Method and apparatus for the production of lead-212 isotope

Abstract

The present invention provides a method and apparatus for producing Pb-212. [Solution] The apparatus comprises a release box equipped with an release source containing a porous, non-reactive material. The release box receives at least one of Th-228 and Ra-224, and at least one of Th-228 and Ra-224 decays into Rn-220 within the release box. The apparatus further includes a carrier gas supply unit coupled to the release box. The carrier gas supply unit introduces an inert gas into the release box, and the inert gas transports Rn-220 out of the release box through the carrier gas outlet port of the release box. The apparatus also includes one or more Rn-220 targets coupled to the carrier gas outlet port. The carrier gas transports Rn-220 from the release box to one or more Rn-220 targets, where Rn-220 decays into Pb-212 within one or more Rn-220 targets. The Pb-212 is introduced into a Pb-212 collection container.

Description

Technical Field

[0001] Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 63 / 241,610, filed on September 8, 2021.

[0002] Generally, the present invention relates to methods and apparatuses for the production / generation and capture / isolation of lead-212 (Pb-212) isotopes.

Background Art

[0003] Alpha particle therapy offers opportunities for the treatment of many cancers. However, the production of alpha particle-emitting radioisotopes is a very complex process involving many technical and regulatory obstacles. Also, the production of alpha particle-emitting radioisotopes is very expensive, difficult to scale up, and so far, alpha particle therapy has resulted in being infeasible for commercialization and patient use. Generally, high-energy accelerators or reactors with complex and cumbersome bombardment, irradiation, and conventional chemical separation processes are required to produce alpha-emitting radioisotopes that can be used in radioactive labeled pharmaceuticals for human injection. Pb-212 is an alpha-emitting radioisotope with a suitable energy profile and chemical properties for radioactive labeling. This makes Pb-212 a very promising candidate for the treatment of various types of cancers used in TAT (Targeted Alpha Therapy). The Pb-212 isotope can be produced from the parent isotope of Th-228, which is available from reactors or nuclear waste generated in industrial or government-based nuclear power plants.

[0004] Previous methods and systems for producing Pb-212 isotopes rely on the chemical separation of radium-224 (Ra-224) from Th-228 as the feedstock / parent isotope. Ra-224 has a half-life of 3.66 days. Due to the short half-life of Ra-224, previous systems require frequent replenishment of the Ra-224 feedstock / isotope source in a generator configuration that produces Pb-212 with limited radioactivity of up to 30 mCi, due to trans index and transport issues. Replenishment and extraction of Ra-224 from Th-228 is a recurring process in the production of Pb-212 isotopes via chemical separation methods previously used in Pb-212 production. Furthermore, previous methods involve a high risk of radiation exposure while purifying Ra-224 from Th-228 and loading Ra-224 into current Pb-212 generators. These methods, which involve repeatedly extracting Ra-224 from Th-228 and replenishing Ra-224 in the Pb-212 generator, increase the risk of radiation exposure during the transport, production, and exchange of Ra-224.

[0005] This existing Ra-224 / Pb-212 generator technology is only viable for small-scale use in research and development and small-scale clinical trials. However, scaling up and commercializing these earlier methods is not feasible from a financial, regulatory, production safety, and patient safety standpoint. Additionally, because the earlier methods rely on the chemical separation of Ra-224 from Th-228, there is a risk that Th-228 and Ra-224 may leak into the Pb-212 final product through this chemical separation. This separation is a limiting step in previously existing methods because the presence of any parent isotope in the Pb-212 drug poses a radioactive and health risk to patients receiving the drug due to the long half-lives and energy profiles of Th-228 and Ra-224.

[0006] The method of this disclosure takes a very different approach from the previous chemical separation methods described above. In addition, the method of this disclosure produces Pb-212 by emission. It has several advantages over existing methods. The weaknesses and drawbacks of current methods for generating Pb-212 via emission include, for example, the use of Ra-224 as the feedstock / parent isotope packed into the emission source, which suffers from the same problems as above with respect to the chemical separation method; the use of solid organic phase target materials such as urea or other organic materials to capture and trap Rn-220; and the use of residual solvent as the final destination for capturing and trapping Rn220. This solid organic material further needs to be dissolved in acid and passed through chemical separation in order to extract Pb-212 resulting from the decay of Rn-220. These previous methods require high-performance liquid chromatography (HPLC) quality control to verify that there is no carryover or cross-contamination of urea or any other organic materials used in the process of separating and extracting Pb-212. Carryover of organic materials used in separation may exceed the maximum permissible dose or limit (MTD / l) that would indicate toxicity in patients.

[0007] The capture of Rn-220 is also carried out using an organic liquid medium (residual solvent) such as methanol or hexanol. This method generally requires further distillation, evaporation, filtration, and chemical separation of Pb-212 due to the decay of Rn-220 in the organic liquid medium to ensure the separation and extraction of Pb-212 isotopes free from methanol, hexanol, or any residual solvent. Such separations are difficult and cumbersome to scale up. This process also requires gas chromatography (GC) to test for any residual organic compounds before releasing the Pb-212 product to the patient, which is not suitable for or easily adaptable to production environments other than small-scale laboratory environments. The presence of residual solvents in the final pharmaceutical product for administration and treatment to patients is hazardous and is considered a limiting step in the final Pb-212 pharmaceutical product currently used for treatment.

[0008] In addition to the Rn-220 capture problem mentioned above, another significant issue associated with existing release technologies in Pb-212 production is the method by which the parent isotope or feedstock is packed into the release source and the materials from which the release source is constructed. Materials used to construct release sources in existing methods include resins, salts, or materials that undergo radiolysis when large quantities of Th-228 or Ra-224 are packed into previously used release sources. All existing methods lack a safe and efficient way to introduce the feedstock / parent isotope into the release source. In current methods, the operator must first manually introduce the feedstock / parent isotope into the release source and then manually position the release source inside the release box. This is a dangerous and cumbersome process that cannot be done when dealing with commercial, high-radioactivity production systems. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Due to the shortcomings of existing methods for the production of Pb-212, there is a need for an efficient and safe method for producing and extracting Pb-212 that addresses the shortcomings of existing methods and systems. [Means for solving the problem]

[0010] This disclosure provides apparatus and methods for the production of Pb-212 using thorium-228 (Th-228) feedstock / parent isotope having a half-life of 1.92 years. For example, according to certain exemplary embodiments, this disclosure covers apparatus for the production of Pb-212. In certain implementations, the apparatus may include a Th-228 feed container, a discharge box, a carrier gas supply unit, a discharge box and source filling unit, a heating block, and a Rn-220 target system. According to certain exemplary embodiments, the Th-228 feed container and carrier gas supply unit may be coupled to the discharge box. In certain embodiments, the discharge box may be coupled to the Rn-220 target system.

[0011] In one embodiment, the present disclosure provides a method for producing the Pb-212 isotope. The method includes introducing Th-228 into an emission chamber, the emission chamber comprising an emission source containing a high surface area material. The method also includes introducing a carrier gas into the emission chamber through a carrier gas supply unit, the carrier gas being an inert gas, and the carrier gas flowing through the emission chamber. Th-228 decays into Rn-220 within the emission chamber, and the carrier gas transports the Rn-220 resulting from the decay of Th-228 in the emission chamber to one or more Rn-220 targets through a multiway valve coupled to the carrier gas outlet port of the emission chamber. The method further includes separating Rn-220 from a carrier gas in one or more Rn-220 targets, guiding the carrier gas out of one or more Rn-220 targets through a carrier gas exhaust port, guiding a liquid into one or more Rn-220 targets through a liquid supply section, and enabling Rn-220 to undergo radioactive decay into Pb-212 isotopes within one or more Rn-220 targets. The liquid dissolves the Pb-212 isotopes produced by the radioactive decay of Rn-220 within one or more Rn-220 targets. The method further includes guiding the liquid containing Pb-212 isotopes from one or more Rn-220 targets to a Pb-212 collection container, and separating the Pb-212 isotopes from the liquid.

