Closed circulation 226Ra solution target system for producing 225Ac

Abstract

The invention relates to a closed circulation 226Ra solution target system for producing 225Ac. The closed circulation 226Ra solution target system comprises a solution type 226Ra target, an isotope target bin, a valve, a 226Ra solution circulation structure, a radium actinide separation structure, a radium lead separation structure, a photon detection system I, a photon detection system II, a heat exchange system, a pressure reduction radon evaporator and a radon treatment system, and the solution type 226Ra target comprises a solution circulation pipeline and a radium-containing solution. The radium-containing solution is contained in the closed solution circulating pipeline; the solution circulating pipeline comprises a main loop pipeline and two branch pipelines; the photon detection system I, the 226Ra solution circulation structure, the pressure reduction radon evaporator, the heat exchange system, the valve and the photon detection system II are sequentially arranged on the main loop pipeline; and the radium actinide separation structure and the radium lead separation structure are respectively arranged on the two branch pipelines. The system can improve the preparation efficiency and yield of 225Ac.

Description

Technical Field

[0001] The present invention relates to the technical field of isotope target systems for medical use in accelerators, and particularly to a closed-loop 225 Ra solution target system for producing 225 Ac. 226 Ra solution target system. Background Technique

[0002] Targeted alpha therapy is a cancer treatment method with characteristics such as high precision, significant efficacy, and relatively small side effects. This method injects drugs carrying short-lived alpha radionuclides into the human body and accumulates them at the tumor site, irradiating and killing cancer cells with alpha particles to achieve the treatment purpose. The key to targeted alpha therapy is to develop applicable alpha radioisotopes. Currently, several candidate isotopes are in clinical and pre-clinical evaluations, including 149 Tb, 211 At, 212 Bi, 212 Pb, 213 Bi, 223 Ra, 224 Ra, 227 Th, and 225 Ac, etc. Among them, 225 Ac is one of the alpha radionuclides with medical prospects due to its short half-life (about 10 days), effective binding with various chelating agents, and efficient irradiation achievable through four alpha decays and two beta decays.

[0003] 225 The production of 229 Ac mainly has the following several methods: (1) Preparation through a thorium-actinium generator, enabling 225 Th to naturally decay to produce 232 Ac; (2) Preparation with a thorium target by high-energy protons, and the nuclear reaction formula is 225 Th(p, x) 225 Ra → 226 Ac; (3) Preparation with a radium target by medium and low-energy proton reactions, and the nuclear reaction formula is 225 Ra(p,2n) → 226 Ac; (4) Preparation with a radium target by photonuclear reactions, and the nuclear reaction formula is 225 Ra(γ, n) 225 Ra → 226 Ac; (5) Preparation based on fast reactors and neutron sources. The nuclear reaction formula based on the fast reactor scheme is 225 Ra(μ-, nv) 225 Fr → 226 Ac, and the nuclear reaction formula based on the neutron source scheme is 225 Ra(n,2n) 225 Ra → 225Ac is produced by bombarding heavy metal conversion targets with medium and high energy electrons generated by an electron linear accelerator to produce a large number of γ photons, which then interact with 226 the Ra target to obtain the product through photonuclear interaction 225 Ra, and then 225 Ra decays to produce 225 Ac. The lower threshold of the photon energy for producing 225 Ra is 6.4 MeV. The feasibility of this preparation 225 route of Ac was confirmed in 2005, and subsequently, the international community began to develop this technical route.

[0004] The technical route for preparing 225 Ac by photonuclear reaction of a radium target using an electron linear accelerator, taking advantage of the strong penetration ability of γ photons, can improve the utilization rate of the target material by increasing the 226 surface area of the Ra target, but there are still 226 difficulties in the supply of Ra raw materials and 226 Ra will continuously decay to release the harmful radioactive gas radon-222 (i.e., 222 Rn), etc. Therefore, recycling 226 Ra and properly handling radon and its daughter nuclides are very crucial. At the same time, in the technical route for preparing 225 Ac by photonuclear reaction of a radium target using an electron linear accelerator, another promising medical isotope 212 Pb will also be generated. Due to 212 the short half-life of Pb (T 1 / 2 = 10.6 hours), compared with 225 the longer half-life of Ac (T 1 / 2 = 9.9 days), 212 Pb needs to be separated and extracted quickly after production, otherwise it will decay and become impossible to extract; while 225 Ac can be separated and processed after the target material has been deposited for a period of time. In the existing preparation methods, usually only one of 212 Pb and 225 Ac is separated and extracted, or both 212 Pb and 225 Ac are separated and extracted simultaneously. Such operations have low extraction efficiency, and also result in large losses and being uncontrollable, leading to a low yield of medical isotopes.

