Method of recycling waste solutions in production of uranium tetrafluoride

FIELD: chemistry.

SUBSTANCE: invention relates to hydrometallurgy of uranium and can be used to recycle mother solutions formed when producing uranium tetrafluoride from nitrate solutions via extraction, re-extraction and heat treatment of uranium compounds obtained from re-extracts to obtain uranium dioxide and further treatment thereof with chloride and fluoride solutions. The method of recycling mother solutions from production of uranium tetrafluoride involves mixing said solutions at pH 4.0-5.2 by bubbling air until pH stabilises and treating with sodium hydroxide at pH 10.5-11.0, separating the uranium-containing residues from the solutions and return thereof to the step of leaching raw products, settling the waste solutions in a tailing pond and pumping the remaining part of the solutions into the ground.

EFFECT: low consumption of nitric acid, sodium hydroxide and lime, reduced discharge of liquid wastes in the tailing pond.

3 cl, 6 tbl

 

The invention relates to hydrometallurgy uranium and can be used for the disposal of waste solutions in obtaining uranium tetrafluoride (TFU) from nitrate leaching solutions concentrates using the processes of extraction, Stripping and heat treatment of uranium compounds derived from reextractors obtaining uranium dioxide and its subsequent fluoride-chloride solutions.

In the scheme of production TFU (with the extraction refining nitrate leaching solutions by tributyl phosphate (TBP) and subsequent solid-phase by re-extraction solution of ammonium carbonate) uranium is precipitated from solution in the form of crystals of tricarbocyanine ammonium (AUTKA). The precipitate is subjected to calcination to obtain UO2directed at getting TFU by treating it with a solution of a mixture of hydrochloric and hydrofluoric acids.

In this scheme there are three types of waste solutions containing uranium and require special processing:

- refined - nitric acid solutions with concentrations of nitric acid, from 50 to 100 g/DM3on HNO3and uranium up to 100 mg/DM3;

fluoride - chloride uterine solutions (FHM) after receiving TFU with HF concentration up to 5 g/DM3HCl up to 50 g/DM3and uranium up to 8 g/DM3;

- carbonate uterine solutions (KM)formed in achiev is Tate solid-phase uranium Stripping of a saturated TBP and separation of crystals AUTKA containing ammonium carbonate to 60 g/DM 3, uranium up to 8 g/DM3and excess ammonia to 20 g/DM3.

Known methods of utilization of parent uranium production by neutralizing alkaline reagents, followed by the separation of sludge and discharge the clarified part on the site.

The closest analogue to the claimed technical solution is known a method of disposal of circulating solutions of uranium production, including treatment with alkali or lime "milk", Department of uranium precipitation from solution and their return to the stage leaching original products, bleaching waste solutions tailings pond [Sabrekova OG, raw HE Methods of preparation of working solutions the production of uranium tetrafluoride to reset. Materials of scientific-practical conference dedicated to the 50th anniversary of Seversk state technological Academy, may 18-22, 2009, "Technology and automation of atomic energy and industry of TAAP-2009", Seversk, 2009. P.26].

According to the method:

- refined (nitric acid solution) to neutralize the lime "milk" and dumped on the site;

KM is subjected to heating for the destruction of ammonium carbonate and distillation of ammonia and carbon dioxide, VAT residue is treated with lime "milk" to deposition of uranium and filtered, after which the precipitation of the TP is to participate in the process cycle, and the clarified portion of the discharge at dam;

- FHM neutralize lime "milk" or a sodium hydroxide solution and filtered, then the precipitation is returned to the process cycle, the clarified part of the shed on the site.

This processing method allows to prevent waste solutions in surface waters and translate the most toxic and radioactive polyvalent metals from the liquid phase into a solid. After filling the tailings resulting precipitation will be securely isolated from contact with the environment.

The main disadvantages of this method are as follows:

- each type of uterine fluids are processed separately, which leads to unjustified increase in the number of units of equipment, including reactors, clarifiers, filters, etc.;

substantial consumption of reagents, in particular lime, sodium hydroxide and flocculants, electricity, steam;

- high residual uranium content after processing KM (>100 mg/l);

- increased liquid waste on the site due to the dilution of the mother liquor lime "milk";

- a large number of impurities, is returned to the process cycle with selected precipitation (including calcium carbonate coming from lime "milk"), which leads to things is to promote increased consumption of nitric acid when dissolved and lower quality TFU.

The task of the invention is to reduce costs nitric acid, lime and sodium hydroxide, the reduction of energy consumption for processing solutions, the reduction of the discharge of effluents on the site.

