METHOD FOR PRODUCING 225ACTINIUM FROM 226RADIUM

Abstract

.sup.225actinium is produced from .sup.226radium by irradiating a liquid .sup.226radium target by means of protons, deuterons or gamma irradiation in an irradiation device (2) and by extracting the produced .sup.225actinium out of the irradiated liquid target solution in a first extraction device (6). The liquid target solution from which the .sup.225actinium has been removed is then irradiated again to produce further .sup.225actinium therein. The liquid target solution is preferably circulated, in a closed loop (4), over the irradiation device and in a further closed loop (7) over the first extraction device (6). An advantage of such a method is that the irradiated target solution does not need to be dried and re-dissolved to be able to separate the produced actinium from the radium and no further drying and re-dissolving step is needed for producing the liquid target again starting from the separated radium. The radium target can thus be recycled in a more efficient and safer way, especially in view of the radon gas which is continuously produced by the decay of .sup.226radium.

Claims

1. A method for producing .sup.225actinium from .sup.226radium, said method comprising the steps of: providing a liquid target solution containing .sup.226radium; irradiating said liquid target solution in an irradiation device (2) to produce .sup.225actinium in the liquid target solution starting from the .sup.226radium contained therein; and separating at least part of the produced .sup.225actinium from the remaining .sup.226radium, wherein said separation step comprises a first extraction step which is carried out in a first extraction device (6) wherein at least part of said .sup.225actinium is extracted from the liquid target solution while the .sup.226radium is maintained in the liquid target solution; and in that the method comprises the further step of: irradiating the liquid target solution from which part of said .sup.225actinium has been extracted again in said irradiation device (2) to produce further .sup.225actinium in the liquid target solution starting from the .sup.226radium contained therein.

2. The method according to claim 1, wherein said liquid target solution is circulated during said irradiation step in a first closed loop (4) over said irradiation device (2) and over a heat exchanger (5).

3. The method according to claim 1, wherein said liquid target solution is circulated during said first extraction step in a second closed loop (7) over said first extraction device (6).

4. The method according to claim 2, wherein said liquid target solution is circulated during said irradiation step, in said first closed loop (4), over a container (1) and said irradiation device (2) and during said first extraction step, in said second closed loop (7), over said container (1) and said first extraction device (6).

5. The method according to claim 1, wherein said liquid target solution is irradiated for less than 16 days, before at least part of said .sup.225actinium is extracted from the liquid target solution.

6. The method according to claim 1, wherein said liquid target solution is irradiated during said irradiation step with protons or deuterons.

7. The method according to claim 1, wherein said liquid target solution is irradiated during said irradiation step with γ irradiation to produce .sup.225actinium by conversion of .sup.226radium into .sup.225radium and by conversion of .sup.225radium into .sup.225actinium.

8. The method according to claim 7, characterised in that wherein during said first extraction step the .sup.225radium is maintained in the liquid target solution.

9. The method according to claim 1, wherein said liquid target solution comprises a solution of a .sup.226radium salt and its corresponding acid, the solution preferably comprising .sup.226radium nitrate and nitric acid.

10. The method according to claim 1, wherein said first extraction device (6) comprises a first adsorbent onto which said .sup.225actinium accumulates during said first extraction step, the method comprising a first elution step wherein at least part of the .sup.225actinium which has been accumulated onto said first adsorbent is eluted therefrom by means of a first eluent (16).

11. The method according to claim 10, wherein said liquid target solution has a predetermined pH value such that said .sup.225actinium accumulates during said first extraction step onto said first adsorbent whilst said first eluent has a pH value which is different from the pH value of the liquid target solution such that said .sup.225actinium is eluted during said first elution step from said first adsorbent.

12. The method according to claim 10, wherein said first eluent (16) comprises a first acid solution which contains the same acid as said target solution, in particular nitric acid.

13. The method according to claim 10, wherein said first eluent (16) is circulated during said first elution step in a fourth closed loop (17) over a second extraction device (18) which comprises a second adsorbent onto which the .sup.225actinium eluted from said first adsorbent by means of said first eluent accumulates during said first elution step, the method comprising a second elution step wherein at least part of the .sup.225actinium which has been accumulated onto said second adsorbent is eluted therefrom by means of a second eluent (19), the second eluent (19) having in particular a pH value which is different from the pH value of said first eluent such that said .sup.225actinium is eluted during said second elution step from said second adsorbent, the second eluent (19) comprising preferably a second acid solution which contains the same acid as said target solution, in particular nitric acid.