[0005] The prior art patent document with the publication number CN112885495B discloses a method for producing Ac-225 from Ra-226. Its main purpose is to propose an electroplating method to solve the problem of chemical separation and extraction of Ac-225 after irradiation, and to avoid the risks generated during the subsequent recovery process of Ra-226. However, in the process of separating and extracting Ac-225, the deposited cathode needs to be taken out for separate separation and purification, still posing a radioactive risk; in addition, the electroplating method will generate electrolysis waste gases such as chlorine gas or nitrogen oxides, also presenting potential safety hazards. The prior art patent document with the publication number CN112366020B discloses a method for producing actinium by liquefying radium, which involves an apparatus for producing actinium by using liquefied radium. Its main purpose is to minimize the loss of Ra-226 generated during the reaction process; this invention conducts gas treatment, Ra raw material treatment, and the separation and purification of radium and actinium in multiple steps in additional containers (vials), belonging to on-line irradiation and off-line treatment, and does not complete the entire process in a single circulation loop. When performing the separation and purification of radium and actinium, it is necessary to interrupt the irradiation to produce actinium; in addition, this invention only collects the harmful radioactive gas radon without treatment. Summary of the Invention

[0006] In view of the problems such as the difficult treatment of radon and its decay daughters generated by the decay of the radium target in the technical route of preparing 225 Ac by using an electron linear accelerator and a radium target through a photonuclear reaction, the present invention proposes a closed-loop 225 Ra solution target system for producing 226 Ac. This closed-loop 226 Ra solution target system can effectively reduce the 225 extraction steps of 225 Ac, improve the 212 preparation efficiency of 226 Ac, and at the same time can also separate another medical isotope 225 Pb generated during the preparation process; moreover, the gas radon and its daughters can be effectively treated through the closed-loop structure designed by the present invention. In addition, the closed-loop

[0007] The technical solution adopted by the present invention is as follows: A closed-loop 225 Ra solution target system for producing 226 Ac, comprising a solution-type 226 Ra target, an isotope target chamber, valves, 226 Ra solution circulation structure, radium-actinium separation structure, radium-lead separation structure, photon detection system I, photon detection system II, heat exchange system, decompression radon evaporator, and radon treatment system. Among them, the solution-type226 The Ra target contains a solution circulation pipeline and a radium-containing solution, and the radium-containing solution is accommodated in the closed solution circulation pipeline; The solution circulation pipeline includes a main loop pipeline, a first branch pipeline, and a second branch pipeline. A section of the main loop pipeline passes through the isotope target chamber and is fixed by the isotope target chamber. The section of the main loop pipeline located in the isotope target chamber is used as the irradiated section for irradiating with the electron beam to produce 225 Ac; The first branch pipeline and the second branch pipeline are located outside the isotope target chamber, and both ends of the first branch pipeline and the second branch pipeline can be connected to the main loop pipeline; The photon detection system I, 226 The Ra solution circulation structure, the decompression radon evaporator, the heat exchange system, the valve, and the photon detection system II are sequentially arranged on the main loop pipeline of the solution circulation pipeline. The valve is arranged at the first connection point between the main loop pipeline and the two branch pipelines, and the photon detection system II is arranged behind the second connection point between the main loop pipeline and the two branch pipelines; The valve is electrically connected to the photon detection system I; The photon detection system I is used to detect the target nuclide generated after irradiation 225 Ac, 212 Pb and photons with specific energies emitted by impurity nuclides generated during the reaction process, and convert them into electrical signals and send them to the valve; The valve is a four-way solenoid valve for adjusting the connection direction; The heat exchange system is used to cool the radium-containing solution in the solution circulation pipeline; 226 The Ra solution circulation structure is a power pump, which is used to provide driving force for the circulating flow of the radium-containing solution and control the flow rate of the radium-containing solution in the solution circulation pipeline; The radon treatment system is connected to the decompression radon evaporator, and the decompression radon evaporator is used to evaporate the radon and its daughters generated in the irradiated radium-containing solution into the radon treatment system; The radium-actinium separation structure is arranged on the first branch pipeline of the solution circulation pipeline for separating and collecting 225 Ac generated after the radium-containing solution is irradiated; The radium-lead separation structure is arranged on the second branch pipeline of the solution circulation pipeline for separating and collecting 212 Pb generated after the radium-containing solution is irradiated; The photon detection system II is used to detect the target nuclide 225 Ac, 212 Pb and photons with specific energies emitted by impurity nuclides.

