A three-cycle process for extracting strontium and americium from high-level liquid waste

Abstract

The present application relates to the field of nuclear chemical technology, and particularly relates to a three-cycle process for extracting strontium and americium from high-level liquid waste. The present application uses an extractant TODGA, and designs a new extraction process (SAREX process) with three cycles, which integrates the extraction of strontium and americium in high-level liquid waste, and simultaneously obtains strontium products and americium products. The SAREX process includes an americium cycle (I), an americium cycle (II) and a strontium extraction cycle; wherein the americium cycle (I) includes three process steps of extracting americium, removing impurities and stripping americium; the americium cycle (II) includes three process steps of extracting americium, regulating and controlling, and stripping americium; and the strontium extraction cycle includes process steps of extracting strontium, regulating and controlling, and stripping strontium. The extractant TODGA used in the process of the present application is easy to obtain, has good stability, and is conducive to the industrialization of the process; and the strontium extraction part does not add a masking agent or other complexing agent, which increases safety and reduces the difficulty of waste liquid treatment.

Description

Technical Field

[0001] This invention relates to the field of nuclear chemical technology, and in particular to a three-cycle process for extracting strontium and americium from high-level radioactive waste. Background Technology

[0002] High-level radioactive waste (HLLW) refers to waste liquid containing various highly radioactive elements generated after spent fuel has undergone the PUREX process. Its main components include actinide elements (americium and curium, etc.) and fragmented elements (strontium, cesium, lanthanides, zirconium, molybdenum, palladium, iron, etc.). Some of these elements have important applications in military and medical fields, such as strontium-90 (…). 90 Sr), can be used in nuclear batteries to provide continuous power for deep-sea exploration and remote or harsh environments. Sr-90-based yttrium generation is an important radioactive source for cancer therapy, treating liver cancer, lung cancer, etc. Americium-241 / 243 ( 241 Am, 243 Strontium (Am) is a raw material for smoke detectors, detectors, neutron source production, and nuclear batteries, possessing high economic and application value. Extracting Strontium-90 and Americium-241 / 243 from high-level radioactive waste not only fully utilizes their value but also reduces the difficulty of high-level radioactive waste treatment. However, due to the complex composition of high-level radioactive waste, separating and extracting Strontium and Americium from it is extremely challenging.

[0003] Existing technology CN201910033588.3 discloses a technique for extracting strontium from solution using N,N-di-p-tolyl-2,6-pyridinedicarboxamide as an extractant. The key feature is that water is used as the back-extraction agent for the back-extraction of strontium in the organic phase, ultimately separating the aqueous phase to obtain strontium. CN201810430465.9 discloses an extractant and extraction method for extracting strontium from high-level radioactive waste, where the extractant is an amide ether compound. However, my country has not yet achieved industrial-scale strontium extraction; therefore, researching a strontium extraction process with industrial feasibility and simple technology is urgently needed. Americium extraction remains a global challenge, and there are currently no reports of industrial-scale americium extraction technologies both domestically and internationally. Therefore, americium extraction technology is also a critical problem that urgently needs to be solved.

[0004] The integrated extraction of strontium and americium (Strontium and Americium Recovery by Extraction, SAREX) not only enables the separate extraction of strontium and americium, but also simplifies the extraction process, standardizes the extraction solvent, and increases industrial feasibility. It is a key breakthrough, a novel, and advanced process for the extraction of these two nuclides. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a three-cycle process for extracting strontium and americium from high-level radioactive waste. This invention utilizes the extractant N,N,N'N'-tetraoctyl-3-oxaprandiamide (TODGA) and designs a novel three-cycle extraction process (SAREX process) to extract strontium and americium from high-level radioactive waste in an integrated manner, simultaneously obtaining strontium and americium products. The SAREX process comprises three stages: americium cycle (I), americium cycle (II), and strontium extraction cycle. Americium cycle (I) includes three steps: americium extraction, impurity removal, and americium back-extraction; americium cycle (II) includes three steps: americium extraction, regulation, and americium back-extraction; notably, the regulation step in these three steps can sometimes be omitted; the strontium extraction cycle includes strontium extraction, regulation, and strontium back-extraction, and the regulation step in these three steps can sometimes be omitted.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention provides a three-cycle process for extracting strontium and americium from high-level radioactive waste, characterized by comprising the following steps:

[0008] (1) The high-level radioactive waste liquid was extracted using the TODGA-TBP-kerosene extraction system to obtain the first organic phase and the first aqueous phase;

[0009] The first organic phase contains elements with a high distribution ratio, while the first aqueous phase contains elements with a low distribution ratio.

