TWI745903B - Self-shielding parts for radioisotope manufacturing equipment - Google Patents

Abstract

[Question] The objective is to provide a self-shielding material for RI manufacturing equipment that can reduce weight. [Solution] In the self-shielding component (6), the first layer (21) shields primary gamma rays (L1), and the second layer (22) shields neutrons (L2), and is closer to the second layer (22) The third layer (23) on the outer peripheral side shields and captures gamma rays (L3). Here, the second layer (22) is arranged on the outer peripheral side of the first layer (21), so the first layer (21) is arranged closer to the target (T) than the second layer (22). With this configuration, the volume of the gamma ray shielding material can be reduced. Therefore, the weight of the first layer (21) can be reduced. In addition, the neutrons (L2) pass through the first layer (21), so the deceleration effect of the neutrons (L2) can be obtained, so that the second layer (22) can more effectively shield the neutrons (L2). Therefore, the second layer (22) can be made thinner than the comparative example, and the weight can be reduced.

Description

Self-shielding parts for radioisotope manufacturing equipment

The present invention relates to a self-shielding member for RI (radioisotope) manufacturing.

As an examination method in precise examinations of the brain, heart, cancer, etc., there is positron emission tomography (PET: Positron Emission Tomography). In this PET test, an inspection agent labeled with a radioisotope (positron ejection nucleus) that emits positrons (positrons) is introduced into the subject's body by injection or inhalation. The inspection agent introduced into the body is metabolized or accumulated in a specific site (for example, tumor or lesion location). When the positron emitted from the radioisotope combines with the surrounding electrons and disappears, it emits radiation (vanishing gamma rays). Therefore, by detecting the radiation and processing it by a computer, it becomes possible to obtain a tomographic image in a specific section.

As an apparatus for manufacturing such a radioisotope (RI), for example, the apparatus of Patent Document 1 is known. In this device, a particle accelerator is arranged inside a self-shield, and a charged particle beam from the particle accelerator is irradiated on a target to produce a radioactive isotope. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2000-105293

[The problem to be solved by the invention]

Here, the self-shielding material for the RI manufacturing apparatus as described above has a plurality of layers for shielding neutrons, gamma rays, and the like. As a material used for this kind of masking, a material with a high specific gravity is sometimes used. Therefore, there is a problem that the weight of the self-shielding member becomes heavier. Since the self-shielding material is installed on the ground of the building, it is required to reduce the weight of the self-shielding material from the viewpoint of the load resistance of the ground and the like.

Therefore, the object of the present invention is to provide a self-shielding member for an RI manufacturing device that can reduce weight. [Means to solve the problem]

The self-shielding member for the RI manufacturing device of the present invention is equipped with an accelerator and an RI manufacturing device inside, and the charged particle beam from the accelerator is irradiated on the target to complete the manufacture of radioisotopes; it is characterized by ：The first layer is formed by the first gamma-ray shielding material that shields gamma rays; the second layer is arranged on the outer peripheral side than the first layer, and is more than the first layer The gamma ray shielding material has higher neutron shielding properties and has a smaller specific gravity than the first layer of gamma ray shielding material. The third layer is formed by the neutron shielding material; and the third layer is arranged closer to the second layer. The position on the outer peripheral side is formed by a second gamma ray shielding material that has higher gamma ray shielding properties than the second layer of neutron shielding material.

In this self-shielding material for the RI manufacturing device, the first layer shields primary gamma rays, the second layer shields neutrons, and the third layer on the outer peripheral side than the second layer shields and captures gamma rays. Specifically, the second layer is arranged on the outer peripheral side of the first layer, and therefore the first layer is arranged closer to the target than the second layer. In this configuration, compared to the structure where the first layer is arranged on the outer peripheral side than the second layer, by setting the thickness of the first layer to be the same, it is possible to obtain equivalent gamma ray shielding performance at the same time. , Can reduce the volume of gamma ray shielding material. Therefore, the weight of the first layer can be reduced. In addition, neutrons pass through the first layer, so the deceleration effect of neutrons can be obtained, and the second layer can more effectively shield neutrons. Therefore, the second layer can be made thinner and the weight can be reduced. On the other hand, the captured gamma rays do not pass through the first layer, so the captured gamma rays that should be shielded by the third layer increase, but the captured gamma rays account for a low proportion of the total radiation, so there is no significant effect on the weight increase . With the above, the weight of the self-shielding member can be reduced.