[0008] Furthermore, the radon treatment system includes a sealed container in which activated carbon is placed to absorb the radon and its daughters generated after the radium-containing solution is irradiated.

[0009] Furthermore, the heat exchange system is a plate heat exchanger.

[0010] Furthermore, the radium-containing solution is226 RaCl2 solution.

[0011] Furthermore, both the photon detection system I and the photon detection system II are photon detectors.

[0012] The beneficial effects of the present invention are as follows: (1) Compared with solid isotope targets, the closed-loop solution-type 226 Ra target adopted in the present invention can directly avoid problems such as target fracture and target melting leakage caused by the poor physical properties of 226 Ra elemental material.

[0013] (2) The closed-loop 226 Ra solution target system adopted in the present invention can effectively cool the solution-type 226 Ra target through the structural design of solution circulation, and can effectively recover and process the decay daughter nucleus 226 Rn of 222 Ra, avoiding the 222 Rn leakage problem; and during the separation and collection of 225 Ac, 212 Pb and the separation and treatment of radon and its daughters, there is no need to interrupt the irradiation production 225 Ac and 212 Pb work, improving the preparation efficiency.

[0014] (3) The photon detection system I adopted in the present invention controls the steering of the four-way solenoid valve to select the separation target by detecting the photons with specific energies released in the decay chain of the target nuclides 225 Ac, 212 Pb generated after irradiation, and converts them into electrical signals, improving the separation and extraction efficiency of the target nuclides.

[0015] (4) The photon detection system II adopted in the present invention can infer the activity of the target nuclides by detecting the photons with specific energies released in the decay chain of the target nuclides 225 Ac, 212 Pb in the radium-containing solution after separation; combined with the photon detection system I, the yield and corresponding separation efficiency of the target nuclides can be inferred; at the same time, the content of impurity nuclides in the radium-containing solution to be irradiated continuously after the separation of the target nuclides can be monitored. When the impurity nuclides accumulate to a certain extent, the radium-containing solution needs to be replaced.

[0016] (5) Using the closed-loop 226 Ra solution target system adopted in the present invention and applied to an electron linear accelerator with an energy of 35 MeV and a beam current of 2 mA, the annual yield of 225 Ac can reach more than 12.33 Ci, and 212 the annual yield of Pb can reach 15.09 Ci.

[0017] (6) Using the solution type 226 Ra target of the present invention, compared with the traditional solid radium target, in the separation 225 of Ac, there is no need for the previous step of dissolving the solid radium isotope sample, and there is no need to perform operations such as drying, pressing, or electrodeposition for solidification during the target preparation process, which greatly simplifies the 225 preparation process of Ac. Description of the Drawings

[0018] Figure 1 is the working schematic diagram of the solution type 226 Ra target in the end target area of the electron beam.

[0019] Figure 2 is the structural schematic diagram of the closed-loop 225 Ac production 226 Ra solution target system of the present invention.

[0020] Figure 3 is the longitudinal sectional view of the solution type 226 Ra target of the present invention.

[0021] Figure 4 is the solution type of the present invention 226 Ra target irradiated in an electron linear accelerator with an energy of 35 MeV and a beam current of 2 mA for 10 days 225 Ra and 225 Ac, 212 Pb production variation curve with time.

[0022] In the figure: 1. Electron beam; 2. Conversion target chamber; 3. Tungsten conversion target; 4. Solution type 226 Ra target; 41. 226 RaCl2 solution; 5. Isotope target chamber; 6. Solution circulation pipeline; 7. Valve; 8. 226 Ra solution circulation structure; 9. Radium-actinium separation structure; 10. Heat exchange system; 11. Decompression radon evaporator; 12. Radon treatment system; 13. Radium-lead separation structure; 14. Photon detection system I; 15. Photon detection system II. Detailed Embodiments

[0023] In order to more clearly understand the above objects, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the limitations of the specific embodiments disclosed below.

