Partitioning americium from an actinide and lanthanide solution during a used nuclear fuel recycling process

Abstract

A method of partitioning americium that includes directing an actinide-lanthanide containing raffinate into a liquid-liquid extraction system, wherein the actinide-lanthanide containing raffinate comprises americum, curium, and one or more lanthanides in an aqueous solvent, contacting the actinide-lanthanide containing raffinate with an organic extracting solution such that the americum, the curium, and the one or more lanthanides bind with the organic extracting solution to form an actinide-lanthanide organic solution, wherein the organic extracting solution comprises an organic neutral extractant, a phase modifier, and a hydrocarbon diluent, and contacting the actinide-lanthanide organic solution with sodium bismuthate in nitric acid such that the sodium bismuthate induces an oxidation state increase in the americum from a first oxidization state to a second oxidation state such that the americum unbinds from the actinide-lanthanide organic solution, thereby partitioning the americum from the curium and the one or more lanthanides.

Description

SHQ0035WO / R24-4-PCT1PARTITIONING AMERICIUM FROM AN ACTINIDE AND LANTHANIDE SOLUTION DURING A USED NUCLEAR FUEL RECYCLING PROCESSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 722,178 filed on November 19, 2024, which is incorporated herein by reference in its entirety.BACKGROUND

[0002] The present disclosure relates generally methods and systems of processing used nuclear fuel.SUMMARY

[0003] According to an embodiment of the present disclosure, a method of partitioning americium includes directing an actinide-lanthanide containing raffinate into a liquid-liquid extraction (LLE) system, wherein the actinide-lanthanide containing raffinate comprises americum, curium, and one or more lanthanides in an aqueous solvent, contacting the actinide-lanthanide containing raffinate with an organic extracting solution such that the americum, the curium, and the one or more lanthanides bind with the organic extracting solution to form an actinide-lanthanide organic solution, wherein the organic extracting solution comprises an organic neutral extractant, a phase modifier, and a hydrocarbon diluent, and contacting the actinide-lanthanide organic solution with sodium bismuthate in nitric acid such that the sodium bismuthate induces an oxidation state increase in the americum from a first oxidization state to a second oxidation state such that the americum unbinds from the actinide-lanthanide organic solution, thereby partitioning the americum from the curium and the one or more lanthanides.

[0004] Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

[0005] It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanyingSHQ0035WO / R24-4-PCT2 drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 schematically depicts a liquid-liquid extraction system, according to embodiments disclosed and described herein.DETAILED DESCRIPTION

[0007] Reference will now be made in detail to embodiments of used nuclear fuel processing that include partitioning americum from an actinide-lanthanide containing raffinate comprising americum, curium, and one or more lanthanides in an aqueous solvent that are separated from used nuclear fuel. The present disclosure comprises directing the actinide-lanthanide containing raffinate into a liquid-liquid extraction (LLE) system and contacting the actinide-lanthanide containing raffinate with an organic extracting solution comprising an organic neutral extractant, a phase modifier, and a hydrocarbon diluent. The americum, the curium, and the one or more lanthanides bind with the organic extracting solution to form an actinide-lanthanide organic solution. In the actinide-lanthanide organic solution, the americium and the curium are in the same oxidation state, for example, a +3 -oxidation state, in which they each readily bind with the organic extracting solution. The method of the present disclosure further includes contacting the actinide-lanthanide organic solution with sodium bismuthate (NaBiCh) in nitric acid. The sodium bismuthate induces an oxidation state increase in the americum, changing americium to a higher oxidation state, such as a +4, +5, +6, or +7-oxidation state, without altering the oxidation state of curium. In this higher oxidation state, the americium unbinds from the actinide-lanthanide organic solution, separating the americium from the curium and the one or more lanthanides.