14. The method according to claim 13, wherein said first eluent (16) is circulated from said first extraction device (6) to said second extraction device (18) over a second radon filter (20), in particular a second activated carbon filter, to extract radon from said first eluent (16).

15. The method according to claim 13, wherein said second eluent (19) is circulated during said second elution step in a fifth closed loop (21) over a third extraction device (22) which comprises a third adsorbent onto which the .sup.225actinium eluted from said second adsorbent by means of said second eluent (19) accumulates during said second elution step, the method comprising a third elution step wherein at least part of the .sup.225actinium which has been accumulated onto said third adsorbent is eluted therefrom by means of a third eluent (24), the third eluent (24) having in particular a pH value which is different from the pH value of said second eluent (19) such that said .sup.225actinium is eluted during said third elution step from said third adsorbent, the third eluent comprising preferably a third acid solution which contains the same acid as said target solution, in particular nitric acid.

Description

[0069] Further details and advantages of the present invention will become apparent from the following description of some examples to the production method according to the invention. This description is only given by way of example and is not intended to limit the scope of the invention as defined in the appended claims. The reference numerals used in this description refer to the accompanying drawings wherein:

[0070] FIG. 1 is a diagram of an installation for carrying out a method according to a first embodiment of the present invention, wherein the liquid target solution contains a relatively small amount of nitric acid, in particular 0.02 M; and

[0071] FIG. 2 is a diagram of an installation for carrying out a method according to a second embodiment of the present invention, wherein the liquid target solution contains a larger amount of nitric acid, in particular 0.5 M.

[0072] In the method of the present invention a liquid target solution is made which contains .sup.226Ra, more particularly .sup.226radium nitrate. This solution comprises in particular between 0.005 and 1.0 M nitric acid. It is preferably contained in a gas tight bottle which is lead shielded.

[0073] The installation as schematically illustrated in FIG. 1 is in particular intended to produce .sup.225Ac in a accordance with a low acidity option, i.e. wherein the liquid target solution has for example an acidity comprised between 0.005 and 0.05 M HNO.sub.3. The concentration of Ra(NO.sub.3).sub.2 in the target solution is preferably as high as possible, and can be as high as 0.4 M.

[0074] The installation comprises a container 1 arranged to contain the liquid target solution. It also contains an irradiation device 2 having a window through which the target solution can be irradiated with protons, deuterons or gamma radiation. The gamma irradiation can be obtained from a synchrotron or a linac, or it can also be obtained by means of a converting material as disclosed in US 2002/0094056. The liquid target is however preferably irradiated with protons (or deuterons) since this is the most efficient way to produce .sup.225Ac from .sup.226Ra. The proton irradiation may be generated by a cyclotron, for example a cyclotron which is already generally known for producing PET radioisotopes such as .sup.18F from .sup.18O.

[0075] The liquid target may be a static target but in order to enable a more efficient cooling, and thus in order to enable a more energetic irradiation of the target to increase the production capacity, the liquid target is preferably a recirculating liquid target as in the embodiment illustrated in FIG. 1. In this embodiment the target solution is pumped by means of a pump 3, in a first closed loop 4, from the container 1 over the irradiation device 2 and subsequently over a heat exchanger 5 back into the container 1. The target is preferably also cooled, in particular water cooled, in the irradiation device 2 itself. The solution is preferably irradiated with protons having preferably an incident energy of 15-20 MeV. During the irradiation the heat generated by stopping the protons in the target solution is totally or partly removed by the target solution itself and is externally exchanged in the primary heat exchanger 5. The complete irradiation loop is set-up so that all wetted parts are of highly inert, gas tight materials, typically hastalloy, inconel, etc. to avoid corrosion and ensure leak tightness. Ceramics or a combination of metal and ceramics could be a good choice as well.

[0076] During irradiation .sup.225Ac is constantly building up in the target solution. Using a static target, when the irradiation is finished, the target solution is collected back into the gas tight target solution bottle. The static target is preferably automatically loaded an emptied. A recirculating liquid target can be reprocessed during the irradiation process. From there, chemical separation and purification of .sup.225Ac is carried out by recirculating flows over extraction chromatography or ion exchange columns. The conditions are set so that actinium is extracted on the columns, whereas impurities are recirculated. The size of the columns, flow-rates, volumes of solutions are dependent on the initial volume of the target solution.

