EP1321948A1 - Method and device for generating radioisotopes from a target - Google Patents

Abstract

The process comprises preparing a target (3) from a precursor of the radio-isotope (1) and an optional metal support (2). The target is irradiated in an irradiation chamber by a beam of accelerated particles to induce transmutation of the precursor into the radio-isotope. The target is then heated to provoke effusion of the radio-isotope (4) outside the target in the form of a gas, which is collected and condensed into a solid or liquid.

Description

Subject of the invention

The present invention relates to a process and device for the production of radioisotopes from an essentially constituted target of an isotope precursor which is irradiated by a beam of accelerated particles, the radioisotope once produced being separated from its precursor.

A particular application of this The invention relates to the production of palladium 103 from of rhodium 103.

State of the art

Usual production of radioisotopes by bombardment or irradiation of a target essentially consisting of an isotope precursor to using a beam of accelerated particles.

There is a nuclear reaction that fact that a fraction of the isotope precursor present is transformed into a radioisotope. It should be noted that in most cases the radioisotope created is intimately mixed with isotope precursor material constituting the target and therefore remains in said target.

It should also be noted that usually only a few percent of the precursor are transformed into exploitable radioisotopes.

Several types of process have been proposed to separate the radioisotope from its precursor. Mon of them basically consists of a separation chemical according to which the target is completely dissolved by example in a strong acid. We then perform a filtration and possibly electro-dissolution of the radioisotope and finally a precipitation of the latter.

As an example of this chemical separation method, the rhodium-palladium 103 pair can be cited. The target consists of rhodium, as an isotope precursor, deposited on a copper support. This target is subjected to irradiation with a 14 MeV proton beam for 6 days, which induces a 103 Rh → ¹⁰³ Pd reaction and makes it possible to obtain that approximately 1% of the rhodium 103 is transformed into palladium 103. Once once the irradiation is complete, the target is discharged and brought to an armored enclosure called a "hot cell" which is intended to allow the separation of the isotope from its precursor.

In order to separate rhodium from palladium, the separation procedure described above is used. In particular, the target consisting of the copper support and of the rhodium-palladium mixture is dissolved in solid form with a solution of strong acid such as a NH ₃ + H ₂ SO ₄ mixture. This dissolves the copper and keeps the rhodium and palladium in the form of precipitates. It then suffices to carry out a filtration at this time. The separation of palladium from the palladium-rhodium mixture will be obtained by electro-dissolution of the mixture in a hydrochloric acid solution with chlorine flow to improve the yield (Applied Radiat. Isot. 38 (2), pp. 151-157 (1987 )), followed by a separation step carried out for example by complexation of palladium using alpha-furil dioxin (AFD) in order to selectively extract the palladium by the liquid-liquid extraction method (Radiochim. Radioanal. Lett. 48 (1), pp. 15-19 (1981)). A final precipitation ends the process to isolate the palladium 103 from the rhodium 103 and condition it in the desired form.

It is also possible to cause a chemical dissolution of rhodium 103 in order to recover only palladium 103 using a solution of NaAuCl4 (Appl. Radiat. Isot. 48 (3), pp. 327-331 (1997)) and to separate rhodium from palladium using a α-benzoinoxime solution (ABO).

However, we observe first of all, that whatever the separation methods used, the maximum yield ever achieved described in the literature is around 90%.

In addition, the implementation of such techniques is complex and there is generation of effluents which can be dangerous and polluting.

It should also be noted that unfortunately this separation process destroys totally the target, and therefore rhodium, which is a particularly expensive material. Therefore, the target cannot be reused for a future irradiation.

In addition, the acid solutions used for separation will be polluted with radioactive waste and will require decontamination, which increases by significantly the cost of the process.

Finally, to perform the last precipitation, a trainer is required, for example the palladium 102, the use of which reduces activity specific for palladium 103.

Aims of the invention

The present invention aims to provide a process and device for producing radioisotopes which does not have the disadvantages of the state of the technical.

The present invention aims to provide a solution that reduces waste generation radioactive.

The present invention further aims to provide a process in which the target is not destroyed, and can therefore be reused for a new production of radioisotope.

The present invention further aims to provide a radioisotope with activity specific high.

Main characteristic features of the invention

• préparation d'une cible comportant le précurseur du radio-isotope, éventuellement lié à un support métallique,
• irradiation, au sein d'une chambre d'irradiation, de ladite cible par un faisceau de particules accélérées, en vue d'induire la transmutation du précurseur en le radio-isotope,
• chauffage de ladite cible en vue de provoquer l'effusion du radio-isotope hors de la cible,
• collecte dudit radio-isotope extrait sous forme gazeuse et condensation dudit radio-isotope sous forme solide ou liquide.