[0024] In the process of producing 225 Ac isotopes through the photonuclear reaction of radium targets, in order to effectively protect against 226 the decay daughter nuclei of 222 Ra, 225 Rn leakage, and to simplify the preparation process of 226 Ac isotopes, the present invention provides a system using a circulating solution-type

[0025] As Figures 1 to 3 shown, a closed-loop 225 Ac production 226 Ra solution target system for an electron linear accelerator, including a solution-type 226 Ra target 4, an isotope target chamber 5, a valve 7, 226 a 226 Ra solution circulation structure 8, a radium-actinium separation structure 9, a heat exchange system 10, a radium-lead separation structure 13, a photon detection system I 14, and a photon detection system II 15. Among them, the solution-type 226 Ra target 4 includes a solution circulation pipeline 6 and a radium-containing solution. In this embodiment, the radium-containing solution used is 226 RaCl2 solution 41, 225 Ac; the 226 RaCl2 solution 41 is accommodated in a closed solution circulation pipeline 6; the solution circulation pipeline 6 includes a main circuit pipeline, a first branch pipeline, and a second branch pipeline. A section of the main circuit pipeline of the solution circulation pipeline 6 passes through the isotope target chamber 5 and is fixed by the isotope target chamber 5. A section of the main circuit pipeline located in the isotope target chamber 5 is used as the irradiated section for cooperating with the electron beam 1 for irradiation to produce 225 Ac; the first branch pipeline and the second branch pipeline are located outside the isotope target chamber 5, and both ends of the first branch pipeline and the second branch pipeline can be connected to the main circuit pipeline. The photon detection system I 14, 212The photons of specific energy released by Pb in the decay chain are converted into electrical signals and transmitted to valve 7, thereby controlling the direction of valve 7, separating and purifying the target nuclides, and being able to monitor the impurity nuclides in the radium-containing solution; 226 The Ra solution circulation structure 8 is a power pump, such as a peristaltic pump of model YZ1525. The material of the internal delivery tube of the peristaltic pump is silicone. 226 The Ra solution circulation structure 8 is used to provide a driving force for the circulation of the radium-containing solution in the solution circulation pipeline 6, and can accurately control the flow rate of the radium-containing solution in the solution circulation pipeline 6; the heat exchange system 10 is used to heat the solution in the solution circulation pipeline 6. 226 The RaCl2 solution 41 is cooled; the valve 7 is a four-way solenoid valve with adjustable connection direction, and the material of the valve 7 can be aluminum or aluminum alloy; the valve 7 is electrically connected to the photon detection system Ⅰ 14, and the valve 7 is used to receive the signal from the photon detection system Ⅰ 14, so as to adjust the connection guide between the main loop pipeline of the solution circulation pipeline 6 and the first branch pipeline and the second branch pipeline; the radium-actinium separation structure 9 is arranged on the first branch pipeline of the solution circulation pipeline 6; the radium-actinium separation structure 9 is a radium-actinium separation system, which specifically includes a radium-actinium separation resin and a leaching container structure, which is used to separate and collect the radium-containing solution generated after being irradiated. 225 Ac, wherein the radium-actinium separation resin is used to separate 225 Ac is separated from the radium-containing solution, and the elution container structure is used to separate the Ac from the radium-containing solution through an acid solution. 225 Ac is extracted from the resin; the radium-lead separation structure 13 is arranged on the second branch pipeline of the solution circulation pipeline 6; the radium-lead separation structure 13 is a radium-lead separation system, specifically including a radium-lead separation resin and a washing container structure, which is used to separate and collect the radium-containing solution generated after being irradiated. 212 Pb, among which, radium-lead separation resin is used to 212 Pb is separated from the radium-containing solution. The elution container structure is used to separate Pb from the radium-containing solution through an acid solution. 212 Pb is extracted from the resin. The radium-actinium separation resin uses separation adsorption materials known in the art, such as Ln resin, DGA resin or MnO2 resin; the radium-lead separation resin can use Sr resin or Pb resin known in the art, both of which are very effective in separating Pb; the resin can directionally absorb the radium-containing solution generated after irradiation through different molecular structures. 225 Ac or 212 Pb is adsorbed and separated separately. Photon detection system II 15 is used to detect the target nuclide in the radium-containing solution after separation. 225 Ac, 212Photons with specific energies released by Pb in the decay chain, so as to facilitate the combination with the photon detection system I 14 to infer the yield of the target nuclide and the separation efficiency. In this embodiment, the photon detection system I 14 and the photon detection system II 15 are signal-connected to a remote server to display the change in yield; the photon detection system I 14 and the photon detection system II 15 monitor photons with specific energies and transmit signals to the existing remote server to form a photon energy spectrum, reflecting the change in yield.

