Purification of targets for radioisotope production

Abstract

A method for purifying a target for reuse in the production of radioisotopes is disclosed. The method comprises obtaining an irradiated target solution comprising Ra-226 and optionally Ra-225 and Ac-225, and subsequently adding a predetermined amount of an acid, HNO3, and providing conditions for quantitatively dissolving the target and avoiding co-precipitation of optionally present radioisotopes. The method further includes selectively removing H2O from the solution by distillation, leaving the acid predominantly within the solution, thereby precipitating the target while increasing the acid concentration in the solution, thereby reducing or avoiding co-precipitation of optionally present radioisotopes and impurities. After removing the excess H2O, the method further includes reducing the temperature of the solution to maximize precipitation of the target, and reducing the solubility of the target in the remaining liquid, separating the liquid containing the optionally present radioisotopes from the precipitated target, and preparing the precipitated target for reuse in the production of radioisotopes, the radioisotope is produced by repeating the irradiation.

Description

Technical Field

[0001] The present invention relates to the field of radioisotopes. More specifically, the present invention relates to methods and systems for purifying irradiated targets for reuse in the production of radioisotopes. Background of the Invention

[0003] Generally, for the production of radioisotopes, solid targets are used in the most advanced systems due to their high yields, since with solid targets a large density of the parent nuclide (from which the radioisotope is produced) is easily achievable.

[0004] For liquid targets, most parent nuclide compounds have limited solubility in water (usually used as the liquid solvent) at room temperature. 1 / 2 : 1600) can be used as a basic chemical for the production of Ac-225 (T 1 / 2 : 10 days) of the radioactive isotope Ra-225 (T 1 / 2 : 14.8 days) provides the parent nuclide, but the solubility of the salt of Ra-226 in water is limited. For example, the solubility of the radium nitrate salt Ra(NO3)2 is 13.9 g / 100 g H2O at 20°C. Recently, however, interest in liquid targets has increased as methods have been found to overcome the problem of limited solubility.

[0005] In both the case of solid and liquid targets, it is necessary to separate the radioisotope from the target, which can usually be accomplished by solid phase extraction in a separation column.

[0006] Some target materials that can be used to produce parent nuclides for radioisotope production have limited stocks available worldwide. In particular, in these cases, such as but not limited to the case of Ra-226, it is useful to reuse the target material.

[0007] The reuse of target materials is mentioned in the international patent application WO 2020 / 260210, which describes a method for producing actinium based on a photonuclear route, namely irradiating a radium-226 liquid target and using a closed-loop system to irradiate (after actinium separation) the radium-226 liquid target solution.

[0008] The purification of actinium during the production of actinium radioisotopes is described in international patent application WO2020 / 148316.

[0009] Nevertheless, there is still a need for good purification methods and systems to be able to reuse the targets for further irradiation in the production of radioisotopes. Summary of the invention

[0010] It is an object of the present invention to provide a method and system for purifying irradiated targets for reuse in the production of radioisotopes.

[0011] 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.

[0012] An advantage of embodiments of the present invention is that systems and methods are provided for reusing irradiated targets, whether the targets were in solid or liquid form when irradiated.

[0013] An advantage of embodiments of the present invention is that the target material can be reused during the production of radioisotopes, thereby increasing the yield of radioisotopes for a given amount of target material. It is also worth noting that, for example, it is not possible to produce non-carrier added (NCA) AC-225 (formed by decay of Ra-225) via the first radium / actinium separation step because of the small amount of Ac-227 (T 1 / 2 : 21.8 years) is also formed in the photonuclide production pathway by neutron capture of the parent nuclide Ra-226. Therefore, taking radium / actinium-based production as an example, it is not desirable to operate a liquid radium target in a closed-loop system when NCA Ac-225 is the primary target of the production process. After the first efficient separation of radium (224+225+226) isotopes and actinium (225+227) isotopes, radium must be stored to allow fresh Ac-225 to grow inwardly by the decay of Ra-225, which ultimately generates NCA Ac-225 after the second Ra / Ac separation step. This therefore increases the amount of parent nuclide Ra-226 required to produce Ac-225 and emphasizes the importance of a good recovery strategy for Ra-226.

[0014] An advantage of embodiments of the present invention is that, due to the provided purification method, problems due to washing (eg dilution of the target) and uncertainties associated with the pH of the irradiated solution can be overcome, thereby enabling the reuse of the target material.