[0008] The americium may then be collected and the curium and the one or more lanthanides may be further processed, for example, the curium and the one or more lanthanides may be stripped from organic phase using an actinide stripping agent and a lanthanide stripping agent. Most of the americium and curium present in used nuclear fuel comprise americium-241 and curium-244, respectively. Partitioning americium-241 allows it to be further processed to generate curium- 242, a valuable radioisotope. For example, separated americium-241 may be irradiated, inducingSHQ0035WG / R24-4-PCT3 neutron absorption to form americium-242, about 82% of which decays into curium-242. Curium- 242 is not present in large quantities in used nuclear fuel and thus, separating and collecting americium allows for the formation of valuable curium-242. The systems and methods described herein overcome some of the challenges of separating and isolating americium and curium from used nuclear fuel, allowing for the recycling of these useful materials, and incentivizing the reprocessing of used nuclear fuel, thereby reducing the longevity and long-term radiotoxicity of nuclear waste, and improving reprocessing economics. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.

[0009] Referring now to FIG. 1, a liquid-liquid extraction (LLE) system 100 is schematically depicted. The LLE system 100 of FIG. 1 may be part of a used nuclear fuel processing system for partitioning and recycling used nuclear fuel. The LLE system 100 comprises an actinide- lanthanide extraction unit 110, a scrubbing unit 115, an actinide-lanthanide stripping unit 120, and a solvent preparation unit 140. The LLE system 100 depicted in FIG. 1 may form a portion of a larger used nuclear fuel processing system, which may further include a fuel rod shearing system, a voloxidation system, a dissolution system, and additional LLE systems configured to selectively extract different subsets of the elements present in used nuclear fuel, for example, to selectively extract or co-extract uranium, plutonium, and neptunium from a main process stream before the main process stream reaches the actinide-lanthanide extraction unit 110.

[0010] The actinide-lanthanide extraction unit 110, the scrubbing unit 115, the actinide-lanthanide stripping unit 120 are fluidly coupled, for example, using any fluid flow and control devices, such as piping, tubing, pumps, and tanks, and may each comprise one or more mixing devices. In operation, the mixing devices induce reactions between elements in an acidic liquid (i.e., in an aqueous phase) and elements in an organic liquid (i.e., in an organic phase). Example mixing devices include centrifugal contactors, pulse columns, counter- current columns, mixer settlers, or combinations thereof. In some embodiments, centrifugal contactors are useful because their compact size allows for the use of smaller hot cells, reducing the capital cost required for facility construction.

[0011] In operation, the LLE system 100 may receive liquid used nuclear fuel, for example, liquid raffinate from a uranium-plutonium extraction process, such as a uranium-plutonium codecontamination (CoDCon) process. This actinide-lanthanide containing raffinate includes minorSHQ0035WG / R24-4-PCT4 actinides (e.g., americium and curium), one or more lanthanides, and other components of used nuclear fuel not removed during the CoDCon process or another upstream process, for example, in some embodiments, one or more non-lanthanide fission products. The actinide-lanthanide containing raffinate is directed into the actinide-lanthanide extraction unit 110 in aqueous phase and an organic extracting solution is also directed into the actinide-lanthanide extraction unit 110 such that the organic extracting solution contacts the actinide-lanthanide containing raffinate. The organic extracting solution is configured to bind with the minor actinides and the one or more lanthanides, for example, when agitated using the one or more mixing devices of the actinide- lanthanide extraction unit 110, while the remainder of the raffinate, for example, the non- lanthanide fission products, remains in aqueous phase and exits the actinide-lanthanide extraction unit 110 for further processing. Indeed, the americum, the curium and the one or more lanthanides bind with the organic extracting solution to form an actinide-lanthanide organic solution.

