Radiation shield

Abstract

A radiation shield is provided that surrounds a radiation measuring instrument to attenuate the influence of environmental radiation doses and enable radiation measurement according to the purpose. [Solution] A radiation shielding body 100 is composed of a plate group 2 made up of multiple stacked plate materials, and is also composed of a front portion 100F and a rear portion 100R. The front portion has a small diameter hole 12 that allows radiation emitted from a measurement object S to pass through, and the rear portion has a large diameter hole 22 into which a radiation measuring instrument can be inserted. Each of the plate materials 10, 20 that make up the plate group is formed with complementary convex portions 10A, 20A and concave portions 10B, 20B that can fit with opposing plate materials.

Description

[Technical Field]

[0001] The present invention relates to a radiation shield that encloses a radiation measuring instrument to attenuate the influence of environmental radiation (background) and enable radiation measurement tailored to the purpose. [Background technology]

[0002] Patent documents 1 to 3 disclose portable radiation shields. These types of radiation shields were developed for decontamination work following the Great East Japan Earthquake, and have become essential tools for accurately measuring radiation doses on target surfaces such as the ground.

[0003] The use of a radiation shield enables radiation measurement that eliminates the influence of background radiation. Furthermore, even when the background radiation is low, the lower limit of radiation detectability can be set to a low level. This reduces radiation measurement errors and significantly increases the reliability of the measured values. Furthermore, by manipulating the radiation shield, the direction of the small holes in the shield that allow radiation to pass through can be changed, enabling measurements tailored to the purpose, such as determining from which direction the majority of radiation is coming. Furthermore, the use of a radiation shield makes it possible to measure partial radiation in the object being measured.

[0004] Conventional radiation shields are primarily made of lead castings. However, it is difficult to ensure dimensional accuracy when manufacturing lead castings. For this reason, a casting method has been adopted in which an outer shell made of iron or stainless steel is made in advance and molten lead is poured into this shell. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Design registration 1455269 [Patent Document 2] Design registration 1485449 [Patent Document 3] Design registration 1502524 Summary of the Invention [Problem to be solved by the invention]

[0006] Problems with the manufacture of conventional radiation shields include the need for special casting techniques and equipment, which increases manufacturing costs and lead times, as well as the need for skilled craftsmanship to prevent thermal deformation of the outer shell that occurs during casting. Specifically, casting is a one-shot job, and if a casting defect occurs, the shield must be remade from scratch.

[0007] Other problems with conventional radiation shields include: (1) the shields are sometimes roughly handled at radiation measurement sites, and even if they are partially deformed, it is difficult to repair them, so the entire shield must be discarded; (2) even if only a portion of the shield is contaminated, the entire shield must be discarded; and (3) if you want to change the shielding performance of the shield, you have no choice but to purchase a shield that suits your purpose.

[0008] In light of the above problems, the present invention aims to provide a radiation shield that can solve the conventional problems. [Means for solving the problem]

[0009] According to the present invention, the above technical problems are solved as follows: A radiation shielding body that surrounds a radiation measuring device and has a radiation passage through which radiation emitted from a measurement object can pass, the radiation shielding body includes a plate group formed by stacking a plurality of plate materials and a fastening member that releasably connects the plate group; the plate group is composed of a plurality of front plate members that form a front portion facing the measurement object, and a plurality of rear plate members that are located on the opposite side of the front portion and form a rear portion of the radiation shielding body, the front panel has relatively small holes; the rear plate has a relatively large hole for receiving the radiation measuring device; the small hole and the large hole are arranged coaxially to form a through hole that extends continuously from the front to the rear of the radiation shield; a small hole in the front plate that defines the radiation passage; a large hole in the rear plate member that constitutes a radiation measuring device housing portion that receives the radiation measuring device in a removable manner; This is achieved by providing a radiation shield characterized in that, between layers of a group of plate materials, convex and concave portions of complementary shapes are formed on each surface of the plate materials facing each other, and the plate materials facing each other are fitted together in a concave-convex manner.

