Purification of Target Substances for the Production of Radioisotopes

Abstract

A method for purifying a target substance for reuse in the production of radioisotopes is disclosed. The method includes obtaining a solution of an irradiated target substance that includes Ra-226 and optionally Ra-225 and Ac-225, and then adding an acid, which is HNO3, in a predetermined amount to provide conditions for quantitatively dissolving the target substance and optionally avoiding coprecipitation of radioisotopes that are present. The method also includes selectively removing H2O from the solution by distillation, leaving mainly the acid in the solution, thereby enabling the target substance to precipitate while the acid concentration in the solution increases, thereby reducing or avoiding coprecipitation of optionally present radioisotopes and impurities. After removing the excess H2O, the method includes lowering the temperature of the solution to maximize precipitation of the target substance and reduce the solubility of the target substance in the residual liquid, separating the liquid containing the optionally present radioisotope from the precipitated target substance, and preparing the precipitated target substance for reuse in the production of radioisotopes by re-irradiation for the production of radioisotopes.

Description

【Technical Field】 【0001】 The present invention relates to the field of radioisotopes. More specifically, the present invention relates to methods and systems for the purification of irradiated targets for reuse in the production of radioisotopes. 【Background Art】 【0002】 In the production of radioisotopes, generally, solid targets are used for high yields in state-of-the-art systems, and for solid targets, a high density of the parent nuclide from which the radioisotope is produced can be easily achieved. 【0003】 In the case of liquid targets, the solubility of most parent nuclide compounds in water at room temperature (typically used as a liquid solvent) is limited. For example, a salt of Ra-226 (T 1 / 2 : 1600 years), a salt of Ra-225 (T 1 / 2 : 10 days), which can decay to the radioisotope Ac-225 (T 1 / 2 : 14.8 days), and can be used as a basic chemical substance to provide a parent nuclide for producing Ra-225, has a limited solubility in water. By way of illustration, the radium nitrate salt Ra(NO3) has a solubility of 13.9 g per 100 g of H2O at 20°C. Nevertheless, recently, methods for overcoming the problem of limited solubility have been found, and thus the interest in liquid targets has been increasing. 【0004】 In both the case of solid targets and the case of liquid targets, it is necessary to separate the radioisotope from the target, which can typically be done in a separation column by solid-phase extraction methods. 【0005】 The world's available inventory of target substances for some parent nuclides capable of producing radioisotopes is limited. In particular, in these cases, such as but not limited to the case of Ra-226, it is useful to reuse the target substances. 【0006】 The reuse of the target substance is mentioned in International Patent Application No. 2020 / 260210, and a method for producing actinium based on a photonuclear route is described, which irradiates a liquid target of radium-226, and after separating actinium, irradiates a liquid target solution of radium-226 using a closed-loop system. 【0007】 The purification of actinium in the process of manufacturing actinium radioisotopes is described in International Patent Application No. 2020 / 148316. 【0008】 Nevertheless, there is still a need for improved purification methods and systems to enable the reuse of the target substance for further irradiation in the production of radioisotopes. 【Summary of the Invention】 【0009】 The object of the present invention is to provide a method and a system for purifying an irradiated target for reuse in the production of radioisotopes. 【0010】 An advantage of embodiments of the present invention is that these systems and methods provide an efficient way to reuse irradiated targets, for example, for the production of radioisotopes. 【0011】 An advantage of embodiments of the present invention is that systems and methods for reusing irradiated targets are provided regardless of whether these targets were in solid form or liquid form during irradiation. 【0012】 An advantage of embodiments of the present invention is that in the production of radioisotopes, the target substance can be reused, enabling an increased production of radioisotopes using a given amount of target substance. Further, for example, the production of non-carrier-added (NCA) Ac-225 formed by the decay of Ra-225 is a small amount of Ac-227 (T 1 / 2: It should also be noted that since it is also formed in the photonuclear production pathway by neutron capture of the parent nuclide Ra-226, it is not possible in the first radium / actinium separation step. Therefore, in the example of radium / actinium-based production, if NCA Ac-225 is the main target of the production process, the operation of the liquid radium target in a closed-loop system is not desirable. After the first highly efficient separation of radium (224+225+226) isotopes from actinium (225+227) isotopes, the radium must be conserved for the internal growth of new Ac-225 due to the decay of Ra-225, which will ultimately become NCA Ac-225 after the second Ra / Ac separation step. As a result, this increases the amount of the parent nuclide Ra-226 required to produce Ac-225 and emphasizes the importance of an excellent recycling strategy for Ra-226. 【0013】 An advantage of an embodiment of the present invention is that the provided purification process can overcome the problems caused by rinsing (e.g., dilution of the target) and the uncertainties associated with the pH of the irradiated solution so that the reuse of the target substance can be carried out. 