JP7169254B2 - Method and apparatus for producing radionuclides - Google Patents

Description

The present invention relates to a technique for producing radionuclides that emit radiation such as gamma rays, alpha rays, and beta rays, and more particularly to a method and apparatus for producing radionuclides using an electron beam accelerator.

Radionuclides that emit gamma rays, typified by technetium-99m (Tc-99m), are widely used as diagnostic agents, and radionuclides that emit alpha rays, typified by actinium-225 (Ac-225), are widely used as therapeutic agents. ing.

These radionuclides have conventionally been produced as fission products using nuclear reactors, but production facilities using nuclear reactors are few and unevenly distributed around the world. Due to problems such as the need for large investment and maintenance costs, manufacturing methods that do not use nuclear fission reactions have been developed.

For example, since technetium-99m is generated by the decay of molybdenum-99 (Mo-99), a method of activating molybdenum-98 using neutrons (Mo-98 (n, γ) Mo-99) or There is a method of producing molybdenum 100 using a reaction with neutrons (Mo-100 (n, 2n) Mo-99), etc. These production methods can be realized by using an accelerator that accelerates neutrons. However, the method using neutrons requires a large accelerator, and also requires a large shield around Mo-98 and Mo-100, which are the targets, resulting in the problem of increasing the size of the apparatus.

As another production method using an accelerator, a method of irradiating Mo-100 with accelerated protons has also been studied. ) is also produced, making it impossible to produce Tc-99m with a high specific radioactivity.

On the other hand, for actinium-225, there are currently only three facilities, such as the Institute for Transuranium Element (ITU) in Germany, that can supply clinically usable amounts. Development of a manufacturing method is desired. In the production of Ac-225 using an accelerator, a production test using a cyclotron using the reaction between naturally occurring radium 226 (Ra-226) and protons (R-226 (p, n) Ac-225) is underway. However, there are various problems in using the proton energy efficiently, and it has not been put to practical use.

As a method for producing actinium-225 using an accelerator, a method of producing actinium-225 by beta decay of Ra-225 produced using the Ra-226 (n, 2n) Ra-225 reaction is also being studied. In the reaction, fast neutrons are generated by irradiating deuterons accelerated by a cyclotron onto a target made of carbon or thorium-occluded metal, etc., so it is necessary to shield the large amount of fast neutrons that are generated. There is a problem that the entire structure is activated.

As a solution to the above-mentioned problems of the production method using the reaction with neutrons or protons, Patent Document 1 discloses a high-speed electron beam generated by an electron beam accelerator and a substance (target ) in combination with bremsstrahlung irradiation to produce a radionuclide using a reaction (γ, n) that generates neutrons upon exposure to bremsstrahlung. Electron beam accelerators are much smaller and lighter than neutron and proton accelerators, and do not require large-scale shielding, etc., unlike neutron irradiation equipment, making it possible to reduce the size and weight of manufacturing equipment. becomes.

JP 2015-99117 A

The technology described in Patent Document 1 has made it possible to reduce the size and weight of radionuclide production equipment, and it produces actinium 225, which is in high demand as a raw material for therapeutic drugs, and technetium Tc99m, which is in high demand as a raw material for diagnostic drugs. In order to do so, it is desired to further improve the manufacturing efficiency.

An object of the present invention is to further improve production efficiency based on a radionuclide production apparatus using an electron beam accelerator.

In the present invention, a plurality of raw materials of different types are arranged side by side with respect to the irradiation direction of the electron beam, and among the plurality of raw materials, the raw material arranged on the upstream side has an atomic number or The above problem is solved by using a material with a low density.

That is, the method for producing a radionuclide of the present invention is a method for producing a radionuclide by irradiating a raw material with electrons emitted from an electron beam accelerator and utilizing the reaction between the raw material and the bremsstrahlung radiation generated from the raw material. A plurality of raw materials are stacked in the direction of electron irradiation, and at least one of atomic number and density is higher than that of subsequent raw materials.

Further, in the radionuclide production apparatus of the present invention, an electron beam accelerator and a raw material for generating a radionuclide are stored in a position (irradiation position) where the electron beam from the electron beam accelerator is irradiated, and the electron beam is used to and a reaction chamber for performing a reaction to generate a radionuclide, wherein the raw materials are arranged on the upstream side along the direction of irradiation of the electron beam, and the second raw material is arranged on the downstream side. wherein the first raw material has at least one of atomic number and density lower than that of the second raw material.

Furthermore, the present invention provides a radionuclide production apparatus having a mechanism for timely taking out a plurality of raw materials. That is, the radionuclide production apparatus of the present invention has a mechanism for withdrawing at least one of a plurality of different types of raw materials arranged side by side in the electron beam irradiation direction from the electron beam irradiation direction.

According to the present invention, radionuclides can be produced from a plurality of raw materials in the same production process, improving production efficiency. When different types of raw materials are used as the plurality of raw materials, it is possible to produce a plurality of types of radionuclides. Further, according to the present invention, by providing a raw material take-out mechanism, even if the reaction time differs depending on the raw material, only the desired raw material can be taken out and exchanged at an appropriate time. Even during this extraction, other raw materials continue to react using electron beam irradiation, so that the production can be continued without wasting electron beam energy.

