阅读说明：本技术 一种生产医用同位素225Ac的方法和装置 (Production of medical isotope225Ac process and apparatus ) 是由 张宇皓 刘伯学 王思弘 王柏松 于 2020-06-09 设计创作，主要内容包括：本发明属于医用放射性治疗核素领域,具体涉及一种生产医用同位素<Sup>225</Sup>Ac方法和装置。解决目前生产<Sup>225</Sup>Ac的方法存在的产量低,成本高、过程复杂等问题,用大功率高能电子束转换为韧致辐射轰击<Sup>226</Sup>Ra样品靶,通过光核反应<Image he="86" wi="631" file="DDA0002530675320000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>产生<Sup>225</Sup>Ac,最后对<Sup>226</Sup>Ra样品靶进行化学溶解,分离出<Sup>225</Sup>Ac,该方法不仅不需要昂贵的<Sup>229</Sup>Th,而且成本低,简单方便,无放射性废物处理问题。(The invention belongs to the field of medical radiotherapeutic nuclides, and particularly relates to a method for producing medical isotope 225 Ac process and apparatus. Solving the existing production 225 The Ac method has the problems of low yield, high cost, complex process and the like, and converts high-power and high-energy electron beams into bremsstrahlung bombardment 226 Ra sample target by photonuclear reaction Generating 225 Ac, last pair 226 Chemical dissolving Ra sample target, and separating 225 Ac, which process does not only require expensive 229 Th, low cost, simple and convenient operation, and no radioactive waste disposal problem.)

1. Production of medical isotope²²⁵Ac process, comprising the steps of:

step 1, irradiating a bremsstrahlung conversion target by using an electron beam to generate an X-ray photon beam;

step 2, irradiating with the X-ray photon beam²²⁶An Ra sample target;

step 3, irradiating²²⁶Ra sample target Cooling set time later, produced²²⁵Ra through β^-Decay into²²⁵Ac, pair²²⁶Chemical dissolving Ra sample target, and separating²²⁵Ac。

2. Production of medical isotopes according to claim 1²²⁵Ac process, characterized in that: the material of the bremsstrahlung conversion target is metal tungsten, metal tantalum or metal platinum; the above-mentioned²²⁶The Ra sample target is a mixture of powdered barium sulfate and radium sulfate or single radium nitrate or radium hydrochloride, and if the Ra sample target is the single radium nitrate or radium hydrochloride, aluminum is used as a carrier;

in the step 1, the energy of the electron beam is between 20MeV and 60 MeV; the average power of the electron beam is between 1kW and 120 kW; the cross-sectional dimension of the electron beam is smaller than²²⁶Ra sample target surface size.

3. Production of medical isotopes according to claim 2²²⁵Ac process, characterized in that: in step 3, the set time is 18 days; the thickness of the bremsstrahlung conversion target is 2-3.5 mm; the above-mentioned²²⁶The thickness of the Ra sample target is 10-20 mm;²²⁶the diameter of the Ra sample target disk or sheet is 20.0-30.0 mm; the cross-sectional diameter of the electron beam is 10.0-15.0 mm.

4. Production of medical isotopes according to any one of claims 1 to 3²²⁵The method for Ac is characterized in that the step 3 adopts the following steps to carry out chemical dissolution and separation²²⁵Ac：

Step 3.1, cooling for a set time²²⁶The Ra sample target was dissolved in 9 MHCl;

step 3.2, evaporating the solution to dryness, and dissolving residues into a solution by using 0.1 MHCl;

step 3.3, transferring the 0.1MHCl solution into a chromatographic column filled with Dowex-50 cation exchanger; with 9MHClO₄Washing the column to remove Al, Fe, Mg, Ra, Pa, Po, Pb and Bi; reuse of 5MHNO₃Elution is carried out²²⁵Ac。

5. Production of medical isotope²²⁵Ac apparatus, characterized by: comprises a target chamber device and at least one electron accelerator;

the target chamber device comprises a box body (1), a conversion target box (2), a cooling pipeline and a sample target bracket (3);

the conversion target box (2) is positioned in the box body (1); the cooling pipeline comprises an air inlet pipeline (22) and an air outlet pipeline (23); one end of the air inlet pipeline (22) is sealed and communicated with the left side wall of the conversion target box (2), and the other end of the air inlet pipeline is connected with an external helium cooling loop system; one end of the air outlet pipeline (23) is sealed and communicated with the right side wall of the conversion target box (2), and the other end of the air outlet pipeline is connected with an external helium cooling loop system; a fixed bremsstrahlung conversion target (20) is arranged in the conversion target box (2), and helium in the cooling pipeline can cool the bremsstrahlung conversion target (20);

the sample target bracket (3) is positioned inside the conversion target box (2) and can be taken out from the conversion target box (2); the sample target bracket (3) is internally fixed²²⁶An Ra sample target (33),²²⁶the target surface of the Ra sample target (33) is opposite to and parallel to the target surface of the bremsstrahlung conversion target (20); helium gas in the cooling pipeline can be used for²²⁶Ra sample target (33) is cooled;

