Process for producing molybdenum-99

Abstract

The present invention relates to a process for the production of molybdenum-99 comprising the following steps: Step 1: supplying a basic suspension comprising at least a liquid phase comprising at least molybdenum-99 ions and iodine radionuclide ions and at least a solid phase comprising at least uranium; Step 2: separating the solid phase from the liquid phase of said basic suspension;Step 3: Purification of said liquid phase by an adsorption process of at least a portion of the iodine radionuclide ions to produce a purified liquid phase comprising at least the molybdenum-99 ions and having a reduced iodine radionuclide ion content of at least 90%, preferably 95%, more preferably 97%, compared to the iodine radionuclide ion content in the liquid phase prior to step 3, the process further comprising adding a reducing agent to said basic suspension prior to step 2 and / or treating said solid phase obtained in step 2 with a reducing agent so as to obtain a solid phase having a reduced iodine radionuclide ion content compared to the iodine radionuclide ion content in the solid phase without the addition of the reducing agent.

Description

Scope of the invention

[0001] The present invention relates to a process for the production of molybdenum-99. State of the art

[0002] The use of radioactive isotopes, also called radionuclides or radioisotopes, is widespread in the medical field of diagnosis and therapy.

[0003] Due to the generally short half-life of radionuclides used in medical imaging, the radionuclide of interest is usually delivered to the practitioner in the form of its parent radionuclide, which has a longer half-life, and is adsorbed onto an adsorbent material.

[0004] Among the wide range of available radionuclides, technetium-99m (99m<Tc), with a half-life of approximately 6 hours, is the most common. 99m<Tc is obtained following the decay of molybdenum-99 (99m<Mo), its parent radionuclide, which has a half-life of approximately 66 hours. It is common to use a 99m<Mo / 99m<Tc radionuclide generator, which includes a chromatographic column in which 99m<Mo is adsorbed onto a sorbent. 99m<Mo spontaneously decays to 99m<Tc, the latter being specifically eluted, generally by a saline solution, due to the difference in affinity between 99m<Mo and 99m<Tc for the sorbent.

[0005] The 99< Mo currently used generally results from the fission of uranium-235 (235< U). Typically, highly enriched (HEU) or low-enriched (LEU) uranium-235 is mixed with aluminum to form a target. The target is then irradiated with neutrons to fission the uranium-235 into lower-mass elements, which are themselves unstable and generate, via a decay chain, other radionuclides such as molybdenum-99, iodine-131, and xenon-133. J. Salacz (J. Salacz, IRE Tijdschrift Review, Vol. 9, No. 3 (1985) "Reprocessing of irradiated Uranium 235 for the production of Mo-99, I-131, Xe-133 radioisotopes") developed a process for producing Mo-99 from highly enriched uranium targets. This process allows the production of Mo-99, I-131, and Xe-133.The process involves supplying a basic suspension containing, in the liquid phase, iodine-131 as iodide (I⁻) and molybdenum as MoO₄²⁻. Uranium and a large portion of the fission products as hydroxides are present as a precipitate. The process then includes a filtration step to separate the precipitate (also called cake) to recover the unfissioned uranium. Acidification of the filtrate then removes the iodide as a gas and recovers the Mo₂⁹⁹ as ions in the acidified filtrate. In this process, the iodine-131 is recovered in gaseous form, which necessitates additional recovery methods and is a disadvantage for process safety. Furthermore, this process cannot process a sufficient number of targets for larger-scale Mo₂⁹⁹ production.

[0006] Document EP 3 264 420 A1 describes the use of targets containing low-enriched uranium to produce a fraction containing a radioisotope of Mo-99. The process described in this document involves obtaining a basic slurry containing aluminum salts, uranium, isotopes resulting from the fission of enriched uranium, and a gaseous phase of Xe-133. The basic slurry is then filtered to isolate, on the one hand, a solid phase containing uranium and, on the other hand, a basic solution of molybdate and iodine salts. This is followed by acidification of the molybdate basic solution, either before or after iodine removal. Consequently, if the acidification step is carried out before the iodine removal step, the iodine transitions to the gaseous phase and must be captured, thus requiring additional handling of radioactive gas, which could compromise the safety of the process.This process also involves an additional step of adding alkali-earth nitrate before the filtration stage. This step significantly increases the amount of waste generated and the number of more complex contaminants to remove, and prevents the large-scale production of Mo-99.

[0007] With the demand for radionuclides constantly increasing, there is therefore a continuous need for a larger-scale Mo-99 production process that meets the high level of purity required in the medical field while limiting process safety issues. Summary of the invention

[0008] The inventors have surprisingly found that it is possible to provide a molybdenum-99 production process that meets the aforementioned needs.

[0009] The present invention therefore relates to a process for the production of molybdenum-99 comprising the following steps: Step 1: Provision of a basic suspension comprising at least one liquid phase comprising at least molybdenum-99 ions and iodine radionuclide ions and at least one solid phase comprising at least uranium; Step 2: Separation of the solid phase from the liquid phase of said basic suspension; Step 3: Purification of said liquid phase by an adsorption process of at least a portion of the iodine radionuclide ions to produce a purified liquid phase comprising at least molybdenum-99 ions and having an iodine radionuclide ion content reduced by at least 90%, preferably 95%, more preferably 97%, compared to the iodine radionuclide ion content in the liquid phase prior to Step 3. characterized by the addition of a reducing agent to said basic suspension before step 2 and / or treatment of said solid phase obtained in step 2 with a reducing agent so as to obtain a solid phase whose iodine radionuclide ion content is reduced compared to the iodine radionuclide ion content in the solid phase without the addition of the reducing agent. Detailed description of the invention

[0010] In the context of the present invention, the term "comprising" is inclusive or open-ended and does not exclude other unstated elements, process steps, or compositional components. This term should be interpreted as specifying the presence of the features, values, steps, or components referred to therein, but does not exclude the presence or addition of one or more features, values, steps, or components. Therefore, the scope of the expression "a process comprising steps A and B" should not be limited to a process consisting solely of steps A and B. This means that the only relevant steps are A and B. Consequently, the term "comprising" includes the more restrictive terms "essentially consisting of" and "consisting of."

[0011] In the context of the present invention, the term "molybdenum-99" or "99< Mo" is used interchangeably and refers to the molybdenum radionuclide having a nucleon number of 99. Step 1 of providing a basic suspension

[0012] According to the present invention, the process includes a step 1 of supplying a basic suspension comprising at least a liquid phase comprising at least molybdenum-99 ions and iodine radionuclide ions and at least a solid phase comprising at least uranium.

[0013] In other words, the liquid phase of the basic suspension as defined according to the present invention therefore comprises at least molybdenum-99 ions and iodine radionuclide ions.

[0014] In particular, the molybdenum-99 ions included in the liquid phase of the basic suspension are molybdate ions. These can exist in different forms, which depend strongly on the conditions of the basic suspension such as pH and can, for example, exist as oxyanions such as MoO 4 2-< , [Mo 2 O 7 ] 2-< , [Mo 6 O 19 ] 2-< , [Mo 7 O 24 ] 6-< , [Mo 8 O 26 ] 4-< or their combination.

