Chloride based volatility for the recovery of uranium from used nuclear fuel containing uranium metal

Abstract

Disclosed herein are methods and systems for the recovery of uranium from used nuclear fuel containing nuclear metal using nonaqueous chemistry without electrometallurgy techniques, such as pyroprocessing. The methods and systems use chloride-based volatility (CBV) as the basis for uranium recovery from the used nuclear fuel containing uranium metal. The solid used nuclear fuel containing uranium metal is maintained under UCl4 sublimating conditions in a chlorinating environment for a period of time sufficient to convert at least some uranium metal into UCl4.

Description

CHLORIDE BASED VOLATILITY FOR THE RECOVERY OF URANIUM FROM USED NUCLEAR FUEL CONTAINING URANIUM METALCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 605,995, filed December 04, 2023; and of U.S. Provisional Patent Application No. 63 / 606,449, filed December 5, 2023, which are incorporated by reference herein in their entireties.STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] The new inventions in this application were made with government support under the ARPA-E ONWARDS program Award No. DE-AR0001612. The government has certain rights in these inventions.INTRODUCTION

[0003] In all operating or proposed commercial nuclear reactors, the majority of the spent or used nuclear fuel (UNF) is composed of uranium. Recovery / reuse of this uranium, enabled by a reduced-cost approach with favorable non-proliferation and safeguards characteristics, could reduce requirements for permanent disposal and be of great interest for the nuclear industry.

[0004] Some majority of the current and future planned nuclear reactors in the United States use a mixture of uranium isotopes, specifically238U and235U. Though uranium remains the primary component (>90%), the buildup of fission products, plutonium and other minor actinides, rare earths, transition metals, and main group elements prevent the fuel from being used further.

[0005] Chemical treatment of used nuclear fuel is typically performed in two media, aqueous solutions (UREX / PUREX) and molten salt (pyroprocessing). Both methods are well understood, with decades of development. Aqueous processing is performed commercially in other areas of the world, specifically France. Aqueous processes tend to generate large volumes of liquid waste and tend to occupy large footprints. Pyroprocessing (practiced at several of the United States National Laboratories) is a collection of electrochemical treatments in molten salts for oxide, halide, and metallic fuels.Pyroprocessing is a low throughput operation that occupies a small facility footprint,compared to aqueous processing, but tends to involve more hands-on operations. Pyroprocessing is not performed commercially.

[0006] Recovery / reuse of the uranium of spent or used nuclear fuel (UNF), enabled by a reduced-cost approach with favorable non-proliferation and safeguards characteristics, could reduce requirements for permanent disposal and be of great interest for the nuclear industry.CHLORIDE BASED VOLATILITY FOR THE RECOVERY OF URANIUM FROM USED NUCLEAR FUEL CONTAINING URANIUM METAL

[0007] A novel approach is proposed herein for the selective removal of uranium from UNF by exploiting the unique physical properties of uranium tetrachloride (UCL), relative to fission products and other materials present in UNF.

[0008] Disclosed herein are methods and systems for the recovery of uranium from used nuclear fuel (UNF) using nonaqueous chemistry without electrometallurgy techniques. The methods and systems described herein use chloride-based volatility (CBV) as the basis for uranium recovery from the UNF. The UNF containing uranium metal is maintained under UCI4 sublimating or volatilizing conditions in a chlorinating environment for a period of time sufficient to convert at least some uranium metal into UCI4 in a gas phase. This CBV method offers efficient bulk uranium separation through fractional sublimation or volatilization and provides scalable pathway towards UNF waste volume reduction, facilitating cost-effective recycling or disposal of uranium. The process can accommodate a variety of advanced reactor waste as feed material including oxide used fuels, metallic used fuels (for example, uranium metal), and molten salt used fuels.

[0009] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.BRIEF DESCRIPTION OF DRAWINGS

[0010] Various aspects of at least one example are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide an illustration and a further understanding of the various aspects and examples, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of a particular example. The figures, togetherwith the remainder of the specification, serve to explain principles and operations of the described and claimed aspects and examples. In the figures, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every figure.

[0011] FIG. 1 illustrates a simple embodiment of a method for the chloride-based volatility (CBV) separation of uranium from UNF.

[0012] FIG. 2 illustrates a flow diagram for the CBV of uranium from UNF.

[0013] FIG. 3 illustrates an embodiment of a larger waste handling process showing how the CBV method of FIG. 1 can be incorporated into a UNF handling and disposal system.

[0014] FIG. 4 illustrates another embodiment of a larger waste handling process showing how the CBV method of FIG. 1 can be incorporated into a UNF handling and disposal system.

[0015] FIG. 5 illustrates the experimental apparatus used for separating uranium from a surrogate UNF material.

[0016] FIG. 6A illustrates a single-zone furnace portion of an example experimental apparatus.