The present invention relates to a method for producing a radioisotope of interest from a target comprising a precursor of said radioisotope, using a beam of accelerated particles, said method comprising the steps following:

• preparation of a target comprising the precursor of the radioisotope, optionally linked to a metal support,
• irradiation, within an irradiation chamber, of said target with a beam of accelerated particles, with a view to inducing the transmutation of the precursor into the radioisotope,
• heating said target in order to cause the radioisotope to effuse out of the target,
• collecting said extracted radioisotope in gaseous form and condensing said radioisotope in solid or liquid form.

Note that in the following description, the expressions "radioisotope" and "radioisotope" of interest "will be used interchangeably to designate the radioisotope that we are trying to produce, while the "precursor" will mean, as its name suggests, the element from which it is sought to obtain said radioisotope interest.

In the method according to the invention, the radioisotope of interest is usually obtained by irradiation at using a proton beam from a solid target containing the precursor, the radioisotope of interest being produced within said target, also preferably in solid form.

The separation of the radioisotope of interest and of the precursor will therefore be to subject the solid target to heat treatment to obtain a reaction effusion, i.e. thermal separation of the radioisotope of interest.

For this purpose, they must be couples precursor / radioisotope of interest which exhibit relatively melting and boiling temperatures different from each other, so that the effusion treatment allows diffusion of the radioisotope within the target itself, its extraction or exhaust by evaporation and sublimation, while the target precursor remains present within said preferably in solid form.

The heat treatment used to getting this shedding can be any treatment operating by Joule effect.

For example, the energy intended for heat treatment can come from irradiation with a beam of charged particles such as electrons, by the beam used for the nuclear reaction, by infrared radiation, by laser treatment, by plasma treatment or any other heat treatment adequate.

For example, vacuum heating or under controlled inert atmosphere will provide quickly the desired bestowal effect.

According to a first embodiment of the present invention, the heat treatment will occur at within an effusion chamber separate from the chamber irradiation in order to obtain said effusion.

According to a still preferred embodiment, the collection and condensation stage can be carried out also within said effusion enclosure.

For this purpose, and particularly advantageous, this effusion chamber will be provided with means for collecting and condensing said radioisotope extract.

Collection and condensation means can consist of a collection substrate such a ceramic, metallic or polymeric support, cold or cooled. Preferably, this substrate will have low adhesion characteristics.

According to this embodiment, a step additional separation of the extracted radioisotope, collected and condensed on the collection substrate should be produce. Eventually, this separation step could be carried out within a separation enclosure separate from the effusion chamber. Advantageously, this separation enclosure includes an acid solution bath in which we can dip the collection substrate in view of obtaining a separation of the radioisotope from said collection substrate. Then it will be necessary to filter and separate said radioisotope for the purpose of condition in the desired form.

According to another embodiment, the heat treatment can be done directly within of the irradiation chamber, for example directly by irradiation by the charged particle beam which has allowed to transmute the radioisotope.

• des moyens d'irradiation d'une cible comportant un précurseur d'isotope en vue d'induire une transmutation du précurseur en le radio-isotope,
• des moyens de chauffage en vue de provoquer l'effusion du radio-isotope au sein de ladite cible,
• des moyens de collecte et de condensation du radio-isotope extrait.

Another object of the invention relates to a device for implementing the process for producing a radioisotope, said device comprising the following means:

• means for irradiating a target comprising an isotope precursor in order to induce a transmutation of the precursor into the radioisotope,
• heating means with a view to causing the radioisotope to shed within said target,
• means for collecting and condensing the extracted radioisotope.

Preferably, the means of collecting and condensation of the extracted radioisotope consist of a cold collection substrate.

Preferably, the collection substrate has an interlayer with low adhesion characteristics with the radioisotope.

Preferably, the device according to the invention further comprises means for separation of the radioisotope from said substrate collection.

Advantageously, the means of decoupling consist of an enclosure of separation comprising an acid solution bath in which is arranged the collection substrate with the radioisotope.

The present invention also relates in particular to the use of said method and of said device for the production of palladium 103 from rhodium 103. In other words, it relates to the reaction ¹⁰³ Rh ( p, n ) ¹⁰³ Pd by irradiation of a proton beam.