[0010] (2) The first organic phase was washed with a cleaning agent to remove some of the fragmented impurity elements, resulting in the second organic phase and the second aqueous phase.

[0011] (3) The second organic phase is back-extracted using a back-extracting agent to obtain a third organic phase and a third aqueous phase: the first americium solution;

[0012] (4) After pretreatment of the third aqueous phase, extraction was performed using the TODGA-TBP-kerosene extraction system to obtain the fourth organic phase and the fourth aqueous phase;

[0013] (5) The fourth organic phase is back-extracted using a back-extraction agent to obtain the fifth organic phase and the fifth aqueous phase: the second americium solution;

[0014] (6) The first aqueous phase was extracted using the TODGA-TBP-kerosene extraction system to obtain the sixth organic phase and the sixth aqueous phase;

[0015] The sixth organic phase contains strontium, and the sixth aqueous phase contains various impurity elements.

[0016] (7) The sixth organic phase is back-extracted using a back-extraction agent to obtain a strontium-containing extract, thereby achieving the extraction of strontium.

[0017] In one embodiment of the present invention, in step (1), the high-level radioactive waste liquid is the high-level radioactive waste liquid generated in the PUREX process of spent fuel reprocessing, and the concentration of nitric acid is 2.5 mol / L to 4 mol / L.

[0018] In one embodiment of the present invention, in step (1), the elements with a high distribution ratio include americium, curium, lanthanides, zirconium, palladium and yttrium, etc.; the elements with a low distribution ratio include strontium, cesium, ruthenium, molybdenum, iron, nickel and sodium, etc.

[0019] In one embodiment of the present invention, in step (1), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.03 mol / L to 0.08 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L.

[0020] The volume ratio of the TODGA-TBP-kerosene extraction system to the high-level radioactive waste liquid is 1:1 to 1:3.

[0021] In one embodiment of the present invention, in step (2), the impurity removal washing reagent is selected from one of oxalic acid, HEDTA, CDTA, DTPA or nitric acid, preferably nitric acid;

[0022] Washing can be done once or twice;

[0023] The volume ratio of the washing reagent to the first organic phase is 1:1 to 3:1.

[0024] In one embodiment of the present invention, when the washing reagent is oxalic acid, the concentration of oxalic acid is 0.2 mol / L to 0.5 mol / L;

[0025] When the washing reagent is HEDTA, the concentration of HEDTA is 0.03 mol / L to 1 mol / L;

[0026] When the washing reagent is CDTA, the concentration of CDTA is 0.03 mol / L to 1 mol / L;

[0027] When the washing reagent is DTPA, the concentration of DTPA is 0.03 mol / L to 1 mol / L;

[0028] When the washing reagent is nitric acid, the concentration of nitric acid is 2 mol / L to 4 mol / L.

[0029] In one embodiment of the present invention, the cleavage impurity elements are zirconium, strontium, molybdenum and other cleavage elements and light lanthanide elements.

[0030] In one embodiment of the present invention, in step (3), the stripping agent is dilute nitric acid or DTPA, preferably dilute nitric acid;

[0031] The volume ratio of the stripping agent to the second organic phase is 1:1 to 1:2.

[0032] In one embodiment of the present invention, when the stripping agent is dilute nitric acid, the concentration of the dilute nitric acid is 0.001 mol / L to 0.1 mol / L;

[0033] When the stripping agent is DTPA, the concentration of DTPA is 0.01 mol / L to 0.02 mol / L, and the pH is 2 to 5.

[0034] In one embodiment of the present invention, in step (4), the pretreatment is a concentration treatment, or a concentration treatment and an acidity adjustment treatment;

[0035] The concentration process is selected from either membrane concentration or evaporative concentration, with a concentration factor of 10 to 40 times;

[0036] During the acidity adjustment process, the target concentration for acidity adjustment in the third aqueous phase is 2 mol / L to 4 mol / L.

[0037] In one embodiment of the present invention, nitric acid is used for acidity adjustment;

[0038] The concentration of the nitric acid is 14 mol / L to 16 mol / L.