[0012] The organic extracting solution comprises an organic neutral extractant, a phase modifier, and a hydrocarbon diluent (e.g., n-dodecane). The organic neutral extractant may comprise a neutral diglycolamide extractant. Example organic neutral extractants include N,N,N',N'-tetra(2- ethylhexyl)diglycolamide (T2EHDGA), N,N,N',N'-tetraoctyldiglycolamide (TODGA), and n- Octyl (phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO). Example phase modifiers include 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEHfEHP]) and di(2- ethylhexyl)phosphoric acid (HDEHP), N,N'-Dimethyl,N,N'-dioctylhexylethoxymalonamide (DMDOHEMA), tributyl phosphate (TBP), octanal, or a combination thereof, and the hydrocarbon diluent comprises n-dodecane. For example, T2EHDGA may be present in the organic extracting solution in a range of from 0.01 M to 2 M, for example, from 0.02 M to 1.5 M, from 0.04 to 1 M, from 0.05 to 0.8 M, from 1 to 0.75 M, or the like. In embodiments in which the phase modifier comprises HEHfEHP] or HDEHP, the HEHfEHP] or HDEHP may be present in the organic extracting solution in a range of from 0.25 M to 2 M, for example, from 0.5 to 1.5 M. In embodiments in which the phase modifier comprises DMDOHEMA, the DMDOHEMA may be present in the organic extracting solution in a range of from 0.1 to 1 M, for example, from 0.2 to 0.7 M. In operation, the phase modifier increases the polarity of the organic extracting solution.

[0013] Next, the actinide-lanthanide organic solution is directed to the scrubbing unit 115 for further processing. The further processing may include a scrubbing step in which the actinide- lanthanide organic solution is contacted with a scrubbing agent comprising a dicarboxylic acidSHQ0035WO / R24-4-PCT5 and a scrub chelator. For example, the actinide-lanthanide organic solution may be fed to the scrubbing unit 115 where it mixes with the scrubbing agent that comprises a dicarboxylic acid and the scrub chelator that removes unwanted species (primarily non-lanthanide fission products and non-radioactive reagents not already removed during the extracting step or another upstream processing step) from the actinide-lanthanide organic solution. In some embodiments, the dicarboxylic acid is oxalic acid (H2C2O4) and the scrub chelator is N-(hydroxyethyl)- ethylenediaminetriacetic acid (HEDTA). The scrubbing agent may further include nitric acid, for example, 0.5 M to 1 M of nitric acid. Embodiments may include a second scrubbing step in which the actinide-lanthanide organic solution is contacted with a second scrubbing agent comprising a carboxylic acid, such as formic acid, lactic acid or a complex carboxylic, such as citric acid. In some embodiments, the second scrubbing agent also includes a second scrub chelator, which may comprise N,N,N',N'-tetraethyldiglycolamide (TEDGA). The second scrubbing agent may further include nitric acid, for example, 0.5 M to 1 M of nitric acid.

[0014] Next, the actinide-lanthanide organic solution (e.g., the scrubbed actinide-lanthanide organic solution) is directed to the actinide-lanthanide stripping unit 120 for further processing. The actinide-lanthanide organic solution comprises americium and curium, which are each in a first oxidation state, for example, a +3 -oxidation state. Sodium bismuthate in nitric acid is also directed into the actinide-lanthanide stripping unit 120. The sodium bismuthate in nitric acid may be prepared in a solvent preparation unit 140, which is radiologically cold and is fluidly coupled to the actinide-lanthanide stripping unit 120. In some embodiments, the sodium bismuthate in nitric acid is formed by combining nitric acid with a powder of sodium bismuthate such that at least a portion of the sodium bismuthate dissolves, thereby forming the sodium bismuthate in nitric acid. Before combining with the nitric acid, the powder of sodium bismuthate may undergo a grinding process to reduce the average particle size, improving the dissolution process. When mixing the powder of sodium bismuthate with the nitric acid, heat may be applied, for example, the mixing may be done at a temperature of about 50 °C to 100 °C, such as about 70 °C, for a period of about 1 to 3 hours. It should be understood that embodiments are contemplated in which not all the sodium bismuthate combined with the nitric acid dissolves in the nitric acid. In some embodiments, the sodium bismuthate in nitric acid comprises 10 to 100 mM of sodium bismuthate in 3 to 6 M of nitric acid.SHQ0035WO / R24-4-PCT6

