Radionuclide production system and radionuclide production method

Abstract

To provide a radioactive nuclide producing system and radioactive nuclide producing method in which a radioactive nuclide can be produced safely and efficiently by a compact and light-weight apparatus.SOLUTION: A radioactive nuclide producing system S according to the present invention comprises: an electron beam accelerator 1 which irradiates electron beam 20; a target 10 for generating Bremsstrahlung radiation which generates Bremsstrahlung radiation 30 by the irradiated electron beam 20; and a target 40 for producing radioactive nuclide which includes a raw material that is irradiated with the generated Bremsstrahlung radiation 30 to produce a radioactive nuclide, where the thickness of the target 10 for generating Bremsstrahlung radiation is set within a range where a production rate of the radioactive nuclide peaks and in a condition that an irradiation dose of the electron beam 20 to the target 40 for producing radioactive nuclide becomes the smallest in the range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a radionuclide production system and a radionuclide production method. [Background technology]

[0002] Actinium-225 (Ac-225), an alpha-ray emitting nuclide that has been used in research and development as a raw material nuclide for therapeutic drugs, 225 Ac) is the parent nuclide thorium-229 (Th-229, 229 Currently, there are only three facilities in the world capable of supplying the clinically available radionuclide Ac-225: the Institute for Transuranium Elements (ITU) in Karlsruhe, Germany, Oak Ridge National Laboratory (ORNL) in the United States, and the Institute of Physics and Power Engineering (IPPE) of the Russian National Science Center in Obninsk, Russia.

[0003] Th-229 does not exist in nature, and uranium 233 (U-233, 223 It is produced by the decay of U), but U-233 will no longer be produced due to nuclear protection reasons. Therefore, the only amount of Ac-225 that can be produced in the world is the amount produced by the decay of Th-229, which is produced by the decay of U-233 currently held in the world. While this is sufficient for preclinical testing, etc., a large shortage is expected in the future, and production using an accelerator is desired.

[0004] Regarding the accelerator-based production of Ac-225, naturally occurring radium-226 (Ra-226, 226Cyclotron production tests using the Ra-226(p,2n)Ac-225 reaction with Ra are underway at ORNL, BNL, and the National Institutes for Quantum and Radiological Science and Technology, but have not yet been commercialized. Cyclotron production has had the problem of mass production being impossible, even if the Ra-226 target is made thicker, due to the short range of accelerated protons in the Ra-226 target. Furthermore, since most of the energy of the accelerated protons is lost in the target, it is difficult to remove heat from the target, making it impossible to increase the current value or energy required for mass production.

[0005] As another method for producing Ac-225, for example, Patent Document 1 describes a method in which electrons accelerated by an electron beam accelerator are irradiated onto a bremsstrahlung target to generate bremsstrahlung, and this bremsstrahlung is then irradiated onto the raw material Ra-226 to produce Ac-225. Furthermore, for example, Patent Document 2 describes a method for producing medical radionuclides by irradiating a converter (a bremsstrahlung generation target) with electrons accelerated by an electron beam accelerator to generate bremsstrahlung radiation, and then irradiating a plurality of plate-shaped target material plates with this bremsstrahlung radiation. In this method, the diameter or average thickness of the target material plates in the front plate group arranged on the front side is made smaller than the diameter or average thickness of the target material plates in the rear plate group arranged on the rear side. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-183926 [Patent Document 2] Patent No. 6752590 specification Summary of the Invention [Problem to be solved by the invention]

[0007] However, the techniques described in Patent Documents 1 and 2 have a problem in that the electron beam accelerated by the electron beam accelerator is irradiated onto a solution or solid radionuclide production target containing raw materials for producing radionuclides, a container for accommodating the radionuclide production target, etc., resulting in a high thermal load, which raises concerns that the radionuclide production target and the container may be damaged or become brittle.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a radionuclide production system and a radionuclide production method that can produce radionuclides safely and efficiently using a small and lightweight device. [Means for solving the problem]