[0026] In this embodiment, the heat exchange system 10 adopted is a plate heat exchanger composed of multiple planes. The plate heat exchanger is an existing efficient heat exchanger formed by stacking a series of metal sheets with a certain corrugated shape. Thin rectangular channels are formed between various plates. The high-temperature fluid and the low-temperature fluid flow through different channels respectively without mixing, and heat exchange is carried out through the plates; in the solution circulation pipeline 6 226 The RaCl2 solution 41 has its temperature increased after passing through the irradiated section. When passing through the heat exchange system 10, it flows out from the high-temperature fluid channel of the heat exchange system 10, and during the process, heat exchange is carried out with the coolant in the low-temperature fluid channel of the heat exchange system 10, thereby achieving the purpose of cooling 226 the RaCl2 solution 41. Deionized water can be used as the coolant in the heat exchange system 10.

[0027] In this embodiment, the production 225 closed-loop 226 Ra solution target system for Ac further includes a reduced-pressure radon evaporator 11 and a radon treatment system 12. The reduced-pressure radon evaporator 11 is arranged on 226 the main circuit pipeline of the solution circulation pipeline 6 between the Ra solution circulation structure 8 and the heat exchange system 10. The radon treatment system 12 is communicated with the reduced-pressure radon evaporator 11; the reduced-pressure radon evaporator 11 belongs to a reduced-pressure evaporator, which evaporates the liquid at a lower temperature by reducing the system pressure, and evaporates the radon and its daughters generated in the irradiated radium-containing solution into the radon treatment system 12. Since the evaporation temperatures of the radium-containing solution and the radon and its daughters are different, the reduced-pressure evaporator can avoid the thermal decomposition of the radium-containing solution and avoid the change of the solution properties, and separate the radon and its daughters with a lower evaporation temperature from the radium-containing solution; the radon treatment system 12 is a closed container, and materials that can absorb radon, such as activated carbon, are stored in the container. In a more preferred embodiment, a maintenance door is provided on the closed container of the radon treatment system 12, and the maintenance door can be opened regularly to replace the activated carbon in the radon treatment system 12 to ensure the radon treatment effect. After being irradiated, the radium-containing solution will continuously decay to generate radioactive gas radon and its daughters, and the heat generated by irradiation will cause a part of the radon and its daughters to evaporate into a gaseous state. To avoid incomplete evaporation of the radon and its daughters in the radium-containing solution, the reduced-pressure radon evaporator 11 can further utilize the reduced-pressure evaporation principle to remove the 226All harmful substances radon and its daughters generated in the RaCl2 solution 41 222 All Rn is separated and transported to the radon treatment system 12 for absorption treatment.

[0028] In radionuclide analysis, the parent radionuclide will transform into another daughter radionuclide during radioactive decay, and is often accompanied by the release of characteristic photons, such as γ-rays or X-rays. These photons have specific energies corresponding to the transitions between nuclear energy levels during the decay process. By using a photon detector to measure the energy and intensity of these photons, it is possible to identify which radionuclide has decayed. Further, by counting the photons of a specific energy and combining parameters such as the detector efficiency, the decay constant of the radionuclide, and the measurement time, the activity of the parent radionuclide can be quantitatively calculated, thereby inferring its yield (this is the existing calculation method in this field). In the technical route of preparing 225 Ac by the photonuclear reaction of a radium target in an electron linear accelerator 225 In the 221 Ac decay chain, 213 by counting the number of photons with an energy of 218 KeV emitted by 225 Fr, and 212 in the 212 Bi decay chain, 212 by counting the number of photons with an energy of 440 KeV emitted by 208 Bi, the yield of 212 Ac is speculated; by 227 detecting the photons with specific energies generated in the decay chains of 223 Ra, 227 Ra, 223 Ra, etc., the activity of impurity radionuclides ( 227 Ac, 227 Th, and 210 Po) and their decay daughters is monitored.

[0029] The said production 225 closed-loop 226 Ra solution target system for 226 Ac operates as follows: The main circuit pipeline of the solution circulation pipeline 6 is successively connected to the photon detection system I 14,The Ra solution circulation structure 8, the reduced-pressure radon evaporator 11, the heat exchange system 10, the valve 7, and the photon detection system II 15 are connected. The initial state of the valve 7 is closed. The valve 7 is connected to the radium-actinium separation structure 9 through the first branch pipeline of the solution circulation pipeline 6. At the same time, the valve 7 is connected to the radium-lead separation structure 13 through the second branch pipeline. The solution output ends of the radium-actinium separation structure 9 and the radium-lead separation structure 13 are respectively connected to the main loop pipeline through the first branch pipeline and the second branch pipeline. When only irradiation is carried out, start 226 the Ra solution circulation structure 8, and directly connect the valve 7 to the irradiated section of the main loop pipeline of the solution circulation pipeline 6 fixed at the isotope target bin 5. The irradiated section, the photon detection system I 14, 226 the Ra solution circulation structure 8, the reduced-pressure radon evaporator 11, the heat exchange system 10, and the photon detection system II 15 are connected in sequence, 226 the Ra solution circulation structure 8 provides power for the solution to circulate, so that the 226 RaCl2 solution 41 in the solution circulation pipeline 6 flows through the irradiated section and then successively through the photon detection system I 14, the reduced-pressure radon evaporator 11, the heat exchange system 10, the valve 7, and the photon detection system II 15, and then returns to the irradiated section, 226 and the RaCl2 solution 41 continuously circulates in the main loop pipeline of the solution circulation pipeline 6; 226 When the RaCl2 solution 41 flows through the irradiated section, it is irradiated by the electron beam 1 to generate 225 Ac and 212 Pb; 226 When the RaCl2 solution 41 flows through the reduced-pressure radon evaporator 11, the radon and its daughters produced in the solution are separated and transported to the radon treatment system 12 for absorption treatment.