[0015] The actinide-lanthanide organic solution and the sodium bismuthate in nitric acid are contacted using the actinide-lanthanide stripping unit 120. For example, the one or more mixing devices of the actinide-lanthanide stripping unit 120 may combine and agitate the actinide- lanthanide organic solution and the sodium bismuthate in nitric acid such that americium is removed from the actinide-lanthanide organic solution (i.e., removed from organic phase) and combined with the nitric acid in aqueous phase. Sodium bismuthate induces an oxidation state increase in the americium from the first oxidation state to a second oxidation state and in the second oxidation state, americium unbinds from the actinide-lanthanide organic solution, thereby partitioning the americum from the curium and the one or more lanthanides. The second oxidation state is a +4-oxidation state, a +5-oxidation state, a +6-oxidation state, or a +7-oxidation state. The americium is removed from organic phase and is aqueous solution with the nitric acid and may be collected. The collected americium may next be separated from aqueous solution by calcination, precipitation, or a combination thereof. The curium, which is in the first oxidation state, remains bound with the actinide-lanthanide organic solution in organic phase. Similarly, the lanthanides, which are each in an oxidation state that is lower than the second oxidation state, remain bound with the bound with the actinide-lanthanide organic solution in organic phase.

[0016] Without intending to be limited by theory, sodium bismuthate is in a +5-oxidation state when in aqueous phase, for example, when in nitric acid, but bismuth has a preferred oxidation state of +3. Moreover, americium is stable in a number of higher oxidation states, such as +5, while curium and the one or more lanthanides are not stable in the +5-oxidation state. In operation, when sodium bismuthate in nitric acid contacts americium, two electrons swap from the sodium bismuthate to the americium, as shown in simplified form in Equation 1 and in more detail in Equation 2. 1)(Equation 2)

[0017] In the higher (e.g., +5) oxidation state, the americium unbinds from organic phase. Unlike americium, the curium and the lanthanides do not swap electrons with the sodium bismuthate and remain bound with the organic phase.SHQ0035WO / R24-4-PCT7

[0018] Unbinding americium from the actinide-lanthanide organic solution forms a modified organic solution that comprises curium and the one or more lanthanides. The modified organic solution may be further processed to partition the curium and the one or more lanthanides. The further processing may include contacting the modified organic solution with an actinide stripping agent comprising a first strip chelator and a first buffer, unbinding the curium from the modified organic solution, thereby stripping the curium from the modified organic solution and thereafter contacting the modified organic solution with a lanthanide stripping agent comprising a second strip chelator and a second buffer, unbinding the one or more lanthanides from the modified organic solution, thereby stripping the one or more lanthanides from the modified organic solution. Without intending to be limited by theory, the minor actinide stripping agent is a more selective stripping agent and removes the minor actinides (e.g., the remaining curium) without removing the lanthanides, while the lanthanide stripping agent is a less selective stripping agent and removes the lanthanides together with any additional species remaining (e.g., any species not removed during the extraction or stripping steps, or other upstream processing of the used nuclear fuel). Thus, the minor actinide stripping agent is introduced before the lanthanide stripping agent.

[0019] In some embodiments, the first strip chelator (i.e., the chelator of the minor actinide stripping agent) comprises diethylene triamine pentaacetic acid (DTP A) and the first buffer comprises a citrate, such as ammonium citrate. Other example first strip chelator of the minor actinide stripping agent include nitric acid, TEDGA, cyclohexanediaminetetraacetic acid (CDTA), HEDTA, and acetohydroxamic acid (AHA). Other example first buffers of the minor actinide stripping agent include lactate, formate, and malonate. The first strip chelator may comprise concentration in the minor actinide stripping agent in a range of from 0.5 mM to 200 mM, for example, from 1 mM to 100 mM, from 10 mM to 80 mM, or from 25 mM to 75 mM, such as 5 mM, 10 mM, 20 mM, 25 mM, 50 mM, 75 mM, 100 mM, 125 mM, 150 mM, 175 mM, or the like. In some embodiments, the first buffer is compatible with the second scrubbing agent. For example, when the second scrubbing agent comprises lactic acid, the first buffer may comprise lactate and when the second scrubbing agent comprises formic acid, the first buffer may comprise formate. In operation, the first buffer adjusts the pH of the minor actinide stripping agent to a first pH, which may be a pH of from 3.5 to 4.5, for example, from 3.8 to 4.2. This pH adjustment also stabilizes the pH, which increases the stability of the process, making the process less sensitive to minor changes in pH.SHQ0035WO / R24-4-PCT8