[0009] The radionuclide production system according to the present invention, which solves the above-mentioned problems, comprises an electron beam accelerator that irradiates electron beams, a bremsstrahlung generation target that generates bremsstrahlung radiation by the irradiated electron beams, and a radionuclide production target containing raw materials that are irradiated with the generated bremsstrahlung radiation to produce a radionuclide, and the thickness of the bremsstrahlung generation target is set within a range that results in a peak production rate of the radionuclide, and under conditions that make the irradiation dose of the electron beam to the radionuclide production target the smallest within the range. [Effects of the Invention]

[0010] The radionuclide production system and radionuclide production method according to the present invention can produce radionuclides safely and efficiently using a small, lightweight device. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a radionuclide production system according to an embodiment of the present invention. [Figure 2]FIG. 1 is a diagram showing an example of the relationship between the thickness of a bremsstrahlung target and the production rate of radioactive nuclides (upper graph), and the relationship between the thickness of a bremsstrahlung target and the amount of electron beams passing through the bremsstrahlung target (lower graph). [Figure 3] FIG. 2 is an explanatory diagram showing an example of a target for generating bremsstrahlung radiation; [Figure 4] FIG. 2 is a schematic diagram showing another configuration example of a radionuclide production system according to an embodiment of the present invention. [Figure 5] FIG. 1 is a schematic diagram illustrating an example of an electron beam removal device. [Figure 6] FIG. 2 is an explanatory diagram illustrating an example of operation of the electron beam removal device. [Figure 7] FIG. 10 is an explanatory diagram illustrating another example of the operation of the electron beam removal device. [Figure 8] 1 is a flow chart illustrating the details of a radionuclide production method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a radionuclide production system and a radionuclide production method according to one embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the description of the embodiment, substantially identical or similar components are denoted by the same reference numerals, and redundant descriptions may be omitted.

[0013] (Radioactive nuclide production system S) Fig. 1 is a schematic diagram showing an example of the configuration of a radionuclide production system S according to this embodiment. As shown in Fig. 1, the radionuclide production system S includes an electron beam accelerator 1, a bremsstrahlung target 10, and a radionuclide production target 40.

[0014] The electron beam accelerator 1 irradiates an electron beam 20. Specifically, the electron beam accelerator 1 accelerates the electron beam 20 and irradiates it toward a bremsstrahlung generation target 10. The bremsstrahlung target 10 generates bremsstrahlung radiation 30 by the electron beam 20 irradiated thereon. The radionuclide production target 40 contains a raw material that produces a radionuclide when irradiated with the generated bremsstrahlung radiation 30. The raw material may be contained in a solution or a solid. When the raw material is solid, it may be composed entirely of the raw material, or may contain elements or compounds other than the raw material, such as unavoidable impurities, in part. Examples of solutions that can contain the raw material include aqueous solutions and acid solutions. The radionuclide production target 40 may be, for example, a cube with a side length of several centimeters (when a solution is used, the solution containing the raw material may be placed in a cubic container with an internal side length of several centimeters), but is not limited to this.

[0015] In the radionuclide production system S according to this embodiment, the thickness of the bremsstrahlung generation target 10 is set within a range that results in a peak in the production rate (production amount) of the radionuclide, and also under conditions that result in the smallest dose of the electron beam 20 irradiating the radionuclide production target 40 within the range. The radionuclide production rate can be determined by the amount of radionuclide produced per unit time (Bq / s). The dose of the electron beam 20 can be grasped by the amount of the electron beam 20 irradiated onto the radionuclide production target 10 per unit time. The amount of the electron beam 20 can be grasped by at least one selected from, for example, the exposure dose (C / kg), the absorbed dose (Gy), the dose equivalent (Sv), the energy (eV), and the like.

