CN111757585A

CN111757585A - Self-shielding body for RI manufacturing apparatus

Info

Publication number: CN111757585A
Application number: CN202010226331.2A
Authority: CN
Inventors: 鹈野浩行
Original assignee: Sumitomo Heavy Industries Ltd
Current assignee: Sumitomo Heavy Industries Ltd
Priority date: 2019-03-29
Filing date: 2020-03-27
Publication date: 2020-10-09
Also published as: JP2020165798A; TW202036598A; TWI745903B; KR20200115287A; JP7309268B2

Abstract

The invention aims to provide a self-shielding body for an RI manufacturing device, which can reduce weight. In the self-shielding body (6), the 1 st layer (21) shields primary gamma rays (L1), the 2 nd layer (22) shields neutrons (L2), and the 3 rd layer (23) on the outer peripheral side of the 2 nd layer (22) shields captured gamma rays (L3). Since the 2 nd layer (22) is disposed on the outer peripheral side of the 1 st layer (21), the 1 st layer (21) is disposed closer to the target (T) than the 2 nd layer (22). The volume of the gamma-ray shielding material can be reduced by this configuration. Therefore, the weight of the 1 st layer (21) can be reduced. Also, since the neutrons (L2) pass through the 1 st layer (21), a deceleration effect of the neutrons (L2) can be obtained, and thus the 2 nd layer (22) can shield the neutrons (L2) more effectively. Therefore, the 2 nd layer (22) can be made thinner than in the comparative example, and the weight can be reduced.

Description

Self-shielding body for RI manufacturing apparatus

Technical Field

The present application claims priority based on japanese patent application No. 2019-066384, applied 3/29/2019. The entire contents of this Japanese application are incorporated by reference into this specification.

The present invention relates to a self-shielding body for RI (radioisotope) production.

Background

As a method for examination in precision examinations of brain, heart, cancer, etc., there is Positron Emission Tomography (PET). In the PET examination, an examination drug labeled with a positron-emitting radioisotope (positron-emitting nuclear species) is introduced into the body of a subject by injection, inhalation, or the like. The test agent introduced into the body is metabolized or accumulated in a specific site (for example, a tumor or a lesion site). Since the positron emitted from the radioisotope is released when combined with surrounding electrons and eliminated (elimination of gamma rays), a tomographic image in a specific cross section can be obtained by detecting the radiation and processing the radiation by a computer.

As an apparatus for producing such a Radioisotope (RI), for example, an apparatus of patent document 1 is known. In this apparatus, a particle accelerator is disposed inside a self-shielding body, and a charged particle beam from the particle accelerator is irradiated onto a target to produce a radioisotope.

Patent document 1: japanese laid-open patent publication No. 2000-105293

Here, the self-shield for RI manufacturing apparatuses as described above has a plurality of layers for shielding neutrons, γ rays, and the like. As a material for performing such shielding, a material having a large specific gravity may be used. Therefore, there is a problem that the weight of the self-shield becomes heavy. Since the self-shield is installed on the floor of a building, it is required to reduce the weight of the self-shield from the viewpoint of load resistance of the floor.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a self-shielding body for an RI manufacturing apparatus, which can reduce weight.

The RI manufacturing apparatus of the present invention is a self-shield for RI manufacturing apparatus in which an accelerator and an RI manufacturing apparatus are arranged inside and manufacturing of a radioisotope is completed by irradiating a charged particle beam from the accelerator onto a target inside the self-shield, the self-shield comprising: a 1 st layer formed by a 1 st gamma-ray shielding material shielding gamma rays; a 2 nd layer which is disposed on the outer peripheral side of the 1 st layer and is formed of a neutron shielding material having higher neutron shielding properties than the gamma-ray shielding material of the 1 st layer and having a lower specific gravity than the gamma-ray shielding material of the 1 st layer; and a 3 rd layer which is disposed on the outer peripheral side of the 2 nd layer and is formed of a 2 nd gamma ray-shielding material having higher gamma ray-shielding properties than the neutron-shielding material of the 2 nd layer.

