RU2282259C1 - METHOD FOR PRODUCING 63Ni RADIONUCLIDE PREPARATION OF HIGHER THAN 10 Cu/g ACTIVITY - Google Patents

Abstract

FIELD: atomic engineering.

SUBSTANCE: proposed method for producing ⁶³Ni radionuclide preparation having specific activity not over 10 Cu/g includes neutron irradiation of source material in nuclear reactor, production of preparation solution from irradiated material and acid, and extraction of target radionuclide preparation from solution obtained. Source material is metal copper of natural isotope composition with mass fraction of nickel dope not to exceed 5 · 10^-3%. Irradiation is conducted in nuclear reactor at fast (E ≥ 0.1` MeV) neutron flow density of not lower than 8 · 10¹⁴ cm^-2s^-1 and flow density ratio of thermal (E ≤ 0.5 eV) and fast neutrons not over 0.01. ⁶³Ni preparation is extracted by settling down copper from solution made of irradiated material and nitric acid, its concentration being minimum 0.01 mole/l.

EFFECT: facilitated procedure, enhanced safety.

4 cl, 1 dwg, 2 tbl

Description

The invention relates to a technology for producing preparations of radioactive elements and can be used in analytical chemistry.

A known method of producing a radionuclide preparation of ⁶³ Ni with a specific activity of 10 to 12 Ci / g [E.A. Karelin, V.T. Filimonov and others. Preparation of radionuclide preparations of high specific activity in the SSC RF RIAR. Report at the All-Russian Conference "50 Years of Production and Use of Isotopes in Russia", Obninsk October 20-22, 1998. Collection of abstracts and theses of reports and reports, p.18]. The method includes irradiating up to 97% ⁶³ Ni metallic nickel enriched in the thermal neutron flux (E _n <0.5 eV) of the SM nuclear reactor, dissolving the irradiated material in hydrochloric acid, and extracting the target radionuclide from the resulting drug solution by extraction chromatography.

The disadvantage of this method is the long duration of the reactor irradiation of the source material. So, to obtain ⁶³ Ni preparation with specific activity in the range of 10-12 Ci / g, it is necessary to irradiate the SM reactor in the thermal neutron flux for 150-210 effective days (effective day), respectively. This drawback is due to the low value of the cross section for the nuclear reaction ⁶³ Ni (n, γ) ⁶³ Ni. The same reason is caused by another disadvantage of the method - the use of expensive isotope-enriched ⁶³ Ni as a starting material. This disadvantage cannot be eliminated by increasing the duration of irradiation of a mixture of natural nickel isotopes due to the very low content (3.59%) of the starting ⁶³ Ni isotope in it.

The above disadvantages are eliminated by the fact that in the method for producing a ⁶³ Ni radionuclide preparation with a specific activity of more than 10 Ci / g, metallic copper of natural isotopic composition with a mass fraction of nickel impurity of not more than 5 × 10 ^-3 % is irradiated in a nuclear reactor with a fast flux density (E≥ 0.1 MeV) of neutrons not less than 8 · 10 ¹⁴ cm ^-2 s ¹ and the ratio of thermal and fast neutron flux densities not more than 0.01, a solution of the irradiated material in nitric acid with a concentration of not less than 0.01 mol / l is obtained, emit ⁶³ Ni preparation by precipitation from copper solution in the form of a sparingly soluble substance.

The sequence of operations for obtaining the drug ⁶³ Ni by the present method is presented in the drawing.

