RU2578039C1 - Method of producing nanostructured target for production of molybdenum-99 radioisotope - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to reactor technology of producing molybdenum-99 radioisotope (⁹⁹Mo), which serves a base for creation of radioisotope technetium-99m generators (^99mTc). This method includes production of molybdenum-99 radioisotope at reaction ⁹⁸Mo(n,γ)⁹⁹Mo, carried out in a stream of slow neutron nuclear reactor and is carried out using a matrix-buffer of mesoporous inorganic materials, which channels are supplied with molybdenum compounds. Production of target is carried out by impregnation of activated carbon with specific surface area more than 300 m²/g of ammonium paramolybdate solution (NH₄)₆Mo₇O₂₄ and subsequent heat treatment, as a result, on the surface of the channels nano-layers MoO₃ are formed. Fraction of recoil atoms ⁹⁹Mo, leaving layers MoO₃ and localized in the buffer depends on thickness of applied layers. Average thickness of nanolayers MoO₃ applied in series into channels is set by number of applications and is limited by the effective diameter of channels. After irradiation the separation of core recoil containing activated carbon and starter nanoparticles MoO₃ is achieved by elution of more than 97% MoO₃ from the target 20% solution of water ammonia. Following the process of extracting cores recoil of a matrix is implemented by gasification of coal component of the matrix by combustion.

EFFECT: technical result provides simple method of making the target, higher efficiency of producing ⁹⁹Mo due to creation of nano-layers over the entire volume of the matrix, which enables to achieve high homogeneity of “nanolayer-Mo - buffer”, providing efficient use of the starting material and increases efficiency of collecting recoil atoms, obtaining a uniform distribution of molybdenum in the volume of activated carbon during precipitation of molybdenum coating on surface of its mesopores.

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Description

Technical field

The invention relates to a reactor technology for producing radioisotopes.

The present invention can be used to produce the molybdenum-99 ( ⁹⁹ Mo) radioisotope, which is the basis for the creation of technetium-99m ( ^99m Tc) radioisotope generators, which are widely used in nuclear medicine for diagnostic purposes.

State of the art

⁹⁹ Mo is one of the most popular radioisotopes in nuclear medicine [Kodina G.E. "Methods for producing radiopharmaceuticals and radionuclide generators for medicine." In the book. ISOTOPES. Properties Receiving. Application. Ed. V.Yu. Baranova. M. Fizmatlit. Volume 2. 2005. S. 389-412]. It is used in ⁹⁹ Mo / ^99m Tc generators for visual monitoring and early diagnosis of cancer, cardiovascular and other diseases. ^99m Tc is formed during the decay of the maternal radioisotope ⁹⁹ Mo.

The widespread use of the ^99m Tc radioisotope is explained by the combination of its nuclear properties, which determines its advantage over many short-lived radioisotopes. Technetium-99m has gamma radiation energy (140 keV) convenient for recording, a short half-life. It lacks beta and hard gamma radiation, which reduces the dose burden on patients and personnel of isotope laboratories. This radioisotope is approved for use in diagnostic studies of pregnant women and newborns. Up to 80% of diagnostic procedures in the world are performed using ^99m Tc. Technetium-99m is one of the isotopes with the least radiotoxicity.

Major global manufacturers generate ⁹⁹ Mo using a uranium target. More than 95% of the ⁹⁹ Mo radioisotope is produced using highly enriched uranium with an isotope content of ²³⁵ U≈90%. A uranium target consists of solid uranium compounds in the form of oxides or a uranium-aluminum alloy. Irradiation occurs in the experimental channel of the reactor with individual forced cooling. After irradiation of the target with reactor neutrons, ⁹⁹ Mo is radiochemically separated from the mixture of fission fragments in a hot chamber.