In the RI manufacturing apparatus, the 1 st layer of the self-shield shields the primary γ rays, the 2 nd layer shields neutrons, and the 3 rd layer, which is on the outer peripheral side of the 2 nd layer, shields and captures the γ rays. Specifically, since the 2 nd layer is disposed on the outer peripheral side of the 1 st layer, the 1 st layer is disposed closer to the target than the 2 nd layer. In this arrangement, by making the thickness of the 1 st layer the same as compared with a structure in which the 1 st layer is arranged on the outer peripheral side of the 2 nd layer, it is possible to obtain equivalent gamma-ray shielding performance and to reduce the volume of the gamma-ray shielding material. Therefore, the weight of the 1 st layer can be reduced. Also, since neutrons pass through the 1 st layer, a deceleration effect of the neutrons can be obtained, and the 2 nd layer can shield the neutrons more effectively. Therefore, the 2 nd layer can be made thin, and the weight can be reduced. On the other hand, the trapped γ rays do not pass through the 1 st layer, and therefore the trapped γ rays to be shielded by the 3 rd layer increase, but the proportion of the trapped γ rays in the entire radiation is low, and therefore there is no significant influence on the weight increase. With this, the weight of the self-shield can be reduced.

The specific gravity of the 2 nd gamma-ray shielding material of the 3 rd layer may be smaller than that of the 1 st gamma-ray shielding material of the 1 st layer. This can reduce the amount of the material having a high specific gravity in the self-shielding body.

The 1 st layer may be disposed on the innermost circumference side of the self-shield. Thereby, the volume of the γ -ray shielding material of the 1 st layer can be reduced.

Effects of the invention

According to the present invention, it is possible to provide a self-shield for an RI manufacturing apparatus that can reduce weight.

Drawings

Fig. 1 is a cross-sectional view along a horizontal plane of an RI manufacturing system having a self-shielding body according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view along a vertical plane of the RI manufacturing system of fig. 1.

In fig. 3, fig. 3(a) is a cross-sectional view showing a layer structure of a self-shield according to an embodiment of the present invention, and fig. 3(b) is a cross-sectional view showing a layer structure of a self-shield according to a comparative example.

In the figure: 2-accelerator, 6-self-shield, 10-target device (RI manufacturing device), 21-layer 1, 22-layer 2, 23-layer 3.

Detailed Description

Hereinafter, embodiments of the self-shield according to the present invention will be described in detail with reference to the drawings. In the description, terms of "upper" and "lower" are sometimes used, and correspond to an upper direction and a lower direction in the drawings.

Fig. 1 is a cross-sectional view of an RI manufacturing system 1. The RI manufacturing system 1 includes a target device 10(RI manufacturing apparatus). The RI production system 1 produces a Radioisotope (RI). The RI production system 1 can be used as, for example, a PET cyclotron, and RI produced by the RI production system 1 is used for, for example, production of a radiopharmaceutical (including a radiopharmaceutical) that is a radioisotope-labeled compound (RI compound). Examples of the radioisotope-labeled compound used in PET examination (positron emission tomography examination) in hospitals and the like include¹⁸F-FLT (fluorothymidine),¹⁸F-FMISO (fluoromethalone nidazole) and¹¹C-Raclepride and the like.

The RI production system 1 is a so-called self-shielding type particle accelerator system, and the RI production system 1 includes an accelerator 2 that accelerates charged particles and a self-shielding body 6 that is a radiation shielding member (wall body) that surrounds the accelerator 2 and shields radiation. In addition to the accelerator 2, a target device 10 for producing RI, a vacuum pump 4 for evacuating the inside of the accelerator 2, and the like are disposed in the internal space S formed so as to be surrounded by the self-shielding body 6. In the internal space S, accessories necessary for operating the accelerator 2, accessories for cooling the target device 10, and the like are disposed.

The accelerator 2 is a so-called vertical cyclotron, and the accelerator 2 includes a pair of magnetic poles, a vacuum box, and an annular yoke surrounding the pair of magnetic poles and the vacuum box. A pair of magnetic poles are partially opposed to each other with their upper surfaces spaced apart from each other by a predetermined gap in the vacuum chamber. In the gap between these pair of magnetic poles, charged particles such as hydrogen ions are multiply accelerated. The vacuum pump 4 is used to maintain a vacuum environment inside the accelerator 2, and is fixed to a side portion of the accelerator 2, for example. The accelerator 2 emits the charged particle beam B in the irradiation direction.

The target device 10 is for receiving the charged particle beam B irradiated from the accelerator 2 to manufacture RI, and has a container material (e.g., target water;¹⁸o water). As shown in fig. 1 and 2, the target device 10 is usually fixed to a side portion of the accelerator 2. The RI production system 1 of the present embodiment includes 2 target devices 10 disposed on both sides with an accelerator 2 interposed therebetween. For example, the target device 10 disposed on the left side in the figure is disposed on the upper layer side, and the target device 10 disposed on the right side in the figure is disposed on the lower layer side (see fig. 2). The target arrangement 10 is covered by a target shield 7 arranged on the accelerator 2.