The technical result is achieved by the utilization of working mother solutions for the production of uranium tetrafluoride, including the operation of the precipitation of uranium from solution by neutralization, characterized in that the acidic chloride-fluoride uterine fluids from the production of uranium tetrafluoride and/or refined, resulting from the extraction of uranium from nitric acid solutions of organophosphorus compounds, jointly processed carbonate mother liquor produced during uranium Stripping and deposition of tricarbocyanine ammonium, blowing solutions air and dosedanjem uranium sodium hydroxide at a pH value of 8.0 to 12.0.

By neutralizing FHM and/or refined at the first stage of processing to pH 4,0-5,2 spent the greatest amount of neutralizing agent from the total amount required for complete neutralization, so the process is continued until the specified pH range. At lower pH values sharply reduced consumption, pH, increasing the pH above these values leads to incomplete precipitation of uranium from solution. The same is observed for the neutralisation of acidic RA the solutions carbonate liquor to pH values below 4.0. The purge air is required for the destruction of carbonate and bicarbonate ions and remove them from solution in the form of CO2. If the solution is not to expose the air purge, the uranium bound in carbonate complex, deposited will not. At the second stage neutralizing solution (slurry) neutralized with sodium hydroxide solution until a pH value of 8.0 to 12.0. Use sodium hydroxide instead of lime "milk" is due to the fact that with the introduction of NaOH does not happen deposition of fluoride (fluorite), together with uranium. Fluorine almost all (90-95%) remains in solution. Therefore, the return obtained uranium precipitation leaching will not lead to an increase in fluoride concentration in the solution and deterioration of extraction. While maintaining the second stage pH values below 8.0 for decreasing the degree of deposition of uranium above 12.0 - is unreasonable consumption of alkali. By neutralizing with sodium hydroxide pulp air is not blown, as in this case, the effect of increasing the degree of deposition of uranium does not occur.

In the patent and scientific literature there are no data on co-processing waste solutions production TFU. Therefore, the proposed technical solution is characterized by novelty and has significant differences.

Thus, the analysis of the proposed technical re the texts shows between the distinctive features of the proposed method and achieve this result there is a new cause-and-effect relationship: the presence of these signs in the claimed method provides a positive effect, but the absence of these signs does not have effect, the aim of the invention.

Comparison of the performance of the proposed and previously known method (prototype) is shown in the examples.

Example 1. In this example the results, showing the range of values of pH at which there is the most complete precipitation of uranium from the uterine fluid during their joint processing and the necessity of purging air from acidic solutions after neutralization KM.

Jointly processed:

- refined and KM;

- FHM and KM;

- mixtures refined with FHM and KM.

With the aim of studying the dependence of the residual concentration of uranium from the pH values (table 1) raised a number of experiments which were conducted neutralization refined solution of ammonium carbonate (imitator carbonate stock solution) to a certain pH values (pHRef), after that the solution was barotiwala the air to stabilize the pH values (pHCN). In separated from the precipitate solution was determined residual concentration of uranium.

Table 1
The dependence of the residual concentration of uranium (Cu) in the treated solutions from pHRefby neutralizing refined KM, followed by blowing air
№ p/pThe deposition parameters
pHRefpHCNThe amount of uranium in the sediment, gWithandin solution, mg/DM3
13,503,62no1940
23,63,74no1900
33,803,91no1856
43,904,06no1778
54,004,720,140 22,8
64,104,740,14222,6
74,204,750,14422,4
84,305,220,14022,4
94,405,31was 0.13820,2
104,505,420,13621,3
114,605,63of 0.13318,6
124,705,850,13018,6
134,806,260,1368,3
144,90 6,83was 0.1382,5
155,007,13was 0.1381,9
165,10of 7.480,1373,2
175,20the 7.65is 0.13513,9
18and 5.307,720,12840,2
19of 5.40to 7.840,115232,2
205,507,890.104 g382,0

For the experiment was taken in 100 ml of solution with a content of nitric acid 70 g/DM3and uranium 2 g/DM3that was poured into the beakers with a volume of 200 ml In a beaker with the solution was placed in the bubbler. From the burette into the beaker submitted a solution of ammonium carbonate and simultaneously introduced air. Stirring the solution ASU is actulaly with a magnetic stirrer.

The results of the experiments showed that the fully refined uranium from sediments in the area of pHReffrom 4.0 to 5.2. Unbalance in the amount of precipitated uranium and its residual concentration in solution is associated with the dilution due to the introduction of a solution of ammonium carbonate.

It should be noted that no air blowing neutralized solutions of uranium practically not deposited, and only in the region of pH 5, you receive a small suspension with the transition of the uranium precipitate from the solution within 15% of its total number. Further neutralization to a pH of 11.5 with sodium hydroxide does not dosageno uranium.

