounded by a wall capable of shielding X-rays or γ-rays) using this method. Also, a large and costly shielding door 9 (Fig. 8-a)
Instead of the above, there is also a shielding facility that uses an ordinary door after bending the entrance passage with a long length as shown in FIG. The effect of attenuation due to the distance and reflection at the shielded passage portion (hereinafter referred to as the attenuation rate.
, If the outlet is Iout, then the attenuation rate = I IN / Iout.
For example, when the strength becomes 1/100 at the entrance and the exit of the shielding part, the attenuation rate at this shielding is 100. ), An empirical formula such as the following formula 1 is used, and the design of the shield passage portion is also performed by formula 1. Where I ₀ is the intensity at the radiation source, I is the intensity at the aperture,
L is the distance from the radiation source to the aperture, R is the attenuation rate per reflection, and N is the number of reflections from the radiation source to the aperture. That is, the attenuation rate η of X-rays or γ-rays at the opening is proportional to the square of the distance from the radiation source, and is proportional to the exponential power of the number of reflections (equation 2).

Since the attenuation rate of X-rays or γ-rays depends on the distance and the number of reflections as shown by the equation 2, in the shielding facility having the shielding passage, the space required for shielding is larger than that in the system of FIG. This results in a large increase in materials (a and b in Fig. 8).
It is easy to understand by comparing). As the amount of generated X-rays or γ-rays increases and the energy increases, the distance required for shielding and the number of reflections increase, and the ratio of increase in space and materials required for shielding also increases. Further, as the amount of substances entering and exiting the facility increases, the cross-sectional area of the shielding passage increases, and the ratio 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 It is an object of the present invention to provide an X-ray or γ-ray shield facility that solves the above-mentioned problems of the prior art and can significantly reduce the space and material required for the shield passage. To do.

[0006]

In order to solve the above-mentioned problems, in the present invention, a source of X-rays or γ-rays is surrounded by a shielding wall having an opening through a passage, and is surrounded by the shielding wall. In an X-ray or γ-ray shielding facility in which the passage is bent, at least a part of the passage surrounded by the shielding wall is divided into a plurality of sections by a partition plate and / or an internal partition wall. Is. The X-ray or γ-ray shielding equipment of the present invention can be used for shielding X-rays or γ-rays generated during electron beam irradiation used in the electron beam exhaust gas treatment method and the like.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, in the present invention, the curved shield passage cross section is divided into a plurality of sections by the partition plate and / or the internal partition wall, and (1) the curved shield passage cross section is divided. The damping efficiency is improved by (2)
It is an invention based on two points that a partitioning plate or an internal partition to be divided does not require sufficient shielding ability (thickness and density). In the method used to design shielding equipment (calculation by Equation 1), it is considered that the attenuation factor does not change even if the passage is divided because the distance from the radiation source and the number of reflections do not change. It was On the other hand, the present inventors have found that the X-ray or γ-ray attenuation rate can be increased by dividing the bent shield passage section into a plurality of sections by the partition plate and / or the internal partition wall. Furthermore, it was confirmed that the partition plate or the internal partition wall has an effect of increasing the attenuation rate even when the partition plate or the internal partition wall has a thickness that hardly shields X-rays or γ-rays.

FIG. 1 shows an example in which the passage cross section is divided by the partition plate or internal partition of the present invention. In FIG. 1, 1 is an X-ray or γ-ray entrance, 2 is the same exit, 3 is an outer wall of a shield passage, and 4 is a partition plate or an internal partition wall. FIG. 2 is for explaining the relationship between the attenuation rate, the passage cross-sectional area, and the distance from the reflection point. The present inventors have found that the X-ray or γ-ray attenuation rate in the shielded passage has the following relationship with the passage cross-sectional area and the distance from the reflection point of the bent portion. In blocking passage as in FIG. 2, the bending portion _{P 1, P 2, ···,} I 1, I 2 X-ray intensity at P _n respectively, ..., if I _n, in P _n The X-ray intensity I _n can be calculated by the following formula based on the intensity I _n-1 at the previous curved portion P _n-1 (n = 4 in FIG. 2). In Formula 3, S is the passage cross-sectional area, L _n is the distance from the passage bent portion P _n-1 , α and β are constants depending on the passage cross-sectional shape, and (α × L ² / S + β) Is the decay rate of.

That is, according to the equation 3, it is understood that the attenuation at the curved portion of the shielded passage is proportional to the square of the distance from the reflection point and is inversely proportional to the sectional area of the passage. Focusing on this action, the damping effect can be enhanced by reducing the passage cross-sectional area in addition to increasing the number of reflections and the distance. For example, if the cross section of the shielding passage is divided into nine equal parts by the partition plate as shown in FIG. 1, the damping effect per bending is about nine times. Therefore, if the curved passage has five bends, the volume of the shielded passage hardly changes, and the shielding effect is almost 60,000.
It can be 0 times (= 9 ^5). Further, at this time, the thickness of the partition plate or the internal partition wall is about 20 minutes of the half-value layer (thickness required to attenuate the intensity of X-rays or γ-rays to half) for the transmitted X-rays or γ-rays. It has been clarified from the experiment that the damping effect can be obtained if 1 or more. This allows
It was another important finding of the present invention that the thickness of the partition plate or the internal partition wall could be made very thin.