[0020] In some embodiments, the second strip chelator (i.e., the chelator of the lanthanide stripping agent) comprises DTP A, for example in a concentration in a range of from 50 mM to about 200 mM (e.g., 100), and the second buffer comprises a citrate, such as ammonium citrate. Other example first strip chelators of the lanthanide stripping agent include TEDGA, CDTA, HEDTA, and AHA. Other example second buffers of the lanthanide stripping agent include lactate, formate, and malonate. The second strip chelator may comprise concentration in the lanthanide stripping agent in a range of from 100 mM to 500 mM, for example, from 150 mM to 450 mM, from 200 mM to 400 mM, or from 100 mM to 300 mM, such as 100 mM, 125 mM, 150 mM, 175 mM, 200 mM, 225 mM, 250 mM, 275 mM, 300 mM, 325 mM, 350 mM, 375 mM, 400 mM, 425 mM, 450 mM, 500 mM, or the like. The lanthanide stripping agent may further include nitric acid, for example, 0.5 M to 1.5 M of nitric acid, such as 1 M of nitric acid. In some embodiments, the second buffer is compatible with the second scrubbing agent. For example, when the second scrubbing agent comprises lactic acid, the second buffer may comprise lactate and when the second scrubbing agent comprises formic acid, the second buffer may comprise formate. Moreover, it should be understood that, in some embodiments, the second buffer may be omitted from the lanthanide stripping agent. The concentration of the second strip chelator (i.e., the chelator in the lanthanide stripping agent) is higher than the concentration of the first strip chelator (i.e., the chelator in the minor actinide stripping agent). Without intending to be limited by theory, the lower concentration of the first strip chelator contributes to the increased selectivity of the minor actinide stripping agent. Moreover, the second buffer adjusts the pH of the minor actinide stripping agent to a first pH, which may be a pH of from about 4.0 to about 6.5, for example, from 4.3 to 6.0, from 4.5 to 5.5, or from 4.8 to 5.2. This pH adjustment also stabilizes the pH, which increases the stability of the process, making the process less sensitive to minor changes in pH. The first pH (e.g., the pH of the minor actinide stripping agent) is lower than the second pH (the pH of the lanthanide stripping agent).

[0021] In operation, the one or more mixing devices of the actinide-lanthanide stripping unit 120 may combine and agitate the modified organic solution and the actinide stripping agent such that the curium is removed from organic phase and combined with the minor actinide striping agent in aqueous phase. Similarly, the one or more mixing devices of the actinide-lanthanide stripping unit 120 may combine and agitate the modified organic solution and the lanthanide stripping agent such that the one or more lanthanides are removed from organic phase and combined with theSHQ0035WO / R24-4-PCT9 lanthanide stripping agent in aqueous phase. Once partitioned, the curium and the one or more lanthanides may be collected and further processed. The collected curium may be separated from aqueous solution by calcination, precipitation, or a combination thereof. Similarly, the collected lanthanides may be separated from aqueous solution by calcination, precipitation, or a combination thereof. The collected lanthanides may also be further partitioned to separated and collect individual lanthanides.