Other examples of pairs of metals can of course be envisaged for the implementation of the method (the couples ¹¹¹ In / ¹¹¹ Cd, ¹⁹⁷ Hg / ¹⁹⁷ Au, ⁹⁵ Tc / ⁹⁵ Mo, ...).

Brief description of the figures

Figures 1a and 1b describe so schematic the various stages of the preparation process of the radioisotope according to a first and a second form of the present invention, respectively.

Figures 2a and 2b respectively describe effusion and separation chambers used for implementation of the methods according to the present invention.

Figure 3 describes a second form of execution in which the irradiation steps and effusion can be performed directly on-line at within the irradiation chamber.

Figures 4a and 4b describe so schematic a particle accelerator which can be used for the implementation of the method. Figure 4a corresponds to a perspective view of this device, while Figure 4b corresponds to a top view.

Description of several preferred embodiments of the invention

FIG. 1a schematically describes the various stages of a first embodiment of the method for producing a radioisotope according to the present invention. Reference is made to the preparation of the radioisotope ¹⁰³ Pd, referenced 4, from a target 3 comprising rhodium ¹⁰³ Rh, isotope precursor, referenced 1, by irradiation with a beam of protons.

Initially, it is first of all a question of target 3 comprising precursor 1 of the radioisotope 4 (step A-target preparation). To do this, we deposits Rh on a metal plate 2 which is in this case a copper plate. This is done usually by electrolysis, so as to obtain a depositing a thickness such as the proton beam used during irradiation (e.g. a beam of 14 MeV protons) loses at least three quarters of its energy within the target. However, other techniques deposits such as evaporation, deposition techniques by plasma (direct current (DC), radio frequency or microwave) vacuum or atmospheric plasma (plasma spraying) can be used.

In the case of a target 3 tilted at 10 ° by relative to the beam direction, a thickness of 50 µm enough for 14 MeV protons.

Once the target 3 has been made, it is loaded into a cyclotron and subjected to a proton beam with an energy of 14 MeV for 6 days (step B-irradiation). The transmutation of ¹⁰³ Rh into ¹⁰³ Pd takes place at the rate of 0.225 mCi / mAH. At the end of 144 hours, a production of 28.8 Ci will be obtained for a continuous current of 1 mA, and taking into account the decrease.

It should be noted that the amount of ¹⁰³ Pd (radioisotope 4) harvested corresponds to less than 1% of the initial amount of ¹⁰³ Rh (precursor 1) present on target 3.

In this first embodiment of the invention, the temperature of the target 3 at any time below temperature effusion of palladium within rhodium. If it weren't not so, the palladium would exit the target, and would condense on the surrounding walls.

The irradiated target 3 is then discharged and transferred (step C-extraction and transfer) to a effusion chamber 17 as shown in FIG. 2a. This effusion enclosure is a shielded enclosure in which is carried out the bestowal (step D).

The bestowal of a constituent out of an alloy (apart from this alloy) is based on the phenomena following physical. The most volatile constituent (here the palladium) goes into the gas phase from the surface, which results in a difference in concentration volatile constituent between the surface and the interior of the target. A flow of volatile constituent, from inside the target, towards the surface, then takes birth. Evaporation of the volatile component continues, and reduces the concentration of volatile constituent within the target. Finally, the vapor of the volatile constituent is condensed and collected on a cold surface.

Note that it is necessary that the volatile constituent has a melting temperature lower than that of the other constituents of the alloy, or a higher partial spray pressure for a given temperature. Palladium and rhodium have melting temperatures of 1554.9 ° C and 1964 ° C.

Within the effusion chamber 17, we heats target 3 for example by heating electric, by Joule effect or by induction, of a beam electrons, infrared, laser, or DC plasma or radio frequency or microwave.

The next step is then to collect and condense the palladium 4 extracted from the target 3 on a collection support 5 (step E) to then separate and collect it (step F), for example in the form of PdCl ₂ .

Figure 2a describes an effusion chamber 17 used according to the first embodiment of the method of the invention. It is of course a shielded enclosure in which the irradiated target 3 is transferred (step C of figure 1a) and which makes it possible to carry out the steps effusion (step D) of the radioisotope 4 out of the target 3 but also of capture and condensation (step E) of said radioisotope 4 extract.

This target 3 is preferably heated under vacuum or under controlled atmosphere using means of heat treatment 18 in order to cause the diffusion of the palladium 4 within target 3 to its surface and its evaporation / sublimation out of it. A temperature between 800 ° C and 1750 ° C suitable for causing the effusion of palladium 4 out of the rhodium matrix (target 3).

