Radiation shielding structure and construction method thereof

Abstract

To provide a radiation shielding structure and a construction method thereof capable of reducing the radiation dose incident into a labyrinth and simplifying construction work.SOLUTION: A radiation shielding structure comprises: an accommodation chamber 16 that houses a radiation generating device 12 and is surrounded by a radiation shielding wall 14 and a radiation shielding ceiling; an inner wall 22 that is provided between the radiation generating device 12 and an entrance / exit 18 to prevent radiation from the radiation generating device 12 from directly reaching the entrance / exit 18 of the accommodation chamber 16; and a labyrinth 24 that is formed by partitioning between the inner wall 22 and the radiation shielding wall 14 and connected to the entrance / exit 18. The radiation shielding structure further comprises a radiation shield body 26 that is provided in a suspended wall form separately without being integrated with the radiation shielding ceiling directly below the radiation shielding ceiling in the labyrinth 24, or directly below the radiation shielding ceiling between the inner wall 22 and the radiation shielding wall 14, in order to reduce the amount of incident radiation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a radiation shielding structure having a maze, such as a medical radiation shielding room, and a construction method thereof.

Background Art

[0002] Conventionally, in a radiation irradiation room where a radiation generating device such as an electron linear accelerator (linac) used for cancer treatment is installed, it is covered with a thick shielding wall made of concrete or iron to shield radiation. Further, at the entrance and exit of the irradiation room, a passage called a maze is provided, and by providing a thick wall, radiation directly reaching the entrance and exit from the radiation source is shielded by the wall, and with respect to radiation that passes through the opening at the boundary between the irradiation room and the maze and scatters in the maze and reaches the entrance and exit, it is attenuated by increasing the distance and scattering until it reaches the entrance and exit. The radiation that has reached the entrance and exit through the above process is finally shielded by a shielding door containing lead or polyethylene to prevent leakage to the outside of the room.

[0003] To prevent radiation from reaching the entrance and exit, it is effective to reduce the radiation incident on the maze. As such a technique, a structure in which a concrete hanging wall integrated with the ceiling is installed between the irradiation room and the maze (see, for example, Patent Document 1), or a structure in which a shielding body is arranged between the radiation source and the opening of the maze (see, for example, Patent Document 2) is known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, it is effective to provide a vertical wall in order to reduce the radiation dose incident in the maze. The vertical wall can be created integrally with the ceiling mainly made of concrete. However, prior to the placement of concrete, a formwork needs to be assembled and the formwork needs to be held by a shoring worker from below.

[0006] When installing the vertical wall, there was a problem that the formwork became more complicated and the necessary shoring work increased compared to the case of placing only the ceiling. In addition, when installing ducts and various pipes near the ceiling of the irradiation room and the maze, it was possible to provide through holes in the vertical wall, but the shape became complicated. For this reason, a structure that can save construction labor has been demanded.

[0007] The present invention has been made in view of the above, and an object thereof is to provide a radiation shielding structure and a construction method thereof that can reduce the dose incident in the maze and can save construction labor.

Means for Solving the Problems

[0008] In order to solve the above-described problems and achieve the object, a radiation shielding structure according to the present invention includes a storage chamber surrounded by a radiation shielding wall and a radiation shielding ceiling that houses a radiation generating device, and radiation from the radiation generating device directly reaches the entrance and exit of the storage chamber. An inner wall provided between the radiation generating device and the entrance and exit to prevent this, and a maze that is partitioned and formed by the inner wall and the radiation shielding wall and is connected to the entrance and exit, and directly below the radiation shielding ceiling in the maze, or directly below the radiation shielding ceiling between the inner wall and the radiation shielding wall. It is provided in a vertical wall shape separately without being integrated with the radiation shielding ceiling, and further includes a radiation shielding body for reducing the incident amount of the radiation.

