System and method for production and separation of decay products of radon

Abstract

There is provided a method for producing and separating at least one decay product of a radon isotope, the method comprising: providing a gaseous radon isotope; flowing the gaseous radon isotope over a solid stationary phase, wherein the solid stationary phase comprises a lipophilic functional group such that gaseous radon isotope is retained on the solid stationary phase; allowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase; and eluting the at least one decay product from the solid stationary phase.

Description

SYSTEM AND METHODFOR PRODUCTION AND SEPARATION OF DECAY PRODUCTS OF RADON

[0001] This application claims benefit of U.S. Provisional Application Serial No. 63 / 755,051, filed 6 February 2025, the entire contents of which are hereby incorporated herein for any and all purposes.FIEED

[0002] This disclosure relates to the production of a product from decay of radon isotopes, in particular methods and systems for the production and separation of at least one decay product of a radon isotope .BACKGROUND

[0003] There are several radionuclides (or “radioisotopes”) derived from the decay of radon isotopes which are useful for medical applications, such as treatment and imaging. However, production of these radionuclides from their respective parent radon isotopes is difficult and improvements are needed, including in the handling and use of the radon isotopes.

[0004] Pb-212 and Bi-212 are two radionuclides derived from one isotope of radon, namely Rn-220, which can be used in medical applications, including alpha radiation therapy. The half-life of these isotopes is short: the half-life of Pb-212 is 10.6 hours and the half-life of Bi-212 is 61 minutes, meaning that the storage and production of these radioisotopes poses challenges. Pb-212 and Bi-212 can be formed through a decay series which includes Rn-220 starting with thorium-228 (Th-228). The Th-228 decay series is illustrated in Fig. 1. Typical routes for producing Pb-212 and Bi-212 through this decay series either use Th-228 as a starting point (a Th-228 generator) or radium-224 (Ra-224 generator) as a starting point. Each type of generator comes with positives and drawbacks, such that operators must usually compromise when selecting a generator.

[0005] For example, Ra-224 based generators have a relatively short lifespan due to the shorter halflife of the Ra-224 (3.6 days), meaning they must be replaced at regular intervals of approximately one week. This adds complexity in the logistics of managing, obtaining and using a system. Further, over the course of that week, the isotope generation (i.e. activity) will decrease by a factor of approximately four, rendering it much less efficient in a short space of time. As such, Ra-224 / Pb-212 generators need to be regularly replaced and / or multiple generators must be used on a single site to avoid down-time during maintenance or replacement of the generators. In contrast, Th-228 has a half-life of 1.91 years meaning that Th-228 / Pb-212 generators have a much longer shelf life and provide a high activity for significant periods of time.

[0006] However, Th-228 / Pb-212 generators have their own downsides. Both generator types are difficult to handle due to high energy gamma rays and alpha-emitting gaseous radon-220 (Rn-220), but Th-228 / Pb-212 generators are particularly difficult to handle due to radiolytic damage to the generator (specifically, the matrix on which the Th-228 is provided) caused by the higher energy of the Th-228.

[0007] Further, existing methods of recovering Pb-212 and Bi-212 from these generators are lacking. Trapping and recovery methods are complex, requiring significant user intervention and handling. Thismeans the systems lack the efficiency and automation needed to enable safe, reliable, and simplified access to these radionuclides.

[0008] Pb-214 and Bi-214 are two other radionuclides of interest for medical applications. These can be derived from another isotope of radon (Rn-222), which itself is a decay product of Ra-226. Rn-222 can be isolated from Ra-226 to create a Pb-214 / Bi-214 generator. However, to-date there has been limited work carried out on improving the production of Pb-214 and Bi-214 in such generators. Further, given the relatively short half-lives of Pb-214 (26.8 min) and Bi-214 (19.7 min), improvements are required to increase availability of these radionuclides.

[0009] Another radionuclide of interest is At-211 , which can be derived from another isotope of radon (Rn-211). At-211 can be produced through irradiation of a Bi-209 target material in a cyclotron, where Rn-211 is an intermediate decay product. As with Pb-214 and Bi-214, to-date there has been limited work into improving methods of production of At-211.

[0010] A method and system which facilitate methods which utilise radon isotopes in manufacturing methods and the safe capture and efficient storage of the decay products of radon isotopes is therefore desirable.SUMMARY

[0011] In a first aspect, a method for producing and separating at least one decay product of a radon isotope is provided. The method comprises: providing a gaseous radon isotope; flowing the gaseous radon isotope over a solid stationary phase, wherein the solid stationary phase comprises a lipophilic functional group such that gaseous radon isotope is retained on the solid stationary phase; allowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase; and eluting the at least one decay product from the solid stationary phase.

[0012] In a second aspect, a system for producing and separating at least one decay product of a radon isotope is provided. The system comprises: a source of gaseous radon isotope; a capture chamber arranged to receive gaseous radon isotope from the source; a solid stationary phase provided within the capture chamber, the solid stationary phase comprising a lipophilic functional group such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationary phase; and an elution system configured to provide eluent to the capture chamber and elute the at least one decay product from the solid stationary phase.

[0013] In a third aspect, a method for producing and separating at least one decay product of a radon isotope is provided. The method comprises providing a source of a gaseous radon isotope; providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas; flowing the entrained carrier gas over a solid stationary phase, wherein the solid stationary phase comprises a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope in the entrained carrier gas can be retained thereon and decay to at least one decay product on the solid stationary phase; and allowing the gaseous radon isotope to reside on thesolid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase.

[0014] In a fourth aspect, a system for producing and separating at least one decay product of a radon isotope is provided. The system comprises a source of gaseous radon isotope; a capture chamber arranged to receive gaseous radon isotope from the source; a solid stationary phase provided within the capture chamber, the solid stationary phase comprising a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationary phase; and a carrier gas supply configured to supply a carrier gas to the system so as to entrain gaseous radon isotope generated by the source to form an entrained carrier gas and further to flow the entrained carrier gas over the solid stationary phase.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present disclosure will now be described in more detail with reference to the accompanying drawings, which are not intended to be limiting:

[0016] Fig. 1 provides a schematic view of the decay series for Th-228.

[0017] Fig. 2 provides a schematic view of a system according to the disclosure;

[0018] Fig. 3 provides a schematic view of a system according to the disclosure;

[0019] Fig. 4 provides a schematic view of apart of a modified version of the system of Fig. 3;

[0020] Fig. 5 schematically depicts a method according to the disclosure; and

[0021] Fig. 6 schematically depicts another method according to the disclosure.DETAILED DESCRIPTION

[0022] The present disclosure relates to improved methods and systems for capturing gaseous radon isotopes and producing at least one radionucleotide decay product from the captured radon isotopes . The methods and systems involve the providing gaseous radon isotopes onto, and its subsequent retention on, a solid stationary phase, where the decay product(s) can then form.

[0023] In a first aspect, a method for producing and separating at least one decay product of a radon isotope is provided. The method comprises: providing a gaseous radon isotope; flowing the gaseous radon isotope over a solid stationary phase, wherein the solid stationary phase comprises a lipophilic functional group such that gaseous radon isotope is retained on the solid stationary phase; allowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase; and eluting the at least one decay product from the solid stationary phase.

[0024] In a second aspect, a system for producing and separating at least one decay product of a radon isotope is provided. The system comprising: a source of gaseous radon isotope; a capture chamber arranged to receive gaseous radon isotope from the source; a solid stationary phase provided within the capture chamber, the solid stationary phase comprising a lipophilic functional group such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationaryphase; and an elution system configured to provide eluent to the capture chamber and elute the at least one decay product from the solid stationary phase.

[0025] The system and method in these aspects provide a system and method in which recovery of a decay product from a generator is maximised, increasing the efficiency of generation of isotopes from the system. This can significantly decrease the cost of the generation of the isotopes and increase availability of the decay product. Systems, including those implementing the method, also require less maintenance and downtime and can provide for automated and continuous production of these isotopes. These advantageous properties are achieved through the use of the solid stationary phase having a lipophilic functional group (and optionally a conjugated pi-system) and the increased trapping and release efficiency that this provides.

[0026] The method in the first aspect accordingly provides a method for obtaining a solid decay product from a source of gaseous radon (i.e. agaseous radon isotope). The method comprises generating a gaseous radon isotope and causing the radon gas to flow over a solid stationary phase. The solid stationary phase comprises a lipophilic functional group. The use of a functional group which is lipophilic may effectively retain the gaseous radon molecules thereon. It is believed that this is particularly effective due to the interactions between the large and polarisable noble gas molecule and the lipophilic solid stationary phase. The interaction of a lipophilic functional group with the radon retains a significant portion of the radon gas thereon even under conditions where a flow is provided. Further, the use of a lipophilic functional group can decrease water retention on the solid stationary phase, which otherwise can be difficult to remove and affect physisorption of radon. Over time, the radon will then decay on the solid stationary phase into at least one decay product and can further decay into other decay products. In the method of the first aspect and the system of the second aspect, the at least one decay product can then be eluted from the solid stationary phase. It has further been found that the lipophilic functional groups not only retain the radon effectively, but further also efficiently release the decay product(s), allowing for a high recovery of the radioactive decay product(s) without significant further work up or intervention. This is in turn provides users with a longer period in which to use the radioisotopes. This is beneficial since many of the decay products useful for medical applications have a short half-life. For example, Bi-212 has a half-life of only 61 mins and Bi-214 a half-life of 19.7 mins. Further, it allows for use of milder eluents, so that less processing and fewer additives are required to make use of the radioactive decay products in a pharmaceutical setting. The high trapping efficiency of the solid stationary phase also decreases the amount of any radioactive radon gas which remains in the system downstream of the solid stationary phase and would otherwise need to be processed or contained. Maintaining a high trapping efficiency accordingly reduces the radioactive waste produced and safety advantages are also provided.

[0027] Accordingly, the benefits above are realised by the use of a solid stationary phase that has lipophilic functional groups, since this increases the retention of radon gas on the solid stationary phase and further provides for straightforward and high yield subsequent release.

[0028] Further, the use of a gas (i.e. gaseous radon) together with an efficient solid stationary phase provides a system and method which are more flexible and easier to use than existing isotope generation systems and methods. For example, the gaseous radon isotope can be flowed directly over the solid stationary phase while still providing high retention. This means the radon isotope source can be separate from the downstream portions of the system, including the solid stationary phase. This also allows for the exposure of the solid stationary phase to the radon isotope to be more controlled, lending itself to a continuous process. The decay product isotopes are then generated directly on the solid stationary phase, each also being in solid form.

[0029] In a third aspect, a method for producing and separating at least one decay product of a radon isotope is provided. The method comprises providing a source of a gaseous radon isotope; providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas; flowing the entrained carrier gas over a solid stationary phase, wherein the solid stationary phase comprises a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope in the entrained carrier gas can be retained thereon and decay to at least one decay product on the solid stationary phase; and allowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase.

[0030] In a fourth aspect, a system for producing and separating at least one decay product of a radon isotope is provided. The system comprises a source of gaseous radon isotope; a capture chamber arranged to receive gaseous radon isotope from the source; a solid stationary phase provided within the capture chamber, the solid stationary phase comprising a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationary phase; and a carrier gas supply configured to supply a carrier gas to the system so as to entrain gaseous radon isotope generated by the source to form an entrained carrier gas and further to flow the entrained carrier gas over the solid stationary phase.

[0031] The method and system in these aspects provide a specific lipophilic functional group in the form of a functional group with a conjugated pi system. Without being bound by theory, it is believed that the conjugated pi-system may provide a high trapping efficiency for radon isotopes while also allowing for the subsequent release of the decay product(s). That is, by virtue of trapping radon gas, recovery of the decay product(s) is improved.

[0032] The end product of the method and system in this aspect can be a solid stationary phase loaded with the decay product(s). This advantageously can allow for transfer of the solid stationary phase thereon, for example to another site. In some cases, transfer of a solid loaded with the radioisotope can be safer compared to a solution comprising the radioisotope. Further, this can reduce the risk of radiolysis, where other products in the solution may be degraded by emitted particles. It may also be beneficial since the solid stationary phase can be transported while decay products are being formed, rather than needing to wait to the optimal decay has occurred before eluting.Solid stationary phase materials

[0033] As set out above, the solid stationary phase material in the first and second aspects comprises a lipophilic functional group and the solid stationary phase material in the third and fourth aspects comprises a conjugated pi-system. The noble gas radon - which can be present in these systems and methods as e.g. Rn-220, Rn-222 or Rn-211, for example - is large and polarizable and has been found to interact with lipophilic functional groups (whether these are conjugated pi-systems or otherwise) on the solid stationary phase, even under flowing conditions. Specifically, the radon gas can interact with e.g., permanent dipoles, in the lipophilic functional groups in the solid stationary phase via Van der Waals forces. After decay, the lipophilic functional group does not prevent recovery of the isotopes and, instead, these can be recovered with a relatively mild eluent in which the radiometal is soluble, enabling fast and simple recovery. These all contribute to the easier and more efficient recovery.

[0034] One example of a lipophilic functional group is one with a conjugated pi-system. These provide efficient trapping of radon on the solid stationary phase and allow for efficient recovery of the subsequently formed decay product(s) therefrom. The solid stationary phase material in the third and fourth aspects comprises a conjugated-pi system and, further, the lipophilic functional group in the first and second aspects may be a functional group with a conjugated pi-system. As used herein, a 'conjugated pi (or a) system' includes a sequence of alternating double and single bonds (or multiple bonds) in a molecule where a-clcctrons are delocalized over adjacent atoms. The conjugation can occur through linear or cyclic structures, and may involve atoms such as carbon, nitrogen, oxygen, sulphur, or other elements capable of participating in a-bonding interactions. For example, a conjugated pi system may arise within a functional group where sp or sp2bonding is present. As such, non-hybridised p orbitals can engage in pi bonding where a p orbital may contribute 0, 1 or 2 electrons. This leads to the p electrons in the functional group being delocalised within a conjugated system.

[0035] The use of a conjugated pi system to retain the radon may also facilitate the use of milder eluents, such as a less concentrated solution for elution, which may reduce the number of further processing stages required. As such, it may be possible to provide the decay product(s) at higher quality and / or more efficiently than was previously achievable if the decay product(s) were produced via conventional methods, i.e., in a solution of highly concentrated acid. Furthermore, the use of a dilute acid concentration as an eluent may prevent the need for additional purification or reconstitution, increasing the time available for use of the isotopes and, accordingly, their availability. The usage of solutions which have a lower concentration also increases the safety of the system overall as the solution in which the decay product(s) is held in is less corrosive.

[0036] Where the functional group has a conjugated pi system, the functional group may comprise a substituted or unsubstituted aromatic functional group. These are examples of a lipophilic solid stationary phase which comprise conjugated pi-systems. In the first and second aspects, the solid stationary phase may accordingly comprise a polymer comprising the lipophilic functional group and the lipophilic functional group may comprise a conjugated pi-system.