【0014】 An advantage of an embodiment of the present invention is that inorganic and organic contaminants can be removed from the target substance. 【0015】 An advantage of an embodiment of the present invention is that these enable the target substance, e.g., Ra, to obtain the minimum chemical purity required for recycling and re-irradiation. 【0016】 An advantage of an embodiment of the present invention is that the complexity caused by the purification process according to the embodiment of the present invention is limited. 【0017】 The above object is achieved by the method and apparatus according to the present invention. 【0018】 In one aspect, the present invention relates to a method for purifying a target substance for reuse in the production of radioactive isotopes, the method comprising - Obtaining a solution of the irradiated target substance, the solution thus containing the target substance which includes at least Ra-226, and optionally also the radioisotopes Ra-225 and Ac-225, and optionally impurities, and then, - Adding an acid which is HNO3 in a predetermined amount and concentration to provide conditions for quantitatively dissolving the target substance and for avoiding coprecipitation of any optionally present radioisotopes and / or impurities, - Selectively removing H2O from the solution by evaporation, leaving mainly the acid in the solution, thereby enabling the target substance to precipitate while the acid concentration in the solution increases, thereby reducing or avoiding coprecipitation of any optionally present radioisotopes, - After removing the excess H2O, lowering the temperature of the solution to maximize precipitation of the target substance and reduce the solubility of the target substance in the residual liquid, - Separating the liquid containing any optionally present radioisotopes and / or impurities from the precipitated target substance, - Preparing the precipitated target substance for reuse in the production of radioisotopes. 【0019】 The latter can be, for example, by re-irradiation for the production of radioisotopes or can involve storage, for example, for the internal growth of new Ac-225. 【0020】 Evaporation can refer to selectively removing by making H2O into the vapor phase. Evaporation can be distillation in some embodiments. 【0021】 Lowering the temperature can include an active cooling step but does not necessarily require an active cooling step. The fact that the temperature drops refers to the fact that the temperature at which evaporation is carried out is higher than the temperature at which liquid separation is carried out. 【0022】 An advantage of an embodiment of the present invention is that in an embodiment of the present invention which is carried out by an evaporation process, for example, a distillation process, at least one concentration step is carried out. 【0023】 For example, when producing actinium-225 from a radium-226 target, Ac-225 is separated from radium on average every two weeks. This facilitates a slow process such as obtained in an evaporation, for example, distillation, process, allows focusing on minimizing the loss of Ra-226, and enables rapid processing of Ac-225 after separation. 【0024】 An acid, such as HNO3, can be added at a concentration of 1% to 100%, for example, with an upper limit of, for example, 90%, for example, 80%, for example, 75%, for example, 70%, for example, 69%, and a lower limit of, for example, 10%, for example, 25%, for example, 40%. The acid can be, for example, HNO3 when producing the Ac-225 isotope using a Ra-226 target. It should be noted that this method can be used to recycle the target even if the separation of the target and the radioisotopes produced during previous irradiations is carried out in different ways. For example, when the target is Ra-226, this method can also be used when the amounts of Ra-225 and Ac-225 are low or completely absent, and the process is mainly carried out to obtain Ra-226, which is in a pure and concentrated form without the presence of inorganic or organic impurities or large amounts of HNO3. 【0025】 Note that the purification method can be applied to newly irradiated targets or targets that have been milled multiple times. 【0026】 Obtaining a solution containing the irradiated target substance means obtaining an irradiated solution of the target substance or a solution of the irradiated target substance, and may include obtaining a solution of the irradiated target substance irradiated when the irradiated target substance is in solid form. The advantages of the embodiments of the present invention are that they provide a purification method that can be used for both solid irradiation targets and liquid irradiation targets. 【0027】 Irradiation of the target substance, in either liquid or solid form, can be by photons, neutrons, or charged particles such as, for example, protons or deuterons. In an advantageous embodiment, the radium-226 target substance is irradiated with photons or neutrons in liquid or solid form for the production of actinium radioisotopes through the production of radium-225. 【0028】 Obtaining a solution of the irradiated target substance may further include obtaining an aqueous solution or a solid, for example, a rinsing substance used to rinse the target capsule / container in solid or liquid form before, simultaneously with, or after the transfer of the main target substance, a rinsing substance used to rinse the transfer piping, and obtaining a secondary process stream containing a smaller amount of the target substance and radioisotopes or mixtures thereof. 【0029】 In some embodiments, the method may be carried out mainly to obtain Ra-226 in a pure and concentrated form in the absence of impurities or a large amount of HNO3. 