To increase the degree of extraction of uranium from solution to precipitate the use of the combined deposition: first, after neutralization of the raffinate KM and sparging air to stabilize the pH values (pH1) (the major part of the uranium turns into sludge)left in solution uranium thosedays further neutralization of the alkali solution (20%NaOH) to pH2(table 2).

Table 2
The dependence of the residual concentration of uranium (Cu) in the treated solutions from pHRefby neutralizing refined KM from blowing Vozduha treatment with sodium hydroxide solution
№ p/ppHRefpHCNC0in a mixture of mg/DM3The uranium concentration in solution (mg/DM3) after treatment with sodium hydroxide to pH2
pH 8pH 9pH 10pH 11the pH of 11.5
5.4,004,7222,820,416,16,66,56,5
6.4,305,2222,418,016,06,36,06,0
7.4,405,3120,216,114,16,05,95,9
8.4,505,4221,314,312,210,05,05,0
9.4,605,6318,614,610,29,85,25,2
10.4,705,8518,612,6the 10.19,55,05,0
11.4,806,268,35,54,33,13,12,5
12.4,906,832,51,20,90,80,60,6
13.5,007,131,90,80,70,70,60,6
14.5,10of 7.483,22,01,51,31,00,9
15.5,20the 7.6513,93,33,12,51,41,1
16.and 5.307,7243,340,040,140,240,140,1
17.of 5.40to 7.84232,2104776351 42
18.5,507,89382,0320289177150156

The results of the experiments show that the refined, neutralized KM to pH 4,0-5,2 with bubbling air after additional treatment with sodium hydroxide contain less uranium than without treatment with alkali.

By neutralizing FHM using KM and further passing air through the solution precipitate falls, which is associated with the formation of stable fluoride and chloride complexes of uranyl. At low pH values, these complexes inhibit the transition of uranium in the sediment. Therefore, for the deposition of uranium required neutralization with alkali to higher pH values than in the case of refined. Source FHM (the pH value was 1,81) was neutralized KM values to pHRefthen after the solution was allowed the air to stabilize the pH values (pH1), after which was added alkali (20% solution of NaOH) to pH2. After filtration the solution was analyzed for uranium content. The results of the experiments are presented in table 3.

Table 3
The dependence of the residual concentration of uranium (Cufrom pHRefby neutralizing FHM
rich3,51as 4.024,604,804,905,005,105,20of 5.4
pH14,14,4to 4.624,844,945,035,13of 5.406,0
pH211,6011,5811,6311,6511,60to 11.5611,5911,55the 11.6
Cuin solution, mg/DM3213,517,615,31,711,22 0,980,980,9842,5

The results of the experiments show that using this method, you can achieve a fairly complete precipitation of uranium by neutralizing FHM KM in the region of pH 4,0-5,2.

The following is an example of deposition of uranium from a mixture of all three types of uterine fluids. For this purpose were prepared mixture of nitrate raffinate FHM in volume ratios of 1:1 and 1:2, which then was kind of balanced out KM.

In experiments with mixtures of deposition of uranium simple transmission of air to achieve without success. As in the case with FHM, for the deposition had to use the alkali solution. The experiments were carried out in the same way as with one FHM. The results are presented in tables 4 and 5.

Table 4
The dependence of the residual concentration of uranium (Cufrom pHRefby neutralizing a mixture of refined and FHM in the ratio of 1:1 KM
rich3,50as 4.024,804,905,005,105,205,50
pH1of 3.774,254,87to 4.985,095,185,286,1
pH211,7are 11.6211,6611,5811,59the 11.611,511,44
Cuin solution, mg/DM364,65,522,201,961J11,471,7148,6

5,00
Table 5
The dependence of the residual concentration of uranium (Cufrom pHRefby neutralizing a mixture of refined and FHM in the ratio 1:2 KM
pHRef3,504,004,804,905,105,20the 5.45
pH13,804,224,854,96of 5.055,18and 5.305,55
pH211,6611,60to 11.6111,6011,6011,5811,5511,60
Cuin solution, mg/DM355,73,431,961,961,221,222,4444,35

Example 2. In glasses with a volume of 1 l was placed a stir bar and the electrodes of the pH meter. Three cups were filled with 0.5 l of a production solution raffinate composition major components: nitric acid 60 g/DM3, ammonium nitrate, about 100 g/DM2, uranium 0.11 g/DM2iron 10 g/DM2. In the other four glasses were injected the same amount FHM composition: 40 g/sup> 3hydrochloric acid, 2 g/DM2hydrofluoric acid and 6 g/DM2uranium. For the next experiment used a mixture FHM and the raffinate at a ratio of 1:1 and 2:1. Each of these mixtures was also poured into three glasses.