the electron accelerator comprises a vacuum pipeline (4), and the vacuum pipeline (4) penetrates through the box body (1) and vertically points to the side wall of the conversion target box (2); the central axis of the vacuum pipeline is vertical to the central axes of the air inlet pipeline (22) and the air outlet pipeline (23), and the electron beam in the vacuum pipeline bombards the bremsstrahlung conversion target (20) in the direction vertical to the bremsstrahlung conversion target (20) to generate an X-ray photon beam which irradiates the bremsstrahlung conversion target (20)²²⁶Ra sample target (33).

6. Production of medical isotopes according to claim 5²²⁵Ac apparatus, characterized by: the material of the conversion target box (2) is stainless steel; the bremsstrahlung conversion target (20) comprises a plurality of target sheets which are arranged in parallel and at intervals; helium is blown into gaps among the target sheets to cool the bremsstrahlung conversion target (20);

the sample target bracket (3) comprises a bracket body (31) and a sample target box (32) fixed at one end of the bracket body (31);the above-mentioned²²⁶Ra sample target (33) is located within a sample target cartridge (32), said²²⁶Ra sample target (33) comprises a plurality of parallel and spaced apart²²⁶Ra sample target pieces, helium gas blown into gaps between respective target pieces, and²²⁶the Ra sample target (33) was cooled.

7. Production of medical isotopes according to claim 6²²⁵Ac apparatus, characterized by: each one of which is²²⁶The thickness of the target sheet of the Ra sample target is 0.5mm-1mm, and two adjacent target sheets²²⁶The gap between the Ra sample target pieces is 0.5-1 mm; the thickness of each target sheet in the bremsstrahlung conversion target (20) is 0.5mm, and the gap between every two adjacent target sheets is 0.5 mm; bremsstrahlung conversion target (20) and²²⁶ra sample targets (33) are spaced 1-3mm apart.

8. Production of medical isotopes according to claim 7²²⁵Ac apparatus, characterized by: the conversion target box is characterized by further comprising a blind plate (21), one end of the conversion target box (2) is opened, the opening end of the conversion target box extends out of the box body (1) and is fixed on the box body, and the blind plate (21) is detachably fixed at the opening end of the conversion target box (2) in a sealing mode; the frame body of the sample target bracket (3) is fixedly connected with the blind plate (21).

9. Production of medical isotopes according to any one of claims 6 to 8²²⁵Ac apparatus, characterized by: the number of the electron accelerators is two; one end of the vacuum pipeline (4) is a vacuum window, and the vacuum window of one of the vacuum pipelines of the electron accelerator is opposite to the front side wall of the conversion target box (2); the vacuum window of the other electron accelerator vacuum pipeline is opposite to the rear side wall of the conversion target box (2); a gap is arranged between the vacuum window and the conversion target box (2).

10. Production of medical isotopes according to any one of claims 6 to 8²²⁵Ac apparatus, characterized by: the number of the electron accelerators is two; one end of one of the electron accelerator vacuum pipelines is hermetically connected with the front side wall of the conversion target box (2); one end of another electron accelerator vacuum pipe andthe rear side wall of the conversion target box (2) is connected in a sealing way;

defining portions of the front and rear side walls of a converted target box (2) bombarded by electron beams as a target window (201); the target window is of a convex-concave lens structure, and the sinking direction points to the inside of the conversion target box (2); the thickness of the center of the recess is smaller than that of the edge; wherein the convex surface is an ellipsoid, a spherical surface or a plane.

Technical Field

The invention belongs to the field of medical radiotherapeutic nuclides, and particularly relates to a method for producing medical isotope²²⁵Ac process and apparatus.

Background

With the continuous update and development of modern medicine on tumor diagnosis and treatment, tumor treatment is developing towards precise targeted treatment. In addition to targeted chemotherapeutic drugs, targeted radionuclide therapeutic drugs are increasingly being receivedRadioactive isotopes, typically such as α, which decay upon release of the particles²²⁵Ac and²¹³Bi(²¹³bi is²²⁵Ac decay daughter) is rapidly becoming a trend and focus area for the diagnosis and treatment of tumors, particularly for the study of tumor-targeted therapies, and pre-clinical animal experimental studies and preliminary clinical practices have been successful. This is mainly because: 1)²²⁵ac has excellent nuclear physical properties, a short half-life (10 days), and a decay body²²¹Fr and²¹⁷at and²¹³bi is mostly α particle releaser with short service life and can be used as a tumor targeted therapeutic nuclide.²²⁵The decay chain of Ac is shown in FIG. 1. 2)²²⁵The mean energy of the α released particles of Ac and its daughter is 6-8MeV, with high Linear Energy Transfer (LET) in the tissue, the high deposited energy density of the high LET radiation results in a large number of double strand breaks in the tumor cell DNA, with a high killing effect on the DNA within the tumor cells.3) these high LET radiation particles, which typically have LET values of 80-99keV/μm, have a very short range of action in the tissue (approximately 2-100 microns, i.e., in the range of 6-8 cells), provide almost all the energy in this short range, so they only kill the tumor target tissue enormously, while they have almost no toxic side effects on normal tissues surrounding the tumor target tissue.this is the same rationale as the current boron neutron Capture Therapy (CT) technique, which is currently very effective in therapy.4) compared to radiation therapy (internal irradiation) using direct electron beams, gamma rays (currently widely used external irradiation radiotherapy techniques) or medical isotopes, which are accurate, and which can kill the prostate cancer cells, prostate cancer, and ovarian cancer.

