By226Production of radium225Process for actinium
阅读说明：本技术 由226镭生产225锕的方法 (By226Production of radium225Process for actinium ) 是由 里卡德·马姆贝克 罗伯托·卡奇乌夫 尼度·拉尔·巴尼克 于 2020-06-22 设计创作，主要内容包括：通过质子、氘核或伽马射线在辐照装置(2)中辐照液态～(226)镭靶材,并且在第一萃取装置(6)中从辐照后的液态靶材溶液中萃取所产生的～(225)锕来由～(226)镭生产～(225)锕。然后再次辐照已经去除了～(225)锕的液态靶材溶液以在其中进一步生产～(225)锕。液态靶材溶液优选地在闭合回路(4)中循环通过所述辐照装置,并且在又一个闭合回路(7)中循环通过第一萃取装置(6)。这种方法的优点在于,辐照后的靶材溶液不需要干燥和再溶解以能够将镭与所产生的锕分离,并且不需要进一步的干燥和再溶解步骤用以从分离的镭开始再次生产液态靶材。因此镭靶材可以以更有效和更安全的方式回收,尤其是考虑到由～(226)镭衰变连续产生的氡气。(Irradiating the liquid state in an irradiation device (2) by protons, deuterons or gamma rays 226 The radium target material is irradiated and the generated liquid target material solution is extracted in a first extraction device (6) 225 Derived from actinium 226 Production of radium 225 And (3) actinium. Then irradiate again to remove 225 Liquid target material solution of actinium for further production therein 225 And (3) actinium. The liquid target solution is preferably circulated through the irradiation arrangement in a closed loop (4) and through the first extraction arrangement (6) in a further closed loop (7). The advantage of this method is that the irradiated target solution does not need to be dried and redissolved to be able to separate radium from the generated actinium, and that no further drying and redissolving steps are needed to produce a liquid again starting from the separated radiumAnd (3) a phase target material. The radium target material can thus be recovered in a more efficient and safer way, especially in view of the fact that 226 Radon gas is continuously generated by the decay of radium.)
1. a kind of quilt226Production of radium225A method of actinium, the method comprising the steps of:
providing a composition comprising226Liquid target solution of radium;
irradiating the liquid target solution in an irradiation device (2) to remove impurities from the liquid target solution226Beginning production of radium in the liquid target solution225Actinium; and
from the rest226Separating at least part of the generated225The process for the preparation of an actinide,
it is characterized in that the preparation method is characterized in that,
the separation step comprises a first extraction step in a first extraction device (6), wherein at least part of the liquid target solution is extracted from the liquid target solution225Actinium to226Retaining radium in the liquid target solution; and is
The method further comprises the steps of:
re-irradiating in said irradiation device (2) a portion of said radiation from which a portion of said radiation has been extracted225Actinium, to a liquid target solution from which it is contained226Starting with radium for further production in the liquid target solution225And (3) actinium.
2. The method according to claim 1, wherein during the irradiation step the liquid target solution is circulated in a first closed loop (4) through the irradiation device (2) and a heat exchanger (5).
3. The method according to claim 1 or 2, characterized in that during the first extraction step the liquid target solution is circulated through the first extraction device (6) in a second closed loop (7).
4. A method according to claims 2 and 3, characterized in that during the irradiation step the liquid target solution is circulated through the container (1) and the irradiation device (2) in the first closed loop (4), and during the first extraction step the liquid target solution is circulated through the container (1) and the first extraction device (6) in the second closed loop (7).
5. The method according to any of claims 1-4, wherein at least part of the liquid target solution is extracted during the extraction from the liquid target solution225Before actinium, the liquid target solution is irradiated for less than 16 days, preferably less than 13 days, more preferably less than 10 days, most preferably less than 7 days.
6. The method according to any of claims 1-5, wherein during the irradiation step the liquid target solution is irradiated with protons or deuterons.
7. The method according to any of claims 1-5, wherein during the irradiation step the liquid target solution is irradiated with gamma rays by subjecting it to a laser treatment226Conversion of radium into225Radium and will225Conversion of radium into225Generation of actinium225And (3) actinium.
8. The method of claim 7, wherein during the first extraction step, the first extraction step is performed in a batch process225Radium remains in the liquid target solution.
9. The method according to any of claims 1-8, wherein the liquid target solution comprises226Solutions of radium salt and its corresponding acid, preferably comprising226Radium nitrate and nitric acid.
10. Method according to any one of claims 1-9, characterized in that the first extraction device (6) comprises a first adsorbent, during which the first extraction step the first extraction is carried out225Actinium accumulates on the first adsorbent, the method comprising a first elution step in which at least a portion of the actinium has accumulated on the first adsorbent225Actinium is eluted from the first adsorbent by a first eluent (16).
11. The method of claim 10, wherein the liquid target solution has a predetermined pH such that during the first extraction step the liquid target solution has a predetermined pH225Actinium is accumulated onto the first adsorbent while the first eluent has a pH value different from the pH value of the liquid target solution, such that the first elution step is performed during the first elution step225Actinium is eluted from the first adsorbent.
12. The method according to claim 10 or 11, wherein the first eluent (16) comprises a first acid solution containing the same acid as the target solution, in particular nitric acid.
13. Method according to any one of claims 10-12, characterized in that during the first elution step the first eluent (16) is circulated in a fourth closed loop (17) through a second extraction device (18) containing a second adsorbent, the first eluent eluting from the first adsorbent during the first elution step225Actinium accumulates on the second adsorbent, the method includes a second stepA second elution step in which at least part of the second adsorbent has accumulated225Actinium is eluted from the second adsorbent by a second eluent (19), the second eluent (19) having in particular a pH value different from the pH value of the first eluent, so that during a second elution step the actinium is eluted from the second adsorbent225Actinium is eluted from the second adsorbent, the second eluent (19) preferably comprising a second acid solution containing the same acid as the target solution, in particular nitric acid.
14. Method according to claim 13, characterized in that the first eluent (16) is circulated from the first extraction device (16) to the second extraction device (18) with a second radon filter (20), in particular a second activated carbon filter, therebetween for extracting radon from the first eluent (16).
15. Method according to claim 13 or 14, characterized in that during the second elution step the second eluent (19) is circulated in a fifth closed loop (21) through a third extraction device (22), the third extraction device (22) containing a third adsorbent, and during the second elution step the second eluent (19) elutes from the second adsorbent225Actinium accumulates on the third adsorbent, the method comprising a third elution step in which at least part of the actinium has accumulated on the third adsorbent225Actinium is eluted from the third adsorbent by a third eluent (24), said third eluent (24) having in particular a pH value different from the pH value of said second eluent (19), so that during said third elution step said third eluent (24) is applied to the substrate225Actinium is eluted from the third adsorbent, the third eluent preferably comprising a third acid solution containing the same acid as the target solution, in particular nitric acid.
Technical Field
The invention relates to a bag made of226Production of radium225A process for actinium, wherein226A liquid target solution of radium, wherein the liquid target solution is irradiated in an irradiation device to have contained therein226Beginning with radium production in liquid target solution225Actinium; and will be at least partially produced225Actinium and the remainder226And Ra is separated.