[0010]

The present invention will be described below in more detail with reference to examples. Example 1 FIG. 3 shows an X-ray source (electron beam generator) 5 and X-ray shielding equipment. Inside the shielded passage of this equipment (shaded area in Figure 3)
4, the partition plate 4 is installed parallel to the floor surface as shown in FIG. 4, and the maximum energy of the generated X-rays is 0.5 MeV and 0.8M.
The test was performed in two ways of eV. The partition plate is 900m wide
m, 1,000m from the floor of the 3,000mm high passage
It was installed at a height of m and the passage was divided into a cross-sectional area of 2: 1.
As the partition plate, as shown in Table 1, aluminum, iron, and lead were measured with different plate thicknesses. The ratio to the half-value layer in Table 1 is the thickness ratio of the partition plate to the half-value layer shown in Table 2.

[0011]

[Table 1]

[0012]

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

With respect to the X-ray intensity (I ₁ ) at the entrance of the shield passage portion, the X-ray intensity (I ₃ ) at the outlet of the shield passage portion was measured,
The shielding effect was compared by the attenuation rate η (η = I ₁ / I ₃ ). FIG. 5 is a graph showing the attenuation rate with respect to the half-value layer ratio. Before installing the partition plate (cross section 2.7m
² ) is represented by the straight line (a), ◯ is the attenuation rate in the upper passage (cross-sectional area 1.8 m ² ) after the partition plate is installed, and △ is the lower side (cross-sectional area 0. It shows the damping rate in the 9 m ² ) passage. As shown in FIG. 5, even at the measurement location where the distance from the radiation source and the number of reflections are the same, the attenuation rate increases as the sectional area of the partitioned passage becomes smaller, and due to the shielding passage division by the partition plate, It can be seen that the shielding effect is improved.

Further, the attenuation rate (I ₁ / I ₂ ) corresponding to the reflection attenuation for one time is shown in FIG. 6, and from this graph, the relational expression as shown in Expression 3 can be obtained. Moreover, even if the thickness of the partition plate is reduced to 1/10 of that of the half-value layer (an iron partition plate having a thickness of 1 mm for the maximum X-ray energy of 0.5 MeV) from FIG. 5, the damping effect does not change. Was confirmed. If the plate thickness is 0.08 times the half-value layer (1 mm thick iron partition plate for maximum X-ray energy of 0.8 MeV), the damping effect will drop slightly, but the shielding efficiency will be maintained without changing the shape of the shielding passage. It is still an effective way to raise the level. On the contrary, even if the partition plate is made thicker, the shielding effect does not change, but the construction or economic demerit only increases, so in reality it is considered that the upper limit is about 10 times the half-value layer. To be

[0015]

According to the present invention, the shielding passage portion of the X-ray or γ-ray shielding facility having an opening is divided by the partition plate or the internal partition wall as described above to shield X-rays or γ-rays. It can improve efficiency and save the installation space and construction cost of shielding equipment.

[Brief description of drawings]

FIG. 1 is a perspective view of an example in which a passage section is divided by a partition plate or an internal partition wall of the present invention.

FIG. 2 is a shielding path diagram for explaining an attenuation rate.

FIG. 3 is a sectional view of the X-ray shielding equipment used in the examples.

FIG. 4 is a cross-sectional view of a shield passage in which the partition plate of FIG. 3 is installed.

FIG. 5 is a graph showing the X-ray attenuation rate with respect to the half-value layer ratio.

FIG. 6 is a graph showing an X-ray attenuation rate with respect to L ² / S.

FIG. 7 is a sectional view showing an example of a known X-ray or γ-ray shielding facility.

FIG. 8 is a cross-sectional view showing another example of known X-ray or γ-ray shielding equipment.

[Explanation of symbols]

1: X-ray or γ-ray entrance, 2: X-ray or γ-ray exit, 3: shield passage outer wall, 4: partition plate or internal partition wall, 5: X-ray or γ
Line generation source, 6: partition plate installation position, 7: opening, 8: shield passage, 9: shield door

Claims (3)

[Claims] 1. An X-ray or γ-ray shielding facility in which an X-ray or γ-ray generation source is surrounded by a shielding wall having an opening through a passage, and the passage surrounded by the shielding wall is bent, X-ray or γ-ray shielding equipment, characterized in that at least a part of the passage surrounded by the shielding wall is divided into a plurality of sections by a partition plate and / or an internal partition wall. 2. The X-ray or γ-ray shielding facility according to claim 1, wherein the X-rays or γ-rays are X-rays or γ-rays generated during electron beam irradiation. 3. The X-ray or γ-ray shielding facility according to claim 2, wherein the electron beam irradiation is performed in an exhaust gas treatment method using an electron beam.