[0015] An advantage of embodiments of the present invention is that both inorganic and organic contaminants can be removed from a target material.

[0016] An advantage of embodiments of the invention is that these allow obtaining the required minimum chemical purity of the target material, such as Ra, to be recovered and irradiated again.

[0017] An advantage of embodiments of the present invention is that the complexity caused by the purification method according to embodiments of the present invention is limited.

[0018] The above object is achieved by the method and device described in the present invention.

[0019] One aspect of the present invention relates to a method for purifying a target material for reuse in the production of radioisotopes, the method comprising:

[0020] - obtaining a solution of irradiated targets, said solution thus comprising at least targets containing Ra-226 and optionally also the radioactive isotopes Ra-225 and Ac-225 and optionally impurities,

[0021] Then,

[0022] - adding HNO3 acid in a predetermined amount and concentration and providing conditions for quantitatively dissolving the target material and avoiding co-precipitation of optionally present radioisotopes and / or impurities,

[0023] - selectively removing H2O from the solution by evaporation, leaving the acid mainly in solution, thereby causing the target to precipitate, while the acid concentration in the solution increases, thereby reducing or avoiding co-precipitation of any radioisotopes present,

[0024] - after removing the excess H2O, lowering the temperature of the solution to maximize the precipitation of the target and reduce the solubility of the target in the remaining liquid,

[0025] - separating the liquid containing the optional radioisotopes and / or impurities from the precipitated target material, and

[0026] - Preparation of precipitated targets for reuse in the production of radioisotopes.

[0027] The latter may for example be the production of radioisotopes by re-irradiation or may for example involve storage for the ingrowth of new Ac-225.

[0028] Evaporation can refer to the selective removal of H2O by bringing it into the gas phase. In some embodiments, evaporation can be distillation.

[0029] Lowering the temperature may include an active cooling step, but an active cooling step is not necessary. Lowering the temperature means that the temperature at which evaporation is performed is higher than the temperature at which liquid separation is performed.

[0030] An advantage of an embodiment of the present invention is that at least one concentration step is performed, which in an embodiment of the present invention is performed by an evaporation process, such as a distillation process.

[0031] For example, in the case of producing actinium-225 from radium-226 targets, Ac-225 is separated from radium every two weeks on average. This facilitates slow evaporation (e.g., distillation processes), which can focus on minimizing the loss of Ra-226 and allow for rapid processing of Ac-225 after separation.

[0032] The acid (e.g. HNO3) can be added in a concentration of 1% to 100%, for example, with an upper range of, for example, 90%, for example, 80%, for example, 75%, for example, 70%, for example, 69%, and a lower range of, for example, 10%, for example, 25%, for example, 40%. For example, in the case of using a Ra-226 target to produce the Ac-225 isotope, the acid can be HNO3. It is worth noting that the method can be used to recover the target even if the separation between the target and the radioactive isotope produced during the earlier irradiation is carried out in a different manner. For example, in the case where the target is Ra-226, the method can also be used when the amounts of Ra-225 and Ac-225 are small or completely absent, and the process is mainly to obtain a pure and concentrated form of Ra-226 without the presence of inorganic or organic impurities or a large amount of HNO3.

[0033] It is worth noting that the purification method can be applied to targets that have just been irradiated or to targets that have undergone multiple extractions.

[0034] Obtaining a solution comprising an irradiated target material may comprise obtaining an irradiated solution of the target material, or obtaining a solution of the irradiated target material, wherein the irradiated target material is irradiated while in solid form. An advantage of embodiments of the present invention is that these embodiments provide purification methods that can be used for both solid irradiated targets and liquid irradiated targets.

[0035] The target material (whether in liquid or solid form) can be irradiated by photons, neutrons or charged particles (e.g., protons or deuterons). In an advantageous embodiment, the radium-226 target material is irradiated by photons or neutrons in liquid or solid form to produce actinium radioisotopes by producing radium-225.

[0036] Obtaining a solution of irradiated target material may also include obtaining an aqueous solution or solid, such as a flushing material for flushing a target capsule / container, a flushing material for flushing a transfer tube, a side process stream containing a small amount of target material and radioactive isotopes or a mixture thereof, in solid or liquid form, before, simultaneously with, or after the main target material transfer.