[0022] Most of the americium and curium present in used nuclear fuel comprise americium-241 and curium-244, respectively. After the americium-241 is partitioned and isolated, it can be further processed to generate curium-242, a valuable radioisotope. For example, the americium- 241 may be irradiated with neutrons such that at least a portion of the americium-241 undergoes a neutron absorption reaction, thereby transmuting the at least a portion of the americium-241 into americium-242, about 82% of which decays into curium-242 via beta decay. Curium-242 is not present in large quantities in used nuclear fuel and thus, separating americium from curium allows for the formation of valuable curium-242. In some embodiments, an accelerator-based system is used to irradiate the americium-241 with neutrons, for example, an accelerator-based system that generates neutrons by fusion, such as deuterium / tritium fusion, spallation, or any other accelerator-based neutron generation technique. In some embodiments, a nuclear reactor is used to irradiate the americium-241 with neutrons, for example, a power reactor, a research reactor, or any other known or yet to be developed nuclear reactor. Moreover, americium-241 has a half-life of about 432 years and contributes a significant of the total decay heat generated in long term storage of used nuclear fuel. In contrast, curicum-242 has much shorter half-life of about 162 days. Thus, transmuting the americium-241 to curium-242 also reduces the total repository volume and long-term decay heat of used nuclear fuel.

[0023] While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. Thus, it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.SHQ0035WO / R24-4-PCT10

[0024] As utilized herein, the terms “approximately,” “about,” “substantially”, and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art to which the subject matter of this disclosure pertains. Indeed, such terms refer to the subsequently listed property or measurement within normal manufacturing tolerances and imperfections in the relevant field. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical values or idealized geometric forms provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and claimed are considered to be within the scope of the disclosure as recited in the appended claims.

[0025] The term “coupled” and variations thereof, as used herein, means the joining of two members directly or indirectly to one another. Such joining may be stationary (e.g., permanent or fixed) or moveable (e.g., removable or releasable). Such joining may be achieved with the two members coupled directly to each other, with the two members coupled to each other using a separate intervening member and any additional intermediate members coupled with one another, or with the two members coupled to each other using an intervening member that is integrally formed as a single unitary body with one of the two members. If “coupled” or variations thereof are modified by an additional term (e.g., directly coupled), the generic definition of “coupled” provided above is modified by the plain language meaning of the additional term (e.g., “directly coupled” means the joining of two members without any separate intervening member), resulting in a narrower definition than the generic definition of “coupled” provided above. Such coupling may be mechanical, electrical, or fluidic.

[0026] References herein to the positions of elements (e.g., “top,” “bottom,” “above,” “below”) are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure.

[0027] Although the figures and description may illustrate a specific order of method steps, the order of such steps may differ from what is depicted and described, unless specified differently above. Also, two or more steps may be performed concurrently or with partial concurrence, unlessSHQ0035WO / R24-4-PCT11 specified differently above. Such variation may depend, for example, on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations of the described methods could be accomplished with standard programming techniques with rule-based logic and other logic to accomplish the various connection steps, processing steps, comparison steps, and decision steps.

Claims

SHQ0035WO / R24-4-PCT12CLAIMS1. A method of partitioning americium, the method comprising: directing an actinide-lanthanide containing raffinate into a liquid-liquid extraction (LLE) system, wherein the actinide-lanthanide containing raffinate comprises americum, curium, and one or more lanthanides in an aqueous solvent; contacting the actinide-lanthanide containing raffinate with an organic extracting solution such that the americum, the curium, and the one or more lanthanides bind with the organic extracting solution to form an actinide-lanthanide organic solution, wherein the organic extracting solution comprises an organic neutral extractant, a phase modifier, and a hydrocarbon diluent; and contacting the actinide-lanthanide organic solution with sodium bismuthate in nitric acid such that the sodium bismuthate induces an oxidation state increase in the americum from a first oxidization state to a second oxidation state such that the americum unbinds from the actinide- lanthanide organic solution, thereby partitioning the americum from the curium and the one or more lanthanides.

