JP7449899B2 - radiation shield - Google Patents

Description

TECHNICAL FIELD This disclosure relates to radiation shielding.

A neutron irradiation device generates neutrons by irradiating a target with charged particles to cause a nuclear fragmentation reaction (see, for example, Patent Document 1). Such neutron irradiation equipment uses a configuration in which the target is placed inside a cylindrical radiation shield made of a material with excellent radiation absorption performance, such as tungsten, in order to shield the radiation generated due to the nuclear spallation reaction. have

Japanese Patent Application Publication No. 2015-145882

The radiation shield described above is manufactured, for example, by connecting a plurality of unit members to each other in a direction around a central axis. In such a radiation shield, in order to shield radiation generated from a target placed inside, the opposing parts of adjacent unit members are formed in a step shape, and when the unit members are connected, the adjacent unit members are The stepped portions are shaped to interlock with each other. With this configuration, when the radiation shield is viewed from the inside to the outside in a straight line direction, the steps between adjacent unit members are closed.

However, in this configuration, since a convex portion due to a stepped portion is formed on the surface of the unit member, there is a problem that the unit members are likely to be damaged if they come into contact with each other during manufacturing, such as transportation and assembly.

The present disclosure has been made in view of the above, and an object of the present disclosure is to provide a radiation shield that can reliably shield radiation while suppressing damage during manufacturing.

In the radiation shield according to the present disclosure, a plurality of unit members formed using heavy metal are connected in a cylindrical shape so as to be separable in a direction around a central axis, and the unit members adjacent in the direction around the axis The opposing surfaces thereof are planar, and a recessed portion along the central axis is provided at the opposing position of each of the opposing surfaces, and the main body accommodates therein a target that generates neutrons when irradiated with charged particles. and a belt-shaped part formed in a belt shape using heavy metal and arranged along the central axis so as to span between the recesses of each of the adjacent unit members when the unit members are connected to each other. Equipped with

According to the present disclosure, it is possible to provide a radiation shield that can suppress damage during manufacturing while reliably shielding radiation.

FIG. 1 is a schematic diagram showing an example of a neutron irradiation device according to this embodiment. FIG. 2 is a diagram showing an example of the arrangement of radiation shields according to this embodiment. FIG. 3 is a perspective view showing an example of the radiation shield according to this embodiment. FIG. 4 is a diagram showing an example of the radiation shield viewed from the axial direction of the central axis. FIG. 5 is a diagram showing the configuration along the AA cross section in FIG. 4. FIG. 6 is a diagram showing main parts in FIG. 4. FIG. 7 is a diagram showing an example of the cross-sectional shape of the band-shaped portion.

Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings, but the present disclosure is not limited thereto. The components of each embodiment described below can be combined as appropriate. Furthermore, some components may not be used. Further, the components in the embodiments described below include those that can be easily replaced by those skilled in the art, or those that are substantially the same.

FIG. 1 is a schematic diagram showing an example of a neutron irradiation device 1 according to this embodiment. The neutron irradiation device 1 irradiates the irradiated object S with neutrons N. The neutron irradiation device 1 is used, for example, for inspection purposes, medical purposes, radioisotope production purposes, and the like.

As shown in FIG. 1, the neutron irradiation device 1 includes an accelerator 2 that accelerates charged particles and ejects charged particles P, and an adjustment device 3 that adjusts the irradiation state of the charged particles P ejected from the accelerator 2. , a target 5 that generates neutrons N by irradiation with charged particles P, a deceleration device 6 that decelerates the neutrons N generated by the target 5, and a collimator 7 that collimates the neutrons N emitted from the deceleration device 6. ing. The irradiated object S is irradiated with neutrons N emitted from the collimator 7. The neutron irradiation device 1 according to this embodiment includes a radiation shield 100 that accommodates the target 5.

Accelerator 2 includes a circular accelerator or a linear accelerator. The accelerator 2 accelerates charged particles (protons, electrons, or heavy particles) to generate charged particles (proton beams, electron beams, or heavy particle beams) P, and injects them in a predetermined irradiation direction.

The adjustment device 3 includes a plurality of electromagnets, and adjusts the irradiation state of the charged particles P ejected from the accelerator 2. The irradiation state of the charged particles P includes adjustment of the traveling direction of the charged particles P and shaping of the charged particles P. The adjustment device 3 suppresses the divergence of the charged particles P and focuses the charged particles P. The adjustment device 3 guides the charged particles P ejected from the accelerator 2 to the scanning device 4 .

The scanning device 4 scans the charged particles P and adjusts the irradiation position of the charged particles P with respect to the target 5. Furthermore, the scanning device 4 shapes the charged particles P that are irradiated onto the target 5. Note that the scanning device 4 may not be provided.