The self-shield 6 is formed by a plurality of parts and is formed to cover the accelerator 2 and the target device 10. The accelerator 2 and the target device 10 are disposed inside the self-shield 6, and the self-shield 6 is a structure in which the charged particle beam B from the accelerator 2 is irradiated onto the target inside to complete the manufacture of RI. The self-shielding body 6 is a structure for shielding radiation generated during the manufacture of the RI and preventing leakage to the outside of the self-shielding body 6.

As shown in fig. 2, the RI manufacturing system 1, which is entirely shielded by the self-shielding body 6, is disposed in an RI manufacturing room 101 of the building 100. The RI manufacturing system 1 is installed on the floor 102 of the RI manufacturing chamber 101.

As shown in fig. 1, the self-shield 6 includes

side wall portions

11 and 12 facing each other in the irradiation direction of the charged particle beam B and

side wall portions

13 and 14 facing each other in the direction orthogonal to the irradiation direction of the charged particle beam B in the horizontal direction. The side wall portion 11 and the side wall portion 12 are disposed apart from each other, and the side wall portion 13 and the side wall portion 14 are disposed apart from each other. One end portions of the

side wall portions

13 and 14 are connected to both end portions of the side wall portion 11, and the other end portions of the

side wall portions

13 and 14 are connected to both end portions of the side wall portion 12. Thereby, the peripheral surface of the internal space S of the shield 6 is surrounded by the

side wall portions

11, 12, 13, and 14 without any gap.

As shown in fig. 2, the upper end of the self-shield 6 is closed by an upper wall 15. That is, the upper wall portion 15 is connected to the upper end portions of the

side wall portions

11, 12, 13, and 14. The lower ends of the

side wall portions

11, 12, 13, 14 are provided on the floor surface 102 of the RI manufacturing chamber 101. Thus, the internal space S surrounded by the

side walls

11, 12, 13, and 14 is sealed without a gap in the vertical direction by the upper wall 15 and the floor surface 102.

As described above, the

side wall portions

11, 12, 13, and 14 of the self-shield 6 are disposed inside the side wall portion 103 of the RI production chamber 101 in which the self-shield 6 is disposed, and are disposed closer to the target device 10 than the side wall portion 103. The upper wall portion 15 of the self-shield 6 is disposed inside the upper wall portion 104 of the RI production chamber 101 in which the self-shield 6 is disposed, and is disposed closer to the target device 10 than the upper wall portion 104. The

side wall portions

11, 12, 13, and 14 are provided directly on the ground 102, but a lower wall portion may be provided to connect lower end portions of the

side wall portions

11, 12, 13, and 14 to each other, and the lower wall portion may be disposed on the ground 102.

The self-shield 6 has a structure that can be divided in the irradiation direction of the charged particle beam B and the direction orthogonal to the horizontal direction (see fig. 1). That is, the

side walls

11 and 12 and the upper wall 15 are detachably divided in the vicinity of the center. Thereby, the self-shield 6 is divided into the 1 st structure 6A and the 2 nd structure 6B. The 2 nd structure 6B reciprocates relative to the 1 st structure 6A along a guide portion (not shown) provided on the floor surface 102. This allows the self-shield 6 to be opened and closed. The 1 st structural body 6A and the 2 nd structural body 6B are connected without a gap therebetween to prevent radiation leakage.

Next, the layer structure of the self-shield 6 will be described in more detail with reference to fig. 3. Fig. 3(a) is a schematic cross-sectional view showing the layer structure of the self-shield 6 according to the present embodiment. Fig. 3(b) is a schematic cross-sectional view showing the layer structure of the self-shield 56 according to the comparative example. Although fig. 3(a) shows only the layer structure of the

side walls

12, 13, and 14, other wall portions not shown have the same layer structure.

As shown in fig. 3(a), the 1 st layer 21, the 2 nd layer 22, and the 3 rd layer 23 are provided in this order from the inner periphery side to the outer periphery side of the shield 6, that is, in this order from the inner space S of the shield 6 to the outside of the shield 6.

The 1 st layer 21 is a layer formed by a 1 st gamma-ray shielding material that shields gamma rays. The 1 st layer 21 is disposed on the innermost peripheral side of the self-shield 6. The term "disposed on the innermost peripheral side" refers to a state in which the layer having a function of shielding radiation is disposed on the innermost peripheral side and no other layer shielding gamma rays or neutrons such as the 1 st to 3 rd layers is formed on the inner peripheral side of the 1 st layer 21. Therefore, even when the 1 st layer 21 is covered with a paint layer formed by coating the inner peripheral surface of the 1 st layer 21 with paint or with a protective material having no radiation shielding function, the 1 st layer 21 is a layer disposed on the innermost peripheral side of the self-shielding body 6.

