RU2291112C2 - Method of extraction-type separation of americian and curium - Google Patents

Abstract

FIELD: radiochemistry; analytical chemistry.

SUBSTANCE: proposed method consists in treatment of solution containing elements to be separated, diethylene triamine, pentaacetic acid, carbamide or formic acid, extracting agent in form of solution of chlorinated cobalt dicarbollide and polyethylene glycol in organic solvent or solution of cobalt dicarbollide, zirconium slat of dibutyl phosphoric acid and polyethylene glycol in organic solvent. Americian passes into organic solution at higher degree as compared with curium. Proposed method takes into account factor of separation of americian and curium and facilitates the process due to avoidance of salting-out agent.

EFFECT: enhanced efficiency.

4 cl, 2 tbl, 2 ex

Description

The invention relates to the field of radiochemistry and, in particular, to the field of extraction of long-lived radionuclides from spent nuclear fuel or irradiated targets, and can be used in analytical chemistry to isolate and concentrate elements

Known methods for the separation of americium and curium, including precipitation, sorption and extraction processes [1 R. Pennomen, T. Keenen. Radiochemistry of America and Curium. M .: Foreign literature; 1961; M. Kamoshida, T. Fukusava in Global-99; Radiochemistry Vol. 21, No. 2, p. 262, 1979].

The disadvantages of these methods are either the complexity of the process or the insufficient radiation and chemical stability of the extractants or sorbents used or the low degree of separation of these elements in one extraction stage, which requires the process to be carried out at a large number of extraction stages with careful monitoring of the ratio of the flows of the organic and aqueous phases.

The closest technical solution to the claimed invention is a method for the extraction separation of americium and curium with an extractant based on amines or their salts in non-polar solvents using a complexing agent diethylenetriaminepentaacetic acid - DTPA [V.M. Nikolayev, E.A. Karelin, R.A. Kuznetsov. Technology of transplutonium elements. SSC RF RIAR, 2000, p.170.].

The method consists in the fact that an aqueous solution containing americium and curium, a lithium, sodium or aluminum nitrate, complexing agent, diethylene triamine pentaacetic acid-DTPA, is contacted with an extractant, an organic solution of an amine or its salt with nitric acid. In this case, americium passes into the organic solution to a greater extent than curium. By the ratio of the distribution coefficients of americium and curium - the separation factor is judged on the effectiveness of the process of separation of elements. The larger the separation factor, the higher the efficiency of the extraction process of americium and curium extraction and the smaller the number of extraction steps required to achieve the necessary indicators for cleaning one element from another.

The disadvantage of this method is that when separating americium and curium, an addition of a salting out agent — lithium or aluminum nitrate — is necessary, which complicates the subsequent handling of the aqueous solution of the released element. In addition, the achieved degree of separation of americium and curium (β _{Am / Cm} ) is relatively low and in most cases (β _{Am / Cm} ≤4), therefore, a sufficiently large number of extraction steps are required for their effective separation.

The objective of the invention is to increase the efficiency of the extraction separation of americium and curium by increasing the value of their separation factor and simplifying the process by eliminating the salting out agent from it.

The problem is solved by contacting an aqueous solution containing americium and curium, diethylene triamine pentaacetic acid and urea or formic acid in an amount of 20-100 g / l with a solution of chlorinated cobalt dicarbolide - CDA and polyethylene glycol - PEG in an organic solvent with a component content of 0.05-0 3 mol / L and 0.001-0.15 mol / L, respectively. In this case, americium passes into the organic solution to a much greater extent than curium, due to which an effective separation of these elements is achieved. A solution of chlorinated cobalt dicarbolide, zirconium salt of dibutylphosphoric acid — CS DBPK and polyethylene glycol in an organic solvent with component concentrations of 0.05-0.3 mol / L, 0.1-0.5 mol / L, can also be used as an organic solution. 0.001-0.15 mol / L, respectively. As the organic solvent, a polar organic solvent or a mixture of polar and non-polar solvents can be used.

Example 1

The effect of the composition of the aqueous solution on the distribution of americium III and curium III in the extractant based on CDK and PEG is shown in Table 1. Organic phase: 0.3 mol / L HDC, 6% PEG in a mixture of polar and nonpolar solvents, orthonitrotoluene-hexachlorobutadiene- (1: 1)

Table 1 Urea, g / l DTPA, g / l Distribution ratios Separation factor Am III Cm III (β _{Am / Cm} ) fifty 2 0.41 0.022 18.6 70 2 0.24 0.033 7.3 one hundred 2 0.25 0.033 7.6 thirty 0.5 5.42 0.48 11.3 one hundred 0.5 1.34 0.24 5.6

Example 2

The effect of the composition of the aqueous solution on the distribution of americium III and curium III in the extractant composition: 0.05 mol / L CDA, 0.5% PEG, 0.07 mol / L CS DBPC in a polar solvent methanitrobenzotrifluoride is shown in Table 2.

table 2 DTPA, g / l Urea, g / l Formic acid, g / l Distribution ratios Separation factor Am III Cm III (β _{Am / Cm} ) four fifty 0.35 0,036 9.7 four 70 0.33 0,050 6.6 four one hundred 0.36 0,054 6.7 2 thirty 1.21 0.10 12.1 2 fifty 0.79 0.15 5.3 2 150 0.4 0,055 7.3 four fifty 1.7 0.1 17 6 fifty 1.82 0.3 6.1 10 150 1,63 0.1 16.3

TS DBPK - zirconium salt of dibutylphosphoric acid - is added to the extractant to increase the degree of extraction of rare earth and transplutonium elements.

The method compared with the prototype can significantly simplify the process of extraction separation of americium and curium due to a significant increase in their separation factor and the refusal to use a salting out agent.

Claims (4)

1. The method of extraction separation of americium and curium by extracting americium from an aqueous solution containing diethylenetriaminepentaacetic acid, characterized in that the extractant is a solution of chlorinated cobalt dicarbollide and polyethylene glycol in an organic solvent or a solution of chlorinated cobalt dicarbollide, polycarbonylphosphoric acid salt the solvent, and the initial aqueous solution contains urea or formic acid. 2. The method according to claim 1, characterized in that the organic solvent used is a polar organic solvent or a mixture of a polar and non-polar solvent. 3. The method according to claim 1, characterized in that the concentrations of chlorinated cobalt dicarbollide, zirconium salt of dibutylphosphoric acid and polyethylene glycol in the extractant are 0.05-0.3 mol / L, ≤0.5 mol / L and 0.001-0.15 mol / l, respectively. 4. The method according to claim 1, characterized in that the concentration of urea or formic acid in the aqueous solution is 20-100 g / L.