[0016] In this way, the radionuclide production system S generates bremsstrahlung radiation 30 by irradiating the bremsstrahlung radiation generating target 10 with an electron beam 20 accelerated by an electron beam accelerator 1. The generated bremsstrahlung radiation 30 is then irradiated onto a solution or solid radionuclide production target 40 containing a radionuclide raw material, causing a nuclear reaction between the bremsstrahlung radiation 30 and the raw material to produce a radionuclide that serves as a raw material for a medical drug. For example, a radionuclide is produced by a (γ,n) reaction in which one neutron is generated by irradiating the raw material nuclide with one bremsstrahlung radiation 30. When Ac-225 is produced as the nuclide to be produced, Ra-226 is used as the raw material nuclide. Ra-225 is produced by a (γ,n) reaction between Ra-226 and the bremsstrahlung radiation 30. The produced Ra-225 becomes the progeny nuclide Ac-225 with a half-life of 14.8 days. Ac-225 is a typical alpha-ray-emitting nuclide used as a raw material for a medical drug. Ac-225 decays into its progeny, francium-221 (Fr-221), with a half-life of 10.0 days. Fr-221 decays into astatine-217 (At-217) with a half-life of 4.9 minutes, and At-217 decays into bismuth-213 (Bi-213) with a half-life of 32 milliseconds. While Ac-225 and its progeny are effective in treatment, Ra-226 and Ra-225 are unnecessary for treatment because they do not emit alpha rays, and therefore require separation and purification from Ac-225. Furthermore, Ra-226, a raw material used in the production of radioactive nuclides, is valuable, so it is desirable to recover and reuse it. Ra-226 decays into radon-222 (Rn-222), a rare gas (boiling point -61.7°C). Rn-222 is a gaseous radionuclide that emits alpha rays. If it is dispersed into the environment, the progeny nuclides of the dispersed Rn-222 will adhere to various locations throughout the environment, causing significant environmental impact. Therefore, it is desirable not to release Rn-222 into the environment during the production, separation, and purification of radionuclides. Because Rn-222 is a rare gas, chemical collection is difficult. Therefore, one method of collecting Rn-222 is to physically adsorb it using cooled activated carbon.

[0017] Electron beam accelerator 1 can be made smaller and lighter than proton accelerators or heavy ion accelerators at the same acceleration energy. Furthermore, the cross section of the (γ,n) reaction (Ra-226(γ,n)Ra-225) used to produce Ra-225 from Ra-226 using electron beam accelerator 1 is comparable to that of the direct production of Ac-225 (Ra-226(p,2n)Ac-225) method, in which protons accelerated by a proton accelerator are irradiated onto Ra-226, resulting in the emission of two neutrons. This allows for the miniaturization of the radionuclide production section. Furthermore, the cross section of the Ra-226(n,2n)Ra-225 method, in which fast neutrons are irradiated onto Ra-226 using a heavy ion accelerator, resulting in the emission of two fast neutrons, is slightly larger by an order of magnitude. However, in this case, in order to generate a large amount of fast neutrons, it is necessary to irradiate a carbon target or a metal target with tritium absorbed with deuterons accelerated by a cyclotron. Also, in this case, shielding is required for the large amount of fast neutrons generated, which makes the equipment large. Furthermore, the large amount of fast neutrons causes the entire equipment structure to become highly activated. In contrast, the radionuclide production system S uses an electron beam accelerator 1, which solves these problems that occur with proton accelerators and heavy particle accelerators.

[0018] A portion of the electron beam 20 accelerated by the electron beam accelerator 1 passes through the bremsstrahlung target 10 and is irradiated onto the radionuclide production target 40, a container 50 containing the radionuclide production target 40, and the like. The electron beam 20 that passes through the bremsstrahlung target 10 makes almost no contribution to the production of radionuclides that are raw materials for medical drugs, but imposes a thermal load on the radionuclide production target 40, the container 50, and the like, or causes damage due to the electron beam 20, thereby reducing the safety of the radionuclide production system S. Therefore, the radionuclide production system S aims to reduce the electron beam 20 that passes through the bremsstrahlung target 10 and is irradiated onto the radionuclide production target 40 and the container 50.

[0019] Here, Figure 2 shows an example of the relationship between the thickness of the bremsstrahlung generating target 10 and the production rate of radioactive nuclides (upper graph), and the relationship between the thickness of the bremsstrahlung generating target 10 and the amount of electron beam 20 passing through the bremsstrahlung generating target 10 (lower graph).