²²⁵Ac is currently mainly a slave²³³With U decaying²²⁹Th, as shown in FIG. 2, not only²²⁹Half-decay of ThLong term (T)_1/27880y) and only a small fraction is converted to²²⁵Ac, is used. Due to the fact that²³³U is very limited in quantity worldwide and therefore valuable. Now worldwide²²⁹Th are mainly derived from three sources and can produce related²²⁵Ac, is used. Each of these sources is derived from an already fissile precursor²³³U is subjected to chemical separation, the process is complex, and radioactive waste is large. Since 1997, ORNL in the United states has supplied only 720mCi of high purity per year²²⁵Ac; the physical and electrical engineering institute of russian obinsk also has similar supply; the transuranic institute of Karlsruhe, Germany, has a small value²²⁹Th source, capable of producing only 350mCi per year²²⁵Ac, is used. Result in the world²²⁵Ac supplies are severely inadequate and up to 1 million dollars/mCi. All of these²²⁵Even if Ac supports a few limited clinical studies, it is far from meeting the demand, let alone the clinical therapeutic application and widespread popularization.

Currently, it is used in clinical research²²⁵The predominant method of Ac is through long lifetime²²⁹Decay of Th, there were also some other studies to investigate the increase²²⁹Th parent or²²⁵Ac itself can be supplied in different ways. But producing quantities meeting market requirements²²⁹Th is challenging because its half-life is very long.

Disclosure of Invention

To solve the current production²²⁵The Ac method has the problems of high cost, complex process and the like, and the invention discloses a method for producing medical isotope²²⁵Ac method and apparatus for converting high power high energy electron beam into bremsstrahlung bombardment²²⁶Ra, by photonuclear reactionGenerating²²⁵Ac, which process does not only require expensive²²⁹Th, high output, low cost, simple process and no radioactive waste.

The technical scheme of the invention is to provide a method for producing medical isotope²²⁵Method of Ac, which is characterized inThe special points are that the method comprises the following steps:

step 1, irradiating a bremsstrahlung conversion target by using an electron beam to generate an X-ray photon beam;

step 2, irradiating with the X-ray photon beam²²⁶An Ra sample target;

step 3, irradiating²²⁶Ra sample target Cooling set time later, produced²²⁵Ra through β^-Decay into²²⁵Ac, pair²²⁶Chemical dissolving Ra sample target, and separating²²⁵Ac。

Further, the bremsstrahlung conversion target is made of metal tungsten, metal tantalum or metal platinum; the above-mentioned²²⁶The Ra sample target is a mixture of powdered barium sulfate and radium sulfate or single radium nitrate or hydrochloric acid, and if the Ra sample target is the single radium nitrate or hydrochloric acid, aluminum is used as a carrier.

Further, in order to improve²²⁵Ra is the specific activity of the sample target, and in the step 1, the energy of the electron beam is between 20MeV and 60 MeV; the average power of the electron beam is between 1kW and 120 kW; the cross-sectional dimension of the electron beam is smaller than²²⁶Ra sample target surface size.

Further, in step 3, the set time is 18 days; the thickness of the bremsstrahlung conversion target is 2-3.5 mm; the above-mentioned²²⁶The thickness of the Ra sample target is 10-20 mm;²²⁶the diameter of the Ra sample target disk or sheet is 20.0-30.0 mm; the incident electron beam has a cross-sectional diameter of 10.0-15.0 mm.

