The method of extraction and separation of uranium and tetravalent actinides from nitric acid solutions

 

The invention relates to processes for extraction allocation of actinides from nitric acid solutions reprocessing plants. The technical result is to simplify the process of separating uranium and tetravalent actinides by excluding recovery processes, ensuring the Stripping of these components in solutions with a high concentration of nitric acid, as well as increasing the capacity of the extractant on the basis of light diluent for tetravalent actinides. As a diluent or a component of the diluent TBP used compounds belonging to the class of monohydroxy alcohols, and the volume fraction of alcohol in the extraction mixture should not be less than 10%. Reextraction uranium and tetravalent actinides carry out nitrate solution with a concentration of from 0.1 to 5 mol/l, and the separation of uranium and tetravalent actinides carried out by varying the concentration of nitric acid in the aqueous phase. The method allows to exclude the operation of restorative Stripping, reextracted target component is nitric acid from 0.1 to 5 mol/l, which prevents the possibility of leakage in these solutions hydrolytic processes, is achieved le=" page-break-before:always;">

The invention relates to the field of radionuclide and can be used in extraction technology selection actinides from nitric acid solutions reprocessing plants.

There is a method of extraction and separation of uranium and tetravalent actinides from nitric-fluoride environments with a solution of tributyl phosphate (TBP) Hexachlorobutadiene (ghri) (Wolf C. I., A. Bakhrushin Y., Mamaev, S. L.//radiochemistry. 1999. So 41, No. 2, S. 116-118). The disadvantage of this method is the complexity of the process of separation of uranium and tetravalent actinides, such as plutonium, by translation in the last dextrogyrate shape recovery. In addition, reextracted target component is nitric acid solutions with concentrations of less than 0.3 mol/l, which does not exclude the probability of occurrence of hydrolytic processes.

The closest in technical essence to the claimed technical solution is the method of extraction and separation of uranium and tetravalent actinides from nitric acid solutions, solutions of TBP in hydrocarbon compounds, having in its composition 12-14 carbon atoms (H. Peterson, P. Weimer. Chemistry in nuclear technology. - M.: Atomizdat, 1967), including extraction of target components and th is sa, since the separation of hexavalent uranium and tetravalent plutonium is due to the recovery of the last to trivalent and purification from non-restorable tetravalent actinides such as thorium, is carried out either in two cycles using different concentrations of the extractant by varying the pH in a narrow range of concentrations of the weak (0,008-0.24 mol/l) nitric acid at a separate stage of Stripping. The probability of hydrolytic processes are also not excluded. In addition, the extraction of tetravalent actinides possible separation of the organic phase due to the relatively low capacity of the extractant according to components.

The objective of the invention is to simplify the process of separating uranium and tetravalent actinides carried out by varying concentrations of nitric acid in the stages of extraction and re-extraction, ensuring the Stripping of these components in solutions with a high concentration of nitric acid, as well as increasing the capacity of the extractant on the basis of light diluent for tetravalent actinides.

It is solved by the method of extraction and separation of uranium and tetravalent actinides from nitric acid concrete the slots, according to the invention as a diluent or component thereof is used as a compound class of monohydroxy alcohols when the volume fraction of alcohol in the extraction mixture from 10% or more, and reextraction lead with a solution of nitric acid of a concentration from 0.1 to 5 mol/L.

With fewer alcohol in the organic phase offset the effect of increasing the capacity of the light organic phase in the extraction of tetravalent actinides, eliminates the possibility of Stripping of actinides in strong nitric acid solutions and the separation of uranium and tetravalent actinides without restoring the last.

Comparative analysis of the prototype allows us to conclude that the claimed technical solution is different from the known fact that as a diluent or a component of the diluent TBP using a new class of solvent - monohydroxy alcohols. Thus, the claimed method meets the requirement of "novelty."

In the literary sources not found information about the use of alcohols as solvents TBP in radiochemical processes. The introduction of alcohol in the extraction system allows reextraction uranium and tetravalent actinides in a wide range of acidity from 0.1 to 5 mol/westline by varying the concentration of nitric acid in the aqueous phase. For example, the interaction of a nitric acid solution of uranium and plutonium (concentration: HNO3- 6 mol/l; Pu and U from 4 to 7 g/l) with the extractant - 30% TBP in 1,1,7-trigidrododekaftorgeptanole (alcohol-telomere brand n3), is the extraction of uranium in the organic phase, and the plutonium remains in solution. The distribution coefficients (Kthe soap) uranium and plutonium respectively 1.1 and 0.3. By increasing the concentration of nitric acid in aqueous solution is above 7 mol/l, begins to be extracted plutonium (Kthe soap=l.2). Similarly, the variation of concentration of nitric acid in reextracted solutions it is possible to achieve separation of these components or their joint selection.

