Radiation shield structure

Abstract

To provide a radiation shield structure capable of reducing leakage dosage at a gateway without increasing the volume of a radiation utilization facility or making a distorted structure.SOLUTION: A maze 22 includes: a first leg 28 which is a passageway extending in a thickness direction of the maze inner wall 20 from an opening part 26 formed between a side end part 24 of the maze inner wall 20 and the radiation shield wall 14; and a second leg 30 which is a passage connecting the first leg 28 and the gateway 18 and extending along the maze inner wall 20. The second leg 30 includes a bent part 34 bending in a chevron shape on a side of the radiation generator 12 when viewed in a vertical direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a radiation shielding structure having a maze at the entrance and exit of, for example, a medical radiation irradiation room. [Background technology]

[0002] Conventionally, in radiation facilities such as medical linac rooms, a maze structure is provided between the irradiation room where radiation is irradiated and the entrance / exit to prevent radiation from leaking outside, and a shielding door is installed at the entrance / exit (see, for example, Patent Document 1). The maze in a linac room often has a two-legged structure.

[0003] 6(1) and (2) show an example of a conventional linac room equipped with a two-legged maze. As shown in these figures, the linac room 1 has an irradiation room 4 that is substantially rectangular in plan view and surrounded by a radiation shielding wall 3 with an iron plate 2 built in, and a two-legged maze 6 that is connected to an entrance 5 of the irradiation room 4. A linac device 7 that emits radiation is provided in the approximate center of the irradiation room 4, from which a usable wire weight C is formed. The maze 6 has a first leg A and a second leg B, and is provided along the maze inner wall 8. The maze inner wall 8 is a wall that protrudes from one radiation shielding wall 3 toward the opposing radiation shielding wall 3 so as to separate the irradiation room 4 from the entrance 5, and an opening 9 that connects the irradiation room 4 to the maze 6 is formed between the protruding end of the maze inner wall 8 and the opposing radiation shielding wall 3.

[0004] The first leg A of the maze 6 is provided on the side closer to the irradiation chamber 4, and the second leg B is provided on the side closer to the entrance / exit 5. The first leg A is short in length because its purpose is to connect the second leg B. In the example of FIG. 6, the length of the first leg A is approximately the same as the sum of the thickness of the maze inner wall 8 and the maze width. The second leg B is installed at a right angle or at a slight angle outward from the first leg A along the maze inner wall 8, and has a length approximately equal to the width of the irradiation chamber 4. The entrance / exit 5 is installed at the end of the second leg B or at a right angle near the end. The entrance / exit 5 is provided with a shielding door 5A having a function of shielding radiation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-097630 A Summary of the Invention [Problem to be solved by the invention]

[0006] The radiation entering the first leg A of the maze 6 from the irradiation chamber 4 is attenuated by the amount of the entrance area being reduced by a hanging wall (not shown) installed on the first leg A, but most of the radiation is scattered by the walls and floor of the first leg A, and some of this enters the second leg B. The scattered radiation that enters the second leg B travels along the straight wall of the second leg B while being collimated, and reaches the entrance 5. The attenuation of the radiation in the second leg B is 1 / L depending on the travel distance L [m]. 2 Since the distance is only subject to the law, it is desirable to make it longer, but due to its structure, it is limited by the width of the linac room 1.

[0007] In order to enlarge the first leg A and greatly reduce the radiation that is scattered and enters the second leg B, it is necessary to make the volume of the space more than double in order to increase the trap structure and distance. However, doing so would increase the volume of the linac chamber 1 and result in a distorted structure, so it cannot be said to have any merit.

[0008] The present invention has been made in consideration of the above, and aims to provide a radiation shielding structure that can reduce the leakage dose at entrances and exits without increasing the volume of a radiation utilization facility or making the structure distorted. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, the radiation shielding structure of the present invention is a radiation shielding structure comprising: a storage chamber that stores a radiation generating device and is surrounded by a radiation shielding wall; a maze inner wall provided between the radiation generating device and the entrance / exit to prevent radiation from the radiation generating device from directly reaching an entrance / exit of the storage chamber; and a maze that is partitioned by the maze inner wall and the radiation shielding wall and connected to the entrance / exit, wherein the maze has a first leg that is a passage extending in a thickness direction of the maze inner wall from a side end of the maze inner wall and an opening formed between the radiation shielding walls; and a second leg that is a passage that connects the first leg to the entrance / exit and extends along the maze inner wall, and the second leg has a bent portion that is bent in a dogleg shape toward the radiation generating device when viewed from the top / bottom direction.