[0017] FIG. 6B illustrates a downstream portion of an example experimental apparatus.

[0018] FIG. 7 illustrates a multi-zone furnace portion of an example experimental apparatus.DETAILED DESCRIPTION

[0019] Before the uranium removal systems and methods are disclosed and described, it is to be understood that this disclosure is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments of the uranium removal systems and methods only and is not intended to be limiting. It must be noted that, as used in this specification, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a lithium hydroxide" is not to be taken as quantitatively or source limiting, reference to "a step" may include multiplesteps, reference to "producing" or "products" of a reaction should not be taken to be all of the products of a reaction, and reference to "reacting" may include reference to one or more of such reaction steps. As such, the step of reacting can include multiple or repeated reaction of similar materials to produce identified reaction products.

[0020] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as those commonly understood to one of ordinary skill in the art to which this technology pertains.

[0021] For the purposes of this application the following terms shall have the following meanings:

[0022] Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein should be understood as modified in all instances by the term “about.” The term “about” when used herein in connection with numerical values means ± 20% and with percentages means ±4%. Note that all percentages (%) are by weight unless otherwise specified.

[0023] As used herein, the term “comprising” refers to a composition, compound, formulation, or method that is inclusive and does not exclude additional elements or method steps.

[0024] As used herein, the term “consisting of’ refers to a compound, composition, formulation, or method that excludes the presence of any additional component or method steps.

[0025] As used herein, the term “consisting essentially of’ refers to a composition, compound, formulation or method that is inclusive of additional elements or method steps that do not materially affect the characteristic(s) of the composition, compound, formulation or method.

[0026] In all operating or proposed commercial nuclear reactors, the majority of the spent or used nuclear fuel (UNF) is composed of uranium. Recovery / reuse of this uranium, enabled by a reduced-cost approach with favorable non-proliferation and safeguards characteristics, could reduce requirements for permanent disposal and be of great interest for the nuclear industry.

[0027] Ideally, the bulk uranium would be separated from the fission products, without greatly increasing the volume, as is characteristic of the methods mentioned above. Primary factors hindering such a process include: a) the chemical similarity of uranium and plutonium, b) the potential for nuclear proliferation if the plutonium is purified from the UNF as a specific process step, and c) the intense radiation from minor actinides. Toaddress these issues, a novel approach is proposed herein for the selective removal of uranium from UNF by exploiting the unique physical properties of uranium tetrachloride (UCh), relative to fission products and other materials present in UNF.

[0028] This disclosure presents a method for the recovery of uranium from used fuel using nonaqueous chemistry without electrometallurgy techniques, such as pyroprocessing. The methods and systems use chloride-based volatility (CBV) as the basis for uranium recovery from UNF. Due to the low volatility of trivalent f-element chlorides, e.g., plutonium, lanthanide and other fission products (FPs), a separation occurs based on the temperature at which the fission products (e.g., uranium (IV) chloride (UCI4)) become volatile chlorides. Thus, a CBV method may be uniquely suited for uranium separation from UNF. Note that the CBV separation process is described below in terms of separating uranium from UNFs containing uranium metal. However, the CBV process is equally applicable to uranium oxides and the processing UNFs containing uranium oxides. The CBV process could also be adapted to the processing of UNFs containing uranium chloride molten salts. Thus, while presented in the terms of processing uranium metal UNFs, the reader should understand that the process equally may be applied to any uranium containing material, generally, regardless of the form of the uranium (e.g., oxide, metal, halide, etc.) and regardless of whether the uranium is UNF.

[0029] Metal chlorides have a wide range of sublimation and boiling points that can be used to create a simple, temperature-based separation. The proposed method of separation uses sublimation and is potentially applicable to common uranium fuels with specific process modifications based on the fuel type. The relatively low sublimation range for UCh, between about 500°C to about 650°C, which is not within about 50°C of any known or anticipated FPs, illustrates the potential to isolate the bulk uranium from UNF. Refer to Table 1 for a list of selected FPs along with their boiling or sublimation points. The chlorination environment coupled with the thermodynamic instability of Pu(IV) will drive plutonium to the trivalent ion as PuCh, which has a significantly higher boiling point of about 1767°C, well beyond the parameters of the process. The high boiling point of PuCh is in line with other FPs such as241Am, all of the rare earth, alkaline earth, and alkali elements, leaving a complex mixture behind. This residual mixture will produce significant radiologic activity due to the241Am isotope, preventing opportunities for proliferation. Further, several main group andtransition metal FPs boil significantly below UC14, allowing for an additional separation. The UCI4 product has a boiling / sublimation point that is well separated from the highly volatile chloride species (namely M0CI5, UCk) or the poorly volatile chlorides (namely PuCh, AmCh, GdCh and PuCh). Therefore, by preferentially controlling the chlorination of U to UCI4 and through subsequent fractional sublimation, uranium may be effectively separated from the other species via the use of a temperature gradient. The highly volatile M0CI5 will volatilize first, which can be separated out by setting the temperature of chlorination to about 300°C. Thereafter, the temperature of the chlorination can be set to between about 400°C to about 600°C to convert U to UCI4, which volatilizes, leaving the higher boiling species behind.

