Shelters and radioactivity suppression structures

Abstract

[Subject] The subject of the present invention is to solve the problems existing in the prior art, that is, to provide a shielding body that does not produce a through gap, that is, can suppress the leakage of neutron rays, and a radioactivity suppression structure using the shielding body. [Solution] The shielding body of the present invention is a shielding body that suppresses the radioactivity of the wall body in the neutron generation room, and is a shielding body formed by a plurality of plate-like panels. The plate-like panel is composed of an n-gonal upper surface (n is a natural number greater than 3), an n-gonal lower surface, and n side surfaces, and is a shape in which the upper surface and the lower surface are arranged approximately in parallel (including parallel), and the side surface is formed by a slope surface inclined relative to the upper surface. Moreover, the side surface of the plate-like panel is butted against the side surface of other plate-like panels, and is assembled in a planar shape by joining two adjacent plate-like panels in a state in which parts of the panels overlap each other.

Description

Technical Field

[0001] The present invention relates to a technology for suppressing the radioactivity of indoor walls of radiation medical facilities or research facilities that generate neutrons, such as so-called neutron capture therapy (BNCT). More specifically, the present invention relates to a shielding body that is assembled by overlapping adjacent plate-like panels on all sides and joining them together, and a radioactivity suppression structure using the shielding body. Background Art

[0002] Neutron capture therapy is a treatment method that allows boron compounds to enter cancer cells and destroy them through nuclear reactions between boron and neutrons. Boron (especially 10B) has the property of reacting strongly with low-energy neutrons, including thermal neutrons. As a result of the nuclear fission reaction between boron and neutrons in cancer cells, powerful particle rays (alpha rays) are generated, which destroy cancer cells.

[0003] Since the range of particle beams generated by nuclear fission reactions is about the diameter of cancer cells (about 10~14μm), they do not affect normal cells other than cancer cells. Conventional treatments using X-rays and gamma rays cause roughly the same physical damage to normal cells as cancer cells, so neutron capture therapy is also called "cancer cell selective treatment" and is currently considered the most ideal treatment method for the treatment of malignant brain tumors, malignant melanoma, etc.

[0004] Furthermore, in neutron capture therapy, although irradiation of neutron rays to the patient is performed using an irradiator, an accelerator, etc., the irradiation is of course performed in a room sealed by a wall or the like that prevents the neutron rays from leaking to the outside. Of course, the irradiated neutron rays are not completely absorbed by the patient, but are partially absorbed by the wall or the like. Since neutrons have no electric charge, it is relatively easy for them to reach the nuclei in the material, and the absorption phenomenon of low-energy neutrons, which are preferably used in neutron capture therapy, is significant. As a result of a part of the material constituting the wall absorbing neutrons, there is a so-called radioactivity phenomenon in which a radioactive isotope is generated from a stable isotope.

[0005] It is known that concrete that has been radioactively treated with short half-life nuclides emits a large amount of radiation. Therefore, people in the room are exposed to unnecessary radiation hazards. In addition, when exposed to neutrons for a long time, radioactivity progresses in the concrete wall, and a large amount of long half-life nuclides are generated. As a result, the radioactive concrete wall needs to be disposed of as radioactive waste, which requires a huge disposal cost compared to ordinary waste.

[0006] As described above, in facilities and the like that generate neutrons that cause radioactivity, radioactivity of the wall becomes a major problem, and radioactivity prevention measures using shielding bodies have been implemented so far. That is, of course, neutron rays reaching the wall body are suppressed by setting a shielding body on the front side of the wall body. The shielding body is sometimes constructed as a whole on site by a foundation concrete construction method or the like, and sometimes it is constructed by assembling parts transported in order to shorten the construction time on site. For example, Patent Document 1 proposes a technology for constructing a shielding body by assembling blocks composed of steel plates and concrete, and Patent Document 2 proposes a technology for constructing a shielding body by assembling strip-shaped parts.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2004-317242

[0010] Patent document 2: Japanese Patent Application Laid-Open No. 08-054495. Summary of the invention

[0011] Problems to be solved by the invention

[0012] If the shielding body is constructed using blocks or parts (hereinafter referred to as “parts etc.”) as in Patent Documents 1 and 2, the construction time on site can be shortened and a certain degree of completion quality can be expected.

[0013] However, according to the conventional technology, it is impossible to avoid the through gaps (small holes that penetrate the shielding body in the thickness direction) generated in the joint surfaces of adjacent parts, etc. For example, in Patent Document 1, although the through gaps can be avoided by the crank-shaped partition wall for the joint surfaces adjacent to the left and right, the through gaps cannot be avoided in the joint surfaces adjacent to the top and bottom. On the other hand, in Patent Document 2, although the through gaps can be avoided by the convex and concave connecting surfaces for the joint surfaces adjacent to the top and bottom, the through gaps cannot be avoided in the joint surfaces adjacent to the left and right. In the shielding body with the through gaps generated as it is, the neutron rays reach the wall through the through gaps, and the effect of preventing the radioactivity of the wall cannot be fully obtained.

[0014] The present invention aims to solve the problems existing in the prior art, that is, to provide a shielding body which does not generate a through gap, that is, can suppress the leakage of neutron rays, and a radioactivity suppression structure using the shielding body.

[0015] Solutions to Solve Problems

[0016] The present invention is an invention made by focusing on the point that a shielding body is assembled while the plate-like panels are partially overlapped with adjacent plate-like panels on all sides, and is an invention based on a conception that has never been seen before.