[0039] In one embodiment of the present invention, in step (4), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.3 mol / L to 0.5 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L;

[0040] The volume ratio of the TODGA-TBP-kerosene extraction system to the third aqueous phase is 1:1 to 1:3.

[0041] In one embodiment of the present invention, in step (5), the stripping agent is 2,6-bis(5,6-bis(sulfonylmethane)-1,2,4-triazine-3-yl)-pyridine (SO3-Ph-BTP), and the volume ratio of the stripping agent to the fourth organic phase is 1:1 to 1:1.5;

[0042] The concentration of the 2,6-bis(5,6-bis(sulfophenyl)-1,2,4-triazin-3-yl)-pyridine is 0.01 mol / L to 0.05 mol / L;

[0043] The stripping agent is used in a nitric acid environment with a nitric acid concentration of 0.2 mol / L to 1 mol / L.

[0044] In one embodiment of the present invention, in step (6), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.18 mol / L to 0.35 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L.

[0045] The volume ratio of the TODGA-TBP-kerosene extraction system to the first aqueous phase is 1:1 to 1:3.

[0046] In one embodiment of the present invention, in step (6), the impurity elements include cesium, ruthenium, molybdenum, barium, iron, nickel and sodium.

[0047] In one embodiment of the present invention, in step (7), the acidity of the sixth organic phase is adjusted and washed using dilute nitric acid with a concentration of 0.5 mol / L to 1.5 mol / L;

[0048] The back-extraction reagent is selected from one of dilute nitric acid, EDTA-2Na, CDTA, and DTPA;

[0049] When the stripping reagent is dilute nitric acid, the concentration of the dilute nitric acid is 0 mol / L to 0.1 mol / L, and the concentration of the dilute nitric acid is not 0.

[0050] When the back-extraction reagent is EDTA-2Na, the concentration of EDTA-2Na is 0.015 mol / L to 0.3 mol / L;

[0051] When the back-extraction reagent is CDTA, the concentration of CDTA is 0.005 mol / L to 0.02 mol / L;

[0052] When the back-extraction reagent is DTPA, the concentration of DTPA is 0.005 mol / L to 0.02 mol / L;

[0053] During the back-extraction process, the volume ratio of the back-extractant to the sixth organic phase is 1:1 to 1:2.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] (1) This invention uses only one extractant, TODGA, to achieve the simultaneous extraction of strontium and americium. The reagent system is simple, easy to industrialize, and conducive to waste liquid treatment.

[0056] (2) The extraction process designed in this invention is a completely new process with a simple technology;

[0057] (3) The extractant TODGA used in this invention is easy to obtain and has good stability, which is conducive to the industrialization of this process;

[0058] (4) The americium back-extraction agent SO3-Ph-BTP used in this invention has high selectivity and can effectively separate americium and lanthanide elements;

[0059] (5) The strontium extraction part of the present invention does not add masking agents or other complexing agents, which increases safety and reduces the difficulty of waste liquid treatment. Attached Figure Description

[0060] Figure 1 This is a three-cycle process flow diagram for extracting strontium and americium from high-level radioactive waste liquid according to the present invention;

[0061] Figure 2 This is a flow chart of the three-cycle process for extracting strontium and americium from high-level radioactive waste liquid in Example 1;

[0062] Figure 3 This is a flow chart of the three-cycle process for extracting strontium and americium from high-level radioactive waste liquid in Example 2. Detailed Implementation

[0063] This invention provides a three-cycle process for extracting strontium and americium from high-level radioactive waste, characterized by comprising the following steps:

[0064] (1) The high-level radioactive waste liquid was extracted using the TODGA-TBP-kerosene extraction system to obtain the first organic phase and the first aqueous phase;

[0065] The first organic phase contains elements with a high distribution ratio, while the first aqueous phase contains elements with a low distribution ratio.

[0066] (2) The first organic phase was washed with a cleaning agent to remove some of the fragmented impurity elements, resulting in the second organic phase and the second aqueous phase.

[0067] (3) The second organic phase is back-extracted using a back-extracting agent to obtain a third organic phase and a third aqueous phase: the first americium solution;

[0068] (4) After pretreatment of the third aqueous phase, extraction was performed using the TODGA-TBP-kerosene extraction system to obtain the fourth organic phase and the fourth aqueous phase;

[0069] (5) The fourth organic phase is back-extracted using a back-extraction agent to obtain the fifth organic phase and the fifth aqueous phase: the second americium solution;

[0070] (6) The first aqueous phase was extracted using the TODGA-TBP-kerosene extraction system to obtain the sixth organic phase and the sixth aqueous phase;

[0071] The sixth organic phase contains strontium, and the sixth aqueous phase contains various impurity elements.