[0030] Table 1. Boiling or Sublimation Temperature for Selected Metal Chlorides at latm

[0031] FIG. 1 illustrates a simple embodiment of a method 100 for the CBV separation of uranium from UNF. The chlorination of uranium metal can be achieved through a direct chlorination process that proceeds via reacting uranium metal with chlorine gas. In the method 100 as shown, the UNF containing the uranium metal (e.g. U) is transported, prepared, and placed in a chlorination chamber in a preparation operation 102. In an embodiment, transportation may include removing the UNF from a reactor or storage facility. The preparation operation 102 may also include pulverization or crushing of solid UNF into a powder, particulate, or other aggregate form to assist in the contacting of the uranium metal in the UNF.

[0032] A chlorination and UCI4 sublimation operation 104 is then performed. In this operation 104, the CBV separation method maintains the UNF under UCI4 sublimating (or volatilizing) conditions in a chlorinating environment. By maintaining the solid UNF under UCI4 sublimating conditions, as the chlorinating environment causes the molecules of U to react to become UCI4. Equation 1 below illustrates such a reaction. The UCI4 may sublimate, i.e., go directly from a solid form to a gaseous form. In some examples, this phase change from solid to gas may prevent the UCI4 from forming acap on the surface of the solid UNF and thereby preventing the further chlorination of the UNF.A

[0033] U + 2Cl2-> UCl4Equation 1

[0034] In embodiments, the UNF material subjected to the chlorination and UC14 sublimation operation 104 is at least 50% by weight uranium metal, and can be at least 75% uranium metal, at least 80% uranium metal, at least 90% uranium metal and even at least 95% uranium metal. The remaining non-uranium material in the UNF can be considered impurities and include the other materials such as FPs and cladding materials as described above. These impurities may be up to 50% by weight of the UNF such as UNF containing at least 0.1%, at least 0.5%, at least 1.0%, at least 5%, at least 10% and at least 25% by weight impurities.

[0035] A chlorinating environment refers to conditions in which the UNF is exposed to Cl. An excess of chlorine gas (Ch) favors the formation of higher chlorides such as UCI5 or UC16. The flow rate of chlorine gas nay be controlled to ensure that it is stoichiometric or slightly less than the amount needed to form UCI4. To have additional control and / or prevent oxygen from entering the system, the chlorine gas may be mixed with argon gas (or another noble or inert gas, in examples). In an example, a chlorinating environment is Ar gas (or another noble or inert gas, in examples) containing at least some Ch so that maintaining the UNF in a chlorinating environment could include placing the UNF, for example as a solid material, in a chamber filled with Ar and CI2. In an example, a chlorinating environment is Ar gas (or another noble or inert gas, in examples) containing at least some hydrogen chloride (HC1) and / or carbon tetrachloride (CC14)-containing gas, so that maintaining the UNF in a chlorinating environment could include placing the UNF, for example as a powdered solid material, in a chamber filled with Ar and HC1 and / or carbon tetrachloride (CCI4). Specific examples described herein, including referring to the Figures, may describe an Ar / Ch chlorinating environment as a particular example for conciseness; however, the technology may also utilize / include other appropriate chlorinating environments (e.g. including other appropriate Cl-containing compounds and / or other noble / inert gasses) in accordance with the disclosures herein.

[0036] UCI4 sublimating conditions in a chlorinating environment refers to pressure and temperature combinations in which UCI4 will sublimate. The actual pressures andtemperatures that result in UC14 sublimating conditions could also vary depending on the chlorinating environment used. Agitation or mixing may also be performed during the chlorination operation and UCI4 sublimation operation 104 to improve kinetics of the chlorination reaction.

[0037] For an example Ar / Ch chlorinating environment and at pressures of about 1 atm, UCI4 sublimates within a temperature range of 400°C-600°C. In some examples, the sublimating conditions in an Ar / Ch environment at a pressure of from 0.1 atm to 10 atm are a temperature from 450°C-700°C. In some examples, sublimating conditions may be a pressure of from 0.9 atm to 1.5 atm and a temperature from 500°C-650°C in an Ar / Ch environment. In some examples, sublimating conditions may be a pressure of from 0.9 atm to 1.5 atm and a temperature from 400°C-650°C in an Ar / Ch environment. In some examples, sublimating conditions may be a pressure of from 0.9 atm to 1.5 atm and a temperature from 500°C-600°C in an Ar / Ch environment. It is believed a significantly increased pressure would increase the temperatures needed to volatilize the UCI4. Similarly, operating at a reduced pressure, i.e., pulling a slight vacuum to decrease the pressure within the chamber to less than 1 atm may reduce the temperature needed to volatilize the materials.