[0037] A substituted or unsubstituted aromatic (i.e. an unsaturated cyclic ring with conjugation) functional group has advantageously been found to provide effective functional groups for retaining radon and releasing the decay product(s). This is thought to be due to the presence of large, conjugated pi-systems both above and below the ring formed within the aromatic group. This region of higher electron density as compared to the rest of the molecule may provide a region in which the trapping efficiency of the radon is increased. This may also increase the trapping efficiency of the decay product(s) which is / are produced from the decay of radon. Substituted aromatic groups may provide larger conjugated pi-systems than unsubstituted aromatic groups, and thus, increased trapping efficiency.

[0038] Substituted or unsubstituted aromatic functional groups may include carbon-based aromatic groups, such as an aryl. An aryl group is a cyclic aromatic hydrocarbon. An aryl may comprise from 3 to 18 carbons in the cyclic ring. The aryl group may also be a heteroaryl where there is at least one heteroatom in the cyclic ring, such as nitrogen, oxygen, sulphur and phosphorus. A heteroaryl may comprise from 3 to 18 carbons and heteroatoms in the cyclic ring. Aryl groups accordingly include phenyl, azulenyl, biphenyl, indacenyl, fluorenyl, phenanthrenyl, triphenylenyl, pyrenyl, naphthacenyl, chrysenyl, biphenylenyl, anthracenyl, and naphthyl groups. Aryl groups can be unsubstituted or substituted. Example substituted aryl groups can be monosubstituted or substituted more than once, such as di-, tri-, and tetra-substituted groups. Aryl groups can be unsubstituted or substituted one or more times with, for example, alkyl, alkynyl, alkenyl, aryl, halide, nitro, amino, ester, ketone, aldehyde, hydroxy, carboxylic acid, or alkoxy groups. Multiple aryl and / or heteroaryl groups can be fused together to create a larger conjugated pi-system.

[0039] The lipophilic functional group may instead comprise a substituted or unsubstituted alkyl. “Alkyl” refers to straight chain and branched saturated hydrocarbon functional groups, which can comprise at least 3 carbon atoms. For example, from 3 to 30 carbon atoms, for example, 10 to 30 carbon atoms. Examples of straight chain alkyl groups include those comprising from 10 to 30 carbon atoms, such as n-decyl, n-undecyl, n-dodecyl, n-hexadecyl and n-icosyl. “Alkyl” as used herein includes cycloalkyl groups - i.e. comprising a non -aromatic carbon -based ring composed of at least 3 carbon atoms (e.g. 3 to 20 carbon atoms). Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. The carbon -based ring may include a heteroatom (i.e. forming a heterocycloalkyl functional group), such as at least one of nitrogen, oxygen, sulphur, or phosphorus.

[0040] The solid stationary phase may comprise a polymer comprising the functional group. The polymer may form a backbone or chain of the solid stationary phase and the functional group may be a functional group constituent of the polymer or the functional group may be an integral part of the backbone. As such, the solid stationary phase may be formed of a monomer comprising the functional group. The solid stationary phase may comprise a copolymer formed from a first monomer comprising the functional group and at least one second monomer. Polymers in general form useful solid stationary phases as the backbone can be selected to provide a robust, inert framework for the absorption of the radon but one which is easy to adapt with the required functional group.

[0041] Given the lipophilic nature of the functional group, example monomers from which the polymers can be derived include a monomer comprising a C2-C20 olefin (e.g. ethylene, propylene or butylene or longer chain alkenyl or alkynyl group, such as C12-C20 alkyls), a monomer comprising a C6-C18 monocyclic or multicyclic group (e.g., a phenyl group, a phenylene group, naphthalene group, etc.), and substituted or unsubstituted aromatic groups (e.g. styrene, divinylbenzene, and vinylbenzyl chloride).

[0042] Example polymers include styrene and / or divinylbenzene-based polymers, i.e. those which are formed from styrene and / or divinylbenzene monomers. These provide aromatic functional groups, for example, styrene providing a phenyl functional group on a polymer backbone. Accordingly, the solid stationary phase may comprise a polymer formed from a monomer of styrene or divinylbenzene. These may contribute to the solid stationary phase having a higher trapping efficiency of radon. The use of larger functional groups such as styrene or divinylbenzene may be advantageous since they provide a large conjugated-pi system which the radon may interact with. Another example polymer includes cross-linked methacrylate, such as methacrylate copolymers with ethylene glycol dimethacrylate (EGDMA) or divinylbenzene (DVB). These provide further pi-bonding which contributes to retention of radon and release of the metal decay product. Further examples include hyper-crosslinked polystyrene, which provides a microporous polymer with a very high surface area for absorption of radon, and phenol formaldehyde resin (PF).

[0043] Copolymers (i.e. polymers formed from at least two types of monomer) can be useful as the different monomers from which the copolymer is derived can be selected to provide different functionality or complimentary functionality. This has the potential advantage of being able to optimise the radon adsorption and the behaviour of the solid stationary phase material within the systems and method here in disclosed for capturing radon. The copolymer may be selected from at least one of poly(divinylbenzene-co-N-vinylpyrrolidone) (DVBco-NVP) copolymer, polystyrene -divinylbenzene (PS-DVB) copolymer, poly(vinyltoluene)-divinylbenzene (VTDVB), poly(ethylstyrene)-divinylbenzene, poly(p-methylstyrene)-divinylbenzene, poly(p-tert-butylstyrene)-divinylbenzene, poly(p-chlorostyrene)-divinylbenzene, poly(vinylphenol)-divinylbenzene or poly(vinylnaphthalene)-divinylbenzene. For example, the copolymer may be selected from poly(divinylbenzene-co-N-vinylpyrrolidone) (DVBco-NVP) copolymer or polystyrene -divinylbenzene (PS-DVB) copolymer. These have been found to advantageously have a very high capture rate of gaseous radon and further permit release under mild conditions. A copolymer of N-vinylpyrrolidone and divinylbenzene may comprise from 5 mole percent to about 60 mole percent N-vinylpyrrolidone, such as from 5 to 55 mole percent, or 12 to 30 mole percent. The balance may be divinylbenzene. Polystyrene -divinylbenzene (PS-DVB) copolymer may be hyper-crosslinked (HCL) PS-DVD (also referred to as post-crosslinked PS-DVB), which provides a microporous polymer with a very high surface area for absorption of radon. For example, such a copolymer may have a surface area of at least 350 m2 / g, such as at least 600 m2 / g (as measured by the methods set out herein). These can be produced by the methods set out in Castaldo R, Gentile G, Avella M, Carfagna C, Ambrogi V. Microporous Hyper-Crosslinked Polystyrenes andNanocomposites with High Adsorption Properties: A Review. Polymers (Basel). 2017 Nov 28;9(12):651. doi: 10.3390 / polym9120651, which is incorporated herein by reference. In another example, the copolymer may be selected from at least one of poly(methyl methacrylate) -ethylene glycol dimethacrylate (EGDMA), poly(butyl methacrylate)-EGDMA, poly(phenyl methacrylate) -EGDMA or poly (phenyl methacrylate) -DVB, poly(glycidyl methacrylate) -EGDMA, poly(benzyl methacrylate) -EGDMA.

[0044] By solid stationary phase, it is meant a solid material incorporating the functional group. The solid stationary phase may take the form of a powder or particles (e.g. beads), a monolithic structure (e.g. a resin or micro / mesoporous material), or a plurality of layers or agglomerated solids held together. In this disclosure, the solid stationary phase is held within a flow path and is separate to the conduit defining the flow path, and over which the radon gas passes. The radon gas may be conveyed by a carrier gas in which it is entrained. The solid phase may be any solid phase exposed to the flow path.

[0045] The solid stationary phase may take the form of a plurality of particles (e.g. a powder). These can be porous or non-porous. The particles may have a diameter or an average (mean) particle size of from 5 to 1000 pm, for example, from about 100 to about 500 pm. Where the particles are porous, these may comprise pores having a diameter ranging from 0.5 nm to 500 nm, such as 0.5 nm to 100 nm.

[0046] It is thought that the surface area of the solid stationary phase is a contributing factor to the ability of the solid stationary phase to effectively retain the radon gas. The solid stationary phase - for example as a porous body or powder - may comprise (i.e. have) a surface area or specific surface area of at least 10 m2 / g, for example at least 20 m2 / g, at least 50 m2 / g , at least 100 m2 / g, at least 200 m2 / g, at least 350 m2 / g, at least 500 m2 / g, at least 600 m2 / g or at least 1000 m2 / g. Higher surface area creates more efficient trapping (capture and then retention, leading to the radioactive decay) of radon as there is more capacity (adsorption sites). For example, excellent retention has been seen with exceptionally high surface areas of 1200 m2 / g (e.g. PS-DVB resin such as HR-P) and very good retention has been seen with HLB solid phases having a surface area of 600 m2 / g. Without wishing to be bound by theory, it is also thought that use of these high surface area materials also contributes to the high recovery of Pb-212 / Bi-212 or Pb-214 / Bi-214 or At-211 since the high surface area can reduce the probability of implanting the formed metal(s) into the trapping material through alpha-recoil and metal ions being available for redissolution in the elution vehicle, such as a dilute acid. This is not necessarily dependent on the presence of the lipophilic phase, but synergistically works with this to provide a phase which not only captures the radon but allows release of the decay product. The solid stationary phase as a porous body or powder may have a specific surface area in the range from 10 to 2000 m2 / g, such as from 20 to 2000 m2 / g , from 50 to 2000 m2 / g, from 200 to 2000 m2 / gram, 350 to 2000 m2 / gram, 200 to 1500 m2 / gram, 500 to 1500m2 / gram, 600 to 1500m2 / gram or 200 to 1200m2 / gram. The specific surface area can be determined using BET gas adsorption method, such as ISO 9277:2022 (Determination of the specific surface area of solids by gas adsorption - BET method). For example, measured using nitrogen adsorption manometry after vacuum degassing at 190° C. for at least two hours and calculated by themulti-point BET method. The above specific surface areas accordingly may be referred to as BET surface areas.

[0047] The amount of solid stationary phase provided, for example, within a single chamber for recovery, may be at least lOmg, such as at least 25mg, such as from 10 mg to 100g. For example, from 25mg to 10g. or 50mg to 5g (i.e. lOOOmg).

[0048] As demonstrated below, it has been found that near complete trapping of gaseous radon was achieved using 100 mg of solid stationary phase (e.g. HR-P resin (PS-DVB)) having a surface area of 1200 m2 / g at 10 mL / min flow rate of nitrogen carrier gas.

[0049] The solid stationary phase may be a water-insoluble solid stationary phase. This is advantageous as it allows for recovery of the isotopes formed thereon in a water-based solution without contamination of the solution with the solid phase material. This can make it easier to elute the decay product(s) which can then in turn be used as a pharmaceutical without contamination of the solid stationary phase. This provides greater freedom for the solid stationary phase materials as the subsequent biocompatibility may not be as important as it is not dissolved by the eluent.

[0050] By lipophilic functional group, it is meant that a functional group present on the solid stationary phase, in isolation, is lipophilic. That is, it has a LogP value of greater than 0 measured at a pH at which the functional group in isolation is in a neutral form and at 25°C. For example, where the solid stationary phase comprises a polymer comprising the functional group, the polymer is formed from a monomer comprising the functional group and it may be that the functional group or the monomer has a LogP value of greater than 0, where LogP is measured at a pH at which the monomer is in a neutral form and at 25°C. The functional group or monomer may have a log P value of 1.5 or more, a log P value of 2.0 or more or a log P value of 2.5 or more. The term “log P” as used herein, refers to the octanol water partition coefficient at 25° C. This is at a pH where the monomer or functional group has no charge (i.e. is neutral). The formula for the partition coefficient is log P=logio[analyte concentration in octanol] / [analyte concentration in water] .

[0051] It will be appreciated that the time required for allowing the gaseous radon to reside on the solid stationary phase such that at least a portion of the gaseous radon decays to the decay product(s) on the solid stationary phase will depend on the specific circumstances and can be readily derived in view of the half-lives of the isotopes involved. This may, for example, comprise waiting for at least 30 seconds, such as at least 1 minute, at least 15 minutes or at least 1 hour after exposure of the solid stationary phase to the radon gas.Radon Isotopes and Decay Product(s)

[0052] The gaseous radon isotope may be any radon isotope. The radon isotope may be selected from the group consisting of Rn-220, Rn-211 and Rn-222 or combinations thereof. Each of these isotopes are precursors to radioisotopes which have uses in nuclear medicine and accordingly are important precursors. Rn-220 has a half-life of 55s and so is suited to a process where the Rn-220 is quickly transferred to the solid stationary phase (e.g. using a carrier gas) as it will quickly decay on the solid stationary phase to the desired decay product(s). Where the radon isotope is Rn-220, the at least onedecay product is or may comprise Pb-212 and / or Bi-212. In some cases, this may be both Pb-212 and Bi-212. These are both useful in medical applications, for example alpha radiation therapy. The methods accordingly can comprise generating gaseous Rn-220, which is formed in the decay series from Th-228 (and therefore also from Ra-224), and causing the Rn-220 to flow over a solid stationary phase. The interaction of a lipophilic functional group with the Rn-220 retains a significant portion of the Rn-220 gas thereon, even under conditions where a flow is provided. Over time, the Rn-220 will then decay on the solid stationary phase into Pb-212 and further into Bi-212. In the method of the first aspect and the system of the second aspect, the Pb-212 and / or Bi-212 can then be eluted from the solid stationary phase. It has further been found that the lipophilic functional groups not only retain the Rn-220 effectively, but further also efficiently release the Pb-212 and / or Bi-212, allowing for a high recovery of the isotopes without significant further work up or intervention. This is in turn provides users with a longer period in which to use the isotopes, particularly for the short -lasting Bi-212 with a half-life of only 61 mins. Further, it allows for use of milder eluents, so that less processing and additives are required to make use of the Pb-212 / Bi-212 in a pharmaceutical setting.

[0053] Where the radon isotope is Rn-222, the at least one decay product is or may comprise Pb-214 and / or Bi-214. In some cases, this may be both Pb-214 and Bi-214. These are two further radioisotopes of interest in nuclear medicine with increasing numbers of studies developing methods based on these decay products.

[0054] Where the radon isotope is Rn-211 , the decay product is or may comprise At-211. At-211 can be produced through irradiation of a Bi-209 target material in a cyclotron, where Rn-211 is an intermediate decay product. For example, Bi-209 can be irradiated to undergo the reaction 209Bi(Li,5n)21 IRn to form Rn-211.