[0012] In another embodiment, the Disclosure provides an apparatus for producing Pb-212, comprising a discharge chamber, the discharge chamber comprising a discharge source comprising a porous, nonreactive material, the discharge chamber receiving at least one of Th-228 and Ra-224 at an inlet, the at least one of Th-228 and Ra-224 decaying into Rn-220 within the discharge chamber. The apparatus also comprises a carrier gas supply unit coupled to the discharge chamber, the carrier gas supply unit introducing an inert gas into the discharge chamber, the inert gas transporting Rn-220 out of the discharge chamber through a carrier gas outlet port of the discharge chamber coupled to a multiway valve. The apparatus further comprises one or more Rn-220 targets coupled to a carrier gas outlet port via a multiway valve, wherein the carrier gas transports Rn-220 from a discharge box to one or more Rn-220 targets, and the Rn-220 disintegrates into Pb-212 within one or more Rn-220 targets. A liquid supply unit is coupled to one or more Rn-220 targets. The liquid supply unit guides liquid into the Rn-220 targets so that the liquid comes into contact with the carrier gas transporting Rn-220 to the Rn-220 targets, and Pb-212 resulting from the disintegration of Rn-220 is migrated into the liquid by contact between the carrier gas and the liquid. A Pb-212 collection container is coupled to the Rn-220 target system, and the generated Pb-212 is guided into the Pb-212 collection container.

[0013] In yet another embodiment, the disclosure includes an emission box comprising an emission source comprising a fin, the fin being made of a non-reactive porous material, and Th-228 in a solvent is induced into the emission box and adsorbed onto the fin of the emission source. A shielding structure is positioned around the emission source and is operable to absorb radiation produced by the radioactive decay of Th-228 in the emission box. The emission box includes a carrier gas supply port, which is operable to provide an inlet for the carrier gas induced into the emission box. The emission box also includes a carrier gas outlet port, which is operable to provide an outlet for the carrier gas from the emission box. An evaporation box further includes an evaporation outlet port, which is operable to provide an outlet for the evaporated solvent. The emission box further includes a heat source, which is operable to provide heat to the emission box to evaporate the solvent.

[0014] This disclosure enables lower frequency of raw material / parent isotope replenishment and higher yields through source design. The present invention provides a safe and efficient filling of an release chamber containing an release source, a safe and efficient method for transferring Rn-220 via a carrier gas, a safe and efficient method for capturing Rn-220 which may include cryogenic effects, and an apparatus and method for producing Pb-212 which requires vibration between a target that captures Rn-220 and holds it while Rn-220 decays to Po-216 and ultimately to Pb-212. Furthermore, in certain embodiments, this novel technology may be operated by GMP operating software. The disclosed method and system are well shielded, easily repairable, can be scaled up using high radioactivity, and provide a higher degree of safety to the apparatus operator than previous systems. The method and system disclosed herein also provide 100% theoretical radioactive purity because there is no Th-228 or Ra-224 carryover or residue in the final Rn-220 / Pb-212 collection target. Additionally, in certain exemplary embodiments, the disclosed methods and systems differ from previous release methods for producing Pb-212 by not using solid organic extraction / collection of Rn-220, by capturing Rn-220 using an organic material such as urea or a liquid phase such as a residual solvent (e.g., methanol or hexanol) that allows Rn-220 to decompose into Pb-212. Furthermore, separating Pb-212 without using organic solvents or residual solvents as disclosed herein is safer for pharmaceutical applications and produces a final product that does not require more rigorous and extensive testing to ensure safety. Yet another advantage of the methods and systems disclosed herein is a higher yield of Pb-212, resulting from converting Rn-220 to Pb-212 in aqueous solution rather than on a solid organic extraction resin or residual solvent as in previous methods.

[0015] These listed advantages are illustrative and are not intended to be an exhaustive list of the advantages of the methods and systems disclosed herein. Other advantages will be obvious to those skilled in the art who are interested in this disclosure. This disclosure may include one or more of the following features, or a combination thereof:

[0016] The disclosed subject matter will be described below with reference to the accompanying drawings, and like reference numerals indicate like elements.

Brief Description of the Drawings

[0017] [Figure 1] A block diagram of an apparatus for producing and separating Pb-212 according to an exemplary embodiment of the present disclosure is shown. [Figure 2] A perspective view of an apparatus for producing and separating Pb-212 according to an exemplary embodiment of the present disclosure is shown. [Figure 3] A perspective view of the emission source within the emission box according to an exemplary embodiment of the present disclosure is shown. [Figure 4] A perspective view of the emission source according to an exemplary embodiment of the present disclosure is shown. [Figure 5] A perspective view of an apparatus for producing and separating Pb-212 according to an exemplary embodiment of the present disclosure is shown. [Figure 6] A perspective view of the emission source within the emission box according to an exemplary embodiment of the present disclosure is shown. [Figure 7] An illustration of the decay chain of thorium-228 (Th-228) is provided. [Figure 8] A flowchart of a method for producing Pb-212 according to a specific exemplary embodiment of the present disclosure is provided.

Modes for Carrying Out the Invention

[0018] The disclosed subject matter has various modifications and alternative forms, but specific embodiments thereof are shown by way of example in the drawings and described in detail herein. However, the description of specific embodiments herein is not intended to limit the disclosed subject matter to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternative forms that fall within the spirit and scope of the disclosed subject matter as defined by the appended claims. It should be understood that it is intended to cover them all.

[0019] The following detailed description illustrates embodiments of the present disclosure. These embodiments are described in sufficient detail to enable those skilled in the art to implement these embodiments without undue experimentation. However, it should be understood that the embodiments and examples described herein are given by way of illustration only and not by way of limitation. Here, specific embodiments of the invention are described with reference to the drawings, but such embodiments are only examples and it should be understood that they are but a few illustrations of many possible specific embodiments that can represent the application of the principles of the invention. Various changes and modifications obvious to those skilled in the art to which the invention pertains are considered to be within the spirit, scope and intent of the invention as further defined in the appended claims.

[0020] As used herein, the terms "coupled" or "coupling" include both direct and indirect connections between components. With respect to a component that directs fluid from one component to another, the terms "coupling" or "coupled" include connections via pipes or other ducts to provide fluid communication between the components.

[0021] For the purposes of this disclosure, an information handling system may include means or sets of means capable of operating to compute, classify, process, transmit, receive, acquire, transmit, switch, store, display, manifest, detect, record, reproduce, handle, or utilize various forms of information, intelligence, or data for business, scientific, control, entertainment, or other purposes. For example, an information handling system may be a server, personal computer, laptop computer, smartphone, PDA, consumer electronic device, network storage device, or other suitable device, which may vary in size, shape, performance, functionality, and price. An information handling system may include one or more processing resources, such as memory and a processor (e.g., a central processing unit (CPU) or hardware or software control logic). Additional components of an information handling system may include one or more storage devices, one or more communication ports for communicating with external devices, and various input / output (I / O) devices, such as a keyboard, mouse, and video display. An information handling system may also include one or more buses capable of transmitting communications between various hardware components.

[0022] Furthermore, in the figures and descriptions, similar numbers are intended to represent similar elements.

[0023] Referring to Figure 1, a block diagram of an apparatus 100 for producing Pb-212 according to an exemplary embodiment of the present disclosure is shown. The apparatus includes a Th-228 supply container 101 coupled to a discharge box 102. An N2 supply unit 103 is coupled to the discharge box 102, and the outlet of the discharge box 102 is coupled to a solution collection container 104. In addition, one or more Rn-220 collection targets 105a, 105b are coupled to the discharge box 102. In some embodiments, the apparatus 100 may additionally include an acid solution supply unit 106 and a Pb-212 collection container 107. In certain embodiments, one or more Rn-220 targets may include a first Rn-220 target container 105a and a second Rn-220 target container 105b, as shown in Figure 1. The function of each component in Figure 1 is described in more detail below with respect to Figure 2.