A diagram for explaining an embodiment of the method for producing a radionuclide of the present invention. The figure which shows the structure of the radionuclide manufacturing apparatus of 1st embodiment. Graph showing the relationship between the thickness of the raw material in the first stage and the strength of the braking compensating diagonal line in the raw material in the second stage The figure which shows the modification of 1st embodiment The figure which shows the structure of the radionuclide manufacturing apparatus of 2nd embodiment The figure explaining the shape of the first stage raw material of the radionuclide manufacturing apparatus of 2nd embodiment. The figure which shows the modification of the shape of the first stage raw material of the radionuclide manufacturing apparatus of 2nd embodiment, or its container. The figure which shows another modification of the shape of the first stage raw material of the radionuclide manufacturing apparatus of 2nd embodiment, or its container. The figure explaining the raw material extraction of the radionuclide manufacturing apparatus of 2nd embodiment (modification) Configuration diagram of the radionuclide production apparatus of the third embodiment The figure explaining the raw material exchange timing of the radionuclide manufacturing apparatus of 3rd embodiment. The figure which shows the control flow of raw material extraction of the radionuclide manufacturing apparatus of 3rd embodiment The figure which shows the modification of 3rd embodiment Configuration diagram of the radionuclide production apparatus of the fourth embodiment The figure which shows the modification of the radionuclide manufacturing apparatus of 4th embodiment

Hereinafter, embodiments of the radionuclide production method and apparatus of the present invention will be described.

<Embodiment of radionuclide production method>
First, a basic embodiment of the method for producing a radionuclide of the present invention will be described.
The method for producing a radionuclide of the present invention involves irradiating a raw material with electrons emitted from an electron beam accelerator, thereby generating bremsstrahlung radiation generated from the raw material, reaction by the bremsstrahlung radiation, and reaction with neutrons generated by the reaction. Different radionuclides are produced from a plurality of raw materials of different types in the same reaction system.

A plurality of raw materials 20 (21, 22) are stacked in the irradiation direction of the electron beam 11 at positions irradiated with electrons emitted from the electron beam accelerator 10, as shown in FIG. Here, "overlapping arrangement" includes the case where the electron beam irradiation direction is shifted in the direction intersecting with the electron beam irradiation direction, and the case where the electron beams are in close contact with each other. It also includes the case where a part of the mechanism for supporting the container or the raw material intervenes.

When distinguishing a plurality of raw materials according to their positions, from upstream to downstream of the electron beam 11, the raw materials are referred to as first-stage, second-stage, . Say.

The raw material 21 in the first stage is a substance that generates bremsstrahlung (mainly γ-rays) when irradiated with electron beams, generates radionuclides by reaction with the bremsstrahlung and emits neutrons, and is placed in the latter stage. The raw material 22 thus obtained is a substance that generates radionuclides by reaction with bremsstrahlung radiation emitted from the first-stage raw material. A material having at least one of atomic number and density higher than that of the material of the subsequent stage is used as the material of the first stage. As a result, bremsstrahlung with high intensity can be generated in the raw material of the first stage, and the nuclear reaction can proceed not only in the raw material of the first stage but also in the raw material of the subsequent stage, and the nuclide production efficiency can be improved.

Specific examples of raw materials will be described below for the case where two raw materials 21 and 22 are used. In this example, the case of producing Ac-225, which is in high demand as a raw material for therapeutic drugs, and Mo-99 and Tc-99m, which are in high demand as raw materials for diagnostic drugs, will be described. In the first stage, a raw material containing Ra-226 and / or a compound thereof, which is a raw material of Ac-225 (hereinafter collectively referred to as a raw material containing Ra-226) is placed, and in the second stage, Mo-99 and A raw material containing Mo-100 and/or a compound thereof (hereinafter collectively referred to as a raw material containing Mo-100), which is a raw material for Tc-99m, is placed.

First, by irradiating the raw material in the first stage with an electron beam, bremsstrahlung is generated in the raw material containing Ra-226. The bremsstrahlung generated in Ra-226 is irradiated to Ra-226 as it is generated, and the reaction (Ra-226 (γ, n) Ra-225) that generates neutrons due to the nuclear reaction between bremsstrahlung and Ra-226 causes Ra-225 is produced. Beta decay of the produced Ra-225 produces Ac-225.

By installing a raw material containing Ra-226, which is a raw material with high density and atomic number, in the first stage, bremsstrahlung with high intensity is generated compared to raw materials with low density and atomic number, so Ra-225 , and the Ac-225 produced by its beta decay can be produced in large quantities.

Of the bremsstrahlung generated by the material containing Ra-226, the remainder not used for the nuclear reaction with Ra-226 is irradiated to the material containing Mo-100 installed in the second stage. Mo-99 is produced by a reaction (Mo-100(γ,n) Mo-99) in which neutrons are generated by a nuclear reaction between irradiated bremsstrahlung and Mo-100. Beta decay of Mo-99 produced produces Tc-99m.

In the first stage, as described above, strong bremsstrahlung is generated, so Mo-100 or its compound installed in the second stage is irradiated with strong bremsstrahlung. Therefore, Mo-99 and Tc-99m produced by its beta decay can also be produced in large amounts.

In this way, in addition to the production of Ac-225, Tc-99m can be produced at the same time in addition to the production of Ac-225 by the reaction of the raw materials in the first stage. can be made smaller.