[0038] The chlorination and UCI4 sublimation operation 104 may be performed until all or substantially of the solid uranium from the original UNF has been sublimated as UCI4. The reduction in mass of the UNF or other parameters may be monitored in real time to determine when to terminate the chlorination. In an embodiment, the chlorination and UCI4 sublimation operation 104 may be performed for a fixed period of time or as necessary to convert 20%, 50%, 90%, 95%, 99% or even 99.9% of the uranium into UCI4. The reaction time may be carefully monitored and controlled to avoid prolonged exposure to chlorine gas and eliminate / minimize to the formation of higher chlorides. If higher chlorides are formed, purification steps such as fractional distillation or sublimation can be employed to isolate UCI4 from UCh.

[0039] In the chlorination chamber, after sublimation, an Ar, Ch, and UCI4 gas mixture is created as the product of the chlorination and UCI4 sublimation operation 104. In the embodiment shown in FIG. 1, after the UCI4 has sublimated into the gas phase, the Ar, CCI4, and UCI4 gas mixture is separated from the remaining UNF material, such as by being transferred to a collection chamber, in a gas removal operation 106.

[0040] After the gas removal operation 106, the conditions (e.g., pressure, temperature) of the UCU-containing gas may be modified to cause the deposition of the UC14 from the gas phase, yielding a solid (or liquid, depending on the conditions) UCfi material that is then collected in a collection operation 108.

[0041] FIG. 2 illustrates an embodiment of a CBV separation system 200 based on the method described in FIG. 1. In the embodiment shown, a solid reactant material (the UNF) containing uranium metal is placed in the chlorination chamber 204. An Ar or other inert gas mixture containing CI2 or another Cl-containing gas (i.e. chlorination gas) is introduced into the chamber. The chlorination chamber 204 is then filled with the chlorination gas to provide the chlorinating environment. In addition, the pressure and temperature of the chlorination chamber 204 are controlled to maintain the UNF under UCI4 sublimating conditions. Over time, uranium metal will react with the Cl of the CI2 to create gaseous UCI4. The sublimation of the UCI4 will then create a combined gas mixture that will include the Ar, any residual unreacted Cb, the newly- generated UCI4, and any other constituents from the UNF that volatilize off under these conditions or that are generated if a different chlorination gas is used.

[0042] In some examples, chlorination chamber 204 that can withstand high temperatures and corrosion by chlorine gas. For example, a chlorination chamber 204 may be constructed of materials such as quartz or ceramics, or other suitable materials of construction. Chlorine gas (for example, as mixed with an inert / noble gas carrier gas) may be slowly introduced into the reaction vessel, in some examples. After the reaction is complete, the system may be allowed to cool down at least slightly, in some examples. Uranium trichloride (UCI3) that may be generated, being a solid at these conditions, may collect at the bottom of the chlorination chamber 204.

[0043] In some examples, pressures within chlorination chamber 204 may be between about 0.1 atm and about 10 atm. In some examples, pressures within chlorination chamber 204 may be between about 0.9 atm and about 1.5 atm. In some examples, pressures within chlorination chamber 204 may be about 1 atm.

[0044] In some examples, temperatures within chlorination chamber 204 may be between about 400°C and about 750°C. In some examples, temperatures within chlorination chamber 204 may be between about 450°C and about 700°C. In some examples, temperatures within chlorination chamber 204 may be between about 500°C and about 700°C. In some examples, temperatures within chlorination chamber 204may be between about 500°C and about 650°C. In some examples, temperatures within chlorination chamber 204 may be between about 500°C and about 600°C. In some examples, temperatures within chlorination chamber 204 may be between about 550°C and about 600°C. In some examples, temperatures within chlorination chamber 204 may be between about 550°C and about 575°C. In some examples, temperatures within chlorination chamber 204 may be between about 500°C and about 600°C. In some examples, temperatures within chlorination chamber 204 may be between about 575°C and about 650°C. In some examples, temperatures within chlorination chamber 204 may be about 500°C. In some examples, temperatures within chlorination chamber 204 may be about 600°C. In some examples, temperatures within chlorination chamber 204 may be about 550°C. In some examples, temperatures within chlorination chamber 204 may be about 575°C.

[0045] In some examples, agitation or mixing may be performed during the chlorination to improve the kinetics of the chlorination operation. In this case, the chlorination chamber 204 may be provided with mixing paddles, injectors for gas injection, or any other component for providing agitation to the UNF in the chlorination chamber 204.

