SU760636A1 - Method of producing preparations of hafnium radioisotope without carrier - Google Patents

Description

The invention relates to methods for producing radioisotopes in a carrier-free state, in particular the release of hafnium radioisotopes produced in deep cleavage reactions of heavy elements by high-energy protons from targets weighing several grams.

A known method for isolating hafnium radioisotopes without a carrier from tantalum irradiated with protons of high energy involves * · ^g "dissolving the target with a mixture of fluoride, hydrochloric and nitric acids, co-precipitating hafnium and rare-earth elements (s. E) with fluoride carriers (barium, zirconium, lanthanum), dissolving the precipitate with a mixture of boric and, for example, nitric acids, removing barium as sulphate, re-co-precipitating hafnium with hydroxide of carrier elements, dissolving the precipitate with concentrated / hydrochloric acid, sorption of hafnium n and anion exchanger. column. and elution of its 6-8-No. NA? / /. . /.

The closest to the described method to the technical essence and the achieved result is a method of extracting preparations of hafnium radioisotopes without a carrier from a tantalum target, according to which tantalum is dissolved in a mixture of hydrofluoric and nitric acids, hafnium and rare-earth elements co-precipitate with fluorine _: which are carriers of radioisotopes, the precipitate is dissolved in a mixture of boric and, for example, nitric acids, barium is removed in the form of sulphate, hafnium and r.s. 40

re-co-precipitate with lanthanum hydroxide; the hydroxide is dissolved in a minimum amount of hydrochloric acid, a solution with a concentration of H ⁺ ions of not more than 0.3 M is passed through a 45 cation column and the adsorbed hafnium is eluted with a 0.1 M solution of oxalic acid.

• The disadvantages of this method, like the previous one, are the complex technology of preparing the preparation for chromatographic purification of hafnium, the long duration of the process (about 4 hours) and the low (not more than 50%) chemical yield. 55

The aim of the invention is to simplify the process of separation of hafnium by reducing the number of operations for the deposition and dissolution of precipitation, reducing the cost of time and increase the chemical yield. The goal is achieved: by using metal rhenium as a target, dissolving it in a minimum, close to stoichiometric, amount of concentrated nitric acid, and the resulting solution rhenium and nitric acids are passed through a cation resin chromatograph that is washed with water before elution of the hafnium.

An example. A rhenium target weighing 2 g is dissolved by heating in 7 ml 12 Μ ΗΝΟι, and 2 mg of lanthanum is added. The solution is centrifuged to remove insoluble impurities and ²⁰ accidental contaminants. The dissolution vessel is washed with 7 mpd vdd and after centrifuging the washing solution is combined with the rhenium solution. The resulting solution in a volume of ²³ about 13 ml, in which the total concentration of rhenium and nitric acids is about 1 M, is transferred to a chromatographic column (diameter 4 mm, height 50 mm, free volume 0.25 mp, resin - Dowex 50 \ 12, And * -form, grain size 3040 microns) and pass with a speed of 3. ml / cm ² · min. The column for rhenium removal is washed with 1 ml of water and hafnium is eluted with a 0.1 M solution of oxalic acid.

The duration of the process of excretion of hafnium is 55-60 minutes.

Of these, 25-28 minutes are spent on passing the target solution through the column and about 30 minutes on all other operations, including elution of hafnium. The chemical yield of 90 + 2%. In comparison with the prototype, the technology for isolating hafnium in the proposed method is significantly simplified, the duration of the process is reduced by 4 times, and the chemical yield is increased almost 2 times.

Metallic rhenium is dissolved in concentrated nitric acid with the formation of strong rhenium acid (5.37 mmol per 1 g of rhenium) and the release of nitrogen dioxide. In this case, the formation of 1 mmol NKeOts consumes 7 th,. ΗΝ0 ₃ . Consequently, as a result of dissolving 2 g of rhenium in 7 ml of 12 M ΗΝΟ-,, as indicated in pp3 760636

the measure forms 10.74 mmol NKeOts and the excess ΗΝΟ ^ should remain in the amount of 9 mmol. But since the dissolution proceeds when heated, part ΗΝΟ} is lost due to evaporation and 5 the actual total content of rhenium and nitric acids in the solution does not exceed 12 mmol, and the concentration of H ions is about 2 M. During sorption of hafnium directly>

from this solution, the duration of the isolation process is reduced by 12 minutes (due to faster passage of the solution through the column), ’but the yield decreases to 80%. 15

A further decrease in the volume of the target solution by evaporation is impractical, since the duration of the release does not decrease, and the yield of hafnium drops sharply.

With a decrease in the concentration of H ^ -ions due to dilution of the solution with water, the chemical yield reaches 90% and then does not change.

But in connection with the increase in the volume of the solution, the duration of the process increases rapidly.

Thus, the optimal concentration of H * ions is in the range of 0.7-1.3 M.

Claims (2)

1. METHOD FOR OBTAINING PREPARATIONS OF HAFNIA VEZ 'MEDIA RADIOESOTOPES by irradiating a target of a heavier metal with high-energy protons, dissolving the target, transferring hafnium into a weakly acidic solution, sorbing it on the cationite and eliminating it with oxalic acid, · differing from simplifying the isolation technology by reducing the number of operations, increasing the chemical yield and shortening the process; rhenium is used as a target, dissolving the irradiated target in the minimum, close to stoichiometric, amount of concentrated nitric acid, the resulting solution is passed through cation exchanger of hafnium washed with water. ^? .2. The method according to claim 1, if you find that after dissolving the target, the solution is diluted with water to a concentration of hydrogen ions of 0.7-1.3 M. z ... 760636 760636