[0017] The shielding body of the present invention is a shielding body for suppressing the radioactivity of the wall body in the neutron generation room (a room where neutrons are generated), and is a shielding body formed of a plurality of plate-like panels. The plate-like panels are composed of an n-gonal upper surface (n is a natural number greater than or equal to 3), an n-gonal lower surface, and n side surfaces, and are in a shape in which the upper surface and the lower surface are arranged substantially in parallel (including parallel), and all the side surfaces are formed by slope surfaces inclined relative to the upper surface. The side surfaces of the plate-like panels are butted against the side surfaces of other plate-like panels, and are assembled in a planar shape by joining the two adjacent plate-like panels in a state in which parts of the panels overlap each other.

[0018] The shielding body of the present invention can also be configured to have a thin plate-shaped engaging protrusion on the side of the plate-shaped panel instead of the slope surface. In this case, the engaging protrusions of two adjacent plate-shaped panels are joined in a state where they overlap each other to be assembled in a planar shape.

[0019] The shielding body of the present invention can also be configured as a plate-like panel stacked in the order of a surface panel, an intermediate panel, and a back panel. In addition, the surface panel is a plate-like member using a quasi-non-combustible material or a non-combustible material, the intermediate panel is a plate-like member using wood with higher strength than the surface panel, and the back panel is a film-like or plate-like member containing a boron compound such as boron carbide. In this case, two adjacent plate-like panels are joined so that the surface panel is continuous for assembly.

[0020] The radioactivity suppression structure of the present invention is a structure for suppressing the radioactivity of the wall body in the neutron generation room, and is a structure having a first shielding body. The first shielding body is the shielding body of the present invention, and is a shielding body using plate-like panels stacked in the order of a surface panel, an intermediate panel, and a back panel. In addition, the first shielding body is provided in such a manner that the surface panel becomes the indoor side and the back panel becomes the wall body side.

[0021] The radioactivity suppression structure of the present invention can also be configured to include a gap portion, a second shielding body, an inspection hole, and a plurality of inspection cores. The gap portion is provided between the inner panel and the wall body, and the second shielding body is a shielding body of the present invention disposed between the gap portion and the wall body. In addition, the inspection hole penetrates the second shielding body and is further perforated in the thickness direction of the wall body, and the inspection core is formed using the same material as the wall body. In addition, the second shielding body is provided in a replaceable manner, and a measuring element for evaluating the degree of radioactivity is provided on the indoor inner surface of the second shielding body, and a plurality of inspection cores are arranged in parallel in the thickness direction of the wall body.

[0022] Effects of the Invention

[0023] The shielding body and the radioactivity suppression structure of the present invention have the following effects.

[0024] (1) No through gaps are generated between adjacent plate-shaped panels, which can suppress the leakage of neutron rays, that is, suppress the radioactivity of the wall, compared with the previous technology. As a result, it is possible to reliably avoid unnecessary radioactive hazards to people in the neutron generating room and to minimize the discharge of radioactive waste.

[0025] (2) Ability to provide clean medical facilities, research facilities, inspection facilities, industrial facilities, etc. at a high cost-effectiveness throughout the entire life cycle and without generating radioactive waste.

[0026] (3) The radioactivity suppression structure including the second shielding body, the inspection hole, and the plurality of inspection cores can confirm the degree of radioactivity at any time even after the start of use, and can replace the second shielding body before radioactivity is generated. This can prevent the second shielding body from becoming radioactive waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a plan view showing a state in which the radioactivity suppression structure of the present invention is installed in a neutron generation chamber.

[0028] Figure 2 (a) is a side view showing an inclined plate-like panel, Figure 2 (b) is a plan view showing a shielding body assembled from inclined plate-like panels.

[0029] Figure 3 (a) is a side view showing a protruding plate-like panel, Figure 3 (b) is a plan view showing a shielding body assembled from protruding plate-like panels.

[0030] Figure 4 It is a cross-sectional view showing the radioactivity suppression structure according to the first embodiment.

[0031] Figure 5 It is a cross-sectional view showing a radioactivity suppression structure according to the second embodiment.

[0032] Figure 6 It is a cross-sectional view showing a radioactivity suppression structure according to a third embodiment.

[0033] Figure 7 It is a flowchart showing the main steps of the wall body management method of the present invention.

[0034] Figure 8 It is a step diagram showing the main steps of the wall body management method of the present invention. DETAILED DESCRIPTION

[0035] 1. General Overview

[0036] An example of an embodiment of the shielding body and the radioactivity suppression structure of the present invention will be described with reference to the drawings. Figure 1 1 is a plan view showing a state where a radioactive suppression structure 200 of the present invention is installed in a room where neutrons are generated (hereinafter referred to as a "neutron generation room"). The neutron generation room shown in the figure is enclosed (sealed) by a wall body made of concrete (hereinafter referred to as a "concrete wall body CW"), and an accelerator ND for generating neutrons is installed in the room. Figure 1 Although a neutron generation chamber provided with an accelerator ND is shown in the figure, the present invention is not limited to the accelerator ND, and any facility that generates neutrons can effectively implement the present invention.

[0037] The radioactive suppression structure 200 of the present invention is as follows Figure 1 As shown in the figure, the first shielding body 210 is provided on the indoor side (front side) of the concrete wall CW, in other words, in a manner covering the surface of the concrete wall CW. In addition, the radioactivity suppression structure 200 is provided with the first shielding body 210 after ensuring a predetermined distance from the surface of the concrete wall CW, that is, it can also be provided with a space (hereinafter referred to as "gap 220") between the concrete wall CW and the first shielding body 210. Further, as Figure 1 As shown, a structure in which the second shielding body 230 is provided between the concrete wall body CW and the gap portion 220 may be adopted.