Background
225Actinium is an interesting radionuclide that can be used in cancer therapy.225Actinium is a radioisotope emitting alpha rays with a half-life of 10 days. It can be used as an agent for radioimmunotherapy. Due to the dense ionizing radiation of alpha particle emitters, it is a promising source of irradiation for lethal irradiation of single cancer cells and micrometastatic lesions. Alpha particles are advantageous for radioimmunotherapy applications because their range in soft tissue is limited to only a few cell diameters.
There are a number of possible methods to produce225Actinium, there is still a need for a new, safer production process which allows the production of the quantities required to meet the requirements225And (3) actinium.
For example, as disclosed in US 5809394,225actinium may be prepared by229Radioactive decay of thorium. This is currently produced for medical applications225The main method of Ac. The method uses229Th/225Ra/225Ac generator (Boll 2005), wherein225Ac is derived from229Th and its daughter225The radioactive ingrowth of the alpha decay of Ra occurs continuously. The generator produces radiochemical purity every 6-8 weeks225Ra and225Ac。225the maximum activity of Ac is limited by the presence of Ac in the generator229Total amount of Th.229Th and225Ra/225chemical separation between Ac is usually based on ion exchange. Three such generators exist in the world today. ORNL (USA) provides up to 720mCi per year225Ac, reported that physical and dynamic engineering institute at Russian Brinning could offer a similar number of products, and that the European Commission G council Carlsrue site maintained a smaller one229Th sources, capable of producing up to 350mCi per year225Ac, is used. However, there is a problem in that225Ac demand is already higher than the total production of existing generators. On the other hand, in the case of a liquid,229th is a rare isotope (derived from233U) and limited in number throughout the world. Due to the fact that233U and229the half-life of Th is long, even though the production method is being investigated (Jost 2013),229the inventory of Th is also unlikely to increase significantly.
Another production225The actinium method comprises irradiation by protons or deuterons232Production of thorium target material225Ac, is used. The method is based on manufacturing the thickness232Th metal targets (natural Th) using intermediate-energy protons or deuterons (24-50MeV) (Morgensten 2006) through a cyclotron or intermediate-to-high-energy protons (>80MeV) was irradiated in an accelerator facility (Ermalaev 2012, Weidner 2012). In use, the intermediate energy proton or the deuteron,225ac production is based on232Th(p,4n)229Pa and232Th(d,5n)229pa, followed by a 0.48% passage of beta in relatively low yield+Decay to isotopically pure225Ac, is used. The proton and deuteron energies required are in the range of commercial cyclotrons today, but very high currents are required to produce favorable yields. By high-energy protons232Direct generation of Th (p, x) reactions225Ac not only on production225Ac is sensitive and produces adjacent isotopes with similar high cross-sections. Facts of factAbove, Ci is horizontal225Ac can be produced by high-energy protons in one week of irradiation (Ermolaev 2012, Griswold 2016), although direct therapeutic use may be subject to concurrent production227Ac, wherein the227Ac is a long-lived (27 years) alpha emitter (Ermolaev 2012), with a ratio of activity227Ac/225Ac ═ 0.2% was produced (Griswold 2016). Chemical separation of actinium from irradiated thorium targets is quite complex due to the presence of a complex mixture of isotopes after irradiation, usually based on a series of ion exchange columns. If necessary, from227Separating and purifying Ac225Ac is an isotope separation that cannot be accomplished by conventional chemical methods. This requires a highly complex mass separation, which can be performed in-line during Irradiation (ISOLDE). Required proton current: (>100uA) and high proton energies (90-200MeV) are outside the range of currently commercialized cyclotrons. In fact, there are a limited number of accelerator facilities in the world that can produce medium to high energy protons of the required intensity (Zhuikov 2011). Less can be done for isotope separation on-line.
Production is disclosed, for example, in EP 0752709B 1 and EP 0962942B 1225Another method of actinium comprising226Proton or deuteron irradiation production of Ra225Ac, is used. The method is based on manufacturing226Thin solid target of Ra, placed in a gas-tight water-cooled target holder and irradiated with protons (Koch 1999, apostolisis 2004) or deuterons (Abbas 2004). Will separate the chemical225After Ac, the rest226Ra is reprocessed and recycled for production of new target material, thus ending the radium irradiation cycle. The irradiation method was successfully demonstrated in a cyclotron irradiation test in which mCi levels were produced225Ac, is used. For the226Ra(p,2n)225Ac reaction, a cross section of 0.71mb may appear at 16.8MeV protons, and is further demonstrated by target dissolution and chemical separation,225the Ac product has a structure of229Th/226Ra/225Generated by an Ac generator225Ac is the same high radiochemical mass. (Apostolisis 2005).
However, it is not limited toDue to the fact that226The complicated handling of the Ra solution, further development and demonstration of the process was stopped.226Ra is a rather long-lived alpha-ray emitter with strong radioactivity and needs shielding even when used in relatively small quantities. However, the main problem is in226Produced directly in alpha decay of Ra222Rn (radon) is present. In fact, if the radon is not continuously separated and removed,226ra and222rn will reach radioactive equilibrium after several weeks, where they will have the same level of activity. Radon (Radon: (A)222Rn) is an inert gas and is therefore very difficult to control, thereby causing serious problems. Thus, deal with a large number226Ra requires low pressure shielding facilities such as hot chambers and glove boxes with large ventilation volumes, and very careful and deliberate treatment methods to minimize radium contamination and/or radon emissions. After solid state irradiation226Dissolving the Ra target material,225Chemical purification of Ac and226the re-treatment of Ra and the production of the target are open processes which make the whole process sensitive to radon emissions.
The processing of the target material is particularly important in such processes, since irradiation is usually carried out outside the hot chamber/glove box. The loaded target must be contamination free and airtight. The water cooling of the target and the thin target window must be optimized for the proton current used to avoid target failure. One advantage of this method is that commercial cyclotrons for producing PET isotopes by proton radiation can be used. They are capable of providing optimized proton energy at a suitable current. However, due to the above disadvantages, this is of interest225Further development of the Ac production process was stopped.
Another production is disclosed, for example, in US 2002/0094056A 1225Actinium process, however, this process has the same disadvantages as the previously described production process. The method consists in irradiating with neutrons or high-intensity gamma rays (in US 2002/0094056 a1 by means of an electron beam, wherein the electron beam is converted into gamma rays using a conversion material)226Ra to produce225Ac, is used. It utilizes226(y, n) or (n,2n) inverse of RaShould produce225Ra, wherein,225ra decays to225Ac, is used. The photon reaction (y, n) utilizes a strong field of hard gamma rays that is generated in the electron accelerator as bremsstrahlung radiation, while neutrons are generated in the fast reactor or by spallation sources in the accelerator facility. Linear accelerator using 18MV226Ra production225Ac, but with a cross section too small to be practical (Melville 2007). In subsequent work it is described that a more intense accelerator irradiates a greater quantity226Ra is a viable process (Melville 2009). This production method has the same disadvantages as proton irradiation of solid Ra targets with respect to the processing of radium.226Ra targets do have to be produced by manufacturing, irradiating, dissolving, separating actinium products and reprocessing radium to produce new targets. Very large (tens of grams or more) are likely to be required226Ra target, but target technology and irradiation may be technically easier to achieve than proton irradiation, since heat dissipation is not an issue and the target window does not have to be thin. However, photon or neutron reactions will require large facilities, such as nuclear reactors, high intensity linacs or synchrotrons, to achieve a suitable production level.