[0010] Furthermore, another radiation shielding structure according to the present invention is characterized in that, in the above-mentioned invention, when a direction perpendicular to the passage direction of the first leg toward the second leg is defined as a reference direction, the angle between the passage direction from the first leg to the bent portion of the second leg and the reference direction is in the range of 10 to 20° when viewed from above and below.

[0011] Further, another radiation shielding structure according to the present invention is characterized in that, in the above-mentioned invention, the labyrinth inner wall is configured to have a thickness corresponding to the bent portion. Effect of the Invention

[0012] The radiation shielding structure according to the present invention is a radiation shielding structure comprising: a storage room for accommodating a radiation generating device and surrounded by a radiation shielding wall; a maze inner wall provided between the radiation generating device and the entrance / exit to prevent radiation from the radiation generating device from directly reaching an entrance / exit of the storage room; and a maze formed by the maze inner wall and the radiation shielding wall and connected to the entrance / exit, wherein the maze has a side end of the maze inner wall, a first leg which is a passage extending from an opening formed between the radiation shielding walls in the thickness direction of the maze inner wall, and a second leg which is a passage connecting the first leg and the entrance / exit and extending along the maze inner wall, and the second leg has a bent portion bent in a dog-leg shape toward the radiation generating device when viewed from above and below. This has the effect of reducing the leakage dose at the entrance / exit without increasing the volume of the radiation shielding structure, which is a radiation utilization facility, or making the structure distorted.

[0013] Furthermore, in another radiation shielding structure according to the present invention, when a direction perpendicular to the passage direction of the first leg toward the second leg is taken as a reference direction, the angle between the passage direction from the first leg to the bent portion of the second leg and the reference direction is in the range of 10 to 20° when viewed from above and below, thereby achieving the effect of effectively reducing the leakage radiation at the entrance and exit.

[0014] In addition, another radiation shielding structure according to the present invention has the above-mentioned invention, and since the inner wall of the maze is configured to have a thickness corresponding to the bent portion, it has the effect of preventing an increase in the leakage dose passing through the inner wall of the maze from the radiation generating device. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional plan view showing an embodiment of a radiation shielding structure according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional plan view showing a comparative example of the present invention. [Diagram 3] FIG. 3 is a contour diagram showing an example of the calculation result of the leakage dose. [Figure 4]FIG. 4 is a contour diagram showing an example of the calculation result of the leakage dose. [Diagram 5] FIG. 5 is a cross-sectional plan view showing another embodiment of a radiation shielding structure according to the present invention. [Figure 6] FIG. 6 is a cross-sectional plan view showing an example of a conventional radiation shielding structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the radiation shielding structure according to the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these preferred embodiments.

[0017] 1, a radiation shielding structure 10 according to an embodiment of the present invention includes a storage room 16 that stores a radiation generating device 12 and is surrounded by a radiation shielding wall 14, a maze inner wall 20 provided between the radiation generating device 12 and the entrance / exit 18 to prevent radiation from the radiation generating device 12 from directly reaching the entrance / exit 18 of the storage room 16, and a two-legged maze 22 that is partitioned by the maze inner wall 20 and the radiation shielding wall 14 and is connected to the entrance / exit 18. A shielding door having a radiation shielding function is provided at the entrance / exit 18.

[0018] The radiation shielding structure 10 of this embodiment is assumed to be the linac chamber 1 of Fig. 6(1) above. The radiation generating device 12 is assumed to be the linac device 7 that emits radiation, and is provided approximately in the center of the accommodation chamber 16. The accommodation chamber 16 is assumed to be the irradiation chamber 4 that is approximately rectangular in plan view. The radiation shielding wall 14 is provided at a position including the vertical width direction X of the accommodation chamber 16 and the horizontal width direction Y perpendicular to the vertical width direction X.

