Method and system for separating thorium from uranium and their decay products

Abstract

A method and system (300) for separating thorium from uranium and its decay products is provided. The method includes combining a nuclear fuel feedstock (102) containing thorium and uranium with a first acid (104, 204) to form a first solution. The first solution is contacted with an ion exchange resin (308) that is selective for thorium or uranium. The thorium or uranium is at least partially removed from the first solution by binding the thorium or uranium to the ion exchange resin (308), thereby forming a second solution (106, 206). The second solution (106, 206) is combined with oxalic acid to precipitate the uranium or thorium from the second solution, forming a precipitate (110, 210). The precipitate (110, 210) is separated from the second solution (106, 206).

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Nonprovisional Patent Application No. 16 / 877,156, filed May 18, 2020, and entitled "METHODS AND SYSTEMS FOR SEPARATION OF THORIUM FROM URANIUM AND THEIR DECAY PRODUCTS," the contents of which are incorporated herein by reference in their entirety. [Background technology]

[0002] Nuclear power plants use nuclear fuel, which can decompose over time. Spent nuclear fuel is typically considered nuisance material in some countries and may require special precautions for handling. Furthermore, recycling spent nuclear fuel into new nuclear fuel or disposing of spent nuclear fuel can be expensive. These costs can be offset to some extent by utilizing radioisotopes from spent fuel for medical applications. Medical element separation requires high separation factors and good recovery, especially for valuable radioisotopes, which may be present in very low concentrations and very small amounts. There are challenges associated with storing, transporting, and / or recycling spent nuclear fuel and producing medical isotopes. Summary of the Invention

[0003] The present disclosure provides a method for separating thorium from uranium and its decay products. The method includes combining a nuclear fuel feedstock containing thorium and uranium with a first acid to form a first solution. In various embodiments, the nuclear fuel feedstock may contain other components, such as plutonium, other formed transuranium elements, such as ammonium, curium, or combinations thereof. The first solution is contacted with an ion exchange resin selective for thorium or uranium. The thorium or uranium is at least partially removed from the first solution by binding the thorium or uranium to the ion exchange resin, thereby forming a second solution. The second solution is combined with oxalic acid to precipitate the uranium or thorium from the second solution, forming a precipitate. In various embodiments, the thorium or uranium can be eluted from the ion exchange resin and then combined with oxalic acid to precipitate the uranium or thorium, forming a precipitate. The precipitate is separated from the second solution.

[0004] The present disclosure also provides a system for separating thorium from uranium and its decay products. The system includes an extraction vessel and a separation vessel. The extraction vessel includes an extraction inlet, an ion exchange resin selective for thorium or uranium, and an extraction outlet. The extraction inlet is configured to receive a nuclear fuel feedstock containing thorium and uranium and a first acid. The extraction vessel is configured to form a first solution from the nuclear fuel feedstock and the first acid. The extraction vessel is configured to contact the first solution with the ion exchange resin to form a second solution. The extraction outlet is configured to transport the second solution out of the extraction vessel. The separation vessel includes a separation inlet and a separation outlet. The separation inlet is in fluid communication with the extraction outlet and configured to receive the second solution and oxalic acid. The separation vessel is configured to combine the second solution with the oxalic acid to precipitate the uranium or thorium in the second solution and form a precipitate.

[0005] It is understood that the invention described herein is not limited to the examples summarized in this Summary of the Invention. Various other embodiments are described and illustrated herein. [Brief explanation of the drawings]

[0006] The features and advantages of the embodiments, as well as the manner in which they are achieved, will become more apparent and the embodiments will be better understood by referring to the following description of the embodiments taken in conjunction with the accompanying drawings.

[0007] [Figure 1] FIG. 1 is a schematic process diagram illustrating a method for separating thorium from uranium and its decay products utilizing an ion exchange resin selective for uranium according to the present disclosure.

[0008] [Figure 2] FIG. 2 is a schematic process diagram illustrating a method for separating thorium from uranium and their decay products utilizing an ion exchange resin selective for thorium according to the present disclosure.

[0009] [Figure 3] FIG. 3 is a schematic diagram of a system for separating thorium from uranium and their decay products according to the present disclosure.

