Method of processing the uranium- and fluorine-containing wastes

FIELD: technology of processing uranium-and fluorine-containing wastes.

SUBSTANCE: proposed method includes preparation of solutions from wastes, concentration of solutions by sedimentation of uranium followed by dissolving of sediments in nitric acid, extraction conversion of concentrated solutions with the use of tributyl phosphate in hydrocarbon thinner and sedimentation of ammonium polyuranates from re-extracts thus obtained. Sedimentation of uranium at stage of concentration is performed with the use of sodium hydroxide at pH= 9-10 and temperature of 60-90C. Proposed method enhances purification of uranium from fluorine due to enhanced sedimentation and filtration properties of sediments at concentration stage. Content of admixtures in triuranium octa-oxide powders obtained from re-extracts by sedimentation of ammonium polyuranates and subsequent calcination does not exceed specified norms.

EFFECT: enhanced efficiency.

1 dwg, 2 tbl, 1 ex

 

The invention relates to technology for processing wrangelstrasse uranium waste.

A method of refining uranium waste (the Straits solutions from decontamination of equipment, damaged fallopian solutions, solid waste), including the dissolution of solid waste in solutions of nitric acid, mixing the obtained solution with liquid waste, filtration solutions, the concentration of the "poor" uranium solutions, extraction uranium extraction and purification from impurities with the use of tributyl phosphate in a hydrocarbon solvent as the extractant (A.A. Mayorov, Braverman IB Technology to obtain powders of ceramic uranium dioxide. - M.: Energoatomizdat, 1985, s-122).

In the above-mentioned method, the concentration of the "poor" uranium solutions produced by the process of evaporation.

In the processing of waste containing fluorine, the latter corrodes the equipment of steel 18CR10NITI because of its highly corrosive. In the process of evaporation does not occur purification solutions from fluorine, and the direction of extraction redistribution of solutions contaminated with fluorine, complicates the extraction stage. For binding of fluoride in solutions directed to the extraction redistribution, enter nitrate iron, forming with fluorine stable complex compounds. (Ritchie G.M., Ashbrook Extra AV is tion. Principles and applications in metallurgy. - M.: metallurgy, 1983, s.285).

A method of refining wrangelstrasse waste (RF Patent No. 2200992, IPC G21 9/04, 9/30, publ. 20.03.2003)adopted for the prototype, including the production of waste solutions, the stage of concentration of solutions by precipitation of uranium and the subsequent dissolution of the precipitate in nitric acid, the extraction of uranium from concentrated solutions using tributyl phosphate in a hydrocarbon diluent, reextraction and deposition of polyuranates ammonium received reextractors.

The concentration of the solutions in the method prototype, including deposition of uranium ammonium hydroxide in the form of polyuranates ammonium and their subsequent dissolution in nitric acid leads to the purification of uranium from fluorine. However, the clearance is insufficient, because during the precipitation of the ammonium hydroxide are formed fine sediments with low sedimentation and filtration properties, "exciting" fluoride from mother solutions.

The objective of the invention is to increase the degree of purification of uranium from fluorine by improving sedimentation and filtration properties of precipitation, obtained by precipitation from solutions on the operations of concentration.

The solution is achieved in that in the method of processing wrangelstrasse waste, including the production of these solutions, the stage to which tsentrirovannaja solutions by precipitation of uranium and the subsequent dissolution of the precipitate in nitric acid, extraction of uranium from concentrated solutions using tributyl phosphate in a hydrocarbon diluent, reextraction and deposition of polyuranates ammonium received reextractors, the deposition of uranium on the stage of concentration carried out with sodium hydroxide at pH 9-10 and the temperature of 60-90°C.

Example

Nitric acid solutions of uranium, recyclable, were obtained by mixing solutions from dissolution Ogarkov with the operation of the fluoridation of octaoxide truran and pastes from cleaning equipment drain water solutions and irrigation fluids, the gas purification system. As a result of mixing of getting initial solution composition: 0.06 mol/l of uranium, 0.3 mol/l of nitric acid, 1.05 mol/l of fluoride ion, which is sent to the stage of concentration.