The operation of irradiating metallic copper of a natural isotopic composition with fast neutrons ensures the accumulation of the ⁶³ Ni radionuclide due to the nuclear reaction ⁶³ Cu (n, p) ⁶³ Ni. The magnitude of the flux density of fast neutrons during irradiation determines the yield of the target radionuclide, to obtain the ⁶³ Ni preparation by the present method, the value of this parameter should be at least 8 · 10 ¹⁴ cm ^-2 s ¹ . The high specific activity of the drug obtained by the present method is determined by the possibility of separating the target radionuclide from the starting material by chemical methods. However, the presence in the starting material of an admixture of natural nickel isotopes leads to a decrease in the specific activity of the final preparation ⁶³ Ni. To obtain the drug ⁶³ Ni according to the present method, copper should be used with a nickel impurity content of not more than 5 · 10 ^-3 %. An increase in the content of nickel impurity in the starting material in excess of the specified value leads to an increase in the duration of its reactor irradiation, necessary to obtain a preparation with a specific activity of more than 10 Ci / g, to a value exceeding 150 effective days. (Thus, a reduction in the duration of exposure by the present method is not achieved in comparison with the prototype). Since an increase in the ratio of thermal and fast neutron flux densities leads to an increase in the fraction of ⁶³ Ni formed by the nuclear reaction ⁶³ Cu (n, γ) ⁶⁴ Cu with subsequent beta decay of ⁶³ Cu → ⁶⁴ Ni and thereby to a decrease in the specific activity of the drug, the value of this parameter according to the claimed method should be not more than 0.01.

The presence of the operation of obtaining a solution of the irradiated material in nitric acid with a concentration of at least 0.01 mol / L provides a high chemical yield of ⁶³ Ni during the subsequent operation of its isolation. The minimum concentration of nitric acid is determined by a decrease in the yield of ⁶³ Ni due to its coprecipitation with a copper-containing precipitate.

The presence of the operation of deposition of copper in the form of a sparingly soluble substance ensures the separation of the starting material and the target product, and thereby obtaining the final preparation of ⁶³ Ni. Unlike the prototype, the inventive method makes it possible to reuse the source material for the accumulation of the target radionuclide. The regeneration of metallic copper from a copper-containing precipitate is carried out by methods known from the scientific and technical literature.

The selection of the drug ⁶³ Ni from a solution of the irradiated material according to the claimed method is carried out by precipitation of copper in the form of a metal or its nitrate.

The deposition of copper in the form of such a sparingly soluble substance as a metal is carried out by electrolysis of a solution of the irradiated material in nitric acid with a concentration in the range of 0.01-0.1 mol / L. The maximum concentration of nitric acid is determined by the decrease in the completeness of the electrochemical deposition of copper at the cathode. The electrolysis of a solution of an irradiated material with an insoluble anode (graphite, glassy carbon, platinum, etc.) provides a deep purification of the ⁶³ Ni preparation from copper (sequence 1 in the drawing). The use of irradiated copper as an anode makes it possible to combine the dissolution of these samples with copper deposition, since during the electrolysis, anode dissolution will occur simultaneously with copper deposition at the cathode. This electrolysis option allows ⁶³ Ni to be isolated from a larger amount of irradiated material without increasing the electrolyte volume. After complete dissolution of the copper anodes, the ⁶³ Ni preparation is isolated by electrolysis of the resulting solution with an insoluble anode (sequence 2 in the drawing).

It is known that copper nitrate - Cu (NO ₃ ) ₂ - is a highly soluble substance in water. The solubility of this compound (in terms of metallic copper) increases in the temperature range 0-30 ° C from 280 to 530 g / l, respectively. The solubility of copper nitrate decreases with increasing concentration of free nitric acid in the solution and at 16 mol / L HNO ₃ in terms of metallic copper is 5 g / L (0 ° C) and 28 g / L (30 ° C). The deposition of copper by the present method in the form of sparingly soluble Cu (NO ₃ ) _{2 is} carried out from a solution of the irradiated material in nitric acid with a concentration of at least 16 mol / l and a final solution temperature of not more than 30 ° C. The minimum concentration of nitric acid and the maximum final temperature of the solution are determined by a decrease in the degree of deposition of copper nitrate. Nickel nitrate has high solubility in concentrated nitric acid (more than 200 g / l in terms of metal at 20 ° C and a concentration of HNO _{3 of} 16 mol / l) and remains in solution upon precipitation of copper nitrate. Isolation of ⁶³ Ni from this solution is carried out by electrolysis with an insoluble anode (sequence 3 in the drawing).

