A method for enriching uranium from a mixed solution of uranium and rare earth

Abstract

The present invention discloses a method for enriching uranium from a mixed solution of uranium and rare earth. The method comprises adding a mixed sample of rare earth ions and uranium into a specific solvent, wherein uranium is concentrated in the solution in the form of uranyl ions (UO2 2+ ) in the form of uranium; then the solution is added to a column containing an adsorbent for separation by solid phase extraction mode; first, a specific eluent is used to separate the rare earth ions, and then an inorganic acid is used as an eluent to wash the column to obtain uranyl. The present invention uses a simple column chromatography separation technology to separate uranium and rare earth mixtures, and finally achieves uranium enrichment. The technology is simple to operate, can quickly achieve the separation of uranium and rare earth, and has high selectivity, and can finally enrich uranium with a purity of more than 99.9%.

Description

Technical Field

[0001] The invention relates to the technical field of metal separation and purification, and in particular to a method for enriching uranium from a mixed solution of uranium and rare earth. Background Art

[0002] In order to understand the atomic changes and energy generated before and after nuclear fuel irradiation in order to control the reactor, the study of nuclear fuel burnup has been started since the 1960s. Burnup measurement can be used to analyze various physical parameters of the reactor, providing a reliable means to improve the operating efficiency of the reactor, the yield and quality of isotopes, etc. The key issue of burnup measurement is to measure the fissile heavy nuclei such as uranium-235 and plutonium-239 and select fission products that can represent the actual burnup depth. Internationally, this representative fission product is usually called a burnup detector. About 96% of the mass of the burning nuclear fuel is unreacted uranium, about 1% of the mass is plutonium, and the remaining 3% is various fission products. Fission products that are easy to migrate are obviously not suitable for burnup detectors. It has been determined that zirconium and rare earths are the only major fission products that do not migrate relative to uranium and plutonium during irradiation. However, zirconium is generally the matrix of nuclear fuel, and its fission products cannot be accurately measured. Therefore, rare earth elements are generally selected as burnup detectors. Since the uranium content is very high relative to the rare earth content, direct measurement will cause the radioactive rays to interfere with each other and cannot be accurately quantified. Burnup measurement requires the separation of uranium and rare earth first, and then the measurement of the uranium and rare earth isotope contents separately through isotope dilution and thermal ionization mass spectrometry.

[0003] Nuclear fuel uranium extracted from natural uranium ore is finally made into nuclear fuel components or military nuclear products through a series of production processes such as acid or alkaline leaching, hydrometallurgy, refining, and isotope separation. Uranium ore and various rare earth impurity elements coexist. The absorption of neutrons by rare earth elements in nuclear fuel will cause neutron loss, affecting 235 U fission chain reaction neutron balance, so minimizing the content of rare earth impurity elements in nuclear fuel is one of the important ways to reduce neutron loss and save uranium resources. The purity of nuclear fuel used in reactors must reach nuclear purity level, that is, the content of rare earth impurity elements that absorb neutrons must be limited below a certain level.

[0004] Spent fuel reprocessing is the most critical link in the later stage of the nuclear fuel cycle. It includes the reprocessing of spent fuel elements after reactor irradiation to separate uranium from plutonium, as well as the treatment, storage and disposal of radioactive waste. First, spent fuel reprocessing can improve the utilization rate of uranium resources and solve the problem of insufficient nuclear fuel resources. Secondly, the separation-transmutation of spent fuel reprocessing can reduce the amount of nuclear waste and optimize waste management. Under the background of the rapid development of nuclear power, the amount of spent fuel discharged from my country's nuclear power plants is constantly increasing, and the capacity of the on-site storage pools of most nuclear power plants has been overloaded. For spent fuel, the international treatment method is to reprocess the spent fuel, recover the uranium and plutonium in it, and then process it into fuel assemblies for reuse, which is called "closed nuclear fuel cycle". my country relies more on foreign "closed nuclear fuel cycle" technology.