[0010] Corresponding reference characters indicate corresponding parts throughout the several views. The examples set forth herein illustrate particular embodiments in one form, and such examples should not be construed as limiting the scope of the embodiments in any manner. DETAILED DESCRIPTION OF THE INVENTION

[0011] Certain exemplary embodiments of the present disclosure will now be described to provide a general understanding of the compositions, functions, principles of manufacture, and uses of the compositions and methods disclosed herein. Example(s) of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the compositions, articles, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments, and that the scope of various embodiments of the present invention is defined only by the claims. Features illustrated or described in connection with one exemplary embodiment may be combined with features of other embodiments. Such modifications and variations are intended to be within the scope of the present invention.

[0012] Throughout this specification, references to "various embodiments," "some embodiments," "one embodiment," "an embodiment," or the like mean that a particular feature, structure, or characteristic described in connection with that embodiment is also included in that embodiment. Thus, appearances of "various embodiments," "some embodiments," "in one embodiment," "in an embodiment," and the like throughout this specification do not necessarily all refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in an embodiment or embodiments. Thus, a particular feature, structure, or characteristic illustrated or described in connection with one embodiment may be combined, in whole or in part, with a feature, structure, or characteristic of another embodiment or other embodiments, without limitation. All such modifications and variations are intended to be included within the scope of the present embodiments.

[0013] Spent nuclear fuel is typically recycled into new nuclear fuel or vitrified for final disposal. During recycling, uranium is usually the desired product, and thorium is considered waste. However, the present inventors believe that the thorium-uranium-233 nuclear fuel cycle has the potential to provide isotopes of interest to the medical community if effective technology is developed to extract these valuable isotopes from nuclear fuel from the thorium-uranium-233 cycle. The present inventors believe that extending the use of the thorium-uranium-233 fuel cycle beyond power generation would improve the benefits of using the thorium-uranium-233 fuel cycle in nuclear power generation needs. Accordingly, the present disclosure provides methods and systems for separating thorium from uranium and their decay products. The disclosed methods and systems can provide a high-purity, medical-grade thorium product that can be used by the medical community or other industries. In various embodiments, the disclosed methods and systems can provide a high-purity, medical-grade uranium product that can be used by the medical community or other industries.

[0014] The present disclosure provides a method for separating thorium from uranium and their decay products. The method includes combining a nuclear fuel feedstock containing thorium and uranium and their decay products with a first acid to form a first solution. The first solution can be contacted with an ion exchange resin selective for thorium or uranium. Ions with high selectivity for the resin can be preferentially adsorbed onto the ion exchange resin, while less selective species can pass through the ion exchange resin, thus separating the elemental species from each other. For example, thorium or uranium can be at least partially removed from the first solution by binding the thorium or uranium to the ion exchange resin, thereby forming a second solution. In various embodiments, the second solution can be recycled for further exposure to additional ion exchange resin to improve uranium or thorium recovery. Once sufficient recovery is achieved, the second solution can be combined with oxalic acid to precipitate the desired elemental species, uranium or thorium. In various examples, if the second solution contains actinide and / or decay product impurities, a secondary solution comprising tributyl phosphate (TBP) and optionally a hydrocarbon can be introduced into the second solution to dissolve the actinide and / or decay product impurities. Dilute nitric acid can then be introduced into the mixture of the second solution and the secondary solution, which can preferentially remove thorium from the mixture (e.g., relative to other actinide and / or decay product impurities) before exposure to oxalic acid. With or without the use of a secondary solution, a precipitate can be separated from the second solution. The precipitate can be processed into various products.

[0015] In various examples, thorium or uranium can be eluted from the ion exchange resin and then combined with oxalic acid to precipitate the uranium or thorium to form a precipitate. The precipitate can be processed into various products. In various examples, if the solution eluted from the ion exchange resin contains actinide or decay product impurities, a secondary solution containing tributyl phosphate (TBP) can be introduced into the elution solution to dissolve the actinide and / or decay product impurities. Dilute nitric acid can then be introduced into the mixture of the elution solution and the secondary solution, which can preferentially remove thorium from the mixture before exposure to oxalic acid.