[0072] (7) The sixth organic phase is back-extracted using a back-extraction agent to obtain a strontium-containing extract, thereby achieving the extraction of strontium.

[0073] In one embodiment of the present invention, in step (1), the high-level radioactive waste liquid is the high-level radioactive waste liquid generated in the PUREX process of spent fuel reprocessing, and the concentration of nitric acid is 2.5 mol / L to 4 mol / L.

[0074] In one embodiment of the present invention, in step (1), the elements with a high distribution ratio include americium, curium, lanthanides, zirconium, palladium and yttrium, etc.; the elements with a low distribution ratio include strontium, cesium, ruthenium, molybdenum, iron, nickel and sodium, etc.

[0075] In one embodiment of the present invention, in step (1), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.03 mol / L to 0.08 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L.

[0076] The volume ratio of the TODGA-TBP-kerosene extraction system to the high-level radioactive waste liquid is 1:1 to 1:3.

[0077] In one embodiment of the present invention, in step (2), the impurity removal washing reagent is selected from one of oxalic acid, HEDTA, CDTA, DTPA or nitric acid, preferably nitric acid;

[0078] Washing can be done once or twice;

[0079] The volume ratio of the washing reagent to the first organic phase is 1:1 to 3:1.

[0080] In one embodiment of the present invention, when the washing reagent is oxalic acid, the concentration of oxalic acid is 0.2 mol / L to 0.5 mol / L;

[0081] When the washing reagent is HEDTA, the concentration of HEDTA is 0.03 mol / L to 1 mol / L;

[0082] When the washing reagent is CDTA, the concentration of CDTA is 0.03 mol / L to 1 mol / L;

[0083] When the washing reagent is DTPA, the concentration of DTPA is 0.03 mol / L to 1 mol / L;

[0084] When the washing reagent is nitric acid, the concentration of nitric acid is 2 mol / L to 4 mol / L.

[0085] In one embodiment of the present invention, the cleavage impurity elements are zirconium, strontium, molybdenum and other cleavage elements and light lanthanide elements.

[0086] In one embodiment of the present invention, in step (3), the stripping agent is dilute nitric acid or DTPA, preferably dilute nitric acid;

[0087] The volume ratio of the stripping agent to the second organic phase is 1:1 to 1:2.

[0088] In one embodiment of the present invention, when the stripping agent is dilute nitric acid, the concentration of the dilute nitric acid is 0.001 mol / L to 0.1 mol / L;

[0089] When the stripping agent is DTPA, the concentration of DTPA is 0.01 mol / L to 0.02 mol / L, and the pH is 2 to 5.

[0090] In one embodiment of the present invention, in step (4), the pretreatment is a concentration treatment, or a concentration treatment and an acidity adjustment treatment;

[0091] The concentration process is selected from either membrane concentration or evaporative concentration, with a concentration factor of 10 to 40 times;

[0092] During the acidity adjustment process, the target concentration for acidity adjustment in the third aqueous phase is 2 mol / L to 4 mol / L.

[0093] In one embodiment of the present invention, nitric acid is used for acidity adjustment;

[0094] The concentration of the nitric acid is 14 mol / L to 16 mol / L.

[0095] In one embodiment of the present invention, in step (4), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.3 mol / L to 0.5 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L;

[0096] The volume ratio of the TODGA-TBP-kerosene extraction system to the third aqueous phase is 1:1 to 1:3.

[0097] In one embodiment of the present invention, in step (5), the stripping agent is 2,6-bis(5,6-bis(sulfonylmethane)-1,2,4-triazine-3-yl)-pyridine (SO3-Ph-BTP), and the volume ratio of the stripping agent to the fourth organic phase is 1:1 to 1:1.5;

[0098] The concentration of the 2,6-bis(5,6-bis(sulfophenyl)-1,2,4-triazin-3-yl)-pyridine is 0.01 mol / L to 0.05 mol / L;

[0099] The stripping agent is used in a nitric acid environment with a nitric acid concentration of 0.2 mol / L to 1 mol / L.