2. The method of claim 1, further comprising collecting the americium.

3. The method of claim 2, wherein collecting the americium comprising collecting the americium in an aqueous solution of the nitric acid and the method further comprises separating the americium from the aqueous solution by calcination or precipitation.

4. The method of claim 2, wherein the americium comprises americium-241 and the method further comprises irradiating the americium-241 with neutrons after collecting the amercium-241 such that at least a portion of the americium-241 undergoes a neutron absorption reaction, thereby transmuting the at least a portion of the americium-241 into americium-242, wherein at least a portion of the americium-242 beta decays into curium-242.

5. The method of claim 1, wherein the americium and curium are each in the first oxidation state in the actinide-lanthanide organic solution.

6. The method of claim 1, wherein the first oxidation state is a +3-oxidation state.SHQ0035WG / R24-4-PCT137. The method of claim 1, wherein the second oxidation state is a +4-oxidation state, a +5- oxidation state, a +6-oxidation state, or a +7-oxidation state.

8. The method of claim 1, wherein the organic neutral extractant comprises T2EHDGA, TODGA, CMPO or a combination thereof, and the phase modifier comprises HEHfEHP], HDEHP, DMDOHEMA, TBP, octanal, or a combination thereof.

9. The method of claim 8, wherein the organic extracting solution comprises from 0.05 to 0.8 M T2EHDGA.

10. The method of claim 8, wherein the organic extracting solution comprises from 0.5 to 1.5 M HEH[EHP],11. The method of claim 8, wherein the organic extracting solution comprises from 0.2 to 0.7 M DMDOHEMA.

12. The method of claim 8, wherein the organic extracting solution comprises from 10 to 100 mM of sodium bismuthate in 3 to 6 M of nitric acid.

13. The method of claim 1, wherein the hydrocarbon diluent comprises n-dodecane.

14. The method of claim 1 , wherein unbinding americium from the actinide-lanthanide organic solution forms a modified organic solution that comprises curium and the one or more lanthanides and the method further comprises: contacting the modified organic solution with an actinide stripping agent comprising a first strip chelator and a first buffer, thereby stripping curium from the modified organic solution; and contacting the modified organic solution with a lanthanide stripping agent comprising a second strip chelator and a second buffer, thereby stripping the one or more lanthanides from the modified organic solution.

15. The method of claim 14, wherein:SHQ0035WO / R24-4-PCT14 the first strip chelator is present in the minor actinide stripping agent in a first concentration and the second strip chelator is present in the lanthanide stripping agent in a second concentration, wherein the first concentration is lower than the second concentration.

16. The method of claim 14, wherein the first strip chelator and the second strip chelator each comprise DTP A.

17. The method of claim 14, wherein the first buffer comprises citrate, lactate, formate, malonate, or a combination thereof and the second buffer comprises citrate, lactate, formate, malonate, or a combination thereof.

18. The method of claim 14, wherein the actinide stripping agent comprises a first pH, the lanthanide stripping agent comprises a second pH and the second pH is greater than the first pH.

19. The method of claim 18, wherein the first pH is in a range of from 3 to 4.5 and the second pH is in a range of from 4 to 6.5.

20. The method of claim 1, further comprising contacting the actinide-lanthanide organic solution with a scrubbing agent comprising a dicarboxylic acid and a scrub chelator prior to contacting the actinide-lanthanide organic solution with the sodium bismuthate in nitric acid.

21. The method of claim 20, wherein the dicarboxylic acid is H2C2O4 and the scrub chelator is HEDTA.

22. The method of claim 1 , wherein before contacting the actinide-lanthanide organic solution with the sodium bismuthate in the nitric acid, the nitric acid is combined with a powder of the sodium bismuthate such that at least a portion of the sodium bismuthate dissolves in the nitric acid.

23. The method of claim 1, wherein the LLE system comprises a plurality of mixing devices.SHQ0035WO / R24-4-PCT1524. The method of claim 23, where the plurality of mixing devices comprise centrifugal contactors, pulse columns, counter-current columns, mixer settlers, or a combination thereof.

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