【0030】 The irradiated target substance may include Ra-226, and optionally Ra-225 and Ac-225, the acid is HNO3, and HNO3 is present at a concentration of 65% - 68% when the precipitation of radium is carried out. The advantage of the embodiments of the present invention is that by using a concentration of 65% - 68% for precipitation, it is possible to avoid the need to remove increased amounts of H2O in a continuous evaporation process, which is often the case when adding lower concentrations, or to avoid an increase in the presence of corrosive vapors (HNO3, NOX), which is often the case when adding higher concentrations. 【0031】 One or more of the method steps can be performed under reduced pressure, i.e., at a pressure below atmospheric pressure. The reduced pressure can be an operating pressure in the range of 50 mbar to 200 mbar. The latter can enable selective capture of volatile isotopes and / or reduction of the diffusion of corrosive fumes. Lowering the pressure can advantageously result in lowering the boiling point of the solution. 【0032】 Heating or cooling of the solution can be carried out using a circulating liquid within the double wall of a double-wall (jacketed) reaction vessel. 【0033】 The method can include visually tracking the process using a transparent reaction vessel. 【0034】 The solution for heating / cooling can mainly be H2O. 【0035】 The method can further include stirring the solution, for example, using magnetic stirring. An advantage of embodiments of the present invention is that stirring can improve the evaporation process, such as evaporation or boiling during distillation. 【0036】 The method can be applied to a rotary evaporator system. An advantage of embodiments of the present invention is that the surface for evaporation is actively increased, and thus the efficiency of the process is improved. 【0037】 The method can be applied in a closed circuit that is heated and / or cooled through a heat exchanger. An advantage of embodiments of the present invention is that when the double wall breaks when using a double-wall reaction vessel, the target substance can be recovered from the liquid by using the closed circuit. 【0038】 After removing excess H2O, the temperature can be lowered below room temperature but above the freezing temperature of the liquid. 【0039】 The solution can be filtered using a filtrate collection container, optionally a buffer container, and an immersion filter connected to a vacuum pump. 【0040】 Preparing the precipitated target substance can include washing the precipitate with a concentrated acid after the first filtration and optionally repeating the filtration process. By washing the precipitate with acid after the first filtration and optionally repeating the filtration process, the recovery of the radioisotope can be improved while minimizing the dissolution of the target substance. 【0041】 After the final filtration, the target substance precipitate can be dried to remove residual acid, and thus the solubility of the target substance in H2O can be further improved. 【0042】 H2O can be added to recover the target substance, thereby completely dissolving the target substance. 【0043】 In some embodiments, the solution can be heated to clean the reaction vessel in which the process is carried out by concentrating and dissolving the solid residues of the target substance. 【0044】 The solution can be refluxed. 【0045】 In one aspect, the invention also relates to a system for purifying a target substance, the system comprising a reaction vessel, an inlet for a solution of the irradiated target substance, and an inlet for adding an acid, the reaction vessel comprising evaporation means, such as distillation equipment, for removing H2O from the solution of the irradiated target substance and leaving the acid mainly in the solution, thereby enabling the target substance to precipitate while the acid concentration in the solution increases, thereby reducing or avoiding the coprecipitation of any optionally present radioisotope, and the system further comprising filtration means for separating a liquid containing any optionally present radioisotope from the precipitated target substance. 【0046】 The irradiated target substance can include Ra-226, and optionally Ra-225 and Ac-225. The inlet for the acid can be an inlet for HNO3. 【0047】 The system may comprise a heating / cooling system for controlling the temperature of the reaction vessel by heating and / or cooling. The heating / cooling system may be a double-walled heating / cooling jacket. The heating / cooling system may connect the heating / cooling jacket to a primary fluid circuit equipped with a liquid circulation pump system. 【0048】 The system may include an air pump system for inducing a reduced pressure within the reaction vessel. 【0049】 The system may be provided with a pressure sensor for measuring the pressure within the reaction vessel. 【0050】 Furthermore, the system may include a controller for controlling the systems, such as, for example, an air pump system, a heating / cooling system, and a system for controlling the amount of acid to be added, for executing the method as described above. 【0051】 Furthermore, the system may be provided with a radon removal device for removing radon. 【0052】 The specific and preferred embodiments of the present invention are set forth in the appended independent and dependent claims. The features from the dependent claims can be combined with the features of the independent claims and the features of other dependent claims as appropriate and as clearly stated. 【0053】 In this field, there have been continuous improvements, changes, and evolutions of devices, but this concept represents a substantial new and innovative improvement that includes a departure from conventional practices and is believed to result in the provision of more efficient, stable, and reliable devices of this nature. 