[0055] The decay product(s) may be eluted when at least 10% of the radon isotope captured on the solid phase has decayed to the desired decay product(s), such as at least 35% or at least 50%.Radon isotope sources

[0056] The gaseous radon isotope may be provided from a number of different sources, with different radon isotopes being a part of different decay series. The sources of the radon isotope may be a direct source, such as generator of the radon isotope . A generator may comprise a parent isotope which decays from the parent isotope to form the gaseous radon isotope as a daughter isotope. The parent isotope may be provided on a matrix or support. Alternatively, the generator may instead be a particle accelerator which uses a precursor material and a particle beam (such as a cyclotron using a proton beam) to irradiate the precursor material and generate radon (which may be through decay of isotopes formed by the irradiation).

[0057] Where the radon isotope is Rn-220, the system and methods may comprise a Th-228 or a Ra-224 source for Rn-220 gas. In other words, the source of Rn-220 as used in the systems and methods may be a Ra-224 generator (i.e. Ra-224 provided on a matrix) and / or a Th-228 generator (i.e. Th-228 provided on a matrix). These may be provided within a source chamber where present, or in place of the source chamber, so as to directly act as a source of Rn-220 gas. One of the advantages of the systemsand methods of the present disclosure is that either a Ra-224 or a Th-228 generator can be used, or both. For example, this means that a system could be fitted with either a Ra-224 generator and later fitted with a Th-228 generator. The Ra-224 and / or Th-228 source may be configured to be replaceable. As such, the source chamber may be releasably connectable to the rest of the system (e.g. a flow path) such that the Ra-224 and / or Th-228 source may be replaced. The disclosed system and method may have the advantage of providing a much safer method of producing Pb-212 and / or Bi-212. Though it may be possible to produce Pb-212 and / or Bi-212 using manual operation, the manual operation of Pb-212 and / or Bi-212 generators is very complex and is associated with radiation hazards. These include high energy gamma rays, alpha particles, and beta particles which are emitted during the production of Pb-212 and / or Bi-212.

[0058] Where the radon isotope is Rn-222, the system and methods may comprise a Ra-226 source for Rn-222 gas. Rn-222 can be isolated from Ra-226. In other words, the source of Rn-222 as used in the systems and methods may be a Ra-226 generator (i.e. Ra-226 provided on a matrix). Ra-226 is an abundant isotope of radon, with significant quantities of Ra-226 left over from legacy Ra-226 brachytherapy. Accordingly, these systems provide a useful way of capturing and using the decay products of Ra-226 and enabling use of these in nuclear medicine.

[0059] Where the radon isotope is Rn-211, the system and methods may comprise a generator for producing Rn-211. This may be a particle accelerator configured to irradiate a target material so as to generate Rn-211. For example, this may be or comprise a cyclotron, such as a cyclotron comprising a Bi-209 target. Rn-211 may be produced as product of Fr-211 electron capture decay, for example as set out in “Development of a preclinical 211Rn / 211At generator system for targeted alpha therapy research with 21 lAt” Crawford et. Al Nuclear Medicine and Biology, Volume 48, 2017, Pages 31-35, the content of which is incorporated herein by reference.System structure

[0060] The disclosed systems for producing at least one decay product comprise: a source of gaseous radon and a capture chamber arranged to receive gaseous radon isotope from the source. In other words, the capture chamber comprises the source or is fluidly connected with the source such that the source provides gaseous radon isotope to the capture chamber. The solid stationary phase is provided within the capture chamber.

[0061] The source of radon may be a direct source, such as generator of the radon isotope, or an indirect source, such as a flow path providing the radon. Where this is a direct source, such as a generator, this can be provided in the capture chamber. Alternatively, the (direct) source of radon may be provided elsewhere and in a source chamber (that is, the system further comprises a source chamber comprising the source of gaseous radon isotope) and the source chamber is connected to the capture chamber via a flow path such that gaseous radon isotope can flow from the source chamber to the capture chamber.

[0062] The flow path accordingly fluidly connects the source chamber to the capture chamber and may take the form of an opening in either or both chambers or a conduit extending therebetween, such as a tube or pipe. This is sealed from the remainder of the environment so as to transfer radon gas to thesolid stationary phase. A pump or other impeller may be used to cause radon to flow from the source chamber to the capture chamber and / or a carrier gas may be used. Where a carrier gas is used, the source of carrier gas may control the flow and pressure in the system (e.g. using a compressed tank of carrier gas) and / or there may be a further pump or other impeller. The flow path may extend beyond the capture chamber and incorporate other components, as will be discussed in more detail below. As used herein, “upstream” or “upstream location” may be used to refer to a location from which radon gas and / or carrier gas (where present) flows from. This may be the source chamber, or a carrier gas source supplying the source chamber. “Downstream” or “downstream location” may be used to refer to the end of the flow path, for example beyond the capture chamber.

[0063] As set out above, the source of the gaseous radon isotope may be a generator of the radon isotope. A generator may comprise a parent isotope which decays from the parent isotope to form the gaseous radon isotope as a daughter isotope. The parent isotope may be provided on a matrix or support. For example, where the gaseous radon isotope is Rn-220, the source of Rn-220 may be a Ra-224 generator (i.e. Ra-224 provided on a matrix) and / or a Th-228 generator (i.e. Th-228 provided on a matrix). These may be provided within the source chamber so as to directly act as a source of Rn-220 gas. Advantageously, for Pb-212 and Bi-212, the disclosed systems and methods allow use with both types of generators. In part, this is because of the ability to effectively use gas phase elution. Gas phase elution provides advantages over liquid phase elution since it allows the parent radionuclide (e.g. Th-228) to be deposited / supported on materials which are not limited to ion exchange resins as would be the case for liquid elution systems. This makes it possible to select the material properties most suited to the mother radionuclide. Gas phase elution thus provides flexibility regarding system design. The use of a solid stationary phase also provides backwards compatibility with existing liquid elution-based generator systems (e.g. Ra-224), thereby increasing the lifetime that these existing generators can be used for. Larger systems can also be constructed. A physically larger system can hold more radioactivity (Ra-224 or Th-228) in a larger volume at the same radioactivity concentration. Maintaining the same radioactivity concentration while scaling up, means that the system is not more sensitive to radiolysis associated decay from the increased amount of radioactivity and its lifetime is not adversely affected. Alternatively, the radioactivity concentration can be reduced to a lower concentration which will reduce radiolysis associated degradation of the solid phase and extend the lifetime of the generator by increasing the physical size of the system more than the amount of radioactivity. Another example is a Ra-226 generator, where the gaseous radon isotope is Rn-222. Rn-222 can be isolated from Ra-226 and in turn be used to provide Pb-214 and / or Bi-214.

[0064] A generator may instead be a particle accelerator. For example, this may be a cyclotron. Where the gaseous radon isotope is Rn-211, the source may be the output from a cyclotron comprising a Bi-209 target. This can be used to provide At-211. The source may therefore comprise a cyclotron comprising a Bi-209 target.

[0065] A carrier gas, which is present in the system of the fourth aspect and may be present in the system of the second aspect, can assist the radon isotope gas in its flow from an upstream to adownstream location. The carrier gas may be supplied from a carrier gas source which is in fluid communication with the capture chamber and, where present, a source chamber.

[0066] The capture chamber may comprise or be defined by a housing or enclosure, and the solid stationary phase may be disposed within the housing or enclosure. For example, the housing or enclosure may at least partially enclose a cavity defining the secondary chamber and a part of the flow path, and the solid stationary phase may be provided within the cavity. For example, it may be a powder received within the cavity. This may position the solid stationary phase in the path of the gaseous radon isotope and it may be that the solid stationary phase is arranged so as to extend across the capture chamber so that radon isotope will encounter the solid stationary phase. A radon isotope molecule which travels through cartridge may be more likely to encounter the solid stationary phase material provided in its path, thus be more likely to be retained upon the solid stationary phase, as compared to walls. Within such examples, the solid stationary phase may be configured such that a gas flowing through the solid stationary phase must traverse a non-linear path to pass from a position upstream of the capture chamber to a position downstream of the capture chamber. This may be in the form of a tortuous path. A non-linear path, or a tortuous path may be advantageous as it may cause the Rn-220 to interact with several portions of the solid stationary phase in order to flow through the cartridge. This may increase the number of interactions with the solid stationary phase, thus increasing the probability of radon isotope capture. Furthermore, the solid stationary phase may, may be present at different depths of the cavity such that when viewed in a cross-sectional projection, the solid stationary phase covers the entire cross section of the cavity.Cartridge

[0067] Within the disclosed systems comprising a source chamber, the system may comprise a removeable cartridge comprising the capture chamber, wherein the removeable cartridge is releasably connectable to the source chamber such that the capture chamber can be disconnected from the source chamber. For example, the systems may comprise a source chamber comprising the source; a flow path fluidly extending from the source chamber to an outlet; and the removeable cartridge comprising the capture chamber may be releasably connectable (e.g. configured to releasably connect to) the outlet of the flow path so that, when connected, gaseous radon can flow from the source chamber to the solid stationary phase via the flow path.

[0068] Similarly, the disclosed methods may comprise providing a source chamber comprising the source of gaseous radon isotope; providing a removeable cartridge comprising the solid stationary phase, wherein the source chamber is connected to the removeable cartridge such that gaseous radon isotope can flow from the source chamber to the solid stationary phase and wherein the removeable cartridge is releasably connectable to the source chamber such that the removeable cartridge can be disconnected from the source chamber. The method may further comprise disconnecting or removing the removable cartridge comprising the solid stationary phase and the at least one decay product from the source chamber prior to eluting the at least one decay product from the solid stationary phase.

[0069] The cartridge being removable such that the stationary phase containing the decay product(s) (and in some cases radon isotope) may be removed from the system may be advantageous since this facilitates the elution of the decay product(s) from the solid stationary phase in a more flexible manner. For example, if the cartridge is removable from the system, the cartridge may be removed from the system and eluted either in the same location, (e.g. adjacent to the capture chamber) or there may be a transportation stage in which the cartridge is transported to a second location such that it is eluted at that the second location. The former gives more flexibility for how it is eluted and can also further reduce the downtime of the system (and losses of radon isotope gas) by enabling the cartridge to be switched out for another cartridge and the decay product(s) to be formed or eluted “offline”. The latter also allows for this switching out but provides flexibility in transportation. For example, there may be a preference by a user to elute immediately prior to use . For example, it may be that there is a preference for a decay product which is further along the decay pathway and so this can be left to form off the system. Or it may be that the solid stationary phase is less prone to radiolysis than a solution, and so there is a preference to defer elution. In such a case, the solid stationary phase may be transferred with the decay product(s) on the solid stationary phase. It may be desirable, therefore, to have the cartridge designed such that there is a sealing mechanism which facilitates easy transportation of the cartridge.

[0070] The cartridge may be formed of any suitable material. Such materials include glass and polymer, such as high density polyethylene and polypropylene. The cartridge may have a volume of at least 0.0 ImL, such as at least 0.05mL. This may be from 0.0 ImL (0.01cm3) to 50mL (50 cm3). The solid stationary phase may be packed into the cartridge so as to extend across the flow path. A retaining element, such as a frit, may be provided at one or both ends of the cartridge retain the solid stationary phase therein.

[0071] The cartridge may comprise or be defined by a housing or enclosure, and the solid stationary phase may be disposed within the housing or enclosure. For example, the housing or enclosure may at least partially enclose a cavity defining the secondary chamber and a part of the flow path, and the solid stationary phase may be provided within the cavity. For example, it may be a powder received within the cavity. This may position the solid stationary phase in the path of the gaseous radon isotope.

[0072] In one example, the disclosed methods may further comprise flowing the gaseous radon isotope over a solid secondary phase provided in a second cartridge. Correspondingly, in one example of the disclosed system, the system may comprise a second cartridge fluidly connected to the source chamber via a flow path such that gaseous radon isotope may flow through. This may be in parallel to or in series with the first cartridge and enable the first cartridge to be removed from the system yet for radon isotope to still be captured. For example, in parallel and in series, this can provide a second cartridge to use once the first cartridge has been filled. In series, this may enable radon isotope to be retained within a second cartridge, or by a second stationary phase if it is not retained by the first cartridge comprising the solid stationary phase. The radon which is not retained by the solid stationary may be fed through a further system such that it can be passed through a cartridge again. In such a system and method, theradon isotope may pass through a series of removeable cartridges. Within such a series, there may be at least 2 removable cartridges.

[0073] Optionally, if there are two cartridges in series, the two cartridges may comprise different solid stationary phase materials. The second cartridge may comprise a solid stationary phase comprising a lipophilic functional group, such as a functional group comprising a conjugated pi system. The use of two different solid stationary phase materials may be advantageous since the interactions with different functional groups may be maximised. Furthermore, the solid stationary phases may be held at different temperatures. This may increase the likelihood of radon isotope adsorption as further flexibility is provided to the operator regarding the operating conditions.

[0074] The disclosed methods may further comprise, after removing the removable cartridge containing the decay product(s) from the outlet of the flow path, eluting the decay product(s)212 from the solid stationary phase.Carrier gas

[0075] The methods may further comprise providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas; and flowing the entrained carrier gas over the solid stationary phase. The systems may further comprise: a carrier gas supply configured to supply a carrier gas to the source chamber so as to entrain gaseous radon isotope to form an entrained carrier gas and further to flow the entrained carrier gas from the source chamber to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase. Within the methods disclosed, flowing the gaseous radon isotope over the solid stationary phase may comprise: providing a carrier gas; entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas; and flowing the entrained carrier gas over the solid stationary phase.

[0076] The provision of a carrier gas advantageously conveys the radon isotope gas from the source chamber to the capture chamber without relying on diffusion. This can, of course, lead to more effective distribution by not simply relying on diffusion of the radon isotope, but it also gives operators more control over the exposure of the solid stationary phase to the radon isotope gas and, further, over the location of the radon isotope gas. Further, the use of the particular disclosed solid stationary materials supports this by providing a stationary phase which can retain the radon isotope gas even under flowing conditions.

[0077] Within the disclosed systems and methods, the carrier gas may optionally be impelled through the system by a pump or impeller, such as a fan, which imparts velocity to the carrier gas molecules such that the carrier gas is moved in a downstream direction. Alternatively or additionally, the carrier gas may be recirculated through the system. For example, the system may be configured to redirect the carrier gas after the capture chamber (e.g. if present, before the delay line and any further filters). This may minimize risk of breakthrough or failure of a downstream charcoal safety trap. Similarly, the method may comprise recirculating the carrier gas to the source of radon isotope after flowing the carrier gas over the solid stationary phase.

[0078] The flow rate of the carrier gas will accordingly influence the manner in which the radon isotope will travel through the system. As such the flow rate of the carrier gas may be controlled such that it is optimised for the conditions of the system. It may further be that the flow rates of the carrier gas influences the adsorption on of the radon isotope gas in the capture chamber.