[0024] In a particular exemplary embodiment, the apparatus of Figure 1 may be controlled by an information handling system 110. For example, the information handling system 110 may be a computerized automation system that utilizes software-based control, such as GMP software. GMP software, as used herein, is "Good Manufacturing Practices" software, i.e., manufacturing automation software that conforms to a set of standards referred to as "Good Manufacturing Practices". The structure and operation of GMP software are well known to those skilled in the art who are interested in this disclosure and are therefore not discussed in detail herein. For example, in certain exemplary embodiments, one or more pumps or valves located between each unit may be controllable by an information handling system 110 implementing the automation system. Additionally, in certain exemplary embodiments, the temperature of each unit and / or the material contained in each unit or transported between each unit may be monitored and / or controlled by an information handling system 110 implementing the automation system. Such an automation system reduces the need for human interaction with the apparatus compared to previous methods for the production and separation of Pb-212, and enhances operator safety as a result of the reduced need for human intervention.

[0025] Figure 2 is a perspective view of the apparatus illustrated in the block diagram of Figure 1. An exemplary embodiment illustrated by Figure 2 includes a Th-228 supply unit 201, a discharge box 202, an N2 carrier gas supply unit 203, an N2 outlet port 208 for transporting Rn-220 to an Rn-220 collection target 205, a discharge box evaporation outlet port 204a coupled to a Peltier system 204b (e.g., any commercially available electric cooler utilizing the Peltier effect, as known to those skilled in the art who are interested in this disclosure), a Pb-212 collection container(s) 207, and a control system 210. As shown in Figure 2, the system further includes various valves and piping used to guide and / or regulate the flow of material between various system components. In a particular exemplary embodiment, the control system 210 may include an information handling system 110, as described above, which is capable of operating to control the valves and pumps through the apparatus of Figure 2 using process control software coupled to various sensors such as flow meters, thermocouples, pressure transducers, etc. The structure and operation of such process control software, and how they control various sensors such as flow meters, thermocouples, and pressure transducers, will be obvious to those skilled in the art who are interested in the teachings herein, and will therefore not be discussed in detail. For example, the control system 210 may be able to monitor the temperature of the Rn-220 target 205 and, if the monitored temperature deviates from a desired setpoint, increase or decrease the cooling to the Rn-220 target 205. In addition, in some embodiments, the control system 210 may be able to house raw material containers, such as containers containing various solutions, acids, and gases described herein, and supply those materials to various modules of the apparatus in Figure 2. In certain exemplary embodiments, a user may be able to regulate the flow rate of materials supplied to, received from, and induced through the apparatus by manually controlling valves (unlabeled) located in lines and pipes throughout the apparatus. In certain embodiments, the control system 210 may be communicatively coupled to the valves and be able to selectively open and close the valves automatically based on predetermined parameters.In yet another embodiment, the control system 210 may provide a user interface that allows the user to adjust the valve through its user interface. An exemplary embodiment includes a Th-228 supply unit 201 coupled to the discharge box 202. Th-228 may be disposed in the Th-228 supply unit 201 and introduced from the Th-228 supply unit 201 to the discharge box 202. In some embodiments, the Th-228 supply unit 201 may be disposed within the discharge box 202. The Th-228 supply unit 201 provides means for supplying Th-228 to the discharge box 202. In an exemplary embodiment, the discharge box 202 has a first distal end 202a and a second distal end 202b. The first distal end 202a of the discharge box 202 is fluidically coupled to an N2 carrier gas supply unit 203 that provides a flow of N2 carrier gas or other inert carrier gas to the discharge box 202. Throughout this disclosure, any inert gas may be used as the carrier gas, although it will be referred to as the N2 carrier gas. The second distal end 202b of the discharge box 202 is coupled to the Rn-220 target 205 through the N2 carrier gas outlet 208. According to a particular exemplary embodiment, the discharge box 202 includes a discharge source, such as the discharge source 506 in Figure 5, and more specifically the discharge source 600 in Figure 6, and a heat source (e.g., the heat source 507 in Figure 5), as will be described in more detail with respect to Figures 3, 4, 5, and 6. The discharge box 202 is supplied to the Th-228 through the Th-228 supply unit 201, as will be described in more detail below. The release source is provided with residence time for Th-228 while Th-228 undergoes radioactive decay to Rn-220. The N2 carrier gas supply unit 203 provides a flow of N2 carrier gas through the release box 202, which carries any Rn-220 resulting from the decay of Th-228 in the release box 202 to the Rn-220 target 205 through the N2 carrier gas outlet 208. According to a particular exemplary embodiment, the Rn-220 target 205 may have an N2 carrier gas inlet port 205c, liquid inlet and outlet ports 205d, and an N2 carrier gas exhaust port 205e. The Rn-220 target 205 functions as a vessel for separating Rn-220 from the N2 carrier gas, as will be described in more detail below, and as a residence space for Rn-220 to undergo radioactive decay to Pb-212. The liquid supply unit 206 may be connected to the Rn-220 target 205 to provide a liquid, such as an acidic solution, for dissolving Pb-212 produced by the radioactive decay of Rn-220 in the Rn-220 target 205. In a particular exemplary embodiment, the same liquid supply line 206 may provide an outlet line for a liquid solution containing Pb-212, and the Rn-220 target 205 may be connected to a Pb-212 collection container 207 through a multiway valve 209 that is operable to control the inflow and outflow of the Rn-220 target 205.

[0026] The Th-228 supply unit 201 is coupled to the release box 202 and provides means for the transfer of Th-228 into the release box 202. In certain embodiments, Th-228 may be dissolved in a liquid before being transferred to the release box 202. In some embodiments, Th-228 may be dissolved in nitric acid (HNO3) or another acid before being transferred to the release box 202. In other embodiments, Th-228 may be obtained in solution, and vials of Th-228 may be loaded into the apparatus shown in Figure 2 and thus transferred to the release box 202. After being loaded into the apparatus, a portion of the Th-228 solution may be transferred to the release box 202, which is described in more detail below. As will be understood by those skilled in the art who are interested in this disclosure, handling radioactive materials such as Th-228 solution involves certain risks, and any accident in the process may lead to undesirable consequences. Therefore, to mitigate such risks, in certain exemplary implementations, the discharge box 202 may store Th-228 for an extended operating period, eliminating the need for repeated handling of Th-228 and minimizing the risks associated with that procedure. For example, in certain exemplary embodiments, the discharge box 202 may store a supply of Th-228 that lasts for one year. In certain embodiments, the discharge box 202 may store 1,000 millicuries (mCi) of Th-228. In some embodiments, Th-228 may be supplied to the system from a vial containing Th-228 through a Th-228 supply unit 201. The Th-228 supply unit 201 is any suitable system for transferring the amount of dissolved Th-228 from a vial or other storage container or medium to the discharge box 202, as will be understood by those skilled in the art who are interested in this disclosure. For example, the Th-228 supply unit 201 may interface with and be controlled by the control system 210, and may be an automatic syringe drive, vacuum system, or pressurization system. For example, in some embodiments, the Th-228 may be filled into the device on a monthly, bimonthly, semi-annual, or yearly basis, which reduces the risks associated with handling radioactive materials.Th-228 can be filled by dissolving it in an acid, such as HCl or 3M HNO3, or any desired molar concentration of an acid capable of dissolving any isotope in its decay chain, such as Th-228 or Ra-224.

[0027] In other embodiments, Th-228 or Ra-224 may be filled into an emission source (e.g., emission source 506) before being incorporated into the apparatus of Figures 2 and 5. For example, Th-228 or Ra-224 in solution may be filled into an emission source, and the solvent (acid) may be evaporated in a centralized remote facility. The emission source filled with Th-228 or Ra-224 is then radiation-shielded in accordance with DOT regulations and incorporated into the apparatus described herein, as understood by those skilled in the art who are interested in this disclosure, to produce Pb-212 as described herein. For production purposes, the Pb-212 can be shipped to a Pb-212 production facility housing the apparatus described herein. In such embodiments, the emission source may be periodically replaced with a newly filled emission source containing Th-228 or Ra-224 after a set period of time, or after the radioactivity of Th-228 or Ra-224 in the previous emission source has decreased to a predetermined level. In some embodiments, the spent emission source may be returned to a centralized Th-228 and Ra-224 filling facility for cleaning and refilling of Th-228 or Ra-224.