[0015] In general, the iodine radionuclides included in the liquid phase of the basic suspension according to the present invention are the radioactive isotopes of iodine and may be, for example, iodine-131, iodine-132 and iodine-133.

[0016] Advantageously, the iodine radionuclide ions are in the form of ions selected from the group consisting of iodides, iodates, periodates or their combination.

[0017] It is understood that the liquid phase may also include uranium-235 fission products soluble in the basic suspension.

[0018] According to the present invention, the basic suspension also comprises at least one solid phase comprising at least uranium.

[0019] It is therefore understood that, within the framework of the present invention, the basic suspension comprises a phase in the form of a solid dispersed in the liquid phase of the basic suspension.

[0020] It is understood that the solid phase comprises at least uranium and may include fission products of uranium-235.

[0021] Uranium can be in different forms and can, for example, be present as sodium diuranate Na2U2O7, at least part of which is insoluble in the basic suspension.

[0022] The basic suspension according to the present invention can be obtained by any means known to a person skilled in the art and can be obtained, for example, from a dissolution of a previously irradiated uranium target (also called a "target").

[0023] Advantageously, according to the present invention, said basic suspension is obtained by dissolving the targets with at least one aqueous solution comprising at least one base (basic solution).

[0024] In particular, the basic solution used during dissolution is chosen to obtain a basic suspension in which at least the molybdenum-99 ions and the iodine radionuclide ions are soluble (liquid phase) and at least some of the uranium is insoluble (solid phase).

[0025] Preferably, the basic solution also includes a nitrate.

[0026] The basic solution according to the present invention can be produced by any means known to a person skilled in the art and can be obtained, for example, by mixing a first aqueous solution comprising at least one base with a second aqueous solution comprising at least one nitrate.

[0027] In general, the base is, for example, an alkali hydroxide or an alkaline earth hydroxide, preferably an alkali hydroxide. The alkali hydroxide can, for example, be lithium hydroxide, sodium hydroxide, potassium hydroxide, or a combination thereof, preferably sodium hydroxide.

[0028] Advantageously, said base is present in the first aqueous solution at a concentration greater than or equal to 3.5 mol / l, preferably greater than or equal to 5.0 mol / l, more preferably greater than or equal to 6.0 mol / l.

[0029] Advantageously, said base is present in the first aqueous solution at a concentration less than or equal to 10.0 mol / l, preferably less than or equal to 9.0 mol / l, more preferably less than or equal to 8.5 mol / l.

[0030] Advantageously, said base is present in the first aqueous solution at a concentration between 3.5 and 10.0 mol / l, preferably between 5.0 and 9.0 mol / l, more preferably between 6.0 and 8.5 mol / l.

[0031] Advantageously, the nitrate is an alkali metal nitrate, an alkali-earth nitrate, an ammonium nitrate, or a combination thereof, preferably an alkali metal nitrate. The alkali metal nitrate may, for example, be lithium nitrate, sodium nitrate, potassium nitrate, or a combination thereof, preferably sodium nitrate.

[0032] Advantageously, the nitrate is present in the second aqueous solution at a concentration greater than or equal to 1.0 mol / l, preferably greater than or equal to 1.2 mol / l, more preferably greater than or equal to 1.5 mol / l.

[0033] Advantageously, the nitrate is present in the second aqueous solution at a concentration less than or equal to 5.0 mol / l, preferably less than or equal to 4.0 mol / l, more preferably less than or equal to 3.0 mol / l.

[0034] Advantageously, nitrate is present in the second aqueous solution at a concentration between 1.0 and 5.0 mol / l, preferably between 1.2 and 4.0 mol / l, more preferably between 1.5 and 3.0 mol / l.

[0035] Advantageously, according to the present invention, said basic suspension is obtained by bringing the targets into contact with the basic solution.

[0036] Preferably, the dissolution of the targets to produce the basic suspension is carried out by adding the basic solution to the targets.

[0037] In general, the volume of basic solution used for dissolving the target can be between 500 ml and 1 l per target, preferably between 600 and 700 ml.

[0038] The dissolution conditions described above ensure, in particular, an appropriate dissolution kinetic.

[0039] Known targets typically have a combustible core containing uranium, for example, in the form of a uranium-aluminum alloy (U-Al). A method known to those skilled in the art for forming a target is the use of a uranium-aluminum aluminide dispersion. Uranium aluminide usually contains a mixture of UAl₄, UAl₃, and UAl₂. Such a composition is called UAlₓ. For example, to produce a target, the UAlₓ composition can be ground and dispersed in an aluminum powder. The mixture can then be compacted and shaped to form the combustible core of the target. The combustible core can then be encased in aluminum for cladding. Such targets are designated "UAlₓ-Al".

[0040] It is understood that the targets are solid and can have various shapes. Generally, a person skilled in the art knows how to choose the target shape to optimize the irradiation process. Targets can, for example, be flat, square, hexagonal, or tubular.

[0041] Advantageously, the uranium in the target is low enriched (LEU for Low Enriched Uranium) in uranium-235 isotopes, also called 235< U, which is a fissile isotope of uranium.

[0042] Advantageously, the uranium-235 enrichment level in the target is less than 20%. Percentages are expressed as a percentage of the total weight of uranium in the target.

[0043] Advantageously, the number of targets previously irradiated is greater than or equal to 3, preferably greater than or equal to 5, more preferably greater than or equal to 6.

[0044] The number of targets previously irradiated depends on the size of the reactor used to implement the process.

[0045] Advantageously, the number of previously irradiated targets is less than or equal to 15, or less than or equal to 12.

[0046] Advantageously, the number of targets previously irradiated is greater than or equal to 3 or greater than or equal to 5, or greater than or equal to 6.

[0047] Advantageously, the number of pre-irradiated targets can vary from 3 to 15, or from 5 to 12.

[0048] In the context of the present invention, the term "pre-irradiated targets" is used to refer to targets that have been irradiated before being dissolved to form a basic suspension. Irradiation of the targets can be carried out by any means known to those skilled in the art and can be achieved, for example, by using neutrons in a reactor to fission at least a portion of the uranium-235. After irradiation, those skilled in the art can wait for the temperature of the irradiated targets to decrease. The irradiated targets can then be placed in armored containers for transport and chemically processed to extract the fission products of interest.

[0049] As discussed previously, this extraction of the fission products of interest can be achieved, for example, by dissolving the targets to obtain a basic suspension. This basic suspension then includes the fission products of interest from uranium-235, such as molybdenum-99 and iodine radionuclides. Generally, molybdenum-99 and iodine radionuclides are in ionic form, while uranium precipitates, for example, as sodium diuranate.

[0050] It is therefore understood that at least some of the uranium from the target is insoluble in said basic suspension and is present in the form of a solid dispersed in the liquid phase of the basic suspension.

[0051] According to a certain embodiment, the basic suspension is diluted by a step of diluting said basic suspension with an aqueous solution [solution D].