[0009] Moreover, another radiation shielding structure according to the present invention is characterized in that, in the above-described invention, the radiation shielding body is supported by at least one of the inner wall and the radiation shielding wall.

[0010] In addition, in another radiation shielding structure according to the present invention, in the above-described invention, the radiation shielding body is provided with a gap between the radiation shielding body and the radiation shielding ceiling.

[0011] In addition, another radiation shielding structure according to the present invention is a method of constructing the above-described radiation shielding structure, in which after casting at least one of the inner wall and the radiation shielding wall, the radiation shielding body is installed on at least one of the inner wall and the radiation shielding wall.

Advantages of the Invention

[0012] According to the radiation shielding structure of the present invention, a radiation shielding structure includes a storage chamber that houses a radiation generating device and is surrounded by a radiation shielding wall and a radiation shielding ceiling, an inner wall provided between the radiation generating device and an entrance / exit to prevent radiation from the radiation generating device from directly reaching the entrance / exit of the storage chamber, and a maze formed by partitioning with the inner wall and the radiation shielding wall and connected to the entrance / exit. Immediately below the radiation shielding ceiling in the maze or immediately below the radiation shielding ceiling between the inner wall and the radiation shielding wall, a radiation shielding body is provided in a hanging wall shape separately from the radiation shielding ceiling. Since the radiation shielding body is further provided to reduce the amount of incident radiation, it is possible to reduce the dose of radiation incident in the maze and to save labor in construction.

[0013] In addition, according to another radiation shielding structure of the present invention, since the radiation shielding body is supported by at least one of the inner wall and the radiation shielding wall, it is possible to easily install the radiation shielding body as a retrofit.

[0014] In addition, according to another radiation shielding structure of the present invention, since the radiation shielding body is provided with a gap between the radiation shielding body and the radiation shielding ceiling, it is possible to save labor in construction and at the same time limit the influence of the effective dose on the entrance / exit.

[0015] Moreover, according to another radiation shielding structure of the present invention, there is provided a method for constructing the above-described radiation shielding structure, in which after casting at least one of the inner wall and the radiation shielding wall, the radiation shielding body is installed on at least one of the inner wall and the radiation shielding wall, so that the effect of saving labor in construction and enabling construction can be achieved.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of a radiation shielding structure and a construction method thereof according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by this embodiment.

[0018] As shown in FIG. 1, a radiation shielding structure 10 according to an embodiment of the present invention houses a medical linac 12 (radiation generating device), and includes a housing chamber 16 surrounded by a shielding wall 14 (radiation shielding wall), a ceiling (radiation shielding ceiling) not shown, and a floor; an inner wall 22 provided between an irradiation chamber 20 where the linac 12 is located and an entrance / exit 18 to prevent radiation from the linac 12 from directly reaching the entrance / exit 18 of the housing chamber 16; a maze 24 partitioned by the inner wall 22 and the shielding wall 14 and connected to the entrance / exit 18; and a hanging wall-shaped shielding body 26 (radiation shielding body). A shielding door 28 having a function of shielding radiation is provided at the entrance / exit 18.

[0019] The accommodation chamber 16 is a room that is substantially rectangular in plan view and surrounded by the shielding wall 14. The linac 12 is installed substantially at the center of the irradiation chamber 20 in plan view. The linac 12 generates radiation such as X-rays, collimates this radiation to form the utilization beam cone 30, and irradiates in the direction of the isocenter of a treatment table (not shown).

[0020] The shielding wall 14 is composed of a metal such as iron and concrete covering this metal. Inside the shielding wall 14 located on the extension of the utilization beam cone 30, a metal plate 32 such as an iron plate with excellent radiation shielding ability is provided.

[0021] The ceiling is provided above the accommodation chamber 16. The floor is provided below the accommodation chamber 16. The ceiling and the floor are composed of a metal such as iron and concrete covering this metal. Inside the ceiling located on the extension of the utilization beam cone 30, a metal plate such as an iron plate with excellent radiation shielding ability is provided.