[0016] Ion exchange resins can be selective for thorium (e.g., thorium(IV) oxide) or uranium (e.g., uranium(VI) oxide), depending on the composition of the resin and acid solution used for dissolution. Separation of actinides using ion exchange resins is described in "SOLID-PHASE EXTRACTION FOR THE SEPARATION OF ACTINIDES FROM RADIOACTIVE WASTE," S. Maischak and J. Fachinger, WM'01 Conference, February 25-March 1, 2001, Tucson, Arizona, which is incorporated herein by reference. For example, a combination of ion exchange resin and acid can be selective for uranium (e.g., comprising a higher affinity for binding with uranium(VI) oxide than with thorium(IV) oxide). Ion exchange resins that can be selective for uranium include, for example, diamyl amylphosphonate, such as UTEVA resin available from EIChroM Darien, Illinois. UTEVA resin is described in EIChroM ideas Newsletter Volume 4, Issue No. 2, published June 1997, entitled "UTEVA Resin," which is incorporated herein by reference. Diamyl amyl phosphonates can form nitrato complexes with actinide elements. Ion exchange resins that may be selective for uranium can include, for example, quaternary ammonium salts, such as TEVA resins available from TRISKEM International, France. TEVA resins are described in a product sheet by TRISKEM International entitled "TEVA Resin," available at https: / / www.triskem-international.com / scripts / files / 5c5855b887c4f4.23796223 / PS_TEVA-Resin_EN_160927.pdf, which is incorporated herein by reference.

[0017] As shown in the process schematic of FIG. 1 , a method is provided for separating thorium from uranium and its decay products using an ion exchange resin that may be selective for uranium. As shown, a nuclear fuel feedstock 102 containing thorium and uranium is provided, and a first acid containing hydrochloric acid is provided (104). In various embodiments, the nuclear fuel feedstock may also contain plutonium, decay products of plutonium, decay products of uranium, or combinations thereof. In some embodiments, the nuclear fuel feedstock may contain generated transuranium elements, such as americium, curium, or combinations thereof, fission products, and other decay products. In various embodiments, it may be desirable to limit the amount of elements present in the nuclear fuel feedstock having an atomic number of 95 or greater. For example, it may be desirable to limit the amount of ameridium present in the nuclear fuel feedstock. In certain embodiments, the nuclear fuel feedstock may be processed through an initial actinide separation (e.g., an ion exchange process, a solvent exchange process) before combining the nuclear fuel feedstock with the first acid.

[0018] As shown in Figure 1, nuclear fuel feedstock can be combined with a first acid to form a first solution. The first solution can be contacted with an ion exchange resin to at least partially remove uranium from the first solution by binding the uranium to the ion exchange resin, thereby forming a second solution (106) having a reduced uranium content relative to the first solution. The concentration of hydrochloric acid in the first solution can be maintained at a sufficient level (e.g., in the range of 2-10 molar) to improve uranium binding to the ion exchange resin and / or minimize thorium binding to the ion exchange resin.

[0019] The second solution can be combined with oxalic acid to precipitate thorium from the second solution to form a precipitate containing thorium (e.g., thorium oxalate, which may have reduced solubility in acidic solutions) (110). Precipitation of uranium and / or thorium can proceed according to "PARAMETRIC STUDY ON CO-PRECIPTATION OF U / TH in MOX FUEL OF AHWR" by SK Tiwari, et al., International Thorium Energy Conference (ThEC 2015), October 12-15, 2015, Mumbai, India, which is incorporated herein by reference. The inventors of the present disclosure surprisingly discovered that the combination of first removing uranium using an ion exchange resin and then precipitating thorium from the first solution can result in unexpectedly improved purity and / or yield of the product produced from the thorium precipitate. In various examples, the concentration of hydrochloric acid in the second solution can be maintained at a level sufficient to limit precipitation of uranium (e.g., greater than 5 Normal). In various other examples, thorium in the second solution can be converted to a salt and precipitated from the second solution by changing the pH of the second solution to reduce the solubility of the dissolved salt.

[0020] Oxalic acid can be added to the second solution at a substantially stoichiometric ratio relative to the thorium present in the second solution. For example, oxalic acid can be added in a range of 0.001% to 1% by weight of the second solution. In various embodiments, maintaining a substantially stoichiometric ratio of oxalic acid relative to thorium can limit excess oxalic acid present in the second solution, thus limiting the presence of oxalic acid in the filtered solution. The filtered solution can then be reused in the process of combining with nuclear fuel feedstock (114). Recycling can capture additional thorium, uranium, plutonium, and other decay products remaining in the solution.

[0021] The thorium precipitate can be separated from the second solution by various processes, such as, for example, filtration to form a filtered thorium material and a filtered solution (112). The filtered thorium material, and optionally, ashless filter paper that may be used in the filtration process, can be oxidized (116), for example, by heating in an oxidizing environment (e.g., heating the filtered thorium material in air at temperatures ranging from 200°C to 500°C). The thorium dioxide can be processed to form a thorium product (118).