[0046] The UCh-containing gas mixture is then transferred from the chlorination chamber 204 to a UC14 collection chamber 206. It should be noted that this gas mixture will be referred to as the UC14-containing gas mixture for the sake of convenience even though the mixture may be much more complex; in reality, UNF can encompass a wide variety of materials include FPs the resulting gas mixture exiting the chlorination chamber may include many different compounds not otherwise discussed herein. In the UCI4 collection chamber 206, temperature or pressure may be slightly reduced from that of the chlorination chamber 204 in order to induce the deposition of solid UCI4 into a solid phase. In the embodiment shown, the temperature of the UCI4 collection chamber 206 is maintained below deposition temperature. In some examples, below 500°C or from about 25°C to about 500°C. The gas mixture is maintained in the collection chamber 206 for sufficient time to allow most or all of the UCI4 to achieve solid form. In an alternative embodiment, the conditions in the collection chamber 206 may be controlled to condense the UCI4 into a liquid form instead of a solid form.

[0047] FIG. 2 further illustrates a third chamber 208 for the collection of low boiling point fission products and any other products that may depose or condense out of thegas. In an embodiment, the conditions of the UCh collection chamber 206 and the other products collection chamber 208 may be controlled so that as pure a UCh deposition product as possible is obtained in the UCI4 collection chamber 206.

[0048] In the embodiment shown in FIG. 2, the different chambers 204, 206, 208 may be physically different vessels connected via valves and piping or may represent different locations in within a single continuous vessel. In a single vessel embodiment, transferring of gas from one chamber to another may be achieved by maintain a flow of gas through the single vessel. If physically different vessels are used for each chamber, the CBV separation process may be done either as a batch process or a continuous process or any combination of the two. Each chamber may be independently temperature controlled and may be provided with independent heating and / or cooling systems. Alternatively, the temperature of the chambers may be controlled solely by selection of the inlet Ar / Ch gas temperature, pressure, and flow rate and the amount of ambient heat loss from the equipment during the separation. As long as the desired conditions are maintained, any method and equipment for controlling the conditions in the different chambers may be utilized.

[0049] FIG. 3 illustrates an embodiment of a larger waste handling process 300 showing how the CBV method of FIG. 1 can be incorporated into a UNF handling and disposal system. The CBV separation method is particularly suitable when considering the larger picture of UNF disposal where, not only can it be used to recover valuable uranium from the UNF, the CBV separation method described herein has the added benefit over other methods of reducing the overall mass of the waste UNF thereby reducing disposal costs.

[0050] As shown in FIG. 3, UNF 302 is chlorinated in a conversion step 304 to convert the uranium into the chloride salt form as described above. Multiple separations and disposal steps then follow based on the material, to separate the constituents of the product mixture(s), which may include a mixture of uranium, high- temperature FPs, and other compounds 306a, and a mixture of low temperature FPs 306b. As mentioned above, significant value lies in the uranium. The uranium is, of course, removed as UCh 308 and can be converted chemically to UCh (a feed for some molten salt reactor designs) or to uranium metal from which new nuclear fuel could be made.

[0051] Plutonium and high melting temperature fission products 410, which remain with the solid UNF after the chlorination and sublimation operation, could be sent to a repository (refer to Option 1) for disposal or, alternatively, could be used as a starter fuel 312 for some advanced reactor designs (refer to Option 2). Furthermore, recovery of plutonium can be done as part of the processing of a co-waste stream laden with noble metals, rare-earth fission products, and minor actinides, which is beneficial for non-proliferation goals.

[0052] Finally, the low temperature FPs 306b that are collected in the other products collection chamber of FIG. 2 could be appropriately packaged and sent to a repository for disposal.

[0053] As noted above, at least 90% of the mass of UNF is typically uranium metal. Thus, using the CBV separation method to selectively remove the uranium metal from the rest of the UNF will drastically reduce the mass of the remaining UNF that must be disposed of. This is very beneficial beyond the normal cost savings in the recovery of the uranium when one considers that the space in a disposal repository is finite and not necessarily subject to normal economic pressures.

[0054] FIG. 4 illustrates another embodiment of a larger waste handling process 400 showing how the CBV method of FIG. 1 can be incorporated into a UNF handling and disposal system. UNF containing uranium metal (which may have been preprocessed at one or more preprocessing steps, for example preparing the solid material by crushing or pulverizing it into a powder or aggregate, not shown) is received at chlorination step 406. Downstream of the chlorination step 406, a stream containing volatiles and UC14 is passed through a condensation step 408 (for example, through a condenser), that causes separation of the UCI4, volatiles, and low-boiling chlorides. The low-boiling chlorides may then pass through a secondary condensation step 410 (for example, at a second condenser), that causes separation of the low-boiling chlorides and any other undesired products (the latter not shown). A waste-processing step 412 may process both the low-boiling chlorides as well as other chlorides (for example, TRU chlorides and FP chlorides of a residue stream generated at chlorination step 406), forming a waste stream.