[0079] The carrier gas may comprise one or more of the following: nitrogen, helium, neon, argon, krypton, xenon and radon (the latter being separate to radon isotope). It has been found that noble gases and nitrogen are well suited to the function of a carrier gas. The carrier gas may comprise helium, neon, argon or nitrogen. The carrier gas may comprise nitrogen or helium gas. The smaller noble gases may be advantageous as these are less polarisable and, therefore, will be less likely to be retained on the solid stationary phase. Furthermore, without wishing to be bound by theory, it is thought that the gas cross-sectional area (nm2) will affect the radon retention on the stationary phase. In particular, it is thought that a higher cross-sectional area carrier gas will lead to fewer interactions between the sorbent and radon and cause reduced trapping efficiency (in part because it is thought that many interactions holding the radon gas on the stationary phase involve the carrier gas absorbed on the stationary phase surface). Nitrogen (0.162 nm2) and helium (0.213 nm2) have lower cross-sectional areas than the other noble gases (and these are similar in size and performed similarly to one another).

[0080] The use of an inert carrier gas may contribute to improved systems and methods as it does not react with the radon isotope gas being transported or, more generally, to radioactivity in the system.

[0081] Example flow rates of the carrier gas which can be used in the disclosed systems and methods include from 0.1 to 250 mL / min of the carrier gas. In some examples, the flow rate of the carrier gas may be from 0.1 to 100 mL / min, such as from 1 to 60 mL / min, from 1-40 mL / min, 1-30 mL / min, 1-20mL / min, 1-10 mL / min, 10-50 mL / min, 10-40 mL / min, 10-30 mL / min, 10-20 mL / min, 1-40 mL / min, or 1-30 mL / min. Optionally, the flow rate may be from 0.1 to 50 mL / min, such as from 1 to 20mL / min. The given flow rate may be the flow rate of nitrogen or helium carrier gas. The flow rate may be measured at atmospheric pressure.

[0082] At a flow rate of from 0.1-60mL / min, such as l-20mL / min, the amount of radon isotope deposited has been found to be up to 10% after 10 seconds, wherein the % is relative to the theoretical amount of radon isotope gas (based on the radioactivity models of the system) which can be collected over time. Advantageously, such a high rate of deposition, increases the throughput of the generator. This may further reduce the cost of operation of a generation site as fewer generators are required to achieve a desired output rate.

[0083] Within the disclosed systems and methods, the term carrier gas refers to a gas which can flow such that assists the flow of radon isotope from an upstream location to a downstream location. This assistance is achieved through the interaction of the radon isotope and the carrier gas.Bypass I Parallel Chambers

[0084] The systems and methods disclosed may include a bypass conduit fluidly connected to the flow path at a position upstream of the solid stationary phase and at a position downstream of the solid stationary phase. In examples where a cartridge is present, this feature provides a bypass around thetrapping cartridge. The systems and methods disclosed may further comprise a valve positioned in the bypass conduit configured to selectively allow flow through the bypass conduit such that the carrier gas and radon gas are selectively flowed through either the solid stationary phase or the bypass conduit. The valve may be operated manually by an operator or electronically via a switch.

[0085] Continuous flow of the radon isotope may be achieved through the operation of one or more bypass conduits within the disclosed systems and methods. For example, a bypass may be used when the capture chamber (e.g. a cartridge) is being replaced.

[0086] The bypass may be in the form of a pipe connecting the upstream and downstream locations and a valve to selectively allow flow either through the bypass or the solid stationary phase to provide an alternative route around the solid stationary phase. This may make the system easier to operate as there is no longer a need to monitor the shutdown and restarting of such a system. In particular, this prevents radioactive radon isotope or even daughter isotopes from building up within the flow path because there is an alternative pathway through which the flow can take place. The use of a carrier gas may assist in changing the direction of the flow of radon isotope.

[0087] In some examples of the disclosed systems and methods, there may be a plurality of capture chambers, each comprising a solid stationary phase. For example, there may be 2 or more chambers in parallel each configured to selectively receive gaseous radon isotope. The systems and methods disclosed may include the flow path and further an additional conduit fluidly connected to the flow path at a position upstream of the solid stationary phase of a first capture chamber and at a position downstream of the solid stationary phase. The other (second) capture chamber may be provided along this additional conduit. The systems and methods disclosed may further comprise a valve positioned in the additional conduit configured to selectively allow flow through the additional conduit such that the carrier gas and radon gas are selectively flowed through either the first capture chamber or the other (second) capture chamber. The valve may be operated manually by an operator or electronically via a switch. Such examples are advantageous since they allow for the radon isotope to flow to a second cartridge if the first trapping cartridge is removed and replaced. Within such a system the wasted radon isotope radioactive gas may be minimised. Within some examples of the disclosed systems and methods, it may be advantageous to remove and replace the cartridges simultaneously. Given the short half-life of some of the decay products, such as Pb-212 and Pb-214, being able to quickly remove and replace the cartridges is particularly advantageous.Elution of decay product(s)

[0088] In the second aspect, the system comprises an elution system configured to provide eluent to the capture chamber and elute the decay product(s) from the solid stationary phase. The system of the fourth aspect and the methods of the first and third aspects may further comprise an elution system provided to provide eluent from the capture chamber to elute the decay product(s) from the solid stationary phase. These may be solid decay product(s), such as solid Pb-214, Pb-212, Bi-214, Bi-212 and / or At-211. The elution system may comprise a source of eluent (such as an eluent reservoir, which may comprise a solution for elution - i.e. an eluent) which can be fluidly connected to the capturechamber. The elution system may further comprise a pump configured to pump eluent from the source of eluent to the capture chamber so that the decay product(s) can be recovered therefrom. The elution system may use the flow path of the system to provide at least part of the fluid connection and an outlet and / or there may further be an inlet conduit extending from the source of eluent and connected to or connectable to the capture chamber. There may be further an outlet conduit connected to or connectable to the capture chamber to provide an outlet for the isotope solution (i.e. the eluent together with the decay product(s)).

[0089] The elution stage may occur with the solid stationary phase still present in the system; in other words, before the solid stationary phase material is removed from the system. Alternatively, the systems and methods disclosed may be such that that elution is performed after the solid stationary phase has been removed from the system. The elution may, in some examples, be performed at a second location. In such an implementation, an eluent may be passed over or through the solid stationary phase to extract decay product(s). This can form an isotope solution, comprising the eluent and the radioisotopes. The elution may be performed using the aforementioned elution system, either manually under control of an operator or automatically via the elution system. Where automatically, this may be under the control of a controller, for example which may actuation the elution system on a particular trigger.

[0090] The system may comprise a sensor configured to monitor a loading level of a particular component on the solid stationary phase. For example, the sensor may be configured to provide a measurement signal indicative of an amount of at least one particular component on the solid stationary phase. This may be an amount of at least one of radon isotope and the decay product(s) (such as Pb-212 and Bi-212). The system may comprise a controller which is configured to determine the amount of at least one of radon isotope, and decay product(s) present on the solid stationary phase and, based on the determination, control the system. For example, control the elution system so as to elute decay product(s) from the solid stationary phase. Similarly, the methods disclosed herein may comprise determining an amount of at least one particular component on the solid stationary phase and, based on the determination, controlling operation of the system. This may be starting or controlling elution of the decay product(s) from the solid stationary phase.

[0091] Advantageously, having the elution stage at least in part controlled by the system can improve safety for the operator as there is no need to interact directly with the decay product(s) during its extraction and production.

[0092] As set out above, the elution stage may take place at a second location from that which the solid stationary phase collected the decay product(s). In the systems, the elution system may be provided at a second location separate to the location in which the source chamber is provided. If elution is performed at a second location, there may be more flexibility regarding the form in which decay product(s) are transported in and the systems and methods can be tailored to the specific use case for the decay product(s). It may be the case that, advantageously, the eluent may be selected according to the intended use of the decay product(s).

[0093] As set out above, the step of elution may comprise providing an eluent to the solid stationary phase. This may comprise flowing the eluent over or through the solid stationary phase. Any decay product(s) present on the solid stationary phase may then be dissolved in the eluent such that the decay product(s) can later be used, forming an isotope solution. The eluent (e.g. an eluent solution) may be an acid. The eluent may comprise a monoprotic acid, a diprotic acid or a triprotic acid. For example, the eluent fluid may comprise one or more of the following: HC1, HNO3, HF, HBr, HI, H2CO3, H2SO4 and H3PO4. Alternatively, the eluent may be a base, for example the eluent may comprise one or more of: NaOH, Li OH, KOH, Ca(OH)2, Mg(OH)2, Sr(OH)2 and Ba(OH)2. The concentration of the acid or base may be less than 4 mol dm-3, such as less than 2 mol dm=3. This may be from 0.005 to 2 mol dm’3, such as 0.01-2, 0.01-.1, 0.1-2, 0.1-1, 0.1-0.5, 0.1-0.3, or 1-2 mol dm’3. Optionally, the eluent may comprise 0.01-0.3, or 0.1 mol / dm’3of HC1, NaOH, or HNO3. Optionally the eluent may be HC1.

[0094] The solid stationary phase may undergo a preconditioning stage prior to elution. Accordingly, in disclosed systems, the elution system may comprise a preconditioning fluid source, which may comprise preconditioning fluid. Without being bound by theory, it is believed that preconditioning may contribute to an increased yield of Pb-212 and / or Bi-212 in the eluent following elution of the stationary phase by prewetting the stationary phase. The preconditioning fluid may be the same fluid as the eluent fluid or may be another acid or base selected from those set out for the eluent fluid or may be water or a water soluble organic solvent such as ethanol, for example.Further trapping of the radon isotope

[0095] The strength of the interaction between the radon isotope and the solid phase is important for the purpose of waste prevention. It may be advantageous to have a high trapping efficiency such that a high percentage of the radon isotope which passes through the solid stationary phase is retained upon the solid stationary phase. The radon isotope which is not trapped by the cartridge is radioactive and therefore must be handled safely. In some examples of the present methods and systems, there may be a trapping member positioned downstream of the solid stationary phase, wherein the trapping member is configured to retain gaseous radon isotope thereon. The trapping member may optionally be in the form of a filter.

[0096] One example of such a trapping member is a trapping member comprising activated carbon or charcoal, for example a charcoal filter. Such a filter may comprise activated carbon to increase the retention of any excess radon isotope. Some radon isotopes, such as Rn-220, are radioactive and have radioactive daughter products, therefore, it may be advantageous is safety terms to prevent radioactive radon isotopes (such as Rn-220) from leaving the system through an outlet.

[0097] Additionally or alternatively, the system may comprise a delay line located downstream of the solid stationary phase. The delay line is an extended part of the conduit defining the flow path, where the extension distance is selected such that at least a large proportion of the gas, for example the radioactive radon isotopes, will decay before the gas reaches the end of the delay line.Distributed network

[0098] Due to the high safety standards required to store and use certain parent isotopes, such as Th-228, in one example, the production of decay products, according to the disclosed systems and methods, can be carried out via a distributed network. That is, the method may further comprise transporting the solid stationary phase on which at least one decay product(s) is provided to a second location, after radon isotope has been retained upon the solid stationary phase at a first location. This second location, in some examples, may be a healthcare facility such that the decay product(s) may be used for a medical application. If the solid stationary phase is transported the second location, the elution may be performed either at the second location or at a third location before being used at a second location. In some examples, the method may comprise transporting the solid stationary phase on which at least one decay product(s) is provided to a second location or the eluent, containing the elution products of the solid stationary phase, to two or more locations. As such, the distributed network is formed from a first location in which radon isotope is retained upon the solid stationary phase, and either a single second location, or a series of locations to which the solid stationary phase with the decay product(s) loaded thereon is transported to.

[0099] The particular solid stationary phase used helps to enable the operating principle of the distributed network, which in turn improves availability of the isotopes and reduces costs. It is also advantageous because healthcare providers may not wish to have the risks and / or cost associated with having a generator on a health site.Sensing

[0100] In some examples, the systems may further comprise a monitoring device or sensor configured to monitor at least one component on the solid stationary phase. This may be at least one of the amount of radon isotope or the amount of at least one decay product (e.g. the amount of Pb-212 and / or the amount of Bi-212). The device or sensor may provide a measurement signal indicative of the amount of the at least one component. A controller of the system may further be configured to determine the amount of the component. The methods may further comprise monitoring and determining at least one of the amount of radon isotope on the solid stationary phase and / or the amount of at least one decay product on the solid stationary phase. Such a method may be called a direct monitoring method. The device or sensor may be configured to measure the radioactivity of a site adjacent to the solid stationary phase, for example for the radioisotope decay product(s) and, where present, a radioactive radon isotope. As such, this can be used as an output directly to the operator or an input piece of data which is used by an automated processing system. Where there are multiple solid stationary phases in the system, each may be provided with a device or sensor.

[0101] The monitoring device or sensor may be a radiation detector provided in proximity to or adjacent to the solid stationary phase which can be used to detect the amount of radiation emitted from the solid stationary phase. Similarly, the method of monitoring may comprise using a radiation detector to monitor the solid stationary phase. A radiation detector can be used to monitor the ionising radiation of a given radioisotope and, accordingly, can be used to monitor the amount of a radioisotope of radon on the solid stationary phase and / or the amount of at least one radioisotopic decay product on the solidstationary phase. For the amount of a radon radioisotope (E.g. Rn-220), the system and method may comprise determining the adhesion of the radon radioisotope with respect to time. The prediction of the rate at which a radon radioisotope adsorbs to the cartridge may be advantageous since it allows the system and / or method to produce a known / desired amount of decay product(s). Operators of devices for collection of gases adsorbed onto a solid phase will appreciate that the rate of adsorption varies with the amount of gas that has already been adsorbed onto a surface.

[0102] Alternatively or additionally, the measurement of the process is achieved indirectly. The method may comprise monitoring the radioactivity of the gaseous radon radioisotope flowing through the system at a position upstream of the solid stationary phase and at a position downstream of the solid stationary phase. The difference in radioactivity provides an indication as to the rate at which radon radioisotope is being disposed upon the solid stationary phase. The system may comprise a first sensor located upstream of the solid stationary phase and configured to provide a signal indicative of the radioactivity of the gaseous radon radioisotope and a second sensor located downstream of the solid stationary phase and configured to provide a signal indicative of the radioactivity of the gaseous radon radioisotope. The signals may be used by a controller to determine the rate at which radon radioisotope is being disposed upon the solid stationary phase.