The specific gravity of the second gamma ray shielding material of the third layer may be smaller than that of the first gamma ray shielding material of the first layer. As a result, the amount of material with a large specific gravity can be reduced in the self-shielding member.

The first layer may be arranged on the innermost peripheral side of the self-shielding member. Thereby, the volume of the gamma ray shielding material of the first layer can be reduced. [Effects of the invention]

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

Hereinafter, the embodiments of the self-shielding member according to the present invention will be described in detail while referring to the drawings. Moreover, in the description, the terms "upper" and "lower" are sometimes used, which correspond to the upper direction and the lower direction of the drawing.

FIG. 1 is a cross-sectional view of the RI manufacturing system 1. The RI manufacturing system 1 includes a target device 10 (RI manufacturing device). The RI manufacturing system 1 manufactures radioisotopes (RI). The RI manufacturing system 1 can be used, for example, as a cyclotron for PET, and the RI manufactured by the RI manufacturing system 1 is used, for example, in the manufacture of radiopharmaceuticals (including radiopharmaceuticals) as radioisotope-labeled compounds (RI compounds). As radioisotope-labeled compounds used in PET examinations (positron emission tomography examinations) in hospitals, there are ¹⁸ F-FLT (fluorothymidine) and ¹⁸ F-FMISO (F-fluoromisonidazole, labelled fluoronitroimidazole) And ¹¹ C-raclopride (raclopride) and so on.

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

The accelerator 2 is a so-called vertical cyclotron. The accelerator 2 has a pair of magnetic poles, a vacuum box, and an annular yoke surrounding the pair of magnetic poles and the vacuum box. A part of a pair of magnetic poles faces each other at a predetermined interval on the upper surface of the pair of magnetic poles in the vacuum box. In this kind of gap between a pair of magnetic poles, charged particles such as hydrogen ions are accelerated multiple times. The vacuum pump 4 is used to maintain a vacuum environment in the accelerator 2, and is fixed to the side of the accelerator 2, for example. The accelerator 2 emits a charged particle beam B in the irradiation direction.

The target device 10 is used to receive the charged particle beam B irradiated from the accelerator 2 to produce RI, and a storage portion for storing raw materials (for example, target water; ¹⁸ O water) is formed inside. As shown in FIGS. 1 and 2, the target device 10 is usually fixed to the side of the accelerator 2. The RI manufacturing system 1 of this embodiment includes two target devices 10 arranged on both sides with an accelerator 2 interposed therebetween. For example, the target device 10 arranged on the left side of the figure is arranged on the upper side, and the target device 10 arranged on the right side of the figure is arranged on the lower side (see FIG. 2). The target device 10 is covered by a target shield 7 arranged on the accelerator 2.

The self-shielding member 6 is composed of a plurality of members, and is formed to cover the accelerator 2 and the target device 10. The self-shielding member 6 is provided with an accelerator 2 and a target device 10 inside, and the structure for RI manufacturing is completed by irradiating the charged particle beam B from the accelerator 2 on the target inside. The self-shield 6 is a structure for shielding the radiation generated when the RI is manufactured to prevent leakage to the outside of the self-shield 6.

As shown in FIG. 2, the RI manufacturing system 1 that is entirely shielded by the self-shielding member 6 is disposed in the RI manufacturing room 101 of the building 100. The RI manufacturing system 1 is installed on the floor 102 of the RI manufacturing room 101.

As shown in FIG. 1, the self-shielding member 6 includes side wall portions 11, 12 facing each other in the irradiation direction of the charged particle beam B, and facing each other in a direction orthogonal to the irradiation direction of the charged particle beam B in the horizontal direction. The side walls 13,14. The side wall portion 11 and the side wall portion 12 are arranged to be separated from each other, and the side wall portion 13 and the side wall portion 14 are arranged to be separated from each other. One end of the side wall portions 13 and 14 is connected to both ends of the side wall portion 11, and the other side end portion of the side wall portions 13 and 14 is connected to both ends of the side wall portion 12. Thereby, the peripheries of the internal space S of the self-shield 6 are surrounded by the side wall portions 11, 12, 13, and 14 without gaps.