[0037] In some embodiments, the method can be used primarily to obtain Ra-226 in a pure and concentrated form without the presence of impurities or significant amounts of HNO3.

[0038] The irradiated target may include Ra-226 and optionally Ra-225 and Ac-225, wherein the acid is HNO3 and wherein when the precipitation of radium is performed, the HNO3 is present in a concentration of 65% to 68%. An advantage of embodiments of the present invention is that by using a concentration of 65% to 68% for precipitation, the need to remove more H2O during the continuous evaporation process (which would normally occur when adding lower concentrations) can be avoided, or the increase of corrosive vapors (HNO3, NOX) (which would normally occur when adding higher concentrations) can be avoided.

[0039] One or more process steps may be carried out under reduced pressure (i.e., pressure below atmospheric pressure). Reduced pressure may be an operating pressure in the range of 50 mbar to 200 mbar. The latter may selectively capture volatile isotopes and / or reduce the spread of corrosive fumes. Reducing the pressure may advantageously result in a reduction in the boiling point of the solution.

[0040] The solution may be heated or cooled using circulating liquid in the double walls of a double-walled (jacketed) reactor vessel.

[0041] The method may include using a transparent reactor vessel to visually track the process.

[0042] The solution used for heating / cooling may be primarily H2O.

[0043] The method may further comprise stirring the solution, for example using magnetic stirring.An advantage of embodiments of the present invention is that stirring may improve the evaporation or boiling process during an evaporation process, such as distillation.

[0044] The method can be applied in a rotary evaporator system. An advantage of the embodiments of the present invention is that the surface used for evaporation is actively increased, thereby improving the efficiency of the method.

[0045] The method can be applied in a closed loop with heating and / or cooling by a heat exchanger.An advantage of embodiments of the present invention is that by using a closed loop, when using a double wall reactor vessel, the target material can be recovered from the liquid in case of a double wall rupture.

[0046] After removing excess H2O, the temperature can be dropped to below room temperature but above the freezing temperature of the liquid.

[0047] The solution may be filtered using an immersed filter connected to a filtrate collection vessel, an optional buffer vessel, and a vacuum pump.

[0048] Preparing the precipitated target material may include washing the precipitate with concentrated acid after initial filtration and optionally repeating the filtration process. By washing the precipitate with acid after initial filtration and optionally repeating the filtration process, the recovery of the radioisotope can be improved while minimizing the dissolution of the target material.

[0049] After the final filtration, the target precipitate can be dried to remove residual acid, which can further increase the solubility of the target in H2O.

[0050] The target can be recovered by adding H2O to completely dissolve the target. .

[0051] In some embodiments, the solution may be heated to clean the reactor vessel where the process occurs by condensation and dissolution of residual target solids.

[0052] The solution may be refluxed.

[0053] In one aspect, the present invention also relates to a system for purifying a target material, the system comprising:

[0054] Reactor vessel,

[0055] inlet for the solution of irradiated target material,

[0056] Acid inlet,

[0057] The reactor vessel comprises an evaporation device (e.g. a distillation device) for removing H2O from the solution of the irradiated target material, leaving the acid mainly in the solution, thereby precipitating the target material while the acid concentration in the solution increases, thereby reducing or avoiding co-precipitation of the optionally present radioactive isotope, and

[0058] The system further comprises a filtering device for separating the liquid containing the optional radioactive isotope from the precipitated target material.

[0059] The irradiated target may include Ra-226 and optionally Ra-225 and Ac-225. The acid inlet may be an inlet for HNO3.

[0060] The system may include a heating / cooling system for controlling the temperature of the reactor 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 main fluid loop having a liquid circulation pumping system.

[0061] The system may include an air extraction system for creating a reduced pressure in the reactor vessel.

[0062] The system may include a pressure sensor for measuring the pressure in the reactor vessel.

[0063] The system may also include a controller for controlling the system (eg, an air extraction system, a heating / cooling system, and a system for controlling the amount of acid added) to perform the method as described above.

[0064] The system may also include a radon removal device for removing radon.

[0065] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate and with features of other dependent claims and not only where explicitly set out in a claim.

[0066] While the apparatus in this field is continually improving, changing and developing, the concepts of the present invention are believed to represent a substantial novel improvement involving a change in existing practice resulting in the provision of a more efficient, more stable and more reliable apparatus of this nature.