In view of the foregoing, the present invention225Ac as229The production of decay products of Th is not easily scalable or scalable to meet future therapeutic needs. Actinium can be produced by irradiating radium by a (p,2n) reaction in a commercially available cyclotron. However, due to the radon daughter,226the handling of Ra is very challenging. The proposed technique is based on cyclotron (proton or deuteron) or synchrotron (gamma) irradiation of solid targets and requires target fabrication, irradiation, target dissolution, actinium separation, and finally re-processing of Ra into new solid targets to end the cycle. When irradiated with charged particles (protons, deuterons), heat dissipation (cooling) of the target and thin target window limits the particle current, thereby limiting throughput. Radon emissions will be of constant concern during such procedures. For (y, n) reactions, the target window will not be limited, but such a process may require large to very large amounts226Ra and electron accelerationAnd (4) equipment facilities. Probably based on232The method of high-energy proton irradiation of Th requires a highly complex isotope separation method based on mass separation to remove227Ac。
The method according to the invention uses a catalyst comprising226And (3) liquid target material of radium solution. The use of such liquid targets is disclosed in US 2002/0094056 a 1. In the case of the known method, it is,226conversion of Ra by gamma irradiation225Ra，225The half-life of Ra was 14.8 days, so that it was followed225Conversion of Ra to225Ac。226Ra to225The conversion of Ra is achieved by directing electrons to a conversion material that generates photons.226The Ra is coated on the conversion material, but it can also be flowed and circulated in solution over the conversion material until sufficient product is produced.226The Ra solution can also be filled in a quartz bottle and irradiated.
To be provided with226The advantage of Ra solutions as targets is that they are present in sufficiently large amounts226Ra can be used and does not require the production and dissolution of solid targets. However, produced225Isolation and purification of Ac still present radioactivity226Ra and thus radon that is continuously produced. In the method disclosed in US 2002/0094056 a1, the liquid target consists essentially of226A solution of radium chloride is formed. The concentration of the solution may be about 0.5 to about 1.5 molar, for example about 1 molar. After about 10 to about 30 days, e.g., about 20 days, of irradiation, the solution contains226Ra and small amounts generated in solution225Ra and225ac, is used. To be separated from226Ra and225ra and produced225Ac, the irradiated solution must be dried and the dried material must be redissolved in 0.03MHNO3In solution. The solution is passed through an ion exchange column, especiallyResin chromatography columns (Eichrom Industries, Inc., Darien, III.).226Ra and225ra is passed through a resin column, and225ac is retained on the resin column. Followed by 0.35M HNO3From the columnEluting the bound225Ac。
Although not disclosed in US 2002/0094056 a1,226ra and225ra can be reused as a target. Since the target is in the form of chloride, the reuse of these radium isotopes requires the evaporation of HNO3And dissolving the obtained dry material in hydrochloric acid again to obtain the radium chloride solution of the liquid target material.
As mentioned above, a problem with this method is that it must be performed in a closed environment where the radon gas that is continuously produced is captured. Due to complicated treatment of irradiated target solutions to extract the produced225Ac and remnants of226Ra in the extraction of the target from the irradiated target225Before Ac, the target solution should be irradiated until it contains enough225Ac, is used. In the method disclosed in US 2002/0094056 a1, more specifically, the liquid target material is irradiated until a maximum throughput is reached, specifically 80-90%. The disadvantage of such a long irradiation time is that,225ac has decayed after production, such that produced225Ac is lost in a significant part of its production.
Disclosure of Invention
The invention aims to provide a coating which contains226Liquid target of Ra consisting of226Ac production225Ac, which method does not require a drying and redissolving step to be able to separate the generated actinium from the radium, and does not require a further drying and redissolving step to produce a liquid target again starting from the separated radium. Thus, the new method enables the recovery of the radium target material in a more efficient and safer way after the removal of the generated actinium from the radium target material.
To this end, the method according to the invention is characterized in that the separation step comprises a first extraction step carried out in a first extraction device, wherein at least part of the separation step is carried out in a second extraction device225Ac is extracted from the liquid target material solution, and simultaneously226Ra is maintained in the liquid target solution; and the method comprises the further steps of: irradiating again in the irradiation device the portion from which has been extractedThe above-mentioned225Ac from a liquid target solution contained in the liquid target solution226Ra begins to further develop in the liquid target solution225Ac。
In the method of the invention, the liquid target solution is irradiated in an irradiation device and, after irradiation, the same target solution is supplied to a first extraction device, in which the actinium produced is extracted from the liquid target solution itself. Therefore, the target material solution after irradiation does not need to be dried or re-dissolved. After extraction of actinium from the irradiated liquid target solution, the liquid target solution is irradiated again as such to further generate actinium in the target solution. Also, drying and re-dissolving steps are not required here to produce a liquid target. Thus, the cycle can be ended without any drying and re-dissolving of the target material.
Due to the fact that the liquid target solution is used as such in the successive irradiation and extraction steps, no drying and re-dissolving steps are required, so that the production process can easily be automated and radon gas escape can easily be avoided.
The liquid target solution may be contained in a static target body. Some work then has to be done on the static target body to empty it in the first extraction device and to fill it again with the liquid target solution from which actinium has been extracted. The transfer of the liquid target solution into the first extraction device or back can be automated or this single step can be easily performed in a closed environment, e.g. in a hot chamber or a glove box. For example, the extraction of the actinium produced can be performed once a day or once every few days, for example once a week.
In a first embodiment of the method according to the invention, during the irradiation step the liquid target solution is circulated in a first closed loop through the irradiation arrangement and a heat exchanger.
In this embodiment, the target body is thus not static, but dynamic. Since the target solution is circulated in a closed loop, the radon gas generated can be easily contained in the system/apparatus. This embodiment has the advantage that the circulating liquid target solution can be easily cooled to control the temperature of the target solution in the irradiation arrangement, thereby cooling the irradiation arrangement, in particular cooling the window separating the target solution from the outside.
When the radium target is irradiated with protons, the proton beam deposits its energy into the target solution, and the temperature and pressure increase during irradiation. The efficiency of heat dissipation is critical and the target body and target window must be precisely designed to withstand the irradiation conditions. Due to the fact that225Ac has a relatively long half-life compared to e.g. PET radioisotopes or other radioisotopes, which are also produced by a cyclotron in liquid target solutions, and inevitably longer irradiation is necessary due to the limited solubility of radium salt in aqueous solutions. In order to achieve a suitable production level, as high a proton current as possible should be applied, which increases the thermal load on the target. However, the closed volume of liquid target is limited in terms of thermal load due to the increase in internal pressure and temperature of the target liquid. The increased heat load can be handled to some extent in liquid targets designed with internal reflow (i.e. thermosiphon design) and is also advantageous for irradiation of the radium solution. However, from a security perspective, the process is ongoing226Ra, allowing for increased target temperature and pressure is problematic.
In order to achieve a relatively high proton current, i.e. a sufficiently high production level, in this first embodiment the target is preferably water-cooled and most of the heat dissipation is handled by external cooling of the target solution itself. This embodiment allows for a significantly higher current and heat load compared to a static liquid target. The recirculated target material liquid will provide effective internal cooling of the target body and the target window itself, thereby improving safety against target window failure.