[0028] In another embodiment, the Ra-224 solution may be periodically filled into the Th-228 supply unit 201, for example, once or twice a week due to the shorter half-life of Ra-224 compared to Th-228. In such embodiments, Ra-228 may be dissolved in an acid such as 3M HNO3 or HCl. After filling, the Th-228 solution or the Ra-224 solution may be heated to evaporate the liquid, as described below, and the Th-228 or Ra-224 may be deposited in the release source in the release box 202.

[0029] Figures 3 and 4 illustrate close perspective views of the release source 300 within the release chamber 202. Upon introduction into the release source 300, Th-228 is dispersed onto the flow distribution fins 301 by evaporation of the carrier solution, as described below. The flow distribution fins 301 are high-surface-area components made of any desired material to which Th-228 can be adsorbed. In certain exemplary embodiments, the high-surface-area material may be a porous material having porosity desirable for a particular application. For example, in certain non-limiting exemplary embodiments, the porosity of the material comprising the flow distribution fins 301 may be approximately 2 μm to approximately 200 μm. As will be understood by those skilled in the art who are interested in this disclosure, other porous materials may be used as desired without departing from the scope of this disclosure. The material of the flow distribution fins 301 may have a large surface area in some embodiments. For example, in certain embodiments, the surface area of ​​the flow distribution fins 301 may be approximately 10,000 m². 2 It may be larger than this. The flow distribution fins 301 may be composed of any desired material, including but not limited to metal, ceramic grids, or foams. In certain embodiments, the high surface area material may be porous titanium, silica, tungsten, zirconium, platinum, gold, iridium, rhenium, ceramic, or a combination thereof. In some embodiments, the flow distribution fins 301 may have a fin-type structure comprising a plurality of fins constituting the high surface area material. The discharge source 300 may also include a flow distribution plate 309 for providing adhesion points to the flow distribution fins 301 and providing additional surface area for Th-228 deposition. The flow distribution plate 309 may be made of a high surface area material. For example, in certain non-limiting exemplary embodiments, the porosity of the material comprising the flow distribution plate 309 may be approximately 2 μm to approximately 200 μm. In some embodiments, the flow distribution plate 309 may be made of the same material as the flow distribution fins 301. In other embodiments, the flow distribution plate 309 may be made of a different material from the flow distribution fins 301, such as porous zirconium, if the flow distribution fins 301 are made of porous titanium.

[0030] The flow distribution fins 301 hold Th-228 as it undergoes radioactive decay. Figure 7 shows the decay pathway 700 of Th-228. Specifically, as seen in Figure 7, Th-228 first decays into Ra-224, which is also adsorbed onto the flow distribution fins 301. Ra-224 then decays into Rn-220, which is not adsorbed onto the flow distribution fins 301. After decaying into Rn-220, Rn-220 can be transported out of the release source 300 through the N2 carrier gas outlet port 308 by the flow of N2 carrier gas supplied to the release source 300 through the N2 carrier gas inlet port 303. As further described herein, the N2 carrier gas may transport Rn-220 to the Rn-220 target 205, where Rn-220 undergoes radioactive decay to Pb-212.

[0031] The discharge box 202 may also include a heat source 302 below the discharge source 300. Several embodiments The heat source 302 may be located outside the emission source 300, or it may be in contact with the emission source 300. In certain exemplary embodiments, the heat source 302 may be an electrically controlled hot plate or heating element, which may be controlled by the information handling system of the control system 210. The heat source 302 supplies heat to evaporate the solvent that carries the Th-228 from the Th-228 supply unit 201. When the liquid portion of the solution evaporates, the Th-228 is left on the flow distribution fin 301.

[0032] The evaporated liquid can exit the discharge source 300 through the evaporation outlet port 304. In certain exemplary embodiments, the evaporation outlet port 304 may be located on the upper surface of the discharge source 300. In certain exemplary embodiments, the evaporation outlet port 304 may be coupled to a heat exchanger, such as a Peltier cooler 204b, to cool the evaporated solution that can be collected in the solution collection container (e.g., the condensing bottle 525 in Figure 5). In other embodiments, the heat exchanger may be located in the line between the evaporation outlet port 304 and the solution collection container. In certain exemplary embodiments, the heat exchanger may be an electrically operated Peltier effect cooling device that cools the evaporated solution for collection as a liquid. A Peltier effect cooling device is an electrically operated cooler that uses the Peltier effect to convert electrical energy into thermal motion, enabling cooling on one side of the device and heat transfer to the other side. Such coolers are well known to those skilled in the art who are interested in the present disclosure. One embodiment of the evaporation outlet port 304 and Peltier effect cooler described above is illustrated in Figure 2.

[0033] Figure 4 provides a close perspective view of the internal components of an embodiment of the emission source 300 described herein. The illustrated emission source 300 includes a flow distribution fin 401 and a flow distribution plate 409. The flow distribution fin 401 may correspond to the component referred to as emission source 301 with respect to Figure 3 and may be composed of any high surface area material described herein. The flow distribution fin 401 has a fin-shaped structure of multiple closely spaced fins to provide multiple paths for the flow of N2 carrier gas through the emission source 300. The flow distribution plate 409 holds the flow distribution fin 401 in place and provides surface area for Th-228 deposition in addition to the surface area provided by the flow distribution fin 401.

[0034] Returning to Figure 2, the release source (e.g., release source 300) in the release box 202 is supplied by the N2 carrier gas supply unit 203. The N2 carrier gas supply unit 203 supplies N2 carrier gas to the Rn-220 target 205, which transports Rn-220 out of the release source (e.g., release source 300) in the release box 202 through the N2 carrier gas outlet port 208. In certain embodiments, the N2 supply rate may be automatically controlled. For example, in a particular exemplary embodiment, the N2 supply rate may be controlled by mass flow using a mass flow meter for controlling the flow of N2 carrier gas at a desired level, and an inlet valve controlled by the control system 210. The N2 supply unit may be operable to shut off the flow to the release box 202 by the inlet valve, which may be followed by one or more manual valves in the event of failure of the inlet valve. In certain embodiments, the flow may be controlled by an information handling system incorporated into the control system 210. For example, in certain exemplary embodiments, it may be desirable to flow the N2 carrier gas through this fixture at a suitable rate. This rate can be adjusted via a mass flow system based on the size and number of collection targets and other variables embedded in this system. In certain embodiments, the N2 supply rate can be controlled to approximately 200 mL / min. The mass flow-controlled N2 carrier gas supply unit 203 may comprise an N2 carrier gas supply line, an inlet valve, and a mass flow meter, as described in more detail with respect to Figure 5. The inlet valve and mass flow meter may be operable to control the mass flow of the N2 carrier gas flowing through the N2 carrier gas supply line using a control methodology evident to those skilled in the art who have a benefit of teaching herein. For example, the inlet valve and mass flow meter may be coupled in a simple feedback control loop. In the exemplary embodiment of Figure 2, the inlet valve and mass flow meter may be coupled to a control system 210. The N2 carrier gas is supplied to the discharge box 2 It flows into 02, carries any Rn-220 produced as a result of the decay of Th-228 and / or Ra-224 in the release box 202, and carries the Rn-220 to the Rn-220 target 205.