[0020] As shown in the upper graph of FIG. 2 , as the thickness of the bremsstrahlung generating target 10 increases, initially, the amount of bremsstrahlung radiation 30 produced increases, thereby increasing the radionuclide production rate. However, as the thickness of the bremsstrahlung generating target 10 increases, the effect of shielding the bremsstrahlung radiation 30 also increases (note that the effect of shielding the bremsstrahlung radiation 30 occurs even when the bremsstrahlung generating target 10 is thin). Therefore, when the bremsstrahlung generating target 10 reaches a certain thickness, the generation (production rate) of bremsstrahlung radiation 30 and the effect of shielding the bremsstrahlung radiation 30 balance each other, and the radionuclide production rate no longer increases. Thereafter, as the thickness of the bremsstrahlung generating target 10 increases, the effect of shielding the bremsstrahlung radiation 30 becomes greater, reducing the amount of bremsstrahlung radiation 30 irradiated, thereby reducing the radionuclide production rate. Furthermore, when the bremsstrahlung generating target 10 is irradiated with the electron beam 20, heat generation and deterioration due to the irradiation occur in the bremsstrahlung generating target 10. This deteriorates the soundness of the bremsstrahlung target 10. From the viewpoint of maintaining the soundness of the bremsstrahlung target 10, it can be said that the thicker the bremsstrahlung target 10, the better. However, if the target is too thick, the production rate of radioactive nuclides decreases, as described above. Therefore, it is preferable to set the thickness of the bremsstrahlung target 10 so that the production rate of radioactive nuclides does not decrease and the deterioration of the soundness of the bremsstrahlung target 10 is minimized.

[0021] 2, the thicker the bremsstrahlung target 10, the less the amount of electron beam 20 that passes through the bremsstrahlung target 10, and the less the amount of electron beam 20 that is irradiated onto the radionuclide production target 40, the container 50, etc. Therefore, in the radionuclide production system S, the thicker the bremsstrahlung target 10, the more the thermal load and damage to the radionuclide production target 40, the container 50, etc. can be reduced.

[0022] 2, the thickness of the bremsstrahlung target 10 is set within a range in which the production rate of radioactive nuclides peaks, as described above, and under conditions in which the amount of irradiation of the electron beam 20 onto the radioactive nuclide production target 40 is minimized within the range (this condition is also a condition in which deterioration of the soundness of the bremsstrahlung target 10 is minimized as much as possible). As a result, the radioactive nuclide production system S reduces the thermal load and damage to the bremsstrahlung target 10, the radioactive nuclide production target 40, the container 50, etc. (high safety), and can efficiently produce radioactive nuclides.

[0023] The thickness of the bremsstrahlung generation target 10 within the above-described range varies depending on the energy of the electron beam 20. Therefore, the thickness of the bremsstrahlung generation target 10 should be set to an optimal value depending on the energy of the electron beam 20. Referring to the upper graph of FIG. 2, for example, when a 35 MeV electron beam 20 is used and tungsten is used as the bremsstrahlung generation target 10, the radionuclide production rate increases up to a tungsten thickness of 2 mm, the radionuclide production rate remains approximately constant between 2 mm and 6 mm, and the radionuclide production rate decreases above 6 mm. Referring to the lower graph of FIG. 2, the amount of electron beam 20 passing through tungsten decreases as the tungsten thickness increases. For this reason, when a 35 MeV electron beam 20 is used, by setting the thickness of the tungsten that is the bremsstrahlung target 10 to 6 mm (i.e., within the range indicated by the diagonal lines in FIG. 2, more preferably within the conditions of the dashed line a), it is possible to reduce the thermal load and damage to the bremsstrahlung target 10, the radionuclide production target 40, the container 50, etc., without reducing the production yield of radioactive nuclides.

[0024] For these reasons, in the radionuclide production system S, for example, when the energy of the electron beam 20 is increased to 40 MeV and tungsten is used as the bremsstrahlung generation target 10, the bremsstrahlung generation target 10 can have any thickness exceeding 6 mm. Also, in the radionuclide production system S, for example, when the energy of the electron beam 20 is decreased to 30 MeV and tungsten is used as the bremsstrahlung generation target 10, the bremsstrahlung generation target 10 can have any thickness less than 6 mm. In other words, the thickness of the bremsstrahlung generation target 10 can be thicker when the energy of the electron beam 20 is high and thinner when the energy is low.