[0077] For a static target, the irradiated target solution contained in the bottle can be transferred and recirculated over a first extraction device 6. In this extraction device 6 the .sup.225Ac is extracted from the irradiated target solution while the .sup.226Ra (and optionally also the .sup.225Ra in case of gamma irradiation of the target solution) is maintained in the target solution. The target solution from which the .sup.226Ac has been extracted is collected again in the bottle and is loaded back into the liquid target to be irradiated again.

[0078] In the installation shown in FIG. 1, extracting the .sup.225Ac from the liquid target solution and loading the liquid target solution from which the .sup.225Ac has been extracted back into the liquid target requires much less handling steps and is much easier to perform, in particular in an automatic way. In the embodiment illustrated in FIG. 1 the irradiated target solution contained in the container 1 is indeed recirculated, in a second closed loop 7 over the first extraction device 6. This is done by means of a pump which has not been indicated in FIG. 1.

[0079] The first extraction device comprises a first adsorbent onto which the .sup.225Ac accumulates during the first extraction step. The first extraction device preferably comprises a first extraction chromatography column which, in the low acidity option, is for example based on the LN-resin (Eichrome, HDEHEP). When the target solution comprises for example between 0.005 and 0.05 M HNO.sub.3, such as for example 0.02 M HNO.sub.3, actinium is retained on the column and .sup.226Ra (and .sup.225Ra, if present) is recirculated. The recirculated volume will determine the efficiency of the uptake of Ac from the target solution and it is important to limit this volume so that Ac breakthrough is avoided.

[0080] Losses of Ra from the target solution are preferably prevented. It is important that the majority of the target solution volume present in the initial column after separation of .sup.225Ac from .sup.226Ra is pushed back into the target solution container 1.

[0081] Any radium still in the first extraction device 6 after the initial separation, i.e. after the liquid target solution has pumped or percolated through the column, is recuperated by rinsing the column of the first extraction device 6 with a rinse solution 8. This rinse solution has a pH similar to the pH of the liquid target solution so that the .sup.225Ac is retained on the column during the rinsing step. The rinse solution is circulated in a third closed loop 9 over the first extraction device 6 and a radium extraction device 10, for example over a strong cation exchange column (for example DOWEX 50W or Biorad 50W or similar). The radium extraction device 10 comprises a radium adsorbent onto which the radium rinsed from the first adsorbent by means of the rinse solution 8 accumulates during the rinsing step.

[0082] To remove any radon that has been accumulated in the first extraction device 6 the rinse solution 8 is preferably also recirculated over a first activated carbon filter 11 to remove radon gas from the first extraction device 6. The activated carbon filter 11 may be a granulated activated carbon filter but is preferably a powdered activated carbon filter.

[0083] Further purification and concentration, as the columns decrease in size and thereby also the elution volume, is carried out by extraction chromatography columns based on Ln resin, Sr resin, DGA resin or branched-DGA resin (all Eichrome). Acidity changes move actinium from one extraction column to the next one each time improving purity and increasing the concentration factor. The last column in the process will determine in which medium the actinium product is leaving the process. In FIG. 1 a SCE (strong cation exchanger) is used and a corresponding high acidity will be used to elute actinium. An alternative would be an extraction chromatography resin selective for trivalent elements such as DGA or DGA-B (Eichrom) in which elution of actinium is carried out at lower acidity.

[0084] In the embodiment illustrated in FIG. 1, the radium that has been accumulated in the radium extraction device 10 is more particularly eluted therefrom by means of a radium eluent 12 which has a pH value or acidity which is different from the pH value or acidity of the rinse solution such that the radium is eluted during the radium elution step from the radium adsorbent. The rinse solution 8 may for example comprise a 0.02 M nitric acid solution whilst the radium eluent 12 may comprise for example a 2 M nitric acid solution. The radium eluent 12 containing the recovered radium is stored in a gastight container 13. This container 13 is provided with a gas inlet 14 and a gas outlet 15. The container 13 can thus be purged with a small volume of, for example, nitrogen gas to remove any radon gas that is produced in the container 13 during the storage of the radium contained therein. Since only a small volume is used, Rn can be trapped and managed by a small active carbon gas filter (not shown in FIG. 1 and FIG. 2). The recovered Ra can, if needed, be reconditioned to the correct acidity, concentrated and transferred back to the target solution.