Further, the following steps are adopted in the step 3 for chemical dissolution and separation²²⁵Ac：

Step 3.1, cooling for a set time²²⁶The Ra sample target was dissolved in 9 MHCl;

step 3.2, evaporating the solution to dryness, and dissolving the solution into a solution by using 0.1 MHCl;

step 3.3, transferring the 0.1MHCl solution into a chromatographic column filled with Dowex-50 cation exchanger; with 9MHClO₄Washing the column to remove Al, Fe, Mg, Ra, Pa, Po, Pb and Bi; reuse of 5MHNO₃Elution is carried out²²⁵Ac。

The invention also provides a method for producing the medical isotope²²⁵Ac, characterized in that: comprises a target chamber device and at least one electron accelerator;

the target chamber device comprises a box body, a conversion target box, a cooling pipeline and a sample target bracket;

the conversion target box is positioned in the box body; the cooling pipeline comprises an air inlet pipeline and an air outlet pipeline; one end of the air inlet pipeline is sealed and communicated with the left side wall of the conversion target box, and the other end of the air inlet pipeline is connected with an external helium cooling loop system; one end of the air outlet pipeline is sealed and communicated with the right side wall of the conversion target box, and the other end of the air outlet pipeline is connected with an external helium cooling loop system; the conversion target box is internally provided with a fixed bremsstrahlung conversion target, and helium in the cooling pipeline can cool the bremsstrahlung conversion target;

the sample target bracket is positioned in the conversion target box and can be taken out of the conversion target box; the sample target holder is internally fixed²²⁶The target of the Ra sample was,²²⁶the target surface of the Ra sample target is opposite to and parallel to the target surface of the bremsstrahlung conversion target; helium gas in the cooling pipeline can be used for²²⁶Cooling the Ra sample target;

the electron accelerator comprises a vacuum pipeline, and the vacuum pipeline penetrates through the box body and vertically points to the side wall of the conversion target box; the central axis of the vacuum pipeline is vertical to the central axes of the air inlet pipeline and the air outlet pipeline, and the electron beam in the vacuum pipeline bombards the bremsstrahlung conversion target in the direction vertical to the bremsstrahlung conversion target to generate an X-ray photon beam which irradiates²²⁶Ra sample target.

Further, the material of the conversion target box is stainless steel; the bremsstrahlung conversion target comprises a plurality of target sheets which are arranged in parallel and at intervals; helium is blown into gaps among the target plates to cool the bremsstrahlung conversion target;

the sample target bracket comprises a bracket body and a sample target box fixed at one end of the bracket body; the above-mentioned²²⁶The Ra sample target is located in a sample target cassette, which²²⁶The Ra sample target comprises a plurality of parallel and spaced-apart sample targets²²⁶Ra sample target piece, helium gas blowingGaps between the respective target pieces, pair²²⁶The Ra sample target was cooled.

Further, each of²²⁶The thickness of the target sheet of the Ra sample target is 0.5mm-1mm, and two adjacent target sheets²²⁶The gap between the Ra sample target pieces is 0.5-1 mm; the thickness of each target sheet in the bremsstrahlung conversion target is 0.5mm, and the gap between every two adjacent target sheets is 0.5 mm; bremsstrahlung conversion target and²²⁶ra sample targets were spaced 1-3mm apart.

Furthermore, in order to take the sample target bracket out of the conversion target box, the device also comprises a blind plate, one end of the conversion target box is opened, the opening end of the conversion target box extends out of the box body and is fixed on the box body, and the blind plate is detachably fixed at the opening end of the conversion target box in a sealing way; the frame body of the sample target bracket is fixedly connected with the blind plate. By withdrawing, removing and installing the blind plate and the attached carrier from the target-converting box²²⁶Ra sample target.

Further, in order to improve²²⁵Ac production efficiency, the number of the electron accelerators is two, one end of the vacuum pipeline is a vacuum window, and the vacuum window of one electron accelerator vacuum pipeline is opposite to the front side wall of the conversion target box; the vacuum window of the other electron accelerator vacuum pipeline is opposite to the rear side wall of the conversion target box; a gap is provided between the vacuum window and the transfor target capsule.

Furthermore, the vacuum pipeline and the conversion target box can also be integrally arranged, and one end of the vacuum pipeline of one of the electron accelerators is hermetically connected with the front side wall of the conversion target box; one end of the other electron accelerator vacuum pipeline is hermetically connected with the rear side wall of the conversion target box; defining portions of the front and rear sidewalls of a transformed target box bombarded by the electron beam as a target window; the target window is of a convex-concave lens structure, and the sinking direction points to the inside of the conversion target box; the thickness of the center of the recess is smaller than that of the edge; wherein the convex surface is an ellipsoid, a spherical surface or a plane.

The invention has the beneficial effects that:

1. the invention utilizes X-ray radiation converted by a conversion target of about 500-1000 mg²²⁶Ra target material for 5 days by photonuclear reaction

That is, about 1-2Ci of²²⁵Ac, is used. Not only do not require expensive²²⁹Th, high yield, simple and convenient, and no radioactive waste treatment problem.

2. Prepared by the invention²²⁵Ac has high purity and cannot generate²²⁷Ac, is used. Other commonly used²²⁵The Ac production process can be commensally equivalent²²⁷Ac，²²⁷Ac is a long life (T)_1/221.8 years) and highly toxic isotopes, the presence of which can seriously affect clinical use and efficacy.