[0030] Through the photon detection system I 14, the photons in the RaCl2 solution 41 in the solution circulation pipeline 6 can be monitored in real time. By monitoring 226 the photons in the RaCl2 solution 41, it is inferred from the photons with specific energies released by 226 Fr, 221 Bi in the RaCl2 solution 41 the 213 Ac yield. When 225 the Ac yield accumulates to a certain extent (which can be a preset threshold, and the threshold can be set or changed according to the separation requirements, such as 10 mCi), the photon detection system I 14 transmits an electrical signal to the valve 7 to adjust the direction of the valve 7, so that the heat exchange system 10 is connected to the radium-actinium separation structure 9, so that 225 the RaCl2 solution 41 flows through the first branch pipeline of the solution circulation pipeline 6 and then returns to the main loop pipeline, continuously circulating, so as to separate 226 the RaCl2 solution 41 through the radium-actinium separation structure 9 226 the Ac generated in the RaCl2 solution 41225 The Ac is separated and collected; when it is detected that 226 in the RaCl2 solution 41 there is 212 Bi, 212 Pb and 208 photons with specific energy released by Ti, and it is prompted that 212 when Pb accumulates to a certain extent (which can be a preset threshold, and the threshold can be set or changed according to separation requirements, for example, 10 mCi), the photon detection system I 14 transmits an electrical signal to the valve 7, adjusts the passage of the valve 7, so that the heat exchange system 10 is connected to the radium-lead separation structure 13, and makes 226 the RaCl2 solution 41 flow through the second branch pipeline of the solution circulation pipeline 6 and then return to the main loop pipeline, and circulate continuously, so as to separate 226 the 212 Pb generated in the RaCl2 solution 41 and collect it. And after separation, the 226 RaCl2 solution 41 will first pass through the photon detection system II 15 and then return to the irradiated section. At this time, the photon detection system II 15 can detect 226 the number of photons with specific energy in the RaCl2 solution 41, so as to infer the separation efficiency of the nuclides, so as to adjust the separation frequency according to the separation efficiency; at the same time, it can monitor 226 the content of impurity nuclides in the RaCl2 solution 41. When the impurity nuclides accumulate to a certain extent, the radium-containing solution in the solution circulation pipeline 6 is replaced.

[0031] During the production process, by adjusting the power pump, that is, 226 the output flow rate of the Ra solution circulation structure 8 to adjust 226 the flow velocity of the RaCl2 solution 41 flowing in the solution circulation pipeline 6, which is beneficial to improving 225 the collection efficiency of Ac and the separation and treatment efficiency of radon and its daughters; at the same time, collecting 225 Ac, collecting 212 Pb and separating radon and its daughters do not affect the irradiated section of the main loop pipeline at the isotope target magazine 5 to continue to receive irradiation, and there is no need to interrupt the irradiation production 225 Ac and producing 212 Pb work, nor does it affect the continuous operation of the decompression radon evaporator 11 and the heat exchange system 10.

[0032] Thus, the closed-loop 226 Ra solution target system of the present invention can seal and treat 226 the decay daughters of 222 Ra 226The RaCl₂ solution 41 circulates in the form of a solution in the solution circulation pipeline 6, the reduced-pressure radon evaporator 11, the heat exchange system 10, and the actinium-radium separation structure 9 and the radium-lead separation structure 13, simplifying the steps of pre-dissolving the solid radium target and the pre-preparation process of the solid 225 Ac in the production method using a solid radium target. 226 The process of pre-preparing the solid