[0035] As described above, the Rn-220 target 205 may consist of one or more containers for collecting Rn-220. For example, in a particular embodiment, the Rn-220 target 205 may include a first container 205a and a second container 205b for collecting Rn-220. In another embodiment, the Rn-220 target 205 may be a single container. In some embodiments, the Rn-220 target 205 may be filled with a cooled acid solution, whether in one, two, or more containers. The acid solution may be any suitable acid solution, such as hydrochloric acid (HCl). The acid solution may be cooled to a temperature in the range of approximately -72°C to -95°C. In another embodiment, the acid may be HNO3. In other embodiments, the Rn-220 target 205 may be filled with an uncooled acid solution at ambient temperature. In further embodiments, the Rn-220 target 205 may comprise one or more containers containing a zeolite, a metallic zeolite-type chalcogenide (e.g., germanium, tin, zinc, or a combination thereof, a chalcogenide having a zeolite-like structure), or a tin-rich germanium surface target. In some embodiments, the containers containing the surface target may also be filled with a cooled or uncooled acid solution, such as an aqueous buffer. In other embodiments, the Rn-220 target 205 containing the surface target may comprise a nozzle for spraying the acid or other aqueous solution onto the walls of the target container. In embodiments in which the Rn-220 target 205 comprises a zeolite, a metallic zeolite-type chalcogenide, or a tin-rich germanium surface target, the Rn-220 target does not need to be filled with liquid.

[0036] In embodiments, the Rn-220 target 205 may function as described below. The first and second Rn-220 targets 205 may include a container containing an acidic solution. The acidic solution may include HCl, HNO3, or any other aqueous, non-organic acid, or buffer solution. For illustrative purposes, the HCl solution is described below, but this description may apply to any acidic aqueous solution, and the methods and systems described herein are not limited to the use of an HCl solution. In some embodiments, the first and second Rn-220 targets 205 may be supplied by an automatic liquid supply unit 206. In certain embodiments, the HCl solution supplied from the liquid supply unit 206 may be a 20% HCl solution. In another embodiment, the HCl solution may have a concentration of 22.5%. In other embodiments, the concentration of HCl may be 10% to 50%. In some embodiments, the concentration of HCl may be 15% to 30%. In certain embodiments, the concentration of HCl may be 20% to 25%. In certain embodiments, the HCl concentration may be 22% to 27%. In certain embodiments, the HCl concentration may be 25%. In another embodiment, the Rn-220 target 205 may be supplied by a 3M HNO3 solution.

[0037] The first and second Rn-220 targets 205 may also include temperature control units / systems (such as the cooling tank 522 illustrated in Figure 5) for cooling the HCl solution to temperatures below -72°C and above -95°C and maintaining the HCl solution at those temperatures. In certain embodiments, the temperature control system may cool the HCl solution to -85°C and maintain the HCl solution at that temperature. In another embodiment, the HCl solution may be cooled to -82°C. In yet another embodiment, the temperature control unit may cool the HNO3 solution to approximately -41°C. In some embodiments, the temperature control unit may be operable to cool the liquid in the Rn-220 target 205 to a temperature above the freezing point of the liquid to increase the solubility of Rn-220 in the liquid.

[0038] When an N2 carrier gas containing Rn-220 comes into contact with a cooled HCl solution, R Since n-220 has a freezing point of -72°C, Rn-220 freezes. In some embodiments, the target material may include a zeolite or zeolite-like chalcogenide material that absorbs the Rn-220 instead of freezing it with a cooling acid solution. In other embodiments, the Rn-220 target 205 may contain a liquid acid solution that dissolves the Rn-220 supplied to the Rn-220 target at a temperature below ambient temperature. The N2 carrier gas may then exit the first or second Rn-220 target 205 without containing the Rn-220. The Rn-220 remaining in the Rn-220 target container dissolves in an HCl solution and decays into Po-216. The Po-216 then rapidly decays into Pb-212 while dissolving in the HCl solution. Since Rn-220 has a half-life of 55.6 seconds and freezes upon contact with an acidic solution, the supply of N2 carrier gas containing Rn-220 may be switched between a first Rn-220 target 205a and a second Rn-220 target 205b approximately once every minute to replenish the supply of Rn-220. However, in some embodiments, only a single Rn-220 target 205 may be used. In other embodiments, the N2 carrier gas flow may be switched between Rn-220 targets 205 at longer intervals, such as 2 or 3 minutes. In yet another embodiment, the N2 carrier gas flow may be switched between Rn-220 targets 205 every 10 minutes. Since Rn-220 has a half-life of 55.6 seconds, 10 minutes provides enough time for approximately 10 Rn-220 half-lives to elapse, which is sufficient for Rn-220 to decay almost completely into Pb-212. While waiting 10 minutes for the other vessels to pass, the Rn-220 flow proceeds to the second Rn-220 target vessel for 10 minutes. At the end of the 10 minutes, the outlet valve of the second Rn-220 target vessel 1 is opened to release N2 gas and prepare for the next cycle. At this point, the outlet valve of the first Rn-220 target is closed for 10 minutes. This oscillating cycle continues until the desired amount of Pb-212 is collected in each Rn-220 target vessel. This oscillating cycle, residence time (i.e., time from capture to release), the volume that each vessel can take, and the number of vessels may be modified based on the needs of the process.In a particular exemplary implementation, the automatic filling system of the apparatus controlled by the control system 210 may alternate between filling a first Rn-220 target 205, waiting 10 minutes for a 10Rn-220 half-life to elapse, filling a second Rn-220 target 205 during this time, returning to filling the first Rn-220 target 205 10 minutes after the previous filling of the first Rn-220 target 205, then filling the second Rn-220 target 205 10 minutes after the previous filling of the second Rn-220 container, and alternating between filling and waiting for a container until the control system 210 determines, based on the flow rate, Rn-220 target 205 volume, number of oscillations, and waiting time, that the Rn-220 target 205 contains a desired amount of Pb-212. At this point, the resulting Pb-212 solution can be emptied from one of the Rn-220 target containers (e.g., 205a). In certain embodiments, this process can be performed by a control system 210, which may be automated and implemented using an information handling system. For example, the automated control system may include a multiway valve 209 controlled by the control system 210, which, upon receiving a command from the control system 210, is operable to switch the filling between a first Rn-220 target 205a and a second Rn-220 target 205b. The Pb-212 dissolved in the HCl solution can then be removed from the Rn-220 target container as needed. Separation of Pb-212 from the HCl solution can be achieved by methods known to those skilled in the art who are interested in this disclosure.

[0039] In other embodiments, one or more Rn-220 targets may be filled based on a known flow rate of carrier gas (measured, for example, by a mass flow meter on the carrier gas supply unit 203) and the pressure measured at each Rn-220 target (for example, by a pressure transducer located within each Rn-220 target). After filling an Rn-220 target to a predetermined pressure or with a predetermined amount of carrier gas based on the mass flow of the carrier gas supply, the control system 210 begins filling a second Rn-220 target, and then a third Rn-220 target. The multiway valve can be guided so that the Rn-220 targets follow. Any number of Rn-220 targets can be used based on the production needs of the device.

[0040] As a non-limiting exemplary embodiment, an Rn-220 target 205 having a volume of 200 mL may be filled at a rate of 20 mL / min and take 10 minutes to fill. Once the first Rn-220 container (e.g., 205a) is filled, the apparatus begins filling the second Rn-220 container (e.g., 205b) at a rate of 20 mL / min and also takes 10 minutes to fill. During this time, 10 half-lives of Rn-220 pass through the first Rn-220 target 205. When one or both Rn-220 targets 205 are emptied (e.g., as necessary, based on a determination by the control system 210), the system stops filling the Rn-220 targets 205 with N2 carrier gas until the emptied container is filled with acid, and then resumes the process. Depending on the size of the emission source 300 and the flow rate of the N2 carrier gas, three, four or more Rn-220 target containers 205 may be incorporated into the apparatus of Figure 1 for continuous, alternating filling. In some embodiments, the Rn-220 targets may have different volumes from one another. It will be apparent to those skilled in the art who are interested in this disclosure that any volumes, times, temperatures, and flow rates described herein are illustrative and non-limiting. For example, depending on the need for Pb-212 production, larger or smaller containers may be used with longer or shorter filling times and higher or lower flow rates.