Advantageously, the processing means thermal 18 are in the form of a simple electrical resistance. They must act in a minimum of time and should be very simple to regulate. In addition, they must allow target 3 to be preserved and saved integrity to allow its later use for future irradiations.

Vacuuming and maintaining vacuum of the effusion chamber 17 are provided by a vacuum pump 19.

Palladium 4 present in the the effusion chamber 17 in gaseous form is captured and condensed (step E of FIG. 1a) on a support 5 of collection. The collection support 5 is cold or cooled, to a temperature below the temperature of condensation of palladium 4. Palladium 4 is collected in solid or liquid form.

Said substrate 5 is arranged close to the target under a protective bell 20.

Particularly advantageously, the collection substrate 5 is a cold ceramic support or metal and it has poor adhesion. he can for example present a non-adherent interlayer (not shown). By way of example, soluble polymers or fats can be used to achieve this interlayer.

At the end of the bestowal operation and collection (steps D and E), target 3 still contains practically the initial amount of rhodium, and it has not affected mechanically or chemically. She can therefore advantageously be reinstalled in the room of irradiation, for a new production campaign of palladium (step G).

Then, the collection substrate 5 is transferred using one transfer system to another enclosure called separation enclosure 21 in which the separation step (step F of FIG. 1a) of the radioisotope 4 and collection substrate 5 is performed. FIG. 2b describes such an enclosure of separation 21 towards which the collection substrate is bring.

Advantageously, this separation enclosure 21 comprises a bath 22 of a solution so as to release the ¹⁰³ Pd (radioisotope 4) in said solution. This separation can be obtained by chemical means, such as dissolving the interlayer and / or palladium, and / or mechanical means such as stirring.

Then, this solution is treated so as to isolate the ¹⁰³ Pd (radioisotope 4) (step F of FIG. 1a) which is packaged in small vials using dose dispensers (“doses dispenser”). The activity of each vial is measured for control, and the product can then be used as a radiochemical.

It should be noted that the different elements of effusion chambers 17 and separation chambers 21 must be such that they can be easily decontaminated, can be integrated into a shielded "hot-cell" enclosure, equipped with an adequate target 3 transfer system, the irradiation chamber 10 towards the effusion chamber 17, and collection substrate 5 of the effusion chamber 17 to the separation enclosure 21 and are easy maintenance.

The target 3 and collection substrate 5 should be itself easily removable, for example for verification, and easily decontaminable. It must also be secure.

The effusion chamber 17 and separation chamber 21 can be combined into a single enclosure.

Figure 1b schematically describes the various stages of a second embodiment of the process for producing a radioisotope according to the present invention in which the bestowal step is carried out on-line, i.e. directly within the room irradiation.

The constitution of the target (step A) is done in the same way as in the first form of production. As shown in Figure 3, a substrate of collection 5 is installed in the irradiation chamber. he therefore it is not necessary to extract the target 3 for proceed to effusion-collection. This device allows simultaneously perform irradiation and effusion-collection (steps B, D and E simultaneously). energy necessary to heat the target is brought in all or partly by the beam of accelerated particles. AT after irradiation, the collection substrate 5 is extract from the irradiation chamber 10. The separation of palladium deposited (step F) is then carried out in the same way way as in the first embodiment. Target 3 can remain within the irradiation chamber 10.

Figure 3 therefore describes a device suitable for the implementation of the second form of carrying out the method of the invention. In the bedroom irradiation 10 are installed target 3 as well as the collection substrate 5. A set of vacuum pumps allows you to gradually reach the vacuum level important required within the accelerator.

Figures 4a and 4b describe so schematic a particle accelerator which can be used for the implementation of the method. More precisely, Figure 24a is a perspective view of this accelerator, while Figure 4b is a top view of this same device.

• une source capable de générer un faisceau de particules,
• l'accélérateur 6 lui-même,
• un circuit 9 d'acheminement du faisceau,
• un aimant de déviation 11 qui permet de diriger le faisceau de particules soit vers un système de pompage 12 destiné à contrôler la qualité des paramètres du faisceau, soit vers une enceinte blindée 10 constituant la chambre d'irradiation placée en bout de ligne.

As illustrated in these figures, the particle accelerator 7 comprises:

• a source capable of generating a particle beam,
• the accelerator 6 itself,
• a beam routing circuit 9,
• a deflection magnet 11 which makes it possible to direct the particle beam either to a pumping system 12 intended to control the quality of the parameters of the beam, or to a shielded enclosure 10 constituting the irradiation chamber placed at the end of the line.