Carried out the deposition of uranium on the stage of concentration. In the deposition reactor with specified expenses filed the original uranium-fluorine-containing solution and a 40%solution of sodium hydroxide with constant stirring. In the reaction zone of deposition maintained pH 9-10 and the temperature of 60-90°

Sedimentation and filtration properties of the obtained precipitation was evaluated by filtration coefficient, the speed and timing of sedimentation and other characteristics, is shown in the drawing and in the table 1.

The drawing shows the dependence of the rate sedimen the purpose of precipitation, formed by deposition on the stage of concentration, V, mm/min, from the time of sedimentation t, min, for the proposed method (precipitation with sodium hydroxide) and the prototype method (precipitation with ammonium hydroxide).

Table 1 presents the characteristics of the sludge formed during the precipitation stage of concentration in the proposed method (lines 4-7) and the method-prototype (lines 1-3).

68
Table 1
PrecipitatorThe temperature of deposition, °The ratio of the volume of the original solution to the volume of reagent precipitatorThe relative amount of sediment, vol.%The filtration coefficient, 10-6cm/secThe cake moisture, wt.%Specific surface area, m2/gDensity based, g/cm3The density of the Sands, g/cm3The content of components in the sediment, wt.%The content of components in the mother solution, g/l
after 20 minafter 24 hoursuraniumfluorideuraniumfluoride
NH4OH200,5361,175393,440,660,20,780,0155,1
NH4OH600,551263,162373,480,7of 60.50,730,015of 5.4
NH4OH800,3538235,150313,550,9559,50,530,0157,6
NaOH6010322010,055313,521,060,10,250,01410,8
NaOH709,88,86,66,532,426,33,661,0160,30,130,01510,8
NaOH809,17,26,4the 5.731,925,23,621,0758,00,130,01 10,8
NaOH908,86,45,65,5of 31.415,43,66the 1.4461,70,20,01310,8

From the data presented in table 1 and in the drawing, it is seen that the use of sodium hydroxide to precipitate uranium operations concentration can increase the permeability of the formed precipitation, rate of sedimentation, bulk and based density, to reduce the moisture content in the sediments, specific surface area and the volume of sediment occupied them after decanting. This increases the degree of purification of uranium from fluoride: fluoride content in the precipitation of uranium is reduced by 3-5 times compared with the prototype, and the uranium content in the mother solution remains on the same level as in the method prototype.

The use of sodium hydroxide on the operation of the concentration of uranium from wrangelstrasse solutions also can significantly reduce the amount of the produced mother solutions, which facilitates their disposal.

The obtained precipitates were dissolved in solutions of nitric acid of a given concentration and directed by extraction redistribution using tributyl phosphate in a hydrocarbon diluent and, further, ammonium deposition of polio is the Anat ammonium from reextractors uranium.

By improving the cleaning of precipitation of the fluorine at the stage of concentration on the extraction redistribution directed solutions with a significantly lower fluorine content than in the prototype that facilitates the extraction process (requires less nitrate of iron to bind fluoride).

The use of sodium hydroxide on the operation of concentrating the waste does not adversely affect the results of the extraction stage. On extraction the redistribution of concentrated solutions of uranium in the ratio of flows in the extraction surgery O:=1:3 were obtained technological indicators, which are presented in table 2 (row 1 - prototype method, line 2 - the proposed method).

250
Table 2
№ p/pThe content in the concentrated solution, g/lThe uranium content, g/lThe purification coefficient of uranium extraction operations
HNO3UFFewater-tail solutionworking extractantFFe
14430912,66,30,0030,005680
2423003,11,60,00250,005260680

The content of impurities in powders octaoxide truran obtained from reextractors by deposition of polyuranates ammonium and subsequent calcination, do not exceed established standards.

A method of processing wrangelstrasse waste, including the production of these solutions, the stage of concentration of solutions by precipitation of uranium and the subsequent dissolution of the precipitate in nitric acid, the extraction of uranium from concentrated solutions using tributyl phosphate in a hydrocarbon diluent, reextraction and deposition of polyuranates ammonium received reextractors, characterized in that the deposition of uranium on the stage of concentration carried out with sodium hydroxide at pH 9-10 and the temperature of 60-90°C.



 

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