[0038] The first shielding body 210 is a shielding body that includes wood (such as hard fiberboard, etc.) and a member containing a boron compound headed by boron carbide, and the neutrons are attenuated by the wood, and further the neutrons are changed into thermal neutrons when passing through the wood, and the neutrons reaching the concrete wall CW are greatly reduced by absorbing the thermal neutrons by boron. In addition, the gap 220 has a function of attenuating the energy of the neutrons by ensuring a predetermined distance until reaching the concrete wall CW. Furthermore, the second shielding body 230 is a shielding body that absorbs the neutrons that reach the concrete wall CW in advance. In addition, the second shielding body 230 is a shielding body that is set in a manner that can be easily replaced, and is scheduled to be replaced with a new second shielding body 230 when it is considered that radioactivity has progressed in the future, and it can be said that it acts as a protective material for the concrete wall CW.

[0039] The shielding body of the present invention is a shielding body used as the first shielding body 210 and the second shielding body 230, and is a shielding body assembled by joining a plurality of plate-like panels. Moreover, the plate-like panels are the components (accessories) used to assemble the shielding body of the present invention, and are plate-like objects that constitute a part of the shielding body of the present invention. The shielding body of the present invention can be transported to the site (in this case, the neutron generation chamber) in a pre-assembled state (that is, the state of a finished product) for installation, or the necessary number of plate-like panels can be transported and assembled on site. In addition, the plate-like panels can be made into a shape that can be easily assembled. Specifically, the plate-like panels can be modularized in such a way that they are all the same shape without having to be selected according to the configuration position, and in such a way that they are symmetrical shapes (point symmetry, line symmetry, etc.) without having to consider the configuration posture (configuration direction).

[0040] 2. Shielding

[0041] An example of the shielding body of the present invention will be described in detail with reference to the drawings. The radioactivity suppression structure 200 of the present invention is a structure formed using the shielding body of the present invention, so the shielding body of the present invention will be described first, followed by the radioactivity suppression structure 200 of the present invention.

[0042] Figure 2 1 is a diagram showing a shielding body 100 of the present invention assembled from plate-like panels (hereinafter referred to as "inclined plate-like panels 110") whose side surfaces are inclined relative to the upper surface and the lower surface. Figure 2 (a) is a side view showing the inclined plate-like panel 110, Figure 2 (b) is a plan view showing the shielding body 100. In addition, Figure 2 In (b), a cross-sectional view taken along the arrow XX is shown below the plan view, and a cross-sectional view taken along the arrow YY is shown on the right side of the plan view.

[0043] like Figure 2 As shown in (a), the inclined plate-like panel 110 is composed of an upper surface 11, a lower surface 112, and a side surface 113. In addition, the upper surface 111 and the lower surface 112 are arranged to be substantially parallel (including parallel), and the side surface 113 is set as a slope surface inclined relative to the upper surface 111 and the lower surface 112. In addition, the shapes of the upper surface 11 and the lower surface 112 are set to be polygonal, and the side surface 113 is set to the amount of the number of sides of the polygon. In other words, the inclined plate-like panel 110 is of course composed of an n-gonal upper surface 111 (n is a natural number greater than 3), an n-gonal lower surface 112, and n side surfaces 113. In order to set it without considering the configuration posture as already described, the shape of the upper surface 111 and the lower surface 112 can be a square or a regular octagon.

[0044] For convenience, Figure 2 Although the left and right side surfaces 113 are shown as sloped surfaces in (a), in reality, all side surfaces 113 are sloped surfaces inclined relative to the upper surface 111 (lower surface 112). For example, if the upper surface 111 and the lower surface 112 are square in shape, all four side surfaces 113 are sloped surfaces.

[0045] In addition, if Figure 2 As shown in (a), the side surfaces 113 (the side surface 113a on the left and the side surface 113b on the right) facing each other are arranged to be substantially parallel (including parallel) to each other. Figure 2 The side surface 113c shown in the front in (a) and the side surface 113 (not shown) arranged on the side of the paper are also arranged to be roughly parallel. That is, when the inclined plate-like panel 110 is viewed from the side, its shape becomes a parallelogram, and the side surfaces 113 facing each other are of course different inclined surfaces even if they are roughly parallel. For example, although Figure 2 The side surface 113a on the left side shown in (a) is inclined from the lower surface 112 to the upper surface 111 inwardly (the center side of the inclined plate-like panel 110) (hereinafter, for convenience, referred to as "inward inclination"), but the side surface 113b on the right side is inclined from the lower surface 112 to the upper surface 111 outwardly (hereinafter, for convenience, referred to as "outward inclination"). In addition, the inclination angle of the side surface 113 relative to the upper surface 111 (lower surface 112) can be appropriately designed to 45°, 60°, etc. according to the conditions on site.

[0046] like Figure 2 As shown in (b), the shielding body 100 of the present invention can be formed by joining a plurality of (four in the figure) inclined plate-like panels 110 in a planar shape. More specifically, as shown in the XX cross-sectional view and the YY cross-sectional view, the side surfaces 113 of the adjacent (adjacent) inclined plate-like panels 110 are joined in a state where they are butted (contacted) with each other. At this time, the upper surface 111 and the lower surface 112 of the adjacent inclined plate-like panels 110 form a series of planes, that is, the "inner inclined side surface 113" in one inclined plate-like panel 110 and the "outer inclined side surface 113" in another inclined plate-like panel 110 are arranged in a state where they are matched.