Between the accelerator 6 and the magnet deviation 11, the device 7 further comprises a series auxiliary magnets which correspond to quadrupoles 13 and to sextupoles 14 and which have the function to focus the beam.

Note also that just outside of there are collimators 15 on the accelerator 6.

Furthermore, a scanning magnet 16 allows, as its name suggests, to sweep target 3 using the radiation beam.

Conventionally, we have target 3 obtained in chamber 10 at the end of the beam line of the accelerator 6 of charged particles. So advantageous, the accelerator 6 can be constituted by a cyclotron which generates a proton beam exhibiting some discrepancy and which is corrected by the presence of collimators 15.

The main purpose of these collimators 15 is to prevent part of the beam (20%) from hitting elements of the beam line and damaging them. Advantageously, these collimators 15 can be removable and themselves coated with a layer of rhodium, so as to take advantage of the beam loss to directly produce ¹⁰³ Pd (radioisotope 4).

For this purpose, the collimators 15 must ability to meet the following requirements: ease of assembly / disassembly and placement in the line, very good cooling of the irradiated surface, ease of transfer to a lead container, easy disassembly in a "hot cell", mass of copper substrate minimal, surface to be covered with minimal rhodium, reuse for each irradiation of a maximum of components.

Target 3 can also be installed directly inside the particle accelerator 6.

Both in the first and in the second embodiment of the invention, target 3 and the collection substrate 5 can be used multiple successively. We thus have a process economical in rhodium, and producing little waste.

The invention should not be considered as limited to the preferred embodiments described above. In particular, the target can be made up entirely in the isotope precursor, or in an alloy comprising this isotope precursor.

Claims (15)

Method for producing a radioisotope (4) from a target (3) comprising a precursor (1) of said radioisotope (4), using a beam of accelerated particles, said method comprising the following steps: preparation of a target (3) comprising the precursor (1) of the radioisotope (4), said precursor being optionally linked to a metal support (2), irradiation, within an irradiation chamber (10), of said target (3) with a beam of accelerated particles, with a view to inducing the transmutation of the precursor (1) into the radioisotope (4), heating said target (3) in order to cause the radioisotope (4) to effuse out of the target (3), collecting said radioisotope (4) extracted in gaseous form and condensing said radioisotope (4) in solid or liquid form. Method according to claim 1, characterized in that the condensation of the radioisotope (4) in liquid or solid form is carried out by contact of the radioisotope (4) in gaseous form with suitable solid means, the radioisotope (4 ) being in a subsequent step separated from said medium. Method according to claim 2, characterized in that it further comprises a step of conditioning said radioisotope (4) produced in a suitable liquid or solid form. Method according to one of claims 1 to 3, characterized in that the heating is obtained by the Joule effect, a treatment with a beam of charged particles such as electrons, by infrared radiation, by a laser treatment, by a plasma treatment . Method according to claim 4, characterized in that the heating is carried out under vacuum or under a controlled inert atmosphere. Method according to any one of the preceding claims, characterized in that the heating is carried out within a shielded effusion chamber (17) situated outside the irradiation chamber (10). A method according to claim 6, characterized in that the collecting and condensing step takes place within said effusion chamber (17). Method according to any one of Claims 1 to 5, characterized in that the steps of irradiation, heating and collection and condensation of the extracted radioisotope are carried out on-line within the irradiation chamber (10 ). Method according to any one of the preceding claims, characterized in that at the end of the heating step, the target (3) is reused for a new irradiation step. Device for implementing the method for producing a radioisotope (4) according to any one of the preceding claims, said device comprising the following means: means for irradiating (6,7,8,9,10) a target (3) comprising an isotope precursor (1) in order to induce a transmutation of the precursor (1) into the radioisotope ( 4), heating means with a view to causing the radioisotope (4) to effuse within said target, means for collecting and condensing the extracted radioisotope. Device according to claim 10, characterized in that the means for collecting and condensing the extracted radioisotope consist of a cold collection substrate (5). Device according to claim 11, characterized in that the collection substrate (5) has an interlayer having low adhesion characteristics with the radioisotope (4). Device according to claim 12, characterized in that it further comprises means for separating the radioisotope from said collection substrate. Device according to Claim 15, characterized in that the separation means consist of a separation enclosure (21) comprising a bath (22) of acid solution in which the collection substrate (5) is disposed with the radioisotope ( 4). Use of the method according to one of the claims 1 to 9 or of the device according to one of claims 10 to 14 for the production of palladium 103 from rhodium 103.

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