A known reactor method for producing a radioisotope of ⁹⁹ Mo, based on the fission reaction of uranium-235 ( ²³⁵ U) by the action of neutrons [Gerasimov AS, Kiselev GI, Lantsov ML "Getting ⁹⁹ Mo in nuclear reactors." Atomic Energy. Volume 67, Issue 1, August 1989, 104-108]. In this process, a target containing uranium dioxide enriched in the ²³⁵ U isotope to 90% is irradiated for 7-10 days in the neutron flux of a nuclear reactor, and then processed using one of the traditional radiochemical methods. The ⁹⁹ Mo radioisotope isolated from fission products by extraction and chromatography has a high specific activity (≈10 ⁵ Ci / g), which is important in the manufacture of ⁹⁹ Mo / ^99m Tc generators.

In the uranium fission reaction, ⁹⁹ Mo is produced in high yield (6%). However, a whole group of other fission products is formed with it. The total activity of the waste generated during the fission of the uranium core significantly exceeds the activity of the target radioisotope ⁹⁹ Mo [Markina MA, Starizny ES, Breger A.Kh. "The energy distribution of gamma radiation of ²³⁵ U fission products with a short exposure time." Atomic Energy, 1979, Volume 46, Issue 6, 411]. Therefore, the main disadvantage of this method of obtaining ⁹⁹ Mo is the need for processing of radioactive materials, since it is necessary to isolate and purify ⁹⁹ Mo from other fission products. Working with fission products requires expensive equipment and special facilities. The “fragmentation” method necessitates solving the issue of transportation and burial of a large number of fission products. In addition, another limiting factor for the further expansion of this method of production of ⁹⁹ Mo is the need to limit or even reduce to zero the circulation of highly enriched uranium in the civilian sphere, since the proliferation of highly enriched uranium carries the danger of a terrorist threat. Programs have been adopted, in particular, the RERTR (Reduced Enrichment for Research and Test Reactors) program to reduce the turnover of highly enriched uranium in peaceful sectors of the economy, according to which the research reactors used to produce ⁹⁹ Mo will be gradually transferred to low enriched uranium fuel and targets from low enriched uranium.

For this reason, the orientation of modern ⁹⁹ Mo production to the use of highly enriched uranium against the background of the gradual removal of this material from civilian traffic in accordance with the IAEA's “non-proliferation” concept creates additional risks for ⁹⁹ Mo consumers.

There is an alternative method for producing ⁹⁹ Mo by the reaction of ⁹⁸ Mo (n, γ) ⁹⁹ Mo — activation. When a target containing molybdenum enriched in the ⁹⁸ Mo isotope is irradiated with neutrons in a nuclear reactor, with a mean thermal neutron flux of 1 · 10 ¹⁴ cm ^-2 × s ^-1 , specific activity of ⁹⁹ Mo can reach 6-8 Ci / g [Skuridin BC, Stasyuk E.S., Nesterov E.A., Larionova L.A. Development of highly active technetium-99m generators based on enriched molybdenum-98 // Medical Physics, No. 4, 2010, 41-47]. The activation method for producing ⁹⁹ Mo has several advantages over the “fragmentation” method: low cost of feedstock, exclusion of fissile materials from the technological process, the absence of long-lived radioactive waste, a significant reduction in capital costs due to lower requirements for radiation safety conditions.

The main disadvantage of the activation method for the production of ⁹⁹ Mo, which impedes its widespread adoption, is the low specific activity of the target radionuclide due to the presence of ⁹⁸ Mo in the target isotope carrier. Such material is inefficient to use in a standard ⁹⁹ Mo / ^99m Tc sorption-type generator, since larger columns are required, as a result of which the mass of radiation protection will increase. To elute ^99m Tc from such a column, a large flow rate is required, which will lead to a decrease in the volumetric activity of the solution and the need for a subsequent concentration of ^99m Tc.

To eliminate this problem, a variant was proposed for producing ⁹⁹ Mo from the radiation capture reaction ⁹⁸ Mo (n, γ), based on the Szillard-Chalmers effect, using structured molybdenum nanoparticles or its compounds as targets.