[0085] The .sup.225Ac which has been accumulated onto the first adsorbent in the first extraction device 6 is eluted therefrom, in a first elution step after the rinsing steps, by means of a first eluent 16. This first eluent 16 has a pH value which is different from the pH value of the liquid target solution such that the .sup.225Ac is eluted during the first elution step from the first adsorbent contained in the first extraction device 6. The first eluent 16 may comprise a first nitric acid solution which has a lower pH, i.e. a higher acidity, and which contains for example 0.5 M HNO.sub.3. With such an eluent, .sup.225Ac can be removed from the Ln resin.

[0086] The first eluent 16 is circulated during the first elution step, in a fourth closed loop 17 over the first extraction device 6 and over a second extraction device 18 which comprises a second adsorbent onto which the .sup.225actinium eluted out of the first extraction device 6 by means of the first eluent 16 accumulates during the first elution step. The second extraction device preferably comprises a second extraction chromatography column which, in the low acidity option illustrated in FIG. 1, is for example based on the DGA-resin (Eichrome, TODGA). When the first eluent 16 comprises for example 0.5 M HNO.sub.3, actinium is retained on the DGA-column and impurities are recirculated. The free column volume of the second extraction device 18 is preferably smaller than the free column volume of the first extraction device 6 so that the actinium can be concentrated thereon, and can be eluted therefrom with a smaller amount of a second eluent 19.

[0087] In order to remove any radon gas which may be present in the fourth closed loop 17 of the installation, the first eluent 16 is circulated from the first extraction device 6 to the second extraction device 18 over a second radon filter 20, in particular a second activated carbon filter, to extract radon from the first eluent 16. The second activated carbon filter 20 may be a granulated activated carbon filter but is preferably a powdered activated carbon filter.

[0088] When the .sup.225actinium has been accumulated onto the second adsorbent contained in the second extraction device 18 it is eluted therefrom, in a second elution step, by means of the second eluent 19. The second eluent has a pH value or acidity which is different from the pH value or acidity of the first eluent 8 such that the .sup.225actinium is eluted during the second elution step from the second adsorbent contained in the second extraction column. The second eluent 19 comprising again preferably a second nitric acid solution and comprises, in the low acidity option illustrated in FIG. 1, for example 0.05 M HNO.sub.3. With such a second eluent, .sup.225Ac can be removed from the DGA resin.

[0089] The second eluent 19 is circulated during the second elution step, in a fifth closed loop 21 over the second extraction device 18 and over a third extraction device 22 which comprises a third adsorbent onto which the .sup.225actinium eluted out of the second extraction device 18 by means of the second eluent 19 accumulates during the second elution step. The third extraction device 22 preferably comprises a third extraction chromatography column which, in the low acidity option illustrated in FIG. 1, is for example based again on the Ln-resin (Eichrome, HDEHEP). When the second eluent 19 comprises for example 0.05 M HNO.sub.3, actinium is retained on the Ln-column and impurities are recirculated. The free column volume of the third extraction device 22 may be equal to the free column volume of the second extraction device 18 if no further concentration is necessary.

[0090] In order to remove any radon gas which may be present in the fifth closed loop 21 of the installation, the second eluent 19 is circulated from the second extraction device 18 to the third extraction device 22 over a third radon filter 23, in particular a third activated carbon filter, to extract radon from the second eluent 19. The third activated carbon filter 23 may be a granulated activated carbon filter but is preferably a powdered activated carbon filter.

[0091] When the .sup.225actinium has been accumulated onto the third adsorbent contained in the third extraction device 22 it is eluted therefrom, in a third elution step, by means of a third eluent 24. The third eluent 24 has a pH value or acidity which is different from the pH value or acidity of the second eluent 19 such that the .sup.225actinium is eluted during the third elution step from the third adsorbent contained in the third extraction column .sup.22. The third eluent 24 comprising again preferably a third nitric acid solution and comprises, in the low acidity option illustrated in FIG. 1, for example 0.5 M HNO.sub.3. With such a third eluent, .sup.225Ac can be removed from the Ln resin.