[0103] It is expected that the various generators will have varying output of radon gas over time, particularly for those generators relying on parent isotopes with a shorter half-life, hence the amount of decay product(s) which can be produced per unit time will be expected to decrease over time as the activity of the source isotope decreases. This can lead to a more complex and variable radiosynthesis. Using a monitor may allow the radioactivity deposition of decay product(s) over time on a solid stationary phase to be monitored more easily. This may provide an operator with much more complete control over the amount of radioactivity that is used in a reaction and will improve radiochemistry reproducibility. The predictability of the output of a decay product(s) is a major factor when determining the suitability of a system, particularly within a healthcare environment.Implementation of System and Method

[0104] A computer program is also provided and comprises computer program code which is configured, when said computer program is run on one or more physical computing devices, to cause said one or more physical computing devices to implement the methods disclosed herein.

[0105] Also provided is one or more non-transitory computer readable media having a computer program stored thereon, the computer program comprising computer program code which is configured, when said computer program is run on one or more physical computing devices, to cause said one or more physical computing devices to implement the methods disclosed herein.

[0106] Control units (or controllers) (such as computing devices or processors) set out herein may be implemented in any suitable manner, with software and / or hardware, to perform the various functions required. One or all of the control units and computing devices may, for example, employ one or more microprocessors programmed using software (for example, microcode) to perform the required functions. Examples of processor components that may be employed in various aspects include, but arenot limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs). In various implementations, control units and computing devices (such as processors) may be associated with one or more non-transitory storage media such as volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM. The non-transitory storage media may be encoded with one or more programs that, when executed on one or more processors and / or controllers, perform the required functions. Various storage media may be fixed within a processor or controller or may be transportable, such that the one or more programs stored thereon can be loaded into the control units and computing devices (such as processors). The system may comprise each of these components, where present, in a single device or at a single location, or these may each individually or as a whole be distributed across a network, such as the internet. The system can also contain antenna, such as RFID structures, such that the outputs can be wirelessly transmitted and / or inputs can be wirelessly transmitted. The apparatus and system can also be configured such that the data generated is encrypted. In some non-limiting examples, the system includes a user interface, such as a display. Alternatively or additionally, the system may include a communications interface device, such as a wireless transmitter, configured to receive and transmit data to an external device, such as a personal computer, tablet, smartphone, remote server, etc.Specific implementations

[0107] Fig . 2 schematically depicts a system 100 for producing decay product(s) in the form of Pb-212 and / or Bi-212. The arrows produced depict a flow path within the system 100.

[0108] The system 100 comprises a generator 101 configured to generate radon gas, specifically Rn-220, and thus acts as a source of gaseous Rn-220, located in a source chamber 105. The generator 101 may be in the form of a Th-228 generator or a Ra-224 generator and may therefore comprise Th-228 on a matrix (such as a resin) or Ra-224 on a matrix (such as a resin). Due to the decay series, as illustrated in Fig. 1, these isotopes provide sources of Rn-220 gas. Such generators 101 may, in some examples, include a single Ra-224 or Th-228 generator or may encompass several generators 101 which act together to provide the system 100 with a source of Rn-220 gas. The source chamber 105 is connected to a flow path 120 which extends from the source chamber 105 to an outlet 160.

[0109] The system 100 also comprises a carrier gas source 110 which provides a carrier gas for conveying the Rn-220 gas from the source chamber 105 downstream towards the outlet 160. The carrier gas source 110 in this system 100 is a source of gas fluidly connected to the source chamber 105 so that the carrier gas can be supplied directly to the source chamber 105 and entrain the Rn-220 gas within the carrier gas. Given the flow imparted to the carrier gas, the carrier gas can then carry the Rn-220 gas from the source chamber 105 and into the flow path 120 through the remainder of the system 100.

[0110] Downstream of the source chamber 105 is a filter 130 (e.g. a filter 130 with pores of diameter 0.22 pm) arranged in the flow path 120 and configured to filter the Rn-220 entrained carrier gas. This can prevent contaminants, such as the parent isotopes of Rn-220 gas, from passing downstream while allowing the Rn-220 and the carrier gas to pass through.

[0111] Downstream of the filter 130 along the flow path 120 is a capture chamber 140. The capture chamber 140 is also fluidly connected to the flow path 120 and comprises a housing 141 in which a solid stationary phase 145 used for the adsorption of Rn-220 is provided. The solid stationary phase 145 comprises a water-insoluble polymer comprising a lipophilic functional group. The solid stationary phase 145 serves the purpose of retaining Rn-220 gas on it. Without being bound by theory, the specific polymer functional group may provide for a strong trapping efficiency of the Rn-220. As the carrier gas carries the Rn-220 gas over the solid stationary phase 145, the conjugated pi-system interacts with the large and polarizable Rn-220 molecules to attract and retain them (i.e. adsorb) on the surface of the solid station phase 145. The solid stationary phase 145 is as a powder provided across the width and height of the capture chamber 140 (in a plane perpendicular to the direction of flow) such that Rn-220-entrained carrier gas must pass through the arrangement of particles defining solid stationary phase 145.

[0112] The capture chamber 140 in this system 100 is provided within a monitoring device 148 in the form of a radiation detector. A radiation detector can be used to monitor the ionising radiation of a given radioisotope and, accordingly, can be used to monitor the amount of Rn-220 on the solid stationary phase 145. The monitoring device 148 is configured to monitor the amount of Rn-220 deposited on the solid stationary phase 145 so that the progression of loading onto the solid stationary phase 145 can be tracked. This can be used to ensure that the solid stationary phase 145 remains at an appropriate level and can avoid oversaturation. The monitoring device 148 may provide an output or indication of the amount.

[0113] Furthermore, in this system 100, an elution system 170 is provided which comprises an eluent reservoir 171 containing an eluent. The elution system 170 is fluidly connected to the capture chamber 140 via an inlet conduit 172 which joins the capture chamber 140 at a point upstream of the solid stationary phase 145 and further via an outlet conduit 173 which connects to the capture chamber 140 at a point downstream of the solid stationary phase 145. The elution system 170 also comprises a pump 174 which can pump eluent from the eluent reservoir 171 into the upstream part of the capture chamber 140 via the inlet conduit 172, through the solid stationary phase 145 and through the outlet conduit 173. The outlet conduit 173 may lead to a separate discharge vessel (not shown) or may lead to a reservoir (not shown) where the recovered isotope solution can be stored.

[0114] Downstream of the capture chamber 140 along the flow path 120 is a further filter 150, in the form of an activated carbon filter, used to trap any Rn-220 gas remaining in the carrier gas.

[0115] Downstream of the further filter 150 along the flow path 120 is a delay line 155 portion of the flow path 120. The delay line 155 is an extended part of the flow path 120 provided so that any Rd-224 remaining in the carrier gas at this stage will travel an extended distance along the flow path 120 before reaching outlet 160, encouraging decay of any remaining Rn-220 in the flow path 120 along this portion before the carrier gas exits the system 100 via the outlet 160.

[0116] In use, the generator 101 generates gaseous Rn-220 through the decay of Rd -224 to Rn-220 within the source chamber 105. The carrier gas is pumped into the source chamber 105 from the carrier gas source 110, which carrier gas entrains the Rn-220 within the source chamber 105 and carries theRn-220 gas into the flow path 120. As the Rn-220-entrained carrier gas passes through the flow path 120, it passes through filter 130 and any remaining parent isotopes of Rn-220 gas are prevented from passing downstream but Rn-220 and the carrier gas are able to continue through.

[0117] The Rn-220 entrained gas is then flowed into the capture chamber 140 and through and over the solid stationary phase 145. As the Rn-220 gas passes over the solid stationary phase 145, the Rn-220 molecules adsorb onto the surface of the solid stationary phase 145 due to the interaction of the lipophilic functional group with the Rn-220 molecules. The monitoring device 148 monitors the deposition of the Rn-220 onto the solid stationary phase 145.

[0118] The gas exiting the capture chamber 140 continues along the flow path 120 until the further filter 150 which traps any Rn-220 gas remaining in the carrier gas. The gas downstream of the further filter 150 then is conveyed into delay line 155 portion of the flow path 120 before eventually reaching outlet 160, at which point sufficient Rn-220 should have decayed that levels of Rn-220 will be below the required safety thresholds.

[0119] For the Rn-220 gas which is adsorbed on the solid stationary phase 145 within the capture chamber 140, this will begin to decay in situ on the solid stationary phase 145, forming Pb-212 and Bi-212 on the solid stationary phase 145. The half-life of Rn-220 is 55 s and the intermediate product of Rn-220 and Pb-212 is Po-216, which has a half-life of 0.146s. Accordingly, in only a matter of seconds of Rn-220 gas being immobilised on the solid stationary phase 145, Pb-212 will begin to form.

[0120] Solid Pb-212 and / or solid Bi-212 are recovered from the solid stationary phase 145 via elution. In the system 100 of Fig. 2, this can be achieved through the use of the elution system 170. Specifically, eluent can be pumped from the eluent reservoir 171 into the upstream part of the capture chamber 140 via the inlet conduit 172 and through the solid stationary phase 145. As eluent passes through the solid stationary phase 145, the Pb-212 and / or Bi-212 present on the solid stationary phase 145 is removed and recovered into the eluent forming an isotope solution. This isotope solution is then removed via the outlet conduit 173. The outlet conduit 173 may lead to a separate discharge vessel (not shown) or may lead to a reservoir (not shown) where the recovered isotope solution can be stored. Gas may be provided, either by the carrier gas source 110 or a separate supply (e.g. in the elution system 170) to remove all eluent from the capture chamber 140.

[0121] Further, it some situations, it may be advantageous with respect to retention and release to precondition the solid stationary phase 145 prior to exposure of the Rn-220 gas to the solid stationary phase 145. This can also be achieved using the elution system 170, for example, or it may be carried out using a separate preconditioning system (not shown) which may have a pump and reservoir which can be fluidly connected to the capture chamber 140 to provide preconditioning fluid thereto.

[0122] Accordingly, the output from the system 100 can be an isotope solution formed of eluent and the desired Pb-212 and / or Bi-212. This can then be used / distributed as required.

[0123] Fig. 3 depicts another system 200 for producing Pb-212 and / or Bi-212 according to the disclosure. The system 200 has a similar structure to the system 100 of Fig. 2 in many respects: it comprises a generator 201 configured to generate Rn-220, and thus acts as a source of gaseous Rn-220,located in a source chamber 205. The source chamber 205 is connected to a flow path 220 which extends from the source chamber 205 to an outlet 260. A carrier gas source 210 provides a carrier gas for conveying the Rn-220 gas from the source chamber 205 downstream towards the outlet 260. The carrier gas source 210 is fluidly connected to the source chamber 205 so that the carrier gas can be supplied directly to the source chamber 205 and entrain the Rn-220 gas within the carrier gas. Given the flow imparted to the carrier gas, this can then carry the Rn-220 gas out of the source chamber 205 and into the flow path 220.

[0124] Downstream of the source chamber 205 is a filter 230 arranged in the flow path 220 and configured to prevent the parent isotopes of Rn-220 gas from passing downstream but allowing the Rn-220 and the carrier gas to pass through.

[0125] Downstream of the filter 230 along the flow path 220 is a capture chamber 240. The capture chamber 240 is also fluidly connected to the flow path 220 and houses a solid stationary phase 245 used for the adsorption of Rn-220 is provided. The capture chamber 240 in this system 200 is also provided within a monitoring device 248 in the form of a radiation detector to monitor the amount of Rn-220 on the solid stationary phase 245.

[0126] Downstream of the capture chamber 240 along the flow path 220 is a further filter 250, in the form of an activated carbon filter, used to trap any Rn-220 gas remaining in the carrier gas. Downstream of the further filter 250 along the flow path 220 is a delay line 255 portion of the flow path 220. The delay line 255 is an extended part of the flow path 220 provided so that any Rd-224 remaining in the carrier at this point will have to travel an extended distance along the flow path 220 before reaching outlet 260, encouraging decay of any remaining Rn-220 in the flow path 220 along this portion before the carrier gas exits the system 200 via outlet 260.

[0127] Where this system 200 differs from the system 100 of Fig. 2 is as follows:

[0128] The capture chamber 240 in this system 200 is provided in the form of a removable cartridge 241, the interior of which defines the capture chamber 240 with the solid stationary phase 245 as a powder provided within the capture chamber 240. The removable cartridge 241 is filled with the solid stationary phase 245 so that Rn-220 gas passing through the cartridge 241 will pass through the solid stationary phase 245. The removable cartridge 241 is removable from the flow path 220 by disconnecting the conduit defining the flow path upstream and downstream of the cartridge 241 from the cartridge 241. This allows the cartridge 241 to be removed from the system 200.

[0129] The system 200 also comprises a bypass conduit 235. The bypass conduit 235 provides a secondary flow path in parallel to the flow path 220 and connects to the flow path 220 at a point upstream of the cartridge 241 (between the cartridge 241 and the filter 230, in this instance) and extends to a point downstream of the cartridge 241 where it is again fluidly connected to the flow path 220. Having a bypass conduit 235 may allow for a system 200 in which there is a continuous flow of the Rn-220 and carrier gas thereby providing a system 200 that does not need to be switched off during replacement of a solid stationary phase 245. This can also avoid or reduce the risks associated with radiolytic damage to one region, since the continued flow of gas will avoid accumulation of gas in aparticular region. A first valve 236 is provided at the upstream connection point and controls flow through the flow path 220 and the bypass conduit 235, such that it can divert flow from the flow path 220 (and accordingly the cartridge 241) into the bypass conduit 235, either in part or fully. A second valve 237 is provided at the downstream connection point and controls flow through the flow path 220 and the bypass conduit 235, such that it can allow flow from the bypass conduit 235 to rejoin the flow path 220, either in part or fully. Accordingly, the first valve 236 and second valve 237 together provide an assembly for selectively allowing flow either through the bypass conduit 235 or the solid stationary phase 245 so that the bypass conduit 235 provides alternative route for the carrier gas (which may be entrained with Rn-220) around the cartridge 241.

[0130] The system 200 of Fig.3 further differs from the system 100 of Fig. 2 in that it comprises an elution system 270, but one which is not fluidly connected to the capture chamber 240 in situ. In particular, the elution system 270 is provided as a component external to the main apparatus defined by the components arranged along the flow path 220 and bypass conduit 235 and is configured so that a cartridge 241 removed from the flow path 220 can be connected thereto to elute the Pb-212 and / or Bi-212. The elution system 270 in this instance comprises an eluent reservoir 271 containing an eluent, an inlet conduit 272 which can be fluidly connected to a cartridge 241 removed from the system so that eluent can be provided to the solid stationary phase 245, an outlet conduit 273 which can be fluidly connected to the opposite side of the cartridge 241 so that isotope solution formed through the elution of Pb-212 and / or Bi-212 can be recovered. The elution system 270 also comprises a pump 274 which can pump eluent from the eluent reservoir 271 into the upstream part of the capture chamber 240 via the inlet conduit 272, through the solid stationary phase 245 and through the outlet conduit 273. The outlet conduit 273 may lead to a separate discharge vessel (not shown) or may lead to a reservoir (not shown) where the recovered isotope solution can be stored.