As shown in FIG. 2, the upper end portion of the self-shielding member 6 is closed by the upper wall portion 15. That is, the upper wall 15 is connected to the upper ends of the side wall parts 11, 12, 13, and 14. The lower ends of the side walls 11, 12, 13, and 14 are installed on the floor 102 of the RI manufacturing room 101. Thereby, the internal space S enclosed by the side wall parts 11, 12, 13, 14 in the up-and-down direction by the upper wall part 15 and the floor surface 102 is plugged without a gap.

With the above, the side wall portions 11, 12, 13, 14 of the self-shield 6 are arranged inside the side wall 103 of the RI manufacturing chamber 101 where the self-shield 6 is arranged, and are arranged closer to the target than the side wall 103 The location of the device 10. In addition, the upper wall portion 15 of the self-shield 6 is arranged inside the upper wall 104 of the RI manufacturing chamber 101 where the self-shield 6 is arranged, and is arranged at a position closer to the target device 10 than the upper wall 104. Furthermore, the side wall portions 11, 12, 13, 14 are directly provided on the ground 102, but a lower wall portion connecting the lower ends of the side wall portions 11, 12, 13, 14 to each other may be provided, and the lower wall portion is arranged on the ground 102 on.

Furthermore, the self-shielding member 6 has a structure that can be divided along the irradiation direction of the charged particle beam B and the direction orthogonal to the horizontal direction (see FIG. 1). That is, the side wall parts 11 and 12 and the upper wall part 15 are divided so that attachment or detachment is possible in the vicinity of the center position. Thereby, the self-shielding material 6 is divided into the 1st structure body 6A and the 2nd structure body 6B. Among them, the second structure 6B reciprocates with respect to the first structure 6A along a guide portion (not shown) provided on the floor 102. Thereby, the self-shield 6 becomes a structure which can be opened and closed. The first structure 6A and the second structure 6B are connected without a gap to prevent radiation leakage.

Next, referring to FIG. 3, the layer structure of the self-shielding member 6 will be described in more detail. FIG. 3(a) is a schematic cross-sectional view showing the layer structure of the self-shielding material 6 according to this embodiment. FIG. 3(b) is a schematic cross-sectional view showing the layer structure of the self-shielding material 56 according to the comparative example. Furthermore, FIG. 3(a) only shows the layer structure of the side wall portions 12, 13, and 14, but other wall portions not shown also have a layer structure of the same principle.

As shown in FIG. 3(a), the shield 6 from the inner peripheral side to the outer peripheral side in order, that is, from the inner space S of the shield 6 to the outside of the shield 6, the first layer 21 and the second Layer 22 and third layer 23.

The first layer 21 is a layer formed of a first gamma ray shielding material that shields gamma rays. The first layer 21 is arranged on the innermost peripheral side of the self shield 6. Among them, "arranged on the innermost peripheral side" means that the layer is arranged on the innermost peripheral side as a layer with the function of shielding radiation, and it means that no other layers such as the first layer 21 are formed on the inner peripheral side than the first layer 21. ~ The state of a layer that shields gamma rays or neutrons like the third layer. Therefore, even when the coating layer formed by coating the inner peripheral surface of the first layer 21 with paint or is covered by a protective material that does not have the function of shielding radiation, the first layer 21 is arranged on the self-shielding member The layer on the innermost peripheral side in 6.

The first layer 21 is a layer that mainly shields the primary gamma ray L1 among the radiation from the target device 10. As the first gamma ray shielding material forming the first layer 21, a metal material made of lead can be used. The metal material made of lead also has the function of decelerating the neutron L2. Furthermore, considering the shielding properties of the primary gamma rays L1 or the deceleration effect of the neutrons L2, as the first gamma ray shielding material, a metallic material made of iron, a metallic material made of tungsten, etc. can be used. Furthermore, a metal material composed of a specific metal component (lead, iron, tungsten, etc.) that has gamma-ray shielding properties means that it does not need to contain a small amount of the metal component, but needs to be able to perform the shielding once. The content rate of the level of the function of the gamma ray L1 includes the metal component. In addition, it is not necessary to contain 100% of the specific metal component, or it may contain other components within a range that does not affect the shielding properties. That is, the specific metal component may be contained at a predetermined content rate. Furthermore, in the case of having a plurality of metal components having the aforementioned primary gamma ray L1 shielding property, the total content of the plurality of metal components may satisfy a predetermined value.