[0052] In general, solution D can be any aqueous solution that reduces the viscosity of the basic suspension and can, for example, be water or water containing at least one base. This solution D is also called dilution water. Generally, the base is, for example, an alkali hydroxide or an alkaline earth hydroxide; preferably, the base is an alkali hydroxide. The alkali hydroxide can, for example, be lithium hydroxide, sodium hydroxide, potassium hydroxide, or a combination thereof; preferably sodium hydroxide or potassium hydroxide, and more preferably sodium hydroxide.

[0053] Advantageously, the concentration of the base, as detailed above, in solution D is between 0.010 and 1.00 M, preferably between 0.025 and 0.750 M, more preferably between 0.050 and 0.50 M.

[0054] The introduction of this solution D aims in particular to reduce the viscosity of the basic suspension before starting step 2 of separation.

[0055] Advantageously, the volume of solution D used during the dilution step is adapted according to the number of targets engaged, and is, for example, at least 750 ml, preferably at least 1.0 l per increment of 3 targets.

[0056] Advantageously, the ratio between the volume of solution D and the volume of the basic suspension remains constant regardless of the number of targets to be dissolved. Preferably, the dilution factor is 1.00, more preferably 2.00, and even more preferably 2.75.

[0057] The basic suspension thus diluted can be homogenized by any means known to a person skilled in the art, for example, by bubbling. Step 2 of separation

[0058] According to the present invention, the process comprises a step 2 comprising a separation of the solid phase from the liquid phase of said basic suspension.

[0059] This step 2 allows in particular the separation of uranium and insoluble fission products from soluble elements such as iodine and molybdenum-99 radionuclide ions. During this separation step, the solid phase containing at least uranium is retained and is also called "cake" or "uranium cake".

[0060] The separation step according to the present invention can be carried out by any means known to those skilled in the art for separating a solid from a liquid and can be, for example, a step of sedimentation, decantation, filtration, or a combination thereof, preferably the separation step is a filtration.

[0061] Advantageously, the separation is carried out by a device known to those skilled in the art, allowing a liquid phase and a solid phase to be separated through a porous medium, preferably a filter.

[0062] Advantageously, the pore size of the porous medium is a maximum of 7.0 µm, preferably a maximum of 6.0 µm, more preferably a maximum of 5.0 µm.

[0063] In particular, the pore size of the porous medium is between 1.5 and 7.0 µm, preferably between 2.0 and 6.0 µm, more preferably between 2.5 and 5.0 µm.

[0064] Non-limiting examples of filters include the nutsche filter, the "Büchner" type filter, the press filter, the bag filter, the belt filter, the drum filter or a combination thereof.

[0065] The material constituting the porous medium that retains the solid phase can be, for example, glass, fiberglass, metal such as stainless steel, or a combination thereof. Preferably, the porous medium is stainless steel, or more preferably, a stainless steel mesh. Advantageously, the stainless steel mesh is obtained by weaving to form pores as described above. In other words, the porous medium is woven stainless steel, preferably having a pore size as defined above.

[0066] Advantageously, the thickness of the porous medium is between 50 and 300 µm, preferably between 100 and 200 µm, more preferably between 100 and 200 µm.

[0067] Advantageously, the separation step can be carried out by pressure or vacuum or a combination thereof.

[0068] Advantageously, the temperature of the basic suspension is lower than its boiling point at the beginning of the separation step. For example, the temperature of the basic suspension is less than 100°C at the beginning of the separation step. Preferably, the temperature of the basic suspension is greater than or equal to 50°C, more preferably greater than or equal to 75°C, and even more preferably greater than or equal to 90°C at the beginning of the separation step.

[0069] In a particular embodiment of the invention, several separation steps can be carried out in series or in parallel. For example, several separation steps carried out in series could improve the efficiency of the separation, while several steps in parallel could reduce the time required for separation.

[0070] In a certain embodiment of the process according to the invention, step 2 may include at least one rinsing of said solid phase obtained during separation with an aqueous solution [solution R]. Preferably, step 2 may include at least two rinsings of said solid phase obtained during separation with an aqueous solution [solution R].

[0071] In general, the solution R is chosen to rinse or clean the solid phase and may, for example, be water or water containing at least one base. Generally, the base is, for example, an alkali hydroxide or an alkaline earth hydroxide; preferably, the base is an alkali hydroxide. The alkali hydroxide may, for example, be lithium hydroxide, sodium hydroxide, potassium hydroxide, or a combination thereof; preferably sodium hydroxide or potassium hydroxide, and more preferably sodium hydroxide.

[0072] Advantageously, the concentration of the base, as detailed above, in the solution R is between 0.010 and 1.00 M, preferably between 0.025 and 0.750 M, more preferably between 0.050 and 0.50 M.

[0073] Advantageously, the volume of solution R is between 1600 and 2000 ml, preferably between 1700 and 1900 ml.

[0074] In a particular embodiment according to the invention, the rinsing can be repeated several times, for example at least three times, preferably at least twice.

[0075] In general, after step 2, a sample of the liquid phase is taken to determine the activity of molybdenum-99 and iodine-131 in the liquid phase.

[0076] In the context of the present invention, the activity of a radionuclide (expressed in Curies, Ci), which is the number of disintegrations the radionuclide produces per unit of time (second), is measured by a high-purity germanium detector (HPGe detector). The nature (qualitative analysis) and activity of the radionuclide (quantitative analysis) present in a sample are thus determined from the analysis of the gamma ray spectra measured over time by the detector.

[0077] According to the present invention, it is envisaged that a reducing agent will be added to said basic suspension before step 2 and / or that said solid phase separated during step 2 will be treated with a reducing agent.

[0078] In prior art processes, the solid phase separated in step 2 may have a content of iodine radionuclides which may result in a process safety problem since iodine radionuclides can decay into xenon radionuclides, in the form of a radioactive gas whose emission must be controlled.

[0079] The inventors have surprisingly found that the addition of a reducing agent, as mentioned above, makes it possible to obtain a solid phase in which the content of iodine radionuclide ions is reduced compared to the content of iodine radionuclide ions in the solid phase without the addition of the reducing agent.

[0080] The addition of the reducing agent can be carried out by any method known to a person skilled in the art, provided that a solid phase is obtained in which the content of iodine radionuclide ions is reduced compared to the content of iodine radionuclide ions in the solid phase without the addition of the reducing agent.

[0081] In the context of the present invention, the reduction of the iodine radionuclide ion content of the solid phase is determined via the increase in the iodine radionuclide ion content in the liquid phase separated in step 2. The increase in the iodine radionuclide ion content in the liquid phase is calculated on the basis of a measurement of the activity of the iodine radionuclide ions in the liquid phase and the expected theoretical activity.

[0082] In the context of the present invention, the term "expected theoretical activity" means the expected activity value for a given radionuclide determined using the Origen 2.1 calculation code (RSICC COMPUTER CODE COLLECTION, Isotope Generation and Depletion Code, Matrix Exponential Method, Oak Ridge National Laboratory, Oak Ridge, Tennessee). This value is a function of certain parameters such as, for example, the reactor type, the nature of the irradiated fuel, the initial fuel enrichment, the specific power of the irradiation cycle, and the irradiation time.