[0019] The maze inner wall 20 is a wall that protrudes in the width direction Y from a radiation shielding wall 14 (not shown) extending in the vertical width direction X toward the opposing radiation shielding wall 14 so as to separate the storage chamber 16 from the entrance / exit 18, and an opening 26 that connects the storage chamber 16 and the maze 22 is formed between the protruding end 24 (side end) of the maze inner wall 20 and the opposing radiation shielding wall 14.

[0020] The maze 22 has a first leg 28 and a second leg 30 and is disposed along the inner maze wall 20 .

[0021] The first leg 28 is a passageway that extends from the opening 26 in the thickness direction (vertical width direction X) of the maze inner wall 20 and abuts the radiation shielding wall 14, which also serves as the maze outer wall 32. The first leg 28 is short in length because its purpose is to connect the second leg 30. The length of the first leg 28 is approximately the same as the sum of the thickness of the maze inner wall 20 and the maze width of the second leg 30.

[0022] The second leg 30 is a passageway that connects the first leg 28 and the entrance 18 and extends from the protruding end 24 of the maze inner wall 20 along the maze inner wall 20 in the width direction Y. The second leg 30 has a bent portion 34 that is bent in a dogleg shape toward the radiation generating device 12 when viewed from the top-bottom direction. Specifically, the maze inner wall 20 forming the second leg 30 does not extend straight in the width direction Y from the outer end 36 of the protruding end 24 of the maze inner wall 20 toward the entrance 18, but extends linearly at an angle θ inward so as to approach the radiation generating device 12 as it proceeds from the outer end 36 in the width direction Y. Then, the angle is reversed at the bent portion 34 near the middle length of the second leg 30 and it is bent outward. In other words, it extends linearly at an angle from the bent portion 34 toward the entrance 18 in the width direction Y so as to move away from the radiation generating device 12. The maze width of the second leg 30 is approximately constant up to the entrance 18. Therefore, the maze outer wall 32 has a curved shape according to the arrangement angle of the maze inner wall 20 when viewed from the top-bottom direction. Note that the bent portion 34 provided on the second leg 30 of the present invention extends from the outer end portion 36 in the width direction Y away from the radiation generating device 12 as shown in Fig. 2, and does not bend toward the radiation generating device 12 near the middle length.

[0023] The angle θ at which the second leg 30 is bent inward is the angle between the width direction Y (reference direction) and the wall surface of the maze inner wall 20 from the outer end 36 to the bent portion 34 when viewed from the top-bottom direction. The larger the angle θ, the more the leakage radiation at the entrance / exit 18 can be reduced. In order to effectively reduce the leakage radiation, it is preferable to set the angle θ in the range of about 10 to 20°. The position of the bent portion 34 at which the second leg 30 is turned from the inward direction to the outward direction is preferably slightly shorter than the mid-length of the second leg 30 (the side closer to the first leg 28 than the mid-length position), because this allows the collimated radiation to be scattered and reduced quickly.

[0024] 3 and 4 are examples of contour diagrams of leakage dose calculated when the angle θ of the second leg 30 is set to 0°, 10°, 15°, and 20°. According to these diagrams, a reduction effect of leakage dose is expected to be about 10% when the angle θ is 10°, about 25% when it is 15°, and about 40% when it is 20°. By bending the second leg 30 inward, the length of the second leg 30 can be made longer than when it is straight, so that the attenuation effect over distance can be increased.

[0025] The thickness of the labyrinth inner wall 20 becomes the thinnest at the bent portion 34 near the angle reversal position when the inward bending angle θ of the second leg 30 becomes large. When the thickness becomes thin, the amount of leakage radiation from the radiation generating device 12 that penetrates the labyrinth inner wall 20 increases, and the leakage radiation may exceed the radiation reduction effect of the inward bending of the second leg 30. For this reason, in order to ensure an inner wall thickness that does not increase the amount of transmission, it is desirable to configure the labyrinth inner wall 20 with a thickness according to the labyrinth shape of the second leg 30. For example, as shown in FIG. 5, when the inward bending angle θ of the second leg 30 is large, it is desirable to form an inclined portion 38 on the accommodation chamber 16 side of the labyrinth inner wall 20 to increase the inner wall thickness so as to ensure a thickness (for example, a thickness of 100 cm or more) that does not increase the amount of transmission even at the bent portion 34 near the angle reversal position. In this way, it is possible to prevent an increase in the amount of leakage radiation that penetrates the labyrinth inner wall 20.