Recycled targets have been investigated for production18F (Clarke 2004), but no conventional use has been found so far. For the18F production, recycling target technology is indeed complex, mainly because of the use18The volume of the O-enriched water solution is small, only a few milliliters. This requires an extremely compact recirculation loop designIt is therefore not obvious to use such a recirculation loop for cooling the liquid target. However, in the method of the invention, the problem of an extremely small recirculation loop design is solved by using a larger volume but lower concentration of target solution, which results in a recirculation loop design with standard techniques for liquid pumping and cooling. Although a higher radium concentration in the target solution is preferred in view of the efficiency of the irradiation process, due to the limited solubility of the radium salt in the aqueous solution, especially when the aqueous solution already contains a relatively large amount of anions in the form of acids, only a lower radium concentration is possible. The total target solution volume used in the production method of the invention is in particular more than 10mL, more in particular more than 20mL, even more in particular more than 30mL, and may even be more than 40 mL. The total target solution volume also determines the size of the separation column and is therefore preferably not too large and is, for example, less than 250mL, preferably less than 150 mL. In a target solution226The Ra concentration is in particular below 1M, more in particular below 0.8M, so that only relatively small amounts are required226Ra。226Ra can be dissolved in the target material solution226Ra salts, especially226Ra(NO3)2Or226RaCl2To obtain the final product. Although with226Ra(NO3)2Compared with, use226RaCl2Slightly higher concentrations can be achieved, but the target solution will need to contain more hydrochloric acid (which will reduce226RaCl2Solubility of the salt) to enable extraction of actinium therefrom. Therefore, the temperature of the molten metal is controlled,226Ra(NO3)2and226RaCl2a higher radium concentration in the target solution cannot be achieved. Although only relatively low radium concentrations can be obtained, it was found that a sufficiently high yield can be obtained with the method according to the invention.
In a second embodiment of the method according to the invention, during the first extraction step the liquid target solution is circulated through the first extraction device in a second closed loop.
Also in this second embodiment, the target solution is again recirculated in a circulation loop design with standard techniques for liquid pumping. This situation is used to extract the actinium produced from the target solution. An advantage of this embodiment is that the radon gas generated can again easily be contained within the system/apparatus due to the fact that the liquid target solution is circulated in a closed loop through the first extraction means. The liquid target solution may be recirculated through the first extraction device more than once. In this way, the first extraction device can be maximally loaded with actinium, in particular when a liquid target solution is contained in a container and recirculated through the container and the first extraction device.
In a third embodiment of the method according to the invention, which is applicable in combination with the first and second embodiments, the liquid target solution is circulated through the container and the irradiation arrangement in the first closed loop during the irradiation step and through the container and the first extraction arrangement in the second closed loop during the first extraction step.
An advantage of this embodiment is that the liquid target solution does not have to be transferred from the irradiation device to the first extraction device and vice versa, but can simply be circulated through the irradiation device and the first extraction device. Radon gas does not escape because it is carried out in two closed loops. Another advantage of this embodiment is that the irradiation step can be continued during the extraction step. In other words, the generated actinium can be removed from the target solution without having to interrupt the irradiation step. The actinium produced can therefore be removed more frequently, i.e. more quickly after it has been produced, thus reducing the actinium lost by decay. Furthermore, the liquid target solution may be recirculated through the first extraction device more than once, or even semi-continuously, i.e. mainly only interrupted at any elution or rinsing step. In this way, despite the relatively large recirculation volume of the target solution and despite the fact that the target solution leaving the first extraction device is mixed again with the target solution being fed to the first extraction device, the largest amount of actinium produced can be extracted from the target solution.
In a fourth embodiment of the method according to the invention, the first extraction step is performed during the irradiation step.
This embodiment has the advantage that the irradiation device can be used optimally, since the irradiation process does not have to be stopped for extracting the actinium produced.
In a fifth embodiment of the method according to the invention, at least part of the target solution is extracted from the liquid target solution225Before actinium, the liquid target solution is irradiated for less than 16 days, preferably less than 13 days, more preferably less than 10 days, most preferably less than 7 days.
Since actinium can be easily extracted from the liquid target solution, i.e. without any drying and re-dissolving steps, it is preferably removed as early as possible to reduce the actinium generated during the irradiation step from decaying itself.
In a sixth embodiment of the process according to the invention, the first extraction step is carried out with a pause time of less than 16 days, preferably less than 13 days, more preferably less than 10 days and most preferably less than 7 days.
Again, since actinium can be easily extracted from the liquid target solution, i.e. without any drying and re-dissolving steps, it is preferred to remove it as early as possible to reduce the actinium self-decay generated during the irradiation step.
In a seventh embodiment of the method according to the invention, during said irradiation step, said liquid target solution is irradiated with protons or deuterons.
By protons or deuterons, can be directly and efficiently formed226Production of radium225And (3) actinium. An important advantage is that commercial cyclotrons for the production of PET (Positron Emission Tomography) isotopes by proton irradiation can be used. They are capable of providing optimal proton energy at a suitable current to produce225And (3) actinium. Thus eliminating the need for large facilities.
In an eighth embodiment of the method according to the invention, during said irradiation step, said liquid target solution is irradiated with gamma rays by subjecting it to a laser irradiation226Conversion of radium into225Radium and its preparation method225Conversion of radium into225Production of actinium225And (3) actinium.
An advantage of this embodiment is that the target technology and irradiation are technically easier to achieve than proton irradiation, since heat dissipation is not an issue and the target window does not have to be very thin.
Preferably, during said first extraction step, when extracting from the liquid target solution225When the compound is actinium, the compound is shown in the specification,225the radium remains in the liquid target solution.
The advantage of this preferred solution is that,225the radium is recycled, so that it is generated again in the liquid target solution225Actinium, without any time lag.
In a ninth embodiment of the method according to the invention, the liquid target solution comprises226Solutions of radium salt and its corresponding acid, preferably containing226Radium nitrate and nitric acid.
As mentioned above, while radium chloride has a higher solubility in water than radium nitrate, it generally requires a greater amount of the corresponding acid, HCl, in solution, which reduces the solubility of radium chloride. For example, the desired HCl concentration may include about 5M.
The advantage of using radium nitrate in combination with nitric acid is that the presence of the extraction solvent enables extraction225Actinium without extraction226Radium (or even in225The radium is not extracted when being generated225Radium) comprising: capable of extracting from a solution with a relatively small content of nitric acid (having only a small effect on the solubility of radium nitrate)225Actinium, and can be eluted with solutions of nitric acid with a greater content of nitric acid (for example LN resins containing dialkylphosphoric acid), and extraction chromatography resins based on, for example, N, N, N ', N' -tetra-N-octyldiglycolamide or N, N, N ', N' -tetra-2-ethylhexyldiglycolamide resins (for example DGA (diglycolamide)), CMPO-based TRU resins, i.e. octylphenyl-N, N-diisobutylcarbamoylphosphine oxide or based on diamides (for example DMDOEMA or DMDBDTDMA), which are capable of extracting from solutions with a greater content of nitric acid225Actinium, and can be eluted with a nitric acid solution having a small nitric acid content. Thus, the use of a series of these different extraction chromatography resins enables extraction from a liquid target solution225Ac, eluted from the first extraction chromatography resin225Actinium and again extracting the purer, more concentrated fraction from the eluate by means of a second extraction chromatography resin225And (3) actinium. The order of the two extraction chromatography resins can be exchanged depending on the nitric acid content of the liquid target solution.