[0083] In the context of the present invention, it is understood that the "recovery yield" (hereinafter RR) determines the efficiency of the process. The recovery yield of a radionuclide (expressed as a percentage) is defined as the ratio between the activity (expressed as Ci) of said radionuclide measured, A m, in the solution and the theoretical activity (expressed in Ci), A t , of said radionuclide: RR = A m A t × 100 %

[0084] In other words, in the context of the present invention, the content of a radionuclide corresponds to the recovery yield (RR) of that radionuclide determined on the basis of equation, eq. 1, above and expressed in %.

[0085] The increase in the content of iodine radionuclide ions in the liquid phase therefore corresponds to the difference between the RR of iodine radionuclide ions in the liquid phase when a reducing agent has been added and the RR of iodine radionuclide ions in the liquid phase without the addition of a reducing agent.

[0086] Advantageously, the addition of the reducing agent makes it possible to obtain a liquid phase in which the iodine radionuclide ion content is increased by at least 3.5%, preferably by at least 5%, preferably by at least 7%, more preferably by at least 15%, and even more preferably by at least 20%. The percentages are expressed relative to the theoretical activity expected for iodine radionuclide ions in the liquid phase after step 2.

[0087] In the context of the present invention, the reducing agent can be any reducing agent known to a person skilled in the art having a reduction potential that allows at least for the generation of a redox reaction during which the oxidation number of iodine is reduced.

[0088] Preferably, the reducing agent comprises at least one anion selected from the group consisting of a sulfite, a hydrosulfite, a thiosulfate, an oxalate, a borohydride, and a hydrazine; preferably the anion is a sulfite or a hydrosulfite. In particular, said reducing agent comprises at least one sulfite.

[0089] In the context of the present invention, the expression "at least one anion" means one or more anions. Combinations of anions are also included within the scope of the present invention. In the following text, the term "anion" may be interpreted, in the context of the present invention, in the singular or plural so as to mean that the reducing agent may comprise one or more anions.

[0090] Advantageously, the reducing agent is a salt whose counterion can be any counterion known to the person skilled in the art and can be, for example, at least one element chosen from the group consisting of hydrogen, lithium, sodium, potassium, rubidium and cesium; preferably, the counterion is sodium.

[0091] In a certain embodiment of the process according to the invention, a reducing agent is added to said basic suspension before step 2. In this way the reducing agent is present in the basic suspension during step 2.

[0092] Advantageously, the concentration of the reducing agent in the basic suspension is greater than or equal to 0.015 mol / l, preferably greater than or equal to 0.10 mol / l, more preferably greater than or equal to 0.20 mol / l, more preferably greater than or equal to 0.30 mol / l, even more preferably greater than or equal to 0.40 mol / l.

[0093] Advantageously, the concentration of the reducing agent in the basic suspension is less than or equal to 1.00 mol / l, preferably less than or equal to 0.60 mol / l, more preferably less than or equal to 0.40 mol / l, more preferably less than or equal to 0.20 mol / l, even more preferably less than or equal to 0.10 mol / l.

[0094] Advantageously, the concentration of the reducing agent in the basic suspension is between 0.015 and 1.00 mol / l, preferably between 0.10 and 0.60 mol / l, more preferably between 0.20 and 0.40 mol / l.

[0095] Alternatively or additionally, when a dilution step of the basic suspension is carried out, the reducing agent may also be added to said solution D.

[0096] In this embodiment, the concentration of the reducing agent in solution D is advantageously greater than or equal to 0.05 mol / l, more advantageously greater than or equal to 0.25 mol / l, preferably greater than or equal to 0.50 mol / l, more preferably greater than or equal to 0.75 mol / l, even more preferably greater than or equal to 1.00 mol / l.

[0097] Advantageously, the concentration of the reducing agent in solution D is less than or equal to 2.00 mol / l, more advantageously less than or equal to 1.50 mol / l, preferably less than or equal to 1.00 mol / l, more preferably less than or equal to 0.50 mol / l, even more preferably less than or equal to 0.25 mol / l.

[0098] Advantageously, the concentration of the reducing agent in solution D is between 0.05 and 2.00 mol / l, preferably between 0.25 and 1.50 mol / l, more preferably between 0.50 and 1.00 mol / l.

[0099] In a second embodiment of the process according to the present invention, said solid phase separated in step 2 is treated with a reducing agent.

[0100] Non-limiting examples of such treatment include washing or cleaning, preferably the treatment is a rinsing treatment.

[0101] Preferably, said treatment of the solid phase separated in step 2 is a step of treating said solid phase with an aqueous solution comprising the reducing agent [solution A].

[0102] In this embodiment, the concentration of the reducing agent in solution A is advantageously greater than or equal to 0.05 mol / l, more advantageously greater than or equal to 0.25 mol / l, preferably greater than or equal to 0.50 mol / l, more preferably greater than or equal to 0.75 mol / l, even more preferably greater than or equal to 1.00 mol / l.

[0103] Advantageously, the concentration of the reducing agent in solution A is less than or equal to 2.00 mol / l, more advantageously less than or equal to 1.50 mol / l, preferably less than or equal to 1.00, more preferably less than or equal to 0.50 mol / l, even more preferably less than or equal to 0.25 mol / l.

[0104] Advantageously, the concentration of the reducing agent in solution A is between 0.05 and 2.00 mol / l, preferably between 0.25 and 1.50 mol / l, more preferably between 0.50 and 1.00 mol / l.

[0105] Alternatively or additionally, when a step of rinsing said solid phase with an aqueous solution is provided in the process according to the invention, the reducing agent is preferably added to solution R (aqueous solution for rinsing the solid phase). It is understood that each of the definitions, preferences, and advantageous embodiments mentioned in relation to solution A of the present invention are also applicable to the embodiment in relation to solution R.

[0106] If necessary, the first and second embodiments detailed above can be combined.

[0107] It is understood according to the present invention that the different embodiments can be carried out independently of each other or in combination. Step 3 of purification

[0108] The liquid phase obtained after the separation in step 2, as detailed above, is then subjected to a step 3 during which the liquid phase undergoes a purification step in which at least some of the iodine radionuclide ions are retained by adsorption so as to recover a purified liquid phase whose iodine radionuclide ion content is reduced compared to the iodine radionuclide ion content in the liquid phase before step 3. This purified liquid phase includes at least the molybdenum-99 ions.

[0109] A person skilled in the art may use any known means of purification provided that a purified liquid phase is obtained in which the iodine radionuclide ion content is reduced by at least 90%, advantageously 95%, more advantageously by at least 97%, compared to the iodine radionuclide ion content in the liquid phase before step 3. The iodine radionuclide ion contents are determined according to eq.1 above.

[0110] In a preferred embodiment of the present invention, the liquid phase obtained after separation in step 2 undergoes a purification step by a liquid-solid adsorption process.

[0111] In general, such liquid-solid adsorption processes are known to those skilled in the art, particularly those involved in chemical processes and purification techniques. In the context of the present invention, the term adsorption includes the use of at least one solid support, such as, for example, at least one sorbent.

[0112] In a preferred embodiment of step 3 of the present invention, the liquid-solid adsorption process is carried out by bringing the liquid phase, as defined above, into contact with at least one sorbent.