The 1 st layer 21 is a layer that mainly shields the primary γ -ray L1 among the radiation from the target device 10. As the 1 st γ -ray shielding material forming the 1 st layer 21, a metal material made of lead may be used. The metal material made of lead also has a function of decelerating neutron L2. In consideration of the shielding property of the primary γ -ray L1 or the deceleration effect of the neutron L2, a metal material made of iron, a metal material made of tungsten, or the like can be used as the 1 st γ -ray shielding material. The metal material composed of a specific metal component (lead, iron, tungsten, or the like) having γ -ray shielding properties is not limited to a small amount of the metal component, and the metal component needs to be contained at a content rate to a degree that can exhibit a function of shielding primary γ -ray L1. Further, the metal powder may not contain 100% of a specific metal component, or may contain other components within a range not affecting the shielding property. That is, the specific metal component may be contained at a predetermined content. In the case where there are a plurality of metal components having the shielding property of the primary γ -ray L1, the total content of the plurality of metal components may satisfy a predetermined value.

The 2 nd layer 22 is a layer that mainly shields the neutrons L2 in the radiation that has passed through the 1 st layer 21. The 2 nd layer 22 is disposed on the outer peripheral side of the 1 st layer 21. Here, the 2 nd layer 22 and the 1 st layer 21 are disposed adjacent to each other on the outer peripheral side. The 2 nd layer 22 is formed of a neutron shielding material having higher neutron shielding property than the 1 st layer 21 and having a smaller specific gravity than the 1 st gamma-ray shielding material of the 1 st layer 21. The phrase "high neutron shielding property" means that the neutron shielding material of the 2 nd layer 22 can shield more neutrons when the 1 st γ -ray shielding material of the 1 st layer 21 and the neutron shielding material of the 2 nd layer 22 are compared with each other at the same thickness. As such a neutron shielding material, a resin material made of polyethylene or the like can be used. In addition, a resin material made of paraffin or the like may be used. The resin material made of a specific resin component (polyethylene, paraffin, or the like) is not limited to a small amount of the resin component, and the resin component needs to be contained at a content rate to a degree that the resin component can exhibit a function of shielding neutrons. Further, the resin composition may not contain 100% of a specific resin component, or may contain other components within a range not affecting the shielding property. That is, the specific resin component may be contained at a predetermined content. In the case where there are a plurality of resin components having shielding properties of the neutron L2, the total content of the plurality of resin components may satisfy a predetermined value.

The 3 rd layer 23 mainly shields the 2 nd layer 22 from the gamma ray L3 generated when the neutron L2 is shielded. The 3 rd layer 23 is disposed on the outer peripheral side of the 2 nd layer 22. Here, the 3 rd layer 23 and the 2 nd layer 22 are disposed adjacent to each other on the outer peripheral side. The 2 nd gamma-ray shielding material of the 3 rd layer 23 has higher gamma-ray shielding property than the neutron shielding material of the 2 nd layer 22. And, the specific gravity of the 2 nd gamma ray-shielding material of the 3 rd layer 23 is smaller than that of the 1 st layer 21. In addition, the phrase "high gamma ray-shielding property" means that the 2 nd gamma ray-shielding material of the 3 rd layer 23 can shield more gamma rays when comparing the neutron-shielding material of the 2 nd layer 22 with the 2 nd gamma ray-shielding material of the 3 rd layer 23 in the same thickness. As such a 2 nd gamma ray-shielding material, heavy concrete can be used.

The thickness of the 1 st layer 21 is smaller than the thickness of the 2 nd layer 22 and the thickness of the 3 rd layer 23. For example, the thickness of the 1 st layer 21 may be set to be thinner than the thickness of the 2 nd layer 22 and the thickness of the 3 rd layer 23 by a predetermined ratio.

Next, the operational effects of the self-shield 6 according to the present embodiment will be described.