Another advantage of using radium nitrate in combination with nitric acid is that corrosion caused by chloride is a greater problem than corrosion in nitrate media. There are many materials that are substantially resistant to corrosion even at relatively high concentrations of nitric acid. And few materials are suitable for hydrochloric acid. This situation is further complicated by irradiation conditions that generate reactive free radicals. These problems can be solved by using nitric acid.
In a tenth embodiment of the method according to the invention, the first extraction device comprises a first adsorbent, during the first extraction step the first adsorbent is contacted with the first adsorbent225Actinium accumulates on the first adsorbent, the method comprising a first elution step in which at least part of the actinium has accumulated on the first adsorbent225Actinium is eluted from the first adsorbent by a first eluent.
In this embodiment, the225Actinium can be easily extracted from the liquid target solution because it accumulates on the first adsorbent during the first extraction step. The first extraction device is preferably an extraction chromatography device, wherein the first adsorbent preferably comprises a support, preferably an inert support, and an extractant as a stationary phase on the support.
In an eleventh embodiment of the method according to the present invention, which is applicable to the tenth embodiment, the liquid target solution has a predetermined pH value such that the liquid target solution has a predetermined pH value225Actinium is accumulated on the first adsorbent during the first extraction step, while the first eluent has a pH value different from the pH value of the liquid target solution, such thatEluting the first adsorbent during the first elution step225And (3) actinium.
An advantage of this embodiment is that both the liquid target solution and the first eluent may contain the same acid, but at different concentrations, so that any acid of the target solution remaining in the first adsorbent does not interfere with the first elution step, and vice versa, so that any acid of the first eluent remaining in the first adsorbent does not interfere with the first extraction step.
In a twelfth embodiment of the method according to the invention, which is applicable to the eleventh embodiment, the method comprises a rinsing step between the first extraction step and the first elution step, wherein the first extraction device is rinsed with a rinsing solution having a pH value different from the pH value of the first eluent, such that the first eluent has a pH value different from the pH value of the first eluent225Actinium remains on the first adsorbent, the rinse solution preferably having a pH substantially equal to the pH of the liquid target solution.
An advantage of this embodiment is that any radium remaining in the first adsorbent at the end of the first extraction step can be washed away before the actinium elutes from the first adsorbent, so radium is not lost, but remains in the system/device and cannot form impurities in the extracted actinium. Radium in this specification refers to any radium isotope, especially226Radium and optionally, if generated during the irradiation step225Radium, also refers to225And (6) radium.
Preferably, the rinsing solution flushes the liquid target solution out of the first extraction device, preferably without mixing with the liquid target solution, during said rinsing step, and the first eluent flushes the rinsing solution out of the first extraction device, preferably without mixing with the rinsing solution, during said first elution step.
In a thirteenth embodiment of the method according to the present invention, which is applicable to the twelfth embodiment, during the rinsing step, the rinsing solution is circulated in a third closed loop through a radium extraction device including a radium sorbent, and radium rinsed from the first sorbent by the rinsing solution is accumulated on the radium sorbent. The method includes a radium eluting step in which at least a portion of the radium that has accumulated onto the radium adsorbent is eluted from the radium adsorbent by a radium eluting agent, the radium eluting agent having, inter alia, a pH different from the pH of the rinsing solution, such that the radium is eluted from the radium adsorbent during the radium eluting step.
An advantage of this embodiment is that any radium flushed from the first extraction device can be recovered. It can be stored in radium eluent for a period of time and recovered by readjusting the radium solution to the correct acidity, concentrating and transferring it back to the target solution. This recovery operation only needs to be performed occasionally, since only a small amount of radium will be washed out of the first extraction device.
In a fourteenth embodiment of the method according to the invention, said fourteenth embodiment is applied to the thirteenth embodiment and is therefore preferably stored in said storage device226From the radium elution step226Eluting on radium adsorbent226Radium and then recycled to the liquid target solution.
In a fifteenth embodiment of the method according to the invention, which is applicable to any of the twelfth to fourteenth embodiments, the flushing solution is circulated through a first radon filter, in particular a first activated carbon filter, for removing radon from the first extraction device.
When the first extraction means is flushed through the first radon filter, radon generated in the first extraction means and radon generated in the irradiation means and collected in the first extraction means can be removed therefrom through the first radon filter. For example, the filter is an activated carbon filter to which radon is attached. The radon subsequently decays to produce210Pb remains in the system/apparatus. To be removed from the system/device210Pb, can be provided therein with lead extraction means, e.g. comprisingSuch as Sr resin or Pb resin (Eichrome), both of which are very effective for removing Pb.
In a sixteenth embodiment of the method according to the invention, which applies to any of the twelfth to fifteenth embodiments, the rinsing solution comprises an acid solution containing the same acid as the target solution, in particular nitric acid.
In a seventeenth embodiment of the method according to the present invention, which applies to any one of the tenth to sixteenth embodiments, the first eluent comprises a first acid solution containing the same acid as the target solution, in particular nitric acid.
The liquid target solution, the rinsing solution and the first elution solution preferably contain the same acid, but do not allow mixing, as this may lead to disturbances in the production process, especially when the production process is carried out for a longer time. Thus, the volume of wash solution contained in the first extraction device is preferably pushed back into its recirculation loop by the first eluent before the first eluent is recirculated through the second extraction device.
In an eighteenth embodiment of the method according to the invention, which is applicable to any of the tenth to seventeenth embodiments, the first eluent is circulated in a fourth closed loop through a second extraction device comprising a second adsorbent during the first elution step, eluted from the first adsorbent by the first eluent during the first elution step225Actinium accumulates on the second adsorbent, the method comprising a second elution step in which at least part of the actinium has accumulated on the second adsorbent225Actinium is eluted from the second adsorbent by a second eluent, in particular having a pH value different from that of the first eluent, so that during the second elution step the actinium is eluted from the second adsorbent225Actinium is eluted from the second adsorbent, the second eluent preferably comprising a second acid solution containing the same as the target solutionAcids, especially nitric acid.
The actinium eluted from the first extraction device can thus be easily collected in the second extraction device and can be eluted therefrom again in a more concentrated and pure form. Preferably, during said second elution step, the second eluent washes the first eluent out of the second extraction device, preferably without mixing with the first eluent.
In a nineteenth embodiment of the method according to the invention, which is applicable to the eighteenth embodiment, the first eluent is circulated from the first extraction device to the second extraction device, during which a second radon filter, in particular a second activated carbon filter, is passed for extracting radon from the first eluent.
When the first extraction means is eluted, the radon generated in the first extraction means and the radon generated in the irradiation means and collected in the first extraction means can be removed therefrom by the second radon filter. For example, the filter is also an activated carbon filter to which radon is attached. The radon subsequently decays to produce210Pb remains in the system/apparatus. To be removed from the system/device210Pb, in which a lead extraction device can be provided, for example, an extraction chromatography column containing, for example, Sr resin or Pb resin (Eichrome), both of which are very effective for removing Pb.