3. Production of the invention²²⁵Compared with a reactor or a production facility of a high-energy proton accelerator, the Ac equipment has less investment and low cost. Fast breeder reactor passable²²⁶Ra(n，2n)²²⁵Ra-and high energy proton accelerators up to 70-500MeV can be passed^natU or²³²Th(p,x)²²⁵Ac production²²⁵Ac, but not only do these two production facilities have investment scales much larger than the present invention, but also have high operational, maintenance and environmental risks.

Drawings

FIG. 1 is a drawing of²²⁵Schematic diagram of the decay chain of Ac;

FIG. 2 is a drawing from²³³With U decaying²²⁹Extraction from Th²²⁵Schematic representation of Ac;

FIG. 3 is a drawing showing²²⁶The reaction cross-sections of Ra photonuclear pathways (γ, n), (γ,2n), (γ,3n), (γ, np) and (γ, p) are related to the radiation energy;

FIG. 4 is a drawing showing²²⁴Decay of Ra to stable isotopes²⁰⁸A schematic diagram of Pb;

FIG. 5 is a drawing showing²²⁶After irradiation of the target of the Ra sample,²²⁵attenuation of Ra and²²⁵generating a relational graph of Ac;

FIG. 6 is a drawing showing²²⁵α spectrum of Ac α decay;

FIG. 7 shows production of medical isotope used in the examples²²⁵Schematic of the target chamber apparatus for Ac;

FIG. 8 is a cross-sectional view of the target chamber assembly taken along the beam current direction;

FIG. 9 is a cross-sectional view of the target chamber arrangement along the gas path;

FIG. 10 is a partially enlarged block diagram of the interior of a translating target cartridge;

FIG. 11a is another enlarged partial view of the interior of a translating target cartridge wherein the convex surface of the target window is spherical;

FIG. 11b is another enlarged partial view of the interior of the switching target box wherein the convex surface of the target window is planar;

FIG. 12 is a schematic view of the structure of the case;

FIG. 13 is a schematic view of the assembly of the cooling conduit with the switched target cartridge;

the reference numbers in the figures are: 1-box body, 12-upper side wall, 13-lower side wall, 14-left side wall, 15-right side wall, 16-opening, 17-gas path fixing flange, 18-bottom plate flange, 2-conversion target box, 20-bremsstrahlung conversion target, 201-target window, 21-blind plate, 22-gas inlet pipeline, 23-gas outlet pipeline, 24-end flange, 3-sample target bracket, 31-frame body, 32-sample target box, 33-sample target and 4-vacuum pipeline.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments.

The invention uses high-energy electron beam to irradiate the bremsstrahlung conversion target to generate enough X-ray photon beam, and uses the X-ray photon beam to irradiate²²⁶An Ra sample target; after 18 days of standing, produced by irradiation²²⁵Ra through β^-Decay to a certain amount²²⁵Ac, then on²²⁶Chemical dissolving and separating Ra sample target²²⁵Ac。

The photonuclear reaction section is generally smaller, but a wider (3-7 MeV) giant dipole formant (GDR) appears in the energy range of 10-25 MeV, and due to the phenomenon of the giant dipole formant, the photonuclear reaction section is suitable for the nuclear reaction with the large dipole formant²²⁶The photonuclear reaction of Ra will have a relatively high photonuclear reaction cross-section, as shown in figure 3,²²⁶Ra(γ，n)²²⁵the photonuclear reaction cross section of Ra is 290 mb. The threshold energy was 6.2MeV and the peak cross-sectional energy was 12 MeV.

Except that²²⁶Ra(γ，n)²²⁵Reaction of Ra to produce²²⁵Outside Ra, X-rayAnd²²⁶ra can also undergo several other photonuclear reactions, such as (γ,2n), (γ,3n), (γ, np) and (γ, p), and FIG. 3 depicts X-ray interaction with²²⁶Ra-the cross-section of the photonuclear reaction-is related to the radiation energy.

The following table lists²²⁶Reaction channel, cross section and reaction of photonuclear reaction of Ra to generate nuclides and half-life:

reaction channel	Threshold energy	Cross section of	Product of	Half life of the product
					(γ,2n)	11.4	500	Ra-224	3.6d
(γ,n)	6.4	290	Ra-225	14.9d
					(γ,3n)	19.5	20	Ra-223	11.43d
(γ,np)	13.4	0.2	Fr-224	3.3m
					(γ,P)	7.5	0.1	Fr-225	3.98m