Ra-225 produced from the raw material of the first stage becomes Ac-225, the progeny nuclide, with a half-life of 14.88 days. Ac-225 is a typical alpha-ray emitting nuclide as a raw material for therapeutic drugs. Raw material Ra-225 for radionuclide production and Ra-225 produced are separated. Separation and purification can employ, for example, the method described in Patent Document 1. Ac-225 also passes through a predetermined half-life and undergoes alpha decay into progeny nuclides such as francium Fr-221, astatine At-217, and bismuth Bi-213. These progeny nuclides are also nuclides that emit alpha rays, It can be used for therapy.

Mo-99 produced by the subsequent reaction of raw materials becomes the progeny nuclide Tc-99m with a half-life of 66 hours. Tc-99m is a gamma-ray emitting nuclide that is typical as a raw material nuclide for diagnostic agents. do.

Ra-226 and Mo-99 remaining after separating and purifying Ac-225 and Tc-99m, respectively, can be reused as raw materials. As a result, the amount of Mo-99 and Ra-226, which are relatively expensive raw materials for producing radionuclides, can be reduced.

In the above description, there are two types of raw materials, and the first stage raw material is a raw material containing Ra-226, and the second stage raw material is a raw material containing Mo-100. A raw material containing Ra-226, provided that the raw material has a higher atomic number or density than the raw material of the eye, receives electron beams to generate bremsstrahlung radiation, and generates radionuclides through nuclear reactions with bremsstrahlung radiation. is not limited to It is also possible to place three or more kinds of raw materials, such as a raw material that reacts with bremsstrahlung that has passed through the second raw material and generates a radionuclide after the second raw material. When three or more kinds of raw materials are stacked and arranged, it is preferable to use a material that does not shield bremsstrahlung radiation, specifically a material with a low atomic number or low density, as the material of the second stage. A specific combination and arrangement of raw materials will be described in detail in embodiments of the apparatus described later.

According to the method for producing a radionuclide of the present invention, production efficiency can be improved by stacking a plurality of raw materials in the direction of electron beam irradiation. Moreover, it becomes possible to produce different kinds of radionuclides in the same reaction system. Furthermore, by arranging raw materials that generate strong bremsstrahlung in the first stage, the production efficiency can be further improved.

Moreover, the method for producing a radionuclide of the present invention has the following advantages over conventional methods.
First, the method for producing a radionuclide of the present invention is an electron beam accelerator that can be miniaturized compared to a proton accelerator or a heavy particle accelerator if the acceleration energy is the same when compared to a method using a proton accelerator or a heavy particle accelerator. is used, it is possible to reduce the size of the accelerator. In addition, the reaction cross-section of the reaction (Ra-226 (γ, n) Ra-225) that generates Ra-225 from Ra-226 is that Ra-226 is irradiated with accelerated protons and two neutrons are emitted. Since the cross-sectional area of the reaction is about the same as that of the method of directly producing Ac-225 by the reaction (Ra-226(p,2n) Ac-225), it is possible to reduce the size of the radionuclide production section.

In addition, when compared with the method of generating and using fast neutrons, for example, the reaction (Ra-226(n,2n)Ra-225) in which two fast neutrons are emitted by irradiating Ra-226 with fast neutrons In the method used, the reaction cross section is slightly larger than the reaction (Ra-226 (γ, n) Ra-225) used in the production method of the present invention, but a large amount of fast neutrons In order to generate it, it is necessary to irradiate deuterons accelerated by a cyclotron onto a carbon target or a tritium-occluded metal target. becomes large. Furthermore, there is a problem that the entire structure of the device is strongly activated by a large amount of fast neutrons. This problem is the same when using a reaction (Mo-100(n,2n) Mo-99) that irradiates Mo-100 with fast neutrons and releases two fast neutrons including the irradiated fast neutrons. be. On the other hand, the manufacturing method of the present invention uses a small electron beam accelerator, so these problems can be solved.

<Embodiment of Radionuclide Production Device>
Based on the above manufacturing method, specific embodiments of the radionuclide manufacturing apparatus of the present invention will be described below.

<First embodiment>
As shown in FIG. 2, the radionuclide production apparatus 100 of this embodiment includes an electron beam accelerator 10 that emits high-speed electron beams, and a reaction chamber 30 in which raw materials for producing radionuclides are placed. The electron beam accelerator 10 is a device that shoots electrons emitted from an electron gun into an acceleration tube, accelerates them by an electric field in the acceleration tube, and emits them as an electron beam 11, and various beam energies are available. . The radionuclide production apparatus of this embodiment can use these known electron beam accelerators.

The reaction chamber 30 is arranged close to the electron beam accelerator 10, has an opening 31 through which the electron beam 11 emitted from the electron beam accelerator 10 passes, and has a mechanism (indicated by a dotted line) for supporting the raw material inside. I have. In this embodiment, the irradiation direction of the electron beam 11 emitted from the electron beam accelerator 10 is horizontal. are arranged so as to overlap each other. The support mechanism may simply be a plate-shaped member on which the raw material is placed or an arm-shaped member that supports the raw material from the side. Further, the support mechanism may be provided with a moving mechanism or a rotating mechanism for taking out the raw material. The reaction chamber 30 is constructed or covered with a material that shields the electron beam and radiation generated during the radionuclide production process.