[0067] The above and other characteristics, features and advantages of the present invention will become apparent in the following detailed description in conjunction with the accompanying drawings, which illustrate the principles of the present invention by way of example. This description is for illustrative purposes only and does not limit the scope of the present invention. The reference figures cited below refer to the accompanying drawings.

[0068] BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 A system for purifying a target material according to an implementation method of the present invention is shown.

[0070] In different drawings, the same reference signs identify the same or similar elements. DETAILED DESCRIPTION

[0071] The present invention will be described in conjunction with specific embodiments and with reference to certain drawings, but the invention is not limited thereto, only by the claims. The drawings described are only schematic and non-limiting. In the drawings, the dimensions of some elements may be exaggerated and not drawn to scale for illustrative purposes. The dimensions and relative dimensions do not correspond to actual reductions in the practice of the invention.

[0072] In addition, the terms first, second, third, etc. in the specification and claims are used to distinguish similar elements and are not necessarily used to describe a sequence in time, space, hierarchy, or any other manner. It should be understood that the terms used in this way are interchangeable under appropriate circumstances, and the embodiments of the invention described herein are capable of operating in other sequences than those described or illustrated herein.

[0073] In addition, in the specification and claims, the terms top, bottom, above, below, etc. are used for descriptive purposes and not necessarily for describing relative positions. It should be understood that the terms so used are interchangeable where appropriate, and the embodiments described in the present invention are capable of operating in other orientations than those described or illustrated herein.

[0074] It should be noted that the term "comprising" used in the claims should not be interpreted as being limited to the parts listed thereafter, and it does not exclude other elements or steps. Therefore, it should be understood to indicate the presence of the features, wholes, steps or components, but this does not exclude the presence or addition of one or more other features, wholes, steps or components or combinations thereof. Therefore, the term "comprising" covers the case where only the features are present, as well as the case where these features and one or more other features are present. Therefore, according to the present invention, as an embodiment, the word "comprising" also includes the case where no other components are present. Therefore, the scope of the expression "a device comprising components A and B" should not be understood to limit the device to be composed only of components A and B. It means that for the present invention, the relevant components of the device are only A and B.

[0075] Also, it is important to note that the term “ Join " should not be interpreted as being limited to only direct connections. The terms "coupled" and "connected," along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Thus, the scope of the expression "device A coupled to device B" should not be limited to devices or systems 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 that includes other devices or components. "Coupled" may mean that two or more elements are either in direct physical contact or in electrical contact, or that two or more elements are not in direct contact with each other, but still cooperate or interact with each other.

[0076] References to "one embodiment" or "an embodiment" in the specification mean that the specific features, structures, or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places in the specification do not necessarily all refer to the same embodiment, but may all refer to the same embodiment. In addition, specific features, structures, or characteristics may be combined in one or more embodiments in any suitable manner, which will be apparent to those of ordinary skill in the art.

[0077] Similarly, it should be understood that in the description of exemplary embodiments of the invention, different features of the invention are sometimes combined into a single embodiment, figure, or description thereof, in order to simplify the disclosure and aid in understanding one or more different aspects of the invention. However, the method in the present disclosure should not be interpreted as reflecting the following intention: the claimed invention requires more features than those expressly recited in the claims. And, as reflected in the appended claims, inventive aspects may include less than all the features of a single embodiment disclosed above. Therefore, the appended claims are expressly incorporated into this detailed description, and each claim itself represents a separate embodiment of the invention.

[0078] In addition, when some embodiments described herein include some but not other features included in other embodiments, the combination of features of different embodiments should be intended to be included within the scope of the present invention and form different embodiments, which should be understood by those skilled in the art. For example, in the attached claims, any embodiment claimed for protection can be used in any combination.

[0079] In addition, some embodiments are described herein as a method or a combination of method elements implemented by a processor of a computer system or by other means of implementing a function. Therefore, a processor with instructions required for implementing the method or method elements forms a device for carrying out the method or method elements. In addition, the elements of the device embodiments described herein are examples of devices for performing functions, and the functions are carried out by elements for implementing the purpose of the present invention.

[0080] In the description provided herein, many details are set forth. However, it should be understood that embodiments of the present invention may be implemented without these specific details. In other cases, well-known methods, structures, and techniques are not described in detail in order not to obscure the understanding of this description.