In the above 5 reaction channels except²²⁶Ra(γ，n)²²⁵Ra and²²⁶Ra(γ，2n)²²⁴in addition to Ra, the remaining reaction cross-sections are small and the half-lives are short, so that the products are few and negligible. The larger amount of by-products being²²⁴Ra, half life 3.6 days.²²⁴Ra-decays 4 times α and 3 times β^-Decay, each with a short half-life, and finally to a stable isotope²⁰⁸The decay chain of Pb is shown in FIG. 4. If irradiated, will²²⁶The Ra sample target can decay away 97% after being cooled for 5 half-lives, namely 18 days²²⁴Ra, and²²⁵ra decays only half as much. This is one of the reasons why the sample target is treated after being left to cool for 18 days after irradiation. To improve²²⁵Ra has a specific activity in the sample target, and the cross-sectional dimension of the electron beam is smaller than²²⁶Ra sample target cross-sectional dimensions. The energy of the high-energy electron beam emitted by the electron accelerator is more than 20MeV, but preferably not more than 60MeV, and the optimal energy is 40 MeV; the electron accelerator preferably emits an electron beam having an average power of greater than 1kW, preferably 40kW, and more preferably 100 kW. Preferably a Rhodotron or an electron linear accelerator (Linac). The electron accelerator can continuously and stably work to emit high-energy electron beams, and can continuously work for at least 1 day (24 hours) to 6 days. Selection of materials for bremsstrahlung conversion targets with high conversion efficiency and high temperature resistanceMetallic tungsten (W), metallic tantalum (Ta), or metallic platinum (Pt). Metallic tungsten (W) is preferred because it has desirable physical properties, such as a high melting point and a high thermal conductivity.

²²⁶Ra is the most stable isotope of Ra (radium) and the half-life is 1600 years. Radium is quite unstable in air and can easily react with nitrogen and oxygen to generate radium nitride or radium oxide. Therefore, the invention²²⁶The Ra sample target is selected from a mixture of powdered barium sulfate and radium sulfate and pressed into a sample plate/sheet, or the Ra sample target can be pressed into the sample plate/sheet by only using radium nitrate or radium hydrochloride, and in this case, aluminum is used as a carrier.

Due to the fact that²²⁵Ac is derived from²²⁵Produced by decay of Ra²²⁵Ac also decays during the accumulation process, so at an optimal point in time, it is desirable that²²⁵Ac and²²⁵and Ra is separated. FIG. 5 is²²⁶After irradiation of the target of the Ra sample,²²⁵attenuation of Ra and²²⁵and (3) a generation relation graph of Ac. Will be provided with²²⁶After the Ra sample target material is cooled and stored for 18 days,²²⁵ac reaches the maximum accumulation and the reaction by-product is produced²²⁴Ra decays to about 3% over 5 half-lives, and is therefore isolated 18 days after irradiation²²⁵Optimal time for Ac.

During separation, firstly, the cooled²²⁶The Ra sample target was dissolved in 9MHCl, the solution was then evaporated to dryness, the residue was dissolved in 0.1MHCl to a solution (initial solution), and the initial solution was finally isolated by the following ion exchange method:

(1) 0.5ml of a 0.1MHCl initial solution was transferred to a 0.2 × 4.0.0 cm column packed with Dowex-50 cation exchanger (200 and 400 mesh), (2) 4ml of a 9MHClO₄Washing the column to remove Al, Fe, Mg, Ra, Pa, Po, Pb, and Bi; (3) finally 1ml of 5MHNO was used₃Elution is carried out²²⁵Ac。

²²⁵Ac and its parent substance²²⁵Ra(T_1/214.9d) every few weeks (14-18 days) and repeating the above procedure again to obtain²²⁵Ac, commonly called "milking" one more time.²²⁵Activity of Ac through its subproducts²²¹Fr(E_r＝217.6keV，Branch ratio 12.5%, T_1/24.8min) and²¹³Bi(E_r439.7keV, branching ratio 27.3%, T_1/245.6 min).

To ensure that the desired product is obtained by the above separation and purification process²²⁵Ac, the invention obtains the thickness of a sample target through experiments and determines the optimal electron beam current sum through MonteCarlo simulation²²⁶Target disk diameter of Ra sample target, etc.

To compare²²⁵Ra in different thicknesses²²⁶The radiation yield formed in the irradiation of the Ra sample target was analyzed using lead chloride as the target. Thin targets (less than 0.05mm thick) containing 9.6mg powdered PbCl₂(7.16 mgPb). By similar irradiation to thin²²⁶Procedure for Ra sample target thin target was irradiated. The thick target (thickness greater than 0.5mm) is a steel cylinder with an internal diameter of 8mm, using 5.4g of PbCl₂The powder (4.00g PbO) was filled to a target sample thickness of 10 mm. Two targets were irradiated for 10 minutes at an electron current of 15 μ A and a maximum photon energy of 50 MeV. The activity of these targets was measured 5 days after the completion of irradiation. In the case of thick targets, the irradiated PbCl is removed from the test tube₂Powder, mixed well, from which 13mg of sample (i.e. 9.7mg pb) can be taken. Lead chloride model experiments show that the specific yield of the target product does not decrease by more than 20% from a thin target to a 4g thick target. The experiment proves that the total thickness of the sample target can reach 10.0-20.0 mm. Therefore, this example selects 20 target slices with thickness of 0.5-1.0mm²²⁶Ra sample target.