It is known that the ⁹⁹ Mo nucleus, formed as a result of the radiation capture of thermal neutrons ⁹⁸ Mo (n, γ), at the moment of excitation removal by emission of γ-quanta acquires a recoil momentum, which is sufficient to break the chemical bonds of atoms in the lattice. A recoil energy of ~ 30–100 eV causes a displacement of the formed ⁹⁹ Mo atoms, which are capable of forming new compounds, moving from one phase to another, etc. The fraction of ⁹⁹ Mo recoil atoms leaving the parent compound of molybdenum depends on the ratio of the path lengths and the size of the target.

Separate work in this direction was carried out in Russia and abroad [Tomar, B.S .; Steinebach, O.M .; Terpstra, B.E .; Bode, P .; Wolterbeek, N.T .: Studies on production of high specific activity ⁹⁹ Mo and ⁹⁰ Y by Szilard Chalmers reaction: Radiochim. Acta. 2010, 98, 499-506]. In the European patent [Wolterbeek HT "A process for the production of no-carrier added ⁹⁹ Mo". European patent. EP 2131369 A1. 06/06/2008. Technische Universiteit Delft (NL)] describes the process of producing ⁹⁹ Mo by irradiating organic compounds of molybdenum hexacarbonyl Mo (CO) ₆ and dioxo dioxinate [C ₄ H ₃ (O) -NC ₅ H ₃ ] ₂ -MoO ₂ CH ₂ Cl ₂ s subsequent extraction of ⁹⁹ Mo from the organic phase of the solutions into the aqueous. The resulting yield was from 10% (with an enrichment factor of 40) to 20% (with an enrichment factor of 20).

Russian authors have proposed using molybdenum compounds in the form of particles with a size of 5 ÷ 100 nanometers (nm) as starting material [RF Patent RU 2426184 C1. 07/02/2010. "A method of producing a radionuclide of ⁹⁹ Mo." Maslakov G.I., Radchenko V.M., Rotmanov K.V. and etc.]. They irradiated refractory radiation and thermally stable Mo ₂ C nanoparticles with neutrons with a flux density of more than 10 ¹⁴ cm ^-2 s ^-1 for 7-15 days. According to the authors, as a result of the Szillard-Chalmers effect during irradiation, the concentration of ⁹⁹ Mo should increase on the surface of nanoparticles, because the surface is a barrier on which radionuclides emitted from the lattice will accumulate. After irradiation, the authors performed the isolation of ⁹⁹ Mo from the surface layer of the starting material by dissolving this layer in a mixture of acids or a mixture of alkalis. However, a large variation in the sizes of nanoparticles of the starting material (5–100 nm) led to a low efficiency of the process. Particles less than 5 nm were washed out of the powder into the solution, and from particles with a size of ~ 100 nm, the recoil nuclei entered the surface layer only from a shallow depth, which led to low yield of the product. When etching the surface layer of molybdenum particles with acid or alkali, mainly the starting material of the particles, ⁹⁸ Mo, got into the solution. The obtained yield of ⁹⁹ Mo was 30.2–37.4%, with an enrichment factor of 1.6–1.5. The main disadvantage of this method of production of ⁹⁹ Mo is the low specific activity of the resulting radioisotope. The authors cite the specific activity 99Mo obtained by this method at the level of 1 Ci / g, which is inferior to the specific activity of the fragmentation ⁹⁹ Mo about five orders of magnitude (≈10 ⁵ Ci / g). With a specific activity of ⁹⁹ Mo at the level of 1 Ci / g, it is impossible to use a standard ⁹⁹ Mo / ^99m Tc sorption-type generator, since large columns will be required and, accordingly, the size of the generator will also become unacceptably large, as a result of which the weight and size characteristics of radiation protection will increase. In addition, elution of ^99m Tc from such a column will require a large flow of liquid, which will lead to a decrease in the volumetric activity of the solution and the need for a subsequent concentration of ^99m Tc.