【0054】 The above and other characteristics, features, and advantages of the present invention will become apparent from the following detailed description in conjunction with the accompanying drawings that illustrate the principles of the invention by way of example. This description is given for the purpose of illustration only and without limiting the scope of the present invention. The reference figures cited below refer to the accompanying drawings. 【Brief Description of the Drawings】 【0055】 【Figure 1】 A system for purifying a target substance according to an embodiment of the present invention is illustrated. 【0056】 In different drawings, the same reference numerals refer to the same or similar elements. 【Modes for Carrying Out the Invention】 【0057】 The present invention has been described with reference to specific drawings with respect to specific embodiments, but the present invention is not limited thereto and is limited only by the claims. The drawings described are only schematic and non-limiting. In the drawings, the sizes of some of the elements may be exaggerated for the purpose of explanation or may not be drawn to scale. The dimensions and relative dimensions do not correspond to the actual reduction for the implementation of the present invention. 【0058】 Furthermore, terms such as first, second, third, etc. in this specification and the claims are used to distinguish similar elements and are not necessarily used to describe an order in a temporal, spatial, ranking, or any other manner. The terms used in this way are interchangeable under appropriate circumstances, and it should be understood that the embodiments of the present invention described in this specification can operate in an order other than that described or illustrated in this specification. 【0059】 Furthermore, terms such as top, bottom, over, under, etc. in this specification and the claims are used for the purpose of explanation and are not necessarily used to describe a relative position. The terms used in this way are interchangeable under appropriate circumstances, and it should be understood that the embodiments of the present invention described in this specification can operate in an orientation other than that described or illustrated in this specification. 【0060】 The term "comprising" as used in the claims should not be construed as being limited to the means listed thereafter; note that it does not exclude other elements or steps. Thus, as defined, it is to be interpreted as identifying the presence of the stated features, elements, steps, or components, but not as precluding the presence or addition of one or more other features, elements, steps, or components, or groups thereof. Accordingly, the term "comprising" encompasses both situations where only the stated features are present and situations where these features and one or more other features are present. Thus, the term "comprising" according to the present invention also includes, as one embodiment, the absence of further components. Accordingly, the scope of the expression "a device comprising means A and B" should not be construed as being limited to a device consisting only of components A and B. This means, with respect to the present invention, that the only relevant components of the device are A and B. 【0061】 Similarly, it should be noted that the term " Combined ( coupled )" should not be construed as being limited to direct connection only. The terms "coupled" and "connected" may be used with their derivatives. It should be understood that these terms are not intended to be synonyms of each other. Accordingly, the scope of the expression "device A coupled to device B" should not be limited to a device or system in which the output of device A is directly connected to the input of device B. This means that there is a path between the output of A and the input of B, which may be a path including other devices or means. "Coupled" means that two or more elements are either in direct physical or electrical contact, or that two or more elements are not in direct contact with each other but still cooperate or interact with each other. 【0062】 References to "one embodiment" or "an embodiment" throughout this specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, though they may. Further, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, as will be apparent to those skilled in the art from the disclosure. 【0063】 Similarly, in the description of exemplary embodiments of the invention, it is to be understood that various features of the invention may be grouped together in a single embodiment, figure, or description thereof for the purpose of simplifying the disclosure and aiding in the understanding of one or more aspects of the invention. However, the method of the disclosure is not to be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, aspects of the invention lie in less than all of the features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of the invention. 【0064】 Furthermore, some embodiments described herein include some features included in other embodiments but not others, while combinations of features of different embodiments are within the scope of the invention and are meant to form different embodiments, as will be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments may be used in any combination. 【0065】 Furthermore, some of the embodiments are described herein as a method or a combination of method elements that can be implemented by a processor of a computer system or by other means for performing functions. Accordingly, a processor having instructions necessary to perform such a method or method elements forms means for performing the method or method elements. Further, the elements described herein of the apparatus embodiments are examples of means for performing the functions for the purpose of carrying out the present invention by the elements. 