[0047] When the side surfaces 113 are arranged in a butted state, the adjacent inclined plate-like panels 110 are connected (fixed) by fasteners such as screws and nails. Alternatively, the adjacent inclined plate-like panels 110 may be connected by adhesives or the like, or may be connected by welding depending on the material of the side surfaces 113.

[0048] As described above, the shielding body 100 of the present invention is assembled by joining the side surfaces 113 of the adjacent inclined plate-like panels 110 in a state where the side surfaces 113 are butted against each other, that is, in a state where a portion (side surface 113) of the adjacent inclined plate-like panels 110 overlap. Therefore, no through gap (a small hole that penetrates the shielding body in the thickness direction) is generated in the horizontal joint portion JH in the horizontal direction indicated by the dotted circle in the XX cross-sectional view and the vertical joint portion JV in the vertical direction indicated by the dotted circle in the YY cross-sectional view. Of course, no through gap is generated in the concentrated joint portion JC where the corners of the four inclined plate-like panels 110 are concentrated, so it is of course possible to suppress the leakage of neutron rays more than before.

[0049] In addition to the inclined plate-like panel 110 , the shielding body 100 of the present invention can also be assembled using a plate-like panel having engaging protrusions provided on the side (hereinafter referred to as a “protrusion-type plate-like panel 120 ”). Figure 3 1 is a diagram showing a shielding body 100 of the present invention assembled using a protruding plate-like panel 120. Figure 3 (a) is a side view showing a protruding plate-like panel 120, Figure 3 (b) is a plan view showing the shielding body 100. Figure 3 In (b), a cross-sectional view taken along the arrow XX is shown below the plan view, and a cross-sectional view taken along the arrow YY is shown on the right side of the plan view.

[0050] like Figure 3 As shown in (a), the protruding plate-like panel 120 is composed of an upper surface 121, a lower surface 122, and a side surface 123, and the upper surface 121 and the lower surface 122 are arranged to be approximately parallel (including parallel). Similar to the inclined plate-like panel 110, the shapes of the upper surface 121 and the lower surface 122 are set to be polygonal, and the side surface 123 is set to the number of sides of the polygon. In other words, the protruding plate-like panel 120 is of course composed of an n-gonal upper surface 121 (n is a natural number greater than 3), an n-gonal lower surface 122, and n side surfaces 123. As already described, in order to set it without considering the configuration posture, the shape of the upper surface 121 and the lower surface 122 can be a square or a regular octagon.

[0051] like Figure 3 As shown in (a), a thin plate-shaped engaging protrusion 124 is provided on the side surface 123 of the protrusion type plate-shaped panel 120. Figure 3 (a) shows the engagement protrusions 124 provided on the left and right side surfaces 123 , but in reality the engagement protrusions 124 are provided on all the side surfaces 123 . For example, if the upper surface 121 and the lower surface 122 are in a square shape, the engagement protrusions 124 are provided on all four side surfaces 123 .

[0052] In addition, if Figure 3 As shown in (a), the engaging protrusions 124 provided on the opposing side surfaces 123 (the left side surface 123a and the right side surface 123b) are arranged so that the two sides are at different positions (heights). Figure 3 In the case of (a), the left side surface 123a is provided with an engagement protrusion 124 at an upper position in the thickness direction (hereinafter referred to as "upper engagement protrusion 124U"). The right side surface 123b is provided with an engagement protrusion 124 at a lower position in the thickness direction (hereinafter referred to as "lower engagement protrusion 124L"). Figure 3 The side surface 123 c shown in the front in (a) and the side surface 123 disposed on the back side of the paper (not shown) are also provided with the upper engaging protrusion 124U on one hand and the lower engaging protrusion 124L on the other hand substantially parallel to each other.

[0053] like Figure 3 As shown in (b), the shielding body 110 of the present invention can be formed by joining a plurality of (four in the figure) protrusion-type plate-like panels 120 in a planar shape. In more detail, as shown in the XX cross-sectional view and the YY cross-sectional view, the protrusion-type plate-like panels 120 that are adjacent (adjacent) are joined in a state where the engaging protrusions 124 overlap with each other. At this time, the upper surface 121 and the lower surface 122 of the adjacent protrusion-type plate-like panels 120 are arranged in a manner such that the upper surface 121 and the lower surface 122 form a series of planes, that is, the "upper segment engaging protrusion 124U" of one protrusion-type plate-like panel 120 overlaps with the "lower segment engaging protrusion 124L" of another protrusion-type plate-like panel 120. Therefore, the protruding lengths (in Figure 3 It is desirable that the lengths (in the horizontal direction in (a)) are set to the same extent. In addition, when the two engaging protrusions 124 (upper engaging protrusion 124U and lower engaging protrusion 124L) are overlapped, the thickness of the engaging protrusion 124 can be made approximately 1 / 2 of the thickness of the general part (central part) of the protrusion type plate-like panel 120 in a manner that is the same as the thickness of the general part (central part) of the protrusion type plate-like panel 120.

[0054] When the upper engaging protrusion 124U and the lower engaging protrusion 124L are arranged in an overlapping state, the adjacent protrusion type plate-like panels 120 are connected (fixed) by fasteners such as screws and nails. Alternatively, the adjacent protrusion type plate-like panels 120 may be connected by adhesives or the like, and may also be connected by welding depending on the material of the engaging protrusion 124.