[0055] FIG. 5 illustrates an example experimental apparatus 500 for the separation of uranium from a surrogate UNF material. FIGS. 6A-6B and FIG. 7 illustrate portions of an experimental apparatus. Note that FIG. 6A illustrates an example single-zonefurnace, while FIG. 7 illustrates an example multi-zone furnace 700, including a first zone 702, second zone 704, and third zone 706. Each of first, second, and third zones 702, 704, and 706 may be controlled separately, and may be maintained / operated at the same or different temperatures over time.

[0056] In some examples, working tubes comprise a material that can withstand the required temperatures and that is suitable for the chemical environment of the chlorination reaction. In examples, quartz working tubes may be utilized. In examples, vacuum seal flanges with barbed connectors may be used for gas supply and outlet gas connections. A quartz boat may be used to contain all starting materials (e.g. uranium metal-containing UNF), and a tube furnace (containing one or more zones) may be used. Tubing for supply and outlet gases should be chosen for chemical and connection (e.g. barbed or swage, etc.) compatibility.

[0057] A chlorination gas 502 mixture of Ch and Ar is prepared and measured (e.g. concentration, flow rate, temperature, pressure, and / or other characteristics) and flowed into the working tube 504. FIG. 6A illustrates an example Ar / Ch gas inlet 610 to the working tube.

[0058] The reactant(s) (e.g. UNF) 506 may be weighed, mixed (if applicable) and added to the quartz boat 506. In some examples, the quartz boat 506 may be positioned in the center of a single heated zone 508 (at the inlet end of the working tube 504 illustrated by the three heating lines in FIG. 5). In some examples, the quartz boat 506 may be positioned in the center of a first heated zone (at the inlet end of the working tube 504 corresponding to a first zone 702 of a multi-zone heater 700). FIG. 6A illustrates an example fumace / heater 612, which at least partially surrounds / encloses an outer diameter of the working tube. A solids / liquids trap 510 may be situated just downstream of the working tube outlet to aid in collection of any excess Ch and / or any solids that flow it past the end of the tube. Following the solids / liquids trap 510 may be a bubbler 512, containing mineral oil and a check valve, for monitoring gas flow and to prevent back flow of normal atmosphere into the working tube. Outlet gases may be plumbed to a KOH scrubber 514 located in an adjacent fume hood 516. FIG. 6B illustrates examples of a liquids / solids trap 614 downstream of the working tube, a mineral oil bubbler 616 downstream of the trap 614, and the gas outlet 618 to a fume hood.

[0059] In some examples, working tube 504 may include one or more features to form a tortuous path through which the gas may flow during the chlorination reaction, thus slowing the linear flow and increasing separation of the products. Such features may include baffles, filters, quarts wool, stainless steel wool, packing, beads, plates, or other suitable features.

[0060] In some examples, the ratio of the diameter of the inlet gas stream and the inner diameter of the working tube 504 may be important when considering gas flow currents inside of the working tube 504 and maintaining the products moving downstream of the working tube. In some examples, a filter material may be useful to prevent the movement of higher uranium chlorides (for example, CCh) beyond a temperature-based freezing zone.

[0061] Bulk separation of uranium from a surrogate used nuclear fuel matrix with yield and purity at least 95% uranium may be possible, utilizing the methods described herein. The basic operating parameters may include a temperature of between about 400°C and about 600°C.

[0062] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained.

[0063] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the technology are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0064] It will be clear that the systems and methods described herein are well adapted to attain the ends and advantages mentioned as well as those inherent therein. Those skilled in the art will recognize that the methods and systems within this specification may be implemented in many manners and as such are not to be limited by the foregoing exemplified embodiments and examples. In this regard, any number of the features of the different embodiments described herein may be combined into onesingle embodiment and alternate embodiments having fewer than or more than all of the features herein described are possible.

[0065] While various embodiments have been described for purposes of this disclosure, various changes and modifications may be made which are well within the scope contemplated by the present disclosure. For example, a number of process optimization changes could be done depending on the scale throughput of a CBV separation system such as using a fluidized bed reactor for the chlorination and sublimation chamber to increase the kinetics of the reaction. Likewise, including filters between chambers to prevent physical carry over of compounds was also seen as potentially beneficial from the examples and tests performed. Numerous other changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the spirit of the disclosure.