[0025] The bremsstrahlung target 10 can be formed of a non-ferromagnetic material such as platinum or tantalum, in addition to tungsten. In this case, the bremsstrahlung target 10 can have any thickness depending on the material. It is advisable to set the thickness of the bremsstrahlung target 10 depending on the material by conducting tests and simulations in advance. In this way, the radionuclide production system S can change the thickness of the bremsstrahlung target 10 depending on the energy and material of the electron beam 20. Therefore, the radionuclide production system S appropriately obtains the effect of reducing the thermal load and damage to the bremsstrahlung target 10, the radionuclide production target 40, the container 50, etc., without reducing the production rate of radionuclides.

[0026] FIG. 3 is an explanatory diagram showing an example of a bremsstrahlung generation target 10. As shown in FIG. 3, the bremsstrahlung generation target 10 may include a plurality of plate-shaped targets (e.g., 10 targets (five targets shown in FIG. 3)) each having a thickness of 1 mm, and the thickness may be adjusted appropriately by inserting or removing the plate-shaped bremsstrahlung generation targets 10 according to the energy of the electron beam 20. In this way, when the output setting of the energy of the electron beam 20 is changed, the thickness of the bremsstrahlung generation target 10 can be adjusted according to the energy. The plurality of plate-shaped bremsstrahlung generation targets 10 may be provided so that they are in close contact with each other after insertion or removal, or may be provided at predetermined intervals (e.g., every other target). When the predetermined intervals are provided, cooling performance can be improved. The thickness of the plate-shaped bremsstrahlung generation target 10 may be, for example, 2 mm or 3 mm. Furthermore, the thicknesses of the plurality of plate-shaped bremsstrahlung generation targets 10 may be different from each other. Whichever of these embodiments is adopted, the radionuclide production system S can flexibly adjust the thickness of the bremsstrahlung generation target 10 according to the energy of the electron beam 20.

[0027] 4 is a schematic diagram showing another example of the configuration of the radionuclide production system S according to this embodiment. As shown in FIG. 4, the radionuclide production system S can have an electron beam removal device 60 installed between the bremsstrahlung generation target 10 and the radionuclide production target 40. This electron beam removal device 60 changes the traveling direction of the electron beam 20 that has passed through the bremsstrahlung generation target 10, and separates and removes it from the bremsstrahlung radiation 30. Therefore, by installing the electron beam removal device 60, the radionuclide production system S can further reduce the thermal load and damage to the radionuclide production target 40, the container 50, etc., and can produce radionuclides safely and efficiently using a small, lightweight device.

[0028] The electron beam removal device 60 can use at least one of a magnetic field generator 60a (see FIG. 5) and an electric field generator 60b (see FIG. 5) using one or more pairs of permanent magnets or electromagnets. While bremsstrahlung radiation 30 is not affected by electric or magnetic fields, the electron beam 20 changes its direction of travel in the presence of an electric or magnetic field. Therefore, if the electron beam removal device 60 equipped with the magnetic field generator 60a or the electric field generator 60b is installed between the bremsstrahlung generation target 10 and the radionuclide production target 40, the electron beam 20 that has passed through the bremsstrahlung generation target 10 changes its direction of travel due to the electric or magnetic field generated by the electron beam removal device 60, and the electron beam 20 is not irradiated to the radionuclide production target 40, the container 50, or the like, or the irradiation can be reduced. Therefore, the radionuclide production system S can reduce the thermal load and damage to the radionuclide production target 40 and the container 50.

[0029] When the magnetic field generator 60a or electric field generator 60b described above is used as the electron beam removal device 60, it is desirable to use a non-ferromagnetic material for the bremsstrahlung target 10 and the container 50. This can suppress the effects of a magnetic field, such as stress acting on the bremsstrahlung target 10 or the container 50. A ferromagnetic material refers to a magnetic material in which the magnetic moments of adjacent magnetic atoms within a crystal are aligned in parallel, thereby exhibiting strong magnetism externally. Examples of such a material include iron, cobalt, nickel, and alloys containing any one of these as the main component. Therefore, a non-ferromagnetic material refers to a material other than these ferromagnetic materials. For example, the bremsstrahlung target 10 can be made of tungsten, platinum, tantalum, or the like, as described above. The container 50 can be made of aluminum, ceramic, or the like, for example.