[0055] As described above, the shielding body 100 of the present invention is assembled by combining the upper engaging protrusions 124U and the lower engaging protrusions 124L of the adjacent protrusion type plate-like panels 120 in a state where the upper engaging protrusions 124U and the lower engaging protrusions 124L overlap, that is, in a state where a part of the adjacent protrusion type plate-like panels 120 overlap. Therefore, no through gap is generated in the horizontal joint portion JH in the horizontal direction indicated by the dotted circle in the XX cross-sectional view and the vertical joint portion JV in the vertical direction indicated by the dotted circle in the YY cross-sectional view. Of course, no through gap is generated in the concentrated joint portion JC where the corners of the four protrusion type plate-like panels 120 are concentrated, so it is of course possible to suppress the leakage of neutron rays more than before.

[0056] The inclined plate-like panel 110 and the protruding plate-like panel 120 can be set as a single-layer structure composed of the same material, or as a multi-layer structure in which two or more components are stacked. For example, the inclined plate-like panel 110 and the protruding plate-like panel 120 can be set as a three-layer structure in which a surface plate, an intermediate plate, and a back plate are stacked in order. In this case, the surface plate can be set as a plate-like member using a gypsum plasterboard, a dolomite plasterboard, or a resin board, and in particular, when a radioactive suppression structure 200 is set for the wall or ceiling, a quasi-non-combustible material or a non-combustible material can also be used. On the other hand, for the intermediate plate, a plate-like wooden member using a hardwood with a high specific gravity such as purple heart wood and heavy ant wood (hereinafter referred to as "hardwood, etc.") can be used, and for the back panel, a film-like or plate-like member composed of a resin containing boron, for example, a member formed by molding a resin containing B4C can be used. Of course, if the resin material contains boron, it is not limited to B4C resin, and other resin materials such as components in which anhydrous boric acid is mixed with resin, components in which powdered gray borate is mixed with resin, etc. can also be used as the inner panel.

[0057] Furthermore, wood containing a large amount of hydrogen can attenuate neutrons. That is, even if only the middle plate has the effect of attenuating neutrons, it can also suppress the radioactivity of the concrete wall CW when a small amount of neutrons is targeted. Therefore, when the radioactivity suppression structure 200 is set in a neutron generation room where a small amount of neutrons are expected to be generated, the inclined plate-like panel 110 and the protruding plate-like panel 120 can be used without the inner panel (i.e., composed of the surface panel and the middle plate), or the inclined plate-like panel 110 and the protruding plate-like panel 120 composed of only the middle plate can be used. In addition, for the sake of convenience, the inclined plate-like panel 110 and the protruding plate-like panel 120 stacked in the order of the surface plate, the middle plate, and the inner plate are referred to as the "three-layer inclined plate-like panel 110" and the "three-layer protruding plate-like panel 120", respectively, and the inclined plate-like panel 110 and the protruding plate-like panel 120 composed of the surface plate and the middle plate are referred to as the "two-layer inclined plate-like panel 110" and the "two-layer protruding plate-like panel 120", respectively, and the inclined plate-like panel 110 and the protruding plate-like panel 120 composed only of the middle plate are referred to as the "single-layer inclined plate-like panel 110" and the "single-layer protruding plate-like panel 120", respectively.

[0058] 3. Radioactive Inhibition Structure

[0059] Next, an example of the radioactivity suppression structure 200 of the present invention will be described in detail with reference to the drawings. In addition, the radioactivity suppression structure 200 of the present invention is a structure formed using the shielding body 100 described so far, so it is assumed that only the contents unique to the radioactivity suppression structure 200 of the present invention will be described to avoid duplication of the contents described using the shielding body 100. That is, the contents not described here are the same as those described in "2. Shielding body".

[0060] As described above, the radioactivity suppression structure 200 of the present invention can be roughly divided into: a method in which the first shielding body 210 is directly provided on the surface of the concrete wall body CW (hereinafter referred to as the "first embodiment"); a method in which the gap 220 and the first shielding body 210 are provided in front of the concrete wall body CW (hereinafter referred to as the "second embodiment"); and a method in which the second shielding body 230, the gap 220 and the first shielding body 210 are provided in front of the concrete wall body CW (hereinafter referred to as the "third embodiment"). Each embodiment will be described in turn below.

[0061] (First embodiment)

[0062] Figure 42 is a cross-sectional view showing a radioactivity suppression structure 200 according to the first embodiment, and is a cross-sectional view obtained by cutting a concrete wall body CW forming a floor along a vertical plane. In addition, in this figure, although a first shielding body 210 is provided on the upper surface of the concrete wall body CW forming the floor, the radioactivity suppression structure 200 of the present invention can also be set to a structure in which the first shielding body 210 is provided in front of the concrete wall body CW forming the ceiling surface or the side surface, not limited to the floor.

[0063] The first shielding body 210 is a shielding body assembled using the shielding body 100 of the present invention, for example, a three-layer inclined plate-like panel 110 and a three-layer protruding plate-like panel 120. More specifically, it is a panel assembled by joining two adjacent three-layer inclined plate-like panels 110 (protruding plate-like panels 120) in a continuous manner of the surface panel (the back panel). Therefore, the first shielding body 210 is as follows Figure 4 As shown in the figure, the structure is formed by stacking the surface plate 211, the middle plate 212, and then the inner plate 213 in the order of thickness (in Figure 4 The surface plate 211 is a plate-like member that is larger than the surface (in which the upper and lower dimensions are shown). Since the three-layer inclined plate-like panel 110 and the three-layer protruding plate-like panel 120 described above are used for assembly, the surface plate 211 becomes a plate-like member using a gypsum plasterboard, a dolomite plasterboard or a resin board, and the intermediate plate 212 becomes a plate-like wooden member using hardwood such as purple heart wood and heavy ant wood. In addition, the reason for using hardwood or the like as the intermediate plate 212 is because it contains a large amount of hydrogen for elastic scattering of neutrons, and it is to ensure a considerable strength (shear force, compression force, tensile force, etc.) as the first shielding body 210. The intermediate plate 212 can also be set as a member with higher strength than the surface plate 211, or it can be set as a member with lower strength than the surface plate 211.