Thus, the process of separating the target component, in this case uranium and plutonium, can be carried out both at the stage of extraction, or by a separate Stripping without surgery recovery of plutonium.

The results of static experiments, shown in Fig. 1, showed that the use of alcohols as solvents, uranium and tetravalent actinides satisfactorily extracted in a wide range of colatosti. It is evident from Fig. 1 shows that the extraction of uranium and thorium extraction is icient distribution over 1 begins at colatosti solution of 2.5 and 7.5 mol/l, respectively. Thus, in the range of concentrations of nitric acid in the solution is from 3 to 7 mol/l there is a principal possibility of the separation of these elements in the extraction step. For extractant 30% TBP in n3this interval is slightly narrower, and is approximately 6 to 7 mol/l Reextracted target elements from a mixture of IVA-TBP is completely in nitric acid with a concentration from 0.5 to 1 mol/l, and for mixtures with n3to 5 mol/L.

In Fig. 2 and 3 presents data illustrating the influence of alcohol (IVA or n3in the thinner mechanicalinternational (f-3) on the extraction ability of TBP with respect to uranium and thorium. Presents the dependence of the minimum acidity of a solution in which the distribution coefficients of thorium or of uranium reaches the value of 1.5, the content of n3or IVA in the extractant with a constant content of TBP (30%) f-3, indicate the possibility of separating these components.

The area enclosed between lines 1 and 2, defines the terms of separation. From the drawings it is seen that for the extraction of a mixture of 30% TBP in n3the absolute width of the range separation of uranium and thorium varies approximately from 2 to 3 mol/l acid. For extractant 30% TBP in You know, that the extraction system 30% TBP in the hydrocarbons of the paraffin fraction (RED) has a low capacity chetyrehjadernym actinides, plutonium she is (222) g/l When reaching this value starts to happen separation of the organic phase. Introduction in the extraction system of alcohol can significantly increase the capacity of the extractant on the specified elements. For example, in case of repeated contact of the extractant - 30% TBP, 10% IVA, 60% RED with nitric acid solution of thorium (concentration: NGO3- 4 mol/l, Th - 45.4 g/l), separation of the organic phase does not occur, the capacity of the extractant on thorium increases almost two times (see table).

Discovered the fundamental possibility of high acid Stripping and separation of six - and tetravalent elements, as in the extraction step, and by separate Stripping without the use of reducing agents, with the simultaneous effect of increasing the capacity of the extractant (on the basis of light diluent) for tetravalent actinides, is new and unexpected.

All this allows to recognize the claimed solution meets the requirement of "inventive step".

In the 1. The aqueous phase consisted of 7.0 mol/l nitric acid solution containing 1.14 g/l plutonium - 239 and 5.0 g/l of uranium. The solvent was a mixture of 30% TBP in IVA. Phase was stirred for 3 min, and then separated by centrifugation. In all the following examples of the operation of extraction and re-extraction was performed in a similar way. The distribution coefficient of PU-239 was 2.9, uranium - 8.8. Reextraction plutonium spent 5 mol/l solution of nitric acid. The distribution coefficient of PU was 0.83, the concentration of uranium in plutonium concentrate - 0.7 g/l Coefficient purification of plutonium from uranium, with one contact of the phases was equal to 2.9. For Stripping uranium extractant was washed with 0.5 mol/l solution of nitric acid. The distribution coefficient of uranium amounted to 0.12, the concentration of plutonium in uranium reextract - 0.19 g/l Coefficient of purification of uranium from plutonium, with one contact of the phases, amounted to 4.8.

Example 2. The aqueous phase consisted of 3.7 mol/l nitric acid solution containing 6.4 g/l of plutonium-239 and 4.3 g/l of uranium. The organic phase contained 50% TBP in n3. The distribution coefficient of PU-239 and uranium, respectively, and 2.7 1.65. When conducting joint Stripping components 1 mol/l solution Adna phase consisted of a 5 mol/l nitric acid solution, containing 1.0 g/l thorium and 4.2 g/l of uranium. The organic phase contained the following volumetric proportions of the components - 30% TBP, 10% n3, 60% f-3. The distribution coefficient of thorium was 1.68, uranium - 13.0. When conducting selective Stripping of thorium 3 mol/l nitric acid distribution coefficient of thorium was 0.7, and the subsequent Stripping of uranium 1 mol/l solution of nitric acid, its distribution coefficient was equal to 0.6. The concentration of uranium in thorium concentrate, 0.69 g/l thorium in uranium reextract not found.