The second layer 22 is a layer that mainly shields neutrons L2 in the radiation passing through the first layer 21. The second layer 22 is arranged on the outer peripheral side than the first layer 21. Here, the second layer 22 and the first layer 21 are arranged adjacent to each other on the outer peripheral side. The second layer 22 is formed of a neutron shielding material having higher neutron shielding properties than the first layer 21 and having a smaller specific gravity than the first gamma ray shielding material of the first layer 21. Furthermore, "high neutron shielding properties" means that when the first gamma ray shielding material of the first layer 21 and the neutron shielding material of the second layer 22 are compared with the same thickness, the neutron shielding of the second layer 22 The material can shield more neutrons. 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 wax or the like can be used. Furthermore, a resin material composed of a specific resin component (polyethylene, paraffin wax, etc.) means that it does not need to contain a small amount of the resin component, but needs to be contained at a content rate that can perform the function of shielding neutrons. The resin component. In addition, 100% of the specific resin component may not be contained, or other components may be contained within a range that does not affect the shielding properties. That is, the specific resin component may be contained at a predetermined content rate. In addition, in the case of having plural kinds of resin components having the shielding properties of the aforementioned neutron L2, the total content of the plural kinds of resin components may satisfy a predetermined value.

The third layer 23 is a layer that mainly shields the trapping gamma rays L3 generated when the second layer 22 shields the neutrons L2. The third layer 23 is arranged on the outer peripheral side than the second layer 22. Here, the third layer 23 and the second layer 22 are arranged adjacent to each other on the outer peripheral side. The second gamma ray shielding material of the third layer 23 has higher gamma ray shielding properties than the neutron shielding material of the second layer 22. In addition, the specific gravity of the second gamma ray shielding material of the third layer 23 is smaller than that of the gamma ray shielding material of the first layer 21. Furthermore, "high gamma ray shielding properties" means that when the neutron shielding material of the second layer 22 and the second gamma ray shielding material of the third layer 23 are compared with the same thickness, the second gamma ray shielding material of the third layer 23 Gamma ray shielding materials can shield more gamma rays. As this second gamma ray shielding material, heavy concrete can be used.

The thickness of the first layer 21 is thinner than the thickness of the second layer 22 and the thickness of the third layer 23. For example, the thickness of the first layer 21 may be set to be thinner than the thickness of the second layer 22 and the thickness of the third layer 23 by a predetermined ratio.

Next, the function/effect of the self-shield 6 according to this embodiment will be described.

First, referring to FIG. 3(b), the layer structure of the self-shielding member 56 according to the comparative example will be described. As shown in FIG. 3( b ), the self-shielding material 56 includes the second layer 22, the first layer 21, and the third layer 23 in this order from the inner peripheral side. At this time, the neutrons L2 from the target device 10 are shielded by the second layer 22. At this time, in the second layer 22, when the neutron L2 is shielded, trapped gamma rays L3 are generated. In contrast, the first layer 21 blocks the gamma ray L1 and captures the gamma ray L3 once. However, the radiation (gamma rays L1, L3, and neutron L2) that cannot be completely shielded by the first layer 21 leaks, so the third layer 23 on the outermost peripheral side shields these radiations.

In contrast, in the self-shielding material 6 according to the present embodiment shown in FIG. 3(a), the first layer 21 shields the primary gamma rays L1, and the second layer 22 shields the neutrons L2, and is higher than the second layer 22 The third layer 23 on the outer peripheral side shields and captures gamma rays L3. Here, the second layer 22 is arranged on the outer peripheral side of the first layer 21, and therefore the first layer 21 is arranged at a position closer to the target T than the second layer 22. In this configuration, compared with the structure related to the comparative example shown in FIG. 3(b), by setting the thickness of the first layer 21 to be the same as that of the comparative example, it is possible to obtain equivalent gamma ray shielding performance at the same time , Can reduce the volume of gamma ray shielding material. Therefore, the weight of the first layer 21 can be reduced. In addition, since the neutrons L2 pass through the first layer 21, the deceleration effect of the neutrons L2 can be obtained, and the second layer 22 can more effectively shield the neutrons L2. Therefore, the second layer 22 can be made thinner than the comparative example, and the weight can be reduced. On the other hand, the trapped gamma rays L3 do not pass through the first layer 21, so the trapped gamma rays L3 that should be shielded by the third layer 23 increase, but the trapped gamma rays L3 account for a low proportion of the total radiation, so the weight The increase has no significant effect. With the above, the weight of the self-shielding member 6 can be reduced.