[0033] In this embodiment, 226 The mass percentage concentration of the RaCl₂ solution 41 is 0.83%. 226 The RaCl₂ solution 41 is contained in the closed solution circulation pipeline 6. 226 The RaCl₂ solution 41 can circulate in the solution circulation pipeline 6; as Figure 3 shown, the inner diameter of the solution circulation pipeline 6 is 25 mm, the wall thickness is 10 mm, and the material is S316 stainless steel. As Figure 1 shown, a section of the main circuit pipeline of the solution circulation pipeline 6 is fixed by the isotope target bin 5 and serves as the irradiated section, which is used to be placed in the conversion target bin 2 and irradiated by the electron beam 1 emitted by the electron linear accelerator to produce 225 Ac, and another medical isotope 212 Pb will also be produced during the process. The length of the irradiated section of the solution circulation pipeline 6 is 138.8 mm. The material of the isotope target bin 5 is S316 stainless steel, and the size is 56 mm × 56 mm × 90 mm. As Figure 2 shown, 226 The RaCl₂ solution 41 is guided to the valve 7 through the solution circulation pipeline 6, and the valve 7 can control 226 the flow direction of the RaCl₂ solution 41. During the irradiation process, the reduced-pressure radon evaporator 11 and the radon treatment system 12 can separate and absorb 222 Rn. Only when irradiation is required, the valve 7 is adjusted to be directly connected to the irradiated section in the main circuit pipeline of the solution circulation pipeline 6 to complete the circulation; when the separation and purification of 225 Ac are required, the connection and guidance of the valve 7 are adjusted to guide the 226 RaCl₂ solution 41 to the first branch pipeline and the actinium-radium separation structure 9; when the separation and purification of 212 Pb are required, the connection and guidance of the valve 7 are adjusted to guide the 226 RaCl₂ solution 41 to the second branch pipeline and the radium-lead separation structure 13; then the separated 226 RaCl₂ solution 41 is guided to the irradiated section in the main circuit pipeline of the solution circulation pipeline 6 to complete the 226 circulation of the RaCl₂ solution 41.

[0034] A closed-loop cycle for producing 225 Ac according to the present invention226 The working schematic diagram of the Ra solution target system irradiated in an electron linear accelerator with an energy of 35 MeV and a beam current of 2 mA is as Figure 1 shown. The solution type 226 In the Ra target 4, the irradiated section in the main loop pipeline of the solution circulation pipeline 6 is fixed in the isotope target chamber 5. The isotope target chamber 5 is placed in the conversion target chamber 2, and a tungsten conversion target 3 is also placed in the conversion target chamber 2. The isotope target chamber 5 is aligned with the center lines of the conversion target chamber 2, the tungsten conversion target 3, and the electron beam 1; the electron beam 1 emitted by the electron linear accelerator passes through the conversion target chamber 2 and hits the tungsten conversion target 3. The tungsten conversion target 3 is used to convert the electrons emitted by the electron linear accelerator into photons and pass through the isotope target chamber 5 to hit the irradiated section of the solution type 226 Ra target 4, thereby irradiating the 226 RaCl2 solution 41 in the solution circulation pipeline 6. Among them, the energy of the electron beam 1 is 35 MeV, the beam current is 2 mA, the spatial distribution of the beam spot of the electron beam 1 is a Gaussian distribution, and the full width at half maximum of the beam spot is 15 mm; the size of the conversion target chamber 2 is 70 mm × 70 mm × 138.8 mm, and the material is Al (aluminum); the size of the tungsten conversion target 3 is 56 mm × 56 mm × 2 mm, the material is tungsten, and the number of tungsten conversion targets 3 is three, and the distance between adjacent tungsten conversion targets 3 is 1.5 mm; the distance between the isotope target chamber 5 and the nearest tungsten conversion target 3 is 10 mm. Using the closed-loop 225 Ac production 226 Ra solution target system of the present invention and using an electron linear accelerator, after irradiating with an electron beam 1 with an energy of 35 MeV and a beam current of 2 mA for 10 days, 226 the changes of 225 Ac, 212 Pb and 225 Ra in the RaCl2 solution 41 with the cooling time are as Figure 4 shown. According to the stage extraction method well-known in the art, in the solution type 226 Ra target 4, after being irradiated by the electron beam 1 for 10 days, 225 Ac is separated and extracted every 15 days. If the simulation calculation is carried out according to the theoretical value of 100% extraction efficiency each time, the total activity of 225 Ac extracted continuously three times is equivalent to the total activity of 225 Ra at the end of irradiation. As Figure 4 shown, after being irradiated by the electron beam 1 for 10 days, cooling starts. 226 The total activity of 225 Ra in the RaCl2 solution 41 is 0.411 Ci. If the annual effective irradiation duration of the electron linear accelerator is 300 days, then 12.33 Ci of 225 Ac can be produced every year. At the end of irradiation212 The total activity of Pb is 212 The maximum total extractable activity of Pb, such as Figure 4 shown, starts to cool after being irradiated by electron beam 1 for 10 days. 226 contained in the RaCl2 solution 41 212 The total activity of Pb is 0.503 Ci. If the annual effective irradiation duration of the electron linear accelerator is 300 days, then 15.09 Ci of 212 Pb can be produced annually.