[0066] Illustrative examples of the systems and methods described herein are provided below. An embodiment of the system or method described herein may include any one or more, and any combination of, the numbered clauses described below:

[0067] 1. A method for separating uranium from a solid material containing uranium metal and at least 1% by weight other material, the method comprising: maintaining the solid material containing the uranium metal under UC14 sublimating conditions in a chlorinating environment for a period of time sufficient to convert at least some solid uranium metal into UCI4 in a gas phase.

[0068] 2. The method of clause 1 , wherein the sublimating conditions include a pressure between about 0.1 atm to about 10 atm.

[0069] 3. The method of any of clauses 1-2, wherein the sublimating conditions include a pressure between about 0.9 atm to about 1.5 atm and a temperature between about 400°C and about 650°C.

[0070] 4. The method of any of clauses 1-3, wherein the sublimating conditions include a between about 0.9 atm to about 1.5 atm and a temperature between about 500°C and about 650°C.

[0071] 5. The method of any of clauses 1-4, wherein the solid material is used nuclear fuel comprising at least one fission product of uranium.

[0072] 6. The method of any of clauses 1-5, further comprising preparing the solid material by crushing or pulverizing it into a powder or aggregate.

[0073] 7. The method of any of clauses 1-6, further comprising placing the solid material into a chlorination chamber, the chlorination chamber containing the chlorinating environment.

[0074] 8. The method of any of clauses 1-7, wherein the maintaining step includes contacting the solid material with Ch.

[0075] 9. The method of clause 8, wherein the CI2 is mixed with argon gas.

[0076] 10. The method of clause 8, further comprising, under the sublimating conditions, reacting the uranium metal with the CI2 to create UCI4.

[0077] 11. The method of any of clauses 1-10, further comprising separating the UCI4 from the gas phase by reducing a temperature of gas phase thereby by causing the UCI4 to depose from the gas phase as a solid.

[0078] 12. The method of clause 11, further comprising disposing of the solid material after removing the gas phase containing UCI4 from the solid material.

[0079] 13. The method of any of clauses 1-12, wherein the period of time is a sufficient to convert at least 20% of the uranium metal into UCI4.

[0080] 14. The method of any of clauses 1-13, further comprising removing the gas phase containing the UCI4 from the solid material.

[0081] 15. The method of any of clauses 1-14, further comprising agitating the chlorinating environment.

[0082] 16. A system, comprising: a chlorination chamber configured to hold a solid material containing uranium metal and a chlorination gas, wherein, within the chlorination chamber, the uranium metal reacts with the chlorination gas to generate a UC14-containing gas mixture; and a UCI4 collection chamber configured to receive the UC14-containing gas mixture from the chlorination chamber, wherein a temperature within the UCI4 collection chamber is maintained below a deposition temperature of the UC14.

[0083] 17. The system of clause 16, comprising a low boiling point fission products collection chamber downstream of the UCI4 collection chamber.

[0084] 18. The system of any of clauses 16-17, further comprising a condenser.

[0085] 19. The system of any of clauses 16-18, wherein the chlorination gas comprises CCI4, HC1, or CI2.

[0086] 20. The system of any of clauses 16-19, wherein a pressure within the UCI4 collection chamber is maintained below a pressure within the chlorination chamber.

[0087] 21. The system of any of clauses 16-20, wherein the chlorination chamber and UC14 collection chamber represent different locations within a single continuous vessel.

[0088] 22. A method for separating uranium from a solid material containing uranium metal and at least 1% by weight other material, the method comprising: maintaining the solid material containing the uranium metal in a chlorinating environment within a chlorination chamber for a period of time sufficient to convert at least some uranium metal into UCI4 in a gas phase; and controlling conditions of a collection chamber to condense the UCI4 in the gas phase into a liquid form, wherein the collection chamber is configured to receive the UCI4 in the gas phase from the chlorination chamber.

[0089] 23. The method of clause 22, wherein the wherein the chlorinating environment includes a pressure between about 0.9 atm to about 1.5 atm and a temperature between about 400°C and about 650°C.

[0090] 24. The method of any of clauses 22-23, wherein the solid material is used nuclear fuel.

[0091] 25. The method of any of clauses 22-24, further comprising preparing the solid material by crushing or pulverizing it into a powder or aggregate.

[0092] 26. The method of any of clauses 22-25, wherein the maintaining step includes contacting the solid material with CI2.

[0093] 27. The method of clause 26, wherein the Ch is mixed with argon gas.

[0094] 28. The method of clause 26, further comprising, within the chlorinating environment, reacting the uranium metal with the CI2 to create UCI4.

[0095] 29. The method of any of clauses 22-28, wherein the period of time is a sufficient to convert at least 20% of the uranium metal into UCI4.

[0096] 30. The method of any of clauses 22-29, further comprising agitating the chlorinating environment within the chlorination chamber.

[0097] 31. The method of any of clauses 22-30, wherein the chlorination chamber and the collection chamber represent different locations within a single continuous vessel.