The raw material 20 includes a plurality of raw materials 21 and 22 of different types that are stacked in the electron irradiation direction. Among the plurality of raw materials, the raw material arranged on the most upstream side, i.e., the first stage, is irradiated with electron beams to generate bremsstrahlung radiation, and by reacting with the bremsstrahlung radiation, it generates radionuclides and emits neutrons. Substances, downstream, ie downstream, sources are substances that generate radionuclides by reaction with bremsstrahlung radiation emitted from the first-stage source. Specifically, the raw material 20 includes, for example, raw materials containing Ra-226 and/or compounds thereof, raw materials containing Mo-100 and/or compounds thereof, and hafnium Hf-178 and/or or a raw material containing a compound thereof, a raw material containing germanium Ge-70 and/or a compound thereof, a raw material containing zinc Zn-68 and/or a compound thereof, and the like. Note that as the compound, for example, an oxide, a salt, a complex, or the like can be used.

In the case of raw materials containing hafnium Hf-178 and/or its compounds, lutetium Lu -177 is produced. When using a raw material containing Ge-70 and its compounds, Ge -68 is produced, and the electron capture reaction of the produced Ge-68 produces gallium Ga-68. When a raw material containing zinc Zn-68 and its compound is used as a raw material, a reaction (Zn-68(γ,p)Cu-67) that generates protons due to a nuclear reaction between bremsstrahlung and Zn-68, Copper Cu-67 is produced. Which one is used as the first stage or the second stage is determined by the atomic number or density of the raw material.

If these raw materials are solids such as powders, they can be molded into plates. Alternatively, it may be placed in a container. In order to reduce the shielding effect of bremsstrahlung radiation, it is desirable to use beryllium, carbon, aluminum, etc., and compounds such as oxides and borides thereof, which have a low density or atomic number, as the material of the container. . By containing the raw materials 21 and 22 in the container, safety can be maintained even when liquid raw materials are used, or when solid raw materials change to liquid state.

The shape and size of the raw material or its container are not particularly limited, but for the first-stage raw material, the thickness of the raw material in the electron irradiation direction is the thickness that maximizes the bremsstrahlung radiation intensity on the surface of the second-stage raw material. is preferred. Maximization of bremsstrahlung intensity is described with reference to FIG.

FIG. 3 is a diagram showing the bremsstrahlung intensity on the surface of the raw material 22 in the second stage on the side of the raw material 21 with respect to the thickness of the raw material 21 in the first stage. As shown in the figure, as the thickness of the raw material 21 in the first stage increases, the intensity of the bremsstrahlung radiation on the surface of the raw material 22 in the second stage increases. The bremsstrahlung intensity is weakened by the shielding effect of the shielding effect and the effect of increasing the distance between the surface of the raw material 22 on the side of the raw material 21 and the surface of the raw material 21 on the side of the electron beam. Therefore, by setting the thickness of the raw material 21 to a thickness that maximizes the bremsstrahlung intensity on the raw material 21 side surface of the raw material 22, the production amount of nuclides produced from the raw material 22 can be maximized.

The radionuclide production apparatus of this embodiment irradiates a plurality of raw materials 20 (21, 22) arranged in the irradiation direction with an electron beam emitted from the electron beam accelerator 10 according to the above-described method for producing a radionuclide. Thus, different radionuclides can be produced by using the (γ, n) reaction, (γ, 2n) reaction, (γ, p) reaction, etc. in the first-stage raw material and the latter-stage raw material, respectively. This makes it possible to reduce the size of the device and improve the production efficiency of radionuclides.

In addition, in the radionuclide production apparatus of the present embodiment, the intensity of bremsstrahlung radiation generated in the first stage can be increased by using a material that has at least one of the atomic number and density higher than those in the latter stage as the raw material in the first stage. It is possible to increase the production of radionuclides produced by each of the multiple sources. In particular, by appropriately designing the thickness of the first-stage raw material, it is possible to reduce the radiation shielding effect and maximize the intensity of bremsstrahlung.

<Modification of First Embodiment>
In the first embodiment, two raw materials are arranged in the reaction chamber, but three raw materials may be arranged. Other than that, the configuration of the apparatus is the same as that of the first embodiment, and different points will be explained. In addition, in the diagrams for explaining this modified example, illustration of a part of the configuration common to the first embodiment is omitted.

As shown in FIG. 4, also in this embodiment, the first raw material 21, the second raw material 22, and the third raw material 23 are arranged in this order so as to overlap along the electron irradiation direction. As in the first embodiment, the first-stage raw material 21 uses a material having at least one of atomic number and density higher than that of the latter-stage raw material. A raw material with a low atomic number or low density is used as the raw material 22 in the second stage. The raw material 22 in the second stage is irradiated with bremsstrahlung generated by irradiating the raw material 21 in the first stage with the electron beam 11 accelerated by the electron beam accelerator 10, thereby becoming radioactive by, for example, the (γ, n) reaction. It produces nuclides, but hardly produces bremsstrahlung. Therefore, in order to allow the bremsstrahlung radiation generated from the raw material 21 in the first stage to reach the raw material 23 in the third stage, the shielding effect of bremsstrahlung is reduced by using a raw material with a small atomic number or density as the raw material in the second stage. . This makes it possible to maintain the intensity of bremsstrahlung radiation generated in the raw material 21 in the first stage and reaching the raw material 23 in the third stage, thereby increasing the amount of radionuclides produced from the raw material 23.

