Method for extracting radioactive elements from liquid wastes

FIELD: recovery of liquid radioactive wastes.

SUBSTANCE: proposed method includes bringing liquid radioactive wastes in contact with matrix saturated with selective ion-exchange material (solid extracting agent). Glass-crystal material with open porous structure is used as matrix for the purpose. Matrix material is produced from hollow glass-crystal cene spheres formed from mineral particles of volatile ash produced as result of black coal combustion and saturated with selective ion-exchange material.

EFFECT: facilitated procedure of radionuclide extraction.

5 cl, 1 tbl, 5 ex

 

The invention relates to the field of processing of liquid radioactive waste (LRW) and can be used in nuclear power. LRW usually along with the fission products and actinides contain significant amounts of non-radioactive salts. Known methods of processing of LRW using porous inorganic materials, in which at different times was studied silica gel (Nardova A.K., Fillippov E.A., Dzekun E.G., Parfanovich B.N. "Technology for Hardening Liquid High-activity Waste by Method of High-temperature Sorption of Radionuclides Using Porous Inorganic Matrices", Journal of Advanced Materials, v.l, No. 1, 1994, p.109-114) [1], porous glass (J.H. Simmons, P.B. Macedo, A. Barkatt, T.A. Litovitz "Fixation of Radioactive Waste in High Silica Glasses", Nature, V.278, 1979, p.729-731) [2] and fireclay (Lazarev, L.N., Kuznetsov, shashukov E.N., Krylov LI and other “Development processes include radioactive waste in glass-ceramic composition and ceramic materials”. The OEWG. Of Int. Symp. on Treatment Radioactive Waste for Interim and Ultimate Storage, Ulrecht, Netherlands, July 21-25, 1982, IAEA, Vienna, 1983, p. 253-263) [3].

There is a method of curing LRW using porous glass-ceramic material on the basis of cenospheres (U.S. Patent 09/721,963, registered 11.27.00) [4]. In the described method, the solidification of liquid radioactive waste is carried out by the inclusion of waste in porous glass crystalline molded block. The porous block is subjected to multiple saturation LRW, drying and after full saturation of calcification for translation salts in bol is stable oxide form. The disadvantages of these methods is the limitation of the capacity of a porous inorganic matrix in relation to radioactive elements due to the high salinity waste non-radioactive elements, resulting in the formation of large amounts of solid compositions, sent to storage and disposal.

To reduce the volume of final waste carry out the separation of radioactive elements from the main volume of waste. For the extraction of radioactive elements can be used in liquid-liquid extraction, resulting in radioactive elements are concentrated in the raffinate. When you enable extractants in a porous matrix-type solid extractants (tax) is the extraction of radioactive elements and their fixation (concentration) in the volume of the matrix, while the non-radioactive components remain in solution.

Closest to the proposed invention is a method of extraction of cesium using molybdophosphate ammonium (AMP), introduced in polyacrylnitrile (PAN) (.J.Tranter, R.S.Herbst, .A.Todd, A.L.Olson and H..Eldredge. "Evaluation and Testing of Ammonium Molybdophosphate-grade polyacrylonitrile (AMP-PAN) as a Cesium Selective Sorbent for the Removal of 137 Cs from Acidic Nuclear Waste Solutions", Advances in Environmental Research, 6 (2), pp.107-121, 2002) [5]. PAN, as usual organic polymer, has a regular porous structure, which provides a good diffusion and hydrodynamic properties.

Under taccom of this method is the need for additional stages - Stripping for separation of radioactive elements in the form of liquid concentrates that are subject to further processing with the aim of curing. The degree of saturation of polyacrylnitrile molybdophosphate ammonium 85 wt.% unlike glass-ceramic cenospheres, for which the maximum saturation of the AMP - 37 wt.%. The degree of extraction of cesium from waste solutions in both cases reaches 95%.

The invention has set itself the task of developing a way to extract radioactive elements using inorganic ion exchange material, which allows to simplify the technological process.

The task is carried out by contacting the liquid waste matrix, intense selective ion exchange material, and as a matrix using a porous glass-ceramic material with an open porous structure obtained from glass-ceramic cenospheres formed from mineral particles of volatile ashes from the combustion of fossil fuels, and rich extractant.