[0131] System 200 further comprises a controller 280 for controlling the operation of the system 200. Controller 280 can be a computing device configured to control operation of the carrier gas supply 210, the first valve 236, the second valve 237 and further configured to receive an indication of the amount of Rn-220 gas loaded onto the solid stationary phase 245 from the monitoring device 248. Depending on the structure of the monitoring device 248, the indication may be a measurement signal indicative of the amount of Rn-220 loaded and the controller 280 may be configured to determine the amount of Rn-220 loaded based on the measurement signal, or the monitoring device 248 (or an intermediate device) may make the determination and provide controller 280 with the determined data.

[0132] In use, and with a cartridge 241 provided within the system, the generator 201 generates gaseous Rn-220 through the decay of Rd -224 to Rn-220 within the source chamber 205. The controller 280 causes carrier gas to be pumped into the source chamber 205 from the carrier gas source 210, which carrier gas entrains the Rn-220 within the source chamber 205 and carries the Rn-220 gas into the flow path 220. As the Rn-220-entrained carrier gas passes through the flow path 220, it passes through filter 230 and any remaining parent isotopes of Rn-220 gas are preventing from passing downstream but Rn-220 and the carrier gas can continue through. The Rn-220 entrained gas is then flowed into the cartridge241 (with the first valve 236 configured so that all of the airflow passes into cartridge 241) and through the capture chamber 240, through and over the solid stationary phase 245. As the Rn-220 gas passes over the solid stationary phase 245, the Rn-220 molecules adsorb onto the surface of the solid stationary phase 245. The monitoring device 248 monitors the deposition of the Rn-220 onto the solid stationary phase 245.

[0133] For the gas exiting the cartridge 241, this continues along the flow path 220 until the further filter 250 which traps any Rn-220 gas remaining in the carrier gas. The gas downstream of the further filter 250 with then move into delay line 255 portion of the flow path 220 before eventually reaching outlet 260, at which point sufficient Rn-220 should have decayed that levels of Rn-220 will be below the required safety thresholds.

[0134] To recover the solid Pb-212 and / or solid Bi-212 on the solid stationary phase 245, the cartridge 241 can be removed from the flow path 220. Specifically, the controller 280 will monitorthe deposition and, after a particular loading threshold is reached, will notify an operator that the cartridge 241 is ready to be removed. Removal of the cartridge 241 is achieved by diverting the flow of the carrier gas through the bypass conduit 235 (by actuating the first valve 236 and the second valve 237) rather than through the cartridge 241. This avoids having to close down the system 200 entirely. If required, the flow rate of the carrier gas may be reduced. Any Rn-220 in the carrier gas will instead be trapped on the further filter 250. In this system 200, the controller 280 controls operation of the first valve 236 and the second valve 237 to redirect the carrier gas into the bypass conduit 235 (although it will be appreciated that in other systems, this may be manually carried out by an operator). If required, a second cartridge 241 can then be introduced into the flow path 220, the carrier gas rediverted back through the flow path 220 (rather than the bypass conduit 235) through the actuation of the first valve 236 and the second valve 237 and the process of capturing Rn-220 on the new, second cartridge 241 can be repeated. The cartridge 241 once removed can then be processed so that the radioisotopes are recovered. For example, in this system 200, this can be connected to the elution system 270. For completeness, we note that the elution system 270 may be located at the same location to the rest of the system 200 or at a different site, such that transportation of the cartridge 241 may occur before elution. Elution here can be achieved through the use of the elution system 270. Specifically, eluent can be pumped from the eluent reservoir 271 into one side of the cartridge 241 via the inlet conduit 272 and through the solid stationary phase 245. As eluent passes through the solid stationary phase 245, the Pb-212 and / or Bi-212 present on the solid stationary phase 145 is removed and recovered into the eluent forming an isotope solution. This isotope solution is then removed via the outlet conduit 273. The outlet conduit 273 may lead to a separate discharge vessel (not shown) or may lead to a reservoir (not shown) where the recovered isotope solution can be stored.

[0135] Fig. 4 schematically depicts a part of a modified version of the system 200 of Fig. 3, where like reference numerals are used to denote like parts. The structure of the modified system 200’ shown in Fig. 4 is identical to that of the system 200 of Fig. 3 except as discussed below.

[0136] In the system 200’ shown in Fig. 4, instead of a bypass conduit 235’ being a bypass, the bypass conduit 235’ instead comprises a second cartridge 241” located along the bypass conduit 235’. As such, the system 200’ comprises two parallel lines: the flow path 220’ which passes through a first cartridge 241’ and the bypass conduit 235’ which comprises a second cartridge 241” and a second monitoring device 248”. Once loading of the first cartridge 241’ is complete, the system 200’ can switch to providing the Rn-220-entrained carrier gas to the second cartridge 241” while the first cartridge 241’ is processed and removed. As such, the bypass conduit 235’ here facilitates the Rn-220 source being operable continuously such that there is no need to close off a Ra-224 or Th-228 generator whilst the first cartridge 241’ is being removed and replaced.

[0137] It will, of course, be appreciated that there may be plural bypass conduits in parallel such that there are plural additional cartridges. Other configurations are also possible. For example, although the first cartridge 241 ’ and second cartridge 241 ” in this system 200’ are loaded separately, these could alternatively be simultaneously be loaded. Alternatively, these could be arranged in series, with one cartridge being replaced while the other(s) continue to be loaded with Rn-220 (e.g. with a local bypass around each cartridge).

[0138] Other modifications are also contemplated.

[0139] For example, although in the systems 100, 200 of Figs. 2 and 3, there is only a single radioactive source (i.e. generator 101, 201), in some examples the radioactive source may comprise multiple radioactive sources. These can provide a more consistent source of Ra-224, since they may be selected so that they do not expire at the same time. One example of this would be the use of two Ra-224 sources, wherein both of the sources are replaced once every 8 days. As such, on day 4, the first source may be replaced, on day 8 the second source may be replaced and on day 12 the first source may be replaced, such that the replacement continues in a similar fashion. This enables the Ra-224 to be supplied at a more constant rate. Though there is a much longer half-life of Th-228, a similar principle may be applied to ensure a semi-constant rate of Th-228 into the system.

[0140] Although in the systems 100, 200 of Figs. 3 and 4, the carrier gas source 110, 210 is provided upstream of the source chamber 105, 205 in series with the rest of the components of the system 100, 200 and providing carrier gas directly to the respective source chamber 105, 205, it will be appreciated that other arrangements are possible. For example, alternatively, the carrier gas source 110, 210 may be fluidly connected to the respective flow path 120, 220 after (i.e. downstream of) the respective source chamber 105, 205. The flow of the carrier gas may be used to draw Rn-220 gas into the flow path 120, 220 without the carrier gas entering the source chamber 105, 205 directly. Furthermore, the carrier gas may be supplied through a pressurised container, where is the flow rate of the carrier gas may be regulated through a pressure valve. This may be monitored by a flow measurement device which may inform the controller 280, where present, of the flow rate. Controller 280, where present, may control the pressure valve.

[0141] Although not depicted, the systems 100, 200, 200’ may further comprise a carrier gas pumping means, such as a pump or impeller. These may be present anywhere along the system 100, 200, 200’and there may be plural of these distributed throughout the system 100, 200, 200’, enabling the flow rate of the Rn-220 and the carrier gas to be controlled adjusted. Without being bound by theory, it is believed that an impelling means being in close proximity to the filter 130 and / or the Ra-224 may assist with the transport of Rn-220 and carrier gas through the system. Alternatively or additionally, the carrier gas may be recirculated through the systems 100, 200, 200’ . For example, the flow paths 120, 220 may each further comprise a conduit extending from a point after the capture chamber 140, 240 back to the source chamber 105, 205 such that the carrier gas may be reintroduced to the source chamber 105, 205 after the capture chamber 140, 240. This may minimize risk of breakthrough or failure of a downstream charcoal safety trap.

[0142] Although the systems 100, 200, 200’ of Figs. 2 to 4 have been described with respect to Rn-220 and the decay products Pb-212 and Bi-212, it will be appreciated that this system could also be used with other radon isotopes. For example, the source of radon could be a generator configured to generate Rn-222, act as a source of gaseous Rn-222, located in the respective source chamber. This may be a Ra-226 generator (i.e. Ra-226 provided on a matrix). The decay products formed on the solid stationary phase would accordingly comprise Pb-214 and / or Bi-214.

[0143] Alternatively, the systems 100, 200, 200’ may provide a source in the form of an output from a particle accelerator. This may be instead of the source chamber, and accordingly provide the radon gas directly to the capture chamber, or the particle accelerator may form a part of or comprise the source chamber. For example, the source may be an output from a cyclotron generating a radon isotope, or the source may comprise a cyclotron generating the radioisotope. The radon isotope in such a system and method is or may comprise Rn-211 and the decay product is or may comprise At-211. The remainder of the system may be as set out for the systems 100, 200, 200’ of Figs. 2 to 4.Automation of the system and / or methods

[0144] Within the disclosed systems and methods, such as those depicted in Figs. 2 to 4, a controller or control system may be used to control the system and method. For example, this may be used to monitor parameters of the systems and to subsequently alert an operator in response to a certain outcome or threshold being reached. The monitoring of such parameters may also then be used to determine the operation of the system. Such parameters may include one or more of: the flow rate of carrier gas and / or radon isotope through the system, the radioactivity of the solid stationary phase, the radioactivity at one or more further positions within the apparatus and the temperature and / or pressure at one or more locations in the apparatus.

[0145] In one example, the radioactivity of the solid stationary phase is monitored by means of a radioactivity measuring device. Using a prediction model, which is based on one or more flow rates measured within the system, the mass of radon isotope deposited on the solid stationary phase is estimated. The controller may adjust the flow rate of the carrier gas and hence the radon isotope gas to increase or decrease the rate of deposition of radon isotope based on a preset section made by an operator regarding the rate of deposition required and / or the unused radon isotope which is tolerable for this rate of deposition. When the solid stationary phase is at a particular loading, the user can be alerted. In oneexample, such alerts to the user may be in the form of data being transmitted to the user or to an output display.

[0146] An automated module, such as an FX2M may be used to implement the disclosed systems and methods. Modules such as this have the advantage of being easy to operate such that the processing stages require minimal manual intervention.Methods

[0147] Fig. 5 schematically depicts a method 390 for producing and separating at least one decay product of a radon isotope, the method comprising: providing a source of gaseous radon isotope; flowing the gaseous radon isotope over a solid stationary phase 394, wherein the solid stationary phase comprises a lipophilic functional group such that gaseous radon isotope is retained on the solid stationary phase; allowing the gaseous radon isotope to reside on the solid stationary phase 396 such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase; and eluting 398 the at least one decay product from the solid stationary phase.

[0148] Fig. 6 schematically depicts a method 490 for producing and separating at least one decay product of a radon isotope, the method comprising: providing a source of a gaseous radon isotope 492; providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas 494; flowing the entrained carrier gas over a solid stationary phase 496, wherein the solid stationary phase comprises a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope in the entrained carrier gas can be retained thereon and decay to at least one decay product on the solid stationary phase; and allowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase 498.Specific examples

[0149] It has been found that suitable solid stationary phases can be found in commercially available cartridges, such as solid phase extraction cartridges. One example is the HR-P cartridge from, Macharey-Nagel having minimum resin load: 380 mg (measured resin load was 510 mg + / - 6mg (n=6)) . The particle size within this cartridge is 50 - 100 pm and the solid stationary phase is a polystyrene -divinylbenzene copolymer (PS / DVB). Another example of a suitable cartridge type are the Oasis HLB series, which use a reversed-phase solid phase derived from the monomers: N-vinylpyrrolidone and divinylbenzene. For example, the Oasis HLB-plus (available from Waters) with a sorbent mass of 225 mg. The solid stationary phase has a particle size of 60 pm and a pore size of 80 x 10’10m. Oasis® HLB Plus Light Cartridge (available from Waters) is also suitable and has a sorbent mass of 30mg, a particle size of 30 pm and a pore size of 80 x 10"10m.Example 1

[0150] In a first example, the ability of HR-P cartridges (HR-P cartridge, Chromafix, Ref 731841, Macharey and Nagel, minimum resin load: 380 mg) to act as a solid stationary phase and retain Rn-220 gas was investigated using a system having a structure similar to system 200 of Fig. 3.Helium carrier gas

[0151] During loading, a Ra-224 generator was used to generate Rn-220 gas. The Rn-220 gas was transferred to the HR-P cartridge using a carrier gas (10 mL / min helium gas using the gas flow controller on a Tracerlab FX C synthesis module). The gas transfer was stopped after 20 hours and 23 minutes. The activity of the solid stationary phase was 70.8 pCi at 3 hours after the gas transfer was stopped indicating that 79% of all the radon emanated from the radium -224 generator was transferred to the HR-P cartridge.

[0152] The cartridge was conditioned with ethanol (5 mL), water (5 mL) and air (10 mL) then eluted using an elution program of: 0.3 mL 0.1M HC1; followed by 5 mL of air; followed by 0.7 mL 0.1M HC1 to form an isotope solution comprising the eluent and radioisotopes. It was calculated that 79.9% of the radioactivity was eluted in 0.7 mL of 0.1 M HC1.Nitrogen carrier gas

[0153] The experiment was repeated under the same conditions, but with a nitrogen carrier gas at a flow rate of 11.5 mL / min. This experiment took place over 182 minutes.FindingsTable 1 : Results of Example 1

[0154] The trapping yield was calculated based on theoretical calculations regarding how much Pb-212 may be obtained at a given time. This is based on the Rn-224 initially present in the system and its activity rate. Using the flow time and the half-lives of the Rn-224 and its decay products, the trapping yield calculated as follows: (Isolated Pb-212 at the end of the experiment) / (Maximum produced Pb-212 at the end of the experiment) expressed as a percentage. This is based on the activity levels of the cartridge and does not account for the subsequent elution.

[0155] Table 1 indicates that high trapping efficiency yields can be obtained through the use of HR-P cartridges. In particular, the carrier gases nitrogen and helium were well suited to transferring Rn-220 gas from a generator to a solid phase and, further, acting as a mobile phase for the solid phase / mobile phase interaction.Example 2

[0156] Example 2 investigated the effect of pre-conditioning the cartridges and the use of different cartridge types and, hence, solid stationary phases.

[0157] During loading, a Ra-224 generator was used to generate Rn-220 gas. The Rn-220 gas was transferred to the solid phase extraction cartridge using a carrier gas (10 mL / min helium gas using the gas flow controller on a Tracerlab FX C synthesis module). The gas transfer was stopped after approximately 1 hour.380 mg (measured resin load was 510 mg + / - 6mg (n=6)).