[0022] In various embodiments, the ion exchange resin may also bind a portion of the thorium. To remove the bound thorium, the ion exchange resin may be washed with hydrochloric acid to preferentially elute the thorium, which may be further separated at 110. The uranium may be recovered from the resin by acid or solvent elution, or the uranium may remain adsorbed on the resin and / or may be immobilized so that it may be suitable for disposal.

[0023] In other specific examples, the ion exchange resin can be selective for thorium (e.g., comprising a higher affinity for binding thorium(IV) oxide than uranium(VI) oxide). Ion exchange resins that can be selective for thorium can include, for example, quaternary ammonium salts, such as TEVA resins available from TRISKEM International, France. TEVA resins can be selective for uranium by using hydrochloric acid as the first acid, or can be selective for thorium by using nitric acid as the first acid.

[0024] As shown in the process schematic of Figure 2, a method for separating thorium from uranium and its decay products is provided using an ion exchange resin that can be selective for thorium. As shown, a nuclear fuel feedstock 102 containing thorium and uranium is provided, and a first acid containing nitric acid is provided (204). The nuclear fuel feedstock can be combined with the first acid to form a first solution. The first solution can be contacted with an ion exchange resin to at least partially remove thorium from the first solution by binding the thorium to the ion exchange resin, thereby forming a second solution having a reduced thorium content compared to the first solution (206). The concentration of nitric acid in the first solution can be maintained at a sufficient level (e.g., in the range of 2-6 molar) to improve binding of thorium to the ion exchange resin and / or minimize binding of uranium to the ion exchange resin.

[0025] The second solution can be combined with oxalic acid to precipitate uranium from the second solution to form a precipitate comprising uranium (e.g., uranium oxalate) (210). The inventors of the present disclosure surprisingly discovered that the combination of first removing thorium using an ion exchange resin and then precipitating uranium from the first solution can result in unexpectedly improved purity and / or yield of the product produced from the uranium precipitate. In various embodiments, the concentration of nitric acid in the second solution can be maintained at a level sufficient to limit thorium precipitation.

[0026] The oxalic acid can be added to the second solution at a substantially stoichiometric ratio relative to the uranium present in the second solution. For example, the oxalic acid can be added in a range of 0.001% to 1% by weight of the second solution. In various embodiments, maintaining a substantially stoichiometric ratio of oxalic acid relative to the uranium can limit excess oxalic acid present in the second solution and, therefore, limit the presence of oxalic acid in the filtered solution. The filtered solution can then be returned to the process and combined with nuclear fuel feedstock as needed.

[0027] The uranium precipitate can be separated from the second solution by various processes, such as, for example, filtration to form a filtered uranium material and a filtered solution (212). The filtered uranium material, and optionally, ashless filter paper that may be used in the filtration process, can be oxidized to form triuranium octoxide (214), for example, by heating in an oxidizing environment (e.g., heating the filtered uranium material in air at temperatures ranging from 200 to 500 degrees Celsius). The triuranium octoxide can be treated to form a uranium product (216).

[0028] In various embodiments, the thorium bound to the ion exchange resin can be eluted using an acid (e.g., <5 molar hydrochloric acid or as little as 0.1 molar nitric acid), a solvent, or a combination thereof to form a third solution containing thorium and acid (220). The third solution can then be processed through precipitation 110, filtration 112, oxidation 116, and product processing 118 as described with reference to FIG. 1 above. The inventors of the present disclosure surprisingly discovered that the combination of first removing thorium using an ion exchange resin, eluting the thorium from the ion exchange resin, and precipitating from the thorium-eluted solution can unexpectedly result in improved purity and / or yield of the product produced from the thorium precipitate.

[0029] In various examples, the second solution or the third solution can be further purified using a second ion exchange resin before separation using precipitation 110 or 210. In certain examples, the second solution and / or the third solution can be further purified using liquid extraction with a secondary solution comprising TBP and optionally a hydrocarbon (e.g., a liquid hydrocarbon), followed by the introduction of dilute nitric acid before separation using precipitation 110 or 210. The liquid hydrocarbon can be in a liquid state at standard temperature and pressure.