In a twentieth embodiment of the method according to the invention, which is applicable to the eighteenth or nineteenth embodiment, during the second elution step the second eluent is circulated in a fifth closed loop through a third extraction device comprising a third adsorbent, during which second elution step the second eluent elutes from the second adsorbent225Actinium accumulates on a third adsorbent, the method comprising a third elution step in which at least part of the actinium has accumulated on the third adsorbent225Actinium is eluted therefrom by a third eluent, in particular having a pH value different from that of the second eluent, so that the second eluent has a pH value higher than that of the first eluent225Actinium during the third elution stepEluting from the third adsorbent, the third eluent preferably comprising a third nitric acid solution.
The actinium eluted from the second extraction device can thus be easily collected in the third extraction device and can be eluted therefrom again in a more concentrated and/or purer form. Preferably, the third eluent flushes the second eluent out of the third extraction device, preferably without mixing with the second eluent, during said third elution step.
In a twenty-first embodiment of the method according to the invention, which is applicable to the twentieth embodiment, the second eluent is circulated from the second extraction device to the third extraction device, during which a third radon filter, in particular a third activated carbon filter, is passed for extracting radon from the second eluent.
Any radon that reaches the second extraction means can be removed therefrom by the second radon filter when the second extraction means is eluted. For example, the filter is also an activated carbon filter to which radon is attached. The radon subsequently decays to produce210Pb remains in the system/apparatus. To be removed from the system/device210Pb, in which a lead extraction device, for example, an extraction chromatography column containing, for example, Sr resin or Pb resin (Eichrome), can be provided, both of which can remove Pb with high efficiency.
Drawings
Further details and advantages of the invention will become more readily apparent from the following description of some embodiments of the production method according to the invention. This description is provided by way of example only and is not intended to limit the scope of the invention, as defined in the appended claims. Reference numerals used in the present specification refer to reference numerals in the drawings, in which:
fig. 1 is a diagram of an apparatus for carrying out the method according to a first embodiment of the invention, wherein the liquid target solution contains a relatively small amount of nitric acid, in particular 0.02M; and
fig. 2 is a diagram of an apparatus for carrying out the method according to a second embodiment of the invention, wherein the liquid target solution contains a relatively large amount of nitric acid, in particular 0.5M.
Detailed Description
In the process of the present invention, the preparation comprises226Ra, more particularly containing226Liquid target solution of radium nitrate. The solution contains in particular between 0.005 and 1.0M nitric acid. Preferably, the solution is contained in a lead-shielded airtight bottle.
The apparatus schematically shown in fig. 1 is particularly useful according to the low acidity option, i.e. where the liquid target solution has e.g. HNO in the range of 0.005-0.05M3Acidity of middle between, production225Ac, is used. Ra (NO) in target solution3)2Is preferably as high as possible, up to 0.4M.
The apparatus comprises a container 1 for containing a liquid target solution. An irradiation device 2 having a window through which the target solution can be irradiated with protons, deuterons or gamma rays is further included. The gamma rays may be obtained by synchrotron or linear accelerator, or may also be obtained by conversion materials as disclosed in US 2002/0094056. However, it is preferred to irradiate the liquid target material with protons (or deuterons) because this is caused by226Ra generation225Ac is the most efficient way. Proton irradiation may be produced by a cyclotron, e.g. as is known for the production of PET radioisotopes, e.g. from18O production18F, cyclotron.
The liquid target may be a static target but in order to enable more efficient cooling and thus higher energy irradiation of the target for increased throughput, the liquid target is preferably a recycled liquid target as in the embodiment shown in fig. 1. In this embodiment, the target solution is pumped from the container 1 through the irradiation arrangement 2 by the pump 3 in the first closed loop 4 and then back into the container 1 through the heat exchanger 5. In the irradiation arrangement 2 itself, the target material is preferably also cooled, in particular water-cooled. The solution is preferably irradiated with protons, preferably with an incident energy of 15-20 MeV. During irradiation, the heat generated by stopping the protons in the target solution is removed, either completely or partially, by the target solution itself and exchanged externally in the primary heat exchanger 5. A complete irradiation loop is provided so that all liquid receiving parts are made of highly inert, gas-tight materials, typically hastelloy, inconel and the like, to avoid corrosion and ensure tightness. Ceramics or a combination of metals and ceramics are also good choices.
During the irradiation period of the light, the light source,225ac is continuously accumulated in the target material solution. With a static target, when irradiation is complete, the target solution is collected back into the airtight target solution bottle. The static target is preferably automatically loaded and emptied. The recycled liquid target material may be reprocessed during irradiation. From this point on, the user can select the target,225the chemical separation and purification of Ac is performed by recycling the liquid stream through an extraction chromatography column or an ion exchange column. These conditions are set so that actinium is extracted on the column and impurities are recycled. The size of the column, flow rate of the solution, volume depend on the initial volume of the target solution.
For static target bodies, the irradiated target material solution contained in the bottle may be transferred and recycled through the first extraction device 6. In the extraction device 6, the extraction liquid is,225ac is extracted from the irradiated target solution, and226ra (and optionally also in the case of gamma irradiation of the target solution225Ra) remained in the target solution. Has already extracted226The target solution of Ac was again collected in the bottle and reloaded into the liquid target for re-irradiation.
In the apparatus shown in FIG. 1, extraction is carried out from a liquid target solution225Ac will have extracted225The loading of the liquid target solution of Ac back into the liquid target body requires fewer process steps and is easier to implement, especially in an automated manner. In the embodiment shown in fig. 1, the irradiated target solution contained in the container 1 is actually recirculated through the first extraction device 6 in the second closed loop 7. This is done by means of a pump not shown in fig. 1.
The first extraction device comprises a first adsorbent which, during the first extraction step,225ac accumulates on the first adsorbent. The first extraction means preferably comprises a first extraction chromatography column, said first extraction in the low acidity optionChromatography columns are for example based on LN resins (Eichrome, FIDEFIEP). For example, when the target solution contains 0.005-0.05M HNO3For example 0.02M HNO3While actinium remains on the column226Ra (and)225Ra, if present) is recycled. The volume of recycling will determine the efficiency of Ac uptake from the target solution, and it is important to limit this volume to avoid actinide breakthrough.
Preferably, the loss of Ra from the target solution is prevented. What is important is that225Ac and226the Ra separation pushes the majority of the target solution volume present in the initial chromatography column back into the target solution container 1.
After the initial separation, i.e. after pumping or permeation of the liquid target solution through the chromatography column, any radium still remaining in the first extraction device 6 is retrieved by flushing the chromatography column of the first extraction device 6 with a flushing solution 8. The pH of the rinsing solution is similar to the pH of the liquid target solution, and therefore during the rinsing step225Ac is retained on the column. The rinse solution is circulated through the first extraction device 6 and the radium extraction device 10 in a third closed loop 9, for example through a strong cation exchange column (e.g., DOWEX 50W or Biorad 50W or the like). The radium extraction device 10 includes a radium adsorbent on which radium flushed from the first adsorbent by the flushing solution 8 accumulates during the flushing step.