Example 4. The aqueous phase consisted of a 7 mol/l nitric acid solution containing 1.1 g/l thorium and 4.0 g/l of uranium. The organic phase contained the following volumetric proportions of the components - 30% TBP, 60% IVA. 10% f-3. The coefficient of the distribution of thorium in the extraction step was 1.12, uranium - 7.0. Reextraction thorium spent 3 mol/l solution of nitric acid. The distribution coefficient of thorium was 0.1, the concentration of uranium - 1.28 g/l For uranium Stripping the extractant was washed with 0.1 mol/l solution of nitric acid. The distribution coefficient of uranium amounted to 0.18, thorium in uranium fraction was not found.

Example 5. The aqueous phase consisted of a 3 mol/l nitric acid solution containing 1.1 g/l thorium and 4.2 g/l of uranium. Org thorium was 0.39, uranium - 3.57. The degree of purification of thorium from uranium (raffinate) was 4,58. Reextraction uranium spent a 1.0 mol/l solution of nitric acid, and the distribution coefficient of uranium amounted to 0.74. the content of thorium in uranium concentrate amounted to - 0.2 g/l Coefficient of purification of uranium from thorium - 3,39.

Example 6. The aqueous phase consisted of a 5 mol/l nitric acid solution containing 4.5 g/l of uranium. The solvent was a mixture of 30% TBP in butyl alcohol. The distribution coefficient of uranium amounted to 1.51. Reextraction uranium was performed 1 mol/l solution of nitric acid, and the distribution coefficient of uranium amounted to 0.63.

Example 7. The aqueous phase consisted of a 6 mol/l nitric acid solution containing 10.6 g/l of uranium. Extraction of uranium spent the organic phase of the following composition: 30% TBP in diluent n3containing 50 g/l 1,1,9-trihydroxyacetophenone (alcohol-telomere n4). The distribution coefficient of uranium amounted to 1.16. Reextraction uranium was performed 1 mol/l solution of nitric acid, and the distribution coefficient of uranium amounted to 0.4.

Example 8. The aqueous phase consisted of a 3 mol/l nitric acid solution containing 5.5 g/l of uranium n3. The distribution coefficient of uranium amounted to 18.9. Rexel 0.8.

Example 9. The aqueous phase consisted of a 1 mol/l nitric acid solution containing 11 g/l of uranium and 45 g/l thorium. Extraction of the components of spent organic phase of the following composition: 30% TBP, 56% RED and 14% IVA. The distribution coefficients of uranium and thorium, respectively, 3.0 and 0.3. The purification coefficient of thorium from uranium in the raffinate was 3.1.

Example 10. The aqueous phase consisted of a 4 mol/l nitric acid solution containing 40 g/l of plutonium. The organic phase contained the following volumetric proportions of the components - 30% TBP, 10% IVA and 60% RED. With four times the contact phase the capacity of the extractant plutonium reached 43 g/L.

Example 11. The aqueous phase consisted of a 4 mol/l nitric acid solution containing 45 g/l thorium. The organic phase contained the following volumetric proportions of the components - 30% TBP, 15% isoamyl alcohol and 55% RED. At three times the contact phase the capacity of the extractant on thorium reached 36 g/L.

Thus, the above examples show that the use of monohydroxy alcohols as solvent TBP or put in the amount of 10% and above as an additional component in the extractant based on TBP allows you to efficiently extract the uranium and tetravalent actinides, conduct their separation on C also increase the capacity of TBP in the lungs thinners for tetravalent actinides while maintaining stability of the organic phase.

Claims

The method of extraction and separation of uranium and tetravalent actinides from nitric acid solutions, including extraction with tributyl phosphate in an organic diluent and re-extraction solution of nitric acid, characterized in that as a diluent or component thereof is used as a compound class of monohydroxy alcohols when volume concentration of alcohol in the extraction mixture from 10% or more, and reextraction lead with a solution of nitric acid of a concentration from 0.1 to 5 mol/L.

 

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FIELD: chemistry.

SUBSTANCE: extractant has bi-phosphorus acid and additionally has tri-phosphate with relation of said components (0,5-1,25):1. Method for producing extractant includes adding to 2-ethylhexanole of chlorine oxide of phosphorus with their relation (4,5-5,1):2,0, and with parameters determined by reaching fullness of passing of reaction, after that reaction mixture is exposed until full removal of formed chlorine hydrogen, then to received mixture 1 mole of water is added, mixture is exposed to full hydrolysis. Then mixture is washed ad water layer is separated from organic remainder, containing said bi-phosphoric acid and tri-phosphate.

EFFECT: higher efficiency.

2 cl, 1 dwg, 2 tbl, 4 ex

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