[0026] According to this embodiment, the labyrinth of the inwardly bent second legs 30 collimates the scattering direction of the radiation so as not to face the entrance / exit 18, and the labyrinth distance is also extended, so that the leakage dose at the entrance / exit 18 can be reduced. Therefore, the leakage dose at the entrance / exit 18 can be reduced without increasing the volume of the radiation shielding structure 10 or making it a distorted structure.

[0027] In addition, the shielding performance required for the shielding door of the entrance / exit 18 can be reduced, thereby reducing the manufacturing and installation costs of the shielding door. The amount of radiation leakage from ducts and sleeve through holes that are generally installed in the maze 22 can also be reduced, making it possible to reduce the size of the shielding shelves.

[0028] As described above, the radiation shielding structure according to the present invention is a radiation shielding structure including: a storage room that stores a radiation generating device and is surrounded by a radiation shielding wall; a maze inner wall provided between the radiation generating device and the entrance / exit to prevent radiation from the radiation generating device from directly reaching an entrance / exit of the storage room; and a maze that is partitioned by the maze inner wall and the radiation shielding wall and is connected to the entrance / exit. The maze has a side end of the maze inner wall, a first leg that is a passage extending from an opening formed between the radiation shielding walls in the thickness direction of the maze inner wall, and a second leg that connects the first leg to the entrance / exit and is a passage that extends along the maze inner wall, and the second leg has a bent portion that is bent in a dogleg shape toward the radiation generating device when viewed from the top / bottom direction. Therefore, it is possible to reduce the leakage dose at the entrance / exit without increasing the volume of the radiation shielding structure, which is a radiation utilization facility, or making the structure distorted.

[0029] In addition, in another radiation shielding structure according to the present invention, when a direction perpendicular to the passage direction of the first leg toward the second leg is taken as a reference direction, the angle between the passage direction from the first leg to the bent portion of the second leg and the reference direction is in the range of 10 to 20° when viewed from above and below, so that the leakage radiation at the entrance and exit can be effectively reduced.

[0030] In addition, in another radiation shielding structure according to the present invention, in the above-mentioned invention, the inner wall of the maze is configured to have a thickness corresponding to the bent portion, so that an increase in the leakage dose passing through the inner wall of the maze from the radiation generating device can be prevented. [Industrial Applicability]

[0031] As described above, the radiation shielding structure of the present invention is useful for radiation utilization facilities equipped with a maze, such as a medical radiation irradiation room, and is particularly suitable for reducing the leakage dose at entrances and exits without increasing the volume of the radiation utilization facility or making the structure distorted. [Explanation of symbols]

[0032] 10 Radiation shielding structure 12 Radiation Generator 14 Radiation shielding wall 16 Containment Room 18 Entrance / Exit 20 Maze inner wall 22 Maze 24 Projecting end (side end) 26 Opening 28 1st leg 30 Second leg 32 Maze outer wall 34 Bend 36 Outer end 38 Slope X-Vertical direction Y Width direction θ angle

Claims

1. A radiation shielding structure comprising: a storage chamber that stores a radiation generating device and is surrounded by a radiation shielding wall; a maze inner wall that is provided between the radiation generating device and the entrance / exit of the storage chamber to prevent radiation from the radiation generating device from directly reaching the entrance / exit of the storage chamber; and a maze that is partitioned and formed by the maze inner wall and the radiation shielding wall and is connected to the entrance / exit, a first leg which is a passageway extending in a thickness direction of the maze inner wall from a side end of the maze inner wall and an opening formed between the radiation shielding walls; and a second leg which is a passageway extending along the maze inner wall, connecting the first leg and the entrance / exit, wherein the second leg has a bent portion which is bent in a dog-leg shape toward the radiation generating device when viewed from above and below.

2. 2. The radiation shielding structure according to claim 1, wherein, when a direction perpendicular to a passage direction of the first leg and toward the second leg is defined as a reference direction, an angle between the passage direction from the first leg to the bent portion of the second leg and the reference direction is in a range of 10 to 20 degrees when viewed from above and below.

3. 3. The radiation shielding structure according to claim 1, wherein the inner wall of the labyrinth is configured to have a thickness corresponding to the bent portion.

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