[0010] Other objects and advantages of the present invention will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a side view illustrating a schematic configuration of a radiation shield according to an embodiment. [Figure 2] FIG. 1 is a plan view of a first example of a plate member constituting the front portion of a radiation shielding body; [Figure 3] FIG. 1 is a plan view of a first example of a plate member constituting the rear portion of a radiation shielding body; [Figure 4] FIG. 1 is a side view of a portable device suitable for carrying a radiation shield and transporting it to a measurement site. [Figure 5] 5 is a plan view of the portable device shown in FIG. [Figure 6] Exploded view of the plates that make up the main part of the radiation shield [Figure 7] FIG. 10 is a plan view of a second example of a plate member constituting the front portion of the radiation shielding body. [Figure 8] FIG. 10 is a plan view of a second example of a plate member constituting the rear portion of the radiation shielding body. [Figure 9] 7 is a diagram corresponding to FIG. 6 for explaining that plate materials of different thicknesses are incorporated into some of the plate materials constituting the plate material group. [Figure 10] 9, this figure is for explaining that plate members of different thicknesses are incorporated into some of the plate members that make up the plate group, and also for explaining that the plate member (end plate) at the rear end of the radiation shielding body is provided with a cable insertion hole. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 is a side view illustrating the schematic configuration of a radiation shielding body 100 according to an embodiment. The radiation shielding body 100 is configured by tightly connecting a plate group 2, which is made up of a plurality of stacked plate materials, with releasable fastening members 4. A typical example of the fastening members 4 is a combination of a bolt and a nut. Each plate constituting the plate group 2 can be selected according to the radiation intensity and energy of a measurement target S (an object shown by imaginary lines in FIGS. 4 and 5, which will be described later) that serves as a radiation source, as long as it is made of a material that can reduce the intensity of gamma rays. Examples of selectable materials include lead plates, stainless steel plates, iron plates, and tungsten plates. The plate group 2 may be configured using one type of plate material selected from these, or may be configured using a combination of multiple types of plate materials.

[0013] The radiation shield 100 is composed of a front section 100F located on the side of the object to be measured S and a rear section 100R located on the opposite side, and has a roughly overall shape of a rectangular parallelepiped with a square cross section. The plate group 2 is composed of a front plate 10 (FIG. 2) constituting the front section 100F and a rear plate 20 (FIG. 3) constituting the rear section 100R. Referring to FIG. 2, the front plate 10 has a square shape in plan view and has a small diameter hole 12 with a diameter of 10 mm at its center. Referring to FIG. 3, the rear plate 20 has a square shape in plan view with the same dimensions as the front plate 10 and has a large diameter hole 22 with a diameter of 30 mm at its center. Although the large diameter hole 22 is illustrated as a circle, it may also be rectangular and may have any shape. The front plate 10 and the rear plate 20 each have a total of four bolt insertion holes 30 at their four corners, and the bolts constituting the fastening members 4 described above are inserted into each bolt insertion hole 30.

[0014] The small diameter hole 12 in the front plate 100F and the large diameter hole 22 in the rear plate 100R form a through hole that extends continuously from the front end to the rear end of the radiation shielding body 100 on the axis Ax (FIG. 1) of the radiation shielding body 100. The large diameter hole 22 in the rear plate 20 forms a radiation measuring device accommodating section in the rear plate 100R into which the radiation measuring device 40 can be inserted and removed freely. Reference numeral 42 shown in FIG. 1 indicates a cable extending from the rear end of the radiation measuring device 40. On the other hand, the small diameter hole 12 in the front plate 10 forms a radiation passage through which radiation emitted by the measurement target S (FIG. 4) passes.

[0015] Radiation emitted from the measurement object S enters the inside of the radiation shielding body 100 through the small diameter hole 12 in the front part 100F and is measured by the radiation measuring device 40 inserted into the large diameter hole 22 in the rear part 100R.