[0030] As shown in FIG. 3 , a system 300 for separating thorium from uranium and its decay products is provided. The system includes an extraction vessel 302 and a separation vessel 310. The extraction vessel 302 may include an extraction inlet 304, an ion exchange resin 308 selective for thorium or uranium, and an extraction outlet 306. The extraction inlet 304 may be configured to receive a nuclear fuel feedstock containing thorium and uranium and a first acid. The extraction inlet 304 may include a single port or multiple ports. The extraction vessel 302 may be configured to form a first solution from the nuclear fuel feedstock and the first acid. The extraction vessel 302 may contact the first solution with the ion exchange resin 308 to form a second solution. The extraction outlet 306 may be configured to transport the second solution out of the extraction vessel 302.

[0031] Separation vessel 310 may include separation inlets 312 and 314 and a separation outlet 316. Separation inlet 312 may be in fluid communication with extraction outlet 306. Separation inlet 312 may be configured to receive the second solution, and separation inlet 314 may be configured to receive oxalic acid. Separation vessel 302 may be configured to combine the second solution with the oxalic acid to precipitate uranium or thorium in the second solution to form a precipitate. Separation outlet 316 may be configured to transport the precipitate and / or the second solution out of separation vessel 310.

[0032] In various embodiments, the separation outlet 316 can be in fluid communication with a filtration system. The filtration system can be configured to recycle the filtered solution to the extraction vessel 302 via a recycle line. In certain other embodiments, the system 300 can include a furnace for oxidizing the precipitate separated by the filtration system. In some embodiments, the system 300 can include other processing equipment.

[0033] The following numbered clauses are directed to various non-limiting embodiments and aspects of the present disclosure. (Article 1) 1. A method for separating thorium from uranium and their decay products, comprising: combining a nuclear fuel feedstock containing thorium and uranium with a first acid to form a first solution; contacting the first solution with an ion exchange resin that is selective for thorium or uranium to at least partially remove thorium or uranium from the first solution by binding the thorium or uranium to the ion exchange resin, thereby forming a second solution; combining the second solution with oxalic acid to precipitate the uranium or thorium from the second solution to form a precipitate; and Separating the precipitate from the second solution. (Article 2) the first acid is hydrochloric acid; The ion exchange resin is selective for uranium, 10. The method of claim 1, wherein the precipitate comprises thorium. (Article 3) 3. The method of claim 2, wherein the separating includes filtering the second solution to form a filtered thorium material and a filtered solution. (Article 4) 4. The method of claim 3, further comprising oxidizing the filtered thorium material to form thorium dioxide. (Article 5) 5. The method of claim 4, further comprising treating thorium dioxide to form a thorium product. (Article 6) combining a second nuclear fuel feedstock containing thorium and uranium with the filtered solution to form a third solution; contacting an ion exchange resin with the third solution to at least partially remove uranium from the third solution by binding the uranium to the ion exchange resin, thereby forming a fourth solution; combining the fourth solution with oxalic acid to precipitate the remaining thorium from the fourth solution to form a second precipitate; and 6. The method of any of clauses 3 to 5, further comprising separating the second precipitate from the fourth solution. (Article 7) The first acid is nitric acid, 7. The method of any of clauses 1 to 6, wherein the ion exchange resin is selective for thorium. (Article 8) 8. The method of claim 7, wherein the separating includes filtering the second solution to form a filtered uranium material and a filtered solution. (Article 9) 9. The method of claim 8, further comprising oxidizing the filtered uranium material to form trianium octoxide. (Article 10) 10. The method of claim 9, further comprising treating the octoxide trianium to form a uranium product. (Article 11) combining a second nuclear fuel feedstock containing thorium and uranium with the filtered solution to form a third solution; contacting an ion exchange resin with the third solution to at least partially remove thorium from the third solution by binding the thorium to the ion exchange resin, thereby forming a fourth solution; combining the fourth solution with oxalic acid to precipitate residual uranium from the fourth solution to form a second precipitate; and 11. The method of any of clauses 8 to 10, further comprising separating the second precipitate from the fourth solution. (Article 12) 12. The method of any of clauses 7 to 11, further comprising utilizing an acid, a solvent, or a combination thereof to elute the thorium from the ion exchange resin to form a third solution comprising thorium and hydrochloric acid. (Article 13) 13. The method of claim 12, further comprising filtering the third solution to form a filtered thorium material and a second filtered solution. (Article 14) 14. The method of claim 13, further comprising oxidizing the filtered thorium material to form thorium dioxide. (Article 15) 15. The method of claim 14, further comprising treating thorium dioxide to form a product. (Article 16) 16. The method of any of clauses 13 to 15, wherein eluting the thorium from the ion exchange resin utilizes hydrochloric acid and further comprises a second elution of thorium from the ion exchange resin utilizing a second filtrate solution. (Article 17) 17. The method of any of clauses 1 to 16, wherein the ion exchange resin comprises a quaternary ammonium salt or diamyl amyl phosphonic acid. (Article 18) 18. The method of any of clauses 1 to 17, wherein the nuclear fuel feedstock is processed through initial actinide separation prior to combining with the first acid. (Article 19) 19. The method of any of clauses 1 to 18, further comprising purifying the second solution using a second ion exchange resin prior to separation. (Article 20) 20. The method of any of clauses 1 to 19, wherein the nuclear fuel further comprises plutonium, a produced transuranium element, a fission product, a decay product, or a combination thereof. (Article 21) 21. The method of any of clauses 1 to 20, further comprising introducing a secondary solution comprising tributyl phosphate and a hydrocarbon to remove actinide product impurities, decay product impurities, or a combination thereof. (Article 22) 1. A system for separating thorium from uranium and their decay products, comprising: An extraction vessel comprising an extraction inlet, an ion exchange resin selective for thorium or uranium, and an extraction outlet; the extraction inlet is configured to receive the nuclear fuel feedstock containing thorium and uranium and the first acid; the extraction vessel is configured to form a first solution from the nuclear fuel feedstock and a first acid and contact the first solution with an ion exchange resin to form a second solution; the extraction outlet is configured to transport the second solution out of the extraction vessel; An extraction vessel; A separation vessel having a separation inlet and a separation outlet, the separation inlet is in fluid communication with the extraction outlet and is configured to receive the second solution and the oxalic acid; the separation vessel is configured to combine the second solution with oxalic acid to precipitate the residual uranium or thorium into the second solution to form a precipitate; A separation container; A system comprising:

[0034] Those skilled in the art will recognize that the methods and systems described herein, and the accompanying discussion, are used as examples for conceptual clarity, and that various configuration modifications are contemplated. Thus, as used herein, the specific examples described and the accompanying discussion are intended to represent a more general class of these examples. In general, the use of any specific example is intended to represent that class, and the absence of specific components (e.g., steps), devices, and objects should not be considered limiting.

[0035] Various features and characteristics are described herein to provide an understanding of the compositions, structures, manufacture, function, and / or processes of the invention, including the disclosed methods and systems. It is understood that the various features and characteristics of the invention described herein may be combined in any suitable manner, regardless of whether such features and characteristics are explicitly described in combination herein. The inventors and applicant expressly intend that combinations of such features and characteristics be included within the scope of the inventions described herein. As such, the claims may be amended to recite any features and characteristics, in any combination, explicitly or inherently described or otherwise explicitly or inherently supported herein. Furthermore, applicant reserves the right to amend the claims to affirmatively disclaim features and characteristics that may exist in the prior art, even if those features and characteristics are not explicitly described herein. Accordingly, any such amendments would not add new matter to the specification or claims, but would be subject to the requirements of written description, sufficiency of description, and additional matter.

[0036] With respect to the appended claims, those skilled in the art will understand that the steps recited therein may generally be performed in any order. Also, while various process flow diagrams are presented sequentially, it should be understood that various steps may be performed in orders other than those illustrated, or may be performed simultaneously. Examples of such alternative orderings may include overlapping, interleaved, interrupted, reordered, incremental, preliminary, supplemental, simultaneous, reverse, or various other orderings, unless the context dictates otherwise. Furthermore, unless the context dictates otherwise, terms such as "responsive to," "related to," or other past tense adjectives are generally not intended to exclude such variations.

[0037] The inventions described herein can comprise, consist of, or consist essentially of various features and characteristics described herein. The terms "comprise" (and any form of comprise, such as "comprises" and "comprising"), "have" (and any form of have, such as "has" and "having"), "include" (and any form of include, such as "includes" and "including"), and "contain" (and any form of contain, such as "contains" and "containing") are open-ended linking verbs. Thus, a composition, method, or system that "comprises," "have," "includes," or "contains" features and / or characteristics has those features and / or characteristics, but is not limited to having only those features and / or characteristics. Similarly, an element, coating, or process of a composition that "comprises," "has," "includes," or "contains" features and / or characteristics has those features and / or characteristics, but is not limited to having only those features and / or characteristics, and may have additional features and / or characteristics.