Depending on the radioactive elements that need to be removed, you can apply various extractants. To extract the various elements can be made of the following ion-exchange materials: molybdophosphate ammonium (NH4)3P(Mo3About10)4·3H2O (the MP) for the extraction of cesium, octyl-(phenyl)-n-n-dibutil-carbamoyl-phosphine oxide (CMPO) to extract americium and plutonium resorcinolformaldehyde resin (RFR) for the extraction of cesium and isoamyl-heptyl-nonyl-phosphine oxide radical (FMR) for the extraction of americium and plutonium. The list of selective extractants that can be used in the present invention is not limited to the given examples.

To obtain offered of inorganic ion exchange material using a porous glass-ceramic material with an open porous structure obtained from hollow glass cenospheres formed from the smallest mineral particles of volatile ashes from the combustion of fossil fuels (U.S. Patent 09/721,962, registered 11.27.00) [6]. The diameter of the cenospheres is usually from 0.1 to 0.5 mm, an Average composition of cenospheres used for the porous material includes oxides of the elements inherent in the glass: up to 65 wt.% silicon dioxide, 25 wt.% aluminum oxide and minor amounts of iron, calcium, magnesium, potassium, sodium and titanium oxide (from one to five percent).

The hallmark of the invention is the preparation of the inorganic matrix of cenospheres in the form of a block or bulk mass by introducing into the pores of the respective ion exchange material. After this operation to retrieve the corresponding e the cops is contacting an inorganic matrix with introduced selective material with liquid waste. The operation of the contacting may be carried out both in static and in dynamic mode.

The advantage of using an inorganic matrix compared to any organic, such as PAN, is in no need of Stripping radioactive elements and subsequent mixing reextract with a matrix of inorganic material for compaction, i.e. reducing the number of stages of the process.

Example 1. To obtain the proposed extraction of material blocks of 3 cm3up to 4.5 cm3and open porosity (internal volume of voids between the cenospheres) about 40% and a total porosity (including both open and closed porosity), approximately 60% were saturated AMP. The AMP was dissolved in 5.8 M NH4OH when the ratio of AMP to a solution of NH4OH as 1 g to 5 ml and was injected into cenospheres, ceramic under vacuum. (This stage can be repeated to increase the mass fraction AMP. Preferably 3 cycles of saturation). Then saturated blocks for 2.5 hours were dried at 105° and under vacuum, washed with a solution of 4 M HNO3. Over the AMP was washed from interporous spaces cenospheres by passing through the unit for approximately 10 ml of 2 M HN3. Share AMP averaged 30 wt.%. For carrying out the extraction process in the static mode, the blocks were hung n the wire stainless steel in 120 ml HNO 3containing cesium - 137. With constant stirring initial solution to determine the total concentration of cesium over time, taking aliquots of approximately 0.10 ml, and analyzed their gamma-ray spectrometer. Gamma measurements for these and all other activities Cs137conducted on germanium detector of high purity. The results indicate a significant extraction of cesium in the range from 20 to 60 mg Cs/g AMB entered in the matrix.

Instead of dissolving the AMP in a solution of NH4OH can be used an alternative method of introducing the AMP in the matrix of cenospheres, which is that NH4NO3and (NH4)6Mo7O24mixed in an aqueous solution of citric acid, then add nitric acid and saturate cenospheres, ceramic solution, as described above. When passing through the saturated cenospheres, ceramic dissolved in water (NH4)2HPO4is deposited AMP inside of cenospheres.

Example 2. Blocks consisting of perforated cenospheres, saturated AMP. The parameters of the blocks differed from the previous example, but the method and conditions of saturation of the AMP were the same. The tests were carried out with one or two blocks arranged sequentially according to the type of the column thereby to form a dense packing and to prevent the possibility of leakage of the solution m is mo blocks along the walls. In the original nitrate solution was injected Cs133(1 mg/l) and Cs137. The flow of solution through the block was carried out by gravity from the top of the column at a constant speed 2 or 4 column volume per hour (Ko/h), maintaining a valveless metering pump. Samples were taken periodically output from the column and analyzed by gamma-spectrometer to detect breakthrough of cesium. 50% breakthrough was detected after transmission 1.6 l of the starting solution.