[0005] Whether it is to accurately measure nuclear fuel burnup, reduce the content of rare earth impurity elements in nuclear fuel, or the post-processing technology of spent fuel, these technologies are inseparable from the separation of rare earth and uranium and the enrichment of uranium. It has been reported in the literature that the separation of uranium and rare earth elements is achieved by using the difference in physical properties without chemical separation. The commonly used classical methods are carrier fractionation and distillation, but these two methods have poor sensitivity to those elements that form non-volatile or insoluble samples. Therefore, it is best to chemically separate uranium and rare earth, that is, to use the difference in chemical properties between uranium and rare earth impurity elements to achieve the separation of the two. The methods widely used in the nuclear industry to separate uranium and rare earth elements are mainly precipitation, solvent extraction and extraction chromatography. Summary of the invention

[0006] The problem to be solved by the present invention is to provide a method for enriching uranium from a mixed solution of uranium and rare earths, which is simple to operate, can quickly separate uranium and rare earths, has high selectivity, and can ultimately enrich uranium with a purity of more than 99.9%.

[0007] The present invention provides a technical solution to solve the above problems: a method for enriching uranium from a mixed solution of uranium and rare earth, the method comprising:

[0008] A mixed sample of rare earth ions and uranium is added to a specific solvent, in which uranium is present in the solution as uranyl ions (UO 2 2+ ) in the form of;

[0009] The above solution is then loaded into a column filled with adsorbent;

[0010] First, the column is flushed with an eluent to separate the rare earth elements;

[0011] Finally, the column is washed with an eluent to obtain the uranyl radical.

[0012] Preferably, the separation process is dynamic adsorption, i.e., solid phase extraction mode.

[0013] Preferably, the mass ratio of uranium to other rare earth ions in the mixed sample is 1000 / 1 to 1 / 1000.

[0014] Preferably, the adsorbent is a hydrophobic porous resin material.

[0015] Preferably, the hydrophobic porous resin material is polymerized by a hydrophobic monomer and a hydrophilic monomer; the volume ratio of the hydrophobic monomer to the hydrophilic monomer is 1 / 2 to 5 / 2; the hydrophobic monomer is a combination of one or more of divinylbenzene, styrene, vinyltrimethoxysilane, and perfluoropolyether; the hydrophilic monomer is a combination of one or more of N-vinylpyrrolidone, polyethylene glycol, pyridine, and 1-vinylimidazole.

[0016] Preferably, the pore size of the adsorbent is ; Particle size is 10-300μm; Specific surface area is 50-1000m 2 / g.

[0017] Preferably, the specific solvent and eluent are one or more combinations of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, α-hydroxyisobutyric acid, 2-hydroxy-2-methylbutyric acid, lactic acid, citric acid, nitrilotriacetic acid, diglycolic acid, etc.

[0018] Preferably, the concentration of the specific solvent and eluent is 50-1000 mM, and the pH is 2.0-8.0.

[0019] Preferably, the eluent is an acid; the acid is one or more combinations of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, etc.

[0020] Preferably, the concentration of the acid is 0.1-12M.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] 1. High selectivity. The present invention focuses on solving the separation of rare earth and uranium. The separation efficiency of uranium and rare earth is high. The present invention adopts a simple column chromatography separation method, and the final uranium yield and purity are high.

[0023] 2. High repeatability. The repeatability is very good within the allowable error range.

[0024] 3. Simple process: The separation process is simple and has strong operability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 Ion chromatography for UO testing in Example 1 2 2+ And chromatograms of four light rare earth elements.

[0027] Figure 2 Ion chromatography for UO testing in Example 2 2 2+ And chromatograms of four heavy rare earth elements.

[0028] Figure 3 Ion chromatography for UO testing in Example 3 2 2+ And chromatograms of eight rare earths (La, Sm, Eu, Gd, Tb, Dy, Ho, Lu).

[0029] Figure 4 A diagram of a solid phase extraction device provided for an embodiment of the invention. DETAILED DESCRIPTION

[0030] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0031] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0032] It should also be understood that the terms used in this description of the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the embodiments of the present invention. As used in the description of the embodiments of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms of "a", "an" and "the" are intended to include plural forms.