For the prototype, a method was chosen for producing a nanostructured target for the production of a ⁹⁹ Mo radioisotope by the radiation capture reaction ⁹⁸ Mo (n, γ) ⁹⁹ Mo in the form of a buffer and nanoparticles of molybdenum or its compounds [RF Patent RU 2490737 C1. 03/29/2012. "A method of producing a molybdenum-99 radioisotope." Chuvilin D.Yu., Zagryadsky V.A., Menshikov L.I., Kravets Y.M., Artyukhov A.A., Ryzhkov A.V.].

In this patent, the target is a structured material consisting of molybdenum nanoparticles or its compounds, surrounded by a buffer in the form of a solid soluble in water or other solvents, with d being the characteristic size of the nanoparticles being chosen from the condition λ / d >> 1, where λ is the mean free path of ⁹⁹ Mo recoil atoms in a substance.

The use of buffered compounds creates the potential for the separation of ⁹⁹ Mo from the parent material. The high specific surface and the small size of the nanoparticles are designed to provide a high yield of recoil atoms in the buffer, a material of an inert medium receiving ⁹⁹ Mo nuclei. According to estimates, the mean free path of recoil atoms in the molybdenum target material is ~ 10 nm [L.I. Menshikov A.N. Semenov, D.Yu. Chuvilin “Calculation of the yield of atoms of the reaction of ⁹⁸ Mo (n, γ) ⁹⁹ Mo from nanoparticles of molybdenum (IV) disulfide.” Atomic Energy. T. 114, no. 4, 2013, 226-229].

After irradiation of the target, the nanoparticles and the buffer are separated by one of the known methods, after which the buffer is sent for radiochemical processing to isolate the ⁹⁹ Mo radioisotope, and the nanoparticles are returned to the reactor core as part of a new target. As the material of the nanoparticles, metal molybdenum of natural isotopic composition or enriched in the ⁹⁸ Mo isotope is used, as well as molybdenum compounds MoS ₂ , MoS ₃ or MoO ₃ . The characteristic size of the nanoparticles should be ≤10 nm. As the material of the buffer, sodium chloride NaCl is used, and the separation of the buffer and nanoparticles is carried out in water. The target is irradiated in the core of a research or nuclear power reactor with a thermal neutron flux density of 10 ¹⁴ cm ^-2 s ^-1 for 7 ÷ 10 days.

The main problem of this method is the complexity of its implementation. The synthesis of nanoparticles with given parameters is a non-trivial task, since nanoparticles have excess surface energy leading to coalescence and coarsening. Existing methods for producing monodispersed 5–10 nm nanoparticles of Mo compounds stabilized by organic ligands cannot be used for the manufacture of targets, since such structures do not have sufficient radiation resistance.

Disclosure of invention

The advantages of using a buffer can be fully manifested only when creating a target containing a uniform set of nanoparticles uniformly distributed in a suitable buffer. Isolated inorganic nanostructures can be created in the pores of solid porous matrices that are resistant to radiation. The most promising for use as such a matrix buffer are sorbents.

The technical result is to simplify the method of manufacturing the target, to increase the productivity of the ⁹⁹ Mo process by creating nanolayers throughout the matrix, which allows achieving high homogeneity of the composition of the “Mo-buffer”, ensuring the efficient use of the starting material and increasing the efficiency of the collection of recoil atoms. Simplification of the technology for manufacturing the target is achieved by eliminating the preliminary steps — the synthesis of nanoparticles and the mechanical homogenization of the nanoparticles and the buffer. The proposed method provides the ability to form the required thickness of the nanolayers of molybdenum compounds in the channels of the matrix by simply varying the number of impregnation procedures, which was unattainable in the prototype. The quality of the target is enhanced by controlling the thickness of the nanolayers and introducing higher concentrations of the parent material into the target. All this will increase the productivity of the process of running ⁹⁹ Mo by the reaction of radiation capture ⁹⁸ Mo (n, γ) in comparison with the prototype.