[0081] The present invention is now described by a detailed description of several embodiments of the present invention. It is obvious that other embodiments of the present invention can be constructed according to the knowledge of those skilled in the art without departing from the technical teachings of the present invention, and the present invention is limited only by the appended claims.

[0082] In a first aspect, the present invention relates to a method for purifying a target material for reuse in the production of a radioisotope. The method can also be applied in the framework of the production of a radioisotope, and therefore the present invention also relates to a method for producing a radioisotope, which method utilizes the purification of a target material and reuses the target material in the production of a radioisotope.

[0083] The method for purifying the target material includes obtaining a solution of the irradiated target material, so that the solution contains at least the target material and optionally also contains a radioactive isotope and optional impurities. Obtaining a solution of the irradiated target material may include obtaining a liquid target that has been irradiated or obtaining a solution obtained by dissolving the irradiated target material irradiated in solid form. In some embodiments, the solution may be a Ra-225 and Ra-226 solution stored before the Ac-225 purification process. Such a solution may be stored for two weeks, for example. The method also includes subsequently adding a predetermined amount and concentration of acid, which may be added under predetermined temperature conditions to quantitatively dissolve the target material and avoid co-precipitation of the optionally present radioactive isotope. Therefore, the temperature, amount and concentration of the added acid may be selected so that co-precipitation of the radioactive isotope and the impurity does not occur or substantially does not occur. Alternatively, during or after the addition, conditions may be selected to quantitatively dissolve or redissolve the target material and avoid or remove co-precipitation of the optionally present radioactive isotope. The method also includes selectively removing H2O from the solution by evaporation (e.g., distillation), leaving the acid primarily in solution, thereby precipitating the target material while increasing the acid concentration in the solution to reduce or avoid co-precipitation of the radioisotope optionally present. The method also includes reducing the temperature of the solution after removing excess H2O to maximize precipitation of the target material and reduce the solubility of the target material in the remaining liquid. This has the particular advantage of reducing the amount of Ra material introduced into the actinium purification step and requiring less Ra to be recovered from the process side stream. Reducing the temperature may include an active cooling step, although it is not required that such cooling be active.

[0084] The method also includes separating the liquid containing the optional radioisotope and impurities from the precipitated target material and preparing the precipitated target material for reuse in radioisotope production. The method may include repeated irradiation to produce radioisotopes and / or storage for ingrowth of new Ac-225 from Ra-225.

[0085] By way of illustration, embodiments of the invention are not limited thereto, and further standard and optional features will be described below in exemplary methods and embodiments.

[0086] In a first exemplary method, a method for purifying a radium target after irradiation to produce actinium is described. The process starts by transferring a liquid target solution having a pH between 1 and 3 and containing Ra-226, Ra-225, Ac-225 and impurities to a precipitation vessel. Subsequently, a rinse solution is transferred, which ensures a (near) quantitative transfer of Ra-226 to the precipitation vessel by maximizing the performance of the rinse process. The liquid target solution can be an irradiated liquid target, or can be derived from an irradiated solid target dissolved in a solvent to obtain a liquid target solution. Now, the Ra solution is diluted to well below the maximum solubility point. Then, an acid (e.g. concentrated HNO3) is added, for example 25-50 ml of concentrated HNO3 (68%) is added, preferably in a molar amount that preferably separates Ac during the filtration process. At this point, some Ra precipitation may occur, because the concentration of HNO3 will increase to 1-3M HNO3 after addition. However, once evaporation (e.g., a distillation process) begins, all Ra is dissolved again by the increase in temperature, thus eliminating the chance of co-precipitation of Ac-225 / Ac-227 and impurities when concentrated HNO3 is added. Alternatively, it is still possible to add even an excess of H2O to a degree that all Ra-226 is dissolved after the addition of concentrated HNO3. In other words, conditions are provided for quantitatively dissolving the target material and avoiding co-precipitation of optionally present radioactive isotopes. Next, H2O is removed from the solution by evaporation (e.g., distillation at high temperature and reduced pressure) and collected in a distillate collection bottle. During the evaporation (e.g., distillation), the concentration of HNO3 rises and the volume decreases, thereby forming more and more Ra(NO3)2 crystals. However, the inclusion of Ac by co-precipitation is effectively avoided by the slow and controlled formation and growth of the crystals during the evaporation (e.g., distillation) and the temperature changes inside the liquid.