[0100] In one embodiment of the present invention, in step (6), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.18 mol / L to 0.35 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L.

[0101] The volume ratio of the TODGA-TBP-kerosene extraction system to the first aqueous phase is 1:1 to 1:3.

[0102] In one embodiment of the present invention, in step (6), the impurity elements include cesium, ruthenium, molybdenum, barium, iron, nickel and sodium.

[0103] In one embodiment of the present invention, in step (7), the acidity of the sixth organic phase is adjusted and washed using dilute nitric acid with a concentration of 0.5 mol / L to 1.5 mol / L;

[0104] The back-extraction reagent is selected from one of dilute nitric acid, EDTA-2Na, CDTA, and DTPA;

[0105] When the stripping reagent is dilute nitric acid, the concentration of the dilute nitric acid is 0 mol / L to 0.1 mol / L, and the concentration of the dilute nitric acid is not 0.

[0106] When the back-extraction reagent is EDTA-2Na, the concentration of EDTA-2Na is 0.015 mol / L to 0.3 mol / L;

[0107] When the back-extraction reagent is CDTA, the concentration of CDTA is 0.005 mol / L to 0.02 mol / L;

[0108] When the back-extraction reagent is DTPA, the concentration of DTPA is 0.005 mol / L to 0.02 mol / L;

[0109] During the back-extraction process, the volume ratio of the back-extractant to the sixth organic phase is 1:1 to 1:2.

[0110] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0111] Unless otherwise specified, all reagents used in the following embodiments are commercially available reagents; and all detection methods and techniques used are conventional detection methods and techniques in the art.

[0112] Example 1

[0113] This embodiment provides a three-cycle process for extracting strontium and americium from high-level radioactive waste liquid, such as... Figure 1 and Figure 2 As shown, it includes the following steps:

[0114] (S1) Americium Cycle (I)

[0115] (S11) Extraction of americium: High-level radioactive waste liquid (high-level radioactive waste liquid generated in the PUREX process of spent fuel reprocessing, containing nitric acid concentration of 3 mol / L) was extracted using a TODGA-TBP-kerosene extraction system (TODGA concentration of 0.05 mol / L and TBP concentration of 0.5 mol / L) to obtain the first organic phase and the first aqueous phase;

[0116] In this process, the ratio of the two phases of extraction is 1:1. Elements with a high partition ratio (including americium, curium, lanthanides, zirconium, palladium, and yttrium, etc.) are extracted into the first organic phase, while elements with a low partition ratio (including strontium, cesium, ruthenium, molybdenum, iron, nickel, and sodium, etc.) remain in the first aqueous phase.

[0117] (S12) First washing of americium: The first organic phase obtained in step (S11) is washed with an oxalic acid-nitric acid solution (oxalic acid concentration of 0.2 mol / L and nitric acid concentration of 3 mol / L) to remove some of the fragment impurity elements (mainly zirconium);

[0118] In the washing process, the ratio of the two components is 1:1.

[0119] (S13) Secondary washing of americium: The first organic phase after the first washing in step (S12) is washed with dilute nitric acid with a concentration of 3 mol / L to remove some light lanthanide element impurities (including lanthanum, cerium, praseodymium and neodymium) to obtain the second organic phase and the second aqueous phase.

[0120] In the washing process, the ratio of the two components is 1:1.

[0121] (S14) Back-extraction of americium: Using a DTPA solution with a concentration of 0.015 mol / L and a pH of 2-3, the second organic phase obtained in step (S13) is back-extracted to obtain a third organic phase and a third aqueous phase (the first americium solution);

[0122] (S2) Americium Cycle (II)

[0123] (S21) Extraction of americium: The third aqueous phase obtained in step (S14) is concentrated by membrane (concentrated 30 times), and 14 mol / L nitric acid is added to adjust the target acidity to 3 mol / L. The americium is extracted again into the organic phase using a TODGA-TBP-kerosene extraction system (TODGA concentration is 0.4 mol / L, TBP concentration is 0.5 mol / L), resulting in a fourth organic phase (organic phase 1-2) and a fourth aqueous phase (aqueous phase 1-2).

[0124] (S22) Acid adjustment: Wash the fourth organic phase obtained in step (S21) with dilute nitric acid with a concentration of 0.5 mol / L.