[0113] Preferably, the sorbent is contained in a chromatographic column. In general, the chromatographic column can be made of any material known to those skilled in the art, such as, for example, glass, stainless steel, or polyetheretherketone (PEEK). Such a chromatographic column is known from the prior art and is described, for example, in the document by MV Wilkinson et al. (Separation of iodine produced from fission using silver-coated alumina, Journal of Radioanalytical and Nuclear Chemistry, Vol. 256, No. 3 (2003) 413-415).

[0114] The sorbent can be any sorbent known to a person skilled in the art having a particular affinity for iodine ions, preferably for iodides, I-< .

[0115] Advantageously, the sorbent is an inorganic compound such as, for example, activated carbon, carbon black, zeolites, or a metal oxide; preferably, the sorbent is a metal oxide. Such a metal oxide is, for example, titanium dioxide, zirconium oxide, aluminum oxide, silicon dioxide, or a combination thereof; preferably, the metal oxide is aluminum oxide.

[0116] Advantageously, the sorbent is doped with a dopant. The dopant can be any dopant known to those skilled in the art that has a particular affinity for iodine ions. Preferably, the dopant is a metal such as, for example, silver, copper, or a noble metal, such as palladium, platinum, gold, or mixtures thereof; preferably, the dopant is silver.

[0117] Advantageously, the sorbent is doped with the dopant at a rate (also called the impregnation rate) of 5% or more, more advantageously 6% or more, preferably 8% or more, more preferably 10% or more, more preferably 12% or more, and even more preferably 15% or more. The percentages are expressed as a percentage of the total weight of the sorbent.

[0118] If necessary, after carrying out the liquid-solid adsorption process, of said at least a part of the iodine radionuclide ions on the sorbent, the sorbent on which at least a part of the iodine radionuclide ions is adsorbed may undergo at least one rinsing with an aqueous solution comprising at least one base [RB solution].

[0119] This optional rinsing step of the sorbent on which at least part of the iodine radionuclide ions are adsorbed can in particular be used to recover residual traces of weakly adsorbed molybdenum-99 and possibly to remove other fission products.

[0120] In general, the base is for example an alkali hydroxide or an alkaline earth hydroxide, preferably the base is an alkali hydroxide.

[0121] The alkali hydroxide can, for example, be lithium hydroxide, sodium hydroxide, potassium hydroxide or their combination, preferably sodium hydroxide or potassium hydroxide, more preferably sodium hydroxide.

[0122] Advantageously, the concentration of the base, as detailed above, in the RB solution is between 0.01 and 0.10 mol / l, more advantageously between 0.02 and 0.07 mol / l, and even more advantageously between 0.03 and 0.06 mol / l.

[0123] In general, the volume of RB solution used for rinsing the sorbent is, for example, between 200 and 1000 ml, preferably between 300 and 750 ml, more preferably between 400 and 600 ml.

[0124] Preferably, a new sample is taken after step 3 to determine the iodine fixation yield on the sorbent and the molybdenum-99 recovery yield in solution. These are determined by measuring the activity of molybdenum-99 and iodine-131 in the purified liquid phase. Acidification step 4

[0125] In a certain embodiment of the invention, at least a portion of the purified liquid phase comprising at least molybdenum-99 ions obtained after step 3 may undergo an acidification step 4. The purified liquid phase comprising at least molybdenum-99 ions obtained after acidification step 4 is also referred to as the acid solution.

[0126] In general, step 4 of acidification is carried out with any acid known to a person skilled in the art. Such an acid may be, for example, acetic acid, acetylsalicylic acid, ascorbic acid, citric acid, hydrochloric acid, sulfuric acid, nitric acid, formic acid, lactic acid, preferably nitric acid.

[0127] Advantageously, the concentration of acid in the acid solution is greater than or equal to 0.10 mol / l, preferably greater than or equal to 0.50 mol / l, more preferably greater than or equal to 0.75 mol / l, even more preferably greater than or equal to 0.90 mol / l.

[0128] Advantageously, the concentration of acid in the acid solution is less than or equal to 1.50 mol / l, preferably less than or equal to 1.25 mol / l, more preferably less than or equal to 1 mol / l.

[0129] Advantageously, the concentration of acid in the acid solution is between 0.10 and 1.50 mol / l, preferably between 0.5 and 1.25 mol / l, more preferably between 0.75 and 1 mol / l, even more preferably between 0.90 and 1 mol / l.

[0130] Advantageously, the acid is used in excess in the acid solution.

[0131] In a certain embodiment of the process according to the invention, the purified liquid phase can be heated before and / or during and / or after acidification step 4, advantageously at a temperature between 60 and 100 °C, preferably between 70 and 100 °C, more preferably between 70 and 100 °C, even more preferably between 90 and 99 °C. Step 5 of molybdenum-99 purification and recovery

[0132] In one embodiment of the invention, at least a portion of the acid solution obtained after step 4 may undergo a purification step by adsorption of at least a portion of the molybdenum-99 ions.

[0133] In a preferred embodiment of the present invention, at least a portion of the acid solution obtained after step 4 undergoes a purification step by a liquid-solid adsorption process.

[0134] In general, such liquid-solid adsorption processes are known to those skilled in the art, particularly those involved in chemical processes and purification techniques. In the context of the present invention, the term adsorption includes the use of at least one solid support, such as, for example, at least one sorbent. In this embodiment of the invention, the liquid-solid adsorption process of step 5 can be carried out by contacting at least a portion of the acidic solution, as defined above, with at least one sorbent so as to adsorb at least some of the molybdenum-99 ions onto the sorbent. In general, the sorbent can be any sorbent known to those skilled in the art that has a particular affinity for molybdenum ions, preferably molybdate ions.Advantageously, the sorbent is an inorganic compound such as activated carbon, carbon black, zeolites, a strong anionic resin (SAR, also called anion exchange resin), a metal oxide, or a combination thereof. Examples of such metal oxides include titanium dioxide, zirconium oxide, aluminum oxide, silicon dioxide, tin oxide, or combinations thereof.

[0135] Advantageously, titanium oxide has a particle size d 50 of between 80 and 160 µm, preferably between 90 and 150 µm, and more preferably between 100 and 120 µm. In the context of the present invention, the notation "dx of y µm" means that x% by number of particles, relative to the total number of particles, have a particle size less than y µm.

[0136] Activated carbon can be any type of activated carbon known to those skilled in the art and may be, for example, granular activated carbon (GAC), extruded activated carbon (EAC), or powdered activated carbon (PAC), preferably powdered activated carbon. Generally, powdered activated carbon has a particle size of 0.5–1.0 mm (18–35 mesh ASTM) or 0.3–0.5 mm (35–50 mesh ASTM), preferably 0.3–0.5 mm (35–50 mesh ASTM). Activated carbon may be doped with a dopant. The dopant can be any dopant known to those skilled in the art that reduces the residual iodine radionuclide ion content, preferably one with a particular affinity for iodine radionuclide ions. Preferably, the dopant is a metal such as, for example, silver, copper or a noble metal, such as palladium, platinum, gold, or mixtures thereof, preferably the dopant is silver.

[0137] The strong anionic resin can be any strong anionic resin known to the person skilled in the art having a particular affinity for molybdenum-99 ions, and can be, for example, a styrene-divinyl benzene resin.