[0035] The closed-loop 225 Ra solution target system designed by the present invention is applicable to the production of 226 Ac through photonuclear reactions, which can effectively reduce the separation and purification steps of preparing 225 Ac by photonuclear reactions of radium targets, improve 225 the preparation efficiency of 212 Ac, and at the same time can also separate another medical isotope 226 Pb generated during the preparation process, and can 222 effectively treat the radon ([[]]ID=27 Rn) gas of the radium decay daughter nuclei during the preparation process to prevent the leakage of radon and its toxic daughter polonium generated by decay into the environment.

Claims

1. A method for producing 225 a closed-loop 226 Ra solution target system for Ac, characterized in that Including solution type 226 Ra target, isotope target magazine, valve, 226 Ra solution circulation structure, radium-actinium separation structure, radium-lead separation structure, photon detection system I, photon detection system II, heat exchange system, decompression radon evaporator and radon treatment system, among which, the solution type 226 The Ra target includes a solution circulation pipeline and a radium-containing solution, and the radium-containing solution is accommodated in a closed solution circulation pipeline; The solution circulation pipeline includes a main loop pipeline, a first branch pipeline, and a second branch pipeline. A section of the main loop pipeline passes through the isotope target chamber and is fixed by the isotope target chamber. The section of the main loop pipeline located in the isotope target chamber serves as the irradiated section, which is used to cooperate with the electron beam for irradiation to produce 225 Ac; the first branch pipeline and the second branch pipeline are located outside the isotope target chamber, and both ends of the first branch pipeline and the second branch pipeline can be connected to the main loop pipeline; The photon detection system I, 226 The Ra solution circulation structure, the vacuum radon evaporator, the heat exchange system, the valve and the photon detection system II are sequentially arranged on the main circuit pipeline of the solution circulation pipeline. The valve is arranged at the first connection point between the main circuit pipeline and the two branch pipelines, and the photon detection system II is arranged behind the second connection point between the main circuit pipeline and the two branch pipelines; the valve is electrically connected to the photon detection system I; the photon detection system I is used to detect the target nuclides generated after irradiation 225 Ac, 212 Pb and photons with specific energies emitted by impurity nuclides generated during the reaction process, and convert them into electrical signals and transmit them to the valve; the valve is a four-way solenoid valve used to adjust the communication direction; the heat exchange system is used to cool the radium-containing solution in the solution circulation pipeline; 226 The Ra solution circulation structure is a power pump, which is used to provide driving force for the circulation of the radium-containing solution and control the flow rate of the radium-containing solution in the solution circulation pipeline; the radon treatment system is connected to the vacuum radon evaporator, and the vacuum radon evaporator is used to evaporate the radon and its daughters generated in the radium-containing solution after irradiation into the radon treatment system; The radium-actinium separation structure is arranged on the first branch pipeline of the solution circulation pipeline and is used for separating and collecting 225 Ac generated after the radium-containing solution is irradiated; the radium-lead separation structure is arranged on the second branch pipeline of the solution circulation pipeline and is used for separating and collecting 212 Pb generated after the radium-containing solution is irradiated; the photon detection system II is used for detecting photons with specific energies emitted by the target nuclides 225 Ac, 212 Pb and impurity nuclides after radium-actinium separation or radium-lead separation.

2. The production according to claim 1 225 Closed-loop cycle of Ac 226 Ra solution target system, characterized in that The radon treatment system includes a sealed container in which activated carbon is placed to absorb radon and its progeny generated after the radium-containing solution is irradiated.

3. The production according to claim 1 225 Closed-loop cycle of Ac 226 Ra solution target system, characterized in that The heat exchange system is a plate heat exchanger.

4. According to the production described in claim 1 225 Closed-loop cycle of Ac 226 Ra solution target system, characterized in that The radium-containing solution is 226 RaCl2 solution.

5. The production according to claim 1 225 Closed-loop cycle of Ac 226 Ra solution target system, characterized in that Both the photon detection system I and the photon detection system II are photon detectors.

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