Specific examples of the second-stage raw material include, for example, a raw material containing germanium Ge-70 and/or a compound thereof, a raw material containing zinc Zn-68 and/or a compound thereof, or other materials. Even if it is a raw material, you may use the thing which made the density low by liquefying.

According to this modification, it is possible to further increase the types of radionuclides that can be produced in the same production process. In addition, by appropriately selecting the density and atomic number of not only the first stage but also the intermediate raw materials, the production efficiency can be improved without reducing the production amount for all of the plurality of raw materials.

<Second embodiment>
This embodiment is based on the configuration of the first embodiment and its modification, and is characterized in that it includes a mechanism that considers the heat generation of the raw material. The configuration of a radionuclide production apparatus 100A of this embodiment including a mechanism for suppressing heat generation will be described with reference to FIGS. 5 and 6. FIG. It is the same as the first embodiment (FIG. 2) except for the mechanism for suppressing heat generation.

In the present embodiment as well, a plurality of (two in the figure) raw materials 21 and 22 are stacked in the irradiation direction of the electron beam 11 in the same manner as in the first embodiment. The first-stage raw material 21 irradiated with the electron beam 11 has an area larger than the area irradiated with the electron beam 11 (irradiation area), and is supported by a moving mechanism capable of changing the irradiation position. It is

Bremsstrahlung radiation (not shown) is generated by irradiating the raw material 21 at the first stage with the electron beam 11 accelerated by the electron beam accelerator 10, and the electron energy is imparted to the raw material 21 along with the generation of the bremsstrahlung radiation. 21 generates heat. However, by irradiating the electron beam 11 only on a partial region of the raw material 21 and changing the irradiation position within the raw material 21 by the moving mechanism, the heat generating portions can be dispersed, and the deterioration of the raw material due to heat generation can be prevented. can be prevented.

As an example, FIGS. 5 and 6 show the case where the raw material 21 or its container is shaped like a cylinder with the inner part of a disc removed, and is arranged so that a part of the circumference is the electron beam irradiation position. ing. Further, in this example, a rotating mechanism 40 is provided as a moving mechanism for changing the irradiation position.

As shown in FIG. 6, the raw material 21 has a shape of half {(L1-L2)/2} obtained by subtracting the inner cylindrical outer diameter L2 from the disk-shaped outer diameter L1. It should be as large as or larger than the diameter D of the wire. Further, the rotating mechanism 40 has a motor 41 to which a rotating shaft 42 is attached. By rotating the raw material 21 when the electron beam 11 is irradiated, the energy of the electrons is dispersed in the raw material 21, heat generation is alleviated, and the soundness of the raw material 21 can be maintained.

On the other hand, since most of the electron energy is imparted to the raw material 21, almost no electron energy is imparted to the raw material 22 placed downstream of the raw material 21, and the energy imparted by bremsstrahlung is very high. Since it is relatively small, the raw material 22 hardly generates any heat. Therefore, as in the first embodiment, it is possible to continuously produce radionuclides through (γ,n) reaction or the like upon irradiation with bremsstrahlung radiation generated in the raw material 21 .

According to this embodiment, it is possible to effectively suppress the heat generated in the raw material in the first stage due to the energy of the electron beam, and it is not necessary to install equipment such as cooling in the reaction chamber, thereby preventing deterioration of the raw material. can.

<Modification of Second Embodiment>
Although FIG. 6 shows the case where the shape of the raw material 21 is continuous in the circumferential direction, for example, as shown in FIGS. good too. In this case, a rotary shaft 42 is provided at the central portion of the plurality of divided portions (divided portions) 21a to 21b or 21a to 21d, and a jig 43 for connecting the rotary shaft 42 and each divided portion is provided. The jig 43 is provided with a take-out mechanism (not shown) that detachably supports each divided portion, and each divided portion is connected to the jig 43 via the take-out mechanism. A known chuck device such as a mechanical chuck or a vacuum chuck can be used as the detachable take-out mechanism.

In this modified example, by temporarily stopping the rotating shaft 42 at an appropriate position, as shown in FIG. , the other portion 21b which has not been irradiated with the electron beam can be removed and replaced with a new divided portion of the raw material 21 which has not been irradiated with the electron beam. The raw material 21 irradiated with the electron beam can be removed while one of the divided portions of the raw material 21 is kept irradiated with the electron beam, and the subsequent raw material 22 is interrupted from being irradiated with the bremsstrahlung. It is possible to take out the nuclides produced from the raw material 21 without having to do so.

6 to 8 show the case where the shape of the raw material is disk-shaped, but the shape of the raw material is not limited to a disk-shaped, for example, a rectangular or oval shape, and a rotating mechanism as a moving mechanism It is also possible to adopt a mechanism for reciprocating in a direction (one direction or two directions) perpendicular to the irradiation direction of the electron beam instead of the mechanism.