[0138] Advantageously, the sorbent is contained in an adsorption device such as, for example, a chromatographic column.

[0139] Advantageously, the chromatographic column has a diameter between 1.0 and 8.0 cm, preferably between 2.0 and 7.0 cm, more preferably between 3.0 and 5.0 cm.

[0140] Advantageously, in this embodiment, after the liquid-solid adsorption process of step 5, at least a portion of the molybdenum-99 ions adsorbed onto the sorbent may undergo at least one elution with at least one eluent. The eluent may be any eluent known to those skilled in the art that allows at least a portion of the molybdenum-99 ions adsorbed onto the sorbent to be dissolved. This results in the recovery of an eluate comprising at least a portion of the previously adsorbed molybdenum-99 ions, preferably in the form of molybdate ions. Advantageously, the eluate comprises at least 70%, preferably 80%, and more preferably at least 90% of the Mo-99 previously adsorbed onto the sorbent.

[0141] Advantageously, the eluent is chosen according to the nature of the sorbent and is preferably an aqueous solution such as, for example, water or water which may also include a salt, an acid or a base.

[0142] If necessary, step 5 may include at least one rinsing step, between the liquid-solid adsorption process and elution, during which said at least a portion of the molybdenum-99 ions adsorbed on the sorbent is rinsed by a rinsing solution.

[0143] Alternatively or additionally, step 5 may include at least one rinsing step, after the elution of at least some of the molybdenum-99 ions, during which the sorbent is rinsed with a rinsing solution.

[0144] Advantageously, the rinsing solution is chosen according to the nature of the sorbent based on the knowledge of a person skilled in the art and is preferably an aqueous solution such as, for example, water or water which may also include a salt, an acid or a base.

[0145] Alternatively or additionally, step 5 may include at least one molybdenum-99 recycling step, after the elution of at least some of the molybdenum-99 ions or after the rinsing step, during which the sorbent is left in contact with an aqueous recycling solution such as, for example, water or water that may also contain a salt, an acid, or a base, preferably water. During this step, the sorbent remains in contact with the aqueous recycling solution until the next production run. This aqueous recycling solution, once drained, contains a non-negligible Mo-99 activity balance representing between 3% and 6% of the Mo-99 source term committed for that production run. Analysis of this aqueous recycling solution has shown that its purity is higher than that of a solution obtained by dissolution.This aqueous recycling solution containing molybdenum-99 can therefore be recycled and injected during acidification step 4 for further production.

[0146] When the sorbent is a titanium oxide, preferably at least one rinsing step is carried out between the liquid-solid adsorption process and the elution described above, using a rinsing solution comprising at least one acid [RA solution]. In general, the acid is, for example, acetic acid, acetylsalicylic acid, ascorbic acid, citric acid, hydrochloric acid, sulfuric acid, nitric acid, formic acid, lactic acid, preferably nitric acid.

[0147] Advantageously, the concentration of the acid in the RA solution is between 0.25 and 1.75 M, preferably between 0.50 and 1.50, more preferably between 0.75 and 1.25.

[0148] Alternatively or additionally, the rinsing solution, for said at least one rinsing step carried out between the liquid-solid adsorption process and the elution, may be water or water comprising a salt, for example a salt comprising at least one sulfite, hydrosulfite, thiosulfate or oxalate, preferably the salt comprising at least one sulfite.

[0149] When the sorbent is titanium dioxide, preferably the elution of the adsorbed molybdenum-99 ions is carried out with an aqueous solution containing at least one base [solution E1]. Generally, the base is, for example, an alkali hydroxide or an alkaline earth hydroxide; preferably, the base is an alkali hydroxide. The alkali hydroxide may, for example, be lithium hydroxide, sodium hydroxide, potassium hydroxide, or a combination thereof; preferably, sodium hydroxide.

[0150] Advantageously, said base is present in solution E1 at a concentration greater than or equal to 0.50 mol / l, preferably greater than or equal to 1.00 mol / l, more preferably greater than or equal to 1.50 mol / l.

[0151] Advantageously, said base is present in solution E1 at a concentration less than or equal to 5.00 mol / l, preferably less than or equal to 4.00 mol / l, more preferably less than or equal to 3.00 mol / l.

[0152] Advantageously, said base is present in solution E1 at a concentration between 0.50 and 5.00 mol / l, preferably between 1.00 and 4.00 mol / l, more preferably between 1.50 and 3.00 mol / l.

[0153] Advantageously, the volume of solution E1 used during elution is between 250 and 750 ml, preferably between 400 and 600 ml.

[0154] Advantageously, the volume of water used during the rinsing step is between 250 and 750 ml, preferably between 400 and 600 ml.

[0155] When the sorbent is a strong anionic resin (SAR, also called anion exchange resin), preferably the optional rinsing step is carried out with water.

[0156] When the sorbent is a strong anionic resin (SAR also called anion exchange resin), the preferred eluent is an aqueous solution comprising at least one nitrate [solution E2].

[0157] Advantageously, the nitrate is an alkali metal nitrate or an alkali-earth nitrate or an ammonium nitrate or a combination thereof, preferably an ammonium nitrate.

[0158] Advantageously, nitrate is present in solution E2 at a concentration between 0.25 and 1.75 mol / l or between 0.5 and 1.5 mol / l, or between 0.75 and 1.25 mol / l.

[0159] When the sorbent is activated carbon, the preferred eluent is an aqueous solution containing at least one base [solution E3]. Generally, the base is, for example, an alkali hydroxide or an alkaline earth hydroxide, preferably an alkali hydroxide. The alkali hydroxide may, for example, be lithium hydroxide, sodium hydroxide, potassium hydroxide, or a combination thereof, preferably sodium hydroxide.

[0160] More advantageously, said base is present in solution E3 at a concentration between 0.05 and 0.75 mol / l or between 0.1 and 0.5 mol / l or between 0.2 and 0.4 mol / l.

[0161] More advantageously, step 5 of the present invention involves the successive use of more than one chromatographic column, even more advantageously at least two chromatographic columns, and preferably at least three. Quite surprisingly, the inventors found that the successive use of three chromatographic columns yielded very good results. In this way, the acidic solution obtained after step 4 undergoes a first liquid-solid adsorption process, as defined above, in the first column. The eluate recovered from the first column is injected into the second column so as to undergo a second liquid-solid adsorption process, as defined above, in the second column.The eluate recovered from the outlet of the second column is injected into the third column to undergo a third liquid-solid adsorption process, as defined above. An eluate is then recovered from the outlet of the third column.

[0162] Alternatively, the eluate recovered at the outlet of the second column can undergo an acidification step before being injected into the third column so as to undergo a third liquid-solid adsorption process, as defined above, in the third column.

[0163] Advantageously, when three chromatographic columns are used successively, the sorbent in the first chromatographic column is titanium oxide, the sorbent in the second chromatographic column is a strong anionic resin, and the sorbent in the third column is activated carbon.

[0164] According to the present invention, the eluate or solution, recovered at the end of the molybdenum-99 production process, comprising at least the molybdenum-99 ions, can also be called molybdenum-99 stock solution (or Mo-99 SF), which can then be distributed for use in medical diagnostic applications.