[0038] As used herein, including the claims, grammatical articles such as "a," "an," and "the" are intended to include "at least one" or "one or more" unless specifically stated otherwise. Accordingly, articles are used herein to refer to one or more than one (i.e., "at least one") of the grammatical object of the article. As an example, "a component" means one or more components, and thus, in some cases, more than one component is contemplated and may be employed or used in the described implementations of compositions, coatings, and processes. Nevertheless, while the terms "at least one" or "one or more" are used in some instances and not in other instances, it is understood that the absence of these terms will not be interpreted as limiting the object of the grammatical articles "a," "an," and "the" to only one. Furthermore, unless the context requires otherwise, the use of a singular noun includes the plural, and the use of a plural noun includes the singular.

[0039] In this specification, unless otherwise indicated, all numerical parameters should be understood in all instances to be prefaced and modified by the term "about," given the inherent variability of the underlying measurement technique used to determine the numerical value of that parameter. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter set forth herein should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0040] Any numerical range recited herein includes all subranges subsumed within the recited range. For example, a range of "1 to 10" includes all subranges between the recited minimum of 1 and the recited maximum of 10 (inclusive), i.e., all subranges with a minimum of 1 or more and a maximum of 10 or less. Also, all ranges recited herein include the recited endpoints. For example, a range of "1 to 10" includes the endpoints 1 and 10. Any maximum numerical limitation recited herein is intended to include all lower numerical limitations subsumed within the range, and any minimum numerical limitation recited herein is intended to include all higher numerical limitations subsumed within the range. Accordingly, applicants reserve the right to amend this specification, including the claims, to explicitly recite any subranges subsumed within an expressly recited range. All such ranges are inherently set forth herein.

[0041] Any patent, publication, or other document identified herein is incorporated by reference in its entirety, unless otherwise stated, but only to the extent that the incorporated material does not contradict existing explanations, definitions, descriptions, examples, or other disclosure material expressly set forth herein. Accordingly, and to the extent necessary, the disclosure expressly set forth herein supersedes any conflicting material incorporated by reference. Any material, or portions thereof, incorporated by reference herein that contradicts existing definitions, descriptions, or other disclosure material set forth herein is incorporated only to the extent that there is no contradiction between the incorporated material and the existing disclosure material. Applicant reserves the right to amend this specification to explicitly recite any subject matter, or portions thereof, incorporated by reference. Amendments to this specification to add such incorporated subject matter will be subject to the requirements of written description, sufficiency of description, and additional matter.

[0042] While particular embodiments of the present invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that many variations in the details of the invention can be made without departing from the invention as defined in the appended claims.

Claims

1. 1. A method for separating thorium from uranium and their decay products, comprising: combining a nuclear fuel feedstock containing thorium and uranium with a first acid, the first acid being hydrochloric acid, to form a first solution; at least partially removing the uranium from the first solution by contacting the first solution with an ion exchange resin that is selective for uranium to bind the uranium to the ion exchange resin, thereby forming a second solution; combining the second solution with oxalic acid to precipitate thorium from the second solution to form a precipitate comprising thorium; separating the precipitate from the second solution, the separating including filtering the second solution to form a filtered thorium material and a filtered solution, the filtered thorium material including a precipitate precipitated with oxalic acid; combining a second nuclear fuel feedstock comprising thorium and uranium, the second nuclear fuel feedstock being different from the nuclear fuel feedstock, with the filtered solution to form a third solution; at least partially removing the uranium from the third solution by contacting the ion exchange resin with the third solution to bind the uranium to the ion exchange resin, thereby forming a fourth solution; combining the fourth solution with oxalic acid to precipitate residual thorium from the fourth solution to form a second precipitate; and separating the second precipitate from the fourth solution. method.

2. 10. The method of claim 1, further comprising oxidizing the filtered thorium material to form thorium dioxide.

3. 3. The method of claim 2, further comprising treating the thorium dioxide to form a thorium product.

4. A method for separating thorium from uranium and their decay products, comprising: combining a nuclear fuel feedstock containing thorium and uranium with a first acid, the first acid being nitric acid, to form a first solution; at least partially removing the thorium from the first solution by contacting an ion exchange resin selective for thorium with the first solution to bind the thorium to the ion exchange resin, thereby forming a second solution; combining the second solution with oxalic acid to precipitate uranium from the second solution to form a precipitate comprising uranium; separating the precipitate from the second solution, the separating including filtering the second solution to form a filtered uranium material and a filtered solution, the filtered uranium material including the precipitate precipitated with oxalic acid; and oxidizing the filtered uranium material to form trianium octoxide; method.