[0022] The maze 24 is provided to prevent the radiation from the linac 12 from directly reaching the entrance / exit 18. More specifically, the inner wall 22 protrudes in the left-right direction from the shielding wall 14 on the left side toward the shielding wall 14 on the right side, partitioning the irradiation chamber 20 and the inside of the maze 24. The maze 24 is formed between this inner wall 22 and the shielding wall 14 on the rear side. The inner wall 22 is composed of concrete. The inner wall 22 may be composed of a metal such as iron and concrete covering this metal. An opening 36 is formed between the right end 34 of the inner wall 22 and the shielding wall 14 on the right side, serving as a common opening connecting the irradiation chamber 20 and the inside of the maze 24. In the example of FIG. 1, the wall surface on the inner side of the maze 24 of the end 34 of the inner wall 22 is inclined in plan view such that the wall thickness gradually becomes thinner as it approaches the opening 36. Also, the wall surface of the shielding wall 14 on the rear side facing the inner wall 22 across the maze 24 is inclined in a shape corresponding to the wall surface of the inner wall 22. For this reason, the passage width of the maze 24 is constant from the opening 36 to the entrance / exit 18.

[0023] The shielding body 26 is a radiation shielding body for reducing the amount of radiation incident into the maze 24, and is provided in a hanging wall shape separately without being integrated with the ceiling directly below the ceiling of the opening 36. Note that the shielding body 26 is not limited to this, and at least one may be provided directly below the ceiling in the maze 24, or it may be provided respectively directly below the ceiling of the opening 36 and directly below the ceiling in the maze 24.

[0024] For the material of the shielding body 26, for example, general radiation shielding materials such as concrete, iron, lead, polyethylene, etc., or materials combining these can be used. The shape of the shielding body 26 may be, for example, a rectangular parallelepiped shape or a plate shape. When the shielding body 26 is composed of concrete alone, a thickness of about 30 cm is sufficient, and the width is set wider than the width of the opening 36.

[0025] Figure 2 shows an installation example of the shielding body 26. As shown in this figure, the shielding body 26 is configured in a rectangular parallelepiped shape and is fixed in a form supported by both the inner wall 22 and the shielding wall 14 facing it. Specifically, a stepped portion 38 notch-shaped concavely is provided on the upper end side of the end portion 34 of the inner wall 22. On the other hand, a stepped portion 40 notch-shaped concavely is also provided on the upper end side of the shielding wall 14 facing the inner wall 22. The bottom surfaces 38A, 40A of the stepped portions 38, 40 are set to a horizontal plane of the same height. The lower surfaces 26A at both left and right ends of the shielding body 26 are placed on the bottom surfaces 38A, 40A of these two stepped portions 38, 40, the shielding body 26 is installed between the inner wall 22 and the shielding wall 14, and by fixing each to the stepped portions 38, 40 with bolts or the like, both ends of the shielding body 26 are supported by both the inner wall 22 and the shielding wall 26. By doing so, the shielding body 26 can be provided in a hanging wall shape separately without being integrated with the ceiling 42 directly below the ceiling 42 of the opening 36. With the hanging wall-shaped shielding body 26, the amount of radiation incident from the irradiation chamber 20 into the maze 24 can be reduced, and the dose at the entrance / exit 18 can be decreased.

[0026] Since the shielding body 26 and the ceiling 42 are not integrated, a gap S may be formed between them. At this time, if the gap S is sufficiently small, the radiation generated by the radiation source of the linac 12 and reaching the entrance / exit 18 through the gap S must undergo multiple scattering within the gap S, so the contribution to the dose at the entrance / exit 18 becomes sufficiently small.

[0027] Also, gaps may be formed between the shielding body 26 installed at the stepped portion 38 of the inner wall 22 and the inner wall 22, and between the shielding body 26 installed at the stepped portion 40 of the shielding wall 14 and the shielding wall 14, respectively. In this case, for the same reason as the above gap S, the contribution to the dose at the entrance / exit 18 becomes sufficiently small.