[0033] Example 1

[0034] Using solid phase extraction device ( Figure 4 ), using porous hydrophobic resin materials to separate a mixture of uranium and four light rare earth elements La, Ce, Pr, and Nd.

[0035] a) Stock solution (loading solution): UO 2 2+ (concentration of 800ppm) and a mixture of four light rare earths (La, Ce, Pr, Nd concentrations of 80ppm each) were dissolved in 400mM, pH=5.5 HIBA solution.

[0036] b) Column packing: Pack the filler into the column with a column bed size of 1.58*2cm and a column volume of about 4mL.

[0037] c) Activation: Activate with 100% methanol, the volume used is 3BV; then activate with pure water, the volume used is 3BV.

[0038] d) Equilibration: Wash the column with 400 mM HIBA (pH = 5.5) solution, the volume used is 3 BV.

[0039] e) Loading: Rinse the column with the original solution (loading solution), the volume used is 1BV, and collect 1 tube of effluent.

[0040] f) Elution: rinse the column with 100 mM HIBA (pH = 5.5), elute 2 BV, and collect 2 tubes of eluent.

[0041] g) Elution: Wash the column with 1 mol / L hydrochloric acid, elute 2BV, and collect 2 tubes of eluate.

[0042] like Figure 1 As shown in Table 1, under the conditions of dissolving the sample in 400 mM, pH = 5.5 α-hydroxyisobutyric acid (HIBA) aqueous solution, uranyl (UO 2 2+ ) can be completely adsorbed on the porous hydrophobic resin material (>99.7%), most of the light rare earth is adsorbed by the filler, and a small part of the rare earth flows through with the solution. 100mM HIBA (pH=5.5) aqueous solution can completely elute the rare earth, of which a small part of UO 2 2+ Hydrochloric acid elutes most of the uranyl ions, with a recovery rate of over 90%, and the rare earth content is very small, and the uranium purity is greater than 99.9%.

[0043] Table 1

[0044]

[0045] Example 2

[0046] A solid phase extraction device is used to separate a mixture of uranium and four heavy rare earth elements, Lu, Yb, Tm and Er, using a porous hydrophobic resin material.

[0047] a) Stock solution (loading solution): UO 2 2+ A mixture of 1, 2, 3, 4, 5, 8, 7, 8, 9 and 10 heavy earth elements (the concentration of Lu, Yb, Tm and Er were 80 ppm each) was dissolved in a 400 mM HIBA solution with a pH of 5.5.

[0048] b) Column packing: Pack the filler into the column with a column bed size of 1.58*2cm and a column volume of about 4mL.

[0049] c) Activation: Activate with 100% methanol, the volume used is 3BV; then activate with pure water, the volume used is 3BV.

[0050] d) Equilibration: Wash the column with 400 mM HIBA (pH = 5.5) solution, the volume used is 3 BV.

[0051] e) Loading: Rinse the column with the original solution (loading solution), the volume used is 1BV, and collect 1 tube of effluent.

[0052] f) Elution: rinse the column with 100 mM HIBA (pH = 5.5), elute 2 BV, and collect 2 tubes of eluent.

[0053] g) Elution: Wash the column with 1 mol / L hydrochloric acid, elute 2BV, and collect 2 tubes of eluate.

[0054] like Figure 2 As shown in Table 2, under the conditions of dissolving the sample in HIBA solution of 400 mM, pH = 5.5, uranyl ion (UO 2 2+ ) can be completely adsorbed on the porous hydrophobic resin material, most of the heavy rare earth is also adsorbed by the filler, and a small part flows out with the solvent and is detected. Then, the rare earth can be completely eluted from the column with 100mM HIBA (pH=5.5), while UO 2 2+ It cannot be eluted. Hydrochloric acid elutes most of the uranyl radicals, with a recovery rate of more than 90% and a purity greater than 99%.

[0055] Table 2

[0056]

[0057] Example 3

[0058] A solid phase extraction device is used to separate uranium and eight rare earth elements La, Sm, Eu, Gd, Tb, Dy, Ho, and Lu using porous hydrophobic resin materials.