5. 5. The method of claim 4, further comprising treating the octoxide trianium to form a uranium product.

6. combining a second nuclear fuel feedstock comprising thorium and uranium, the second nuclear fuel feedstock being different from the nuclear fuel feedstock, with the filtered solution to form a third solution; contacting the ion exchange resin with the third solution to at least partially remove the thorium from the third solution by binding the thorium to the ion exchange resin, thereby forming a fourth solution; combining the fourth solution with oxalic acid to precipitate residual uranium from the fourth solution to form a second precipitate; and 6. The method of claim 4 or 5, further comprising separating the second precipitate from the fourth solution.

7. A method for separating thorium from uranium and their decay products, comprising: combining a nuclear fuel feedstock containing thorium and uranium with a first acid, the first acid being nitric acid, to form a first solution; at least partially removing the thorium from the first solution by contacting an ion exchange resin selective for thorium with the first solution to bind the thorium to the ion exchange resin, thereby forming a second solution; combining the second solution with oxalic acid to precipitate uranium from the second solution to form a precipitate comprising uranium; separating the precipitate from the second solution; and eluting the thorium from the ion exchange resin using an acid, a solvent, or a combination thereof to form a third solution comprising the thorium and hydrochloric acid. method.

8. filtering the third solution to form a filtered thorium material and a second filtered solution; 8. The method of claim 7, wherein the filtered thorium material comprises an oxalic acid precipitate.

9. 9. The method of claim 8, further comprising oxidizing the filtered thorium material to form thorium dioxide.

10. 10. The method of claim 9, further comprising treating the thorium dioxide to form a product.

11. 11. The method of claim 8, wherein the eluting of the thorium from the ion exchange resin utilizes hydrochloric acid and further comprises a second elution of the thorium from the ion exchange resin utilizing the second filtrate solution.

12. A method for separating thorium from uranium and their decay products, comprising: combining a nuclear fuel feedstock containing thorium and uranium with a first acid, which is hydrochloric acid or nitric acid, to form a first solution; contacting the first solution with an ion exchange resin selective for thorium or uranium to at least partially remove the thorium or uranium from the first solution by binding the thorium or uranium to the ion exchange resin, thereby forming a second solution; combining the second solution with oxalic acid to precipitate uranium or thorium from the second solution to form a precipitate; and separating the precipitate from the second solution; the nuclear fuel feedstock is processed through an initial actinide separation prior to combining with the first acid; the initial actinide separation is an ion exchange process or a solvent exchange process; method.

13. A method for separating thorium from uranium and their decay products, comprising the steps of: combining a nuclear fuel feedstock containing thorium and uranium with a first acid, which is hydrochloric acid or nitric acid, to form a first solution; contacting the first solution with an ion exchange resin selective for thorium or uranium to at least partially remove the thorium or uranium from the first solution by binding the thorium or uranium to the ion exchange resin, thereby forming a second solution; combining the second solution with oxalic acid to precipitate uranium or thorium from the second solution to form a precipitate; separating the precipitate from the second solution; and further purifying the second solution using a second ion exchange resin prior to said separation; the second ion exchange resin is selective for thorium or uranium and at least partially removes the thorium or uranium remaining in the second solution after the first solution has contacted the ion exchange resin; method.

14. A method for separating thorium from uranium and their decay products, comprising the steps of: combining a nuclear fuel feedstock containing thorium and uranium with a first acid, which is hydrochloric acid or nitric acid, to form a first solution; contacting the first solution with an ion exchange resin selective for thorium or uranium to at least partially remove the thorium or uranium from the first solution by binding the thorium or uranium to the ion exchange resin, thereby forming a second solution; combining the second solution with oxalic acid to precipitate uranium or thorium from the second solution to form a precipitate; separating the precipitate from the second solution; and introducing a secondary solution comprising tributyl phosphate and a hydrocarbon to remove actinide product impurities, decay product impurities, or a combination thereof; method.

15. 15. The method of any one of claims 1 to 14, wherein the ion exchange resin comprises a quaternary ammonium salt or diamyl amyl phosphonic acid.

16. 16. The method of any one of claims 1 to 15, wherein the nuclear fuel feedstock further comprises plutonium, produced transuranium elements, fission products, decay products, or combinations thereof.

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