[0125] (S23) Americium back-extraction: Americium is back-extracted from the fourth organic phase after step (S22) using a 0.02 mol / L SO3-Ph-BTP solution (used in a nitric acid environment with a nitric acid concentration of 0.5 mol / L) to obtain a fifth organic compound and a fifth aqueous phase (americium product).

[0126] (S3) Strontium extraction cycle

[0127] (S31) Extraction of strontium: Using the TODGA-TBP-kerosene extraction system (TODGA concentration of 0.2 mol / L, TBP concentration of 0.5 mol / L) to extract the first aqueous phase obtained in step (S11), a sixth organic phase (organic phase 1-3) and a sixth aqueous phase (aqueous phase 1-3) are obtained.

[0128] In the extraction operation, the ratio of the two phases is 1:1; strontium is extracted to the sixth organic phase, while impurity elements (including cesium, ruthenium, molybdenum, barium, iron, nickel, and sodium) remain in the sixth aqueous phase.

[0129] (S32) Strontium back-extraction: Strontium is back-extracted using the sixth organic phase obtained in step (S31) with dilute nitric acid at a concentration of 0.001 mol / L to obtain the strontium product;

[0130] In the back-extraction operation, the ratio of the two components is 1:1; the strontium product is a strontium nitrate solution.

[0131] The product composition of each stage is shown in Table 1.

[0132] Table 1 Elemental Content Table

[0133]

[0134] Example 2

[0135] This embodiment provides a three-cycle process for extracting strontium and americium from high-level radioactive waste liquid, such as... Figure 1 and Figure 3 As shown, it includes the following steps:

[0136] (S1) Americium Cycle (I)

[0137] (S11) Extraction of americium: High-level radioactive waste liquid (high-level radioactive waste liquid generated in the PUREX process of spent fuel reprocessing, containing nitric acid concentration of 3 mol / L) was extracted using a TODGA-TBP-kerosene extraction system (TODGA concentration of 0.08 mol / L and TBP concentration of 0.5 mol / L) to obtain the first organic phase and the first aqueous phase;

[0138] In this process, the ratio of the two phases of extraction is 1:1. Elements with a high partition ratio (including americium, curium, lanthanides, zirconium, palladium, and yttrium, etc.) are extracted into the first organic phase, while elements with a low partition ratio (including strontium, cesium, ruthenium, molybdenum, iron, nickel, and sodium, etc.) remain in the first aqueous phase.

[0139] (S12) First washing of americium: The first organic phase obtained in step (S11) is washed with an oxalic acid-nitric acid solution (oxalic acid concentration of 0.5 mol / L and nitric acid concentration of 3 mol / L) to remove some of the fragment impurity elements (mainly zirconium);

[0140] In the washing process, the ratio of the two components is 1:1.

[0141] (S13) Secondary washing of americium: The first organic phase after the first washing in step (S12) is washed with dilute nitric acid with a concentration of 3 mol / L to remove some light lanthanide element impurities (including lanthanum, cerium, praseodymium and neodymium) to obtain the second organic phase and the second aqueous phase.

[0142] In the washing process, the ratio of the two phases is 1:1.5 (organic phase: aqueous phase).

[0143] (S14) Back-extraction of americium: The second organic phase obtained in step (S13) is back-extracted using a nitric acid solution with a concentration of 0.01 mol / L to obtain a third organic phase and a third aqueous phase (the first americium solution);

[0144] (S2) Americium Cycle (II)

[0145] (S21) Americium purification: The third aqueous phase obtained in step (S14) is concentrated by membrane (30 times concentration), and the acidity is adjusted to the target acidity of 3 mol / L with 16 mol / L nitric acid. Then, it is extracted with a TODGA-TBP-kerosene extraction system (TODGA concentration is 0.5 mol / L, TBP concentration is 0.5 mol / L). At the same time, SO3-Ph-BTP (concentration is 0.02 mol / L) is used to complex americium to obtain a fourth organic phase and a fourth aqueous phase.

[0146] In this process, heavy lanthanides are re-extracted into the fourth organic phase, while americium is complexed into the fourth aqueous phase, thus achieving the purpose of separating and purifying americium.

[0147] (S3) Strontium extraction cycle

[0148] (S31) Extraction of strontium: The first aqueous phase obtained in step (S11) is extracted using the TODGA-TBP-kerosene extraction system (TODGA concentration is 0.2 mol / L, TBP concentration is 0.5 mol / L) to obtain the fifth organic phase (organic phase 1-3) and the fifth aqueous phase (aqueous phase 1-3).