To achieve this result, a method for manufacturing a nanostructured target for the production of a ⁹⁹ Mo radioisotope by the radiation capture reaction of ⁹⁸ Mo (n, γ) in the form of a buffer of solids and nanoparticles containing molybdenum with a characteristic nanoparticle size d, λ / d >> 1, where λ - length of the return path ⁹⁹ atoms in the material Mo nanoparticles, wherein the buffer is configured in a matrix of a mesoporous inorganic material with cavities and channels with a characteristic size in the range of 2-50 nm, and the surface of the n cavities and channels are nanolayer molybdenum oxide MoO _3, the thickness of which is less than the mean free path of the recoil atom ⁹⁹ of Mo in the material nanolayer, and used as a template granular activated carbon with a specific surface of more than 300 m ² / g, previously calcined at 700 ÷ 750 ° C.

Besides:

- form a nanolayer of molybdenum oxide MoO ₃ by impregnating the cavities and channels of the matrix with a solution of ammonium paramolybdate (NH ₄ ) ₆ Mo ₇ O ₂₄ followed by heat treatment of the target to decompose the paramolybdate;

- use ammonium paramolybdate obtained by conversion from a precursor - molybdenum hexafluoride enriched in the ⁹⁸ Mo isotope.

In nanotechnology, mesoporous materials are used as matrices (nanoreactors) for the synthesis of nanoscale isolated particles, nanorods, etc. Rigid matrices with fixed cavities and channels are used to create and stabilize nanoparticles [S.P. Gubin, Yu.A. Koksharov, G.B. Khomutov, G.Yu. Yurkov. "Magnetic nanoparticles: production methods, structure and properties." Advances in Chemistry, 74, (6). 2005, 539-574]. The structure of activated carbon obtained on the basis of coal is characterized by a large proportion of mesopores with a diameter in the range of 2-50 nm [GOST 6217-74]. Such coals, for example, grade AG-3, are made in the form of granules from coal dust [GOST 20464-75]. Thus, the activated carbon matrix provides the formation of a nanolayer of the parent MoO ₃ and at the same time serves as an acceptor of ⁹⁹ Mo recoil atoms. Such a matrix has an average characteristic channel size of ≈20 nm. The thickness of sequentially applied in the cavity of the layers of MoO _{3 is} limited to this value. A similar method for creating an ordered ensemble of molybdenum nanoparticles in targets has not yet been used in nuclear reactions using the Szillard-Chalmers method.

The chemical properties of the buffer – molybdenum compound pair were considered as another factor on which the possibility of efficiently extracting ⁹⁹ Mo recoil atoms after irradiation depends. These compounds can be separated using aqueous ammonia, which according to [R.A. Lidin, V.A. Milk, L.L. Andreeva. "Chemical properties of inorganic substances." Ed. Lidina. M. Chemistry. 2000. 480] readily dissolves MoO ₃ . The possibility, after irradiation, to separate the initial ⁹⁸ MoO ₃ and the carbon matrix buffer, in which the ⁹⁹ Mo recoil nuclei are localized, was demonstrated during elution of the parent MoO ₃ . The subsequent process of extracting ⁹⁹ Mo recoil nuclei from the matrix can be realized by gasification of the coal component of the matrix by burning.

Granules of activated carbon with a high specific surface are penetrated by a branched network of open nanoscale capillaries. It is important that a self-organized array of pores formed during the manufacturing of this sorbent is characterized by a uniform density. This makes it possible to obtain a uniform distribution of molybdenum over the volume of activated carbon during the deposition of molybdenum coatings on the surface of its mesopores.

The preparation of the targets was carried out by impregnation of activated carbon granules with a solution of molybdenum compounds and subsequent removal of the solvent. The advantage of this method is that it allows you to get molybdenum layers of different thicknesses by varying the number of applications and the concentration of the impregnating solution.