[0158] All of the cartridges used provided good trapping of Rn-220, with the HLB plus cartridge and the HR-P cartridge having the highest mean trapping percentages. Without wishing to be bound by theory it is believed that the high trapping percentage observed within the HR-P and the HLB plus cartridges is due to the presence of the lipophilic groups having conjugated pi-systems. Although the HLB light cartridge had a lower trapping rate of just 24% with 30mg or sorbent, it is thought that this is primarily as a result of the low sorbent mass. The effect of sorbent mass on trapping yield was further investigated. Despite having the highest sorbent mass, the tC18 cartridge had a mean trapping percentage of 33%.

[0159] With regard to release, a HC1 eluent was used to extract the daughter products of Rn-220 gas, namely Pb-212 and Bi-212. Notably, tC18 plus had a much lower trapping percentage than the other cartridges tested. Without being bound by theory, it is theorised that the polymer based cartridges HLB plus, HLB light and HR-P cartridges contributed to the much higher release percentages than the trimethylsilyl end capped C18 functionalized silica based tC18 cartridge. The easy release of the daughter products of Rn-220 by means of an eluent may be advantageous since this provides an operator with the ability to generate a solution and, importantly, a mild solution requiring minimal modification in order to generate a pharmacologically-acceptable solution. Specifically, this may be advantageous from a further processing perspective since chemically milder eluents require fewer processing stages before being used within many desired applications. This example includes examples where the concentration of the eluent was altered for the HR-P cartridge for four samples. It was found that the release percentage was still very high (98%) for 0. IM HC1 as compared to the IM HC1. As such, it may be possible to have a low concentration of acid and still retain a high mean release percentage.Example 3

[0160] Example 3 investigated the influence of flow rate of a helium carrier gas on the ability of the HR-P solid stationary phases (HR-P cartridge 510mg) to retain Rn-220 gas. The flow rate was varied from 10 mL / min to 60 mL / min. As shown in Table 3, below, the ability of the cartridges to trap the Rn-220 is not significantly negatively affected by the faster carrier gas flow rate. This allows for significant flexibility within the systems and methods, since it allows for increased distance between the generators and the solid stationary phase without reducing the trapping yield. The maintained high trapping yield at higher flowrates also mean that a generator holding the parent radionuclide (Th-228 or Ra-224) can be physically larger to for instance either have more radioactivity at a maintained radioactivity concentration or the same amount of radioactivity at a lower concentration.Table 3.Example 4

[0161] Different sized HR-P cartridges were used to investigate the relationship between the mass of the solid stationary phase within a HR-P cartridge and the trapping yield of Rn-220.

[0162] The stationary phase inside the HR-P cartridge was removed by first opening the cartridge and gently removing the top frit. The packing material was emptied into a glass vial. 50-400 mg of packing material was added back into the cartridges and the frits were put in place holding the packing material. The caps were also put back on. All of the HR-P cartridges holding 50-400 mg of packing material (and the original cartridge with -510 mg packing material**) were conditioned in the following manner: 10 mb EtOH was added followed by 10 mb 1.0 M HC1 (Tritpur, IM, Supelco, #1.09057.1000). After 5 minutes 10 mb water (until the eluted water is no longer acidic) (Cytiva, HyPure WFI, Quality Water) and 10 mb EtOH was added. The cartridges were dried using compressed air for 30 minutes until the weight of the cartridge was less than or equal to the weight before conditioning it. After this procedure, the powder within these samples was deemed to be free-flowing.

[0163] The HR-P cartridges were then loaded with Pb-212 from a Ra-224 generator by passing Rn-220 gas in a stream of helium gas flowed at 10 mL / min through the HR-P cartridge for times varying between approximately 30 minutes and 20 hours (as set out in Table 3, below).

[0164] Elution was then carried out using 0.1M HC1 into Eppendorf vials. The Eppendorf vials were weighed before to determine the volume in each vial. The vials were also assayed inside a dose calibrator after waiting for at least 12 hours after elution to allow Pb-212 to come into equilibrium with its radioactive daughter nuclides.

[0165] The trapping efficiency was calculated by modelling the theoretical yield of Pb-212 and from measurements taken during the experiment.Table 4: Example 4 results*0.7mL eluent was used for this sample. ** This sample was eluted with 0.04M HC1 instead of 0.1M HC1 as was the case with the other samples.

[0166] It is clear from the results that there is good retention performance across all of the solid stationary phase masses, and a strong release across all sizes. The performance is higher at lOOmg (99.5mg) and above.

[0167] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope. These and other features, aspects, and advantages of the apparatus, systems and methods of the present disclosure can be better understood from the description, appended claims or aspects, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the figures to indicate the same or similar parts.

[0168] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the disclosure, from a study of the drawings, the disclosure, and the appended aspects or claims. In the aspects or claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent aspects or claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

[0169] The systems and methods will now be disclosed with reference to clauses:

[0170] Clause 1. A method for producing and separating at least one decay product of a radon isotope, the method comprising:providing a gaseous radon isotope;flowing the gaseous radon isotope over a solid stationary phase, wherein the solid stationary phase comprises a lipophilic functional group such that gaseous radon isotope is retained on the solid stationary phase;allowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase; andeluting the at least one decay product from the solid stationary phase.

[0171] Clause 2. The method of clause 1, wherein the solid stationary phase comprises a polymer comprising the lipophilic functional group and wherein the lipophilic functional group comprises a conjugated pi-system.

[0172] Clause 3. The method of clause 2, wherein the functional group comprises a substituted or unsubstituted aromatic functional group.

[0173] Clause 4. The method of any preceding clause, wherein the solid stationary phase comprises a polymer comprising the functional group.

[0174] Clause 5. The method of clause 4, wherein the polymer is formed from at least one monomer, the at least one monomer comprising styrene or divinylbenzene.

[0175] Clause 6. The method of clause 5, wherein the solid stationary phase comprises a copolymer formed from a first monomer comprising the functional group and at least one second monomer, optionally wherein the copolymer is selected from poly(divinylbenzene-co-N-vinylpyrrolidone) (DVB-co-NVP) copolymer or polystyrene -divinylbenzene (PS-DVB) copolymer.

[0176] Clause 7. The method of clause 1, wherein the functional group comprises a substituted or unsubstituted alkyl.

[0177] Clause 8. The method of any preceding clause, wherein the radon isotope is selected from the group consisting of Rn-220, Rn-211 and Rn-222.

[0178] Clause 9. The method of clause 8, wherein the radon isotope is Rn-220 and the at least one decay product comprises Pb-212 and / or Bi-212.

[0179] Clause 10. The method of clause 8, wherein the radon isotope is Rn-222 and the at least one decay product comprises Pb-214 and / or Bi-214.

[0180] Clause 11. The method of clause 8, wherein the radon isotope is Rn-211 and the at least one decay product comprises At-211.

[0181] Clause 12. The method of any preceding clause, wherein flowing the gaseous radon isotope over the solid stationary phase comprises providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas; and flowing the entrained carrier gas over the solid stationary phase, optionally wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

[0182] Clause 13. The method of any preceding clause, further comprising providing:providing a source chamber comprising a source of gaseous radon isotope;providing a removeable cartridge comprising the solid stationary phase, wherein the source chamber is connected to the removeable cartridge such that gaseous radon isotope can flow from the source chamber to the solid stationary phase and wherein the removeable cartridge is releasably connectable to the source chamber such that the removeable cartridge can be disconnected from the source chamber; anddisconnecting the removable cartridge comprising the solid stationary phase and the at least one decay product from the source chamber prior to eluting the at least one decay product from the solid stationary phase.

[0183] Clause 14. The method of any preceding clause, wherein the solid stationary phase is a waterinsoluble solid stationary phase.

[0184] Cause 15. The method of any preceding clause, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

[0185] Clause 16. A system for producing and separating at least one decay product of a radon isotope, the system comprising:a source of gaseous radon isotope;a capture chamber arranged to receive gaseous radon isotope from the source;a solid stationary phase provided within the capture chamber, the solid stationary phase comprising a lipophilic functional group such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationary phase; andan elution system configured to provide eluent to the capture chamber and elute the at least one decay product from the solid stationary phase.

[0186] Clause 17. The system of clause 16, wherein the radon isotope is Rn-220, Rn-211 and / or Rn-222 and wherein the source is a source of gaseous Rn-220, Rn-211 and / or Rn-222.

[0187] Clause 18. The system of clause 17, wherein the radon isotope is Rn-220 and the at least one decay product comprises Pb-212 and / or Bi-212.

[0188] Clause 19. The system of clause 17, wherein the radon isotope is Rn-222 and the at least one decay product comprises Pb-214 and / or Bi-214.

[0189] Clause 20. The system of clause 16, wherein the lipophilic functional group is a functional group comprising a conjugated pi-system.

[0190] Clause 21. The system of any of clauses 16 to 20, wherein the functional group comprises a substituted or unsubstituted aromatic functional group, optionally wherein the functional group comprises divinylbenzene.

[0191] Clause 22. The system of any of clauses 16 to 21, wherein the solid stationary phase comprises a polymer comprising the functional group.

[0192] Clause 23. The system of any of clauses 16 to 22, wherein the polymer is formed from at least one monomer, the at least one monomer comprising styrene or divinylbenzene.

[0193] Clause 24. The system of clause 23, wherein the solid stationary phase comprises a copolymer formed from a first monomer comprising the functional group and at least one second monomer, optionally wherein the copolymer is selected from poly(divinylbenzene-co-N-vinylpyrrolidone) (DVB-co-NVP) copolymer or polystyrene -di vinylbenzene (PS-DVB) copolymer.

[0194] Clause 25. The system of any of clauses 16 to 19, wherein the functional group comprises a substituted or unsubstituted alkyl.

[0195] Clause 26. The system of any of clauses 16 to 25, further comprising: a carrier gas supply configured to supply a carrier gas so as to entrain gaseous radon isotope to form an entrained carrier gas and further to flow the entrained carrier gas to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase, optionally wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

[0196] Clause 27. The system of any of clauses 16 to 26, wherein the system further comprises a source chamber comprising the source of gaseous radon isotope and wherein the source chamber is connected to the capture chamber via a flow path such that gaseous radon isotope can flow from the source chamber to the capture chamber.

[0197] Clause 28. The system of clause 27, further comprising a carrier gas supply configured to supply a carrier gas to the source chamber so as to entrain gaseous radon isotope to form an entrained carrier gas and further to flow the entrained carrier gas from the source chamber to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase, optionally wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

[0198] Clause 29. The system of any of clauses 16 to 28, wherein the solid stationary phase is a water-insoluble solid stationary phase.

[0199] Clause 30. The system of any of clauses 16 to 29, wherein the system comprises a removeable cartridge comprising the capture chamber, wherein the removeable cartridge is releasably connectable to the source such that the capture chamber can be disconnected from the source.

[0200] Cause 31. The system of any of clauses 16 to 30, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

[0201] Clause 32. A method for producing and separating at least one decay product of a radon isotope, the method comprising:providing a source of a gaseous radon isotope;providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas;flowing the entrained carrier gas over a solid stationary phase, wherein the solid stationary phase comprises a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope in the entrained carrier gas can be retained thereon and decay to at least one decay product on the solid stationary phase; andallowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase.

[0202] Clause 33. The method of clause 32, wherein the radon isotope is selected from the group consisting of Rn-220, Rn-211 and Rn-222.

[0203] Clause 34. The method of clause 33, wherein the radon isotope is Rn-220 and the at least one decay product comprises Pb-212 and / or Bi-212.

[0204] Clause 35. The method of clause 33, wherein the radon isotope is Rn-222 and the at least one decay product comprises Pb-214 and / or Bi-214.

[0205] Clause 36. The method of clause 33, wherein the radon isotope is Rn-211 and the at least one decay product comprises At-211.

[0206] Clause 37. The method of any of clauses 32 to 36, wherein flowing the gaseous radon isotope over the solid stationary phase comprises providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas; and flowing the entrained carrier gas over the solid stationary phase.

[0207] Clause 38. The method of any of clauses 32 to 37, further comprising eluting the at least one decay product from the solid stationary phase.

[0208] Clause 39. The method of any of clauses 32 to 38, further comprising providing:providing a source chamber comprising the source of gaseous radon isotope;providing a removeable cartridge comprising the solid stationary phase, wherein the source chamber is connected to the removeable cartridge such that gaseous radon isotope can flow from the source chamber to the solid stationary phase and wherein the removeable cartridge is releasably connectable to the source chamber such that the removeable cartridge can be disconnected from the source chamber; anddisconnecting the removable cartridge comprising the solid stationary phase and the at least one decay product from the source chamber prior to eluting the at least one decay product from the solid stationary phase.

[0209] Clause 40. The method of clause 39, further comprising, after removing the removable cartridge containing the at least one decay product from the source chamber, eluting the at least one decay product from the solid stationary phase.

[0210] Clause 41. The method of any of clauses 32 to 40, wherein the functional group comprises a substituted or unsubstituted aromatic functional group.

[0211] Clause 42. The method of any of clauses 32 to 41, wherein the polymer is formed from at least one monomer, the at least one monomer comprising styrene or divinylbenzene.

[0212] Clause 43. The method of any of clauses 32 to 42, wherein the solid stationary phase comprises a copolymer formed from a first monomer comprising the functional group and at least one second monomer, optionally wherein the copolymer is selected from poly(divinylbenzene-co-N-vinylpyrrolidone) (DVB-co-NVP) copolymer or polystyrene -divinylbenzene (PS-DVB) copolymer.

[0213] Clause 44. The method of any of clauses 32 to 43, wherein the solid stationary phase is a waterinsoluble solid stationary phase.

[0214] Clause 45. The method of any of clauses 32 to 44, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

[0215] Clause 46. The method of any of clauses 32 to 45, wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

[0216] Clause 47. A system for producing and separating at least one decay product of a radon isotope, the system comprising:a source of gaseous radon isotope;a capture chamber arranged to receive gaseous radon isotope from the source;a solid stationary phase provided within the capture chamber, the solid stationary phase comprising a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationary phase; anda carrier gas supply configured to supply a carrier gas to the system so as to entrain gaseous radon isotope generated by the source to form an entrained carrier gas and further to flow the entrained carrier gas over the solid stationary phase.

[0217] Clause 48. The system of clause 47, wherein the system further comprises an elution system configured to provide eluent to the capture chamber and elute the at least one decay product from the solid stationary phase.

[0218] Clause 49. The system of clause 47 or clause 48, wherein the radon isotope is selected from the group consisting of Rn-220, Rn-211 and Rn-222.

[0219] Clause 50. The system of clause 49, wherein the radon isotope is Rn-220 and the at least one decay product comprises Pb-212 and / or Bi-212.

[0220] Clause 51. The system of clause 49, wherein the radon isotope is Rn-222 and the at least one decay product comprises Pb-214 and / or Bi-214.