[0087] When the evaporation process (e.g. distillation process) is complete, the reduced pressure is removed, the boiling process stops immediately, and the liquid should now be cooled to a minimum. The heating jacket should be cooled from 70-80° C. to, for example, 5° C. This will minimize the residual solubility of Ra in concentrated HNO3.

[0088] After complete cooling, the filter dip tube was inserted into the reactor and the filter was guided to the bottom of the round bottom reactor vessel. The filter dip tube was connected to a collection vessel for the actinium fraction, a small buffer vessel and a vacuum pump connected to the Rn capture system. The filtration process was performed.

[0089] With the filter dip tube still in place, 25-50 ml of cold concentrated HNO3 (68%) is added to the reactor and this additional volume is again transferred to the actinium collection vessel. This process focuses on removing all Ac from the Ra while minimizing additional dissolution of Ra and can be repeated multiple times while keeping the volume to a minimum. After quantitative transfer of Ac from the Ra, the filter dip tube is removed and washed with H2O to remove all Ra present therein.

[0090] These washing solutions can be, for example, recycled distillate (low in HNO3) or fresh H2O. The main focus is to minimize the additional transfer of Ra to Ac in concentrated HNO3, since it is more difficult to recover Ra-226 from this side stream. Now, the distillate can be used to dilute the concentrated HNO3 containing Ac to conditions suitable for DGA Ra / Ac separation, typically 2-4M HNO3.

[0091] After removing the filter dip tube, the evaporation process is started again to remove any remaining traces of concentrated HNO3 in the reactor and H2O / HNO3 separator. By removing the last amount of HNO3, the solubility of Ra is maximized and the possible transfer of acid into the irradiated liquid target system is minimized.

[0092] 120-200 ml of fresh H2O is added to the reactor vessel and the evaporation (e.g., distillation) process is started again by heating the jacket and applying reduced pressure. This process effectively removes the residual Ra-226 on the walls by refluxing the H2O. The process is then stopped and the liquid is removed using a dip tube. Fresh H2O can be added to the reactor and the process repeated until any residual Ra-226 in the reactor is effectively purified.

[0093] Depending on whether the Ra-226+Ra-225 is sent to a decay storage vessel for two weeks of Ac-225 ingrowth or is sent back to the irradiation process, the rinse solution is added or not to the main Ra solution. In the first case, the rinse solution can be added to the Ra batch, which is extracted one last time before being sent back to the irradiation process. This strategy closes the cycle of Ra-226 in this precipitation reactor.

[0094] The volume in the decay tank is comparable to the volume of the liquid target + rinse fluid. By doing so, the process will not differentiate between a just irradiated target and a continuously extracted target, further simplifying the process.

[0095] In order to successfully reuse the target material (e.g., Ra), a minimum chemical purity is required. Therefore, the process used in the method of producing isotopes from the target material by reusing the target material should avoid or minimize the introduction of organic matter or leaching extracts. The purification method according to an embodiment of the present invention is conducive to helping reduce impurities. Such impurities include, for example, fission products (e.g., products of photo-fission processes), products derived from the target material (e.g., in the case of radium, stable and / or radioactive Pb and Po-210 appear), leached products [e.g., products derived from packaging materials such as Ti, Fe, Ni, Cr, Zr, Nb or Si, Al, Na, B (derived from quartz or borosilicates, etc.)], activation products, etc.

[0096] In some exemplary embodiments, the reactor vessel is operated under reduced pressure. The reduced pressure may be, for example, in the range of 50 mbar to 200 mbar, for example, in the range of 100 mbar to 200 mbar. This can avoid leakage of acidic fumes and radon (Rn-220, Rn-222) from the container into the hot chamber containment. Radon can be filtered and captured at low flow rates. Leakage of acidic fumes and radon can be reduced alternatively or additionally using a moisture capture column, Ag-ETS10 column or by using a decay tank. In one embodiment, the volume of the decay tank may be, for example, 100 liters, and the maximum pressure may be, for example, 10 bar. The reactor vessel is operated under a pressure of 100 mbar to 200 mbar, and the boiling point of the liquid is reduced 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. A similar device known to, for example, a rotary evaporator system can be used. An advantage of an embodiment of the present invention is that the device used is radiation-resistant and therefore hardly increases the complexity of the system. An advantage of embodiments of the present invention is that pressure and pressure differences in a system, such as a thermal cell, can be easily measured.