For example, when lead is used as the material of the first layer 21, the specific ^{gravity is as high as 11.3 g/cm 3} , so the first layer accounts for a large proportion of the total weight of the self-shielding material 6. Therefore, by reducing the volume of the first layer 21, the weight of the self-shielding member 6 can be reduced. By reducing the weight of the self-shielding member 6 in the above-mentioned manner, the floor 102 of the building 100 can have a sufficient load-bearing capacity, and the transportation operation during installation can also be facilitated. In addition, the weight unit price of lead is expensive, so by reducing the volume of lead, the material cost of the entire self-shielding member 6 can be reduced.

The specific gravity of the second gamma ray shielding material of the third layer 23 is smaller than that of the first gamma ray shielding material of the first layer 21. Thereby, in the self-shielding member 6, the amount of material with a high specific gravity can be reduced.

The first layer 21 is arranged on the innermost peripheral side of the self shield 6. Thereby, the volume of the gamma ray shielding material of the first layer 21 can be reduced.

As mentioned above, an embodiment of the present invention has been described, but the present invention is not limited to the above-mentioned embodiment, and may be modified without changing the technical idea described in the scope of each patent application.

For example, in the above-mentioned embodiment, the third layer 23 is formed of a material having a smaller specific gravity than the first layer 21. Instead, as the third layer 23, the same gamma ray shielding material as that of the first layer 21 can be used.

In the above embodiment, the layers are directly joined to each other, but a member that does not have radiation shielding properties may be inserted.

2: accelerator 6: Self-shielding 10: Target device (RI manufacturing device) 21: Level 1 22: Layer 2 23: layer 3

[Fig. 1] is a cross-sectional view along a horizontal plane of an RI manufacturing system having a self-shielding member according to an embodiment of the present invention. [Fig. 2] is a vertical cross-sectional view of the RI manufacturing system in Fig. 1. [Fig. [FIG. 3] (a) is a cross-sectional view showing the layer structure of the self-shielding material according to the embodiment of the present invention, and (b) is a cross-sectional view showing the layer structure of the self-shielding material according to the comparative example.

6: Self-shielding

10: Target device

12: Side wall

13: side wall

14: side wall

21: Level 1

22: Layer 2

23: layer 3

56: Self-shielding

L1: One gamma ray

L2: Neutron

L3: Capture gamma rays

S: Internal space

Claims (3)

A self-shielding member for a radioisotope manufacturing device is equipped with an accelerator and a radioisotope manufacturing device inside, and the radioisotope is manufactured by irradiating a charged particle beam from the aforementioned accelerator on a target in the interior; it is characterized by Equipped with: the first layer, which is formed by the first gamma-ray shielding material that shields gamma rays; the second layer, which is arranged on the outer peripheral side than the first layer, and is more The first layer of gamma ray shielding material has higher neutron shielding properties and has a smaller specific gravity than the aforementioned gamma ray shielding material of the first layer. The gamma ray shielding material is formed by the neutron shielding material; The second layer is located closer to the outer peripheral side, and is formed of a second gamma ray shielding material that has higher gamma ray shielding properties than the neutron shielding material of the second layer; The first gamma ray shielding material has at least one material selected from lead, iron, and tungsten; the second gamma ray shielding material of the third layer is heavy concrete. The self-shielding member for a radioisotope manufacturing device according to claim 1, wherein the specific gravity of the second gamma ray shielding material in the third layer is smaller than that of the first gamma ray shielding material in the first layer. For example, the self-shielding member for the radioisotope manufacturing device of claim 1 or 2, in which, The first layer is arranged on the innermost peripheral side of the self-shield.

Images