[0064] In addition, as already described, the surface plates of the three-layer inclined plate-shaped panel 110 and the three-layer protruding plate-shaped panel 120 are film-shaped or plate-shaped members made of a resin containing boron, so the inner panel 213 of the first shielding body 210 is also a film-shaped or plate-shaped member made of a resin containing boron, for example, a member formed by molding a resin including B4C. Of course, if it is a resin material containing boron, it is not limited to B4C resin, and it can also be a member made of other resin materials such as a member made of anhydrous boric acid mixed with resin, a member made of powdered gray borate mixed with resin, etc.

[0065] Regarding the first shielding body 210, Figure 4As shown in the figure, the surface plate 211 is set on the indoor side and the inner plate 213 is set on the concrete wall CW side by screws, nails or adhesives. As a result, the neutrons that pass through the surface plate 211 and reach the middle plate 212 are slowed down by the large amount of hydrogen included in the hardwood, etc., and the slowed-down neutrons reach thermal equilibrium with the surroundings and become thermal neutrons (so-called elastic scattering). In addition, the thermal neutrons that reach the inner plate 213 are absorbed by boron, thereby greatly suppressing the amount of neutrons that reach the concrete wall CW, that is, of course, suppressing the radioactivity of the concrete wall CW.

[0066] The first shielding body 210 may be a shielding body using a two-layer inclined plate-like panel 110, a two-layer protruding plate-like panel 120, or a single-layer inclined plate-like panel 110, a single-layer protruding plate-like panel 120, in addition to the three-layer inclined plate-like panel 110 and the three-layer protruding plate-like panel 120. When the two-layer inclined plate-like panel 110 and the two-layer protruding plate-like panel 120 are used, the first shielding body 210 is installed by screws, nails, adhesives, etc. in such a manner that the surface plate 211 is on the indoor side and the middle plate 212 is on the CW side of the concrete wall.

[0067] (Second embodiment)

[0068] Figure 5 2 is a cross-sectional view showing a radioactivity suppression structure 200 according to the second embodiment, and is a cross-sectional view obtained by cutting a concrete wall CW forming the floor along a vertical plane. As shown in the figure, the radioactivity suppression structure 200 according to the second embodiment is configured to include a void 220 in addition to the first shielding body 210. In the case of a neutron generation chamber that generates a large number of neutrons, there is a case where the first shielding body 210 cannot absorb all the neutrons, and the void 220 is used to attenuate the neutrons that pass through the first shielding body 210. The void 220 can be formed by arranging a partition wall between the concrete wall CW and the first shielding body 210. For example, the void 220 can be formed by arranging the partition wall discretely (dispersedly) at a plurality of positions, or by arranging the groove steel or H-shaped steel in a linear or grid-like manner.

[0069] By providing the gap 220, neutrons that are not absorbed by the back panel 213 and pass through the first shielding body 210 are forced to move a predetermined distance to reach the concrete wall CW, thereby attenuating the energy of the neutrons, that is, naturally suppressing the radioactivity of the concrete wall CW.

[0070] (Third Embodiment)

[0071] Figure 62 is a cross-sectional view showing a radioactivity suppression structure 200 according to a third embodiment, and is a cross-sectional view obtained by cutting a concrete wall body CW forming a side wall along a horizontal plane. As shown in the figure, the radioactivity suppression structure 200 according to the third embodiment is configured to include a second shielding body 230 in addition to a first shielding body 210 and a gap 220. The second shielding body 230 is a shielding body assembled using an inclined plate-like panel 110 and a protruding plate-like panel 120 (hereinafter collectively referred to as "plate-like panels") using the shielding body 100 of the present invention. In this case, the inclined plate-like panel 110 and the protruding plate-like panel 120 can be a plate-like member of a so-called RC (Reinforced Concrete) panel. In addition, the second shielding body 230 is arranged in a manner in contact with the surface of the concrete wall body CW, and is provided in a manner that can be easily replaced by using expansion bolts or the like.

[0072] like Figure 6 As shown, a gap portion 220 is formed inside the room of the second shielding body 230, and a first shielding body 210 is further provided inside the room. Moreover, a measuring element 240 is attached to a portion of the surface of the second shielding body 230 so as to be located in the gap portion 220. At this time, the measuring element 240 may be attached to a representative plate-shaped panel among the plate-shaped panels constituting the second shielding body 230, or may be attached to a plurality of (or all) selected plate-shaped panels. The measuring element 240 is a measuring element for obtaining a measurement value for evaluating the degree of radioactivity, and may be manufactured as a dedicated measuring element, or may utilize a measuring element that has been used in the past (e.g., circulated in the market).

[0073] Although the thermal neutrons are absorbed by the back panel 213 of the first shielding body 210 and the energy of the neutrons is attenuated by the gap 220, there is still a concern that some neutrons may reach the concrete wall CW, so in the third embodiment, a second shielding body 230 is further provided in front of the concrete wall CW. However, when the second shielding body 230 continuously receives neutrons for a long time, it is also considered that the second shielding body 230 will become radioactive and must be treated as radioactive waste. Therefore, the structure is set to be able to replace the second shielding body 230 before it becomes radioactive, so the measuring element 240 is provided in a manner that the degree of radioactivity of the second shielding body 230 can be grasped regularly, and of course, it is provided so that the second shielding body 230 can be replaced.