Example 3. Two experiments were performed in static mode with blocks of perforated cenospheres, the saturated octyl(phenyl)-n-n-Diisobutyl-carbamoyl-methyl-phosphine oxide (CMPO). Under vacuum, as described above, was performed saturation blocks, consisting of hollow cenospheres, CMPO, dissolved in hexane or acetone, and then dried at moderate temperatures for evaporation of the solvent. Test parameters:

Experiment No. 1:

Unit: No. 105

CMPO: 0.4149 g

Solvent: Acetone

Drying time: 2 hours at 100°

Original solution: 2.5 M NGO374 Bq/ml Am-241

Temperature: 23°

Experiment No. 2:

Unit: No. 106

CMPO: 0.2854 g

Solvent: Hexane

Drying time: 2 hours 100°

Original solution: 2.5 M HNO3with 70 Bq/ml Am-241

Temperature: 23°

In each experiment, the block was suspended on a stainless steel wire 120 ml source rest the RA. The solution was constantly stirred and after a certain period of time, samples were taken at 0.5 ml, which was analyzed using a gamma spectrometer. The results indicate a significant (90%) extraction of americium from acidic waste in both cases.

Example 4. The experiment in dynamic mode was performed similarly to example 2 described above, with two blocks arranged sequentially. The difference was used in the original solution, which was a model solution of radioactive waste. The average composition of model waste listed in the table. Model solution doped active Cs137(600 Bq/ml)was applied at a rate of 1 to/h Mass loaded AMP - 2.21 g, which amounted to about 35 wt.%.

Table 1
Component(M)Component(M)
AgE-05Na1.9E+00
InE-02Pb1.4E-03
CAE-02Sr2.0E-05
CdE-03Zr9.0E-03
SGE-03 Al7.0E-01
CsE-06-2 E-05SO43.0E-02
FeE-02PO42.04E-02
Hg1.60E-03F6.8E-02
K2.0E-01Cl3.05E-02
Mn1.2E-02HNO31.8
Mo7.3E-04

The results of this experiment showed that using two small blocks of approximately 9 cm3saturated AMP, learned Cs137of the approximately 4.1 l of waste. At the end of the extraction process, the material was processed by the method of the axial hot pressing. The value of the final volume was about 30% of the original, and the total reduction of the volume reached about 1400.

Example 5. The experiment in dynamic mode was performed to verify the ability of the porous glass-ceramic cenospheres to extract the plutonium in a continuous mode. The column was loaded with cenospheres (approximately 6 cm3), saturated 2.86 g CMPO the method described in example 3. In the original 2.5 M HNO the solution was injected into PU-239 with an activity of 100 Bq/ml More than 400 column volumes was omitted at speeds of 1.5, 2.7 and 5.3 to/h before PU-239 was detected at the outlet of the column.

1. The method of extraction of radioactive elements from liquid wastes, including their contact with the matrix, intense selective ion exchange material is a solid extractant, characterized in that the matrix quality use of glass-crystalline material with an open porous structure obtained from hollow glass cenospheres formed from mineral particles of volatile ashes from the combustion of fossil fuels, and intense selective ion exchange material.

2. The method according to p. 1, characterized in that the extraction of radioactive elements cesium as the ion exchange material used molybdophosphate ammonium.

3. The method according to p. 1, characterized in that the extraction of americium and plutonium as the ion exchange material used octyl(phenyl)-n-n-Diisobutyl-carbamoyl-methyl-phosphine oxide or isoamyl-heptyl-nonyl-phosphine oxide radical.

4. The method according to any of paragraphs. 1-3, characterized in that the contacting of the solid extractant liquid waste is carried out in a static mode.

5. The method according to any of paragraphs. 1-3, characterized in that the contacting of the solid extractant liquid waste hold Dean in the economic mode.



 

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FIELD: recovery of liquid radioactive wastes.

SUBSTANCE: proposed method includes bringing liquid radioactive wastes in contact with matrix saturated with selective ion-exchange material (solid extracting agent). Glass-crystal material with open porous structure is used as matrix for the purpose. Matrix material is produced from hollow glass-crystal cene spheres formed from mineral particles of volatile ash produced as result of black coal combustion and saturated with selective ion-exchange material.

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5 cl, 1 tbl, 5 ex

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5 cl, 1 tbl, 7 ex

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35 ex, 9 dwg, 9 tbl, 5 ex

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4 cl, 1 tbl, 11 ex

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2 cl, 10 ex

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11 cl, 3 tbl

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

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1 cl, 2 dwg, 3 tbl

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24 cl, 3 tbl, 6 ex

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