Activated carbon is suitable for reactor experiments because of its high radiation resistance and low thermal neutron capture cross section - σ _n , _γ (C) = 3 · 10 ^-3 barn. As for MoO ₃ , in addition to its radiation resistance, the sufficient simplicity of the technological problem of obtaining ⁹⁸ MoO ₃ from molybdenum hexafluoride (MoF ₆ ) was taken into account. This problem arose due to the fact that natural molybdenum contains only 24.13% ⁹⁸ Mo, which is necessary for the production of ⁹⁹ Mo. Since in industry the enrichment of molybdenum by the ⁹⁸ Mo isotope is carried out on centrifugal separation cascades using molybdenum hexafluoride MoF ₆ , it is precisely ⁹⁸ MoF _{6 that} should be used as an isotope-enriched precursor to obtain ⁹⁸ MoO ₃ .

In addition to MoO ₃ , other molybdenum compounds, for example MoS ₂ , Mo ₂ C, can be used as the target irradiated substance. However, the use of these compounds by the proposed impregnation method is ineffective due to their extremely low solubility. MoS ₂ , Mo ₂ C can be used in the form of nanoparticles, but for this it is first necessary to separately manufacture such nanoparticles (which is not an easy independent task). The difficulties in this way are that the nanoparticle powder can have a wide size distribution. In addition, when mixing the powder with a buffer in such a mechanical mixture, inhomogeneities, aggregation of nanoparticles, changes in their size, etc. are possible.

Target manufacturing example

Step 1. Preparation of activated carbon granules. Commodity granular activated carbon was calcined at a temperature of 700 ÷ 750 ° C for 3 hours to remove sorbed substances.

Operation 2. Hydrolysis of MoF ₆ . At a temperature of liquid nitrogen, a certain amount of molybdenum hexafluoride was condensed from a container with MoF ₆ into a chemical reactor lined with Teflon. The reactor was evacuated, weighed, and a ten-fold (relative to the weight of MoF ₆ ) excess water was added to it, after which the reactor was warmed to room temperature. Hydrolysis resulted in a clear, colorless solution. The presence of a Teflon coating guaranteed the absence of metal impurities in the solution.

Operation 3. The solution was poured into a container of glassy carbon and evaporated in air at 120 ÷ 140 ° C until a dry residue of light green color appeared.

Operation 4. A light green powder was placed in a quartz reactor and calcined at 700–750 ° C in an atmosphere of pure oxygen. The result was a white powder, the composition of which according to the results of its chemical analysis corresponded to the formula MoO ₃ .

The introduction of the obtained MoO ₃ into the pores of activated carbon by impregnation of the granules with its aqueous solution is not sufficiently ineffective due to the low solubility of MoO ₃ (~ 2 g / l). Therefore, an intermediate substance, ammonium paramolybdate (NH ₄ ) ₆ Mo ₇ O ₂₄ , was prepared from MoO ₃ , the solubility of which is much higher and reaches 20 g per 100 ml of water at 20 ° C.

Step 5. The MoO ₃ obtained in Step 4 was converted to ammonium paramolybdate by dissolving it in a 10% aqueous ammonia solution according to the reaction

7MoO ₃ +6 (NH ₃ · H ₂ O) [decomp.] = (NH ₄ ) ₆ Mo ₇ O ₂₄ + 3H ₂ O

Operation 6. The formation of nanolayers of MoO ₃ on the surface of the channels of activated alumina was carried out by impregnating the granules with an aqueous solution of ammonium paramolybdate (NH ₄ ) ₆ Mo ₇ O ₂₄ and their subsequent heat treatment:

- several grams of activated carbon granules were immersed in a 20% solution of ammonium paramolybdate and kept there for a day. Then the solution was drained and wet granules were weighed. As a result of such an operation, activated carbon granules absorbed a solution of ammonium paramolybdate;

- after impregnation, the granules were dried in a stream of argon grade HF at a temperature of 130 ° C for 2 hours. Weighing the granules at the end of the drying process showed that a film of ammonium paramolybdate weighing up to 2.5 g was planted;

- dried granules, with ammonium paramolybdate in the pores, were subjected to heat treatment at 700 ÷ 750 ° C to decompose the paramolybdate to form MoO ₃ .