[0041] In another embodiment, as described above, the Rn-220 target 205 may contain an uncooled acid or aqueous solution. In such an uncooled system, Rn-220 dissolves directly in the solution, so 10 half-life times must elapse to provide sufficient time for the Rn-220 isotope to completely decay, after which the flow changes to the next Rn-220 target 205.

[0042] In another embodiment, two or more Rn-220 targets 205 may be included in the system 200. For example, three, four, five, or more Rn-220 targets may be included in the system. In such a system, the supply of Rn-220 containing the N2 carrier gas may be periodically circulated between the Rn-220 targets, while being extracted from other Rn-220 targets that are not supplied with Pb-212.

[0043] In embodiments where the solution in the Rn-220 target 205 is cooled below the freezing point of Rn-220, for example, when the solution is cooled to -82°C, Rn-220 is helped to remain in the liquid phase while decaying into Pb-212. At this temperature, Rn-220 is retained in the liquid phase within the cooling acid and leaves the Rn-220 target 205 by evaporation or gas diffusion, with or without vibration filling of the Rn-220 target 205 with Rn-220 containing the N2 carrier gas. During vibration filling, while one target is filled with the N2 carrier gas carrying Rn-220, the other container holds the Rn-220 and N2 gas until the temperature of the contents of the container (i.e., the liquid and gas contained in the Rn-220 target 205) is below or below the freezing point of Rn-220. At this temperature, Rn-220 is in liquid form (for example, with a cooling acid, Rn-220 is below its freezing point, but when it exceeds the freezing point of the acid, it forms a miscible liquid with the acid), and when the outlet valve is opened, only N2 gas leaves the Rn-220 target 205. This oscillating filling process can be continued for as long as necessary to reach the desired amount of Pb-212.

[0044] Regardless of whether the solution in Rn-220 target 205 is cooled, when Rn-220 decays, it decays into Po-216, which has a half-life of only 0.145 seconds, before decaying into Pb-212. The decay from Po-216 to Pb-212 is very high energy, and as a result the Pb-212 ion has a considerable rate. This is known to those skilled in the art as a rebound effect. These rates are high enough that, in previous methods utilizing solid Rn-220 targets such as ion exchange resins and urea, some of the Pb-212 atoms become embedded on the surface of the solid Rn-220 target material, thereby reducing the yield of Pb-212. In the liquid-filled Rn-220 target container described herein, the decay from Pb-216 to Pb-212 occurs in the liquid medium. The liquid solution mediates the rate of the Pb-212 atoms, enabling a higher Pb-212 yield than previously possible.

[0045] In embodiments of the Rn-220 target 205 described above, which include a solid Rn-220 target surface such as zeolite, metallic zeolite chalcogenide, or tin-rich germanium material, the Rn-220 target 205 may include a spray nozzle for spraying an acid or buffer solution, such as the HCl solution described above, onto the walls of the Rn-220 target 205. The spray nozzle located on the top of the Rn-220 target 205 may be configured to spray a small amount of liquid solution, such as the HCl solution, onto the sides of the Rn-220 target 205, thereby forming a thin film of liquid solution on the sides of the Rn-220 target 205. Such a spray nozzle may include any atomizing or fine mist nozzle suitable for such an application, as will be obvious to those skilled in the art who are interested in the present disclosure, and may be supplied, for example, by a pump liquid solution supplied from a control system 210. The thin liquid film provides sufficient liquid for any Pb-212 atoms produced, thereby mitigating the rebound effect and loss of Pb-212 onto the surface of the Rn-220 target 205.

[0046] In some embodiments, the Rn-220 target 205 may include a sparger or bubbler device and a conical target material. The sparger or bubbler device may be operable to create many small N2 carrier gas bubbles when the Rn-220 target is supplied with N2 carrier gas and filled with acid, thereby increasing the surface area of ​​the N2 carrier gas within the Rn-220 target and enhancing the migration of Rn-220 from the N2 carrier gas to the solvent (acid) within the Rn-220 target. The Rn-220 target 205 may include an inlet port for the N2 carrier gas carrying Rn-220 and an outlet port for releasing N2 that does not contain Rn-220. The arrangement of tubes and valves may be operated via software that provides a sequence of vibrations between Rn-220 targets 205 to capture Rn-220, and that provides sufficient time for Rn-220 to completely disintegrate into Pb-212 in the medium described above (e.g., aqueous solution or solution sprayed through a nozzle). In certain embodiments, the software may be implemented using the information handling system of the control system 210.

[0047] Figure 5 is an exploded perspective view of an apparatus for producing and separating Pb-212 according to a particular exemplary embodiment. In some embodiments, the apparatus of Figure 5 may function substantially the same way as that of the apparatus described herein with respect to the block diagram of Figure 1 and the exemplary embodiment of Figure 2. The apparatus of Figure 5 may include, or be communicatively coupled to, an information handling system (not shown), and may include a control unit 501 that is operable to control the flow rate, temperature, valve cycle, and other aspects of the apparatus of Figure 5. A dispensing system 502 may be coupled to the control system 501 and may be operated to distribute aqueous solutions to various units of the apparatus of Figure 5. For example, the dispensing system 502 may be operable to distribute aqueous solutions, such as HCl solution, to RN-220 targets 520 and 521. The dispensing system may also independently, or when it receives a command from the control system 501, distribute aliquots of Pb-212 in solution from the RN-220 targets 520 or 521. In some embodiments, the dispensing system 502 may be housed in the same housing as the control system 501. As will be understood by those skilled in the art who have an interest in this disclosure, the control system 1 may be coupled to any one or more sensors, control valves, coolers, and heaters described herein, and may process information obtained from such sensors, and control valves, heaters, and coolers, It may be possible to operate in a way that provides control output signals for alarms, etc.

[0048] The N2 carrier gas supply unit 503 may include a mass flow meter and a mass inlet valve 504 to control the flow of N2 carrier gas to the emission source 506. The emission source 506 may also be coupled to a Th-228 supply unit 526, which may be coupled to a control system 501 or otherwise controlled to deliver Th-228 dissolved in an aqueous solution to the emission source 506. The emission source 506 may contain a high surface area material, such as those described in conjunction with Figures 3, 4, and 6, to provide retention for Th-228 within the emission source 506. The emission source 506 may also include a heat source 507 to provide heat for evaporating any solvent used to transport Th-228 to the emission source 506, as described herein. Such evaporated solvent may flow out of the emission source 506, through an evaporation outlet valve port 511, and through a Peltier condenser 517 that operates to condense the evaporated solvent, to a condensing bottle 525.

[0049] As described above, the Th-228 contained in the emission source 506 undergoes radioactive decay within the emission source 506, constantly decaying into Rn-220. To provide shielding from the radiation emitted by the radioactive decay of Th-228, the emission source 506 is contained within a lead shield 528 that may be thick enough to block the radiation produced by the radioactive decay of Th-228 and the radioactive decay of its isotopes resulting from the decay of Th-228. Additionally, the lead shield 528 is positioned within a stainless steel shield cover 527 that may provide an outer cover for the emission source 506, which is corrosion-resistant as well as providing additional radiation shielding.

[0050] Since Rn-220 is produced from the decay of Th-228, it is transported out of the emission source 506 by a flow of N2 carrier gas through an N2 carrier gas outlet valve 514, an ultra-high purity gas filter 515, and an inlet valve 516 to Rn-220 targets 520 and 521. The gas filter 515 can remove impurities such as small particles detached from the high-surface-area material of the emission source 506, or Th-228 particles, from the flow of Rn-220 containing the N2 carrier gas. The inlet valve 516 may be coupled to a control system 501 and may be operable to direct the flow of N2 carrier gas to either the Rn-220 target 520 or the Rn-220 target 521. As described herein, in some embodiments, the inlet valve 516 may be operable to periodically circulate the flow of N2 carrier gas between the Rn-220 target 520 and the Rn-220 target 521.