[0097] In some exemplary embodiments, a liquid-based heating / cooling system can be used to control the temperature for controlling evaporation (i.e., distillation). An advantage of embodiments of the present invention is that an electric heating device that is in direct contact with the reactor vessel is not required. A liquid-based heating / cooling system can, for example, be a double-walled heating / cooling system, such as a double-walled heating / cooling jacket. Such a double-walled heating / cooling system can, for example, be water-based. Since the double-walled heating system can be operated at, for example, 80°C, the system can be advantageously used when the reactor vessel is operated under reduced pressure, and since the boiling temperature of the liquid is typically reduced to a temperature in the range of 50°C to 70°C, it is entirely possible to control the temperature with water. Since a double-walled heating / cooling jacket with water can be operated at, for example, 80°C, the above conditions can advantageously provide a significant temperature difference, thereby making it possible to control and / or accelerate the evaporation process.

[0098] The double wall heating / cooling system can be connected to the main liquid loop with a circulation pump. An advantage of embodiments of the present invention is that in case of use of water and in case of failure of the double wall heating system, the radium will be diluted in the water, but this will make recovery easier (compared to heating / cooling using silicone oil, for example).

[0099] An advantage of some embodiments is that electrical heating jackets and thermocouples are not required to control evaporation (e.g., distillation for precipitation). Since the use of electrical heating jackets and the use of thermocouples increase the complexity of isotope production systems and / or target purification systems, the possibility of avoiding electrical heating jackets and / or thermocouples makes such systems easier to control / use.

[0100] An advantage of embodiments of the present invention is that they can utilize forced cooling (eg, prior to filtration) to reduce the concentration of residual target material (eg, Ra-226), and / or accelerate the cooling process after evaporation (eg, distillation).

[0101] An advantage of embodiments of the present invention is that subsequent precipitation of Ra-226 can be avoided by filtering the liquid containing Ac-225 at a temperature lower than room temperature.

[0102] In an embodiment according to the present invention, a stirring device can be used to perform a stirring action in a reactor vessel, such as at the bottom of a reactor vessel. In one embodiment, such a stirring device can be a magnetic stirrer. In one embodiment, the magnetic stirrer can be an elliptical stirrer, such as coated with borosilicate instead of PTFE. The stirrer can be advantageously used in a round bottom reactor vessel, although embodiments are not limited thereto. By using a stirring device, the bubble size of the boiling process can be reduced (which may be very violent at low pressures), and the formation of gas can be concentrated in the middle of the reactor.

[0103] According to an embodiment of the present invention, the parameters of evaporation (e.g., distillation) are adjusted to HNO3 to a degree that is almost completely retained in the solution, and when concentrated HNO3 azeotropes are reached, the evaporation process can slow down a lot. This improves safety and reduces the chance of accidental evaporation of liquid to dryness. In some embodiments, the Weiss column between the reactor vessel and the distillation bridge can effectively separate HNO3 from H2O, and the maximum practical concentration of 68% HNO3 can be reached relatively easily. When higher than the azeotropic point, brown NOX fumes will generally appear in the solution, which needs to be avoided. Unless the pressure is significantly reduced, the distillate is relatively free of HNO3.

[0104] In a second aspect, the present invention relates to a system for purifying a target material. The system includes a reactor vessel, an inlet for an irradiated target solution, and an inlet for adding an acid. The reactor vessel includes an evaporation device (e.g., a distillation device) for removing H2O from the irradiated target solution, leaving the acid (e.g., HNO3) mainly in the solution, thereby precipitating the target material, while increasing the acid concentration in the solution, thereby reducing or avoiding the co-precipitation of the optional radioactive isotope and impurities. It also includes a filtering device for separating a liquid containing an optional radioactive isotope from the precipitated target material. The system may also include an inlet for adding a solvent (e.g., H2O). The system may also include a heating / cooling system for controlling the temperature of the reactor vessel by heating and / or cooling. The heating / cooling system may be a double-walled heating / cooling jacket. The system may also include an exhaust system for generating a reduced pressure in the reactor vessel. The system may further include a pressure sensor for sensing the pressure in the reactor vessel. According to some embodiments, the system may also include a controller for controlling a system for performing the method as described in the first aspect. The system may also include a radon removal device for removing radon. Additional features and components may be provided to perform the functions described in the first aspect of the present invention. By way of illustration, the embodiments of the present invention are not limited thereto, and different components may be as follows Figure 1 as shown in .