【0066】 In the description provided herein, many specific details are set forth. It should be understood, however, that embodiments of the present invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description. 【0067】 Here, the present invention will be described by way of a detailed description of some embodiments of the present invention. Other embodiments of the present invention may be constructed according to the knowledge of those skilled in the art without departing from the technical teachings of the present invention, and it is clear that the present invention is limited only by the terms of the appended claims. 【0068】 In a first aspect, the present invention relates to a method for purifying a target substance for reuse in the production of a radioisotope. Further, the method can be applied within the framework of the production of radioisotopes, and as a result, the present invention also relates to a method for producing a radioisotope, utilizing the purification of the target substance, and reusing the target substance in the production of the radioisotope. 【0069】 The method for purifying a target substance comprises obtaining a solution of the irradiated target substance, where the solution thus contains at least the target substance and optionally also a radioisotope and optionally impurities. Obtaining a solution of the irradiated target substance can include obtaining an irradiated liquid target or obtaining a solution obtained by dissolving the irradiated target substance irradiated in solid form. In some embodiments, the solution can be a Ra-225 and Ra-226 solution that is stored prior to the Ac-225 purification process. Such a solution can be stored, for example, for two weeks first. The method can also include adding an acid at a predetermined temperature condition, which can be for quantitatively dissolving the target substance and optionally for avoiding coprecipitation of any present radioisotope, in a predetermined amount and concentration. Thus, the temperature at which the acid is added, as well as the amount and concentration of the acid, can be selected such that coprecipitation of the radioisotope and impurities does not occur or occurs substantially not. Alternatively, during or after the addition, conditions can be selected to quantitatively dissolve or redissolve the target substance and optionally avoid or remove coprecipitation of any present radioisotope. The method can also include selectively removing H2O from the solution by evaporation, such as distillation, leaving mainly the acid in the solution, thereby allowing the target substance to precipitate while the acid concentration in the solution increases, thereby reducing or avoiding coprecipitation of any optionally present radioisotope. The method can also include lowering the temperature of the solution after removing the excess H2O to maximize precipitation of the target substance and reduce the solubility of the target substance in the residual liquid. This has the particular advantage that the amount of Ra substance introduced into the actinium purification step is reduced and less Ra needs to be recovered from this process sidestream. Lowering the temperature can include an active cooling step, although it is not necessary for such cooling to be active. 【0070】 The method further includes separating a liquid containing optionally present radioisotopes and impurities from a precipitated target substance, and preparing the precipitated target substance for reuse in the production of radioisotopes. The method may include re-irradiation for the production of radioisotopes and / or storage for new in-growth of Ac-225 from Ra-225. 【0071】 By way of illustration, embodiments of the present invention, without limitation thereto, further standards and optional features are illustrated below in exemplary methods and embodiments. 【0072】 In a first exemplary method, a method for purifying a radium target substance after irradiation for the production of actinium is described. The process is initiated by transferring a liquid target solution having a pH of 1 to 3 and containing Ra-226, Ra-225, Ac-225 and impurities into a precipitation vessel. Thereafter, a rinse solution is transferred and by maximizing the performance of the rinsing process, (substantially) quantitative transfer of Ra-226 to the precipitation vessel is ensured. The liquid target solution can be an irradiated liquid target or can be derived from a solid target dissolved in a solvent to obtain the liquid target solution. Here, the Ra solution is diluted well below the maximum solubility level. Next, an acid such as concentrated HNO3, for example 25 to 50 ml of concentrated HNO3 (68%), is added preferably in a molar amount in which Ac is preferably separated in the filtration process. At this stage, since the HNO3 concentration can be increased to 1 to 3 M HNO3 after this addition, some Ra precipitation may occur. However, when evaporation, for example, starting a distillation process, all Ra is redissolved by the increase in temperature, thus excluding the possibility of coprecipitation of Ac-225 / Ac-227 and impurities upon addition of concentrated HNO3. Alternatively, even excess H2O can be added after addition of concentrated HNO3 until all Ra-226 is in a dissolved state. In other words, conditions are provided for quantitatively dissolving the target substance and for avoiding coprecipitation of any optionally present radioisotopes. Next, H2O is removed from the solution by evaporation at high temperature and reduced pressure, for example by distillation, and collected in a distillate collection flask. During evaporation, for example, during distillation, as the HNO3 concentration increases and the volume decreases, more and more Ra(NO3)2 crystals are formed. However, such slowly controlled crystal formation and growth during temperature fluctuations in the liquid during evaporation, for example during distillation, effectively avoids the inclusion of Ac by coprecipitation. 