The charged particles P ejected from the accelerator 2 and passed through the adjustment device 3 and the scanning device 4 are irradiated onto the target 5 . The target 5 generates neutrons N by being irradiated with the charged particles P. In the target 5, high-energy fast neutrons are generated as the neutrons N, for example. The target 5 is a neutron generating member that generates neutrons. The target 5 includes a liquid or solid plate-shaped member made of, for example, beryllium (Be), lithium (Li), or a compound containing them. The target 5 may be a circular or rectangular plate-shaped solid member, or may be heated liquid lithium. For example, liquid lithium that is continuously poured so as to have a constant thickness may be used as the target 5. The target 5 is housed in a radiation shield 100, which will be described later.

The deceleration device 6 decelerates the neutrons N generated at the target 5. The decelerator 6 is arranged between the target 5 and the irradiated body S in the path of the neutrons N. The deceleration device 6 reduces the energy of fast neutrons generated by the target 5 to generate slow and low energy neutrons (thermal neutrons, epithermal neutrons, or cold neutrons).

The collimator 7 collimates the neutron beam N emitted from the decelerator 6. The neutron beam N is collimated by the collimator 7 and emitted from the collimator 7, and the irradiated object S is irradiated with the neutron beam N.

Next, the radiation shield 100 will be explained. FIG. 2 is a diagram showing an example of the arrangement of the radiation shield 100 according to this embodiment. As shown in FIG. 2, the radiation shield 100 has a cylindrical shape, is housed inside an outer tube 101, and is fixed while being supported by the SUS shield 102. As shown in FIG.

FIG. 3 is a perspective view showing an example of the radiation shield 100 according to this embodiment. FIG. 4 is a diagram showing an example of the radiation shield 100 viewed from the axial direction of the central axis. FIG. 5 is a diagram showing the configuration along the AA cross section in FIG. 4. FIG. 6 is a diagram showing main parts in FIG. 4.

As shown in FIGS. 3 to 6, the radiation shield 100 includes a main body portion 10 and a strip portion 20. As shown in FIGS. The main body 10 has a cylindrical shape and accommodates the target 5 described above therein. The main body portion 10 has a plurality of unit members 11. The unit members 11 are each formed using heavy metals such as tungsten, iron, lead, and copper. The unit members 11 are connected in a cylindrical shape so that they can be divided in a direction around the central axis AX. Each unit member 11 is connected by, for example, a bolt (not shown) or the like.

Each unit member 11 has a shape obtained by cutting a cylindrical member radially by a plurality of planes passing through the central axis AX. Each unit member 11 is formed to have equal dimensions in the direction around the central axis AX. Each unit member 11 has an inner peripheral surface 12, an outer peripheral surface 13, opposing surfaces 14 and 15, and end surfaces 16 and 17. The inner circumferential surface 12 and the outer circumferential surface 13 are part of a cylindrical surface. The opposing surfaces 14 and 15 are surfaces on which adjacent unit members 11 face each other in the direction around the center axis AX. In the following description, it is assumed that the opposing surfaces 14 of each unit member 11 face each other, and the opposing surfaces 15 of each unit member 11 face each other. The opposing surfaces 14 and 15 are each planar and have the same shape and size. The end surface 16 is formed at one end of the unit member 11 in the axial direction of the central axis AX. The end surface 17 is formed at the other end of the unit member 11 in the axial direction of the central axis AX. The end surfaces 16 and 17 are each planar.

Each unit member 11 has a recess 18 on opposing surfaces 14 and 15. The recesses 18 are arranged at positions of the opposing surfaces 14 and 15 that face each other when the adjacent unit members 11 are connected to each other. As a result, a space K is formed in the main body portion 10 by the recessed portion 18 of each unit member 11 in a state in which adjacent unit members 11 are connected.

The recess 18 is arranged, for example, at the center of the opposing surfaces 14 and 15 in the radial direction. The recess 18 may be arranged inside (on the inner peripheral surface 12 side) or outside (on the outer peripheral surface 13 side) with respect to the center in the radial direction. The recess 18 is provided linearly along the central axis AX. Note that the recess 18 may be provided in a curved or bent state along the inner circumferential surface 12. The recess 18 is provided over the entire length between one end surface 16 and the other end surface 17 of the unit member 11 in the longitudinal direction. The recess 18 has, for example, a rectangular shape when viewed in the axial direction of the central axis AX (or in a cross-sectional view taken from a plane orthogonal to the central axis AX), but is not limited to this shape, and may have a triangular shape, a circular shape, etc. , may have other shapes.