First, a layer structure of the self-shield 56 according to a comparative example will be described with reference to fig. 3 (b). As shown in fig. 3(b), the 2 nd layer 22, the 1 st layer 21, and the 3 rd layer 23 are provided in this order from the inner peripheral side of the shield 56. At this time, neutrons L2 from the target apparatus 10 are shielded by the layer 2 22. At this time, when neutron L2 is shielded in layer 2 22, captured γ -ray L3 is generated. On the other hand, the 1 st layer 21 shields the primary γ -ray L1 and captures the γ -ray L3. However, since the radiation (γ rays L1, L3, and neutrons L2) that cannot be completely shielded by the 1 st layer 21 leaks, the 3 rd layer 23 on the outermost periphery shields these radiations.

In contrast, in the self-shield 6 according to the present embodiment shown in fig. 3(a), the 1 st layer 21 shields the primary γ -ray L1, the 2 nd layer 22 shields the neutron L2, and the 3 rd layer 23 on the outer peripheral side of the 2 nd layer 22 shields the captured γ -ray L3. Here, since the 2 nd layer 22 is disposed on the outer peripheral side of the 1 st layer 21, the 1 st layer 21 is disposed at a position closer to the target T than the 2 nd layer 22. In this arrangement, by setting the thickness of the 1 st layer 21 to be the same as that of the comparative example, it is possible to obtain equivalent gamma-ray shielding performance and to reduce the volume of the gamma-ray shielding material, as compared with the structure according to the comparative example shown in fig. 3 (b). Therefore, the weight of the 1 st layer 21 can be reduced. Also, the neutron L2 passes through the 1 st layer 21, and therefore, a deceleration effect of the neutron L2 can be obtained, so that the 2 nd layer 22 can shield the neutron L2 more effectively. Therefore, the 2 nd layer 22 can be made thinner than in the comparative example, and the weight can be reduced. On the other hand, the captured gamma ray L3 does not pass through the 1 st layer 21, and therefore the captured gamma ray L3 that the 3 rd layer 23 should shield increases, but the captured gamma ray L3 occupies a low proportion of the entire radiation, and therefore has no significant influence on the weight increase. This reduces the weight of the self-shield 6.

For example, in the case of using lead as the material of the 1 st layer 21, the specific gravity is as large as 11.3g/cm³Therefore, the ratio of the 1 st layer to the total weight of the self-shield 6 is large. Therefore, by reducing the volume of the 1 st layer 21, the weight of the self-shield 6 can be reduced. By reducing the weight of the self-shielding body 6 in the above manner, the floor 102 of the building 100 can have a sufficient margin space in terms of load resistance, and the transportation work and the like at the time of installation can also be facilitated. Also, lead is expensive in weight unit price, and thereforeBy reducing the volume of lead, the material cost of the entire self-shield 6 can be reduced.

The specific gravity of the 2 nd gamma-ray shielding material of the 3 rd layer 23 is smaller than that of the 1 st gamma-ray shielding material of the 1 st layer 21. This can reduce the amount of the material having a high specific gravity in the self-shield 6.

The 1 st layer 21 is disposed on the innermost peripheral side of the self-shield 6. This can reduce the volume of the γ -ray shielding material of the 1 st layer 21.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and may be modified within a scope not changing the gist described in each technical means.

For example, in the above embodiment, the 3 rd layer 23 is formed of a material having a lower specific gravity than the 1 st layer 21. Alternatively, as the 3 rd layer 23, the same γ -ray shielding material as the 1 st layer 21 may be used.

In the above embodiment, the layers are directly bonded to each other, but a member having no shielding property against radiation may be inserted.

Claims

1. A self-shield for an RI manufacturing apparatus, in which an accelerator and an RI manufacturing apparatus are arranged inside and production of a radioisotope is completed by irradiating a charged particle beam from the accelerator onto a target inside the self-shield, the self-shield for the RI manufacturing apparatus comprising:

a 1 st layer formed by a 1 st gamma-ray shielding material shielding gamma rays;

a 2 nd layer which is disposed on the outer peripheral side of the 1 st layer and is formed of a neutron shielding material having higher neutron shielding properties than the gamma-ray shielding material of the 1 st layer and having a lower specific gravity than the gamma-ray shielding material of the 1 st layer; and

and a 3 rd layer which is disposed on the outer peripheral side of the 2 nd layer and is formed of a 2 nd gamma ray-shielding material having higher gamma ray-shielding properties than the neutron-shielding material of the 2 nd layer.

2. The self-shield for the RI manufacturing apparatus according to claim 1,

the 2 nd gamma-ray shielding material of the 3 rd layer has a lower specific gravity than the 1 st gamma-ray shielding material of the 1 st layer.

3. The self-shield for the RI manufacturing apparatus according to claim 1 or 2, wherein,

the 1 st layer is disposed on an innermost peripheral side of the self-shield.