The optimal electron beam current and sample target disc diameter were determined by MonteCarlo simulations. Preferably, the optimum beam diameter is about 10.0-15.0 mm. The diameter of the sample target disk is 20.0-30.0 mm. Especially in cases where the sample material is very rare or expensive, e.g.²²⁶And Ra. The sample target should be as small as possible. If the mass of the sample is small, the diameter of the sample target is also small because the cross-section or diameter of the electron beam is about 10% to 50% smaller relative to the sample. For example, a 20mm diameter target may pass a 12mm diameter beam and a 10mm diameter target may pass a 5mm diameter beam.

With an active area of 0.6cm with a resolution of 16keV²The final product was measured by α rays using an α Si (Au) detector, and the final product was coated on a stainless steel support²²⁵Ac solution, then evaporating α sample made from the solution, measured²²⁵The α spectrum of the Ac sample is shown in fig. 6, it is clear that,²²⁵the four α decaying nuclides in the Ac decay chain are very clear and have energy E respectively_α(²²⁵Ac)＝5.8MeV，E_α(²²¹Fr)＝6.3MeV，E_α(²¹⁷At)＝7.1MeV，E_α(²¹³Po) ═ 8.4 MeV. Obtained by illustrating the invention²²⁵The Ac purity is very high, and meets the requirement.

The measured data from the α spectrum show that the invention²²⁵The yield of Ac was 550Bq/(μ A. multidot.h. multidot.mg). Extrapolating when the maximum electron energy reaches 50MeV and the beam current is 1mA or more, irradiating 0.5-1.0g with converted X-ray²²⁶Ra samples produced over 150 hours, greater than 1-2Ci²²⁵Ac。

In this embodiment, to improve cooling efficiency, the coolant directly contacts the bremsstrahlung conversion target and²²⁶ra sample target. To prevent the coolant from oxidizing and corroding the bremsstrahlung conversion target and the sample target, the coolant is chosen to be helium, an inert gas. The transducer and sample container are maintained at or below their respective melting points. The bremsstrahlung conversion target and the sample target are independent but well centered with respect to each other and are closely arranged to form a compact system as a whole, the distance between the conversion target cartridge and the sample target cartridge must be minimized and these two components cannot be in thermal contact.

Therefore, the apparatus shown in fig. 7 may be used in this embodiment, which includes a target chamber device and two electron accelerators; of course, in other embodiments, an electron accelerator may be used according to actual requirements.

Referring to fig. 8 to 10, it can be seen that the target chamber device includes a case 1, a convertible target cartridge 2, a cooling duct, a sample target holder 3, and a blind plate 21; the conversion target box 2 is positioned in the box body 1, one end of the conversion target box is opened, the opening end of the conversion target box extends out of the box body and is fixed on the box body 1, and the blind plate 21 is detachably fixed at the opening end of the conversion target box 2 in a sealing manner; the bremsstrahlung conversion target 20 is fixed inside the conversion target box 2. The material of the conversion target box 2 is stainless steel, and other radiation-resistant and pressure-resistant materials can be selected according to actual requirements, such as; the thickness of the bremsstrahlung conversion target 20 is 2-3.5 mm; can be a conversion target, and also can comprise a plurality of target sheets which are arranged in parallel and at intervals; helium is blown into gaps among the target plates through a cooling pipeline to cool the bremsstrahlung conversion target. Preferably, metallic tungsten (W) is used as the bremsstrahlung conversion target material, and the diameter of the tungsten conversion target is 4 cm.

The cooling pipeline comprises an air inlet pipeline 22 and an air outlet pipeline 23, one end of the air inlet pipeline 22 is sealed and communicated with the left side wall of the conversion target box 2, and the other end of the air inlet pipeline is connected with an external helium cooling loop system; one end of the air outlet pipeline 23 is sealed and communicated with the right side wall of the conversion target box 2, and the other end is connected with an external helium cooling loop system.

Sample target bracket 3 is located conversion target box 2 inside, including support body 31 and fix the sample target box 32 in support body 31 one end, support body 31 links firmly with blind plate 21, can take out sample target bracket 3 from conversion target box 2 inside through dismantling blind plate 21. The material of the sample target box is stainless steel. The end of the sample target box 32 facing the bremsstrahlung conversion target is open; as shown in figures 10 and 11 of the drawings,²²⁶the Ra sample target 33 is fixed within the sample target cassette 32,²²⁶the target surface of the Ra sample target disk is opposite to and parallel to the target surface of the conversion target, and the bremsstrahlung conversion target 20 is²²⁶Ra sample targets 33 are spaced 1-3mm apart. Helium in the cooling pipeline can be simultaneously paired²²⁶The Ra sample target 33 was cooled.²²⁶ Ra sample target 33 comprises a plurality of parallel and spaced apart²²⁶Ra sample target. Each one of which is²²⁶The thickness of the Ra sample target piece is 0.5mm-1mm, and two adjacent target pieces²²⁶The gap between the Ra sample target pieces is 0.5-1 mm.