[0098] 32. The method of any of clauses 22-31 , further comprising maintaining the solid material containing the uranium metal under UCI4 sublimating conditions within the chlorinating environment for the period of time.

Claims

CLAIMSWhat is claimed is:

1. A method for separating uranium from a solid material containing uranium metal and at least 1% by weight other material, the method comprising: maintaining the solid material containing the uranium metal under UC14 sublimating conditions in a chlorinating environment for a period of time sufficient to convert at least some solid uranium metal into UCI4 in a gas phase.

2. The method of claim 1, wherein the sublimating conditions include a pressure between about 0.1 atm to about 10 atm.

3. The method of any of claims 1-2, wherein the sublimating conditions include a pressure between about 0.9 atm to about 1.5 atm and a temperature between about 400°C and about 650°C.

4. The method of any of claims 1-3, wherein the sublimating conditions include a between about 0.9 atm to about 1.5 atm and a temperature between about 500°C and about 650°C.

5. The method of any of claims 1-4, wherein the solid material is used nuclear fuel comprising at least one fission product of uranium.

6. The method of any of claims 1-5, further comprising preparing the solid material by crushing or pulverizing it into a powder or aggregate.

7. The method of any of claims 1-6, further comprising placing the solid material into a chlorination chamber, the chlorination chamber containing the chlorinating environment.

8. The method of any of claims 1-7, wherein the maintaining step includes contacting the solid material with Ch.

9. The method of claim 8, wherein the Ch is mixed with argon gas.

10. The method of claim 8, further comprising, under the sublimating conditions, reacting the uranium metal with the Ch to create UC14.

11. The method of any of claims 1-10, further comprising separating the UCI4 from the gas phase by reducing a temperature of gas phase thereby by causing the UCI4 to depose from the gas phase as a solid.

12. The method of claim 11, further comprising disposing of the solid material after removing the gas phase containing UCI4 from the solid material.

13. The method of any of claims 1-12, wherein the period of time is a sufficient to convert at least 20% of the uranium metal into UCI4.

14. The method of any of claims 1-13, further comprising removing the gas phase containing the UCI4 from the solid material.

15. The method of any of claims 1-14, further comprising agitating the chlorinating environment.

16. A system, comprising: a chlorination chamber configured to hold a solid material containing uranium metal and a chlorination gas, wherein, within the chlorination chamber, the uranium metal reacts with the chlorination gas to generate a UCh-containing gas mixture; and a UCI4 collection chamber configured to receive the UCU-containing gas mixture from the chlorination chamber, wherein a temperature within the UCI4 collection chamber is maintained below a deposition temperature of the UCI4.

17. The system of claim 16, comprising a low boiling point fission products collection chamber downstream of the UCI4 collection chamber.

18. The system of any of claims 16-17, further comprising a condenser.

19. The system of any of claims 16-18, wherein the chlorination gas comprises cci4, HC1, or CI2.

20. The system of any of claims 16-19, wherein a pressure within the UCI4 collection chamber is maintained below a pressure within the chlorination chamber.

21. The system of any of claims 16-20, wherein the chlorination chamber and UCI4 collection chamber represent different locations within a single continuous vessel.

22. A method for separating uranium from a solid material containing uranium metal and at least 1% by weight other material, the method comprising: maintaining the solid material containing the uranium metal in a chlorinating environment within a chlorination chamber for a period of time sufficient to convert at least some uranium metal into UCI4 in a gas phase; and controlling conditions of a collection chamber to condense the UCI4 in the gas phase into a liquid form, wherein the collection chamber is configured to receive the UCI4 in the gas phase from the chlorination chamber.

23. The method of claim 22, wherein the wherein the chlorinating environment includes a pressure between about 0.9 atm to about 1.5 atm and a temperature between about 400°C and about 650°C.

24. The method of any of claims 22-23, wherein the solid material is used nuclear fuel.

25. The method of any of claims 22-24, further comprising preparing the solid material by crushing or pulverizing it into a powder or aggregate.

26. The method of any of claims 22-25, wherein the maintaining step includes contacting the solid material with CI2.

27. The method of claim 26, wherein the CI2 is mixed with argon gas.

28. The method of claim 26, further comprising, within the chlorinating environment, reacting the uranium metal with the Ch to create UCI4.

29. The method of any of claims 22-28, wherein the period of time is a sufficient to convert at least 20% of the uranium metal into UCI4.

30. The method of any of claims 22-29, further comprising agitating the chlorinating environment within the chlorination chamber.

31. The method of any of claims 22-30, wherein the chlorination chamber and the collection chamber represent different locations within a single continuous vessel.

32. The method of any of claims 22-31 , further comprising maintaining the solid material containing the uranium metal under UCI4 sublimating conditions within the chlorinating environment for the period of time.

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