In order to remove all radon gas accumulated in the first extraction means 6, it is preferred that the flushing solution 8 is also recirculated through the first activated carbon filter 11 to remove radon gas from the first extraction means 6. The activated carbon filter 11 may be a granular activated carbon filter, but is preferably a powdered activated carbon filter.
Due to the reduced column size and the reduced elution volume, further purification and concentration was performed by extraction chromatography columns based on Ln resin, Sr resin, DGA resin or branched DGA resin (all from Eichrome). Each change in acidity will cause the actinides to move from one extraction column to the next, thereby increasing purity and increasing the concentration factor. In the process, the last column will determine in what medium the actinide product leaves the process. In fig. 1, actinium is eluted using SCE (strong cation exchanger) and using a correspondingly high acidity. Another option is an extraction chromatography resin selective for trivalent elements, such as DGA or DGA-B (Eichrom), where the elution of actinides is performed at a lower acidity.
In the embodiment shown in FIG. 1, more specifically, radium that has accumulated in the radium extraction device 10 is eluted therefrom by a radium eluting agent 12, the pH or acidity of the radium eluting agent 12 being different from the pH or acidity of the rinsing solution, such that radium is eluted from the radium adsorbent during the radium eluting step. The rinse solution 8 may comprise, for example, a 0.02M nitric acid solution, and the radium eluent 12 may comprise, for example, a 2M nitric acid solution. Radium eluting agent 12 containing the recovered radium is stored in an airtight container 13. The vessel 13 is provided with a gas inlet 14 and a gas outlet 15. The container 13 can thus be purged with a small volume of, for example, nitrogen gas to remove all radon gas generated in the container 13 during storage of the radium. Because only a small volume is used, Rn can be captured and carried (manage) by a small activated carbon gas filter (not shown in fig. 1 and 2). The recovered Ra can be readjusted to the correct acidity, concentrated and transferred back into the target solution if necessary.
In a first elution step after the rinsing step, the accumulated first adsorbent in the first extraction device 6 is eluted by a first eluent 16 from the first adsorbent225Ac, is used. The pH of the first eluent 16 is different from the pH of the liquid target solution so that it elutes from the first adsorbent contained in the first extraction device 6 during the first elution step225Ac, is used. The first eluent 16 may contain a first nitric acid solution having a lower pH, i.e. higher acidity, containing, for example, 0.5M HNO3. Using this eluent, it is possible to remove from Ln resins225Ac。
The first eluent 16 circulates in a fourth closed loop 17 through the first extraction device 6 and the second extraction device 18 during the first elution step, the second extraction device 18 containing the second adsorbent, the eluent 16 eluting from the first extraction device 6 during the first elution step225Ac accumulates on the second adsorbent. Second extractThe extraction device preferably comprises a second extraction column, which in the low acidity option shown in fig. 1 is for example a DGA-resin (Eichrome, TODGA) based column. When the first eluent 16 comprises, for example, 0.5M HNO3In time, actinium is retained on the DGA column and impurities are recycled. The empty column volume of the second extraction device 18 is preferably smaller than the empty column volume of the first extraction device 6, so that actinium can be concentrated thereon and can be eluted therefrom with a smaller amount of the second eluent 19.
In order to remove any radon gas that may be present in the fourth closed circuit 17 of the apparatus, the first eluent 16 is circulated from the first extraction device 6 to the second extraction device 18, during which it is passed through a second radon filter 20, in particular a second activated carbon filter, to extract radon from the first eluent 16. The second activated carbon filter 20 may be a granular activated carbon filter, but is preferably a powdered activated carbon filter.
When in use225Having accumulated actinium on the second adsorbent contained in the second extraction device 18, in a second elution step a second eluent 19 will pass225Actinium is eluted from the second adsorbent. The pH or acidity of the second eluent is different from the pH or acidity of the first eluent 8, so that elution from the second adsorbent contained in the second extraction column during the second elution step occurs225And (3) actinium. The second eluent 19 again preferably comprises a second nitric acid solution and, in the low acidity option shown in figure 1, comprises, for example, 0.05M HNO3. Using this second eluent, it can be removed from the DGA resin225Ac。
The second eluent 19 circulates in a fifth closed circuit 21 through the second extraction device 18 and through a third extraction device 22 containing a third adsorbent during a second elution step, during which the second eluent 19 elutes from the second extraction device 18225Actinium accumulates on the third adsorbent. The third extraction device 22 preferably comprises a third extraction column, which, in the low acidity option shown in fig. 1, is also a Ln resin (HDEHEP) based column, for example. When the second eluent 19 containsFor example 0.05M HNO3In time, actinium remains on the Ln column, while impurities are recycled. If no further concentration is required, the void column volume of the third extraction device 22 may be equal to the void column volume of the second extraction device 18.
In order to remove any radon gas that may be present in the fifth closed circuit 21 of the apparatus, the second eluent 19 is circulated from the second extraction device 18 to the third extraction device 22, during which it is passed through a third radon filter 23, in particular a third activated carbon filter, to extract radon from the second eluent 19. The third activated carbon filter 23 may be a granular activated carbon filter, but is preferably a powdered activated carbon filter.
When in use225When actinium has accumulated on the third adsorbent contained in the third extraction device 22, in a third elution step, a third eluent 24 will pass through225Actinium is eluted from the third adsorbent. The pH or acidity of the third eluent 24 is different from the pH or acidity of the second eluent 19, so that elution from the third adsorbent contained in the third extraction column 22 during the third elution step occurs225And (3) actinium. The third eluent 24 again preferably comprises a third nitric acid solution and, in the low acidity option shown in fig. 1, comprises, for example, 0.5M HNO3. Using this third eluent, it is possible to remove from Ln resin225Ac。
In the embodiment of figure 1 of the drawings,225further purification and optional concentration of Ac is obtained by: circulating the third eluent 24 in a sixth closed loop 25 through the third extraction device 22 and a fourth extraction device 26 during a third elution step, said fourth extraction device 26 comprising a fourth adsorbent, the third eluent 24 eluting from the third extraction device 22 during the third elution step225Actinium accumulates on the fourth adsorbent. The fourth extraction device 26 may again comprise a DGA or DGA-B (branched) column, in which the acidity can be as low as 0.1M, to be removed therefrom in a final step225Ac, is used. However, the fourth extraction device 26 preferably comprises SCE (strong cation exchanger). When the third eluent 24 comprises, for example, 0.5M HNO3While actinium remains on SCE 26, the impurities are recycled. Empty column volume of the fourth extraction device 26May be equal to or less than the empty column volume of the second extraction device 18, and may be equal to about half of its empty column volume to enable further concentration225Ac。
In order to remove any radon gas that may be present in the sixth closed circuit 25 of the apparatus, the third eluent 24 is recycled from the third extraction device 22 to the fourth extraction device 26, during which it is passed through a fourth radon filter 27, in particular a fourth activated carbon filter, to extract radon from the third eluent 24. The fourth activated carbon filter 27 may be a granular activated carbon filter, but is preferably a powdered activated carbon filter.
When in use225Having accumulated actinium on the fourth adsorbent comprised in the fourth extraction device 26, in a fourth elution step the actinium will be eluted by a fourth eluent 28225Actinium is eluted from the fourth adsorbent.