[0149] In the extraction operation, the ratio of the two phases is 1:1; strontium is extracted to the fifth organic phase, while impurity elements (including cesium, ruthenium, molybdenum, barium, iron, nickel, and sodium) remain in the fifth aqueous phase.

[0150] (S32) Adjustment: Wash the fifth organic phase with 0.8 mol / L dilute nitric acid to remove some impurity elements entrained in the fifth organic phase and adjust the acidity.

[0151] (S33) Strontium back-extraction: Strontium is back-extracted using the fifth organic phase after the back-extraction step (S32) with dilute nitric acid at a concentration of 0.001 mol / L to obtain the strontium product;

[0152] In the back-extraction operation, the ratio of the two components is 1:1; the strontium product is a strontium nitrate solution.

[0153] The results obtained in this embodiment are at the same level as those obtained in Embodiment 1.

[0154] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A three-cycle process for extracting strontium and americium from high-level radioactive wastewater, characterized in that, Includes the following steps: (1) The high-level radioactive waste liquid was extracted using the TODGA-TBP-kerosene extraction system to obtain the first organic phase and the first aqueous phase; In step (1), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.03 mol / L to 0.08 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L; the volume ratio of the TODGA-TBP-kerosene extraction system to the high-level radioactive waste liquid is 1:1 to 1:

3. (2) The first organic phase was washed with a cleaning agent to remove some of the fragmented impurity elements, resulting in the second organic phase and the second aqueous phase. (3) The second organic phase is back-extracted using a back-extracting agent to obtain a third organic phase and a third aqueous phase: the first americium solution; (4) After pretreatment of the third aqueous phase, extraction was performed using the TODGA-TBP-kerosene extraction system to obtain the fourth organic phase and the fourth aqueous phase; In step (4), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.3 mol / L to 0.5 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L; the volume ratio of the TODGA-TBP-kerosene extraction system to the third aqueous phase is 1:1 to 1:

3. (5) The fourth organic phase is back-extracted using a back-extraction agent to obtain the fifth organic phase and the fifth aqueous phase: the second americium solution; (6) The first aqueous phase was extracted using the TODGA-TBP-kerosene extraction system to obtain the sixth organic phase and the sixth aqueous phase; In step (6), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.18 mol / L to 0.35 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L; the volume ratio of the TODGA-TBP-kerosene extraction system to the first aqueous phase is 1:1 to 1:

3. (7) The sixth organic phase is back-extracted using a back-extraction agent to obtain a strontium-containing extract, thereby achieving the extraction of strontium.

2. The three-cycle process for extracting strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (1), the high-level radioactive waste liquid is the high-level radioactive waste liquid generated in the PUREX process of spent fuel reprocessing, and contains nitric acid with a concentration of 2.5 mol / L to 4 mol / L.

3. The three-cycle process for extracting strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (2), the impurity removal washing reagent is selected from one of oxalic acid, HEDTA, CDTA, DTPA or nitric acid; Washing can be done once or twice; The volume ratio of the washing reagent to the first organic phase is 1:1 to 3:

1.

4. The three-cycle process for extracting strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (3), the stripping agent is dilute nitric acid or DTPA; The volume ratio of the stripping agent to the second organic phase is 1:1 to 1:

2.

5. The three-cycle process for extracting strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (4), the pretreatment is a concentration treatment, or a concentration treatment and an acidity adjustment treatment; The concentration process is selected from either membrane concentration or evaporative concentration, with a concentration factor of 10 to 40 times; During the acidity adjustment process, the target concentration for acidity adjustment is 2 mol / L to 4 mol / L.

6. The three-cycle process for extracting strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (5), the stripping agent is 2,6-bis(5,6-bis(sulfonylmethane)-1,2,4-triazine-3-yl)-pyridine (SO3-Ph-BTP), and the volume ratio of the stripping agent to the fourth organic phase is 1:1 to 1:1.

5.

7. The three-cycle process for extracting strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (7), the sixth organic phase is washed and its acidity is adjusted using dilute nitric acid with a concentration of 0.5 mol / L to 1.5 mol / L; The back-extraction reagent is selected from one of dilute nitric acid, EDTA-2Na, CDTA, and DTPA; During the back-extraction process, the volume ratio of the back-extractant to the sixth organic phase is 1:1 to 1:2.

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