【0073】 When the evaporation process, e.g., the distillation process, is completed, the reduced pressure is removed, and the boiling process stops immediately. Here, the liquid needs to be cooled to a minimum. The heating jacket needs to be cooled from 70 - 80 °C to, for example, 5 °C. This minimizes the residual solubility of Ra in the concentrated HNO3. 【0074】 After complete cooling, insert the filter dipping tube into the reactor and direct the filter towards the bottom of the round - bottom reaction vessel. The filter dipping tube is connected to a collection container for the actinium fraction, a small buffer container, and a vacuum pump connected to the Rn capture system. The filtration process is carried out. 【0075】 Add 25 - 50 ml of low - temperature concentrated HNO3 (68%) into the reactor with the filter dipping tube still in place, and then remove this additional volume again towards the actinium collection container. This process focuses on removing all Ac from Ra while minimizing additional dissolution of Ra and can be repeated several times while keeping the volume to a minimum. After quantitatively transferring Ac from Ra, remove the filter dipping tube and wash it with H2O to remove all Ra present in the tube. 【0076】 These wash liquids can be, for example, recycled (low in HNO3) distillates or fresh H2O. Since Ra - 226 is more difficult to recover from this side stream, the main focus is on minimizing additional transfer of Ra towards Ac in the concentrated HNO3. Here, the distillate can be used to dilute the concentrated HNO3 containing Ac to appropriate conditions for DGA Ra / Ac separation, typically 2 - 4 M HNO3. 【0077】 After removing the filter dipping tube, restart the evaporation process to remove all residual traces of concentrated HNO3 in the reactor and the H2O / HNO3 separator. By removing the last remaining amount of HNO3, the Ra solubility is maximized, and a minimum amount of acid is transferred, in some cases, to the irradiated liquid target system. 【0078】 Add 120 - 200 ml of fresh H2O to the reaction vessel and restart evaporation, e.g., the distillation process, by heating the jacket and applying a vacuum. This process effectively cleans the walls from residual Ra - 226 by refluxing the H2O. Next, stop the process and use the dip tube to remove the liquid. Fresh H2O can be added to the reactor and the process is repeated until the reactor is effectively purified from residual Ra - 226. 【0079】 Depending on whether Ra - 226+Ra - 225 is sent to the decay storage container for 2 - week internal growth of Ac - 225 or returned to the irradiation process, rinsing is added to or not added to the main Ra solution. In the former case, the rinse solution can be added to the Ra batch that is last milked before returning to irradiation. This strategy closes the loop of Ra - 226 in this precipitation reactor. 【0080】 The volume in the decay tank corresponds to the volume of the liquid target + rinse. By doing so, the process does not distinguish between newly irradiated targets and continuous milking, further simplifying the process. 【0081】 For example, a minimum chemical purity is required to successfully reuse target substances such as Ra. Therefore, in the process used to produce isotopes from target substances by reusing the target substances, it is necessary to avoid or minimize the introduction of organic substances or leaching extractants. The purification method according to the embodiments of the present invention advantageously aids in reducing impurities. Such impurities include, for example, fission products such as photofission process products, products derived from the target substance (e.g., in the case of radium, the generation of stable and / or radioactive Pb, and Po - 210), products derived from encapsulating substances such as Ti, Fe, Ni, Cr, Zr, Nb, or leaching products such as Si, Al, Na, B derived from quartz or silicate, and activation products. 【0082】 In some exemplary embodiments, the reaction vessel is operated under reduced pressure. The reduced pressure can be, for example, in the range of 50 mbar to 200 mbar, for example, in the range of 100 mbar to 200 mbar. In this way, leakage of acid smoke and radon (Rn-220, Rn-222) from the vessel into the hot cell storage container can be avoided. Radon can be filtered and captured at a low flow rate. The leakage of acid smoke and radon can alternatively or additionally be reduced by using a moisture trap column, an Ag-ETS10 column, or a decay tank. In one embodiment, the decay tank can have a volume of 100 liters, for example, pressurized to a maximum of 10 bar, by way of example. By operating the reaction vessel at a pressure of 100 mbar to 200 mbar, the boiling point of the liquid drops to a temperature in the range of 50°C to 70°C. In some embodiments, a pressure sensor is installed between the condenser and the distillate collection container. For example, similar equipment known in a rotary evaporator system can be used. An advantage of embodiments of the present invention is that the equipment used is radiation resistant, and thus the complexity added to the system is nil or near nil. An advantage of embodiments of the present invention is that pressure and pressure differences can be easily measured in a system, for example, a hot cell. 