[0105] In another aspect, the invention also relates to the use of the purification method according to the first aspect for producing a target material which can be used again for irradiation to produce radioisotopes.

Claims

1. A method for purifying a target material for reuse in the production of radioisotopes, the method comprising: - obtaining a solution of the irradiated target material, said solution thus comprising at least the target material and optionally also the radioactive isotope and optionally impurities, Then, - adding the acid in a predetermined amount and concentration and providing conditions for quantitatively dissolving the target material and avoiding co-precipitation of the radioactive isotope that is optionally present, - selectively removing H2O from the solution by evaporation, leaving the acid mainly in solution, thereby causing the target to precipitate, while the acid concentration in the solution increases, thereby reducing or avoiding co-precipitation of any radioisotopes present, - after removing the excess H2O, lowering the temperature of the solution to maximize the precipitation of the target and reduce the solubility of the target in the remaining liquid, - separating the liquid containing the optional radioactive isotope from the precipitated target material, and - preparation of precipitated targets for reuse in the production of radioisotopes, Characterized in that the irradiated target comprises Ra-226 and optionally Ra-225 and Ac-225, and the acid is HNO3.

2. The method of claim 1, wherein obtaining a solution comprising an irradiated target material comprises obtaining an irradiated solution of the target material, or obtaining a solution of the irradiated target material, wherein the irradiated target material is irradiated while in solid form.

3. The method of any of the preceding claims, wherein obtaining a solution of irradiated target material further comprises obtaining an aqueous solution or solid, such as a flushing material for flushing a target capsule / container, a flushing material for flushing a transfer tube, a side process stream containing a small amount of target material and radioactive isotopes or a mixture thereof, in solid or liquid form, before, simultaneously with or after the main target material transfer.

4. A method as claimed in any one of the preceding claims, wherein the HNO3 is present in a concentration of between 65% and 68% when added to the reactor vessel.

5. A method as claimed in any one of the preceding claims, wherein one or more steps of the method are carried out at a pressure below atmospheric pressure.

6. The process as claimed in any one of the preceding claims, wherein the heating or cooling of the solution is carried out using a circulating liquid in the double wall of a double-walled reactor vessel and / or the process is applied in a closed circuit of heating and / or cooling by means of a heat exchanger.

7. A method as claimed in any one of the preceding claims, wherein the method comprises using a transparent reactor vessel to visually track the process.

8. A method as claimed in any preceding claim, wherein the method further comprises stirring the solution, for example using magnetic stirring.

9. The method according to any one of the preceding claims, wherein the method is applied to a rotary evaporation system.

10. A method as claimed in any one of the preceding claims, wherein after removal of excess H2O, the temperature is lowered to below room temperature but above the solidification temperature of the liquid.

11. A method as claimed in any one of the preceding claims, wherein the solution is filtered using a submerged filter connected to a filtrate collection vessel and a vacuum pump or an optional buffer vessel.

12. A method as claimed in any preceding claim, wherein preparing the precipitated target comprises washing the precipitate with an acid after an initial filtration and optionally repeating the filtration process.

13. A system for purifying a target material, the system comprising: Reactor vessel, Inlet for the irradiated target solution, Acid inlet, The reactor vessel comprises an evaporation device for removing H2O from the solution of the irradiated target material, leaving the acid mainly in the solution, thereby precipitating the target material, while the acid concentration in the solution increases, thereby reducing or avoiding co-precipitation of the optionally present radioactive isotope, and Filtration device for separating the liquid, optionally containing radioactive isotopes, from the precipitated target material.

14. The system of claim 13, comprising one or more heating / cooling systems for controlling the temperature of the reactor vessel by heating and / or cooling, and / or a pumping system for generating a subatmospheric pressure in the reactor vessel, a pressure sensor for measuring the pressure in the reactor vessel, and / or Radon removal devices for removing radon.

15. The system according to any one of claims 13 to 14, further comprising a controller for controlling the system to perform the method according to any one of claims 1 to 12.

Images