JPS5999397A - Method of attenuating leaked radiation - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of attenuating leakage radiation, and more particularly to a method of attenuating leakage radiation at bent ducts, wall joints, etc. in a radiation shielding structure.

Conventionally, reactor containment vessel walls, reactor coolant piping.

So-called radiation shielding structures that require radiation shielding properties, such as biological shielding walls, have bent ducts, and due to construction or assembly requirements, for example, as shown in Fig. 1, the structure wall IA , IB is provided. If there is a gap in this seam 2, a radiation leakage path 8 is formed, so this is bent to reduce the amount of radiation leakage.

By the way, among radiation, neutrons, r-rays, etc. have a large power to penetrate materials, and therefore freely enter into the atomic nuclei of the materials forming the walls IA and IB. Then, the phenomenon of gradual deceleration due to elastic scattering, which changes the direction of travel by colliding with the atomic nucleus, is repeated.

Therefore, there is a possibility P that a radiation leakage phenomenon will occur near the bent portion of the radiation leakage passage 8 such as a bent duct or joint, as shown by the chain line in FIG.

That is, near the inner corner of the bending part of the radiation leakage passage 8, the wall IA
Radiation IIi has entered inside! After passing through a mean free path of approximately X (which varies depending on the energy of the neutron and the material of the wall), the radiation 4A is scattered at random points and enters the radiation leakage path 8.
and leaks outside the wall IAjIB as shown by the chain line 4B. Furthermore, if there is radiation 5A that has entered the bend along the radiation leakage path 8, it will be scattered at the position of point S, which has reached the mean free path, and the radiation will fly out in the direction of chain i5B. It leaks outward along the passageway 3. Roughly speaking, the radiation i6A that has entered the wall IB near the outside corner of the bend of the radiation leakage path 8 is scattered at a point T near the path, and is directed outward along the radiation leakage path 8 as shown by the chain line 6B. Jump out.

These leakage phenomena are caused by scattering occurring near the bends, as shown by points R, S, and T in FIG.

One possible solution to this problem is to increase the number of bends in the radiation leakage path formed in the radiation shielding structure, but this poses a problem of complicating the structure and requiring highly accurate machining.

The present invention has been made based on the above-mentioned circumstances, and its purpose is to avoid the scattering phenomenon of radiation in the shielding body near the bend of the radiation leakage path, and to avoid the radiation scattering phenomenon that occurs only as a result of multiple scattering. It is an object of the present invention to provide a method that can significantly reduce radiation leakage by preventing radiation from passing through, and can be easily applied to various radiation shielding structures.

In order to achieve this object, the present invention provides a structure in which each radiation leakage path has a bent portion with a dimension slightly larger than the radiation mean free path, which is formed at a bent duct, joint, etc. in a radiation shielding structure. It is characterized by the fact that it expands around the curve and does not scatter radiation near the bend.

Hereinafter, one embodiment of the present invention will be described based on FIG. 3.

In FIG. 3, a space or an expansion hole 7 is provided at the bend of the radiation leakage passage 8 to largely enclose the bend.

As shown in FIG. 3, this space 7 is formed by cutting off the bent portion in both directions of the radiation leakage passage 8 to form a space having, for example, a parallelepiped or square cross section.

The reason for this will be explained below. For example, the radiation 5A that has proceeded into the space 7 along the radiation leakage path 8 enters the hole inner wall 8A and causes first scattering at a point S1 at a depth of approximately the mean free path. As in the case of Fig. 2, if the radiation progresses as shown by the chain line 5B, then the point S
2 causes the second scattering. If the direction of the radiation generated by this scattering is the direction shown by tam5c, the third scattering occurs at point S8, and the radiation in the direction shown by chain M5D is
It advances along the radiation 1m path 8 and jumps out.

The energy of the radiation is attenuated by these three scatterings,
Furthermore, the amount of radiation emitted from the walls IA and IB is also extremely reduced.

Radiation 4 that roughly progressed toward the inner corner of the bend
Since the space 7 exists, the light A travels straight through the space, and is scattered at a point where the light passes through the mean free path X on the inner wall 8A of the hole. However, the position of the dotbo is away from the radiation leakage path 8 by the expansion dimension Y, so it almost never reaches the radiation leakage path 8 and directly jumps out, and it takes several more scatterings to jump out. I need. Furthermore, the six radiation beams that have proceeded toward the outer corner of the bend also disperse at point T, so they exhibit a similar tendency.

In this way, if the space 7 is provided at the bend of the radiation leakage path 8, the radiation scattering effect near the bend will not occur in the vicinity of the leakage path 3, and the radiation will be scattered by only one scattering phenomenon. Mi hardly jumps out along the radiation leakage path 8, the energy is attenuated each time it is scattered, and moreover, the amount of Mi that jumps out is also reduced.

In the embodiment described so far, an example has been described in which the bent portion is expanded to have a parallelepiped or quadrilateral cross section, but other shapes such as a sphere, a spheroid, a circular cross section, an ellipse, a polygon, etc. are described. , the space may have a non-geometric shape.

As explained above, the present invention utilizes a novel idea of expanding the bending part of the radiation leakage passage formed at the bending duct of the radiation shielding structure or the seam of the wall, thereby preventing radiation from being scattered near the bending part. When going to the next passage after turning a bend, several scatterings are required to promote the energy attenuation of the radiation, and it is easy to reduce the dose, which improves the safety of nuclear power generation facilities. This has effects such as improving sexual performance.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing an example of the structure of a duct and a seam provided in a conventional radiation shielding wall, Fig. 2 is an enlarged view illustrating the radiation leakage phenomenon of Fig. 1, and Fig. It is an enlarged view explaining one example. IA, IB...wall, 2...joint,
8...Radiation leakage passage, 7...Space part.

Claims (1)

[Claims] Radiation leakage paths formed at bent ducts and wall joints in radiation shielding structures q) Expand each radiation leakage path in both directions with a slightly larger dimension due to the mean free path of the radiation at the bent portion to bend the radiation. A method of attenuating leakage radiation characterized by preventing scattering in the vicinity of the leakage radiation.