[0030] Furthermore, it is desirable that the structure be such that there are no structures between the electron beam 20 whose direction of travel has been changed by the electron beam removal device 60 and the electron beam 20, at least until the electron beam 20 disappears. In this way, the absence of structures prevents the electron beam 20 from being subjected to a thermal load or damage. A structure without structures may be achieved, for example, by providing a space with a radius of at least several tens of centimeters to 1 meter in a direction perpendicular to the bremsstrahlung radiation 30 passing between the electron beam removal device 60 and the radionuclide production target 40, with no structures provided. By providing such a space, the electron beam 20 whose direction of travel has been changed by the electron beam removal device 60 is sufficiently reduced or disappeared, so that even if there is a structure ahead, the electron beam 20 will not be subjected to a thermal load or damage.

[0031] FIG. 5 is a schematic diagram showing an example of an electron beam removal device 60. FIG. 5 shows the passage of the electron beam 20 from the front side to the back side of the page of FIG. 5. As shown in FIG. 5, the electron beam removal device 60 is provided with a magnetic field generator 60a made of a permanent magnet or an electromagnet so as to generate a magnetic field perpendicular to the direction of passage of the electron beam 20. In this embodiment, the electric field generated by the electric field generator 60b is set so as to change the direction of travel of the electron beam 20 in the same direction as the direction of travel of the electron beam 20 changed by the magnetic field generator 60a. For example, the electric field generator 60b may be installed at a position rotated 90° around the electron beam 20 relative to the pair of magnetic field generators 60a installed on either side of the electron beam 20. In this manner, the direction of travel of the electron beam 20 can be more powerfully changed due to the synergistic effect of the magnetic field and the electric field.

[0032] 6 is an explanatory diagram illustrating an example of the operation of the electron beam removal device 60. In the radionuclide production system S, as shown in the lower diagram of FIG. 6, the electron beam 20 from the electron beam accelerator 1 may be pulsed. In contrast, as shown in the upper diagram of FIG. 6, the strength (magnetic field or electric field strength) of the magnetic field generator 60a and / or the electric field generator 60b of the electron beam removal device 60 can be kept constant. In this way, a special control device is not required, and the traveling direction of the electron beam 20 can be changed with a simple configuration and at lower cost.

[0033] FIG. 7 is an explanatory diagram illustrating another example of the operation of the electron beam removal device 60. In the radionuclide production system S, the electron beam 20 from the electron beam accelerator 1 may be pulsed, as shown in the lower diagram of FIG. 7. Alternatively, as shown in the upper diagram of FIG. 7, the polarity (magnetic field or electric field strength) of the magnetic field generator 60a and / or the electric field generator 60b of the electron beam removal device 60 can be changed for each pulse. In this way, the traveling direction of the electron beam 20 passing through the bremsstrahlung generation target 10 changes for each pulse. Because the traveling direction of the electron beam 20 changes for each pulse, even if a structure is located in the changed traveling direction, the intensity of the electron beam 20 irradiated onto the structure can be reduced by half. Therefore, the radionuclide production system S can reduce the thermal load and damage to the structure. This is a preferred embodiment when the electron beam removal device 60 uses an electromagnet. In other words, by changing the polarity of the electromagnet at regular intervals (for each pulse) in accordance with the pulsed electron beam 20 irradiated from the electron beam accelerator 1, the direction of travel of the electron beam 20 passing through the bremsstrahlung generation target 10 can be changed for each pulse.

[0034] (Radioactive nuclide production method) 8 is a flow diagram illustrating the details of the radionuclide production method according to this embodiment. The radionuclide production method according to this embodiment produces a radionuclide using the above-mentioned radionuclide production system S. Therefore, detailed explanations of the elements described in the radionuclide production system S will be omitted. As shown in FIG. 8, the radionuclide production method includes an electron beam irradiation step S1, a bremsstrahlung generation step S2, and a radionuclide production step S3.