[0165] The inventors have found, surprisingly, that the said process of the invention makes it possible to achieve a good recovery yield of molybdenum-99 having a purity in terms of radionuclide impurity content conforming to the specifications required by the Pharmacopoeia while improving the safety of the process by reducing the adsorption of iodine radionuclide ions, in particular iodates, on the solid phase comprising uranium.

[0166] The molybdenum-99 stock solution obtained by the process of the invention can therefore be used in the medical field of diagnostics, since it meets the requirements of Monograph 1923 of the European Pharmacopoeia for a fission-derived sodium molybdate (Mo-99) solution. Indeed, the inventors have shown, surprisingly, that the molybdenum-99 stock solution obtained by the process of the invention exhibits very good results in terms of critical quality attributes (CQAs), which are the physical, chemical, biological, or microbiological properties or characteristics that must satisfy the requirements of Monograph 1923 of the European Pharmacopoeia so that the molybdenum-99 stock solution can be used in the medical field. Examples

[0167] The present invention will now be described by means of examples, the purpose of which is primarily illustrative and should not be considered as limiting the scope of the invention. Basic suspension preparation

[0168] Targets containing a UAlx-Al fuel core were used. The targets consisted of metallic uranium, uranium-aluminum alloy (U-Al) powder, aluminum powder, and aluminum cladding.

[0169] The uranium-235 enrichment level was 19.75% ± 0.2%. Percentages are expressed as a percentage of the total weight of uranium in the target.

[0170] Targets were irradiated and then cooled before being used to produce the basic suspension.

[0171] The basic suspension was obtained by dissolving the targets in 3780 ml of a basic solution consisting of a 6.3 M sodium hydroxide solution and a 2.4 M sodium nitrate solution. Separation stage

[0172] The solid and liquid phases of the basic suspension were separated using a Büchner funnel, leaving the solid phase on the filter. The liquid phase that passed through the filter was collected so that a sample could be taken to determine the activity of molybdenum-99 and iodine-131. Measurement of the activity of iodine-131 and molybdenum-99 in the liquid phase

[0173] The activities of iodine-131 and molybdenum-99 were measured using a high-purity germanium detector (HPGe detector). Recovery yields (RR) were calculated as described above based on the theoretical activities indicated for each example listed below. Counter-example 1 (CE1)

[0174] Counterexample 1 was carried out as described in the general procedure above. The expected theoretical activities for this example are 4355 Ci for molybdenum-99 and 1319 Ci for iodine-131

[0175] The basic suspension underwent a dilution step with 2160 ml of water before undergoing the separation step. The resulting solid phase was then rinsed with 1800 ml of water.

[0176] The recovery yields (RR) of molybdenum-99 and iodine-131 in the liquid phase after the separation step and the first rinse are shown in Table 1. Example 1 (E1)

[0177] Example 1 was carried out in the same way as counter-example 1 except that the solid phase underwent a second rinse with 1500 ml of a 1M Na2SO3 solution followed by a third rinse with 400 ml of water.

[0178] The recovery yields (RR) of molybdenum-99 and iodine-131 in the liquid phase after the separation step and the two rinsing steps are shown in Table 1.

[0179] It was observed that using a reducing agent, Na₂SO₃, to rinse the solid phase after the separation step (E1) reduces the iodine-131 ion content compared to the iodine-131 ion content in the solid phase without the addition of the reducing agent (CE1). This reduction is determined by the 17.99% increase in the iodine-131 recovery yield in the liquid phase obtained after the second rinse with a 1.0 M Na₂SO₃ solution (E1, 52.34%) compared to the iodine-131 recovery yield in the liquid phase without the addition of the reducing agent (CE1, 34.35%).

[0180] It has also been observed that the recovery yields of molybdenum-99 are very good and are not negatively affected by the addition of the reducing agent, Na2SO3. Example 2a (E2a)

[0181] Example 2a was carried out in the same way as counter-example 1 except that the dilution step of the basic suspension was carried out with a 1M Na₂SO₃ solution. The expected theoretical activities are 3239 Ci for molybdenum-99 and 1073 Ci for iodine-131.

[0182] The recovery yields (RR) of molybdenum-99 and iodine-131 in the liquid phase after the separation step and the first rinse are shown in Table 2. Example 2b (E2b)

[0183] Example 2b was carried out under the same conditions as example 2a except that the solid phase underwent a second rinse with 1500 ml of a 1M Na2SO3 solution followed by a third rinse with 400 ml of water.

[0184] The recovery yields (RR) of molybdenum-99 and iodine-131 in the liquid phase after the separation step and the two rinsing steps are shown in Table 2. Table 2 Examples Terms Results (RR%) Dilution Rinse 1 Rinse 2 I-131 Mo-99 E2 a Na₂SO₃ 1.0 M H2O / 89,75 94,66 E2 b Na₂SO₃ 1.0 M H2O Na₂SO₃ 1.0 M 95,48 95,48

[0185] It was observed that using a reducing agent, 1M Na₂SO₃, to dilute the basic suspension resulted in a high iodine-131 recovery yield of 89.75% (E2a). This recovery yield was further improved to 95.48% (E2b) when the solid phase was rinsed with a 1M Na₂SO₃ solution.

[0186] It has also been observed that the recovery yields of molybdenum-99 are very good and are not negatively affected by the addition of the reducing agent, Na2SO3. Example 3a (E3a)

[0187] Example 3a was carried out in the same way as counter-example 1, except that the dilution step of the basic suspension was performed with a 0.5 M Na₂SO₃ solution and no rinsing of the solid phase was performed. The expected theoretical activities are 3628 Ci for molybdenum-99 and 995 Ci for iodine-131.

[0188] The recovery yields (RR) of molybdenum-99 and iodine-131 in the liquid phase after the separation step are shown in Table 3. Example 3b (E3b)

[0189] Example 3b was carried out in the same way as example 3a except that the solid phase underwent a first rinse with 1800 ml of a 0.5M Na 2 SO 3 solution.

[0190] The recovery yields (RR) of molybdenum-99 and iodine-131 in the liquid phase after the separation step and the first rinse are shown in Table 3. Example 3c (E3c)

[0191] Example 3b was carried out in the same way as example 3a except that the solid phase underwent a second rinse with 1800 ml of water.

[0192] The recovery yields (RR) of molybdenum-99 and iodine-131 in the liquid phase after the separation step and the two rinsing steps are shown in Table 3. Table 3 Examples Terms Results (RR%) Dilution Rinse 1 Rinse 2 I-131 Mo-99 E3 a Na₂SO₃ 0.5 M / / 77,69 89,88 E3 b Na₂SO₃ 0.5 M Na₂SO₃ 0.5 M / 90,25 94,29 E3 c Na₂SO₃ 0.5 M Na₂SO₃ 0.5 M H2O 93,17 92,36

[0193] It was observed that using a reducing agent, 0.5M Na₂SO₃, to dilute the basic suspension resulted in a high iodine-131 recovery yield of 77.69% (E3a). This recovery yield was further improved to 95.48% (E3b) when the solid phase was rinsed with a 0.5M Na₂SO₃ solution.