The electron accelerator comprises a vacuum pipeline 4 for transmitting electron beam, the vacuum pipeline 4 penetrates into the box body 1 and vertically points to the side wall of the conversion target box 2, and the central axis of the vacuum pipeline is vertical to the central axes of the air inlet pipeline 22 and the air outlet pipeline 23; the helium flow direction, the electron beam flow direction and the sample target bracket taking-out or inserting direction are orthogonal (forming an angle of 90 degrees with each other), and the electron beam in the vacuum pipeline bombards in a direction vertical to the conversion target surfaceThe conversion target generates X-ray photon beam and irradiates²²⁶Ra sample target. As shown in fig. 10, one end of the vacuum tube 4 is a vacuum window, and the vacuum window of one of the electron accelerator vacuum tubes is opposite to the front side wall of the convertible target box 2; the vacuum window of the other electron accelerator vacuum pipeline is opposite to the rear side wall of the conversion target box 2; a gap is formed between the vacuum window and the conversion target box 2, the vacuum window can also be combined with the side wall of the conversion target box 2 into a whole, as shown in fig. 11, one end of a vacuum pipeline of one of the electron accelerators is hermetically connected with the front side wall of the conversion target box 2; one end of the other electron accelerator vacuum pipeline is hermetically connected with the rear side wall of the conversion target box 2. Portions of the front and rear sidewalls of the transformed target box 2, which are bombarded by the electron beam, are defined as a target window 201; the target window is of a convex-concave lens structure, and the sinking direction points to the inside of the conversion target box 2; the thickness of the center of the recess is smaller than that of the edge; wherein the convex surface is ellipsoidal, spherical (FIG. 11a) or planar (FIG. 11b), and the thickness at the center of the target window is thinnest, preferably 0.25-0.5 mm. The material of the target window is selected from heat-resistant and corrosion-resistant alloy chromium-nickel-iron alloy or Inconel (Inconel: nickel 80%, chromium 14%, iron 6%), Maraging steel (Maraging steel) and the like.

As shown in fig. 12, the box 1 is a square housing, the upper side wall 12, the lower side wall 13, the left side wall 14 and the right side wall 15 of the box are all provided with openings 16, and the size of the openings 16 can ensure that the target transforming box 2 can be taken out from the box 1; the upper side wall 12, the left side wall 14 and the right side wall 15 are provided with air path fixing flanges 17 at the hole opening positions, and the lower side wall 13 is provided with a bottom plate flange 18 at the hole opening position; all the gas circuit fixing flanges 17 are formed by two half flanges. With reference to fig. 8 and 9, an end flange 24 is disposed on the lower end surface of the blind plate 21, a flange hole of the end flange 24 is matched with the cross-sectional shape of the target box 2, and one end of the target box 2 penetrates through the flange hole of the end flange 24 and is fixedly connected with the blind plate 21; and the end flange 24 is positioned on the upper end surface of the gas circuit fixing flange 17 of the upper side wall 12 of the box body and is fixedly connected with the gas circuit fixing flange; the gas path fixing flanges 17 of the left side wall 14 and the right side wall 15 of the box body fix the box body 1 from the side surfaces of the gas inlet pipeline 22 and the gas outlet pipeline 23. In order to improve the sealing performance of the cavity, a sealing ring is arranged between the blind plate 21 and the end flange 24.

As shown in fig. 13, the inlet duct 22 and the outlet duct 23 both include a main duct 231 and a bell mouth 232, and the small end of the bell mouth 232 is a rectangular opening. The main pipe 231, the bell mouth 232, the conversion target box 2 and the end flange 24 are welded together by argon arc welding, so that the high-pressure sealing performance is ensured. Wherein the main pipeline 231 is welded with the big end of the horn mouth 232, and the left and right side walls of the air channel assembly cavity 21 are welded with the small end of the horn mouth 232. The maximum working pressure of the high-pressure helium gas circuit is 2MPa, so that a 316L stainless steel pipeline with the inner diameter of 50mm and the wall thickness of 4mm is selected as the main pipeline, the pressure of 4MPa can be borne, and the safety of the gas cooling system is ensured. The flow rate of the high-pressure helium gas at 2MPa is 300 g/s.

Further, it is to be understood that the positional terms such as "front, back, upper, lower, left, right", and the like are generally used herein based on the positional or orientational relationships shown in the drawings for convenience in describing the present invention and for simplicity in description, and that, unless otherwise specified, these positional terms are not intended to indicate and imply that the referenced device or element must have a particular orientation or be constructed and operated in a particular orientation and therefore are not to be considered limiting of the scope of the present invention; the terms "inner" and "outer" refer to the inner and outer contours of the respective component itself, and unless otherwise stated, the terms do not have any special meaning, and therefore, should not be construed as limiting the scope of the present invention. It is to be noted, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended drawings.