In case the fourth extraction device 26 comprises DGA or DGA-B resin, the pH or acidity of the fourth eluent 28 is different from the pH or acidity of the third eluent 24, so that elution from the fourth adsorbent contained in the fourth extraction column 26 occurs during the fourth elution step225And (3) actinium. The fourth eluent 28 again preferably comprises a fourth nitric acid solution and, in the low acidity option shown in fig. 1, comprises, for example, 0.1M HNO3. Using this fourth eluent, it is possible to remove from DGA or DGA-B resin225Ac。
Where the fourth extraction device 26 is an SCE, the fourth eluent 28 has a pH or acidity high enough to elute from the SCE225Ac, is used. The fourth eluent 28 again preferably comprises a fourth nitric acid solution, in which case the fourth nitric acid solution has high acidity, comprising, for example, 2M HNO3。
The obtained purified and concentrated225Ac may be removed through outlet 29 of the fourth extraction unit and may subsequently be dried to obtain a dried product. During the drying step, not only the water but also the acid contained in the fourth eluent can be removed by evaporation.
For example, the different extraction devices and solutions used in the apparatus shown in fig. 1 may have the following composition:
table 1: examples of extraction devices and compositions of solutions that can be used in the apparatus shown in figure 1.
Target material solution
0.02M HNO3And 0.4M226Ra(NO3)2
First extraction device 6
Ln resin (Eichrome, HDEHEP)
Rinsing solution 8
0.02M HNO3
Radium extraction device 10
SCE(DOWEX 50W)
Radium eluent 12
2M HNO3
First eluent 16
0.5M HNO3
Second extraction device 18
DGA(Eichrome,TODGA)
Second eluent 19
0.05M HNO3
Third extraction device 22
Ln resin (Eichrome, HDEHEP)
Third eluent 24
0.5M HNO3
Fourth extraction device 26
SCE(DOWEX 50W)
Fourth eluent 28
2M HNO3
Fig. 2 shows another embodiment of the method according to the invention, in which the liquid target solution has a higher acidity (lower pH). This high acidity option is based on an initial Ac/Ra separation using a DGA column. For example, here the acidity of the target solution will be between 0.1M-0.5M nitric acid acidity, and if the lower acidity is compensated by the addition of nitrate, e.g. by ammonium nitrate, the target solution will have226The concentration of Ra may be as high as 0.35M. Actinium will be removed by recycling through the DGA column. The volume of recycle should be large enough to effectively remove Ac, but should be within the capacity of the column to avoid Ac breakthrough. As in the low acidity option, the strong cation exchanger will carry any Ra left on the column after the initial actinium separation. Further purification was performed by reducing the acidity and the amount of absorption on the Ln resin column. The acidity is here chosen to avoid co-extraction of Pb, i.e. 0.03M to 0.075M. There are different options in this regard, but subsequent purification and concentration using DGA or DGA B columns may be the preferred method.
Parts of the apparatus shown in figure 2 which correspond to parts of the apparatus shown in figure 1 are indicated by the same reference numerals. The apparatus shown in fig. 2 functions in the same way as the apparatus described above with reference to fig. 1, and therefore a description of the function of the common components is not repeated. Instead, the following table gives one specific example of the different extraction devices and solutions used in the high acidity equipment shown in fig. 2:
table 2: examples of extraction apparatus and solution compositions that can be used in the high acidity equipment shown in figure 2.
Target material solution
0.5M HNO3And 0.35M226Ra(NO3)2
First extraction device 6
DGA(Eichrome,TODGA)
Rinsing solution 8
0.5M HNO3
Radium extraction device 10
SCE(DOWEX 50W)
Radium eluent 12
2M HNO3
First eluent 16
0.05M HNO3
Second extraction device 18
Ln resin (Eichrome, HDEHEP)
Second eluent 19
0.5M HNO3
Third extraction device 22
DGA(Eichrome,TODGA)
Third eluent 24
0.1M HNO3
Lead extraction device 30
Sr resin (Eichrome)
It can be seen that the product is concentrated and purified225Ac has been removed from the third extraction unit 22. However, in the fifth closed loop 21, an additional extraction column, i.e. a lead extraction device 30, is provided between the second extraction device 18 and the third extraction device 22. A third radon filter 23 is provided before the lead extraction device 30 and an additional radon filter 23' is provided after that.
The lead extraction plant 30 comprises in particular a Sr resin, which is very efficient for Pb and can be used for removing Pb from the plant/system. Lead is produced by radon decay. Radon decays by alpha decay and produces radiation damage to the column material which will affect the separation performance of the column. Thus, it is preferable to prevent radon from moving downstream in the process flow, thereby extending the life of the column and avoiding radon contamination225Ac product. Radon is carried by a radon filter, i.e. a small chromatographic column containing Powdered Activated Carbon (PAC) or Granular Activated Carbon (GAC). Radon is absorbed/strongly delayed and decayed in PAC/GAC chromatographic column210Pb, a gamma emitter.210Pb will be eluted into the aqueous phase and included in the process flow. PAC/GAC chromatography columns can be used multiple times. The Sr resin column is very effective for Pb and therefore can be used to remove Pb from the process flow. The Sr resin column contains dicyclohexyl-18-crown-6 derivative as stationary phase, which is soluble in octanol.
Also in the low acidity apparatus of fig. 1, a lead extraction device (Sr resin column) can be easily incorporated, especially between the third extraction device 22 and the fourth extraction device 26, preferably with a fourth radon filter 27 before the lead extraction device and an additional radon filter after the lead extraction device.
Although it is not limited toBecause of the limited solubility (e.g., ratio) of radium nitrate68The solubility of the zinc nitrate is over 10 times less, wherein,68the zinc nitrate is used in the liquid target material by68Zn(p,n)68Reaction of Ga to form68Ga) in the target solution226The lower concentration of Ra, the process according to the invention enables commercially advantageous yields to be achieved.
225The Ac yield can be calculated.226Energy-dependent cross-section of Ra (p,2n) reactions (IAEA ENDF database) and compositions containing up to 0.4M226Ra(NO3)2The energy dependent stopping energy (energy dependent stopping power) of the protons in the aqueous solution (nucleonic) of (a) is used to obtain a yield in small layers of the liquid target, adding up to give225The overall formation amount of Ac. The weekly yields as a function of the proton current used are shown in table 1.
Table 3:225ac production as a function of proton current. 0.35M of226Ra, irradiation time 7 days, cooling time 0 days, cross section 500 mb.
Current (μ A)
A(Bq)
A(mCi)
Heat quantity (W)
10
1.27E+09
34.4
225
20
2.54E+09
68.8
450
30
3.82E+09
103.2
675
40
5.09E+9
137.6
900
50
6.36E+9
171.9
1125
60
7.63E+9
206.3
1350
70
8.91E+9
240.7
1575
80
1.02E+10
275.1
1800
90
1.15E+10
309.5
2025
100
1.27E+10
343.9
2250
As for economic feasibility, it is assumed that225Treatment of Ac is approved for225Ac demand will increase significantly. Except for227Ac has been subjected to a complex isotopic separation otherwise produced by the proposed method225Ac will be smaller than by proton irradiation232Production of Th target225The Ac quality is higher. If allocated on a production basis, assuming 40 weeks of production per year225Ac may cover more than 25000 treatments. It is therefore most likely to ensure economic viability in the actinide production process.
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