[0051] The liquid supply unit 518 is fluidically coupled to the Rn-220 targets 520 and 521 through a multiway valve 519. The liquid supply unit 518 may be coupled to and / or controlled by a control system 501 and may be operable to supply a liquid, such as an aqueous HCl solution as described herein, to the Rn-220 targets 520 and / or 521. The multiway valve 519 may be operable to periodically circulate the flow of liquid supply between the Rn-220 targets 520 and 521. The Rn-220 targets 520 and 521 are positioned within a cooling tank 522. The cooling tank 522 may be any temperature control unit / system, cooler or heat exchanger known in the art and may be operable to cool the Rn-220 targets 520 and 521, and their contents, to a temperature sufficient to freeze the Rn-220 being transported into the Rn-220 targets 520 and 521. For example, in certain embodiments, the cooling tank 522 may be operable to cool the contents of the Rn-220 targets 520 and 521 to -82°C. The temperature of the cooling tank may depend on and correlate with the freezing point of the type of acid and its molar concentration. The cooling tank 522 is positioned within a lead shield for the cooling tank 529. The lead shield for the cooling tank 529 may be thick enough to block radiation resulting from the decay of Rn-220 to Pb-212 connected to the Rn-220 targets 520 and 521. After the Rn-220 collected in the Rn-220 target 521 has disintegrated into Pb-212, the aqueous solution containing Pb-212 can be removed from the Rn-220 target 520 or Rn-220 target 521 through the multiway valve 519 into the Pb-212 collection container 523. The Rn-220 target 520 or Rn-220 target 521 is also coupled to a rinse bottle 524. The rinse bottle 524 can collect any liquid supplied through the Rn-220 target 520 or Rn-220 target 521 to clean the target container before introducing Rn-220 during the operation of the apparatus illustrated by Figure 5.

[0052] The apparatus in Figure 5 also includes a PTFE airtight box 530. The PTFE airtight box 530 may be constructed of PTFE or any other impermeable, nonreactive polymer or material. The PTFE airtight box 530 is configured to be airtight and contains the emission source 506. In some embodiments, the PTFE airtight box 530 may have an air inlet and an outlet, the outlet of which is connected to an exhaust system. Even if the emission source 506 produces a leak, the PTFE airtight box 530 may contain the leak and provide the leaked Rn-220 / carrier gas to be delivered through the exhaust system. Such an exhaust system may include charcoal or other high-surface-area material capable of adsorbing any Rn-220 in the event that the emission source 506 produces a leak. The exhaust system may also be coupled to an air compression system (ACS) that collects the radioactive gas, compresses it, and releases it based on its radioactivity half-life.

[0053] Finally, the apparatus of Figure 5 has safety ball valves, 505, 508, 509, 510, 512, and 513 on various supply outlet lines of the illustrated apparatus. Such safety ball valves are operable to shut off the flow in the line in order to allow isolation of the components constituting the apparatus of Figure 5. Isolation of these components may be used for maintenance such as cleaning or replacement of parts. In some embodiments, safety ball valves 505, 508, 509, 510, 512, and 513 may be operable to receive open / close signals from a control system 501 and may be operable to return to a safe position if communication from the control system 501 is lost (e.g., “fail-safe” operation).

[0054] Figure 6 provides a close view of the emission source 506 of Figure 5 as described herein, according to several embodiments. The emission source 600 of Figure 6 has an upper plate 601 and a lower plate 602, which include flow distribution fins 603 and flow distribution plate 604 and have inlet and outlet ports for N2 carrier gas, Th-228 supply, and solvent evaporation. The upper plate 601 and the lower plate 602 may be joined together in a manner sufficient to form a seal between the two plates suitable for preventing N2 carrier gas or any evaporating solvent from escaping between the plates. For example, the upper plate 601 and the lower plate 602 may be welded together at chamfered portions for welded connections 618 and 619. Other methods for joining the upper plate 601 and the lower plate 602 will be obvious to those skilled in the art who have been given the benefit of this disclosure.

[0055] The flow distribution fins 603 and flow distribution plate 604 may be made of any high-surface-area (i.e., porous) material as described herein. The flow distribution fins 603 may contain a plurality of fins closely spaced together to provide a channel for the N2 carrier gas to pass through the high-surface-area material fins of the flow distribution fins 603. These fins made of high-surface-area material, as described herein, absorb Th-228 introduced into the emission source and provide retention for Th-228 until the Th-228 decays into Rn-220, at which point it is transported out of the emission source by the N2 carrier gas.

[0056] The lower plate 602 has a carrier gas inlet port 605 that is operable to provide an inlet for the carrier gas, an inlet shut-off safety and transport plug 606, and a carrier gas from the emission source The upper plate 601 has an outlet port 607 operable to provide an outlet for the gas, an outlet shut-off safety and transport plug 608, service plugs 609 and 610, a focusing outlet cavity 615, a main cavity 616, and an inlet carrier gas distribution cavity 617. The upper plate 601 has a carrier gas blade 613, a vent cavity 614, a vent port 612 operable to provide an outlet for evaporated solvent, and a vent shut-off safety and transport plug 611. The main cavity 616 provides housing for the flow distribution plate 604 and flow distribution fins 603. The upper plate 601 and lower plate 602 may be made of any non-reactive metal such as titanium, zirconium, gold, platinum, iridium, tungsten, and non-reactive alloys such as Monel or Inconel.

[0057] During operation, Th-228 in solution can be introduced into the emission source shown in Figure 6, for example, through the N2 carrier gas inlet port 605. As discussed above, the introduction of Th-228 into the emission source occurs periodically, for example, only once a year. After the introduction of the Th-228 solution, heat can be applied to the emission source 506 to evaporate any solvent, for example, by the heat source 507 shown in Figure 5. The evaporated solvent can then be discharged out of the emission source through the vent cavity 614 and vent port 612.

[0058] Next, the N2 carrier gas flow is introduced to the emission source 506 through the N2 carrier gas inlet port 605. In some embodiments, the N2 carrier gas flow may be introduced to the emission source while the flow distribution fins are still "wet," for example, before all of the solvent carrying Th-228 has evaporated. In other embodiments, the N2 carrier gas flow may be introduced to the emission source 6 after the flow distribution fins have "dried," for example, after all or substantially all of the solvent carrying Th-228 has evaporated. The N2 carrier gas flow is guided across the fins of the flow distribution fins 603 by the inlet carrier gas distribution cavity 617, the flow distribution plate 604, and the carrier gas blade 613, and flows into the converged outlet cavity 615 before exiting the emission source through the outlet port 607. The carrier gas blade 613 may be operable to guide and distribute the inflow N2 carrier gas flow across the flow distribution fins 603 and flow distribution plate 604 to ensure a uniform and homogeneous distribution of the gas flow through the emission source 506. As described above, the N2 carrier gas flow through the flow distribution fins 603 carries Rn-220 formed from the radioactive decay of Th-228 absorbed onto the material of the flow distribution fins 603 out of the emission source.

[0059] The safety plugs 606, 608, and 611 of the emission source 600 in Figure 6 may be operable to isolate the interior of the emission source from the external environment. Since Th-228 has a half-life of 1.91 years, the interior of the emission source 600 may remain radioactive for a considerable period (e.g., 10 half-lives of Th-228) after Th-228 has been introduced into the emission source 600. Therefore, it is important to be able to isolate the interior of the emission source to ensure that radioactive material does not escape from the emission source, for example, if the emission source needs to be moved or if maintenance needs to be performed on the equipment.