The strip portion 20 is inserted into the space K of the main body portion 10 . The strip portion 20 is formed into a strip shape using heavy metal such as tungsten, iron, lead, copper, or the like. The strip portion 20 is arranged so as to straddle the recesses 18 of adjacent unit members 11 . The strip portion 20 is held between the bottom portions 18a of the respective recesses 18. An indium layer may be sandwiched between the strip 20 and the bottom 18a of the recess 18. By sandwiching the indium layer, the thermal conductivity between the strip portion 20 and the unit member 11 is increased.

FIG. 7 is a diagram showing an example of the cross-sectional shape of the strip portion 20. As shown in FIG. As shown in FIG. 7, the strip portion 20 has a base layer 21 and coating layers 22 and 23. The base layer 21 is formed using heavy metals such as tungsten, iron, lead, and copper. The covering layers 22 and 23 are formed using a metal such as copper, and are arranged on the front and back sides of the base layer 21 so as to sandwich the base layer 21 therebetween. The base layer 21 and the covering layers 22 and 23 may be joined by, for example, welding or the like, or may be joined by a fixing member such as a bolt. When joining using a fixing member such as a bolt, an indium layer may be sandwiched between the base layer 21 and the covering layers 22 and 23. By sandwiching the indium layer, the thermal conductivity between the base layer 21 and the covering layers 22 and 23 is increased.

When the band-shaped part 20 is held inside the space part K, the base layer 21 and the base layer 21 are disposed at a position corresponding to the position where the facing surfaces 14 and 15 of the adjacent unit members 11 contact each other. The thickness of the covering layers 22 and 23 is set. That is, when viewed in the radial direction from the central axis AX, the base layer 21 is configured to shield the opposing surfaces 14 and 15 of the adjacent unit members 11 from each other.

The covering layers 22 and 23 are provided with tubular portions 22a and 23a, respectively. The tubular portions 22a and 23a are formed along the longitudinal direction of the strip portion 20. The tubular portions 22a, 23a are formed, for example, to communicate with both end surfaces of the coating layers 22, 23 in the longitudinal direction. The tubular portions 22 a and 23 a constitute a flow path T through which the refrigerant flows inside the strip portion 20 . For example, a refrigerant is supplied to the tubular portions 22a and 23a from one end in the longitudinal direction, and the refrigerant is discharged from the other end.

The radiation shield 100 configured as described above accommodates the target 5 and blocks radiation generated when the target 5 is irradiated with the charged particles P. The radiation generated from the target 5 travels radially around the central axis AX. Of the generated radiation, a component that reaches, for example, the inner circumferential surface 12 of the unit member 11 is absorbed by the inner circumferential surface 12 or the inside of the unit member 11. Furthermore, the component of the generated radiation that reaches the portion between the adjacent unit members 11 travels between the opposing surfaces 14 and 15 of the adjacent unit members 11, but is absorbed by the band-shaped portion 20. Therefore, the generated radiation is shielded by the radiation shield 100.

As described above, in the radiation shield 100 according to the present embodiment, a plurality of unit members 11 formed using heavy metal are connected in a cylindrical shape in the direction around the center axis AX, and units adjacent in the direction around the axis The opposing surfaces 14 and 15 of the members 11 are planar, and a recess 18 along the central axis AX is provided at the opposing position of each opposing surface 14 and 15, and when charged particles P are irradiated, neutrons N A main body part 10 that houses a target 105 that generates a The belt-shaped portion 20 is arranged along the central axis AX.

Therefore, since the opposing surfaces 14 and 15 of the adjacent unit members 11 are planar, the unit members 11 constituting the main body 10 have a protrusion compared to a structure in which the opposing surfaces 14 and 15 are provided with stepped portions. Since damage is suppressed during manufacturing such as transportation and assembly, damage can be suppressed. In addition, since the recessed portion 18 is provided at a position where the opposing surfaces 14 and 15 face each other, and the strip portion 20 is arranged so as to straddle between the recessed portions 18, it passes between the opposing surfaces 14 and 15 of the adjacent unit members 11. The band-shaped portion 20 can also shield radiation components. This makes it possible to reliably shield radiation while suppressing damage during manufacturing.

In the radiation shield 100 according to the present embodiment, the recess 18 is arranged at the center of the main body 10 in the radial direction between the opposing surfaces 14 and 15. Therefore, heat dissipation can be ensured by the recess 18 at the radial center of the main body 10.

In the radiation shield 100 according to the present embodiment, the recess 18 is provided linearly along the central axis AX. Therefore, the unit member 11 and the strip portion 20 can be easily manufactured.

In the radiation shield 100 according to the present embodiment, the strip portion 20 is held between the bottom portions 18a of the respective recesses 18 of the adjacent unit members 11. Therefore, the belt-like part 20 can be stably held without separately providing a fixing member or the like for fixing the belt-like part 20.