[0074] In addition, in the radioactivity suppression structure 200 of the third embodiment, as Figure 6As shown, an inspection hole 250 can also be provided. In addition, a plurality of (four in the figure) inspection cores 260 are arranged in the inspection hole 250. The inspection hole 250 is a hole formed by connecting the through hole formed in the second shielding body 230 and the horizontal hole formed by punching the concrete wall CW in the thickness direction to form a series of continuous holes, and can be provided at one or more than two positions.

[0075] The inspection core 260 is a test body used to inspect the degree of radioactivity of the concrete wall CW for the sake of caution, and therefore the inspection core 260 is formed of the same material as the concrete wall CW. In addition, a plurality of inspection cores 260 are arranged in parallel in the depth direction of the concrete wall CW so that the degree of radioactivity corresponding to the depth direction (wall thickness direction) of the concrete wall CW can be confirmed.

[0076] 4. Wall management methods

[0077] Next, refer to Figure 7 and Figure 8 At the same time, a wall management method using the radioactivity suppression structure 200 of the present invention (hereinafter referred to as "the wall management method of the present invention") is described. In addition, the wall management method of the present invention is a management method for the radioactivity suppression structure 200 described so far, so it is assumed that only the contents unique to the wall management method of the present invention are described to avoid duplication of the contents described using the shielding body 100 and the radioactivity suppression structure 200. That is, the contents not described here are the same as the contents described in "2. Shielding Body" and "3. Radioactivity Suppression Structure".

[0078] Figure 7 is a flow chart showing the main steps of the wall management method of the present invention, Figure 8 1 is a step diagram showing the main steps of the wall management method of the present invention. First, Figure 8 As shown in (a), the core CR inserted into the confirmation hole HC provided in the first shielding body 210 is taken out (step 101), and Figure 8 After the state shown in (b), the measurement value of the measuring element 240 is confirmed (step 102). When the measurement result of the measuring element 240 is obtained, the presence or absence of radioactivity of the concrete wall CW is evaluated based on the result (step 103). If radioactivity is not confirmed, the core CR is restored to its original state in the confirmation hole HC (step 109). On the other hand, if radioactivity is confirmed, the core is inspected to evaluate the depth of the radioactivity. Specifically, Figure 8As shown in (c), after the first shielding body 210 is removed, the inspection core 260 is extracted (step 104), and a predetermined inspection is performed on the extracted inspection core 260 (step 105). Then, based on the measurement results of the measuring element 240 and the inspection results of the inspection core 260, it is determined whether the second shielding body 230 needs to be replaced (step 106).

[0079] Furthermore, when the measuring elements 240 are attached to a plurality of (or all) selected plate-like panels of the plate-like panels constituting the second shielding body 230, all (or part) of the attached measuring elements 240 can be checked (step 102). In this case, only the inspection core 260 located around the measuring element 240 for which the measurement result of radioactivity was confirmed can be extracted (step 104) and a predetermined inspection can be performed (step 105), and it can be determined whether the second shielding body 230 needs to be replaced (step 106).

[0080] If it is determined that the second shielding body 230 does not need to be replaced, the inspected inspection core 260 is stored in the inspection hole 250 (step 109). On the other hand, if it is determined that the second shielding body 230 needs to be replaced, Figure 8 As shown in (d), the first shielding body 210 and the second shielding body 230 that has been set are taken out, and a new second shielding body 230 is set (step 107). When the second shielding body 230 is replaced, as shown in Figure 8 As shown in (e), the inspected inspection core 260 is stored in the inspection hole 250. Figure 8 As shown in (f), the first shielding body 210 is restored to its original state (step 109). At this time, the inspected inspection core 260 that has been confirmed to be radioactive may be replaced with a new inspection core 260 and then stored in the inspection hole 250 (step 108).

[0081] Industrial Applicability

[0082] The shielding body and radioactivity suppression structure of the present invention can be particularly effectively used in research facilities, inspection facilities, industrial facilities, etc., including medical facilities that generate neutrons such as proton beam therapy, heavy particle beam therapy, and neutron capture therapy. The present invention is an invention that solves the problems that neutron-generating facilities currently have, that is, it promotes the popularization of particle beam cancer therapy and, if it takes into account the reduction of unnecessary radioactive hazards to radioactive beam business practitioners and the reduction of radioactive waste generation, the present invention is an invention that can be used not only in industry but also can be expected to make a great contribution to society.

[0083] Explanation of symbols

[0084] 100 Shielding body of the present invention; 110 Inclined plate-like panel (of shielding body); 111 Upper surface (of inclined plate-like panel); 112 Lower surface (of inclined plate-like panel); 113 Side surface (of inclined plate-like panel); 120 Protruding plate-like panel (of shielding body); 121 Upper surface (of protruding plate-like panel); 122 Lower surface (of protruding plate-like panel); 123 Side surface (of protruding plate-like panel); 124 Engaging protrusion (of protruding plate-like panel); 124U Upper engaging protrusion (of protruding plate-like panel); 124L Lower engaging protrusion (of protruding plate-like panel); 200 Radioactive suppression structure of the present invention ; 210 (radioactive suppression structure) first shielding body; 211 (first shielding body) surface plate; 212 (first shielding body) middle plate; 213 (first shielding body) inner plate; 220 (radioactive suppression structure) gap; 230 (radioactive suppression structure) second shielding body; 240 (radioactive suppression structure) measuring element; 250 (radioactive suppression structure) inspection hole; 260 (radioactive suppression structure) inspection core; CR (confirmation hole) core; CW concrete wall; HC confirmation hole; JC concentrated joint; JH horizontal joint; JV vertical joint; ND accelerator.