[0035] In the electron beam irradiation step S1, the electron beam accelerator 1 irradiates the electron beam 20. Specifically, the electron beam accelerator 1 accelerates the electron beam 20 and irradiates it toward the bremsstrahlung generation target 10. In the bremsstrahlung generating step S2, the bremsstrahlung target 10 is irradiated with the electron beam 20 to generate bremsstrahlung radiation 30. In the radionuclide production step S3, a radionuclide is produced by irradiating a radionuclide production target 40 containing raw materials that are irradiated with the generated bremsstrahlung 30 to produce a radionuclide.

[0036] In the radionuclide production method according to this embodiment, as described in the radionuclide production system S, the thickness of the bremsstrahlung target 10 is set within a range in which the production yield of the radionuclide peaks, and under conditions in which the dose of the electron beam 20 irradiated onto the radionuclide production target 40 is minimized within the range. As a result, as described in the radionuclide production system S, the radionuclide production method reduces the thermal load and damage to the bremsstrahlung target 10, the radionuclide production target 40, the container 50, etc. (high safety), and can efficiently produce radionuclides. Furthermore, since the radionuclide production method uses the electron beam accelerator 1, it can be made smaller and lighter than a proton accelerator, a heavy ion accelerator, etc.

[0037] The radionuclide production system S and radionuclide production method according to the present invention have been described in detail above using embodiments. However, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0038] S Radionuclide Production System 1 Electron beam accelerator 10. Bremsstrahlung target 20 Electron beam 30 Bremsstrahlung 40 Radionuclide production targets 50 containers 60 Electron beam removal device 60a magnetic field generator 60b Electric field generator S1 Electron beam irradiation step S2 Bremsstrahlung generation step S3 Radionuclide production step

Claims

1. an electron beam accelerator that irradiates electron beams; a bremsstrahlung generating target that generates bremsstrahlung radiation by the irradiated electron beam; a radionuclide production target containing a raw material for producing a radionuclide by being irradiated with the generated bremsstrahlung radiation; Equipped with The thickness of the bremsstrahlung target is set within a range in which the production rate of the radioactive nuclide peaks, and under conditions in which the amount of irradiation of the electron beam onto the target for producing the radioactive nuclide is minimized within the range. A radionuclide production system comprising:

2. 2. The radionuclide production system according to claim 1, The thickness of the bremsstrahlung generation target is changed depending on the energy of the electron beam. A radionuclide production system comprising:

3. 2. The radionuclide production system according to claim 1, Between the bremsstrahlung generation target and the radionuclide production target, an electron beam removal device is provided which changes the traveling direction of the electron beam that has passed through the bremsstrahlung generation target and separates and removes it from the bremsstrahlung radiation. A radionuclide production system comprising:

4. 4. The radionuclide production system according to claim 3, The electron beam removal device uses at least one of a magnetic field generator and an electric field generator using one or more sets of permanent magnets or electromagnets. A radionuclide production system comprising:

5. 4. The radionuclide production system according to claim 3, The electron beam removal device is configured to remove any structures in the direction of travel of the electron beam, at least until the electron beam disappears. A radionuclide production system comprising:

6. 2. The radionuclide production system according to claim 1, The container for accommodating the radionuclide production target and the bremsstrahlung generation target are formed of a material that is not ferromagnetic. A radionuclide production system comprising:

7. 5. The radionuclide production system according to claim 4, The electron beam removal device uses the electromagnet and changes the polarity of the electromagnet at regular intervals. A radionuclide production system comprising:

8. an electron beam irradiation step of irradiating an electron beam using an electron beam accelerator; a bremsstrahlung generating step of irradiating a bremsstrahlung generation target with the electron beam to generate bremsstrahlung radiation; a radionuclide production step of irradiating a radionuclide production target, which includes a raw material to be irradiated with the generated bremsstrahlung radiation to produce the radionuclide, with the bremsstrahlung radiation; Including, The thickness of the bremsstrahlung target is set within a range in which the production rate of the radioactive nuclide peaks, and under conditions in which the amount of irradiation of the electron beam onto the target for producing the radioactive nuclide is minimized within the range. A method for producing a radionuclide.

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