All of these party solutions subjected to the treatment according to the following schema:

1. Neutralization of 10% lime "milk".

2. Neutralization KM to the value of pH 5.0, followed by neutralization with 20% sodium hydroxide solution until a pH value of 10.5.

3. Neutralization KM to the value of pH 5.0, followed by blowing air for 20-30 min to stabilize the pH values of about 7 and neutralized with 20% sodium hydroxide solution until a pH value of 10.5.

4. In addition to the listed methods of neutralization FHM processed only 20% solution of sodium hydroxide to a pH of 11.5.

MILES had the following composition: ammonium carbonate 79 g/DM3the uranium - 3.2 g/DM3.

As can be seen from the presented results (table 6), with the joint treatment of uterine solutions residual uranium concentration is slightly higher than in the processing of lime or sodium hydroxide.

406
Table 6
The results of processing waste solutions of different methods.
Perera is atively solution The composition of the solutionThe processing circuitry solutionsThe specific reagent consumption, ml/DM3The residual uranium content, mg/DM3The volume of solution after neutralization, ml
The raffinateHNO3- 60 g/DM3, NH4NO395 g/DM3U (VI) 0.11 g/DM3, Fe (III) 10 g/DM31 scheme3803690
2 scheme368 CMR to pH of 4.95+6,6 NaOH1960874,6
scheme 3368 CMR to pH 4.9 purge air to a pH of 6.9+4,2 ml of 20% NaOH to pH 11the 9.7872,2
FHMHCl - 40 g/DM3, HF - 2 g/DM3U (VI) - 6 g/DM31 scheme410About 1705
2 scheme385 CMR to pH of 4.9+6,8 NaOH4150scheme 3385 CMR to pH 4,85 air blowing to pH 6,85+4,5 ml of 20% NaOH to pH 11of 5.4589,5
4 schemea 20% solution of NaOHAbout 1530
The mixture FHM and the raffinate at a ratio of 1:1HNO3- 30 g/DM3, NH4NO347,5 g/DM3HCl - 20 g/DM3, HF - 1 g/DM3, Fe (III) 5 g/DM3U (VI) was 3.05 g/DM31 scheme40010700
2 scheme394 CMR to pH of 4.95+NaOH to 7.22910901,2
scheme 3372 CMR to pH 4.9 air purge to pH 7.0+4,6 ml of 20% NaOH to pH 118,5876,6
A mixture of chloride and fluoride of the mother liquor and the raffinate in the ratio 2:1HNO3- 20 g/DM3, NH4NO331,7 g/DM3HCl - 26,6 g/DM, HF - 1.3 g/DM3, Fe (III) and 3.3 g/DM3U (VI) - a 4.03 g/DM31 scheme4,5703
2 scheme394 CMR to pH of 4.95+NaOH to 7.23000
scheme 3372 CMR to pH 4.9 air purge to pH 7.0+4,6 ml of 20% NaOH to pH 118,1

However, it should be borne in mind that KM after the distillation of ammonia at elevated temperature and subsequent treatment with lime VAT residue contain 60-80 mg/DM3uranium. When mixing all mother solutions after neutralization, the average content of uranium in waste solutions is significantly less than 30-40 mg/DM3.

In the proposed method, in addition to reducing the residual concentration of uranium decreases the total amount of wastewater is about 1.5 times due to the fact that they do not enter the lime milk for neutralisation are used primarily KM.

Thus, by reducing the volume of waste solutions and the concentration of uranium in a significant reduction of the total uranium sent to the tailings pond.

1. The method of disposal of waste fluids production of uranium tetrafluoride, including the operation of the precipitation of uranium from solution by neutralization notable is the acid chloride-fluoride uterine fluids from the production of uranium tetrafluoride and/or refined, resulting from the extraction of uranium from nitric acid solutions of organophosphorus compounds, jointly processed carbonate mother liquor produced during uranium Stripping and deposition of tricarbocyanine ammonium with simultaneous blowing of the neutralized solution with air to stabilize the pH, followed by processing the resulting pulp with sodium hydroxide without air blowing.

2. The method according to claim 1, characterized in that the joint processing of the chloride-fluoride uterine fluids and/or refined spend carbonate mother liquor to pH 4,0-5,2.

3. The method according to claim 2, characterized in that the obtained solution is further processed with sodium hydroxide to a pH of 8.0 to 12.0.