[0092] A further purification, and optional concentration, of the .sup.225Ac is obtained in the embodiment of FIG. 1 by circulating the third eluent 24 during the third elution step, in a sixth closed loop 25 over the third extraction device 22 and over a fourth extraction device 26 which comprises a fourth adsorbent onto which the .sup.225actinium eluted out of the third extraction device 22 by means of the third eluent 24 accumulates during the third elution step. The fourth extraction device 26 may comprise again a DGA or a DGA-B (branched) column in which the acidity may be lowered to 0.1 M to remove the .sup.225Ac therefrom in the last step. The fourth extraction device 26 preferably comprises however an SCE (strong cation exchanger). When the third eluent 24 comprises for example 0.5 M HNO.sub.3, actinium is retained on the SCE 26 and impurities are recirculated. The free column volume of the fourth extraction device 26 may be equal to or smaller than the free column volume of the second extraction device 18, and may be equal to about half the free column volume thereof to be able to further concentrate the .sup.225Ac.

[0093] In order to remove any radon gas which may be present in the sixth closed loop 25 of the installation, the third eluent 24 is circulated from the third extraction device 22 to the fourth extraction device 26 over a fourth radon filter 27, in particular a fourth activated carbon filter, to extract radon from the third eluent 24. The fourth activated carbon filter 27 may be a granulated activated carbon filter but is preferably a powdered activated carbon filter.

[0094] When the .sup.225actinium has been accumulated onto the fourth adsorbent contained in the fourth extraction device 26 it is eluted therefrom, in a fourth elution step, by means of a fourth eluent 28.

[0095] In case the fourth extraction device 26 comprises a DGA or DGA-B resin, the fourth eluent 28 has a pH value or acidity which is different from the pH value or acidity of the third eluent 24 such that the .sup.225actinium is eluted during the fourth elution step from the fourth adsorbent contained in the fourth extraction column 26. The fourth eluent 28 comprising again preferably a fourth nitric acid solution and comprises, in the low acidity option illustrated in FIG. 1, for example 0.1 M HNO.sub.3. With such a fourth eluent, .sup.225Ac can be removed from the DGA or DGA-B resin.

[0096] In case the fourth extraction device 26 is an SCE, the fourth eluent 28 has a sufficiently high pH or acidity to elute the .sup.225Ac from the SCE. The fourth eluent 28 comprising again preferably a fourth nitric acid solution which has in this case a high acidity, and which comprises for example 2 M HNO.sub.3.

[0097] The obtained purified and concentrated .sup.225Ac can be removed through the outlet 29 of the fourth extraction device and can subsequently be dried to obtain a dry product. During the drying step not only the water but also the acid contained in the fourth eluent can be removed by evaporation.

[0098] As an example, the different extraction devices and solutions used in the installation as illustrated in FIG. 1 may have the following compositions:

TABLE-US-00001 TABLE 1 Example of compositions of extraction devices and solutions which may be used in the installation as illustrated in FIG. 1. Target solution 0.02M HNO.sub.3 and 0.4M .sup.226Ra(NO.sub.3).sub.2 First extraction device 6 Ln resin (Eichrome, HDEHEP) Rinse solution 8 0.02M HNO.sub.3 Radium extraction device 10 SCE (DOWEX 50W) Radium eluent 12 2M HNO.sub.3 First eluent 16 0.5M HNO.sub.3 Second extraction device 18 DGA (Eichrome, TODGA) Second eluent 19 0.05M HNO.sub.3 Third extraction device 22 Ln resin (Eichrome, HDEHEP) Third eluent 24 0.5M HNO.sub.3 Fourth extraction device 26 SCE (DOWEX 50W) Fourth eluent 28 2M HNO.sub.3

[0099] FIG. 2 illustrates an alternative embodiment of the method according to the present invention wherein the liquid target solution has a higher acidity (lower pH). This high acidity option is based on an initial Ac/Ra separation using a DGA column. Here the acidity in the target solution will be for example between 0.1 M and 0.5 M nitric acidity and the concentration of .sup.226Ra in the target solution can be up to 0.35 M, if the lower acidity is compensated with addition of nitrates, e.g. through ammoniumnitrate. The actinium will be removed by recirculation over the DGA column. The recirculated volume should be high enough to efficiently remove the Ac but within the capacity of the column to avoid Ac breakthrough. As in the low acidity option, a strong cation exchanger will manage any Ra left on the column after the initial actinium separation. Further purification takes place by lowering the acidity and the uptake on a Ln resin column. Here the acidity is chosen to avoid co-extraction of Pb, i.e. 0.03 M-0.075 M. Different options are available from this point but the subsequent purification and concentration using a DGA or DGA B column will probably be the preferred method.