[0016] The radiation shielding body 100 shown in Fig. 1 is designed to have the ability to block gamma rays derived from cobalt to 1 / 100. Specifically, the front plate material 10 and the rear plate material 20 are both made of square iron plate material with a thickness of 10 mm and a side length of 330 mm. The front portion 100F is made of 15 plates 10, and the rear portion 100R is made of 20 plates 20. Therefore, the illustrated radiation shielding body 100 can exhibit substantially the same shielding performance as a structure in which the front portion 100F is made of iron material with a thickness of 150 mm and the rear portion 100R is made of iron material with a thickness of 200 mm. The thickness of the plates 10 and 20 is optional, and for example, multiple types of plates 10 and 20 with different thicknesses may be prepared, and plates 10 and / or 20 with different thicknesses may be assembled on-site to change the length of the front portion 100F and / or rear portion 100R to achieve the desired shielding performance.

[0017] When the front end portion of the front part 100F becomes radioactively contaminated through use, for example, several front plates 10 constituting the contaminated portion can be replaced by releasing the fastening members 4, eliminating the need to discard the entire radiation shield as in the past.

[0018] Furthermore, lead plates, stainless steel plates, iron plates, and tungsten plates can be prepared in advance as the plates 10, 20 constituting the front section 100F and the rear section 100R, and the number of plates 2 in the front section 100F can be increased on-site depending on the radiation intensity and energy of the object to be measured, or some or all of the plates 2 in the front section 100F and the rear section 100R can be replaced with plates made of a material other than iron. By adopting a laminated structure, the radiation shielding body 100 can be repaired on-site, or can be transformed into a radiation shielding body 100 that corresponds to the radiation intensity and energy of the object to be measured S. This eliminates the need to obtain multiple types of radiation shielding bodies with different shielding performances.

[0019] 2 and 3, the plate materials 10 and 20 can be manufactured by simply drilling holes in an available plate material having a desired thickness or by performing a cutting operation, which will be described later. As a result, unlike conventional radiation shielding methods that require special casting techniques and equipment and are made by skilled craftsmen, the radiation shielding 100 of the present invention can significantly reduce manufacturing costs and lead times.

[0020] The cross-sectional shape of the radiation shield 100 of the embodiment, that is, the outer contours of the plate members 20 and 30, do not have to be square, and may be circular, hexagonal, octagonal, or the like.

[0021] 4 and 5 show a portable device 200 that is convenient for carrying the radiation shielding body 100 of the embodiment and transporting it to the site to measure radiation emitted from the measurement target S. Fig. 4 is a side view with a portion cut away, and Fig. 5 is a plan view.

[0022] 4, the portable device 200 has four wheels 202 arranged at the four corners, and in addition, it has extendable position fixing legs 204. After the fixed portable device 200 is moved to a predetermined location with the position fixing legs 204 contracted, the position fixing legs 204 can be extended to fix the portable device 200 in place.

[0023] 5, the top surface of the portable device 200 is divided into two areas 210 and 220. The first area 210 is an area for placing the radiation shielding body 100, and the second area 220 is an area for placing the measurement target S.

[0024] A vertically movable lifting table 222 is installed in the second measurement object placement area 220. A measurement object S can be placed on this table 222. Referring to FIG. 4, a shielded space surrounded by a radiation shielding wall 224 is provided inside the portable device 200, and a table lifting mechanism 226 is disposed in this shielded space. The table lifting mechanism 226 includes a guide rod 228 that guides the vertical movement of the table 222 and a drive motor 230, and can electrically raise and lower the table 222 to a desired height position. As a result, after the measurement object S is placed on the table 222, the measurement object S can be positioned at a height position facing the small diameter hole 12 opening in the front end surface of the radiation shielding body 100. The table 222 has a shaft 232 extending downward and is configured as a rotary table that can rotate about the shaft 232.

[0025] The current problem is how to deal with the fuel debris from the Fukushima nuclear power plant. Fuel debris refers to the solidified material that has formed when the nuclear fuel in the reactor melted and mixed with the surrounding metal and concrete. Fuel debris contains both highly radioactive and less radioactive parts.

[0026] The table 222 of the portable device 200 can measure the radiation dose at a plurality of locations on the measurement target S by changing the vertical height position and the rotation position of the axis of rotation.