The accumulation of the ⁶³ Ni radionuclide was carried out by irradiating samples of metallic copper of natural isotopic composition in the BOR-60 fast neutron reactor core (SSC RF RIAR). The fast neutron flux density in the irradiation cell of the reactor was 1.5 · 10 ¹⁵ cm ^-2 s ¹ . The samples were made of bar copper M1k grade (according to GOST 859-78), the content of nickel impurities in the used chalk was 1.8 · 10 ^-3 %. The characteristics of the irradiated samples are presented in table 1.

Table 1 Sample No. Sample weight, g Irradiation time, eff. one 4,250 46.2 2 51,019 92.2

The selection of ⁶³ Ni from the irradiated sample No. 1

The irradiated sample was dissolved by heating in nitric acid with a concentration of 8 mol / L. An aqueous solution of ammonia was introduced into the resulting solution to a final pH of 1.0 (corresponding to 0.1 mol / L of the concentration of free nitric acid). Received 0.100 l of a solution of irradiated material. Isolation of ⁶³ Ni was carried out by electrolysis of this solution with an anode of glassy carbon (cathode — copper plate). During the electrolysis, the cathode current density was gradually reduced from 30 to 5 mA / cm ² . After completion of the electrolysis, the electrolyte was profiled, evaporated to dryness. The final preparation ⁶³ Ni was obtained by dissolving the dry residue in 5.0 ml of nitric acid with a concentration of 0.5 mol / L.

The selection of ⁶³ Ni from the irradiated sample No. 2

The irradiated sample was dissolved in nitric acid with a concentration of 10 mol / L. The resulting solution was evaporated to a final volume corresponding to a copper concentration of 500 g / l in it, after which it was diluted with hot (~ 80 ° C) nitric acid with a concentration of 16.1 mol / l, introduced in a ratio of 2.5: 1 relative to the volume of the original solution. The solution was slowly cooled to 22 ° C and kept at this temperature for 18 hours, after which the solution was separated from the precipitate of copper nitrate. The copper content in the resulting solution was 12% relative to the original. This solution was evaporated to dryness, the salts were dissolved in 0.100 L of nitric acid with a concentration of 0.05 mol / L. Subsequent isolation of ⁶³ Ni was carried out similarly to the operations described above for sample No. 1.

The characteristics of the final preparations of ⁶³ Ni isolated from the irradiated samples are presented in Table 2.

table 2 Sample No. Activity ⁶³ Ni in the preparation, mCi The specific activity of ⁶³ Ni in the drug, Ci / g Coefficient of cleaning ⁶³ Ni from copper one 7.1 11.6 ≥100 2 193 13.7 ≥1000

Claims (4)

1. A method of producing a radionuclide preparation of ⁶³ Ni with a specific activity of more than 10 Ci / g, including neutron irradiation of the starting material in a nuclear reactor, obtaining a solution of the irradiated material in acid and isolating the target radionuclide from the resulting solution of the preparation, characterized in that the starting material is used metallic copper of natural isotopic composition with a mass fraction of nickel impurity of not more than 5 · 10 ^-3 %, irradiation is carried out in a nuclear reactor with a flux density of fast (E≥0.1 MeV) neutrons of not less than 8 · 10 ¹⁴ cm ^-2 s ^-1 and the ratio of thermal flux densities (E≤0.5 eV) and fast neutrons is not more than 0.01, and ⁶³ Ni is isolated by precipitation of copper from a solution of irradiated material in nitric acid with a concentration of at least 0.01 mol / l 2. The method according to claim 1, characterized in that the copper is precipitated in the form of a metal by electrolysis of a solution of the irradiated material in nitric acid with a concentration in the range of 0.01-0.1 mol / L. 3. The method according to claim 2, characterized in that during electrolysis, the irradiated copper is used as an anode. 4. The method according to claim 1, characterized in that the copper is precipitated in the form of its nitrate from a solution of the irradiated material in nitric acid with a concentration of at least 16 mol / l and a solution temperature of not more than 30 ° C.