[0100] The parts of the installation illustrated in FIG. 2 which correspond to the installation illustrated in FIG. 1 are indicated with the same reference numerals. The installation illustrated in FIG. 2 functions in a same way as the installation described hereabove with reference to FIG. 1 so that the description of the functioning of the common parts is not repeated. Instead, a specific example, the different extraction devices and solutions used in the high acidity installation as illustrated in FIG. 2 is given in the following table:

TABLE-US-00002 TABLE 2 Example of compositions of extraction devices and solutions which may be used in the high acidity installation as illustrated in FIG. 2. Target solution 0.5M HNO.sub.3 and 0.35M .sup.226Ra(NO.sub.3).sub.2 First extraction device 6 DGA (Eichrome, TODGA) Rinse solution 8 0.5M HNO.sub.3 Radium extraction device 10 SCE (DOWEX 50W) Radium eluent 12 2M HNO.sub.3 First eluent 16 0.05M HNO.sub.3 Second extraction device 18 Ln resin (Eichrome, HDEHEP) Second eluent 19 0.5M HNO.sub.3 Third extraction device 22 DGA (Eichrome, TODGA) Third eluent 24 0.1M HNO.sub.3 Lead extraction device 30 Sr resin (Eichrome,)

[0101] As can be seen, the concentrated and purified .sup.225Ac is removed already from the third extraction device 22. An additional extraction column, namely a lead extraction device 30, is however provided in the fifth closed loop 21 in between the second 18 and the third extraction device .sup.22. The lead extraction device 30 is preceded by the third radon filter 23 and is followed by an additional radon filter 23′.

[0102] The lead extraction device 30 comprises in particular a Sr resin which is highly effective towards Pb and can be used to remove Pb from the installation/system. Pb is produced by decay of radon. Radon decays by alpha decay and generates radiation damage to the column materials which will affect column separation performance. Radon is therefore preferably be prevented from moving downstream in the process so that the life-time of the columns is extended and to avoid radon contamination of the .sup.225Ac product. Radon is managed by the radon filter, i.e. by the small columns containing powdered activated carbon (PAC) or granulated activated carbon (GAC). The radon is absorbed/strongly delayed in the PAC/GAC column and decays into .sup.210Pb, a gamma emitter. .sup.210Pb will be eluted into the aqueous phase and contained within the process. The PAC/GAC columns can be used multiple times. The Sr resin column is highly efficient towards Pb and can thus be used to remove Pb from the process. The Sr resin column comprises as stationary phase dicyclohexano-18-crown-6 derivative which is dissolved in octanol.

[0103] Also in the low acidity installation of FIG. 1, a lead extraction device (Sr resin column) can easily be incorporated, in particular in between the third extraction device 22 and the fourth extraction device 26, with preferably the fourth radon filter 27 before and an additional radon filter after the lead extraction device.

[0104] The method according to the present invention enables to achieve commercially interesting production rates notwithstanding the relatively low concentration of .sup.226Ra in the target solution as a result of the limited solubility of radium nitrate (which is for example more than ten times smaller than the solubility of .sup.68zinc nitrate which is used in liquid targets to produce .sup.68Ga by the .sup.68Zn(p,n).sup.68Ga reaction).

[0105] The .sup.225Ac production rate can be calculated. The energy dependent cross-section (IAEA ENDF database) for the .sup.226Ra(p,2n) reaction together with the energy dependent stopping power for protons in an aqueous solution (Nucleonica) containing up to 0.4 M .sup.226Ra(NO.sub.3).sub.2 is used to obtain production rates in small layers of the liquid target which are summed to yield the overall formation of .sup.225Ac. Weekly production rates are shown in Table 1 as a function of the used proton current.

TABLE-US-00003 TABLE 3 .sup.225Ac production as a function of proton current. 0.35M .sup.226Ra, Irradiation time = 7 days, Cooling time = 0 days, Cross-section = 500 mb. Current (μA) A (Bq) A (mCi) Heat (W) 10 1.27E+09 34.4 225 20 2.54E+09 68.8 450 30 3.82E+09 103.2 675 40 5.09E+9  137.6 900 50 6.36E+9  171.9 1125 60 7.63E+9  206.3 1350 70 8.91E+9  240.7 1575 80 1.02E+10 275.1 1800 90 1.15E+10 309.5 2025 100 1.27E+10 343.9 2250

[0106] As to the economic feasibility, assuming that therapeutic treatments using .sup.225Ac are approved, the demand for .sup.225Ac will significantly increase. The .sup.225Ac produced by the proposed method will be of higher quality than .sup.225Ac produced by proton irradiation of .sup.232Th targets, unless a complicated isotopic separation of .sup.227Ac is undertaken. If distributed as produced, assuming 40 weeks production per year, the produced .sup.225Ac could cover an excess of 25000 treatments. The economic feasibility in an actinium production process can thus most likely be guaranteed.