<Third embodiment>
In this embodiment, when the second or third raw material is placed after the first raw material, a moving mechanism for taking out the raw material in the latter stage is added, and furthermore, the moving mechanism for each raw material is controlled. It is possible to provide a control unit for

A specific configuration of the radionuclide production apparatus of this embodiment will be described below with reference to FIG. In FIG. 10, elements having the same functions as the elements in FIG. 2 are denoted by the same reference numerals, and overlapping descriptions are omitted. As shown in FIG. 10, a radionuclide production apparatus 100B of this embodiment includes an electron beam accelerator 10 and a reaction chamber 30 connected to an electron beam emission port of the electron beam accelerator 10. In the reaction chamber 30, A support mechanism is provided for arranging the three kinds of raw materials 21 to 23 so as to overlap each other in the electron beam irradiation direction. Also in this embodiment, bremsstrahlung radiation is generated by irradiating the raw material 21 in the first stage with the electron beam 11 accelerated by the electron beam accelerator 1, and the generated bremsstrahlung radiation irradiates the raw material 22 and the raw material 23 placed in the latter stage. and produce radionuclides, respectively.

In this embodiment, a rotation mechanism is provided in the supporting mechanism that supports the raw materials 21 to 23, respectively, and the raw materials 21 to 23 are removed from the position where the electron beam is irradiated (electron beam irradiation position) or replaced with a new raw material. It is possible to move to a position (removal position) for loading and unloading. The rotation mechanism may be manually operated, but is automatically controlled by the control unit 60 when the control unit 60 for controlling the support mechanism is provided.

Of the three types of raw materials, the raw material in the first stage has a disc-shaped shape divided in the circumferential direction, as described in the modified example of the second embodiment, and its support mechanism is the same as that of the second embodiment. Similar to the rotating mechanism 40, it includes a rotating motor 41, a rotating shaft 42 rotated by the rotating motor 41, and a connecting jig 43 fixed to the rotating shaft 42 and attached to the raw material 21 or its container. The connection jig 43 may be provided with a mechanism (take-out mechanism) for detachably fixing the raw material 21, although illustration is omitted. As the attachment/detachment mechanism, a known chuck device such as a mechanical chuck or a vacuum chuck can be employed. The raw material 21 at the first stage is positioned by the rotating mechanism 40 such that one of the plurality of divided portions is at the irradiation position of the electron beam, and the portion at the irradiation position changes as the rotating shaft 42 rotates. do.

The raw materials 22 and 23 in the latter stage have a shape in which the area of the surface irradiated with the electron beam is the same as or slightly larger than the irradiation area of the electron beam, and are attached to a rotary motor 44 different from the rotary motor 41. is detachably attached to the rotating shaft 45 of the via a connection jig 46 . By rotating the rotary shaft 45, the raw materials 22 and 23 can be moved between the electron beam irradiation position and the raw material extraction position.

The rotation motor 41 and the rotation motor 44 of the rotation mechanism are arranged outside the reaction chamber 30, and the rotation shaft 42 and the rotation shaft 45 are partially inside the reaction chamber 30 while keeping the reaction chamber 30 sealed. It is connected to motors 41, 44 arranged outside. In order to keep the reaction chamber 30 airtight when taking out the raw materials, the reaction chamber 30 may be provided with a spare chamber 35 having an opening/closing door capable of maintaining airtightness with the reaction chamber 30 at the position where the raw materials are taken out. In this case, the raw material is moved to the preliminary chamber 35 with the space between the reaction chamber 30 and the preliminary chamber 35 opened, and after the space between the reaction chamber 30 and the preliminary chamber 35 is closed, the raw material is taken out from the preliminary chamber 35. Alternatively, the raw material is exchanged in the spare room.

The timing of taking out and exchanging raw materials differs depending on the type of raw material. work under the time management of Further, when the time required to reach the required production amount and the replacement period are known in advance, the control unit 60 can automatically control based on that information.

An example of automatic control by the control unit 60 will be described below.
FIG. 11 shows an example of raw material exchange times for each production nuclide. In the figure, the horizontal axis is the time from the start of the electron beam irradiation, and the vertical axis is the nuclide production amount. The amount of nuclide produced varies depending on the amount of raw material, the intensity of bremsstrahlung, and the size of the generated cross section. , the replacement time is also early. Also, if the material is divided like the raw material in the first stage and the electron beam irradiation time per rotation of each divided portion is short, the replacement time may be delayed. The amount of production that differs depending on the nuclide in this way can be obtained in advance by means of experiments or simulations. Controls rotation start and rotation stoppage.

An example of control is shown in FIG. After setting the raw materials in the reaction chamber, the production is started. First, the electron beam irradiation is started (S101), and the rotating mechanism (rotating motor 41) for the raw material 21 in the first stage is driven to rotate the raw material 21 to allow the nuclear reaction to proceed (S102). If no instruction to finish production has been given (S103), the timing for replacing raw materials is monitored, and it is determined whether or not any of the three raw materials has reached the replacement time (S104). If the raw material that reaches the replacement time is the first-stage raw material, and if a predetermined amount of nuclide is produced in the first-stage raw material (S105), the driving of the rotation motor 41 of the rotating mechanism 40 of the first-stage raw material 21 is controlled. Then, the material is intermittently rotated at every angle determined by the number of divisions of the raw material in the first stage, and the divided portions sequentially moved to the take-out position are replaced with new divided portions of the raw material (S107). When the replacement of all divided parts is completed, the process returns to step S102, and the rotation mechanism 40 is switched to continuous rotation. During this time, the electron beam irradiation (S101) continues, and nuclide production using the first-stage divided portion at the electron beam irradiation position and the raw materials 22 and 23 arranged behind it continues.