[0027] Fig. 2 is a plan view of a first specific example of the plate material 10 constituting the front part 100F of the radiation shield. Fig. 3 is a plan view of a first specific example of the plate material 20 constituting the rear part 100R of the radiation shield. The plate material 10 constituting the front part 100F and the plate material 20 constituting the rear part 100R are formed by cutting a material with a plate thickness of 10 mm as described above, to form the recessed parts 10B and 20B, respectively, and accordingly the plate materials 10 and 20 are provided with the protruding parts 10A and 10B.

[0028] 2 and 3 show one side of the plate materials 10 and 20. The protrusions 10A and 20A have an elongated shape that extends continuously along the outer periphery of the plate materials 10 and 20, and the central portions surrounded by the protrusions 10A and 20A are cut to form the recesses 10B and 20B that are square in plan view.

[0029] As can be seen from FIG. 6, on the surface opposite to one side of the plate material 10, 20 shown in FIG. 2 and FIG. 3, recesses 10B, 20B are formed at positions corresponding to the protrusions 10A, 20A shown in FIG. 2 and FIG. 3, and protrusions 10A, 20A are formed at positions corresponding to the recesses 10B, 20B shown in FIG. 2 and FIG. 3.

[0030] In Figure 6, the thickness of the plate materials 10, 20 is exaggerated to make it easier to see the presence of the convex portions 10A, 20A and the concave portions 10B, 20B. Referring to Figure 6, the convex portions 10A (20A) and concave portions 10B (20B) on the abutting surfaces of one plate material 10 (20) and another plate material 10 (20) located immediately in front of or behind it have complementary shapes and heights, so that the convex and concave portions fit together when the plate materials 10, 20 are stacked. As a result, the radiation shielding body 100 is composed of a stacked plate material group 2 in which all of the plate materials 10, 20 fit together.

[0031] The interlayer steps formed by the above-mentioned complementary shaped convex portions 10A, 20A and concave portions 10B, 20B extend along the rectangular outline that crosses the plate group 2, forming a barrier to the penetration of radiation emitted by the measurement object S, i.e., a maze that blocks the penetration of radiation that attempts to enter the interior of the radiation shielding body 100, thereby ensuring the shielding performance of the plate group 2 as designed.

[0032] In the first specific example shown in Figures 2 and 3, the width of the convex portions 10A, 20A extending along the outer peripheral edges of the plate materials 10, 20 shown in Figures 2 and 3 is set to a dimension such that the bolt insertion hole 30 is contained within the convex portions 10A, 20A, but is not limited to this.

[0033] 7 and 8 show plate materials 210 and 220 of a second specific example. Fig. 7 is a view corresponding to the plate material 10 of Fig. 2. Fig. 8 is a view corresponding to the plate material 20 of Fig. 3. Referring to Figs. 7 and 8, the protrusions 10A and 20A included in the plate materials 210 and 220 are narrow, and the bolt insertion holes 30 are located inside the protrusions 10A and 20A, i.e., at the corners of the recesses 10B and 20B.

[0034] The convex portions 10A, 20A may have any shape, and may have, for example, outer convex portions 10A, 20A and inner convex portions 10B, 20B on the inside and outside of the plate material 10 (210), 20 (220), or may be discontinuous in the circumferential direction, with the outer convex portions and the inner convex portions offset in the extension direction. In this case, it is preferable that the ends of the outer convex portions and the inner convex portions overlap each other when viewed from the side.

[0035] 6, an example is shown in which the front surface of the plate material 10(F) located at the forefront of the front part 100F is formed as a flat surface without being cut, but it may have convex parts 10A and concave parts 10B on both sides, like the second and subsequent plate materials 10. Similarly, the rear surface of the plate material 20(R) located at the rearmost end of the rear part 100R is formed as a flat surface without being cut, but this rear surface may have convex parts 20A and concave parts 20B.