Claims

1. A shielding body which suppresses the radioactivity of a wall body in a neutron generating room, the shielding body being formed of a plurality of plate-like panels, wherein: The plate-like panel is composed of a quadrilateral upper surface, a quadrilateral lower surface, and four side surfaces, and is in a shape in which the upper surface and the lower surface are arranged in parallel or substantially parallel, and all the side surfaces are slope surfaces inclined relative to the upper surface. The side surfaces of the four plate-like panels are butted against the side surfaces of the other adjacent plate-like panels so that no through gap is generated at the joint portion where the corners of the four plate-like panels are concentrated, and the plate-like panels are assembled in a planar shape by joining them in a state where parts of the plate-like panels overlap each other. The shielding body is provided with a confirmation hole penetrating the shielding body, and the confirmation hole is provided with a core body that can be taken out from the confirmation hole and inserted into the confirmation hole.

2. A shielding body which suppresses the radioactivity of a wall in a neutron generating chamber, the shielding body being formed of a plurality of plate-like panels, wherein: The plate-like panel is composed of a quadrilateral upper surface, a quadrilateral lower surface, and four side surfaces, and is in a shape in which the upper surface and the lower surface are arranged in parallel or substantially parallel, and thin plate-like engaging protrusions are provided on all the side surfaces. The four plate-like panels are assembled in a planar shape by joining the engaging protrusions of the four plate-like panels in a state where the engaging protrusions of the side surfaces of the other adjacent plate-like panels overlap in a manner that no through gap is generated at the joint portion where the corners of the four plate-like panels are concentrated. The shielding body is provided with a confirmation hole penetrating the shielding body, and the confirmation hole is provided with a core body that can be taken out from the confirmation hole and inserted into the confirmation hole.

3. A shielding body which suppresses the radioactivity of a wall body in a neutron generating chamber, the shielding body being formed of a plurality of plate-like panels, wherein: The plate-like panel is a structure formed by stacking a surface panel, an intermediate panel, and an inner panel in the order of a surface panel, and is composed of an n-gonal upper surface, an n-gonal lower surface, and n side surfaces, and is a shape in which the upper surface and the lower surface are arranged in parallel or approximately in parallel, and all the side surfaces are slope surfaces inclined relative to the upper surface, wherein n is a natural number greater than 3, The surface plate is a plate-shaped member made of a quasi-non-combustible material or a non-combustible material. The intermediate plate is a plate-shaped member made of wood having a higher strength than that of the surface plate. The inner panel is a thin film or plate-like member containing boron carbide. The side surface of the plate-like panel is butted against the side surface of another plate-like panel in a manner that the surface plate is continuous, and the panels are assembled in a planar shape by joining them in a state where they partially overlap each other in a manner that no through gap is generated at the joint portion where the corners of the adjacent plate-like panels are gathered, The shielding body is provided with a confirmation hole penetrating the shielding body, and the confirmation hole is provided with a core body that can be taken out from the confirmation hole and inserted into the confirmation hole.

4. A shielding body which suppresses the radioactivity of a wall in a neutron generating chamber, the shielding body being formed of a plurality of plate-like panels, wherein: The plate-like panel is a structure formed by stacking a surface panel, an intermediate panel, and an inner panel in the order of a surface panel, an n-gonal upper surface, an n-gonal lower surface, and n side surfaces, and is a shape in which the upper surface and the lower surface are arranged in parallel or approximately in parallel, and thin plate-like engaging protrusions are provided on all the side surfaces, wherein n is a natural number greater than 3, The surface plate is a plate-shaped member made of a quasi-non-combustible material or a non-combustible material. The intermediate plate is a plate-shaped member made of wood having a higher strength than that of the surface plate. The inner panel is a thin film or plate-like member containing boron carbide. The panels are assembled in a planar shape by continuously joining them in an overlapping state so that no through gap is generated at the joint portion where the engaging protrusions at the corners of the adjacent plate-like panels are concentrated. The shielding body is provided with a confirmation hole penetrating the shielding body, and the confirmation hole is provided with a core body which can be taken out from the confirmation hole and inserted into the confirmation hole to restore the original state.

5. A radioactivity suppression structure, wherein the structure suppresses radioactivity of a wall in a neutron generation chamber, wherein: A first shielding body comprising the shielding body according to claim 3 or claim 4, The first shielding body is provided so that the front panel faces the indoor side and the back panel faces the wall side.

6. The radioactivity suppression structure according to claim 5, characterized in that: Further possesses: a gap portion, which is arranged between the inner panel and the wall body; A second shielding body, which is arranged between the gap and the wall, and is composed of the shielding body according to claim 1 or claim 2; an inspection hole penetrating through the second shielding body and further perforated in the thickness direction of the wall body; and A plurality of inspection cores are arranged in the inspection hole, The second shielding body is arranged in a replaceable manner, A measuring element for evaluating the degree of radioactivity is provided on the indoor inner surface of the second shielding body. The inspection core is formed of the same material as the wall. Furthermore, the plurality of inspection core bodies are arranged in parallel in the thickness direction of the wall body.

Images