[0194] It has also been observed that the recovery yields of molybdenum-99 are very good and are not negatively affected by the addition of the reducing agent, Na2SO3.

Claims

1. A method for producing molybdenum-99 comprising the following steps Step 1: providing a basic suspension comprising at least one liquid phase comprising at least molybdenum-99 ions and iodine radionuclide ions and at least one solid phase comprising at least uranium; Step 2: separating the solid phase from the liquid phase of said basic suspension; Step 3: purifying said liquid phase by a method of adsorbing at least a portion of the iodine radionuclide ions to produce a purified liquid phase comprising at least molybdenum-99 ions and having a reduced content of iodine radionuclide ions of at least 90%, preferably 95%, more preferably 97%, compared to the content of iodine radionuclide ions in the liquid phase before step 3 characterized by adding a reducing agent to said basic suspension before step 2 and / or treating said solid phase obtained in step 2 with a reducing agent so as to obtain a solid phase whereof the content of iodine radionuclide ions is reduced with respect to the content of iodine radionuclide ions in the solid phase without addition of the reducing agent.

2. The method according to claim 1, wherein the addition of the reducing agent makes it possible to obtain a liquid phase whose content of iodine radionuclide ions is increased by at least 3.5%, preferably at least 5%, more preferably at least 7%, more preferably by at least 15%, and most preferably by at least 20%, the percentages being expressed relative to the theoretical activity expected for iodine radionuclide ions in the liquid phase after step 2.

3. The method according to any one of claims 1 or 2, wherein the reducing agent comprises at least one anion selected from the group consisting of sulfite, hydrosulfite, thiosulfate, oxalate, borohydride, and hydrazine.

4. The method according to any one of claims 1 to 3, wherein the concentration of the reducing agent in the basic suspension is between 0.015 and 1.00 mol / l, preferably between 0.10 and 0.60 mol / l, more preferably between 0.20 and 0.40 mol / l.

5. The method according to any one of claims 1 to 4, further comprising a step of diluting said basic suspension with an aqueous solution [solution D] and wherein the reducing agent is added to said solution D and the concentration of the reducing agent in the solution D is between 0.05 and 2.00 mol / l, preferably between 0.25 and 1.50 mol / l, more preferably between 0.50 and 1.00 mol / l.

6. The method according to any one of claims 1 to 5, wherein said treatment of the solid phase separated in step 2 is a step of treating said solid phase with an aqueous solution comprising the reducing agent [solution A], and wherein the concentration of the reducing agent in solution A is between 0.05 and 2.00 mol / l, preferably between 0.25 and 1.50 mol / l, more preferably between 0.50 and 1.00 mol / l.

7. The method according to any one of claims 1 to 6, wherein said basic suspension is obtained by dissolving at least one previously irradiated uranium target, said previously irradiated uranium target having an enrichment level of uranium-235 of less than 25%, preferably less than 20%.

8. The method according to any one of claims 1 to 7, wherein step 2 of separation is carried out using a porous medium made of woven stainless steel.

9. The method according to any one of claims 1 to 8, wherein step 3 is a step in which the liquid phase obtained after the separation of step 2 undergoes a purification step by a liquid-solid adsorption method and wherein the liquid-solid adsorption method is carried out by contacting the liquid phase with at least one sorbent, said sorbent being a metal oxide selected from the group consisting of titanium oxide, zirconium oxide, aluminum oxide, silicon oxide, tin oxide, or a combination thereof.

10. The method according to claim 9, wherein said sorbent is doped with a dopant at a rate greater than or equal to 5%, more advantageously greater than or equal to 6%, preferably greater than or equal to 8%, more preferably greater than or equal to 10%, more preferably greater than or equal to 12%, and even more preferably greater than or equal to 15%, the percentages are expressed by weight relative to the total weight of the sorbent, said dopant being a metal selected from the group consisting of silver, copper, a noble metal, or a mixture thereof.

11. The method according to any one of claims 1 to 10, further comprising a step 4 in which at least part of the purified liquid phase comprising at least molybdenum-99 ions obtained after step 3 undergoes an acidification step carried out by adding an acid to at least part of the purified liquid phase to form an acidic solution, said acid being selected from the group consisting of acetic acid, acetylsalicylic acid, ascorbic acid, citric acid, hydrochloric acid, sulfuric acid, nitric acid, formic acid, lactic acid, or a mixture thereof.

12. The method according to claim 11, wherein the acid concentration in the acidic solution is between 0.10 and 1.50 mol / l, preferably between 0.5 and 1.25 mol / l, more preferably between 0.75 and 1 mol / l, and even more preferably between 0.90 and 1 mol / l.

13. The method according to any one of claims 11 or 12, further comprising a step 5 in which at least part of the acid solution obtained after step 4 undergoes a purification step by adsorption of at least part of the molybdenum-99 ions, said adsorption being a liquid-solid adsorption method carried out by bringing at least part of the acid solution into contact with at least one sorbent so as to adsorb at least part of the molybdenum-99 ions onto said sorbent.

14. The method according to claim 13, wherein said sorbent is an inorganic compound selected from the group consisting of activated carbon, carbon black, zeolites, a strong anionic resin, a metal oxide, or a combination thereof, said sorbent being contained in an adsorption device, preferably in a chromatographic column.

15. The method according to any one of claims 13 or 14, further comprising, after the liquid-solid adsorption method of step 5, at least one elution using at least one eluent of said at least one part of the molybdenum-99 ions adsorbed on the sorbent to recover an eluate comprising at least a part of the previously adsorbed molybdenum-99 ions, said eluate comprising at least 70%, preferably 80%, more preferably at least 90% of the molybdenum-99 previously adsorbed on the sorbent, the percentages being expressed by weight with respect to the total weight of molybdenum-99 previously adsorbed on the sorbent.

16. The method according to claim 15, wherein the sorbent is a titanium oxide and wherein the eluent is an aqueous solution comprising at least one base [solution E1], said base being sodium hydroxide present in the solution E1 at a concentration of between 0.50 and 5.00 mol / l, preferably between 1.00 and 4.00 mol / l, more preferably between 1.50 and 3.00 mol / l.

17. The method according to claim 15, wherein the sorbent is a strong anionic resin and wherein the eluent is an aqueous solution comprising at least one nitrate [solution E2], said nitrate being ammonium nitrate present in the solution E2 at a concentration between 0.25 and 1.75 mol / l or between 0.5 and 1.5 mol / l, or between 0.75 and 1.25 mol / l.

18. The method according to claim 15, wherein the sorbent is activated carbon and wherein the eluent is an aqueous solution comprising at least one base [solution E3], said base being sodium hydroxide present in the solution E3 at a concentration between 0.05 and 0.75 mol / l or between 0.1 and 0.5 mol / l or between 0.2 and 0.4 mol / l.

19. The method according to any one of claims 15 to 18, wherein step 5 involves the successive use of a first chromatographic column followed by a second chromatographic column followed by a third chromatographic column.

20. The method according to claim 19, wherein the sorbent contained in said first chromatographic column is titanium oxide, the sorbent contained in said second chromatographic column is a strong anionic resin, and the sorbent contained in said third column is activated carbon.

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