[0221] Clause 52. The system of clause 49, wherein the radon isotope is Rn-211 and the at least one decay product comprises At-211.

[0222] Clause 53. The system of any of clauses 47 to 52, wherein the system comprises a removeable cartridge comprising the capture chamber, wherein the removeable cartridge is releasably connectable to the source such that the capture chamber can be disconnected from the source.

[0223] Clause 54. The system of any of clauses 47 to 53, further comprising: a carrier gas supply configured to supply a carrier gas so as to entrain gaseous radon isotope to form an entrained carrier gas and further to flow the entrained carrier gas to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase.

[0224] Clause 55. The system of any of clauses 47 to 54, wherein the system further comprises a source chamber comprising the source of gaseous radon isotope and wherein the source chamber isconnected to the capture chamber via a flow path such that gaseous radon isotope can flow from the source chamber to the capture chamber.

[0225] Clause 56. The system of clause 55, further comprising a carrier gas supply configured to supply a carrier gas to the source chamber so as to entrain gaseous radon isotope to form an entrained carrier gas and further to flow the entrained carrier gas from the source chamber to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase.

[0226] Clause 57. The system of any of clauses 47 to 56, wherein the functional group comprises a substituted or unsubstituted aromatic functional group.

[0227] Clause 58. The system of any of clauses 47 to 57, wherein the polymer is formed from at least one monomer, the at least one monomer comprising styrene or divinylbenzene.

[0228] Clause 59. The system of clause 58, wherein the solid stationary phase comprises a copolymer formed from a first monomer comprising the functional group and at least one second monomer, optionally wherein the copolymer is selected from poly(divinylbenzene-co-N-vinylpyrrolidone) (DVB-co-NVP) copolymer or polystyrene -divinylbenzene (PS-DVB) copolymer.

[0229] Clause 60. The system of any of clauses 47 to 59, wherein the solid stationary phase is a water-insoluble solid stationary phase.

[0230] Clause 61. The system of any of clauses 47 to 60, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

[0231] Clause 62. The method of any of clauses 47 to 61, wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

[0232] Clause 63. A method for producing and separating at least one decay product of a radon isotope, the method comprising:

[0233] providing a gaseous radon isotope;

[0234] flowing the gaseous radon isotope over a solid stationary phase such that gaseous radon isotope is retained on the solid stationary phase;

[0235] allowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase; and

[0236] eluting the at least one decay product from the solid stationary phase.

[0237] Clause 64. The method of clause 63, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

[0238] Clause 65. The method of clause 64 or clause 65, wherein the solid stationary phase comprises a lipophilic functional group.

[0239] Clause 66. The method of clause 65, wherein the solid stationary phase comprises a polymer comprising the lipophilic functional group and further optionally wherein the lipophilic functional group comprises a conjugated pi-system.

[0240] Clause 67. The method of clause 66, wherein the functional group comprises a substituted or unsubstituted aromatic functional group.

[0241] Clause 68. The method of clause 65 or 66, wherein the polymer is formed from at least one monomer, the at least one monomer comprising styrene or divinylbenzene.

[0242] Clause 69. The method of clause 68, wherein the solid stationary phase comprises a copolymer formed from a first monomer comprising the functional group and at least one second monomer, optionally wherein the copolymer is selected from poly(divinylbenzene-co-N-vinylpyrrolidone) (DVB-co-NVP) copolymer or polystyrene -divinylbenzene (PS-DVB) copolymer.

[0243] Clause 70. The method of clause 66, wherein the functional group comprises a substituted or unsubstituted alkyl.

[0244] Clause 71. The method of any of clauses 63 to 70, wherein the radon isotope is selected from the group consisting of Rn-220, Rn-211 and Rn-222.

[0245] Clause 72. The method of clause 71, wherein the radon isotope is Rn-220 and the at least one decay product comprises Pb-212 and / or Bi-212.

[0246] Clause 73. The method of clause 71, wherein the radon isotope is Rn-222 and the at least one decay product comprises Pb-214 and / or Bi-214.

[0247] Clause 74. The method of clause 71, wherein the radon isotope is Rn-211 and the at least one decay product comprises At-211.

[0248] Clause 75. The method of any of clauses 63 to 74, wherein flowing the gaseous radon isotope over the solid stationary phase comprises providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas; and flowing the entrained carrier gas over the solid stationary phase, optionally wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

[0249] Clause 76. The method of any of clauses 63 to 75, further comprising providing:providing a source chamber comprising the source of gaseous radon isotope;providing a removeable cartridge comprising the solid stationary phase, wherein the source chamber is connected to the removeable cartridge such that gaseous radon isotope can flow from the source chamber to the solid stationary phase and wherein the removeable cartridge is releasably connectable to the source chamber such that the removeable cartridge can be disconnected from the source chamber; anddisconnecting the removable cartridge comprising the solid stationary phase and the at least one decay product from the source chamber prior to eluting the at least one decay product from the solid stationary phase.

[0250] Clause 77. The method of any of clauses 63 to 76, wherein the solid stationary phase is a water-insoluble solid stationary phase.

[0251] Clause 78. A system for producing and separating at least one decay product of a radon isotope, the system comprising:a source of gaseous radon isotope;a capture chamber arranged to receive gaseous radon isotope from the source;a solid stationary phase provided within the capture chamber such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationary phase; and an elution system configured to provide eluent to the capture chamber and elute the at least one decay product from the solid stationary phase.

[0252] Clause 79. The system of clause 78, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

[0253] Clause 80. The system of clause 78 or clause 79, wherein the solid stationary phase comprises a lipophilic functional group.

[0254] Clause 81. The system of clause 80, wherein the lipophilic functional group is a functional group comprising a conjugated pi-system.

[0255] Clause 82. The system of clause 80 or clause 81, wherein the functional group comprises a substituted or unsubstituted aromatic functional group, optionally wherein the functional group comprises divinylbenzene.

[0256] Clause 83. The system of any of clauses 80 to 82, wherein the solid stationary phase comprises a polymer comprising the functional group.

[0257] Clause 84. The system of any of clauses 80 to 83, wherein the polymer is formed from at least one monomer, the at least one monomer comprising styrene or divinylbenzene.

[0258] Clause 85. The system of clause 84, wherein the solid stationary phase comprises a copolymer formed from a first monomer comprising the functional group and at least one second monomer, optionally wherein the copolymer is selected from poly(divinylbenzene-co-N-vinylpyrrolidone) (DVB-co-NVP) copolymer or polystyrene -divinylbenzene (PS-DVB) copolymer.

[0259] Clause 86. The system of clause 81, wherein the functional group comprises a substituted or unsubstituted alkyl.

[0260] Clause 87. The system of any of clauses 78 to 86, further comprising: a carrier gas supply configured to supply a carrier gas so as to entrain gaseous radon isotope to form an entrained carrier gas and further to flow the entrained carrier gas to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase, optionally wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

[0261] Clause 88. The system of any of clauses 78 to 87, wherein the system further comprises a source chamber comprising the source of gaseous radon isotope and wherein the source chamber is connected to the capture chamber via a flow path such that gaseous radon isotope can flow from the source chamber to the capture chamber.

[0262] Clause 89. The system of clause 88, further comprising a carrier gas supply configured to supply a carrier gas to the source chamber so as to entrain gaseous radon isotope to form an entrained carrier gas and further to flow the entrained carrier gas from the source chamber to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase, optionally wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

[0263] Clause 90. The system of any of clauses 78 to 89, wherein the solid stationary phase is a water-insoluble solid stationary phase.

[0264] Clause 91. The system of any of clauses 78 to 90, wherein the system comprises a removeable cartridge comprising the capture chamber, wherein the removeable cartridge is releasably connectable to the source such that the capture chamber can be disconnected from the source.

[0265] Clause 92. The system of any of clauses 78 to 91. wherein the radon isotope is Rn-220, Rn-211 and / or Rn-222 and wherein the source is a source of gaseous Rn-220, Rn-211 and / or Rn-222.

[0266] Clause 93. The system of clause 92, wherein the radon isotope is Rn-220 and the at least one decay product comprises Pb-212 and / or Bi-212.

[0267] Clause 94. The system of clause 92, wherein the radon isotope is Rn-222 and the at least one decay product comprises Pb-214 and / or Bi-214.

[0268] Clause 95. The system of clause 92, wherein the radon isotope is Rn-211 and the at least one decay product comprises At-211

Claims

CLAIMS1. A method for producing and separating at least one decay product of a radon isotope, the method comprising:providing a gaseous radon isotope;flowing the gaseous radon isotope over a solid stationary phase, wherein the solid stationary phase comprises a lipophilic functional group such that gaseous radon isotope is retained on the solid stationary phase;allowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase; andeluting the at least one decay product from the solid stationary phase.

2. The method of claim 1, wherein the solid stationary phase comprises a polymer comprising the lipophilic functional group and wherein the lipophilic functional group comprises a conjugated pi-system.

3. The method of claim 1 or claim 2, wherein the functional group comprises a substituted or unsubstituted aromatic functional group, optionally wherein the solid stationary phase comprises a copolymer formed from a first monomer comprising the lipophilic functional group and at least one second monomer, optionally wherein the copolymer is selected from poly(divinylbenzene-co-N-vinylpyrrolidone) (DVB-co-NVP) copolymer or polystyrene -di vinylbenzene (PS-DVB) copolymer.

4. The method of any preceding claim, wherein the radon isotope is selected from the group consisting of Rn-220, Rn-211 and Rn-222, optionally wherein the radon isotope is Rn-220 and the at least one decay product comprises Pb-212 and / or Bi-212.

5. The method of any preceding claim, wherein flowing the gaseous radon isotope over the solid stationary phase comprises providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas; and flowing the entrained carrier gas over the solid stationary phase, optionally wherein the carrier gas is selected from nitrogen, helium or combinations thereof.

6. The method of any preceding claim, further comprising:providing a source chamber comprising a source of gaseous radon isotope;providing a removeable cartridge comprising the solid stationary phase, wherein the source chamber is connected to the removeable cartridge such that gaseous radon isotope can flow from the source chamber to the solid stationary phase and wherein the removeable cartridge is releasablyconnectable to the source chamber such that the removeable cartridge can be disconnected from the source chamber; anddisconnecting the removable cartridge comprising the solid stationary phase and the at least one decay product from the source chamber prior to eluting the at least one decay product from the solid stationary phase.

7. The method of any preceding claim, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

8. A system for producing and separating at least one decay product of a radon isotope, the system comprising:a source of gaseous radon isotope;a capture chamber arranged to receive gaseous radon isotope from the source;a solid stationary phase provided within the capture chamber, the solid stationary phase comprising a lipophilic functional group such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationary phase; andan elution system configured to provide eluent to the capture chamber and elute the at least one decay product from the solid stationary phase.

9. The system of claim 8, wherein the source is a source of gaseous Rn-220, Rn-211 and / or Rn-222.

10. The system of claim 8 or claim 9, wherein the solid stationary phase comprises a polymer comprising the lipophilic functional group and wherein the lipophilic functional group is a functional group comprising a conjugated pi-system; and / or wherein the solid stationary phase is a waterinsoluble solid stationary phase.

11. The system of any of claims 8 to 10, wherein the functional group comprises a substituted or unsubstituted aromatic functional group, optionally wherein the functional group comprises divinylbenzene.

12. The system of any of claims 8 to 11, wherein the system further comprises a source chamber comprising the source of gaseous radon isotope and wherein the source chamber is connected to the capture chamber via a flow path such that gaseous radon isotope can flow from the source chamber to the capture chamber,optionally further comprising a carrier gas supply configured to supply a carrier gas to the source chamber so as to entrain gaseous radon isotope to form an entrained carrier gas and further to flow the entrained carrier gas from the source chamber to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase.

13. The system of any of claims 8 to 12, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

14. A method for producing and separating at least one decay product of a radon isotope, the method comprising:providing a source of a gaseous radon isotope;providing a carrier gas and entraining gaseous radon isotope in the carrier gas to form an entrained carrier gas;flowing the entrained carrier gas over a solid stationary phase, wherein the solid stationary phase comprises a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope in the entrained carrier gas can be retained thereon and decay to at least one decay product on the solid stationary phase; andallowing the gaseous radon isotope to reside on the solid stationary phase such that at least a portion of the gaseous radon isotope decays to at least one decay product on the solid stationary phase.

15. The method of claim 14, wherein the radon isotope is selected from the group consisting of Rn-220, Rn-211 and Rn-222, optionally wherein the radon isotope is Rn-220 and the at least one decay product comprises Pb-212 and / or Bi-212.

16. The method of claim 14,providing a source chamber comprising the source of gaseous radon isotope; providing a removeable cartridge comprising the solid stationary phase, wherein the source chamber is connected to the removeable cartridge such that gaseous radon isotope can flow from the source chamber to the solid stationary phase and wherein the removeable cartridge is releasably connectable to the source chamber such that the removeable cartridge can be disconnected from the source chamber; anddisconnecting the removable cartridge comprising the solid stationary phase and the at least one decay product from the source chamber prior to eluting the at least one decay product from the solid stationary phase.

17. The method of claim 16, further comprising, after disconnecting the removable cartridge containing the at least one decay product from the source chamber, eluting the at least one decay product from the solid stationary phase.

18. The method of any of claims 14 to 17, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

19. A system for producing and separating at least one decay product of a radon isotope, the system comprising:a source of gaseous radon isotope;a capture chamber arranged to receive gaseous radon isotope from the source;a solid stationary phase provided within the capture chamber, the solid stationary phase comprising a polymer comprising at least one functional group having a conjugated pi-system such that gaseous radon isotope can be retained thereon and decay to at least one decay product on the solid stationary phase; anda carrier gas supply configured to supply a carrier gas to the system so as to entrain gaseous radon isotope generated by the source to form an entrained carrier gas and further to flow the entrained carrier gas over the solid stationary phase.

20. The system of claim 19, wherein the system further comprises a source chamber comprising the source of gaseous radon isotope and wherein the source chamber is connected to the capture chamber via a flow path such that gaseous radon isotope can flow from the source chamber to the capture chamber; andwherein the carrier gas supply is configured to supply a carrier gas to the source chamber so as to entrain gaseous radon isotope therein to form an entrained carrier gas and further to flow the entrained carrier gas from the source chamber to the capture chamber so as to pass the entrained carrier gas over the solid stationary phase.

21. The system of claim 20, wherein the system comprises a removeable cartridge comprising the capture chamber, wherein the removeable cartridge is releasably connectable to the source chamber such that the capture chamber can be disconnected from the source chamber.

22. The system of any of claims 19 to 21, wherein the solid stationary phase comprises a specific surface area of at least 10 m2 / g, optionally at least 100 m2 / g and further optionally at least 200 m2 / g.

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