[0059] a) The stock solution (sample solution) is 800ppm UO 2 2+ and 80 ppm of La, Sm, Eu, Gd, Tb, Dy, Ho, Lu were dissolved in 400 mM, pH = 5.5 HIBA solution.

[0060] b) Column packing: Pack the PS-NVP filler into the column with a column bed size of 1.58*2cm and a column volume of about 4mL.

[0061] c) Activation: Activate with 100% methanol, the volume used is 3BV; then activate with pure water, the volume used is 3BV.

[0062] d) Equilibration: Wash the column with 400 mM HIBA (pH = 5.5) solution, the volume used is 3 BV.

[0063] e) Loading: Rinse the column with a stock solution of known concentration (loading solution), the volume used is 1BV, and collect 1 tube of effluent.

[0064] f) Elution: rinse the column with 100 mM HIBA (pH = 5.5), elute 3 BV, and collect 3 tubes of eluent.

[0065] g) Elution: Wash the column with 1 mol / L hydrochloric acid, elute 2BV, and collect 1 tube of eluate.

[0066] like Figure 3 As shown in Table 3, in this embodiment, eight rare earth elements La, Sm, Eu, Gd, Tb, Dy, Ho, and Lu were selected, and a porous hydrophobic resin filler column was used to separate the mixture of the eight rare earth elements and uranyl. The test results show that UO 2 2+ It can be completely adsorbed on the filler, and very little rare earth can be detected in the effluent. The eluent can completely elute the rare earth from the column, but UO 2 2+ It cannot be eluted. Hydrochloric acid elutes most of the uranyl radicals, with a recovery rate of over 97%, and the rare earth content is very low, with a uranium purity of more than 99%.

[0067] Table 3

[0068]

[0069] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. All changes made within the scope of protection of the independent claims of the present invention are within the scope of protection of the present invention.

Claims

1. A method for enriching uranium from a mixed solution of uranium and rare earth, characterized in that: The method comprises A mixture of rare earth and uranium is added to a specific solvent, wherein the mass ratio of uranium to total rare earth elements in the mixture is 1000 / 1 to 1 / 1000, wherein uranium is present in the solution as uranyl ions (UO2 2+ ) in the form of; then the above solution is loaded into a column containing an adsorbent; the column is first rinsed with a specific eluent to separate the rare earth; The specific solvent and eluent are one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, α-hydroxyisobutyric acid, 2-hydroxy-2-methylbutyric acid, lactic acid, citric acid, nitrilotriacetic acid, and diglycolic acid; the concentration of the specific solvent and eluent is 50mM to 1000mM, the pH is 2.0 to 8.0, Then, the column is washed with an eluent to obtain uranyl radicals; the eluent is an inorganic acid; the inorganic acid is one or more combinations of nitric acid, hydrochloric acid, sulfuric acid, and phosphoric acid; The adsorbent is a hydrophobic porous resin material; The hydrophobic porous resin material is polymerized by hydrophobic monomers and hydrophilic monomers; the volume ratio of the hydrophobic monomers to the hydrophilic monomers is 1 / 2 to 5 / 2; the hydrophobic monomers are a combination of one or more of divinylbenzene, styrene, vinyltrimethoxysilane, and perfluoropolyether; the hydrophilic monomers are a combination of one or more of N-vinylpyrrolidone, polyethylene glycol, pyridine, and 1-vinylimidazole.

2. A method for enriching uranium from a mixed solution of uranium and rare earths according to claim 1, characterized in that: The adsorption separation process is dynamic adsorption or static adsorption.

3. The method for enriching uranium from a mixed solution of uranium and rare earth according to claim 1, characterized in that: The pore size of the adsorbent is The particle size is 10μm~300μm; the specific surface area is 50m 2 / g~1000m 2 / g.

4. A method for enriching uranium from a mixed solution of uranium and rare earths according to claim 3, characterized in that: The concentration of the inorganic acid is 0.1M to 12M.

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