[0028] (Verification of the effects of the present invention) To verify the effects of the present invention, the dose inside the shielding door of the entrance / exit 18 was calculated when there was a gap S between the shielding body 26 and the ceiling 42. The three-dimensional Monte Carlo calculation code MCNP5 was used for the calculation. The radiation source was a 10 MeV monoenergetic electron beam, and the effective dose at a point near the shielding door and inside the maze 24 was evaluated for the bremsstrahlung generated when irradiating a copper target. The plan view and cross-sectional view of the irradiation chamber 20 and the maze 24 during the calculation are shown in FIG. 3, and the effective dose of the height x of the gap S is shown in FIG. 4. However, FIG. 4 shows the effective dose in terms of the ratio to x = 0. In this calculation example, the increase in the effective dose inside the shielding door was limited to within 1% when the gap S between the shielding body 26 and the ceiling 42 was 10 cm or less, within 10% when it was 30 cm or less, and within 15% when it was 50 cm or less.

[0029] On the other hand, when the shielding body 26 is installed, gaps are formed between the ceiling 42 and the shielding body 26, between the inner wall 22 and the shielding body 26, and between the shielding wall 14 and the shielding body 26, respectively. Depending on the installation method, it may be necessary to make the gap wider, but if the wall thickness is sufficient, the influence on the leakage to the outside is limited. Therefore, the shielding body 26 can be installed by providing a gap that is not difficult to construct with respect to the ceiling 42, the inner wall 22, and the shielding wall 14.

[0030] According to the present embodiment, even if a gap S is generated between the shielding body 26 and the ceiling 42, the influence on the effective dose applied to the entrance / exit 18 is limited. Therefore, similar to the conventional vertical wall, the dose in the maze 24 can be reduced by the shielding body 26. As a result, it is possible to reduce the shielding body of the shielding door 28 provided at the entrance / exit 18 and the shielding body for the duct sleeve provided in the maze 24.

[0031] In addition, unlike the conventional vertical wall integrated with the ceiling 42, since it is not necessary to construct simultaneously during the concrete placement of the shielding wall 14 or the ceiling 42, it is possible to avoid the complication of the ceiling shape, formwork, and shoring required when installing the conventional vertical wall, and the cost can be suppressed.

[0032] Further, the shielding body 26 is installed at the stepped portions 38 and 40 after the shielding wall 14 and the inner wall 22 are placed. In this case, the stepped portions 38 and 40 may be formed in a part near the ceiling of the shielding wall 14 and a part near the ceiling of the inner wall 22, and the prefabricated shielding body 26 may be placed on these stepped portions 38 and 40 and fixed with bolts or the like. The timing of installing the shielding body 26 may be either before or after the placement of the ceiling 42. Note that the present invention is not limited to this, and the shielding body 26 may be fixed to the stepped portion provided on either the shielding wall 14 or the inner wall 22 and provided in a cantilever beam shape. In this case, the shielding body 26 is installed at the stepped portion after either the shielding wall 14 or the inner wall 22 is placed. Further, the shielding body 26 may be provided in a cantilever beam shape from the stepped portion 40 of the shielding wall 14 and the stepped portion 38 of the inner wall 22, respectively, and arranged so as to abut against each other. The shielding body 26 may be suspended and fixed to the ceiling 42 with steel materials or the like. Further, the shielding body 26 may be fixed by combining these.

[0033] The gap S between the shielding body 26 and the ceiling 42 may be appropriately widened and designed, and ducts or pipes may be passed through this gap S. Alternatively, at the stage of prefabricating the shielding body 26, through holes for ducts or pipes may be provided in the shielding body 26.