(NH ₄ ) ₆ Mo ₇ O ₂₄ = 6NH ₃ + 7MoO ₃ + 3H ₂ O

The manufacturing process was completed and the target sample was analyzed for MoO ₃ content. So, after several cycles of impregnation, drying and heat treatment (step 6) according to the results of chemical analysis (by the ICP-AES method), the molybdenum content in the target sample increased to 25 weight. %

Subsequently, the fabricated target sample was used to determine the possible degree of separation of the starting MoO ₃ and the matrix material. Elution of maternal MoO ₃ from the target after irradiation was carried out with a 20% solution of ammonia in water. The process needed to be accelerated since the half-life of ⁹⁹ Mo is 66 hours. The operation was performed as follows:

- obtained granules of activated carbon with MoO ₃ obtained by the above method were ground and loaded into a vertical glass tube;

- then 20 ml of a 20% solution of ammonia in water were poured into the tube;

- a nitrogen cylinder was connected to the tube;

- the nitrogen pressure was selected so that the flow rate of the solution was ~ 20 ml / hour.

The elution process was repeated several times. The resulting solutions and the washed powder were analyzed for MoO ₃ content. For three elutions, more than 97 weight was recovered from the pores of the activated carbon. % MoO ₃ , which allows us to consider this process quite effective.

The proposed method for manufacturing a target for the production of ⁹⁹ Mo is based on the formation of molybdenum nanolayers in the channels and cavities of existing mesoporous inorganic materials with a narrow pore size distribution. Compared with the method chosen for the prototype, this approach can significantly simplify the technology of manufacturing the target, abandoning the preliminary steps - synthesis of nanoparticles and mechanical homogenization of nanoparticles and buffer. The proposed method provides the ability to form the required thickness of the nanolayers of molybdenum compounds in the channels of the matrix by simply varying the number of impregnation procedures, which was unattainable in the prototype. The higher efficiency of using the starting material and the collection of recoil atoms after washing out the parent MoO ₃ by gasification of the carbon matrix allows to increase the productivity of the ⁹⁹ Mo production process by the radiation capture reaction of ⁹⁸ Mo (n, γ) in comparison with the prototype.

Claims (3)

1. A method of manufacturing a nanostructured target for the production of a ⁹⁹ Mo radioisotope by a radiation capture reaction of ⁹⁸ Mo (n, γ) in the form of a buffer of solids and nanoparticles containing molybdenum with a characteristic nanoparticle size d, where λ / d >> 1, where λ - the mean free path of ⁹⁹ Mo recoil atoms in the substance of the nanoparticle,
characterized in that
the buffer is made in the form of a matrix of mesoporous inorganic material with cavities and channels with characteristic sizes in the range of 2-50 nm, and a nanolayer of molybdenum oxide MoO ₃ is applied to the surface of the cavities and channels, the thickness of which is less than the mean free path of the ⁹⁹ Mo recoil atom in the nanolayer material, and granular activated carbon with a specific surface of more than 300 m ² / g, preliminarily calcined at 700 ÷ 750 ° C, is used as a matrix. 2. The method according to p. 1, characterized in that the nanolayer of molybdenum oxide is formed of MoO ₃ by impregnation of the cavities and channels of the matrix with a solution of ammonium paramolybdate (NH ₄ ) ₆ Mo ₇ O ₂₄ , followed by heat treatment of the target for decomposition of paramolybdate. 3. The method according to p. 1, characterized in that they use ammonium paramolybdate obtained by conversion from a precursor - molybdenum hexafluoride enriched in the ⁹⁸ Mo isotope.