[0060] As described above, in some embodiments, the apparatus of Figures 1, 2 and 5 can be operated by an automated control system. In certain exemplary embodiments, the automated control system may be implemented using an information handling system. Such a system can automatically control several different system variables, such as flow rate, timing, and temperature, based on one or more sensors placed throughout the apparatus of Figure 1. For example, an automated system can operate the apparatus disclosed herein to produce Pb-212 by performing method 1000 of Figure 8. First, in step 1001, Th-228 is introduced into an emission box 202 containing an emission source 300 containing a high surface area material, as described above with respect to Figures 1 to 6. Next, in step 1002, a carrier gas containing nitrogen is supplied to the emission box 202. As described above, the automated system controls the measured mass flow Based on this, the flow rate of the carrier gas can be controlled. Next, in step 1003, after flowing through the discharge box 202, the carrier gas is introduced into a pre-cooled hydrochloric acid solution or any other acid or aqueous solution. Finally, in step 1004, Pb-212 is separated from the hydrochloric acid solution. As described above, the pre-cooled hydrochloric acid solution may have a temperature of -72°C or lower and may contain a target that can operate to collect Rn-220.

[0061] The specific embodiments disclosed above are illustrative only, as the disclosed subject matter can be modified and implemented in different but equivalent ways that are obvious to those skilled in the art who have an interest in the teachings of this specification. Furthermore, this specification is not intended to limit the scope to the structural or design details shown herein, except as described in the following claims. It is therefore obvious that the specific embodiments disclosed above can be modified or altered, and all such variations are considered to be within the scope and spirit of the subject matter of the disclosure. Accordingly, the protection sought herein is as described in the following claims.

Claims

1. A method for producing the Pb-212 isotope, This involves introducing Th-228 into the discharge box. The aforementioned discharge box is equipped with a discharge source containing a high surface area material, and is introduced as follows: This involves introducing carrier gas into the discharge box through the carrier gas supply unit, The carrier gas is an inert gas, The carrier gas flows through the discharge box, The aforementioned Th-228 disintegrates into Rn-220 within the discharge box. The carrier gas is introduced to transport the Rn-220 resulting from the disintegration of Th-228 in the discharge box to one or more Rn-220 targets through a multiway valve connected to the carrier gas outlet port of the discharge box. To separate the Rn-220 from the carrier gas in one or more Rn-220 targets, The carrier gas is guided outside the one or more Rn-220 targets through the carrier gas exhaust port, The liquid is guided into one or more Rn-220 targets through the liquid supply unit, The Rn-220 is made capable of undergoing radioactive decay to a Pb-212 isotope within one or more Rn-220 targets, The liquid is capable of dissolving the Pb-212 isotope produced by the radioactive decay of Rn-220 in one or more Rn-220 targets. The liquid containing the Pb-212 isotope is guided from one or more Rn-220 targets to a Pb-212 collection container. A method comprising separating the Pb-212 isotope from the liquid.

2. The method according to claim 1, wherein the carrier gas is nitrogen.

3. The liquid is HCl or HNO ３ The method according to claim 1, wherein the acid solution is selected from the group consisting of the following.

4. The method according to claim 1, wherein the liquid is cooled to a temperature of -72°C or lower by a cooling unit coupled to one or more Rn-220 targets.

5. The method according to claim 1, further comprising introducing Ra-224 into the discharge box instead of introducing Th-228.

6. The method according to claim 1, wherein the flow rate of the carrier gas passing through the discharge box is controlled based on the mass flow rate.

7. During the first period, the carrier gas is guided to the first Rn-220 target through the multi-way valve coupled to the carrier gas outlet port of the discharge box, After the first period has elapsed, the first carrier gas exhaust port on the first Rn-220 target is opened, The method according to claim 1, further comprising, after the first period has elapsed, guiding the carrier gas to a second Rn-220 target through the multi-way valve coupled to the carrier gas outlet port of the discharge box for a second period.

8. In the aforementioned one or more Rn-220 targets, separating the Rn-220 from the carrier gas is The method according to claim 1, comprising bringing the carrier gas into contact with the liquid in one or more Rn-220 targets until the Rn-220 migrates from the carrier gas to the liquid.

9. The aforementioned high surface area material is approximately 1 m ２ ~100,000m ２ The method according to claim 1, comprising a porous metal or porous ceramic material having a surface area.

10. The method according to claim 9, wherein the porous metal includes one or more of titanium, zirconium, gold, platinum, iridium, tungsten, or combinations thereof.

11. An apparatus for producing Pb-212, It is a discharge box, The discharge box comprises a discharge source containing a porous, non-reactive material, The discharge box receives at least one of Th-228 and Ra-224 at its inlet. At least one of Th-228 and Ra-224 disintegrates into Rn-220 within the discharge box, A carrier gas supply unit coupled to the aforementioned discharge box, The carrier gas supply unit guides the inert gas into the discharge box. The inert gas is supplied by a carrier gas supply unit that transports the Rn-220 to the outside of the discharge box through the carrier gas outlet port of the discharge box, which is coupled to a multi-way valve. One or more Rn-220 targets coupled to the carrier gas outlet port through the multi-way valve, The carrier gas transports the Rn-220 from the discharge box to one or more Rn-220 targets. The Rn-220 comprises one or more Rn-220 targets that decay into Pb-212 within the one or more Rn-220 targets, A liquid supply unit coupled to one or more Rn-220 targets, The liquid supply unit guides the liquid into the Rn-220 target such that the liquid comes into contact with the carrier gas that transports the Rn-220 to the Rn-220 target. The Pb-212 resulting from the collapse of Rn-220 is transferred to the liquid by contact between the carrier gas and the liquid, in a liquid supply unit, A Pb-212 collection container coupled to the Rn-220 target system, An apparatus comprising a Pb-212 collection container, wherein the generated Pb-212 is guided into the Pb-212 collection container.

12. The aforementioned discharge box is Heat source and The system further comprises a shield structure positioned around the emission source, The shield structure absorbs the radiation generated by the decay of at least one of Th-228 and Ra-224 in the emission box. The porous, non-reactive material is 1 m ２ ~100,000m ２ The apparatus according to claim 11, comprising a metal, ceramic, or silica having a surface area.

13. The apparatus according to claim 11, wherein the emission source comprises porous, non-reactive metal fins selected from the group consisting of titanium, zirconium, gold, platinum, tungsten, iridium, or combinations thereof.

14. The carrier gas supply unit is N ２ gas source and The aforementioned N ２ A mass flow meter coupled to a gas source, The mass flowmeter is the N ２ N from the gas source ２ A mass flowmeter operable to measure the mass flow rate of the gas, The aforementioned N ２ It further comprises a control valve coupled to a gas source, The control valve is the N ２ N from the gas source ２ The apparatus according to claim 11, which is operable to control the flow rate of gas.

15. The apparatus according to claim 11, wherein the one or more Rn-220 targets include a zeolite or a metal chalcogenide having a zeolite-like structure.

16. The apparatus according to claim 11, wherein the liquid is an acid solution.

17. The system further comprises a temperature control unit coupled to one or more Rn-220 targets, The apparatus according to claim 11, wherein the temperature control unit is operable to cool the liquid introduced into the one or more Rn-220 targets through the liquid supply unit to a temperature of -72°C or lower.

18. It is a discharge box, A discharge source equipped with fins, The fins are made of a non-reactive porous material. Th-228 in the solvent is induced into the release chamber and adsorbed onto the fins of the release source, A shield structure positioned around the aforementioned emission source, The shielding structure is operable to absorb radiation generated by the radioactive decay of Th-228 in the release chamber. A carrier gas supply port, The carrier gas supply port is operable to provide an inlet for the carrier gas guided into the discharge box, It is a carrier gas outlet port, The carrier gas outlet port is operable to provide an outlet for the carrier gas from the discharge box, It is an evaporation outlet port, The evaporation outlet port is operable to provide an outlet for the evaporated solvent, It is a heat source, A discharge box comprising a heat source that is operable to provide heat to the discharge box in order to evaporate the solvent.

19. The aforementioned non-reactive porous material is approximately 1 m ２ ~100,000m ２ The discharge box according to claim 16, having a surface area.

20. The discharge box according to claim 16, further comprising a carrier gas blade operable to distribute the carrier gas entering the discharge box through a carrier gas supply port across the fins in a homogeneous flow.

Images