【0083】 In some exemplary embodiments, the temperature for controlling evaporation, i.e., distillation, can be controlled using a liquid heating / cooling system. An advantage of embodiments of the present invention is that it does not require electrical heating equipment in direct contact with the reaction vessel. The liquid heating / cooling system can be, for example, a double-wall heating / cooling system, for example, a double-wall heating / cooling jacket. Such a double-wall heating / cooling system can be, for example, water-based. Since the double-wall heating system can operate, for example, at 80°C, the boiling temperature of the liquid typically drops to a temperature in the range of 50°C to 70°C, and thus, since temperature control with water is fully possible, the system can be advantageously used when operating the reaction vessel at low pressure. The double-wall heating / cooling jacket using water can operate, for example, at 80°C, and thus the above conditions can advantageously provide a significant temperature difference such that the evaporation process can be controlled and / or accelerated. 【0084】 The double-wall heating / cooling system can be connected to a primary liquid circuit equipped with a circulation pump. An advantage of embodiments of the present invention is that when using water, and in the case of a problematic double-wall heating system, the radium concentration in the water decreases, which enables easier recovery (e.g., compared to heating / cooling using silicone oil). 【0085】 An advantage of some embodiments is that they do not require an electric heating jacket and a thermocouple for controlling evaporation, e.g., distillation, for precipitation. Using an electric heating jacket and a thermocouple makes the isotope production system and / or the target substance purification system more complex. The possibility of avoiding the electric heating jacket and / or the thermocouple makes the control / use of such systems easier. 【0086】 An advantage of embodiments of the present invention is that, for example, before filtration, forced cooling can be utilized to reduce the concentration of residual target substances (e.g., Ra-226), and / or speed up the cooling process after evaporation, e.g., distillation. 【0087】 An advantage of embodiments of the present invention is that precipitation after Ra-226 can be avoided by filtering a liquid containing Ac-225 at a temperature lower than room temperature. 【0088】 In embodiments according to the present invention, a stirring device can be used to perform a stirring action inside a reaction vessel, e.g., at the lower part of the reaction vessel. In one embodiment, such a stirring device can be a magnetic stirrer. The magnetic stirrer can be, in one embodiment, an elliptical stirrer covered with borosilicate instead of PTFE, for example. Advantageously, the stirrer can be used in a round-bottom reaction vessel, but the embodiments are not limited thereto. By using the stirring device, the bubble size of the boiling process, which may become intense at low pressure, can be reduced, and the formation of gas can be concentrated in the center of the reactor. 【0089】 According to an embodiment of the present invention, the parameters of evaporation, for example, distillation, are adjusted such that HNO3 remains almost completely in the solution, and when reaching the azeotropic mixture of concentrated HNO3, the evaporation process significantly decelerates. This enhances safety and reduces the possibility of unnecessarily evaporating the liquid to dryness. In some embodiments, the Vigreux column between the reaction vessel and the distillation bridge is efficient in separating HNO3 from H2O and can relatively easily reach the maximum practical concentration of HNO3 of 68%. Beyond this azeotropic point, typically, brown NOx fumes are seen in the solution, which should be avoided. The distillate remains relatively free of HNO3 unless the pressure drops significantly. 【0090】 In a second aspect, the present invention relates to a system for the purification of a target substance. The system comprises a reaction vessel, an inlet for a solution of the irradiated target substance, and an inlet for adding an acid. The reaction vessel is an evaporation device, for example, a distillation device, which removes H2O from the solution of the irradiated target substance, leaving mainly an acid (e.g., HNO3) in the solution, thereby enabling the target substance to precipitate while the acid concentration in the solution increases, thereby reducing or avoiding coprecipitation of any optionally present radioisotopes and impurities. Further, it comprises filtration means for separating a liquid containing any optionally present radioisotopes from the precipitated target substance. The system may also comprise an inlet for adding a solvent, for example, H2O. The system may also comprise a heating / cooling system for controlling the temperature of the reaction vessel by heating and / or cooling. The heating / cooling system may be a double-wall heating / cooling jacket. The system may also comprise an air pump system for inducing a reduced pressure within the reaction vessel. Further, the system may comprise a pressure sensor for sensing the pressure within the reaction vessel. According to some embodiments, the system may also comprise a controller for controlling a system for performing the method as described in the first aspect. The system may also comprise a radon removal device for removing radon. Further features and components may be provided for performing the functionality as described in the first aspect of the present invention. By way of illustration, embodiments of the present invention, without being limited thereto, may be as shown in FIG. 1 for different components. 【0091】 In a further aspect, the present invention also relates to the use of the purification method according to the first aspect for producing a target substance that can be reused again for irradiation for the production of radioisotopes.