[0034] As described above, according to the radiation shielding structure of the present invention, there is provided a housing chamber surrounded by a radiation shielding wall and a radiation shielding ceiling for housing a radiation generating device, an inner wall provided between the radiation generating device and the entrance / exit to prevent radiation from the radiation generating device from directly reaching the entrance / exit of the housing chamber, and a maze formed by partitioning with the inner wall and the radiation shielding wall and connected to the entrance / exit. A radiation shielding structure, wherein directly below the radiation shielding ceiling in the maze or directly below the radiation shielding ceiling between the inner wall and the radiation shielding wall, a radiation shielding body is provided in a hanging wall shape separately without being integrated with the radiation shielding ceiling. Since a radiation shielding body for reducing the incident amount of radiation is further provided, it is possible to reduce the dose incident in the maze and to save labor in construction.

[0035] Also, according to another radiation shielding structure of the present invention, since the radiation shielding body is supported by at least one of the inner wall and the radiation shielding wall, the radiation shielding body can be easily installed retroactively.

[0036] Also, according to another radiation shielding structure of the present invention, since the radiation shielding body is provided with a gap between it and the radiation shielding ceiling, it is possible to save labor in construction and at the same time limit the influence on the effective dose at the entrance / exit.

[0037] Also, according to another radiation shielding structure of the present invention, there is provided a method of constructing the above-described radiation shielding structure, wherein after placing at least one of the inner wall and the radiation shielding wall, the radiation shielding body is installed on at least one of the inner wall and the radiation shielding wall. Therefore, it is possible to save labor in construction and perform the construction.

[0038] Note that there are 17 international goals adopted at the United Nations Summit in September 2015, namely "Sustainable Development Goals (SDGs)". The radiation shielding structure and its construction method according to the present embodiment can contribute to the achievement of, for example, the goal of "9. Build the foundation for industry and technological innovation" among the 17 goals of these SDGs.

Industrial Applicability

[0039] As described above, the radiation shielding structure and its construction method according to the present invention are useful for radiation utilization facilities equipped with a maze such as a medical radiation shielding room. In particular, they are suitable for reducing the dose incident in the maze and saving labor in construction work.

Explanation of Reference Numerals

[0040] 10 Radiation shielding structure 12 Linac (radiation generating device) 14 Shielding wall (radiation shielding wall) 16 Accommodation room 18 Entrance / exit 20 Irradiation room 22 Inner wall 24 Maze 26 Shielding body (radiation shielding body) 28 Shielding door 30 Utilization plumb bob 32 Metal plate 34 End part 36 Opening 38, 40 Step part 42 Ceiling (radiation shielding ceiling)

Claims

1. A radiation shielding structure comprising a housing chamber surrounded by a radiation shielding wall and a radiation shielding ceiling, which houses a radiation generator, and an inner wall provided between the radiation generator and an entrance / exit of the housing chamber to prevent radiation from the radiation generator from directly reaching the entrance / exit of the housing chamber, and a maze connected to the entrance / exit, which is partitioned by the inner wall and the radiation shielding wall, wherein: A radiation shielding body, which is provided in a hanging wall shape separately from and not integrated with the radiation shielding ceiling directly below the radiation shielding ceiling in the maze or directly below the radiation shielding ceiling between the inner wall and the radiation shielding wall, is further provided to reduce the amount of incident radiation. The radiation shielding structure is characterized by this.

2. The radiation shielding structure according to claim 1, wherein the radiation shielding body is supported by at least one of the inner wall and the radiation shielding wall.

3. The radiation shielding structure according to claim 1 or 2, wherein the radiation shielding body is provided with a gap between the radiation shielding body and the radiation shielding ceiling.

4. A method for constructing the radiation shielding structure according to claim 1 or 2, wherein: After placing at least one of the inner wall and the radiation shielding wall, the radiation shielding body is installed on at least one of the inner wall and the radiation shielding wall. The method for constructing the radiation shielding structure is characterized by this.

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