[0036] As a modification of the plate materials 10, 20, the plate materials 10, 20 having the convex portions 10A, 20A and the concave portions 10A, 20A formed thereon may be plated. By surrounding the surfaces of the plate materials 10, 20 with a plated layer, not only can an anti-rust effect be obtained, but also the local plastic flow of the plated layer can increase the adhesion between the layers of the plate materials 10, 20, making it easier to ensure the shielding performance of the plate material group 2 as designed.

[0037] Figures 9 and 10 are diagrams specifically illustrating modified examples and correspond to Figure 6. Figure 9 shows an example in which the plate material 10(F) constituting the tip of the radiation shielding body 100 and the plate material 20(F) constituting the tip of the rear portion 100R are made of a plate material that is thicker than the other plate materials 10, 20.

[0038] FIG. 10 illustrates a modified example in which the plate member 20(F) constituting the tip of the rear portion 100R is made of a plate member having a greater thickness than the other plates 10, 20, and also illustrates a modified example in which an additional end plate 50 is added to the rear end of the radiation shielding body 100. The end plate 50 has a cable insertion hole 52 through which the cable 42 (FIG. 4) of the radiation measuring device 40 can pass. The end plate 50 also has a recess 54 for receiving the end (bolt head or nut) of the fastening member 4. The end plate 50 is releasably fixed to the rear end of the plate group 2 of the radiation assembly 100. Specific examples of fixing means include a releasable structure in which the end plate 50 is hinged to the plate group 2 and fastened in close contact with the plate group 2 using a buckle. [Explanation of symbols]

[0039] 100 Radiation shield of the embodiment 100F Front of radiation shield 100R Radiation Shield Rear 2 Plate groups 4 Fastening components (bolts and nuts) 10 Front plate material 10A Front plate protrusion 10B Recess in front plate 12 Small diameter hole 20 Rear plate material 20A Rear plate protrusion 20B Rear plate recess 22 Large diameter hole 30 Bolt insertion hole S Measurement object 40 Radiation detector 50 End Plate 52 Cable insertion hole

Claims

1. A radiation shielding body that surrounds a radiation measuring device and has a radiation passage through which radiation emitted from a measurement object can pass, the radiation shielding body includes a plate group formed by stacking a plurality of plate materials and a fastening member that releasably connects the plate group; the plate group is composed of a plurality of front plate members that form a front portion facing the measurement object, and a plurality of rear plate members that are located on the opposite side of the front portion and form a rear portion of the radiation shielding body, the front panel has relatively small holes; the rear plate has a relatively large hole for receiving the radiation measuring device; the small hole and the large hole are arranged coaxially to form a through hole that extends continuously from the front to the rear of the radiation shield; a small hole in the front plate that defines the radiation passage; a large hole in the rear plate member that constitutes a radiation measuring device housing portion that receives the radiation measuring device in a removable manner; A radiation shield characterized in that between layers of a group of plate materials, convex and concave portions of complementary shapes are formed on each surface of the plate materials facing each other, and the plate materials facing each other are fitted together in a concave-convex manner.

2. The radiation shield according to claim 1 , A radiation shield, wherein the front plate and the rear plate have the same outer shape.

3. The radiation shield according to claim 2, A radiation shield, wherein the front plate member and the rear plate member have a square outer shape.

4. The radiation shield according to claim 1 , The fastening member is formed by a combination of a bolt and a nut, The radiation shield, wherein the front plate member and the rear plate member have bolt insertion holes formed therein through which bolts are inserted.

5. The radiation shield according to claim 1 , A radiation shield, wherein each of the plates constituting the group of plates is made of one type of plate material selected from lead plates, stainless steel plates, iron plates, and tungsten plates, or a combination of multiple types of plate materials.

6. The radiation shield according to any one of claims 1 to 5, a radiation shielding body, wherein the convex portion and the concave portion extend continuously along the outer peripheral edges of the mutually facing surfaces of one plate member constituting the plate group and another plate member adjacent to the one plate member.

7. The radiation shield according to claim 6, Further, an end plate is disposed at a rear end of the plate group, the end plate has a cable insertion hole through which a cable of the radiation measuring device can pass, The radiation shield, wherein the end plates are releasably secured to the plate group.

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