On the other hand, when a predetermined amount of nuclide is produced in raw materials other than the first-stage raw material, the rotation motor 44 of the rotation mechanism of the raw material to be replaced is driven, and the rotating shaft 42 is moved from the electron beam irradiation position to the extraction position. By rotating by the corresponding rotation angle, the raw material containing the production nuclide is moved to the take-out position and replaced with a new raw material (S108). After the replacement of the raw material is completed (S109), the rotating shaft 42 is rotated again to position the new raw material from the take-out position to the electron beam irradiation position. During this time, the raw material 21 of the first stage and the raw material 22 or 23 not to be exchanged are at the electron beam irradiation position, and nuclide production continues.
The above steps are continued until the end of manufacturing is finally instructed (S103).

As described above, according to this embodiment, by providing a mechanism for taking out each raw material that can be driven independently, it is possible to take out separately at a desired timing according to the required production amount of each nuclide to be produced. can. As a result, it is possible to perform optimum production for each nuclide without under-manufacturing or over-manufacturing.

Further, according to this embodiment, automatic control becomes possible by providing a control unit for controlling the take-out mechanism.

<Modified example of the third embodiment>
In the third embodiment, a rotating mechanism including a rotating motor, a rotating shaft, and a jig was used as the moving mechanism for the raw materials 22 and 23 in the second and subsequent stages, but the moving mechanism is limited to such a rotating mechanism. Instead, any mechanism may be used as long as the material can be moved from the electron beam irradiation position to the extraction position. For example, as shown in FIG. 13, a rod-like or plate-like expandable part 47 and a driving device 48 thereof may be used. The expansion/contraction part 47 is provided for each raw material, is independently driven by a driving device 48, and can expand/contract or slide in the direction intersecting the electron beam irradiation direction, as indicated by the arrow in the drawing. When taking out the raw materials, the raw materials 22 and 23 detachably fixed to one end of the expandable portion 47 are independently moved from the electron beam irradiation position to the raw material take-out position. By extending and contracting or reciprocating the rod-shaped or plate-shaped extensible portion 47 by the driving device 48, the raw material (including the production nuclide) can be taken out at an arbitrary time. Also in this case, as in the third embodiment, manual operation or automatic control by the control unit 60 is possible.

<Fourth embodiment>
In the drawings for explaining the first to third embodiments, the electron beam irradiation direction in the reaction chamber 30 is shown in the horizontal direction, but in the radionuclide production apparatus of the present embodiment, the electron beam irradiation direction is vertical. It is characterized in that the electron beam accelerator 10, the reaction chamber 30, and the raw materials are arranged in the same direction. The type of raw material, the electron beam, and the reaction with the bremsstrahlung radiation caused by the electron beam are the same as in the above-described embodiments, and the description thereof is omitted here.

As shown in FIG. 14, in the radionuclide production apparatus 100C of the present embodiment, the electron beam accelerator 10 is installed vertically on the upper part of the reaction chamber 30, and the raw materials 21 to 23 are irradiated in the electron beam direction (vertical direction ) are arranged so as to overlap each other. In this embodiment as well, the raw material 21 at the first stage has a doughnut-like shape surrounded by two concentric circles when viewed from the electron beam irradiation direction, and is rotated by the rotating shaft 42a of the rotary motor 41 via the jig 43a. Fixed. The raw materials 22 and 23 in the latter stage are fixed to rotating shafts 42b and 42c coaxial with the rotating shaft 42a via jigs 43a, respectively. The rotary shaft motor 41 separately controls the rotation speed, the number of rotations, the start of rotation, and the stoppage of rotation of each of the rotation shafts 42a to 42c. As a result, at any time, the nuclides that have reached a predetermined production amount can be moved from the atomic beam irradiation position to the removal position and removed from the jig (lower diagram in FIG. 14).

According to the present embodiment, in addition to the same effect as the third embodiment, by adopting a coaxial rotation mechanism as a mechanism for moving each raw material, it is possible to reduce the size of the mechanism. In addition, the take-out side of each raw material can be concentrated in one place, and the apparatus can be simplified. The configuration in which a plurality of raw material moving mechanisms are coaxial can also be adopted, for example, in the manufacturing apparatus shown in FIG. 10 of the third embodiment, and similar effects can be obtained. Conversely, in the present embodiment as well, it is possible to employ an expansion mechanism having an expansion and contraction portion as a moving mechanism for raw materials other than the first stage.

Further, according to the present embodiment, since the electron beam irradiation direction is vertical, for example, even if the raw material is liquid or powder, it can be arranged in the container evenly with respect to the electron beam irradiation surface. No electron beam irradiation can be performed.

<Modified example of the fourth embodiment>
In FIG. 14, the electron beam accelerator 10 was placed vertically above the reaction chamber 30, but as shown in FIG. A bending magnet device 70 that deflects the direction of the electron beam may be arranged between the upper opening 35 and the upper opening 35 . Also in this case, the arrangement of the raw materials in the reaction chamber 30 is the same as in the fourth embodiment, and the raw materials are arranged so as to overlap with the electron beam irradiation direction, and are irradiated with the electron beam in the vertical direction. This eliminates the need for a robust support mechanism for installing the relatively heavy electron beam accelerator 10 above the reaction chamber 30 . Alternatively, the reaction chamber 30 may be placed in a radiation-shielded basement or the like, and the electron beam accelerator 10 may be installed on the upper floor and connected by a bending magnet device 70, depending on the facility where the manufacturing apparatus is installed. It becomes possible to select the direction of irradiation, which increases the degree of freedom in terms of installation locations and arrangements of the electron beam accelerator and the reaction chamber.