 

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1 cl

FIELD: technology of handling of the liquid nuclear wastes of the nuclear fuel and power cycle; methods of reprocessing of the liquid nuclear wastes.

SUBSTANCE: the invention is pertaining to the procedure of the liquid nuclear wastes handling of the nuclear fuel and power cycle and may be used during reprocessing of the liquid nuclear wastes (LNW). The method includes the preliminary concentration, ozonization, microfiltration of the vat residue with fractionation of the permeate and the concentrate and the ion-selective purification of the permeate using the ion-selective a sorbent. At that the microfiltration is conducted at least in two stages: the permeate of each previous stage of the microfiltration is directed to the microfiltration as the source solution for the subsequent stage of the microfiltration, and at the final stage of the permeate from the microfiltration is sent to the utilization. The concentrate produced at each next stage of the microfiltration is mixed with the source solution of the previous stage of the microfiltration. The concentrate produced at the first stage of the microfiltration is directed to the conditioning and dumping. The ion-selective sorbent is added in the permeate of the previous stage of the microfiltration before the final stage of the microfiltration. The invention ensures: reduction of the volume of the liquid nuclear wastes due to the deep purification of the LNW with the high saline share from the radionuclides and extraction of the radionuclides in the compact form of the sparingly soluble compounds at the corresponding increase of the factor of purification of the salts extracted at the stage of the vat residue treatment; reduction and optimization of the consumption of the permeate and concentrate interacting with the source solution as well as produced at the further stages.

EFFECT: the invention ensures: reduction of the volume of the liquid nuclear wastes; the deep purification of the LNW with the high saline share from the radionuclides and extraction of the radionuclides in the compact form of the sparingly soluble compounds at the corresponding increase of the factor of purification of the salts extracted at the stage of the vat resudue treatment; reduction and optimization of the consumption of the permeate and concentrate interacting with the source solution ands produced at the further stages.

FIELD: environment protection against radioactive pollutants; immobilization of nuclear radioactive wastes.

SUBSTANCE: proposed method for solidifying liquid radioactive wastes includes their spray drying and calcination, calcination product vitrification using flux dopes, melt draining to tank, and annealing of solid block. Liquid radioactive wastes are heated in advance in continuous flow to evaporate 30-80 percentage ratio of water contained in them, and steam-water mixture produced in the process is sprayed under its own pressure in chamber heated to temperature of 600-800 °C. Solid particles of calcination product are separated from steam-gas mixture by sedimentation at temperature below 300 °C and filtration.

EFFECT: extended service life of equipment, enhanced productivity and radiation safety for personnel handling highly radioactive products.

1 cl

FIELD: nuclear engineering; preservation of dry, wet, and liquid radioactive wastes.

SUBSTANCE: proposed composition has resin portion of cold-cured compound ATOMIK and filler. Resin portion ingredients are as follows, parts by weight: epoxy oligomer, 100;, curing agent (aromatic amines), 38-50 furfural, 9-11. Used as filler is composition incorporating following ingredients, parts by weight: cement, 50-100; marshalite, 50-100 or bentonite, 50-100, or when they are jointly used: marshalite, 90-100 and bentonite, 90-100. Such composition provides for desired radiation resistance in absence of leaching of alpha-, beta-, and gamma-active radionuclides from preserved specimens of reactor graphite.

EFFECT: enhanced radiation stability of preserved specimens free from pits and voids, and adequate lifetime of preserved wastes; ability of their depreservation.

1 cl, 2 dwg, 2 tbl, 2 ex

FIELD: treatment of radioactive effluents and solid-phase saturated waters.

SUBSTANCE: some portion of organic fraction is reduced in first reactor by way of biological aerobic treatment. Filtrate/permeate taken from tangential filtering device is either directly used or supplied to first or next reactor. Solid phase is gravitationally extracted within tank of partial-flow filtering device and compacted in bottom region; concentrated effluents flowing from tangential filtering device are fed in next sedimentation region which is above first sedimentation region or above next one through intake channel; then effluents flowing above or from one side of sedimentation region are discharged through branch channel.

EFFECT: ability of selecting and technically optimizing separate modules.

34 cl, 5 dwg

FIELD: recovery of irradiated nuclear fuel.

SUBSTANCE: proposed method for reconditioning reusable extractant includes treatment of the latter with aqueous alkali solution. Extractant containing uranium in amount of minimum 5 g/l is treated with alkali solution whose concentration is over 10 mole/l followed by sediment separation.

EFFECT: reduced radionuclide content of reusable extractant including difficult-to-remove radioactive ruthenium.

5 cl, 2 tbl, 2 ex

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