Claims

[Claim 1] A method for purifying target material for reuse in the production of radioactive isotopes, The method described above is A step of obtaining a solution of an irradiated target substance, wherein the solution thus contains at least the target substance, optionally also containing radioactive isotopes, and optionally containing impurities, and thereafter, A step of adding an acid in a predetermined amount and concentration to provide conditions for quantitatively dissolving the target substance and for avoiding coprecipitation of optionally present radioactive isotopes, By evaporation, H ２ A step of selectively removing O, leaving mainly the acid in the solution, thereby allowing the target substance to precipitate while the acid concentration in the solution increases, thereby reducing or avoiding the coprecipitation of the optionally present radioactive isotope, Excessive H ２ After removing O, the temperature of the solution is lowered to maximize the precipitation of the target substance and reduce the solubility of the target substance in the remaining solution. The steps include separating the liquid containing the optionally present radioactive isotope from the precipitated target substance, The steps include preparing the precipitated target material for reuse in the production of radioactive isotopes, Includes, The irradiated target material contains Ra-226, optionally containing Ra-225 and Ac-225, and the acid is HNO ３ Characterized by, method. [Claim 2] Obtaining a solution containing the irradiated target substance is possible. A step of obtaining a solution irradiated with a target substance; or A step of obtaining a solution of an irradiated target substance, wherein the irradiated target substance was irradiated while in a solid state; The method according to claim 1, including the method described in claim 1. [Claim 3] The method according to claim 1 or 2, further comprising obtaining a solution of the irradiated target material, for example, obtaining a sub-process stream in solid or liquid form, before, simultaneously with, or after the transfer of the main target material, a rinsing material used to rinse the target capsule / container, a rinsing material used to rinse the transfer piping, a smaller amount of the target material and radioisotopes or mixtures thereof. [Claim 4] The aforementioned HNO ３ The method according to claim 1 or 2, wherein the substance is present at a concentration of 65% to 68% when added to the reaction vessel. [Claim 5] The method according to claim 1 or 2, wherein one or more of the steps of the method are performed at a pressure lower than atmospheric pressure. [Claim 6] The method according to claim 1 or 2, wherein the heating or cooling of the solution is carried out using a circulating fluid within the double wall of a double-walled reaction vessel, and / or the method is applied in a closed circuit that is heated and / or cooled through a heat exchanger. [Claim 7] The method according to claim 1 or 2, wherein the method includes visually tracking the process using a transparent reaction vessel. [Claim 8] The method according to claim 1 or 2, further comprising, for example, stirring the solution using magnetic stirring. [Claim 9] The method according to claim 1 or 2, wherein the method is applied to a rotary evaporator system. [Claim 10] Excessive H ２ The method according to claim 1 or 2, wherein, after removing oxygen, the temperature is lowered to below room temperature but above the freezing point of the liquid. [Claim 11] The method according to claim 1 or 2, wherein the solution is filtered using a filtrate collection container and a vacuum pump, or optionally an immersion filter connected to a buffer container. [Claim 12] The method according to claim 1 or 2, wherein preparing the precipitated target substance comprises washing the precipitate with acid after the initial filtration and optionally repeating the filtration process. [Claim 13] A system for purifying target substances, The aforementioned system Reaction vessel and An inlet configured to introduce a solution of an irradiated target substance, wherein the irradiated target substance includes Ra-226 and optionally Ra-225 and Ac-225, An inlet configured for adding HNO3 acid, Equipped with, The reaction vessel receives H from the irradiated target substance solution. ２ A system comprising: an evaporator for removing oxygen and leaving the acid mainly in the solution, thereby allowing the target substance to precipitate while the acid concentration in the solution increases, thereby reducing or avoiding the coprecipitation of optionally present radioactive isotopes; and a filtration means for separating the liquid containing the optionally present radioactive isotopes from the precipitated target substance. [Claim 14] The system includes a heating / cooling system for controlling the temperature of the reaction vessel by heating and / or cooling, and / or a pumping system for inducing a pressure below atmospheric pressure in the reaction vessel. The system according to claim 13, further comprising one or more of a pressure sensor for measuring the pressure inside the reaction vessel, and / or a radon removal device for removing radon. [Claim 15] The system according to claim 13, further comprising a controller for controlling the system in order to carry out the method according to claim 1.

Images