REFERENCES

[0107] Boll, R. A., Malkemus, D., Mirzadeh, S., Production of actinium-225 for alpha particle mediated radioimmunotherapy. Appl. Radiat. Isot. 62, 667-679 (2005)
Jost, C. U., Griswold, J. R., Bruffey, S. H., Mirzadeh, S., Stracener, D. W., Williams, C. L., Measurement of cross sections for the .sup.232Th(p,4n).sup.229Pa reaction at low proton energies. AIP Conference Proceedings: International Conference on Application of Accelerators in Research and Industry. Vol. 1525, pp. 520-524. (2013)
Koch, L, Fuger, J, van Geel J., Process for producing Actinium-225, EP0752709, 1999
Apostolidis, C., Molinet, R., McGinley, J., Abbas, K., Möllenbeck, J., Morgenstern, A., Cyclotron production of Ac-225 for targeted alpha therapy, Appl. Radiat. Isot., 62, 383-387 (2005)
Abbas, K., Apostolidis, C., Janssens, W., Stamm, H., Nikula, T., Carlos, R., Method for produing Actinium 225, EP1455364, 2004
Apostolidis, C., Janssens, W., Koch, L., Mcginley, J., Molinet, R., Ougier, M., Van Geel, J., Möllenbeck, J., Schweickert, H., Method for producing Ac-225 by irradiation of Ra-226 with protons, EP062942, 2004
Morgenstern, A., Apostolidis, C., Molinet, R., Lutzenkirchen, K., Method for producing actinium-225, US patent 20060072698, (2006)

Ermolaev, S. V., Zhuikov, B. L. Kokhanyuk, V. M., Matushko, V. L., Kalmykov Stepan, N., Aliev Ramiz, A. Tananaev Ivan, G.

[0108] Myasoedov, B. Production of actinium, thorium and radium isotopes from natural thorium irradiated with protons up to 141 MeV Radiochim. Acta, 100, p. 223 (2012)
Weidner, J. W., Mashnik, S. G., John, K. D., Hemez, F., Ballard, B., Bach, H., Birnbaum, E. R., Bitteker, L. J. Couture, A., Dry, D., et al. Proton-induced cross sections relevant to production of .sup.225Ac and .sup.223Ra in natural thorium targets below 200 MeV, Appl. Radiat. Isot., 70, pp. 2602-2607, (2012)
Griswold, J. R., Medvedev, D. G., Engle, J. W., Copping, R. Fitzsimmons, J. M., Radchenko, V., Cooley, J. C., Fassbender, M. E., Denton, D. L., Murphy, K. E., Owens, A. C., Birnbaum, E. R., John, K. D., Nortier, F. M., Stracener, D. W., Heilbronn, L. H., Mausner, L. F. Mirzadeh, S., Large Scale Accelerator Production of .sup.225Ac: Effective Cross Sections for 78-192 MeV Protons Incident on 232Th targets, Applied Radiation and Isotopes, 118, 366-374, (2016)
Zhuikov, B. L., Kalmykov, S. N., S. V. Ermolaev, S. V., Aliev, R. A., Kokhanyuk, V. M., Matushko, V. L., Tananaev, I. G., Myasoedov B. F., Production of .sup.225Ac and .sup.223Ra by irradiation of Th with accelerated protons, Radiochemistry, 53, pp. 73-80, (2011)
Koch, L, Fuger, J, van Geel J., Process for producing Actinium-225 from radium-226, EP0752710, 1999-1
Melville, G. Meriarty, H., Metcalfe, P., Knittel, T., Allen, B. J. Production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226, Applied Radiation and Isotopes, 65, 1014-1022, (2007)
Melville G., Allen, B. J., Cyclotron and linac production of Ac-225, Applied Radiation and Isotopes, 67, 549-555, (2009)

Clarke, J. C., High-Powered Cyclotron Recirculating Target for Production of the .SUP.18.F Radionuclide, PhD Thesis, North Carolina State University (2004)