Although various embodiments of the radionuclide production apparatus of the present invention have been described above, the configuration of each element described in these embodiments can be appropriately combined, and these are also included in the present invention. Further, the radionuclide production apparatuses of the above embodiments are all based on the radionuclide production method of the present invention, and the raw materials and the like described in the embodiments are raw materials applied to the radionuclide production method of the present invention. are all applicable.

10: electron beam accelerator, 11: electron beam, 20 (21, 22, 23): raw materials for radionuclide production, 30: reaction chamber, 40: movement mechanism (rotation mechanism), 60: control unit, 70: bending magnet Apparatus, 100: radionuclide production apparatus.

Claims (15)

A method of producing a radionuclide by irradiating a raw material with electrons emitted from an electron beam accelerator, thereby utilizing the reaction between the raw material and the bremsstrahlung radiation generated from the raw material,
A method for producing a radionuclide, wherein a plurality of raw materials are stacked in the electron irradiation direction as the raw materials, and at least one of atomic number and density is used as the raw material in the first stage is larger than that of the raw materials in the latter stage. A method for producing the radionuclide according to claim 1,
The raw material is one or more selected from radium Ra-226, molybdenum Mo-100, hafnium Hf-178, germanium Ge-70, and zinc Zn-68 or compounds thereof. Production method. A method for producing the radionuclide according to claim 2,
A method for producing a radionuclide, wherein the first-stage raw material is a raw material containing radium Ra-226 and/or a compound thereof, and the second-stage raw material is a raw material containing molybdenum Mo-100 and/or a compound thereof. A method for producing the radionuclide according to claim 1,
Two or more kinds of raw materials are stacked behind the first-stage raw material in the irradiation direction of the electron beam, and as a second-stage raw material, the raw material having the smallest atomic number and density among the two or more kinds of raw materials. A method for producing a radionuclide, characterized by using An electron beam accelerator, and a reaction chamber containing a raw material for generating a radionuclide at a position where the electron beam from the electron beam accelerator is irradiated, and performing a reaction to generate the radionuclide using the electron beam. ,
The raw material includes a first raw material arranged on the upstream side and a second raw material arranged on the downstream side along the irradiation direction of the electron beam,
The radionuclide production apparatus, wherein at least one of atomic number and density of the first raw material is higher than that of the second raw material. The radionuclide production apparatus according to claim 5,
A radionuclide production apparatus, wherein the thickness of the first raw material in the direction of irradiation is a thickness that maximizes the bremsstrahlung radiation generated from the first raw material upon irradiation with the electron beam. The radionuclide production apparatus according to claim 5,
A radionuclide production apparatus, wherein at least one of the first raw material and the second raw material is stored in a container. The radionuclide production apparatus according to claim 5,
The first raw material or a container for storing the first raw material has a shape surrounded by concentric circles having different diameters when viewed from the electron beam irradiation direction, and is eccentric with respect to the electron beam irradiation direction. and is arranged so that the electron beam is irradiated to a part of the region in the circumferential direction, and is rotatably supported about the center of the concentric circle as a rotation axis. The radionuclide production apparatus according to claim 8,
The radionuclide production apparatus, wherein the first raw material is divided into a plurality of parts in the circumferential direction of the concentric circle. The radionuclide production apparatus according to claim 9,
a rotating mechanism for rotating the first raw material around the rotating shaft;
A radionuclide production apparatus, further comprising: a take-out mechanism for taking out a part located at a position other than the electron beam irradiation position from among the plurality of divided parts of the first raw material. The radionuclide production apparatus according to claim 5,
further comprising a third raw material arranged behind the second raw material along the irradiation direction of the electron beam;
further comprising a moving mechanism for moving at least one of the second raw material and the third raw material from the electron beam irradiation position to the raw material extraction position; and a control device for controlling the operation of the moving mechanism. A radionuclide production device characterized by: The radionuclide production apparatus according to claim 11,
The moving mechanism rotates the second raw material and the third raw material, or the container containing the second raw material and the third raw material, with an axis parallel to the irradiation direction of the electron beam as a rotation axis. A radionuclide production apparatus characterized by being a rotation mechanism for rotating or an expansion and contraction mechanism for parallel movement in a direction orthogonal to the irradiation direction of the electron beam. The radionuclide production apparatus according to claim 5,
A radionuclide production apparatus, wherein the irradiation direction of the electron beam is horizontal, and the first raw material and the second raw material are arranged along the horizontal direction. The radionuclide production apparatus according to claim 5,
A radionuclide production apparatus, wherein the irradiation direction of the electron beam is a vertical direction, and the first raw material and the second raw material are arranged vertically in the vertical direction. The radionuclide production apparatus according to claim 14,
The electron beam accelerator is arranged so that the electron beam irradiation direction is horizontal, and a bending magnet device for changing the electron beam irradiation direction is arranged between the electron beam accelerator and the reaction chamber. A radionuclide production apparatus characterized by:

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