In the radiation shield 100 according to this embodiment, the strip portion 20 has tubular portions 22a and 23a through which a refrigerant flows. Therefore, the cooling efficiency of the main body portion 10 that holds the strip portion 20 can be increased.

In the radiation shield 100 according to the present embodiment, the strip portion 20 includes a base layer 21 made of heavy metal, and coating layers 22 and 23 disposed on the front and back sides of the base layer 21 so as to sandwich the base layer 21 therebetween. Therefore, thermal conductivity can be improved while shielding against radiation is maintained.

In the radiation shield 100 according to this embodiment, the plurality of unit members 11 have equal dimensions in the axial direction. Therefore, the recesses 18 and the strips 20 can be arranged at a constant pitch in the direction around the axis.

In the radiation shield 100 according to this embodiment, the main body 10 has a cylindrical shape. Thereby, radiation can be reliably shielded by the cylindrical main body portion 10 and the belt-shaped portion 20.

The neutron irradiation device 1 according to the present embodiment includes an accelerator 2 that accelerates and injects charged particles P, a target 5 that is irradiated with the charged particles P ejected from the accelerator 2 and generates neutrons, and a target 5 that generates neutrons. and a radiation shield 100 housed inside. Therefore, it is possible to obtain the neutron irradiation device 1 including the radiation shield 100 that has a high ability to shield radiation generated by the target 5.

The technical scope of the present invention is not limited to the above embodiments, and changes can be made as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, the case where the main body part 10 is cylindrical is described as an example, but the present invention is not limited to this. The main body portion 10 may have a polygonal cylindrical shape.

Further, in the embodiment described above, the configuration in which the strip portion 20 includes the base layer 21 and the coating layers 22 and 23 has been described as an example, but the present invention is not limited to this. The strip portion 20 may have a configuration in which at least one of the coating layers 22 and 23 is not provided.

Further, in the above embodiment, a configuration in which the plurality of unit members 11 have the same dimensions in the axial direction has been described as an example, but the present invention is not limited to this. The plurality of unit members 11 may have a configuration in which at least one of the unit members 11 has a different dimension in the direction around the axis.

Further, in the embodiment described above, the configuration in which the strip portion 20 includes the tubular portions 22a and 23a through which the refrigerant flows is described as an example, but the present invention is not limited to this. At least one of the tubular portions 22a and 23a may not be provided. Moreover, the structure is not limited to the inside of the coating layers 22 and 23, and for example, at least a part of the flow path (tubular part) may be provided inside the base layer 21.

Further, in the embodiment described above, the configuration in which the strip portion 20 is held between the bottom portions 18a of the respective recesses 18 of the adjacent unit members 11 has been described as an example, but the present invention is not limited to this. The strip portion 20 may be fixed to the recess 18 by other means such as a fixing member (not shown).

1 Neutron irradiation device 2 Accelerator 3 Adjustment device 4 Scanning device 5 Target 6 Deceleration device 7 Collimator 10 Main body 11 Unit member 12 Inner circumferential surface 13 Outer circumferential surfaces 14, 15 Opposing surfaces 16, 17 End surface 18 Recessed portion 18a Bottom portion 20 Band-shaped portion 21 Base layer 22, 23 Covering layer 22a, 23a Tubular part 100 Radiation shield 101 Outer cylinder 102 SUS shield AX Central axis K Space part N Neutron, neutron beam P Charged particle S Irradiated object T Flow path

Claims (8)

A plurality of unit members formed using heavy metal are connected in a cylindrical shape in a direction around a central axis, and opposing surfaces of the unit members adjacent to each other in the direction around the axis are planar, and the opposing faces of each unit member are planar. a main body portion having a recessed portion along the central axis at opposing positions of the surfaces and housing therein a target that generates neutrons when irradiated with charged particles;
a belt-shaped part formed in a belt shape using a heavy metal and arranged along the central axis so as to span between the recesses of each of the adjacent unit members in a state where the unit members are connected to each other. shield. The radiation shield according to claim 1, wherein the recess is arranged in the center of the main body in the radial direction of the opposing surface. The radiation shield according to claim 1 or 2, wherein the recess is provided linearly along the central axis. The radiation shield according to any one of claims 1 to 3, wherein the band-shaped portion is held between the bottoms of the respective recesses of the adjacent unit members. The radiation shield according to any one of claims 1 to 4, wherein the strip portion has a flow path through which a refrigerant flows. The radiation shield according to any one of claims 1 to 5, wherein the band-shaped portion includes a base layer made of a heavy metal, and coating layers arranged on the front and back sides of the base layer so as to sandwich the base layer. The radiation shield according to any one of claims 1 to 6, wherein the plurality of unit members have equal dimensions in a direction around the axis. The radiation shield according to any one of claims 1 to 7, wherein the main body has a cylindrical shape.

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